LSFM perovskites as cathodes for the electrochemical reduction of NO

Six La0.6Sr0.4Fe1−xMnxO3−δ (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) perovskite compounds have been synthesised by the citric-acid route. The perovskites have been characterised by powder XRD and are shown to belong to the hexagonal crystal system. The perovskites are also evaluated by TG-measurements in 50% oxygen in nitrogen and in nitrogen. From this the redox capacity is calculated and shown to be highest for the iron rich compounds. Cyclic voltammetry has been recorded on cone shaped electrodes of the LSFM compounds in atmospheres containing either NO or O2 at temperatures of 300, 400 and 500 °C on a ceria based electrolyte. Only La0.6Sr0.4Fe0.8Mn0.2O3−δ (LSFM020) and La0.6Sr0.4FeO3−δ (LSFM000) show significant activity for the reduction of NO. This can probably be related to the high redox capacity of these compounds. The activity of the perovskites for the reduction of oxygen increases systematically with increasing iron content. The selectivity of the perovskites towards the reduction of NO with regard to the reduction of O2 is highest at the lowest temperatures.