Design of a thermally resistant core@shell/halloysite catalyst with optimized structure and surface properties for a Pd-only three-way catalyst

Abstract

In this study, two types of core@shell nanoparticles, CeO2@Pd and inverse Pd@CeO2 nanoparticles, were synthesized by sequential deposition and electrostatic attraction-induced deposition method, respectively. Then, the core@shell nanoparticles supported on halloysite were thermally treated at different temperatures, and the nascent core@shell/H-x catalysts were characterized and evaluated for their three-way catalytic performance. During the thermal treatment (650 °C, 800 °C, and 1100 °C), the CeO2@Pd/H-x catalysts showed strong temperature sensitivity, resulting in aggregation of the active metal particles, degradation of the textural properties, and weak interactions between the active sites and support, accompanied by the deactivation of the three-way reaction. Remarkably, Pd@CeO2/H-800 exhibits excellent catalytic performance because it has an appropriate Pd-CeO2 interaction and high thermal stability, which effectively suppresses the encapsulation and aggregation of Pd@CeO2 nanoparticles and imparts a high content of Ce3+ species and oxygen vacancies and equivalent of Pd2+/Pd° ratio.