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. 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: 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: An improved method reduces fuel cell performance degradation of an electrode comprising porous components. Electrochemical solid polymer electrolyte fuel cells typically have present therein a liquid which expands upon freezing, such as, for example water. The presence of such a liquid within the pores of the electrode components may cause performance degradation of the liquid freezes. The present method comprises employing an impregnant within at least some of the pores of the electrode components. The impregnant inhibits the deterioration of porous fuel cell components caused by expansion of the liquid within the pores when the fuel cell components are subjected to a temperature below the freezing temperature of the liquid. Preferably the impregnant does not expand when changing phases from a liquid to a solid. The impregnant may comprise an organic fluid, an organic acid, an inorganic acid, a polymer or dispersion.

Abstract: The electrocatalysts in certain fuel cell systems can be poisoned by impurities in the fuel stream directed to the fuel cell anodes. Introducing a variable concentration of oxygen into the impure fuel stream supplied to the fuel cells can reduce or prevent poisoning without excessive use of oxygen. The variation may be controlled based on the voltage of a carbon monoxide sensitive sensor cell incorporated in the system. Further, the variation in oxygen concentration may be periodic or pulsed. A variable air bleed method is particularly suitable for use in solid polymer fuel cell systems operating on fuel streams containing carbon monoxide.

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: Carbon-supported catalysts are frequently employed in the electrodes of solid polymer fuel cells in order to make efficient use of the catalyst therein. The catalyst utilization in the electrode and the fuel cell performance can be further improved by introducing acidic surface oxide groups on the carbon-supported catalyst. The introduction of acidic surface oxide groups on the carbon-supported catalyst can be accomplished by treating the carbon-supported catalyst with a suitable acid, such as nitric acid, before incorporating the carbon-supported catalyst in a fuel cell electrode. The present technique is particularly suitable for use in solid polymer fuel cell cathodes.

Abstract: The electrocatalysts in certain fuel cell systems can be poisoned by impurities in the fuel stream directed to the fuel cell anodes. Introducing a variable concentration of oxygen into the impure fuel stream supplied to the fuel cells can reduce or prevent poisoning without excessive use of oxygen. The variation may be controlled based on the voltage of a carbon monoxide sensitive sensor cell incorporated in the system. Further, the variation in oxygen concentration may be periodic or pulsed. A variable air bleed method is particularly suitable for use in solid polymer fuel cell systems operating on fuel streams containing carbon monoxide.

Abstract: Liquid feed fuel cell performance can be increased by impregnating electrode substrates with a proton conducting ionomer prior to incorporation of the electrocatalyst, and optionally also after application of the electrocatalyst. Ionomer impregnation is particularly effective for direct methanol fuel cell anodes that comprise carbonaceous substrates.

Abstract: Fuel cell performance in liquid feed fuel cells with an electrode comprising a carbonaceous substrate and an electrocatalyst can be increased by oxidizing the carbon substrate, particularly by electrochemical methods in acidic aqueous solution, prior to incorporation of the electrocatalyst. The treated substrate may thereafter be advantageously impregnated with a proton conducting ionomer to prevent excessive penetration of the applied catalyst into the substrate. The treatment method is particularly effective for direct methanol fuel cell anodes.

Abstract: A method and apparatus is provided for operating an electrochemical fuel cell with periodic momentary fuel starvation at the anode. It is believed that such momentary periodic fuel starvation conditions cause the anode potential to increase, resulting in the oxidation and removal of electrocatalyst poisons from the anode electrocatalyst and improved fuel cell performance. In a preferred method, while successive localized portions of the fuel cell anode are momentarily periodically fuel starved, the remainder of the fuel cell anode remains electrochemically active and saturated with fuel such that the fuel cell is continually available to generate power.

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: A membrane electrode assembly for an electrochemical fuel cell includes a pair of electrodes and an ion exchange membrane interposed therebetween. At least one of the electrodes comprises a porous electrode substrate. The substrate comprises a preformed macroporous web having a through-plane resistivity of greater than 1 .OMEGA.*cm. The web contains an electrically conductive filler. A method for preparing the membrane electrode assembly includes the steps of (a) forming a porous electrode substrate for an electrochemical fuel cell by filling a preformed macroporous web, the web having a through-plane resistivity of greater than 1 .OMEGA.*cm, with an electrically conductive filler and (b) consolidating the electrode pair and ion exchange membrane to form a unitary assembly.

Abstract: An electrochemical fuel cell comprises a pair of separator plates and a pair of fluid distribution layers interposed between the separator plates. At least one of the fluid distribution layers comprises a sealing region and an electrically conductive, fluid permeable active region, and a preformed sheet material extending into each of the sealing region and the active region. An ion exchange membrane is interposed between at least a portion of the fluid distribution layers, and a quantity of electrocatalyst is interposed between at least a portion of each of the fluid distribution layers and at least a portion of the membrane, thereby defining the active region. Compression of the preformed sheet material by urging of the pair of plates towards each other renders the at least one fluid distribution layer substantially fluid impermeable in a direction parallel to the major planar surfaces, in the sealing region.

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: An electrode suitable for use in fuel cells, for example in solid polymer fuel cells, comprises a non-uniform electrode layer and has improved electrochemical performance.

Abstract: A porous electrode substrate for an electrochemical fuel cell comprises at least one preformed web having low or poor electrical conductivity. The web contains an electrically conductive filler. A method for preparing a porous electrode substrate for an electrochemical fuel cell comprises the step of filling a preformed web, the web having low or poor electrical conductivity, with an electrically conductive filler.

Abstract: In an electrochemical fuel cell, an electrode substrate has an in-plane nonuniform structure. The electrode substrate having an in-plane nonuniform structure enables controlled transport of reactant toward the electrocatalyst layer and controlled transport of reaction product away from the electrocatalyst layer.

Abstract: A fuel cell assembly within an electrochemical fuel cell stack has an anode layer and a cathode layer. A cooling layer is disposed adjacent the fuel cell assembly. Each layer comprises channels for directing a fluid stream from an inlet to a an outlet. The coolant stream channels extend such that, in operation, the coolest region of the cooling layer coincides with the region of the cathode layer having the highest concentration of oxygen (and/or the lowest water content), and the warmest region of the cooling layer coincides with the region of the cathode layer having the lowest concentration of oxygen (and/or the highest water content).

Abstract: A method and apparatus detects and locates perforations in membranes used in electrochemical cells. The membrane has first and second oppositely facing major planar surfaces. The first surface is exposed to a first reactant fluid, preferably a gaseous mixture comprising hydrogen, while the second surface is exposed to a second reactant fluid, preferably ambient air comprising oxygen. The first and second reactant fluids are substantially fluidly isolated from each other by the membrane when no perforations are present in the membrane. The first reactant fluid contacts the second reactant fluid when at least one perforation is present in the membrane. The first and second reactant fluids exothermically react upon contact, preferably in the presence of a catalyst, to generate heat, which is then detected using an infrared thermal detector or thermal imaging device or a layer of thermally sensitive film positioned in proximity with the membrane.

Abstract: An electrode suitable for use in fuel cells, for example in solid polymer fuel cells, comprises a non-uniform electrode layer and has improved electrochemical performance.