Mild Strategy to Fabricate MnxCo3-xO4 Multi-Shelled Hollow Spheres with Superior Catalytic Property in CO Oxidation

Complex hollow structures of transition metal oxides, especially Co3O4-based mixed metal oxides, exhibit promising catalytic performances for CO oxidation and electro-catalysis. However, it still remains a challenge to synthesize hollow nanostructures with complex shell structures under mild and green conditions. Herein, a facile approach was developed to synthesize the MnxCo3-xO4 multi-shelled hollow spheres, involving the penetration of Mn(II) and Co(II) ions into the carbonaceous spheres and the subsequent calcination in air with a low heating rate. The formation of the unique multi-shelled hollow structures is based on a heterogeneous contraction process caused by non-equilibrium heat treatment. Characterization techniques such as SEM, TEM, XRD, Raman, BET, XPS, and H-2-TPR were used to measure the physicochemical properties and correlate the structure-activity properties of the resulting MnxCo3-xO4 sample. Catalytic results indicated that the as-prepared MnxCo3-xO4 sample exhibited impressive catalytic properties for CO oxidation in comparison to pure Co3O4 with the similar morphology and structure. The enhancement of the catalytic activity could be ascribed to the high special surface area, large pore volume and the synergistic interaction between the redox couples of Mn3+/Mn4+ and Co2+/Co3+. Importantly, the synthesis method can be easily extended to fabricate other metal oxides multi-shelled hollow spheres, such as ZnxCo3-xO4.