A dual transfer strategy for boosting reactive oxygen species generation in ultrathin Z-scheme heterojunction driven by electronic field

Reactive oxygen species (ROS), which are generated from molecular oxygen activation and oxidization of H2O/OH- in photocatalysis process, are vital for environmental remediation. In this study, a dual strategy for boosting ROS generation is proposed by construction of ultrathin Z-scheme heterojunction of Bi5O7I/g-C3N4. The charge-carrierquenching effect is inhibited attributed to the prepared ultrathin 2D/2D heterojunction. Profiting from the interfacial charge properties, the boosting molecular oxygen activation and oxidization ability are obtained in the heterojunction. In comparison with pristine catalysts, the yield amount of superoxide (center dot O-2(-)) in Bi5O7I/g-C3N4 case shows enhancement. Furthermore, controllable experiments demonstrate that the generation of hydrogen peroxide (H2O2) is through two-step electron reduction strategy, and it can decompose into hydroxyl radicals (center dot OH) assisted with photoelectrons. The singlet oxygen (O-1(2)) is produced by two transfer pathways including charge transfer and energy transfer. Through DFT calculation, the built-in electronic field (IEF) is formed owing to the electron configuration. The IEF in the heterojunction tunes the charge transfer from type-II to Z-scheme model. Simultaneously, the short charge transfer distance enables more high energy charge carriers to reach the surface of solid catalyst for catalytic reactions. Owing to the boosting ROS generation, the novel composite shows enhanced photocatalytic performance for ciprofloxacin (CIP) degradation. This study gives a proof-of-concept perspective on fabrication of 2D/2D Z-scheme heterojunction with boosting ROS generation for environmental remediation and energy conversion.