Membrane electrode assemblies and fuel-cell systems with surface-modified electrocatalysts and methods for electrocatalyst surface modification

Abstract

Fuel-cell assemblies containing a membrane electrode assembly, methods for preparing the membrane electrode assembly, and methods for functionalizing catalytic surfaces of catalyst particles in the membrane electrode assembly of the fuel cell assembly have been described. The fuel-cell assemblies and their membrane electrode assemblies contain cathode catalyst materials having catalytic surfaces that are functionalized with cyano groups to improve catalyst activity. The cathode catalyst materials may include a catalytic metal such as platinum or a platinum alloy. The cyano groups may be derived from a cyanide source that is electro-oxidized onto the catalytic surfaces. Nonlimiting examples of cyanide sources include amino acids such as glycine, alanine, and serine. The cyano groups may improve catalyst activity toward the oxygen-reduction reaction in a hydrogen fuel cell by blocking catalyst surface adsorption of contaminant species such as sulfates or sulfonates while allowing access of oxygen molecules to the catalyst surface.