STUDY OF THE HETEROGENEOUS DECOMPOSITION OF HYDROGEN-PEROXIDE - ITS APPLICATION TO THE DEVELOPMENT OF CATALYSTS FOR CARBON-BASED OXYGEN CATHODES

The heterogeneous decomposition of hydrogen peroxide was studied in alkaline electrolytes on LaFexNi1-xO3 perovskite-type oxides. The reaction is first order in HO2- concentration. Maximum catalytic activity was found for x = 0.25. This increase in activity was attributed to the appearance of mixed oxidation states of iron and nickel. The optimum temperature of synthesis was between 600-degrees-C and 700-degrees-C, this being a compromise between a sufficiently high temperature to synthesize the perovskite structure and a sufficiently low temperature to produce a high surface area catalyst with a low number of oxygen vacancies. The catalytic activity for O2 reduction on carbon-based electrodes correlates very well with the catalytic activity for HO2- decomposition. A linear relationship was derived between the electrode potential at constant current and the logarithm of the peroxide decomposition rate constant. This relationship is followed quite well at relatively low current densities.