Interfacial facet engineering on the Schottky barrier between plasmonic Au and TiO2 in boosting the photocatalytic CO2 reduction under ultraviolet and visible light irradiation

Hybrid photocatalytic nanostructures composed of plasmonic metal and wide-band-gap semiconductor components have been widely developed, in which metal not only acts as a cocatalyst to trap the photogenerated electrons from semiconductor for improved charge separation and provide highly active sites for accelerated reaction kinetics, but also serves as a light-harvesting antennae to extend the light absorption region based on the injection of plasmonic hot electrons into the semiconductor. In both circumstances, rational design of metal/semiconductor interface is highly desirable to smooth the migration of electrons and promote the separation of carriers. Herein, based on the deposition of Au on TiO2 nanocrystals with different exposed facets, it is found that the formation of Au/TiO2(1 0 1) interface lowers the height of Schottky barrier in comparison with Au/TiO2(0 0 1) interface, enhancing the transfer of conduction band (CB) electrons from TiO2 to Au cocatalysts under ultraviolet light irradiation and promoting the hot electron injection from plasmonic Au into the CB of TiO2 with the excitation of Au by visible light. The more efficient interfacial charge transfer and separation enable more electrons participating in the conversion of CO2 to CO and CH4. As a result, at both excitation wavelengths, the Au-TiO2 sample with exclusive Au/TiO2(1 0 1) interfaces significantly ameliorates the photocatalytic activities in CO and CH4 production compared to other samples containing Au/TiO2(0 0 1) interfaces. The interfacial facet engineered Schottky barrier may open a new window to rationally designing metal–semiconductor hybrid structures for photocatalysis.