The Ovs surface defecting of an S-scheme g-C3N4/H2Ti3O7 nanoheterostructures with accelerated spatial charge transfer

Abstract

Semiconductor photocatalysis was a rising star in the sustainable transformation of solar energy for environmental problems governance. Herein, an S-scheme g-C3N4/H2Ti3O7 heterostructure was constructed and applied to tetracycline hydrochloride (TCH) destruction. The g-C3N4/H2Ti3O7 composite has a superior photocatalytic property to degrade TCH in contrast with bare g-C3N4 and H2Ti3O7. The 20% g-C3N4/H2Ti3O7 (CNHTO20) composite exhibited the optimum photocatalytic performance, and the degradation efficiency of 20 mg/L TCH reached 87.37% within 3 h (K = 0.572 min−1). The affluent active sites of the g-C3N4 nanosheet and effective interfacial charge separation of the S-scheme pathway facilitated the excellent performance. Moreover, the ample oxygen vacancies (Ovs) act as the electron mediator, not only reducing the band gap energy by producing the formation of defect levels, but also broadening the photo response range and promoting the interfacial charge transfer. The coordination complexes formed between TCH molecules and Ti (IV) ions in CNHTO20 composites induce strong visible light absorption through ligand–metal charge transfer (LMCT). The Ti4+/Ti3+ metal cycle in CNHTO20 was conducive to the separation of the photogenerated electron-hole pairs on the heterojunction interface as well. The ESR characterization and trapping experiments certified that the dominant substances were OH, O2– and h+. The AQY calculated by the COD removal rate was 0.16%. Conclusively, the S-scheme heterojunction between H2Ti3O7 and g-C3N4 enabled the CNHTO photocatalyst with high redox ability and boosted photocatalytic performance accordingly. This study may shed some enlightenment on the construction of heterojunctions and the realistic treatment of wastewater.