Effect of core@shell (Au@Ag) nanostructure on surface plasmon-induced photocatalytic activity under visible light irradiation

We prepared Au-Ag nanoparticles (NPs) with two different morphologies over SrTiO3 to investigate the effect of composite nanostructure on surface plasmon-induced photocatalytic activity; core@shell (Au@Ag) NPs were synthesized by a multi-step citric reduction method, and Au-Ag bimetallic NPs were prepared by a photo-reduction method. (Au@Ag)/SrTiO3 and Au-Ag/SrTiO3 showed strong photoabsorption in the visible light response due to a localized surface plasmon resonance (LSPR) of Ag. Moreover, they could oxidize 2-propanol to acetone and CO2 under visible light irradiation (440 < λ < 800 nm). From a comparison of action spectra for acetone evolution and the Kubelka-Munk function, it was confirmed that photocatalytic activities of (Au@Ag)/SrTiO3 and Au-Ag/SrTiO3 were induced by photoabsorption based on LSPR excitation of Ag. Interestingly, the rate of acetone evolution over (Au@Ag)/SrTiO3 was 1.5-times higher than that of over Au-Ag/SrTiO3, suggesting that the core@shell (Au@Ag) nanostructure contributes to the efficient surface plasmon-induced photocatalytic activity