Negative differential capacitance from composition-dependent Stern capacitance in a binary mixture.

Authors

Yuki Uematsu

Published in

The Journal of chemical physics. Volume 165. Issue 18. Nov 14, 2026.

Abstract

We develop a thermodynamic theory of electric double layers in binary liquid mixtures by allowing the Stern-layer capacitance to depend on the local solvent composition. This coupling produces an additional negative contribution to the inverse differential capacitance. As a result, the surface potential can become a nonmonotonic function of the surface charge density, leading to negative differential capacitance and a voltage-induced first-order transition between two electric-double-layer states. We determine the coexistence condition using a common-tangent construction for the surface-charge-controlled grand potential and obtain phase diagrams in terms of the inverse-capacitance contrast of the Stern layer, surface charge density, bulk composition, and surface potential. We also compare the theory with capacitance data for tetrabutylammonium chloride in water/1-propanol mixtures, finding semi-quantitative agreement in the continuous-response regime. These results suggest that solvent exchange inside the Stern layer can strongly control the capacitance and interfacial phase behavior of binary mixtures.

PMID:
43001870
Bibliographic data and abstract were imported from PubMed on 09 Nov 2026.

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