Metal to non-metal sites of metallic sulfides switching products from CO to CH₄ for photocatalytic CO₂ reduction

The active center for the adsorption and activation of carbon dioxide plays a vital role in the conversion and product selectivity of photocatalytic CO₂ reduction. Here, we find multiple metal sulfides CuInSnS₄ octahedral nanocrystal with exposed (1 1 1) plane for the selectively photocatalytic CO₂ reduction to methane. Still, the product is switched to carbon monoxide on the corresponding individual metal sulfides In₂S₃, SnS₂, and Cu₂S. Unlike the common metal or defects as active sites, the non-metal sulfur atom in CuInSnS₄ is revealed to be the adsorption center for responding to the selectivity of CH₄ products. The carbon atom of CO₂ adsorbed on the electron-poor sulfur atom of CuInSnS₄ is favorable for stabilizing the intermediates and thus promotes the conversion of CO₂ to CH₄. Both the activity and selectivity of CH₄ products over the pristine CuInSnS₄ nanocrystal can be further improved by the modification of with various co-catalysts to enhance the separation of the photogenerated charge carrier. This work provides a non-metal active site to determine the conversion and selectivity of photocatalytic CO₂ reduction.