Partially Oxidized SnS₂ Atomic Layers Achieving Efficient Visible-Light-Driven CO₂ Reduction

Unraveling the role of surface oxide on affecting its native metal disulfide's CO₂ photoreduction remains a grand challenge. Herein, we initially construct metal disulfide atomic layers and hence deliberately create oxidized domains on their surfaces. As an example, SnS₂ atomic layers with different oxidation degrees are successfully synthesized. In situ Fourier transform infrared spectroscopy spectra disclose the COOH* radical is the main intermediate, whereas density-functional-theory calculations reveal the COOH* formation is the rate-limiting step. The locally oxidized domains could serve as the highly catalytically active sites, which not only benefit for charge-carrier separation kinetics, verified by surface photovoltage spectra, but also result in electron localization on Sn atoms near the O atoms, thus lowering the activation energy barrier through stabilizing the COOH* intermediates. As a result, the mildly oxidized SnS₂ atomic layers exhibit the carbon monoxide formation rate of 12.28 μmol g⁻¹ h⁻¹, roughly 2.3 and 2.6 times higher than those of the poorly oxidized SnS₂ atomic layers and the SnS₂ atomic layers under visible-light illumination. This work uncovers atomic-level insights into the correlation between oxidized sulfides and CO₂ reduction property, paving a new way for obtaining high-efficiency CO₂ photoreduction performances.