Research On Shape-Controllable Synthesis And Electrochemical Properties Of Nano-structured Manganese Oxides

Manganese oxide nanomaterials with good molecular ionexchange/adsorption, electrochemical and catalytic properties have attracted greatinterests of chemistry and materials workers. How to reasonably control of materialstargeted growth and farther achieve the controllable synthesis of their shape,composition and crystal structure and the properties are of great significance for deeplyresearching the relationship between morphology and properties and eventualrealization of the controllable synthesis of nanomaterials. Useful explorations havebeen done on the development of new synthesis method, synthesis of the manganeseoxide nanomaterials with new uniform morphology, and research of formationmechanism and electrochemical properties of nanomaterials.This thesis mainly consists of three sections, introduction, experiments andconclusion. Introduction part (Chapterâ… ) discussed the crystal structure of manganeseoxides, shape controllable synthesis status, development trends, and application areasof manganese oxide nanomaterials. The main research purpose was also indicated.Various nano-structured manganese oxides have been synthesized using layeredNa-type birnessite manganese oxide and potassium permanganate as starting materialsin experimental part, respectively (Chapterâ…¡, Chapterâ…¢). Meanwhile, a newsynthesis method for nanomaterials has been developed. In addition, the crystal growthmechanisms and electrochemical properties of the obtained manganese oxidenanomaterials have been researched based on above. The research conclusion isdescribed in Chapterâ…£.Hydrothermal and new controllable synthesis methods of manganese oxidenanomaterials are described in Chapterâ…¡, with layered Na-type birnessite manganeseoxide as precursor. A variety of manganese oxide nanomaterials with differentmorphologies have been synthesized by hydrothermal treatment and surging reactionapproaches on the basis of in-depth analysis of the manganese oxide crystal structures.Various nano-structured manganese oxides, including the tetragonous nanorods,semi-nanotubes, nanorolls, layered microspheres, nanowires bundles morphologies,have achieved the controllable synthesis with water as solvent by changing reaction parameters, such as temperature, time, and the acidity of the solutions. A "phasetransformation-anisotropic growth" mechanism for tetragonous nanorods and a rollingrice glue ball formation mechanism for layered microspheres have been studied andproposed. The structure and the electrochemical performance of all the synthesizedmanganese oxide nanomaterials have been characterized by XRD, DSC-TGA, SEM,TEM, IR, AAS, elemental analysis and cyclic voltammetry means. The resultsindicated that manganese oxides could show different shapes due to the differentcrystal growth mode, and their electrochemical properties have relationship withcrystal structure, morphology and the average oxidation of manganese oxides.Nanowire bundles manganese oxide modified glass carbon electrode has beenconducted a number of cyclic voltammetry scan in testing drugs (acetaminophentablets). The results showed that manganese oxide modified electrode could improvetest signals three times compared with the bare electrode, and potential negative shiftwas up to 200 mV vs. Ag electrode. All these results indicate that manganese oxidenanomaterials have good electrochemical and catalytic properties.The controllable synthesis of manganese oxide nano-materials with differentmorphologies was described in Chapterâ…¢, with KMnO₄ as raw. Based on thecharacteristics of the structure growth, manganese oxides with flower microspheresand cryptomelane nanobelts shapes have been controllably synthesized usinghydrothermal treatment potassium permanganate solutions on the optimized reactionconditions. Their crystal growth mechanisms and electrochemical properties wereinvestigated. The structural characterization and electrochemical performance ofsynthesized manganese oxide nanomaterials were conducted by XRD, DSC-TGA,SEM, TEM, AAS, N₂ adsorption and cyclic voltammetry. Research shows that themorphology of the obtained materials is closely connected with the reactiontemperature and time; the crystal structures and shapes of obtained manganese oxidenanomaterials affect their electrochemical properties.By developing new synthesis methods for functional manganese oxidenano-materials, a series of manganese oxide nanomaterials with different morphologieshave been controllably synthesized. Various new shapes of manganese oxidenanomaterials enrich the species and research contents, which build a foundation forpromoting controllable synthesis methods and applying materials in catalysis,adsorption and electrochemical areas.