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arXiv · 2407.13472

On the origin of univalent Mg$^+$ ions in solution and their role in anomalous anodic hydrogen evolution

Florian Deißenbeck·Sudarsan Surendralal·Mira Todorova·Stefan Wippermann·Jörg Neugebauer
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Abstract

Aqueous metal corrosion is a major economic concern in modern society. A phenomenon that has puzzled generations of scientists in this field is the so-called anomalous hydrogen evolution: the violent dissolution of magnesium under electron-rich (anodic) conditions, accompanied by strong hydrogen evolution, and a key mechanism hampering Mg technology. Experimental studies have indicated the presence of univalent Mg$^+$ in solution, but these findings have been largely ignored because they defy our common chemical understanding and evaded direct experimental observation. Using recent advances in the \emph{ab initio} description of solid-liquid electrochemical interfaces under controlled potential conditions, we described the full reaction path of Mg atom dissolution from a kinked Mg surface under anodic conditions. Our study reveals the formation of a solvated [Mg$^{2+}$(OH)$^-$]$^+$ ion complex, challenging the conventional assumption of Mg$^{2+}$ ion. This insight provides an intuitive explanation for the postulated presence of (coulombically) univalent Mg$^+$ ions and the absence of protective oxide/hydroxide layers normally formed under anodic/oxidizing conditions. The discovery of this unexpected and unconventional reaction mechanism is crucial for identifying new strategies for corrosion prevention and can be transferred to other metals.

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Florian Deißenbeck, Sudarsan Surendralal, Mira Todorova, Stefan Wippermann, Jörg Neugebauer. 2024-07-18. On the origin of univalent Mg$^+$ ions in solution and their role in anomalous anodic hydrogen evolution. https://doi.org/10.1021/jacs.4c10086

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