(393f) Justification of a Pseudo-Initial State in Proton Transfer during the Volmer Reaction

Protons play a vital role in electrochemical reactions, particularly in the Volmer reaction, the most basic electrochemical process. This reaction involves the adsorption of a hydrogen atom on a surface by combining a proton with electrons. To simulate the Volmer reaction, we first consider an initial scenario where a proton originates from a bulk reservoir while a vacant metal slab is present on the surface. Before assessing the reaction barrier, the proton needs to migrate from the reservoir to the vicinity of the electrode surface. This transition to the near-surface layer is termed the pseudo-initial state. A key inquiry arises regarding how the proton travels from the bulk to the near-surface and whether this pseudo-initial state is indeed observable. If the proton doesn't localize at the near-surface layer but instead follows a concerted mechanism, the existence of the pseudo-initial state becomes doubtful. In this research, we explored proton pathways within the grand canonical system using the solvated jellium approach. Additionally, we investigated proton localization near the surface, confirming the presence of pseudo-initial states.