Low-Coordinated Nitrogen Vacancies for Robust Visible-Light-Driven H2O2 Production

The solar-powered photocatalytic oxygen reduction reaction is considered a promising alternative method for H2O2 production under mild reaction conditions. However, the intrinsic competitive pathway grossly inhibits the selectivity and final yield of H2O2 accompanying the loss of photogenerated electrons during the oxygen reduction reaction process. Herein, two-coordinate nitrogen (N2C) vacancy-rich g-C3N4 (DCN1.2) was developed by polymerization pyrolysis using the bottom-up strategy. DCN1.2 with a low-coordinated N2C-vacancy enabled an enhanced H2O2 production in a wide pH range. The optimized DCN1.2 demonstrated a H2O2 yield of 556.2 μmol·gcat–1·h–1 at pH = 10, which was approximately 3 times higher than that of pristine CN (202.7 μmol gcat–1·h–1). DFT calculations and photochemical experimental results revealed that N2C-vacancies induced the asymmetric electron distribution of DCN, thereby facilitating electron transfer and promoting the O2 adsorption/activation for H2O2 production. Additionally, EPR and situ FTIR measurements indicated that DCN1.2 could produce H2O2 via a sequential two-step single-electron pathway, thereby achieving efficient H2O2 production with good selectivity. This study provides guidance for the rational design of defect-engineering g-C3N4 catalysts for efficient photocatalytic H2O2 generation.