Fig. 2.

Three plausible reaction mechanisms (RMs) for the CO₂RR and one for the HER occurring over Ag(110). The HER follows the Volmer–Heyrovsky reaction, whereas CO₂RR can proceed via three different hydrogen donors such as *H (RM-1), **H₂O (RM-2), or free H₂O (RM-3). (A) RM-1 and (B) RM-2 have nine elementary reactions and seven species. (C) RM-3 has 10 elementary reactions and eight species. Reactions 0, 1, and 2 represent CO₂RR; reactions 3 and 4 represent HER; reactions 5, 6, 7, and 8 represent quasiequilibrated adsorption and desorption of reactants and products; and reaction 9 shows the direct release of OH⁻ to the bulk electrolyte, as it does not adsorb to the cathode.