Partially Oxidized SnS Atomic Layers Achieving Efficient Visible-Light-Driven CO Reduction.

Unraveling the role of surface oxide on affecting its native metal disulfide's CO 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, SnS 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 SnS atomic layers exhibit the carbon monoxide formation rate of 12.28 μmol g h, roughly 2.3 and 2.6 times higher than those of the poorly oxidized SnS atomic layers and the SnS atomic layers under visible-light illumination. This work uncovers atomic-level insights into the correlation between oxidized sulfides and CO reduction property, paving a new way for obtaining high-efficiency CO photoreduction performances.