Efficient visible-light-driven selective oxygen reduction to hydrogen peroxide by oxygen-enriched graphitic carbon nitride polymers

Abstract

H₂O₂ is a green, environmentally friendly potential energy source. The photocatalytic reduction of molecular oxygen to synthesise H₂O₂ is an eco-friendly strategy compared with the anthraquinone method and H₂/O₂ direct synthesis. We proposed oxygen-enriched carbon nitride polymer (OCN) models, which were proven to more easily produce 1,4-endoperoxide species and have a high selectivity for molecular oxygen reduction to H₂O₂, rather than superoxide radicals, through theoretical calculations and experiments. The apparent quantum yield for H₂O₂ production by OCNs reached 10.2% at 420 nm under an O₂ atmosphere, which was 3.5 times higher than that of g-C₃N₄ and the activity did not decay over 20 h. OCN has a better oxygen reducibility and electron–hole separation efficiency than g-C₃N₄ and is more prone to 2-electron reduction in the ORR. This work promotes understanding of the mechanism of photocatalytic oxygen reduction and provides a new idea for the design and synthesis of new materials for the preparation of H₂O₂.