On the deconvolution of the concurrent cathodic processes with cobalt deposition onto graphite from feebly acidic bath

Abstract

Electrodeposition of non-precious metal group elements (NPG) is widely utilized to produce electrode materials for specific electrocatalytic reactions. The efficiency of cobalt electrodeposition on graphite substrate is largely affected by two concurrent cathodic processes: the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER). The contribution of the currents, originated from the ORR and the HER to the overall recorded cathodic current, hampers the fitting of current transient data of cobalt electrodeposition by Scharifker and Mostany model and the determination of the nucleation mechanism. The recent model proposed by Altimari attempted to deconvolute the observed cathodic current of cobalt electrodeposition into its major components. This study applied the mathematical model of Altimari to the Co electrodeposition from 0.05 M CoCl2 solution without and with 0.05 M sodium citrate. The main purpose of this application is to exclude the contribution of HER current from the total cathodic current. Consequently, the extracted component of the deposition current (ID) fits nicely the Scharifker model for the instantaneous nucleation mechanism of cobalt in the presence of citrate ions. Moreover, our results demonstrate that the cobalt deposition in absence of citrate is initiated by larger contribution of the progressive nucleation mechanism. Graphic abstract: [Figure not available: see fulltext.]