ELECTROCATALYTIC PROPERTIES OF LANTHANUM MANGANITES OBTAINED BY A NOVEL MALIC ACID-AIDED ROUTE

Electrochemical properties of lanthanum manganite and its substituted derivatives for oxygen evolution in KOH solutions were studied by cycl ic voltammetry, AC impedance and Tafel polarization techniques. The ox ides were obtained by a sol-gel route, using malic acid as precursor. The catalytic activity of LaMnO3 electrode, prepared by this new metho d, was found to be approximately 15 limes higher than the one obtained by ceramic method. The introduction of 0.2-0.4 mole Sr in the perovsk ite lattice further improved the activity of the catalyst. However, ot her Sr-substitutions (0.1 and 0.6 mole) appeared to be less beneficial . 0.2 mole Pb-substitution showed to be highly detrimental From the el ectrocatalysis point of view. The oxygen evolution reaction followed a first-order kinetics with respect to OH- concentration. The Tafel slo pe value was 108 +/- 5 mV decade(-1). (C) 1998 International Associati on for Hydrogen Energy.