Effect of TiO<inf>2</inf> crystal structure on CO<inf>2</inf> photoreduction using Au nanoparticles on TiO<inf>2</inf> catalyst

Abstract

Two types of gold-supported TiO 2 catalysts (anatase and rutile) were prepared using a deposition precipitation method, and their photocatalytic activity towards CO 2 reduction was tested in the gas phase using H 2 O as an electron donor and a xenon lamp as the energy sources. The crystal structures were verified using a scanning electron microscope (SEM) and the loaded Au nano-particles (NPs) had no effect on the surface structure. Fourier transform infrared spectroscopy (FTIR) was used to evaluate the photoreduction products. CO and CH 4 were the major products detected in the bare rutile and anatase TiO 2 , respectively. It was observed that the deposition of Au NPs on the TiO 2 catalyst surface (anatase and rutile) quantitatively enhances the reduction of CO 2 to methane (major product). Relative CH 4 production efficiencies following 2–5 h of irradiation were 5.2 for Au/TiO 2 anatase, 5.0 for Au/TiO 2 rutile, 1.7 for TiO 2 anatase and 1.0 for TiO 2 rutile. The CH 4 /CO production ratios following 2–5 h of irradiation were 18.7 for Au/TiO 2 anatase, 3.8 for Au/TiO 2 rutile, 6.0 for TiO 2 anatase and 1.1 for TiO 2 rutile. Based on these results, it can be inferred that CH 4 production was enhanced by Au loading independent of the crystal structure of TiO 2 , and the CH 4 production ratio was dependent on the crystal structure of TiO 2 .