Ck. Lee et al., THERMAL-TREATMENT OF LA0.6CA0.4COO3 PEROVSKITES FOR BIFUNCTIONAL AIR ELECTRODES, Journal of the Electrochemical Society, 144(11), 1997, pp. 3801-3806
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.