Revealing the dynamic evolution of interfacial water during Mg anodic dissolution

Though magnesium alloys possess attractive mechanical properties, their applications are severely limited by galvanic corrosion, due to the rapid anodic dissolution and anomalous hydrogen evolution. In this work, well-tempered metadynamics simulations combined with fine-tuned machine-learning potentials are employed to investigate the anodic dissolution of pure magnesium, as well as the concurrent dynamic evolution of interfacial water. The simulated free-energy landscape and the activation barriers enable the construction of an anodic polarization curve for Mg corrosion, comparable to experimental results. The dynamic evolution of interfacial water during the Mg dissolution process was investigated from the perspective of the water dissociation energy, reorientation and spatial redistribution, vibrational mode, and the hydrogen bonds of water molecules, as well as the interfacial electron-density distribution. The dynamic changes of interfacial water elucidate the origin of the enhanced hydrogen evolution reaction (HER) activity under anodic polarization and provide an atomistic-level explanation for the negative difference effect of Mg.