Synthesis of Cu–TiO2/CuS p-n heterojunction via in situ sulfidation for highly efficient photocatalytic NO removal

Cu doped TiO2/CuS (Cu–TiO2/CuS) p-n heterojunction was synthesized via in situ sulfidation method for efficient photocatalytic removal of NO at ppb-level. The results show that optimized Cu–TiO2/CuS heterojunction possessed a maximum efficiency of 85% for the removal of NO under visible light irradiation, which was approximately 8.5, 4.3 and 1.2 times that of CuS, TiO2 and Cu–TiO2, respectively. The improved photocatalytic performance is attributed to the enhancement of visible light absorption and charge carrier separation induced by the construction of p-n heterojunction. Meanwhile, the p-n heterojunction charge transfer mechanism of Cu–TiO2/CuS was verified by systematic investigations. The appropriate band structures of the two components and the internal electric field formed at the interface of the heterojunction were two factors for this charge transfer mechanism. Furthermore, the role of active species in NO removal was explored, and the corresponding mechanism for NO removal of the heterojunction was proposed. This work provides a promising approach for the synthesis of heterojunction photocatalysts and facilitates the application of photocatalysts in sustainable and efficient pollutant removal.