A Multi-Yolk-Shell Structured Nanocatalyst Containing Sub-10nm Pd Nanoparticles in Porous CeO2
- 萨本栋－已发表论文 
The fabrication of catalytically stable nanocatalysts containing fine noble metal nanoparticles is an important research theme. We report a method for the synthesis of a hierarchically structured Pd@hm-CeO2 multi-yolk-shell nanocatalyst (h=hollow; m=mesoporous) containing sub-10nm Pd nanoparticles from pre-made hydrophobic Pd nanoparticles. In the developed method, monodisperse hydrophobic Pd nanoparticles are first reacted with an iron oxide precursor iron(III) acetylacetonate to allow the deposition of iron oxide on their surface. In a Brij56-water-cyclohexane reverse micelle system, the surface growth of iron oxide is found to mediate and, thus, facilitate the encapsulation of hydrophobic Pd nanoparticles in SiO2 to yield Pd-Fe2O3@SiO2 nanoparticles in a high concentration. After removal of Fe2O3 by acid, the obtained Pd@SiO2 core-shell particles are reacted solvothermally with Ce(NO3)3 in an ethylene glycol-water-acetic acid mixture to produce multi-core-shell Pd@SiO2@m-CeO2 nanospheres. In each multi-core-shell Pd@SiO2@m-CeO2 nanosphere, several Pd@SiO2 particles are separately embedded in mesoporous CeO2. After selective removal of silica by NaOH, Pd@SiO2@m-CeO2 nanospheres are transformed into the multi-yolk-shell Pd@hm-CeO2 nanocatalyst. Even with a low Pd loading at 0.4wt%, the as-prepared multi-yolk-shell Pd@hm-CeO2 nanocatalyst displays high catalytic activity in CO oxidation with 100% CO conversion at 110掳C. In comparison, under the same catalytic conditions, the same amount of the same-sized Pd nanoparticles supported on SiO2 achieves 100% CO conversion at 180掳C. More importantly, the multi-yolk-shell structure of the Pd@hm-CeO2 nanocatalyst significantly enhances the stability of the catalyst. No loss in catalytic activity was observed on the Pd@hm-CeO2 nanocatalyst treated at 550掳C for six hours. The Pd@hm-CeO2 nanocatalyst also exhibited excellent catalytic performance and stability in the aerobic selective oxidation of cinnamyl alcohol to cinnamaldehyde. 漏 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.