Efficient photosynthesis of H2O2 via two-electron oxygen reduction reaction by defective g-C3N4 with terminal cyano groups and nitrogen vacancies

[Display omitted] •Introduing N defects over g-C3N4 significantly increased photocatalytic activity.•An IEF was built to further strengthened the transport of photoexcited carriers.•The excellent O2 adsorption capacity promoted H2O2 production via 2e− ORR.•A possible H2O2 generation pathway formed via 1O2 was proposed. The development of photocatalysts for the efficient generation of hydrogen peroxide (H2O2) and degradation of antibiotic pollutants is a mutual-beneficial solution to the chemical resource demands and environmental remediation. Herein, efficient visible-light-driven H2O2 production and antibiotic degradation are achieved by using nitrogen-deficient modified polymeric carbon nitride (g-C3N4) to facilitate the reduction of dioxygen. The N defects modified g-C3N4 reached an excellent H2O2 generation rate of 623.5 μmol g−1h−1 without O2 bubbling. The structural features and entire photocatalytic conversion process were systematically studied via experiments and theoretical calculations. It was found that the N defects in the framework constructed a giant internal electric field (IEF), which effectively inhibited carrier recombination. Revealed the neglected H2O2 production via 1O2 pathway, which effectively promoting the selective 2e− oxygen reduction reaction (ORR). More interestingly, the N defects structure greatly improved the O2 adsorption ability and O2 production ability of the material, while inhibiting the in situ generated H2O2 from being decomposed and maintaining high efficiency of H2O2 production under air conditions. This study thoroughly revealed the synergistic effects of the terminal cyano group and nitrogen vacancies over g-C3N4 for efficient H2O2 photogeneration photosynthesis.