The Superior Properties of La 0.6 Ba 0.4 CoO 3-δ Thin Film Electrodes for Oxygen Exchange in Comparison to La 0.6 Sr 0.4 CoO 3-δ

Abstract

The electrochemical properties of La0.6Ba0.4CoO3-δ (LBC) and La0.6Sr0.4CoO3-δ (LSC) dense thin film model electrodes, deposited by pulsed laser deposition at 600◦C on yttria-stabilized zirconia (100) electrolytes, were investigated by electrochemical impedance spectroscopy (EIS) at 450–600◦C and 10−4 to 1 bar pO2. This comparative study reveals the influence of the A-site dopant size on the catalytic activity for the oxygen exchange, chemical capacitance and electronic conductivity. For both thin films the overall oxygen reduction is still limited by the oxygen surface exchange, although an extraordinarily high activity for the oxygen reduction reaction (ORR) was measured (LBC ∼0.18 cm2/LSC ∼0.6 cm2 at 604◦C and 0.21 bar pO2). Moreover, LBC exhibits a rather low activation energy for the ORR (1.19 ± 0.11 eV) together with a high electronic conductivity (839 S · cm−1 at ∼442◦C). Based on these excellent electrochemical properties, LBC may also be a highly promising material for porous cathodes in intermediate temperature (400–600◦C) solid oxide fuel cells.