Noble-metal-free Ni-W dual-atom sites with bifunctional synergy for efficient photocatalytic CO₂ conversion

Solar-driven conversion of CO₂ into valuable chemicals is a promising strategy to address global energy and environmental challenges. However, exploiting efficient photocatalysts for CO₂ reduction remains a huge challenge, limited by the slow surface reaction kinetics of CO₂ conversion and the rapid recombination of photogenerated charges. In this work, a unique noble-metal-free Ni-W dual-atom catalyst on polymeric carbon nitride was developed. Atomic Ni-N₄ and W-N₄ coordination structure were determined via AC-HAADF-STEM and EXAFS, and the in-depth catalytic mechanism was systematically investigated through theoretical calculations, KPFM and temperature-dependent PL spectroscopy. Importantly, the results displayed that the atomic W site owns strong interactions with the CO₂ molecule, serving as a superior CO₂ adsorption and activation site. Simultaneously, the embedding of atomic Ni site can effectively modify the HOMO composition, thus accelerating the orderly separation of photogenerated charges. With the joint contributions of Ni-W dual-atom sites on the surface reactivity and photogenerated charge separation, the optimal catalyst (Ni-W/CN) exhibits significantly enhanced performance for photocatalytic CO₂-to-CO conversion (80.4 μmol g⁻¹ h⁻¹), up to 10.5 times higher than that of pure carbon nitride. This work deeply reveals the bifunctional synergistic mechanism of dual-atom sites and provides valuable experience for constructing efficient photocatalysts with multi-atomic sites.