Preparation Of Two-Dimensional DAAQ-TFP COF Based Transparent Electrode For Energy Storage/Electrochromic Applications

"2030 carbon peak,2060 carbon neutral"is an important national"green energy"strategic decision.As a kind of green and efficient ideal energy storage equipment,supercapacitor has attracted wide attention.With the development of transparency of electronic devices,transparent supercapacitors（TSCs）have become the key energy storage devices of hyperoptical transparent electronic devices,and the preparation of transparent electrodes（TCEs）as the core components of TSCs is particularly important.Electrochromic devices（ECDs）have multilayer structures and electrochemical principles similar to TSCs,and it is possible to construct EC supercapacitors by preparing TCEs with electrochromic（EC）performance.Two-dimensional（2D）covalent organic frameworks（COFs）have the advantages of large specific surface area,high active sites and rapid ion transport,and have high research value and application potential in the field of transparent energy storage and EC.At present,the construction of 2D COFs TCEs with excellent photoelectric performance,capacitive properties and EC properties is still rarely reported.In order to improve the lack of active sites in the electrochemical reaction process of inorganic nanomaterials,it is of great significance to develop porous materials with high active sites.In this paper,2D COFs thin film electrode with high density active site was designed and synthesized,and its application in the fields of transparent energy storage and electrochromism was studied.The specific contents are as follows:（1）To solve the problem that TCEs are difficult to have both good transparency and high capacitance,2D Dq Tp COFs nanoscale films were synthesized on the substrate by solvothermal strategy,and COFs TCEs were successfully prepared and assembled into symmetric/asymmetric TSCs.The optical properties(T_{550 nm}=71.6%)and capacitance properties of TSCs were coordinated by adjusting the thickness of COF film by changing the concentration of reactive monomer.By reducing the thickness of the film（t=87.66 nm）,the transmission path of electrolyte ions/electrons is shortened,and the transmission and diffusion rate is accelerated,thus the electrochemical performance of the electrode is improved,and large capacity and excellent magnification performance are produced.In addition,the anthraquinone active units in COFs nanoscale films are fully exposed,helping Dq Tp COFs TCEs to complete rapid and reversible redox reactions,which contributes to improving electrochemical pseudocapacitance performance,area/volume capacitance,energy/power density and cycle life of the devices.（2）Based on the first work,we further investigate the electrochromic properties of COFs TCEs in order to achieve device versatility.The COFs TCEs with different thickness of Dq Tp-1,Dq Tp-4and Dq Tp-8 were prepared by the same method,among which Dq Tp-4 TCes had the best electrochemical properties and the fastest response speed（coloring time 4.72 s,fading time 10.70 s）.By nanocrystalizing COF films,the charge transport path is effectively shortened and the ion/electron transport and diffusion rates in electrochemical testing are improved.After the thickness of COFs film is reduced,the anthraquinone active groups on the surface of Dq Tp COF film are fully exposed,and the active sites in the internal pores also have the opportunity to participate in the reoxidation reaction.This method improves the utilization of the active sites of anthraquinone.It also provides a theoretical basis for the rapid color switching of Dq Tp TCEs in redox reaction under applied electric field.It is found that the charge transfer resistance increases with the increase of COF film thickness.This work not only enriches EC materials,but also provides a new idea for the preparation of ECD and EC supercapacitors.