Preparation And Electrochemical Storage Properties Of Carbon/Heteropoly Acid-Derived Materials

The development of new energy can effectively alleviate the consumption of non-renewable energy,and high-performance electrical storage equipments are usually used to store and convert renewable energy.Supercapacitors,which possess the advantages including long cycle capability,low cost and high power density,can release and deliver stored energy at high power densities.Carbon materials can be combined with materials like heteropoly acid to fabricate nanocomposite with prominent electrochemical performance.The composites can be applied as electrode materials for supercapacitors,which are promising to effectively solve the problems including the poor capacitive property and low conductivity of single component.In this thesis,nitrogen-doped carbon microsphere/heteropoly acid composites,bismuth vanadate/graphene/phosphotungstic acid and manganese dioxide/graphene/phospho-tungstic acid nanocomposites are prepared by simple chemical methods.The morphology of the composites is analyzed by scanning electron microscopy and transmission electron microscopy.The chemical composition is examined by energy dispersive X-ray spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,Fourier-infrared spectroscopy and Raman spectroscopy.The electrochemical storage properties of the composites are further investigated by measurements like galvanostic charge and discharge test and cyclic voltammetry.Results show that the composite composed of phosphotungstic acid and nitrogen-doped carbon microspheres with a mass ratio of 1:10 shows the best electrichemical storage performance,which exhibits a specific capacitance of 436.3 F g^-1 at a current density of 0.2 A g^-1.The bismuth vanadate/graphene/phosphotungstic acid composite with the mass ratio of 1:3:0.2 possesses the best performance.The specific capacitance can reach 673.6 F g^-1 at a current density of 2 A g^-1.Besides that,the composite composed by phosphotungstic acid,manganese dioxide and grapheme with a mass ratio of 1:5:5 also owns high specific capacitance and well-performed stability.Results show that the introduction of heteropoly acid can significantly enhance the electrochemical storage properties of the composites,which enables the prepared nanocomposites to possess promising prospect in supercapacitor applications.