Silver Electrochromic Device Based On Eutectic Solvent

Electrochromism(EC)is the phenomenon by which reversible optical changes are induced by electronic energy and resulting electrochemical redox reactions of materials.The obtained color changes are based on a change in the electronic state of a material caused by electron transfer between the EC material and an electrode.Recently,many inorganic EC materials have emerged.EC material uses the reversible electrodeposition of metals,such as Ag,Bi,Cu,Ni,and Pb.In the system,the reduction of metal cations which dissolved in solution results in deposition of metal particles or films on a transparent electrode and lead to its colored state.For most electrochromic devices(ECD),having simple sandwich-type structure consisted of the electrolyte,electrodeposition components,and a pair of transparent electrodes.When the voltage is applied to the electrodes,the metal element which dissolved in the electrolyte will be reduced and deposited on the electrode surface.This thin film of metal depostied on the transparent electrode caused the color or transparency change.On the contrary,the deposited metal will be dissolved again into the electrolyte upon reverse voltage.These EC materials compared with traditional devices offer many advantages,including low operation voltages,memory effects,and high visibilities under sunlight.Therefore,inorganic EC materials are expected to achieve promising applications in information displays like electronic paper and other low information display devices,or in light-modulating devices like light shutters,smart windows and variable reflectance mirrors.In the category of green chemistry,solvent occupies a crucial position.As a green medium must meet the following conditions:raw materials easy to get,no toxicity,low cost and biodegradable.Ionic liquid have the advantages of low vapor pressure,non flammability,good conductivity and solubility.But they have some problems such as complex synthesis and high production cost.Therefore,it isnecessary to develop a new kind of solvent which can combine the excellent physical and chemical properties of ionic liquids with degradable materials.It is possible to improve the overall performance of electrochromic devices by the application of eutectic solvent or eutectic solvent gel electrolyte.The attempt to modify electrodes at the molecular level began in the 1960 s and early 1970 s.F.C.Anson of California Institute of Technology studied the electrochemical behavior of a large number of coordination compounds.From then on,electrochemists began a set of rules for the preparation and control of surface materials on electrodes.At present,it has been widely used in analytical chemistry,electrocatalysis,battery electrodes and so on.Because of the small particle size,nano-platinum has many specificities.Because of its good chemical stability and excellent catalytic performance,nano-platinum has become one of the most attractive nano-materials in recent years.In this paper,electrochromic devices were prepared by using low eutectic solvent made as electrolyte,silver as main electrochromic material and copper as additive.Then,copper ion was added as the reactant of the device to reduce the working voltage and increase the working life of the device.Nano-platinum was deposited on ITO surface by pulse potential method,and nano-platinum modified electrochromic devices were obtained.The results show that the electrochromic device with copper as the electrode reaction material can effectively reduce the working voltage from-2.5V to-0.7V,and has more stable performance and longer cycle life.The ITO electrode modified by nano-platinum can effectively advance the initial reduction potential from-0.7V to-0.15 V in the three-electrode system without adding colored copper additives,so that the device is transparent as a whole.