Fuel cell having a hydrophilic substrate layer

Abstract

A fuel cell power plant ( 10 ) includes a fuel cell ( 12 ) having a membrane electrode assembly (MEA) ( 16 ), disposed between an anode support plate ( 14 ) and a cathode support plate ( 18 ), the anode and/or cathode support plates include a hydrophilic substrate layer ( 80, 82 ) having a predetermined pore size. The pressure of the reactant gas streams ( 22, 24 ) is greater than the pressure of the coolant stream ( 26 ), such that a greater percentage of the pores within the hydrophilic substrate layer contain reactant gas rather than water. Any water that forms on the cathode side of the MEA will migrate through the cathode support plate and away from the MEA. Controlling the pressure also ensures that the coolant water will continually migrate from the coolant stream toward the anode side of the MEA, thereby preventing the membrane from becoming dry. Proper pore size and a pressure differential between coolant and reactants improves the electrical efficiency of the fuel cell.

1 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, one of said support plates comprising a hydrophilic substrate layer having pores therein and a diffusion layer disposed between said hydrophilic substrate layer and said membrane electrode assembly, said diffusion layer being a porous carbon-fluoropolymer particulate composite comprising less than about 50% fluoropolymer;   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.   
     
     
         2 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, one of said support plates comprising a hydrophilic substrate layer having pores therein, and a diffusion layer disposed between said hydrophilic substrate layer and said membrane electrode assembly, said diffusion layer having pores therein with a mean pore size less than or equal to about 4 micron and a porosity equal to or greater than about 60%; and   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.   
     
     
         3 . A fuel cell power plant of  claim 2  wherein said diffusion layer has a critical surface energy equal to or less than about 30 dyne per centimeter. 
     
     
         4 . A fuel cell power plant of  claim 2  wherein said diffusion layer comprises a fluoropolymer, thereby rendering said diffusion layer at least partially hydrophobic. 
     
     
         5 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, one of said support plates comprising a hydrophilic substrate layer having pores therein, and a diffusion layer disposed between said hydrophilic substrate layer and said membrane electrode assembly, said diffusion layer being about 0.0005 inches to about 0.002 inches thick; and   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.   
     
     
         6 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, each of said support plates comprising a hydrophilic substrate layer having pores therein, one of said substrates in intimate contact with said membrane electrode assembly;   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.   
     
     
         7 . A fuel cell power plant according to  claim 6  wherein:
 each of said substrates are in intimate contact with said membrane electrode assembly. 
 
     
     
         8 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, one of said support plates being a porous carbon substrate layer comprising an oxide selected from the group consisting of niobium oxide (Nb 2 O 5 ), ruthenium oxide (RuO 2 ), tantalum oxide (Ta 2 O 5 ), titanium oxide (TiO 2 ), zinc oxide (ZnO 2 ), zirconium oxide (ZrO 2 ), and mixtures thereof, thereby rendering said porous carbon substrate layer hydrophilic;   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.   
     
     
         9 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, each of said support plates comprising a hydrophilic substrate layer having pores therein, one of said substrates being a porous carbon substrate layer comprising a hydroxide selected from the group consisting of tin hydroxide, aluminum hydroxide, niobium hydroxide, ruthenium hydroxide, tantalum hydroxide, titanium hydroxide, zinc hydroxide, zirconium hydroxide, and mixtures thereof, thereby rendering said porous carbon substrate layer hydrophilic;   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.   
     
     
         10 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, one of said support plates being a porous carbon substrate layer comprising an oxyhydroxide selected from the group consisting of tin oxyhydroxide, aluminum oxyhydroxide, niobium oxyhydroxide, ruthenium oxyhydroxide, tantalum oxyhydroxide, titanium oxyhydroxide, zinc oxyhydroxide, zirconium oxyhydroxide, and mixtures thereof, thereby rendering said porous carbon substrate layer hydrophilic;   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.   
     
     
         11 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, one of said support plates comprising a tin oxyhydroxide hydrophilic substrate layer, having pores therein;   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.   
     
     
         12 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, one of said support plates being a hydrophilic substrate layer, having pores therein, and comprising an amount of tin oxide, tin hydroxide, or tin oxyhydroxide equal to greater than about 2 mg for each gram of said hydrophilic substrate layer;   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.   
     
     
         13 . The fuel cell power plant of  claim 12  wherein said hydrophilic substrate layer comprises about 20 mg to 50 mg of tin oxide, tin hydroxide, or tin oxyhydroxide for each gram of said hydrophilic substrate layer. 
     
     
         14 . A fuel cell power plant, comprising:
 (a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between an anode and a cathode, one of said support plates comprising a hydrophilic substrate layer having pores with a mean pore size greater than about 4 microns therein;   (b) a porous water transport plate adjacent to said one support plate, said water transport plate configured to have a coolant stream in one passageway and a reactant gas stream in another passageway; and   (c) means for providing a predetermined pressure differential between said reactant gas stream and said coolant stream such that a greater percentage of said pores within said hydrophilic substrate layer contain reactant gas rather than coolant.