Accelerating photocatalytic H₂O₂ rate over inter-molecular Z-scheme heterojunction via dual production paths

The major problem faced by photocatalytic H₂O₂ process was the slow production rate. Herein, an inter-molecular Z-scheme heterojunction was designed to maximize H₂O₂ yield via extending production paths, where heptazine-C₃N₄ (HCN) and triazine-C₃N₄ (TCN) were coupled together by one-step molten salt method. The separation efficiency of hole-electron pairs in heptazine-C₃N₄/triazine-C₃N₄ (HTCN) was improved due to good interfacial compatibility and well-matched band alignment, ensuring plenty of electrons were responsible for H₂O₂ production. Mechanism study revealed only two-step single-electron reduction performed on HCN and TCN surfaces, while both two-step single-electron reduction and one-step two-electron reduction simultaneously took place on HTCN surface. DFT calculation indicated reaction barriers of HTCN was much lower than those of HCN and TCN. By taking advantage of the enough released electrons, dual production paths and low reaction barriers, H₂O₂ production rate over HTCN was 76.1 mM·g^‐1·h^‐1, about 2.9 and 4.2 times higher than those of HCN and TCN.