Gold-nanoparticle-modified TiO2 nanowires for plasmon-enhanced photocatalytic CO2 reduction with H-2 under visible light irradiation

Abstract

Gold-nanoparticles (Au-NPs) incorporated TiO2-nanowires (TiO2-NWs) of controlled sizes prepared via hydrothermal and chemical reduction method have been investigated for CO2 photoreduction with H2 under visible light irradiations. The nanocatalysts have been characterized by XRD, FESEM, TEM, N2 adsorption-desorption, XPS, UV-vis and PL spectroscopy. Highly crystalline TiO2 nanowires of mesoporous structure were obtained in Au-deposited TiO2 NWs. Au-NPs, uniformly distributed over TiO2-NWs as Au-metal state, hindered charges recombination rate and increased TiO2 activity under visible light through plasmon excitation. With the deposition of Au-NPs, the efficiency of CO2 reduction to CO was greatly enhanced under lower energy visible light irradiations. The maximum CO and CH3OH yield rate over 0.5 wt.% Au-NPs/TiO2 NWs reached to 1237 and 12.65 µmole g catal.-1 h-1, respectively. High quantum yield was also observed over Au-NPs/TiO2 NWs using H2 as reductant. The significantly improved photoactivity was evidently due to efficient electron-hole separation and surface plasmon response of Au-NPs. The reaction-pathway is proposed to provide insights over the mechanism of Au-plasmon-enhanced CO2 conversion