FUEL CELL SYSTEM WITH CARBON MONOXIDE TOLERANT CATALYST COMPOSITION (16-Sep-2009)

FUEL CELL SYSTEM WITH CARBON MONOXIDE TOLERANT CATALYST COMPOSITION

BACKGROUND

   Technical Field
5 This disclosure relates generally to a fuel cell system, a fuel supply containing carbon monoxide and a fuel cell including a carbon monoxide tolerant catalyst composition comprising a catalyst and a catalyst support.

Description of the Related Art

         Fuel cells convert fuel and oxidant to electricity and reaction product. Solid polymer fuel cells typically employ a membrane electrode assembly ("MEA") consisting of a proton exchange membrane ("PEM") disposed between two porous, electrically conductive gas diffusion layers ("GDLs"). As GDLs also provide for the ingress and egress of liquids, GDLs are also known in the art as fluid diffusion layers or fluid distribution layers. Catalytic material is disposed at the interface between the PEM and the GDL forming two electrodes, namely an anode and cathode.

         The MEA is typically further disposed between flow field plates to form a fuel cell assembly. Flow fields are typically incorporated into the flow field plates to direct reactants across the electrochemically active surfaces of electrodes. Flow fields also provide for the removal of reaction products and depleted reactant streams. Ports and other fluid distribution features are typically formed in the surfaces at the periphery of such flow field plates. Fuel cells are sealed around the edges of the MEAs and flow field plates in order to appropriately isolate the different fluids within the fuel cell and in order to prevent leaks.

         A plurality of fuel cells may be combined in series to form a fuel cell stack. In a fuel cell stack, a flow field plate is usually shared between two adjacent

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MEAs, and thus also serves as a separator to fluidly isolate the fluid streams of the two adjacent MEAs. When assembled into a fuel cell stack, the stacked ports can form internal manifolds for distribution of the fluids throughout the stack. The other distribution features typically are provided to distribute fluids from the ports to the appropriate flow fields.

         At the anode, fuel, typically in the form of hydrogen gas, reacts at the catalyst to form hydrogen ions and electrons. At the cathode, oxidant reacts at the catalyst to form anions. The PEM isolates the fuel stream from the oxidant stream and facilitates the migration of the hydrogen ions from the anode to the cathode where they react with anions formed at the cathode. The electrons pass through an external circuit, creating a flow of electricity. The net reaction product is water. The anode and cathode reactions in hydrogen gas fuel cells are shown in the following reactions:

H₂ → 2H⁺ + 2e^- (1)

½O₂ + 2H⁺ + 2e^- → H₂O (2)

         Fuel cells typically employ platinum as a catalyst. Platinum is a significant component of fuel cell cost. Therefore, efforts have...