Synthesis of Dispersible Pd@CeO2 Core-Shell Nanostructures by Self-Assembly

A methodology is described for the preparation of Pd @ CeO2 core-shell nanostructures that are easily dispersible in common organic solvents. The method involves the synthesis of Pd nanoparticles protected by a monolayer of 11-mercaptoundecanoic acid (MUA). The carboxylic groups on the nanoparticle surfaces are used to direct the self-assembly of a cerium(IV) alkoxide around the metal particles, followed by the controlled hydrolysis to form CeO2. The characterization of the nanostructures by means of different techniques, in particular by electron microscopy, allowed us to demonstrate the nature of core-shell systems, with CeO2 nanocrystals forming a shell around the MUA-protected Pd core. Finally, an example of the use of these nanostructures as flexible precursors for the preparation of heterogeneous catalysts is reported by investigating the reactivity of Pd@CeO2/Al2O3 nanocomposites toward CO oxidation, water-gas shift (WGS), and methanol steam reforming reactions. Together with CO adsorption data, these observations suggest the accessibility of the Pd phase in the nanocomposites.