Non-metal electrochromic intelligent window based on reversible bromine deposition and preparation method of non-metal electrochromic intelligent window

Abstract

The invention discloses a non-metal electrochromic smart window based on reversible bromine deposition and a preparation method thereof.The smart window comprises a working electrode and a counter electrode, the space between the working electrode and the counter electrode is filled with electrolyte, the working electrode is transparent conductive glass or transparent conductive glass with the surface modified with a catalyst, and the counter electrode is transparent conductive glass or transparent conductive glass with the surface modified with a catalyst. The counter electrode is glass attached with a zinc foil frame or a zinc grid, the electrolyte comprises a core electrolyte and an auxiliary electrolyte, and the core electrolyte is brominated organic salt. The intelligent window is simple in structure, high in optical modulation rate and excellent in cycling stability, and a new thought is provided for diversification of the electrochromic intelligent window.

Description

Technical Field

[0001] The present invention relates to a non-metallic electrochromic smart window and a preparation method thereof, and in particular to a non-metallic electrochromic smart window based on reversible bromine deposition and a preparation method thereof, belonging to the technical field of electrochromism. Background Art

[0002] Electrochromic smart windows are an advanced window technology that can control the color and transmittance of windows through electrical signals, thereby achieving intelligent regulation of indoor light, heat, and privacy. They have significant advantages in building energy conservation, comfort, and intelligence. The main structure of the electrochromic smart windows reported so far is a sandwich structure, also known as a multilayer thin film structure, which includes an electrochromic electrode, an electrolyte layer, and an ion storage layer. The electrolyte acts as an ion-conducting medium between the electrochromic material and the ion storage layer, promoting efficient ion transfer, thereby achieving reversible color change.

[0003] However, electrochromic smart windows do have drawbacks. Electrochromic materials can degrade over long periods of use, leading to performance degradation. During large-area thin-film deposition, uniform thickness and composition are difficult to maintain, affecting the consistency of the color-changing effect. Currently, commercial electrochromic devices primarily display blue or gray, with limited color options.

[0004] Due to the dissolution and shuttle effect of ions generated by non-metallic electrochromic devices after the oxidation of non-metallic materials such as iodine and bromine under applied voltage, there are few related studies. The literature "Li et al. Electrochromism via reversible electrodeposition of solid iodine. Nat Commun 16, 724 (2025)" first proposed non-metallic electrodeposition technology, using the redox reaction of iodine ions (I-) to achieve electrochromism, and developed an electrochromic dynamic window based on non-metallic iodine electrodeposition using a salt-in-water electrolyte containing iodine ions. The unique electrolyte environment and solvation structure of the salt-in-water electrolyte inhibit the dissolution and shuttle effect of iodine, thereby achieving a reaction pathway different from that of traditional electrolytes. This pathway involves a reversible solid-liquid transition between solid iodine ions and solvated iodine ions. However, the oxidation / reduction kinetics of elemental iodine are slow and require high voltage driving. This results in shortcomings such as uneven coloring and slow response time in electrochromic smart windows. Summary of the Invention

[0005] The purpose of the present invention is to provide a non-metallic electrochromic smart window based on reversible bromine deposition. The electrochromic smart window has a simple structure and is easy to process. It achieves significant optical modulation from colorless to bright yellow based on the reversible conversion of Br- / Br3-, has a high optical modulation rate and excellent cyclic stability, and provides new ideas for the diversification of electrochromic smart windows.

[0006] The specific technical solutions of the present invention are as follows:

[0007] A non-metallic electrochromic smart window based on reversible bromine deposition, the smart window comprising a working electrode and a counter electrode, wherein an electrolyte is filled between the working electrode and the counter electrode, the working electrode being transparent conductive glass, or transparent conductive glass with a catalyst modified on its surface, wherein the catalyst comprises a carbon material or a transition metal oxide, the counter electrode being glass with a zinc foil frame or a zinc grid, the electrolyte comprising a core electrolyte and an auxiliary electrolyte, wherein the core electrolyte is a brominated organic salt.

[0008] Furthermore, the transparent conductive oxide glass may be FTO conductive glass, ITO conductive glass, etc.

[0009] Furthermore, the catalyst modified on the surface of the transparent conductive oxide glass is a carbon material or a transition metal oxide. The carbon material is carbon nanotubes or graphene, preferably carbon nanotubes. The transition metal oxide includes at least one of RuO2, CuO, Co3O4, CeO2, TiO2, WO3, and IrO. The catalyst is in contact with the transparent conductive oxide, and the modification of the catalyst can reduce the Gibbs free energy of the reversible conversion of Br- / Br3-, thereby promoting Br - To Br3 - The catalyst's excellent electrical conductivity reduces electrode resistance and facilitates electron transfer. The catalyst is dispersed on the surface of the transparent conductive oxide glass, increasing the specific surface area and providing more active sites, enhancing the catalytic effect, speeding up the smart window's response, and reducing the driving voltage.

[0010] Furthermore, the thickness of the catalyst layer modified on the surface of the transparent conductive oxide glass is 0.1 nm-20 nm, for example, 0.1 nm, 0.5 nm, 1 nm, 5 nm, 10 nm, 15 nm, and 20 nm.

[0011] Furthermore, the catalyst is uniformly attached to the surface of the transparent conductive oxide glass in a layered manner, and the attachment method can be spin coating, blade coating, spray coating, etc.

[0012] Furthermore, the outer diameter of the carbon nanotube is 30-80 nm, and the length is less than 10 μm.

[0013] Furthermore, in the electrolyte, the organic bromide salt includes at least one of imidazole bromide, pyridinium bromide, methylpropylmorpholine bromide, and quaternary ammonium salt, and the auxiliary electrolyte includes at least one of ZnSO4, ZnBr2, AlCl3, and KCl. Among them, the imidazole bromide includes 1-methyl-3-propylimidazolium bromide (CAS No. 85100-76-1, molecular formula C7H 13 BrN2), etc., the pyridinium bromide includes N-butylpyridinium bromide, etc., and the quaternary ammonium salt includes tetrabutylammonium bromide, etc.

[0014] Furthermore, the concentration of the organic bromide salt in the electrolyte is 0.4-0.6 mol / L. The concentration of the auxiliary electrolyte in the electrolyte is 0.4-0.6 mol / L. The solvent of the electrolyte is water.

[0015] Preferably, the organic bromide salt is 1-methyl-3-propyl imidazolium bromide, and the complexing agent MPI is introduced into the electrolyte. + , can stabilize the generation and consumption of Br3-, Br3- and MPI + The formed complex can be deposited on the working electrode, realizing a reversible change in the color of the smart window from colorless to bright yellow.

[0016] Furthermore, the present invention also provides a method for preparing the above-mentioned non-metallic electrochromic smart window based on reversible bromine deposition, which method comprises the following steps:

[0017] (1) uniformly mixing a catalyst, a surfactant, and water to obtain a catalyst dispersion;

[0018] (2) coating the surface of the transparent conductive oxide glass with a binder solution and a catalyst dispersion, and repeating this step until the catalyst layer thickness meets the requirements;

[0019] (3) immersing the transparent conductive oxide glass with the catalyst layer in concentrated nitric acid for acid treatment;

[0020] (4) washing and drying the acid-treated sample;

[0021] (5) attaching a zinc foil frame or a zinc grid to the glass to obtain glass with a zinc foil frame or a zinc grid;

[0022] (6) Using transparent conductive oxide glass or transparent conductive oxide glass with a catalyst layer on the surface as the working electrode and glass with a zinc foil frame or zinc grid as the counter electrode, the two are sealed with tape and then filled with electrolyte to obtain a non-metallic electrochromic smart window based on reversible bromine deposition.

[0023] Furthermore, in step (1), the surfactant is a non-ionic surfactant, such as Triton X-100, Tween-20, etc.

[0024] Furthermore, in step (1), the selection of the catalyst is consistent with the above description, the concentration of the catalyst in the dispersion is 0.5-1.5 mg / ml, and the concentration of the surfactant in the dispersion is 9-11 mg / ml.

[0025] Furthermore, in step (2), the binder can make the catalyst adhere more firmly to the surface of the transparent conductive oxide glass, and the binder can be 3-aminopropyltriethoxysilane. The concentration of the binder solution can be 0.05-0.15 g / ml.

[0026] Furthermore, in step (2), a layer of binder solution is first spin-coated, followed by a layer of catalyst, so that the catalyst adheres uniformly to the surface of the transparent conductive oxide glass in a layered manner. If the required thickness cannot be achieved after a single spin-coating, the steps of spin-coating the binder solution and then the catalyst dispersion can be repeated until the required thickness is achieved.

[0027] Furthermore, in step (3), the concentration of concentrated nitric acid is 60-80 wt%, for example, 60%, 65%, 70%, 75%, or 80%. The concentrated nitric acid is used to remove residual surfactants and binders. The sample is typically immersed in concentrated nitric acid for 50-60 minutes. If the immersion time is too long, the catalyst layer will fall off; if the immersion time is too short, the residual binder will affect the performance.

[0028] The present invention has the following beneficial effects:

[0029] 1. The present invention proposes for the first time a non-metallic electrochromic device based on the reversible conversion of Br- / Br3- to achieve electrochromic performance. The surface of transparent conductive glass is modified with carbon nanotubes (CNTs) or graphene or other carbon materials or transition metal oxides to reduce the Gibbs free energy of the reversible conversion of Br- / Br3-, thereby promoting the efficient conversion of Br- to Br3-. Preferably, the complexing agent MPI is introduced into the electrolyte. + To stabilize Br3 - The generation and consumption of bromine achieves significant optical modulation from colorless to bright yellow. Through the cooperation of these two, a highly controllable and reversible bromine deposition / dissolution process is achieved.

[0030] 2. The electrochromic smart window of the present invention has a simple structure and is easy to process. It uses a non-metallic bromine system to replace precious metals, reducing material costs by 60%.

[0031] 3. The electrochromic smart window of the present invention is preferably produced by MPI + Complex Br3 - , MPI +The powerful complexing ability for Br3- effectively inhibits the shuttle effect within the smart window. After 3000 cycles, the modulation rate remains at a maximum of 96%, showing excellent cyclic stability.

[0032] 4. The electrochromic smart window of the present invention can play a catalytic role by modifying CNTs, graphene or transition metal oxides on the working electrode, catalytically reducing the activation energy of the reaction, and the coloring / fading time can be shortened to 41.1s and 6.6s respectively, which is correspondingly fast.

[0033] 5. The electrochromic smart window of the present invention has high optical performance, with a maximum modulation rate of 69% (780nm) in the visible light region and a distinct bright yellow color, filling the market gap of neutral color of electrochromic devices and enriching the color of electrochromic devices.

[0034] 6. The electrochromic smart window of the present invention has a wide voltage window, and the operating voltage (0.8-2.1V) is lower than the oxygen evolution potential (2.6V), thus avoiding side reactions.

[0035] 7. The electrochromic smart window of the present invention has a simple structure, is easy to process, has low cost, high stability, fast response, high optical performance, and a wide voltage window. It provides new ideas for the diversified application of electrochromic technology in the future and is suitable for fields such as building energy-saving glass and automobile smart sunroofs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the structure and electrochromic mechanism of the non-metallic electrochromic smart window based on reversible bromine deposition of the present invention.

[0037] Figure 2 is the carbon nanotube (CNTs) to Br - / Br3 - Catalytic mechanism of redox reaction and its relationship with MPI + Schematic diagram of the complexation effect.

[0038] Figure 3 These are the transmittance curves of the non-metallic electrochromic smart window based on reversible bromine deposition prepared in Example 1 in the tinted (2.1 V) and faded (0.8 V) states.

[0039] Figure 4 The response time of coloring and fading of the non-metallic electrochromic smart window based on reversible bromine deposition prepared in Example 1.

[0040] Figure 5 Transmittance change of the non-metallic electrochromic smart window based on reversible bromine deposition prepared in Example 1 during 3000 coloring / fading cycles.

[0041] Figure 6These are photos of the tinted and faded states of the non-metallic electrochromic smart window based on reversible bromine deposition prepared in Example 1.

[0042] Figure 7 Transmittance change during tinting / fading cycle of the non-metallic electrochromic smart window based on reversible bromine deposition prepared in Example 2.

[0043] Figure 8 Transmittance change of the non-metallic electrochromic smart window based on reversible bromine deposition prepared in Example 3 during 100 coloring / fading cycles.

[0044] Figure 9 Transmittance change during tinting / fading cycle of the non-metallic electrochromic smart window based on reversible bromine deposition prepared in Example 4. DETAILED DESCRIPTION

[0045] The following description of exemplary embodiments of the present invention includes various details to facilitate understanding, which should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions, operations, and structures are omitted from the following description.

[0046] Unless otherwise defined, technical and scientific terms used in this specification have the same meanings as commonly understood by those skilled in the art. Although methods and materials similar or equivalent to those described herein can be used in experiments or applications, the present invention describes the materials and methods below. In the event of conflict, the present specification, including definitions, will control.

[0047] In the following examples and comparative examples, the carbon nanotubes used were from Aladdin Company, with an outer diameter of 30-80 nm and a length of less than 10 μm.

[0048] Example 1

[0049] like Figure 1 Figure 2 shows the schematic diagram of the structure of the non-metallic electrochromic smart window based on reversible bromine deposition according to the present invention. The window consists of a working electrode, an electrolyte, and a counter electrode, with the electrolyte located between the working and counter electrodes. The working electrode is an FTO / CNTS composite electrode, the counter electrode is a zinc electrode, and the electrolyte is an aqueous solution containing 1-methyl-3-propylimidazolium bromide (MPIBr) and ZnSO4. The FTO / CNTS composite electrode is attached to the bare glass surface, and the zinc electrode is attached to the bare glass surface in the form of a zinc foil frame.

[0050] The assembly method of the non-metallic electrochromic smart window is as follows:

[0051] 1. Preparation of CNTs dispersion: 0.01 g of carbon nanotubes (CNTs) and 0.1 g of Triton X-100 surfactant were dissolved in 10 ml of deionized water and sonicated for 2 h to form a uniform dispersion.

[0052] 2. Preparation of adhesive solution: Dissolve 1.0 g of 3-aminopropyltriethoxysilane (APTS) in 10 ml of deionized water and mix well.

[0053] 3. Spin coating process: 3×3cm after cleaning 2 On the FTO conductive glass substrate, APTS solution and CNTs dispersion were spin-coated in sequence, and the above spin-coating APTS solution-spin-coating CNTs dispersion steps were repeated twice to enhance the loading uniformity. The final thickness of the CNTs layer was about 10 nm.

[0054] 4. Acid treatment: The spin-coated FTO conductive glass with CNTs film was immersed in 70wt% nitric acid (HNO3) solution for 50 minutes to remove residual surfactant and APTS.

[0055] 5. Cleaning and drying: After acid treatment, the conductive glass was removed, rinsed thoroughly with deionized water, and then dried in a 60°C oven overnight to obtain the FTO / CNTs composite electrode.

[0056] 6. Take 3×3cm 2 The bare glass is then taken from a commercially available zinc foil frame, which is a hollow square with a size of 3×3 cm. 2 The zinc foil frame has a width of 5 mm and a thickness of 0.1 mm. The zinc foil frame is adhered to the bare glass surface using 1 mm thick double-sided tape to obtain a counter electrode.

[0057] 7. Preparation of 0.5M MPIBr + 0.5M ZnSO4 electrolyte: Use a precision balance to accurately weigh 1.0254g MPIBr (1-methyl-3-propylimidazolium bromide) and 0.8073g ZnSO4. Dissolve each in a small amount of deionized water. Transfer both solutions to the same container. Rinse the beaker with deionized water and combine the liquids. Finally, dilute to 10mL using a volumetric flask or graduated cylinder and shake thoroughly.

[0058] 8. Use the prepared FTO / CNTs composite electrode as the working electrode and the glass with a zinc foil frame as the counter electrode. Use 3 mm thick double-sided tape to stick the working electrode and the counter electrode together. Then inject the electrolyte into them through a syringe to ensure that there are no bubbles and no leakage.

[0059] Example 2

[0060] The non-metallic electrochromic smart window was assembled in the manner of Example 1, except that the carbon nanotubes were replaced with graphene of equal mass, and the graphene size was less than 10 μm.

[0061] Example 3

[0062] The non-metallic electrochromic smart window was assembled in the manner of Example 1, except that the working electrode was FTO conductive glass.

[0063] Example 4

[0064] The non-metallic electrochromic smart window was assembled in the manner of Example 1, except that the concentration of MPIBr in the electrolyte was 1 M (1 mol / L) and the concentration of ZnSO4 was 0.5 M.

[0065] Performance Verification

[0066] 1. Optical contrast test

[0067] 1.1 Experimental sample: the smart window device prepared in Example 1.

[0068] 1.2 Experimental Procedure: Using a UV-Vis spectrophotometer (Hitachi UH5700), set the wavelength range to 400-1000 nm. Apply 2.1 V to the device for 60 seconds. After the device is fully colored, measure the transmittance at 400-1000 nm. Apply 0.8 V to the device for 30 seconds. After the device is completely faded, measure the transmittance at 400-1000 nm.

[0069] 1.3 Experimental results: The transmittance of the device in the tinted and faded states is as follows Figure 3 As shown in the figure, the device has the highest optical modulation rate at 780nm, the transmittance in the faded state at 780nm is 75%, the transmittance in the colored state is 6%, and the modulation rate at 780nm is 69%. The high optical contrast of the device of the present invention is due to the light blocking effect of the MPIBr3 complex, which is significantly better than that of traditional EC materials (usually <50%). After the device is colored, the color changes from colorless to bright yellow, as shown in the figure. Figure 6 As shown, the bright yellow color expands the application scenarios of EC devices, such as privacy protection and decorative windows.

[0070] 2. Optical contrast and response time test

[0071] 2.1 Experimental sample: the smart window device prepared in Example 1.

[0072] 2.2 Experimental procedures: Using a UV-visible spectrophotometer (Hitachi UH5700), the response time of the device in the faded state (0.8 V) and the colored state (2.1 V) was measured at a wavelength of 780 nm, where the response time is the time required for the device transmittance to reach 90% of the maximum modulation rate.

[0073] 2.3 Experimental results: The response time curves of device coloring and fading are as follows Figure 4 As shown in the figure, the device of the present invention exhibits a high optical modulation rate, with a coloring time of 41.1 seconds and a fading time of 6.6 seconds, demonstrating a rapid response. The high optical modulation rate is attributed to the light-blocking effect of the MPIBr3 complex, while the rapid response is attributed to the high conductivity of the CNTs. The device of the present invention combines high dynamic range with rapid response, making it suitable for the real-time control needs of smart windows.

[0074] 3. Cyclic stability test

[0075] 3.1 Experimental samples: smart window devices prepared in Example 1, Example 2, Example 3, and Example 4.

[0076] 3.2 Experimental steps:

[0077] 3.2.1 Set the cycle conditions: coloring voltage 2.1 V (60 seconds) → fading voltage 0.8 V (30 seconds), wavelength 780 nm.

[0078] 3.2.2 Use an electrochemical workstation (Chenhua Chi660E) to automatically record the transmittance of each device after each cycle, for a total of 3000 cycles. Pause the test after every 500 cycles and calibrate the transmittance using a UV spectrophotometer.

[0079] 3.3 Data processing: Optical modulation retention rate after device cycling = optical modulation rate after cycling n times / initial optical modulation rate * 100%.

[0080] 3.4 Experimental results:

[0081] The transmittance variation curve of the device prepared in Example 1 during 3000 coloring / fading cycles is shown in FIG. Figure 5 As shown in the figure, the optical modulation retention rate of the device is 100% after 2000 cycles, and the optical modulation retention rate drops to 96% after 3000 cycles, indicating that the device has excellent cycle stability. This excellent cycle stability is attributed to the MPIBr to Br3 - The fixation effect of CNTs and the high catalytic efficiency of CNTs are the main reasons for the slight attenuation of the optical modulation rate after 3000 cycles, which may be related to the local accumulation of by-products in the electrolyte.

[0082] The transmittance change curve of the device prepared in Example 2 during 50 coloring / fading cycles in 4500s is as follows: Figure 7 As shown in the figure, the optical modulation retention rate of the device is 100% after 50 cycles. Compared with Example 1, it also has good cycle stability during this period, but the optical modulation rate of the device (transmittance in the faded state - transmittance in the colored state) is less than 50%, which may be mainly due to the different structural dimensions and electronic band characteristics of graphene and carbon nanotubes.

[0083] The transmittance variation curve of the device prepared in Example 3 during 100 coloring / fading cycles is shown in FIG. Figure 8 As shown, with the increase of cycle time and number, the modulation rate of the device decreases significantly, and the cycle stability is much worse than that of the device in Example 1.

[0084] The transmittance change curve of the device prepared in Example 4 after a total of 166 coloring / fading cycles in 15000s is as follows: Figure 9 As shown in the figure, with the increase of cycle time and number, the modulation rate of the device decreases significantly compared with Example 1, and the cycle stability is very poor.

Claims

1. A non-metallic electrochromic smart window based on reversible bromine deposition, characterized by: The invention comprises a working electrode and a counter electrode, wherein an electrolyte is filled between the working electrode and the counter electrode, wherein the working electrode is transparent conductive glass or transparent conductive glass with a catalyst modified on the surface, wherein the catalyst comprises a carbon material or a transition metal oxide, and the counter electrode is glass with a zinc foil frame or a zinc grid. The electrolyte comprises a core electrolyte and an auxiliary electrolyte, wherein the core electrolyte is a brominated organic salt, wherein the brominated organic salt comprises imidazole bromide, pyridinium bromide, methylpropylmorpholine bromide, and quaternary ammonium salt, and the auxiliary electrolyte comprises ZnSO4, ZnBr2, AlCl3, and KCl.

2. The non-metallic electrochromic smart window according to claim 1, wherein: The imidazole bromide includes 1-methyl-3-propyl imidazole bromide, the pyridinium bromide includes N-butylpyridinium bromide, and the quaternary ammonium salt includes tetrabutylammonium bromide.

3. The non-metallic electrochromic smart window according to claim 1, wherein: The transparent conductive oxide glass is FTO conductive glass or ITO conductive glass.

4. The non-metallic electrochromic smart window according to claim 1, wherein: The carbon material is carbon nanotube or graphene; the transition metal oxide includes at least one of RuO2, CuO, Co3O4, CeO2, TiO2, WO3, and IrO.

5. The non-metallic electrochromic smart window according to claim 1 or 4, characterized in that: The thickness of the catalyst layer is 0.1-20 nm.

6. The non-metallic electrochromic smart window according to claim 1, characterized in that: In the electrolyte, the concentration of the brominated organic salt is 0.4-0.6 mol / L, and the concentration of the auxiliary electrolyte is 0.4-0.6 mol / L.

7. A method for preparing a non-metallic electrochromic smart window based on reversible bromine deposition according to any one of claims 1 to 6, characterized in that The following steps are involved: (1) uniformly mixing a catalyst, a surfactant, and water to obtain a catalyst dispersion; (2) coating the surface of the transparent conductive oxide glass with a binder solution and a catalyst dispersion, and repeating this step until the catalyst layer thickness meets the requirements; (3) immersing the transparent conductive oxide glass with the catalyst layer in concentrated nitric acid for acid treatment; (4) washing and drying the acid-treated sample; (5) attaching a zinc foil frame or a zinc grid to the glass to obtain glass with a zinc foil frame or a zinc grid; (6) Using transparent conductive oxide glass or transparent conductive oxide glass with a catalyst layer on the surface as the working electrode and glass with a zinc foil frame or zinc grid as the counter electrode, the two are sealed with tape and then filled with electrolyte to obtain a non-metallic electrochromic smart window based on reversible bromine deposition.

8. The preparation method according to claim 7, characterized in that: In step (1), the surfactant is a nonionic surfactant, preferably Triton X-100; preferably, in step (1), the concentration of the catalyst in the dispersion is 0.5-1.5 mg / ml, and the concentration of the surfactant is 9-11 mg / ml.

9. The preparation method according to claim 7, characterized in that: In step (2), the binder is 3-aminopropyltriethoxysilane, and the concentration of the binder solution is 0.05-0.15 g / ml.

10. The preparation method according to claim 7, characterized in that: In step (3), the concentration of the concentrated nitric acid is 60-80 wt %, and the acid treatment time is 50-60 min.

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