Facile synthesis of hierarchical Mn₃O₄ superstructures and efficient catalytic performance

The development of novel materials with excellent performance depends not only on the constituents but also on their remarkable micro/nanostructures. In this work, manganese oxide (Mn₃O₄) hausmannite structures with a uniform three-dimensional (3D) flower-like hierarchical architecture have been successfully synthesized by a novel chemical route using surfactants as structure-directing agents. Microstructure analysis indicates that the obtained 3D flower-like Mn₃O₄ superstructure consists of a large number of two-dimensional (2D) Mn₃O₄ nanosheets, which is different from the reported 3D Mn₃O₄ hierarchical structures based on zero-dimensional nanoparticles or one-dimensional nanowires and nanorods. This 3D Mn₃O₄ hierarchical architecture provides us with another type of manganese oxide with different superstructural characteristics, which may have potential practical applications in the catalytic degradation of organic pollutants. The catalytic performance of this hierarchical Mn₃O₄ superstructure, which was prepared by three different types of structure-directing agents, including cetyltrimethylammonium bromide (CTAB), poly(vinylpyrrolidone) (PVP), and poly(ethylene oxide)-poly(propylene oxide) (P123), was evaluated for the catalytic degradation of organic pollutants, e.g. methylene blue. Interestingly, the hierarchical Mn₃O₄ superstructure prepared using CTAB as a template showed efficient catalytic degradation. The formation processes and possible growth mechanism of this novel 3D Mn₃O₄ hierarchical superstructure assembled by 2D Mn₃O₄ nanosheets are discussed in detail.