Preparation Of Polyaniline-based Nanocomposites And Their Electrochromic Properties

Electrochromic material is a kind of materials that realize their own controllable optical and color changes through voltage regulation.It can be used not only in smart windows,but also in low-energy displays,electronic paper,sensors,satellites and sunscreens.In addition,electrochromic material can also be used in car to prevent dazzling rearview mirror,avoid the safety hidden trouble that bright light enters to bring to the eye.In these composite materials are based on three transition metal oxides?MoO₃,WO₃ and V₂O₅?widely studied in electrochromic field,aiming to improve their electrochemical properties and enhance their electrochromic properties by combining with conductive polymers.Inorganic/organic nanocomposite structures are constructed,and the electrochromic properties of the materials are improved by the synergistic effect of two components in the composite.By regulating the morphology and size of the composite,increasing the specific surface area of the composite electrode,shortening the ion transmission distance,improving the response time of the composite,the stability of cyclic test and the optical performance of the composite.There are many advantages for PANI,such as a variety of color changes,fast response time and high optical contrast.In this study,three transition metal oxides?MoO₃,WO₃ and V₂O₅?were used to synthesize transition metal oxide/PANI nanocomposites.These composite materials had many advantages,such as abundant color change,good electrochemical cycle stability,fast response time,good electrical conductivity and wide range of spectrum regulation.Three dimensional network MoO₃@PANI nanosheets were synthesized by hydrothermal-electrodeposition method.Three dimensional nanosheets were constructed on ITO glass by combination of the simple hydrothermal method and freeze-drying process.Then,the three dimensional network MoO₃@PANI nanosheets were obtained by coating PANI on the surface of MoO₃ nanosheets by electrochemical deposition process.The optinal condition for the electrodeposition experiment is in 0.01mol/L aniline and 0.1 mol/L sulfuric acid solution,the deposition potential between-0.2¹.2 V,the sweep rate for 50 mV s^-1,and the cyclic deposition about 4 cycles.The nanosheets coated with PANI improved the conductivity of the electrode and electrolyte interface,together with the ionic charge migration ability.The results showed that the composite films had higher electrochemical activity and electrode reactivity.In addition,the nanosheets structure of composite facilitates the radial conduction of ions and electrons.The three dimensional networks composite had a large number of voids,which can effectively increase the electrochemical contact area between the electrolyte and the electrode materials.The cyclic stability of the composite film and reach 500 cycles.At this time,the change value of transmittance is 30%,which becomes 75%of the initial change value of transmittance,and average attenuation per cycle is 0.05%.And the composite had a rapid response time,the coloring time for 1.0 s,and the fading time for 0.9 s.The ionic diffusion coefficient in the reduced state of MoO₃@PANI nanosheets is 5.66×10^-1010 cm² s^-1,and 8.65×10^-1111 cm² s^-11 in the oxidized state.The ionic diffusion coefficients of MoO₃@PANI nanosheets are several times higher than that of pure MoO₃ nanosheets.The composite has a variety of colors,ranging from blue,gray,yellow,green and purple.WO₃@PANI core-shell nanobelts similar to sea urchin were constructed by the same experimental methods as above.The composite film still maintained good stability after 1000 cycles.The change value of transmittance is 87%of that in the initial state,and average attenuation by only 0.013%per cycle.The coloring time for 1.9 s,and the fading time for 1.5 s.The ionic diffusion coefficient in the reduced state of WO₃@PANI core-shell nanobelts is 2.98×10^-99 cm² s^-1,and 3.20×10^-1010 cm²s^-11 in the oxidized state.The ionic diffusion coefficients of WO₃@PANI core-shell nanobelts are several times higher than that of pure WO₃ nanobelts.The adjustment range of transmittance spectra is larger.Color can be changed from blue,gray,yellow,green to purple.V₂O₅ nanobelts were prepared by recrystallization at room temperature.Three dimensional network V₂O₅@PANI core-shell nanowires were synthesized by coated PANI using chemical synthesis method.The optimal reaction time of the composite experiment was 4 h,and the response times of the composite were the shortest and change value of transmittance was the largest.The advantages of these methods are less investment in equipments and easy operation.After testing for 1000 cycles,the change value of transmittance changed to 64%of the initial state,and the average attenuation per cycle was 0.036%,still maintaining excellent cyclic test stability.The ionic diffusion coefficient in the reduced state of V₂O₅@PANI core-shell nanowires is 8.65×10^-1111 cm² s^-1,and 1.10×10^-1010 cm² s^-11 in the oxidized state.The ionic diffusion coefficients of V₂O₅@PANI core-shell nanowires are several times higher than that of pure V₂O₅ nanobelts.Color changes take up a rich color system,can from black,light yellow,yellow,red to green.V₂O₅ is the only transition metal oxide that can be colored in the high oxidation state and the low reduction state,so the composite material has more abundant color changes by coated PANI.