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 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 LED365nm, irradiation, increasing nearly 2 similar to 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 introduces boron-nitrogen bonds into the structure of g-C3N4 nanosheets through a simple doping method, resulting in enhanced photocatalytic activity, selectivity, and stability. The electron-deficient B-N units serve as electron acceptors, improving charge separation and transfer, and act as superior active sites for efficient H2O2 production via the 2e(-) oxygen reduction reaction pathway.