| In recent years,the demand for economic and environmental-friendly energy storage devices with high performance is increasing due to the energy crisis and environmental pollution problems.As an important component of sustainable energy system,supercapacitor has aroused great research interest.Polyoxometalates have shown excellent performance in the field of electrochemical storage owing to their reversible redox property and ability to transfer electrons rapidly.The introduction of polyoxometalate into materials with good electrical conductivity can result in the formation of polyoxometalate functionalized composite,which is expected to effectively improve the conductivity and electrochemical storage performance of polyoxometalate.In this dissertation,polyoxometalate-based composites are prepared by liquid-phase approaches,including phosphomolybdic acid/polypyrrole/metal-organic framework,porous carbon/vanadium sodium phosphate and K-birnessite/polyaniline/vanadium potassium phosphate composites.The structure,morphology and chemical composition of the prepared electrode materials are characterized by various measurements including X-ray diffraction,Fourier-infrared spectroscopy,nitrogen adsorption-desorption measurement,scanning electron microscopy,transmission electron microscopy,energy dispersive X-ray spectroscopy,and X-ray photoelectron spectroscopy.Cyclic voltammetry,galvanostatic charge-discharge test and electrochemical impedance spectroscopy are applied to study the electrochemical storage performance of the prepared electrode materials.Electrochemical results show that the when 0.03 g phosphomolybdic acid is introduced into the preparation process,the resulted phosphomolybdic acid/polypyrrole/metal-organic framework composite as electrode material exhibits better electrochemical storage performance,which possesses wider prospect in practical application of supercapacitor.Besides,when porous carbon material and vanadium sodium phosphate are combined in a mass ratio of 5:1,the resulting composite shows enhanced electrocapacitive performance,as well as good rate performance and cycle stability.Furthermore,composite combined by birnessite/polyaniline and vanadium potassium phosphate in the mass ratio of 10:1 owns better electrochemical storage behavior.The results indicate that the amount of polyoxometalates can affect the electrochemical performance of the composites,and suitable amount of polyoxometalate can significantly improve the electrocapacitive performance of composite,indicating that polyoxometalates possess great application prospects in the field of electrochemical storage. |
