Electrochemical activity of solid solutions La1 -x Sr x CoO3 in the oxygen electroreduction reaction in carbonate melts

Solid solutions Lad_1-xSr_xCoO₃ are synthesized. An X-ray diffraction study reveals the formation of a rhombohedrically distorted perovskite-like phase. The kinetics and mechanism of the electroreduction of oxygen at the synthesized compounds in Li₂CO₃-K₂CO₃ (62: 38 mol %) and Na₂CO₃-Cs₂CO₃ (39:61 mol %) melts are studied by static coulometry and chronoamperometry. The exchange current grows with the strontium content in samples. The obtained apparent reaction orders of 0 and 0.14 by O₂ and CO₂ contradict all mechanisms offered earlier for the oxygen electroreduction at a gold electrode. A new mechanism is offered, in which the limiting step is the transfer of oxygen ions from the solid phase into the melt with corresponding changes in the electron subsystem of the electrode material. Dedicated to the ninetieth anniversary of Ya.M. Kolotyrkin’s birth.