Title:

Molecular engineering towards dual surface local polarization sites on poly(heptazine imide) framework for boosting H2O2 photo-production

Abstract

The selective 2e⁻ ORR reaction on polymeric carbon nitride framework is one of the most promising approaches for solar-driven hydrogen peroxide production. Poly(heptazine imide) (PHI) as a class of K⁺-incorporated crystalline carbon nitride framework, is highly active for photocatalytic H₂O₂ production. An upgrade on the H₂O₂ photoproduction performance of PHI is realized and the mechanistic insights are revealed in this work. By photochemical reaction, the electron withdrawing groups of hydroxyl group and cyano group are grafted on the surface of PHI frameworks. The dual polarization sites on the surface contribute significantly to the enhancement of the exciton dissociation. The optimized PHI with dual polarization sites exhibits a remarkable photocatalytic H₂O₂ production performance, which is 2 times of the active pristine PHI. Most importantly, the photochemical reaction method is generally applicable to improve the exciton dissociation of a wide range of polymeric carbon nitride frameworks with various structure and compositions; and the thiourea-derived polymeric carbon nitride framework with dual surface polarization sites exhibits a remarkable photocatalytic performance with a high H₂O₂ production rate of 40.5 mmol h⁻¹ g⁻¹