Dealloyed Nanoporous Metals for PEM Fuel Cell Catalysis

Abstract

Although the majority of PEM fuel cell catalysts are made of nanoparticles, similar surface area/volume, specific surface area, and precious metal loading can be made by using ultrathin (~100 nm) nanoporous metal membranes. We discuss here how ultrathin porous membranes can be made using electrochemical dealloying, and how to integrate such membranes into functional fuel cells. Dealloying is the selective dissolution of one or more components from a non-porous precursor alloy. Under the right electrochemical conditions, the remaining alloy component(s) are driven to diffuse along the alloy/electrolyte interface to form a porous metal with pores even smaller than 5 nm. Nanoporous metals can be intrinsically catalytic toward oxygen reduction, or can be coated with thin catalyst layers to form low Pt core-shell catalysts. Using nanoporous metal electrodes for fuel cell catalysis may remove stability issues associated with carbon supports, and opens new avenues for catalyst design.