Preparation And Properties Of The Polyoxometalates And Its Derivatives Of Electrochromic Composite Film

Polyoxometalate?POMs?also known as metal-oxygen cluster.Many of their properties are based on their molecular size,shape,charge density and reversible oxidation-reduction potential,and their huge structural diversity.Polyoxometalate has a variety of structure and good electrochemical reversibility.It has a wide application prospect in electrochromic field.In this paper,a composite film based on TiO₂ was prepared by using the isopolyacid[W₁₀O₃₂]^6-and a WO₃-TiO₂ electrochromic composite film was prepared by using the heteropolyacid[P₂W₁₇O₆₂]^11-as precursor.Their structures have been characterized by X-ray powder diffraction?XRD?,uv-vis spectrum analysis?UV-vis?,infrared analysis?IR?,scanning electron microscope?SEM?,atomic force microscope?AFM?and its electrochemical properties are studied.This paper is divided into four parts:The first chapter introduces the electrochromic material and its main preparation methods,briefly introduces the polyacid and its research progress,and explains the significance of this thesis.The second chapter mainly introduces that the porous W₁₀O₃₂-TiO₂electrochromic composite thin film has been prepared by the electrodeposition method.The advantages of electrochromic materials are discussed,and the electrochromic properties of composite films are studied systematically.At the wavelength of 50 nm,the penetration rate decreased from 98.0%to 50.8%when the applied potential was-0.8 V.It can also be observed in the process of discoloration with good reversibility and reproducibility.The porous structure of the composite thin film not only provides a large specific surface area for the W₁₀O₃₂ polyanion,but also facilitates the rapid diffusion of H⁺,which leads to high performance electrochromic film.The third chapter mainly introduces the selection of Dawson heteropolyacid[P₂W₁₇O₆₁]^10-as precursor,and the film of P₂W₁₇-TiO₂ is prepared by electrodeposition.WO₃-TiO₂ composite electrochromic films were further prepared by sintering under different temperatures.And the composite of the system is confirmed by XRD and SEM.We have successfully proved that the main component of the film is WO₃-TiO₂.The results showed that the compounds 1 and 2 showed good electrochemical performance and optical modulation in H⁺aqueous solution.The maximum optical contrast of compound 1 is 72%at the wavelength of 542 nm when the applied voltage is-1.2 V.The fourth chapter is the summary part.The properties of the two composite films of W₁₀O₃₂-TiO₂ and WO₃-TiO₂ are summarized in chapter 2 and chapter 3.