New Mechanistic Insights into CO₂/CO Electroreduction to Acetate by Combining Computations and Experiments

It is firmly believed that the electroproduction of acetate via CO2/CO electroreduction follows the same C-C coupling pathway as other multicarbon (C2+) products in previously proposed mechanisms. However, this view is completely contradictory to the experimentally observed high CO pressure dependence of acetate formation. Herein, we propose deep mechanistic insights to uncover this puzzle by combining comprehensive computations and experiments. Our results elucidated that high CO pressure can induce *CO thermo-oxidation by surface *OH, where the produced *COOH opens the pathway to acetate formation. Instead of *CO dimerization, the C-C bond of acetate forms via the coupling of *COOH with another *CO, which is the rate-determining step of the whole process. More importantly, our CO and O-2 coelectrolysis experiments confirm the key role of surface *OH for acetate formation in addition to CO pressure. On this basis, insights into the effect of different factors (including the CO partial pressure, pH value, surface structure, presence of O-2, and applied potential) were gained, all of which are in perfect agreement with the reported experiments. Therefore, this mechanism answers how acetate is generated and offers powerful guidelines for precise optimization of the catalytic efficiency as well.