Unravelling the role of reactive oxygen species in ultrathin Z-scheme heterojunction with surface zinc vacancies for photocatalytic H2O2 generation and CTC degradation

Photo-induced reactive oxygen species (ROS) produced by molecular oxygen activation and oxidization of H2O/ OH- during photocatalytic reaction are extremely important in environmental remediation. Herein, a dual pathway to improve ROS formation was designed through establishing ultrathin 2D/2D Z-scheme heterojunction and defect engineering in O-doped g-C3N4/ZnIn2S4-Zn (ZIS-Z/OCN) composite. The results of experiment and density functional theory (DFT) calculation indicate that the charge-carriers are spatially separated in composite driven by different work functions and ultrathin 2D/2D interface, boosting charge-transfer efficiency from 42.05 % (ZnIn2S4-Zn) to 59.93 % (40ZIS-Z/OCN). Benefiting by this fact, improving molecular oxygen activation capacity can induce more ROS generation. In consequence, 40ZIS-Z/OCN reveals optimal chlortetracycline hydrochloride (CTC) removal efficiency (88.43 %) and hydrogen peroxide (H2O2) yield (168.67 mu mol/L) under visible light irradiation. The results of control experiments show that H2O2 is generated via two-step electron reduction route and singlet oxygen (1O2) conversion. This study provides new views on the construction of costeffective and reusable photocatalysts for environmental remediation and energy conversion.