N-vacancy engineering Zn single-atom site boosts efficient photosynthesis of hydrogen peroxide
Photocatalytic oxygen reduction reaction (ORR) for hydrogen peroxide (H2O2) production via the two-electron pathway offers an environmentally friendly oxidant and a clean fuel. However, challenges exist in optimal oxygen (O2) adsorption capacities and maintaining O–O bond during O2 activation. Herein, we present a zinc single-atom catalyst (Zn/VN-CN) incorporating nitrogen vacancies (VN), designed to modulate the electronic structure of the photocatalyst, leading to optimized O2 adsorption energy and a remarkable enhancement in H2O2 yield. Benefiting from the synergistic effect between nitrogen vacancies and Zn single atoms, the optimized Zn/VN-CN catalyst exhibits a photocatalytic H2O2 production rate of 2.399 mmol g−1 h−1 under visible-light irradiation, representing a 12-fold enhancement compared to pristine g-C3N4 (CN), along with a high H2O2 selectivity of 87.4%. Combined experimental and theoretical studies indicate that the Zn-N3 sites act as highly active reaction centers, while nitrogen vacancies increase the charge density and downshift the d-band center of the Zn sites, thereby moderating O2 adsorption strength, lowering the activation energy barrier for the formation of *H2O2, and further converting it to H2O2. This work proposes an effective strategy for tuning O2 adsorption behavior to achieve highly selective and active photocatalytic H2O2 production.