Ultrahigh Photocatalytic Oxygen Reduction to Hydrogen Peroxide by a True Oxygen-Bridged Heptazine Polymer

Abstract

Solar-H2O2 production presents an eco-friendly and sustainable strategy over the existing anthraquinone process. The present photocatalytic systems suffer from low two-electron oxygen reduction reaction (ORR) selectivity. The current study reports an easy approach to produce a true oxygen-bridged heptazine polymer with periodic arrangement of oxygen atoms (CNO) by introducing C–O–C bridging species through the right precursor selection. The C–O–C species in CNO dramatically promotes ORR compared to the benchmark carbon nitride synthesized from melamine (CNM), which has been proved by electrochemical analysis. To our surprise, the CNO has produced 1.5 mmol/g of H2O2 after 4 h in natural sunlight, which is the highest among the existing carbon-nitride-based photocatalysts. In addition, the challenging biomass-derived chemicals, glycerol, glucose, and 1,2-propanediol were also utilized as sacrificial electron donors in H2O2 production to synthesize fine chemicals. Overall, this work provides an easy approach to tune the two-electron ORR to boost H2O2 production and paves the way for practical solar-H2O2 production from biomass using polymeric O-bridged heptazines (CNO).