Investigating the accuracy of the diffusion coefficient estimation based on the rotating ring-disk electrode transient measurements in the cases of kinetic-limited regime and disk surface passivation

TL;DR

This study uses numerical simulations to evaluate the accuracy of diffusion coefficient estimation via rotating ring-disk electrode measurements, considering kinetic limitations and surface passivation effects.

Contribution

It provides insights into how passivation and kinetic regimes influence diffusion coefficient estimates, highlighting potential errors and robustness of the method.

Findings

Estimation errors can reach up to two times depending on potential.

Passivation does not significantly affect diffusion coefficient estimation.

Linear segments in transient indicate passivation coverage time.

Abstract

The chronoamperometric measurements performed with rotating ring-disc electrode become a one of the standard techniques for the diffusion coefficient determination. However, the theoretical estimation of the transit time on which the technique is based is not strictly connected to the apparent time interval measured in the experiments. Therefore, we employed numerical simulation of RRDE in order to predict possible error of the diffusion coefficient estimation in respect to the disc electrode conditions. According to the results the obtained estimation can vary up to two times depending on the disk electrode potential. On the other hand, even an intense disk passivation process leading to the peak-like shape of the ring current transient does not affect significantly the apparent transit time and the diffusion coefficient estimation. Additionally, it was showed, that the presence of a linear segment in the disk current transient indicates that the time it took to cover most of the disk electrode with the passivation film is close to the RRDE characteristic time.