Elucidating the Role of Aqueous Solvent and Cations in Selectivity of Cobalt-Porphyrin Catalyzed CO2 Reduction Over Hydrogen Evolution.

Density functional theory-based molecular dynamics simulations with explicit solvent representation were employed to investigate the mechanism of electrochemical reduction of CO2-to-CO (CO2RR), catalyzed by a cobalt porphyrin complex (CoTPP) in aqueous solution. Our study focuses on the role of solvent molecules and a solvated potassium cation. The simulations reveal that solvent molecules play an active role in key reaction steps, significantly lowering the reaction barrier compared to previous results, primarily due to H-bond stabilization of the transition state. Additionally, the calculations indicate that the presence of water molecules disfavors the competing hydrogen evolution reaction. These findings underscore the importance of incorporating an explicit molecular description of the solvent to accurately estimate reaction energies, providing a realistic model that highlights the high selectivity of the CoTPP catalyst.