Unlocking Atomic Degrees of Freedom in Liquid Metals for Accelerated Electrocatalytic Reactions

Liquid metals (LMs) exhibit superior conductivity, flexibility, and malleability, empowering their versatility across multiple fields. It was prevalently believed, albeit lacking in-depth mechanistic insights, that these features stem from high atomic degrees of freedom. In this work, we substantiate the intense and random atomic motion in LMs through the interplay of theory and in situ/operando experiments. In particular, we visualize structural oscillations and crystallographic orientation variations in near-melting LMs; the disordered LM atoms are not confined by rigid crystal lattices, in contrast to their solid counterparts. Owing to the high atomic degrees of freedom, LMs possess adaptive surfaces capable of dynamically conforming to adsorbate configurations during electrocatalysis, especially electrochemical CO₂ reduction (CO₂R) that has been hindered by the hardship of key species adsorption/activation/desorption on solid-state catalysts. We then pressurize the CO₂ to further enhance the adaptability of the LM surface in its interactions with adsorbates. As a result, the reactants and key intermediates are greatly enriched on the liquid metal surface, yielding an even higher CO₂R reactivity compared to the ambient-pressure scenario and reaffirming the mechanistic insights.