Ultrafast Hole Transfer in Graphitic Carbon Nitride Imide Enabling Efficient H₂O₂ Photoproduction

Solar-driven photocatalysis is a promising approach for renewable energy application. H₂O₂ photocatalysis by metal-free graphitic carbon nitride has been gaining attention. Compared with traditional thermal catalysis, metal-free graphitic carbon nitride photocatalysis could lower material cost and achieve greener production of H₂O₂. Also, to better guide photocatalyst design, a fundamental understanding of the reaction mechanism is needed. Here, we develop a series of model cost-effective metal-free H₂O₂ photocatalysts made from graphitic carbon nitride (melem) and common imide groups. With 4,4'-oxydiphthalic anhydride (ODPA)-modified g-C₃N₄, a H₂O₂ yield rate of 10781 μmol/h·g·L could be achieved. Transient absorption and ex situ Fourier transform infrared (FTIR) measurements revealed an ultrafast charge transfer from the melem core to water with ∼3 ps to form unique N-OH intermediates. The electron withdrawing ability of the anhydride group plays a role in governing the rate of electron transfer, ensuring efficient charge separation. Our strategy represents a new way to achieve a low material cost, simple synthesizing strategy, good environment impact, and high H₂O₂ production for renewable energy application.