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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.
Zheng et al. (Thu,) studied this question.