Cerium-zinc redox flow battery: Positive half-cell electrolyte studies

Experimental work was performed to evaluate the Ce3+/Ce4+ redox couple in methane sulfonic acid (MSA) electrolyte for use in redox flow battery (RFB) technology. The electrochemical behaviour of the Ce3+/Ce4+ in MSA media was investigated using cyclic voltammetry, linear sweep voltammetry, chronoamperometry and rotating disc electrode. The standard rate constant of the Ce3+/Ce4+ redox reaction on graphite electrode in MSA was 4.06×10−4 cm/s. The diffusion coefficient of Ce3+ in MSA was 5.87-6.15×10−6 cm2/s, and was 2.56-2.68×10−6 cm2/s for Ce4+. The energy efficiency of a cerium-zinc test cell was 74.8%. The high stability of cerium salts in MSA media and relatively fast redox kinetics of the Ce3+/Ce4+ redox reaction at graphite ectrode indicated that the Ce3+/Ce4+ might be well suited for use in RFB technology.