Photoconversion of CO2 to methanol over plasmonic Ag/TiO2 nano-wire films enhanced by overlapped visible-light-harvesting nanostructures

Plasmonic Ag nanoparticles (NPs) deposited on TiO2 nano-wire films (Ag/TiO2 NWFs) were successfully fabricated by the combination of ethylene glycol assisted hydrothermal route and microwave assisted chemical reduction process. The investigations indicated that Ag NPs were well dispersed on the anatase/rutile mixed-phase TiO2 film and the composites exhibited visible-light-harvesting properties based on SPR effect of Ag and unique nano-wire structure of TiO2 film. Ag NPs could also effectively restrain the recombination of photoexcited electrons and holes, and fluorescence quenching was observed after deposition of Ag NPs under the excitation of 220 nm. Photocatalytic reduction of CO2 with H2O was conducted over Ag/TiO2 NWFs to obtain CH3OH, and the experimental results indicated that the activity of TiO2 was greatly enhanced due to the charge transfer property of Ag NPs and the efficient light utilization based on the overlapped visible-light-harvesting of Ag NPs and TiO2 NWF. The CH3OH yield can reach 8.3 μmol cm−2 over the optimal sample with energy efficiency of about 0.012. Additionally, a synergetic photocatalytic mechanism is proposed to understand the mechanism of plasmon enhanced photocatalysis based on the experimental results under different conditions.