Light modulating Ni electronic structure to create dual single-atom Ni and Ni on ZnInS for enhanced photoreduction of CO.

Constructing dual single-atom catalysts with distinct electronic structures holds significance for the design of catalytic active centers, yet it remains highly challenging. Here, a novel light-induced approach was created to construct Ni and Ni dual single-atom sites on ZnIn₂S₄ nanosheets (Ni-Ni/ZIS) for the photocatalytic reduction of CO₂. Characterizations and density functional theory (DFT) calculations results indicate that Ni and Ni single-atom sites can be selectively anchored in the Zn vacancies and lattice interstitials on the surface of ZIS, respectively. Ni atoms are in a low-spin state without unpaired electrons. In contrast, Ni atoms are in an intermediate-spin state with an unpaired electron, which can be migrated from the 3d orbital of N to the 2π orbitals of CO₂. Ni and Ni sites decouple the competitive pathways of CO₂ reduction and H₂ evolution via distinct adsorption of H₂O and CO₂ on Ni or Ni sites (ΔG > 0.5 eV), respectively. Ni sites facilitate the generation of H₂ from H₂O, whereas Ni sites preferentially reduce CO₂ to CO. Furthermore, the Ni-Ni dual single-atom sites significantly enhance the efficiency of charge separation and transfer. Therefore, the catalyst attains a high syngas yield of 58.66 mmol·g·h under visible light, with adjustable CO/H₂ ratios from 1:1.3 to 1:4.1. This work presents a promising light-induced strategy for constructing dual single-atom catalysts via modulating metal electronic structure.