Solvation enthalpy determination for aqueous-phase reaction adsorbates from first principles ab initio molecular dynamics

The interplay between covalent and non-covalent interactions at the solid-liquid interface strongly influences electrocatalytic reactions. Although methods to determine the former interactions have been rigorously developed, the latter are often described with static bilayer models or similarly approximate methods. In this study, we account for disorder and dynamics at complex electrochemical interfaces by proposing a simple theory to estimate the enthalpy of solvation for adsorbed intermediates. In a strategy reminiscent of Born-Haber cycles, the enthalpy of solvation is expressed in terms of two sub-processes: vacancy creation by water reorganization, and adsorbate interaction with solvent molecules. The magnitude of the solvation enthalpy is then determined as a mean value from statistical sampling of hydrated adsorbate-catalyst configurations obtained from simulated annealing with ab initio molecular dynamic (AIMD) simulations. This theory is generalizable for many combinations of surfaces and adsorbates. Its application improves treatment of energetics at electrified solid-liquid interfaces, as well as corresponding structure-activity-stability predictions, as demonstrated for electrochemical oxygen reduction on Pt(111) and on Fe-N-C catalysts and for ethanol electrooxidation on Pt(111).