The rational design of sandwich-like MnO-Pd-CeO hollow spheres with enhanced activity and stability for CO oxidation.

The development of strategies for the facile fabrication of noble metal/metal oxide nanomaterials with high catalytic activity and thermal stability is very challenging in the field of catalysis and for other relevant applications. Herein, we report a delicate multi-assembly method to prepare sandwich-like MnO2-Pd-CeO2 hollow spheres wherein carbon spheres were employed as sacrificial templates. Typically, tiny Pd nanoparticles were deposited on the outer surface of the MnO2 shell, and the CeO2 overcoating served as a nanotrap to anchor the Pd particles on the MnO2 supports. The unique sandwich-like structure effectively prevents the Pd nanoparticles from aggregation during high-temperature calcination and catalyzation. The as-prepared MnO2-Pd-CeO2 hollow spheres exhibited enhanced stability and activity for CO oxidation. The excellent stability and activity exhibited by the as-synthesized MnO2-Pd-CeO2 hollow spheres can be ascribed to the sandwich-like structure and the strong synergistic effects between Pd and the hierarchical porous MnO2-CeO2 shell. We believe that this optimal structure design demonstrates a new approach for the synthesis of noble-metal-based catalysts with superior activity and stability.