THERMAL-TREATMENT OF LA0.6CA0.4COO3 PEROVSKITES FOR BIFUNCTIONAL AIR ELECTRODES

The perovskite La0.6Ca0.4CoO3 has been of interest as a bifunctional e lectrocatalyst for the bifunctional air electrode. The calcination and subsequent cooling steps in the amorphous citrate precursor (ACP) pro cess have been optimized to prepare La0.6Ca0.4CoO3 powders with high s urface area, and consequently improved electrocatalytic performance in an air electrode. The surface area of the final powder depends on the thermal treatment and the surface area increases with increasing the cooling rate. A sample quenched rapidly from 650 degrees C had a surfa ce area of 33 m(2)/g, which is more than double the value obtained wit h a slower cooling rate. Polytetrafluorene-ethylene (PTFE) bonded gas diffusion electrodes loaded with La0.6Ca0.4CoO3 catalysts prepared by the ACP method show good bifunctional performance. An electrode loaded with only 10 mg/cm(2) of powder prepared by quenching from 65O degree s C showed the best bifunctional performance, i.e., 280 mA/cm(2) for o xygen reduction ana 300 mA/cm(2) for the oxygen evolution, at 0.6 and 1.6 V vs. RHE, respectively. This performance compares well with resul ts from lower area La0.6Ca0.4CoO3 at much higher loadings.