Dynamic rearrangement of surface atoms has been observed in a wide range of electrocatalysts and was demonstrated to play a key role in the surface chemistry. Here we propose a grand canonical ensemble representation scheme to explore the fluxionality and off-stoichiometric restructuring at electrochemical interfaces of various types, ranging from small dynamic clusters to bulk terminations. (i) Fluxionality of supported subnano metal clusters leads to different isomeric distribution under coverage of different adsorbates and at different electrode potentials, which not only shift the apex of the activity volcano but also enable going beyond the Sabatier principle by breaking the linear scaling relationships. (ii) The crystalline Cu(100) surface under H coverage forms a multi-stage row-shifting pattern which is induced by weakening of surface bonds by H adsorption. The simulated STM images agree with and help interpret experimental <i>in situ</i> STM. The onset of reconstruction during the cathodic scan is hindered compared to thermodynamics-based prediction, due to metastability and entropic factors. In these collection of works we demonstrate the necessity of ensemble representation (of metastable surface states) in interpreting, understanding, and further optimization of surface chemistry at an electrochemical interface.

Modeling fluxionality and off-stoichiometric restructuring at electrochemical interfaces

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