Showing papers on "Direct methanol fuel cell published in 2000"
TL;DR: In this paper, the authors describe methanol flux measurements across Nafion, 1100 equivalent weight membranes under conditions of a direct methanoline fuel cell but in which methanols is completely electro-oxidized on the opposite side in an inert atmosphere at sufficiently high electrode potential.
Abstract: This paper describes methanol flux measurements across Nafion, 1100 equivalent weight membranes under conditions of a direct methanol fuel cell but in which methanol is completely electro-oxidized on the opposite side in an inert atmosphere at sufficiently high electrode potential. Both the diffusion coefficient and the methanol concentration in the membrane were determined from the measured transient limiting current density following a potential step. Corrections for electro-osmotic drag effects are developed and found necessary even for low MeOH concentrations. The results agree well with those obtained from nuclear magnetic resonance measurements. The partition coefficient [{rho} = [MeOH]{sub membrane}/[MeOH]{sub solution}] was approximately constant for the membranes in contact with methanol solutions of various concentration and from room temperature to 90 C. The activation energy of methanol diffusion in a fully hydrated Nafion membrane between 30 and 130 C is 4.8 kcal/mol, and that for protonic conduction under the same conditions is 2.3 kcal/mol. For a membrane dried in vacuum at above 100 C, lower values of methanol permeation rate and protonic conductance were found.
480 citations
TL;DR: In this article, a homogeneuosly sulfonated poly(styrene) poly(SPS) was prepared with various concentration of sulfonic acid groups in the base polymer.
287 citations
TL;DR: In this paper, an in-situ probe of surface composition for a direct methanol fuel cell (DMFC) catalyst is presented, based on voltammetry of CO adsorbed at bulk PtRu alloy electrode surfaces.
267 citations
TL;DR: In this paper, the authors investigated the methanol permeability of two commercial partially fluorinated ionomeric membranes: IonClad{reg_sign} R-1010 and R-4010, both manufactured by Pall Company.
Abstract: Proton conductivities as well as methanol permeabilities were investigated for two commercial partially fluorinated ionomeric membranes: IonClad{reg_sign} R-1010 and R-4010, both manufactured by Pall Company. The investigation was carried out in the temperature range 20 to 60 C. The results were compared with data for Nafion{reg_sign} 117 (DuPont) obtained in the same temperature range. The authors found that IonClad membranes, while exhibiting proton conductivity approximately equal to that of Nafion 117, are considerably less permeable to methanol. The permeability measured for R-4010 membranes was almost four times smaller than for the Nafion membrane. These characteristics together with the low cost make the IonClad membranes interesting potential candidates for application in the direct methanol fuel cell.
199 citations
TL;DR: In this article, the oxygen reduction reaction (ORROC) activity of a Ru 1.92 Mo 0.08 SeO 4 catalyst, a Vulcan XC72-supported Ru catalyst and a VXC72 supported Pt catalyst was studied with a rotating ring-disk electrode.
Abstract: The oxygen reduction reaction (ORR) activity of a Ru 1.92 Mo 0.08 SeO 4 catalyst, a Vulcan XC72-supported Ru catalyst and, for comparison, a Vulcan XC72-supported Pt catalyst was studied with a rotating ring-disk electrode. The very similar reaction characteristics of the two Ru catalysts in pure and CH 3 OH-containing H 2 SO 4 electrolyte, which differ markedly from those of the Pt catalyst, indicate that the reactive centers in both Ru catalysts must be identical. They are highly selective (>95%) toward reduction to H 2 O (four electron pathway), independent of the presence of methanol. In the latter case, they are 100% selective toward the ORR, i.e., completely methanol tolerant, while the ORR on Pt catalysts is accompanied by significant CH 3 OH oxidation. Based on mass specific current densities, however, the Ru catalysts are significantly less active than the standard Pt catalysts. Only at methanol concentrations above 10-30 mM does their methanol tolerance make them more active than Pt/Vulcan. Implications for their use as cathode catalysts in a direct methanol fuel cell are discussed.
199 citations
TL;DR: In this article, the authors reported performance data for the direct methanol fuel cell (DMFC) using membrane electrode assemblies using radiation-grafted proton exchange membranes based on polyethylene and ETFE.
157 citations
TL;DR: In this paper, the oxygen reduction activity and methanol tolerance of a range of transition metal sulfide electrocatalysts have been evaluated in a liquid-feed solid-polymer-electrolyte direct-methanol fuel cell.
140 citations
TL;DR: A direct methanol fuel cell (DMFC) model has been developed and experimentally verified, with which fundamental calculations of the DMFC were carried out as discussed by the authors, which comprises the mass transport of the gases in the diffusion layers and catalyst layers, mass transport in the membrane, as well as the reaction and the potential distribution in the catalyst layers.
135 citations
TL;DR: In this article, the authors investigated the use of interdigitated flow fields in a direct methanol fuel cell (DMFC) and found that the IFFs achieved high power densities of 450 and 290 mW cm−2 in the presence of oxygen and air feed, respectively, at 130°C.
131 citations
TL;DR: In this paper, the structure, chemistry and morphology of commercial unsupported Pt-RuOx and in-house prepared Pt−Ru catalysts were analyzed and the catalytic activity of these materials towards electro-oxidation of methanol in solid-polymer-electrolyte direct methanoline fuel cells were investigated at 130°C.
120 citations
TL;DR: In this article, a numerical simulation of a direct methanol fuel cell with liquid methanoline feed is presented, where the velocity of the liquid is governed by gradients of membrane phase potential (electroosmotic effect) and pressure.
Abstract: The results of a numerical simulation of a direct methanol fuel cell (DMFC) with liquid methanol feed are presented. A two-dimensional numerical model of a DMFC is developed based on mass and current conservation equations. The velocity of the liquid is governed by gradients of membrane phase potential (electroosmotic effect) and pressure. The results show that, near the fuel channel, transport of methanol is determined mainly by the pressure gradient, whereas in the active layers, and in the membrane, diffusion transport dominates. ‘Shaded’ zones, where there is a lack of methanol, are formed in front of the current collectors. The results reveal a strong influence of the hydraulic permeability of the backing layer K
p
BL
on methanol crossover through the membrane. If the value of K
p
BL
is comparable to that of the membrane and active layers, electroosmotic effects lead to the formation of an inverse pressure gradient. The flux of liquid driven by this pressure gradient is directed towards the anode and reduces methanol crossover.
TL;DR: In this paper, a two-dimensional numerical model of the direct methanol fuel cell with gas fuel is developed and a new design of current collectors is suggested based on the simulation results.
Abstract: A two-dimensional numerical model of the direct methanol fuel cell with gas fuel is developed. Simulation of the cell with current collectors of conventional geometry reveal the formation of fuel-depleted, shaded regions in the cathode and anode catalyst layers. These regions are positioned in front of current collectors, farther from the gas channel windows. Another disadvantage of the conventional geometry is the concentration of electron current at the edges of current collectors. Based on the simulation results, a new design of current collectors is suggested. It is beneficial to position current collectors inside the backing and catalyst layers, parallel to the flow of the fuel. These embedded collectors do not produce shaded regions in the catalyst layers. Two plausible geometries of such collectors are considered: of rectangular and circular shape. Simulations show that depending on the transport properties of the backing and catalyst layers the embedded current collectors may significantly improve the performance of the fuel cell. This conclusion is valid also for hydrogen-oxygen fuel cells.
01 Jan 2000
TL;DR: In this article, the authors presented the preparation and characterization results of different types of acid-base ionomer blends, which were applied to fuel cells and showed good performance both in H2 and direct methanol fuel cells.
Abstract: In our contribution we present the preparation and characterization results of different types of acid-base ionomer blends. As acidic blend components sulfonated polyetherketone and sulfonated polysulfone have been applied, while as basic components PSU(NH 2)2, poly(4- vinylpyridine), and polybenzimidazole have been used. The thermal stabilities of the observed blend membranes ranged from 270 t o 350°C. Membranes showing low ionic resistances of <50 Ohm . cm were prepared. Some of the acid-base blend membranes were investigated in electronmicroscopy (TEM and SEM). The TEM micrographs showed a fine structure in the Angstrom size range, and at some of the me also structures in the 50-200 nm size range were observed. The FTIR analysis of the acid-base blends showed characteristic band s indicating ionic crosslink formation in the blends. Some of the membranes were applied to fuel cells. These membranes showed good performa nce both in H2 and direct methanol fuel cells. The experiments yielded the result that the electrical power which is obtained with these membr anes is comparable with the power obtained with Nafion® if the ion-exchange capacity of the membrane is high enough and if its thickness is in the range of 30-40 μm. The maximum power densitiy achieved with one of the acid-base membranes in a direct methanol fuel cell amounted to approxima tely 50 mW/ cm 2 at 100 mA/cm 2 in air mode, which is a value comparable to that obtainable with Nafion®.
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15 Dec 2000TL;DR: In this article, a fuel cell device and method of forming the fuel cell devices including a base portion, formed of a singular body, and having a major surface is presented, where at least one fuel cell membrane electrode assembly formed on the major surface of the base portion.
Abstract: A fuel cell device and method of forming the fuel cell device including a base portion, formed of a singular body, and having a major surface. At least one fuel cell membrane electrode assembly formed on the major surface of the base portion. A fluid supply channel including a mixing chamber is defined in the base portion and communicating with the fuel cell membrane electrode assembly for supplying a fuel-bearing fluid to the membrane electrode assembly. An exhaust channel is defined in the base portion and communicating with the membrane electrode. A multi-dimensional fuel flow field is defined in the multi-layer base portion and in communication with the fluid supply channel, the membrane electrode assembly and the exhaust channel. The membrane electrode assembly and the cooperating fluid supply channel, multi-dimensional fuel flow field, and cooperating exhaust channel forming a single fuel cell assembly.
TL;DR: In this paper, the effect of the loading pattern and operating conditions on the response time and performance of a single direct methanol fuel cell (DMFC) was evaluated with the aid of a computer-controlled load unit.
TL;DR: In this article, the effect of operating conditions, such as methanol solution concentration, flow rate and air pressure on the voltage response of a small-scale direct methanoline fuel cell (DMFC) under a range of variable current loads is reported.
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28 Apr 2000
TL;DR: In this article, the authors proposed a direct methanol fuel cell, which consists of a fuel cell 1 with a fuel electrode layer 12, an electrolyte layer 13, and an air electrode layer 14 formed in this sequence on the outer surface of a current collector 11 with the shape of cylinder or pipe with bottom, a fuel container 2 filled with liquid fuel 21, and a fuel supplying pipe 3 supplying the liquid fuel in the fuel container to the inner space of the current collector with bottom.
Abstract: PROBLEM TO BE SOLVED: To provide a direct methanol fuel cell usable as a power source of portable electronic device. SOLUTION: The direct methanol fuel cell comprises a fuel cell 1 with a fuel electrode layer 12, an electrolyte layer 13, and an air electrode layer 14 formed in this sequence on the outer surface of a current collector 11 with the shape of cylinder or pipe with bottom, a fuel container 2 filled with liquid fuel 21, and a fuel supplying pipe 3 supplying the liquid fuel 21 in the fuel container 2 to the inner space of the current collector 11 with the shape of cylinder or pipe with bottom, and the liquid fuel 21 is filled in the fuel container by pressurized inert gas. COPYRIGHT: (C)2001,JPO
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14 Nov 2000TL;DR: In this article, an air breathing direct methanol fuel cell is provided with a membrane electrode assembly (14), a conductive cathode assembly (18) that is permeable to air and directly open to atmospheric air, and an anode assembly(16) that was permeable and directly concacting a liquid methanoline source.
Abstract: An air breathing direct methanol fuel cell is provided with a membrane electrode assembly (14), a conductive cathode assembly (18) that is permeable to air and directly open to atmospheric air, and a conductive anode assembly (16) that is permeable to methanol and directly concacting a liquid methanol source (12). Water loss from the cell is minimized by making the conductive cathode assembly (18) hydrophobic and the conductive anode assembly (16) hydrophilic.
Patent•
18 Jul 2000TL;DR: In this paper, a fuel cell system and method of forming the fuel cell including a base portion, formed of a singular body, and having a major surface is described, where at least one fuel cell membrane electrode assembly is formed on the major surface of the base portion.
Abstract: A fuel cell system and method of forming the fuel cell system including a base portion, formed of a singular body, and having a major surface At least one fuel cell membrane electrode assembly is formed on the major surface of the base portion A fluid supply channel including a mixing chamber is defined in the base portion and communicating with the fuel cell membrane electrode assembly for supplying a fuel-bearing fluid to the membrane electrode assembly An exhaust channel including a water recovery and recirculation system is defined in the base portion and communicating with the membrane electrode assembly The membrane electrode assembly and the cooperating fluid supply channel and cooperating exhaust channel forming a single fuel cell assembly
TL;DR: In this paper, a simulation model of a direct methanol fuel cell (DMFC) based on a solid polymer electrolyte fuel cells (PEFC) is presented to calculate system efficiencies on the basis of thermodynamic engineering calculations.
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16 Jun 2000TL;DR: In this paper, the authors introduce the fuel as an aerosol of liquid fuel droplets suspended in a gas and use a particle size conditioner to control the particle size of the droplets.
Abstract: Improvements to fuel cells include introduction of the fuel as an aerosol of liquid fuel droplets suspended in a gas. The particle size of the liquid fuel droplets may be controlled for optimal fuel cell performance by selection of different aerosol generators or by separating droplets based upon size using a particle size conditioner.
TL;DR: In this paper, partial electrodeposited tin was used as anodes for catalytic electrooxidation of methanol in acid medium, and the performance of the anode over repeated cycles was investigated.
Abstract: Pt electrodes, modified by partial electrodeposited tin, were used as anodes for the catalytic electrooxidation of methanol in acid medium. Sn was electrodeposited galvanostatically and potentiostatically. Cyclic voltammetry was used to study the methanol electrooxidation. Pt modified with Sn proved superior to pure platinum as shown from the methanol peak current densities. Sn also improved the performance regarding the stability of the anode over repeated cycles. It was found that electrodeposited Sn facilitates the oxidation of intermediate poison products through a mixed homogeneous–heterogeneous catalytic mechanism.
TL;DR: In this paper, a model for the liquid feed, direct methanol fuel cell (DMFC), based on the homogeneous two-phase flow theory and mass conservation equation, which describes the hydraulic behaviour of internally manifolded cell stacks, is presented.
Abstract: A model for the liquid feed, direct methanol fuel cell (DMFC), based on the homogeneous two-phase flow theory and mass conservation equation, which describes the hydraulic behaviour of internally manifolded cell stacks, is presented. The model predicts the pressure drop behaviour of the anode side of an individual DMFC cell and is used to determine the channel depth and width for fast and efficient carbon dioxide removal with minimum pressure drop. The model is used to calculate flow distribution through fuel cell stack internal manifolds. The effect of inlet and outlet manifold diameters on flow distribution is also determined. Two types of manifold design are compared, reverse flow and parallel flow. An iterative numerical scheme is used to solve the differential equations for longitudinal momentum and continuity.
Patent•
15 Dec 2000
TL;DR: In this article, a fuel cell membrane electrode assembly is formed on the major surface of the base portion of the fuel cell and a fluid supply channel including a mixing chamber is defined in the base part and communicating with the membrane electrode assemblies for supplying a fuel-bearing fluid to the membrane assembly.
Abstract: A fuel cell system and method of forming the fuel cell system including a base portion, formed of a singular body, and having a major surface. At least one fuel cell membrane electrode assembly is formed on the major surface of the base portion. A fluid supply channel including a mixing chamber is defined in the base portion and communicating with the fuel cell membrane electrode assembly for supplying a fuel-bearing fluid to the membrane electrode assembly. A methanol concentration sensor is positioned to communicate with the fuel cell membrane electrode assembly and the fuel-supply channel for regulating the mixture of fuel to the electrode assembly. An exhaust channel including a water recovery and recirculation system is defined in the base portion and communicating with the membrane electrode assembly.
TL;DR: In this article, a model is presented to predict the local pressure and chemical composition in the anode and cathode sides of a direct methanol fuel cell, based on the homogeneous two-phase flow theory and mass conservation equation, which describes the hydraulic behaviour of an experimental large cell.
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27 Sep 2000
TL;DR: In this paper, the authors proposed a direct methanol fuel cell with high output and high utilization rate of the fuel by controlling a crossover of methanols at the first half of a fuel flow path.
Abstract: PROBLEM TO BE SOLVED: To provide a direct methanol fuel cell having a high output and high utilization rate of the fuel by controlling a crossover of methanol at the first half of a fuel flow path and a short supply of the methanol at the latter half of the fuel flow path so as to optimize a fuel supply to a fuel electrode. SOLUTION: In a direct methanol fuel cell 10 having a membrane electrode joint body 18, wherein a fuel electrode 14 and an air electrode 16 is bonded on the both sides of a solid polymer electrolytic membrane 12, a methanol permeability coefficient of a diffusion layer 14b of the fuel electrode 14 side increases as it goes to the downstream side of fuel. Specifically, when the diffusion layer of the fuel electrode is formed by applying a compound of carbon black and polytetrafluoroethylene to the surface of a base material comprising a carbon paper, the weight ratio of the polytetrafluoroethylene in the compound and/or the applying amount of the compound are changed in accordance with the flow of the fuel. COPYRIGHT: (C)2002,JPO
TL;DR: In this paper, a direct methanol fuel cell (DMFC) stack has been designed and built at Newcastle University, based on a flow bed design developed with the aid of a flow visualization study and fluid flow modelling.
Abstract: A prototype direct methanol fuel cell (DMFC) stack has been designed and built at Newcastle University, based on a flow bed design developed with the aid of a flow visualization study and fluid flow modelling. In addition, a series of engineering models have been developed that predict the stack voltage, fluid distribution from the stack manifolds, the overall system pressure, the chemical equilibrium in both anode and cathode flow beds and the thermal management of the stack. The results of this work are presented in terms of an overall engineering model that incorporates all the aforementioned models. The initial steady state performance data of the prototype stack presented was obtained as a result of our experience of scaling up the system to achieve the designed power outputs.
TL;DR: In this article, a model is presented for the liquid feed direct methanol fuel cell, which describes the hydraulic behavior of an internally manifolded cell stack, based on the homogeneous two-phase flow theory and mass conservation equation.
Abstract: A model is presented for the liquid feed direct methanol fuel cell, which describes the hydraulic behavior of an internally manifolded cell stack The model is based on the homogeneous two-phase flow theory and mass conservation equation The model predicts the pressure drop behavior of an individual fuel cell, and is used to calculate flow distribution through fuel cell stack internal manifolds The flow distribution of the two-phase fluids in the anode and the cathode chambers is predicted as a function of cell operating parameters An iterative numerical scheme is used to solve the differential equations for longitudinal momentum and continuity
Patent•
04 Dec 2000
TL;DR: In this paper, a passive air breathing methanol fuel cell is provided with a membrane electrode assembly (14), a conductive cathode permeable to air and open to atmospheric air, and which includes a backing (18) and a current collector (22).
Abstract: A passive air breathing methanol fuel cell is provided with a membrane electrode assembly (14), a conductive cathode permeable to air and open to atmospheric air, and which includes a backing (18) and a current collector (22), a conductive anode assembly permeable to methanol, which inculdes a backing (16) and current collector (24), and which directly contacts a liquid methanol source, such as a sponge (12).
Patent•
29 Nov 2000
TL;DR: In this paper, the dielectric constant of the fuel mix comprising the source fuel and the diluting fluid is measured to determine the relative proportions of source and diluting fluids within this fuel mix.
Abstract: For a direct oxidation fuel cell system in which the source fuel is diluted with a diluting fluid prior to entering the fuel cell generally, and for a Direct Methanol Fuel Cell System (DMFC) in which the methanol source fuel is diluted with water, the dielectric constant of the fuel mix comprising the source fuel and the diluting fluid is measured to determine the relative proportions of source fuel and diluting fluid within this fuel mix. This measurement may then be used in a feedback loop to control the subsequent mixing of the source fuel with the diluting fluid, and in particular, to adjust the mix in the event the fuel mix is too rich or too dilute as compared to a desired mixing proportion. Additionally, a second dielectric constant measurement is used to determine the source fuel level of a fuel tank providing source fuel to the fuel cell. Finally, an optional telecommunications link is used to automatically order a source fuel refill when the source fuel runs low.