Co-reporter:Kui Li;Zhao Jin;Junjie Ge;Changpeng Liu
Journal of Materials Chemistry A 2017 vol. 5(Issue 37) pp:19857-19865
Publication Date(Web):2017/09/26
DOI:10.1039/C7TA06700C
Pt-based catalysts are considered as the most efficient and indispensable catalysts for methanol electro-oxidation reactions (MORs) in acidic media; however, issues linked to cost and stability impede their large-scale application. Here, we present a novel structured catalyst with Pt nanoparticles partially embedded in resorcinol-formaldehyde carbon spheres (Pt@RFC) towards MORs. Pt@RFC exhibits excellent CO-tolerance and MOR activity, and specifically, the CO electro-oxidation peak-potential is negatively shifted by ∼150 mV and the electrocatalytic activity is 2 times that of commercial Pt/C. These enhancements are due to the endowed high Pt utilization (decreased particle size) from strong metal-support interaction and the decorated electronic properties. Moreover, the firmly anchored Pt nanoparticles are prevented from possible dissolution, agglomeration and detachment during long-term use. Remarkably, after an accelerated degradation test through a 3000 cycle cyclic voltammetry test, the mass activity for Pt@RFC is well maintained and 5.8 times that of the commercial Pt/C. Upon integration into a DMFC, Pt@RFC (58.5 mW cm−2) exhibits a competitive power density at 60 °C compared to a commercial PtRu/C catalyst (52.3 mW cm−2) with only 1/3 of the noble metal loading, as well as a slower degradation rate during discharge testing. The present findings indicate that Pt@RFC might be a viable alternative as a commercial catalyst applied in DMFCs.
Co-reporter:Ergui Luo;Meiling Xiao;Junjie Ge;Changpeng Liu
Journal of Materials Chemistry A 2017 vol. 5(Issue 41) pp:21709-21714
Publication Date(Web):2017/10/24
DOI:10.1039/C7TA07608H
Developing cost-effective and highly efficient oxygen reduction electrocatalysts, such as non-precious metal and metal-free catalysts, is undoubtedly crucial for the commercialization of low-temperature fuel cells. Here, edge-rich nitrogen doped porous carbon catalysts for the oxygen reduction reaction (ORR) with a high proportion of pyridinic and pyrrolic N (up to 94%) were synthesized by an in situ released CO2 activation method, using glucose and melamine as precursors and nano-CaCO3 as the template. The catalysts exhibit a three-dimensional structure, hierarchical pores and large pore volumes. Benefiting from the increased active site density and structural advantage, the optimized catalyst shows excellent ORR activity with a half-wave potential of 0.853 V and long-term stability in alkaline media, which is among the best for metal-free catalysts reported to date.
Co-reporter:Jinfa Chang, Qing Lv, Guoqiang Li, Junjie Ge, Changpeng Liu, Wei Xing
Applied Catalysis B: Environmental 2017 Volume 204(Volume 204) pp:
Publication Date(Web):5 May 2017
DOI:10.1016/j.apcatb.2016.11.050
•A novel core-shell structured Ni12P5/Ni3(PO4)2 hollow spheres was successfully fabricated.•The Ni12P5/Ni3(PO4)2 hollow spheres exhibited excellent electrochemical performance as bifunctional electrocatalyst material for HER and OER.•The Ni12P5/Ni3(PO4)2 hollow spheres generates a current density of 357.6 mA cm−2 at 1.8 V and stable at 300 mA cm−2 for at least 100 h.•The potential catalytic degradation mechanism has been systematically studied and discussed.Non-precious metal catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are the cost-effective materials for overall water splitting. Here, we report that the core-shell structured Ni12P5/Ni3(PO4)2 hollow spheres (Ni12P5/Ni3(PO4)2-HS) exhibits high activity and stability towards both HER and OER in strong alkaline media. A current density of 10 mA cm−2 is generated at an overpotential of 0.114 V and 0.318 V in 1 M KOH for HER and OER, respectively. The high activity is attributed to the hollow core-shell (Ni12P5/Ni3(PO4)2) structure that the material adopts under catalytic conditions. The Ni12P5/Ni3(PO4)2-HS can serve as both cathode and anode catalysts for a real water electrolysis cell, which generates a current density of 357.6 mA cm−2 at 1.8 V and stable at 300 mA cm−2 for at least 100 h, the potential catalytic degradation mechanism has been systematically studied and discussed.Core-shell structured Ni12P5/Ni3(PO4)2 hollow spheres (Ni12P5/Ni3(PO4)2-HS) was prepared and found to be an effective and robust catalyst material for OER and HER in basic solution. When integrated into a practical water electrolyzer (WE) using Ni12P5/Ni3(PO4)2-HS as anode as well as cathode catalyst with alkaline membrane as electrolyte, the current density reached 357.6 mA cm−2 at 1.8 V, which is rather competitive to the state-of-the-art Pt/IrO2 catalyst at much lower cost. Thus, the current material is promising to simplify water splitting devices and promote mass production of WEs.Download high-res image (172KB)Download full-size image
Co-reporter:Long Yang, Junjie Ge, Changpeng Liu, Guiling Wang, Wei Xing
Current Opinion in Electrochemistry 2017 Volume 4, Issue 1(Volume 4, Issue 1) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.coelec.2017.10.018
•Alloy with high-index facets catalyst.•Core–shell structure catalyst.•Non-Pt catalyst apply in anode methanol oxidation reaction.Fuel cells are promising energy conversion devices which do not require the electrical charging process in comparison with a traditional secondary battery. Polymer electrolyte membrane fuel cells (PEMFCs), including direct methanol fuel cells (DMFCs), are the key technologies in the future due to the high energy conversion efficiency, low emission, and high energy density. DMFCs are promising to be used in mobile electronic devices (power under a few hundred watts) due to the easily and safely transport feature of methanol. Platinum is regarded as the most effective catalyst for the methanol oxidation reaction (MOR). However, the poor performance and the high cost of Pt block the DMFC large-scale applications. The essential method to overcome this shortfall is to develop effective modified-Pt, low-Pt and non-Pt catalysts. This short review paper will focus on the solution to improve the performance of anode MOR in the past 2 years. The structure of this article displays in Figure 1.
Co-reporter:Na Sun;Minglei Wang;Jinfa Chang;Junjie Ge
Frontiers in Energy 2017 Volume 11( Issue 3) pp:310-317
Publication Date(Web):19 August 2017
DOI:10.1007/s11708-017-0491-5
Pd nanoparticles supported on nitrogen doped carbon black (Vulcan XC-72R) with two different levels of doping were prepared by the microwave-assisted ethylene glycol reduction process and used as catalyst for the formic acid electro-oxidation (FAEO). The results indicate that the different nitrogen doping contents in Pd/N-C catalysts have a significant effect on the performance of FAEO. A higher N content facilitates the uniform dispersion of Pd nanoparticles on carbon black with narrow particle size distribution. Furthermore, the electrochemical results show that the catalyst with a higher N-doping content possesses a higher catalytic activity and a long-term stability for FAEO. The peak current density of the Pd/N-C (high) catalyst is 1.27 and 2.31 times that of the Pd/N-C (low) and homemade Pd/C-H catalyst. The present paper may provide a simple method for preparation of high-performance anode catalyst for direct formic acid fuel cells (DFAFCs).
Co-reporter:Jinfa Chang, Liang Liang, Chenyang Li, Minglei Wang, Junjie Ge, Changpeng Liu and Wei Xing
Green Chemistry 2016 vol. 18(Issue 8) pp:2287-2295
Publication Date(Web):08 Jan 2016
DOI:10.1039/C5GC02899J
Low-temperature electricity-driven water splitting is an established technology for hydrogen production, yet only few materials are able to catalyze hydrogen and oxygen evolution reactions in the same medium. Herein, ultrathin CoP nanosheets (CoP NS) as durable bifunctional catalysts for electrochemical water splitting are reported. The OER and HER activity for CoP NS/C reaching 10 mA cm−2 needs an overpotential of only 0.277 V and 0.111 V in a basic solution. What's more, when integrated into a practical anion exchange membrane water electrolysis cell using CoP NS as both anode and cathode catalysts, a current density of 335 mA cm−2 at 1.8 V is achieved, which is rather competitive to the state-of-the-art Pt/IrO2 catalyst. This work would open a new avenue to explore the use of transition metal phosphides as green and attractive bifunctional catalysts toward mass production of hydrogen fuel for applications.
Co-reporter:Jianbing Zhu, Meiling Xiao, Yelong Zhang, Zhao Jin, Zhangquan Peng, Changpeng Liu, Shengli Chen, Junjie Ge, and Wei Xing
ACS Catalysis 2016 Volume 6(Issue 10) pp:6335
Publication Date(Web):August 10, 2016
DOI:10.1021/acscatal.6b01503
Rational design of electrocatalysts to replace the noble-metal-based materials for oxygen reactions is highly desirable but challenging for rechargeable metal–air batteries. Herein, we demonstrate a unique two stage encapsulation strategy to regulate the structure and performance of catalysts featured with thin graphene nanosheets coupling with full encapsulated ultrafine and high-loaded (∼25 wt %) transition metal nanoparticles (TMs@NCX) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). By optimizing the electronic modulation effect from suitable metal cores, the best NiFe@NCX catalyst exhibits high stability and activity with an onset potential of 1.03 V for ORR and an overpotential of only 0.23 V at 10 mA cm–2 for OER, which is superior to commercial Pt/C and IrO2 catalysts. Rechargeable Zn–air battery using NiFe@NCX catalyst exhibited an unprecedented small charge–discharge overpotential of 0.78 V at 50 mA cm–2, high reversibility, and stability, holding great promise for the practical implementation of rechargeable metal–air batteries.Keywords: bifunctional electrocatalyst; electronic structure; metal−organic framework; non-noble metal; rechargeable Zn−air battery
Co-reporter:Jianbing Zhu, Kai Li, Meiling Xiao, Changpeng Liu, Zhijian Wu, Junjie Ge and Wei Xing
Journal of Materials Chemistry A 2016 vol. 4(Issue 19) pp:7422-7429
Publication Date(Web):05 Apr 2016
DOI:10.1039/C6TA02419J
Developing highly active non-noble metal oxygen reduction reaction (ORR) catalysts is crucial for a variety of renewable energy applications including fuel cells and metal–air batteries. Heteroatom doped carbon materials, known as metal-free catalysts, show potential applications in the ORR, and may be promising replacement candidates for expensive, scarce platinum catalysts. Despite the inspiring progress made, the performance of the current metal-free carbon catalysts is still far from satisfactory for large-scale applications. Herein, we introduce an effective and robust ORR catalyst based on N, S co-doped carbon materials with abundant surface active sites. Electrochemical results indicate that the incorporation of sulfur into nitrogen-doped carbon (S-NCx) can dramatically improve the stability of the catalyst by improving the selectivity of O2 electro-reduction to H2O. Density functional theory calculations reveal that sulfur doping lowers the energy barrier of O2(ads) hydrogenation to form OOH(ads), thus leading to enhanced intrinsic activity. In particular, the correlation between ORR activity and nitrogen and sulfur species in these materials is studied in-depth, and it is found the ORR performance of S-NCx catalysts is significantly affected by pyridinic N and C–S–C contents.
Co-reporter:Jinfa Chang, Songtao Li, Guoqiang Li, Junjie Ge, Changpeng Liu and Wei Xing
Journal of Materials Chemistry A 2016 vol. 4(Issue 25) pp:9755-9759
Publication Date(Web):01 Jun 2016
DOI:10.1039/C6TA03481K
Monocrystalline Ni12P5 hollow spheres with ultrahigh specific surface areas were prepared by a water-in-oil microemulsion method. The novel structured Ni12P5 catalyst exhibited excellent catalytic activity and stability towards the hydrogen evolution reaction in acidic solutions.
Co-reporter:Jianbing Zhu, Meiling Xiao, Kui Li, Changpeng Liu, Xiao Zhao, and Wei Xing
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 44) pp:30066
Publication Date(Web):October 13, 2016
DOI:10.1021/acsami.6b04237
Highly active, durable oxygen reduction reaction (ORR) electrocatalysts are extremely important for fuel cell applications. Herein, we provide an efficient way to synthesis of activity Pt3M icosahedra by the one-pot hydrothermal method in the presence of glucosamine which can well adjust the reduction rate of Pt4+ and efficiently control the morphology of final catalysts. Compared to Pt/C, the Pt3Ni icosahedra show 32-fold and 12-fold enhancement in specific and mass activity, respectively. Furthermore, robust durability was also observed in the accelerated durability test. Thus, this Pt3Ni icosahedron is found among the best Pt-based ORR catalysts, moreover, the findings also demonstrate how to mimic active extended surfaces in nanoscale.Keywords: core−shell; hydrothermal method; icosahedrons; oxygen reduction reaction; Pt3M
Co-reporter:Qing Lv, Kui Li, Changpeng Liu, Junjie Ge, Wei Xing
Carbon 2016 Volume 98() pp:126-137
Publication Date(Web):March 2016
DOI:10.1016/j.carbon.2015.10.097
Commercially available carbon black is a widely applied support material for nanocatalysts but notorious for its microporous structure, which is deleterious for catalysts utilization in the fuel cell application and causes numerable problems in other application areas. The development of mesoporous carbon as a substitute was proved successful but not scalable due to their intrinsic complex synthesis. In this work, we demonstrate a new perspective to circumvent the problem through blocking the micropores of carbon black by the in-situ formed TiO2 nano/sub-nano particles. A decompression absorption method was developed where tetrabutyl titanate was pressurized into carbon pores with diameter <3 nm, succeeded by hydrolysis and calcination to form the TiO2 inserted commercial carbon black, such as BP2000 and Vulcan XC-72. The TiO2–C hybrid material with reduced micropore volume was found an excellent support for noble catalysts, such as Pt and Pd nanoparticles, where their insertion into carbon micropores during synthesis were prevented, thus leading to improved metal utilization. The TiO2–C supported catalysts exhibited much superior activity and stability for methanol or formic acid electrooxidation in comparison to the plain carbon black. This work also demonstrated the negative effects of micropores in carbon support.
Co-reporter:Yao Xiao, Junjie Ge, Meiling Xiao, Vladimir Fateev, Changpeng Liu, Wei Xing
Electrochimica Acta 2016 Volume 209() pp:551-556
Publication Date(Web):10 August 2016
DOI:10.1016/j.electacta.2016.05.121
•Nitrogen, Iron-codoped Ordered Mesoporous Carbon with bimodal-pores (NFe-OMC) was synthesized using a soft template method.•NFe-OMC has extremely high surface area and tunable pore structure.•NFe-OMC exhibited significantly enhanced electrocatalytic activity for ORR and a 4-electron process was shown in domination of the ORR, indicating the direct reduction of O2 to H2O.•The high surface area and structure advantage of NFe-OMC appear to contribute concomitantly to the enhanced performance.Nitrogen, iron-codoped ordered mesoporous carbon (NFe-OMC) with bimodal-pores and extremely high BET area was fabricated and investigated as non-platinum catalysts for oxygen reduction reaction (ORR). The catalysts show significantly enhanced electrocatalytic activity for ORR in comparison to the doped commercial carbon black. A 4-electron process was shown in domination of the ORR, indicating the direct reduction of O2 to H2O. Moreover, the stability of the catalyst was comparable to the state-of-the-art Pt catalyst, which renders it a promising replacement for Pt. The increase in activity was ascribed to the increase in active site density and more importantly, the increase in activity per active site, which is due to the advanced pore structure of OMCs and the possible desolvation process of O2 in the micropores.Nitrogen, iron-codoped ordered mesoporous carbon (NFe-OMC) with bimodal-pores and extremely high BET area was fabricated and investigated as non-platinum catalysts for oxygen reduction reaction (ORR). The catalysts show significantly enhanced electrocatalytic activity for ORR in comparison to the doped commercial carbon black. A 4-electron process was shown in domination of the ORR, indicating the direct reduction of O2 to H2O. Moreover, the stability of the catalyst was comparable to the state-of-the-art Pt catalyst, which renders it a promising replacement for Pt. The increase in activity was ascribed to the increase in active site density and more importantly, the increase in activity per active site, which is due to the advanced pore structure of OMCs and the possible desolvation process of O2 in the micropores.
Co-reporter:Weiwei Cai, Jing Li, Yao Jiang, Changpeng Liu, Liang Ma, Wei Xing
Journal of Electroanalytical Chemistry 2016 Volume 761() pp:68-73
Publication Date(Web):15 January 2016
DOI:10.1016/j.jelechem.2015.12.021
•FA electro-oxidation mechanism at fuel cell operation temperature is studied.•Supporting electrolyte free system is used for the electrochemical measurements.•FA decomposition on Pd at high temperature will suppress the electro-oxidation.•Inviting Pt will further change the FA electro-oxidation mechanism.As a potential fuel for proton exchange membrane fuel cell, formic acid (FA) is easily decomposed on palladium (Pd) based catalysts, which are also the most effective and commonly used FA electro-oxidation catalysts in the direct formic acid fuel cell (DFAFC). Here we try to study the interaction between these two reactions in a supporting electrolyte free electrochemical cell. Considering the operation condition in the anode of DFAFC, influence of FA decomposition on FA electro-oxidation is detected and confirmed by mechanistic study. By doping platinum (Pt) into Pd, stability of the FA electro-oxidation can be extremely improved at fuel cell operation temperature.
Co-reporter:Jinfa Chang, Yao Xiao, Meiling Xiao, Junjie Ge, Changpeng Liu, and Wei Xing
ACS Catalysis 2015 Volume 5(Issue 11) pp:6874
Publication Date(Web):October 16, 2015
DOI:10.1021/acscatal.5b02076
Electrochemical water splitting in alkaline solution plays a growing role in alternative energy devices due to the need for clean and sustainable energy. However, catalysts that are active for both hydrogen evolution and oxygen evolution reactions are rare. Herein, we demonstrate that cobalt phosphide (CoP), which was synthesized via the hydrothermal route and has been shown to have hydrogen evolution activity, is highly active for oxygen evolution. A current density of 10 mA cm–2 was generated at an overpotential of only 320 mV in 1 M KOH for a CoP nanorod-based electrode (CoP NR/C), which was competitive with commercial IrO2. The Tafel slope for CoP NR/C was only 71 mV dec–1, and the catalyst maintained high stability during a 12 h test. This high activity was attributed to the formation of a thin layer of ultrafine crystalline cobalt oxide on the CoP surface.Keywords: cobalt phosphide; electrocatalysts; nanorods; oxygen evolution reaction (OER); water splitting
Co-reporter:Meiling Xiao, Ligang Feng, Jianbing Zhu, Changpeng Liu and Wei Xing
Nanoscale 2015 vol. 7(Issue 21) pp:9467-9471
Publication Date(Web):30 Apr 2015
DOI:10.1039/C5NR00639B
A rapid strategy to synthesize a highly active PtRu alloy nano-sponge catalyst system for methanol electro-oxidation is presented. The greatly increased Pt utilization, anti-CO poisoning ability and electronic effect resulting from the porous nano-sponge structure could account for the performance improvement.
Co-reporter:Yang Hu, Jens Oluf Jensen, Wei Zhang, Santiago Martin, Régis Chenitz, Chao Pan, Wei Xing, Niels J. Bjerrum and Qingfeng Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 4) pp:1752-1760
Publication Date(Web):21 Nov 2014
DOI:10.1039/C4TA03986F
We present a detailed study of a novel Fe3C-based spherical catalyst with respect to synthetic parameters, nanostructure formation, ORR active sites and fuel cell demonstration. The catalyst is synthesized by high-temperature autoclave pyrolysis using decomposing precursors. Below 500 °C, melamine-rich microspheres are first developed with uniformly dispersed amorphous Fe species. During the following pyrolysis at temperatures from 600 to 660 °C, a small amount of Fe3C phase with possible Fe–Nx/C active sites are formed, however, with moderate catalytic activity, likely limited by the low conductivity of the catalyst. At high pyrolytic temperatures of 700–800 °C, simultaneous formation of Fe3C nanoparticles and encasing graphitic layers occur within the morphological confinement of the microspheres. With negligible surface nitrogen or iron functionality, the thus-obtained catalysts exhibit superior ORR activity and stability. A new ORR active phase of Fe3C nanoparticles encapsulated by thin graphitic layers is proposed. The activity and durability of the catalysts are demonstrated in both Nafion-based low temperature and acid doped polybenzimidazole-based high temperature proton exchange membrane fuel cells.
Co-reporter:Shikui Yao, Guoqiang Li, Changpeng Liu, Wei Xing
Journal of Power Sources 2015 Volume 284() pp:355-360
Publication Date(Web):15 June 2015
DOI:10.1016/j.jpowsour.2015.02.056
•Pd/C for formic acid electrooxidation is synthesized by in-situ method from PdO/C.•The synthesized Pd/C shows smaller particle size as Ostwald ripening is limited.•The Pd/C shows enhanced performance towards formic acid electrooxidation.The development of facile, surfactant-free strategy for the scale-up production of catalysts with superior performance for energy science is an interesting challenge. Pd/C is synthesized using an in-situ method from PdO/C for formic acid electrooxidation based on the reducibility of formic acid. The morphology, composition and electrocatalytic properties are investigated using transmission electronmicroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, linear scan voltammograms (LSV) and chronoamperometry. The in-situ synthesized Pd nanoparticles show better distribution and smaller average particle size than the normally synthesized Pd/C, which indicates that the well-known Ostwald ripening is most limited in the synthesis process. The electrochemical measurements show that the Pd/C catalyst exhibits enhanced performance towards formic acid electrooxidation. For example, the peak current of the Pd/C catalyst is approximately three times that of the homemade Pd/C catalyst and twice as high as that of the commercial Pd/C catalyst in the LSV test. The in-situ synthesized Pd/C catalyst has potential application for direct formic acid fuel cells, and the in-situ route should be an effective strategy to synthesize high performance catalysts.
Co-reporter:Qing Lv, Ligang Feng, Chaoquan Hu, Changpeng Liu and Wei Xing
Catalysis Science & Technology 2015 vol. 5(Issue 5) pp:2581-2584
Publication Date(Web):05 Mar 2015
DOI:10.1039/C5CY00245A
High-quality hydrogen can be generated from formic acid triggered by facilely in situ prepared Pd/C catalyst in ambient conditions. The obtained gas can be directly fed into proton exchange membrane fuel cells indicating a very promising application.
Co-reporter:Yao Xiao, Ligang Feng, Chaoquan Hu, Vladimir Fateev, Changpeng Liu and Wei Xing
RSC Advances 2015 vol. 5(Issue 76) pp:61900-61905
Publication Date(Web):20 Jul 2015
DOI:10.1039/C5RA08848H
Water electrolysis plays a fundamental role in the development of a sustainable energy system. In practice the efficiency of water electrolysis is severely limited by the sluggish kinetics of the oxygen evolution reaction. We reported a kind of integrated 3 dimensional oxygen evolution reactions (OER) catalyst by growing NiCo2O4 nanosheet arrays directly on conductive substrates. Such self-supported NiCo2O4 nanosheet electrodes exhibit high catalytic activity, good durability and nearly 100% faradic efficiency (FE) in alkaline electrolyte due to the enlarged electrochemical surface area and reduced electron transference resistance.
Co-reporter:Ligang Feng, Kui Li, Jinfa Chang, Changpeng Liu, Wei Xing
Nano Energy 2015 Volume 15() pp:462-469
Publication Date(Web):July 2015
DOI:10.1016/j.nanoen.2015.05.007
•Nanostructured PtRu catalyst for methanol oxidation is greatly promoted by CoP.•The presence of CoP could largely slow down the loss of Ru and Pt in fuel cells.•The catalytic activity is increased about 3–4 times owing to CoP.•A maximum power density of 85.7 mW cm−2 was achieved at 30 °C.Nanostructured PtRu material is considered as the best catalyst for direct methanol fuel cells (DMFCs), but the performance decay resulting from Ru loss seriously hinders the commercial application. Here we demonstrated that the performance of nanostructured PtRu catalyst for methanol oxidation could be significantly improved by CoP material; the presence of CoP could largely slow down the loss of Ru and Pt in PtRu catalyst system, thus promising a highly active and durable performance in DMFCs. Cyclic Voltammetry results showed the peak current is 2.89 times higher than that of state-of-the-art commercial PtRu/C–JM (231.9 mA mg−1PtRu) and 3.86 times higher than that of the home-made reference (PtRu/C–H) catalyst (173.6 mA mg−1PtRu); kinetics study probed by electrochemical impedance spectroscopy showed a large reduced charge transfer resistance in the rate determining step. The highest maximum power density was achieved on this novel PtRu–CoP/C catalyst among all the evaluated catalysts at different temperatures. Specifically, a maximum power density of 85.7 mW cm−2 achieved at 30 °C is much higher than that of state-of-the-art commercial PtRu/C catalyst at 70 °C (63.1 mW cm−2). Outstanding catalytic activity and stability observed on this novel PtRu–CoP/C catalyst should be attributed to a synergistic effect between the nanostructured PtRu and CoP, in which the presence of CoP increases PtRu physical stability and anti-CO poisoning ability. The present work is a significant step that opens an avenue in the development of highly active and durable catalysts for fuel cells technology, and makes PtRu catalyst system much closer for commercial application in DMFCs.The performance of nanostructured PtRu catalyst for methanol oxidation could be significantly improved by CoP material; the presence of CoP could largely slow down the loss of Ru and Pt in PtRu catalyst system, thus promising a highly active and durable performance in DMFCs
Co-reporter:Yuwei Zhang, Zhiguang Zhang, Wei Chen, Changpeng Liu, Wei Xing, Suobo Zhang
Journal of Power Sources 2014 Volume 258() pp:5-8
Publication Date(Web):15 July 2014
DOI:10.1016/j.jpowsour.2014.01.016
•Proton resistance increased due to phase separation at different polymer interface.•Phase separation is adverse to proton transfer process between different polymers.•Continuous distribution of polymer is needed for good proton conduction.The proton conductivity at the interface of Nafion and sulfonated polypyrrolone composite membrane decreases by 56% from 0.039 S cm−1 to 0.017 S cm−1, due to phase separation after annealing this binary composite membrane at 140 °C, which is 10 °C above the glass transition temperature of Nafion polymer. After annealing the membrane, the change in the relative intensity of the lower angles of the X-ray diffraction (XRD) peaks located at ca. 11.9°, 17.5° and 19.7° indicates an increase of the low spacing region for the polymer chains of the composite membrane and atomic force microscopy (AFM) measurement depicts a morphological evolution from an uniform dispersion to a spherules micro-structure, implying the aggregation of polymer chains of the annealed composite membrane. These results are combined to reveal there is a microphase separation of this binary composite membrane as it is annealed at 140 °C.
Co-reporter:Shikui Yao, Guoqiang Li, Meiling Xiao, Junjie Ge, Changpeng Liu and Wei Xing
RSC Advances 2014 vol. 4(Issue 101) pp:57819-57822
Publication Date(Web):29 Oct 2014
DOI:10.1039/C4RA11121D
A Pd sub-layer on a Pt substrate is fabricated stoichiometrically using chemisorbed CO as an in situ reductant. The Pd sub-layer of the Pd@Pt/C catalysts exhibits a more negative oxidation peak and 3 times higher mass activity for formic acid oxidation than commercial Pd/C.
Co-reporter:M.Sc. Yang Hu;Dr. Jens Oluf Jensen;Dr. Wei Zhang;Dr. Lars N. Cleemann; Wei Xing; Niels J. Bjerrum;Dr. Qingfeng Li
Angewandte Chemie 2014 Volume 126( Issue 14) pp:
Publication Date(Web):
DOI:10.1002/ange.201401098
Co-reporter:Kui Li;Jianbing Zhu;Meiling Xiao;Dr. Xiao Zhao;Shikui Yao;Dr. Changpeng Liu;Dr. Wei Xing
ChemCatChem 2014 Volume 6( Issue 12) pp:3387-3395
Publication Date(Web):
DOI:10.1002/cctc.201402478
Abstract
Vanadium carbide incorporated on resorcinol–formaldehyde resin carbon (V8C7@RFC) was synthesized as a novel mesoporous catalyst-support material by pyrolysis of the resorcinol–formaldehyde resin and NaVO3 mixture. The material’s BET surface area was 564 m2 g−1 and thus much higher than that of 389 m2 g−1 for the carbon powders yielded by resin carbonation. Physical characterization revealed that the supporting material possesses a mesoporous structure and Pt nanoparticles are homogeneously dispersed on the V8C7@RFC surface. Electrochemical measurements demonstrated that the V8C7-modified Pt catalyst exhibits a negative shift of over 100 mV in the onset potential for COads electrooxidation and a dramatically enhanced activity in methanol oxidation reaction. The enhancement was mainly attributed to the electronic effect between Pt and V8C7 and the mesoporous structure providing ideal anchor sites for Pt dispersion.
Co-reporter:Yang Hu;Dr. Jens Oluf Jensen;Dr. Wei Zhang;Dr. Yunjie Huang;Dr. Lars N. Cleemann; Wei Xing; Niels J. Bjerrum;Dr. Qingfeng Li
ChemSusChem 2014 Volume 7( Issue 8) pp:2099-2103
Publication Date(Web):
DOI:10.1002/cssc.201402183
Abstract
We present a novel approach to direct fabrication of few-layer graphene sheets with encapsulated Fe3C nanoparticles from pyrolysis of volatile non-graphitic precursors without any substrate. This one-step autoclave approach is facile and potentially scalable for production. Tested as an electrocatalyst, the graphene-based composite exhibited excellent catalytic activity towards the oxygen reduction reaction in alkaline solution with an onset potential of ca. 1.05 V (vs. the reversible hydrogen electrode) and a half-wave potential of 0.83 V, which is comparable to the commercial Pt/C catalyst.
Co-reporter:M.Sc. Yang Hu;Dr. Jens Oluf Jensen;Dr. Wei Zhang;Dr. Lars N. Cleemann; Wei Xing; Niels J. Bjerrum;Dr. Qingfeng Li
Angewandte Chemie International Edition 2014 Volume 53( Issue 14) pp:3675-3679
Publication Date(Web):
DOI:10.1002/anie.201400358
Abstract
Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low-temperature fuel cells. A novel type of catalysts prepared by high-pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide-based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts.
Co-reporter:M.Sc. Yang Hu;Dr. Jens Oluf Jensen;Dr. Wei Zhang;Dr. Lars N. Cleemann; Wei Xing; Niels J. Bjerrum;Dr. Qingfeng Li
Angewandte Chemie International Edition 2014 Volume 53( Issue 14) pp:
Publication Date(Web):
DOI:10.1002/anie.201401098
Co-reporter:M.Sc. Yang Hu;Dr. Jens Oluf Jensen;Dr. Wei Zhang;Dr. Lars N. Cleemann; Wei Xing; Niels J. Bjerrum;Dr. Qingfeng Li
Angewandte Chemie 2014 Volume 126( Issue 14) pp:3749-3753
Publication Date(Web):
DOI:10.1002/ange.201400358
Abstract
Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low-temperature fuel cells. A novel type of catalysts prepared by high-pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide-based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts.
Co-reporter:Jinfa Chang, Ligang Feng, Kun Jiang, Huaiguo Xue, Wen-Bin Cai, Changpeng Liu and Wei Xing
Journal of Materials Chemistry A 2016 - vol. 4(Issue 47) pp:NaN18613-18613
Publication Date(Web):2016/11/09
DOI:10.1039/C6TA07896F
PtRu/C material is one of the most well-known and efficient anode catalysts in direct methanol fuel cells. Nevertheless, new anode catalysts with even higher performance and lower cost are highly demanded for the further development of this fuel cell technology. Herein, we present a CoP-promoted Pt catalyst as a highly active, anti-poisoning and low-Pt loading catalyst for direct methanol fuel cells (DMFCs). The in situ attenuated total reflection surface-enhanced infrared radiation absorption spectroscopy (ATR-SEIRAS) technique revealed that the presence of CoP in the Pt-based catalyst can promote the methanol oxidation to CO2. A maximum power density of 88.5 mW cm−2 is achieved on a fuel cell based on this novel anode catalyst, which is ca. 1.4 times as high as that based on the state-of-the-art commercial PtRu/C catalyst with the same Pt loading. The present work demonstrates that the Pt–CoP/C will be a very competitive alternative to PtRu/C as the promising anode catalyst for the scale-up production of DMFCs in terms of overall performance and cost effectiveness.
Co-reporter:Yang Hu, Jens Oluf Jensen, Wei Zhang, Santiago Martin, Régis Chenitz, Chao Pan, Wei Xing, Niels J. Bjerrum and Qingfeng Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 4) pp:NaN1760-1760
Publication Date(Web):2014/11/21
DOI:10.1039/C4TA03986F
We present a detailed study of a novel Fe3C-based spherical catalyst with respect to synthetic parameters, nanostructure formation, ORR active sites and fuel cell demonstration. The catalyst is synthesized by high-temperature autoclave pyrolysis using decomposing precursors. Below 500 °C, melamine-rich microspheres are first developed with uniformly dispersed amorphous Fe species. During the following pyrolysis at temperatures from 600 to 660 °C, a small amount of Fe3C phase with possible Fe–Nx/C active sites are formed, however, with moderate catalytic activity, likely limited by the low conductivity of the catalyst. At high pyrolytic temperatures of 700–800 °C, simultaneous formation of Fe3C nanoparticles and encasing graphitic layers occur within the morphological confinement of the microspheres. With negligible surface nitrogen or iron functionality, the thus-obtained catalysts exhibit superior ORR activity and stability. A new ORR active phase of Fe3C nanoparticles encapsulated by thin graphitic layers is proposed. The activity and durability of the catalysts are demonstrated in both Nafion-based low temperature and acid doped polybenzimidazole-based high temperature proton exchange membrane fuel cells.
Co-reporter:Jinfa Chang, Songtao Li, Guoqiang Li, Junjie Ge, Changpeng Liu and Wei Xing
Journal of Materials Chemistry A 2016 - vol. 4(Issue 25) pp:NaN9759-9759
Publication Date(Web):2016/06/01
DOI:10.1039/C6TA03481K
Monocrystalline Ni12P5 hollow spheres with ultrahigh specific surface areas were prepared by a water-in-oil microemulsion method. The novel structured Ni12P5 catalyst exhibited excellent catalytic activity and stability towards the hydrogen evolution reaction in acidic solutions.
Co-reporter:Qing Lv, Ligang Feng, Chaoquan Hu, Changpeng Liu and Wei Xing
Catalysis Science & Technology (2011-Present) 2015 - vol. 5(Issue 5) pp:NaN2584-2584
Publication Date(Web):2015/03/05
DOI:10.1039/C5CY00245A
High-quality hydrogen can be generated from formic acid triggered by facilely in situ prepared Pd/C catalyst in ambient conditions. The obtained gas can be directly fed into proton exchange membrane fuel cells indicating a very promising application.
Co-reporter:Jianbing Zhu, Kai Li, Meiling Xiao, Changpeng Liu, Zhijian Wu, Junjie Ge and Wei Xing
Journal of Materials Chemistry A 2016 - vol. 4(Issue 19) pp:NaN7429-7429
Publication Date(Web):2016/04/05
DOI:10.1039/C6TA02419J
Developing highly active non-noble metal oxygen reduction reaction (ORR) catalysts is crucial for a variety of renewable energy applications including fuel cells and metal–air batteries. Heteroatom doped carbon materials, known as metal-free catalysts, show potential applications in the ORR, and may be promising replacement candidates for expensive, scarce platinum catalysts. Despite the inspiring progress made, the performance of the current metal-free carbon catalysts is still far from satisfactory for large-scale applications. Herein, we introduce an effective and robust ORR catalyst based on N, S co-doped carbon materials with abundant surface active sites. Electrochemical results indicate that the incorporation of sulfur into nitrogen-doped carbon (S-NCx) can dramatically improve the stability of the catalyst by improving the selectivity of O2 electro-reduction to H2O. Density functional theory calculations reveal that sulfur doping lowers the energy barrier of O2(ads) hydrogenation to form OOH(ads), thus leading to enhanced intrinsic activity. In particular, the correlation between ORR activity and nitrogen and sulfur species in these materials is studied in-depth, and it is found the ORR performance of S-NCx catalysts is significantly affected by pyridinic N and C–S–C contents.
![Cobalt, [μ-[carbonato(2-)-κO:κO']]dihydroxydi-, hydrate](/data/chemimg/142453-73-4.png)
![Cobalt, [μ-[carbonato(2-)-κO:κO']]dihydroxydi-, hydrate](/data/chemimg/142453-73-4_b.png)
