K-intercalated polymeric carbon nitride with nitrogen defects for efficient photocatalytic H2O2 production

Graphitic carbon nitride (g-C3N4) is considered as an ideal semiconductor for photocatalytic H2O2 production due to its abundant raw materials, facile synthesis, and convenient structure regulation. However, in terms of photocatalysis, pristine carbon nitride (CN) is limited by fast electron-hole pair recombination and low utilization of visible light. Herein, we optimized the electronic structure by intercalating K ions into the g-C3N4 layers and introducing nitrogen defects, which achieved remarkable results. A simple KOH-assisted thermal carbon nitride polymerization method was used to achieve the one-step synthesis of K-intercalated polymeric carbon nitride (K-CN), resulting in a maximum H2O2 productivity of 19 663 mu mol L-1 h(-1) (14 times that of CN) and apparent quantum efficiency of 15.37%. In this strategy, on the one hand, the K ion intercalation optimizes the internal energy band structure, narrowing the bandgap from 2.82 eV to 2.73 eV; on the other hand, because of the strong electronegativity of the N atom in -C(sic)N, K-2-CN has an obvious ability to trap electrons to inhibit charge recombination. This research presents a promising synthetic route through K ion doping to better manipulate the electronic structure of g-C3N4, which offers a reference for further improving the performance of photocatalytic H2O2 and understanding its generation mechanism.