Of Manganese Oxide Prepared By Sol - Gel Aerogel And Capacitance Properties Research

Because manganese oxide materials have low cost, low toxicity, environmental safety, as well as variable structure, they have been widely used in ion-exchange, molecular absorption, catalysis, and electrochemical supercapacitor. Although there are many advantages, manganese oxide materials also show some drawbacks such as poor electronic and ionic conductivity, low surface area and dissolution problem in their application. In order to overcome these drawbacks, many studies on the fabrication and functionalization of maganese oxides with different structures and morphlogies have been carried out. In this thesis, Mn3O4and NiMn2O4nanomaterials with large surface area and mesopore characteristic are prepared though sol-gel process and followed by calcining treatment. Meanwhile, the obtained Mn3O4and NiMn2O4nanomaterials are characterized and their capacitance is investigated.This thesis mainly consists of three sections, reviewer, experiments and conclusion. Introduction part (chapter1) reviews the structure, classfications, the formation and drying of the gel, the preparation method and application of manganese oxides Experiment section (chapter2,3) consists of the fabrication, characterization and property of Mn3O4and NiMn2O4nanomaterials with large surface area and mesopore characteristic. Mn(NO3)2-6H2O is used as precursor and epoxide is used as gelation agent, the maganese oxide aerogel has been firstly prepared though sol-gel technology and then combined with supercritical drying. MnO4nanomaterial with large surface area and mesopore characteristic is prepared by calcining the maganese oxide aerogel at different temperature and its capacitance is investigated in chpter2. The nickel maganese oxide aerogel has been prepared via the same method, and NiMn2O4nanomaterial with large surface area and mesopore characteristic is prepared by calcining the nickel maganese oxide aerogel at different temperature and its capacitance is investigated in chpter3. And the conclusion and the advices for the study is conclused in chapter4.(1) Mn(NO3)2-6H2O is used as precursor and epoxide is used as gelation agent, the maganese oxide aerogel has been firstly prepared though sol-gel technology and then combined with supercritical drying. Mn3O4nanomaterial with large surface area and mesopore characteristic is prepared by calcining the maganese oxide aerogel at300℃ for5hours. The N2adsorption/desorption results show that Mn3O4nanomaterial has a specific surface area of106m2/g with a mesoporous structure. The electrochemical property is characterized by cyclic voltammetry in1mol/L Na2SO4electrolyte. The Mn3O4nanomaterial shows an ideal capacitive behavior, and its initial capacitance value is209F/g at a scan rate of5mV/s. The capacitance of Mn3O4nanomaterial connects with the scan rate, and the values are respectively209F/g,194F/g,144F/g, and109F/g at a corresponding scan rate of5mV/s,10mV/s,20mV/s, and50mV/s.(2) Mn(NO3)2·6H2O and Ni(NO3)2·6H2O are used as precursor and epoxide is used as gelation agent, the nickel maganese oxide aerogel has been firstly prepared though sol-gel technology and then combined with supercritical drying. NiMn2O4nanomaterial with large surface area and mesopore characteristic is prepared by calcining the nickel maganese oxide aerogel at300℃for5hours. The N2adsorption/desorption results show that NiMn2O4nanomaterial has a specific surface area of201m2/g with a mesoporous structure and a suitable pore size around8-10nm. The electrochemical property is characterized by cyclic voltammetry both in1mol/L Na2SO4electrolyte and9mol/L KOH electrolyte. The prepared NiMn2O4material not only exhibits an ideal capacitive behavior, but also shows good cycling stability in a neutral electrolyte, and its initial capacitance value is243F/g at a scan rate of5mV/s. The initial capacitance value of98%can be maintained after5000cycles of the operation. In addition, although NiMn2O4material shows a large capacitance in9mol/L KOH electrolyte in compare with that in1mol/L Na2SO4electrolyte at the same scan rates, a relative poor cycling stability is observed due to the dissolution of NiMn2O4material in KOH electrolyte(3) Sol-gel process combined with supercritical CO2drying is one of the effective methods to prepare the maganese oxide areogels with large surface aera, mesoporous structure and different morphology.