New insights into the effect of morphology on catalytic properties of MnOx-CeO2 mixed oxides for chlorobenzene degradation

We synthesized four CeO2-MnOx mixed oxides with different morphologies using simple hydrothermal methods. The catalytic activity for chlorobenzene (CB) degradation decreases in the following order: rod-CeO2-MnOx > plate-CeO2-MnOx > polyhedra-CeO2-MnOx > cube-CeO2-MnOx. CeO2 and MnOx in the mixed oxides are highly dispersed and two new phases of both todorokite (S.G.: P2/m:b) and vernadite (S.G.: I4/m) with a special tunnel-like structure are found. Both rod-CeO2-MnOx and plate-CeO2-MnOx exhibit increased lattice microstrains generated from lattice distortion and defects; further, there are more oxygen vacancies and more MnOx (Mn4+ and Mn2+) species on the surface, particularly when compared to cube-CeO2-MnOx. Therefore, this promotes deeper oxidation activity for CB. Moreover, the strong interaction between CeO2 and MnOx also promotes the redox ability of CeO2-MnOx mixed oxides, while their oxygen storage capacity (OSC) properties are not only intrinsic to their structures but also limited to their surfaces and by their particle sizes.