Lattice expansion enables interstitial Ni-sulfur vacancy pairs to trigger charge redistribution for boosted H₂...

The central limitation in photoreforming of waste plastics for hydrogen production is that the oxidation and reduction half-reactions share the same set of charge carriers, while surface reactions lag far behind bulk recombination. Strategies that focus only on interfacial charge separation and active-site regulation therefore cannot construct spatially separated charge-trapping centers within the bulk that feed the two half-reactions at the surface. We prepared a lattice-expansion interstitial doping photocatalyst (CZS-LE-Ni) by introducing interstitial Ni into solvent-pre-expanded CdZnS (CZS). Under visible light, this catalyst achieved a hydrogen production rate of 67.88 mmol g^-1 h^-1 during PLA reforming. This is 13.2 times that of pristine CZS and 1.97 times that of conventionally doped catalysts at the same Ni loading. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and density functional theory (DFT) calculations together reveal that, at the atomic scale, lattice expansion generates sulfur vacancies and simultaneously facilitates interstitial Ni doping. The resulting Ni-Sulfur Vacancy (Ni-V_S) defect pairs trigger localized charge redistribution within the bulk, spatially separating electrons and holes. This work not only demonstrates the potential of lattice-expansion interstitial doping (LEID) in the efficient photoreforming of waste plastics but also elucidates the core mechanism of Ni-V_S defect pairs in spatial charge separation.