PREPARATION OF PEROVSKITE-TYPE OXIDES OF COBALT BY THE MALIC-ACID AIDED PROCESS AND THEIR ELECTROCATALYTIC SURFACE-PROPERTIES IN RELATION TO OXYGEN EVOLUTION

The electrocatalytic properties of perovskite-type cobalt oxides (La1-xSrxCoO3, where x = 0, 0.2, 0.4), in the form of thin films on conductive supports, were studied by cyclic voltammetry and Tafel polarization techniques. The films had conductive and satisfactory adherent properties. The oxides were synthesized by a low temperature malic acid aided method. The cyclic voltammetry showed a pair of redox peaks prior to the onset of oxygen evolution on the oxide film with nickel support, while similar peaks were absent in the same oxide film on Pt and Ti. The anodic polarization studies indicated two Tafel slopes: 57 to 64 mV decade(-1) at low and 100 to 130 mV decade(-1) at high overpotentials, and first-order kinetics with respect to OH- concentration. The electrocatalytic activity of La0.8Sr0.2CoO3 film on Ni was the highest among all the electrodes prepared. The Sr substitution enhanced the electrochemically active area greatly. Results of the present investigation have been compared to those reported for similar oxides obtained by other methods.