Title of your abstract: Efficacy of non-metallic cations in electrochemical CO2 reduction on Bi(111) electrode: a first principles study.

While it is known that CO₂ electroreduction necessitates the involvement of metal cations, questions have arisen regarding the potential efficacy of non-metallic cations. To address this inquiry, we have delved into a comparative analysis of the influence of Na⁺, and NH₄⁺ in the conversion of CO₂ into formate (HCOO^-) and CO on a Bi(111) electrode, employing grand canonical density functional theory. We find that the hydrogenation process, in which a proton (H⁺) migrates from the electrode toward CO₂ primarily drives the reduction of CO₂ into formate (HCOO^-) in the presence of cations. Notably, we find that the activation energy barrier for HCOO- formation in the presence of Na⁺ is 0.03 eV and rises to 0.08 eV in the presence of NH₄^⁺. Furthermore, we discover that CO₂ can also preferentially undergo reduction to CO through a proton shuttling process. This process involves the transfer of a proton (H^⁺ ion) from the electrode to the adsorbed CO₂* species through a water molecule, resulting in the formation of the intermediate COOH*. The activation energy barrier for this step is determined to be 1.17 eV and 1.04 eV in the presence of Na⁺ and NH₄⁺, respectively. Finally, our investigation finds that the activation energy barrier for COOH* dissociation is 0.48 eV and 0.04 eV in the presence of Na^⁺ and NH_₄^⁺, respectively. These outcomes suggest that non-metallic cations can be as effective as metallic cations in facilitating the CO₂ electroreduction process, in agreement with experimental findings [1].

[1] K. Shi, D. Le, T. Panagiotakopoulos, T. S. Rahman, and X. Feng, Effect of Quaternary Ammonium Cations on CO2 Electroreduction (Submitted, 2023).