Gas/solid/liquid triphase interface of carbon nitride for efficient photocatalytic H2O2 production

Abstract

The photocatalytic two-electron oxygen reduction offers a sustainable method to produce hydrogen peroxide (H2O2). The efficiency of carbon nitride (CN) in this process is hindered by the serious charge recombination and slow diffusion of oxygen. This work reports the thermal vapor-assisted surface chemical modification of CN by 4-aminobenzoyl groups (PABA/CN), which alters the conjugation system, extends the light absorption range, and enhances the charge separation and electron transfer. Besides, it tunes the CN surface to be hydrophobic, which forms a gas/solid/liquid triphase interface in photocatalytic H2O2 production, thus significantly improves O2 diffusion and proton supply for photosynthesis of H2O2. Photocatalytic experiments revealed that PABA/CN delivered a H2O2 yield of up to 745 μmol/g/h in pure water, 8 times as that of pristine CN, ranking among the top performances by CN-based photocatalysts. The selectivity reached 70%. Mechanism studies identified a two-step 1-electron oxygen reduction reaction pathway for H2O2 photoproduction. Overall, this work simultaneously addresses the issues of mass transfer of O2, light harvesting, and charge separation of CN in photosynthesis of H2O2 by surface chemical modification with 4-aminobenzoyl moieties which extends the π-conjugation and imparts the hydrophobic surface.