Co-reporter:Yongjie Chen;Ping Li;Sijia Zhao;Yan Zhuang;Shiyong Zhao;Qun Zhou
RSC Advances (2011-Present) 2017 vol. 7(Issue 46) pp:29233-29239
Publication Date(Web):2017/05/30
DOI:10.1039/C7RA04206J
Microstructures of active materials may definitively determine the performance of lithium ion batteries. Herein, we develop a facile approach to synthesize porous LiNi0.8Co0.15Al0.05O2 (NCA) with uniform Al distribution by a two-step solid reaction with assistance of spray drying. Relative to the randomly aggregated counterpart, the NCA microspheres with an integrated framework and porous structure result in not only a profitable accessibility of the electrolyte, but also a favorable interfacial behavior. The porous NCA spheres exhibit a superior electrochemical performance with a discharge capacity of 202.1 mA h g−1 at 0.1C and 151 mA h g−1 at 2C, and capacity retention of 74.5% after 500 cycles at 2C. These are ascribed to the integrated network accumulating the stress generated during cycling to maintain the structural stability of the spheres. As a result, less solid electrolyte interphase (SEI) film is formed at the interface of the resulting electrode, consequently leading to a lower resistance of charge transfer, and better rate capability and cycling performance, compared to those of the electrode with the aggregated counterpart. Thereby, a purposeful engineering of the microstructures of the NCA materials would be important to achieve an optimal electrochemical performance of the electrode material.
Co-reporter:Yanqing Zhang, Qun Zhou, Wei Zhao, Wenya Chu, Junwei Zheng
Electrochimica Acta 2016 Volume 212() pp:25-31
Publication Date(Web):10 September 2016
DOI:10.1016/j.electacta.2016.06.126
•Recessed gold nanoelectrode arrays with precisely controlled patterns were fabricated.•Electrostatic interaction existed between the nanocylinder and the charged analytes.•The electrostatic interaction promoted the diffusion of dopamine but postponed that of ascorbic acid and urea acid.A series of recessed gold nanoelectrode arrays with different array densities are patterned on polymethylmethacrylate (PMMA) coated gold substrate by precisely controlled patterning through electron beam lithography. The influence of the nanoelectrode density of the arrays and scan rate on the diffusion regimes and hence electrochemical behaviors are systematically investigated. It is demonstrated that the electrostatic interaction exists between the oxygen-containing groups of the PMMA nanocylinder and the charged analytes in solution. The difference in the electrostatic interaction of dopamine (DA), ascorbic acid (AA), and uric acid (UA) with PMMA nanocylinders leads to differentiation of the oxidation of the three species. Thus, an electrochemical sensing platform for the detection of individual components in a mixture of DA, AA, and UA is developed. The linear ranges and detection limits of individual components in the mixture are 3.5–125 μM and 0.66 μM for DA, 30–190 μM and 7.5 μM for AA, 20–170 μM and 6.38 μM for UA, respectively, on the array electrode.
Co-reporter:Yanqing Zhang, Wenya Chu, Qun Zhou, Shuangshuang Li, Na Li, Junwei Zheng
Journal of Electroanalytical Chemistry 2016 Volume 775() pp:105-109
Publication Date(Web):15 August 2016
DOI:10.1016/j.jelechem.2016.05.042
•An array of tunable polyaniline cavity microelectrode was fabricated.•Polyaniline grew independently in ordered SiO2 cavities and eventually covered entire electrode.•The cavity structure enlarged effective electrode area.•The radial diffusion enhanced the electrochemical oxidation of ascorbic acid.An array of microelectrodes is fabricated with highly ordered SiO2 cavities modified on an indium-doped tin oxide (ITO) electrode, benefiting from the confinement of the insulating SiO2 cavities. Aniline can be electrochemically polymerized to form polyaniline (PANI) independently inside each SiO2 cavity. The edge effect of the microelectrodes leads to the radial diffusion of aniline in the SiO2 cavities; as a result, the PANI grows uniformly along the wall of the cavities and eventually covers the whole surface area of the SiO2 cavities to form an array of PANI cavities. Thus, the effective area of the PANI modified electrode could be greatly enlarged through such a surface structure modification. Moreover, it is demonstrated that the electrochemical reaction of ascorbic acid can be enhanced due to the radial diffusion of ascorbic acid inside PANI cavities. The specific features of the PANI cavity array enables us to develop a sensing platform of ascorbic acid detection with a detection limit of 0.14 μM (S/N = 3) and a linear range of 0.5–131 μM.
Co-reporter:Wei Zhao, Qun Zhou, Yanqing Zhang, Yongjie Chen, Jianxin Ren, Sijia Zhao, Junwei Zheng
Journal of Electroanalytical Chemistry 2016 Volume 768() pp:41-46
Publication Date(Web):1 May 2016
DOI:10.1016/j.jelechem.2016.02.039
Two-dimensional array of SiO2 cavities is fabricated on an indium-doped tin oxide (ITO) electrode by using highly ordered self-assembly of polystyrene spheres as a template. Silver nanoparticles electrodeposited at the bottom of the SiO2 cavities are fused and recrystallized via aggregative and Ostwald ripening mechanisms under annealing treatment conditions. Due to the confinement effect of the SiO2 cavity, the vaporized silver atoms preferentially deposit on the surface of the relative large silver particles at near equilibrium state, leading to the formation of silver single crystal polyhedron dominated with (111) facets in each SiO2 cavity, which can functionalize as a nanoelectrode and exhibit excellent electrocatalytic activity toward oxidation of ascorbic acid. Based on the array of the silver single crystal polyhedra, an electrochemical sensing platform of ascorbic acid is developed with high sensitivity and rapid response.
Co-reporter:Wenjuan Wei, Yanqing Zhang, Qun Zhou, Wei Zhao, Jianxin Ren, Junwei Zheng
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2016 Volume 489() pp:305-310
Publication Date(Web):20 January 2016
DOI:10.1016/j.colsurfa.2015.11.011
•Silica/gold cavity array microelectrodes were fabricated.•Silica surface was sulfonated to provide negative charges.•The modified cavities exhibited excellent ion selectivity.•The ion selective gate of the cavities selectively detected dopamine in the presence of ascorbic acid and uric acid.A silica/gold (SiO2/Au) cavity array microelectrode was fabricated on a gold film-coated glass slide by using highly ordered monodispersed polystyrene spheres as a template. The surface of the silica, as the upper part of the cavity, was sulfonated by 1,3-propanesultone, providing negative charges on the surface of the cavities in a media with pH > 2. The ion selectivity of the sulfonated SiO2/Au cavities was revealed by voltammetric response of potassium ferricyanide and methyl viologen dichloride as the electrochemical probes. Due to the electrostatic interaction, the positively charged methyl viologen cations can transport through the negatively charged SiO2 gate and react on active sites at the bottom of the cavities, whereas the diffusion access of the negatively charged ferricyanide anions into the cavities is blocked by the SiO2 gate. The ion selective gate of the cavities enables the electrode to selectively detect dopamine in the presence of ascorbic acid and uric acid, giving a linear range from 15 μM to 160 μM and a low detection limit of 85 nM.
Co-reporter:Hai Ming, Jun Ming, Won-Jin Kwak, Wenjing Yang, Qun Zhou, Junwei Zheng, Yang-Kook Sun
Electrochimica Acta 2015 Volume 169() pp:291-299
Publication Date(Web):1 July 2015
DOI:10.1016/j.electacta.2015.04.108
•A new anode of fluorine-doped porous Fe3O4-FeF2@CFx composite is readily prepared.•The CFx layer enhances the conductivity of Fe3O4 and ensures a fast Li+ diffusion.•The FeF2 can stabilize the structure of Fe3O4 during the (dis) charge process.•The Fe3O4-FeF2@CFx can deliver a high capacity with a robust rate capability.•A full cell of Fe3O4-FeF2@CFx/LiNi0.5Mn1.5O4 with high performance is assembled.A new fluorine-doped porous carbon-decorated Fe3O4-FeF2 composite, referred to as Fe3O4-FeF2@CFx, was prepared for the first time. The formation mechanism is discussed, and a new concept of introducing double layers of FeF2 and CFx into the oxide-based anode is presented for lithium ion batteries. Varying the amount of fluorine precursor, derivatives of Fe3O4@CFx and FeF2@CFx were further obtained, allowing an original analysis of their electrochemical behaviors. As-prepared Fe3O4-FeF2@CFx can deliver a high capacity of 718 mAh g−1 at 50 mA g−1. Under a hash rate of 1600 mAg−1, the capacity of Fe3O4-FeF2@CFx (around 338 mAh g−1) is higher than that (200 mAh g−1) of FeF2@CFx. Further, its capacity retention of 97% over 100 cycles is much better than the 59.4% observed for Fe3O4@CFx. The positive effect of the CFx layer on the electronic conductivity and ionic diffusion ability was confirmed. The role of FeF2 in the stabilization of the structure of CFx and Fe3O4 is also discussed. Further, a new battery composed of Fe3O4-FeF2@CFx/LiNi0.5Mn1.5O4 with a robust rate capability was assembled and delivered a reversible capacity of 565 mAh g−1 (vs. anode) at 100 mA g−1 with a high potential of 3.3 V and a capacity retention of 81.5% over 50 cycles.A new anode of fluorine doped porous Fe3O4-FeF2@CFx composite with double layers of FeF2 and CFx was presented for the first time, and a high rate capability was obtained in lithium ion battery. Besides, a new full battery of Fe3O4-FeF2@CFx/LiNi0.5Mn1.5O4 with a high capacity of 565 mAh g−1 (vs. anode) at the current density of 100 mA g−1 was successfully introduced. It demonstrated a robust rate capability, high operating potential of 3.3 V and fine cycle ability over 50 cycles with capacity retention of 81.5%.
Co-reporter:Zhenyong Jia, Qun Zhou, Xiaowei Li, Yu Fu, Hai Ming, Junwei Zheng
Electrochimica Acta 2015 Volume 156() pp:216-222
Publication Date(Web):20 February 2015
DOI:10.1016/j.electacta.2015.01.017
•Rigid porous framework of Li4Ti5O12 microspheres can be fabricated by mutual molten growth of primary particles.•Well-confined nanosized tortuous channels are formed inside Li4Ti5O12 microspheres.•Li4Ti5O12 microspheres with rigid porous structures exhibit greatly enhanced electrochemical performance.Highly controllable porous architecture is desirable to tailor the physical and chemical properties of functional materials in advanced lithium ion batteries. Here, porous microspheres of spinel lithium titanate (Li4Ti5O12), a promising alternative anode material for lithium ion batteries, are fabricated by mutual molten growth method in a controllable manner. The key role of the rigidity of the porous structure on the performance of the electrode materials in lithium ion batteries is demonstrated. Rigid framework of the materials is formed by second growth of the primary particles that fused together to generate an interconnected nanopore system inside the spheres, leading to better electrolyte diffusion and lower interparticle contact resistance, relative to the non-porous counterpart. The pristine Li4Ti5O12 microspheres with uniform pore distribution and continuous framework exhibit high tap density, remarkable reversible capacity and rate capability, as well as excellent cycling stability. The present method is scalable and may provide a new approach to fabricate other candidate electrode materials for applications that require both high power and high volumetric energy density.
Co-reporter:Yu Fu, Hai Ming, Shiyong Zhao, Jun Guo, Muzi Chen, Qun Zhou, Junwei Zheng
Electrochimica Acta 2015 Volume 185() pp:211-217
Publication Date(Web):10 December 2015
DOI:10.1016/j.electacta.2015.10.124
Lithium titanium oxyphosphate LiTiOPO4 is synthesized by a solution route and modified with a carbon layer using polyvinylidene difluoride as carbon source. It is demonstrated that the performance of LiTiOPO4 strongly depends on cycling potential range. In the potential range from 0.5 to 3.0 V, limited capacity (less than 161 mA h g−1) is obtained, which is ascribed to a mechanism involving the insertion of lithium ions into vacant sites of crystalline structure. As the cut-off potential is set down to 0.1 V, a conversion of LiTiOPO4 occurs in the initial cycle, as a result, a relative high and reversible capacity of 285 mA h g−1 at the current rate of 0.1 C can be achieved during the subsequent cycles. However, resembling that of transition metal oxides, possible charging/discharging mechanism, in this case, may involve the formation and decomposition of Li2O formed in the conversion of LiTiOPO4. The new strategy also enables LiTiOPO4 as the electrode material with superior cycleability and rate capability of 195 mA h g−1 at the current rate of 2.0 C. The results indicate that carbon-coated LiTiOPO4 could be a promising anode material with relative high capacity and good rate capability for lithium ion batteries.
Co-reporter:Hai Ming, Pushpendra Kumar, Wenjing Yang, Yu Fu, Jun Ming, Won-Jin Kwak, Lain-Jong Li, Yang-kook Sun, and Junwei Zheng
ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 12) pp:3086
Publication Date(Web):November 3, 2015
DOI:10.1021/acssuschemeng.5b00553
A green hydrothermal strategy starting from the Ti powders was developed to synthesis a new kind of well dispersed anatase TiO2 nanosheets (TNSTs) with dominant (001) facets, successfully avoiding using the HF by choosing the safe substitutes of LiF powder. In contrast to traditional approaches targeting TiO2 with dominant crystal facets, the strategy presented herein is more convenient, environment friendly and available for industrial production. As a unique structured anode applied in lithium ion battery, the TNSTs could exhibit an extremely high capacity around 215 mAh g–1 at the current density of 100 mA g–1 and preserved capacity over 140 mAh g–1 enduring 200 cycles at 400 mA g–1. As a further step toward commercialization, a model of lithiating TiO2 was built for the first time and analyzed by the electrochemical characterizations, and full batteries employing lithiated TNSTs as carbon-free anode versus spinel LiNixMn2–xO4 (x = 0, 0.5) cathode were configured. The full batteries of TNSTs/LiMn2O4 and TNSTs/LiNi0.5Mn1.5O4 have the sustainable advantage of cost-effective and cobalt-free characteristics, and particularly they demonstrated high energy densities of 497 and 580 Wh kganode–1 (i.e., 276 and 341 Wh kgcathode–1) with stable capacity retentions of 95% and 99% respectively over 100 cycles. Besides the intriguing performance in batteries, the versatile synthetic strategy and unique characteristics of TNSTs may promise other attracting applications in the fields of photoreaction, electro-catalyst, electrochemistry, interfacial adsorption photovoltaic devices etc.Keywords: Anode; Battery; Cathode; Hydrothermal; Lithiation; Titanium dioxide
Co-reporter:Shuangshuang Li, Qun Zhou, Wenya Chu, Wei Zhao and Junwei Zheng
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 27) pp:17638-17645
Publication Date(Web):03 Jun 2015
DOI:10.1039/C5CP02409A
Molecular recognition based on specific intermolecular interactions is essential for the design of sensors with high selectivity. Herein, we report the surface-enhanced Raman scattering (SERS) behaviour of 4-mercaptophenyl boronic acid (MPBA) on self-assembled silver nanoparticles and its interaction with D-glucose. It is demonstrated that the orientation and existing form of the MPBA strongly depend on the pH value of the media. The surface-immobilized MPBA can be reversibly associated with OH− in solution, along with a molecular orientation alteration. A self-condensation reaction among the OH−-associated MPBA molecules results in irreversible conversion of OH−-associated MPBA to anhydride, which may hinder the interaction between D-glucose and the B-moiety of MPBA. However, the self-condensation reaction can be diminished under optimized conditions. By taking advantage of the difference in the kinetics of dissociation of the OH−-associated MPBA and D-glucose-associated MPBA in acidic media, a proper scheme of the SERS detection of D-glucose is proposed to illuminate the spectral interference of OH−-associated MPBA, which exhibits SERS features similar to those of D-glucose-associated MPBA species. Based on those strategies, the SERS detection of D-glucose can be achieved in the physiologically-relevant concentration range.
Co-reporter:Shuangshuang Li, Qun Zhou, Wenya Chu, Wei Zhao and Junwei Zheng
RSC Advances 2015 vol. 5(Issue 69) pp:55720-55726
Publication Date(Web):18 Jun 2015
DOI:10.1039/C5RA03987H
Metal nanoparticles assembled with functional molecules to form advanced structures have proven to have wide applications in molecular electronics and sensors. The microenvironments of the assemblies may largely influence the properties of the advanced structures. Herein, silver/4-aminothiophenol/silver (Ag/PATP/Ag) structures are constructed to generate nanosized metal/molecule/metal junctions via a layer-by-layer assembly technique. The effect of the microenvironments, such as adsorption of molecules on the junctions, on the properties of the molecular junctions is investigated by surface-enhanced Raman scattering of the PATP molecules interconnected in Ag/PATP/Ag junctions. It is demonstrated that the modification of molecules such as n-octanethiol, 1,8-octanedithiol, thiophenol 1,4-benzendithiol, and 4-mercaptopyridine, shows negligible effects on the enhanced electromagnetic field arising from the plasmon coupling of neighboring silver nanoparticles. The contributions from photoinduced charge transfer (CT) between the silver nanoparticles through the interconnected PATP molecules could be altered by the modification of the molecules. The large influence from the aromatic thiols is ascribed to the delocalization of the free electrons in the metal nanoparticles to the conjugated structure of the modified molecules.
Co-reporter:Wenya Chu, Qun Zhou, Shuangshuang Li, Wei Zhao, Na Li, Junwei Zheng
Applied Surface Science 2015 Volume 353() pp:425-432
Publication Date(Web):30 October 2015
DOI:10.1016/j.apsusc.2015.06.141
Highlights
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Gold nanoparticles assembled on electrodes are incorporated into polyaniline film.
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Composite film electrodes exhibit synergistic effect on electrocatalytic oxidation.
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Ascorbic acid and dopamine can be detected simultaneously on composite electrodes.
Co-reporter:Hongbo Geng;Danhua Ge;Shuanglong Lu;Jiaqing Wang;Zhengmao Ye; Yonggang Yang; Junwei Zheng; Hongwei Gu
Chemistry - A European Journal 2015 Volume 21( Issue 31) pp:11129-11133
Publication Date(Web):
DOI:10.1002/chem.201500819
Abstract
In this study, we report the design and synthesis of a silver nanowire-γ-Fe2O3 coaxial nanocable architecture (Ag NWs@γ-Fe2O3 nanocable) through mild oxidation of [Fe(CO)5] on the surface of silver nanowires followed by a calcination process. After optimization of the structural design, the Ag NWs@γ-Fe2O3 nanocable could deliver superior lithium storage performance in terms of high reversible capacity, good rate performance, and excellent stability, such as a high reversible capacity of about 890 mA h g−1 after 60 cycles at a current rate of 0.1 C (1.0 C=1005 mA g−1). The reversible capacity remains as high as about 550 mA h g−1 even at a high current rate of 2.0 C. This dramatic performance is mainly attributed to the smart coaxial design, which can not only alleviate the large volume change and prevent the aggregation of γ-Fe2O3 nanoparticles, but also enables good conductivity and thus enhances fast charge transfer. The unique structural features of the Ag NWs@γ-Fe2O3 nanocable represent a promising anode material in lithium-ion battery applications.
Co-reporter:Hongbo Geng, Qun Zhou, Yue Pan, Hongwei Gu and Junwei Zheng
Nanoscale 2014 vol. 6(Issue 7) pp:3889-3894
Publication Date(Web):27 Jan 2014
DOI:10.1039/C3NR06409C
Herein we report the design and synthesis of fluorine-doped, carbon-encapsulated hollow Fe3O4 spheres (h-Fe3O4@C/F) through mild heating of polyvinylidene fluoride (PVDF)-coated hollow Fe3O4 spheres. The spheres exhibit enhanced cyclic and rate performances. The as-prepared h-Fe3O4@C/F shows significantly improved electrochemical performance, with high reversible capacities of over 930 mA h g−1 at a rate of 0.1 C after 70 cycles, 800 mA h g−1 at a rate of 0.5 C after 120 cycles and 620 mA h g−1 at a rate of 1 C after 200 cycles. This improved lithium storage performance is mainly ascribed to the encapsulation of the spheres with fluorine-doped carbon, which not only improves the reaction kinetics and stability of the solid electrolyte interface film but also prevents aggregation and drastic volume change of the Fe3O4 particles. These spheres thus represent a promising anode material in lithium-ion battery applications.
Co-reporter:Hai Ming, Jun Ming, Seung-Min Oh, Eung-Ju Lee, Hui Huang, Qun Zhou, Junwei Zheng and Yang-Kook Sun
Journal of Materials Chemistry A 2014 vol. 2(Issue 44) pp:18938-18945
Publication Date(Web):03 Sep 2014
DOI:10.1039/C4TA03557G
A new and simple strategy was developed to effectively disperse titanium dioxide (TiO2) nanocrystals into porous carbon (PC), and a series of hierarchical PC–TiO2 composites with different architectures were synthesized. By varying the amount of TiO2, from 30 wt% to 64 wt%, the lithium storage capacity of PC–TiO2 could be controllably varied from 546 mA h g−1 to 446 mA h g−1 under a current density of 50 mA g−1. Also, very stable cycling performances and rate capabilities could be obtained at the rates of 50 mA g−1 to 1600 mA g−1. By further increasing the content of TiO2 to 93%, another new composite of TiO2–C was also prepared and it demonstrated a storage capacity of 352 mA h g−1 at 50 mA g−1, which is much higher than that for most reported TiO2 materials. Based on these results, new full cells with a LiNi0.5Mn1.5O4 cathode, such as PC–TiO2/LiNi0.5Mn1.5O4, were successfully assembled and investigated. This full cell not only delivered a high energy density of 413 W h kg−1 but also showed a good rate capability and an energy retention of 90.5% over 100 cycles.
Co-reporter:Hai Ming, Jun Ming, Seung-Min Oh, Shu Tian, Qun Zhou, Hui Huang, Yang-Kook Sun, and Junwei Zheng
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 17) pp:15499
Publication Date(Web):August 20, 2014
DOI:10.1021/am504144d
A simple surfactant-assisted reflux method was used in this study for the synthesis of cocklebur-shaped Fe2O3 nanoparticles (NPs). With this strategy, a series of nanostructured Fe2O3 NPs with a size distribution ranging from 20 to 120 nm and a tunable surface area were readily controlled by varying reflux temperature and the type of surfactant. Surfactants such as cetyltrimethylammonium bromide (CTAB), polyvinylpyrrolidone (PVP), poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (F127) and sodium dodecyl benzenesulfonate (SDBS) were used to achieve large-scale synthesis of uniform Fe2O3 NPs with a relatively low cost. A new composite of Fe3O4@CFx was prepared by coating the primary Fe2O3 NPs with a layer of F-doped carbon (CFx) with a one-step carbonization process. The Fe3O4@CFx composite was utilized as the anode in a lithium ion battery and exhibited a high reversible capacity of 900 mAh g–1 at a current density of 100 mA g–1 over 100 cycles with 95% capacity retention. In addition, a new Fe3O4@CFx/LiNi0.5Mn1.5O4 battery with a high energy density of 371 Wh kg–1 (vs cathode) was successfully assembled, and more than 300 cycles were easily completed with 66.8% capacity retention at 100 mA g–1. Even cycled at the high temperature of 45 °C, this full cell also exhibited a relatively high capacity of 91.6 mAh g–1 (vs cathode) at 100 mA g–1 and retained 54.6% of its reversible capacity over 50 cycles. Introducing CFx chemicals to modify metal oxide anodes and/or any other cathode is of great interest for advanced energy storage and conversion devices.Keywords: batteries; carbon; electrochemical properties; nanoparticles; oxides
Co-reporter:Hai Ming, Jun Ming, Xiaowei Li, Qun Zhou, Haohe Wang, Lingling Jin, Yu Fu, Jason Adkins, Junwei Zheng
Electrochimica Acta 2014 Volume 116() pp:224-229
Publication Date(Web):10 January 2014
DOI:10.1016/j.electacta.2013.11.038
•Hierarchical Li4Ti5O12 particles composed of numerous nanocrystals were prepared.•Li4Ti5O12 particles were co-modified by carbon and nitrogen successfully.•These Li4Ti5O12 particles exhibit excellent performance in lithium-ion batteries.•The amount of C&N-modifying is a critical parameter for improving the final properties.Carbon and nitrogen, (C&N), co-modified hierarchical Li4Ti5O12 (LTO) particles with excellent perfomance in lithium-ion batteries were prepared via a facile synthesis with the proper modifying of C and N successfully reducing the polarization and enhancing the conductivity of LTO while also giving rise to Ti3+ sites due to the reduction ability of C&N. Together, with primary nanocrystals less than 10 nm and a relatively high specific surface area (16.9 m2 g−1), as-prepared samples exhibit excellent electrochemical performance, such as a high capacity around 174.7 mAh g−1 at the current rate of 0.1 C and reversible capacity over 171 and 150 mAh g−1 after 100 cycles at the current rate of 1 and 10 C (1 C = 175 mAh g−1). More importantly, the optimal amount of C&N modifying in LTO was investigated for the first time. It was found that excessive modifying of C&N can introduce a lot of amorphous TiONx and also create undesirable Ti2+ to induce a structural transformation of LTO, directly leading to a low rate capacity.
Co-reporter:Yu Fu, Hai Ming, Qun Zhou, Lingling Jin, Xiaowei Li, Junwei Zheng
Electrochimica Acta 2014 Volume 134() pp:478-485
Publication Date(Web):10 July 2014
DOI:10.1016/j.electacta.2014.04.130
Alternative anode materials with more positive lithium intercalation potential than that of graphite are desirable for lithium ion batteries with high safety particularly required for electric vehicles and sustainable energy sources. Thermally stable, mesoporous anatase TiO2 spheres are successfully synthesized, using ethylene diamine as a precursor, via a facile solution-phase process incorporating a nanoscopic carbon coating doped with a relatively high nitrogen content which formed a conducting network with mesoporous TiO2 upon calcination. The structural characterizations demonstrate the crucial function of ethylene diamine in stabilizing and maintaining the well-confined mesoporous structure for TiO2 during calcination. The porous TiO2 material with a conducting network exhibits a highly reversible capacity of 182 mA h g −1 after 60 cycles at the current density of 0.5 C and an improved rate capability compared to porous TiO2 without modification, indicating the composite is a promising anode material for Li-ion batteries.
Co-reporter:Meng Wu, Xiaowei Li, Qun Zhou, Hai Ming, Jason Adkins, Junwei Zheng
Electrochimica Acta 2014 Volume 123() pp:144-150
Publication Date(Web):20 March 2014
DOI:10.1016/j.electacta.2013.12.192
•An open and continuous Sn film was fabricated by magnetron sputtering.•The Sn film anode was used as a model to investigate the capacity decay.•Sn particles with limited size due to pulverization can provide a stable capacity.•The capacity of Sn electrode can be improved by introducing a conductive layer.A Sn thin film composed of numerous continuous Sn particles (ranging from 25 to 200 nm) was prepared on a copper foil via magnetron sputtering. Electrochemical properties of the Sn thin film, as anode electrode in lithium ion batteries, were studied by conventional charge/discharge tests and cyclic voltammograms. The as-prepared Sn electrode showed high initial discharge capacity of 908 mAh g−1 at a current density of 100 mA g−1. After the gradual capacity decay (in the first 15 cycles), the capacity of this electrode recovered with sustained stability during the subsequent charge/discharge processes. Such a gradual capacity decay is ascribed to the decrease of the conductivity and active materials of the surface of the anode, due to agglomeration, pulverization, and cracking of the particles and the formation of the SEI film. Considering this phenomenon, a layer of conductor (copper or carbon) was sputtered on the surface of the Sn electrode after 30 cycles in order to counteract capacity decay. The as-prepared Cu/C-modified Sn electrode exhibited an improved capacity due to enhanced conductivity. The strategy provides a better understanding of anode materials with inevitable volume change which is useful for efficient lithium-ion battery application.
Co-reporter:Haohe Wang, Xiaowei Li, Qun Zhou, Hai Ming, J. Adkins, Lingling Jin, Zhenyong Jia, Yu Fu, Junwei Zheng
Journal of Alloys and Compounds 2014 Volume 604() pp:217-225
Publication Date(Web):15 August 2014
DOI:10.1016/j.jallcom.2014.03.101
•Three types of Li1.2Ni0.2Mn0.6O2 were synthesized from birnessite.•Morphologies of the types heavily influenced their electrochemical performance.•The sample composed of nano-sized particles delivered 136.4 mA h g−1 at 7 C rate.•We investigated the transformation of crystallinity and morphology in calcination.•Sodium ions doped in the structure may reduce its charge and discharge capacity.In the present work, three types of Li1.2Ni0.2Mn0.6O2 were synthesized from sodium birnessite (NaBir) and each type exhibited distinct morphological features created by varying preparation (with or without ball milling) or varying the sequential order of the preparation steps. Three processes were employed, including (1) ion-exchange, simply mechanical mixing, calcination (Without-BM), (2) ion-exchange, ball milling, calcination (EX-priority), (3) ball milling, ion-exchange, calcination (BM-priority). The three as-prepared sample types exhibited different performance characteristics, depending on their respective preparation processes. The “Without-BM” sample exhibited a reversible capacity of 240 mA h g−1 between 2.0 V and 4.8 V with a current density of 0.1 C (30 mA g−1), having almost no capacity fading after 80 cycles. The “EX-priority” sample exhibited a desirable rate performance with a reversible capacity of 213.4 mA h g−1 at 1 C and 136.4 mA h g−1 at 7 C; however, the capacity retention was 88.3% after 80 cycles at 0.1 C. The “BM-priority” sample displayed a moderate rate and cycle performance. The differences between these samples demonstrated that the ball milling treatment and its sequence have substantial effects on performance of materials. The experimental data indicated that the different performances can be attributed to the different morphologies of the respective materials as well as the effect of sodium ion concentration within the structure. Therefore, controlling the morphology of the material and the amount of sodium ions in its structure may be advantageous for developing high quality cathode materials which can be diversified for specific applications in Li-ion batteries.
Co-reporter:Lingling Jin, Xiaowei Li, Hai Ming, Haohe Wang, Zhenyong Jia, Yu Fu, Jason Adkins, Qun Zhou and Junwei Zheng
RSC Advances 2014 vol. 4(Issue 12) pp:6083-6089
Publication Date(Web):19 Dec 2013
DOI:10.1039/C3RA45904G
In this study, Co3O4 with different morphologies (leaf, sheet, and cube) are successfully synthesized by a facile hydrothermal method followed by calcination treatment. Representative samples with different morphological structures are compared and evaluated as anode materials in lithium-ion batteries. Relative to the Co3O4-sheet and Co3O4-cube samples, the Co3O4-leaf samples exhibit excellent electrochemical performance with high storage capacity (1245 mA h g−1 after 40 cycles at 0.1 C) and superior rate capability (0.1, 0.2, 0.5, 1, and 2 C for 1028, 1085, 1095, 1038, and 820 mA h g−1, respectively); interestingly, the thinner the samples are, the better their performance. Moreover, assisted by characterization by cyclic voltammetry and electrochemical impedance spectroscopy, we draw a conclusion that the ultra-thin structures result in shorter path lengths for the transport of lithium ions and electrons, benefiting conductivity and fast charge–discharge rates. More importantly, for Co3O4, the respective structure's degree of thickness has a great effect on the electrochemical performance in lithium-ion batteries. This new concept might be extended to prepare other anode and cathode materials for advanced energy storage and conversion devices.
Co-reporter:Yabin Li, Yuerong Yan, Hai Ming, Junwei Zheng
Applied Surface Science 2014 Volume 305() pp:683-688
Publication Date(Web):30 June 2014
DOI:10.1016/j.apsusc.2014.03.169
Highlights
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We developed a one-step strategy to prepare core@shell (Fe3O4@Fe3N) nanoparticles.
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Fe3O4@Fe3N exhibits excellent electrochemical performance as an anode material.
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The mechanism of forming core@shell structure and Fe3N layer are discussed.
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We provide a new way for preparing other nitrogen functionalized materials.
Co-reporter:Hai Ming, Yuerong Yan, Jun Ming, Xiaowei Li, Qun Zhou, Hui Huang and Junwei Zheng
RSC Advances 2014 vol. 4(Issue 25) pp:12971-12976
Publication Date(Web):20 Jan 2014
DOI:10.1039/C4RA00133H
Porous TiO2 nanoribbons and TiO2 nanoribbon/carbon dot composites with excellent performances in lithium-ion batteries were prepared via a simple and efficient method.
Co-reporter:Na Li, Qun Zhou, Xiaowei Li, Wenya Chu, Jason Adkins, Junwei Zheng
Sensors and Actuators B: Chemical 2014 196() pp: 314-320
Publication Date(Web):
DOI:10.1016/j.snb.2014.02.017
Co-reporter:Hai Ming, Yuerong Yan, Jun Ming, Jason Adkins, Xiaowei Li, Qun Zhou, Junwei Zheng
Electrochimica Acta 2014 120() pp: 390-397
Publication Date(Web):
DOI:10.1016/j.electacta.2013.12.096
Co-reporter:Na Li, Qun Zhou, Shu Tian, Hong Zhao, Xiaowei Li, Jason Adkins, Zhuomin Gu, Lili Zhao, Junwei Zheng
Electrochimica Acta 2013 Volume 109() pp:546-553
Publication Date(Web):30 October 2013
DOI:10.1016/j.electacta.2013.07.136
In the present work, we report a new and simple approach for preparing a highly ordered Au (1 1 1) nanoparticle (NP) array in SiO2 cavities on indium-doped tin oxide (ITO) electrodes. We fabricated a SiO2 cavity array on the surface of an ITO electrode using highly ordered self-assembly of polystyrene spheres as a template. Gold NPs were electrodeposited at the bottom of the SiO2 cavities, and single gold NPs dominated with (1 1 1) facets were generated in each cavity by annealing the electrode at a high temperature. Such (1 1 1) facets were the predominate trait of the single gold particle which exhibited considerable electrocatalytic activity toward oxidation of methanol, ethanol, and glycerol. This has been attributed to the formation of incipient hydrous oxides at unusually low potential on the specific (1 1 1) facet of the gold particles. Moreover, each cavity of the SiO2 possibly behaves as an independent electrochemical cell in which the methanol molecules are trapped; this produces an environment advantageous to catalyzing electrooxidation. The oxidation of methanol on the electrodes is a mixed control mechanism (both by diffusion and electrode kinetics). This strategy both provided an approach to study electrochemical reactions on a single particle in a microenvironment and may supply a way to construct alcohols sensors.
Co-reporter:Zhigang Mou, Shunli Yin, Mingshan Zhu, Yukou Du, Xiaomei Wang, Ping Yang, Junwei Zheng and Cheng Lu
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 8) pp:2793-2799
Publication Date(Web):14 Dec 2012
DOI:10.1039/C2CP44270A
A novel composite composed of TiSi2, graphene and RuO2 nanoparticles was fabricated by a one-pot deposition method using reduced graphene oxide (RGO) as a supporting matrix and RuCl3 as the RuO2 precursor. The resulting RuO2/TiSi2/RGO composite was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectra, photoelectrical response and electrochemical impedance spectra. The results indicated that the three components in the composite were effectively contacted, thus facilitating the photogenerated charges transfer and separation through multiple routes. By using the composite as a photocatalyst for visible-light water splitting the average hydrogen production rate could reach 97.5 μmol h−1 g−1, which is higher than that from RuO2/TiSi2 and pure TiSi2 systems under the same conditions.
Co-reporter:Shu Tian, Qun Zhou, Zhuomin Gu, Xuefang Gu and Junwei Zheng
Analyst 2013 vol. 138(Issue 9) pp:2604-2612
Publication Date(Web):07 Feb 2013
DOI:10.1039/C3AN36792D
In this study, a metal sandwich substrate bridged by an immunocomplex has been created for a surface enhanced Raman scattering (SERS)-based immunoassay. The bottom bowl-shaped silver cavity thin film layer was prepared by electrodeposition using a closely packed monolayer of 700 nm diameter polystyrene spheres as a template. The reflection spectra of the films were recorded as a function of film thickness, and then correlated with SERS enhancement using p-aminothiophenol as the probe molecule. The results demonstrate that SERS enhancement can be maximized when both the frequency of the incident laser and Raman scattering approach the resonance frequency of the localized surface plasmon resonance, providing a guideline for the fabrication and further application of these nanocavity arrays. The second layer of silver was introduced by the interactions between the immunocomplexes in the middle layer of the sandwich architecture and the silver nanoparticles. The proposed structure was used to perform the SERS-based immunoassay. The labeled protein can be detected over a wide concentration range and the detection limit of TRITC and Atto610 labeled proteins were 50 and 5 pg mL−1, respectively. The results demonstrate that the new SERS substrate is suitable for the quantitative identification of biomolecules.
Co-reporter:Mangmang Liu, Xiaowei Li, Hai Ming, Jason Adkins, Xiaomei Zhao, Lele Su, Qun Zhou and Junwei Zheng
New Journal of Chemistry 2013 vol. 37(Issue 7) pp:2096-2102
Publication Date(Web):10 Apr 2013
DOI:10.1039/C3NJ00242J
Tin dioxide (SnO2) attracts considerable attention as an anode material due to its high theoretical capacity compared with graphite. However, the practical use of a SnO2 anode is significantly hampered by its large volume changes during lithium insertion and extraction processes, which leads to poor cyclic performance. To overcome this problem, a simple and efficient method was employed to fabricate SnO2-based nanocomposites with controlled titanium nitride (TiN) modification. The as-prepared samples were characterized by XRD, Raman, XPS, TEM and electrochemical measurements. Compared with the pristine SnO2, the appropriate TiN modified SnO2 nanocomposite electrodes exhibited improved lithium storage performance. Particularly, the hybrid anode with 2 wt% TiN delivered a high first capacity of 1580.6 mA h g−1 and a stable capacity of 404 mA h g−1 after 50 cycles at a charge–discharge rate of 0.1 C. The improved lithium storage performance was attributed to the inactive TiN matrix, which significantly enhanced the structural stability and electronic conductivity of the SnO2–TiN nanocomposites.
Co-reporter:Hai Ming, Xiaowei Li, Qun Zhou, Mangmang Liu, LeLe Su, Lijuan Bu, Zhenhui Kang and Junwei Zheng
New Journal of Chemistry 2013 vol. 37(Issue 7) pp:1912-1918
Publication Date(Web):04 Mar 2013
DOI:10.1039/C3NJ41144C
In this study, a new acid-assisted hydrothermal method was presented for the synthesis of dandelion-like mesoporous rutile TiO2 microspheres (MSPs) without using any template and surfactant. With this strategy, the spherical structure and pore size of the obtained TiO2 particles could be readily controlled just through varying the kind of acid (e.g., HNO3–TiO2 and HCl–TiO2 MSPs show different pore size distribution of 6 ± 2 nm and 12 ± 2 nm, respectively). Benefiting from the mesoporous structure, high specific surface area, and especially the high percentage of exposed (002) crystal facets, the samples of HNO3–TiO2 and HCl–TiO2 MSPs exhibit excellent electrochemical performance in lithium-ion batteries. For example, a high capacity of around 164.5 and 160.6 mA h g−1 at a rate of 0.1 C, and a reversible capacity of over 141.9 and 133.3 mA h g−1 after 100 cycles at a rate of 1 C were demonstrated respectively for the samples of HNO3–TiO2 and HCl–TiO2 MSPs (1 C = 168 mA h g−1). Moreover, another two kinds of mesoporous Li4Ti5O12 spheres (HNO3–Li4Ti5O12 and HCl–Li4Ti5O12 MSPs) were further prepared based on the above TiO2 precursors. Promisingly, they also showed a higher improved performance in lithium battery application, such as a high capacity of around 173.6 and 174 mA h g−1 at a rate of 0.1 C and a reversible capacity of over 161.9 mA h g−1 and 170.4 mA h g−1 after 100 cycles at a rate of 1 C (1 C = 175 mA h g−1).
Co-reporter:Hai Ming, Xiaowei Li, Ying Wei, Lijuan Bu, Zhenhui Kang and Junwei Zheng
RSC Advances 2013 vol. 3(Issue 11) pp:3655-3660
Publication Date(Web):09 Jan 2013
DOI:10.1039/C3RA23343J
Graphite oxide nanosheets (GONs) functionalized by 1-butyl-3-methylimidazolium ([BMI]), which was named as [BMI]-GONs, were synthesized by a “green” electrochemical method with the assistance of an ionic liquid ([BMI][CF3CO2]). Notably, based on the ordered sandwich structures and modified properties of the GONs, in the present synthetic process, Pt nanoparticles can easily assemble on the surfaces and margins of the [BMI]-GONs. Therefore, a novel [BMI]-GONs/Pt nanohybrid (porous Pt nanospheres with diameters ranging from 50 to 100 nm, which were composed of the Pt nanocrystals with the diameter ranging from 1 to 5 nm, evenly dispersed on the GONs surface) have been synthesized successfully. Furthermore, [BMI]-GONs/Pt nanohybrids were demonstrated to exhibit a much better electro-catalytic activity (the current density is 41.8 mA mg−1) and stability (the current density still remains 78.9% after one thousand cycles under a scan rate at 50 mV s−1) toward methanol electro-oxidation, as well as a much better resistance to toxic CO (the ratio of If/Ib is 1.97).
Co-reporter:Hai Ming, Xiaowei Li, Lele Su, Mangmang Liu, Lingling Jin, Lijuan Bu, Zhenhui Kang and Junwei Zheng
RSC Advances 2013 vol. 3(Issue 12) pp:3836-3839
Publication Date(Web):18 Jan 2013
DOI:10.1039/C3RA22703K
C&N co-doped mesoporous TiO2 with excellent performance in lithium-ion batteries was prepared via a one-step synthesis method.
Co-reporter:Hai Ming, Jun Ming, Xiaowei Li, Qun Zhou, Lingling Jin, Yu Fu, Jason Adkins, Zhenhui Kang and Junwei Zheng
RSC Advances 2013 vol. 3(Issue 36) pp:15613-15617
Publication Date(Web):17 Jul 2013
DOI:10.1039/C3RA42241K
A new kind of metal oxide nanoparticle coated with a uniform layer of N-doped carbon (e.g., Fe3O4@CNy, CoOx@CNy) was prepared readily in one-step. The nanoparticles show a high and stable lithium storage ability for lithium-ion battery applications.
Co-reporter:Xuefang Gu, Shu Tian, Qun Zhou, Jason Adkins, Zhuomin Gu, Xiaowei Li and Junwei Zheng
RSC Advances 2013 vol. 3(Issue 48) pp:25989-25996
Publication Date(Web):03 Oct 2013
DOI:10.1039/C3RA43442G
Trace detection of polycyclic aromatic hydrocarbons (PAHs) by surface-enhanced Raman scattering (SERS) on a metal sandwich substrate bridged by 1,10-decanedithiolis is reported in this work. The bowl-shaped silver cavity (BSSC) thin film bottom layer was prepared by electrodeposition using a closely packed monolayer of 500 nm diameter polystyrene spheres as a template. The as-prepared silver cavity array has proven to be a SERS-active substrate with excellent performance and reproducibility when using p-aminothiophenol (PATP) as the probe molecule. A 1,10-decanethiol monolayer was then assembled on the silver film to concentrate PAHs within the hot-spot of SERS detection. The top layer of silver was introduced by an S–Ag bond between the thiols of the 1,10-decanethiol and the silver nanoparticles. The proposed structure was employed to perform the SERS-based PAH detection. The measured SERS spectra enabled the easy detection of anthracene and pyrene; the two PAH compounds can be detected over a wide concentration range and the detection limit of anthracene and pyrene was 8 and 40 nM, respectively. The results demonstrate that the new SERS substrate is suitable for the quantitative identification of non-polar organic pollutants like PAHs.
Co-reporter:Xiaomei Zhao;Qun Zhou;Hai Ming;Jason Adkins;Mangmang Liu;Lele Su
Ionics 2013 Volume 19( Issue 12) pp:1843-1848
Publication Date(Web):2013 December
DOI:10.1007/s11581-013-0918-x
Surface nitridation of the Li4Ti5O12 particles was carried out by thermal treatment with urea as the nitrogen source in a controllable manner. The titanium nitride (TiN) was formed in the well-dispersed zones on the surface of the Li4Ti5O12 particles, depending on the coverage of the nitride. The surface TiN formed led to a great improvement of the conductivity of the oxide. The extent of the surface nitridation exhibited a large effect on electrochemical behaviors of the Li4Ti5O12 particles, with the Li4Ti5O12/TiN composite (prepared using 6 % urea) providing the best initial capacity and rate capability. Thus, the electrochemical performance of the Li4Ti5O12 particles can be achieved by optimizing surface nitridation of the oxide. The chemically inert TiN occupied the surface sites of the Li4Ti5O12 particles which may have prevented the electrolyte from decomposition and stabilized the surface structure of the Li4Ti5O12 particles, endowing the oxide with excellent cycleability
Co-reporter:Shu Tian, Qun Zhou, Zhuomin Gu, Xuefang Gu, Lili Zhao, Yan Li, Junwei Zheng
Talanta 2013 Volume 107() pp:324-331
Publication Date(Web):30 March 2013
DOI:10.1016/j.talanta.2013.01.050
Hydrogen peroxide biosensor based on the silica cavity array modified indium-doped tin oxide (ITO) electrode was constructed. An array of silica microcavities was fabricated by electrodeposition using the assembled polystyrene particles as template. Due to the resistance gradient of the silica cavity structure, the silica cavity exhibits a confinement effect on the electrochemical reactions, making the electrode function as an array of “soft” microelectrodes. The covalently immobilized microperoxidase-11(MP-11) inside these SiO2 cavities can keep its physiological activities, the electron transfer between the MP-11 and electrode was investigated through electrochemical method. The cyclic voltammetric curve shows a quasi-reversible electrochemical redox behavior with a pair of well-defined redox peaks, the cathodic and anodic peaks are located at −0.26 and −0.15 V. Furthermore, the modified electrode exhibits high electrocatalytic activity toward the reduction of hydrogen peroxide and also shows good analytical performance for the amperometric detection of H2O2 with a linear range from 2×10−6 to 6×10−4 M. The good reproducibility and long-term stability of this novel electrode not only offer an opportunity for the detection of H2O2 in low concentration, but also provide a platform to construct various biosensors based on many other enzymes.Highlights► Hydrogen peroxide biosensor based on silica cavity array electrode was constructed. ► The electron transfer of MP-11 was investigated through electrochemical method. ► The linear range for Hydrogen peroxide determination was from 2×10−6 to 6×10−4 M. ► The detection limit was 4×10−7 M.
Co-reporter:Shu Tian, Qun Zhou, Chuanhong Li, Zhuomin Gu, John R. Lombardi, and Junwei Zheng
The Journal of Physical Chemistry C 2013 Volume 117(Issue 1) pp:556-563
Publication Date(Web):December 18, 2012
DOI:10.1021/jp309224m
Silver nanoparticles were assembled onto the bottom of closed-packed silica cavity using polystyrene (PS) spheres as template. Charge transfer between the adsorbed 4-aminothiophenol (PATP) and the silver nanoparticles was studied using surface-enhanced Raman spectroscopy with 514, 633, 785, and 1064 nm excitation, and compared to that of the immobilized silver nanoparticles without the modification of silica cavity. Using the concept of degree of charge transfer, we directly observed the additional chemical enhancement without a deliberate distinction between electromagnetic (EM) enhancement and chemical enhancement. It was demonstrated that the negative charges of the silica could induce the formation of the dipole in the nanoparticles, thus enlarging the electron density at the sites where probe molecules adsorbed, and leading to higher charge transfer from the metal to the adsorbed PATP molecules. We also proposed another model to further elucidate the relationship between the electron density and the charge transfer. The result showed that the reduction of the electron density of silver nanoparticles will cause the redistribution of the dipole, thereby reducing the charge transfer degree.
Co-reporter:Chuanhong Li, Qun Zhou, Zhuomin Gu, Lili Zhao, Junwei Zheng
Electrochemistry Communications 2012 Volume 22() pp:113-115
Publication Date(Web):August 2012
DOI:10.1016/j.elecom.2012.06.012
An array structure of SiO2 cavities was fabricated on the surface of an indium-doped tin oxide (ITO) electrode by using highly ordered self-assembly of polystyrene spheres as a template. The SiO2 cavities exhibited a confinement effect on the electrochemical deposition of gold nanoparticles, which are formed only at the bottom of the SiO2 cavities. A single particle dominated with the [111] facets was generated in the cavity by annealing the gold nanoparticles at high temperature. The single gold particles showed excellent electrocatalytic activity for the oxidation of glucose. This strategy might provide an approach to study electrochemical reactions on a single particle in a microenvironment.Highlights► Silica cavities were fabricated with the template of highly ordered polystyrene spheres. ► A single gold particle was formed by fusion of gold nanoparticles in the SiO2 cavity. ► Electrocatalytic oxidation reaction of glucose was achieved on a single gold particle.
Co-reporter:Zhi Li, Yajing Chen, Yukou Du, Xiaomei Wang, Ping Yang, Junwei Zheng
International Journal of Hydrogen Energy 2012 Volume 37(Issue 6) pp:4880-4888
Publication Date(Web):March 2012
DOI:10.1016/j.ijhydene.2011.12.045
A new type of graphene-based nanohybrid was prepared from graphene nanosheets and 4-(diphenylamino)benzaldehyde (TPA-CHO) through 1,3-dipolar cycloaddition. The nanohybrid was modified by platinum nanoparticles via photodeposition. The nanohybrid and its Pt modified nanocomposite were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Ultraviolet–visible absorption (UV–vis), Fourier transform infrared (FTIR), and Raman spectra confirmed that triphenylamine moiety grafted on the graphene surface. The results of fluorescence quenching and photocurrent enhancement of the triphenylamine-functionalized graphene revealed that photoinduced electron transfer from triphenylamine moiety to the graphene sheet. The investigation of using the Pt modified graphene-based nanocomposite as a photocatalyst for H2 evolution showed that under UV–vis light irradiation, the average H2 evolution rate and the quantum efficiency is 2.3 μmol h−1 and 0.45% mol E−1, respectively. This work demonstrated a potential application of an organic sensitizer covalently functionalized graphene as a novel photocatalyst in the field of solar energy conversion.Highlights► A novel nanocomposite composed of triphenylamine covalently functionalized graphene and Pt nanoparticles has been synthesized. ► Hydrogen evolution took place using the graphene-based nanocomposite as a photocatalyst under UV–vis light irradiation. ► The TPA moiety of G-TPA may harvest irradiation light and transfer photoinduced electrons to graphene, improving separation efficiency of carriers.
Co-reporter:Juan Ma, Hanjun Sun, Fu Su, Yu Chen, Yawen Tang, Tianhong Lu, Junwei Zheng
International Journal of Hydrogen Energy 2011 Volume 36(Issue 12) pp:7265-7274
Publication Date(Web):June 2011
DOI:10.1016/j.ijhydene.2011.02.142
A novel self-reduction of Pt-complex method is used to prepare Vulcan XC-72 carbon-supported Pt nanoparticles (Pt/C) catalysts by employing ethylenediamine-tetramethylene phosphonic acid (EDTMP) as a complexing reagent. During the preparation of Pt/C catalysts, the particle size of Pt nanoparticles (Pt–NPs) can be controlled effectively in the range of 1.7–13.5 nm by adjusting reaction solution pH values. TEM images demonstrate that the Pt–NPs well disperse on the Vulcan XC-72 carbon support with a relatively narrow particle size distribution by using the complex self-reduction method. Therefore, the Pt/C catalysts prepared by the same method are suitable for evaluating the size effect of the Pt–NPs on electrocatalytic performance for ethanol electrooxidation. A correlation between the electrocatalytic activity of ethanol oxidation and particle size of the Pt/C catalysts indicates that Pt–NPs with mean particle size of ca. 2.5 nm possesses the highest electrocatalytic performance for ethanol electrooxidation.
Co-reporter:Juan Ma, Yigang Ji, Hanjun Sun, Yu Chen, Yawen Tang, Tianhong Lu, Junwei Zheng
Applied Surface Science 2011 Volume 257(Issue 24) pp:10483-10488
Publication Date(Web):1 October 2011
DOI:10.1016/j.apsusc.2011.07.007
Abstract
A highly dispersed and ultrafine carbon supported Pd nanoparticles (Pd/C) catalyst is synthesized by a facile homogeneous precipitation-reduction reaction method. Under the appropriate pH conditions, [PdCl4]2− species in PdCl2 solution are slowly transformed into the insoluble palladium oxide hydrate (PdO·H2O) precipitation by heat treatment due to a slow hydrolysis reaction, which results in the generation of carbon supported PdO·H2O nanoparticles (PdO·H2O/C) sample with the high dispersion and small particle size. Consequently, a highly dispersed and ultrafine Pd/C catalyst can be synthesized by PdO·H2O → Pd0 in situ reduction reaction path in the presence of NaBH4. As a result, the resulting Pd/C catalyst possesses a significantly electrocatalytic performance for formic acid electrooxidation, which is attributed to the uniformly sized and highly dispersed nanostructure.
Co-reporter:Juan Ma, Yawen Tang, Gaixiu Yang, Yu Chen, Qun Zhou, Tianhong Lu, Junwei Zheng
Applied Surface Science 2011 Volume 257(Issue 15) pp:6494-6497
Publication Date(Web):15 May 2011
DOI:10.1016/j.apsusc.2011.02.050
Abstract
The carbon supported PtP (PtP/C) catalysts were synthesized from Pt(NO3)2 and phosphorus yellow at the room temperature. The content of P in the PtP/C catalysts prepared with this method is high and the average size of the PtP particles is decreased with increasing the content of P. The electrocatalytic performances of the PtP/C catalysts prepared with this method for the oxygen reduction reaction (ORR) are better than that of the commercial Pt/C catalyst. The promotion action of P for enhancing the electrocatalytic performance of the PtP/C catalyst for ORR is mainly due to that Pt and P form the alloy and then the electron density of Pt is decreased.
Co-reporter:Qun Zhou, Guozhu Qian, Yan Li, Gui Zhao, Yanwen Chao, Junwei Zheng
Thin Solid Films 2008 Volume 516(Issue 6) pp:953-956
Publication Date(Web):30 January 2008
DOI:10.1016/j.tsf.2007.06.012
Silver nanoparticles were assembled into a two-dimensional submonolayer structure on the surface of glass slides. The immobilized silver nanoparticles showed excellent catalytic activity for the reduction of 4-nitroaniline by borohydride. The immobilized catalyst can be conveniently recovered from the reaction system, leading to easy monitoring of the catalytic reaction by the spectroscopic methods. Results indicate that the silver nanoparticles function as the electron relay in the catalytic reduction process. The direct contact of 4-nitroaniline molecules with silver nanoparticles is necessary for the electron transfer from the electron-donating molecules to the accepting molecules through the silver nanoparticles.
Co-reporter:Qun Zhou;Yanwen Chao;Yan Li;Wei Xu;Ying Wu
ChemPhysChem 2007 Volume 8(Issue 6) pp:921-925
Publication Date(Web):16 MAR 2007
DOI:10.1002/cphc.200600776
Surface-enhanced Raman scattering under near-IR excitation is investigated for p-aminothiophenol (PATP) molecules that are either adsorbed on an electrochemically roughened silver electrode or embedded in an Au/PATP/Ag molecular junction assembled on an indium-doped tin oxide electrode. The contribution from chemical enhancement can be amplified relative to the contribution from electromagnetic enhancement, because the energy of the near-IR excitation is far from the surface plasmon resonance of the nanosized metal particles. The energy required for the charge-transfer process for the Au/PATP/Ag molecular junction is much lower than that of the PATP molecules adsorbed on the electrochemically roughened silver electrode. Coadsorption of chloride ions on the metal nanoparticles may result in an alteration of the local Fermi level of the metal nanoparticles, thus leading to better energy matching between the energy level of the interconnecting PATP molecules and the Fermi level of the metal nanoparticles.
Co-reporter:Qun Zhou ;Xiaowei Li;Qiang Fan;Xingxia Zhang
Angewandte Chemie International Edition 2006 Volume 45(Issue 24) pp:
Publication Date(Web):9 MAY 2006
DOI:10.1002/anie.200504419
Good vibrations: Metal–molecule–metal nanosystems are fabricated by the self-assembly of gold and silver nanoparticles interconnected with 4-aminothiophenol (PATP) molecules (see picture). The b2 vibrational modes of the PATP molecules are greatly enhanced by near-infrared excitation, as a result of charge transfer between the metal nanoparticles coupled with the vibrations of the PATP molecules.
Co-reporter:Fengbin Wang, Junwei Zheng, Xiaowei Li, Yuan Ji, Ying Gao, Wei Xing, Tianhong Lu
Journal of Electroanalytical Chemistry 2003 Volume 545() pp:123-128
Publication Date(Web):27 March 2003
DOI:10.1016/S0022-0728(03)00133-5
The conformation of microperoxidase-11 (MP-11) adsorbed on roughened silver electrodes was studied using surface-enhanced Fourier transform Raman spectroscopy. The results demonstrate that MP-11 was initially adsorbed via its polypeptide chain with a α-helix conformation, as indicated by the enhancement of the characteristic bands related to the amides I and III. The weak resonance effect of the porphyrin macrocycle in the near IR region contributes to the spectrum of the heme group. The presence of imidazole as the sixth ligand to the heme iron influences the conformation of the polypeptide chain of MP-11 on the electrode surface. Evaporation of solvent water results in an opened conformation of the adsorbed MP-11, which allows the heme group to contact the electrode surface directly.
Co-reporter:Junwei Zheng, Tianhong Lu, Therese M Cotton, George Chumanov
Journal of Electroanalytical Chemistry 2002 Volume 518(Issue 1) pp:6-12
Publication Date(Web):11 January 2002
DOI:10.1016/S0022-0728(01)00690-8
The photoelectrocatalytic effect for the reduction of CO2 mediated with methylviologen (MV) was studied at mercury, polished silver and roughened silver electrodes using electrochemical and surface-enhanced Raman scattering (SERS) techniques. A large photoelectrocatalytic effect for the reduction of CO2 in the presence of MV was observed at the roughened silver electrode, whereas there was only a very small photoelectrocatalytic current at a more negative potential on mercury and polished silver electrodes. The SERS spectra of MV in the presence and absence of CO2, along with the electrochemical results, demonstrate that the surface adsorbed complexes, MV+–Ag and MV0–Ag, played a role as the mediator for photoinduced electron transfer to CO2 in the solution. The results also suggest that the surface plasmon resonance of the nanoscale silver particle contributes to the overall photoelectrocatalytic effect on a roughened silver electrode.
Co-reporter:Junwei Zheng, George Chumanov, Therese M Cotton
Chemical Physics Letters 2001 Volume 349(5–6) pp:367-370
Publication Date(Web):7 December 2001
DOI:10.1016/S0009-2614(01)01149-6
EPR spectroscopy was employed in study of photoinduced electron transfer on nanosized silver particles. Radicals were observed for the silver colloid with methylviologen (MV), nitrophenol and methanol with irradiation of UV lights. The wavelength dependence of EPR spectra of silver colloid with methanol indicates that plasmon resonance may be critical for the formation of the radicals on the nanosized silver particles.
Co-reporter:Zhigang Mou, Shunli Yin, Mingshan Zhu, Yukou Du, Xiaomei Wang, Ping Yang, Junwei Zheng and Cheng Lu
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 8) pp:NaN2799-2799
Publication Date(Web):2012/12/14
DOI:10.1039/C2CP44270A
A novel composite composed of TiSi2, graphene and RuO2 nanoparticles was fabricated by a one-pot deposition method using reduced graphene oxide (RGO) as a supporting matrix and RuCl3 as the RuO2 precursor. The resulting RuO2/TiSi2/RGO composite was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectra, photoelectrical response and electrochemical impedance spectra. The results indicated that the three components in the composite were effectively contacted, thus facilitating the photogenerated charges transfer and separation through multiple routes. By using the composite as a photocatalyst for visible-light water splitting the average hydrogen production rate could reach 97.5 μmol h−1 g−1, which is higher than that from RuO2/TiSi2 and pure TiSi2 systems under the same conditions.
Co-reporter:Hai Ming, Jun Ming, Seung-Min Oh, Eung-Ju Lee, Hui Huang, Qun Zhou, Junwei Zheng and Yang-Kook Sun
Journal of Materials Chemistry A 2014 - vol. 2(Issue 44) pp:NaN18945-18945
Publication Date(Web):2014/09/03
DOI:10.1039/C4TA03557G
A new and simple strategy was developed to effectively disperse titanium dioxide (TiO2) nanocrystals into porous carbon (PC), and a series of hierarchical PC–TiO2 composites with different architectures were synthesized. By varying the amount of TiO2, from 30 wt% to 64 wt%, the lithium storage capacity of PC–TiO2 could be controllably varied from 546 mA h g−1 to 446 mA h g−1 under a current density of 50 mA g−1. Also, very stable cycling performances and rate capabilities could be obtained at the rates of 50 mA g−1 to 1600 mA g−1. By further increasing the content of TiO2 to 93%, another new composite of TiO2–C was also prepared and it demonstrated a storage capacity of 352 mA h g−1 at 50 mA g−1, which is much higher than that for most reported TiO2 materials. Based on these results, new full cells with a LiNi0.5Mn1.5O4 cathode, such as PC–TiO2/LiNi0.5Mn1.5O4, were successfully assembled and investigated. This full cell not only delivered a high energy density of 413 W h kg−1 but also showed a good rate capability and an energy retention of 90.5% over 100 cycles.
Co-reporter:Shuangshuang Li, Qun Zhou, Wenya Chu, Wei Zhao and Junwei Zheng
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 27) pp:NaN17645-17645
Publication Date(Web):2015/06/03
DOI:10.1039/C5CP02409A
Molecular recognition based on specific intermolecular interactions is essential for the design of sensors with high selectivity. Herein, we report the surface-enhanced Raman scattering (SERS) behaviour of 4-mercaptophenyl boronic acid (MPBA) on self-assembled silver nanoparticles and its interaction with D-glucose. It is demonstrated that the orientation and existing form of the MPBA strongly depend on the pH value of the media. The surface-immobilized MPBA can be reversibly associated with OH− in solution, along with a molecular orientation alteration. A self-condensation reaction among the OH−-associated MPBA molecules results in irreversible conversion of OH−-associated MPBA to anhydride, which may hinder the interaction between D-glucose and the B-moiety of MPBA. However, the self-condensation reaction can be diminished under optimized conditions. By taking advantage of the difference in the kinetics of dissociation of the OH−-associated MPBA and D-glucose-associated MPBA in acidic media, a proper scheme of the SERS detection of D-glucose is proposed to illuminate the spectral interference of OH−-associated MPBA, which exhibits SERS features similar to those of D-glucose-associated MPBA species. Based on those strategies, the SERS detection of D-glucose can be achieved in the physiologically-relevant concentration range.
