CN110824803B - Flexible electrochromic paper single-side electrode and preparation method thereof - Google Patents

Abstract

The invention relates to a single-sided thin film electrode of flexible electrochromic paper and a preparation method thereof. First, a transparent conductive layer is formed on the surface of a flexible base layer, and then an electrochromic layer is deposited on the surface of the transparent conductive layer by an electrochemical polymerization method. A single-sided thin-film electrode of flexible electrochromic paper is obtained; the prepared single-sided thin-film electrode has a composite layer structure, the flexible base layer is a silk fibroin nanofiber film, and the transparent conductive layer is a polyaniline fiber dispersed with silk fibroin nanofibers The film, the electrochromic layer is a polyaniline film with a nano-sheet structure; the polyaniline film with a nano-sheet structure is mainly composed of a polyaniline fiber film and a nano-sheet polyaniline dispersed on the surface of the polyaniline fiber film. , the polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction. The preparation method of the invention is simple, and the prepared single-sided thin film electrode has excellent electrochromic performance.

Description

Single-sided electrode of flexible electrochromic paper and preparation method thereof

technical field

The invention belongs to the technical field of functional polymer materials, and relates to a flexible electrochromic paper single-sided electrode and a preparation method thereof.

Background technique

Electrochromic materials undergo a redox reaction under an external electric field, resulting in a reversible color change. They have been widely used in smart windows, automotive anti-glare rearview mirrors, and electronic displays that do not require rapid color change. In terms of color type, contrast and response speed, organic polymer electrochromic materials make up for the defects of long discoloration response time, high oxidation potential, poor cycle stability and low brittleness and toughness of common inorganic electrochromic materials such as tungsten trioxide. And it is more suitable for flexible devices, which can be accurately printed, stamped, sprayed, and spin-coated into the desired device pattern. Among them, polyaniline has the advantages of simple preparation, stable chemical properties, unique doping mechanism, and reversible electrochemical properties. It is one of the most promising conductive polymer electrochromic materials for practical applications.

Unlike conventional electronic devices, flexible electrochromic devices (ECDs) require good performance under bending, folding and stretching, and even good biocompatibility for integration in wearable or implantable devices . This requires the development of suitable flexible substrate materials. The current flexible ECD often uses polyethylene terephthalic acid (PET), polyimide (PI) or polycarbonate (PC) as the substrate. Although it has certain flexibility, it still cannot resist large-angle bending. and lack of biocompatibility. Using bio-based materials derived from natural renewable resources as flexible substrates to build sustainable electronic devices is an important research direction for future development. Some researchers (Foldable Electrochromics Enabled by NanopaperTransfer Method.Advanced Functional Materials, 2015.25(27):4203-4210.) used the adhesion of the nanocellulose film surface to transfer silver nanowires (AgNW) to its surface, and then transferred it to its surface. Tungsten trioxide was deposited on top to construct a flexible electrochromic paper, which can withstand 180° folded front and back, the contrast ratio reached the maximum (41%) at 633nm, and the coloring time and fading time were 11.8s and 20.1s, respectively. s. Another scholar (Freestanding electrochromicpaper. Journal of Materials Chemistry C, 2016.4(41): 9680-9686.) mixed PEDOT, _TiO and CNF to make a self-supporting flexible electrochromic paper with _TiO dispersed in bulk The particles play the role of reflecting light, and the ECD constructed on this substrate still maintains good electrochromic performance after 100 cycles. Silk fibroin (SF) is a natural biopolymer with good mechanical strength and flexibility. When it is exfoliated to the nanoscale and processed into a film, a transparent flexible SF film (Single Molecular Layer of Silk Nanoribbon) can be obtained. as Potential BasicBuilding Block of Silk Materials.ACS Nano,2018.12:11860-11870), is an ideal sensor substrate/encapsulation material. However, there is no report on the use of SF film for flexible electrochromic paper.

ECD generally has a multi-layer structure, including a transparent conductive layer, an electrochromic layer, an electrolyte layer and an ion storage layer, wherein the transparent conductive layer plays an important role as the energy supply unit of the device. Indium tin oxide (ITO) conductive glass is used for the transparent conductive layer of many electronic devices or optoelectronic devices, including ECD, but its high production cost and hard and brittle physical properties are not compatible with the development direction of green and low-cost flexible devices. contradict. Researchers have used various materials to construct transparent conductive layers to replace ITO, including carbon nanotubes (CNTs), graphene, metal nanowires, metal meshes, organic conductive polymers, and composites of the above-mentioned materials. Some researchers (A highly bendable transparent electrode for organic electrochromic devices. Organic Electronics, 2019.66:86-93.) used the excellent conductivity and flexibility of CNTs to grow PANI (PANI-CNT) on it in situ as a transparent electrode. Conductive layer, constructing a PANI/PANI-CNT/PET flexible device, which can maintain its electrochemical performance after 100 bending tests, but its electrochromic contrast ratio is low (about 34%), and the coloring and fading time are large. (20～40s).

The conduction of electrons in the organic polymer color-changing layer has a great influence on the optical contrast, response speed and stability of the device; at the same time, the transmission speed of ions in the electrolyte layer and the color-changing layer determines the response speed of the entire ECD. The entry depth of ions in the color-changing layer is related to the optical contrast and coloring efficiency of the device. There are researchers (Free-Standing Single-Molecule Thick Crystals Consisting of Linear Long-Chain Polymers. Nano Letters, 2017.17(3): 1655-1659.; Highly oriented lamellarpolyaniline films via electrochemical polymerization and post-growthannealing. RSC Advances, 2017.7(7 ): 3819-3822.) Improved the traditional electrochemical polymerization method, and prepared highly regular layered amorphous and crystalline PANI under the condition of no template. The following offset structure arrangement, there are a large number of "groove" structures between the molecular chains. Although this unique "groove" structure increases the internal space of the system and is conducive to the transport of ions or protons, its regular level may It prevents the electrolyte from entering the system, thereby reducing the contrast and response speed.

Therefore, it is of great significance to study a flexible electrochromic paper single-sided electrode with excellent electrochromic properties and its preparation method.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problem that the electrochromic performance of the single-sided electrode of the flexible electrochromic paper in the prior art needs to be further improved, and to provide a single-sided electrode of the flexible electrochromic paper and a preparation method thereof. In the present invention, silk fibroin nanofiber film is used as a flexible base layer, a transparent conductive layer is made on the surface of the flexible base layer, aniline and protonic acid are prepared into an electrolyte according to a certain proportion, and an electrochemical polymerization method is used on the surface of the transparent conductive layer. The electrochromic layer is deposited to obtain a single-sided thin film electrode of flexible electrochromic paper. The preparation process of this method is simple and does not require any template; the obtained polyaniline film has excellent electrochromic properties (that is, the electrochromic contrast is high, and the faster response).

For achieving the above object, the scheme that the present invention adopts is as follows:

The single-sided film electrode of the flexible electrochromic paper has a composite layer structure, including an adjacent flexible base layer, a transparent conductive layer and an electrochromic layer, and the flexible base layer is a silk fibroin nanofiber film (made of silk fibroin nanofibers). composition, with excellent optical properties, the transmittance is as high as 95% in the visible light range of 400-800nm), the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers, and the electrochromic layer is nanosheet-like Structured polyaniline film;

The polyaniline film with nano-sheet structure is mainly composed of polyaniline fiber film and nano-sheet-shaped polyaniline distributed on the surface of the polyaniline fiber film in a dispersed state. ;

The polyaniline fiber in the polyaniline fiber film is formed by the arrangement of stretched polyaniline molecular chains, and the repeating unit of polyaniline is a 1,4-disubstituted configuration; nano-sheet polyaniline is stacked by polyaniline molecular chains of cross-linked structure The repeating unit of polyaniline is a 1,2,4-trisubstituted configuration;

The nitrogen atom connecting the quinone ring in the stretched polyaniline molecular chain and the polyaniline molecular chain of the cross-linked structure combines with the cation of the protonic acid to form -NH ⁺ =, and the anion of the protonic acid is attached to -NH ⁺ = in the form of ionic bond, And hanging on the stretched polyaniline molecular chain, the protonic acid is camphorsulfonic acid;

The polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction, respectively.

The single-sided thin-film electrode of the electrochromic paper of the present invention has excellent electrochromic performance, mainly due to:

(1) It contains nano-sheet polyaniline. The interface between the film and the electrolyte is composed of many nano-sheets. The dispersed two-dimensional sheet structure increases the specific surface area and the utilization rate of electrolyte ions is higher. In the electrochromic test When the charge consumption is less, a larger electrochromic contrast ratio can be achieved, and the coloring efficiency is high;

(2) The cross-linking configuration of nano-sheet polyaniline, that is, a single polyaniline sheet is formed by cross-linking of polyaniline molecular chains with repeating units of 1,2,4-trisubstituted polyaniline, and electrons and carriers can move along the molecular chain. Conducted in the entire plane, in the electrochromic test, less charge consumption can successfully discolor a larger film area, and the coloring efficiency is high; from the perspective of the whole film, these sheet-like polyaniline although large area Covering, but the sheets are not connected to each other, and there are many gaps, which makes the ions in the electrolyte less hindered in and out, and provides a short ion path. In the electrochromic test, the short ion path makes the film color. , The fading time is greatly shortened, that is, fast response;

(3) Polyaniline-containing fiber film, during the electrochromic test, when ions are intercalated/extracted from nano-sheet polyaniline, a small amount of ions will be intercalated into the fiber film and stored in the gaps between fibers. This part of the stored Ions can speed up coloring and fading;

(4) The anion (X ^- ) of protonic acid is suspended on the polyaniline molecular chain that constitutes the nano-sheet polyaniline, and the protonic acid is camphorsulfonic acid, which has a sulfonic acid group (-SO ₃ H) and a C=O Stereo groups of chemical bonds, as follows:

The -SO ₃ H on X ^- hangs on the molecular chain in the form of ionic bond, and at the same time, C=O and -NH- on the adjacent molecular chain have a hydrogen bond, so as to fix the adjacent molecular chain and make the nanosheet structure stable Existing, it is not easy to crack and decompose during the electrochromic test. As the functional layer of the flexible electrochromic paper, the performance does not decrease significantly after 100 to 200 times of bending;

(5) Nano-sheet polyaniline and polyaniline fiber film, as well as the polyaniline fiber film and the polyaniline fiber film in the transparent conductive layer are combined by hydrogen bonds and electrostatic interactions between polyaniline molecular chains, and the overall structure is stable. The film can still maintain good electrochromic performance after 500-1000 cycles. Compared with the initial state, the contrast ratio after cycling is only reduced by 5-12%, and the coloring time and fading time have no obvious change;

(6) The transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers. The silk fibroin nanofibers are hydrophilic. When the film electrode is fully infiltrated with the electrolyte, the β-sheet crystals of the silk fibroin can absorb and store the part. Electrolyte ions, in the process of discoloration, provide a shorter ion pathway for polyaniline, accelerate the coloring and fading of polyaniline, and improve the response speed of the electrochromic layer; The two conformations of the nanofiber (amorphous region) and random coil (amorphous region) endow the nanofibers with higher mechanical strength and toughness, and introduce them into the flexible substrate layer and transparent conductive layer, which is beneficial to improve the mechanical properties of the thin film electrode, so that it can bend , folded and stretched.

As a preferred solution:

The single-sided film electrode of the flexible electrochromic paper as described above, the electrochromic contrast ratio of the electrochromic layer of the single-sided film electrode of the flexible electrochromic paper is 60-73%, the coloring time is 1.5-3.0s, and the color is faded. The time is 3.0～6.0s. The polyaniline electrochromic data of the prior art are shown in the following table, and the data source is J.Mater.Chem.C, 2018, 6, 5707-5715.

For the single-sided thin-film electrode of the flexible electrochromic paper described above, the thicknesses of the flexible base layer, the transparent conductive layer and the electrochromic layer are respectively 30-40 μm, 10-20 μm and 5-10 μm, and each layer should have an appropriate thickness. If the thickness is too large, the transmittance of the entire electrode will be low, the discoloration effect will not be significant, and the contrast will be low; if the thickness is too low, the supporting effect will be reduced, and it will not be able to withstand bending and folding during use.

The single-sided thin-film electrode of the flexible electrochromic paper as described above, the nano-sheet-like polyaniline is distributed on the one-side surface of the polyaniline fiber film away from the transparent conductive layer, and the one-side surface of the polyaniline fiber film is covered by nano-sheet-like polyaniline The ratio is 70-90%, the length of the nano-sheet polyaniline is 2-10 μm, the width is 0.5-2 μm, the thickness is 0.5-1 μm, and the width of the slit is 50-100 nm.

For the single-sided thin film electrode of the flexible electrochromic paper as described above, the content of silk fibroin nanofibers in the transparent conductive layer is 5-10 wt%; the content of silk fibroin nanofibers in the transparent conductive layer can be adjusted appropriately, but the adjustment range Not too big. If the content is too low, the layer is almost all polyaniline, which cannot combine the silk fibroin in the layer with the underlying silk fibroin, resulting in poor interlayer adhesion; if the content is too high, the transmittance of the film will decrease .

The present invention also provides a method for preparing the single-sided thin film electrode of the flexible electrochromic paper as described in any one of the above, firstly preparing a transparent conductive layer on the surface of the flexible base layer to obtain the transparent conductive layer/flexible base layer, An electrochromic layer is deposited on the surface by electrochemical polymerization to prepare a single-sided thin-film electrode of flexible electrochromic paper;

When the electrochromic layer is deposited by the electrochemical polymerization method, the adopted electrolyte includes aniline and protonic acid in a molar ratio of 1:10-1:30, and the protonic acid is camphorsulfonic acid;

When the electrochemical polymerization method is used for deposition, the constant potential mode or the constant current mode is adopted, and the voltage or current application time is 300-600 s, and the voltage or current application time should not be too long or too short. If the application time is too short, the amount of nanosheet-like polyaniline will be small; if the application time is too long, the film thickness will be large, which will adversely affect the contrast.

In the prior art, when the polyaniline film is prepared by doping with protonic acid, the chemical oxidation polymerization method is mostly used, and an oxidant and a surfactant need to be added, and the morphology of the obtained polyaniline is mostly nanofibrous. Aniline films do not require oxidizing agents, and the morphology can be controlled by adjusting the polymerization parameters, without the need for surfactants.

The electrochromic layer of the present invention is prepared by an electrochemical polymerization method, and a fibrous and nano-sheet composite polyaniline film is prepared from a specific protonic acid (camphorsulfonic acid) and a monomer. The formation process of the film is as follows:

In the aniline/camphorsulfonic acid electrolyte, camphorsulfonic acid (HX) ionizes protons (H ⁺ ) and camphorsulfonate ions (X ^- ), and if a voltage is applied to the electrolyte, H ⁺ combines with aniline to form aniline cation free radicals And adsorbed on the electrode surface to become a nucleation site, the activation energy of growth along this site is low, so aniline oligomers grow at each site on the electrode surface. The cationic radical of aniline is positively charged, ^and X- will enter the molecular chain and hang near the nitrogen atom on the polyaniline molecular chain in the form of ionic bond. In the early stage of the reaction, the rate is slow, aniline cations and X ^- form micelles, one end of X ^- is connected to the polyaniline molecular chain, and the other end faces the inside of the micelle, aniline polymerizes to form fibrous polyaniline staple fibers, and the polyaniline at this time is The repeating unit is in the 1,4-disubstituted configuration. When the polyaniline staple fibers are arranged in a large area on the surface of the substrate, and the fiber film grows to a certain thickness, the reaction also enters the accelerated stage, and the polymerization at this time is in the second stage in Figure 1. Due to the self-acceleration of the reaction, the ortho-position carbon atoms on the benzene ring in some aniline radicals also react to form a 1,2,4-trisubstituted polyaniline configuration, and the cross-linked polyaniline forms nanosheets structure, but only cross-linked with adjacent molecular chains, the formed sheet-like polyaniline has a limited area, and the sheets are disconnected, and a large number of nanosheets cover the surface of the fiber membrane.

In the process of film formation, the molar ratio of aniline/protic acid and the application time of voltage/current are particularly important. Only by jointly controlling the molar ratio of aniline/protic acid and the application time of voltage/current, can films with specific morphology be obtained. When the molar ratio of aniline/protic acid is too large, that is, when aniline is in excess, a few protonic acids still have the doping effect, but cannot function as templates and supports, polyaniline tends to grow randomly, and the internal structure of the formed film is dense The granular structure of aniline; when the molar ratio of aniline/protic acid is too small, that is, when the doping acid is excessive, aniline is coated in X-, and it is difficult to polymerize to form polyaniline fibers, which are 1,2,4-trisubstituted. The polyaniline configuration forms a film with a cross-linked network structure. If the voltage/current application time is too short, that is, the polymerization time is too short, no nanosheets are formed; if the voltage/current application time is too long, that is, the polymerization time is too long, the film thickness of the film will increase, which is not conducive to subsequent electrochromic application, because too thick film will make discoloration not obvious.

As a preferred solution:

As mentioned above, the electrolyte is composed of aniline, protonic acid and water, and the concentration of aniline is 0.05 to 0.5 mol/L; the concentration of aniline can be adjusted appropriately, but it should not be too high. The molar ratio of acid to it can also form the same structure, but from the macroscopic scale, the color of the film will be greatly deepened, which may be related to the larger number of total polyaniline molecules, which is not conducive to the optimization of electrochromic properties; If the concentration is too low, it is difficult to polymerize, and even if polymerized, the obtained film is not uniform and discontinuous.

As described above, the deposition by electrochemical polymerization is carried out at a temperature of 20 to 30° C. The reaction temperature can be adjusted appropriately, but the adjustment range should not be too large. If the temperature is too low, the reaction speed will be slow, and it will be difficult to initiate the oxidative polymerization of aniline; if the temperature is too high, the reaction speed will be accelerated, the molecular chains will not be arranged regularly, the film structure will be dense, and the internal morphology will be randomly oriented, and the electrochromic performance will be reduced. When using constant potential mode, the voltage is 0.7~0.85V; when using constant current mode, the current is 3~10mA. When the electrochemical polymerization method is used for deposition, a three-electrode system is used, and the three electrodes are the working electrode, the counter electrode and the reference electrode; the working electrode is a transparent conductive layer/flexible base layer; the counter electrode is a platinum electrode; the reference electrode is saturated calomel electrode.

The flexible substrate layer was prepared by vacuum filtering the silk fibroin nanofiber solution as described above.

In the method described above, the transparent conductive layer is obtained by adding an aqueous oxidant solution to the composite solution, and reacting at a temperature of 0 to 5 ° C for 12 to 24 hours to obtain a polyaniline/silk fibroin nanofiber composite suspension, and then take the polyaniline/silk fibroin nanofiber composite suspension. The supernatant of the silk fibroin nanofiber composite suspension is spin-coated on the flexible base layer;

Wherein, the composite solution is composed of aniline, silk fibroin nanofibers, hydrochloric acid and water, and the concentrations of aniline, silk fibroin nanofibers and hydrochloric acid are 1-3 mmol/L, 0.1-0.5 wt% and 0.5-1.5 mol/L respectively; In order to ensure the high transmittance of the transparent conductive layer, the content of the obtained polyaniline should not be too high. Polyaniline only plays a conductive role in this layer. The aniline concentration is lower than the above range, and it is difficult to initiate a polymerization reaction; if it is higher than the above range, more polyaniline will be obtained, which is not conducive to constructing a transparent conductive layer. If the concentration of silk fibroin nanofibers is lower than the above, it will be too dispersed and will be completely covered by polyaniline. This layer is almost all polyaniline, which cannot combine the silk fibroin in the layer with the underlying silk fibroin, and the layers adhere to each other. The property is not good; above the above concentration, silk fibroin will agglomerate to form a precipitate, which cannot be compounded into this layer. Hydrochloric acid plays the role of doping to improve the conductivity and maintain the pH of the electrolyte. Below the above concentration, the pH of the electrolyte is low, and the reaction is not easy to carry out; this range is enough to initiate polymerization, and it is not necessary to be higher than the above concentration;

The oxidant is ammonium persulfate, ferric chloride or potassium permanganate, and the concentration of the oxidant aqueous solution is 0.5-1.5mmol/L;

The volume ratio of the composite solution to the oxidant aqueous solution is 1:4 to 4:1.

Beneficial effects:

(1) The preparation method of the single-sided electrode of the flexible electrochromic paper of the present invention is simple and easy to implement, does not require any template, and has great promotion value;

(2) The single-sided electrode of the flexible electrochromic paper of the present invention has large electrochromic contrast ratio, fast response and high coloring efficiency;

(3) The single-sided electrode of the flexible electrochromic paper of the present invention can be assembled into an electrochromic paper by adding an ion-conducting film, an ion-storing film, etc., and has wide applications in the fields of electronic display (such as electronic paper).

Description of drawings

Fig. 1 is the time-current curve diagram in the process of electrochemical polymerization deposition of polyaniline;

Fig. 2 is the scanning electron microscope picture of nano-sheet polyaniline;

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

A preparation method of a flexible electrochromic paper unilateral electrode, the steps of which are as follows:

(1) Preparation of the flexible base layer: the flexible base layer was prepared by vacuum filtering the silk fibroin nanofiber solution on the PC membrane;

(2) Preparation of polyaniline/silk fibroin nanofiber composite suspension: the concentration of aniline, silk fibroin nanofibers and hydrochloric acid are respectively 1 mmol/L, 0.1 wt% and 0.5 mol/L composite solutions, the solvent is water, Then add 0.5 mmol/L ammonium persulfate aqueous solution to the composite solution (the volume ratio of composite solution and ammonium persulfate aqueous solution is 2:3), and react at 5 °C for 12 h to obtain polyaniline/silk fibroin nanoparticles. Fiber composite suspension;

(3) Preparation of transparent conductive layer: take the supernatant of the polyaniline/silk fibroin nanofiber composite suspension obtained in step (2) and spin-coat the surface of the flexible base layer obtained in step (1) to obtain a transparent conductive layer ;

(4) Preparation of flexible electrochromic paper unilateral thin film electrode: on the surface of the transparent conductive layer obtained in step (3), an electrochromic layer is deposited by an electrochemical polymerization method to prepare a unilateral thin film of flexible electrochromic paper electrode;

When the electrochromic layer is deposited by electrochemical polymerization, a three-electrode system consisting of a working electrode, a counter electrode and a reference electrode is selected, wherein the working electrode is the transparent conductive layer/flexible base layer prepared in step (3), and the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode; choose aniline and camphorsulfonic acid electrolyte with a molar ratio of 1:10, wherein the concentration of aniline is 0.05mol/L, and the solvent is water; choose constant potential mode, in A voltage of 0.7 V was applied at a temperature of 20 °C for 600 s to obtain a single-sided thin film electrode of the flexible electrochromic paper;

The single-sided thin film electrode of the finally prepared flexible electrochromic paper has an electrochromic contrast ratio of the electrochromic layer of 70%, a coloring time of 1.5s, and a fading time of 3.0s;

The single-sided thin film electrode of the flexible electrochromic paper has a composite layer structure, including an adjacent flexible base layer with a thickness of 30 μm, a transparent conductive layer with a thickness of 10 μm and an electrochromic layer with a thickness of 5 μm; wherein, the flexible base layer is silk fibroin nano-layers. Fiber film, the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers with a content of 7wt%, and the electrochromic layer is a polyaniline film with a nano-sheet structure;

In the electrochromic layer of the single-sided thin film electrode of the flexible electrochromic paper prepared above, the polyaniline film with nano-sheet structure is mainly composed of polyaniline fiber film and nano-sheet polyaniline (the scanning electron microscope is shown in Figure 2) composition, wherein the length of the nano-sheet polyaniline is 2 μm, the width is 0.5 μm, and the thickness is 0.5 μm. The polyaniline is distributed on the one-side surface of the polyaniline fiber film away from the transparent conductive layer, and the coverage rate of nano-sheet polyaniline on the one-side surface of the polyaniline fiber film is 83%;

In the above electrochromic layer, the nano-sheet polyaniline is formed by stacking polyaniline molecular chains of cross-linked structure with repeating units of 1,2,4-trisubstituted configuration, while the polyaniline fibers in the polyaniline fiber film are stacked. It is formed by the arrangement of the stretched polyaniline molecular chain whose repeating unit is 1,4-disubstituted; The cations combine to form -NH ⁺ =, the anion of camphorsulfonic acid is attached to -NH ⁺ = in the form of ionic bonds, and hangs on the stretched polyaniline molecular chain;

The polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction, respectively.

Comparative Example 1

A preparation method of a flexible electrochromic paper unilateral electrode is basically the same as that of Example 1, except that the molar ratio of aniline to camphorsulfonic acid is 1:1, and finally a flexible electrochromic paper unilateral is obtained. The electrode, the electrochromic contrast ratio was 50%, the coloring time was 6.5 s, and the fading time was 17.0 s.

Comparing Example 1 with Comparative Example 1, it can be seen that the electrochromic performance of the single-sided electrode of the flexible electrochromic paper in Example 1 is better, because the aniline in Comparative Example 1 is excessive, and the amount of camphorsulfonic acid is relatively high. If it is less, the effect of fixing the adjacent molecular chains to stabilize the nanosheet structure becomes smaller, and the number of protons entering between the molecular chains in the electrolyte solution is small, so the electrical conductivity between the molecular chains decreases. Therefore, the electrochromic contrast of camphorsulfonic acid is greatly reduced, and the coloring time and fading time are prolonged.

Comparative Example 2

A preparation method of a flexible electrochromic paper unilateral electrode is basically the same as that in Example 1, except that the molar ratio of aniline to camphorsulfonic acid is 1:40, and finally a flexible electrochromic paper unilateral is obtained. electrode, the electrochromic contrast ratio was 43%, the coloring time was 9.5s, and the fading time was 19.8s.

Comparing Example 1 with Comparative Example 2, it can be seen that the electrochromic performance of the one-sided electrode of the flexible electrochromic paper in Example 1 is better, because the excess of camphorsulfonic acid in Comparative Example 2 causes aniline to be coated. Covered in -SO ₃ H, it is difficult to polymerize to form a nano-two-dimensional sheet structure, which reduces the specific surface area of the membrane in contact with the electrolyte. In the electrochromic test, more charge consumption is required to achieve electrochromic. Therefore, the electrochromic contrast is lowered, and the coloring efficiency is low.

Comparative Example 3

A preparation method of a single-sided electrode of a flexible electrochromic paper is basically the same as that of Example 1, except that the protonic acid in the electrolyte in step (4) is sulfuric acid, and finally a flexible electrochromic paper sheet is obtained. For the side electrode, the electrochromic contrast ratio was 25%, the coloring time was 10.5 s, and the fading time was 19.9 s.

Comparing Example 1 with Comparative Example 3, it can be seen that the electrochromic performance of the single-sided electrode of the flexible electrochromic paper in Example 1 is better, because the use of camphorsulfonic acid as the protonic acid can induce the formation of gap separators. Opened nanosheet polyaniline. This discontinuous structure greatly improves the electrochromic contrast and response speed of the film, while the sulfuric acid-doped film has a regular and continuous layered structure. The regular continuous layer makes the electrolyte and the film contact only on the solid/liquid surface. The internal layered structure cannot be utilized, and the electrochromic contrast and response speed are both lowered.

Comparative Example 4

A preparation method of a flexible electrochromic paper unilateral electrode is basically the same as that in Example 1, except that the voltage application time in step (4) is 200s, and finally a flexible electrochromic paper unilateral electrode is obtained , the electrochromic contrast ratio is 45%, the coloring time is 5.1s, and the fading time is 15.7s.

Comparing Example 1 with Comparative Example 4, it can be seen that the electrochromic performance of the single-sided electrode of the flexible electrochromic paper in Example 1 is better. This is because the voltage application time in Comparative Example 4 is too short, that is, the polymerization time is too short, and there is no time to form a nano-sheet structure, so the specific surface area is small, and the electrochromic contrast is small.

Comparative Example 5

A preparation method of a flexible electrochromic paper unilateral electrode is basically the same as that of Example 1, except that the voltage application time in step (4) is 800s, and finally a flexible electrochromic paper unilateral electrode is obtained. , the electrochromic contrast ratio is 15%, the coloring time is 5.5s, and the fading time is 16.2s.

Comparing Example 1 with Comparative Example 5, it can be seen that the electrochromic performance of the single-sided electrode of the flexible electrochromic paper in Example 1 is better. This is because the voltage application time in Comparative Example 5 is too long, that is, the polymerization time is too long, and the thickness of the film increases, and too thick film will make the discoloration not obvious, which is not conducive to the subsequent application of electrochromic.

Example 2

A preparation method of a flexible electrochromic paper unilateral electrode, the steps of which are as follows:

(1) Preparation of a flexible base layer: a flexible base layer is made by vacuum-filtering the silk fibroin nanofiber solution on a PC membrane;

(2) Preparation of polyaniline/silk fibroin nanofiber composite suspension: the concentration of aniline, silk fibroin nanofibers and hydrochloric acid are respectively 2 mmol/L, 0.23 wt% and 1.1 mol/L composite solutions, the solvent is water, Then add 1.1 mmol/L ferric chloride aqueous solution to the composite solution (the volume ratio of composite solution and ferric chloride aqueous solution is 3:2), and react for 18 hours at 3 °C to obtain polyaniline/silk fibroin nanoparticles. Fiber composite suspension;

(3) Preparation of transparent conductive layer: take the supernatant of the polyaniline/silk fibroin nanofiber composite suspension obtained in step (2) and spin-coat the surface of the flexible base layer obtained in step (1) to make a transparent conductive layer layer to obtain a transparent conductive layer/flexible base layer;

(4) Preparation of flexible electrochromic paper unilateral thin film electrode: on the surface of the transparent conductive layer obtained in step (3), an electrochromic layer is deposited by an electrochemical polymerization method to prepare a unilateral thin film of flexible electrochromic paper electrode;

When the electrochromic layer is deposited by electrochemical polymerization, a three-electrode system consisting of a working electrode, a counter electrode and a reference electrode is selected, wherein the working electrode is the transparent conductive layer/flexible base layer prepared in step (3), and the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode; choose aniline and camphorsulfonic acid electrolyte with a molar ratio of 1:12, wherein the concentration of aniline is 0.25mol/L, and the solvent is water; choose constant current mode, in A voltage of 6 mA was applied at a temperature of 25 °C for 450 s to obtain a single-sided thin film electrode of the flexible electrochromic paper;

The single-sided thin film electrode of the finally prepared flexible electrochromic paper has an electrochromic contrast ratio of the electrochromic layer of 70%, a coloring time of 1.5s, and a fading time of 3.0s;

The single-sided thin film electrode of the flexible electrochromic paper has a composite layer structure, including an adjacent flexible base layer with a thickness of 35 μm, a transparent conductive layer of 15 μm and an electrochromic layer of 7.5 μm; wherein, the flexible base layer is silk fibroin Nanofiber film, the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers with a content of 7.5wt%, and the electrochromic layer is a polyaniline film with a nano-sheet structure;

In the electrochromic layer of the single-sided thin-film electrode of the flexible electrochromic paper prepared above, the polyaniline film with nano-sheet structure is mainly composed of polyaniline fiber film and nano-sheet-shaped polyaniline, wherein the nano-sheet-shaped polyaniline is The length is 6 μm, the width is 1.3 μm, and the thickness is 0.75 μm. The nano-sheet polyaniline is not connected to each other, and is separated by a gap with a width of 50-70 nm. The nano-sheet polyaniline is distributed on the polyaniline fiber membrane away from each other. The single-sided surface of the transparent conductive layer, and the coverage rate of nano-sheet polyaniline on the single-sided surface of the polyaniline fiber film is 85%;

In the above electrochromic layer, the nano-sheet polyaniline is formed by stacking polyaniline molecular chains of cross-linked structure with repeating units of 1,2,4-trisubstituted configuration, while the polyaniline fibers in the polyaniline fiber film are stacked. It is formed by the arrangement of the stretched polyaniline molecular chain whose repeating unit is 1,4-disubstituted; The cations combine to form -NH ⁺ =, the anion of camphorsulfonic acid is attached to -NH ⁺ = in the form of ionic bonds, and hangs on the stretched polyaniline molecular chain;

The polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction, respectively.

Example 3

A preparation method of a flexible electrochromic paper unilateral electrode, the steps of which are as follows:

(1) Preparation of a flexible base layer: a flexible base layer is made by vacuum-filtering the silk fibroin nanofiber solution on a PC membrane;

(2) Preparation of polyaniline/silk fibroin nanofiber composite suspension: the concentration of aniline, silk fibroin nanofibers and hydrochloric acid are respectively 3 mmol/L, 0.5 wt % and 1.5 mol/L composite solutions, the solvent is water, Then add potassium permanganate aqueous solution with a concentration of 1.5 mmol/L to the composite solution (the volume ratio of the composite solution to the potassium permanganate aqueous solution is 2:3), and react at 0 °C for 24 h to obtain polyaniline/silk fibroin. Protein nanofiber composite suspension;

(3) Preparation of transparent conductive layer: take the supernatant of the polyaniline/silk fibroin nanofiber composite suspension obtained in step (2) and spin-coat the surface of the flexible base layer obtained in step (1) to make a transparent conductive layer layer to obtain a transparent conductive layer/flexible base layer;

(4) Preparation of flexible electrochromic paper unilateral thin film electrode: on the surface of the transparent conductive layer obtained in step (3), an electrochromic layer is deposited by an electrochemical polymerization method to prepare a unilateral thin film of flexible electrochromic paper electrode;

When the electrochromic layer is deposited by electrochemical polymerization, a three-electrode system consisting of a working electrode, a counter electrode and a reference electrode is selected, wherein the working electrode is the transparent conductive layer/flexible base layer prepared in step (3), and the counter electrode It is a platinum electrode, and the reference electrode is a saturated calomel electrode; choose aniline and camphorsulfonic acid electrolyte with a molar ratio of 1:15, wherein the concentration of aniline is 0.5mol/L, and the solvent is water; choose constant potential mode, in A voltage of 0.85V was applied at a temperature of 30°C for 300s to prepare a single-sided film electrode of the flexible electrochromic paper;

The single-sided thin film electrode of the finally prepared flexible electrochromic paper has an electrochromic contrast ratio of 60% of the electrochromic layer, a coloring time of 3s, and a fading time of 3.0s;

The single-sided thin film electrode of the flexible electrochromic paper has a composite layer structure, including an adjacent flexible base layer with a thickness of 40 μm, a transparent conductive layer of 20 μm and an electrochromic layer of 10 μm; wherein, the flexible base layer is silk fibroin nano-layers. Fiber film, the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers with a content of 7.3wt%, and the electrochromic layer is a polyaniline film with a nano-sheet structure;

In the electrochromic layer of the single-sided thin-film electrode of the flexible electrochromic paper prepared above, the polyaniline film with nano-sheet structure is mainly composed of polyaniline fiber film and nano-sheet-shaped polyaniline, wherein the nano-sheet-shaped polyaniline is The length is 10 μm, the width is 2 μm, and the thickness is 1 μm. The nano-sheet polyaniline is not connected to each other, and is separated by a gap of 55-68 nm in width. The nano-sheet polyaniline is distributed in the polyaniline fiber film away from the transparent conductive The single-sided surface of the layer, and the coverage rate of nano-sheet polyaniline on the single-sided surface of the polyaniline fiber film is 90%;

In the above electrochromic layer, the nano-sheet polyaniline is formed by stacking polyaniline molecular chains of cross-linked structure with repeating units of 1,2,4-trisubstituted configuration, while the polyaniline fibers in the polyaniline fiber film are stacked. It is formed by the arrangement of the stretched polyaniline molecular chain whose repeating unit is 1,4-disubstituted; The cations combine to form -NH ⁺ =, the anion of camphorsulfonic acid is attached to -NH ⁺ = in the form of ionic bonds, and hangs on the stretched polyaniline molecular chain;

The polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction, respectively.

Example 4

A preparation method of a flexible electrochromic paper unilateral electrode, the steps of which are as follows:

(1) Preparation of a flexible base layer: a flexible base layer is made by vacuum-filtering the silk fibroin nanofiber solution on a PC membrane;

(2) Preparation of polyaniline/silk fibroin nanofiber composite suspension: the composite solutions of aniline, silk fibroin nanofibers and hydrochloric acid with concentrations of 2.5 mmol/L, 0.15 wt% and 1.1 mol/L were prepared, and the solvent was water , and then add a concentration of 1.2mmol/L ferric chloride aqueous solution to the composite solution (the volume ratio of the composite solution and the ferric chloride aqueous solution is 1:1), and react at a temperature of 3 ℃ for 18h to obtain polyaniline/silk fibroin Nanofiber composite suspension;

(3) Preparation of transparent conductive layer: take the supernatant of the polyaniline/silk fibroin nanofiber composite suspension obtained in step (2) and spin-coat the surface of the flexible base layer obtained in step (1) to make a transparent conductive layer layer to obtain a transparent conductive layer/flexible base layer;

(4) Preparation of flexible electrochromic paper unilateral thin film electrode: on the surface of the transparent conductive layer obtained in step (3), an electrochromic layer is deposited by an electrochemical polymerization method to prepare a unilateral thin film of flexible electrochromic paper electrode;

When the electrochromic layer is deposited by electrochemical polymerization, a three-electrode system consisting of a working electrode, a counter electrode and a reference electrode is selected, wherein the working electrode is the transparent conductive layer/flexible base layer prepared in step (3), and the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode; choose aniline and camphorsulfonic acid electrolyte with a molar ratio of 1:18, wherein the concentration of aniline is 0.25mol/L, and the solvent is water; choose constant current mode, in A voltage of 3 mA was applied at a temperature of 25 °C for 420 s to obtain a single-sided thin film electrode of the flexible electrochromic paper;

The single-sided thin-film electrode of the finally prepared flexible electrochromic paper has an electrochromic contrast ratio of 68% of the electrochromic layer, a coloring time of 2.5s, and a fading time of 6.0s;

The single-sided thin film electrode of the flexible electrochromic paper has a composite layer structure, including an adjacent flexible base layer with a thickness of 35 μm, a transparent conductive layer with a thickness of 14 μm and an electrochromic layer with a thickness of 7.5 μm. Wherein, the flexible base layer is a silk fibroin nanofiber film, the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers with a content of 5wt%, and the electrochromic layer is a polyaniline film with a nano-sheet structure;

In the electrochromic layer of the single-sided thin film electrode of the flexible electrochromic paper prepared above, the polyaniline film with nano-sheet structure is mainly composed of polyaniline fiber film and nano-sheet polyaniline. Among them, the length of the nano-sheet polyaniline is 4 μm, the width is 1.1 μm, and the thickness is 0.4 μm. The nano-sheet polyaniline is not connected to each other, and is separated by a gap with a width of 65-93 nm. It is distributed on the one-side surface of the polyaniline fiber film away from the transparent conductive layer, and the coverage rate of nano-sheet polyaniline on the one-side surface of the polyaniline fiber film is 80%;

In the above electrochromic layer, the nano-sheet polyaniline is formed by stacking polyaniline molecular chains of cross-linked structure with repeating units of 1,2,4-trisubstituted configuration, while the polyaniline fibers in the polyaniline fiber film are stacked. It is formed by the arrangement of the stretched polyaniline molecular chain whose repeating unit is 1,4-disubstituted; The cations combine to form -NH ⁺ =, the anion of camphorsulfonic acid is attached to -NH ⁺ = in the form of ionic bonds, and hangs on the stretched polyaniline molecular chain;

The polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction, respectively.

Example 5

A preparation method of a flexible electrochromic paper unilateral electrode, the steps of which are as follows:

(1) Preparation of a flexible base layer: a flexible base layer is made by vacuum-filtering the silk fibroin nanofiber solution on a PC membrane;

(2) Preparation of polyaniline/silk fibroin nanofiber composite suspension: the composite solutions of aniline, silk fibroin nanofibers and hydrochloric acid with concentrations of 1.5 mmol/L, 0.45 wt% and 1.1 mol/L were prepared, and the solvent was water , and then add 1.3 mmol/L ferric chloride aqueous solution to the composite solution (the volume ratio of composite solution and ferric chloride aqueous solution is 3:7), and react at 3 °C for 18 h to obtain polyaniline/silk fibroin. Nanofiber composite suspension;

(3) Preparation of transparent conductive layer: take the supernatant of the polyaniline/silk fibroin nanofiber composite suspension obtained in step (2) and spin-coat the surface of the flexible base layer obtained in step (1) to make a transparent conductive layer layer to obtain a transparent conductive layer/flexible base layer;

(4) Preparation of flexible electrochromic paper unilateral thin film electrode: on the surface of the transparent conductive layer obtained in step (3), an electrochromic layer is deposited by an electrochemical polymerization method to prepare a unilateral thin film of flexible electrochromic paper electrode;

When the electrochromic layer is deposited by electrochemical polymerization, a three-electrode system consisting of a working electrode, a counter electrode and a reference electrode is selected, wherein the working electrode is the transparent conductive layer/flexible base layer prepared in step (3), and the counter electrode It is a platinum electrode, and the reference electrode is a saturated calomel electrode; choose aniline and camphorsulfonic acid electrolyte with a molar ratio of 1:20, wherein the concentration of aniline is 0.25mol/L, and the solvent is water; choose constant current mode, in A voltage of 10 mA was applied at a temperature of 25 °C for 415 s to obtain a single-sided thin film electrode of the flexible electrochromic paper;

The single-sided thin-film electrode of the finally prepared flexible electrochromic paper has an electrochromic contrast ratio of 63%, a coloring time of 2.1s, and a fading time of 4.0s;

The single-sided thin film electrode of the flexible electrochromic paper has a composite layer structure, including an adjacent flexible base layer with a thickness of 35 μm, a transparent conductive layer with a thickness of 18 μm and an electrochromic layer with a thickness of 7.5 μm; wherein, the flexible base layer is silk fibroin Nanofiber film, the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers with a content of 10wt%, and the electrochromic layer is a polyaniline film with a nano-sheet structure;

In the electrochromic layer of the single-sided thin-film electrode of the flexible electrochromic paper prepared above, the polyaniline film with nano-sheet structure is mainly composed of polyaniline fiber film and nano-sheet-shaped polyaniline, wherein the nano-sheet-shaped polyaniline is The length is 7 μm, the width is 1.5 μm, and the thickness is 0.78 μm. The nano-sheet polyaniline is not connected to each other, and is separated by a gap with a width of 71-100 nm. The nano-sheet polyaniline is distributed in the polyaniline fiber membrane away from each other. The single-sided surface of the transparent conductive layer, and the coverage rate of nano-sheet polyaniline on the single-sided surface of the polyaniline fiber film is 80%;

In the above electrochromic layer, the nano-sheet polyaniline is formed by stacking polyaniline molecular chains of cross-linked structure with repeating units of 1,2,4-trisubstituted configuration, while the polyaniline fibers in the polyaniline fiber film are stacked. It is formed by the arrangement of the stretched polyaniline molecular chain whose repeating unit is 1,4-disubstituted; The cations combine to form -NH ⁺ =, the anion of camphorsulfonic acid is attached to -NH ⁺ = in the form of ionic bonds, and hangs on the stretched polyaniline molecular chain;

The polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction, respectively.

Example 6

A preparation method of a flexible electrochromic paper unilateral electrode, the steps of which are as follows:

(1) Preparation of a flexible base layer: a flexible base layer is made by vacuum-filtering the silk fibroin nanofiber solution on a PC membrane;

(2) Preparation of polyaniline/silk fibroin nanofiber composite suspension: the composite solutions of aniline, silk fibroin nanofibers and hydrochloric acid with concentrations of 2.2 mmol/L, 0.27 wt% and 1.1 mol/L were prepared, and the solvent was water , and then add a potassium permanganate aqueous solution with a concentration of 1.4 mmol/L to the composite solution (the volume ratio of the composite solution to the potassium permanganate aqueous solution is 4:1), and react at a temperature of 3 °C for 18 h to obtain polyaniline/silk Vegetarian protein nanofiber composite suspension;

(3) Preparation of transparent conductive layer: take the supernatant of the polyaniline/silk fibroin nanofiber composite suspension obtained in step (2) and spin-coat the surface of the flexible base layer obtained in step (1) to make a transparent conductive layer layer to obtain a transparent conductive layer/flexible base layer;

(4) Preparation of flexible electrochromic paper unilateral thin film electrode: on the surface of the transparent conductive layer obtained in step (3), an electrochromic layer is deposited by an electrochemical polymerization method to prepare a unilateral thin film of flexible electrochromic paper electrode;

When the electrochromic layer is deposited by electrochemical polymerization, a three-electrode system consisting of a working electrode, a counter electrode and a reference electrode is selected, wherein the working electrode is the transparent conductive layer/flexible base layer prepared in step (3), and the counter electrode It is a platinum electrode, and the reference electrode is a saturated calomel electrode; choose aniline and camphorsulfonic acid electrolyte with a molar ratio of 1:22, wherein the concentration of aniline is 0.14mol/L, and the solvent is water; choose constant current mode, in A voltage of 6 mA was applied at a temperature of 25 °C for 520 s to obtain a single-sided thin film electrode of the flexible electrochromic paper;

The single-sided thin film electrode of the final flexible electrochromic paper has an electrochromic contrast ratio of 71%, a coloring time of 1.9s, and a fading time of 5.2s;

The single-sided thin film electrode of the flexible electrochromic paper has a composite layer structure, including an adjacent flexible base layer with a thickness of 35 μm, a transparent conductive layer of 15 μm and an electrochromic layer of 7.5 μm; wherein, the flexible base layer is silk fibroin Nanofiber film, the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers with a content of 7.5wt%, and the electrochromic layer is a polyaniline film with a nano-sheet structure;

In the electrochromic layer of the single-sided thin-film electrode of the flexible electrochromic paper prepared above, the polyaniline film with nano-sheet structure is mainly composed of polyaniline fiber film and nano-sheet-shaped polyaniline, wherein the nano-sheet-shaped polyaniline is The length is 5 μm, the width is 1.2 μm, and the thickness is 0.71 μm. The nano-sheet polyaniline is not connected to each other, and is separated by a gap with a width of 75-95 nm. The nano-sheet polyaniline is distributed in the polyaniline fiber membrane away from The single-sided surface of the transparent conductive layer, and the coverage rate of nano-sheet polyaniline on the single-sided surface of the polyaniline fiber film is 80%;

In the above electrochromic layer, the nano-sheet polyaniline is formed by stacking polyaniline molecular chains of cross-linked structure with repeating units of 1,2,4-trisubstituted configuration, while the polyaniline fibers in the polyaniline fiber film are stacked. It is formed by the arrangement of the stretched polyaniline molecular chain whose repeating unit is 1,4-disubstituted; The cations combine to form -NH ⁺ =, the anion of camphorsulfonic acid is attached to -NH ⁺ = in the form of ionic bonds, and hangs on the stretched polyaniline molecular chain;

The polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction, respectively.

Example 7

A preparation method of a flexible electrochromic paper unilateral electrode, the steps of which are as follows:

(1) Preparation of a flexible base layer: a flexible base layer is made by vacuum-filtering the silk fibroin nanofiber solution on a PC membrane;

(2) Preparation of polyaniline/silk fibroin nanofiber composite suspension: the composite solutions of aniline, silk fibroin nanofibers and hydrochloric acid with concentrations of 1.8 mmol/L, 0.35 wt% and 1.2 mol/L were prepared, and the solvent was water , and then add 1.1 mmol/L ferric chloride aqueous solution to the composite solution (the volume ratio of composite solution and ferric chloride aqueous solution is 1:4), and react for 18 h at 3 °C to obtain polyaniline/silk fibroin. Nanofiber composite suspension;

(3) Preparation of transparent conductive layer: take the supernatant of the polyaniline/silk fibroin nanofiber composite suspension obtained in step (2) and spin-coat the surface of the flexible base layer obtained in step (1) to make a transparent conductive layer layer to obtain a transparent conductive layer/flexible base layer;

(4) Preparation of flexible electrochromic paper unilateral thin film electrode: on the surface of the transparent conductive layer obtained in step (3), an electrochromic layer is deposited by an electrochemical polymerization method to prepare a unilateral thin film of flexible electrochromic paper electrode;

When the electrochromic layer is deposited by electrochemical polymerization, a three-electrode system consisting of a working electrode, a counter electrode and a reference electrode is selected, wherein the working electrode is the transparent conductive layer/flexible base layer prepared in step (3), and the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode; choose aniline and camphorsulfonic acid electrolyte with a molar ratio of 1:25, wherein the concentration of aniline is 0.25mol/L, and the solvent is water; choose constant potential mode, in A voltage of 0.75V was applied at a temperature of 25°C for 550s to prepare a single-sided film electrode of the flexible electrochromic paper;

The single-sided thin-film electrode of the finally prepared flexible electrochromic paper has an electrochromic contrast ratio of 73%, a coloring time of 2.3s, and a fading time of 3.9s;

The single-sided thin film electrode of the flexible electrochromic paper has a composite layer structure, including an adjacent flexible base layer with a thickness of 32 μm, a transparent conductive layer with a thickness of 11 μm and an electrochromic layer with a thickness of 7.2 μm; wherein, the flexible base layer is silk fibroin Nanofiber film, the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers with a content of 7.1wt%, and the electrochromic layer is a polyaniline film with a nano-sheet structure;

In the electrochromic layer of the single-sided thin-film electrode of the flexible electrochromic paper prepared above, the polyaniline film with nano-sheet structure is mainly composed of polyaniline fiber film and nano-sheet-shaped polyaniline, wherein the nano-sheet-shaped polyaniline is The length is 5.5 μm, the width is 1.3 μm, and the thickness is 0.69 μm. The nano-sheet polyaniline is not connected to each other and is separated by a gap with a width of 82-100 nm. The nano-sheet polyaniline is distributed in the polyaniline fiber membrane. It is far from the one-side surface of the transparent conductive layer, and the coverage rate of nano-sheet polyaniline on the one-side surface of the polyaniline fiber film is 70%;

In the above electrochromic layer, the nano-sheet polyaniline is formed by stacking polyaniline molecular chains of cross-linked structure with repeating units of 1,2,4-trisubstituted configuration, while the polyaniline fibers in the polyaniline fiber film are stacked. It is formed by the arrangement of the stretched polyaniline molecular chain whose repeating unit is 1,4-disubstituted; The cations combine to form -NH ⁺ =, the anion of camphorsulfonic acid is attached to -NH ⁺ = in the form of ionic bonds, and hangs on the stretched polyaniline molecular chain;

The polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction, respectively.

Example 8

A preparation method of a flexible electrochromic paper unilateral electrode, the steps of which are as follows:

(1) Preparation of a flexible base layer: a flexible base layer is made by vacuum-filtering the silk fibroin nanofiber solution on a PC membrane;

(2) Preparation of polyaniline/silk fibroin nanofiber composite suspension: the composite solutions of aniline, silk fibroin nanofibers and hydrochloric acid with concentrations of 2.6 mmol/L, 0.33 wt% and 1.4 mol/L were prepared, and the solvent was water , and then add 1.2 mmol/L ammonium persulfate aqueous solution to the composite solution (the volume ratio of the composite solution to the ammonium persulfate aqueous solution is 1:1), and react at 3 °C for 18 h to obtain polyaniline/silk fibroin. Nanofiber composite suspension;

(3) Preparation of transparent conductive layer: take the supernatant of the polyaniline/silk fibroin nanofiber composite suspension obtained in step (2) and spin-coat the surface of the flexible base layer obtained in step (1) to make a transparent conductive layer layer to obtain a transparent conductive layer/flexible base layer;

(4) Preparation of flexible electrochromic paper unilateral thin film electrode: on the surface of the transparent conductive layer obtained in step (3), an electrochromic layer is deposited by an electrochemical polymerization method to prepare a unilateral thin film of flexible electrochromic paper electrode;

When the electrochromic layer is deposited by electrochemical polymerization, a three-electrode system consisting of a working electrode, a counter electrode and a reference electrode is selected, wherein the working electrode is the transparent conductive layer/flexible base layer prepared in step (3), and the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode; choose aniline and camphorsulfonic acid electrolyte with a molar ratio of 1:30, wherein the concentration of aniline is 0.08mol/L, and the solvent is water; choose constant current mode, in A voltage of 6 mA was applied at a temperature of 25 °C for 350 s to obtain a single-sided thin film electrode of the flexible electrochromic paper;

The single-sided thin film electrode of the finally prepared flexible electrochromic paper has an electrochromic contrast ratio of 69%, a coloring time of 2.4s, and a fading time of 5.6s;

The single-sided thin film electrode of the flexible electrochromic paper has a composite layer structure, including an adjacent flexible base layer with a thickness of 48 μm, a transparent conductive layer with a thickness of 16 μm and an electrochromic layer with a thickness of 6.8 μm; wherein, the flexible base layer is silk fibroin Nanofiber film, the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers with a content of 8wt%, and the electrochromic layer is a polyaniline film with a nano-sheet structure;

In the electrochromic layer of the single-sided thin-film electrode of the flexible electrochromic paper prepared above, the polyaniline film with nano-sheet structure is mainly composed of polyaniline fiber film and nano-sheet-shaped polyaniline, wherein the nano-sheet-shaped polyaniline is The length is 6.2 μm, the width is 1.4 μm, and the thickness is 0.76 μm. The nano-sheet polyaniline is not connected to each other and is separated by a gap with a width of 78-100 nm. The nano-sheet polyaniline is distributed in the polyaniline fiber membrane. It is far away from the one-side surface of the transparent conductive layer, and the coverage rate of nano-sheet polyaniline on the one-side surface of the polyaniline fiber film is 76%;

In the above electrochromic layer, the nano-sheet polyaniline is formed by stacking polyaniline molecular chains of cross-linked structure with repeating units of 1,2,4-trisubstituted configuration, while the polyaniline fibers in the polyaniline fiber film are stacked. It is formed by the arrangement of the stretched polyaniline molecular chain whose repeating unit is 1,4-disubstituted; The cations combine to form -NH ⁺ =, the anion of camphorsulfonic acid is attached to -NH ⁺ = in the form of ionic bonds, and hangs on the stretched polyaniline molecular chain;

The polyaniline fiber film in the electrochromic layer is combined with the nano-sheet polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonding and electrostatic interaction, respectively.

Claims (10)

1. The single-side film electrode of the flexible electrochromic paper has a composite layer structure, and comprises an adjacent flexible substrate layer, a transparent conductive layer and an electrochromic layer, and is characterized in that: the flexible substrate layer is a silk fibroin nanofiber film, the transparent conductive layer is a polyaniline fiber film dispersed with silk fibroin nanofibers, and the electrochromic layer is a polyaniline film with a nano-sheet structure;

the polyaniline film with the nano-sheet structure mainly comprises a polyaniline fiber film and nano-sheet polyaniline which is distributed on the surface of the polyaniline fiber film in a dispersion shape, wherein the nano-sheet polyaniline is not connected with each other and has a certain gap;

polyaniline fibers in the polyaniline fiber membrane are formed by arranging stretched polyaniline molecular chains, and the repeating unit of polyaniline is in a 1, 4-disubstituted configuration; the nano flaky polyaniline is formed by stacking polyaniline molecular chains with a cross-linked structure, and the repeating unit of the polyaniline is in a 1,2, 4-trisubstituted configuration;

stretched polyaniline molecular chain and polyaniline molecular chain with cross-linked structureWherein the nitrogen atom to which the quinone ring is attached is combined with the cation of the protonic acid to form-NH⁺The anion of the protic acid is attached to-NH in the form of an ionic bond⁺The polymer is suspended on a stretched polyaniline molecular chain, and the protonic acid is camphorsulfonic acid;

the polyaniline fiber film in the electrochromic layer is respectively combined with the nano-flaky polyaniline and the polyaniline fiber film in the transparent conductive layer through hydrogen bonds and electrostatic interaction.

2. The single-sided film electrode of flexible electrochromic paper as claimed in claim 1, wherein the electrochromic contrast of the electrochromic layer of the single-sided film electrode of flexible electrochromic paper is 60 to 73%, the coloring time is 1.5 to 3.0s, and the fading time is 3.0 to 6.0 s.

3. The single-sided film electrode of flexible electrochromic paper according to claim 1, wherein the flexible base layer, the transparent conductive layer and the electrochromic layer have thicknesses of 30 to 40 μm, 10 to 20 μm and 5 to 10 μm, respectively.

4. The single-sided thin film electrode of flexible electrochromic paper according to claim 1, wherein the nano-flaky polyaniline is distributed on the surface of the polyaniline fiber film on the single side away from the transparent conductive layer, the coverage rate of the nano-flaky polyaniline on the surface of the polyaniline fiber film on the single side is 70-90%, the length of the nano-flaky polyaniline is 2-10 μm, the width of the nano-flaky polyaniline is 0.5-2 μm, the thickness of the nano-flaky polyaniline is 0.5-1 μm, and the width of the gap is 50-100 nm.

5. The single-sided thin film electrode of flexible electrochromic paper as claimed in claim 1, wherein the content of the silk fibroin nanofibers in the transparent conductive layer is 5-10 wt%.

6. A method for preparing a single-sided thin film electrode of flexible electrochromic paper as claimed in any of claims 1 to 5, characterized in that: firstly, preparing a transparent conductive layer on the surface of a flexible substrate layer to obtain a transparent conductive layer/flexible substrate layer, and then depositing an electrochromic layer on the surface of the transparent conductive layer by adopting an electrochemical polymerization method to prepare a single-side film electrode of flexible electrochromic paper;

when an electrochromism layer is deposited by adopting an electrochemical polymerization method, the adopted electrolyte comprises aniline and protonic acid with the molar ratio of 1: 10-1: 30, and the protonic acid is camphorsulfonic acid;

when the electrochemical polymerization method is adopted for deposition, a constant potential mode or a constant current mode is adopted, and the voltage or current application time is 300-600 s.

7. The method according to claim 6, wherein the electrolyte comprises aniline, protonic acid and water, and the concentration of aniline is 0.05-0.5 mol/L.

8. The method of claim 6, wherein the deposition by electrochemical polymerization is carried out at a temperature of 20 to 30 ℃; when a constant potential mode is adopted, the voltage is 0.7-0.85V; when a constant current mode is adopted, the current is 3-10 mA; when the electrochemical polymerization method is adopted for deposition, a three-electrode system is adopted, and three electrodes are a working electrode, a counter electrode and a reference electrode; the working electrode is a transparent conductive layer/flexible substrate layer; the counter electrode is a platinum electrode; the reference electrode is a saturated calomel electrode.

9. The method of claim 6, wherein the flexible substrate layer is made by vacuum suction filtering a solution of silk fibroin nanofibers on a Polycarbonate (PC) membrane.

10. The method as claimed in claim 6, wherein the transparent conductive layer is prepared by adding an oxidant aqueous solution into the composite solution, reacting at 0-5 ℃ for 12-24 h to obtain a polyaniline/silk fibroin nanofiber composite suspension, and then spin-coating the supernatant of the polyaniline/silk fibroin nanofiber composite suspension on the flexible substrate layer;

the composite solution comprises aniline, silk fibroin nano-fibers, hydrochloric acid and water, wherein the concentrations of the aniline, the silk fibroin nano-fibers and the hydrochloric acid are respectively 1-3 mmol/L, 0.1-0.5 wt% and 0.5-1.5 mol/L;

the oxidant is ammonium persulfate, ferric chloride or potassium permanganate, and the concentration of the oxidant aqueous solution is 0.5-1.5 mmol/L;

the volume ratio of the composite solution to the oxidant aqueous solution is 1: 4-4: 1.

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