Inhibition of Metal–Support Interactions by Rare-Earth Doping in Palladium/Ceria Zirconia Three-Way Catalysts

Abstract

The impact of rare-earth (RE) doping in ceria-zirconia─critical for enhancing thermal stability and optimizing redox properties─on surface palladium (Pd) behavior has been investigated. RE doping was found to weaken metal–support interactions, leading to increased Pd mobility, with notable effects on oxygen storage capacity and light-off performance under model exhaust conditions. The mobility and redox characteristics of Pd were assessed through in situ thermal experiments using X-ray absorption spectroscopy at the Pd K-edge and synchrotron powder diffraction. Complementary Ce K-edge EXAFS and Rietveld refinements confirmed the structure and composition of the doped ceria-zirconia material. Deactivation studies and lifetime prediction are essential for commercial catalysts, particularly for three-way catalysts (TWCs) designed for decade-long operation. To probe long-term stability, in situ thermal treatments were conducted to induce separation of the metastable ceria–zirconia solid solution. These accelerated thermal aging treatments were then compared with a prolonged, seven week aging protocol, and regular in situ synchrotron PXRD measurements provided insights into the phase separation process. The influence of thermal aging on metal–support interactions was further assessed through catalytic performance testing.