Nanocellulose-induced defect engineering in carbon nitride enables two-electron oxygen reduction for H2O2 photosynthesis.

Herein, a nanocellulose-assisted molecular engineering strategy is developed to construct oxygen-doped and nitrogen-deficient g-C3N4 (OCN-x) photocatalysts. Nanocellulose serves as an oxygen-containing biomass-mediated structural regulator, promoting oxygen incorporation and nitrogen vacancy formation during thermal polymerization. The resulting defect-modulated structure promotes electron delocalization, carrier migration, and interfacial charge transfer. As a result, the optimized OCN-0.04 achieves a H2O2 production rate of 3.21 mmol g-1 h-1 under visible-light irradiation, comparing favorably with most reported g-C3N4-based photocatalysts. Mechanistic studies reveal that the nanocellulose-induced coupled defects enhance O2 adsorption and activation, facilitate ˙O2- intermediate formation, and lower the energy barrier of the two-electron oxygen reduction pathway.