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

Abstract

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 °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 O₂, 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.