Oxygen sorption and catalytic properties of La1−xSrxCo1−yFeyO3 Perovskite-type oxides

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 2 O 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 0.4 Fe 0.6 O 3 , maximum activity was obtained at x = 0.2. La 0.2 Sr 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 2 O 2 decomposition in an alkaline solution, on the other hand, La 1− x Sr x Co 0.4 Fe 0.6 O 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.