| Summary: | Abstract Electroreduction of CO2 (CO2R) to formate enables the storage of renewable electricity in liquid chemical bonds in an efficient manner. However, hydrogen evolution competes with CO2R, decreasing Faradaic efficiency (FE) and energy efficiency (EE) for formate production, particularly under acidic and neutral conditions. The deterioration of the catalysts during CO2R further hinders long‐term and effective operation. To overcome these challenges, we fabricate nanostructured Sn/SnO2 through physical evaporation and wet‐chemical etching, improving the CO2‐to‐formate conversion with finely tuned *OCHO adsorption. The in‐situ formation of Sn/SnO2 surfaces during CO2R stabilizes the active sites for reliable formate production across a broad range of electrolyte pH from base to neutral. Our results show a 94 % CO2R‐to‐formate FE and a 58 % formate cathodic EE at 100 mA cm−2 in 1 M KOH over 70 hours of continuous operation. Under neutral conditions (pH=7), the CO2‐to‐formate conversion remains stable for 100 h with a selectivity of >90 %.
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