Two-Step Excitation-Driven Au–TiO₂–CuO Three-Component Plasmonic Photocatalyst: Selective Aerobic Oxidation of Cyclohexylamine to Cyclohexanone

The chemisorption of (acetylacetonato)copper(II) on gold-nanoparticle- (Au-NP-) loaded rutile TiO 2 and subsequent heating in the air at 773 K yields molecular-scale CuO clusters on the TiO 2 surface with varying CuO loading amounts (Au/TiO 2 –CuO) ( J. Phys. Chem. C 2013, 117, 23848−23857). The three-component Au/TiO 2 –CuO plasmonic photocatalyst exhibits a high level of visible-light activity for the selective aerobic oxidation of cyclohexylamine to cyclohexanone at room temperature. The photocatalytic activity far exceeds those of the Au/TiO 2 and TiO 2 –CuO two component systems. Photoelectrochemical experiments indicate that the electrons injected from Au NPs into TiO 2 by the localized surface plasmon resonance excitation are transferred to the CuO clusters through simultaneous visible-light excitation from the valence band of TiO 2 to the surface CuO-derived levels. Consequently, the high activity originates from the electron-collecting and -concentrating effects of the CuO clusters with an electrocatalytic activity for the oxygen reduction reaction.