Pulsed Electrocatalysis on SnO 2 Electrodes for Boosting Formate Selectivity and Activity during CO 2 Electroreduction

Abstract Tin oxide (SnO 2 ) is considered a candidate catalyst for the electrocatalytic CO 2 reduction (CO 2 R) to formate conversion. However, the self‐reduction of SnO 2 to metallic Sn at high current densities leads to an unavoidable sharp decrease in formate selectivity. Herein, a SnO 2 ‐based catalyst (Pul‐SnO 2 ) is synthesized via pulsed electrocatalysis of SnO 2 precursors. Due to the ability to maintain the high oxidation valence states and promote the formation of oxygen vacancies, Pul‐SnO 2 exhibited a high formate selectivity of 90% at a high current density of 600 mA cm −2 , significantly higher than that of a conventional Sn‐based catalyst (81% and 100 mA cm −2 ) obtained via constant potential electrocatalysis. The in situ Raman spectra, kinetic isotope effect, cyclic voltammetry, and theoretical calculations demonstrated that the high oxidation states of SnO 2 promote CO 2 molecules activation and the oxygen vacancies enhance water dissociation, thereby accelerating the proton‐coupled electron transfer process to reduce the free energy of *OCHO intermediate generation. Moreover, the identified adsorbed hydroxyls (*OH) with suitable coverage during CO 2 R also promote the *OCHO formation and further make the formation of *OCHO more energy‐favorable. As a result, the Pul‐SnO 2 catalyst showed a super selectivity in CO 2 R to formate, while maintaining excellent activity and stability.