Development of manganese oxide based nanostructures by wet chemical methods for enhanced energy storage and photocatalytic applications

摘要

Owing to wide diversity of crystal forms, defect chemistry, morphology, porosity and textures, manganese oxides exhibit a variety of distinct electrochemical and dye degradation applications. This work mainly comprised of development of manganese oxide nanostructures via wet chemical approaches such as electrochemical deposition and solvothermal techniques. The impacts of deposition parameters of manganese oxides were studied in details to tune the morphology, crystallinity and electrochemical energy storage applications. Furthermore, a core-shell structure with copper oxides as core materials and manganese oxides as shells were designed with distinct morphologies for excellent photocatalyst applications.In the former part of this thesis, hausmannite Mn3O4 thin films were prepared for the applications of electrochemical capacitors (supercapacitors) by an effective, simple, and cost-effective strategy of electrochemical deposition approach. Various precursor concentrations and deposition durations were manipulated to tailor the surface morphologies of Mn3O4 nanostructures and to optimize their electrochemical performances. Supercapacitors with a large gravimetric specific capacitance and a good rate capability were successfully achieved. Moreover, a nanocomposite film based on Mn3O4/carbon foam was fabricated by utilizing the already developed optimized conditions and the capacitance was dramatically improved. In the later section of this work, different morphologies of Cu2O and porous Cu2O-Mn2O3 micro-nanocomposites (cubes, octahedras and 26-facet polyhedras) with core@shell structure were successfully fabricated via hydrothermal method. Furthermore, the photocatalytic activities of as-synthesized nanostructures were further studied by the decomposition of methyl orange and methyl blue under UV irradiation. The results indicated that the 26-facet polyhedral Cu2O-Mn2O3 composite expressed excellent photocatalytic activities.