Enhanced photocatalytic activity of TiO2–Cu/C with regulation and matching of energy levels by carbon and copper for photoreduction of CO2 into CH4

Abstract

A novel copper and carbon co-modified TiO₂ photocatalyst (TiO₂–Cu/C) was prepared using a simple sol–gel method. The properties of the photocatalysts were investigated by XRD, Raman, BET, HRTEM, EDAX, XPS, absorption spectroscopy and PL techniques. It was revealed that copper was present as –O–Cu–O– species and carbon existed as elementary substance carbon nanoparticles on the surface of TiO₂. Based on the experimental results, the band structure and electronic density of states of TiO₂, TiO₂–Cu and elementary substance carbon are predicted by theoretical calculations. The energy levels of the –O–Cu–O– species and the carbon nanoparticles were located above the valence band, which extends the absorption into the visible light region, facilitate the separation of photogenerated charge carriers and provide hole reactive sites on the surface. Thus, the photocatalytic activity of TiO₂–Cu/C is much higher than that of pure TiO₂, TiO₂/C and TiO₂–Cu for photoreduction of CO₂ and H₂O into CH₄ under UV-light irradiation.