Catalyst for auotomotive emissions control in next generation; Relation of the intelligent property to its structure

Mizuki, Junichiro; Nishihata, Yasuo; Tanaka, Hirohisa*

We use X-ray diffraction and absorption to show that the perovskite-based Pd catalyst retains its high metal dispersion owing to structural responses to the fluctuations in exhaust-gas composition that occur in state-of-the-art petrol engines. We find that as the catalyst is cycled between oxidative and reductive atmospheres typically encounttered in exhaust gas, Pd reversibly moves into and out of the perovskite lattice. This movement appears to suppress the growth of metallic Pd particles, and hence explains the retention of high catalytic activity.