Introducing oxygen-doped g-C3N4 onto g-C3N4/TiO2 heterojunction for efficient catalytic gatifloxacin degradation and H2O2 production

Abstract

Developing multi-functional high-efficiency photocatalysts to solve environmental pollution and the global energy crisis remains challenging. In this work, a novel oxygen-doped g-C3N4 modified g-C3N4/TiO2 (OCN@CNT-2) with double Z-scheme heterojunction was fabricated through electrostatic self-assembly. This strategy facilitates the uniform and tight adhesion of g-C3N4 and oxygen doping on g-C3N4 (OCN) to the surface TiO2 arrays. The ternary heterojunction could significantly enhance photocatalytic activity and removal of 91.7% gatifloxacin (GAT) within 2 h. Furthermore, the OCN@CNT-2 demonstrated the highest photosynthetic rate, and the concentration of H2O2 was recorded to be approximately 133.04 μmol/L after 60 min of irradiation. The enhanced photocatalytic activity is due to the formation of a double Z-type heterojunction, which amplifies the absorption edge and effectively separates electron-hole pairs through the influence of an internal electric field (IEF). Suggestions for GAT decomposition were put forward, and the toxicity of GAT and its decomposed components was evaluated. Moreover, the mechanism of charge transfer in a double Z-scheme heterojunction has been elucidated.