Impact of charging in constant potential electrochemistry modeling

A huge issue in computational electrochemistry is that different modeling approaches, used to study electron transfer reactions, give different results that cannot easily be reconciled with each other. One discrepancy is their handling of interface charging. I study charging of electrolyte-Cu(111) interfaces with electrons and cations (or positive continuum charge) and observe that the charging energy depends strongly on the electrolyte model. When the electrolyte is a film containing water, there is a significant stabilization of the energy with more negative potential. This is in contrast to the charging of an interface with implicit solvent, where charge repulsion result in low stabilization of the energy with more negative potential. This could give the erroneous impression that charging can be ignored in electrochemistry modeling. I further consider constant potential CO2 adsorption to highlight the importance of charging and using an electrolyte model with water molecules, and show that other modeling approaches gives significantly different CO2 adsorption energies.