An electrochemical study on the positive electrode side of the zinc–cerium hybrid redox flow battery

• Published in: Electrochimica acta 2014-01, Vol.115, p.621-629
• Main Authors: Nikiforidis, Georgios, Berlouis, Léonard, Hall, David, Hodgson, David
• Format: Article
• Language: English
• Subjects: Carbon; Cerium; Coatings; Current density; Electric batteries; Electrochemical impedance spectroscopy; Electrodes; Methanesulfonic acid; Platinum; Pt–Ir electrodes; Rechargeable batteries; Zn–Ce redox flow battery
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2013.09.081

•Elevated temperatures favoured the Ce3+/4+ reaction on the Pt, Pt–Ir and carbon substrates.•jo increased with temperature over the range 25°C to 60°C for all substrates.•Non-porous carbon substrates showed higher reversibility on the Ce3+/4+ reaction.•Surface degradation of the carbon electrodes occurred due to the high positive potentials.•The Pt–Ir coatings gave the largest jo at 60°C and appear best suited for use as the positive electrode in the Zn–Ce RFB. In this study, the electrochemical behaviour of the Ce3+/4+ redox couple in methanesulfonic acid medium on various electrode substrates was investigated as a function of temperature. Carbon composite electrodes as well as platinum and platinum iridium coated electrodes were studied for their suitability in carrying out the Ce3+/4+ redox reaction. Cyclic voltammetry in 0.8moldm−3 cerium and 4.5moldm−3 methanesulfonic acid solution showed that elevated temperatures favoured the Ce3+/Ce4+ reaction on the various platinum and platinum–iridium coated substrates as well as on carbon composite surfaces. The latter electrodes showed better kinetics than the metal coatings but deteriorated badly under the high positive potentials required for the cerium reaction. The exchange current density (jo), obtained through Tafel extrapolation, polarisation resistance and electrochemical impedance spectroscopy measurements, increased with temperature over the range 25°C to 60°C. The Pt–Ir coatings gave the largest jo at 60°C and appear best suited for use as the positive electrode in the Zn–Ce redox flow battery.