Effect of the Electrode Material on the Reduction of La3+ and Ce3+ in Fluoride-Conducting Solid Electrolytes

Abstract

The reduction of immobile cations La 3+ and Ce 3+ in fluoride-conducting solid electrolytes (FSE) LaF 3 ( Eu 2+ 0.8 mol %), LaF 3 ( Sr 2+ 5 mol %), and CeF 3 ( Sr 2+ 5 mol %) in contact with Ag, Bi, Si, La, Ce, and Sm working electrodes is studied by chronoamperometry and voltammetry with linear potential scan. Discovered is linear dependence of initial segments of potentiostatic transients of cathodic current on t 1/2 at FSE interfaces with Ag, Bi, La, Ce, and Sm. The dependence is due to diffusion-controlled instantaneous nucleation of Ln and Ce. The La 3+ and Ce 3+ reduction at the FSE/Ag interface is reversible in a narrow region. The reduction and oxidation of La 3+ and Ce 3+ (cations of the FSE rigid lattice) at the FSE/Me (Me = La, Ce and Sm, Bi, Si) interface is irreversible and involves a chemical reaction.

Cyclic Voltammetry of a Fluoride-Selective Electrode in Contact with Metals

“…These trends have been found for the interface between a metallic electrode and a membrane of FSE with an aqueous [12314] or solid-state reference system [15]. We have also reported relationships between the peak current and the contact area of Bi [16] and Ag [17] with the membrane.…”

Voltammetric study of PrF3:Sr2+ and NdF3:Ba2+ solid electrolytes

“…Earlier, it was found in experi ments with single crystals of lanthanum and cerium fluorides that such treatment allows renovating the solid electrolyte surface and providing reproducibility of results of studying the processes both with partici pation of FCSE fluoride ions at the two-phase inter face [4,5] and with participation of gaseous oxygen at the three-phase interface [7,8]. The treatment qual ity was controlled on the basis of the linear depen dence in the I,E curve of the symmetrical cell of The choice of the working voltage range is limited by the reduction potentials of cations of the rigid fluo ride sublattice [14]: …”

“…Measurements were carried out at the room temperature of (22.0 ± 0.5)°C. The tech nique of studying FCSE interfaces with metals is described in more detail in [7,14].…”