Mellitic Triimide-Doped Carbon Nitride as Sunlight-Driven Photocatalysts for Hydrogen Peroxide Production

Generating hydrogen peroxide (H2O2) from water and dioxygen (O2) by photocatalysis is one ideal artificial photosynthesis for solar fuel production. Several early reported powdered photocatalysts, however, produce small amounts of H2O2 (<0.1 mM). We prepared graphitic carbon nitride (g-C3N4) doped with mellitic triimide (MTI) units by thermal condensation of melem and mellitic acid anhydride. The g-C3N4/MTI photocatalyst, when irradiated by visible light (λ > 420 nm) in pure water with O2, successfully produces millimolar levels of H2O2 via water oxidation by valence band holes and selective two-electron reduction of O2 by conduction band electrons. The incorporation of triply branched MTI units creates a condensed melem layer. This facilitates efficient intra- and interlayer transfer of photogenerated charge carriers and shows high electrical conductivity. The solar-to-chemical conversion efficiency for H2O2 production on the catalyst is 0.18%, which is higher than that of natural photosynthesis (∼0.1%) and similar to the highest values obtained by semiconductor water-splitting catalysts.