Synthesis And Electrochromic Properties Of Porous Tungsten Oxide Films

Tungsten trioxide is considered as a typical inorganic electrochromic material.With the rapid development of research, tungsten trioxide film show itsapplication in smart window, rearview mirror and so on. What’s more, it’s aoutstanding candidate for dye-sensitized solar cell, hydrogen generator, methanolsensor and hydrophilic-hydrophobic switchable material. In this work, tungstentrioxide film is prepared by electrodeposition. With electrochemical lithiation/delithiation method, the film is further modified. Optical measurement andelectrochemical test are used to investigate the electrochromic and diffusionproperties.The balance between peroxopolytungstic acids and tungstic acid isinvestigated for dense film. This balance can also be broken with the decreasingof hydrogen peroxide. At the meantime, colloid particles are aggregated for theporous film at the surface of ITO glass. Electrodeposition is controlled frombalance to colloid. As a result, the film is consisted with double structure. EDS,XRD and SEM are carried out for the details of the film.In different kind of electrolytes, optical measurement is performed underconstant current in situ. Spectrum analysis is based on color center module,which is proved in photochromic behavior. Fitting the curve with GaussEquitation, two different kinds of color center can be distinguished. Comparedwith the photochromic phenomena, electrochromic can also be explained by thebasic hypothesis. It is interesting that the insertion of hydrogen and lithium havesomething in common.Electrochemical test is regarded as the main method to evaluate the diffusionof hydrogen in tungsten trioxide film. With the increasing of scan rate in cyclicvoltammetry, two bleach current peak overlap with each other. This is inaccordance with the optical density change in the process of electrochromism.The film is further modified with microporous surface with electrochemicallithiation/delithiation method. It helps the film with the improvement of surfacearea and the active site for hydrogen. In this respect, tungsten trioxide film havea bright future with better electrochromism and diffusion.