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.