Fuel Cell with Porous Metal Foam

Abstract

An innovative fuel cell system with membrane electrode assemblies (MEAs) includes a polymer electrolyte membrane, a gas diffusion layer (GDL) made of porous metal foam, and a catalyst layer. A fuel cell has a metal foam layer that improves efficiency and lifetime of the conventional gas diffusion layer, which consists of both gas diffusion barrier (GDB) and microporous layer (MPL). This metal foam GDL enables consistent maintenance of the suitable structure and even distribution of pores during the operation. Due to the combination of mechanical and physical properties of metallic foam, the fuel cell is not deformed by external physical strain. Among many other processing methods of open-cell metal foams, ice-templating provides a cheap, easy processing route suitable for mass production. Furthermore, it provides well-aligned and long channel pores, which improve gas and water flow during the operation of the fuel cell.

The invention claimed is: 
     
         1 . A fuel cell comprising:
 a polymer electrolyte, a gas diffusion layer, and a catalyst layer, wherein the gas diffusion layer is made of porous metal foam.   
     
     
         2 . The fuel cell of  claim 1 , wherein a manufacturing process to form the porous metal foam comprises at least one of the following: powder sintering, space holder method, ice-template method, dealloying, electroplating, and electroless plating. 
     
     
         3 . The fuel cell of  claim 1 , wherein the porous metal foam is made of a metal that is selected from a group consisting of the following metal or one of its alloys: platinum, palladium, titanium, nickel, copper, aluminum, zirconium, tungsten, cobalt, manganese, magnesium, bismuth, chromium, silver, gold, niobium, tantalum, silicon, iridium, indium, molybdenum, zinc, tin, antimony, and stainless steel. 
     
     
         4 . The fuel cell of  claim 1 , wherein the gas diffusion layer is characterized as a cathode. 
     
     
         5 . The fuel cell of  claim 1 , wherein the gas diffusion layer is characterized as an anode. 
     
     
         6 . The fuel cell of  claim 1 , wherein the catalyst layer is selected from a group of the following catalysts: platinum catalyst, platinum-metal alloy catalyst, platinum-copper alloy catalyst, platinum-cobalt alloy catalyst, platinum-nickel alloy catalyst, platinum-palladium alloy catalyst, platinum-manganese alloy catalyst, platinum-chromium alloy catalyst, platinum-iron alloy catalyst, metal-platinum core shell structured catalyst, copper-platinum core shell structured catalyst, cobalt-platinum core shell structured catalyst, nickel-platinum core shell structured catalyst, palladium-platinum core shell structured catalyst, manganese-platinum core shell structured catalyst, chromium-platinum core shell structured catalyst, and iron-platinum core shell structured catalyst. 
     
     
         7 . The fuel cell of  claim 1 , wherein the catalyst is selected from a group of nonplatinum catalysts as follows: cobalt/polyaniline/carbon nanotubes (Co/PANI/CNT), iron/cobalt/carbon (Fe/Co/C), and tungsten carbide/iron/polyaniline (WC/Fe/PANI). 
     
     
         8 . A method of making the fuel cell of  claim 1  comprising:
 forming a first porous metal foam component, wherein the first porous metal foam comprises a plurality of pores aligned in a first direction, and the forming first porous of the metal foam component comprises 
 immersing a copper rod into liquid nitrogen and placing onto the copper rod a slurry containing water, binder, and metal particles, 
 lowering a temperature of the slurry to form ice dendrites, wherein the metal particles interposed between the ice dendrites become frozen, 
 forming a green-body porous structure by freeze drying the ice dendrites in the slurry below a freezing point of the water, 
 forming a metal foam structure by sintering the porous green-body structure in a vacuum furnace, and 
 machining the metal foam structure into the first porous metal foam component comprising a thickness of less than 230 microns; 
 forming a second porous metal foam component, wherein the second porous metal foam comprises a plurality of pores aligned in the first direction; 
 using the first porous metal foam as a first electrode of the fuel cell; 
 using the second porous metal foam as a second electrode of the fuel cell; 
 forming an electrolyte between the first and second electrodes; 
 forming a first catalyst between the first electrode and the electrolyte; and 
 forming a second catalyst between the second electrode and the electrolyte. 
 
     
     
         9 . The method of  claim 8 , wherein the first direction is transverse to an interface between the first electrode and the first catalyst, and transverse to an interface between the second electrode and the second catalyst. 
     
     
         10 . The method of  claim 8 , wherein the thickness of the first porous metal foam component in the first direction is greater than a thickness of the first catalyst. 
     
     
         11 . The method of  claim 8 , wherein electrons flow from the first electrode to the second electrode, without passing through the electrolyte. 
     
     
         12 . The method of  claim 8 , wherein the metal particles are selected from the group of the following metals and their alloys: platinum, palladium, titanium, nickel, copper, aluminum, zirconium, tungsten, cobalt, manganese, magnesium, bismuth, chromium, silver, gold, niobium, tantalum, silicon, iridium, indium, molybdenum, zinc, tin, antimony, and stainless steel. 
     
     
         13 . The method of  claim 8 , wherein the first porous metal foam component is an electrical conductor. 
     
     
         14 . The method of  claim 8 , wherein the first porous metal foam component is a titanium metal foam. 
     
     
         15 . The method of  claim 8 , wherein the metal particles are titanium particles. 
     
     
         16 . The method of  claim 8 , wherein the metal particles are titanium particles, and the first porous metal foam component is an anode of the fuel cell. 
     
     
         17 . The method of  claim 8 , wherein the first porous metal foam component is a titanium metal foam and comprises pores comprising a pore diameter on the order of tens of microns in diameter. 
     
     
         18 . The method of  claim 8 , wherein the binder comprises polyvinyl alcohol. 
     
     
         19 . The method of  claim 8 , wherein the first catalyst is selected from the group of the following catalysts: platinum catalyst, platinum-metal alloy catalyst, platinum-copper alloy catalyst, platinum-cobalt alloy catalyst, platinum-nickel alloy catalyst, platinum-palladium alloy catalyst, platinum-manganese alloy catalyst, platinum-chromium alloy catalyst, platinum-iron-alloy catalyst, metal-platinum core shell structured catalyst, copper-platinum core shell structured catalyst, cobalt-platinum core shell structured catalyst, nickel-platinum core shell structured catalyst, palladium-platinum core shell structured catalyst, manganese-platinum core shell structured catalyst, chromium-platinum core shell structured catalyst, and iron-platinum core shell structured catalyst. 
     
     
         20 . The method of  claim 8 , wherein the first catalyst is selected from the group of nonplatinum catalysts as follows: cobalt/polyaniline/carbon nanotubes (Co/PANI/CNT), iron/cobalt/carbon (Fe/Co/C), and tungsten carbide/iron/polyaniline (WC/Fe/PANI).