Engineering Interfacial Cd–O Bonds in CdS/3-Hydroxythiophenol-formaldehyde Resin S-Scheme Heterojunction for Enhanced Photocatalytic H2O2 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 H2O2 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.