Nanostructured core-shell electrocatalysts for fuel cells

Abstract

Catalytic layers for use in the electrodes of fuel cells including a non-noble metal substrate layer coated with one or a few monolayers of noble metal, such as Pt. These thin, highly porous structures with large catalytically active surface areas, should exhibit a significantly higher power output per mg of Pt and per cm 2 of the membrane than the current Polymer Electrolyte Fuel Cells catalytic layers.

1 . A fuel cell comprising an ion exchange membrane positioned between first and second porous catalytic layers and first and second electrodes, each of said catalytic layers comprising a carbon-free non-noble porous metal nanostructured substrate and a coating layer comprising a noble metal. 
     
     
         2 . A fuel cell according to  claim 1 , wherein said noble metal is platinum. 
     
     
         3 . A fuel cell according to  claim 1 , wherein said nanostructure comprises at least one of nanoparticles, nanowires, honeycombs, and inverse opals. 
     
     
         4 . A fuel cell according to  claim 1  wherein said first electrode is an oxygen or air cathode. 
     
     
         5 . A fuel cell according to  claim 4  wherein said second electrode is a hydrogen anode. 
     
     
         6 . A fuel cell according to  claim 5 , wherein a platinum loading in said catalyst layers is from 0.2 to 0.017 mg/cm 2 . 
     
     
         7 . A fuel cell according to  claim 4 , wherein said second electrode is a methanol anode. 
     
     
         8 . A fuel cell according to  6 , wherein a platinum loading in said catalyst layers is from 0.1 to 0.04 mg/cm 2 . 
     
     
         9 . A fuel cell according to  claim 2 , wherein the thickness of the nanoporous catalytic layer is from 0.1 to 10 μm. 
     
     
         10 . A fuel cell according to  claim 1 , wherein a pore diameter of the nanostructure is from 3 to 200 nm. 
     
     
         11 . A fuel cell according to  claim 10  wherein a pore diameter is from 5 to 50 nm. 
     
     
         12 . A fuel cell according to  claim 1 , wherein said ion exchange membrane comprises a proton-conducting polymer and it fills at least part of the pores of said substrate. 
     
     
         13 . A fuel cell according to  claim 1 , wherein said non-noble metal comprises a first-row transition element, valve metal or coinage metal or a combination thereof. 
     
     
         14 . A fuel cell according to  claim 1 , wherein said fuel cell is capable of achieving an energy output of 0.02 g Pt/kW. 
     
     
         15 . A membrane-electrode assembly comprising a proton conducting membrane separating two porous electrodes, and positioned between two porous catalytic layers, each of said catalytic layers comprising a carbon-free non-noble metal porous nanostructured substrate and a noble metal surface layer. 
     
     
         16 . A membrane-electrode assembly according to  claim 15 , wherein said nanostructure comprises at least one of nanoparticles, nanowires, honeycombs, and inverse opals. 
     
     
         17 . A membrane-electrode assembly according to  claim 15 , wherein said first electrode is an oxygen or air cathode. 
     
     
         18 . A membrane-electrode assembly according to  claim 17  wherein said second electrode is a hydrogen anode. 
     
     
         19 . A membrane-electrode assembly according to  claim 18 , wherein a noble metal loading in said catalyst layers is from 0.2 to 0.017 mg/cm 2 . 
     
     
         20 . A membrane-electrode assembly according to  claim 17  wherein said second electrode is a methanol anode. 
     
     
         21 . A membrane-electrode assembly according to  20 , wherein a noble metal loading in said catalyst layers is from 0.1 to 0.04 mg/cm 2 . 
     
     
         22 . A membrane-electrode assembly according to  claim 15 , wherein the nanoporous catalytic layer thickness is between 0.1 and 10 (im. 
     
     
         23 . A membrane-electrode assembly according to  claim 15 , wherein a pore diameter of the nanostructure is from 3 to 200 nm. 
     
     
         24 . A membrane-electrode assembly according to  claim 15 , wherein said ion exchange membrane comprises a proton-conducting polymer and it fills at least part of the pores of said substrate. 
     
     
         25 . A membrane-electrode assembly according to  claim 15 , wherein said non-noble metal comprises a first-row transition element, valve metal or coinage metal or a combination thereof. 
     
     
         26 . A membrane-electrode assembly according to  claim 15 , further comprising first and second gas diffusion layers in contact with said catalytic layers. 
     
     
         27 . A method for preparing a fuel cell comprising the steps of: providing first and second electrodes; positioning an ion conducting membrane between said electrodes; and disposing first and second porous catalytic layers on opposing surfaces of said membrane, each of said catalytic layers comprising a carbon-free non-noble metal porous nanostructured substrate and a noble metal surface layer. 
     
     
         28 . A method according to  claim 27 , wherein said non-noble metal comprises a first-row transition element, valve metal or coinage metal or a combination thereof. 
     
     
         29 . A method according to  claim 27 , wherein said noble metal comprises a platinoid.