Ballard Power Systems Corporation

Ford Motor Company Limited

Daimler Ag

Societe Bic

Bdf IP Holdings Ltd.

Joy A Roberts

David P Wilkinson

Jean St-Pierre

Marian E Van Der Geest

Joerg Zimmermann

Stephen A Campbell

Herwig Haas

Francine Berretta

Jeremy Schrooten

Nicholas J Fletcher

Cindy J Longley

Alvin Lee

Abderrahmane Atbi

Amy Shun-Wen Yang

Stephanie Moroz

Shanna Denine Knights

Kevin M Colbow

Clarence Y Chow

Jiujun Zhang

Peter Urban

Erik Paul Johannes

Jens M&uuml;ller

John Ka Chan

NengYou Jia

J&uuml;rgen Stumper

Regina Wezel

Stephen J Lee

Bien Hung Chiem

Stanley Tam

Yvonne Hsieh

Eagranie Yuh

Guy Pepin

By Patricia Allan, Administrator

Derek E Allan, Deceased

Use of a selectively conducting anode component in solid polymer electrolyte fuel cells can reduce the degradation associated with repeated startup and shutdown, but can also adversely affect a cell's tolerance to voltage reversal along with its performance. It was shown that these adverse affects can be mitigated against in certain ways. However, improved results can be obtained by employing a selectively conducting component which comprises a mixed layer of a selectively conducting material and carbon. The mixed layer contacts the side of the anode opposite the solid polymer electrolyte.

Fuel cell with selectively conducting anode

The degradation associated with repeated startup and shutdown of solid polymer electrolyte fuel cells comprising PtCo alloy cathode catalysts can be particularly poor. However, a marked and unexpected improvement in durability is observed as a result of incorporating a selectively conducting component in electrical series with the anode components in the fuel cell.

Durable fuel cell with platinum cobalt alloy cathode catalyst and selectively conducting anode

A method for operating a passive, air-breathing fuel cell system is described. In one embodiment, the system comprises one or more fuel cells, and a closed fuel plenum connected to a fuel supply. In some embodiments of the method, the fuel cell cathodes are exposed to ambient air, and the fuel is supplied to the anodes via the fuel plenum at a pressure greater than that of the ambient air.

Method for operating fuel cells with passive reactant supply

By incorporating a selectively conducting component in electrical series with the anode components in a solid polymer fuel cell, degradation during startup and shutdown can be reduced. As a result, the startup and shutdown procedures can be simplified and consequently certain system apparatus may be omitted. The anode does not need to be rapidly purged with hydrogen on startup or with air on shutdown. Additionally, the auxiliary load usually employed during such purging is not required.

Fuel cell with selectively conducting anode component

An electric power generation system has elements that improve the cold start capability and freeze tolerance of a constituent fuel cell stack cooperate to reduce the amount of water remaining within the passages of the stack. The system includes a purge system that is connectable to the oxidant supply, fuel supply and/or coolant passages upstream of the stack. When the stack is shut down, the stack is disconnected from an external circuit, and purge fluid is transmitted by the purge system through the stack before the stack falls below the freezing point of water. In systems where fuel and/or oxidant streams are humidified prior to entry into the stack, a humidifier bypass system may be provided in place of the purge system. The humidifier bypass system transmits reactant fluid to the stack in fluid isolation from the humidifier, so that the inlet reactant streams are unhumidified.

Apparatus for improving the cold starting capability of an electrochemical fuel cell

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&#xb0; C. or less than 0&#xb0; C.) as well as operation at low relative humidity.

Impregnation of ion-exchange membranes to improve electrochemical fuel cell performance

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&deg; C.

Method and apparatus for increasing the temperature of a fuel cell

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.

Method and apparatus for controlling the temperature within an electrochemical fuel cell

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. The impregnant improves the mass transport properties for the movement of reactants and reaction products within the micropores of the electrocatalyst particles, thereby improving electrocatalyst utilization and electrochemical fuel cell performance for a fixed amount of electrocatalyst.

Impregnation of microporous electrocatalyst particles for improving performance in an electrochemical fuel cell

A method of ceasing operation of an electric power generation system improves the cold start capability and freeze tolerance of a fuel cell stack by reducing the amount of water remaining within the passages of the stack. The method involves purging one or more of the fuel cell stack oxidant and fuel passages at shutdown prior to allowing the fuel cell stack to drop to temperatures below the freezing point of water. Preferably purging at shutdown is conducted at a temperature below the stack operating temperature.

Method for improving the cold starting capability of an electrochemical fuel cell

An electrochemical fuel cell is operated with periodic reactant starvation at either or both electrodes. Periodic reactant starvation conditions cause a change in the potential of the starved electrode and may result in the removal of electrocatalyst poisons and in improved fuel cell performance. This technique may have other beneficial effects at the electrodes, including performance improvements due to water management effects or localized heating effects at the starved electrode. In a preferred method, while successive localized portions of a fuel cell electrode are periodically reactant starved, the remainder of the fuel cell electrode remains electrochemically active and saturated with reactant such that the fuel cell is able to continue to generate power.

Method and apparatus for operating an electrochemical fuel cell with periodic reactant starvation

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&deg; C.

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.

Method of reducing fuel cell performance degradation of an electrode comprising porous components

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.

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Coquitlam, Canada

Joy A Roberts