Speaker
Description
In order to achieve a reasonable computational efficiency, state-of-the-art first-principles modelling of electrified solid-liquid interfaces is characterized by harsh approximations regarding the surrounding electrolyte and the applied potential. In the prevalent computational hydrogen electrode (CHE) approach the electrochemical environment is merely mimicked by thermodynamic reservoirs, while the system’s electronic structure always remains at the potential of zero charge (PZC). Aiming to maintain a comparable efficiency, we pursued the use of implicit solvation models in this context [1]. Within fully grand-canonical (FGC) simulations, they notably allow to mimic a polarization of the electrode’s electronic density under the applied potential and the concomitant capacitive charging of the entire double layer beyond the limitations of typically employed periodic boundary condition supercells [2].
Notwithstanding, accounting for the electrolyte only on the level of a continuous polarizable medium is still highly effective. Systematic comparison to measurable observables is therefore mandatory to scrutinize and advance the models. To this end, we here focus on the interfacial capacitance and its measurement in wide-spread cyclic voltammetry (CVs).
The application to 2D materials clarifies that a potential-dependent description is essential for understanding their capacitance, in particular for semiconducting electrodes. Here, the presence of a band gap in the density of states leads to a vanishing capacitance around the PZC – a phenomenon that is typically referred to as a quantum capacitance effect. Our detailed analysis provides first steps towards understanding electrified semiconductor-liquid junctions, as e.g. present at oxide-covered electrodes. In realistic systems, the potential-induced adsorption of species from the solution can lead to additional electron transfer and thus to additional, so-called pseudo-capacitance contributions. These contributions can be directly accessed from the study of CVs. In the application to Ag(111) in halide solutions we show that FGC level of theory is mandatory to capture non-Nernstian peak shifts and overall peak shapes [3,4]. The capability to efficiently simulate CVs thereby allows to systematically analyze and disentangle effects of the approximate density functional, the implicit solvation model and the sampling of the adsorbate ensemble.
[1] S. Ringe, N.G. Hörmann, H. Oberhofer, and K. Reuter, Chem. Rev. 122, 10777 (2022).
[2] N.G. Hörmann, N. Marzari, and K. Reuter, npj. Comput. Mater. 6, 136 (2020).
[3] N.G. Hörmann and K. Reuter, J. Chem. Theory Comput. 17, 1782 (2021).
[4] N.G. Hörmann and K. Reuter, J. Phys. Cond. Mat. 33, 264004 (2021).
| Abstract Number (department-wise) | TH 07 |
|---|---|
| Department | TH (Reuter) |
