Understanding the electric double layer at electrode–electrolyte interfaces, Part III: crystallographic-face dependence of silver capacitance in aqueous NaF solutions

Electrochimica Acta. 2026. Vol. 577. Article 149729.

Mazur D., Petr E. Brandyshev, Doronin S., Yury A. Budkov

The electric double layer (EDL) at a single-crystal metal surface is controlled not only by the electrolyte composition and the electrode potential, but also by the atomic structure of the surface itself. This makes the Ag(hkl)/NaF interface a stringent test for continuum theories of the EDL. In the third part of our series, we examine whether a single self-consistent field (SCF) description, constrained by microscopic adsorption and charge-transfer data, can reproduce the face dependence of the differential capacitance of silver in aqueous NaF. The model combines a modified Poisson--Boltzmann framework with ion hydration, dielectric decrement, steric effects, short-range Morse adsorption potentials, and partial charge transfer. The face-dependent parameters are constrained by quantum-chemical calculations and \textit{ab initio} molecular dynamics estimates for Na$^+$, F$^-$, and interfacial water. With one internally consistent set of physically grounded parameters, the model reproduces the camel-shaped capacitance curves of Ag(100), Ag(110), and Ag(111) measured by Valette at $0.1~\mathrm{M}$ and predicts the lower-concentration data over $0.005$--$0.04~\mathrm{M}$ without further adjustment. The effective fluoride charge-transfer fraction required by the capacitance fit is of the same order as the screened AIMD charge redistribution, although the two quantities are not identified one-to-one because they have different operational definitions. Water charge transfer is found to have a negligible capacitance contribution in the investigated potential window. A cautious comparison with X-ray scattering data in an alkaline electrolyte shows qualitative consistency in the location and face ordering of the first interfacial water layer, while higher-order layering remains beyond the local mean-field description. These results demonstrate cross-facet and cross-concentration consistency within Ag/NaF and support the transferability of the modeling framework, while the fitted numerical parameters themselves remain system-specific and require recalibration beyond the present conditions.

Keywords: двойной электрический слой, Electric double layer, electrolytes, электролиты, self-consistent field theory, теория самосогласованного поля, квантовая молекулярная динамика, Ab initio molecular dynamics

Publication based on the results of: Прогнозирование свойств молекулярных систем: совмещение методов машинного обучения и классических методов моделирования (2026)