Interfacial fluxionality in electrocatalysis: in and out of equilibrium

Electrocatalytic interfaces under applied potential and in the presence of adsorbates dramatically reshape, as seen, for example, in in situ STM. I will present a theoretical framework to describe the dynamics of electrocatalytic interfaces, combining grand canonical DFT, global optimization under potential and adsorbate coverage, and the network of concurrent reaction pathways constituting the catalytic mechanism. Conditions radically reshape the interface, and change the accessible reaction mechanisms. To illustrate this, I will discuss size-selected supported Pt cluster electrocatalysts for HER. By combination of theory and experiment, we demonstrate that these clusters have exhibit strong fluxionality of structure and coverage as a function of voltage and the stage of the catalyzed reaction. Metastable local minima are involved in the mechanism. The nature of the active sites strongly depends on the potential. This behavior inevitably leads to breaking scaling relations. I will further show how fluxionality can actually be used as a tool in cluster electrocatalyst design. Finally, the Cu cathode in the presence of CO and H or OH, characteristic of CO(2)RR, strongly restructures, and exhibits obvious off-equilibrium, kinetically-controlled reconstruction that we capture with frontier theoretical methods, and experiment.