Change of band-gap position of MTiO₂ particle doped with 3d-transition metal and control of product selectivity on carbon dioxide photoreduction

This study attempted to obtain various products from carbon dioxide photoreduction using TiO₂ catalysts doped with different transition metals of Mn, Fe, Co, Ni, Cu, and Zn (MTiO₂). The band-gaps of MTiO₂ catalysts decreased compared to pure TiO₂, except for ZnTiO₂. The intensities in photoluminescence curves, which can predict the recombination of excited electrons and holes, were weaker in MTiO₂ catalysts than that of pure TiO₂. The products obtained from carbon dioxide photoreduction were strongly related to the redox potential of carbon dioxide and the locations of band-gaps of MTiO2 catalysts. Methane was predominantly obtained in pure TiO₂, FeTiO₂, and NiTiO₂ catalysts, and methanol and carbon monoxide were selectively produced in the CuTiO₂ and ZnTiO₂ catalysts, respectively. This result suggests that the desired product from carbon dioxide photoreduction can be selectively synthesized by doping certain metals.