C₃N₄/PDA S‐Scheme Heterojunction with Enhanced Photocatalytic H₂O₂ Production Performance and Its Mechanism

Abstract Developing a high‐performance photocatalyst is important for realizing efficient photocatalytic H₂O₂ generation. Herein, a novel step‐scheme (S‐scheme) heterojunction photocatalyst C₃N₄/PDA (CNP) comprised of ultrathin g‐C₃N₄ (U‐CN) and polydopamine (PDA) is constructed by in situ self‐polymerization. The optimal photocatalyst presents an excellent H₂O₂ production rate of 3801.25 µmol g⁻¹ h⁻¹ under light irradiation, which is about 2 and 11 times higher than that of pure U‐CN and PDA, respectively, and exceeds most of the reported C₃N₄‐based photocatalysts. The improvement of photocatalytic activity is ascribed to the synergistic effect of improved light absorption and promoted charge separation and transfer induced by the S‐scheme heterojunction. In situ irradiated X‐ray photoelectron spectroscopy (ISI‐XPS) reveals that the charge transfer route matches the S‐scheme mechanism. Rotating disk electrode (RDE) measurements and electron spin resonance (ESR) spectroscopy verify that H₂O₂ is produced by a two‐step one‐electron process. This work highlights a promising method to construct high‐performance S‐scheme heterojunction photocatalysts through the hybridization of PDA and C₃N₄.