Structural Stability of Pd-Perovskite Catalysts after Heat Treatment Under Redox Condition

Abstract

We have reported that the Pd-perovskite catalyst regenerates itself through the solid solution and segregation of Pd in and out of the perovskite crystal during the inherent fluctuation of engine exhaust gases. We named this innovative ceramic the “intelligent catalyst.” In this study, the structural stability and the catalytic activity of Pd-perovskite catalysts such as LaFePdO3, LaCoPdO3 and LaMnPdO3 prepared by the alkoxide method are compared. Although it was reported that the catalytic activity of perovskite catalysts without Pd is, in the order, LaCoO3>LaMnO3»LaFeO3, the catalytic activity of perovskite catalysts containing Pd after heat treatment under redox conditions was superior and in the order LaFePdO3»LaMnPdO3>LaCoPdO3. It was confirmed that the LaFePdO3 catalyst's superior catalytic activity was due to a highly efficient suppression of particle growth. We found out that the structural stability of perovskite crystal was the key to suppressing the particle growth of Pd, and thereby maintaining the catalytic activity of Pd-perovskite.