Interfacial Amide Bonding in Single-Atom TCPP(Pt)@Zn_<i>x</i>Cd_1–<i>x</i>S-Cysteine Photocatalyst for Enhanced Sunlight-Driven Hydrogen Production

In this study, a novel approach for synthesizing TCPP(Pt)@ZnxCd1–xS-Cys (TCPP(Pt)@ZCS x-Cys) nanocomposites was developed by coupling cysteine-functionalized ZnxCd1–xS (ZCS x-Cys) with single platinum atom-integrated TCPP through amide bond formation. This covalent linkage markedly enhances interfacial charge transfer, thereby promoting efficient electron utilization. In addition, the incorporation of TCPP(Pt) provides exposed Pt single-atom active sites, contributing to improved photocatalytic reduction performance. Among the series of composites with different TCPP(Pt) concentrations (1, 2, and 4 wt %), the 2% TCPP(Pt)@ZCS 0.25-Cys sample exhibited the highest H2 production rate, achieving 33.96 mmol·g–1·h–1 after the first hour of light irradiation, which was 16.3-fold higher than that of ZCS 0.25-Cys. Impressively, the apparent quantum yield (AQY) of this composite reached approximately 60.4% at λ = 420 nm, 53.8% at 460 nm, and 40.1% at 500 nm, respectively, ranking among the highest reported for photocatalytic hydrogen generation. The physical, optical, and electronic properties confirmed the formation of a type-II heterojunction, which facilitates spatial charge separation and directional charge transfer, thereby enhancing photocatalytic efficiency under solar irradiation. This work not only offers a promising strategy for the development of TCPP(Pt)@ZCS x-Cys photocatalysts for solar-driven hydrogen production but also addresses critical limitations associated with charge recombination and catalytic site accessibility in photocatalytic systems.