Oxygen-doped defects modified C3N5 in enhanced molecule oxygen photoactivation for tetracycline hydrochloride degradation and H2O2 in situ production: Double pathways of 1O2 and O2–· high yield

The study aims to investigate the mechanism by which O-doped defect engineering in C3N5 enhances molecular oxygen photoactivation. A feasible one-step roasting method was adopted to synthesize a novel C3N5 with multiple O-doped defects sites (O-C3N5). The experimental characterizations and DFT analysis reveal that O atoms were doped into the in-plane structure of C3N5 to form O-doped defects located at both linked and terminal positions on triazine units. The O-doped defects transform C3N5 morphologies and diminish the band gap, favoring charge migration and electron accumulation under visible-light irradiation. Furthermore, O-doped defects improve the adsorption performance for molecular oxygen, which provides the prerequisite for photoactivating molecular oxygen. The prominent photoelectric property can high effectively photoactivate the adsorbed O2 to directly generate 1O2 in the energy transfer-mediated pathway and O2–· in the electron oxygen reduction reaction pathway. In addition, the well photoelectric property also facilitates the interconversion between 1O2 and O2–·, which enables diverse reaction applications to be achieved. Hence, the outstanding performance of O-C3N5 can be verified in photoactivating molecular oxygen for TC degradation and H2O2 in situ production. The results not only demonstrate the universality and feasibility of utilizing O-C3N5 photoactivating molecular oxygen for the advanced treatment of the complicated sewage, but also provide a comprehensive understanding on the enhanced molecule oxygen photoactivation of C3N5 through O-doped defects.