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 O-2 played a pivotal role in the photoproduction of H2O2 by GO and that superoxide (O-2(-)) 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 GOs long-term photostability. Our results indicate that GO is a promising, metal-free photocatalyst to generate H2O2 in an environmentally sustainable manner.