Fe-substituted nanometric La 0.9K 0.1Co 1− xFe xO 3− δ perovskite catalysts used for soot combustion, NO x storage and simultaneous catalytic removal of soot and NO x

Abstract

A series of nanometric Fe-substituted La 0.9K 0.1Co 1− x Fe x O 3− δ ( x = 0, 0.05, 0.1, 0.2, 0.3) perovskite catalysts were prepared by citric acid complexation, which show novel activity for diesel soot oxidation, NO x storage, and simultaneous NO x–soot removal. Their structures and physical–chemical properties were examined by XRD, BET, SEM, XPS and EXAFS techniques. In La 0.9K 0.1Co 1− x Fe x O 3− δ catalysts, the partial substitution of Co 3+ by Fe 3+ significantly enhances the catalytic activity towards soot oxidation or NO x storage and reduction. The catalyst La 0.9K 0.1Co 0.9Fe 0.1O 3− δ shows the highest activity for simultaneous NO x–soot removal, over which the maximal soot oxidation rate is achieved at only 362 °C ( T m), the NO x storage capacity reaches 213 μmol g −1, and the percentage for NO x reduction by soot is 12.5%. Compared with the unsubstituted one (La 0.9K 0.1CoO 3− δ ), the activity enhancement of Fe-substituted samples results from the formation of high valence ion (Fe 4+) at B-site, relative high content of surface lattice oxygen and the high concentration of NO 2. Different from the widely accepted viewpoint that surface adsorbed oxygen species are responsible for soot combustion over perovskite catalysts, the surface lattice oxygen is identified as active oxygen species for soot combustion.