Electrochemical performance of lanthanum calcium cobalt ferrite cathode interfaced to LAMOX electrolyte

Lanthanum calcium cobalt ferrite (LCCF), a potential cathode composition for the LAMOX electrolyte, is studied on its electrocatalytic performance in oxygen reduction reaction (ORR) using impedance spectroscopy. Nyquist plots of LCCF impedance at 600-800 degrees C display two arcs, in which the low-frequency arc is constantly larger than the high-frequency arc. When interfaced to the electrolyte containing 20 mol% tungsten, the ORR polarization resistance of LCCF exhibits a strong temperature dependency whose activation energy increases with increasing Co content, 190 (10 mol%)-220 (90 mol%) kJ mol(-1). Among the cathode compositions, LCCF82 (80 mol% Co) exhibits the best catalytic performance. Its zero-bias ORR resistance is 242.4 at 600 degrees C, 0.845 Omega cm(2) at 800 degrees C, along with the capacitance 7.79 (600 degrees C), 14.93 mF cm(-2) (800 degrees C). The ORR resistance of LCCF82 decreases with increasing dc bias at 600 and 700 degrees C, hardly changes at 800 degrees C. The electrocatalytic activity of LCCF82 is also influenced by the tungsten content of its interfacing electrolyte. The exchange current density of LCCF82 correlates positively with the electrolyte ion conductivity which increases with decreasing tungsten content. (C) 2008 Elsevier B.V. All rights reserved.