Abstract: An improved membrane electrode assembly (“MEA”) comprises coextensive ion exchange membrane and electrode layers and a resilient fluid impermeable integral seal comprising a sealant material impregnated into the porous electrode layers in the sealing regions. The integral seal preferably circumscribes the electrochemically active area of the MEA. The integral seal preferably also extends laterally beyond the edge of the MEA. An integral seal may also be provided around any openings, such as external manifold openings formed outside the MEA. Preferably, the uncured sealant material is a flow processable elastomer applied using an injection molding process. In preferred embodiments the seal has a plurality of spaced, parallel raised ribs with cross-ribs extending therebetween at spaced intervals. The raised ribs and cross-ribs provide compartmentalized seals that provide improved protection against fluid leaks.

Abstract: Reactant gas supply streams for solid polymer fuel cells may be heated and humidified using heat generated by the fuel cell and water vapor from the fuel cell exhaust. The heat and water vapor in the oxidant exhaust stream are sufficient to heat and humidify a reactant gas supply stream, preferably the oxidant supply stream. The heating and humidifying can be accomplished by flowing a reactant gas supply stream and a fuel cell exhaust gas stream on opposite sides of a water permeable membrane in a combined heat and humidity exchange apparatus. The method and apparatus are particularly suitable for use with air-cooled fuel cell systems and systems which employ near ambient pressure air as the oxidant gas supply.

Abstract: A fuel processing reactor is provided, comprising a shift catalyst bed disposed in a shell and tube reactor. The thermal stress on the present reactor during normal operation is reduced by cooling/heating both the shell and the tubes in the reactor. The present reactor may further comprise other beds such as hydrodesulfurizer catalyst beds, metal oxide beds, or sulfur polisher beds.

Abstract: An electrically conductive, substantially fluid impermeable fuel cell separator plate comprises a substantially planar major surface for facing a fluid permeable fuel cell electrode, a fluid inlet through which a fluid may be directed to the planar major surface, a fluid outlet through which fluid may be removed from the planar major surface, and at least one discrete fluid distribution feature, such as a channel, formed in the planar major surface. Within the thickness of the plate, the fluid distribution feature is fluidly isolated from the fluid inlet and the fluid outlet, such that in a fuel cell assembly the reactant fluid must pass through the adjacent fluid permeable electrode to travel between the discrete fluid distribution feature and each of the fluid inlet and the fluid outlet.

Abstract: A method of commencing operation of a fuel cell system which includes a fuel reformer is provided. During a start-up period, the same fuel which is used in the feedstock to the reformer is directed to at least a portion of the fuel cells in the system. These fuel cells provide output power by direct oxidation of the fuel, at least until the reformer is operational, producing a hydrogen-containing gas stream suitable for the fuel cells. Thus, useful output power can be obtained from the system without the delay typically associated with start-up of the reformer.

Abstract: Graft polymeric membranes in which one or more trifluorovinyl aromatic monomers are radiation graft polymerized to a preformed polymeric base film are provided, as well as ion-exchange membranes prepared therefrom. Preferred monomers include substituted &agr;, &bgr;, &bgr;-trifluorostyrenes and trifluorovinyl naphthalenes which are activated towards the grafting reaction or facilitate the introduction of more than one ion-exchange group per monomer unit in the grafted chains. The ion-exchange membranes are useful in dialysis applications, and particularly in electrochemical applications, for example as membrane electrolytes in electrochemical fuel cells and electrolyzers.

Abstract: A 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 thermoplastic polymeric 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. Melt-bonding the thermoplastic material in the sealing region renders the at least one fluid distribution layer substantially fluid impermeable in a direction parallel to the major planar surfaces.

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: A method and apparatus are provided for distributing water produced by the electrochemical reaction to ion-exchange membranes in an array comprising a plurality of electrochemical fuel cell stacks. Water distribution within individual fuel cell stacks within the array is improved to reduce membrane dryness near the oxidant stream inlet and to also reduce saturation of the oxidant stream near the oxidant stream outlet, thereby reducing electrode flooding. The method comprises periodically reversing the oxidant stream flow direction within at least one of the plurality of fuel cell stacks. The apparatus comprises an oxidant stream flow switching device for periodically switching the flow direction of an oxidant stream through an individual fuel cell stack.

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: A process for impregnating at least one porous part with an impregnant comprises: (a) immersing at least one porous part in a fixed volume of impregnant, (b) measuring at least one parameter indicative of the effective volume of the impregnant as the impregnant impregnates the porous part(s), and (c) interrupting impregnation when the measured parameter(s) indicates a desired level of impregnation is achieved. An apparatus for impregnating porous parts comprises a vessel for holding at least one porous part and a fixed volume of impregnant, and at least one device for measuring the change in effective volume of the impregnant within the vessel.

Abstract: A continuous method manufactures a laminated electrolyte and electrode assembly (“laminated assembly”) comprising at least one pre-formed electrode layer, at least one catalyst layer and at least one electrolyte layer for an electrochemical cell. The method comprises forming at least one of the catalyst or electrolyte layers in situ and using it as a laminating medium. The method produces a laminated assembly in a continuous sheet, which may be later cut to size and shape for use in electrochemical cells. The method may comprise co-extruding granular catalyst and/or electrolyte materials. In one embodiment, the catalyst and electrolyte layers are co-extruded. The co-extruded tri-layer extrusion is laminated with immediately adjacent pre-formed electrode layers. In another embodiment the catalyst layer is extruded and the catalyst layer acts as the laminating medium between immediately adjacent pre-formed electrode and electrolyte layers.

Abstract: An improved rotary piston blower supplies an oxidant stream to a fuel cell. In one embodiment, the improved rotary piston blower includes cantilevered shafts. The improved rotary piston blower is also able to supply an oil-free oxidant stream to an electrochemical fuel cell. The improved rotary piston blower has fewer components, fewer seals, and is easier to fabricate, in comparison to conventional, prior art rotary piston blowers.

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: In a process for manufacturing an electrode for a PEM fuel cell or an electrochemical energy converter, an ion-exchange polymer is applied to one face of an electrode substrate. An electrocatalyst is then applied to the substrate by electrochemical deposition, preferably from a solution containing one or more complexes or salts of the electrocatalyst. The electrochemical deposition occurs by application of a voltage between a pair of electrodes, one of which is the electrode under preparation. The voltage between the two electrodes is controlled by controlling the potential of the working electrode. A pulsed voltage profile is applied across the two electrodes during the electrodeposition process.

Abstract: A composite membrane is provided in which a porous substrate is impregnated with a polymeric composition comprising various combinations of &agr;, &bgr;, &bgr;-trifluorostyrene, substituted &agr;, &bgr;, &bgr;-trifluorostyrene and ethylene-based monomeric units. Where the polymeric composition includes ion-exchange moieties, the resultant composite membranes are useful in electrochemical applications, particularly as membrane electrolytes in electrochemical fuel cells.

Abstract: An electrochemical fuel cell stack with improved reactant manifolding and sealing includes a pair of separator plates interposed between adjacent membrane electrode assemblies. Passageways fluidly interconnecting the anodes to a fuel manifold, and interconnecting the cathodes to an oxidant manifold, comprise at least one fluid passageway formed between adjoining non-active surfaces of the pairs of separator plates. The passageways extend through one or more ports penetrating the thickness of one of the plates thereby fluidly connecting the manifold to the opposite active surface of that plate, and the adjacent electrode. The ports comprise walls that have surfaces that are angled more than 0 degrees and less than 90 degrees with respect to the direction of fluid flow in the fluid passageway upstream of the port. During operation, electrochemical fuel cell stacks comprising fluid ports with angled walls benefit from reduced pressure loss.

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: An electrochemical fuel cell stack with an improved compression assembly comprises a tension member which is electrically non-conductive and preferably non-metallic. The tension member can be made from a composite material which has similar expansion and contraction properties as the stack materials, thereby reducing undesirable fluctuations in the compressive force applied to the stack. An improved apparatus for securing the improved tension member to the rest of the compression assembly is also provided. Preferred embodiments of an improved compression assembly employ a collet and wedges to grip the tension member and compress a resilient member which imparts a tensile force to the tension member and a compressive force to the fuel cell assemblies. In other embodiments, an improved compression assembly employs a unitary resilient member and fastener in combination with a tension member.

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.