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Jos Ricardo Cezar Salgado Ermete Antolini Ernesto Rafael Gonzalez 《Applied catalysis. B, Environmental》2005,57(4):283-290
The electrocatalysis of the oxygen reduction reaction on carbon supported Pt and Pt–Co (Pt/C and Pt–Co/C) alloy electrocatalysts was investigated in sulphuric acid (both in the absence and in the presence of methanol) and in direct methanol fuel cells (DMFCs). In pure sulphuric acid Pt–Co/C alloys showed improved specific activity towards the oxygen reduction compared to pure platinum. In the methanol containing electrolyte a higher methanol tolerance of the binary electrocatalysts than Pt/C was observed. The onset potential for methanol oxidation at Pt–Co/C was shifted to more positive potentials. Accordingly, Pt–Co/C electrocatalyts showed an improved performance as cathode materials in DMFCs. 相似文献
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In this study, imidazolium functionalized poly(vinyl alcohol) (PVA) was synthesized by acetalization and direct quaternization reaction. Afterwards, composite anion exchange membranes based on imidazolium‐ and quaternary ammonium‐ functionalized PVA were used for direct methanol alkaline fuel cell applications. 1H NMR and Fourier transform infrared spectroscopy data indicated that imidazole functionalized PVA was successfully synthesized. Inductively coupled plasma mass spectrometry data demonstrated that the imidazolium structure was efficiently obtained by direct quaternization of the imidazole group. Composite anion exchange membranes were fabricated by application of the functionalized PVA solution on the surface of porous polycarbonate (PC) membranes. Fuel cell related properties of all prepared membranes were investigated systematically. The imidazolium functionalized composite membrane (PVA‐Im/PC) exhibited higher ionic conductivity (7.8 mS cm?1 at 30 °C) despite a lower water uptake and ion exchange capacity value compared to that of quaternary ammonium. In addition, PVA‐Im/PC showed the lowest methanol permeation rate and the highest membrane selectivity as well as high alkaline and oxidative stability. Dynamic mechanical analysis results reveal that both composite membranes were mechanically resistant up to 107 Pa at 140 °C. The superior performance of imidazolium functionalized PVA composite membrane compared to quaternary ammonium functionalized membrane makes it a promising candidate for direct methanol alkaline fuel cell applications. © 2020 Society of Chemical Industry 相似文献
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Li Liu Cong Pu Rameshkrishnan Viswanathan Qinbai Fan Renxuan Liu E.S Smotkin 《Electrochimica acta》1998,43(24):9547
A comparative study of the use of supported and unsupported catalysts for direct methanol fuel cells has been performed. The effect of catalyst loading, fuel concentration and temperature dependence on the anode, cathode and full fuel cell performance was determined in a fuel cell equipped with a reversible hydrogen reference electrode. Although the measured specific activities of supported catalysts were as much as 3-fold greater than the unsupported catalysts, membrane electrode assemblies prepared with supported catalysts showed no improvement with loadings above 0.5 mg/cm2. Fuel cells utilizing 0.46 mg/cm2 supported catalyst electrodes performed as well as unsupported catalyst electrodes with 2 mg/cm2. The temperature dependence and methanol concentration dependence studies both suggest increased methanol permeation through the thinner supported catalyst layers relative to the unsupported catalyst layers. 相似文献
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Philip N. Ross 《Electrochimica acta》1991,36(14):2053-2062
The most active catalysts known for the direct electrochemical oxidation of methanol have a bimetallic or multimetallic composition, which are usually used in practice with the metals dispersed on an inert, electronically conductive support. One of the limitations to understanding the behavior of such catalysts has been the absence of methods for the systematic characterization of these complex materials, eg whether the metals are present in alloy phases, the particle size and surface area of the alloy phases, the surface composition, etc. The purpose of this paper is to review recent developments in characterization methodologies, both in situ and ex situ, and to show how these may be applied to multimetallic electrocatalysts. 相似文献
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T. Schultz U. Krewer T. Vidaković M. Pfafferodt M. Christov K. Sundmacher 《Journal of Applied Electrochemistry》2007,37(1):111-119
The dynamic operating behaviour of the direct methanol fuel cell (DMFC) is governed by several physico-chemical phenomena
which occur simultaneously: double layer charging, electrode kinetics, mass transport inside the porous structures, reactant
distributions in the anode and cathode flowbeds etc. Therefore it is essential to analyse the interactions of these phenomena
in order to fully understand the DMFC. These phenomena were initially analysed independently by systematic experiments and
model formulations. Electrode kinetics were determined by fitting models of varying complexity to electrochemical impedance
spectroscopy (EIS) measurements. Reaction intermediates adsorbed on the catalyst seem to play a key role here. To describe
mass transport across the DMFC a one-dimensional model was formulated applying the generalised Maxwell–Stefan equations for
multi-component mass transport and a Flory–Huggins model for the activities of mobile species inside the membrane (PEM). Also
swelling of the PEM as well as heat production and transport were considered. Finally, the anode flowbed was analysed by observing
flow patterns in different flowbed designs and measuring residence time distributions (RTDs). Detailed CFD models as well
as simpler CSTR network representations were used to compare to the experimental results. Even the simpler models showed good
agreement with the experiments. After these investigations the results were combined: the electrode kinetics model was implemented
in the mass transport model as well as in the CSTR network flowbed model. In both cases, good agreement, even to dynamic experiments,
was obtained. 相似文献
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This research aims at increasing the utilization of platinum-ruthenium alloy (Pt-Ru) catalysts and thus lowering the catalyst
loading in anodes for methanol electrooxidation. The direct methanol fuel cell’s (DMFC) anodic catalysts, Pt-Ru/C, were prepared
by chemical reduction with a reducing agent added in two kinds of solutions under different circumstances. The reducing agent
was added in hot solution with the protection of inert gases or just air, and in cold solution with inert gases. The catalysts
were treated at different temperatures. Their performance was tested by cyclic voltammetry and potentiostatic polarization
by utilizing their inherent powder microelectrode in 0.5 mol/L CH3OH and 0.5 mol/LH2SO4 solution. The structures and micro-surface images of the catalysts were determined and observed by X-ray diffraction and
transmission electron microscopy, respectively. The catalyst prepared in inert gases showed a better catalytic performance
for methanol electrooxidation than that prepared in air. It resulted in a more homogeneous distribution of the Pt-Ru alloy
in carbon. Its size is small, only about 4.5 nm. The catalytic performance is affected by the order of the reducing agent
added. The performance of the catalyst prepared by adding the reductant at constant temperature of the solution is better
than that prepared by adding it in the solution at 0°C and then heating it up to the reducing temperature. The structure of
the catalyst was modified, and there was an increase in the conversion of ruthenium into the alloyed state and an increase
in particle size with the ascension of heat treatment temperature. In addition, the stability of the catalyst was improved
after heat treatment.
Translated from Journal of Harbin Institute of Technology, 2006, 38 (4): 541-545 [译自: 哈尔滨工业大学学报] 相似文献
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Koji Makino 《Electrochimica acta》2005,51(5):961-965
The electrodes prepared by a sputtering method were evaluated as the cathodes for direct methanol fuel cells (DMFCs). Pt loading below 0.25 mg cm−2 achieved higher mass activities than that of 0.5 mg cm−2 prepared by the paste method, which was general conventional method. However, an increase in Pt loading reduced the catalyst activity for the oxygen reduction reaction (ORR). This result may suggest an increase in only electrochemically inactive Pt. Pt utilization efficiency can be found about ten times higher at Pt loading of 0.04 mg cm−2. Moreover, addition of Nafion to sputter-deposited Pt cathodes is found possible to improve the catalyst activity for the ORR, but the excess Nafion over the optimum condition reduces the active sites. 相似文献
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In this study, a series of micro/nanostructured polyanilines were synthesized and their morphology-dependent electrochemical properties for acting as a catalyst supporter for direct methanol fuel cell (DMFC) applications were investigated. These micro/nanostructures include submicron spheres, hollow microspheres, nanotubes, and nanofibers. Among the four micro/nanostructures, polyaniline nanofibers (PANF) manifest their superiority in high electrochemical active surface. Accordingly, PANF is adopted as the catalyst supporter thereafter. To couple with the use of the alternative catalyst supporter, this study also investigates the effect of reductant type on morphology and electrocatalytic properties of the PANF-supported Pt particles through a chemical reduction reaction. TEM images indicate that formic acid as a reductant results in well-dispersed Pt particles on the PANF surface. On the other hand, aggregations of Pt are observable when NaBH4 is selected as a reductant. Moreover, the methanol oxidation current density measured with the Pt/PANF electrode being prepared by using formic acid is double that by using NaBH4. Compared with Pt/XC-72, the Pt/PANF electrode possesses higher electrocatalytic activity and exhibits double power density. Moreover, Pt/PANF is superior to Pt/XC-72 in the aspect of operation stability based on a continuous discharge for 5 h. 相似文献
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阳极催化剂是影响直接甲醇燃料电池(DMFC)性能及成本的主要因素之一,从催化剂载体选择、复合催化剂的制备、非贵金属催化剂研究三方面综述了DMFC阳极催化剂国内外研究现状,并进行了简要分析,展望了其应用前景。 相似文献
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Gui‐Cheng Liu Yi‐Tuo Wang Jing Zhang Meng Wang Chao‐Jie Zhang Xin‐Dong Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(5):818-822
BACKGROUND: The commercialization of DMFCs is seriously restricted by its relatively low power density. Lots of work has been concentrated on catalysts with high activity, the optimization of flow path design, development of new kinds of proton exchange membrane and modification of Nafion membrane. Meanwhile, very few reports have involved the structure optimization of the membrane electrode assembly (MEA). To improve the performance of direct methanol fuel cells (DMFCs), the catalyst layer (CL) structures of anode and cathode were optimized by utilizing ammonium carbonate as pore forming agent. RESULTS: The polarization curves showed that in catalyst slurry the optimal content of ammonium carbonate was 50 wt%, and the DMFC performance was enhanced from 75.65 mW cm?2 to 167.42 mW cm?2 at 55 °C and 0.2 MPa O2. Electrochemical impedance spectroscopy and electrochemical active surface area (EASA) testing revealed that the improved performance of optimized MEAs could be mainly attributed to the increasing EASA and the enhanced mass transfer rate of CLs. But poor methanol crossover limited the performance enhancement of MEAs with porous anodes. CONCLUSION: With regard to improving cell performance, this pore‐forming technology is better applied to the cathode catalyst layer to improve its structure rather than the anode catalyst layer. © 2012 Society of Chemical Industry 相似文献
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This research aims to enhance the activity of Pt catalysts, thus to lower the loading of Pt metal in fuel cell. Highly dispersed platinum supported on single-walled carbon nanotubes (SWNTs) as catalyst was prepared by ion exchange method. The homemade Pt/SWNTs underwent a repetition of ion exchange and reduction process in order to achieve an increase of the metal loading. For comparison, the similar loading of Pt catalyst supported on carbon nanotubes was prepared by borohydride reduction method. The catalysts were characterized by using energy dispersive analysis of X-ray (EDAX), transmission electron micrograph (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrum (XPS). Compared with the Pt/SWNTs catalyst prepared by borohydride method, higher Pt utilization was achieved on the SWNTs by ion exchange method. Furthermore, in comparison to the E-TEK 20 wt.% Pt/C catalyst with the support of carbon black, the results from electrochemical measurement indicated that the Pt/SWNTs prepared by ion exchange method displayed a higher catalytic activity for methanol oxidation and higher Pt utilization, while no significant increasing in the catalytic activity of the Pt/SWNTs catalyst obtained by borohydride method. 相似文献
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A highly efficient synthesis approach of urea-assisted homogeneous deposition (HD) coupled with H2 reduction has been employed to synthesize carbon-supported Pt-Ru catalyst with high metal loading of 60 wt%. The urea-assisted HD method permits in situ gradual and homogeneous generation of hydroxide ions, resulting in smaller Pt-Ru nanaoparticles deposited on the carbon support along with better particle size distribution compared with the catalyst prepared by the conventional impregnation-NaBH4 reduction. The Pt-Ru catalyst prepared by the HD-H2 method has demonstrated greatly enhanced catalytic activity towards methanol oxidation and much improved fuel cell performance compared with the one prepared by impregnation-NaBH4 reduction. HD-H2 method is simple with mild synthesis condition, but provides very efficient approach for the preparation of Pt-based catalysts for fuel cells. 相似文献