First-principles modeling of electrochemical reactions at the metal-water interface under applied voltages

Ab initio modelling using density functional theory (DFT) is a powerful technique to study reactivity at electrochemical interfaces. We have recently developed an approach that allows to describe electrochemical systems under applied voltages and that can be easily implemented in existing DFT codes [1]. We apply this method to study Mg aqueous corrosion at anodic conditions, for which unusually high H₂ evolution rates are observed. The DFT based molecular dynamics simulations we perform for the Mg(0001)/H₂O system under increasing anodic polarization show dissociation events, proton transfer as well as H₂ evolution at the Mg-water interface. A detailed analysis of our calculations reveals a novel and hitherto unconsidered reaction mechanism for the H₂ evolution reaction, caused by an unusual adsorption phenomenon triggering a reaction resembling the cathodic Heyrovsky reaction.

[1] S. Surendralal, M. Todorova, M. W. Finnis, and J. Neugebauer, Phys. Rev. Lett. 120, 246801 (2018).