ELECTROCATALYTIC PROPERTIES OF LANTHANUM MANGANITE-BASED OXIDES OBTAINED BY A LOW-TEMPERATURE METHOD

Pure and Sr-doped lanthanum manganites have been synthesized by a non- conventional hydroxide solid solution precursor route at 500 degrees C . Their electrochemical and electrocatalytic properties in relation to O-2 evolution in KOH solutions have been investigated as film electro des by cyclic voltammetry, AC impedance and Tafel polarization techniq ues. The oxide powders have been used to obtain catalytic films on the nickel supports by painting with a slurry of the oxide followed by si ntering at 400 degrees C. The electrochemically active area vis-a-vis the electrocatalytic activity of the oxides increases considerably wit h increasing Sr-content from 0.1 to 0.4 mole in the perovskite lattice . Both, the apparent as well as the true, catalytic activities of the oxide are found to be many times higher than those of the samples prep ared by conventional ceramic methods. The electrolytic evolution of O- 2 follows approximately first order kinetics in OH- concentration. The Tafel slopes are in the range 90 - 140 mV decade(-1).