Tungsten-niobium bimetal oxide electrochromic thin film, electrochromic thin film electrode and preparation method thereof

Abstract

The present application relates to a tungsten-niobium bimetallic oxide electrochromic film, an electrochromic film electrode and a preparation method thereof. The electrochromic film comprises tungsten-niobium bimetallic oxide in a nanowire structure or a nanowire cluster structure formed by self-agglomeration of nanowires. In the tungsten-niobium bimetallic oxide, the atomic ratio of tungsten to niobium is 2:1-1:6. The electrochromic film electrode comprises a conductive substrate and the electrochromic film grown on the conductive substrate, and the preparation method comprises the following steps: dissolving a tungsten source and a niobium source in an acidic solvent to obtain a precursor solution according to the atomic ratio of tungsten to niobium; immersing the conductive substrate in the precursor solution to perform a hydrothermal reaction; and after the reaction is completed, the tungsten-niobium bimetallic oxide electrochromic film electrode is obtained after cleaning and drying. Compared with the prior art, the present application has the advantages of wide wavelength range, large light modulation, high coloring efficiency, multiple response time options and the like.

Description

Technical Field

[0001] This invention relates to the field of electrochromic thin films, specifically to a tungsten-niobium bimetallic oxide electrochromic thin film, an electrochromic thin film electrode, and a method for preparing the same. Background Technology

[0002] Electrochromic technology is a technique that utilizes electrochromic materials to alter their reflection and transmission properties through the injection and extraction of electrons and ions under electrochemical action, resulting in changes in valence state and chemical composition. This manifests as reversible changes in color and transparency. Electrochromic materials can be categorized into organic and inorganic types. Transition metal oxides, among inorganic electrochromic materials, are a class of electrochromic materials with stable chemical properties.

[0003] Tungsten oxide and niobium oxide are two important transition metal oxides and also two excellent electrochromic materials. Since their electrochromic properties were discovered in the 1970s, tungsten oxide and niobium oxide have consistently attracted great attention from researchers. Both niobium oxide and tungsten oxide are cathodic electrochromic materials, meaning they change color (from colorless to blue) when a negative voltage is applied and fade (from blue to colorless) when a positive voltage is applied. However, due to the limitations of the materials themselves, the electrochromic properties of tungsten oxide and niobium oxide films cannot meet the needs of practical applications.

[0004] To address this issue, research on the application of niobium-tungsten bimetallic oxides in electrochromism has emerged in recent years. Since ordinary conductive substrates cannot withstand high temperatures, Nb... 18 W 16 O 93 The technology of reprocessing powder materials into thin films is gradually becoming mainstream. For example, Cai et al. (Advanced Energy Materials, 2021, 12(5): 2103106) used electrospray aerosol deposition pyrolysis to form films, and Liu et al. (ACS Nano, 2022, 16(2): 2621-2628) used spin coating to prepare films. These film preparation processes are relatively complex and costly, involving both powder preparation and film preparation. Moreover, their performance is relatively average, lacking wide-wavelength high light modulation performance, low coloring efficiency, long response time, and no tunability. Summary of the Invention

[0005] The purpose of this invention is to overcome at least one of the defects of the prior art and provide a tungsten-niobium bimetallic oxide electrochromic thin film with a wide wavelength range that can achieve large light modulation, high coloring efficiency, and multiple selectable response times, as well as an electrochromic thin film electrode and its preparation method.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] The inventors believe that, in order to address the issues of insufficient light modulation, low coloring efficiency, and long response time in practical applications, a simple and low-cost preparation method can be used to fabricate a tungsten-niobium bimetallic oxide thin film with a wide wavelength range capable of large light modulation, high coloring efficiency, and multiple selectable response times. This method promises to provide a strategy for truly meeting the various needs for electrochromic properties of materials in real-world applications. The following solution is proposed:

[0008] This invention employs a one-step hydrothermal method to prepare a series of tungsten-niobium bimetallic oxide nanocluster / nanowire structure thin film electrodes, achieving large optical modulation over a wide wavelength range. By adjusting the tungsten-niobium ratio, tungsten-niobium bimetallic oxide thin films with high coloring efficiency and various selectable response times are obtained. Different response times and different coloring efficiencies can be applied to different needs in practical scenarios, which helps to promote the application of bimetallic oxides in the field of electrochromism. The specific scheme is as follows:

[0009] A tungsten-niobium bimetallic oxide electrochromic thin film, the thin film comprising a tungsten-niobium bimetallic oxide having a nanowire structure or a nanowire cluster structure formed by the self-aggregation of nanowires.

[0010] Furthermore, in the tungsten-niobium bimetallic oxide, the atomic ratio of tungsten to niobium is 2:1 to 1:6.

[0011] Furthermore, in the tungsten-niobium bimetallic oxide, the atomic ratio of tungsten to niobium is (1-2):1.

[0012] An electrochromic thin-film electrode includes a conductive substrate and an electrochromic thin film as described above grown on the conductive substrate. The tungsten-niobium bimetallic oxide thin-film electrode is composed of FTO conductive glass and a tungsten-niobium bimetallic oxide thin film. The tungsten-niobium bimetallic oxide thin-film electrodes with various tungsten-niobium ratios are fabricated to control the proportion of tungsten and niobium in the tungsten-niobium bimetallic oxide. The tungsten-niobium bimetallic oxide thin films with various tungsten-niobium ratios exhibit a nanowire structure or a nanowire cluster structure formed by the self-aggregation of nanowires. The high performance is characterized by large average light modulation, high coloring efficiency, and multiple selectable response times in the visible and short-wave near-infrared light regions.

[0013] Tungsten-niobium bimetallic oxide films exhibit large average light modulation in the visible light region (390-780 nm) and the short-wave near-infrared region (780-1100 nm).

[0014] The specific strategy for adjusting the response time is as follows: In tungsten-niobium bimetallic oxide, when the tungsten-niobium ratio is between 2:1 and 1:6, changing the tungsten-niobium ratio in the tungsten-niobium bimetallic oxide film can give the tungsten-niobium bimetallic oxide film a variety of selectable response times without changing the light modulation capability.

[0015] The specific strategy for controlling the coloring efficiency is as follows: In tungsten-niobium bimetallic oxides, when the tungsten-niobium ratio is between 2:1 and 1:6, changing the tungsten-niobium ratio in the tungsten-niobium bimetallic oxide film can obtain various coloring efficiencies without changing the light modulation capability. Among them, the film with a tungsten-niobium ratio of 2:1 has the highest coloring efficiency. This is because the coloring performance is related to the crystallinity of the (001) and (002) crystal planes. According to the color center theory, higher crystallinity results in higher lattice vibration frequencies, leading to stronger resonance of photons and the transfer of photon energy into the lattice. Furthermore, the higher the tungsten content, the higher the crystallinity of these two crystal planes in the film prepared by this method.

[0016] Nanoclusters are simply one manifestation of high crystallinity in film morphology, just like the low-crystallinity nanowires in other embodiments, which have relatively low crystallinity. For example, the difference in morphology is that the film structure in Examples 1-2 is nanoclusters, while the film morphology in Examples 3-7 is nanowires with different degrees of aggregation, which is also related to the crystallinity of different crystal planes.

[0017] A method for preparing an electrochromic thin-film electrode as described above, wherein the method for preparing the thin-film electrode is also a method for preparing an electrochromic thin film, the method comprising the following steps:

[0018] According to the atomic ratio of tungsten and niobium, the tungsten source and the niobium source are dissolved in an acidic solvent to obtain a precursor solution;

[0019] The conductive substrate is immersed in the precursor solution to carry out a hydrothermal reaction;

[0020] After the reaction was completed, the tungsten-niobium bimetallic oxide electrochromic thin film electrode was obtained after cleaning and drying.

[0021] Furthermore, the conductive substrate is a double-layer FTO conductive glass. During immersion, the two SiO2 surfaces of the FTO conductive glass are in contact with each other, and the FTO surface faces outward and is in contact with the reactants.

[0022] Furthermore, the tungsten source includes ammonium paratungstate, the niobium source includes ammonium niobate oxalate hydrate, and the acidic solvent is an aqueous solution of ethanol and oxalic acid in a ratio of (30-40) mL:5g.

[0023] Furthermore, the volume fraction of the ethanol-water solution is 35-45%.

[0024] Furthermore, the temperature of the hydrothermal reaction is 180-200℃, and the holding time is 4-6 hours.

[0025] Furthermore, the ratio of ammonium niobate oxalate hydrate, ammonium paratungstate, oxalic acid, and aqueous ethanol solution in the precursor solution is (0.1167-0.7002)g:(0.05-0.1)g:5g:(30-40)mL.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The present invention adopts a simple and easy-to-operate one-step solvothermal method without seed layer, which is conducive to the rapid preparation of tungsten-niobium bimetallic oxide films with various tungsten-niobium ratios, and is conducive to exploring and realizing the electrochromic properties regulation of tungsten-niobium bimetallic oxide films. It requires fewer types of reagents, has low cost, and is easy to realize industrial application of film preparation on glass surface.

[0028] (2) The tungsten-niobium bimetallic oxide thin film prepared by the present invention has excellent wide wavelength modulation performance, especially in the visible light region and short-wave near-infrared light region, which is conducive to promoting the application of electrochromic technology in practical life and production.

[0029] (3) The strategy for regulating the electrochromic properties of tungsten-niobium bimetallic oxide thin films in this invention provides experience for the preparation of other bimetallic oxide thin films and the regulation of their electrochromic properties. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the preparation process of the tungsten-niobium bimetallic oxide thin film in the examples;

[0031] Figure 2 A digital photograph of the electrochromic effect prepared in Example 1, wherein a is the faded state and b is the colored state;

[0032] Figure 3 X-ray diffraction patterns of the electrochromic thin films prepared in Examples 1-7;

[0033] Figure 4 Scanning electron microscope image of the electrochromic thin film prepared in Example 1;

[0034] Figure 5 Scanning electron microscope image of the electrochromic thin film prepared in Example 2;

[0035] Figure 6 Scanning electron microscope image of the electrochromic thin film prepared in Example 3;

[0036] Figure 7 Scanning electron microscope image of the electrochromic thin film prepared in Example 4;

[0037] Figure 8 Scanning electron microscope image of the electrochromic thin film prepared in Example 5;

[0038] Figure 9 Scanning electron microscope image of the electrochromic thin film prepared in Example 6;

[0039] Figure 10 Scanning electron microscope image of the electrochromic thin film prepared in Example 7;

[0040] Figure 11 Transmittance curves of the tungsten-niobium bimetallic oxide nanocluster structure electrochromic thin film prepared in Example 1 under colored and faded states;

[0041] Figure 12 Bar graphs showing the maximum coloring efficiency of the tungsten-niobium bimetallic oxide nanocluster / wire structure electrochromic films prepared in Examples 1-7 as a function of the tungsten-niobium ratio. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0043] A tungsten-niobium bimetallic oxide electrochromic thin film electrode and its preparation method are disclosed. The tungsten-niobium bimetallic oxide electrochromic thin film exhibits a nanowire structure or a cluster structure formed by the self-assembly of nanowires. Its performance characteristics lie in the ultra-high average light modulation in the visible light region (390-780 nm) and the short-wave near-infrared light region (780-1100 nm), achieving approximately 70% light modulation in the visible light region and approximately 80% light modulation in the short-wave near-infrared light region. Without sacrificing light modulation, different coloring efficiencies and response times can be obtained by changing the tungsten-niobium ratio. The preparation method is as follows:

[0044] a) Weigh 0.1167-0.7002 g of ammonium niobate oxalate hydrate and 0.05-0.1 g of ammonium paratungstate in air at room temperature, and dissolve them together in 35 mL of 40% ethanol aqueous solution containing 5 g of oxalic acid to obtain precursor solutions with different niobium-tungsten atomic ratios of 2:1 to 1:6.

[0045] b) The double-layer FTO conductive glass is vertically immersed in a hydrothermal reactor containing the above reaction solution for hydrothermal reaction. The hydrothermal reaction temperature is 180-200℃, and the holding time is 4-6 hours. After the hydrothermal reaction is completed, it is naturally cooled to room temperature, washed with water, and then air-dried to obtain the tungsten-niobium bimetallic oxide thin film electrode.

[0046] See Figure 1 The flowchart illustrates a process for preparing a tungsten-niobium bimetallic oxide thin film according to the present invention. In the flowchart, the blank FTO glass, which serves as the substrate for film growth, needs to be covered with polytetrafluoroethylene tape before the hydrothermal reaction to leave a blank area for testing. The figure shows a double-layer structure with two identical blank FTO glass pieces having their conductive surfaces facing outwards and overlapping, ensuring that they stand vertically in the center of the reactor liner. The electrolyte used for electrochromic performance testing is selected as 0.1-3 mol / L, preferably 1-2 mol / L of lithium sulfate aqueous solution, sulfuric acid aqueous solution, or lithium perchlorate aqueous solution.

[0047] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the description of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0048] Example 1

[0049] A tungsten-niobium bimetallic oxide electrochromic thin film electrode and its preparation method are disclosed below:

[0050] Weigh out 0.1g of ammonium paratungstate, 0.1167g of ammonium niobate oxalate hydrate and 5g of oxalic acid respectively, and dissolve them together in 35mL of 40% ethanol aqueous solution. Stir magnetically at room temperature for more than 30min to dissolve.

[0051] The reaction solution was then transferred to a hydrothermal reactor. To avoid contact between the reactants and the non-conductive surfaces of the FTO transparent conductive glass, two FTO glass pieces of the same shape and size were overlapped, with their two SiO2 surfaces in contact and their two FTO surfaces facing outwards to contact the reactants. The reactor was then wrapped with polytetrafluoroethylene tape (leaving a 0.5 cm wide conductive strip around the perimeter for easy electrode clamping). The reactor was filled to 80% capacity and kept at 180°C for 4 hours. Finally, it was allowed to cool naturally to room temperature. The FTO conductive glass was then removed, washed with water, and purged with air at room temperature to obtain two identical tungsten-niobium bimetallic oxide thin film electrodes with a tungsten-niobium ratio of 2:1.

[0052] Figure 3 a shows the X-ray diffraction pattern of the obtained thin film. Comparing it with the standard X-ray diffraction pattern, it can be seen that the thin film is Nb. 18 W 16 O 93 It corresponds to the standard card JCPDS No. 75-0561.

[0053] Figure 4The image shows a scanning electron microscope (SEM) image of the tungsten-niobium bimetallic oxide thin film with a tungsten-niobium ratio of 2:1. It can be seen that the film is composed of a nanocluster structure made up of tungsten-niobium bimetallic oxide nanowire clusters.

[0054] The prepared tungsten-niobium nanocluster structure film with an atomic ratio of 2:1 was placed in a three-electrode electrolytic cell with a platinum electrode as the counter electrode, the prepared FTO glass supporting the film as the working electrode, silver / silver chloride as the reference electrode, and a 1 mol / L aqueous lithium sulfate solution as the electrolyte. The electrochromic properties of the tungsten-niobium nanocluster structure film with an atomic ratio of 2:1 prepared in the above examples were characterized using an electrochemical workstation and a UV-Vis spectrophotometer.

[0055] The results show that when voltages of -1.4V and 0.4V are applied, see Figure 2 The electrochromic thin film with a tungsten-niobium atomic ratio of 2:1 nanocluster structure can reversibly change between blue-black and colorless transparent. Figure 11 The transmittance curves of the tungsten-niobium bimetallic oxide film with a tungsten-niobium ratio of 2:1 in the colored and faded states in the 300-1100 nm wavelength range are shown. The light modulation (amplitude) reaches 81.2% at λ = 980 nm.

[0056] It should be noted that optical modulation refers to the optical modulation amplitude, which is the difference in transmittance between the colored state and the faded state; the two have the same meaning. For example, in Example 1, the optical modulation amplitude reaches 81.2% at λ = 980 nm, calculated using the formula ΔT = T b –T c The obtained, T b The transmittance of the faded state at this wavelength is 82.1%, T c The transmittance of the colored state at this wavelength is 0.9%.

[0057] The average modulation (amplitude) of the nanocluster structure film with a tungsten-niobium atomic ratio of 2:1 over a wide wavelength range in the visible light region (390-780 nm) and the short-wavelength near-infrared region (780-1100 nm) is shown in Table 1; the response time of the nanocluster structure film with a tungsten-niobium atomic ratio of 2:1 is shown in Table 2. The maximum coloring efficiency is as follows... Figure 12 As shown above, the nanocluster structure film with a tungsten-niobium atomic ratio of 2:1 prepared in Example 1 exhibits excellent electrochromic properties.

[0058] It should be noted that the average light modulation amplitude is the average of the difference between the bleached state transmittance and the colored state transmittance at all wavelengths within a wavelength range. The calculation formula is: T=∫T(λ)dλ / ∫dλ, where T is the transmittance and λ is the wavelength. The integration wavelength range selected in this invention is two wavelength ranges: 390-780nm and 780-1100nm.

[0059] In addition, the maximum tinting efficiency is derived from the tinting efficiency calculation formula, which is CE = ΔOD / ΔQ; ΔOD = log(T) b / T c ); ΔQ=Q / A, here a curve is obtained by fitting optical density (ΔOD) and charge density (ΔQ), the slope of the curve is the tinting efficiency (CE), and the maximum value of the slope is the maximum tinting efficiency.

[0060] It is easy to see that a large average light modulation amplitude in the visible light region (390-780nm) means that the film can modulate visible light within the visible light range; similarly, a large average light modulation amplitude in the short-wavelength near-infrared region (780-1100nm) means that the film can modulate light within the short-wavelength near-infrared range. Both represent the film's ability to modulate light across the entire wavelength range, which is more practical and convincing than the light modulation amplitude at a single wavelength.

[0061] Example 2

[0062] A tungsten-niobium bimetallic oxide electrochromic thin film electrode and its preparation method are disclosed below:

[0063] Weigh out 0.05 g of ammonium paratungstate, 0.1167 g of ammonium niobate oxalate hydrate and 5 g of oxalic acid respectively, and dissolve them in 35 mL of 40% ethanol aqueous solution. Stir magnetically at room temperature for more than 30 min to dissolve.

[0064] The reaction solution was then transferred to a hydrothermal reactor. To avoid contact between the reactants and the SiO2 surface of the FTO transparent conductive glass, two FTO glass pieces of the same shape and size were overlapped, with their two SiO2 surfaces in contact and their two FTO surfaces facing outwards to contact the reactants. The reactor was then wrapped with polytetrafluoroethylene tape (leaving a 0.5cm wide conductive strip around the perimeter for easy electrode clamping). The reactor was filled to 80% capacity and kept at 180℃ for 4 hours. Finally, it was allowed to cool naturally to room temperature. The FTO conductive glass was then removed, washed with water, and purged with air at room temperature to obtain two identical tungsten-niobium bimetallic oxide thin film electrodes with a 1:1 tungsten-niobium ratio.

[0065] Figure 3 b shows the X-ray diffraction pattern of the obtained thin film. Comparing it with the standard X-ray diffraction pattern, it can be seen that the thin film is Nb. 18 W 16 O 93 It corresponds to the standard card JCDPS No.75-0561.

[0066] It should be emphasized that Nb was observed in the XRD spectra of Examples 1 and 2. 18 W 16 O93 The two main characteristic peaks are at 2θ = 22.5° and 2θ = 45.9°, corresponding to orthogonal Nb 18 W 16 O 93 Phase (JCPDS No. 75-0561). As the niobium content increases, the characteristic peaks of the (002) crystal plane in Examples 4-7 gradually disappear, indicating that the (002) crystal plane is more difficult to detect and the crystallinity of the film gradually decreases. However, it is still the same material, only with different crystallinity.

[0067] Figure 5 The image shows a scanning electron microscope (SEM) image of the tungsten-niobium bimetallic oxide thin film with a tungsten-niobium ratio of 1:1. It can be seen that the film is composed of a cluster structure of tungsten-niobium bimetallic oxide nanowires.

[0068] Electrochromic properties of nanocluster thin films with a tungsten-niobium atomic ratio of 1:1 were tested. The tungsten-niobium bimetallic oxide thin film with a tungsten-niobium ratio of 1:1 achieved a light modulation efficiency of 83.9% at λ = 980 nm. The average modulation across a wide wavelength range (390-780 nm) and short-wave near-infrared region (780-1100 nm) for the nanocluster thin film with a tungsten-niobium atomic ratio of 1:1 is shown in Table 1. The response time of the nanocluster thin film with a tungsten-niobium atomic ratio of 1:1 is shown in Table 2. The maximum coloring efficiency is as follows: Figure 12 As shown.

[0069] Example 3

[0070] A tungsten-niobium bimetallic oxide electrochromic thin film electrode and its preparation method are disclosed below:

[0071] Weigh out 0.05g of ammonium paratungstate, 0.2333g of ammonium niobate oxalate hydrate and 5g of oxalic acid respectively, and dissolve them together in 35mL of 40% ethanol aqueous solution. Stir magnetically at room temperature for more than 30min to dissolve.

[0072] The reaction solution was then transferred to a hydrothermal reactor. To avoid contact between the reactants and the SiO2 surface of the FTO transparent conductive glass, two FTO glass pieces of the same shape and size were overlapped, with their two SiO2 surfaces in contact and their two FTO surfaces facing outwards to contact the reactants. The reactor was then wrapped with polytetrafluoroethylene tape (leaving a 0.5cm wide conductive strip around the perimeter for easy electrode clamping). The reactor was filled to 80% capacity and kept at 180℃ for 4 hours. Finally, it was allowed to cool naturally to room temperature. The FTO conductive glass was then removed, washed with water, and purged with air at room temperature to obtain two identical tungsten-niobium bimetallic oxide thin film electrodes with a tungsten-niobium ratio of 1:2.

[0073] Figure 3 c is the X-ray diffraction pattern of the obtained thin film. Figure 6The image shows a scanning electron microscope (SEM) image of the tungsten-niobium bimetallic oxide thin film with a tungsten-niobium ratio of 1:2. It can be seen that the film is composed of a tungsten-niobium bimetallic oxide nanowire structure.

[0074] Electrochromic properties of nanowire-structured thin films with a tungsten-niobium atomic ratio of 1:2 were tested. The tungsten-niobium bimetallic oxide film with a tungsten-niobium ratio of 1:2 achieved light modulation of 84.1% at λ = 980 nm. The average modulation over a wide wavelength range (390-780 nm) and short-wave near-infrared region (780-1100 nm) of the nanowire-structured thin film with a tungsten-niobium atomic ratio of 1:2 is shown in Table 1. The response time of the nanowire-structured thin film with a tungsten-niobium atomic ratio of 1:2 is shown in Table 2. The maximum coloring efficiency is as follows: Figure 12 As shown.

[0075] Example 4

[0076] A tungsten-niobium bimetallic oxide electrochromic thin film electrode and its preparation method are disclosed below:

[0077] Weigh out 0.05 g of ammonium paratungstate, 0.3501 g of ammonium niobate oxalate hydrate and 5 g of oxalic acid respectively, and dissolve them in 35 mL of 40% ethanol aqueous solution. Stir magnetically at room temperature for more than 30 min to dissolve.

[0078] The reaction solution was then transferred to a hydrothermal reactor. To avoid contact between the reactants and the SiO2 surface of the FTO transparent conductive glass, two FTO glass pieces of the same shape and size were overlapped, with their two SiO2 surfaces in contact and their two FTO surfaces facing outwards to contact the reactants. The reactor was then wrapped with polytetrafluoroethylene tape (leaving a 0.5cm wide conductive strip around the perimeter for easy electrode clamping). The reactor was filled to 80% capacity and kept at 180℃ for 4 hours. Finally, it was allowed to cool naturally to room temperature. The FTO conductive glass was then removed, washed with water, and purged with air at room temperature to obtain two identical tungsten-niobium bimetallic oxide thin film electrodes with a tungsten-niobium ratio of 1:3.

[0079] Figure 3 d represents the X-ray diffraction pattern of the obtained thin film. Figure 7 The image shows a scanning electron microscope (SEM) image of the tungsten-niobium bimetallic oxide thin film with a tungsten-niobium ratio of 1:3. It can be seen that the film is composed of a tungsten-niobium bimetallic oxide nanowire structure.

[0080] Electrochromic properties of nanowire-structured thin films with a tungsten-niobium atomic ratio of 1:3 were tested. The tungsten-niobium bimetallic oxide film with a tungsten-niobium ratio of 1:3 achieved a light modulation efficiency of 82.8% at λ = 980 nm. The average modulation across a wide wavelength range (390-780 nm) and short-wavelength near-infrared region (780-1100 nm) for the nanowire-structured thin film with a tungsten-niobium atomic ratio of 1:3 is shown in Table 1. The response time of the nanowire-structured thin film with a tungsten-niobium atomic ratio of 1:3 is shown in Table 2. The maximum coloring efficiency is as follows: Figure 12 As shown.

[0081] Example 5

[0082] A tungsten-niobium bimetallic oxide electrochromic thin film electrode and its preparation method are disclosed below:

[0083] Weigh out 0.05g of ammonium paratungstate, 0.4668g of ammonium niobate oxalate hydrate and 5g of oxalic acid respectively, and dissolve them in 35mL of 40% ethanol aqueous solution. Stir magnetically at room temperature for more than 30min to dissolve.

[0084] The reaction solution was then transferred to a hydrothermal reactor. To avoid contact between the reactants and the SiO2 surface of the FTO transparent conductive glass, two FTO glass pieces of the same shape and size were overlapped, with their two SiO2 surfaces in contact and their two FTO surfaces facing outwards to contact the reactants. The reactor was then wrapped with polytetrafluoroethylene tape (leaving a 0.5cm wide conductive strip around the perimeter for easy electrode clamping). The reactor was filled to 80% capacity and kept at 180℃ for 4 hours. Finally, it was allowed to cool naturally to room temperature. The FTO conductive glass was then removed, washed with water, and purged with air at room temperature to obtain two identical tungsten-niobium bimetallic oxide thin film electrodes with a tungsten-niobium ratio of 1:4.

[0085] Figure 3 e represents the X-ray diffraction pattern of the obtained thin film. Figure 8 The image shows a scanning electron microscope (SEM) image of the tungsten-niobium bimetallic oxide thin film with a tungsten-niobium ratio of 1:4. It can be seen that the film is composed of a tungsten-niobium bimetallic oxide nanowire structure.

[0086] Electrochromic properties of nanowire-structured thin films with a tungsten-niobium atomic ratio of 1:4 were tested. The tungsten-niobium bimetallic oxide film with a tungsten-niobium ratio of 1:4 achieved light modulation of 85.9% at λ = 980 nm. The average modulation over a wide wavelength range (390-780 nm) and short-wave near-infrared region (780-1100 nm) of the nanowire-structured thin film with a tungsten-niobium atomic ratio of 1:4 is shown in Table 1. The response time of the nanowire-structured thin film with a tungsten-niobium atomic ratio of 1:4 is shown in Table 2. The maximum coloring efficiency is as follows: Figure 12 As shown.

[0087] Example 6

[0088] A tungsten-niobium bimetallic oxide electrochromic thin film electrode and its preparation method are disclosed below:

[0089] Weigh out 0.05g of ammonium paratungstate, 0.5835g of ammonium niobate oxalate hydrate and 5g of oxalic acid respectively, and dissolve them in 35mL of 40% ethanol aqueous solution. Stir magnetically at room temperature for more than 30min to dissolve.

[0090] The reaction solution was then transferred to a hydrothermal reactor. To avoid contact between the reactants and the SiO2 surface of the FTO transparent conductive glass, two FTO glass pieces of the same shape and size were overlapped, with their two SiO2 surfaces in contact and their two FTO surfaces facing outwards to contact the reactants. The reactor was then wrapped with polytetrafluoroethylene tape (leaving a 0.5cm wide conductive strip around the perimeter for easy electrode clamping). The reactor was filled to 80% capacity and kept at 180℃ for 4 hours. Finally, it was allowed to cool naturally to room temperature. The FTO conductive glass was then removed, washed with water, and purged with air at room temperature to obtain two identical tungsten-niobium bimetallic oxide thin film electrodes with a tungsten-niobium ratio of 1:5.

[0091] Figure 3 f is the X-ray diffraction pattern of the obtained thin film. Figure 9 The image shows a scanning electron microscope (SEM) image of the tungsten-niobium bimetallic oxide thin film with a tungsten-niobium ratio of 1:5. It can be seen that the film is composed of a tungsten-niobium bimetallic oxide nanowire structure.

[0092] Electrochromic properties of nanowire-structured thin films with a tungsten-niobium atomic ratio of 1:5 were tested. The tungsten-niobium bimetallic oxide film with a tungsten-niobium ratio of 1:5 achieved light modulation of 84.8% at λ = 980 nm. The average modulation over a wide wavelength range (390-780 nm) and short-wave near-infrared region (780-1100 nm) for the nanowire-structured thin film with a tungsten-niobium atomic ratio of 1:5 is shown in Table 1. The response time of the nanowire-structured thin film with a tungsten-niobium atomic ratio of 1:5 is shown in Table 2. The maximum coloring efficiency is as follows: Figure 12 As shown.

[0093] Example 7

[0094] A tungsten-niobium bimetallic oxide electrochromic thin film electrode and its preparation method are disclosed below:

[0095] Weigh out 0.05 g of ammonium paratungstate, 0.7002 g of ammonium niobate oxalate hydrate and 5 g of oxalic acid respectively, and dissolve them in 35 mL of 40% ethanol aqueous solution. Stir magnetically at room temperature for more than 30 min to dissolve.

[0096] The reaction solution was then transferred to a hydrothermal reactor. To avoid contact between the reactants and the SiO2 surface of the FTO transparent conductive glass, two FTO glass pieces of the same shape and size were overlapped, with their two SiO2 surfaces in contact and their two FTO surfaces facing outwards to contact the reactants. The reactor was then wrapped with polytetrafluoroethylene tape (leaving a 0.5cm wide conductive strip around the perimeter for easy electrode clamping). The reactor was filled to 80% capacity and kept at 180℃ for 4 hours. Finally, it was allowed to cool naturally to room temperature. The FTO conductive glass was then removed, washed with water, and purged with air at room temperature to obtain two identical tungsten-niobium bimetallic oxide thin film electrodes with a tungsten-niobium ratio of 1:6.

[0097] Figure 3 g represents the X-ray diffraction pattern of the obtained thin film. Figure 10 The image shows a scanning electron microscope (SEM) image of the tungsten-niobium bimetallic oxide thin film with a tungsten-niobium ratio of 1:6. It can be seen that the film is composed of a tungsten-niobium bimetallic oxide nanowire structure.

[0098] Electrochromic properties of nanowire-structured thin films with a tungsten-niobium atomic ratio of 1:6 were tested. The tungsten-niobium bimetallic oxide film with a tungsten-niobium ratio of 1:6 achieved a light modulation efficiency of 84.1% at λ = 980 nm. The average modulation across a wide wavelength range (390-780 nm) in the visible light region and the short-wave near-infrared region (780-1100 nm) is shown in Table 1. The response time of the nanowire-structured thin film with a tungsten-niobium atomic ratio of 1:6 is shown in Table 2. The maximum coloring efficiency is as follows: Figure 12 As shown.

[0099] Table 1 shows the average light modulation of the electrochromic film in the visible light region (390-780 nm) and the short-wave near-infrared region (780-1100 nm) in the embodiments.

[0100] Electrochromic thin film Average light modulation within 390-780nm Average optical modulation within 780-1100nm Example 1 76.2％ 79.7％ Example 2 78.0％ 81.6％ Example 3 75.4％ 79.1％ Example 4 69.5％ 79.8％ Example 5 79.8％ 82.3％ Example 6 75.5％ 81.1％ Example 7 70.2％ 80.2％

[0101] Table 2 shows the transmittance changes, coloring time, and fading time of the electrochromic film in the examples.

[0102] Electrochromic thin film Transmittance change value Coloring time Fading time Example 1 81.2％ 3.4s 7.2s Example 2 83.9％ 4.6s 5.4s Example 3 84.1％ 5.0s 5.8s Example 4 82.8％ 6.9s 4.1s Example 5 85.9％ 4.7s 4.4s Example 6 84.8％ 5.7s 4.8s Example 7 84.1％ 5.7s 3.7s

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A tungsten-niobium bimetallic oxide electrochromic thin film, characterized in that, The thin film was prepared by a one-step solvothermal method at 180-200℃, including tungsten niobium bimetallic oxides with nanowire structure or nanowire cluster structure formed by self-aggregation of nanowires. In the tungsten-niobium bimetallic oxide, the atomic ratio of tungsten to niobium is 2:1 to 1:6, allowing the response time and coloring efficiency to be adjusted by regulating the atomic ratio of tungsten to niobium. Tungsten-niobium bimetallic oxide thin films achieve 70% optical modulation in the visible light region of 390-780 nm and 80% optical modulation in the short-wave near-infrared region of 780-1100 nm.

2. The tungsten-niobium bimetallic oxide electrochromic thin film according to claim 1, characterized in that, In the tungsten-niobium bimetallic oxide, the atomic ratio of tungsten to niobium is (1-2):

1.

3. An electrochromic thin-film electrode, characterized in that, The thin-film electrode includes a conductive substrate and an electrochromic thin film as described in any one of claims 1-2 grown on the conductive substrate.

4. A method for preparing an electrochromic thin-film electrode as described in claim 3, characterized in that, The method includes the following steps: According to the atomic ratio of tungsten and niobium, the tungsten source and the niobium source are dissolved in an acidic solvent to obtain a precursor solution; The conductive substrate is immersed in the precursor solution to carry out a hydrothermal reaction; After the reaction was completed, the tungsten-niobium bimetallic oxide electrochromic thin film electrode was obtained after cleaning and drying.

5. The method for preparing an electrochromic thin-film electrode according to claim 4, characterized in that, The conductive substrate is a double-layer FTO conductive glass. During immersion, the two SiO2 surfaces of the FTO conductive glass are in contact with each other, and the FTO surface faces outward and is in contact with the reactants.

6. The method for preparing an electrochromic thin-film electrode according to claim 4, characterized in that, The tungsten source includes ammonium paratungstate, the niobium source includes ammonium niobate oxalate hydrate, and the acidic solvent is an aqueous solution of ethanol and oxalic acid in a ratio of (30-40) mL: 5 g.

7. The method for preparing an electrochromic thin-film electrode according to claim 6, characterized in that, The volume fraction of the ethanol-water solution is 35-45%.

8. The method for preparing an electrochromic thin-film electrode according to claim 4, characterized in that, The hydrothermal reaction is carried out at a temperature of 180-200℃ for 4-6 hours.

9. The method for preparing an electrochromic thin-film electrode according to claim 6, characterized in that, The ratio of the amounts of ammonium niobate oxalate hydrate, ammonium paratungstate, oxalic acid, and aqueous ethanol in the precursor solution is (0.1167-0.7002) g : (0.05-0.1) g : 5 g : (30-40) mL.

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