Electrochemistry of Yb 3+ and Eu 3+ at Nafion modified electrodes

Abstract

The influence of the electrodeposition of a thin mercury film on the voltammetric behaviour of Yb 3+ and Eu 3+ incorporated by ion-exchange in Nation ® coated glassy carbon electrodes is examined. A significant role of the nature of the electrode material is observed only in the case of Yb 3+ and the improvement in the reversibility and reproducibility of the voltammograms observed after mercury deposition is attributed to the higher overpotential required for hydrogen evolution on mercury. No such effect is observed in fact in the case of Eu 3+, which is reduced at far less negative potential values than Yb 3+ and, in this case, reversible and reproducible voltammetric patterns are obtained at both modified electrodes. The detailed analysis of the ion-exchange process demonstrates that mercury deposition does not cause deterioration of the ion-exchange properties of the Nation coating, while the nature of the supporting electrolyte cations examined (Li +, Na +, K +, Rb +, NH + 4, tetraethylammonium) proves to influence significantly both the extent and rate of incorporation. The ion-exchange distribution and selectivity coefficients of Nation for the two rare earth cations studied are also reported together with the relevant apparent diffusion coefficients.