Oxygen sorption and catalytic properties of La 1− xSr xCo 1− yFe yO 3 Perovskite-type oxides

Abstract

Oxygen desorption from La 1− x Sr x Co 1− y Fe y O 3 perovskite-type oxides below 850°C was examined by a temperature-programmed desorption (TPD) technique. The catalytic activities of the oxides for the combustion of n-butane and methane as well as H 2O 2 decomposition in an alkaline solution were also measured and were discussed in relation to oxygen sorption properties. The amount of oxygen desorbed increased with increasing Sr content at a fixed B-site composition, for which an increase in the number of oxide ion vacancies with x was responsible. On the other hand, the total amount of oxygen desorbed was hardly affected by B-site composition, but partial substitution of Fe for Co enhanced desorption and sorption of oxygen particularly in the low-temperature region. Substitution of Sr for La as well as of Fe for Co was found to promote catalytic activity, though the activity changed with oxide composition in a manner dependent on the kind of reactant. For n-butane combustion over La 1− x Sr x Co 0.4Fe 0.6O 3, maximum activity was obtained at x = 0.2. La 0.2Sr 0.8 Co 1− y Fe y O 3 activity was highest at y = 0.4 for n-butane combustion, while it was independent of y for methane combustion. For H 2O 2 decomposition in an alkaline solution, on the other hand, La 1− x Sr x Co 0.4Fe 0.6O 3 and La 1− x Sr x CoO 3 activities increased monotonically with an increase in x, and the former oxides were more active than the latter. These variations in catalytic activities with oxide composition were well accounted for by the oxygen sorption properties revealed by TPD.