Mg-doped CdS/NiCoAl-LDH S-scheme-like heterojunction with optimized band alignment and enhanced photocatalytic hydrogen evolution

Advancing toward “dual-carbon” goals and clean hydrogen production, developing visible-light photocatalysts with high activity and durability remains a challenge. Here, Mg-doping engineered CdS/NiCoAl-LDH heterojunctions are constructed and investigated to clarify how Mg incorporation co-modulates structure, band energetics, and hydrogen-evolution behavior. Multiscale characterizations combined with density functional theory (DFT) calculations show that appropriate Mg doping strengthens visible-light absorption, suppresses photogenerated electron-hole recombination, reduces interfacial charge transfer resistance, and optimizes band alignment, with the conduction band shifting to more negative potential and the valence band shifting upward, thereby strengthening the reducing power of photogenerated electrons and enhancing the thermodynamic driving force for HER. Under 4 h of visible-light irradiation, CdS/NiCoAlMg(10 %)-LDH achieves a hydrogen evolution rate of 5984.12 μmol·g⁻ 1 ·h⁻ 1 , 2.82 times that of the undoped sample, and retains over 95 % of its initial activity after four cycles, indicating good activity and cycling stability. DFT analysis reveals that Mg partially substitutes Ni, redistributes electronic states near the Fermi level, and optimizes hydrogen adsorption at Co active sites, thereby lowering reaction barriers for the hydrogen evolution reaction. Overall, Mg doping tunes band edges, optimizes active-site electronic structure, and accelerates interfacial charge transport in CdS/NiCoAl-LDH, leading to enhanced photocatalytic hydrogen evolution under visible light.