Preparation And Properties Of Long Cyclic Life Tungsten Oxide Electrochromic Nanofilm

Under the action of applied electric field,the optical properties（absorptivity and reflectance）of electrochromic materials can change reversibly.It has a wide application prospect in the fields of automobile anti-glare mirror,smart window and military camouflage.For electrochromic materials,WO₃ nanofilm has the characteristics of fast response speed,high optical contrast and high coloring efficiency.WO₃ nanofilm has been widely studied by people.But the structural stability of WO₃ nanofilm is existing some defects.The worse structural stability of WO₃ nanofilm leads to lowering its electrochromic cycle life and hindering its application.Therefore,it has great significance to prepare tungsten oxide electrochromic nanofilm which has long cycle life.In this paper,polydopamine（PDA）and rare earth samarium（Sm）are used to enhance the structural stability of WO₃ nanofilm,in order to obtain WO₃electrochromic nanofilm with long cycle life.The specific research contents are as follows:（1）Now the bond strength between WO₃ nanofilm obtained by one-step hydrothermal method and ITO electrode is not high,which results in the worse electrochromic cycle life.This study first should modify a layer of PDA on ITO glass electrode,and then deposit WO₃ nanofilm on PDA by one-step hydrothermal method,finally obtain hybrid PDA/WO₃ nanofilm.In order to obtain its microstructure,chemical composition,electrochemical properties and electrochromic properties,this work use characterization methods to study.It is found that dendritic WO₃ nanofilm can be prepared by one-step hydrothermal method at low temperature.PDA film enhances the bonding strength between ITO glass electrode and WO₃ nanofilm,which improves the cycle life of WO₃ electrochromic nanofilm.Among them,the hybrid PDA/WO₃ electrochromic nanofilm prepared by hydrothermal method 2 h can still retain 90.8%of its initial optical contrast after 5000 cycles.（2）Against the intrinsic structure stability of WO₃ nanofilm obtained by one-step hydrothermal method is not high,so that to improve the electrochromic cycle life of WO₃nanofilm by doping rare earth in this work.In this study,rare earth metal Sm³⁺is added into the reaction system,the Sm³⁺doped WO₃ nanofilm prepared by one-step hydrothermal method.In order to obtain its microstructure,chemical composition,electrochemical properties and electrochromic properties,this work use characterization methods to study.It is found that Sm³⁺doping could transform the microstructure of WO₃ nanofilm prepared by hydrothermal method from dendritic to nest porous structure.The structural stability of nest porous Sm³⁺doped WO₃nanofilm is higher than the dendritic WO₃ nanofilm.Therefore,the doping of Sm³⁺improves the electrochromic cycle life of WO₃ nanofilm.When the molar ratio of Sm to W is 1:25 in the hydrothermal reaction system,the electrochromic cycle life of Sm³⁺doped WO₃ nanofilm（WO₃-4%Sm）is the highest.It retains 73.6%of the initial optical contrast after 10000electrochromic cycles.（3）Before study found that the WO₃-4%Sm hybrid nanofilm has the lower optical contrast,slower response speed and worse coloring efficiency in lithium electrolyte.While in H⁺electrolyte,the WO₃-4%Sm hybrid nanofilm has high optical contrast,fast response speed and high coloring efficiency.But its electrochromic cycle life is not high.In view of the above contradiction,in this study,a layer of PDA film is modified on the surface of WO₃-4%Sm hybrid nanofilm,so that to prepare WO₃-4%Sm/PDA hybrid nanofilm.In order to obtain its microstructure,chemical composition,electrochemical properties and electrochromic properties,this work use characterization methods to study.It is found that PDA has strong adhesion and corrosion resistance,which can effectively enhance the electrochemical structure stability of WO₃-4%Sm hybrid nanofilm in H⁺electrolyte,so that to increase the electrochromic cycle life.Among them,the WO₃-4%Sm/PDA-1 h hybrid nanofilm has the highest cycle life.It retains the 89.9%of the initial optical contrast after 5000 cycles.In addition,the WO₃-4%Sm/PDA-1 h hybrid nanofilm has optical contrast of 68.4%at 633 nm and colored efficiency of 79.1 cm²/C.