Sintering-resistant, highly thermally stable and well-dispersed Pd@CeO₂/halloysite as an advanced three-way catalyst

The high thermal stability of halloysite (H)-supported core-shell Pd@CeO₂ endowed it with promising catalytic performance and superior sintering resistance as a three-way catalyst. In this work, the synthesis of Pd@CeO₂ nanoparticles with various shell thicknesses was performed, and the properties of the shell and support were examined. From the results, the Pd@6CeO₂/H catalyst (Ce/Pd = 6) without any pretreatment or activation was achieved with a well-dispersed and optimal shell thickness of Pd@6CeO₂ nanoparticles to inhibit sintering and aggregation via electrostatic attractions with halloysite. Moreover, the halloysite support imparted thermal stability for enhanced catalytic stability under long-term and high-temperature reaction conditions compared with Pd@6CZ/H (cerium-zirconium shell) and Pd@6CeO₂/Al₂O₃ catalysts. To further ascertain the electronic effect on halloysite, Pd@6CeO₂/H-12 (halloysite solution at pH = 12) was prepared. The results showed that Pd@6CeO₂/H-12 enhanced the catalytic activity and decreased the light-off temperature compared with the other studied catalysts, and these results were attributed to the high content of Ce³⁺ and oxygen vacancies and the strong interaction between Pd@6CeO₂ and halloysite, making it a promising three-way catalyst.