Photocatalytic Generation of H₂O₂ by Graphene Oxide in Organic Electron Donor-Free Condition under Sunlight

Graphene family nanomaterials are emerging, two-dimensional photocatalysts consisting of Earth-abundant elements. This study evaluated the potential of graphene oxide (GO) toward photocatalytic H₂O₂ production in water driven by renewable sunlight and visible light without synthetic organic electron donors. We reported for the first time that GO can efficiently photocatalyze the generation of H₂O₂ to millimolar levels under simulated sunlight in a few hours. The concentration of H₂O₂ produced is among the greatest values reported in current photocatalytic systems without organic electron donors. We showed that dissolved O₂ played a pivotal role in the photoproduction of H₂O₂ by GO and that superoxide (O₂^•-) was not involved. A 2-fold increase in H₂O₂ photoproduction can be readily achieved by raising pH from 3 to 7. The addition of oxalate as the electron donor only enhanced H₂O₂ photoproduction at low pH, but not at high pH where GO suffered greater photocorrosion. As a result, GO had a greater long-term stability at low pH 4. The reduced photocatalytic activity at low pH can be fully compensated by adding oxalate while maintaining GO’s long-term photostability. Our results indicate that GO is a promising, metal-free photocatalyst to generate H₂O₂ in an environmentally sustainable manner.