Details

Autor(en) / Beteiligte

• López-García, José Juan
• Horno, José
• Grosse, Constantino

Titel

Combined Ionic Size and Electrode Spacing Effects on the Differential Capacitance of Confined Electrolytic Cells

Ist Teil von

• Journal of physical chemistry. C, 2022-06, Vol.126 (21), p.9154-9160

Ort / Verlag

American Chemical Society

Erscheinungsjahr

2022

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Differential surface capacitance is a powerful analytical tool in electrochemistry being often used in the characterization of electrode–solution interfaces. In a recent work [López-Garcı́a, et al., J. Electroanal. Chem. 904 (2022) 115925], we analyzed the dependence of the differential capacitance of electrolytic cells on the potential, solving the Poisson–Boltzmann equation but avoiding the commonly used infinite solution approximation. We showed that the system behavior changes significantly even for a large, but finite, spacing between electrodes. Instead of growing exponentially with the potential, as classically expected, the differential capacitance attains a maximum and decreases monotonously at large potentials. In the present study, we extend our preceding work to analyze the implications of considering the combined effect of the ionic size and finite electrode spacing. A modified Poisson–Boltzmann equation is used to account for finite ionic sizes, subject to the conservation condition of the total number of ions in the closed confinement. Equilibrium ion distributions and differential capacitance curves are investigated as functions of the electrode potential, electrolyte concentration, and electrode spacing. We find that the combined effect of finite ionic size and finite solution hypothesis has a strong bearing on the differential capacitance. Moreover, a simple expression for the differential capacitance that combines the effects of the finite ionic size and electrode spacing is presented.