Karsten Reuter

(Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany)

Electrocatalytic processes gain an ever-increasing importance for a future sustainable energy system. Electrolytic generation of hydrogen, electroreduction of CO2 to synthetic fuels or the reverse fuel cell processes are key components for the required storage, transport and provision of energy on a global scale. Unfortunately, the transition to corresponding energy technologies is still largely impeded by insufficient efficiencies or stabilities of hitherto employed materials or devices. Many of these limitations arise at the involved solid-liquid interfaces, which often undergo strong structural and compositional changes in the operating device. Such operando evolution presents already a severe challenge to the predictive-quality modeling and simulation of working thermal catalysts ^[1]. In interfacial electrocatalysis, this is further aggravated by the simultaneous need to reliably capture solvent dynamics and the long-range electrostatics in the diffuse double layer (DL). The present state-of-the-art is therefore largely characterized by harsh approximations. Operando evolution is generally not treated, solvation effects are often ignored and the applied bias at best considered through thermodynamic potentials. In particular, the prevalent computational hydrogen electrode (CHE) approach considers the surface electronic structure to constantly remain at the potential of zero charge (PZC) and therefore precludes capacitive charging effects by construction.
In recent years, implicit solvation approaches have experienced a renaissance in the context of interfacial electrochemistry ^[2], not least because in conjunction with ab initio thermodynamics they allow to mimic the polarization of the electrode at potentials beyond the PZC. In this talk, I will tutorially introduce this context and corresponding fully-grand canonical (FGC) calculations ^[3]. Specifically, I will discuss the application to compute thermodynamic cyclic voltammograms (CVs) and demonstrate that only FGC calculations are able to capture non-Nernstian peak shifts and other DL-effects on the CV shape ^[4]. Relevant for catalysis is in particular the ability to predict potential-induced variations of adsorption energies and concomitant effects on detailed reaction mechanisms.

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