Studies On The Preparation And Properties Of NiO Film And NiO/TiO₂ Composite Film

Electroehromism is a phenomenon that materials can reversibly change their optical properties under an applied electric field. NiO electrochromic film can be applied to smart windows, display devices, non-glare glass and other optical devices, and in many fields such as information, electronics, construction and national defense. NiO electrochromic film is considered to be one of the most promising anodic electrochromic materials. However, NiO electrochromic film is far from large-scale application now and needs be deeply studied, especially in cycle life and response time. In this thesis, the electrochromic properties and microstructure of the NiO film prepared by electrodeposition method in ionic liquids were studied through a variety of technical means to explore the optimal preparation process. Then a new composite film, which has dual function of electrochromic and photocatalytic properties, was prepared by coating a layer of TiO2 on the NiO film using sol-gel method.Firstly, the preparation process of NiO film synthesized in choline chloride-urea ionic liquids by electrodeposition method was explored. It was proved that the preparation method is feasible by studying the electrochemical behavior of Ni2+in this system and analyzing the oxidation peak and reduction peak in cyclic voltammetry test of the chemical reaction.Then the preparation process of NiO film was optimized by adjusting the viscosity of ionic liquids, main salt concentration and deposition potential in the electrodeposition process in order to determin the appropriate electrodeposition process parameters. It was found that NiO film showed excellent properties when ionic liquid and anhydrous ethanol volume ratio was 1:2, concentration of nickel chloride was 0.2 mol L1 and the deposition potential was 3.9 V. The microstructure of the NiO film was observed by scanning electron microscope (SEM) and the elements composition of the NiO electrochromic film was obtained by energy dispersive spectrometer (EDS). The NiO film can maintain good electrochromic property after 8000th cycling in 0.5 mol L-1 KOH solution and its response time was approximately 0.11 s. All of the results revealed that NiO film prepared in choline chloride-urea ionic liquid system has improved cycle life and reduced response time.At last, the performance of composite film was tested. Scanning electron microscope (SEM) was used to observe the microstructure, and energy dispersive spectrometer (EDS) was used to get the element composition of the composite film. The thickness of TiO2 film is about 6 times of that of the NiO film. The electrochromic property of the composite film was compared with the NiO film and there has no significantly difference between them. Degradation of methyl orange solution proved that the composite film has photocatalytic performance. Different calcination temperature has obvious influence on the photocatalytic property of composite film. The best calcining temperature is 450℃. The composite film prepared in this temperature has the optimized photocatalytic property. The states (colored state, bleached stat and original state) of composite film have interesting effect on its photocatalytic activity.