Preparation And Application Of Cellulose Nanocrystals-viologen Electrochromic Devices

Cellulose nanocrystals are a kind of nanoscale biomass material with high strength,high modulus,degradable,good transparency and environment-friendly.It has a wide range of sources and a variety of preparation methods.With the improvement of people's awareness of environmental protection,it is worthwhile to promote the use of green and environmentally friendly methods to extract and prepare cellulose nanocrystals.In addition,cellulose nanocrystals can be used as a base material,and can be applied to electronic fields such as solar cells,super capacitors,electrochromic devices,or energy storage and the like.In this paper,inorganic acid,phosphotungstic acid,which can be recovered and reused without corrosion of the instrument,was used to prepare cellulose nanocrystals suspension P-CNC with a high yield of 56%,and compared with the suspension S-CNC prepared by sulfuric acid.The former has a significantly higher thermal stability and crystallinity than the latter,but its dispersibility is not good.Therefore,we used the sodium carboxymethyl cellulose to modify the P-CNC to improve the dispersion stability.And we obtained film material with high strength and toughness.The cellulose nanocrystals suspension prepared by using sulfuric acid is mixed with different alkyl viologens,naturally volatilized into a film,and we then added with electrolyte potassium chloride and assembled with conductive glass coated with ITO.The devices have fast response and high optical contrast.Multi-color electrochromic devices are expected to have great application prospects in fields such as photochromic mirrors.Based on the previous work,we prepared a cellulose nanocrystalline-polyviologen electrochromic thin-film electrode.The difference between the electrochromic device of the cellulose nanocrystalline-viologen composite membrane is that it does not use a sandwich structure with two conductiveglass intermediate clips,electrochromic thin film and an electrolyte,but a conductive glass with composite film is used as a working electrode,a Ag/AgCl electrode is used as a reference electrode,a platinum wire is used as a counter electrode,an electrochemical workstation and UV spectrophotometer were used together to measure the change of absorbance with wavelength under different voltages.And the effects of different ratios of cellulose nanocrystals and polyviologen on its electrochemical performance were investigated.