Ni Single Atoms/Nanoparticles-Decided Spatial Adjustment of Photocatalytic Redox Sites Boosting CO₂ Reduction in H₂O Vapour

The kinetics matching of CO₂ reduction and H₂O oxidation is required in sacrificial agent-free photocatalytic CO₂ reduction. It indicates that the modification engineering on photocatalytic H₂O oxidation half-reaction except that on photocatalytic CO₂ reduction half-reaction should be equally paid attention, which has been easily ignored in most of the literatures. Herein, Ni single atoms (NiSAs) and nanoparticles (NiNPs) co-loaded Ti-MOF-derived TiO₂ having a flower-like nanosphere microstructure (NiSAs@NPs/TC) was developed for synchronous design of well-defined redox active sites of photocatalytic CO₂ reduction and H₂O oxidation. It was verified that NiNPs and NiSAs as the active sites of CO₂ reduction and H₂O oxidation, respectively, synergically accelerated photocatalytic redox reactions and enhanced separation of photo-generated carriers. NiSAs@NPs/TC showed a remarkable photocatalytic CO₂-reduction performance (CO and CH₄ products: 35.60 and 3.41 μmol g⁻¹ h⁻¹, respectively) in H₂O vapour which was at the advanced level in published relevant studies. Furthermore, the reaction process of CO₂ reduction on NiNPs was proposed based on the key intermediates capture of CO and CH₄ production in photocatalytic CO₂ reduction by in situ analysis.