Mechanism of C–C bond formation in the electrocatalytic reduction of CO2 to acetic acid. A challenging reaction to use renewable energy with chemistry

Abstract

Copper nanoparticles on carbon nanotubes are used in the reduction of CO₂ to acetic acid (with simultaneous water electrolysis) in a flow electrocatalytic reactor operating at room temperature and atmospheric pressure. A turnover frequency of about 7000 h⁻¹ and a carbon-based Faradaic selectivity to acetic acid of about 56% were observed, indicating potential interest in this approach for using renewable energy. The only other products of reaction detected were formic acid and methanol (the latter in some cases), besides H₂. The reaction mechanism, particularly the critical step of C–C bond formation, was studied by comparing the reactivity in tests with CO₂ or CO, where formic acid or formaldehyde where initially added. The results indicate the need for having dissolved CO₂ to form acetic acid, likely via the reaction of CO₂˙⁻ with surface adsorbed –CH₃ like species. The pathway towards formic acid is instead different from the route of the formation of acetic acid.