Engineering Interfacial Cd–O Bonds in CdS/3-Hydroxythiophenol-formaldehyde Resin S-Scheme Heterojunction for Enhanced Photocatalytic H ₂ O ₂ Production

Constructing organic/inorganic heterojunctions via interfacial engineering is a promising yet challenging strategy for advanced photocatalysis. This work reports an interfacially engineered S-scheme heterojunction achieved by in situ growing 3-hydroxythiophenol-formaldehyde resin (HTPF) onto CdS, wherein atomic-level interfacial Cd–O bonds are constructed. This precise interface engineering establishes a robust built-in electric field and directs charge transfer along the S-scheme pathway, enabling efficient spatial separation of photogenerated carriers while preserving their potent redox potentials. Consequently, the optimized CdS/HTPF-4 composite delivers a high H 2 O 2 production rate of 2138.95 μmol h –1 g –1 under simulated solar light, outperforming pristine HTPF and CdS by 9.3 and 2.5 times, respectively. Notably, an appreciable activity of 989.45 μmol h –1 g –1 (∼46% of that with methanol) is retained even in the absence of sacrificial agents. The combination of experimental characterizations and DFT calculations collectively confirms the pivotal role of the interfacial Cd–O bond in facilitating charge redistribution, which underlies the significantly enhanced performance. This work provides a compelling example of rational heterojunction design through atomic-level bonding engineering, offering a broadly applicable strategy for high-efficiency solar-to-chemical energy conversion.