Introducing B-N unit boosts photocatalytic H2O2 production 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 graphitic carbon nitride (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 O-2 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 365 nm-monochrome light emitting diode (LED365,) 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.

Automated summary

This study reports a simple doping method to introduce boron-nitrogen (B-N) bonds into the structure of graphitic carbon nitride nanosheets, improving the photocatalytic activity and selectivity for H2O2 production. The electron-deficient B-N units serve as active sites to reduce the energy barrier and enable efficient H2O2 synthesis.