A CO-TAP study of the reducibility of La1−xSrxFe(Pd)O3±δ perovskites

In order to obtain useful information about the effect of Sr, Pd promotion and calcination temperature on the reducibility of La1−xSrxFe(Pd)O3±δ perovskites, CO-TAP in combination with XRD, BET, TG-DTA, and SEM were employed to characterise the perovskite oxides prepared by the method of sol–gel auto-combustion. Reducibility of the perovskites was studied by means of the oxygen release capacity measurement in which a TAP reactor system was used to perform the CO pulse or alternate CO–O2 pulse experiments. Partial substitution of La3+ by Sr2+ in LaFeO3 significantly enhanced the reducibility and La0.6Sr0.4FeO3±δ showed the highest reducibility among the La1−xSrxFeO3±δ perovskites. An incorporation of Pd in replacement of 5 mol% of Fe into La0.6Sr0.4FeO3±δ caused a significant decrease of reduction temperature and an enhancement of reducibility. Moreover, the thermal stability was improved in the presence of Pd. It was found that the reducibility was strongly affected by the calcination temperatures. Extremely high reducibility (ca. 650 μmol-CO2 g−1 of OSC and ca. 800 μmol-CO2 g−1 of OSCC) was observed on the 1000 °C calcined La0.6Sr0.4Fe0.95Pd0.05O3±δ although its BET specific surface area was very low. We concluded that calcination of La0.6Sr0.4Fe0.95Pd0.05O3±δ at relatively high temperatures was favourable of creating more lattice defects and the lattice defects instead of surface area were mainly responsible for the reducibility.