Enhanced Photoelectrocatalytic Reduction of Oxygen Using Au@TiO 2 Plasmonic Film.

Novel Au@TiO ₂ plasmonic films were fabricated by individually placing Au nanoparticles into TiO ₂ nanocavity arrays through a sputtering and dewetting process. These discrete Au nanoparticles in TiO ₂ nanocavities showed strong visible-light absorption due to the plasmonic resonance. Photoelectrochemical studies demonstrated that the developed Au@TiO ₂ 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 ^-2 . A superior ORR activity of 310 mA mg ^-1 is achieved using low Au loading mass. The isolated Au nanoparticle size remarkably affected the catalytic activities of Au@TiO ₂ , and TiO ₂ coated with 5 nm Au (Au ₅ @TiO ₂ ) 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 ₂ 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.