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.