Thermally stable Pd/CeO 2 @SiO 2 with a core-shell structure for catalytic lean methane combustion.

Noble metal catalysts exhibit high catalytic activity in lean CH 4 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 2 core and a SiO 2 shell (denoted as Pd/CeO 2 @SiO 2 ) was designed and prepared to enhance the thermal stability for catalytic lean CH 4 combustion. A series of characterization methods demonstrated the successful encapsulation of SiO 2 and the modified thermal stability. The results of activity tests indicated that Pd/CeO 2 @SiO 2 exhibited the optimal catalytic performance. After seven runs, Pd/CeO 2 @SiO 2 achieved 90% conversion of CH 4 at 385 °C compared to Pd/CeO 2 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 2 shell layer. On the other hand, the SiO 2 shell layer further enhanced the interactions between the Pd nanoparticles and CeO 2 , thus promoting the formation of Pd x Ce 1- x O 2- δ solid solutions and active oxygen species, which were beneficial for the improvement of the stability and redox capacity of the catalyst.