Plasmon excitation facilitating generation of electrons and reactive oxygen species for broad spectrum photocatalytic activity

Abstract

The coupling of semiconductor and plasmonic nanoparticles (NPs) has attracted significant attention due to improved light harvesting and charge separation for photocatalysis. However, the enhancement effect of surface plasmon resonance (SPR) has not been fully utilized, since it is related to a variety of factors, and the dominant factors remain unclear. It is realized that the spatial arrangement of semiconductor and plasmonic NPs may be of critically importance. To prove this concept, Au/TiO2 plasmonic nanostructures were fabricated as model system by distributing Au nanorods (AuNRs) uniformly on TiO2 nanosheets through mercaptopropionic acid assisted method. AuNRs/TiO2 possesses tunable SPR induced light absorption centered at 520 nm and 795 nm, ranging from visible to NIR that depends on the shape of AuNPs. The sample exhibits simultaneously enhanced photocatalytic activity toward reduction of H2O to produce H2 and oxidation of 3,3′,5,5′-tetramethylbenzidine when exposed to visible or NIR light. The production and reactive behaviors of electrons and ROS including ·OH, ⋅O2– and 1O2 from irradiated Au/TiO2 were detected by electron spin resonance, and correlated with SPR enhanced photocatalytic activity. These results unveil critical factor in SPR enhanced photocatalysis and suggest a highly preferred form of the hybrid nanostructures for their photocatalytic applications.