Insights into Electrochemical CO2 Reduction on SnS2: Main Product Switch from Hydrogen to Formate by Pulsed Potential Electrolysis

Abstract Tin disulfide (SnS 2 ) is a promising candidate for electrosynthesis of CO 2 ‐to‐formate while the low activity and selectivity remain a great challenge. Herein, we report the potentiostatic and pulsed potential CO 2 RR performance of SnS 2 nanosheets (NSs) with tunable S‐vacancy and exposure of Sn‐atoms or S‐atoms prepared controllably by calcination of SnS 2 at different temperatures under the H 2 /Ar atmosphere. The catalytic activity of S‐vacancy SnS 2 (V s ‐SnS 2 ) is improved 1.8 times, but it exhibits an exclusive hydrogen evolution with about 100 % FE under all potentials investigated in the static conditions. The theoretical calculations reveal that the adsorption of *H on the V s ‐SnS 2 surface is energetically more favorable than the carbonaceous intermediates, resulting in active site coverage that hinders the carbon intermediates from being adsorbed. Fortunately, the main product can be switched from hydrogen to formate by applying pulsed potential electrolysis benefiting from in situ formed partially oxidized SnS 2− x with the oxide phase selective to formate and the S‐vacancy to hydrogen. This work highlights not only the V s ‐SnS 2 NSs lead to exclusively H 2 formation, but also provides insights into the systematic design of highly selective CO 2 reduction catalysts reconstructed by pulsed potential electrolysis.