Voltammetry study of Cr(III)/Cr(II) system in methanesulfonate and sulfate solutions: Temperature dependences

Effect of temperature on electrochemical characteristics of methanesulfonate and sulfate complexes of Cr(III) ions in aqueous solutions was investigated by means of linear sweep voltammetry. A simple method for processing the temperature responses of linear voltammograms for irreversible electrochemical reactions was proposed. The values of the activation energies for electroreduction processes of Cr(III) in methanesulfonate and sulfate solutions were found to be equal to 52.5 and 61.3 kJ mol−1, respectively. The values of the activation energies for diffusion processes of electroactive species in those solutions were shown to be equal to 19.5 and 11.6 kJ mol−1, correspondingly. The differences between the calculated activation energies of electron transfer reactions in Cr(III) methanesulfonate and sulfate electrolytes were discussed and explained using results of quantum-chemical simulation.

► Electroreduction of methanesulfonate (MS) and sulfate (S) Cr(III) complexes. ► Activation energies (AE) for MS and S complexes 52.5 and 61.3 kJ mol−1, respectively. ► AE for diffusion of MS and S complexes 19.5 and 11.6 kJ mol−1, respectively. ► Equilibrium geometric structures of the corresponding Cr(III) and Cr(II) complexes.