Аннотация:The ethanol electro-oxidation catalyzed by Pd in alkaline environment involves several intermediate reaction steps promoted by the hydroxyl radical, OH*. In this work, we report on dynamical paths of the first step of this oxidation reaction, namely the hydrogen atom abstraction CH3CH2OH + OH* -> CH3CHOH* + H2O, occurring at the Pd(111) surface and address the thermodynamic stability of the adsorbed reactants by means of quantum and molecular mechanics calculations, with special focus on the effect of the solvent. We have found that the impact of the solvent is significant for both EtOH and OH, contributing to decrease their adsorption free energies by a few dozen of kcal mol-1 with respect to the adsorption energy in vacuum. Furthermore, we observe that hydrogen atom abstraction is enhanced for those simulation paths featured by large surface-reactant distances, namely, when the reactants weakly interact with the catalyst. The picture emerging from our study is therefore that of a catalyst whose coverage into aqueous environment is largely dominated by OH with respect to ethanol. Nevertheless, only a small amount of them, specifically those weakly bounded to the catalyst, is really active in the ethanol electro-oxidation reaction. These results open to the idea of a rational design of co-catalysts based on the tuning of surface chemical properties to eventually enhance exchange current density.