Theoretical and experimental studies of highly efficient all-solid Z-scheme TiO2–TiC/g-C3N4 for photocatalytic CO2 reduction via dry reforming of methane

Abstract

An all-solid Z-scheme heterojunction TiO₂–TiC/g-C₃N₄ was proposed and synthesized successfully by a facile calcination method and used for photocatalytic CO₂ reduction in the presence of CH₄. Under sub-atmospheric pressure and at room temperature, the Z-scheme heterojunction TiO₂–TiC/g-C₃N₄ presented enhanced photocatalytic performance compared to g-C₃N₄, TiO₂–TiC and TiO₂/g-C₃N₄. Both in situ XPS results and DFT calculations results verified the formation of the Z-scheme heterojunction. The theoretical calculations showed that TiC acts as an electron mediator in which the electrons from the conduction band (CB) of TiO₂ recombine with the holes in the valence band (VB) of g-C₃N₄. Therefore, higher redox potentials are preserved, achieving high photocatalytic reaction efficiency. Besides, the DFT calculations established a stable TiO₂–TiC/g-C₃N₄ model. Orthogonal experiments were carried out to explore the optimal conditions, and under optimal conditions the TOF of CO and H₂ reached 11.3 μmol g⁻¹ h⁻¹ and 2.15 μmol g⁻¹ h⁻¹, respectively.