Synergistic effect in plasmonic Au/Ag alloy NPs co-coated TiO2 NWs toward visible-light enhanced CO2 photoreduction to fuels

Abstract Plasmonic Au/Ag alloy NPs supported on TiO 2 nanowires (TiO 2 NWs) have been designed and synthesized through a facile hydrothermal and photo-deposition method. The samples were characterized by XRD, FE-SEM, TEM, N 2 -adsorption-desorption, XPS, Raman, UV–vis and PL spectroscopy. Bimetallic Au/Ag NPs were presented over the TiO 2 NWs as an alloy, thus exhibited strong absorption of visible light due to the localized surface plasmon resonance (LSPR) excitation. The synergistic effect in plasmonic Au/Ag alloy NPs for selective photocatalytic CO 2 reduction with H 2 to CO and hydrocarbons under visible light irradiation was investigated. The present design of plasmonic Au/Ag NPs co-decorated TiO 2 NWs leads to remarkably enhanced photoactivity of CO 2 reduction to CO. The CO evolution rate as a main product over the Au-Ag alloy NPs coated TiO 2 NWs was 1813 μmole-g-catal. −1  h −1 at selectivity 98%. This amount was approximately 1.72 time larger comparing to Au-NPs/TiO 2 NWs, 1.84 fold more than the Ag-NPs/TiO 2 NWs, 72.52 fold than the TiO 2 NWs and 201 fold more than the amount of CO produced over the bare TiO 2 -NPs. This great enhancement can be attributed to synergistic effects in Au/Ag-NPs, enhanced visible light absorption due to Au-Ag alloy formation and improved charge separation in LSPR-excited TiO 2 NWs. In addition, turnover productivity is introduced to investigate the effect of operating parameters on the performance of photocatalysts. The plasmonic reaction mechanism of Au-Ag NPs in conjunction with LSPR excitation and charge transport to understand the reaction pathway is described.