Atomically Precise Pd Species Accelerating CO₂ Hydrodeoxygenation into CH₄ with 100% Selectivity

High-rate CO₂-to-CH₄ photoreduction with high selectivity is highly attractive, which is a win-win strategy for mitigating the greenhouse effect and the energy crisis. However, the poor photocatalytic activity and low product selectivity hinder the practical application. To precisely tailor the product selectivity and realize high-rate CO₂ photoreduction, we design atomically precise Pd species supported on In₂O₃ nanosheets. Taking the synthetic 1.30Pd/In₂O₃ nanosheets as an example, the aberration-correction high-angle annular dark-field scanning transmission electron microscopy image displayed the Pd species atomically dispersed on the In₂O₃ nanosheets. Raman spectra and X-ray photoelectron spectra established that the strong interaction between the Pd species and the In₂O₃ substrate drove electron transfer from In to Pd species, resulting in electron-enriched Pd sites for CO₂ activation. Synchrotron-radiation photoemission spectroscopy demonstrated that the Pd species can tailor the conduction band edge of In₂O₃ nanosheets to match the CO₂-to-CH₄ pathway, instead of the CO₂-to-CO pathway, which theoretically accounts for the high CH₄ selectivity. Moreover, in situ X-ray photoelectron spectroscopy unveiled that the catalytically active sites had a change from In species to Pd species over the 1.30Pd/In₂O₃ nanosheets. In situ FTIR and EPR spectra reveal the atomically precise Pd species with rich electrons prefer to adsorb the electrophilic protons for accelerating the *COOH intermediates hydrogenation into CH₄. Consequently, the 1.30Pd/In₂O₃ nanosheets reached CO₂-to-CH₄ photoconversion with 100% selectivity and 81.2 μmol g^-1 h^-1 productivity.