Abstract: The activity of catalysts used in promoting the oxidation of certain oxidizable species in fluids can be enhanced via electrochemical methods, e.g., NEMCA. In particular, the activity of catalysts used in the selective oxidation of carbon monoxide can be enhanced. A purification system that exploits this effect is useful in purifying reformate supplied as fuel to a solid polymer electrolyte fuel cell stack. The purification system comprises an electrolytic cell with fluid diffusion electrodes. The activity of catalyst incorporated in the cell anode is enhanced.

Abstract: The electrochemical performance of an ion-exchange membrane in a fuel cell system may be improved by impregnating therein a perfluoroamine. The amine may be primary, secondary or tertiary. Further, the amine is preferably water insoluble or only slightly water soluble. For example, the amine may be perfluorotriamylamine or perfluorotributylamine. Use of such a membrane system within a fuel cell may allow high or low temperature operation (i.e. at temperatures greater than 100° C. or less than 0° C.) as well as operation at low relative humidity.

Abstract: A method and apparatus increase the temperature of a fuel cell via reactant starvation at one or both electrodes. Reactant starvation at an electrode results in an increased overvoltage at the electrode and hence increased internal heat generation under load. Further, starvation techniques may be used to prevent poisoning of electrode catalysts, a potential problem that is aggravated at lower temperatures. Starvation conditions can be prolonged or intermittent and can be obtained, for example, by suitably reducing the supply rate of a reactant or by operating the fuel cell at sufficiently high current density so as to consume reactant faster than it is supplied. The method can allow for some generation of useful power by the fuel cell during start-up. The method is particularly suitable for starting up a solid polymer electrolyte fuel cell from temperatures below 0° C.

Abstract: A solid polymer electrolyte fuel cell stack having a plurality of fuel cells, wherein at least one cell of the fuel cell stack has a resistance to corrosion that is greater than a significant portion of the other fuel cells of the stack. In one embodiment, the at least one fuel cell of the fuel cell stack that is more resistant to corrosion is one or both end cells of the stack. Also disclosed is a fuel cell system containing such a stack, as well as methods for reducing degradation of the same during operation.

Abstract: An improved fuel cell anode structure comprises a substrate and a first carbon-based component. The first carbon-based component exhibits little or no resistance to corrosion. When said anode structure is incorporated into a membrane electrode assembly, the membrane electrode assembly is tolerant to incidences of cell voltage reversal.

Abstract: In a solid polymer fuel cell series, various circumstances can result in a fuel cell being driven into voltage reversal. For instance, cell voltage reversal can occur if that cell receives an inadequate supply of fuel. In order to pass current, reactions other than fuel oxidation may take place at the fuel cell anode, including water electrolysis and oxidation of anode components. The latter may result in significant degradation of the anode, particularly if the anode employs a carbon black supported catalyst. Such fuel cells can be made more tolerant to cell reversal by using higher catalyst loading or coverage on the anode catalyst support or a more oxidation resistant anode catalyst support, such as a more graphitic carbon or Ti4O7.

Abstract: A method and apparatus increase the temperature of a fuel cell via reactant starvation at one or both electrodes. Reactant starvation at an electrode results in increased internal heat generation under load. Starvation conditions can be prolonged or intermittent and can be obtained, for example, by suitably reducing the supply rate of a reactant or by operating the fuel cell at sufficiently high current density so as to consume reactant faster than it is supplied. The method can allow for some generation of useful power by the fuel cell during start-up. The method is particularly suitable for starting up a solid polymer electrolyte fuel cell from temperatures below 0° C.

Abstract: Water management is improved in solid polymer electrolyte fuel cells by employing capillary channels or wicks in the lands that separate the reactant distribution channels in the flow fields. Capillary action moves water within these micro-sized capillary channels or wicks. Appropriate designs can be used to assist in the removal of water from the cell and/or in the redistribution of water from relatively wet regions in the cell to relatively dry regions.

Abstract: Fluid diffusion layers with favorable mechanical and electrical properties are prepared for fuel cell electrodes by impregnating a porous carbonaceous web with a carbonizable polymer having pyrrolidone functionality and then carbonizing the pyrrolidone polymer. The polymer having pyrrolidone functionality is stabilized against vaporization by use of an oxidization step prior to carbonization. The fluid diffusion layers are particularly suitable for use as gas diffusion layers in solid polymer electrolyte fuel cells.

Abstract: The electrochemical performance of an ion-exchange membrane in a fuel cell system may be improved by impregnating therein a perfluoroamine. The amine may be primary, secondary or tertiary. Further, the amine is preferably water insoluble or only slightly water soluble. For example, the amine may be perfluorotriamylamine or perfluorotributylamine. Use of such a membrane system within a fuel cell may allow high or low temperature operation (i.e. at temperatures greater than 100° C. or less than 0° C.) as well as operation at low relative humidity.

Abstract: In an electrochemical fuel cell, a sufficient quantity of catalyst, effective for promoting the reaction of reactant supplied to an electrode, is disposed within the volume of the electrode so that a reactant introduced at a first major surface of the electrode is substantially completely reacted upon contacting the second major surface. Crossover of reactant from one electrode to the other electrode through the electrolyte in an electrochemical fuel cell is thereby reduced.

Abstract: A method of controlling the temperature within an electrochemical fuel cell stack comprises introducing a reactant fluid stream comprising both a heat transfer liquid and a reactant into a fuel cell assembly such that the reactant fluid stream contacts an electrode. The heat transfer liquid is other than water. Preferably, the method further comprises recirculating heat transfer liquid which is in the reactant exhaust stream, typically via a heat exchanger, and re-introducing it into the fuel cell assembly in the reactant fluid stream. The recirculated heat transfer liquid may be directed to a reservoir which in turn supplies heat transfer liquid to the reactant fluid stream as it is needed. In a further embodiment, the method may comprise using the heat transfer liquid to heat a fuel cell stack to a desired operating temperature rather than cooling the stack.

Abstract: In a solid polymer fuel cell series, various circumstances can result in a fuel cell being driven into voltage reversal. For instance, cell voltage reversal can occur if that cell receives an inadequate supply of fuel. In order to pass current, reactions other than fuel oxidation can take place at the fuel cell anode, including water electrolysis and oxidation of anode components. The latter can result in significant degradation of the anode, particularly if the anode employs a carbon black supported catalyst. Such fuel cells can be made substantially more tolerant to cell reversal by using certain anodes employing both a higher catalyst loading or coverage on a corrosion-resistant support and by incorporating, in addition to the typical electrocatalyst for promoting fuel oxidation, certain unsupported catalyst compositions to promote the water electrolysis reaction.

Abstract: An electrochemical fuel cell stack includes a plurality of fuel cells. At least one of the fuel cells is a sensor cell. The sensor cell has at least one structural dissimilarity with respect to the remaining fuel cells of the plurality. The structural dissimilarity may include, for example, a reduced sensor cell electrochemically active area, reduced electrocatalyst loading, modified anode or cathode flow field, different electrocatalyst composition, or a modified coolant flow field configuration. The sensor cell operates under substantially the same conditions as the remaining cells in the stack. However, in response to a change in a particular stack operating condition, an electrical or thermal response, preferably a voltage change, is induced in the sensor cell which is not simultaneously induced in the remaining fuel cells. Thus, the sensor cell can detect undesirable conditions and its response can be used to initiate corrective action.

Abstract: Fluid diffusion layers with favorable mechanical and electrical properties are prepared for fuel cell electrodes by impregnating a porous carbonaceous web with a carbonizable polymer having pyrrolidone functionality and then carbonizing the pyrrolidone polymer. The polymer having pyrrolidone functionality is stabilized against vaporization by use of an oxidization step prior to carbonization. The fluid diffusion layers are particularly suitable for use as gas diffusion layers in solid polymer electrolyte fuel cells.

Abstract: A method of detecting transfer leaks within a solid polymer electrolyte fuel cell stack comprising a plurality of fuel cell assemblies includes supplying reactants and inert gas to the fuel, oxidant and/or coolant manifolds of the stack, as appropriate, and measuring the voltage across at least one of the fuel cell assemblies. An apparatus for detecting transfer leaks within solid polymer electrolyte fuel cell stacks comprises a device for measuring the voltage across at least one of the fuel cell assemblies. Transfer leaks across the polymer electrolyte membrane, and across reactant-coolant bipolar plates, may be detected according to the present method and apparatus.

Abstract: An integrated fuel cell and pressure swing adsorption system is disclosed for operating a solid polymer fuel cell on an enriched reactant stream. The fuel and/or oxidant streams may be enriched; for example, air and reformate streams may be oxygen and hydrogen enriched, respectively. The system may advantageously combine periodic reversal of the reactant flows through the fuel cell with use of an integrated pressure swing adsorption system.

Abstract: In an electrochemical fuel cell, a sufficient quantity of catalyst, effective for promoting the reaction of reactant supplied to an electrode, is disposed within the volume of the electrode so that a reactant introduced at a first major surface of the electrode is substantially completely reacted upon contacting the second major surface. Crossover of reactant from one electrode to the other electrode through the electrolyte in an electrochemical fuel cell is thereby reduced.

Abstract: A method is provided for treating electrocatalyst particles and using the treated electrocatalyst for improving performance in an electrochemical fuel cell. The treatment method comprises impregnating pores of the electrocatalyst particles with an impregnant wherein the pores comprise micropores which have an aperture size less than 0.1 micron. The impregnant is preferably ion-conducting and may comprise an organic acid, an inorganic acid, or a polymer. Alternatively, or in addition, the impregnant has an oxygen permeability greater than that of water. The method of impregnating the electrocatalyst particles preferably comprises the steps of contacting the electrocatalyst particles with an impregnant and subjecting the electrocatalyst particles to a vacuum and/or an elevated pressure above atmospheric pressure. The treated electrocatalyst particles are incorporated into an electrochemical fuel cell.

Abstract: Flow fields comprising a set of fluid distribution channels may be employed in fuel cells for purposes of distributing fluid reactants to an electrochemically active area of the fuel cell. Water management and reactant distribution may be improved by increasing pressure gradients between adjacent channels. Such pressure gradients may be increased by engineering the channels such that the resistance to reactant flow differs along the length of adjacent channels.