A porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface, and its preparation method and application

Abstract

The present invention discloses a porous electrochromic material formed by the self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions, as well as a preparation method and application thereof. The present invention does not require a template and directly synthesizes the porous electrochromic material formed by the self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions on an FTO conductive glass substrate via a one-step solvothermal method using hydrofluoric acid as an auxiliary agent and ethanol as a solvent. The titanium source is a mixture of tetrabutyl titanate and titanium isopropoxide. The surface fluoride ion-modified porous titanium dioxide nanocrystal electrochromic material prepared by the present invention has abundant oxygen vacancies and excellent dual-band electrochromic properties, enabling independent and selective optical transmittance regulation for visible and near-infrared light. The preparation method of the present invention is simple and reproducible, supporting large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of electrochromic thin film materials, and in particular to a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluorine ions on the surface, and a preparation method and application thereof. Background Art

[0002] Many current electrochromic windows can switch between bright and dark modes by blocking visible light, or by blocking both visible and near-infrared light, without any spectral selectivity. Since the near-infrared region accounts for approximately 50% of total solar radiation, independently regulating near-infrared radiation is key to achieving solar thermal management. Most current dual-band electrochromic materials are complex composites, making the synthesis of single-phase electrochromic materials with independent control of VIS and NIR transmittance a highly pressing task.

[0003] Titanium dioxide nanocrystals have attracted considerable attention due to their excellent chemical stability, high transparency in the visible light region, non-toxicity, environmental friendliness, and abundant reserves. To achieve the desired dual-band response, titanium dioxide nanocrystals are often doped with heterovalent metal atoms, such as niobium and tantalum, to increase the free electron density and induce localized surface plasmon resonance absorption in the near-infrared range. However, heterovalent atom doping can introduce lattice strain and lattice distortion, adversely affecting the structural stability of the host. Summary of the Invention

[0004] The purpose of the present invention is to provide a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluorine ions on the surface, as well as a preparation method and application thereof, which can solve the technical problems raised by the above-mentioned background technology.

[0005] In one aspect, the present invention provides a porous electrochromic material formed by the self-assembly of fluoride-modified titanium dioxide nanocrystals. According to an embodiment of the present invention, the porous electrochromic material is formed by preparing a titanium source precursor solution and using a solvothermal method to induce the self-assembly of fluoride-modified titanium dioxide nanocrystals on a FTO conductive glass substrate.

[0006] In addition, the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions according to the above embodiment of the present invention may also have the following additional technical features:

[0007] In some embodiments of the present invention, the porous electrochromic material has excellent dual-band electrochromic performance and can achieve rapid independent and selective optical transmittance adjustment of visible light and near-infrared light at a voltage of +1.5V--1.5V.

[0008] In some embodiments of the present invention, the porous electrochromic material has a contrast ratio of 71.4%-77.5% at 700nm, a contrast ratio of 25.4%-62.5% at 1300nm, and a coloring efficiency of 23.4-38.5cm 2 / C.

[0009] In some embodiments of the present invention, the absorption peaks of the absorption spectrum of the porous electrochromic material in the colored state exist at 453 nm and 700 nm in the visible light region.

[0010] In another aspect of the present invention, a method for preparing a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface is provided. According to an embodiment of the present invention, the method comprises the following steps:

[0011] (1) Cleaning the surface of FTO conductive glass substrate;

[0012] (2) preparing a titanium source precursor solution: adding a titanium source and hydrofluoric acid to ethanol according to a ratio, and stirring to obtain a titanium source precursor solution;

[0013] (3) Solvothermal reaction: adding the titanium source precursor solution prepared in step (2) into a high-pressure reactor, fixing the conductive surface of the FTO conductive glass substrate facing downward in the titanium source precursor solution to carry out the reaction, and obtaining a solvent thermal reaction product;

[0014] (4) Drying treatment: The solvent thermal reaction product obtained in step (3) is repeatedly rinsed with deionized water, and the solvent thermal reaction product after rinsing is dried to obtain a dense and uniform transparent film on the FTO conductive glass substrate, which is a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface.

[0015] In addition, the method for preparing a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions according to the above embodiment of the present invention may also have the following additional technical features:

[0016] In some embodiments of the present invention, the specific operation of step (1) is as follows: the FTO conductive glass substrate is placed in acetone, ethanol, and deionized water in turn, and ultrasonically cleaned for 8-12 minutes respectively. The FTO conductive glass substrate after ultrasonic cleaning is placed on filter paper and dried using an infrared lamp.

[0017] In some embodiments of the present invention, in step (2), the titanium source is a mixture of tetrabutyl titanate and titanium isopropoxide, and the molar ratio of tetrabutyl titanate, titanium isopropoxide, hydrofluoric acid and ethanol is 2:2:1:50-5:5:3:50.

[0018] In some embodiments of the present invention, in step (3), the conductive surface of the FTO conductive glass substrate is fixed at 45° downward in the titanium source precursor solution for reaction, the reaction temperature is 150-200°C, and the reaction time is 12-24h.

[0019] In some embodiments of the present invention, in step (4), the drying temperature is 50-100° C. and the drying time is 12-24 hours.

[0020] In another aspect, the present invention provides an electrochromic window. According to an embodiment of the present invention, a glass substrate is covered with the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals with surface fluoride ions modified.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The titanium oxide nanocrystalline film prepared by the one-step solvothermal method of the present invention has a porous structure, which can effectively increase the electron transmission speed and particle diffusion rate, accelerate the reaction kinetics process, and significantly improve the response speed and cycle stability of the electrochromic material;

[0023] 2. Since the electronegativity of surface fluorine is greater than that of oxygen, surface fluoride ion modification can promote the expulsion of lattice oxygen, thereby forming oxygen vacancies. Moreover, the fluoride ions are in a surface adsorbed state and will not be incorporated into the lattice, thus avoiding the occurrence of lattice distortion. Secondly, the appropriate oxygen vacancy concentration is conducive to the transmission of lithium ions and the increase of free electron concentration, thereby increasing the localized surface plasmon resonance absorption and achieving selective modulation of near-infrared light.

[0024] 3. Since LSPR absorption strongly depends on the size of nanocrystals, using hydrofluoric acid as an auxiliary agent can refine the grains and play a key role in controlling the size of nanocrystals;

[0025] 4. The porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluorine ions on the surface of the present invention has a simple preparation method, easy equipment operation, good repeatability, short production cycle, low process cost, and is conducive to large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 XRD characterization diagram of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface and the pure titanium oxide material obtained in Example 1 of the present invention;

[0027] Figure 2 This is a Raman characterization image of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface obtained in Example 1 of the present invention and a pure titanium oxide material;

[0028] Figure 3 This is an infrared characterization image of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface obtained in Example 1 of the present invention and the pure titanium oxide material;

[0029] Figure 4 This is the XPS characterization of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface and the pure titanium oxide material obtained in Example 1 of the present invention;

[0030] Figure 5 This is a characterization diagram of oxygen vacancies in a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on their surfaces and a pure titanium oxide material obtained in Example 1 of the present invention;

[0031] Figure 6 (ab) are electron microscope scanning images of pure titanium oxide. Figure 6 (cd) are electron microscope scanning images of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions prepared in Example 1 of the present invention;

[0032] Figure 7 (a) is the transmission electron microscope morphology of pure titanium oxide. Figure 7 (b) is a transmission electron microscopy image of the porous electrochromic material formed by self-assembly of surface fluoride-modified titanium dioxide nanocrystals prepared in Example 1 of the present invention;

[0033] Figure 8 Figures (a), (b), (c) and (d) are respectively the transmission electron microscope dark field image of the porous electrochromic material formed by self-assembly of surface fluoride ion-modified titanium dioxide nanocrystals prepared in Example 1 of the present invention, and the electron energy spectrum of Ti atoms, O atoms and F atoms;

[0034] Figure 9 (a) is the nitrogen adsorption-desorption curve of pure titanium oxide. Figure 9 (b) is the nitrogen adsorption / desorption curve of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 1 of the present invention;

[0035] Figure 10 This is a schematic diagram of the kinetic electrochromic performance of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 1 of the present invention under an applied voltage of -1.5 V;

[0036] Figure 11 This is a schematic diagram of the kinetic electrochromic performance of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 1 of the present invention under an applied voltage of -1V;

[0037] Figure 12This is a schematic diagram of the coloring efficiency of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 1 of the present invention;

[0038] Figure 13 Schematic diagram of the kinetic electrochromic performance of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface prepared in Example 2 of the present invention;

[0039] Figure 14 This is a schematic diagram of the coloring efficiency of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 2 of the present invention;

[0040] Figure 15 Schematic diagram of the kinetic electrochromic performance of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface prepared in Example 3 of the present invention;

[0041] Figure 16 Schematic diagram of the coloring efficiency of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 3 of the present invention;

[0042] Figure 17 These are digital photos of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 4 of the present invention at different voltages. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0044] Example 1

[0045] A method for preparing a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface, comprising the following steps:

[0046] (1) Surface cleaning of FTO conductive glass substrate: The FTO conductive glass substrate was placed in acetone, ethanol, and deionized water in turn, and ultrasonically cleaned for 8 min each. The ultrasonically cleaned FTO conductive glass substrate was placed on filter paper and dried using an infrared lamp.

[0047] (2) preparing a titanium source precursor solution: adding a titanium source and hydrofluoric acid to ethanol according to a ratio, and stirring to obtain a titanium source precursor solution; wherein the titanium source is a mixture of tetrabutyl titanate and titanium isopropoxide, and the molar ratio of tetrabutyl titanate, titanium isopropoxide, hydrofluoric acid and ethanol is 2:2:1:50-3:4:1:50;

[0048] (3) Solvothermal reaction: The titanium source precursor solution prepared in step (2) was added to a high-pressure reactor, and the conductive surface of the FTO conductive glass substrate was fixed at 45° downward in the titanium source precursor solution to carry out the reaction at a reaction temperature of 150°C and a reaction time of 12 h to obtain a solvent thermal reaction product;

[0049] (4) Drying treatment: The solvent thermal reaction product obtained in step (3) is repeatedly rinsed with deionized water, and the solvent thermal reaction product after rinsing is dried in a forced air drying oven at a drying temperature of 50° C. for 12 h. A dense and uniform transparent film is obtained on the FTO conductive glass substrate, which is a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface.

[0050] The structure of the porous electrochromic material formed by self-assembly of surface fluoride-modified titanium dioxide nanocrystals prepared in Example 1 was observed using X-ray diffractometer (XRD, Rigaku D / MAX2500V), microconfocal laser Raman spectrometer (LabRAMhR Evolution) and Fourier transform infrared spectrometer (Thermo Nicolet). Figure 1 As shown in FIG. 1 , the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluorine ions on the surface prepared in Example 1 is anatase titanium oxide. Figure 2 As shown, the Raman spectra are at about 150 cm -1 , 400cm -1 , 515cm -1 and 638cm -1 The vibration mode is shown at E, which represents the anatase structure. g 、B 1g 、A 1g +B 1g and E g The results show that the structure of the prepared titanium dioxide film is mainly anatase structure, and compared with pure titanium dioxide, the peak of the fluoride ion modified titanium dioxide nanocrystalline film shifts to the high wavenumber direction. This is because fluoride ions can refine the grains, and the small size effect of nanocrystals will cause the Raman peak to shift to high wavenumbers. Figure 3 As shown in the figure, the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluorine ions prepared in Example 1 has a wavelength of 500 cm -1 The peak at 1630 cm is the stretching vibration peak of Ti-O bond. -1and 3400cm -1 The peak at 1630 cm is the vibration peak of water and -OH. Different from pure titanium oxide, the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluorine ions on the surface has a peak at 1630 cm -1 There is a weak absorption peak at , which is attributed to the stretching vibration of the surface F-Ti bond.

[0051] The surface atomic state of the porous electrochromic material formed by self-assembly of the surface fluoride ion-modified titanium dioxide nanocrystals prepared in Example 1 was observed using an X-ray photoelectron spectrometer (ESCALAB250Xi). Figure 4 As shown, the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluorine ions prepared in Example 1 has a fluorine peak at 684.5 eV, which proves that the fluorine ions are modified on the surface of the film in the form of adsorption and are not incorporated into the interior of the crystal lattice to replace oxygen.

[0052] The oxygen vacancy characteristics of the porous electrochromic material formed by self-assembly of the surface fluoride ion-modified titanium dioxide nanocrystals prepared in Example 1 were characterized by para-nuclear magnetic resonance spectroscopy (Bruker A300). Figure 5 As shown, the porous electrochromic material formed by self-assembly of surface fluorine ion-modified titanium dioxide nanocrystals prepared in Example 1 has an absorption peak of oxygen vacancies at a g value of 2.002, while pure titanium oxide does not have oxygen vacancies. Since fluorine has a relatively strong electronegativity, the fluorine ions adsorbed on the surface of titanium oxide will lead to charge imbalance, so it is necessary to discharge oxygen inside the lattice to balance the charge, thereby leading to the generation of oxygen vacancies. The presence of oxygen vacancies will reduce the insertion barrier of lithium ions and improve electronic conductivity, and provide a larger free space to facilitate the insertion of lithium ions. In addition, the presence of oxygen vacancies will lead to an increase in the concentration of free electrons to increase LSPR absorption and improve absorption in the infrared region, thereby obtaining the desired dual-band modulation function.

[0053] The morphology of the porous electrochromic material formed by self-assembly of the surface fluoride ion-modified titanium dioxide nanocrystals prepared in Example 1 was observed using a SU-8200 scanning electron microscope. Figure 6 As shown in (ab), the pure titanium oxide film has an irregular morphology consisting of disordered agglomerations of particles of uneven size. Figure 6 As shown in (cd), the porous electrochromic material formed by self-assembly of surface fluoride ion-modified titanium dioxide nanocrystals prepared in Example 1 is assembled into an ordered porous structure by nanocrystalline particles of uniform size, which promotes the penetration of electrolyte and increases the contact area between electrolyte and film, can effectively improve the electron transmission speed and particle diffusion rate, accelerate the reaction kinetics process, reduce the fading voltage of the film, and greatly improve the response speed and cycle stability of the electrochromic material.

[0054] The organization and lattice structure of the thin film formed by the self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 1 were observed using a field emission transmission electron microscope (JEM-2100F). Figure 7 As shown in (a), the particle size of pure titanium oxide is not uniform and the particle size is large. Figure 7 As shown in (b), the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals with surface modified by fluorine ions prepared in Example 1 has a distinct porous structure, and the nanocrystals have a uniform size of about 4 nm.

[0055] Figure 8 This is the energy spectrum of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 1. Figure 8 As shown in (a), the electronic energy spectra of Ti atoms, O atoms and F atoms are respectively as follows Figure 8 As shown in Figures 8(b), 8(c) and 8(d), it can be observed that titanium, oxygen and fluorine atoms are evenly distributed, and no other impurities are present.

[0056] The specific surface area and pore size of the porous electrochromic material formed by self-assembly of surface fluoride-modified titanium dioxide nanocrystals prepared in Example 1 were tested using a gas adsorption instrument (Autosorb-IQ3). Figure 9 As shown in (a), the specific surface area of ​​pure titanium oxide is 55.26 m 2 / g, the average pore size is 7.79nm. Figure 9 As shown in (b), the specific surface area of ​​the porous electrochromic material formed by self-assembly of surface fluoride-modified titanium dioxide nanocrystals prepared in Example 1 is 169.968 m 2 / g, with an average pore size of 4.3nm. The fluoride-modified nanocrystalline film has a large specific surface area and a small pore size, which can increase the penetration of the electrolyte and provide more active sites for the electrochromic reaction.

[0057] Example 2

[0058] A method for preparing a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface, comprising the following steps:

[0059] (1) Surface cleaning of FTO conductive glass substrate: The FTO conductive glass substrate was placed in acetone, ethanol, and deionized water in turn, and ultrasonically cleaned for 10 min each. The ultrasonically cleaned FTO conductive glass substrate was placed on filter paper and dried using an infrared lamp.

[0060] (2) preparing a titanium source precursor solution: adding a titanium source and hydrofluoric acid to ethanol according to a ratio, and stirring to obtain a titanium source precursor solution; wherein the titanium source is a mixture of tetrabutyl titanate and titanium isopropoxide; wherein the titanium source is a mixture of tetrabutyl titanate and titanium isopropoxide, and the molar ratio of tetrabutyl titanate, titanium isopropoxide, hydrofluoric acid and ethanol is 2:2:1:50-4:3:2:50;

[0061] (3) Solvothermal reaction: The titanium source precursor solution prepared in step (2) was added to a high-pressure reactor, and the conductive surface of the FTO conductive glass substrate was fixed at 45° downward in the titanium source precursor solution to carry out the reaction at a reaction temperature of 180°C and a reaction time of 24 h to obtain a solvent thermal reaction product;

[0062] (4) Drying treatment: The solvent thermal reaction product obtained in step (3) is repeatedly rinsed with deionized water, and the solvent thermal reaction product after rinsing is dried in a forced air drying oven at a drying temperature of 80° C. for 18 h. A dense and uniform transparent film is obtained on the FTO conductive glass substrate, which is a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface.

[0063] Example 3

[0064] A method for preparing a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface, comprising the following steps:

[0065] (1) Surface cleaning of FTO conductive glass substrate: The FTO conductive glass substrate was placed in acetone, ethanol, and deionized water in turn, and ultrasonically cleaned for 12 min each. The ultrasonically cleaned FTO conductive glass substrate was placed on filter paper and dried using an infrared lamp.

[0066] (2) preparing a titanium source precursor solution: adding a titanium source and hydrofluoric acid to ethanol according to a ratio, and stirring to obtain a titanium source precursor solution; wherein the titanium source is a mixture of tetrabutyl titanate and titanium isopropoxide, and the molar ratio of tetrabutyl titanate, titanium isopropoxide, hydrofluoric acid and ethanol is 2:2:1:50-5:4:2:50;

[0067] (3) Solvothermal reaction: The titanium source precursor solution prepared in step (2) was added to a high-pressure reactor, and the conductive surface of the FTO conductive glass substrate was fixed at a 45° angle downward in the titanium source precursor solution to carry out the reaction at a reaction temperature of 200°C and a reaction time of 24 h to obtain a solvent thermal reaction product;

[0068] (4) Drying treatment: The solvent thermal reaction product obtained in step (3) is repeatedly rinsed with deionized water, and the solvent thermal reaction product after rinsing is dried in a forced air drying oven at a drying temperature of 100° C. for 24 h. A dense and uniform transparent film is obtained on the FTO conductive glass substrate, which is a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface.

[0069] Example 4

[0070] A method for preparing a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface, comprising the following steps:

[0071] (1) Surface cleaning of FTO conductive glass substrate: The FTO conductive glass substrate was placed in acetone, ethanol, and deionized water in turn, and ultrasonically cleaned for 12 min each. The ultrasonically cleaned FTO conductive glass substrate was placed on filter paper and dried using an infrared lamp.

[0072] (2) preparing a titanium source precursor solution: adding a titanium source and hydrofluoric acid to ethanol according to a ratio, and stirring to obtain a titanium source precursor solution; wherein the titanium source is a mixture of tetrabutyl titanate and titanium isopropoxide, and the molar ratio of tetrabutyl titanate, titanium isopropoxide, hydrofluoric acid and ethanol is 2:2:1:50-5:5:3:50;

[0073] (3) Solvothermal reaction: The titanium source precursor solution prepared in step (2) was added to a high-pressure reactor, and the conductive surface of the FTO conductive glass substrate was fixed at a 45° angle downward in the titanium source precursor solution to carry out the reaction at a reaction temperature of 200°C and a reaction time of 24 h to obtain a solvent thermal reaction product;

[0074] (4) Drying treatment: The solvent thermal reaction product obtained in step (3) is repeatedly rinsed with deionized water, and the solvent thermal reaction product after rinsing is dried in a forced air drying oven at a drying temperature of 100° C. for 24 h. A dense and uniform transparent film is obtained on the FTO conductive glass substrate, which is a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface.

[0075] The kinetics, visible and near-infrared transmission (absorption) spectra, and coloring efficiency of the porous electrochromic materials formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions obtained in Examples 1, 2, 3, and 4 were tested as follows: by using an electrochemical workstation (CHI760E) and a UV-visible-near-infrared spectrophotometer (UV-3600, Japan), the electrochemical and electrochromic properties of the samples were recorded in a three-electrode system (the electrochromic film on the FTO substrate was the working electrode, Ag / AgCl was the reference electrode, the platinum wire was the counter electrode, and the 1.0 mol / L LiClO4 / PC solution was the electrolyte). In order to ensure that the light path was unobstructed, the reference electrode and the counter electrode were placed on one side of the working electrode. The reference electrode and the counter electrode were placed on one side. The transmission spectrum was recorded in the wavelength range of 250 to 1650 nm at voltages of -1.5 V and +1 V. By applying square wave voltages of -1.5 V (30 seconds), -1 V, and +1 V (30 seconds) at 700 nm, the dynamic optical transmittance changes at 700 nm and 1300 nm were recorded, and the coloring efficiency of the film was calculated.

[0076] like Figure 10 and Figure 11 As shown, the porous electrochromic material formed by self-assembly of surface fluoride ion-modified titanium dioxide nanocrystals prepared in Example 1 has a coloring and fading time of 12.8s / 4.4s at 700nm, and contrast ratios of 77.5% and 53% at 700nm and 1300nm, respectively, with dual-band selective modulation function.

[0077] like Figure 12 As shown in the figure, the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluorine ions prepared in Example 1 has a coloring efficiency of 38.5 cm 2 / C.

[0078] like Figure 13 As shown, the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluorine ions prepared in Example 2 has a coloring and fading time of 16.5s / 4.7s at 700nm and a contrast ratio of 71.5% at 700nm.

[0079] like Figure 14 As shown in the figure, the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluorine ions prepared in Example 2 has a coloring efficiency of 26.5 cm 2 / C.

[0080] like Figure 15 As shown, the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluorine ions prepared in Example 3 has a coloring and fading time of 19.8s / 5.9s at 700nm and a contrast ratio of 71.4% at 700nm.

[0081] like Figure 16 As shown in the figure, the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 3 has a coloring efficiency of 23.4 cm 2 / C.

[0082] like Figure 17 As shown, digital photos of the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with surface fluoride ions prepared in Example 4 at different coloring voltages.

[0083] The above content is merely an example and explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals with surface fluoride ions modified, characterized in that: The following steps are involved: (1) Cleaning the surface of FTO conductive glass substrate; (2) preparing a titanium source precursor solution: adding a titanium source and hydrofluoric acid to ethanol according to a ratio, and stirring to obtain a titanium source precursor solution, wherein the titanium source is a mixture of tetrabutyl titanate and titanium isopropoxide, and the molar ratio of tetrabutyl titanate, titanium isopropoxide, hydrofluoric acid and ethanol is 2:2:1:50-5:5:3:50; (3) Solvothermal reaction: adding the titanium source precursor solution prepared in step (2) into a high-pressure reactor, fixing the conductive surface of the FTO conductive glass substrate downward in the titanium source precursor solution for reaction to obtain a solvent thermal reaction product, wherein the conductive surface of the FTO conductive glass substrate is fixed downward at a 45° angle in the titanium source precursor solution for reaction, the reaction temperature is 150-200°C, and the reaction time is 12-24h; (4) Drying treatment: The solvent thermal reaction product obtained in step (3) is repeatedly rinsed with deionized water, and the solvent thermal reaction product after rinsing is dried to obtain a dense and uniform transparent film on the FTO conductive glass substrate, which is a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface.

2. The method for preparing a porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals with surface fluoride ions modified according to claim 1, characterized in that: The specific operation of step (1) is as follows: the FTO conductive glass substrate is placed in acetone, ethanol, and deionized water in sequence, and ultrasonically cleaned for 8-12 minutes respectively. The FTO conductive glass substrate after ultrasonic cleaning is placed on filter paper and dried using an infrared lamp.

3. The porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals with surface fluoride ions modified according to claim 1 and the preparation method thereof, characterized in that: In the step (4), the drying temperature is 50-100° C. and the drying time is 12-24 hours.

4. A porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals modified with fluoride ions on the surface, prepared by the preparation method according to any one of claims 1 to 3.

5. The porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals with surface fluoride ions modified according to claim 4, characterized in that: The porous electrochromic material has excellent dual-band electrochromic performance and can achieve rapid independent and selective optical transmittance adjustment of visible light and near-infrared light at a voltage of +1.5V--1.5V.

6. The porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals with surface fluoride ions modified according to claim 4, characterized in that: The porous electrochromic material has a contrast ratio of 71.4%-77.5% at 700nm, a contrast ratio of 25.4%-62.5% at 1300nm, and a coloring efficiency of 23.4-38.5cm 2 / C.

7. The porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals with surface fluoride ions modified according to claim 4, characterized in that: The absorption peaks of the absorption spectrum of the porous electrochromic material in the color state exist at 453 nm and 700 nm in the visible light region.

8. An electrochromic window, characterized in that: The glass substrate is covered with the porous electrochromic material formed by self-assembly of titanium dioxide nanocrystals with surface fluoride ions modified as claimed in claim 4.

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