Electrochemical study of cerium(IV) in the presence of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetate (DTPA) ligands

Abstract

The electrochemical behaviour of the complexation of cerium(IV) with EDTA and DTPA was studied using both cyclic voltammetry (CV) and rotating disc electrode (RDE). The Ce(IV)–DTPA complex at various scan rates gave a linear correlation between the peak potential (Ep) and square root of scan rate, showing that the kinetics of the overall process was controlled by mass transport. However, when the EDTA ligand was added to the Ce(IV) there was no specific change to the potential peak, i.e. the Ce(IV)–EDTA complex has the same redox potential as the Ce(IV)/(III) couple. Kinetic parameters such as potential, limiting current, diffusion coefficients, transfer coefficient and rate constants were studied. The results from RDE experiments confirmed that the parameters measured by CV are similar under hydrodynamic conditions and can be used to determine the kinetic parameters of the redox couples. The use of DTPA as a ligand for complexation of Ce(IV) gaves more favourable results compared to the Ce–(EDTA) complex reported previously. The results of kinetic studies of Ce(IV)–DTPA complex shows promise as an electrolyte for redox flow battery.