A hydroxyl-induced carbon nitride homojunction with functional surface for efficient photocatalytic production of H2O2

Scalable solar-driven H2O2 evolution from water holds great promise for industrial applications. Efficient H2O2 generation relies on excellent spatial charge separation but simultaneously suffers from severe surface H2O2 backreaction, which becomes a bottleneck for scalable H2O2 evolution. Herein, a hydroxyl-induced carbon nitride (CN) homojunction coherently optimizes the bulk charge separation and suppresses surface backreaction. Surface hydroxyls provide extra electron accommodation bands for electron extraction from the bulk to the surface which are visually observed with KPFM and rationalized by DFT calculations. 2e- oxygen reduction reaction (ORR) kinetic became more favorable than 4e- ORR in the presence of hydroxyl, showing suppressed H2O2 decomposition. This homojunction achieves a 4.5-fold improvement in H2O2 production compared to pristine CN, and an apparent quantum yield (AQY) of 2.1 % at 500 nm in water. This work demonstrates a strategy for coherently improving spatial charge separation and surface reaction kinetics, which is applicable for various photocatalytic reactions.