Abstract: An electrochemical fuel cell stack comprises a plurality of fuel cell assemblies, wherein, each fuel cell assembly comprises a cell compressed between a pair of flow field plates, a perimeter seal circumscribing the cell and interposed between the pair of flow field plates, and a first diode, having an aspect ratio greater than 10:1, positioned adjacent to, and outside of, the perimeter seal along a first edge of the cell and interposed between the pair of flow field plates.

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: Certain fuel cells (e.g., solid polymer electrolyte fuel cells) may temporarily exhibit below normal performance after initial manufacture or after prolonged storage. While normal performance levels may be obtained after operating such fuel cells for a suitable time period, this process can take of order of days to fully complete. However, exposing the cathode to a reductant (e.g., hydrogen) can provide for normal performance levels without the need for a lengthy initial operating period.

Abstract: A controller in a fuel cell system performs various operating parameter checks at a predefined schedule, including one or more of a stack current check; a stack voltage check; a cell voltage check; a purge cell check; an oxygen concentration check; a hydrogen concentration check; a stack temperature check; an ambient air temperature check; a fuel pressure check; and an airflow rate check; a hydrogen sensor heater check; a battery voltage check; a microcontroller self-check; and/or toggling a watchdog. The frequency of the checks are set relative to achieve an efficient control of the fuel cell system by selectively distributing the load on the microcontroller.

Abstract: Contamination of the ion-exchange membrane in an electrochemical fuel cell can significantly reduce the lifetime. One source of contamination is from sealant materials, particularly if the sealant is silicone and impregnated into the peripheral region of the membrane electrode assembly (MEA) and thus in close proximity to the ion-exchange membrane. Contamination may be reduced or eliminated by separating the electrochemical reaction and/or the ion-exchange membrane from the sealant material. In an embodiment, this is done by having the sealing region substantially free of active electrocatalyst particles (for example, selectively printing the catalyst to avoid the sealing region or poisoning catalyst in the sealing region). In another embodiment, a barrier film is interposed between the ion-exchange membrane and the sealant material impregnated into the MEA. In yet another embodiment, a barrier plug is impregnated into the fluid diffusion layer adjacent to the sealant material impregnated into the MEA.

Abstract: A method for locating a fluid leak in a fuel cell stack is disclosed. The method comprises pressurizing a first fluid stream passage with a tracer fluid, introducing a flow fluid to a second fluid stream passage, maintaining a substantially constant flow of the flow fluid through the second fluid stream passage toward an exit point of the fuel cell stack, inserting a probe, adapted to monitor for the presence of the tracer fluid in the flow fluid, into the exit point, moving the probe through the second fluid stream passage and monitoring for the presence of the tracer fluid in the flow fluid at various locations of the second fluid stream passage. An apparatus for locating a fluid leak in a fuel cell stack is also provided.

Abstract: An electric power generation system has a multiple jet ejector assembly for recirculating an exhaust stream. The system includes a fuel cell stack having a reactant stream inlet, a reactant stream outlet and at least one fuel cell. A pressurized reactant supply provides a reactant to the multiple jet ejector assembly. The multiple jet ejector assembly includes two motive flow inlets, one suction inlet, fluidly connected to the reactant stream outlet to receive a recirculated flow from the fuel cell stack, and one discharge outlet, fluidly connected to the reactant stream inlet to provide an inlet stream to the fuel cell stack. A pressure regulator is interposed between the pressurized reactant supply and the two motive flow inlets of the multiple jet ejector assembly. A first solenoid valve is interposed between the first motive flow inlet and the regulator. A second solenoid valve is interposed between the second motive flow inlet and the regulator.

Abstract: A disclosed method for coating a substrate with an ionomer, applies the ionomer as a component of a stable foam, then dries the applied foam layer. The substrate to be so coated, in particular embodiments, is an electrode substrate, with or without a catalyst layer applied thereon. In another embodiment, the substrate is an ion-exchange membrane. In yet more particular embodiments, the substrate is suitable for use in an electrochemical fuel cell. Also disclosed are products made by the disclosed methods, namely, ionomer-coated substrates, including ionomer-coated electrode substrates and electrodes. The foam layer may also comprise catalyst powder to form a catalyst layer. Membrane electrode assemblies, fuel cells, and fuel cell stacks that incorporate the substrates are also disclosed, as are motor vehicles, and stationary and portable electrical power-generating plants that incorporate the fuel cell stacks.

Abstract: A receptacle having an end cap, a pliable sidewall, and a fastener, for receiving and retaining a fuel cell stack in its stacked configuration during fabrication of a multi-stack fuel cell assembly, is shown and described. Methods of fabricating the assembly include stacking the fuel cell in the receptacle, compressing the fuel cell, and engaging the fastener to retain the stack in its stacked configuration and, or to retain the stack under at least partial compression.

Abstract: Fuel cells are disclosed that operate directly on fuel streams comprising tetramethyl orthocarbonate in which tetramethyl orthocarbonate is directly oxidized at the anode and, more particularly, to solid polymer fuel cells operating directly on liquid fuel streams comprising tetramethyl orthocarbonate. Also disclosed are methods relating thereto.

Abstract: A membrane exchange humidifier employs a water permeable membrane comprising a microporous polymer and a hydrophilic additive. In operation, the membrane preferably has favorable water transmission properties and resists transmission of reactant gas or other components. The membrane is suitable for use even when permeable in its dry condition to the wet or dry gases in the humidifier, and/or when the wet and dry gases are of different composition. By wetting the membrane, the presence of an amount of liquid water in the wet gas can reduce gas transmission through the membrane to an acceptable level. The humidifier is useful in fuel cell systems in which a reactant gas supply stream, such as the oxidant supply stream, is humidified primarily using water vapor from a fuel cell reactant exhaust stream. The humidifier is particularly suitable for use in conjunction with solid polymer fuel cell systems. The improved mechanical and welding properties of the membrane allow for a simpler humidifier configuration.

Abstract: Graft polymeric membranes and methods for making graft polymeric membranes have one or more trifluorovinyl aromatic monomers that are radiation graft polymerized to a polymeric base film. The membranes comprise a polymeric base film to which has been graft polymerized substituted ?,?,?-trifluorostyrene and/or ?,?,?-trifluorovinylnaphthylene monomers, which are activated towards graft polymerization. As ion-exchange membranes, the membranes are suitable for use in electrode apparatus, including membrane electrode assemblies in, for example, fuel cells. The membranes can also be crosslinked.

Abstract: A fuel cell system includes fuel cells forming a fuel cell stack, having a fuel passage and an oxidant passage. A purge valve is coupled to the fuel passage to exhaust contaminants, and a controller is coupled to temporarily increase the oxidant stream flow rate through the oxidant passage, and to temporarily open the fuel purge valve, if a voltage across a pair of fuel cells is less than a defined threshold voltage. In this resuscitation step, the oxidant flow rate can be temporarily increased by increasing a duty cycle of an air compressor by approximately 50% for a duration of between approximately 5 to 10 seconds. The controller can further shut down fuel cell operation if a voltage across a pair of fuel cells is less than a defined threshold voltage in an inter-resuscitation period immediately following the resuscitation step.

Abstract: A fuel cell assembly has an improved gas sensor. The improved sensor measures the gas concentrations in the interior fluid passages within a fuel cell assembly or within fluid passages employed to transport reactant fluid streams to or from the fuel cell(s). The improved sensor is particularly suited for use in the environment within the reactant fluid passages of a solid polymer fuel cell assembly and is tolerant to the presence of water. The sensor employs an active electrode; a passive electrode; and an electrolyte in contact with both electrodes. The electrolyte is disposed on a substrate and a heater is located in thermal contact with the substrate for heating the substrate and the electrolyte.

Abstract: Electrochemically inactive separators may be employed at the periphery of membrane electrode assemblies in fuel cells (such as solid polymer electrolyte fuel cells) to separate the various fluids within (for example, reactants, coolant). Complex fluid distribution features may be incorporated into these separators, thereby desirably simplifying the design and manufacture of other fuel cell components, such as the flow field plates employed to distribute fluids to the cell electrodes. This is particularly advantageous in fuel cells comprising thin, corrugated flow field plates. The separators may be bonded to the membrane electrode assemblies to form convenient, unitary structures.

Abstract: A fuel cell system electrically couples a battery in parallel with the fuel cell stack to power a load. An operational condition of the battery is compared to a desired operating condition and a partial pressure of a reactant flow to at least a portion of the fuel cell stack is adjusted based on the determined amount of deviation. The operational condition can include voltage, charge of the battery. Individual fuel cell systems can be combined in series and/or parallel to produce a combined fuel cell system having a desired output voltage and current.

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: An ultracapacitor based power storage device suitable for use in hybrid fuel cell systems and other power systems includes circuitry for simulating the response of a battery. A voltage current limiting circuit may be employed with a variety of electrical storage devices, for example, ultracapacitors and batteries.

Abstract: A membrane electrode assembly may be made using a one-sided catalyst coated membrane (CCM) wherein only one catalyst layer, either the anode or the cathode, is coated directly on the ion-exchange membrane. In particular, a one-sided CCM may be used where it may not be practicable to coat both sides of the ion-exchange membrane with catalyst layers such as when PTFE is added to the anode catalyst layer to render it reversal tolerant.

Abstract: An electrochemical fuel cell comprises an anode electrocatalyst layer, a cathode electrocatalyst layer, a polymer electrolyte membrane interposed between the anode and cathode electrocatalyst layers, an anode flow field plate, a cathode flow field plate, an anode fluid distribution layer interposed between the anode flow field plate and the anode electrocatalyst layer, and a cathode fluid distribution layer interposed between the cathode flow field plate and the cathode electrocatalyst layer, wherein at least one of the anode and cathode fluid distribution layers decreases in permeability from an inlet to an outlet of the electrochemical fuel cell. Methods for making a substantially fluid impermeable sheet material having a non-uniform pattern of perforations are also provided.