An electrochromic compound, a hybrid film and a method for preparing the same

Abstract

The application discloses an electrochromic compound, makes respective advantages of organic and inorganic electrochromic materials fully play, and therefore the hybrid film containing the electrochromic compound prepared has the advantages of reversible color change, faster response time, high cycle stability and high coloring efficiency; the application adopts a hydrothermal method in preparation of the hybrid film, and through first electrodepositing a Cu2O base, under the induction and participation of the metal oxide base, makes triphenylamine triformic acid and copper ions in the solution react through the hydrothermal method, so as to prepare the organic-inorganic electrochromic hybrid film; the preparation method is simple in process, low in cost, can be mass-produced, and reduces the use of organic solvents in the preparation process, and is more environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of electrochromic materials technology, and in particular to an electrochromic compound, a hybrid film, and a method for preparing the same. Background Technology

[0002] Electrochromism (EC) refers to the phenomenon where a material's color changes reversibly under the influence of an electric field. This change is caused by the electric field leading to charge transfer or electron rearrangement within the material, thus affecting the material's ability to absorb or reflect light. This color-changing phenomenon can be observed in the visible spectrum (400–800 nm) and the near-infrared region (1000–2000 nm).

[0003] Electrochromic materials, due to their variability in color and low energy consumption, show promise for applications in smart windows, displays, and military camouflage. Electrochromic materials are generally divided into two categories: inorganic and organic. Inorganic electrochromic materials are mainly metal oxides such as tungsten trioxide, molybdenum trioxide, iridium oxide, or titanium oxide. They possess advantages such as good stability, strong adhesion, and high device durability, but also suffer from drawbacks such as a narrow color range, slow response time, and low coloring efficiency, limiting their applications. Organic electrochromic materials mainly include polyaniline, polythiophene, amethyst, or phenothiazine compounds and their derivatives. They offer advantages such as fast response speed, rich and diverse colors, and easy structural modification. However, the production cost of conductive organic polymers is currently high, the production process requires the use of oily solvents, posing environmental safety concerns, and the stability of organic electrochromic materials is relatively poor.

[0004] Therefore, the formation of organic-inorganic composite electrochromic materials by doping organic and inorganic materials allows for the full utilization of the advantages of both organic and inorganic electrochromic materials, which has significant research value and broad application potential.

[0005] For example, Chinese invention patent application publication number CN103172274A discloses a method for preparing a nickel oxide / polyaniline composite electrochromic film. The optical properties and response speed of the composite electrochromic material prepared by this method are improved, but its stability is poor, which is not conducive to the application of composite electrochromic materials. Summary of the Invention

[0006] To address the aforementioned problems, in a first aspect, the present invention provides an electrochromic compound.

[0007] An electrochromic compound, wherein the electrochromic compound is composed of triphenylamine 4,4,4-tricarboxylic acid coordinated with copper ions; the structural formula of the electrochromic compound is as follows:

[0008]

[0009] On the other hand, the present invention also provides an electrochromic hybrid membrane and a method for preparing the same, which can reduce the use of organic solvents and the resulting hybrid membrane has a faster response speed and higher cycling stability.

[0010] An electrochromic hybrid film comprising the aforementioned electrochromic compound.

[0011] The method for preparing the electrochromic hybrid film includes the following steps:

[0012] S1. A conductive substrate is provided. The conductive substrate is cleaned with an alkaline solution, distilled water and organic solution respectively. Then, a three-electrode system is used to electrodeposit the conductive substrate in an aqueous solution containing copper acetate and sodium acetate. The substrate is then cleaned with deionized water and dried to obtain a conductive substrate loaded with a cuprous oxide substrate film.

[0013] S2. Take a container, put in 4,4,4-triphenylamine tricarboxylate and copper acetate, then add N,N-dimethylformamide to the container and sonicate. Place the conductive substrate cuprous oxide film obtained in S1 with the conductive side facing down into the container at an angle. Place the container in a hydrothermal reactor for reaction. After the reaction, cool the hydrothermal reactor and wash and dry the film after the reaction to obtain an electrochromic hybrid film.

[0014] When a voltage is applied to the electrochromic hybrid membrane, the N in the above compound is easily oxidized into N free radical cations, thereby changing the color of the hybrid membrane from light green to dark blue. As the voltage continues to increase, the dark blue deepens and turns into purple.

[0015] Preferably, the conductive substrate in S1 is selected from one of indium tin oxide conductive glass, indium tin oxide conductive film, silver nanowire conductive film, fluoride-doped tin oxide glass, and polymer conductive film.

[0016] Preferably, the alkaline solution in S1 comprises a 0.5-1 wt% sodium hydroxide solution; the organic solvent is selected from one or more of ethanol, toluene, and acetone.

[0017] Preferably, the concentration of the aqueous solution of copper acetate in S1 is 0.01–0.03 mol / L; and the concentration of the aqueous solution of sodium acetate is 0.07–0.13 mol / L.

[0018] Preferably, the electrodeposition time in S1 is 5 to 15 seconds.

[0019] Preferably, in S2, the concentration of 4,4,4-tricarboxylic acid triphenylamine in N,N-dimethylformamide is 0.005–0.015 mol / L; and the concentration of copper acetate in N,N-dimethylformamide is 0.02–0.04 mol / L.

[0020] Preferably, the reaction conditions in S2 are 100–140°C for 1–4 hours.

[0021] The invention also provides applications of the above-mentioned electrochromic hybrid film, which can be applied in fields such as electrochromic devices.

[0022] This invention provides a method for preparing triphenylamine 4,4,4-tricarboxylic acid (H3TCA):

[0023] (1) Dissolve p-aminobenzonitrile in DMSO. Then slowly add CsF to the solution with continuous stirring. When CsF is added, the solution first turns yellow and then green. After all CsF is added, some CsF remains undissolved. Then add p-fluorobenzonitrile. After reacting overnight, a brown transparent solution is formed. After cooling, the reaction mixture is poured into ice water to precipitate the product. Filter, wash with water and ethanol, dry, and purify by silica gel column chromatography to obtain pure 4,4,4-tricyanotriphenylamine (TCTPA);

[0024] (2) Add TCTPA and potassium hydroxide to a three-necked flask, then add ethylene glycol and heat to reflux. The turbid liquid changes from white to orange-red, then to a brown transparent solution. Cool the reaction to room temperature, add water to the reaction flask, and adjust the pH to 1 with hydrochloric acid. Filter the reaction mixture under reduced pressure, wash the white solid with water and dry it to obtain H3TCA.

[0025] The reaction formulas in the above H3TCA preparation method are as follows:

[0026]

[0027] The present invention has the following beneficial effects:

[0028] (1) The electrochromic compound of this invention fully leverages the advantages of both organic and inorganic electrochromic materials. Therefore, the hybrid film containing this electrochromic compound prepared exhibits advantages such as reversible color change, fast response time, high cycle stability, and high coloring efficiency, with a coloring efficiency of 243.86 cm⁻¹. 2 / C, contrast ratio 70.90%, coloring time 8.19s, fading time 2.33s;

[0029] (2) The present invention prepares a hybrid film containing the above-mentioned electrochromic compound by reacting 4,4,4-tricarboxylic acid triphenylamine (H3TCA) with copper ions to form coordination bonds via a hydrothermal method. The electrochromic hybrid film is prepared by first electrodepositing a Cu2O substrate, and then reacting tricarboxylic acid triphenylamine with copper ions in the solution via a hydrothermal method under the induction and participation of the metal oxide substrate. The preparation method is simple, low-cost, and can be mass-produced. In addition, the use of organic solvents is reduced during the preparation process, making it more environmentally friendly. Attached Figure Description

[0030] Figure 1 Scanning electron microscope images of a cuprous oxide substrate and a hybrid film Cu2O-H3TCA;

[0031] Figure 2 Cyclic voltammetry curves of the hybrid Cu2O-H3TCA film;

[0032] Figure 3 The response time and stability of the hybrid Cu2O-H3TCA film at a wavelength of 700 nm are shown in the figure.

[0033] Figure 4 The coloring efficiency diagram of the hybrid film Cu2O-H3TCA;

[0034] Figure 5 This is a flowchart of the preparation process of the hybrid film Cu2O-H3TCA. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0037] Example 1

[0038] This embodiment provides a method for preparing an electrochromic hybrid film (Cu2O-H3TCA hybrid film), which includes the following steps:

[0039] (1) Preparation of Cu2O substrate

[0040] The conductive substrate, indium tin oxide (ITO), was ultrasonically cleaned using 0.5 wt% NaOH solution, distilled water, ethanol, toluene, and acetone solutions, respectively. Then, a three-electrode system was used for deposition at room temperature, where the working electrode was ITO, the counter electrode was a platinum sheet, and the silver electrode was the reference electrode. The deposition solution was an aqueous solution of 0.02 M copper acetate ((CH3COO)2Cu) and 0.1 M sodium acetate (CH3COONa). The deposition voltage was -0.3 V for 10 s, yielding a yellow cuprous oxide film. The film was then washed three times with deionized water and dried in a 50 °C oven for 12 hours. Scanning electron microscopy images of the cuprous oxide film are shown below. Figure 1 As shown.

[0041] (2) Synthesis of 4,4,4-tricarboxylic acid triphenylamine

[0042] 10 mmol of p-aminobenzonitrile was dissolved in 50 mL of DMSO. Then, 40 mmol of CsF was slowly added to the solution with continuous stirring. When 2.00 g of CsF was added, the solution first turned yellow and then green, and some CsF remained undissolved after all the CsF was added. Then, 22 mmol of p-fluorobenzonitrile was added. After reacting overnight, a brown transparent solution was obtained. The mixture was reacted at 140 °C for 14 hours. After cooling, the reaction mixture was poured into ice water to precipitate the product. The precipitate was filtered, washed with water (200 mL) and ethanol (100 mL), dried, and purified by silica gel column chromatography to obtain 2.10 g of pure 4,4,4-tricyanotriphenylamine (TCTPA). TCTPA (1.80 g, 5.62 mmol) and potassium hydroxide (1.89 g, 33.72 mmol) were added to a 100 mL three-necked flask, followed by the addition of ethylene glycol (25 mL). The mixture was heated to reflux, and the turbid solution changed from white to orange-red, and then to a brown transparent solution. The reaction was completed in 14 hours. The reaction mixture was cooled to room temperature, and 50 mL of water was added to the reaction flask. The pH was adjusted to 1 using 4 M hydrochloric acid. The reaction mixture was filtered under reduced pressure, and the white solid was washed with water and dried. 2.05 g of triphenylamine 4,4,4-tricarboxylic acid (H3TCA) was obtained.

[0043] (3) Preparation of hybrid membranes

[0044] Preparation flow chart as follows Figure 5As shown, 0.0377 g (0.01 M) of H3TCA and 0.06 g (0.03 M) of copper acetate were weighed into a polytetrafluoroethylene bottle in a hydrothermal reactor. 10 mL of N,N-dimethylformamide (DMF) was added to the bottle, and the mixture was sonicated for 15 minutes. A dried cuprous oxide film, with its conductive side facing down, was tilted and placed into the bottle. The hydrothermal reactor was then assembled and placed in an oven at 120 °C for 2 hours. After the reaction, the hydrothermal reactor was removed from the oven and cooled in air for 1 hour. The film was then removed and washed sequentially with DMF, water, and ethanol, and dried at 50 °C for 3 hours to obtain a light green Cu2O-H3TCA hybrid film. A bio-scanning electron microscope image of this hybrid film is shown below. Figure 1 As shown.

[0045] Example 2

[0046] In this embodiment, the electrochemical properties of the Cu2O-H3TCA hybrid film were tested.

[0047] The hybrid membrane prepared in Example 1 was placed in a three-electrode electrolytic cell, using a 0.1 mol / L lithium perchlorate / propylene carbonate solution as the electrolyte. The working electrode was an ITO glass coated with a Cu₂O-H₃TCA hybrid membrane, the counter electrode was a platinum wire, and the reference electrode was a silver-silver chloride electrode. Cyclic voltammetry was used for scanning, with a scanning voltage range of 0–1.8 V and a scanning rate of 100 mV / s. The results are as follows: Figure 2 As shown, Figure 2 The image on the left shows the electrochemical properties of the Cu2O-H3TCA hybrid film. As can be seen from the image, the Cu2O-H3TCA hybrid film has a pair of obvious redox peaks. Furthermore, as the voltage increases, the color of the film changes from light green to dark blue. The Cu2O-H3TCA hybrid film can achieve a purple color change at 1.61V.

[0048] Example 3

[0049] In this embodiment, the response speed and stability of the Cu2O-H3TCA hybrid film were tested.

[0050] The hybrid membrane prepared in Example 1 was placed in a three-electrode electrolytic cell, using a 0.1 mol / L lithium perchlorate / propylene carbonate solution as the electrolyte. The working electrode was an ITO glass coated with a Cu₂O-H₃TCA hybrid membrane, the counter electrode was a platinum wire, and the reference electrode was a silver-silver chloride electrode. An electrochemical workstation coupled with a UV spectrometer was used. The electrochemical workstation was configured with a multi-potential step method: initial potential 0 V, termination potential 1.8 V, potential pulse width 15 s, and scan time 6000 s. The UV spectrometer was configured with spectral kinetics and a wavelength of 700 nm. The final data are shown below. Figure 3As shown, the coloring time of the Cu2O-H3TCA hybrid film is 8.19 s, the fading time is 2.33 s, and the film retains 96.28% contrast after 200 cycles. The results demonstrate that the hybrid film provided by this invention exhibits good stability under multiple cycles.

[0051] Example 4

[0052] This embodiment tested the coloring efficiency of the Cu2O-H3TCA hybrid film. Coloring efficiency refers to the change in optical density caused by the consumption of one unit of charge per unit area.

[0053] The hybrid film prepared in Example 1 was placed in a three-electrode electrolytic cell, using a 0.1 mol / L lithium perchlorate / propylene carbonate solution as the electrolyte. The working electrode was an ITO glass coated with a Cu₂O-H₃TCA hybrid film, the counter electrode was a platinum wire, and the reference electrode was a silver-silver chloride electrode. The electrochemical workstation employed a multi-potential step method to test the following: Figure 4 The image shows the test results for the Cu2O-H3TCA hybrid film. According to... Figure 4 It can be seen that the Cu2O-H3TCA hybrid film has a high coloring efficiency of 243.86 cm⁻¹. 2 / C.

Claims

1. A method for preparing an electrochromic hybrid film, characterized in that, The electrochromic hybrid film contains an electrochromic compound, which is composed of triphenylamine 4,4,4-tricarboxylic acid coordinated with copper ions; the structural formula of the electrochromic compound is as follows: The method for preparing the electrochromic hybrid film includes the following steps: S1. A conductive substrate is provided. The conductive substrate is cleaned with an alkaline solution, distilled water and organic solvent respectively. Then, a three-electrode system is used to electrodeposit the conductive substrate in an aqueous solution containing copper acetate and sodium acetate. The substrate is then cleaned with deionized water and dried to obtain a conductive substrate loaded with a cuprous oxide substrate film. S2. Take a container, put in 4,4,4-triphenylamine tricarboxylate and copper acetate, then add N,N-dimethylformamide to the container and sonicate. Place the conductive substrate cuprous oxide film obtained in S1 with the conductive side facing down into the container at an angle. Place the container in a hydrothermal reactor for reaction. After the reaction, cool the hydrothermal reactor and wash and dry the film after the reaction to obtain an electrochromic hybrid film.

2. The preparation method according to claim 1, characterized in that, The conductive substrate mentioned in S1 is selected from one of the following: indium tin oxide conductive glass, indium tin oxide conductive film, silver nanowire conductive film, fluoride-doped tin oxide glass, and polymer conductive film.

3. The preparation method according to claim 1, characterized in that, The alkaline solution in S1 comprises a 0.5-1 wt% sodium hydroxide solution; the organic solvent is selected from one or more of ethanol, toluene, and acetone.

4. The preparation method according to claim 1, characterized in that, In S1, the concentration of copper acetate in the aqueous solution of copper acetate and sodium acetate is 0.01–0.03 mol / L; the concentration of sodium acetate in the aqueous solution of copper acetate and sodium acetate is 0.07–0.13 mol / L.

5. The preparation method according to claim 1, characterized in that, The electrodeposition time described in S1 is 5–15 s.

6. The preparation method according to claim 1, characterized in that, In S2, the concentration of 4,4,4-tricarboxylic acid triphenylamine in N,N-dimethylformamide is 0.005–0.015 mol / L; the concentration of copper acetate in N,N-dimethylformamide is 0.02–0.04 mol / L.

7. The preparation method according to claim 1, characterized in that, The reaction conditions in S2 are 100–140℃ for 1–4 hours.

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