Ammonia Oxidation Enhanced by Photopotential Generated by Plasmonic Excitation of a Bimetallic Electrocatalyst

We study how visible light influences the activity of an electrocatalyst composed of Au and Pt nanoparticles. The bimetallic composition imparts a dual functionality: the Pt component catalyzes the electrochemical oxidation of ammonia to liberate hydrogen and the Au component absorbs visible light by the excitation of localized surface plasmon resonances. Under visible-light excitation, this catalyst exhibits enhanced electrochemical ammonia oxidation kinetics, outperforming previously reported electrochemical schemes. We trace the enhancement to a photochemical potential resulting from electron-hole carriers generated in the electrocatalyst by plasmonic excitation. The photopotential responsible for enhanced kinetics scales linearly with the light intensity-a general design principle for eliciting superlative photoelectrochemical performance from catalysts comprised of plasmonic metals or hybrids. We also determine a photochemical conversion coefficient.