A study of the Ce3+/Ce4+ redox couple in sulfamic acid for redox battery application

Highlights: ► SA served as media electrolyte for Ce3+/Ce4+ was reported. ► A Zn–Ce redox battery was assembled and it showed impressive charge–discharge performance. ► The performance of Zn–Ce battery was improved by adding carbonate such as NH4HCO3. Its energy efficiency reached up to 53%. -- Abstract: The present paper reports a cerium sulfamate electrolyte for use in redox battery. The electrochemical behavior of Ce3+/Ce4+ in sulfamic acid (SA) media has been investigated using linear-sweep voltammetry and cyclic voltammetry. The formal potential of the Ce3+/Ce4+ redox couple in SA is approximately 1.52 V vs. NHE. The exchange current density and standard rate constant of the Ce3+/Ce4+ redox reaction on platinum electrode in SA are determined as 5.95 × 10−4 A cm−2 and 4.95 × 10−5 cm s−1 respectively. The diffusion coefficient of Ce3+ in SA is 5.93 × 10−6 cm2 s−1. The conductivity of cerium(III) sulfamate solution is improved significantly by adding NH4+. A zinc–cerium test cell with Ce3+/Ce4+ sulfamate solution as the positive electrolyte is constructed and the charge-discharge performance is evaluated. The coulombic efficiency of the Zn–Ce cell is calculated to be 90%. The preliminary exploration shows that the cerium sulfamate electrolyte is promising for redox battery application and is worthy of further study.