Protection of Sn-BasedElectrocatalysts via FluorinationEnsuring Efficient Electrochemical CO₂‑to-FormicAcid Conversion in Acidic Electrolytes

Electrochemical reduction of CO₂ to formic acid for industrial production necessitates not only high selectivity and conversion rate but also efficient CO₂ utilization and minimal carbon loss to reduce overall production costs and energy consumption. Despite acidic CO₂ reduction reaction being able to greatly alleviate carbon loss, it is often hindered by the aggressive hydrogen evolution reaction and the degradation of catalysts. This study puts forward an effective fluorination-hydrolysis protection mechanism for Sn-based electrocatalysts under acidic conditions. F-doped Sn oxides form a protective layer containing Sn oxide and fluoride, which safeguards the inner reduced Sn from significant degradation in acidic environments. Leveraging this strategy, we achieve impressive performance for formic acid generation without the adverse effects of a violent hydrogen evolution reaction during acidic electrolysis, attaining a Faradaic efficiency of 92% and a partial current density of 722 mA cm^–2. This approach not only provides an additional avenue for preventing corrosion of Sn-based catalysts in acidic media but also significantly improves their performance in formic acid production.