Perovskite lattice oxygen contributes to low-temperature catalysis for exhaust gas cleaning.

A Pd catalyst supported on Ba-substituted LaAlO 3 perovskite (Pd/La 0.9 Ba 0.1 AlO 3- δ ) was investigated for NO reduction at low temperature by propylene, which revealed that Pd/La 0.9 Ba 0.1 AlO 3- δ has remarkably higher activity than other Pd catalysts at low temperatures (≤573 K) for NO reduction by propylene. To elucidate the surface reaction pathway, transient response tests were conducted using 18 O 2 . Also, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were conducted. Comparison with a Ba-impregnated catalyst (Pd/Ba/LaAlO 3 ) demonstrated that Pd/La 0.9 Ba 0.1 AlO 3- δ shows higher activity for the formation of oxygenated species (C x H y O z ) as an intermediate for NO reduction because the surface lattice oxygen has improved mobility via Ba 2+ substitution in LaAlO 3 . Therefore, Pd/La 0.9 Ba 0.1 AlO 3- δ have high activity for NO reduction, even at low temperatures in a humid condition.