Home About us Contact
|
Home About us Contact | ||
|
|
||
Methanol Fuel Cell (methanol + fuel_cell)
Kinds of Methanol Fuel Cell Selected AbstractsAnalysis of Direct Methanol Fuel Cell (DMFC)-Performance via FTIR Spectroscopy of Cathode ExhaustFUEL CELLS, Issue 4 2003F. Meier Abstract Water and methanol flux through NafionÔ and polyaryl-blend membranes prepared at ICVT were studied under DMFC operation. The water, methanol, and CO2 content in the cathode exhaust were measured by FTIR spectroscopy. Both the water and methanol flux turned out to be strongly dependent on the operating temperature and thus on membrane swelling. Apart from this, water flux through the membrane is primarily affected by the gas volume flux on the cathode side. A coupling between water flux and methanol flux was observed, which leads to the conclusion that methanol is transported both by diffusion and by convection caused by the superimposed water flux. Polyaryl-blend membranes showed a reduced diffusive methanol transport when compared to NafionÔ due to their different internal microstructure. The impact of methanol cross-over on cathode losses at high current density needs further clarification with respect to the prevailing mechanism of methanol oxidation at the cathode. [source] Polymer Electrolyte Membranes with a Pore-Filling Structure for a Direct Methanol Fuel Cell,ADVANCED MATERIALS, Issue 14 2003T. Yamaguchi Pore-filling membranes that are composed of a porous substrate and a filling polymer electrolyte have been developed. These polyelectrolyte membranes demonstrate low permeation with respect to methanol, high proton conductivity, good mechanical strength, chemical stability, and low cost, making them ideal for use in direct methanol fuel cells. The necessary characteristics can also be controlled by changing the substrate and the filling polymer electrolyte. [source] Catalysts for Direct Methanol Fuel CellsFUEL CELLS, Issue 2 2002M. Neergat [source] Deposition of PtxRu1,x Catalysts for Methanol Oxidation in Micro Direct Methanol Fuel CellsISRAEL JOURNAL OF CHEMISTRY, Issue 3-4 2008William E. Mustain Platinum-ruthenium electrodes (PtxRu1-x) have been prepared by electrochemical and electroless deposition and investigated as catalysts for the oxidation of methanol in acidic solutions. PtxRu1-x deposits were electrochemically deposited from acidic chloride electrolytes at potentials between ,0.46 and 0.34 V (vs. NHE). The composition of the electrodeposit was estimated by energy dispersive X-ray spectroscopy and is a strong function of the electrode potential. An empirical model for the deposition process is presented and kinetic parameters are estimated and discussed. Also, the methanol oxidation activity of the PtxRu1-x catalysts was characterized by cyclic voltammetry in 1.0 M CH3OH, 1.0 M H2SO4 solutions. Electroless PtxRu1-x samples were prepared in a modified Leaman bath with hydrazine dihydrochloride as the reducing agent. The kinetic results for the electrochemical deposition of PtxRu1-x were directly applied and the deposition potential was estimated as approximately 0.40 V. [source] Electrocatalysis of Direct Methanol Fuel Cells.ANGEWANDTE CHEMIE, Issue 37 2010From Fundamentals to Applications. Wiley-VCH, Weinheim 2009. 606,pp., geb. 139.00,,.,ISBN 978-3527323777 [source] Membranen für Polymerelektrolyt-Brennstoffzellen,CHEMIE-INGENIEUR-TECHNIK (CIT), Issue 11 2003A. Glüsen Dr. rer. nat. Abstract Die Polymerelektrolyt-Membran ist das Herzstück von wasserstoffbetriebenen Polymerelektrolyt-Brennstoffzellen (PEFC) und methanolbetriebenen Direktmethanol-Brennstoffzellen (DMFC). Membranen aus sulfonierten Fluoropolymeren sind derzeit kommerziell erhältlich. Wichtige Forschungs- und Entwicklungsziele sind derzeit für die PEFC die Erhöhung der Betriebstemperatur, ohne die Membran zusätzlich befeuchten zu müssen, und für die DMFC die Verringerung des Methanoltransportes durch die Membran. Zusätzlich sollen durch die Verwendung fluorfreier Polymere die Kosten der Membran und die Umweltbelastung reduziert werden. Dabei spielen bereits in der industriellen Entwicklung befindliche Membranen ebenso eine Rolle wie neue Membrankonzepte aus der Grundlagenforschung. Membranes for Polymer Electrolyte Fuel Cells The polymer electrolyte membrane is the heart of hydrogen fuelled Polymer Electrolyte Fuel Cells (PEFC) and methanol fuelled Direct Methanol Fuel Cells (DMFC). Membranes of sulfonated fluoropolymers are already commercially available. Important goals for research and development are for PEFCs an increased operating temperature without the need for additional humidification and for DMFC the reduction of methanol transport through the membrane. The use of non-fluorinated polymers aims at a reduction in membrane cost and environmental hazards. Membranes already in industrial product development are considered as well as novel membrane concepts in fundamental research. [source] ChemInform Abstract: Pt,Ru/Carbon Fiber Nanocomposites: Synthesis Characterization, and Performance as Anode Catalysts of Direct Methanol Fuel Cells.CHEMINFORM, Issue 16 2002A Search for Exceptional Performance. Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Performance Tests and Pressure Drop Measurements in the Anode Flowfield of a ,DMFCFUEL CELLS, Issue 4 2010S.-S. Hsieh Abstract Cell performance tests and measurements of the pressure drops in the anode flow channels of a custom-made microdirect methanol fuel cell (,DMFC) are conducted and studied for different methanol concentrations (0.5,2,M), flow rates (10,20,sccm) and operating temperatures (40,80,°C). The anode flowfields consist of three channel/four pass flow channels with widths of 500,2000,,m and a total length of 300,400,mm. Moreover, flow characteristics of the CO2 gas bubbles and methanol solution in the anode flow channels are identified and analysed for CO2 fraction through visualisation. Finally, an optimal channel size for the present ,DMFC is obtained. [source] A Pumpless Methanol Feeding Method for Application in Direct Methanol Fuel Cell SystemsFUEL CELLS, Issue 4 2010J. Geng Abstract This paper presents a simple and reliable pumpless methanol feeding (PLMF) method for application in direct methanol fuel cell (DMFC) systems. The primary feature and advantage of the PLMF is as follows: it employs an approach that allows the cathode gas pressure to be connected with a fuel container for supplying the methanol fuel into the anode fuel loop, instead of using any feeding pump or other specially designed apparatuses. The PLMF has been used in a portable 25,W DMFC system and realised feeding methanol in real time for meeting the requirements of the system. The PLMF method not only is suitable for the DMFC system, but also can be used in other liquid-feeding fuel cell systems. [source] The Effect of the Anode Loading and Method of MEA Fabrication on DMFC PerformanceFUEL CELLS, Issue 3 2007T. V. Reshetenko Abstract The influence of the Pt-Ru anode loading and MEA preparation techniques on direct methanol fuel cell (DMFC) performance is studied. Two different anode catalyst layer preparation techniques are employed. One is the direct coating of anode catalyst ink on a membrane to form a catalyst coated membrane, CCManode, and the other is the coating of the ink on the diffusion layers, which generates a catalyst coated substrate, CCSanode. The power density of a combined CCManode/CCScathode MEA is higher than for a CCSanode/CCScathode MEA. The main difference in the performance is observed in the high current density region, where two-phase flow is present and mass transfer processes govern the performance. The CCManode and CCSanode have different macroscopic structures, while showing the same microscopic morphology. Based on their morphological differences, it is expected that the combination of the CCManode and carbon paper provides the more homogeneous removal of CO2 at high currents. The authors suggest that the application of the CCManode with an optimal anode loading improves anode mass transfer, reduces methanol crossover, and enhances the electrochemical reactions. [source] Comparison between Nafion® and a Nafion® Zirconium Phosphate Nano-Composite in Fuel Cell ApplicationsFUEL CELLS, Issue 3-4 2006F. Bauer Abstract A comparative investigation of the electrical, mechanical, and chemical behaviour of zirconium phosphate-Nafion® composite membranes and Nafion® by means of ex-situ measurements, as well as with fuel cell operation, reveals a slight reduction of ionic conductivity, a significant improvement of mechanical stability, and increased water retention for the composite materials. The overall efficiency at 130,°C is increased during direct methanol fuel cell (DMFC) operation because the reduction in the ionic conductivity is overcompensated for by the decrease in methanol crossover. With H2 as the fuel, the slight reduction in overall efficiency corresponds to the decrease in ionic conductivity. The dimensional stability of the membrane and the membrane electrode assembly (MEA) is significantly improved for operating temperatures above 100,°C. A model for the microstructure-property relation for PFSA-Zr(HPO4)2,·,n,H2O composite membranes is presented, based on the experimental results from membranes with varying filler contents and distributions, obtained through different synthesis routes. It is aimed at the improvement of water distribution in the membrane upon fuel cell operation. [source] Effect of anode current collector on the performance of passive direct methanol fuel cellsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2009Qin-Zhi Lai Abstract The effect of anode current collector on the performance of passive direct methanol fuel cell (DMFC) was investigated in this paper. The results revealed that the anode of passive DMFC with perforated current collector was poor at removing the produced CO2 bubbles that blocked the access of fuel to the active sites and thus degraded the cell performance. Moreover, the performances of the passive DMFCs with different parallel current collectors and different methanol concentrations at different temperatures were also tested and compared. The results indicated that the anode parallel current collector with a larger open ratio exhibited the best performance at higher temperatures and lower methanol solution concentrations due to enhanced mass transfer of methanol from the methanol solution reservoir to the gas diffusion layer. However, the passive DMFC with a smaller open ratio of the parallel current collector exhibited the best performance at lower temperatures and higher methanol solution concentrations due to the lower methanol crossover rate. Copyright © 2009 John Wiley & Sons, Ltd. [source] On mass transport in an air-breathing DMFC stackINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2005G. Q. Lu Abstract An 8-cell air-breathing direct methanol fuel cell (DMFC) stack with the active area of 5 cm2 of each cell has been developed. Stainless steel plates of 500 µm thickness with flow channels were fabricated using photochemical etching method as the current collectors. Different conditioning methods for membrane electrode assembly (MEA) activation were discussed. With proper control of water crossover to the cathode, cathode flooding was avoided in the DMFC stack. Methanol crossover at open circuit voltage (OCV) in the air-breathing DMFC was measured. Further, it was found that flow maldistribution might occur in the parallel flow field of the stack, making carbon dioxide gas management at the anode necessary. Using humidified hydrogen in the anode with a high flow rate, the oxygen transport limiting current density was characterized and found to be sufficient in the air-breathing cathode. The stack produced a maximum output power of 1.33 W at 2.21 V at room temperature, corresponding to a power density of 33.3 mW cm,2. Copyright © 2005 John Wiley & Sons, Ltd. [source] Intelligent structure design of membrane cathode assembly for direct methanol fuel cellINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2005K. Furukawa Abstract The performance and the structural model of membrane electrode assembly (MEA) have been developed and experimentally verified with fundamental calculations of the direct methanol fuel cell (DMFC). The model provides information concerning the influence of the operating and structural parameters. The composition and performance optimization of MEA structure in DMFC has been investigated by including both electrochemical reaction and mass transport process. In the experimentation, the effect of Nafion content and loading method in the catalyst layer of cathode for DMFC was investigated. For the spray method electrode (SME), the cell performance and cathode performance using a dynamic hydrogen electrode (DHE) as a reference electrode was improved in comparison with those of the PME electrode by decreasing cathode potential. From ac impedance measurements of the cathode, the adsorption resistance of the SME electrode was decreased compared with that of the PME electrode. The higher cell performance was mostly dependent on the adsorption resistance. In the modelling, the cathode overpotential was decreased with increasing ionomer content, due to increasing ionic conductivity for proton transfer and the larger reaction site. The resistance to oxygen transport was increased at the same time, and became dominant at higher ionomer loadings, leading to an increase in the voltage loss. The ratio of ionomer to void space in the cathode affected the cathode polarization, which had the lowest resistance of oxygen diffusion at the ratio of 0.1,0.2. Copyright © 2005 John Wiley & Sons, Ltd. [source] Poly(vinyl alcohol),polyacrylamide blends with cesium salts of heteropolyacid as a polymer electrolyte for direct methanol fuel cell applicationsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010M. Helen Abstract A class of inorganic,organic hybrid membranes with low methanol permeability characteristics for possible direct methanol fuel cell (DMFC) applications was architected, formulated, and fabricated through the blending of poly(vinyl alcohol) (PVA) and polyacrylamide (PAM) followed by crosslinking with glutaraldehyde (Glu). Cesium salts of different heteropolyacids, including phosphomolybdic acid (PMA), phosphotungstic acid (PWA), and silicotungstic acid (SWA), were incorporated into the polymer network to form corresponding hybrid membrane materials, namely, PVA,PAM,CsPMA,Glu, PVA,PAM,CsPWA,Glu, and PVA,PAM,CsSWA,Glu, respectively (where "Cs" together with a heteropolyacid abbreviation indicates the cesium salt of that acid). All the three hybrid polymer membranes fabricated exhibited excellent swelling, thermal, oxidative, and additive stability properties with desired proton conductivities in the range 10,2 S/cm at 50% relative humidity. A dense network formation was achieved through the blending of PVA and PAM and by crosslinking with Glu, which led to an order of magnitude decrease in the methanol permeability compared to the state-of-the-art commercial Nafion 115 membrane. The hybrid membrane containing CsSWA exhibited a very low methanol permeability (1.4 × 10,8 cm2/s) compared to other membranes containing cesium salt of heteropolyacids such as PMA and PWA. The feasibility of these hybrid membranes as proton-conducting electrolytes in DMFC was investigated, and the preliminary results were compared with those of Nafion 115. The results illustrate the attractive features and suitability of the fabricated hybrid membranes as an electrolyte for DMFC applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] A semi-empirical cell voltage model for polymer electrolyte/methanol systems: Applicability of the group contribution methodJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Ji Yun Seong Abstract A new group contribution model is established to describe the cell voltage of a direct methanol fuel cell as a function of the current density. The model equation is validated with experimental data over a wide range of methanol concentrations and temperatures. The proposed model focuses on very unfavorable conditions for cell operation, that is, low methanol solution concentrations and relatively low cell temperatures. The proposed group contribution method includes a methanol crossover effect that plays a major role in determining the cell voltage of a direct methanol fuel cell. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Permeability and Conductivity Studies on Ionomer-Polysilsesquioxane Hybrid MaterialsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2006Chedarampet S. Karthikeyan Abstract Summary: Hybrid materials based on sulphonated poly(ether ether ketone) (SPEEK, ionomer) and (RSiO1.5)n network (polysilsequioxane) were prepared by sol-gel process. Two different precursors namely aminopropyl trimethoxysilane (APTMS) and imidazoleglycidoxypropyl trimethoxysilane (IGPTMS) were utilized to generate (RSiO1.5)n in SPEEK matrix by sol-gel process. 29Si MAS NMR confirmed the formation of RSiO3/2 network structure inside the matrix. Characterisation of the hybrid materials showed lower methanol and water permeability compared to the plain SPEEK. They are therefore promising materials as membranes for direct methanol fuel cells applications. The hybrid material derived from amino group was more effective in decreasing the permeability than the material derived from imidazole group. However, the proton conductivity of the latter was higher than the material derived from amino group. The results indicate that hybrid material prepared from imidazole containing silane is more suitable as a membrane for direct methanol fuel cell than the one prepared from amino carrying silane because it fulfils the two main requirements, namely low methanol permeability and reasonably good proton conductivity. Figure shows a network of silica phase in SPEEK matrix. [source] Different nanostructure cathode catalysts application for direct methanol fuel cellPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007Sharmin Sultana Dipti Abstract Direct methanol fuel cell (DMFC) belongs to the same family of energy conversion device and the application of new hydrogen storage nanomaterials such as carbon nanotube (CNTs) supported catalysts is being addressed in an increasing industrial approach. In this present study, multiwall carbon nanotube supported Pt and Pt-Ni nanoparticles were prepared as cathode catalysts for direct methanol fuel cell application. Transmission electron microscopy and X-ray diffraction analyses indicated the formation of well-dispersed Pt and Pt-Ni nanoparticles having sizes of around 2 , 4 nm on carbon nanotube. Furthermore, the electrochemical characterization by the cyclic voltammetry (CV) demonstrated that these catalysts have higher catalytic activity and the methanol oxidation reaction of the Pt-Ni/CNTs is respectively almost similar and slightly higher than Pt/CNTs electrocatalysts. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Modification of Nafion membrane using poly(4-vinyl pyridine) for direct methanol fuel cellPOLYMER INTERNATIONAL, Issue 5 2006Jeon Chan Woong Abstract Perfluorinated membrane such as Nafion (from Du-Pont) has been used as a polymer electrolyte membrane. Nafion 117 membrane, which was usually used as the electrolyte membrane for the polymer electrolyte membrane fuel cell (PEMFC), was modified by using poly(4-vinyl pyridine) (P4VP) to reduce the methanol crossover, which cause fuel losses and lower power efficiency, by the formation of an ionic crosslink structure (sulfonic acid-pyridine complex) on the Nafion 117 surface. Nafion film was immersed in P4VP/N -methyl pyrrolidone (NMP) solution. P4VP weight percent of modified membrane was controlled by changing the concentration of P4VP/NMP solution and the dipping time. P4VP weight percent increased with increasing concentration of dipping solution and dipping time. The thickness of the P4VP layer increased with increasing concentration of dipping solution and dipping time when the concentration of the dipping solution was low. At high P4VP concentration, the thickness of the P4VP layer was almost constant owing to the formation of acid,base complex which interrupted the penetration of P4VP. FTIR results showed that P4VP could penetrate up to 30 µm of Nafion 117 membrane. Proton conductivity and methanol permeability of modified membrane were lower than those of Nafion 117. Both decreased with increasing concentration of dipping solution and dipping time. Methanol permeability was observed to be more dependent on the penetration depth of P4VP. Water uptake of the modified membrane, the important factor in a fuel cell, was lower than that of Nafion 117. Water uptake also decreased with increasing of P4VP weight. On the basis of this study, the thinner the P4VP layer on the Nafion 117 membrane, the higher was the proton conductivity. Methanol permeability decreased exponentially as a function of P4VP weight percent. Copyright © 2006 Society of Chemical Industry [source] Enhancement of Methanol Tolerance in DMFC Cathode: Addition of Chloride IonsCHEMPHYSCHEM, Issue 10 2008Sunghyun Uhm Dr. Abstract In the operation of a direct methanol fuel cell, the modification by chloride ions on the surface of a Pt cathode can facilitate the extraordinary increase of power performance and long-term stability. Analyzing the results of cyclic voltammograms and electrochemical impedance spectroscopy, the positive shift of Pt oxidation onset potential and the depression of oxidation current are observed, which results from the role of chloride as surface inhibitor. In addition, O2 temperature-programmed desorption and X-ray photoelectron spectroscopy also reveal that the suppression of Pt surface oxide can be best understood in terms of lower binding of oxygen species by the alteration of electronic state of Pt atoms. Such a reduced surface oxide formation not only provides more efficient proton adsorption sites with high selectivity but also decreases the mixed potential by crossover methanol, resulting in higher performance and stability even under high voltage long-term operation. [source] Prospects for Alkaline Anion-Exchange Membranes in Low Temperature Fuel Cells,FUEL CELLS, Issue 2 2005J. R. Varcoe Abstract This article introduces the radical approach of applying alkaline anion-exchange membranes (AAEMs) to meet the current challenges with regards to direct methanol fuel cells (DMFCs). A review of the literature is presented with regards to the testing of fuel cells with alkaline membranes (fuelled with hydrogen or methanol) and also to candidate alkaline anion-exchange membranes for such an application. A brief review of the directly related patent literature is also included. Current and future research challenges are identified along with potential strategies to overcome them. Finally, the advantages and challenges with the direct electrochemical oxidation of alternative fuels are discussed, along with how the application of alkaline membranes in such fuel cells may assist in improving performance and fuel efficiency. [source] A Review of Mathematical Models for Hydrogen and Direct Methanol Polymer Electrolyte Membrane Fuel CellsFUEL CELLS, Issue 1-2 2004K.Z. Yao Abstract This paper presents a review of the mathematical modeling of two types of polymer electrolyte membrane fuel cells: hydrogen fuel cells and direct methanol fuel cells. Models of single cells are described as well as models of entire fuel cell stacks. Methods for obtaining model parameters are briefly summarized, as well as the numerical techniques used to solve the model equations. Effective models have been developed to describe the fundamental electrochemical and transport phenomena occurring in the diffusion layers, catalyst layers, and membrane. More research is required to develop models that are validated using experimental data, and models that can account for complex two-phase flows of liquids and gases. [source] Effect of anode current collector on the performance of passive direct methanol fuel cellsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2009Qin-Zhi Lai Abstract The effect of anode current collector on the performance of passive direct methanol fuel cell (DMFC) was investigated in this paper. The results revealed that the anode of passive DMFC with perforated current collector was poor at removing the produced CO2 bubbles that blocked the access of fuel to the active sites and thus degraded the cell performance. Moreover, the performances of the passive DMFCs with different parallel current collectors and different methanol concentrations at different temperatures were also tested and compared. The results indicated that the anode parallel current collector with a larger open ratio exhibited the best performance at higher temperatures and lower methanol solution concentrations due to enhanced mass transfer of methanol from the methanol solution reservoir to the gas diffusion layer. However, the passive DMFC with a smaller open ratio of the parallel current collector exhibited the best performance at lower temperatures and higher methanol solution concentrations due to the lower methanol crossover rate. Copyright © 2009 John Wiley & Sons, Ltd. [source] Polymer Electrolyte Membranes with a Pore-Filling Structure for a Direct Methanol Fuel Cell,ADVANCED MATERIALS, Issue 14 2003T. Yamaguchi Pore-filling membranes that are composed of a porous substrate and a filling polymer electrolyte have been developed. These polyelectrolyte membranes demonstrate low permeation with respect to methanol, high proton conductivity, good mechanical strength, chemical stability, and low cost, making them ideal for use in direct methanol fuel cells. The necessary characteristics can also be controlled by changing the substrate and the filling polymer electrolyte. [source] Sulfonated poly(ether imide) and poly(ether sulfone) blends for direct methanol fuel cells.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Abstract This investigation examines characteristics of sulfonated polyether imides (SPEI) with various ion exchange capacity values (IEC) and completes previous work to enable its blends to be adopted as polyelectrolyte in direct methanol fuel cells (DMFC). Polyether imides (PEI) were sulfonated by using chlorosulfonic acid as the sulfonating agent and chloroform as the solvent. The structure of SPEI was observed by FTIR and 1H NMR. The sulfonate or sulfonic acid content of the polymers, expressed as a number per repeat unit of the polymer, was accurately determined by elemental analysis and conductometric titration. Physical properties such as solubility, intrinsic viscosities, thermal stability, and glass transition temperature (Tg) were studied for both PEI and SPEI. TGA-FTIR verified that sulfonic groups, attached to the aromatic ring in the PEI backbone, are split at 230,350°C, but the main-chain splitting temperature of SPEI is similar to that of pure polymer. The sulfonated samples exhibited good solubilities and increased glass transition temperatures (Tg values) as degree of sulfonation (DS) increased; two Tg values were detected when IEC was sufficiently high. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] | |||||||||||||