Enhanced Photoelectrocatalytic Reduction of Oxygen Using Au@TiO Plasmonic Film.

Novel Au@TiO plasmonic films were fabricated by individually placing Au nanoparticles into TiO nanocavity arrays through a sputtering and dewetting process. These discrete Au nanoparticles in TiO nanocavities showed strong visible-light absorption due to the plasmonic resonance. Photoelectrochemical studies demonstrated that the developed Au@TiO plasmonic films exhibited significantly enhanced catalytic activities toward oxygen reduction reactions with an onset potential of 0.92 V (vs reversible hydrogen electrode), electron transfer number of 3.94, and limiting current density of 5.2 mA cm. A superior ORR activity of 310 mA mg is achieved using low Au loading mass. The isolated Au nanoparticle size remarkably affected the catalytic activities of Au@TiO, and TiO coated with 5 nm Au (Au@TiO) exhibited the best catalytic function to reduce oxygen. The plasmon-enhanced reductive activity is attributed to the surface plasmonic resonance of isolated Au nanoparticles in TiO nanocavities and suppressed electron recombination. This work provides comprehensive understanding of a novel plasmonic system using isolated noble metals into nanostructured semiconductor films as a potential alternative catalyst for oxygen reduction reaction.