Photoelectrochemical water splitting with cobalt oxide coated gold nanorods under visible excitation

Photocatalytic water splitting is a promising approach for converting solar energy to chemical energy in the form of hydrogen and oxygen molecules. Plasmonic nanoparticles have shown great potential as photocatalysts for water splitting due to their large absorption efficiency across the entire solar spectrum. Light absorption by nanoparticles leads to the formation of highly energetic electrons and holes, termed as hot carriers, which catalyse many chemical reactions. However, the rapid decay of these hot carriers often limits their practical applications. Recently, it was demonstrated that efficient extraction of hot carriers could be achieved with bimetallic nanoparticles consisting of a plasmonic nanoparticle in close proximity of a more reactive catalytic species such as palladium or platinum, where the catalysis takes place [1, 2]. We report a new plasmonic catalyst consisting of a thin layer of cobalt oxide on a gold nanorod (CoO@AuNRs) that shows appreciable efficiency for photoelectrochemical water oxidation with a marginal onset overpotential at pH 13 and large photocurrent when excited by visible light.