Implicit Solvation Methods for Catalysis at Electrified Interfaces

Abstract

Implicit solvation is an effective, highly coarse-grained approach in atomic-scale simulations to account for a surrounding liquid electrolyte on the level of a continuous polarizable medium. Originating in molecular chemistry with finite solutes, implicit solvation techniques are now increasingly used in the context of first-principles modeling of electrochemistry and electrocatalysis at extended (often metallic) electrodes. The prevalent ansatz to model the latter electrodes and the reactive surface chemistry at them through slabs in periodic boundary condition supercells brings its specific challenges. Foremost this concerns the difficulty of describing the entire double layer forming at the electrified solid–liquid interface (SLI) within supercell sizes tractable by commonly employed density functional theory (DFT). We review liquid solvation methodology from this specific application angle, highlighting in particular its use in the widespread ab initio thermodynamics approach to surface catalysis. Notably, implicit solvation can be employed 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 the employed DFT supercell. Most critical for continuing advances of this effective methodology for the SLI context is the lack of pertinent (experimental or high-level theoretical) reference data needed for parametrization.

Epitaxial Core‐Shell Oxide Nanoparticles: First‐Principles Evidence for Increased Activity and Stability of Rutile Catalysts for Acidic Oxygen Evolution

“…Here, any treatment of aqueous surrounding is not included in our model. We note that both the solvent dielectric environment and specific interactions with surrounding water molecules can lead to different absolute energetics [57,58] . In contrast, we assume such solvent effects to be small when comparing the energetics of materials within the same class differing due to mechanical modifications.…”

How to Gain Atomistic Insights on Reactions at the Water/Solid Interface?

“…While the electrostatic interaction can be computed by the Poisson-Boltzmann equation, the cavitation energy generally relies on semi-empirical parameters, fitted to molecular benchmark data. 16 In practice it turns out that the cavitation energy is generally negligible compared with the electrostatic interaction. 18,19 However, the definition of the solute cavity, and thus the transition of the dielectric constant from its vacuum value (in the solute) to the bulk solvent value, directly impacts the quality of the implicit solvent model, 20,21 including work functions 22 and adsorption energies.…”

Challenges in the modelling of elementary steps in electrocatalysis

“…However, typically such force fields cannot properly take into account long-range electrostatic and electrode potential effects which are crucial for electrochemical interfaces. Instead of an explicit atomistic modelling of the electrolyte, implicit solvent models can be used [20] in which the electrolyte is described as polarizable dielectric continuum. Such models have been extensively used in the description of solvated molecules [21], but they are now also used routinely in the modelling of electrochemical interfaces [20].…”

“…Instead of an explicit atomistic modelling of the electrolyte, implicit solvent models can be used [20] in which the electrolyte is described as polarizable dielectric continuum. Such models have been extensively used in the description of solvated molecules [21], but they are now also used routinely in the modelling of electrochemical interfaces [20]. Interestingly enough, this approach is best-suited for the description of non-polar molecules, so that its reliability in the description of strong polar solvents such as water is not clear.…”