The influence of solvent on surface adsorption and desorption

The adsorption and desorption of reactants and products from a solid surface is essential for achieving sustained surface chemical reactions. At a liquid-solid interface, these processes can involve the collective reorganization of interfacial solvent molecules in order to accommodate the adsorbing or desorbing species. Identifying the role of solvent in adsorption and desorption is important for advancing our understanding of surface chemical rates and mechanisms and for enabling the rational design and optimization of surface chemical systems. In this manuscript we use all-atom molecular dynamics simulation and transition path sampling to identify water's role in the desorption of CO from a Pt(100) surface in contact with liquid water. We demonstrate that the solvation of CO, as quantified by the water coordination number, is an essential component of the desorption reaction coordinate. We use meta dynamics to compute the desorption free energy surface and conclude based on its features that desorption proceeds via a two-step mechanism whereby the final detachment of CO from the surface is preceded by the formation of a nascent solvation shell.