STUDIES ON INDIAN-OCEAN MANGANESE NODULES .6. PHYSICOCHEMICAL CHARACTERIZATION AND CATALYTIC ACTIVITY OF STRONTIUM-LANTHANUM OXIDE MIXED MANGANESE NODULES

A series of strontium-lanthanum oxide mixed manganese nodules were pre pared and characterized by X-ray diffraction, nitrogen adsorption-deso rption, electrical conductivity, and surface excess oxygen. X-ray diff raction patterns confirm the formation of perovskite-type oxides at lo w strontium content (x less than or equal to 0.5, in La(1-x)Sr(x)MO(3) , where M denotes the transition metal present in nodules), whereas at 0.6 less than or equal to x less than or equal to 0.8, La2O3 and SrO are detected in addition to the perovskite-type oxides. The catalytic activities for hydrogen peroxide decomposition and carbon monoxide oxi dation increase with an increase in Sr substitution for La, attain a m aximum at x = 0.4, and then decrease with further increase in Sr. The activities have been correlated with various physicochemical propertie s. (C) 1997 Academic Press.