Potentiometry of the Interface between a Solid
Sodium-Conducting Electrolyte and SmCo_1xM_xO₃ (M = Ti, Mn)
in the Presence of Oxygen

N. S. Tkacheva, A. I. Korosteleva, and N. G. Bukun

Institute of New Chemical Problems, Russian Academy of Sciences,
p/o Chernogolovka, Noginskii raion, Moscow oblast, 142432 Russia

Received May 13, 1997

Abstract—The potentiometry method is employed to study the behavior of the electrochemical cell
SmCo_1xM_xO₃ Na⁺SE Na_0.65CoO₂ in mixtures of molecular oxygen and argon. The cell contains a sodium-
conducting solid electrolyte (Na⁺–SE) and an oxygen electrode based on a binary Sm–Co oxide doped by
oxides of Ti and Mn. The -phase of a Na–Co bronze, Na_0.65CoO₂, is selected as the reference electrode. With
compounds prone to hydration, such as -Al₂O₃, ''-Al₂O₃, and Na₅GdSi₄O₁₂, used as Na⁺–SE, the solid-phase
system is reversible towards oxygen at temperatures exceeding 150°C. The oxygen reduction is shown to pro-
ceed at these temperatures as a single-electron process, probably, with the formation of the superperoxide ion
. The reversibility by oxygen can be ensured even at room temperature, provided finely divided platinum
(~5 wt %) is deposited on the oxide electrode surface. In the low-temperature region, the oxygen reduction
mechanism is determined by the dopant M in the oxygen electrode composition. With M = Ti, the process
involves two electrons and leads to the ion formation, whereas with M = Mn, the process is a four-electron
one and yields the OH^– ion. The concentration dependence of the cell’s emf is described by the Nernst equation
up to 80 vol % of oxygen.

Pleiades Publishing home page | journal home page | top

If you have any problems with this server, contact webmaster.