Catholyte-Free Electrocatalytic CO₂ Reduction to Formate

Electrochemical reduction of carbon dioxide (CO₂ ) into value-added chemicals is a promising strategy to reduce CO₂ emission and mitigate climate change. One of the most serious problems in electrocatalytic CO₂ reduction (CO₂ R) is the low solubility of CO₂ in an aqueous electrolyte, which significantly limits the cathodic reaction rate. This paper proposes a facile method of catholyte-free electrocatalytic CO₂ reduction to avoid the solubility limitation using commercial tin nanoparticles as a cathode catalyst. Interestingly, as the reaction temperature rises from 303 K to 363 K, the partial current density (PCD) of formate improves more than two times with 52.9 mA cm^-2 , despite the decrease in CO₂ solubility. Furthermore, a significantly high formate concentration of 41.5 g L^-1 is obtained as a one-path product at 343 K with high PCD (51.7 mA cm^-2 ) and high Faradaic efficiency (93.3 %) via continuous operation in a full flow cell at a low cell voltage of 2.2 V.