Construction of ZnCdS/C ₃ N ₄ S‐Scheme Heterojunction for Superior Photocatalytic H ₂ O ₂ Production and Benzylamine Coupling

Abstract The photocatalytic production of H 2 O 2 from water and oxygen represents a sustainable alternative to the energy‐intensive anthraquinone process. While graphitic carbon nitride (g‐C 3 N 4 ) has shown promise for this transformation, its practical implementation is hindered by inefficient charge separation and limited visible‐light absorption. Here, it has developed an S‐scheme heterojunction by integrating g‐C 3 N 4 with ZnCdS quantum dots (QDs) for achieving enhanced visible‐light response and superior photocatalytic efficiency through an in situ growth approach. Spectroscopic and computational studies reveal that this ZnCdS/C 3 N 4 heterostructure architecture simultaneously achieves three critical functions: (i) extended visible‐light harvesting through quantum confinement effects, (ii) enhanced carrier separation via S‐scheme electron transfer, and (iii) preserved redox potentials for both H 2 O 2 generation and organic transformations. This optimized system achieves an exceptional H 2 O 2 production rate of 102.82 mmol g −1 h −1 from water and oxygen under visible light irradiation, which represents a 33‐fold and 9‐fold improvement over pristine g‐C 3 N 4 (3.12 mmol g −1 h −1 ) and ZnCdS (11.03 mmol g −1 h −1 ), respectively. Remarkably, the photocatalyst simultaneously enables efficient organic transformations, demonstrating 93% conversion in benzylamine coupling reactions. This work not only establishes an effective strategy for designing high‐performance g‐C 3 N 4 ‐based photocatalysts but also develops heterojunction systems that bridge artificial photosynthesis and sustainable chemical synthesis.