Using single fibre electrodes to determine the spatial variability of rate constants across carbon felt electrodes

Abstract

The spatial variation of rate constants for the ferri/ferrocyanide redox reaction in carbon felt was been determined through the analysis of single fibre electrodes. The rate constant for the reaction at each single fibre electrode was measured using electrochemical impedance spectroscopy (EIS) data. Qualitative rate constant data was also determined from the peak separation extracted from cyclic voltammograms. Both EIS and cyclic voltammetry showed a wide variation in the kinetics for the ferri/ferrocyanide redox reaction over the single fibre samples. Analysis then revealed that fibres taken from one face of the carbon felt sample were statistically different to the other face of the felt, suggesting that the manufacturing process of carbon felt can lead heterogeneity in the activity of the felt. Given the importance of carbon felt electrodes in applications such as redox flow batteries, understanding, controlling and possibly minimising this spatial variation could lead to better flow battery performance.