Electrocatalytic properties of lanthanum manganite-based oxides obtained by a low temperature method

Abstract

Pure and Sr-doped lanthanum manganites have been synthesized by a-non-conventional hydroxide solid solution precursor route at 500°C. Their electrochemical and electrocatatytic properties in relation to O2 evolution in KOH solutions have been investigated as film electrodes by cyclic voltammetry, AC impedance and Tafel polarization techniques. The oxide powders have been used to obtain catalytic films on the nickel supports by painting with a slurry of the oxide followed by sintering at 400°C. The electrochemically active area vis-a- vis the electrocatalytic activity of the oxides increases considerably with 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 prepared by conventional ceramic methods. The electrolytic evolution of O2 follows approximately first order kinetics in OH- concentration. The Tafel slopes are in the range 90-140 mV decade-1.