Introducing B-N unit boosts photocatalytic H2O2 production on metal-free g-C3N4 nanosheets

Metal-free catalyst for photocatalytic production of H2O2 is highly desirable with the long-term vision of artificial photosynthesis of solar fuel. In particular, the specific chemical bonds for selective H2O2 photosynthesis via 2e− oxygen reduction reactions (ORR) remain to be explored for understanding the forming mechanism of active sites. Herein, we report a facile doping method to introduce boron-nitrogen (B-N) bonds into the structure of g-C3N4 nanosheets (denoted as BCNNS) to provide significant photocatalytic activity, selectivity and stability. The theoretical calculation and experimental results reveal that the electron-deficient B-N units serving as electron acceptors improve photogenerated charge separation and transfer. The units are also proved to be superior active sites for selective O2 adsorption and activation, reducing the energy barrier for *OOH formation, and thereby enabling an efficient 2e− ORR pathway to H2O2. Consequently, with only bare loss of activity during repeated cycles, the optimal H2O2 production rate by BCNNS photocatalysts reaches 1.16 mmol·L−1·h−1 under LED365nm irradiation, increasing nearly 2∼5 times as against the state-of-art metal-free photocatalysts. This work gives the first example of applying B-N bonds to enhance the photocatalytic H2O2 production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.