Optical Excitation of a Nanoparticle Cu/p-NiO Photocathode Improves Reaction Selectivity for CO2 Reduction in Aqueous Electrolytes.

We report the light-induced modification of catalytic selectivity for photoelectrochemical CO2 reduction in aqueous media using copper nanoparticles dispersed onto p-type nickel oxide photocathodes. Optical excitation of Cu nanoparticles generates hot electrons available for driving CO2 reduction on the Cu surface while charge separation is accomplished by hot hole injection from the Cu nanoparticles into the underlying p-NiO support. Photoelectrochemical studies demonstrate that optical excitation of plasmonic Cu/p-NiO photocathodes imparts increased selectivity for CO2 reduction over hydrogen evolution in aqueous electrolytes. Specifically, we observed that plasmon-driven CO2 reduction increased the production of carbon monoxide and formate, while simultaneously reducing the evolution of hydrogen. Our results demonstrate an optical route towards steering the selectivity of artificial photosynthetic systems with plasmon-driven photocathodes for photoelectrochemical CO2 reduction in aqueous media.