Search

• For the first time, the kinetics of the reduction process of Eu(III) to Eu(II) in perchlorate, nitrate, and chloride electrolytes were examined using rotating disk electrode. • The diffusion coefficients based on experimental calculations were in a good agreement with literature data from polarographic methods. • The Eu(III) reduction reaction is found to be quasi-reversible in all the electrolytes. • The minor differences in the nitrate and chloride electrolytes compared to the perchlorate media were due to the differences in concentration and viscosity. All lanthanides have a stable trivalent oxidation state, but some of them can also occur in the divalent or tetravalent state. Europium is well-known for its divalent oxidation state, which has been investigated in aqueous, organic, and molten salt media. In contrast to other lanthanides, Eu3+ can be easily reduced (Eo=−0.34 V vs. SHE) via chemical, electrochemical or photochemical routes, and Eu2+ is quite stable in a variety of electrolytes, including nitrate salts. To date, the kinetics of the Eu3+/Eu2+ reduction reaction has been investigated only by polarography and chronopotentiometry, most often in perchlorate medium. In this study, the kinetics of the Eu3+/Eu2+ couple were analysed in nitrate, chloride and perchlorate media by cyclic voltammetry and linear sweep voltammetry with a rotating disk electrode (RDE). The diffusion coefficient, charge transfer coefficient and rate constants were calculated based on the Levich and Koutecký-Levich analysis and Tafel plot to gain insight in the electrochemical process and the influence of the electrolyte type on it. Given the pre-existing characterization of this redox couple in perchlorate medium, it is selected as a reference system to both compare the kinetic parameters and to validate whether the methodology can be applied to other electrolytes. The Eu3+ reduction reaction was found to be quasi-reversible in these electrolytes and the calculated kinetic parameters are in line with the previously reported values. [Display omitted] [ABSTRACT FROM AUTHOR]