Study On Preparation And Properties Of MnO_x-TiO₂ Composite Films

In this thesis,the MnO2-TiO2 nanotube array composite films were prepared by a one-step redox-precipitation method.Morphologies,crystal structures,elemental valence states,and supercapacitor performances of the samples were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?,and electrochemical analysis,and the effects of preparation conditions on the morphologies and electrochemical properties of composite films were studied.Then the influences of three methods for depositing a layer of TiO2 on the surface of MnO2-TiO2composite film,adding different concentrations of MnSO4 and KMnO4 in electrolyte on the cycle stability of the composite films were investigated.Mn-doped TiO₂ nanotube array films were obtained by an anodisation method.The effects of different electrolytes of LiCl,NaCl,KCl,and NH₄Cl on the electrochemical properties of the Mn-doped TiO₂ nanotube array films and MnO2-TiO2 composite films were studied in detail.1.The MnO2-TiO2 nanotube array composite films were fabricated by a one-step redox-precipitation approach.The effects of the temperatures of KMnO4 solution,the concentrations of MnSO4 solution and calcination temperatures,etc.on the morphologies and electrochemical properties of the composite films were investigated by changing the preparation conditions.The optimal conditions of MnO2-TiO2 nanotube array composite films were optimized through experiments.Both the charge-discharge performances and cycling performances of MnO2-TiO2 composite films obtained under the optimal conditions were studied.The capacitance value of the composite films reached 31.11 mF/cm² at a current density of 1.0?A/cm² and the capacitance retention value was 85.31%after 1,000cycles.2.The water solubility of Mn²⁺would lead to the loss of MnO₂ on the surface of MnO₂-TiO₂ composite films during the charge-discharge processes,and the decrease of capacitance retention value.In order to solve the problem of the loss of MnO₂ and further improve the cycle stability of MnO₂-TiO₂ nanotube array composite films,the cycle properties of MnO2-TiO2 composite films were improved in different degrees by depositing a layer of TiO₂ on the surface of MnO₂-TiO₂ composite films,adding different concentrations of MnSO4 and KMnO4 in Na2SO4 electrolyte.3.Mn-doped TiO₂ nanotube array films were successfully obtained by an anodisation method.The cyclic voltammetry and galvanostatic charge-discharge tests of Mn-doped TiO₂ nanotube array films and MnO₂-TiO₂ composite films were carried out in the electrolytes of LiCl,NaCl,KCl and NH₄Cl,respectively.The results show that the electrochemical properties of Mn-doped TiO₂ nanotube array films were mainly affected by the size of the cation radius,and the capacitance performances of Mn-doped TiO₂ nanotube array films were best in LiCl electrolyte.The electrochemical properties of the MnO2-TiO2nanotube array composite films were mainly affected by the interaction between cationic and manganese oxygen anion groups,and the capacitance performances of MnO2-TiO2nanotube array composite films were best in NaCl and KCl electrolytes.