Thermally stable Pd/CeO@SiO with a core-shell structure for catalytic lean methane combustion.

Noble metal catalysts exhibit high catalytic activity in lean CH combustion at low temperatures. However, the high surface energy of noble metal nanoparticles makes them susceptible to deactivation due to migratory-aggregation during the catalytic process. Herein, a core-shell structure with a Pd/CeO core and a SiO shell (denoted as Pd/CeO@SiO) was designed and prepared to enhance the thermal stability for catalytic lean CH combustion. A series of characterization methods demonstrated the successful encapsulation of SiO and the modified thermal stability. The results of activity tests indicated that Pd/CeO@SiO exhibited the optimal catalytic performance. After seven runs, Pd/CeO@SiO achieved 90% conversion of CH at 385 °C compared to Pd/CeO at 440 °C. The remarkable catalytic performance was attributed to the synergistic effect of strengthened metal-support interactions and the core-shell structure. On the one hand, the migration and aggregation of Pd nanoparticles were limited due to the protection of the SiO shell layer. On the other hand, the SiO shell layer further enhanced the interactions between the Pd nanoparticles and CeO, thus promoting the formation of PdCeO solid solutions and active oxygen species, which were beneficial for the improvement of the stability and redox capacity of the catalyst.