Low Platinum Fuel Cells, Catalysts, and Method for Preparing the Same

Abstract

This invention provides novel fuel cell electrodes and catalysts comprising a series of catalytically active thin-film metal alloys with low platinum concentration supported on nanostructured materials (nanoparticles). Processing of the electrodes and catalysts can include electrodeposition methods, and high-pressure coating techniques. In certain embodiments, an integrated gas-diffusion/electrode/catalyst layer can be prepared by processing catalyst thin films and nanoparticles into gas-diffusion media such as Toray or SGL carbon fiber papers. The catalysts can be placed in contact with an electrolyte membrane for PEM fuel cell applications.

1  to  42 . (canceled) 
     
     
         43 . A method of coating a plurality of nanoparticles with an ionomer, the method comprising:
 contacting the nanoparticles with the ionomer;   placing the nanoparticles in the pressure vessel; and,   pressurizing the pressure vessel, whereby said pressurizing enhances coating of the nanoparticles with the ionomer.   
     
     
         44 . The method of  claim 43 , wherein the nanoparticles are selected from the group consisting of nanotubes, nanofibers, nanohorns, nanopowders, nanospheres, and quantum dots. 
     
     
         45 . The method of  claim 44 , wherein the nanoparticles are carbon nanotubes. 
     
     
         46 . The method of  claim 45 , wherein the carbon nanotubes are seeded with one or more catalysts comprising one or more materials selected from the group consisting of Co, Ni, V, Cr, Pt, Ru, Mo, W, Ta, and Zr. 
     
     
         47 . The method of  claim 45 , wherein the carbon nanotubes are seeded with one or more catalysts selected from the group consisting of Fe x Ni y Co 1-x-y  where 0≦x≦1 and 0≦y≦1, Co 1-x Mo x  where 0≦x≦0.3, Co 1-x-y Ni x Mo y  where 0.1≦x≦0.7 and 0≦y≦0.3, Co 1-x-y-z Ni x V y Cr z  where 0≦x≦0.7 and 0≦y≦0.2, 0≦z≦0.2, Ni 1-x-y Mo x Al y  where 0≦x≦0.2 and 0≦y≦0.2, and Co 1-x-y Ni x Al y  where 0≦x≦0.7 and 0≦y≦0.2. 
     
     
         48 . The method of  claim 45 , wherein the carbon nanotubes are seeded with one or more catalysts selected from the group consisting of Co 8.8 Mo 1.2 , Co 2.2 Ni 5.6 Mo 2.2 , Co 5.7 Ni 2.1 V 1.1 Cr 1.1 , Ni 8.0 Mo 1.0 Al 1.0 , and Co 6.4 Ni 2.4 Al 1.2 . 
     
     
         49 . The method of  claim 43 , further comprising contacting the nanoparticles with additional ionomer and pressurizing the nanoparticles again to increase the thickness or weight percentage of the ionomer coating the nanoparticles. 
     
     
         50 . The method of  claim 43 , further comprising drying the nanoparticles. 
     
     
         51 . The method of  claim 43 , further comprising pretreating the nanoparticles by exposure to a vacuum or by sonication. 
     
     
         52 . The method of  claim 43 , further comprising pretreating the nanoparticles by etching in an argon plasma. 
     
     
         53 . The method of  claim 52 , further comprising controlling the depth of ionomer coating by adjusting the extent of said etching. 
     
     
         54 . The method of  claim 43 , wherein said contacting comprises spraying or brushing the ionomer onto the nanoparticles. 
     
     
         55 . The method of  claim 43 , wherein said pressurizing comprises pressurizing the vessel to a pressure of at least about 100 psi. 
     
     
         56 . The method of  claim 54 , wherein said pressurizing comprises contacting the nanoparticles with isopropyl alcohol. 
     
     
         57 . The method of  claim 43 , wherein the pressure vessel is pressurized by introducing a pressurized gas, or by applying force to a liquid with a mechanically driven piston. 
     
     
         58 . The method of  claim 43 , wherein the pressure vessel is pressurized using an impact or an explosive. 
     
     
         59 . The method of  claim 43 , wherein said contacting the nanoparticles with the ionomer precedes said placing the nanoparticles in the pressure vessel. 
     
     
         60 . The method of  claim 43 , wherein the ionomer comprises a polymer or copolymer. 
     
     
         61 . The method of  claim 43 , wherein the ionomer comprises a perfluorocarbonsulfonic acid ionomer. 
     
     
         62 . The method of  claim 43 , wherein the nanoparticles are attached to a substrate. 
     
     
         63 . The method of  claim 62 , wherein the substrate comprises a plurality of conductive fibers. 
     
     
         64 . The method of  claim 63 , wherein the conductive fibers comprise carbon fibers. 
     
     
         65 . The method of  claim 63 , wherein the plurality of conductive fibers comprise a porous electrode. 
     
     
         66 . The method of  claim 63 , wherein the plurality of conductive fibers comprise a carbon paper, or a carbon cloth, or a carbon-impregnated polymer. 
     
     
         67 . The method of  claim 63 , wherein the plurality of conductive fibers comprise a porous metal sheet. 
     
     
         68 . A method of forming a nanoparticle composite material, the method comprising:
 combining a collection of nanoparticles with a liquefied polymer to form a mixture; and,   pressurizing the mixture to form a composite of the polymer and nanoparticle material.   
     
     
         69 . The method of  claim 68 , wherein said pressurizing comprises pressurizing the mixture to a pressure of at least about 100 psi. 
     
     
         70 . The method of  claim 68 , wherein the nanoparticles comprise carbon nanotubes or quantum dots. 
     
     
         71 . The method of  claim 68 , wherein the liquefied polymer comprises an ionomer or a perfluorocarbonsulfonic acid ionomer. 
     
     
         72  to  127 . (canceled) 
     
     
         128 . The method of  claim 43 , further comprising applying a thin film to the nanoparticles by chemical vapor deposition (CVD).