Modeling of electric double layer at solid-liquid interface with spatial complexity

TL;DR

This paper introduces a fractional calculus-based reformulation of the Poisson-Boltzmann equations to model the electrical double layer with spatial complexity, revealing how impurity effects influence potential decay and charge distribution.

Contribution

It develops a novel fractional-space generalized model that incorporates spatial complexity effects in EDL modeling, extending classical approaches.

Findings

Potential decays more slowly at D<1, indicating a wider saturated layer.

Model recovers classical results at D=1, validating its consistency.

Spatial complexity affects ion distribution and potential decay profiles.

Abstract

Electrical double layer (EDL) is formed when an electrode is in contact with an electrolyte solution, and is widely used in biophysics, electrochemistry, polymer solution and energy storage. Poisson-Boltzmann (PB) coupled equations provides the foundational framework for modeling electrical potential and charge distribution at EDL. In this work, based on fractional calculus, we reformulate the PB equations (with and without steric effects) by introducing a phenomenal parameter $D$ (with a value between 0 and 1) to account for the spatial complexity due to impurities in EDL. The electrical potential and ion charge distribution for different $D$ are investigated. At $D$ = 1, the model recover the classical findings of ideal EDL. The electrical potential decays slowly at $D <$1, thus suggesting a wider region of saturated layer under fixed surface potential in the presence of spatial complexity. The fractional-space generalized model developed here provides a useful tool to account for spatial complexity effects which are not captured in the classic full-dimensional models.