Synthesis And Properties Of Novel Electrochromic Hybrid Materials Based On Metal Oxides And Conjugated Polymers

Electrochromism?EC?is defined as a phenomenon that the colors reversible changed under applied potential accompanied by the material undergoes a redox reaction.Electrochromic materials have the advantages of rich color changes,fast response speed,high optical contrast and good stability.More importantly,users can easily adjust the color change state of the material according to environmental conditions and self preferences.However,single organic electrochromic materials or inorganic electrochromic materials usually have defects in performance.The use of organic-inorganic composite electrochromic materials has gradually become the focus of researchers.On the other hand,with the rapid development of wearable,portable and intelligent electronic products,which put forward more urgent requirements for the intelligentization of energy storage components.The research of electrochromic supercapacitors integrating electrochromic performance and energy storage function has attracted more and more attention.Titanium-oxo clusters?TOCs?are important member of polyoxometalates?POMs?that have unique structure characters and physicochemical properties,and can be converted into high-quality Ti O₂ materials.The research on the synthesis of TOCs and modulation on their structure and photoelectrochemical properties have attracted growing interests.Poly?3,4-ethylenedioxythiophene??PEDOT?is a conjugated polymer with a small energy gap,high electrical conductivity and simple molecular structure,it is possible to produce a significant color change while a stable redox reaction occurs,and it has been studied as an electrode material of an electrochromic material or a supercapacitor.In the second chapter of this thesis,we designed and synthesized a new thiophene-3-carboxylic acid modified titanium oxide cluster[C₄₀H₇₆O₁₆S₂Ti₄].The structure was characterized by single crystal X-ray diffraction analysis.We further in-situ electropolymerized the 3,4-ethylenedioxythiophene?EDOT?solution containing the titanium oxide cluster[C₄₀H₇₆O₁₆S₂Ti₄]by potentiostatic polymerization to obtain PEDOT-Ti hybrid films,and carried out structural analysis and characterization of the hybrid film material.We found that the PEDOT-Ti film has excellent electrochemical performance and electrochromic performance compared to the PEDOT film.The PEDOT-Ti film has a maximum optical contrast of 52.3%at 603.5 nm and the coloring time is 2.34 s while the fading time is 1.85 s.The PEDOT-Ti film has an area specific capacitance of 1.53 m F·cm^-2when the current density is 0.01 m A·cm^-2,and can be used as a supercapacitor electrode material.Since both WO₃ and PEDOT are cathode coloring materials,it is expected that the hybridization between WO₃ and PEDOT will complement each other in performance.In the third chapter of this thesis,we constructed a one-dimensional WO₃-PEDOT core-shell hybrid nanostructure.The porous PEDOT nanometer-thin layers were uniformly encapsulated on WO₃ nanorods by potentiostatic polymerization.Compared with WO₃nanorods,the electrochromic properties such as response time?coloring time for 24.13 s and fading time for 7.59 s?and optical contrast?33.6%at 550.5 nm?of the WO₃-PEDOT material have been improved.Further studies show that the organic/inorganic hybrid growth between the porous thin shell of PEDOT and the WO₃ nanorods provides an effective interface interaction and a rich channel of ion intercalation.The one-dimensional core-shell structure has a large active specific surface area,reduces the grain boundary area and provides a direct electron transport channel,which enhances the transmission ability of electrons,and improves the electrochromic properties of the materials.Under electrochemical oxidation conditions,triphenylamine derivatives easily lose electrons to form stable cationic radicals,accompanied by significant color changes.Thus,electrochromic materials based on triphenylamine derivatives have attracted people's attention.In the fourth chapter of this thesis,we prepared soluble oligomersofpoly?tris[4-?2-bithienyl?phenyl]amine??PPT2N?and poly?tris[4-?3,4-ethylenedioxythiophene?phenyl]amine??PTEPA?by chemical polymerization.The PPT2N film and PTEPA film were prepared on the ITO glass by the drop coating method,and their electrochromic properties were studied.It was found that the polymer films exhibited a reversible color change upon applying voltage.The polymer PPT2N film's optical contrast was 7.5%at 555.5 nm,the coloring time was 1.56 s and the fading time was 2.58 s;The polymer PTEPA film's optical contrast was 23.8%at 440 nm,the coloring time was 0.97 s and the fading time was 1.92 s.Polymer PTEPA exhibited a better electrochromic cyclic stability compared to polymer PPT2N.Titanium-oxygen cluster hybrid PTEPA-Ti films obtained by electrochemical polymerization also have relatively better electrochromic properties than PTEPA films.