Polymer-templated synthesis of hollow Pd-CeO2 nanocomposite spheres and their catalytic activity and thermal stability

Developing methods for the fabrication of active and thermally stable noble metal/metal oxide nanomaterials are very important for catalysis and material fields. Herein, we used a polymer-template synthesis approach to prepare hollow Pd-CeO2 nanocomposite spheres (NCSs) with Pd nanoparticles evenly distributed inside the CeO2 shell, in which the aggregation of Pd nanoparticles can be well inhibited with the help of the protection of CeO2 nanocrystallites even after being calcined at 700 degrees C. The Pd nanoparticles are partially buried in the CeO2 shell and the surface Pd species are highly ionic, which is caused by the electron exchange at the Pd-CeO2 interface during calcination. This hollow structure Pd-CeO2 nanocatalyst shows excellent catalytic activity and stability in the aqueous selective reduction of 4-nitrophenol and gaseous CO oxidation. For the selective reduction of 4-nitrophenol, the reaction rate of this h-Pd-CeO2 NCS catalyst compared to those of the supported Pd/CeO2 and physically mixed Pd + CeO2 catalysts is almost 14 times and 5 times faster, respectively. For the CO oxidation, the larger Pd-CeO2 interface in h-Pd-CeO2 NCSs could facilitate the reaction between the adsorbed CO and O-2, thus showing better low temperature activity. This paper emphasizes the advantages of a core-shell hollow structure and provides a new way for obtaining novel functional nanocatalysts.