Migration of sulfur regulates products distribution of electrochemical reduction of carbon dioxide

By synthesizing Cu7S4 catalysts with abundant structural defects from Cu2O aerogels as precursors, the influence of sulfur on CO2RR is investigated. On the surface of the Cu7S4 catalyst, the conversion of CO2 to C2H5OH can be achieved under less negative potential conditions. At more negative conditions, Cu7S4 undergoes reconstruction, and the dominant product shifts to HCOOH due to the dissolution of sulfur elements, which is caused by the adsorption of sulfur atoms on the metal Cu surface after the restructuring of Cu7S4. On the surface of Cu aerogels with low concentration of adsorbed sulfur atoms, a maximum FE of 79.4 % for HCOOH is achieved at –1.2 V vs. RHE. Density functional theory (DFT) calculations indicate that sulfur atoms located the lattice and those adsorbed on the surface post-dissolution favor the formation of C2 products and HCOOH, respectively.