| Electrochromism is a phenomenon in which the optical properties of the material occur stable and reversible color change under the applied voltage, there are some disadvantages in both inorganic electrochromic material tungsten trioxide(WO3) and organic electrochromic material polyaniline(PANI), which have been extensively studied. PANI/WO3 composite film overcomes the shortcomings of a single material, becoming a kind of electrochromic material which has complementary performance. WO3 ? PANI and PANI/WO3 composite films were prepared by chemical and electrochemical methods, respectively. And the electrochemical properties and surface morphology of these three films were compared and analyzed.First, the sol-gel method was used to prepare WO3 electrochromic film, the effect of heat temperature on color characteristics and structure of WO3 electrochromic film was discussed. Integrating the closed area of cyclic voltammetry curves and the ability of WO3 film to combine the substrate, the performance of WO3 film is better which was treated by 300 ?, the coloration efficiency of WO3 film under this condition is up to 30.13 cm2/C; the results of XRD spectra show that WO3 film treated by 300? is crystalline state with a higher degree of crystallinity compared with the WO3 films treated by room temperature(R.T.) and low temprature. SEM results show that the surface of sample treated by 300? has significant snowflake-like crystals phenomenon.Then the growth kinetic of PANI films prepared by cyclic voltammetry(CV) was studied, and electrochemical properties and surface morphology of PANI films were tested by CV?chronoamperometry(CA)?transmission spectra and SEM. The charge densities continuously increase in the complete CV method during the whole CV, the varying between the charge density and the number of scan cycles is a continuously smooth curve, and the growth rate of PANI is the fastest in the range of 11-20 circles. According to the research idea of complete CV method, segmented CV method shows that the growth rate of PANI is the fastest at the preparation condition of 50 mV/s?20 circles. Studying the effect of scan rate for the preparation of PANI film, the slope of charge density versus scan cycles of the sample is up to 0.225 at 20mV/s and 20 circles, proving that the growth rate of PANI is the fastest under this condition. The redox reversibility of PANI film is high at 20mV/s?20 circles, and the coloration efficiency is 24.6 cm2/C, which is higher than PANI films prepared by other scan rates, SEM results show that PANI film prepared in this condition has the "fish-net" three-dimensional structure, which is beneficial to the injection and extraction of ions and electron, there by enabling its electrochromic characteristcs.Finally, the PANI/WO3 composite film was prepared by sol-gel and CV method. The CV curve of composite membrane has matched redox peaks both in the cathode and anode, theoretically proving its dual electrochromic properties; the composite membrane exhibits light blue, colorless, yellow, green and dark blue at-0.5V?-0.1V?0.2V?0.4Vand 0.8V, respectively, experimentally confirming its dual electrochromic properties; and the redox reversibility of composite film is better than single PANI film. The coloration efficiency of composite membrane is 64.4 cm2/C, the ratios are increased by 1.14 times and 1.62 times compared with WO3 and PANI films, respectively. SEM image of the composite film shows that PANI is on the surface of WO3 uniformly, nano-fiber structure arranging in neat rows, having more and even channels on the surface. Composite membrane has much more uniform microstructure compared with WO3 film and PANI film, it is because WO3 and PANI consist of the donor-acceptor system of electron pair, forming a synergistic effect, which is beneficial to the electrochromism of composite film. |
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