Co-reporter:Zhuang Zhuang, Yunfeng Li, Duo Qi, Chengji Zhao, Hui Na
Sensors and Actuators B: Chemical 2017 Volume 242() pp:801-809
Publication Date(Web):April 2017
DOI:10.1016/j.snb.2016.09.179
•SPEEKs were successfully synthesized by a direct aromatic nucleophilic substitution polymerization of sulfonated monomers.•The sensor showed wide operating work range and excellent humidity-sensing properties.•The sensor is capable of detecting the small hysteresis (less than 3% RH).•Protons and ions contribution contributed to the conductance of the SPEEK polymer in low and high relative humidity according to the complex impedance spectra.Sulfonated poly (ether ether ketone)s (SPEEKs) with different values of sulfonation degree were successfully synthesized by a direct aromatic nucleophilic substitution polymerization of sulfonated monomers. By the direct-synthesis method, the number of sulfonic acid groups can be precisely controlled. They were then fabricated by spin coating on a ceramic substrate to be used as a novel polymeric humidity sensor. The morphology of the ionic polymers especially the microstructure of ionic clusters, water sorption and the complex impedance spectra of the sensors were investigated to explain the humidity sensing characteristics and the sensing mechanism under different relative humidity. In addition, SPEEK-6 polymer with sulfonation degree (Ds = 1.18) was chosen as the optimal humidity sensing materials, which possessed high sensitivity and satisfactory linearity ranging from 11% RH to 97% RH. Furthermore, it exhibited a small hysteresis (less than 3% RH) during the sorption processes, an acceptable response/recovery time (100 s response and 105 s of recovery time) and an excellent repeatability. These results indicated SPEEKs could be promising for applications in humidity sensor.
Co-reporter:Zhuang Zhuang, Duo Qi, Chunyu Ru, Jing Pan, Chengji Zhao, Hui Na
Sensors and Actuators B: Chemical 2017 Volume 253(Volume 253) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.snb.2017.06.133
•CaCl2 was employed not only as dopant to significantly improve the sensitivity, but also as cross-linker to reduce the sorption hysteresis.•The sensor showed wide operating work range and excellent humidity-sensing properties.•The sensor is capable of detecting little hysteresis (1.14%), fast response (2 s).•Based on the complex impedance spectra of humidity sensors, the process of conductivity is a combination of intrinsic charge transport (charge doping by water molecules), ion transport and diffusion processes over the whole RH range.This study presented a novel polymeric humidity sensor based on CaCl2-doped sulfonated poly (ether ether ketone) (SPEEK). For the first time, we developed a crosslinking procedure to modify SPEEK for humidity sensors application. SPEEKs with fixed value of sulfonation degree were synthesized by a direct aromatic nucleophilic substitution polymerization of sulfonated monomers. The obtained polymer was used to prepare humidity sensitive composites by doping CaCl2, and then they were fabricated by spin coating on a ceramic substrate to use as a novel polymeric humidity sensor. Humidity-sensing performances were investigated by varying both CaCl2 concentration and relative humidity. Comparing with the pristine polymer, CaCl2-doped SPEEK showed improved humidity sensing properties and the 10 wt%- CaCl2/SPEEK sensor showed the best sensing properties for high sensitivity, little hysteresis (1.14%), fast response (2 s)/recovery time (65 s) and outstanding stability. Additionally, the morphology and thermal properties of composites and the humidity sensing mechanism of the sensors were discussed in detail. Most importantly, CaCl2 was employed not only as dopant to significantly improve the sensitivity, but also as cross-linker to reduce the sorption hysteresis. This study demonstrated that these humidity sensors could offer a great potential for applications.In the case of doped SPEEK membranes, the process of conductivity is a combination of intrinsic charge transport (charge doping by water molecules), ion transport and diffusion processes over the whole RH range.Download high-res image (93KB)Download full-size image
Co-reporter:Lihua Hong, Yu Wang, Lin Wang, Hong Zhang, Hui Na, Zhimin Zhang
Journal of Dentistry 2017 Volume 59(Volume 59) pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.jdent.2017.01.006
ObjectiveIn this study, we designed and synthesized a novel macromolecule (tetramethyl bisphenol F acrylate, TMBPF-Ac) with low viscosity, excellent mechanical properties, and good biocompatibility. It could be used as a monomer for dental resin composites, which could reduce the risk of human exposure to bisphenol A derivatives in the oral environment. In addition, the monomer could be used without diluent, thereby avoiding the negative effect of a diluentMethodsTMBPF-Ac was synthesized by a multistep condensation reaction. Its structure was confirmed by 1H NMR spectra. Different resin mixtures were prepared, and then a number of performance and cytotoxicity tests were performed on these specimens.Results1H NMR spectra showed that the structure of TMBPF-Ac was in accordance with the design. The viscosity of TMBPF-Ac was obviously lower than that of bisphenol-A diglycidyl methacrylate. The three kinds of resins used in this study were in line with ISO 4049:2009 and ISO 10993-5:2009. TMBPF-Ac-based resin had better physical and biological properties.Download high-res image (142KB)Download full-size image
Co-reporter:Baolong Wang, Lihua Hong, Yunfeng Li, Liang Zhao, Yuxue Wei, Chengji Zhao, and Hui Na
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 36) pp:24079
Publication Date(Web):August 24, 2016
DOI:10.1021/acsami.6b06983
Novel sulfonated poly(arylene ether ketones) (SDN-PAEK-x), consisting of dual naphthalene and flexible sulfoalkyl groups, were prepared via polycondensation, demethylation, and sulfobutylation grafting reaction. Among them, SDN-PAEK-1.94 membrane with the highest ion exchange capacity (IEC = 2.46 mequiv·g–1) exhibited the highest proton conductivity, which was 0.147 S· cm–1 at 25 °C and 0.271 S·cm–1 at 80 °C, respectively. The introduction of dual naphthalene moieties is expected to achieve much enhanced properties compared to those of sulfonated poly(arylene ether ketones) (SNPAEK-x), consisting of single naphthalene and flexible sulfoalkyl groups. Compared with SNPAEK-1.60 with a similar IEC, SDN-PAEK-1.74 membrane showed higher proton conductivity, higher IEC normalized conductivity, and higher effective proton mobility, although it had lower analytical acid concentration. The SDN-PAEK-x membranes with IECs higher than 1.96 mequiv·g–1 also exhibited higher proton conductivity than that of recast Nafion membrane. Furthermore, SDN-PAEK-1.94 displayed a better single cell performance with a maximum power density of 60 mW·cm–2 at 80 °C. Considering its high proton conductivity, excellent single cell performance, good mechanical stabilities, low membrane swelling, and methanol permeability, SDN-PAEK-x membranes are promising candidates as alternative polymer electrolyte membranes to Nafion for direct methanol fuel cell applications.Keywords: fuel cell; naphathalene moieties; poly(arylene ether ketone); polymer electrolyte membranes; proton conductivity; sulfoalkyl groups
Co-reporter:Duo Qi, Chengji Zhao, Zhuang Zhuang, Guibin Li, Hui Na
Electrochimica Acta 2016 Volume 197() pp:39-49
Publication Date(Web):10 April 2016
DOI:10.1016/j.electacta.2016.03.056
•Novel side-chain type sulfonated poly (arylene ether ketone)s were prepared, and the Ds can be controlled precisely.•The water sorption behaviour of the polymers has been discussed from the mechanism.•The effect of the structure on the humidity sensitivity properties has been discussed in detail.•High Ds materials show excellent sensitivity and stability in a wide humidity range.A series of novel side-chain-type sulfonated polymer aromatic electrolytes (PAEK-SO3Na-x) with different sulfonation degrees (Ds) were synthesized through a polycondensation of 1,5-bis(4-fluorobenzoyl)-2,6-dimethoxynaphthalene and hydroquinone, followed by a demethylation and sulfobutylation reaction. The structures and Ds of the polymers were confirmed by their 1H NMR spectra and the hydrophilic nature of the membranes was characterized by water uptake and contact angle test. A dual-mode sorption model was applied to analyze the water vapor sorption of the polymers. Humidity sensors were prepared from PAEK-SO3Na-x. Then the sensitivity and responsibility of the sensors were characterized in detail. The variation range of the impedance of the sensors was from 107 Ω to 102 Ω between 11% RH and 97% RH, which was wider than many other polymeric humidity sensors reported and indicated a good sensitivity. The response time of PAEK-SO3Na-80 was 90 s and 100 s for desorption and adsorption, respectively. It is for the first time to apply side-chain-type sulfonated polymer electrolyte to humidity sensors and this new kind of sensitivity material showed a good application prospect.
Co-reporter:Zhuang Zhuang, Duo Qi, Chengji Zhao, Hui Na
Sensors and Actuators B: Chemical 2016 Volume 236() pp:701-711
Publication Date(Web):29 November 2016
DOI:10.1016/j.snb.2016.06.063
•SPEEK and SPEEK with metal salts-ion substitution is successfully synthesized.•The sensor showed highly sensitive and excellent humidity-sensing properties.•The sensor is capable of detecting the small hysteresis (less than 2% RH).•Ionic conductivities contributed to the transmission in low and high relative humidity according to the complex impedance spectra.Sulfonated poly (ether ether ketone) (SPEEK) was successfully synthesized by post-sulfonation. A novel humidity sensor was made of SPEEK and SPEEK with metal salts-ion (Ca2+, Cu2+) substitution and fabricated by spin coating on a ceramic substrate. The effect of different counter-ion forms on the electrical and humidity-sensing properties of SPEEK membranes was investigated. The chemical structure of SPEEK was confirmed using its 1H NMR spectrum. The polymeric materials were detailed characterized, including FTIR spectra, thermogravimetric analysis (TGA), and contact angle measurement. These results indicated there were significant differences in their chemical structure, thermal and transport properties for SPEEK when exchanged with the different metal salts-ions. In addition, comparing with SPEEK, the humidity-sensing properties of SPEEK-Ca2+ exhibited high sensitivity from 33% RH to 97% RH, satisfactory linearity, small hysteresis during the sorption processes, short response/recovery time, excellent repeatability and complex impedance in low and high relative humidity. This means that the water molecules in the SPEEK-Ca2+ membranes interact with the Ca2+ cations more strongly when exchanged with the different metal salts-ions, and in result the diffusion of the water molecules is reduced. These results inditated this novel polymer electrolyte with metal salts-ion would be a promising candidate for humidity sensor applications.
Co-reporter:Cong Liu, Sinan Feng, Zhuang Zhuang, Duo Qi, Guibin Li, Chengji Zhao, Xuefeng Li and Hui Na
Chemical Communications 2015 vol. 51(Issue 63) pp:12629-12632
Publication Date(Web):26 Jun 2015
DOI:10.1039/C5CC03462K
We have developed basic ionic liquid-based hybrid membranes with ionic liquid modified zeolitic imidazolate frameworks (ZIFs) as fillers, aiming to enhance the electrochemical and physical properties of the membrane.
Co-reporter:Guibin Li, Chengji Zhao, Xuefeng Li, Duo Qi, Cong Liu, Fanzhe Bu and Hui Na
Polymer Chemistry 2015 vol. 6(Issue 32) pp:5911-5920
Publication Date(Web):30 Jun 2015
DOI:10.1039/C5PY00700C
A new bisphenol monomer, 3,3′,5,5′-tetramethoxy-4,4′-dihydroxybiphenyl, was synthesized and copolymerized to prepare diphenyl-based poly(arylene ether sulfone) copolymers containing tetra-methoxy groups (MOPAES). After converting the methoxy group to the reactive hydroxyl group, the resulting side-chain-type sulfonated copolymers (SOPAES) with a hydrogen bonded network were obtained by a sulfobutylation reaction. The copolymers were characterized and confirmed by 1H NMR, FT-IR, thermogravimetric analysis (TGA) and small-angle X-ray scattering. The water uptake, proton and methanol transport properties of the resulting membranes were also determined for fuel cell applications. These SOPAES series membranes showed high proton conductivity in the range of 0.032–0.054 and 0.084–0.142 S cm−1 at 25 and 80 °C under hydrated conditions, respectively. SOPAES-40 (IEC = 1.38 mequiv. g−1) showed comparable proton conductivity with Nafion 117 in the hydrated state. The methanol permeability of these membranes was in the range of 1.58–4.29 × 10−7 cm2 s−1, which is much lower than Nafion (1.55 × 10−6 cm2 s−1). It should be noted that the intra/inter hydrogen bonds formed between sulfonic acid and hydroxyl groups or between hydroxyl and hydroxyl groups improved the mechanical properties and reduced the methanol permeability of the membranes effectively. A combination of suitable proton conductivity, low water uptake, and low methanol crossover for selected SOPAES indicates that they are good candidates as proton exchange membrane materials for fuel cells.
Co-reporter:Duo Qi, Chengji Zhao, Liyuan Zhang, Xuefeng Li, Guibin Li and Hui Na
Polymer Chemistry 2015 vol. 6(Issue 28) pp:5125-5132
Publication Date(Web):12 Jun 2015
DOI:10.1039/C5PY00768B
A novel in situ-foaming material was successfully prepared by a naphthalene-based hydroxyl-containing poly(arylene ether ketone) (PAEK) modified with thermally labile tert-butyloxycarbonyl which can decompose and in situ generate CO2 and isobutene as the foaming agents. The structure and thermal properties of the polymers were characterized by using 1H NMR spectra and thermogravimetry coupled time-resolved mass spectrogram (TG/MS). The resulting polymers exhibited relatively high Tg because of the existence of a rigid naphthalene moiety. Then closed microcellular porous membranes with a wide range of expansion ratio (ER) were obtained by a simple thermal treatment from 140 °C to 280 °C for 60 seconds, without using any other physical or chemical foaming agents. The highest ER was 53.98%. This method has never been reported before on high-performance poly(aryl ether) materials. Furthermore, we investigated the relationship between the foaming temperature and the morphology of membranes in detail by using density measurement and scanning electron microscopy (SEM).
Co-reporter:Fanzhe Bu, Chengji Zhao, Baolong Wang, Na Zhang, Hao Lu, Zhenzhen Cai, Yurong Zhang and Hui Na
RSC Advances 2015 vol. 5(Issue 70) pp:57067-57075
Publication Date(Web):24 Jun 2015
DOI:10.1039/C5RA09546H
A novel cross-linking strategy for imidazolium-functionalized poly(arylene ether ketone) containing tetramethyl groups, used as anion exchange membranes, is presented in this paper. The preparation of anion exchange membranes comprised of converting benzylic methyl to bromomethyl groups by a radical reaction, quaternization of the bromometylated poly(arylene ether ketone) with 1-vinylimidazole and subsequent anion exchange reaction. The photo-crosslinking reaction, induced by UV-light under the activation of a photo-initiator, was simple and controllable compared to the conventional cross-linking process via a multifunctional cross-linking agent. All the vinylimidazolium-founctionalized poly(arylene ether ketone) membranes showed good mechanical and thermal stabilities. Moreover, the cross-linked membranes exhibited better dimensional stabilities. The ionic conductivity of cross-linked membranes was still acceptable although that property decreased with UV irradiation time due to the compact cross-linked structure. For example, the VImPAEK-15 min-HCO3 membrane with irradiation time of 15 min showed a moderate bicarbonate anion conductivity of 0.021 S cm−1 and a low swelling ratio of 10.74% at 70 °C. The alkaline stability test under both high and relatively low alkaline conditions was carried out. Although the vinylimidazolium cation is unstable in strong alkaline solution, the cross-linked vinylimidazolium-based membranes are chemically stable in the bicarbonate anion form under relatively low alkaline conditions. The results showed that the cross-linked membrane induced by UV irradiation could be used for electrochemical devices that were operated at less extreme pHs.
Co-reporter:Baolong Wang, Zhenzhen Cai, Na Zhang, Bin Zhang, Duo Qi, Chengji Zhao and Hui Na
RSC Advances 2015 vol. 5(Issue 1) pp:536-544
Publication Date(Web):24 Nov 2014
DOI:10.1039/C4RA12651C
A series of sulfonated naphthalene-based poly (arylene ether ketone)s (SNPAEK-xx) with pendant sulfoalkyl groups were prepared by polycondensation of 1,5-bis(4-fluorobenzoyl)-2,6-dimethoxynaphthalene and o-methylhydroquinone, followed by a demethylation and sulfobutylation reaction. The sulfonate degree of SNPAEK-xx could be controlled easily by adjusting the ratio of 1,4-butane sultone to the hydroxyl content in the demethylated polymers. Flexible and tough membranes with reasonably high mechanical strength were prepared. SNPAEK-xx membranes showed a high ionic exchange capacity (IEC) in the range of 1.13 to 2.27 mequiv. g−1, and the highest proton conductivity of 0.191 S cm−1 at 80 °C. They exhibited low methanol permeability in the range of 1.25–10.22 × 10−7 cm2 s−1, which was much lower than that of Nafion 117. Transmission electron microscopy analysis of SNPAEK-xx revealed that they had a more obvious phase separated structure between the hydrophilic side chain and hydrophobic fully aromatic domains at a higher IEC. Combining their high thermal and mechanical stability, high selectivity, lower water swelling ratio, SNPAEK-xx membranes could be promising materials as alternative to Nafion membranes for direct methanol fuel cell applications.
Co-reporter:Na Zhang, Baolong Wang, Chengji Zhao, Shuang Wang, Yurong Zhang, Fanzhe Bu, Ying Cui, Xuefeng Li and Hui Na
Journal of Materials Chemistry A 2014 vol. 2(Issue 34) pp:13996-14003
Publication Date(Web):02 Jul 2014
DOI:10.1039/C4TA01931H
Quaternized poly(ether ether ketone)s (QPEEKs), which were aminated by trimethylamine (TMeA), triethylamine (TEtA), tripropylamine (TPrA) and 1-methylimidazole (MeIm), were prepared and used as phosphoric acid (PA)-doped high-temperature proton exchange membranes. These QPEEK membranes showed high glass transition temperature (Tg was higher than 483 K) and high thermal stability (T5% was higher than 486 K). The tensile strengths of these QPEEK membranes were higher than 60 MPa. The PA-doped im-QPEEK, which was aminated by MeIm, had the highest Wdoping (159 wt%) and proton conductivity (0.05 S cm−1 at 473 K). For the other three PA-doped QPEEK membranes, the Wdoping and proton conductivity decreased with the increase of the length of trialkyl side chains on quaternary ammonium groups. According to our study, the PA absorbing ability was subjected to the structures of quaternary ammonium groups instead of the basicities of quaternary aminating reagents. All PA-doped membranes had great oxidative stability and could last for more than 5 h in 3 wt% H2O2, 4 ppm Fe2+ Fenton solution at 353 K.
Co-reporter:Na Zhang, Baolong Wang, Yurong Zhang, Fanzhe Bu, Ying Cui, Xuefeng Li, Chengji Zhao and Hui Na
Chemical Communications 2014 vol. 50(Issue 97) pp:15381-15384
Publication Date(Web):21 Oct 2014
DOI:10.1039/C4CC07791A
Functionalized graphene oxide (FGO) reinforced quaternized poly(ether ether ketone) membranes were prepared for high temperature proton exchange membrane applications. The introduction of FGO significantly improved the mechanical strength and oxidative stability of these membranes at a high doping level. These reinforced membranes showed high tensile strength up to 40 MPa and high proton conductivity up to 58 mS cm−1 at 200 °C.
Co-reporter:Cong Liu, Gang Zhang, Chengji Zhao, Xuefeng Li, Mingyu Li and Hui Na
Chemical Communications 2014 vol. 50(Issue 91) pp:14121-14124
Publication Date(Web):19 Sep 2014
DOI:10.1039/C4CC05526H
The liquid nature of ionic liquids (ILs) limits their use in potential electrolytes due to the problem of leakage. Herein, we design a new strategy to immobilize an ionic liquid by incorporating it within ZIF-8 (ZIF = zeolitic imidazolate framework) by the ionothermal method.
Co-reporter:Na Zhang, Chengji Zhao, Wenjia Ma, Shuang Wang, Baolong Wang, Gang Zhang, Xuefeng Li and Hui Na
Polymer Chemistry 2014 vol. 5(Issue 17) pp:4939-4947
Publication Date(Web):14 Apr 2014
DOI:10.1039/C4PY00234B
Poly(ether ether ketone) bearing benzyl bromide groups (Br–PEEK) was synthesized and a series of cross-linked membranes (Br–PEEK–x%PBI) based on Br–PEEK with polybenzimidazole (PBI) as a macromolecular cross-linker was prepared to improve the dimensional stability and tensile strength without reducing proton conductivity. X-ray photoelectron spectroscopy (XPS) confirmed the success of the cross-linking reaction. After being ammoniated, the quaternary ammonium PEEK membranes were immersed in phosphoric acid and anhydrous phosphoric acid doped membranes were obtained. The phosphoric acid doped membranes without PBI as the cross-linker had excess volume swelling and could not remain integrated. The other cross-linked membranes had good dimensional stabilities. Because PBI could absorb phosphoric acid, the proton conductivities of cross-linked membranes first increased and then decreased with the content of PBI increasing. The highest proton conductivity was 0.081 S cm−1 at 200 °C for the PA–PEEK–20%PBI membrane. The dimensional stabilities, oxidative stabilities and tensile strength of PA–PEEK–x%PBI membranes improved. The PA–PEEK–30%PBI membrane could last for 7.5 h in 3 wt.% H2O2, 4 ppm Fe2+ Fenton solution at 80 °C before breaking into pieces. Energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA) were used for detailed research.
Co-reporter:Mingyu Li, Gang Zhang, Shuai Xu, Chengji Zhao, Miaomiao Han, Liyuan Zhang, Hao Jiang, Zhongguo Liu, Hui Na
Journal of Power Sources 2014 Volume 255() pp:101-107
Publication Date(Web):1 June 2014
DOI:10.1016/j.jpowsour.2013.12.116
•Cross-linker with proton conductive group was designed and synthesized.•A comparison between the sulfonated and non-sulfonated cross-linkers was made.•By using the sulfonated cross-linker, SPEEK has been successfully modified.•The result membranes showed low methanol crossover as well as high conductivity.•The oxidative stability of the result membranes was much improved also.A novel type of cross-linked proton exchange membrane of lower methanol permeation and high proton conductivity is prepared, based on a newly synthesized sulfonated cross-linker: carboxyl terminated benzimidazole trimer bearing sulfonic acid groups (s-BI). Compared to membranes cross-linked with non-sulfonated cross-linker (BI), SPEEK/s-BI-n membranes show higher IEC values and proton conductivities. Meanwhile, oxidative stability and mechanical property of SPEEK/s-BI-n membranes are obviously improved. Among SPEEK/s-BI-n membranes, SPEEK/s-BI-2 exhibits high proton conductivity, low swelling ratio (0.122 S cm−1 and 15.2% at 60 °C, respectively) and low methanol permeability coefficient. These results imply that the cross-linked membranes prepared with the newly sulfonated cross-linker are promising for the direct methanol fuel cells (DMFCs) application.
Co-reporter:Liyuan Zhang, Duo Qi, Gang Zhang, Chengji Zhao and Hui Na
RSC Advances 2014 vol. 4(Issue 94) pp:51916-51925
Publication Date(Web):08 Oct 2014
DOI:10.1039/C4RA08919G
A series of cross-linked sulfonated poly (arylene ether ketones) containing tri-side-chain pendent sulfonic groups (SQNPAEK) were prepared by the Friedel–Crafts acylation reaction in order to solve the problem of high methanol crossover and maintain high proton conductivity for direct methanol fuel cells. For this purpose, sulfonated poly(arylene ether ketones) with pendent carboxylic acid groups were synthesized based on phenolphthalein carboxylic monomers to be used as a macro-crosslinker. The cross-linked membranes showed improved mechanical properties, chemical resistance and oxidative stability. The water uptake and swelling ratio of cross-linked membranes decreased from 57.3% to 18.7%, and from 12.2% to 3.03%, respectively. And the methanol permeability decreased from 0.94 × 10−7 cm2 s−1 to 0.37 × 10−7 cm2 s−1. Regarding the high proton conductivity, it showed enhanced performance over the pristine membrane, up to 0.29 S cm−1. Thus, the cross-linked membranes possessed the better performance implying their potential for practical application in high-energy-density devices.
Co-reporter:Shuang Wang, Chengji Zhao, Wenjia Ma, Na Zhang, Yurong Zhang, Gang Zhang, Zhongguo Liu and Hui Na
Journal of Materials Chemistry A 2013 vol. 1(Issue 3) pp:621-629
Publication Date(Web):12 Oct 2012
DOI:10.1039/C2TA00216G
Silane-cross-linked polybenzimidazole (PBI) membranes with high proton conductivity and excellent mechanical properties were successfully prepared by using a silane monomer, γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), as a cross-linker. Fourier transform infrared spectroscopy and solubility tests were used to characterize and confirm the cross-linked structure in the membranes. The silane-cross-linked membranes displayed excellent chemical stability and improved mechanical strength. Especially at high temperature (130 °C), where the tensile strength value was in the range of 68.6 to 99.3 MPa, while that of the pristine PBI was 61.7 MPa. Moreover, the proton conductivity was significantly enhanced because the silane-cross-linked structure in the membranes could absorb more phosphoric acid. Considering the tradeoff of mechanical properties and proton conductivity, 3% KH560 in weight was demonstrated to be the optimum content in the membranes, for instance, the SCPBI-3/7.95 PA (the cross-linker content was 3 wt% and the PA doping level was 7.95) had a proton conductivity of 0.081 S cm−1 and that of the SCPBI-3/9.07 PA was 0.114 S cm−1 at 200 °C, while that of pristine PBI was 0.015 S cm−1 at 200 °C.
Co-reporter:Hao Jiang, Xin Guo, Gang Zhang, Jing Ni, Chengji Zhao, Zhongguo Liu, Liyuan Zhang, Mingyu Li, Shuai Xu, Hui Na
Journal of Power Sources 2013 Volume 241() pp:529-535
Publication Date(Web):1 November 2013
DOI:10.1016/j.jpowsour.2013.04.151
•Prepared the water soluble polymer as an ionomer in the catalyst layer of DMFCs.•“Click” reaction was selected in order to make the membranes.•The cross-linked membranes possess high proton conductivity.In this paper, a series of proton exchange membranes prepared by “Click Reaction” are reported. The cross-linked membranes are based on water soluble sulfonated poly (ether ether ketone) containing dipropenyl groups (SDPEEK-nE/nH). Compared with self-crosslinked membranes (SDPEEK-nS), this “Click” cross-linked membranes using 1,2-Ethanedithiol and 1,6-Hexanedithiol as the cross-linker exhibit extremely reduced water uptake and swelling ratio. The lowest proton conductivity at 80 °C of the “Click” cross-linked membranes reaches to 0.168 S cm−1, and the highest methanol permeability of the “Click” cross-linked SDPEEK-8E is only 4.13 × 10−7 cm2 s−1, which is 5 times lower than that of Nafion 117 membrane. All the results imply that the cross-linked membranes with novel thiol cross-linker are promising alternative material for fuel cell application.
Co-reporter:Shuang Wang, Chengji Zhao, Wenjia Ma, Na Zhang, Zhongguo Liu, Gang Zhang, Hui Na
Journal of Power Sources 2013 Volume 243() pp:102-109
Publication Date(Web):1 December 2013
DOI:10.1016/j.jpowsour.2013.05.181
•A series of macromolecular cross-linked polybenzimidazole membranes were prepared.•The macromolecule BrPAEK was first used as a cross-linker in PBI-based system.•The CBrPBI-X membranes were prepared by an easy facile heating method.•The chemical stability, oxidative stability and mechanical properties were improved.•The results indicated that CBrPBI-10 was a promising candidate as HT-PEM.A series of macromolecular cross-linked polybenzimidazole (PBI) membranes have been successfully prepared for the high temperature proton exchange membrane fuel cell (HT-PEMFC) applications. Bromomethylated poly (aryl ether ketone) (BrPAEK) is synthesized and used as a macromolecular cross-linker, the cross-linking reaction can be accomplished at 160 °C using an easy facial heating treatment. The resulting cross-linked membranes CBrPBI-X (X is the weight fraction of the cross-linker) display excellent mechanical strength. After phosphoric acid (PA) doping, the mechanical strength and proton conductivity of the PA/CBrPBI-X membranes are both enhanced comparing with the pristine PA/PBI. Considering the tradeoff of the mechanical strength and proton conductivity, 10 wt% BrPAEK is demonstrated to be an optimum content in the matrix. For instance, the proton conductivity of PA/CBrPBI-10 is 0.038 S cm−1 at 200 °C, which is higher than that of pristine PA/PBI with the proton conductivity of 0.029 S cm−1 at the same temperature. Other properties of the cross-linked membranes are also investigated in detail, including the oxidative stability, solubility and thermal stability. All the results indicate that the PA/CBrPBI-10 membrane has the potential application in HT-PEMFCs.A series of phosphoric acid doped macromolecular-cross-linked polybenzimidazole (PBI) membranes were prepared for high-temperature proton exchange membrane fuel cell applications. The introduction of macromolecular cross-linker (BrPAEK) not only enhanced the proton conductivity, but also improved the chemical stability and mechanical strength of the membranes.
Co-reporter:Liyuan Zhang, Gang Zhang, Chengji Zhao, Zhongguo Liu, Hao Jiang, Shuai Xu, Mingyu Li, Dan Xu, Hui Na
International Journal of Hydrogen Energy 2013 Volume 38(Issue 28) pp:12363-12373
Publication Date(Web):19 September 2013
DOI:10.1016/j.ijhydene.2013.07.066
•Multi-side-chain-type polymer with sulphonic acid groups was synthesized.•The hydroxyl groups made great efforts to the high proton conductivity.•The SQNPAEK-x membranes had excellent dimensional stability.•The SQNPAEK-x membranes had excellent mechanical and thermal properties.A novel side-chain poly(arylene ether ketone) functionalized with 1,4-butane-sultone (SQNPAEK-x, “x” refers to the number of the attaching sulfobutyl groups in one unit) were synthesized for proton exchange membrane fuel cell. SQNPAEK-x showed high proton conductivity up to 0.317 S cm−1 at 80 °C and excellent dimensional stability due to the remaining hydroxyl groups. Morphological investigations revealed that SQNPAEK-x contained more uniform ionic clusters than the main-chain sulfonated poly(arylene ether ketone), which increased the proton conductivity. Other properties such as water uptake, mechanical properties were also investigated. It should be noted that SQNPAEK-1.5 possesses the best overall performance with proton conductivity (0.204 S cm−1 at 80 °C) higher that Nafion 117, while the swelling ratio was equivalent (13.2% at 80 °C). All the results indicate that the SQNPAEK-x membranes are promising candidates for proton exchange membrane fuel cells.
Co-reporter:Wenjia Ma, Chengji Zhao, Jingshuai Yang, Jing Ni, Shuang Wang, Na Zhang, Haidan Lin, Jing Wang, Gang Zhang, Qingfeng Li and Hui Na
Energy & Environmental Science 2012 vol. 5(Issue 6) pp:7617-7625
Publication Date(Web):02 Apr 2012
DOI:10.1039/C2EE21521G
Diamine-cross-linked membranes were prepared from cross-linkable poly(arylene ether ketone) containing pendant cationic quaternary ammonium group (QPAEK) solution by a facile and general thermal curing method using 4,4′-diaminodiphenylmethane with rigid framework and 1,6-diaminohexane with flexible framework as cross-linker, respectively. Self-cross-linked cationic polymer electrolytes membranes were also prepared for comparison. The diamines were advantageously distributed within the polymeric matrix and its amine function groups interacted with the benzyl bromide of QPAEK, resulting in a double anchoring of the molecule. Combining the excellent thermal stability, the addition of a small amount of diamines enhanced both the chemical and mechanical stability and the phosphoric acid doping (PA) ability of membranes. Fuel cell performance based on impregnated cross-linked membranes have been successfully operated at temperatures up to 120 °C and 180 °C with unhumidified hydrogen and air under ambient pressure, the maximum performance of diamine-cross-linked membrane is observed at 180 °C with a current density of 1.06 A cm−2 and the peak power density of 323 mW cm−2. The results also indicate that the diamine-cross-linked membranes using the rigid cross-linker show much improved properties than that using the flexible cross-linker. More properties relating to the feasibility in high temperature proton exchange membrane fuel cell applications were investigated in detail.
Co-reporter:Shuai Xu, Gang Zhang, Yang Zhang, Chengji Zhao, Liyuan Zhang, Mingyu Li, Jing Wang, Na Zhang and Hui Na
Journal of Materials Chemistry A 2012 vol. 22(Issue 26) pp:13295-13302
Publication Date(Web):30 May 2012
DOI:10.1039/C2JM16593G
A series of novel poly(ether ether ketone) copolymers containing methyl groups on the side chain were prepared based on a new monomer (3,4-dimethyl)phenylhydroquinone. Then a series of hydroxide exchange membranes with different IEC values were obtained through bromination and quaternary amination of the copolymers. By adjusting the contents of methyl groups in the copolymers, we could control the final structures of the membranes. The chemical structures of the monomers and copolymers were analyzed by 1H NMR spectroscopy. After that, for the purpose of enhancing the dimensional stability and methanol resistance of the membrane, we prepared cross-linked membranes through a Friedel–Crafts reaction between bromomethyl groups and aromatic rings. The properties of the membranes related to fuel cell application were evaluated in detail. All the membranes showed good thermal and mechanical stabilities and conductivities. Moreover, the cross-linked membranes exhibit better dimensional stabilities and selectivities. Among those membranes, xPEEK–Q-100 showed a high conductivity (0.036 S cm−1 at 80 °C), a low swelling ratio of 6.6% and a methanol permeation coefficient of 2.9 × 10−7 cm2 s−1. The outstanding properties indicated that the application of PEEK–Q-xx membranes in fuel cells was promising.
Co-reporter:Shuai Xu, Gang Zhang, Yang Zhang, Chengji Zhao, Wenjia Ma, Hongcheng Sun, Na Zhang, Liyuan Zhang, Hao Jiang, Hui Na
Journal of Power Sources 2012 Volume 209() pp:228-235
Publication Date(Web):1 July 2012
DOI:10.1016/j.jpowsour.2012.02.076
A series of poly(ether ether ketone) anion exchange membranes with tunable IEC (Ion-exchange capacity) values are polymerized from a novel bisphenol monomer (4-methyl)phenylhydroquinone. These poly(ether ether ketone) copolymers contain methyl groups on the rigid side chain. The degrees of bromination and quaternary amination of the copolymers are controlled by manipulating the contents of methyl groups in the copolymers. Hence, the IEC tunability of the membrane is achieved. The resulting PEEK-Q-xx membranes show good dimensional stability. The highest swelling ratio (PEEK-Q, with an IEC value of 0.90 mequiv. g−1) is only 9.0% at 80 °C, at which temperature, the hydroxide conductivity of PEEK-Q membrane is 0.031 S cm−1. The methanol permeability values of the membranes are all below 1.5 × 10−7 cm2 s−1, which are much lower than that of Nafion 117. These properties make the membranes good candidate materials for anion exchange membranes for alkaline direct methanol fuel cells.Graphical abstractHighlights► We prepared a novel side-chain-type quaternary-aminated poly(ether ether ketone)s. ► The IEC values of the membranes were well controlled. ► The membranes had excellent selectivity and good stabilities.
Co-reporter:Shuang Wang, Chengji Zhao, Wenjia Ma, Gang Zhang, Zhongguo Liu, Jing Ni, Mingyu Li, Na Zhang, Hui Na
Journal of Membrane Science 2012 Volumes 411–412() pp:54-63
Publication Date(Web):1 September 2012
DOI:10.1016/j.memsci.2012.04.011
A new approach has been proposed to obtain high-temperature proton exchange membranes based on novel cross-linked porous polybenzimidazole (PBI). The cross-linked porous PBI membranes (CpPBI) were prepared by leaching out a low-molecular-weight compound dibutyl phthalate and mixing 4,4′-diglycidyl (3,3′,5,5′-tetramethylbiphenyl) epoxy resin as a cross-linker. The porous PBI membranes (pPBI) were also prepared for comparison. Compared with pPBI membranes, the mechanical properties and the chemical stability of CpPBI membranes were significantly improved. Both the uncross-linked and cross-linked membranes were doped with phosphoric acid, which may be used as proton exchange membranes for high temperature fuel cell. The doping level of all the pPBI membranes was higher than that of pristine PBI, thus leading to a higher proton conductivity. Especially the CpPBI-10 (with a cross-linker content of 10 wt.% and a porogen content of 50 wt.%) had a relative high proton conductivity of 0.046 S cm−1 at 200 °C, which is higher than some of the known porous PBI membranes measured under similar conditions. All the remarkable results of the epoxy-cross-linked porous PBI membranes indicated that the CpPBI membranes could be a suitable candidate for high temperature proton exchange membrane fuel cell (HT-PEMFC) applications.Graphical abstractHighlights► The cross-linking reaction could be completed by heating at a low temperature. ► The porous PBI membranes could effectively elevate doping level. ► The CpPBI-10 could be suitable for HT-PEMFCs applications.
Co-reporter:Shanshan Gao, Chengji Zhao, Hui Na
Journal of Power Sources 2012 Volume 214() pp:285-291
Publication Date(Web):15 September 2012
DOI:10.1016/j.jpowsour.2012.04.060
A series of cross-linked hybrid membranes with low water uptake, high dimensional stabilities, as well as high oxidative stabilities are prepared by a combination of silane-crosslinking and thiol-ene click chemistry based on a sulfonated poly (arylene ether ketone) (SPAEK) with propenyl groups. 1H NMR measurement and Fourier transform infrared spectroscopy are used to characterize and confirm the chemical structure of SPAEK and its cross-linked hybrid polymer exchange membranes. We also investigate the changes in methanol permeability, proton conductivity and mechanical properties. Our findings demonstrate that the Si–O–Si cross-linked structure makes a great contribution to the improvement of dimensional and chemical stabilities. Therefore, these cross-linked hybrid membranes could be considered as promising materials for direct methanol fuel cell applications.Highlights► A series of cross-linked hybrid membranes were prepared by a combination of silane-crosslinking and thiol-ene click chemistry. ► The cross-linked structure makes a great contribution to the improvement of dimensional and chemical stabilities. ► The cross-linked hybrid membranes showed lower swelling, lower methanol permeability and high selectivity for direct methanol fuel cells.
Co-reporter:Liyuan Zhang, Gang Zhang, Chengji Zhao, Hao Jiang, Jing Wang, Dan Xu, Yang Zhang, Ke Shao, Zhongguo Liu, Wengjia Ma, Hongtao Li, Mingyu Li, Shuang Wang, Hui Na
Journal of Power Sources 2012 Volume 201() pp:142-150
Publication Date(Web):1 March 2012
DOI:10.1016/j.jpowsour.2011.11.004
In order to enhance the ion exchange capacity (IEC) in the proton exchange membrane materials, a novel sulfonated poly(arylene ether ketone) (SQNPAEK) containing tri-side chains in one unit is synthesized by direct polymerization. The SQNPAEK membrane shows excellent proton conductivity up to 0.102 S cm−1 at 80 °C, which are superior to previous side-chain-type and main-chain-type sulfonated polymer membranes at similar IEC. Cross-linked membranes are then obtained by a heating reaction at 190 °C, using 4,4′-diglycidyl (3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP) as the cross-linker. As expected, the water uptake and the methanol permeability of the cross-linked membranes decrease with increasing the content of TMBP. Compared to Nafion 117, the cross-linked membranes show comparable proton conductivities and much higher selectivities, which are in the range of 5.18 × 105–1.46 × 106 S s−1 cm3. Other properties of the cross-linked membranes, such as mechanical properties, thermal properties, are also investigated. All the results indicated that the cross-linked membranes based on SQNPAEKs and TMBP are promising candidate for direct methanol fuel cells.Graphical abstractHighlights► Novel side-chain-type polymer with sulphonic acid groups was synthesized. ► Cross-linked membranes were obtained by thermal curing with TMBP. ► The cross-linked membranes had excellent selectivities and high proton conductivity. ► Other measurement showed that the cross-linked membranes had excellent properties.
Co-reporter:Zhongguo Liu, Gang Zhang, Zhuang Liu, Hongcheng Sun, Chengji Zhao, Shuang Wang, Guibin Li, Hui Na
Polymer Degradation and Stability 2012 Volume 97(Issue 5) pp:691-697
Publication Date(Web):May 2012
DOI:10.1016/j.polymdegradstab.2012.02.012
The epoxy resin with a trifluoromethyl side chain, (3-trifluoromethyl) phenylhydroquinone epoxy resin (3F-PQE), was synthesized via a three-step procedure. The chemical structures were confirmed by FT-IR, 1H NMR, 13C NMR and elemental analysis. A series of trifluoromethyl epoxy networks has been prepared with four curing agents: poly (propylene glycol) bis (2-aminopropy) ether (D230), 2-methylimidazole (2MI), 4, 4-methylene-dianiline (DDM) and phthalicacidanhydride (PA). All samples exhibited excellent thermal stabilities (the decomposition temperature of 5% weight loss (Td)) ranged from 335 to 362 °C in N2 and 291–355 °C in air). The 3F-PQE-DDM sample showed the highest Tg of all the samples. Moisture absorption of 3F-PQE-DDM and 3F-PQE-PA at 80 °C for 24 h was no more than 1 wt %. The cured fluorinated epoxy resins exhibited that the contact angles were more than 90°, which is the hydrophobic properties.
Co-reporter:Jing Wang, Chengji Zhao, Liyuan Zhang, Mingyu Li, Jing Ni, Shuang Wang, Wenjia Ma, Zhongguo Liu, Hui Na
International Journal of Hydrogen Energy 2012 Volume 37(Issue 17) pp:12586-12596
Publication Date(Web):September 2012
DOI:10.1016/j.ijhydene.2012.06.003
A highly sulfonated poly (ether ether ketone) with pendant amino groups (Am-SPEEK) has been synthesized. The resulting copolymer showed good solubility in common organic solvents. Then the pendant amino groups of the Am-SPEEK were utilized to react with two kinds of cross-linker, epoxy resin and dibromide, to yield various cross-linked membranes. After cross-linking, the membranes could not dissolve in common solvents, just became swollen. In generally, all the cross-linked membranes showed improved mechanical properties and high dimensional stabilities, whereas the uncross-linked membranes highly swollen or even dissolved in water at high temperature. The proton conductivity of the membranes increased with an increase in temperature. At 80 °C, all the cross-linked membranes showed high proton conductivity, in the range of 0.111–0.140 S cm−1. Especially, the TMBP cross-linked membrane showed a proton conductivity of 0.140 S cm−1, which was higher than that of Nafion 117 (0.125 S cm−1). The membranes with high proton conductivity, good oxidative stability, and improved methanol residence have been successfully developed. Furthermore, the influence of different main chain of the cross-linker on the performance of the cross-linked membranes was also investigated.Highlights► Water soluble Am-SPEEK with active sites was synthesizes successfully. ► Epoxy resin and dibromide with different structures were used as cross-linkers. ► After cross-linked, all the membranes showed improved performance. ► Flexible chain made a less dense cross-linking network than that of rigid chain. ► TMBP-cross-linked membrane with rigid main chain showed the best performance.
Co-reporter:Hongcheng Sun, Gang Zhang, Zhongguo Liu, Na Zhang, Liyuan Zhang, Wenjia Ma, Chengji Zhao, Duo Qi, Guibin Li, Hui Na
International Journal of Hydrogen Energy 2012 Volume 37(Issue 12) pp:9873-9881
Publication Date(Web):June 2012
DOI:10.1016/j.ijhydene.2012.03.115
Novel self-crosslinked alkaline electrolyte membranes with high hydroxide ion conductivity, excellent dimensional stability and extraordinary solvent resistance stability are synthesized successfully without using any catalyst or separate crosslinker. Monitored by 1H NMR analysis, the synthetic process of trimethyl poly (ether sulfone)-methylene quaternary ammonium hydroxide (TPQAOH) is found to be simple and efficient. The chemical and thermal stability of the synthetic SCL-TPQAOH-x membranes are better than other anion exchange membranes. At the same time, the hydroxide ion conductivity of SCL-TPQAOH-0.67 membrane reaches 33 mS cm−1 with an IEC value of 1.07 mmol g−1 at 80 °C, which complies with the requirements of alkaline fuel cells. This investigation also proves that self-crosslinking technology is a very simple and effective approach in improving the performance of alkaline electrolyte membranes.Highlights► We prepared a class of CH3- substituted PES with –CH2- group in the polymer backbone. ► Self-crosslinking membranes were obtained by simple heating method. ► The resulting membranes exhibited ultra-low swelling ratio and great stability. ► The membranes showed appropriate hydroxide ion conductivity with great durability.
Co-reporter:Jing Wang, Chengji Zhao, Mingyu Li, Liyuan Zhang, Jing Ni, Wenjia Ma, Hui Na
International Journal of Hydrogen Energy 2012 Volume 37(Issue 11) pp:9330-9339
Publication Date(Web):June 2012
DOI:10.1016/j.ijhydene.2012.03.035
Sulfonated poly(ether ether ketone)s with pendent amino groups (Am-SPEEKs) have been prepared for direct methanol fuel cells (DMFCs). With the goal of improving the dimensional stability and reducing the methanol permeability of membranes, Benzimidazole trimer is synthesized as a cross-linker. The cross-linking reaction is induced by heating at 120 °C for 6 h and then the effects of different contents of cross-linker on the properties of the cross-linking membranes are investigated in detail. Combining covalent cross-linking with ionic cross-linking, the cross-linking network structure causes significant enhancement in oxidative and mechanical property. Meanwhile, water uptake, swelling ratio and methanol permeability of the membranes substantially decrease with increasing the content of cross-linker. Although the conductivity of the membranes is lower than that of the pristine membrane, the relative selectivity is much higher. All the results indicate that the cross-linked membrane is potential candidate as membrane for applications in fuel cells.Highlights► Am-SPEEK with active sites for cross-linking was synthesized successfully. ► Carboxyl-terminated benzimidazole trimer was prepared as cross-linker. ► The cross-linked membranes showed high dimensional stability and fuel resistance. ► The cross-linked membranes showed relative high proton conductivity.
Co-reporter:Zhongguo Liu;Gang Zhang;Hongcheng Sun;Hao Jiang;Chengji Zhao;Dan Xu;Hongtao Li;Xingwu Sun
Polymer International 2012 Volume 61( Issue 4) pp:565-570
Publication Date(Web):
DOI:10.1002/pi.3205
Abstract
Tetramethylbisphenol F epoxy resin (TMBPFE) was successfully synthesized based on tetramethylbisphenol F (TMBPF) and epichlorohydrin with tetrabutylammonium bromide as the catalyst. The structure of TMBPFE was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance and elemental analysis. Then, a mixed system composed of TMBPFE and 4,4′-diglycidyl (3,3′,5,5′-tetramethylbiphenyl) epoxy (TMBP) was prepared by a melting method, i.e. without any solvent. Both the TMBPFE and the mixed system were cured using 4,4′-diaminodiphenyl methane (DDM) as the curing agent. The thermal properties of TMBPFE and the mixed system were studied using differential scanning calorimetry, dynamic mechanical analysis and thermogravimetric analysis (TGA). The results showed that the TMBP mixed in the TMBPFE matrix had little effect on the thermal properties of TMBPFE. However, the glass transition temperature improved markedly with increasing content of TMBP. Moreover, the TGA results showed that the degradation characteristics of TMBPFE resins did not seriously decrease when TMBP was incorporated into the TMBPFE matrix, although there are large steric hindrance biphenyl groups in TMBP. Both TMBPFE and the TMBPFE/TMBP system have potential applications in electrical and electronic fields. Copyright © 2011 Society of Chemical Industry
Co-reporter:Mingyu Li, Gang Zhang, Huiping Zuo, Miaomiao Han, Chengji Zhao, Hao Jiang, Zhongguo Liu, Liyuan Zhang, Hui Na
Journal of Membrane Science 2012 s 423–424() pp: 495-502
Publication Date(Web):
DOI:10.1016/j.memsci.2012.08.058
Co-reporter:Miaomiao Han, Gang Zhang, Zhongguo Liu, Shuang Wang, Mingyu Li, Jing Zhu, Hongtao Li, Yang Zhang, Christopher M. Lew and Hui Na
Journal of Materials Chemistry A 2011 vol. 21(Issue 7) pp:2187-2193
Publication Date(Web):20 Dec 2010
DOI:10.1039/C0JM02443K
Cross-linked polybenzimidazole membranes were obtained by heating at 160 °C, using 4,4′-diglycidyl(3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP) as the cross-linker. The cross-linking reaction temperature was determined by DSC and the successful completion of the cross-linking reaction was shown by FTIR and solubility tests. The cross-linked membranes showed high proton conductivity and strong mechanical properties, as well as low swelling after immersion in 85% phosphoric acid at 90 °C. For instance, the membrane with a cross-linker content weight percent of 20% (PBI-TMBP 20%) with a PA doping level of 4.1 exhibited a proton conductivity of 0.010 S cm−1 and a low swelling volume of 50%. Moreover, the cross-linked membranes showed excellent oxidative stability. The PBI-TMBP 20% cross-linked membrane tested in Fenton's reagent (3% H2O2 solution, 4 ppm Fe2+, 70 °C) kept its shape for more than 480 h and did not break. In particular, the proton conductivity of the PA-PBI-TMBP 20% membrane after Fenton's test (30% H2O2, 20 ppm Fe2+, 85 °C) remained at a high level of 0.009 S cm−1. This investigation proved that cross-linking is a very effective approach for improving the performance of proton exchange membranes.
Co-reporter:Gang Zhang, Hongtao Li, Wenjia Ma, Liyuan Zhang, Christopher M. Lew, Dan Xu, Miaomiao Han, Yang Zhang, Jing Wu and Hui Na
Journal of Materials Chemistry A 2011 vol. 21(Issue 14) pp:5511-5518
Publication Date(Web):24 Feb 2011
DOI:10.1039/C0JM04385K
With the goal of reducing water swelling and methanol permeability in sulfonated proton exchange membranes (PEM), bromomethylated poly(ether ether ketone) was synthesized and used as a macromolecular cross-linker. The cross-linking reaction was performed at 195 °C for 5 h and resulted in cross-linked membranes with high cross-linked density. Compared to the pristine membrane, the cross-linked membranes displayed greatly reduced water uptake and methanol permeability. Other properties of the cross-linked membranes, including proton conductivity, mechanical properties, and oxidative stability, were also investigated and compared with the pristine membrane. All the results indicated that the novel macromolecular cross-linker and the resulting cross-linked membranes are promising for fuel cell applications.
Co-reporter:Jing Ni, Chengji Zhao, Gang Zhang, Yang Zhang, Jing Wang, Wenjia Ma, Zhongguo Liu and Hui Na
Chemical Communications 2011 vol. 47(Issue 31) pp:8943-8945
Publication Date(Web):28 Jun 2011
DOI:10.1039/C1CC12430G
Novel self-crosslinked alkaline anion exchange membranes with high alkaline stability, excellent dimensional stability and extraordinary methanol resistance were synthesized successfully without using any catalyst or a separate crosslinker.
Co-reporter:Haidan Lin, Chengji Zhao, Yingnan Jiang, Wenjia Ma, Hui Na
Journal of Power Sources 2011 Volume 196(Issue 4) pp:1744-1749
Publication Date(Web):15 February 2011
DOI:10.1016/j.jpowsour.2010.10.003
In order to prepare a hybrid proton exchange membrane with low methanol permeability and high proton conductivity, two silane monomers, namely 3-glycidoxypropyl-trimethoxysilane (GPTMS) and 3-mercaptopropyl-trimethoxysilane (MPTMS) are first blended with a sulfonated poly(arylene ether ketone) (SPAEK). Then the blended membrane is heated to induce the grafting of GPTMS onto SPAEK. Finally, a hydrolysis-condensation is performed on the grafted membrane to induce cross-linking. The –SH groups of MPTMS are oxidized to sulfonic acid groups, which are attributed to enhance the proton conductivity of hybrid membranes. Fourier transform infrared spectroscopy is used to characterize and confirm the structures of SPAEK and these cross-linked hybrid membranes. The proton conductivity of a cross-linked hybrid membrane G50M50 reaches up to 0.20 S cm−1 at 80 °C, which is comparable to that of SPAEK and much higher than that of Nafion. Meanwhile, the methanol permeability is nearly three times lower than that of Nafion and two times lower than that of SPAEK. The ion-exchange capacity, water uptake, membrane swelling and thermal stability are also investigated to confirm their applicability in fuel cells.Research highlights▶ A cross-linked hybrid SPAEK membrane was obtained through a silane-crosslinking technique. ▶ The MPTMS was introduced into the system to decrease the diluting effect of cross-linker. ▶ The cross-linked hybrid membranes showed excellent proton conductivities. ▶ The methanol permeability and selectivity were significantly improved.
Co-reporter:Jing Zhu, Gang Zhang, Ke Shao, Chengji Zhao, Hongtao Li, Yang Zhang, Miaomiao Han, Haidan Lin, Mu Li, Hui Na
Journal of Power Sources 2011 Volume 196(Issue 14) pp:5803-5810
Publication Date(Web):15 July 2011
DOI:10.1016/j.jpowsour.2011.03.021
A series of novel hybrid membranes based on sulfonated poly(arylene ether ketone)s (SNPAEKs), polysiloxane (KH-560) and sulfonated curing agent (BDSA) has been prepared by sol–gel and cross-linking reaction for direct methanol fuel cells (DMFCs). All the hybrid membranes (SKB-xx) show high thermal properties and improved oxidative stability compared with the pristine SNPAEK membrane. The sulfonated cross-linked polysiloxanes networks in the hybrid membranes enhance the mechanical properties and reduce the swelling ratio. The swelling ratio of SKB-20 is 22%, which is much lower than that of the pristine SNPAEK (37%) at 80 °C. Meanwhile, SKB-xx membranes with greatly reduced methanol permeabilities show comparative proton conductivities to pristine SNPAEK membranes. Notably, the proton conductivities of SKB-5 and SKB-10 reach to 0.192 S cm−1 and 0.179 S cm−1 at 80 °C, respectively, which are even higher than the 0.175 S cm−1 of SNPAEK.Graphical abstractHighlights► A novel hybrid membrane is prepared for DMFC. ► Side-chain-type SNPAEK acts as matrix. ► KH-560 forms polysiloxane cross-linked structure. ► BDSA acts as both curing agent and proton conductor.
Co-reporter:Miaomiao Han, Gang Zhang, Mingyu Li, Shuang Wang, Zhongguo Liu, Hongtao Li, Yang Zhang, Dan Xu, Jing Wang, Jing Ni, Hui Na
Journal of Power Sources 2011 Volume 196(Issue 23) pp:9916-9923
Publication Date(Web):1 December 2011
DOI:10.1016/j.jpowsour.2011.08.049
A diamine-terminated polybenzimidazole oligomer (o-PBI) has been synthesized for introducing the benzimidazole groups (BI) into sulfonated poly(ether ether ketone) (SPEEK) membranes. SPEEK/o-PBI/4,4′-diglycidyl(3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP) composite membranes in situ polymerization has been prepared for the purpose of improving the performance of SPEEK with high ion-exchange capacities (IEC) for the usage in the direct methanol fuel cells (DMFCs). The composite membranes with three-dimensional network structure are obtained through a cross-linking reaction between PBI oligomer and TMBP and the acid–base interaction between sulfonic acid groups and benzimidazole groups. Resulting membranes show a significantly increasing of all of the properties, such as high proton conductivity (0.14 S cm−1 at 80 °C), low methanol permeability (2.38 × 10−8 cm2 s−1), low water uptake (25.66% at 80 °C) and swelling ratio (4.11% at 80 °C), strong thermal and oxidative stability, and mechanical properties. Higher selectivity has been found for the composite membranes in comparison with SPEEK. Therefore, the SPEEK/o-PBI/TMBP composite membranes show a good potential in DMFCs usages.An approach of introducing the benzimidazole groups (BI) into sulfonated poly(ether ether ketone) (SPEEK) membranes has been proposed to prepare SPEEK/o-PBI/4,4′-diglycidyl(3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP) composite membranes via in situ polymerization. The composite membranes with three-dimensional network structure are obtained through a cross-linking reaction between the o-PBI and TMBP and the acid–base interaction between sulfonic acid groups and benzimidazole groups. The resulting composite membranes show a significantly increasing of all of the properties, such as high proton conductivity, low methanol permeability, low water uptake and swelling ratio, strong thermal and oxidative stability, and mechanical properties.
Co-reporter:Wenjia Ma, Chengji Zhao, Haidan Lin, Gang Zhang, Jing Ni, Jing Wang, Shuang Wang, Hui Na
Journal of Power Sources 2011 Volume 196(Issue 22) pp:9331-9338
Publication Date(Web):15 November 2011
DOI:10.1016/j.jpowsour.2011.08.003
Poly(arylene ether ketone) containing pendant quaternary ammonium groups (QPAEKs) are anion-conducting polymers synthesized from benzylmethyl-containing poly(arylene ether ketone)s (PAEK-TM). Then QPAEK membranes doped with different concentrations of H3PO4 are prepared and evaluated as high temperature proton exchange membranes. The H3PO4 doping ability of quaternary ammonium groups in QPAEK system is found to be stronger than that of imidazole groups in polybenzimidazole system. The doping level of resulting QPAEK/H3PO4 composite membranes increases with both the concentration level of soaking H3PO4 solution and the ion exchange capacity. For example, the highest doping level of composite membranes is 28.6, which is derived from QPAEK-5 with an ion exchange capacity of 2.02 mmol g−1 saturated with concentrated phosphoric acid. A strong correlation between the doping level and the proton conductivity is observed for all the membranes. Besides their low cost, novel high temperature proton exchange membranes, QPAEK/H3PO4, show really high proton conductivity and possess excellent thermal and mechanical stability, suggesting a bright future for applications in high temperature fuel cell.Highlights► Poly(arylene ether ketone)s with quaternary ammonium groups (QPAEKs) are prepared. ► QPAEK membranes are doped with H3PO4 as high temperature proton exchange membranes. ► QPAEK membranes show strong interaction with H3PO4. ► The doped membranes show great proton conductivity and excellent mechanical stability. ► The proton conductivity increases with quaternary ammonium group content.
Co-reporter:Jing Wang, Chengji Zhao, Haidan Lin, Gang Zhang, Yang Zhang, Jing Ni, Wenjia Ma, Hui Na
Journal of Power Sources 2011 Volume 196(Issue 13) pp:5432-5437
Publication Date(Web):1 July 2011
DOI:10.1016/j.jpowsour.2011.02.038
Sulfonated poly (arylene ether ketone) bearing carboxyl groups (SPAEK-C) membranes have been prepared as proton exchange membranes for applications in direct methanol fuel cells (DMFCs). Multilayered polyelectrolyte complexes (PECs) which applied as methanol barrier agents are prepared by alternate deposition of the oppositely charged amino-containing poly (ether ether ketone) (Am-PEEK) and the highly sulfonated SPAEK-C via a layer-by-layer method. The cross-linked PEC (c-PEC) is derived from a simple heat-induced cross-linking reaction between Am-PEEK and SPAEK-C. Fourier transform infrared spectroscopy confirms that Am-PEEK and SPAEK-C are assembled successfully in the multilayers. The morphology of the membranes is studied by scanning electron microscopy, which shows the presence of the thin layers coated on the SPAEK-C membrane. After PEC and c-PEC modification, the methanol permeability decreases obviously when compared to that of the pristine membrane. Notably, improved proton conductivities are obtained for the PEC modified membranes in comparison with the pristine membrane. Moreover, the selectivity of these modified membranes is one order of magnitude higher than that of Nafion 117. The thermal stability, oxidative stability, water uptake and swelling of PEC and c-PEC modified membranes are also investigated.Research highlights► Am-PEEK, as the active polycation was synthesized, and the SPAEK-C was used as the polyanion. ► Lower methanol permeability membranes with higher proton conductivity were obtained via layer-by-layer method. ► The cross-linked network structure greatly improved the oxidative stability as compared to SPAEK-C membrane.
Co-reporter:Shuang Wang, Gang Zhang, Miaomiao Han, Hongtao Li, Yang Zhang, Jing Ni, Wenjia Ma, Mingyu Li, Jing Wang, Zhongguo Liu, Liyuan Zhang, Hui Na
International Journal of Hydrogen Energy 2011 Volume 36(Issue 14) pp:8412-8421
Publication Date(Web):July 2011
DOI:10.1016/j.ijhydene.2011.03.147
An approach has been proposed to prepare the reinforced phosphoric acid (PA) doped cross-linked polybenzimidazole membranes for high temperature proton exchange membrane fuel cells (HT-PEMFCs), using 1,3-bis(2,3-epoxypropoxy)-2,2-dimethylpropane (NGDE) as the cross-linker. FT-IR measurement and solubility test showed the successful completion of the crosslinking reaction. The resulting cross-linked membranes exhibited improved mechanical strength, making it possible to obtain higher phosphoric acid doping levels and therefore relatively high proton conductivity. Moreover, the oxidative stability of the cross-linked membranes was significantly enhanced. For instance, in Fenton’s reagent (3% H2O2 solution, 4 ppm Fe2+, 70 °C), the cross-linked PBI-NGDE-20% membrane did not break into pieces and kept its shape for more than 480 h and its remaining weight percent was approximately 65%. In addition, the thermal stability was sufficient enough within the operation temperature of PBI-based fuel cells. The cross-linked PBI-NGDE-X% (X is the weight percent of epoxy resin in the cross-linked membranes) membranes displayed relatively high proton conductivity under anhydrous conditions. For instance, PBI-NGDE-5% membrane with acid uptake of 193% exhibited a proton conductivity of 0.017 S cm−1 at 200 °C. All the results indicated that it may be a suitable candidate for applications in HT-PEMFCs.An approach has been proposed to prepare the reinforced phosphoric acid (PA) doped cross-linked polybenzimidazole membranes for high temperature proton exchange membrane fuel cells (HT-PEMFCs), using 1,3-bis(2,3-epoxypropoxy)-2,2-dimethylpropane (NGDE) as the cross-linker. The resulting cross-linked membranes exhibited improved mechanical strength, making it possible to obtain higher phosphoric acid doping levels and therefore relatively high proton conductivity. Moreover, the oxidative stability of cross-linked membranes was significantly enhanced.Highlights► We demonstrated a strategy to synthesize epoxy-based cross-linked polybenzimidazole. ► The cross-linked PBI-NGDE-X% membranes were prepared by easy facile heating method. ► The oxidative stability was improved significantly. ► The membranes could achieve relatively high proton conductivity without sacrificing chemical stability.
Co-reporter:Miaomiao Han, Gang Zhang, Mingyu Li, Shuang Wang, Yang Zhang, Hongtao Li, Christopher M. Lew, Hui Na
International Journal of Hydrogen Energy 2011 Volume 36(Issue 3) pp:2197-2206
Publication Date(Web):February 2011
DOI:10.1016/j.ijhydene.2010.11.065
A novel benzimidazole trimer (alkyl-BI) was synthesized using 3,3′-diaminobenzidine and succinic acid as monomers, and then a series of cross-linked membranes (c-SPEEK-Xs) were prepared by a heating method using the alkyl-BI as the cross-linker. We systematically studied the water uptake and swelling ratio, thermal and chemical stability, mechanical properties, proton conductivity, and methanol permeability of the cross-linked membranes as a function of different loading ratios of the alkyl-BI trimer. All of the properties of the cross-linked membranes were significantly improved over membranes consisting of unmodified SPEEK. In particular, the performance of the c-SPEEK-Xs membranes was compared to that of a cross-linked membrane, c-SPEEK-BI7, which was prepared by using rigid-BI as the cross-linker. The latter cross-linker was synthesized by using 3,3′-diaminobenzidine and isophthalic acid as monomers in order to investigate how cross-linkers with different structures affect the morphology and properties of the membranes. Transmission electron microscopy (TEM) analysis showed that c-SPEEK-BI7 and the c-SPEEK-6.5% possess different hydrophilic/hydrophobic two-phase separation morphologies, which have dramatic effects on the proton conductivity and methanol permeability.To improve the performance of SPEEK, one type of cross-linked SPEEK membrane by benzimidazole trimer was prepared for DMFC application in this paper.
Co-reporter:Na Zhang, Gang Zhang, Dan Xu, Chengji Zhao, Wenjia Ma, Hongtao Li, Yang Zhang, Shuai Xu, Hao Jiang, Hongcheng Sun, Hui Na
International Journal of Hydrogen Energy 2011 Volume 36(Issue 17) pp:11025-11033
Publication Date(Web):August 2011
DOI:10.1016/j.ijhydene.2011.05.158
A series of cross-linked membranes based on SPEEK/Nafion have been prepared to improve methanol resistance and dimension stability of SPEEK membrane for the usage in the direct methanol fuel cells (DMFCs). Sulfonated diamine monomer is synthesized and used as cross-linker to improve the dispersion of Nafion in the composite membranes and decrease the negative effect of cross-linking on proton conductivity of membranes. FT-IR analysis shows that the cross-linking reaction is performed successfully. The effects of different contents of Nafion on the properties of cross-linked membranes are investigated in detail. All the cross-linked membranes show lower methanol permeability and better dimensional stability compared with the pristine SPEEK membrane. SPEEK-N30 with the 30 wt % Nafion shows a methanol permeability of 0.73 × 10−6 cm2 s−1 and a water uptake of 24.4% at 25 °C, which are lower than those of the pristine membrane. Meanwhile, the proton conductivity of SPEEK-N30 still remains at 0.041 S cm−1 at 25 °C, which is comparable to that of the pristine SPEEK membrane. All the results indicate that these cross-linked membranes based on SPEEK/Nafion show good prospect for the use as proton exchange membranes.Highlights► The incompatibility behavior between SPEEK and Nafion has been resolved. ► The cross-linked membranes exhibit improved dimensional stability. ► The methanol permeability of cross-linked membranes decrease. ► The cross-linked membranes show improved relative selectivity.
Co-reporter:Chengji Zhao;Haidan Lin;Xianfeng Li
Polymers for Advanced Technologies 2011 Volume 22( Issue 12) pp:2173-2181
Publication Date(Web):
DOI:10.1002/pat.1741
Abstract
A series of block sulfonated poly(arylene ether ketone) (SPAEK) copolymers with different block lengths and ionic contents were synthesized by a two-stage process. The morphology of these block SPAEK copolymers was investigated by various methods, such as differential scanning calorimetry (DSC), transmission electron microscope (TEM), and small angle X-ray scattering (SAXS). Dark colored ionic domains of hundreds of nanometers spreading as a cloud-like belt were observed in TEM images. The sizes of the ionic domains as a function of block copolymer composition were determined from SAXS curves. The results for the evolution of ionic domains revealed that the block copolymers exhibited more clearly phase-separated microstructure with increasing ionic contents and hydrophobic sequence lengths. Proton conductivity is closely related to the microstructure, especially the presence of large interconnected ionic domains or ionic channels. Block SPAEK membranes have interconnected ionic clusters to provide continuous hydrophilic channels, resulting in higher proton conductivity. Copyright © 2010 John Wiley & Sons, Ltd.
Co-reporter:Zhongguo Liu;Gang Zhang;Kuifeng Tu;Sen Zhao;Miaomiao Han;Jing Ni;Wenjia Ma
Polymer International 2011 Volume 60( Issue 10) pp:1556-1562
Publication Date(Web):
DOI:10.1002/pi.3119
Abstract
A series of novel composites based on different ratios of epoxidised cresol novolac (ECN) and 4,4′-diglycidyl(3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP) have been prepared with the curing agent 4,4′-methylenediamine (DDM) and 4,4′-diaminodiphenylsulfone (DDS), respectively. The investigation of cure kinetics was performed by differential scanning calorimetry using an isoconversional method. The high thermal stabilities of the cured samples were also studied by thermogravimetric analysis. In addition, no phase separation was observed for cured ECN/DDM and ECN/DDS blending with different amounts of TMBP by dynamic mechanical analysis and scanning electron microscopy. Moreover, the cured systems also exhibited excellent impact properties and low moisture absorption. All the results indicate that the ECN/TMBP/DDM and ECN/TMBP/DDS systems are promising materials in electronic packaging. Copyright © 2011 Society of Chemical Industry
Co-reporter:Wenjia Ma;Chengji Zhao;Haidan Lin;Gang Zhang
Journal of Applied Polymer Science 2011 Volume 120( Issue 6) pp:3477-3483
Publication Date(Web):
DOI:10.1002/app.33483
Abstract
A series of bromomethylated poly(arylene ether ketone)s (PAEKs) with different contents of bromine tethered to the benzyl groups were successfully synthesized and characterized in this work. For this purpose, poly(arylene ether ketone) with 3,3′,5,5′-tetramethyl-4,4′-dihydroxybipheny moiety (PAEK-TM) was prepared by the aromatic nucleophilic polycondensation, and then the PAEK-TM has benzylic methyl groups that were converted to bromomethyl groups by a radical reaction using N-bromosuccinimide. Then, the bromomethylbenzyl groups in the membrane was converted to quaternary ammonium moieties in TMPAEK-NOH. 1H-NMR measurements were used to characterize and confirm the structures of the resulting PAEK-x-BrTM and TMPAEK-NBr derivatives (x refers to the molar percentage of bromine introduced per repeating units). TGA analysis showed that PAEK-x-BrTM exhibited a very low-decomposition temperature at about 200°C corresponding to the CBr bond cleavage. The hydroxide conductivity of TMPAEK-NOH membrane was 8 mS cm−1 at room temperature, while the water uptake of TMPAEK-NOH membrane was 22.3% at 20°C and 32.6% at 60°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Dan Xu, Gang Zhang, Na Zhang, Hongtao Li, Yang Zhang, Ke Shao, Miaomiao Han, Christopher M. Lew and Hui Na
Journal of Materials Chemistry A 2010 vol. 20(Issue 41) pp:9239-9245
Publication Date(Web):21 Sep 2010
DOI:10.1039/C0JM02167A
A series of SPEEK/HPW/Ppy-n composite membranes with a sandwich structure were successfully prepared by surface modification with polypyrrole (Ppy) in order to stabilize phosphotungstic acid (HPW) in poly(ether ether ketone)s (SPEEKs) and reduce the methanol crossover. Ppy coatings with a large number of secondary ammonium groups (NH2+) interact with anions of HPW to decrease HPW leaching from the membrane. In addition, the hydrophobic Ppy layers allow for little methanol transport, which leads to a significant decline in methanol crossover with reasonable levels of proton conductivity. The properties of the membranes were investigated in detail by UV, SEM, ac impedance, and TGA. As observed, Ppy-modified membranes were better at immobilizing HPW and exhibited higher selectivities than previously reported SPEEK/HPW composite membranes. All the results indicate that the SPEEK/HPW/Ppy-n composite membranes are excellent candidates for direct methanol fuel cells.
Co-reporter:Jing Ni, Gang Zhang, Chengji Zhao, Hongtao Li, Tiezhu Fu, Ke Shao, Miaomiao Han, Jing Wang, Wenjia Ma and Hui Na
Journal of Materials Chemistry A 2010 vol. 20(Issue 30) pp:6352-6358
Publication Date(Web):02 Jun 2010
DOI:10.1039/C0JM00444H
Proton exchange membranes with high dimensional stabilities and low water uptakes were constructed by incorporating phosphotungstic acid (PWA) into a cross-linked network composed of a crosslinkable sulfonated poly(ether ether ketone) containing dipropenyl groups (SDPEEK) and γ-methacryloxypropyltrimethoxysilane (KH570). The chemical structures of the hybrid membranes were confirmed by FT-IR spectroscopy and scanning electron microscopy (SEM). The results indicated that PWA particles were well dispersed in these membranes. The influences of the dispersed PWA on the properties of membranes such as thermal stability, water uptake, swelling ratio, proton conductivity, methanol permeability and mechanical property were researched. The addition of KH570-5/PWA in the hybrid membranes contributed to the improvement of the dimensional stabilities. And the hybrid membranes with 10–40wt% PWA showed higher proton conductivities than Nafion 117 at 80 °C, while the methanol permeabilities of these membranes were much lower than that of Nafion 117. The membranes also exhibited excellent mechanical properties. These results imply that the SDPEEK/KH570-5/PWA-x membranes are promising materials in the direct methanol fuel cells (DMFC) applications.
Co-reporter:Miaomiao Han, Gang Zhang, Ke Shao, Hongtao Li, Yang Zhang, Mingyu Li, Shuang Wang and Hui Na
Journal of Materials Chemistry A 2010 vol. 20(Issue 16) pp:3246-3252
Publication Date(Web):05 Mar 2010
DOI:10.1039/B926354C
A carboxyl-terminated benzimidazole trimer was synthesized as a crosslinker by controlling the ratio of 3,3′-diaminobenzidine and isophthalic acid. Composite membranes were obtained by mixing the benzimidazole trimer and sulfonated poly(ether ether ketone) (SPEEK) together. Cross-linked membranes were obtained by heating the composite membranes at 160 °C. All of the properties of the cross-linked membranes were significantly increased, including proton conductivity, methanol permeability and water uptake due to the more compact structure compared to the non-cross-linked membranes. The cross-linked SPEEK-BI7 and cross-linked SPEEK-BI11 had excellent proton conductivities (0.22 and 0.19 S cm−1) at 80 °C, which were higher than that of Nafion 117 (0.125 S cm−1). Transmission electron microscopy (TEM) analysis revealed a clear microphase separated structure of cross-linked membranes. Other properties, such as thermal and mechanical stability, required for use as a proton exchange membrane (PEM) have been investigated. The cross-linked membranes showed improved properties over membranes without crosslinking.
Co-reporter:Jing Wang, Chengji Zhao, Gang Zhang, Yang Zhang, Jing Ni, Wenjia Ma, Hui Na
Journal of Membrane Science 2010 Volume 363(1–2) pp:112-119
Publication Date(Web):1 November 2010
DOI:10.1016/j.memsci.2010.07.022
In this paper, a sulfonated poly(arylene ether ketone) bearing carboxylic acid groups (C-SPEEK) was first synthesized. Then a new series of covalent-ionically cross-linked membranes using a poly(ether ether ketone) bearing amino groups (Am-PEEK) as a cross-linker were prepared for direct methanol fuel cell applications. Lower water swelling and lower methanol permeability membranes with higher mechanical strength were obtained via this covalent-ionically cross-linking method. The cross-linked network structure greatly improved the thermal and oxidative stability as compared to C-SPEEK membrane. The proton conductivity of C-SPEEK/Am-PEEKs was lower than that of non-cross-linked membrane, but its selectivity was higher. The properties of the cross-linked membranes in particular C-SPEEK/Am-PEEK-10 were investigated to confirm their potential applicability in fuel cells.Research highlights▶ C-SPEEK, as the hydrophilic part, and Am-PEEK, as a cross-linkable moiety were synthesized. ▶ Lower water swelling and lower methanol permeability membranes with higher mechanical strength were obtained via covalent-ionically cross-linking method. ▶ The cross-linked network structure greatly improved the thermal and oxidative stability as compared to C-SPEEK membrane. ▶ C-SPEEK/Am-PEEK-10 showed the best membrane performances among the cross-linked membranes.
Co-reporter:Yang Zhang, Ying Wan, Gang Zhang, Ke Shao, Chengji Zhao, Hongtao Li, Hui Na
Journal of Membrane Science 2010 Volume 348(1–2) pp:353-359
Publication Date(Web):15 February 2010
DOI:10.1016/j.memsci.2009.11.025
A series of cross-linkable sulfonated poly(arylene ether ketone)s bearing carboxylic acid groups (C-SPAEKs) have been prepared for direct methanol fuel cells (DMFCs). The chemical structure of the cross-linkable copolymers was analyzed by 1H NMR and 13C NMR spectra. Cross-linked membranes were obtained by thermal curing cross-linkable copolymers. The cross-linked network structure caused significant enhancement in the mechanical properties and large reduction in water uptake (WU), swelling ratio and methanol permeability of the membranes. The water uptake and methanol permeability of C-SPAEK-50 membrane was 506.9% (80 °C) and 14.83 × 10−7 cm2/s, but after cross-linking they reduced to 75.2% and 1.74 × 10−7 cm2/s, while maintaining proton conductivity of 0.197 S/cm, which was higher than 0.146 S/cm of Nafion 117.
Co-reporter:Chengji Zhao, Haidan Lin, Miaomiao Han, Hui Na
Journal of Membrane Science 2010 Volume 353(1–2) pp:10-16
Publication Date(Web):1 May 2010
DOI:10.1016/j.memsci.2010.01.066
To prepare a novel covalently cross-linked proton exchange membrane with high proton conductivity, sulfonated poly(arylene ether ketone)s bearing carboxylic acid groups (SPAEK-C) and o-diamino functional polybenzimidazole oligomers (PBI) were consequently synthesized. Then the SPAEK-C/PBI blend membranes were dried at 110 °C for 3 h to induce cross-links between amino groups of PBI oligomer and carboxylic acid groups of SPAEK-C. 1H NMR measurements and Fourier transform infrared spectroscopy were used to characterize and confirm the structures of SPAEK-C, PBI oligomers and the cross-linked membranes. The cross-linked membranes were immersed in various concentrations of phosphoric acid solution to enhance proton conductivity. These H3PO4 doped SPAEK-C/PBI membranes displayed comparable or even higher proton conductivity than that of Nafion 117, especially under low humidity conditions. Moreover, the water uptake, acid uptake, mechanical and thermal stability were also investigated in detail.
Co-reporter:Haidan Lin, Chengji Zhao, Wenjia Ma, Ke Shao, Hongtao Li, Yang Zhang, Hui Na
Journal of Power Sources 2010 Volume 195(Issue 3) pp:762-768
Publication Date(Web):1 February 2010
DOI:10.1016/j.jpowsour.2009.08.020
Co-reporter:Hongtao Li, Gang Zhang, Jing Wu, Chengji Zhao, Yang Zhang, Ke Shao, Miaomiao Han, Haidan Lin, Jing Zhu, Hui Na
Journal of Power Sources 2010 Volume 195(Issue 19) pp:6443-6449
Publication Date(Web):1 October 2010
DOI:10.1016/j.jpowsour.2010.03.062
A novel poly(ether ether ketone) (PEEK) containing pendant carboxyl groups has been synthesized by a nucleophilic polycondensation reaction. Sulfonated polymers (SPEEKs) with different ion exchange capacity are then obtained by post-sulfonation process. The structures of PEEK and SPEEKs are characterized by both FT-IR and 1H NMR. The properties of SPEEKs as candidates for proton exchange membranes are studied. The cross-linking reaction is performed at 140 °C using poly(vinyl alcohol) (PVA) as the cross-linker. In comparison with the non-cross-linked membranes, some properties of the cross-linked membranes are significantly improved, such as water uptake, methanol resistance, mechanical and oxidative stabilities, while the proton conductivity decreases. The effect of PVA content on proton conductivity, water uptake, swelling ratio, and methanol permeability is also investigated. Among all the membranes, SPEEK-C-8 shows the highest selectivity of 50.5 × 104 S s cm−3, which indicates that it is a suitable candidate for applications in direct methanol fuel cells.
Co-reporter:Haidan Lin, Chengji Zhao, Hui Na
Journal of Power Sources 2010 Volume 195(Issue 11) pp:3380-3385
Publication Date(Web):1 June 2010
DOI:10.1016/j.jpowsour.2009.12.044
In this study, a new type of cross-linked composite membrane is prepared and considered for its potential applications in direct methanol fuel cell. Nafion and sulfonated poly(arylene ether ketone) bearing carboxylic acid groups (SPAEK-C) are blended and subsequently cross-linked by a Friedel–Craft reaction using the carboxylic acid groups in the SPAEK-C to achieve lower methanol permeability. The perfluoroalkyl sulfonic acid groups of Nafion act as a benign solid catalyst, which assist the cross-linking of SPAEK-C. The physical and chemical characterizations of the cross-linked composite membranes are performed by varying the contents of SPAEK-C. The c-Nafion-15% membrane exhibits appropriate water uptake (10.49–25.22%), low methanol permeability (2.57 × 10−7 cm2 s−1), and high proton conductivity (0.179 S cm−1 at 80 °C). DSC and FTIR analyze suggest the cross-linking reaction. These results show that the self-cross-linking of SPAEK-C in the Nafion membrane can effectively reduce methanol permeability while maintaining high proton conductivity.
Co-reporter:Hongtao Li, Gang Zhang, Jing Wu, Chengji Zhao, Qiong Jia, Christopher M. Lew, Liyuan Zhang, Yang Zhang, Miaomiao Han, Jing Zhu, Ke Shao, Jing Ni, Hui Na
Journal of Power Sources 2010 Volume 195(Issue 24) pp:8061-8066
Publication Date(Web):15 December 2010
DOI:10.1016/j.jpowsour.2010.06.106
Sulfonated poly(ether ether ketone) containing hydroxyl groups (SPEEK-OH) has been prepared for use as a proton exchange membrane (PEM) by reducing the carbonyl groups on the main chain of the polymers. With the goal of reducing water uptake and methanol permeability, a facile thermal-cross-linking process is used to obtain the cross-linked membranes. The properties of the cross-linked membranes with different cross-linked density are measured and compared with the pristine membrane. Notably, SPEEK-4 with the highest cross-linked density shows a water uptake of 39% and a methanol permeability of 2.52 × 10−7 cm2 s−1, which are much lower than those of the pristine membrane (63.2% and 5.37 × 10−7 cm2 s−1, respectively). These results indicate that this simple approach is very effective to prepare cross-linked proton exchange membranes for reducing water uptake and methanol permeability.
Co-reporter:Hongtao Li, Gang Zhang, Wenjia Ma, Chengji Zhao, Yang Zhang, Miaomiao Han, Jing Zhu, Zhongguo Liu, Jing Wu, Hui Na
International Journal of Hydrogen Energy 2010 Volume 35(Issue 20) pp:11172-11179
Publication Date(Web):October 2010
DOI:10.1016/j.ijhydene.2010.07.091
Poly(ether ether ketone) (PEEK) and sulfonated poly(ether ether ketone) (SPEEK, IEC = 2.07 mequiv.g−1) have been synthesized via nucleophilic aromatic substitution reaction. Bromomethylated poly(ether ether ketone) (PEEK-Br) is then prepared and reacted with 2-benzimidazolethiol to obtain the benzimidazole grafted poly(ether ether ketone) (PEEK-BI). The structures of PEEK-Br and PEEK-BI are characterized by 1H NMR spectra. Composite membranes based on SPEEK and PEEK-BI are prepared and their properties used for fuel cells are studied in detail. The results show that the composite membranes exhibit greatly improved mechanical properties as well as reduced water uptake and methanol permeability compared with the pristine SPEEK membrane. The increased oxidative stability and selectivity indicate that the composite membranes are promising to be used as proton exchange membranes.
Co-reporter:Chengji Zhao, Haidan Lin, Qiang Zhang, Hui Na
International Journal of Hydrogen Energy 2010 Volume 35(Issue 19) pp:10482-10488
Publication Date(Web):October 2010
DOI:10.1016/j.ijhydene.2010.07.157
Sulfonated poly(arylene ether ketone) bearing carboxyl groups (SPAEK-C) membranes were first modified by alternating deposition of oppositely charged polyaniline (PANI) and phosphotungstic acid (PWA) via the layer-by-layer method in order to prevent the crossover of methanol in a direct methanol fuel cell. The methanol permeability of SPAEK-C–(PANI/PWA)5 is 2 orders of magnitude less than those of Nafion 117 and pristine SPAEK-C. Furthermore, the modified membrane shows a proton conductivity of 0.093 Scm−1 at 25 °C and 0.24 Scm−1 at 80 °C, which are superior to those of Nafion 117 and pristine SPAEK-C. Fourier transform infrared spectroscopy confirms that PANI and PWA are assembled in the multilayers. The SEM images show the presence of thin PANI/PWA layers coated on the SPAEK-C membrane. Thermal stability, water uptake, water swelling, proton and electron conductivity at different temperature of the SPAEK-C and SPAEK-C-(PANI/PWA)n membranes are also investigated.
Co-reporter:Yang Zhang, Xu Fei, Gang Zhang, Hongtao Li, Ke Shao, Jing Zhu, Chengji Zhao, Zhongguo Liu, Miaomiao Han, Hui Na
International Journal of Hydrogen Energy 2010 Volume 35(Issue 12) pp:6409-6417
Publication Date(Web):June 2010
DOI:10.1016/j.ijhydene.2010.03.116
Sulfonated poly(arylene ether ketone) bearing pendant carboxylic acid group (C-SPAEK) had been prepared for direct methanol fuel cell applications, and subsequently cross-linked by a thermal curing reaction using hexafluoro-bisphenol-A novolac epoxy resin (HFANER) as a cross-linker. The cross-linked network structure caused significant enhancement in the mechanical properties and oxidative stability. Meanwhile, water uptake, swelling ratio and methanol permeability substantially decreased with increasing the content of cross-linker. Notably, the water uptake of C-SPAEK was 506.9% at 80 °C, but after cross-linking, Cr-SPAEK-17 exhibited a water uptake of 32.3%. Meanwhile, a 12.1% of swelling ratio was obtained which was lower than that of Nafion 117 (17.2%). Although the proton conductivities of the cross-linked membranes were lower than that of the pristine membrane, the higher selectivity defined as the proton conductivity to methanol permeability was obtained for the cross-linked membranes.
Co-reporter:Chengji Zhao, Haidan Lin, Hui Na
International Journal of Hydrogen Energy 2010 Volume 35(Issue 5) pp:2176-2182
Publication Date(Web):March 2010
DOI:10.1016/j.ijhydene.2009.12.149
To prepare a cross-linked proton exchange membrane with low methanol permeability and high proton conductivity, poly (vinyl alcohol) is first blended with sulfonated poly (arylene ether ketone) bearing carboxylic acid groups (SPAEK-C) and then heated to induce a cross-linking reaction between the carboxyl groups in SPAEK-C and the hydroxyl groups in PVA. Fourier transform infrared spectroscopy is used to characterize and confirm the structure of SPAEK-C and the cross-linked membranes. The proton conductivity of the cross-linked membrane with 15% PVA in weight reaches up to 0.18 S cm−1 at 80 °C (100% relative humidity), which is higher than that of Nafion membrane, while the methanol permeability is nearly five times lower than Nafion. The ion-exchange capacity, water uptake and thermal stability are investigated to confirm their applicability in fuel cells.
Co-reporter:Gang Zhang;Tiezhu Fu;Jing Wu;Xianfeng Li
Journal of Applied Polymer Science 2010 Volume 116( Issue 3) pp:1515-1523
Publication Date(Web):
DOI:10.1002/app.31712
Abstract
A novel series of sulfonated poly(ether ether ketone ketone)s (SPEEKKs) were prepared by aromatic nucleophilic polycondensation with different ratios of 1,3-bis(3-sodium sulfonate-4-fluorobenzoyl)benzene to 1,3-bis(4-fluorobenzoyl)benzene. 1H-NMR spectroscopy was used to confirm the degrees of sulfonation (DS) of the polymers. Thermal stabilities of the SPEEKKs in acid form were characterized by thermogravimetric analysis (TGA), which showed that SPEEKKs were excellently thermally stable at high temperatures. SPEEKK polymers can be easily cast into tough membranes. Both of proton conductivity and methanol diffusion coefficient have been tested in this article. Other properties of the SPEEKK membranes were investigated in detail. The results show that the SPEEKK membranes are promising in proton exchange membrane fuel cells (PEMFCs) application. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Yang Zhang;Gang Zhang;Ying Wan;Chengji Zhao;Ke Shao;Hongtao Li;Miaomiao Han;Jing Zhu;Shuai Xu;Zhongguo Liu
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 24) pp:5824-5832
Publication Date(Web):
DOI:10.1002/pola.24390
Abstract
A bisphenol monomer (2,5-dimethoxy)phenylhydroquinone was prepared and further polymerized to obtain poly(arylene ether ketone) copolymers containing methoxy groups. After demethylation and sulfobutylation, a series of novel poly(arylene ether ketone)s bearing pendant sulfonic acid group (SPAEKs) with different sulfonation content were obtained. The chemical structures of all the copolymers were analyzed by 1H NMR and 13C NMR spectra. Flexible and tough membranes with reasonably good mechanical properties were prepared. The resulting side-chain-type SPAEK membranes showed good dimensional stability, and their water uptake and swelling ratio were lower than those of conventional main-chain-type SPAEK membranes with similar ion exchange capacity. Proton conductivities of these side-chain-type sulfonated copolymers were higher than 0.01 S/cm and increased gradually with increasing temperature. Their methanol permeability values were in the range of 1.97 × 10−7–5.81 × 10−7 cm2/s, which were much lower than that of Nafion 117. A combination of suitable proton conductivities, low water uptake, low swelling ratio, and high methanol resistance for these side-chain-type SPAEK films indicated that they may be good candidate material for proton exchange membrane in fuel cell applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Co-reporter:Jing Zhu, Ke Shao, Gang Zhang, Chengji Zhao, Yang Zhang, Hongtao Li, Miaomiao Han, Haidan Lin, Dan Xu, Hubei Yu, Hui Na
Polymer 2010 Volume 51(Issue 14) pp:3047-3053
Publication Date(Web):24 June 2010
DOI:10.1016/j.polymer.2010.05.009
A series of novel side-chain-type sulfonated hydroxynaphthalene poly(aryl ether ketone)s (SHNPAEKs) containing hydroxyl groups was synthesized by post grafted method and the sulfonated degree (Ds) of the polymers could be well controlled. The resulting polymers were characterized by 1H NMR, FT-IR and thermogravimetric analysis (TGA). Meanwhile, the membrane properties for fuel cell applications such as water uptake, proton conductivity and methanol transport have been studied. The influence of pendent structure and inter-/intramolecular H-bonded to the properties of SHNPAEKs has been investigated. The proton conductivities of SHNPAEK membranes showed a range of 0.020–0.197 S/cm and the highest conductivity of 0.197 S/cm was obtained for SHNPAEK-90 (IEC = 2.08 meq./g) at 80 °C. The methanol permeability of SHNPAEK membranes was in the range from 2.65 × 10−7 to 11.9 × 10−7 cm2/s, which was much lower than that of Nafion 117.
Co-reporter:Haidan Lin, Chengji Zhao, Wenjia Ma, Hongtao Li, Hui Na
Journal of Membrane Science 2009 Volume 345(1–2) pp:242-248
Publication Date(Web):1 December 2009
DOI:10.1016/j.memsci.2009.09.005
Multilayered polyelectrolyte complexes (PECs) modified proton exchange membranes are successfully prepared from alternating deposition of oppositely charged polyelectrolyte chitosan (CS) and sulfonated poly (aryl ether ketone) bearing carboxyl groups (SPAEK-C) on the surface of Nafion®117 via the layer-by-layer (LBL) method. The cross-linked PEC-coated Nafion® membranes (c-PEC-coated Nafion® membranes) are prepared from heat-induced cross-linking between CS and SPAEK-C via formation of amide bonds. Fourier transform infrared spectroscopy (FT-IR) verifies that cross-linking between ammonium groups of CS and carboxyl groups of SPAEK-C occurs by the formation of amide bonds. The morphology of the membranes is studied in detail by SEM. The c-PEC-coated Nafion® membranes exhibit low water uptake (23.5%, 80 °C), water swelling (14.0%, 80 °C) and methanol permeability (2.7 × 10−7 cm2 s−1). Proton conductivity of the c-PEC-coated Nafion® membranes increase at elevated temperature, reaching the value of 0.131 S cm−1 at 80 °C. These results show that cross-linking of layered CS/SPAEK-C films can effectively reduce water uptake, water swelling and methanol permeability while improve the dimensional stability and maintain high proton conductivity.
Co-reporter:Hongtao Li, Zhiming Cui, Chengji Zhao, Jing Wu, Tiezhu Fu, Yang Zhang, Ke Shao, Haiqiu Zhang, Hui Na, Wei Xing
Journal of Membrane Science 2009 Volume 343(1–2) pp:164-170
Publication Date(Web):1 November 2009
DOI:10.1016/j.memsci.2009.07.021
Bisphenol monomer 4-carboxylphenyl hydroquinone (4C-PH) containing carboxyl groups was synthesized by diazotization reaction of p-aminobenzoic acid and 1,4-benzoquinone and subsequent reductive reaction. Copolymerization of bisphenol A, 4C-PH, sodium 5,5′-carbonylbis(2-fluorobenzene-sulfonate) and 4,4′-difluorobenzophenone at various molar ratios through aromatic nucleophilic substitution reaction resulted in a new sulfonated poly(ether ether ketone) containing pendant carboxyl groups (C-SPEEK). The structures of the monomer 4C-PH and copolymers were confirmed by FT-IR and 1H NMR. Flexible and transparent membranes with sulfonic and carboxylic acid groups as the proton conducting sites were prepared. The dependence of ion-exchange capacity (IEC), water uptake, proton conductivity and methanol permeability on the degree of sulfonation has been studied. The highest proton conductivity of 0.16 S cm−1 was obtained from C-SPEEK-4 (IEC = 1.44 mequiv. g−1) at 80 °C, higher than that of Nafion117 (0.12 S cm−1). Incorporating carboxylic acid groups into copolymers led to higher dimensional stability and lower water uptake. The methanol permeability coefficients of C-SPEEK membranes were in the range of 3.54 × 10−7 cm2 s−1 to 5.9 × 10−9 cm2 s−1, which were significantly lower than that of Nafion117 (1.61 × 10−6 cm2 s−1). Accordingly, the C-SPEEK membranes exhibited much higher selectivity (conductivity/methanol permeability coefficient) compared with Nafion117 membrane.
Co-reporter:Shuangling Zhong, Chenguang Liu, Hui Na
Journal of Membrane Science 2009 Volume 326(Issue 2) pp:400-407
Publication Date(Web):20 January 2009
DOI:10.1016/j.memsci.2008.10.029
The crosslinkable sulfonated poly(ether ether ketone)s (SPEEKs) were synthesized by nucleophilic substitution reaction of diallyl bisphenol A, tert-butylhydroquinone, 4,4′-difluorobenzophenone and sodium 5,5′-carbonylbis(2-fluorobenzene-sulfonate). The SPEEKs with high intrinsic viscosity showed good solubility and could be cast into flexible and transparent membranes. The SPEEK membranes containing benzophenone (BP) and triethylamine (TEA) photo-initiator system were treated by UV light to promote crosslinking. The experimental results revealed that the crosslinked membrane with 10 min irradiation time showed the most potential as proton exchange membrane for direct methanol fuel cell applications. When the irradiation time increased from 0 to 10 min, the water uptake decreased from 29.1 to 26.1%, and the tensile modulus and the tensile strength enhanced sharply from 0.80 to 1.44 GPa and from 40.3 to 63.4 MPa, respectively. In addition, the methanol diffusion coefficient reduced sharply from 1.70 × 10−6 to 7.42 × 10−7 cm2/s with only slight sacrifice in the proton conductivity, which made the crosslinked membrane with 10 min irradiation time possess the highest selectivity.
Co-reporter:Yang Zhang, Zhiming Cui, Chengji Zhao, Ke Shao, Hongtao Li, Tiezhu Fu, Hui Na, Wei Xing
Journal of Power Sources 2009 Volume 191(Issue 2) pp:253-258
Publication Date(Web):15 June 2009
DOI:10.1016/j.jpowsour.2009.02.032
A series of novel side-chain-type sulfonated poly(arylene ether ketone)s with pendant carboxylic acid groups copolymers (C-SPAEKs) were synthesized by direct copolymerization of sodium 5,5′-carbonyl-bis(2-fluorobenzenesulfonate), 4,4′-difluorobenzophenone and 4,4′-bis(4-hydroxyphenyl) valeric acid (DPA). The expected structure of the sulfonated copolymers was confirmed by FT-IR and 1H NMR. Membranes with good thermal and mechanical stability could be obtained by solvent cast process. It should be noted that the proton conductivity of these copolymers with high sulfonatation degree (DS > 0.6) was higher than 0.03 S cm−1 and increased with increasing temperature. At 80 °C, the conductivity of C-SPAEK-3 (DS = 0.6) and C-SPAEK-4 (DS = 0.8) reached up to 0.12 and 0.16 S cm−1, respectively, which were higher than that of Nafion 117 (0.10 S cm−1). Moreover, their methanol permeability was much lower than that of Nafion 117. These results showed that the synthesized materials might have potential applications as the proton exchange membranes for DMFCs.
Co-reporter:Haidan Lin, Chengji Zhao, Zhiming Cui, Wenjia Ma, Tiezhu Fu, Hui Na, Wei Xing
Journal of Power Sources 2009 Volume 193(Issue 2) pp:507-514
Publication Date(Web):5 September 2009
DOI:10.1016/j.jpowsour.2009.04.036
A novel strategy in which the benzimidazole group and sulfonic group are simultaneously attached to an aromatic polymer has been reported in this paper. For this purpose, sulfonated poly(arylene ether ketone) copolymers containing carboxylic acid groups (SPAEK-x-COOH, x refers to the molar percentage of sulfonated repeating units) are prepared by the aromatic nucleophilic polycondensation of sodium 5,5′-carbonyl-bis(2-fluobenzene-sulfonate) (SDFBP), 4,4′-difluorobenzophenone (DFBP) and phenolphthalin (PPL). Then the carboxylic acid groups attached to the SPAEK-x-COOH are transformed to benzimidazole units through condensation reactions (referred to as SPAEK-x-BI). Fourier transform infrared spectroscopy and 1H NMR measurements are used to characterize and confirm the structures of these copolymers. SPAEK-x-COOH membranes exhibit superior mechanical properties with maximum elongations at break up to 133%, meanwhile SPAEK-x-BI also shows good thermal and mechanical stability. The proton conductivity, swelling ratio and methanol permeability of the polymers with benzimidazole are lower than those with carboxylic groups, which indicated that there is an acid–base complex between benzimidazole and sulfonic acid groups. A balance of proton conductivity, methanol permeability, thermal and mechanical stabilities can be designed by incorporation of functional groups to meet the requirements for the applications in direct methanol fuel cells.
Co-reporter:Chengji Zhao, Haidan Lin, Zhiming Cui, Xianfeng Li, Hui Na, Wei Xing
Journal of Power Sources 2009 Volume 194(Issue 1) pp:168-174
Publication Date(Web):20 October 2009
DOI:10.1016/j.jpowsour.2009.05.021
Co-reporter:Yang Zhang, Ke Shao, Chengji Zhao, Gang Zhang, Hongtao Li, Tiezhu Fu, Hui Na
Journal of Power Sources 2009 Volume 194(Issue 1) pp:175-181
Publication Date(Web):20 October 2009
DOI:10.1016/j.jpowsour.2009.05.022
A series of sulfonated poly(ether ether ketone)s bearing pendant carboxylic acid groups (C-SPEEKs) have been prepared and subsequently react with 1,2-diaminobenzene to obtain sulfonated poly(ether ether ketone)s with pendant benzimidazole groups (BI-SPEEKs). The expected structures of the sulfonated copolymers are confirmed by 1H NMR. The resulting copolymers all show good thermal and mechanical properties. It should be noted that the introduction of benzimidazole groups into the copolymer improves its thermal and oxidative stability obviously. Meanwhile, compared to C-SPEEK, BI-SPEEK membranes show much lower water uptake and methanol permeability with the same sulfonation degree (DS). In order to study morphological changes of C-SPEEK and BI-SPEEK membranes, hydrophilic domains sizes from an atomic force microscopy (AFM) are investigated.
Co-reporter:Gang Zhang, Tiezhu Fu, Ke Shao, Xianfeng Li, Chengji Zhao, Hui Na, Hong Zhang
Journal of Power Sources 2009 Volume 189(Issue 2) pp:875-881
Publication Date(Web):15 April 2009
DOI:10.1016/j.jpowsour.2008.12.155
A novel series of sulfonated poly(ether ether ketone ketone)s (SPEEKKs) with different degrees of sulfonation (Ds) were synthesized from 1,3-bis(3-sodium sulfonate-4-fluorobenzoyl)benzene (1,3-SFBB-Na), 1,3-bis(4-fluorobenzoyl)benzene (1,3-FBB) and 3,3′,5,5′-tetramethyl-4,4′-biphenol (TMBP) by aromatic nucleophilic polycondensation. The chemical structures of SPEEKKs were confirmed by FT-IR spectroscopy and the Ds values of the polymers were calculated by 1H NMR and titration methods, respectively. The thermal stabilities of the SPEEKKs in acid and sodium forms were characterized by thermogravimetric analysis (TGA), which showed that SPEEKKs had excellent thermal properties at high temperatures. All the SPEEKK polymers were easily solution cast into tough membranes. Water uptakes, proton conductivities and methanol diffusion coefficients of the SPEEKK membranes were measured. Water uptake increased with Ds and temperature. Compared to Nafion, the SPEEKK-60, -70 and -80 membranes showed higher proton conductivities at 80 °C, while the other SPEEKK membranes showed relatively lower proton conductivities. This may be due to the different distribution of ion-conducting domains in membrane. However, these membranes showed lower methanol diffusions in the range of 8.32 × 10−9 to 1.14 × 10−7 cm2 s−1 compared with that of Nafion (2 × 10−6 cm2 s−1) at the same temperature. The membranes also showed excellent mechanical properties (with a Young's modulus > 1 GPa and a tensile strength > 40 MPa). These results indicate that the SPEEKK membranes are promising materials for use in direct methanol fuel cell (DMFC) applications.
Co-reporter:Hongtao Li, Jing Wu, Chengji Zhao, Gang Zhang, Yang Zhang, Ke Shao, Dan Xu, Haidan Lin, Miaomiao Han, Hui Na
International Journal of Hydrogen Energy 2009 Volume 34(Issue 20) pp:8622-8629
Publication Date(Web):October 2009
DOI:10.1016/j.ijhydene.2009.08.021
A series of sulfonated poly(ether ether ketone) containing pendant carboxyl (C-SPEEKs) have been synthesized using a nucleophilic polycondesation reaction. A condensation reaction between 1,2-diaminobenzene and carboxyl resulted in a new series of copolymers containing benzimidazole groups (SPEEK-BIms). The expected structures of the sulfonated copolymers are confirmed by 1H NMR. The dependence of ion exchange capacity, water uptake, proton conductivity and methanol diffusion coefficient of SPEEK-BIm membranes has been studied and compared with their carboxyl acid form. The results suggest that the introduction of benzimidazole groups may be responsible for many excellent properties of the membranes for fuel cell. It is noticeable that the markedly improved oxidative stability is benefit for the application of membrane.
Co-reporter:Jing Wu, Zhiming Cui, Chengji Zhao, Hongtao Li, Yang Zhang, Tiezhu Fu, Hui Na, Wei Xing
International Journal of Hydrogen Energy 2009 Volume 34(Issue 16) pp:6740-6748
Publication Date(Web):August 2009
DOI:10.1016/j.ijhydene.2009.06.051
Composite membranes based on Sulfonated poly(ether ether ketone) (SPEEK) and sulfonated organically modified Si-SBA-15 (S-SBA-15) were investigated with the purpose of increasing the proton conductivity. The novelty of the composite membranes was attributed to two special structures and different ion exchange capacities (IEC) of S-SBA-15 fillers, which were embedded in membranes. The typical hexagonal channels array of S-SBA-15 was confirmed by XRD and TEM. The regular vermiculate and amorphous structures of the inorganic fillers were proved by SEM. Composite membranes were prepared through common solvent casting method. SEM images indicated that the inorganic filler with regular structure dispersed homogeneously in the composite membranes, but the amorphous filler caused an agglomeration phenomenon at the same loading content. The composite membranes exhibited good thermal stability, enhanced water uptake and proton conductivity. The proton conductivity of the composite membranes with low IEC filler was higher than the composite membranes with high IEC filler at the same loading content. The highest proton conductivity value of 0.156 S cm−1 was obtained for the composite membrane containing 5 wt.% S-SBA-15 with the IEC of 1.41 mequiv g−1 at 80 °C. This composite membrane also showed other promising properties such as good thermal and mechanical stability which exceeded the other composite membranes with different loading contents.
Co-reporter:Haidan Lin, Chengji Zhao, Wenjia Ma, Hongtao Li, Hui Na
International Journal of Hydrogen Energy 2009 Volume 34(Issue 24) pp:9795-9801
Publication Date(Web):December 2009
DOI:10.1016/j.ijhydene.2009.10.012
The surface of sulfonated poly(arylene ether ketone) bearing carboxyl groups (SPAEK-C) was modified by alternating deposition of oppositely charged polypyrrole (PPY) and phosphotungstic acid (PWA) via the layer-by-layer (LBL) method in order to prevent the crossover of methanol in the direct methanol fuel cell (DMFC). FT-IR confirms that PPY and PWA are assembled in the multilayers successfully. The morphology of the membranes studied in detail by SEM shows the presence and stability of thin PPY/PWA layers coated on SPAEK-C membranes. Methanol permeability was determined and was shown to be effectively reduced. The selectivity of SPAEK-C-(PPY/PWA)n is 1 order more than Nafion® 117, which is attractive in DMFCs. Thermal stability, water uptake, water swelling and proton conductivity of the SPAEK-C and SPAEK-C-(PPY/PWA)n membranes were also investigated.
Co-reporter:Tiezhu Fu;Shuangling Zhong;Zhiming Cui;Chengji Zhao;Yuhua Shi;Wenzhi Yu;Wei Xing
Journal of Applied Polymer Science 2009 Volume 111( Issue 3) pp:1335-1343
Publication Date(Web):
DOI:10.1002/app.29150
Abstract
A crosslinked epoxy [4,4′-diglycidyl-(3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP)], cured by phenol novolac (PN), was introduced into a sulfonated poly(ether ether ketone) (SPEEK) membrane (ion-exchange capacity = 2.0 mequiv/g) with a casting-solution, evaporation, and heating crosslinking method to improve the mechanical properties, dimensional stability, water retention, and methanol resistance. By Fourier transform infrared analysis, the interactions between the sulfonic acid groups and hydroxyl groups in the blend membranes were confirmed. The microstructure and morphology of the blend membranes were investigated with atomic force microscopy. As expected, the blend membranes showed excellent mechanical properties, good thermal properties (thermal stability above 200°C), lower swelling ratios (1.4% at 25°C and 7.0% at 80°C), higher water retention (water diffusion coefficient = 9.8 × 10−6 cm2/s), and a lower methanol permeability coefficient (3.6 × 10−8 cm2/s) than the pristine SPEEK membrane. Although the proton conductivity of the blend membranes decreased, a higher selectivity (ratio of the proton conductivity to the methanol permeability) was obtained than that of the pristine SPEEK membrane. The results showed that the SPEEK/TMBP/PN blend membranes could have potential use as proton-exchange membranes in direct methanol fuel cells. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Tiezhu Fu;Lianxiang Yu;Zhe Wang;Wenzhi Yu;Chengji Zhao;Shuangling Zhong;Jiwen Cui;Ke Shao
Polymer Composites 2009 Volume 30( Issue 7) pp:948-954
Publication Date(Web):
DOI:10.1002/pc.20639
Abstract
A new type of organophilic clay grafted with the protonated 4, 4′-methylenediamine was prepared. The epoxy was modified using the organophilic clay and was prepared by “acetone-clay slurry” method. The morphology of the clay platelets into epoxy matrix were characterized by wide angle X-ray diffraction and transmission electron microscopy. The results indicated that the epoxy resin/exfoliated clay hybrid materials were successfully prepared and the exfoliation of clay into epoxy matrix occurred in the curing process. The excellent thermal mechanical properties of the hybrid materials with the values of the storage modulus and glass transition temperature (Tg) of the hybrid materials were studied by dynamic mechanical analysis. When 7 wt% of modified clay was added into epoxy, the storage modulus of hybrid materials increased to 1131 MPa at 110°C, and 51 MPa at 220°C in comparison to the pristine cured epoxy (661 MPa at 110°C and 6 MPa at 220°C). The high thermal stabilities of the hybrid materials especially in high temperature were also been researched by thermogravimetric analysis. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Co-reporter:Tiezhu Fu;Jia Liu;Jing Wang
Polymer Composites 2009 Volume 30( Issue 10) pp:1394-1400
Publication Date(Web):
DOI:10.1002/pc.20703
Abstract
The samples of rigid rod epoxy resin (4,4′-diglycidyl (3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP)) with different weight contents of polyaniline (PANI) as a curing agent were prepared. The kinetics of curing reaction between TMBP and PANI was analyzed by dynamic differential scanning calorimetry in the temperature range of 25–300°C. The results showed that the heat of cure reaction of TMBP/PANI sample with 10 wt% PANI was larger than those of others. The active energies with different curing conversions of TMBP/PANI sample with 10 wt% PANI were calculated by iso-conversional method using the Coats-Redfern approximation. The results showed that the activation energy was dependent on the degree of conversion. The morphology of the cured samples was detected by scanning electron microscopy measurements. The relationship between morphology and conductivity of cured samples was researched. The conductivities increased from 2.7 × 10−4 to 9.5 × 10−4 S/cm with the increase of PANI from 5 to 20 wt% in cured samples. The thermal stabilities of cured TMBP/PANI samples were examined by thermogravimetric analysis. The results showed that the cured TMBP/PANI can be promising to use as a conducting adhesive. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Co-reporter:Ke Shao;Jing Zhu;Chengji Zhao;Xianfeng Li;Zhiming Cui;Yang Zhang;Hongtao Li;Dan Xu;Gang Zhang;Tiezhu Fu;Jing Wu;Wei Xing
Journal of Polymer Science Part A: Polymer Chemistry 2009 Volume 47( Issue 21) pp:5772-5783
Publication Date(Web):
DOI:10.1002/pola.23621
Abstract
A new monomer 1,5-bis(4-fluorobenzoyl)-2,6-dimethoxynaphthalene (DMNF) was prepared and further polymerized to form naphthalene-based poly(arylene ether ketone) copolymers containing methoxy groups (MNPAEKs). The side-chain-type sulfonated naphthalene-based poly(arylene ether ketone) copolymers (SNPAEKs) were obtained by demethylation and sulfobutylation. Flexible and tough membranes with reasonably high mechanical strength were prepared. The SNPAEKs membrane showed anisotropic membrane swelling with larger swelling in thickness than in plane. Transmission electron microscopy (TEM) analysis revealed clear nanophase separated structure of SNPAEKs membranes, which composed of hydrophilic side chain and hydrophobic main-chain domains. Proton conductivities of copolymers increased gradually with increase in temperature. The highest conductivity of 0.179 S/cm was obtained for SNPAEK-80 (IEC = 1.82 mequiv/g) at 80 °C, which is higher than that of Nafion117 (0.146 S/cm). The SNPAEKs membranes exhibit the methanol permeability in the range of 3.42 × 10−8−4.49 × 10−7 cm2/s, which are much lower than that of Nafion117. They could be the promising materials as alternative to Nafion membrane for direct methanol fuel cells applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47:5772–5783, 2009
Co-reporter:Yang Zhang, Ying Wan, Chengji Zhao, Ke Shao, Gang Zhang, Hongtao Li, Haidan Lin, Hui Na
Polymer 2009 50(19) pp: 4471-4478
Publication Date(Web):
DOI:10.1016/j.polymer.2009.07.036
Co-reporter:Tiezhu Fu, Chengji Zhao, Shuangling Zhong, Gang Zhang, Ke Shao, Haiqiu Zhang, Jing Wang, Hui Na
Journal of Power Sources 2008 Volume 182(Issue 2) pp:653
Publication Date(Web):1 August 2008
DOI:10.1016/j.jpowsour.2008.04.041
Co-reporter:Haiqiu Zhang, Xianfeng Li, Chengji Zhao, Tiezhu Fu, Yuhua Shi, Hui Na
Journal of Membrane Science 2008 Volume 308(1–2) pp:66-74
Publication Date(Web):1 February 2008
DOI:10.1016/j.memsci.2007.09.045
In the present work, the acid–base composite membranes were prepared using highly sulfonated poly(aryl ether ether ketone) (SPEEK) and polybenzimidazole (PBI). The morphology characteristics of composite membranes with different content of PBI were studied in detail by SEM, AFM, SAXS, FT-IR and UV. The results show that the structures of composite membrane become more compact than that of SPEEK, due to the acid–base interaction between the sulfonic acid groups and amine groups, which could lead to the increase of mechanical properties and the reduction of excess swelling. The performances of the composite membranes were characterized. The study showed that the proton conductivity of the composite membranes was dependent on the content of PBI. The thermal stabilities and mechanical properties of the SPEEK membranes were improved greatly. The composite membranes exhibited moderated swelling properties and ion exchange capacities. All the data proved that the composite membranes to be potential for usages in PEMFC.
Co-reporter:Tiezhu Fu, Zhiming Cui, Shuangling Zhong, Yuhua Shi, Chengji Zhao, Gang Zhang, Ke Shao, Hui Na, Wei Xing
Journal of Power Sources 2008 Volume 185(Issue 1) pp:32-39
Publication Date(Web):15 October 2008
DOI:10.1016/j.jpowsour.2008.07.004
A new type of sulfonated clay (clay-SO3H) was prepared by the ion exchange method with the sulfanilic acid as the surfactant agent. The grafted amount of sulfanilic acid in clay-SO3H was 51.8 mequiv. (100 g)−1, which was measured by thermogravimetric analysis (TGA). Sulfonated poly(ether ether ketone) (SPEEK)/clay-SO3H hybrid membranes which composed of SPEEK and different weight contents of clay-SO3H, were prepared by a solution casting and evaporation method. For comparison, the SPEEK/clay hybrid membranes were produced with the same method. The performances of hybrid membranes for direct methanol fuel cells (DMFCs) in terms of mechanical and thermal properties, water uptake, water retention, methanol permeability and proton conductivity were investigated. The mechanical and thermal properties of the SPEEK membranes had been improved by introduction of clay and clay-SO3H, obviously. The water desorption coefficients of the SPEEK and hybrid membranes were studied at 80 °C. The results showed that the addition of the inorganic part into SPEEK membrane enhanced the water retention of the membrane. Both methanol permeability and proton conductivity of the hybrid membranes decreased in comparison to the pristine SPEEK membrane. However, it was worth noting that higher selectivity defined as ratio of proton conductivity to methanol permeability of the SPEEK/clay-SO3H-1 hybrid membrane with 1 wt.% clay-SO3H was obtained than that of the pristine SPEEK membrane. These results showed that the SPEEK/clay-SO3H hybrid membrane with 1 wt.% clay-SO3H had potential usage of a proton exchange membrane (PEM) for DMFCs.
Co-reporter:Shuangling Zhong, Xuejun Cui, Tiezhu Fu, Hui Na
Journal of Power Sources 2008 Volume 180(Issue 1) pp:23-28
Publication Date(Web):15 May 2008
DOI:10.1016/j.jpowsour.2008.02.043
A drawback of sulfonated aromatic main-chain polymers such as sulfonated poly(ether ether ketone)s (SPEEKs) is their high methanol crossover when the proton conductivity is sufficient for direct methanol fuel cell (DMFC) applications. To overcome this disadvantage, in this paper, the SPEEK substrate was coated with the crosslinked chitosan (CS) barrier layer to form the two-layer composite membranes. Scanning electron microscope (SEM) micrographs showed that the CS layer was tightly adhered on the SPEEK substrate and the thickness of CS layer could be adjusted by varying the concentration of CS solution. It was noticed that with the increment of thickness of CS layer, the methanol diffusion coefficient of the composite membranes significantly dropped from 3.15 × 10−6 to 2.81 × 10−7 cm2 s−1 at 25 °C which was about one order of magnitude lower than those of the pure SPEEK and Nafion® 117 membranes. In addition to the effective methanol barrier, the composite membranes possessed adequate thermal stability (the 5% weight lose temperature exceeded 240 °C) and good proton conductivity. The proton conductivity of all composite membranes was in the order of 10−2 S cm−1 and increased with the elevation of temperature. Furthermore, the composite membranes exhibited much higher selectivity (conductivity/methanol diffusion coefficient) compared with the pure SPEEK and Nafion® 117 membranes. These results indicated that introducing the crosslinked CS layer onto the SPEEK surface was an effective method for improving the performance of the SPEEK membrane, especially for reducing the methanol crossover.
Co-reporter:Chengji Zhao;Xianfeng Li;Haidan Lin;Ke Shao
Journal of Applied Polymer Science 2008 Volume 108( Issue 1) pp:671-680
Publication Date(Web):
DOI:10.1002/app.27696
Abstract
Sulfonated poly(aryl ether ketone)s (SPAEK) copolymers were synthesized by aromatic nucleophilic polycondensation from 3,3′, 5,5′-tetramethyl-4, 4′–biphenol, 1,4-bis(4-fluorobenzoyl) benzene, and disulfonated difluorobenzophenone. The SPAEK membranes did not exhibit excessive swelling in hot water and at the same time show the proton conductivities in the range of 0.030 S/cm to 0.099 S/cm at 80°C. The methanol diffusion coefficients of the SPAEK membranes were in the range of 4.7 × 10−7 to 8.1 × 10−7cm2/s measured at 25°C. The transport properties of this series of SPAEK copolymers were compared to poly(aryl ether ether ketone)s (SPEEK), poly(aryl ether ether ketone ketone)s (SPEEKK), and Nafion® membranes. It was found that the transport properties (including proton conductivity and methanol permeability) follows the trend of SPEEKK-60 < SPAEK-60 < SPEEK-60 < Nafion® 117, the order of which is also attributed to the differences in the chemical structure of the polymers and the membrane morphology. In general, this novel series of SPAEK membranes possess various advantages, such as low cost of the initial monomers, high thermal and mechanical stability, and low methanol permeability while simultaneously possessing sufficient proton conductivity, which makes them notably promising as proton exchange membrane (PEM) materials in direct methanol fuel cell (DMFC) applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Zhiyu Dou;Shuangling Zhong;Chengji Zhao;Xianfeng Li;Tiezhu Fu
Journal of Applied Polymer Science 2008 Volume 109( Issue 2) pp:1057-1062
Publication Date(Web):
DOI:10.1002/app.25127
Abstract
Through sol-gel reactions, a series of sulfonated poly(ether ether ketone) (SPEEK)/TiO2 hybrid membranes with various contents of nano-sized TiO2 particles were prepared and characterized. It was found that with the increasing of the TiO2 contents in the hybrid membranes, the water uptake and water retention increased. Meanwhile, the introduction of inorganic particles reduced the methanol permeability. The proton conductivity was enhanced by introduction of hydrophilic inorganic particles into the SPEEK membranes, which might be an effective approach to increase the working temperature of PEM. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Xianfeng Li, Xiufeng Hao, Hubei Yu, Hui Na
Materials Letters 2008 Volume 62(8–9) pp:1155-1158
Publication Date(Web):31 March 2008
DOI:10.1016/j.matlet.2007.08.003
One simple method was introduced to prepare core–shell nanostructured conductive Ppy composite. Core Ppy particles were first introduced in the flexible shell solutions and then different core–shell structures can be prepared by electrospinning method. The results showed that: this method is very powerful to form core–shell nanostructures with electroconductive Ppy.
Co-reporter:Tiezhu Fu, Jing Wang, Jing Ni, Zhiming Cui, Shuangling Zhong, Chengji Zhao, Hui Na, Wei Xing
Solid State Ionics 2008 Volume 179(Issue 39) pp:2265-2273
Publication Date(Web):15 December 2008
DOI:10.1016/j.ssi.2008.08.009
Sulfonated poly(ether ether ketone) (SPEEK) and aminopropyltriethoxysilane (KH550) hybrid membranes doped with different weight ratio of phosphotungstic acid (PWA) were prepared by the casting procedure, as well as PWA as a catalyst for sol–gel process of KH550. The chemical structures of hybrid membranes were characterized by energy dispersive X-ray spectrometry (EDX) and Fourier transform infrared spectroscopy (FTIR). The morphology of hybrid membranes was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results had proved the uniform and homogeneous distribution of KH550 and PWA in these hybrid membranes. The influence of the dispersed PWA on the properties of membranes such as thermal stability, water uptake, swelling ratio, and proton conductivity was researched. Thermogravimetry analysis (TGA) results indicated that the hybrid membranes had high thermal stability below 200 °C. The dimensional stabilities of the hybrid membranes were improved by addition of KH550-10/PWA compared with the pristine SPEEK. The proton conductivity of the hybrid membrane with 5 wt.% PWA into SPEEK/KH550-10 reached the maximum of 0.084 S cm− 1 at 25 °C and 0.16 S cm− 1 at 80 °C under the 100% relative humidity condition. The proton conductivity mechanism in the hybrid membranes was discussed. Therefore, the possibility of the hybrid membranes for usage in proton exchange membrane fuel cells (PEMFCs) was explored.
Co-reporter:Shuangling Zhong, Xuejun Cui, Hongli Cai, Tiezhu Fu, Chengji Zhao, Hui Na
Journal of Power Sources 2007 Volume 164(Issue 1) pp:65-72
Publication Date(Web):10 January 2007
DOI:10.1016/j.jpowsour.2006.10.077
In the present study, a series of the crosslinked sulfonated poly(ether ether ketone) (SPEEK) proton exchange membranes were prepared. The photochemical crosslinking of the SPEEK membranes was carried out by dissolving benzophenone and triethylamine photo-initiator system in the membrane casting solution and then exposing the resulting membranes after solvent evaporation to UV light. The physical and transport properties of crosslinked membranes were investigated. The membrane performance can be controlled by adjusting the photoirradiation time. The experimental results showed that the crosslinked SPEEK membranes with photoirradiation 10 min had the optimum performance for proton exchange membranes (PEMs). Compared with the non-crosslinked SPEEK membranes, the crosslinked SPEEK membranes with photoirradiation 10 min markedly improved thermal stabilities and mechanical properties as well as hydrolytic and oxidative stabilities, greatly reduced water uptake and methanol diffusion coefficients with only slight sacrifice in proton conductivities. Therefore, the crosslinked SPEEK membranes with photoirradiation 10 min were particularly promising as proton exchange membranes for direct methanol fuel cell (DMFC) applications.
Co-reporter:Xianfeng Li, Gang Zhang, Dan Xu, Chengji Zhao, Hui Na
Journal of Power Sources 2007 Volume 165(Issue 2) pp:701-707
Publication Date(Web):20 March 2007
DOI:10.1016/j.jpowsour.2006.12.011
The morphological changes of sulfonated poly(ether ether ketone ketone) (SPEEKK) membranes with different sulfonated degrees (Ds) were investigated by small angle X-ray scattering (SAXS), atom force microscopy (AFM) and transmission electron microscope (TEM). The small angle scattering maximum shifts to little vectors with sulfonated degree increasing. Porod analysis for SPEEKK and Guinier analysis for silver exchanged SPEEKK (SPEEKK-Ag) were carried out to study the microstructures of SPEEKK membranes. All the results showed that: more clearly phase-separated structures will be formed with the increasing of Ds of SPEEKK membranes. The membranes with high Ds will provide much larger and more continuous transport channels for protons. The properties changes that derived from the structures’ difference were discussed in detail. The relationship between the properties and microstructures of SPEEKK membranes was established. The study will provide more instructive information on the molecular design of excellent proton exchange membranes.
Co-reporter:Tiezhu Fu, Chengji Zhao, Shuangling Zhong, Gang Zhang, Ke Shao, Haiqiu Zhang, Jing Wang, Hui Na
Journal of Power Sources 2007 Volume 165(Issue 2) pp:708-716
Publication Date(Web):20 March 2007
DOI:10.1016/j.jpowsour.2006.12.023
Sulfonated poly(ether ether ketone) (SPEEK)/4,4′-diglycidyl(3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP) composite membranes in situ polymerization were prepared for the purpose of improving the methanol resistance and mechanical properties of SPEEK membranes with high ion-exchange capacities (IEC) for the usage in the direct methanol fuel cells (DMFCs). The effects of introduction of TMBP content on the properties of the composite membranes were investigated in detail. The composite membranes have good mechanical, thermal properties, lower swelling ratio, lower water diffusion coefficient (0.87 × 10−5 cm2 s−1 at 80 °C) and better methanol resistance (5.26 × 10−7 cm2 s−1 at 25 °C) than SPEEK membranes. The methanol diffusion coefficients of the composite membranes are much lower than that of SPEEK membrane (17.5 × 10−7 cm2 s−1 at 25 °C). Higher selectivity was been found for the composite membranes in comparison with SPEEK. Therefore, the SPEEK/TMBP composite membranes show a good potential in DMFCs usages.
Co-reporter:Shuangling Zhong, Xuejun Cui, Hongli Cai, Tiezhu Fu, Ke Shao, Hui Na
Journal of Power Sources 2007 Volume 168(Issue 1) pp:154-161
Publication Date(Web):25 May 2007
DOI:10.1016/j.jpowsour.2007.03.028
The crosslinked sulfonated poly (ether ether ketone)/2-acrylamido-2-methyl-1-propanesulfonic acid (SPEEK/AMPS) blend membranres were prepared and evaluated as proton exchange membranes for direct methanol fuel cell (DMFC) applications. The structure and morphology of SPEEK/AMPS membranes were characterized by FTIR and SEM, respectively. The effects of crosslinking and AMPS content on the performance of membranes were studied and discussed in detail. The proton conductivity and methanol diffusion coefficient of SPEEK/AMPS membranes increased gradually with the increase of AMPS content. Most SPEEK/AMPS membranes exhibited higher proton conductivity than Nafion® 117 (0.05 S cm−1 at 25 °C). However, all the membranes possessed much lower methanol diffusion coefficient compared with Nafion® 117 (2.38 × 10−6 cm2 s−1) under the same measuring conditions. Even the methanol diffusion coefficient (8.89 × 10−7 cm2 s−1) of SPEEK/AMPS 30 sample with the highest proton conductivity (0.084 S cm−1 at 25 °C) was only about one third of that of Nafion® 117. The selectivity of all the SPEEK/AMPS membranes was much higher in comparison with Nafion® 117 (2.8 × 104 S s cm−3). In addition, the SPEEK/AMPS membranes possessed relatively good thermal and hydrolytic stability. These results suggested that the SPEEK/AMPS membranes were particularly promising to be used as proton exchange membranes in DMFCs, and the high proton conductivity, low methanol diffusion coefficient and high selectivity were their primary advantages for DMFC applications.
Co-reporter:Chengji Zhao;Xianfeng Li;Zhe Wang;Hongzhe Ni;Zhe Wang;Hongzhe Ni;Chengji Zhao;Xianfeng Li
Journal of Applied Polymer Science 2007 Volume 104(Issue 3) pp:1443-1450
Publication Date(Web):26 FEB 2007
DOI:10.1002/app.24933
Novel aromatic sulfonated poly(ether ether sulfone)s (SPEESs) with tert-butyl groups were synthesized by aromatic nucleophilic polycondensation of disodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (SDCDPS), 4,4′-dichlorodiphenylsulfone (DCDPS), and tert-butylhydroquinone (TBHQ). The resulting copolymers showed very good thermal stability and could be cast into tough membranes. The morphology of the membranes was investigated with atomic force microscopy. The proton conductivity of SPEES-40 membranes increased from 0.062 S/cm at 25°C to 0.083 S/cm at 80°C, which was higher than the 0.077 S/cm of Nafion 117 under the same testing conditions. These copolymers are good candidates to be new polymeric electrolyte materials for proton exchange membrane fuel cells. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1443–1450, 2007
Co-reporter:Tiezhu Fu;Shuangling Zhong;Gang Zhang;Chengji Zhao;Ke Shao;Lifeng Wang
Journal of Applied Polymer Science 2007 Volume 105(Issue 5) pp:2611-2620
Publication Date(Web):11 MAY 2007
DOI:10.1002/app.26340
Epoxy resins, 4, 4′-diglycidyl (3, 3′, 5, 5′-tetramethylbiphenyl) epoxy resin (TMBP) containing rigid rod structure as a class of high performance polymers has been researched. The investigation of cure kinetics of TMBP and diglycidyl ether of bisphenol-A epoxy resin (DGEBA) cured with p-phenylenediamine (PDA) was performed by differential scanning calorimeter using an isoconversional method with dynamic conditions. The effect of the molar ratios of TMBP to PDA on the cure reaction kinetics was studied. The results showed that the curing of epoxy resins contains different stages. The activation energy was dependent of the degree of conversion. At the early of curing stages, the activation energy showed the activation energy took as maximum value. The effects of rigid rod groups and molar ratios of TMBP to PDA for the thermal properties were investigated by the DSC, DMA and TGA. The cured 2/1 TMBP/PDA system with rigid rod groups and high crosslink density had shown highest Tg and thermal degradation temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Co-reporter:Xianfeng Li, Dan Xu;Gang Zhang;Zhe Wang;Chengji Zhao
Journal of Applied Polymer Science 2007 Volume 103(Issue 6) pp:4020-4026
Publication Date(Web):27 DEC 2006
DOI:10.1002/app.25543
The sulfonated poly(ether ether ketone ketone)/phosphotungstic acid (SPEEKK/PWA) composite membranes were researched for proton exchange membranes. The effect of casting condition on the properties of membranes was studied in detail. The study showed that the casting condition has great influence on the membrane properties because of the hydrogen bond between the SPEEK and PWA and the interaction between the SPEEKK and dimethylformamide (DMF). The PWA particles are well crystallized on the surface when the velocity of the solvent volatilization is very slow under the SEM. The study will favor further research on excellent composite membranes for proton exchange membrane fuel cells. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4020–4026, 2007
Co-reporter:Xianfeng Li, Xiufeng Hao, Hui Na
Materials Letters 2007 Volume 61(Issue 2) pp:421-426
Publication Date(Web):January 2007
DOI:10.1016/j.matlet.2006.04.074
By using the interaction between the sulfonated groups and silver ions, nanosilver particles were successfully introduced into S-PEEK nanostructures (nanospheres and nanofibers) by electrospinning. The nanoparticles were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectra (XPS), UV/vis, etc. The size of the spheres increases with the weight concentration of silver exchanged sulfonated poly(ether ether ketone) (S-PEEK-Ag) increasing. The size of the silver particles can be controlled by adjusting the sulfonated degree (number of sulfonate groups per repeating unit) of sulfonated poly(ether ether ketone) (S-PEEK) and the weight ratio of the S-PEEK solutions. This paper provides a new method for the preparation of nanometal particles into nanostructures.
Co-reporter:Shuangling Zhong;Xuejun Cui;Hongli Cai;Tiezhu Fu
Journal of Polymer Science Part B: Polymer Physics 2007 Volume 45(Issue 20) pp:2871-2879
Publication Date(Web):4 SEP 2007
DOI:10.1002/polb.21284
A series of sulfonated poly(ether ether ketone)/monoethanolamine/adipic acid (SPEEK/MEA/AA) composite membranes are prepared and investigated to assess their possibility as proton exchange membranes in direct methanol fuel cells (DMFCs). A preliminary evaluation shows that introducing MEA and AA into SPEEK matrix decreases the thermal stability of membrane. However, the degradation temperatures are still above 260 °C, satisfying the requirement for fuel cell operation. Compared with the pure SPEEK membrane, the composite membranes exhibit not only lower water uptake and swelling ratios but also better mechanical property and oxidative stability. Noticeably, the methanol diffusion coefficient of the composite membranes decrease significantly from 3.15 × 10−6 to 0.76 × 10−6 cm2/s with increasing MEA and AA content, accompanied by only a small sacrifice in proton conductivity. Although both the methanol diffusion coefficient and the proton conductivity of composite membranes are lower than those of pure SPEEK and Nafion® 117 membranes, their selectivity (conductivity/methanol diffusion coefficient) are higher. In addition, the composite membranes show excellent stability in aqueous methanol solution. The good thermal and chemical stability, low swelling ratio, excellent mechanical property, low methanol diffusion coefficient, and high selectivity make the use of these composite membranes in DMFCs quite attractive. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2871–2879, 2007
Co-reporter:Zhe Wang, Hongzhe Ni, Chengji Zhao, Xianfeng Li, Gang Zhang, Ke Shao, Hui Na
Journal of Membrane Science 2006 Volume 285(1–2) pp:239-248
Publication Date(Web):15 November 2006
DOI:10.1016/j.memsci.2006.08.038
Three series of sulfonated poly(ether ether sulfone) (SPEES) copolymers with controlled degrees of sulfonation (DS) were prepared by aromatic nucleophilic polycondensation of disodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (SDCDPS), 4,4′-dichlorodiphenylsulfone (DCDPS) and three hydroquinone with different pendant groups (hydroquinone (HQ), tertbutylhydroquione (TBHQ) and p-toluhydroquinone (PTHQ)). Synthesized sulfonated copolymers were characterized by FT-IR, TGA and DSC. Moreover, the microstructure of membrane was investigated by TEM. All copolymers had high molecular weight and could be cast into tough membranes. Performances of all membranes were studied thoroughly. The copolymers with different bisphenol structures show different physical and electrochemical behaviors, such as water retention, glass transition temperature (Tg) and proton conductivity, etc. Water retention and proton conductivity of SPEES membranes with tertbutylhydroquione were much better than other series membranes with same DS because of the hydrophilic channel formed by bulk pendant groups.
Co-reporter:Xianfeng Li, Xiufeng Hao, Dan Xu, Gang Zhang, Shuangling Zhong, Hui Na, Dayang Wang
Journal of Membrane Science 2006 Volume 281(1–2) pp:1-6
Publication Date(Web):15 September 2006
DOI:10.1016/j.memsci.2006.06.002
Microstructures of SPEEKK membranes were realized the changes from spheres to nanofibers by introducing electrospinning method into membranes preparation. The SPEEKK membranes with spherical structures exhibit the highest proton conductivity, 0.37 S/cm, which is 37 times as high as the convenient SPEEKK membranes (0.01 S/cm). The membranes prepared by this method should hold immense promise in proton exchange membrane fuel cells applications.
Co-reporter:Xianfeng Li, Changpeng Liu, Dan Xu, Chengji Zhao, Zhe Wang, Gang Zhang, Hui Na, Wei Xing
Journal of Power Sources 2006 Volume 162(Issue 1) pp:1-8
Publication Date(Web):8 November 2006
DOI:10.1016/j.jpowsour.2006.06.030
Polypyrrole (Ppy) was successfully introduced into methyl substituted sulfonated poly(ether ether ketone) (SPEEK) membranes by polymerization in SPEEK solutions to improve their methanol resistance. Uniform polypyrrole (Ppy) distributed composite membranes were formed by this method by the interaction between SPEEK and Ppy. The properties of the composite membranes were characterized in detail. The composite membranes show very good proton conductive capability (25 °C: 0.05–0.06 s cm−1) and good methanol resistance (25 °C: 5.3 × 10−7–1.1 × 10−6 cm2 s−1).The methanol diffusion coefficients of composite membranes are much lower than that of pure SPEEK membranes (1.5 × 10−6 cm2 s−1). The composite membranes show very good potential usage in direct methanol fuel cells (DMFCs).
Co-reporter:Shuangling Zhong, Tiezhu Fu, Zhiyu Dou, Chengji Zhao, Hui Na
Journal of Power Sources 2006 Volume 162(Issue 1) pp:51-57
Publication Date(Web):8 November 2006
DOI:10.1016/j.jpowsour.2006.06.067
A series of crosslinkable sulfonated poly(ether ether ketone)s (SPEEKs) containing propenyl groups were synthesized by aromatic nucleophilic substitution reactions. 1H NMR spectra were used to confirm the DS of polymers. The resulting polymers showed high molecular weights and good solubility and could be cast into tough membranes. The SPEEK membranes in acid form possessed good thermal stabilities and mechanical properties. The methanol diffusion coefficients ranged from 9.70 × 10−8 to 4.18 × 10−7 cm2 s−1, which were much lower than that of Nafion 117® (2.38 × 10−6 cm2 s−1). The proton conductivity of the SPEEK-3 membranes (0.072 S cm−1) was close to that of Nafion 117® (0.083 S cm−1) at 85 °C under the same testing conditions. These results showed that the synthesized materials might have potential applications as the proton exchange membranes for PEMFCs.
Co-reporter:Chengji Zhao, Haidan Lin, Ke Shao, Xianfeng Li, Hongzhe Ni, Zhe Wang, Hui Na
Journal of Power Sources 2006 Volume 162(Issue 2) pp:1003-1009
Publication Date(Web):22 November 2006
DOI:10.1016/j.jpowsour.2006.07.055
A series of block SPEEK copolymers with high ion-exchange capacities (IEC) consisting of hydrophobic and hydrophilic blocks were synthesized successfully. Membranes were cast from their DMF solutions, and characterized by determining the ion-exchange capacity, water uptake, water retention, proton conductivity and thermal properties. Membranes exhibited conductivities from 0.027 to 0.068 S cm−1 at 30 °C and from 0.049 to 0.11 S cm−1 at 80 °C; water uptake from 34% to 54% and IEC from 1.25 to 1.48 mequiv. g−1. Block-3 membrane with IEC 1.38 mequiv. g−1 showed relatively higher proton conductivity compared to that of a random SPEEK membrane with IEC 1.37 mequiv. g−1. The SAXS profiles of block SPEEK copolymers exhibited a well-defined ionomer peak at low angles due to the phase separation between ionic domains and hydrophobic domains. It is believed that their microstructure features attribute to the enhanced proton conductivity of block SPEEK membranes.
Co-reporter:Zhe Wang;Hongzhe Ni;Chengji Zhao;Xianfeng Li;Tiezhu Fu
Journal of Polymer Science Part B: Polymer Physics 2006 Volume 44(Issue 14) pp:1967-1978
Publication Date(Web):1 JUN 2006
DOI:10.1002/polb.20841
The sulfonated poly(ether ether ketone sulfone) (SPEEKS)/heteropolyacid (HPA) composite membranes with different HPA content in SPEEKS copolymers matrix with different degree of sulfonation (DS) were investigated for high temperature proton exchange membrane fuel cells. Composite membranes were characterized by Fourier transfer infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). FTIR band shifts suggested that the sulfonic acid groups on the copolymer backbone strongly interact with HPA particles. SEM pictures showed that the HPA particles were uniformly distributed throughout the SPEEKS membranes matrix and particle sizes decreased with the increment of copolymers' DS. The holes were not found in SPEEKS-4/HPA30 (consisting of 70% SPEEKS copolymers with DS = 0.8 and 30% HPA) composite membrane after composite membranes were treated with boiling water for 24 h. Thermal stabilities of the composite membranes were better than those of pure sulfonated copolymers membranes. Although the composite membranes possessed lower water uptake, it exhibited higher proton conductivity for SPEEKS-4/HPA30 especially at high temperature (above 100 °C). Its proton conductivity linearly increased from 0.068 S/cm at 25 °C to 0.095 S/cm at 120 °C, which was higher than 0.06 S/cm of Nafion 117. In contrast, proton conductivity of pure SPEEKS-4 membrane only increased from 0.062 S/cm at 25 °C to 0.078 S/cm at 80 °C. At 120 °C, proton conductivity decreased to poor 0.073 S/cm. The result indicated that composite membranes exhibited high proton conductivity at high temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1967–1978, 2006
Co-reporter:Xianfeng Li, Zhe Wang, Hui Lu, Chengji Zhao, Hui Na, Chun Zhao
Journal of Membrane Science 2005 Volume 254(1–2) pp:147-155
Publication Date(Web):1 June 2005
DOI:10.1016/j.memsci.2004.12.051
Membranes with improved selectivity, stability, and non-fouling properties will be important in future chemical and waste treatment applications. Sulfonated poly(ether ether ketone)s (S-PEEKs) based membranes have been studied due to their good mechanical properties, thermal stability and ion exchange property. In this study, S-PEEKs based membranes were evaluated for ion exchange application. The microstructures of S-PEEKs membranes were studied by TEM and SAXS. The distribution of ion domains which mainly influence the properties of membranes was characterized. The fixed ion concentration, cation transport number and membrane selective permeability with different sulfonated degree or different micro structures were investigated. The relationship between the microstructures and properties of S-PEEK membranes was established.
Co-reporter:Xianfeng Li, Changpeng Liu, Hui Lu, Chengji Zhao, Zhe Wang, Wei Xing, Hui Na
Journal of Membrane Science 2005 Volume 255(1–2) pp:149-155
Publication Date(Web):15 June 2005
DOI:10.1016/j.memsci.2005.01.046
Novel sulfonated poly(ether ether ketone ketones) (SPEEKKs) based membranes have been prepared and evaluated for proton exchange membranes (PEMs). Directly aromatic and nucleophilic substituting polycondensation was adapted to control the sulfonated process. SPEEKKs with different sulfonated degrees were prepared by adjusting the content of sulfonated monomer. All the SPEEKKs can easily be cast into tough membranes and show high thermal stability. SPEEKKs membranes exhibit conductivities (25 °C) from 3.6 × 10−4 to 0.05 S/cm, (80 °C) from 0.001 to 0.06 S/cm; water swelling from 9.14 to 26.71%, ion-exchange capacities (IEC) from 0.63 to 1.57 mmol/g and methanol diffusion coefficients at 25 °C from 6.6 × 10−7 to 8.6 × 10−7 cm2/s. These diffusing coefficients are much lower than that of Nafion® (2 × 10−6 cm2/s) and make SPEEKK membranes with a good alternative that can reduce problems which associates with high methanol crossover in direct methanol fuel cells.
Co-reporter:Xianfeng Li;Chengji Zhao;Hui Lu;Zhe Wang;Wei Jiang
Journal of Applied Polymer Science 2005 Volume 98(Issue 6) pp:2481-2486
Publication Date(Web):29 SEP 2005
DOI:10.1002/app.22456
Novel sulfonated poly(ether ether ketone ketone)s were prepared directly by nucleophilic polycondensation. They showed excellent thermal stability and good solubility and could be easily cast into tough membranes. The sulfonated membranes showed swelling of 16.08–26.71% and an ion-exchange capacity of 1.01–1.57. The transport properties of different cations (H+, Na+, and K+) of membranes based on these polymers were evaluated. The potential for ion-exchange membranes looks good. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2481–2486, 2005
Co-reporter:Maria Gil, Xiangling Ji, Xianfeng Li, Hui Na, J. Eric Hampsey, Yunfeng Lu
Journal of Membrane Science 2004 Volume 234(1–2) pp:75-81
Publication Date(Web):1 May 2004
DOI:10.1016/j.memsci.2003.12.021
Proton exchange membrane fuel cells (PEMFC) are promising new power sources for vehicles and portable devices. Membranes currently used in PEMFC are perfluorinated polymers such as Nafion®. Even though such membranes have demonstrated good performances and long-term stability, their high cost and methanol crossover makes them unpractical for large-scale production. Sulfonated aromatic poly(ether ether ketones) (S-PEEKs) based membranes have been studied due to their good mechanical properties, thermal stability and conductivity. In this study, PEEK membranes directly prepared from the sulfonated monomer were evaluated for possible fuel cell applications by determining the degree of sulfonation, water swelling, proton conductivity, methanol diffusivity and thermal stability. As synthesized S-PEEK membranes exhibit conductivities (25 °C) from 0.02 to 0.07 S/cm, water swelling from 13 to 54%, ion-exchange capacities (IEC) from 0.7 to 1.5 meq/g and methanol diffusion coefficients from 3×10−7 to 5×10−8 cm2/s at 25 °C. These diffusion coefficients are much lower than that of Nafion® (2×10−6 cm2/s), making S-PEEK membranes a good alternative to reduce problems associated with high methanol crossover in direct methanol fuel cells.
Co-reporter:Hui Na;Xianfeng Li;Hui Lu
Journal of Applied Polymer Science 2004 Volume 94(Issue 4) pp:1569-1574
Publication Date(Web):20 SEP 2004
DOI:10.1002/app.20861
A series of sulfonated poly(ether ether ketone ketone)s derived from bisphenol S were prepared by nucleophilic polycondensation. They showed high thermal resistance and good solubility. Most of the polymers were easily cast into tough membranes. The swelling of the membranes (6.02–16.02%) was lower than that of Nafion membranes, and the ion-exchange capacity of the membranes (0.67–1.44) was higher than that of Nafion membranes. The proton conductivity of the membranes was 0.022–0.125 s/cm. They could be used as proton-exchange membranes in fuel cells. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1569–1574, 2004
Co-reporter:Cong Liu, Sinan Feng, Zhuang Zhuang, Duo Qi, Guibin Li, Chengji Zhao, Xuefeng Li and Hui Na
Chemical Communications 2015 - vol. 51(Issue 63) pp:NaN12632-12632
Publication Date(Web):2015/06/26
DOI:10.1039/C5CC03462K
We have developed basic ionic liquid-based hybrid membranes with ionic liquid modified zeolitic imidazolate frameworks (ZIFs) as fillers, aiming to enhance the electrochemical and physical properties of the membrane.
Co-reporter:Cong Liu, Gang Zhang, Chengji Zhao, Xuefeng Li, Mingyu Li and Hui Na
Chemical Communications 2014 - vol. 50(Issue 91) pp:NaN14124-14124
Publication Date(Web):2014/09/19
DOI:10.1039/C4CC05526H
The liquid nature of ionic liquids (ILs) limits their use in potential electrolytes due to the problem of leakage. Herein, we design a new strategy to immobilize an ionic liquid by incorporating it within ZIF-8 (ZIF = zeolitic imidazolate framework) by the ionothermal method.
Co-reporter:Dan Xu, Gang Zhang, Na Zhang, Hongtao Li, Yang Zhang, Ke Shao, Miaomiao Han, Christopher M. Lew and Hui Na
Journal of Materials Chemistry A 2010 - vol. 20(Issue 41) pp:NaN9245-9245
Publication Date(Web):2010/09/21
DOI:10.1039/C0JM02167A
A series of SPEEK/HPW/Ppy-n composite membranes with a sandwich structure were successfully prepared by surface modification with polypyrrole (Ppy) in order to stabilize phosphotungstic acid (HPW) in poly(ether ether ketone)s (SPEEKs) and reduce the methanol crossover. Ppy coatings with a large number of secondary ammonium groups (NH2+) interact with anions of HPW to decrease HPW leaching from the membrane. In addition, the hydrophobic Ppy layers allow for little methanol transport, which leads to a significant decline in methanol crossover with reasonable levels of proton conductivity. The properties of the membranes were investigated in detail by UV, SEM, ac impedance, and TGA. As observed, Ppy-modified membranes were better at immobilizing HPW and exhibited higher selectivities than previously reported SPEEK/HPW composite membranes. All the results indicate that the SPEEK/HPW/Ppy-n composite membranes are excellent candidates for direct methanol fuel cells.
Co-reporter:Miaomiao Han, Gang Zhang, Ke Shao, Hongtao Li, Yang Zhang, Mingyu Li, Shuang Wang and Hui Na
Journal of Materials Chemistry A 2010 - vol. 20(Issue 16) pp:NaN3252-3252
Publication Date(Web):2010/03/05
DOI:10.1039/B926354C
A carboxyl-terminated benzimidazole trimer was synthesized as a crosslinker by controlling the ratio of 3,3′-diaminobenzidine and isophthalic acid. Composite membranes were obtained by mixing the benzimidazole trimer and sulfonated poly(ether ether ketone) (SPEEK) together. Cross-linked membranes were obtained by heating the composite membranes at 160 °C. All of the properties of the cross-linked membranes were significantly increased, including proton conductivity, methanol permeability and water uptake due to the more compact structure compared to the non-cross-linked membranes. The cross-linked SPEEK-BI7 and cross-linked SPEEK-BI11 had excellent proton conductivities (0.22 and 0.19 S cm−1) at 80 °C, which were higher than that of Nafion 117 (0.125 S cm−1). Transmission electron microscopy (TEM) analysis revealed a clear microphase separated structure of cross-linked membranes. Other properties, such as thermal and mechanical stability, required for use as a proton exchange membrane (PEM) have been investigated. The cross-linked membranes showed improved properties over membranes without crosslinking.
Co-reporter:Jing Ni, Gang Zhang, Chengji Zhao, Hongtao Li, Tiezhu Fu, Ke Shao, Miaomiao Han, Jing Wang, Wenjia Ma and Hui Na
Journal of Materials Chemistry A 2010 - vol. 20(Issue 30) pp:NaN6358-6358
Publication Date(Web):2010/06/02
DOI:10.1039/C0JM00444H
Proton exchange membranes with high dimensional stabilities and low water uptakes were constructed by incorporating phosphotungstic acid (PWA) into a cross-linked network composed of a crosslinkable sulfonated poly(ether ether ketone) containing dipropenyl groups (SDPEEK) and γ-methacryloxypropyltrimethoxysilane (KH570). The chemical structures of the hybrid membranes were confirmed by FT-IR spectroscopy and scanning electron microscopy (SEM). The results indicated that PWA particles were well dispersed in these membranes. The influences of the dispersed PWA on the properties of membranes such as thermal stability, water uptake, swelling ratio, proton conductivity, methanol permeability and mechanical property were researched. The addition of KH570-5/PWA in the hybrid membranes contributed to the improvement of the dimensional stabilities. And the hybrid membranes with 10–40wt% PWA showed higher proton conductivities than Nafion 117 at 80 °C, while the methanol permeabilities of these membranes were much lower than that of Nafion 117. The membranes also exhibited excellent mechanical properties. These results imply that the SDPEEK/KH570-5/PWA-x membranes are promising materials in the direct methanol fuel cells (DMFC) applications.
Co-reporter:Miaomiao Han, Gang Zhang, Zhongguo Liu, Shuang Wang, Mingyu Li, Jing Zhu, Hongtao Li, Yang Zhang, Christopher M. Lew and Hui Na
Journal of Materials Chemistry A 2011 - vol. 21(Issue 7) pp:NaN2193-2193
Publication Date(Web):2010/12/20
DOI:10.1039/C0JM02443K
Cross-linked polybenzimidazole membranes were obtained by heating at 160 °C, using 4,4′-diglycidyl(3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP) as the cross-linker. The cross-linking reaction temperature was determined by DSC and the successful completion of the cross-linking reaction was shown by FTIR and solubility tests. The cross-linked membranes showed high proton conductivity and strong mechanical properties, as well as low swelling after immersion in 85% phosphoric acid at 90 °C. For instance, the membrane with a cross-linker content weight percent of 20% (PBI-TMBP 20%) with a PA doping level of 4.1 exhibited a proton conductivity of 0.010 S cm−1 and a low swelling volume of 50%. Moreover, the cross-linked membranes showed excellent oxidative stability. The PBI-TMBP 20% cross-linked membrane tested in Fenton's reagent (3% H2O2 solution, 4 ppm Fe2+, 70 °C) kept its shape for more than 480 h and did not break. In particular, the proton conductivity of the PA-PBI-TMBP 20% membrane after Fenton's test (30% H2O2, 20 ppm Fe2+, 85 °C) remained at a high level of 0.009 S cm−1. This investigation proved that cross-linking is a very effective approach for improving the performance of proton exchange membranes.
Co-reporter:Gang Zhang, Hongtao Li, Wenjia Ma, Liyuan Zhang, Christopher M. Lew, Dan Xu, Miaomiao Han, Yang Zhang, Jing Wu and Hui Na
Journal of Materials Chemistry A 2011 - vol. 21(Issue 14) pp:NaN5518-5518
Publication Date(Web):2011/02/24
DOI:10.1039/C0JM04385K
With the goal of reducing water swelling and methanol permeability in sulfonated proton exchange membranes (PEM), bromomethylated poly(ether ether ketone) was synthesized and used as a macromolecular cross-linker. The cross-linking reaction was performed at 195 °C for 5 h and resulted in cross-linked membranes with high cross-linked density. Compared to the pristine membrane, the cross-linked membranes displayed greatly reduced water uptake and methanol permeability. Other properties of the cross-linked membranes, including proton conductivity, mechanical properties, and oxidative stability, were also investigated and compared with the pristine membrane. All the results indicated that the novel macromolecular cross-linker and the resulting cross-linked membranes are promising for fuel cell applications.
Co-reporter:Shuai Xu, Gang Zhang, Yang Zhang, Chengji Zhao, Liyuan Zhang, Mingyu Li, Jing Wang, Na Zhang and Hui Na
Journal of Materials Chemistry A 2012 - vol. 22(Issue 26) pp:NaN13302-13302
Publication Date(Web):2012/05/30
DOI:10.1039/C2JM16593G
A series of novel poly(ether ether ketone) copolymers containing methyl groups on the side chain were prepared based on a new monomer (3,4-dimethyl)phenylhydroquinone. Then a series of hydroxide exchange membranes with different IEC values were obtained through bromination and quaternary amination of the copolymers. By adjusting the contents of methyl groups in the copolymers, we could control the final structures of the membranes. The chemical structures of the monomers and copolymers were analyzed by 1H NMR spectroscopy. After that, for the purpose of enhancing the dimensional stability and methanol resistance of the membrane, we prepared cross-linked membranes through a Friedel–Crafts reaction between bromomethyl groups and aromatic rings. The properties of the membranes related to fuel cell application were evaluated in detail. All the membranes showed good thermal and mechanical stabilities and conductivities. Moreover, the cross-linked membranes exhibit better dimensional stabilities and selectivities. Among those membranes, xPEEK–Q-100 showed a high conductivity (0.036 S cm−1 at 80 °C), a low swelling ratio of 6.6% and a methanol permeation coefficient of 2.9 × 10−7 cm2 s−1. The outstanding properties indicated that the application of PEEK–Q-xx membranes in fuel cells was promising.
Co-reporter:Shuang Wang, Chengji Zhao, Wenjia Ma, Na Zhang, Yurong Zhang, Gang Zhang, Zhongguo Liu and Hui Na
Journal of Materials Chemistry A 2013 - vol. 1(Issue 3) pp:NaN629-629
Publication Date(Web):2012/10/12
DOI:10.1039/C2TA00216G
Silane-cross-linked polybenzimidazole (PBI) membranes with high proton conductivity and excellent mechanical properties were successfully prepared by using a silane monomer, γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), as a cross-linker. Fourier transform infrared spectroscopy and solubility tests were used to characterize and confirm the cross-linked structure in the membranes. The silane-cross-linked membranes displayed excellent chemical stability and improved mechanical strength. Especially at high temperature (130 °C), where the tensile strength value was in the range of 68.6 to 99.3 MPa, while that of the pristine PBI was 61.7 MPa. Moreover, the proton conductivity was significantly enhanced because the silane-cross-linked structure in the membranes could absorb more phosphoric acid. Considering the tradeoff of mechanical properties and proton conductivity, 3% KH560 in weight was demonstrated to be the optimum content in the membranes, for instance, the SCPBI-3/7.95 PA (the cross-linker content was 3 wt% and the PA doping level was 7.95) had a proton conductivity of 0.081 S cm−1 and that of the SCPBI-3/9.07 PA was 0.114 S cm−1 at 200 °C, while that of pristine PBI was 0.015 S cm−1 at 200 °C.
Co-reporter:Na Zhang, Baolong Wang, Chengji Zhao, Shuang Wang, Yurong Zhang, Fanzhe Bu, Ying Cui, Xuefeng Li and Hui Na
Journal of Materials Chemistry A 2014 - vol. 2(Issue 34) pp:NaN14003-14003
Publication Date(Web):2014/07/02
DOI:10.1039/C4TA01931H
Quaternized poly(ether ether ketone)s (QPEEKs), which were aminated by trimethylamine (TMeA), triethylamine (TEtA), tripropylamine (TPrA) and 1-methylimidazole (MeIm), were prepared and used as phosphoric acid (PA)-doped high-temperature proton exchange membranes. These QPEEK membranes showed high glass transition temperature (Tg was higher than 483 K) and high thermal stability (T5% was higher than 486 K). The tensile strengths of these QPEEK membranes were higher than 60 MPa. The PA-doped im-QPEEK, which was aminated by MeIm, had the highest Wdoping (159 wt%) and proton conductivity (0.05 S cm−1 at 473 K). For the other three PA-doped QPEEK membranes, the Wdoping and proton conductivity decreased with the increase of the length of trialkyl side chains on quaternary ammonium groups. According to our study, the PA absorbing ability was subjected to the structures of quaternary ammonium groups instead of the basicities of quaternary aminating reagents. All PA-doped membranes had great oxidative stability and could last for more than 5 h in 3 wt% H2O2, 4 ppm Fe2+ Fenton solution at 353 K.
Co-reporter:Jing Ni, Chengji Zhao, Gang Zhang, Yang Zhang, Jing Wang, Wenjia Ma, Zhongguo Liu and Hui Na
Chemical Communications 2011 - vol. 47(Issue 31) pp:NaN8945-8945
Publication Date(Web):2011/06/28
DOI:10.1039/C1CC12430G
Novel self-crosslinked alkaline anion exchange membranes with high alkaline stability, excellent dimensional stability and extraordinary methanol resistance were synthesized successfully without using any catalyst or a separate crosslinker.
Co-reporter:Na Zhang, Baolong Wang, Yurong Zhang, Fanzhe Bu, Ying Cui, Xuefeng Li, Chengji Zhao and Hui Na
Chemical Communications 2014 - vol. 50(Issue 97) pp:NaN15384-15384
Publication Date(Web):2014/10/21
DOI:10.1039/C4CC07791A
Functionalized graphene oxide (FGO) reinforced quaternized poly(ether ether ketone) membranes were prepared for high temperature proton exchange membrane applications. The introduction of FGO significantly improved the mechanical strength and oxidative stability of these membranes at a high doping level. These reinforced membranes showed high tensile strength up to 40 MPa and high proton conductivity up to 58 mS cm−1 at 200 °C.
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