# Current Distribution on Capacitive Electrode-Electrolyte Interfaces

## TL;DR

This paper presents an analytical model describing how current distribution evolves on capacitive electrode-electrolyte interfaces over time, with experimental validation, relevant for electrochemical and neural interface design.

## Contribution

It introduces a new analytical model for current distribution dynamics at capacitive interfaces, validated experimentally, enhancing understanding of electrochemical interface behavior.

## Key findings

- Steady current distribution is proportional to capacitance per unit area.
- Non-uniform initial current distribution becomes uniform over time.
- Model applies to electrode geometries like disks with experimental support.

## Abstract

The distribution of electric current on an electrode surface in electrolyte varies with time due to charge accumulation at a capacitive interface, as well as due to electrode kinetics and concentration polarization in the medium. Initially, the potential at the electrode-electrolyte interface is uniform, resulting in a non-uniform current distribution due to the uneven ohmic drop of the potential in the medium. Over time, however, the non-uniform current density causes spatially varying rate of the charge accumulation at the interface, breaking down its equipotentiality. We developed an analytical model to describe such transition at a capacitive interface when the current is below the mass-transfer limitation, and demonstrated that the steady distribution of the current is achieved when the current density is proportional to the capacitance per unit area, which leads to linear voltage ramp at the electrode. More specific results regarding the dynamics of this transition are provided for a disk electrode, along with an experimental validation of the theoretical result. These findings are important for many electrochemical applications, and in particular, for proper design of the electro-neural interfaces.