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