Increasing electron density by surface plasmon resonance for enhanced photocatalytic CO2 reduction

The photocatalytic CO2 reduction reaction is a multi-electron process, which is greatly affected by the surface electron density. In this work, we synthesize Ag clusters supported on In2O3 plasmonic photocatalysts. The Ag–In2O3 compounds show remarkedly enhanced photocatalytic activity for CO2 conversion to CO compared to pristine In2O3. In the absence of any co-catalyst or sacrificial agent, the CO evolution rate of optimal Ag–In2O3-10 is 1.56 μmol/g/h, achieving 5.38-folds higher than that of In2O3 (0.29 μmol/g/h). Experimental verification and DFT calculation demonstrate that electrons transfer from Ag clusters to In2O3 on Ag–In2O3 compounds. In Ag–In2O3 compounds, Ag clusters serving as electron donators owing to the SPR behaviour are not helpful to decline photo-induced charge recomnation rate, but can provide more electron for photocatalytic reaction. Overall, the Ag clusters promote visible-light absorption and accelerate photocatalytic reaction kinetic for In2O3, resulting in the photocatalytic activity enhancement of Ag–In2O3 compounds. This work puts insight into the function of plasmonic metal on enhancing photocatalysis performance, and provides a feasible strategy to design and fabricate efficient plasmonic photocatalysts.