Adjustment and Matching of Energy Band of TiO2-Based Photocatalysts by Metal Ions (Pd, Cu, Mn) for Photoreduction of CO2 into CH4

A series of the metal ions (Pd, Cu, and Mn) modified TiO2 photocatalysts are synthesized via simple sol–gel method. Characterized by X-ray diffraction, Raman, UV–vis absorption spectra, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, time-resolved photoluminescence (PL) decay curves, and PL, it was revealed these introduced metal ions existed as O–Me–O species (Me: Pd, Cu, and Mn) on the surface of TiO2. The corresponding theory calculation is used to investigate the electronic density of states and band structure of the metal ions (Pd, Cu, and Mn) modified TiO2. The modified TiO2 photocatalysts exhibit an improved photocatalytic performance on reduction of CO2 and H2O into methane (CH4), attributed to the contribution of surface species by enhancing the visible absorption efficiently, separating charge carriers, and matching of the redox potential on the photoreduction of CO2 into CH4. This article could provide a wider understanding about the adjustment and matching of the energy...