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

摘要

We synthesized four CeO _(2) –MnO _( x ) mixed oxides with different morphologies using simple hydrothermal methods. The catalytic activity for chlorobenzene (CB) degradation decreases in the following order: rod-CeO _(2) –MnO _( x ) > plate-CeO _(2) –MnO _( x ) > polyhedra-CeO _(2) –MnO _( x ) > cube-CeO _(2) –MnO _( x ) . CeO _(2) and MnO _( x ) in the mixed oxides are highly dispersed and two new phases of both todorokite (S.G.: P 2/ m : b ) and vernadite (S.G.: I 4/ m ) with a special tunnel-like structure are found. Both rod-CeO _(2) –MnO _( x ) and plate-CeO _(2) –MnO _( x ) exhibit increased lattice microstrains generated from lattice distortion and defects; further, there are more oxygen vacancies and more MnO _( x ) (Mn ~(4+) and Mn ~(2+) ) species on the surface, particularly when compared to cube-CeO _(2) –MnO _( x ) . Therefore, this promotes deeper oxidation activity for CB. Moreover, the strong interaction between CeO _(2) and MnO _( x ) also promotes the redox ability of CeO _(2) –MnO _( x ) 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.