A large-area prussian blue film and a preparation method thereof

Abstract

The application discloses a large-area Prussian blue film and a preparation method thereof, and belongs to the technical field of electrochromic and ion battery, and solves the problem that large-scale production of the current large-area Prussian blue film is difficult to realize. The preparation method utilizes MXene low-valence titanium element to reduce trivalent iron ions to generate divalent iron ions, realizes in-situ growth of the Prussian blue film based on coordination of the divalent iron ions and ferricyanide in a solution, and obtains the Prussian blue film with a proper thickness by adjusting MXene concentration, coating times and reaction time. The preparation process of the large-area Prussian blue film provided by the application does not need high-temperature treatment, severe preparation conditions and complex preparation equipment, the process is simple and fast, and the size of the conductive substrate is not limited, so that large-scale preparation of the Prussian blue film is easy to realize, and an efficient approach is provided for practical application of the Prussian blue film in electrochromic devices and ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of electrochromic and ion battery technology, specifically relating to a large-area Prussian blue thin film and its preparation method. Background Technology

[0002] The development and application of new energy materials and devices is an effective way to alleviate energy shortages. Among them, electrochromic devices are considered a new type of energy-saving product with development and application potential. Electrochromic devices can regulate the optical properties of materials, such as transmission, absorption, or reflection, under the action of an applied voltage. Applying electrochromic devices to different occasions has led to the development of smart products such as electrochromic smart windows, anti-glare rearview mirrors, and electrochromic glasses. Since the working principle of ion insertion and migration of electrochromic materials is similar to that of ion batteries, electrochromic materials can also be used in the positive electrode materials of ion batteries. Devices constructed in this way have the characteristics of multi-functional integration of electrochromism and charging / discharging. This multi-functional device, as an electrochromic smart window, can reduce the energy consumption for lighting and cooling by regulating the transmission of light and heat entering buildings and vehicles, while simultaneously storing the electrical energy generated during the color-changing reaction process as an ion battery, making electrochromic devices more efficient and practical. Multi-functional smart windows applied to buildings and transportation vehicles require the preparation of electrochromic films with controllable and uniform thickness on large-area substrates; therefore, the development of large-area thin-film preparation technology for electrochromism and batteries is of great significance.

[0003] Prussian blue is an electrochromic material with rich color variations. Its open framework structure facilitates the insertion and extraction of ions. This structural characteristic allows it to serve as a host material for accommodating monovalent and polyvalent metal ions. Therefore, it has also been applied in the research of cathode materials for lithium, sodium, potassium, zinc and other ion batteries. Thus, Prussian blue has broad application scenarios and important research significance in the fields of electrochromism and ion batteries. The currently reported methods for preparing Prussian blue thin films mainly include hydrothermal methods (Solar Energy Materials and Solar Cells, 2018, 177: 9-14), electrodeposition methods (ThinSolidFilm, 2013, 542: 45-5(1)), and spray pyrolysis methods (Optik, 2017, 129: 130-139). Hydrothermal methods are limited by the size of the high-pressure reaction vessel, making it difficult to prepare large-area thin films. During electrodeposition, due to the poor conductivity of the transparent electrode, uneven film deposition occurs when depositing over a large area. Spray pyrolysis requires spraying the solution at high temperatures, posing safety hazards and energy consumption issues.

[0004] In summary, none of the above methods can achieve the preparation of large-area Prussian blue films. With the rapid development of urban modernization, glass curtain walls are gradually replacing building walls, while new energy vehicles are continuously innovating in energy conservation and emission reduction technologies. Therefore, developing a simple method suitable for large-scale preparation of large-area Prussian blue films is of great significance for the research and practical application of multifunctional electrochromic smart windows. Summary of the Invention

[0005] The purpose of this invention is to provide a large-area Prussian blue thin film and its preparation method, which solves the problem that existing Prussian blue thin film preparation methods are difficult to achieve uniform and rapid preparation on large-size substrates.

[0006] To achieve the above objectives, the present invention provides a method for preparing a large-area Prussian blue thin film, comprising the following steps:

[0007] (1) Ti3C2T x MXene nanosheets are dispersed in a dispersion solvent and uniformly coated onto the surface of a conductive substrate.

[0008] (2) Dissolve ferricyanide, ferric salt and potassium salt in water to obtain a homogeneous solution;

[0009] (3) The conductive substrate obtained in step (1) is immersed in the solution in step (2) to carry out the reaction. After the reaction is completed, a Prussian blue film is formed on the surface of the conductive substrate.

[0010] Preferably, in step (1), the dispersion solvent is deionized water or anhydrous ethanol, Ti3C2T x The concentration of MXene nanosheets in the dispersion solvent is 1–5 mg / mL, and the coating method can be either blade coating or spray coating.

[0011] Preferably, in step (1), the conductive substrate is any one of the following electrode materials: transparent tin-doped indium oxide substrate, fluorine-doped tin oxide substrate, aluminum-doped zinc oxide substrate, silver nanowire transparent conductive substrate, or opaque carbon nanotube substrate, graphene substrate, or metal foil, and the size of the conductive substrate is not limited.

[0012] Preferably, in step (2), the ferricyanide is one or more of potassium ferricyanide and sodium ferricyanide, with a molar concentration of 2 to 50 mmol / L;

[0013] The iron salt is one or more of ferric chloride, ferric nitrate and ferric sulfate, with a molar concentration of 2 to 50 mmol / L;

[0014] The potassium salt is one or more of potassium chloride, potassium sulfate, and potassium nitrate, with a molar concentration of 2–100 mmol / L.

[0015] Preferably, the total immersion time in step (3) is 30-200 seconds. Immersion can be done in one or multiple sessions. Before each immersion, Ti3C2T must be coated on the conductive substrate. x MXene nanosheet dispersion.

[0016] Preferably, in step (1), the Ti3C2T x MXene nanosheets were prepared by in-situ etching of the Ti3AlC2MAX phase using a mixed solution of lithium fluoride and concentrated hydrochloric acid.

[0017] The present invention also provides a large-area Prussian blue thin film prepared by the above preparation method.

[0018] Mechanism of this invention:

[0019] like Figure 1 The present invention involves pre-coating Ti3C2Tx MXene nanosheets onto a conductive substrate. The low-valence titanium in MXene exhibits reducing properties. The precursor solution contains ferric salts and ferricyanides. The ferric salts are reduced by the low-valence titanium to ferrous ions. These ferrous ions coordinate with ferricyanides in the solution, forming a Prussian blue / MXene composite material in situ on the MXene surface. The uniformity and size of the Prussian blue film are determined by the nanosheet deposition process. The size of the conductive substrate can be arbitrary and customized according to requirements. The thickness of the Prussian blue film can be increased by repeatedly depositing the MXene-immersion reaction and adjusting experimental parameters.

[0020] Therefore, the present invention employs the above-mentioned large-area Prussian blue thin film and its preparation method, and its beneficial effects are as follows:

[0021] 1. Based on the redox reaction between low-valent titanium element MXene and ferric ions to generate ferrous ions, ferrous ions coordinate with ferric cyanide ions in solution to form a Prussian blue film in situ on the MXene surface. By controlling the MXene concentration, the number of coatings and the soaking time, a Prussian blue film of appropriate thickness can be obtained.

[0022] 2. Compared with existing technologies, this method has a simple and quick preparation process, does not require stringent preparation conditions or complex preparation equipment, and can prepare Prussian blue films larger than 30×30cm, providing an economical and efficient approach for the practical application of electrochromic devices.

[0023] 3. The prepared Prussian blue / MXene composite material utilizes the excellent conductivity and porous properties of MXene, which is beneficial to the transport of ions and electrons during electrochromism and charge-discharge processes, thereby improving the color change rate and charge-discharge stability of the device.

[0024] 4. The device constructed using the Prussian blue thin film and zinc electrode prepared by the present invention has an optical modulation range of 60% as an electrochromic device, and the optical modulation range remains at 96% of the initial value after 200 cycles.

[0025] 5. A device constructed using the Prussian blue thin film prepared according to this invention and a zinc electrode has a discharge capacity of 56.3 mAh m³ as a zinc-ion battery. -2 And after 100 cycles, the capacity still remains at 70% of the initial value.

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the preparation mechanism of the present invention.

[0028] Figure 2 This is a photograph of a Prussian blue thin film with an area of ​​30×30cm obtained in Example 1 of the present invention.

[0029] Figure 3 This is a planar image of the Prussian blue thin film obtained by scanning electron microscopy in Example 1 of the present invention.

[0030] Figure 4 This is a cross-sectional image of the Prussian blue thin film obtained by scanning electron microscope in Example 1 of the present invention.

[0031] Figure 5 This is a schematic diagram of the structure of the Prussian blue thin film and zinc electrode assembly device prepared in Example 1 of the present invention.

[0032] Figure 6 The time-transmission spectrum is that of the Prussian blue electrochromic thin film prepared in Example 1 of the present invention.

[0033] Figure 7 This is a test diagram of the cycling stability of the Prussian blue electrochromic thin film prepared in Example 1 of the present invention.

[0034] Figure 8 This is a test diagram of the charge-discharge cycle stability of the Prussian blue thin film prepared in Example 1 of the present invention used in a zinc-ion battery. Detailed Implementation

[0035] Based on the appendix Figure 1 Based on the mechanism shown, this invention provides a method for preparing a large-area Prussian blue thin film, comprising the following steps:

[0036] (1) Ti3C2T xMXene nanosheets are dispersed in a dispersion solvent and uniformly coated onto the surface of a conductive substrate; the dispersion solvent is deionized water or anhydrous ethanol, and Ti3C2T x The concentration of MXene nanosheets in the dispersion solvent is 1–5 mg / mL, and the coating method can be either blade coating or spray coating.

[0037] The conductive substrate is any one of the following electrode materials: transparent tin-doped indium oxide substrate, fluorine-doped tin oxide substrate, aluminum-doped zinc oxide substrate, transparent conductive substrate of silver nanowires, or opaque carbon nanotube substrate, graphene substrate, or metal foil, and the size of the conductive substrate is not limited.

[0038] (2) Dissolve ferricyanide, ferric salt and potassium salt in water to obtain a homogeneous solution; the ferricyanide is one or more of potassium ferricyanide and sodium ferricyanide, with a molar concentration of 2 to 50 mmol / L; the ferric salt is one or more of ferric chloride, ferric nitrate and ferric sulfate, with a molar concentration of 2 to 50 mmol / L; the potassium salt is one or more of potassium chloride, potassium sulfate and potassium nitrate, with a molar concentration of 2 to 100 mmol / L.

[0039] (3) Immerse the conductive substrate obtained in step (1) in the solution of step (2) to carry out the reaction. After the reaction is completed, a Prussian blue film is formed on the surface of the conductive substrate. The total immersion time in step (3) is 30 to 200 seconds. The immersion can be carried out in one immersion or multiple immersions. Before each immersion, Ti3C2T should be coated on the conductive substrate. x MXene nanosheet dispersion.

[0040] In step (1), Ti3C2T x MXene nanosheets were prepared by in-situ etching of the Ti3AlC2MAX phase using a mixed solution of lithium fluoride and concentrated hydrochloric acid.

[0041] 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. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the invention should be considered equivalent substitutions and are included within the scope of protection of the invention. Furthermore, it should be understood that after reading the contents 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 and are all within the scope of protection of the invention.

[0042] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0043] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0044] Unless otherwise specified, the reagents, instruments, and equipment used in this invention are all commonly used by those skilled in the art.

[0045] Example 1:

[0046] Ti3C2T was prepared by in-situ etching of the Ti3AlC2MAX phase using a mixed solution of lithium fluoride and concentrated hydrochloric acid. x MXene nanosheets were prepared using an etching solution containing 2 g of lithium fluoride, 10 mL of deionized water, 30 mL of concentrated hydrochloric acid, and 1.6 g of Ti3AlC2. Ti3C2T x MXene nanosheets were dissolved in anhydrous ethanol at a concentration of 5 mg / mL. Ti3C2T... x MXene dispersion was sprayed onto 2×3 cm and 30×30 cm tin-doped indium oxide substrates. Potassium ferricyanide, ferric chloride trihydrate, and potassium chloride were dissolved in deionized water. The concentrations of potassium ferricyanide, ferric chloride trihydrate, and potassium chloride were 10 mmol / L and 50 mmol / L, respectively. The conductive substrates with deposited MXene were immersed in the above solution for 30 s, and the reaction was repeated five times with Ti3C2T. x MXene dispersion - immersion reaction, Ti3C2T x The dosage of MXene dispersion per spray is 0.01 mL / cm². 2 After washing and drying, a Prussian blue electrochromic film can be obtained on both sizes of tin-doped indium oxide substrates.

[0047] Figure 2 A photograph of a large-area (30×30cm) Prussian blue film. Figure 3 The image shows a scanning electron microscope image of a Prussian blue electrochromic thin film (planar), which reveals that nanoparticles of Prussian blue are uniformly distributed on the surface of the conductive substrate. Figure 4This is a scanning electron microscope image of a cross-section of a Prussian blue electrochromic thin film, showing that the average thickness of the Prussian blue film is approximately 300 nm.

[0048] To test the performance of the prepared Prussian blue thin film, a device was constructed using a 2×3 cm Prussian blue electrode and a zinc electrode. The device structure is shown in the schematic diagram below. Figure 5 As shown.

[0049] The test results of electrochromic properties and energy storage characteristics are as follows: Figure 6 , Figure 7 and Figure 8 As shown:

[0050] Figure 6 The time-transmittance spectrum of the electrochromic reaction of the Prussian blue thin film in an embodiment of the present invention shows that the optical modulation of the Prussian blue electrochromic film at a wavelength of 700 nm is 60%.

[0051] Figure 7 The figure shows the cyclic stability test of the Prussian blue thin film electrochromic chromaticity in this embodiment of the invention. As can be seen from the results, after 200 cycles at a wavelength of 700 nm, the optical modulation range of the material remains at 96% of the initial value, indicating good stability.

[0052] Figure 8 This invention relates to an embodiment of the Prussian blue thin film used in a charge-discharge cycle stability test of a zinc-ion battery. The results in the figure show that the initial capacity of the battery is 56.3 mAh m³. -2 After 100 cycles, the capacity remains at 70% of the initial value, demonstrating good stability.

[0053] Example 2:

[0054] Ti3C2T was prepared by in-situ etching of the Ti3AlC2MAX phase using a mixed solution of lithium fluoride and concentrated hydrochloric acid. x MXene nanosheets, with Ti3C2T x MXene nanosheets were dissolved in deionized water at a concentration of 5 mg / mL. Ti3C2T... x MXene aqueous dispersion was sprayed onto a tin-doped indium oxide substrate. Potassium ferricyanide, ferric chloride trihydrate, and potassium chloride were dissolved in deionized water. The concentrations of potassium ferricyanide, ferric chloride trihydrate, and potassium chloride were 10 mmol / L and 50 mmol / L, respectively. The deposited Ti3C2T... x The MXene substrate was immersed in the above solution and reacted for 30 seconds. The resulting blue Prussian blue film no longer deepened in color. After removal, washing, and drying, a layer of Prussian blue electrochromic film was obtained.

[0055] Example 3:

[0056] Ti3C2T x MXene nanosheets were dissolved in anhydrous ethanol at a concentration of 3 mg / mL. The aqueous MXene dispersion was sprayed onto a tin-doped indium oxide substrate. Potassium ferricyanide, ferric chloride trihydrate, and potassium chloride were dissolved in deionized water. The concentrations of potassium ferricyanide, ferric chloride trihydrate, and potassium chloride were 10 mmol / L and 50 mmol / L, respectively. The deposited Ti3C2T... x The MXene substrate was immersed in the above solution and reacted for 30 seconds. The resulting blue Prussian blue film no longer deepened in color. After removal, washing, and drying, a layer of Prussian blue electrochromic film was obtained.

[0057] Example 4:

[0058] Ti3C2T x MXene nanosheets were dissolved in deionized water at a concentration of 3 mg / mL. Aqueous Ti3C2T... x MXene dispersion was sprayed onto a tin-doped indium oxide substrate. Sodium ferricyanide, ferric chloride trihydrate, and potassium chloride were dissolved in deionized water, with potassium ferricyanide concentration of 10 mmol / L, ferric chloride trihydrate concentration of 10 mmol / L, and potassium chloride concentration of 50 mmol / L. The deposited Ti3C2T... x The MXene substrate was immersed in the above solution and reacted for 30 seconds. The resulting blue Prussian blue film no longer deepened in color. After removal, washing, and drying, a layer of Prussian blue electrochromic film was obtained.

[0059] Example 5:

[0060] Ti3C2T x MXene nanosheets were dissolved in anhydrous ethanol at a concentration of 5 mg / mL. Ti3C2T... x MXene dispersion was sprayed onto a tin-doped indium oxide substrate. Sodium ferricyanide, ferric nitrate, and potassium sulfate were dissolved in deionized water, with concentrations of 2 mmol / L for sodium ferricyanide, 2 mmol / L for ferric nitrate, and 2 mmol / L for potassium sulfate. The substrate with deposited MXene was immersed in the above solution for 30 seconds, then removed, washed, and dried to obtain a Prussian blue electrochromic film formed in situ on the surface of the conductive substrate.

[0061] In summary, the large-area Prussian blue thin film and its preparation method proposed in this invention are methods that can be carried out at room temperature, are simple and fast, have no limitation on the size of the conductive substrate, and are easy to prepare on a large scale.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a large-area Prussian blue film, characterized by, Based on the redox reaction of MXene low-valence titanium elements and ferric ions to generate ferrous ions, the ferrous ions are coordinated with ferricyanide in the solution to form a Prussian blue film with a size of more than 30*30 cm on the surface of MXene in situ; The method comprises the following steps: (1) Ti3C2T x MXene nanoplatelets are dispersed in a dispersion solvent and uniformly coated onto the surface of a conductive substrate; (2) dissolving ferricyanide, ferric salt and potassium salt in water to obtain a uniform solution; (3) soaking the conductive substrate obtained in step (1) in the solution of step (2) to react, and forming a layer of Prussian blue film on the surface of the conductive substrate after the reaction is completed; In step (1), the dispersion solvent is deionized water or anhydrous ethanol, Ti3C2T x The concentration of MXene nanosheets in the dispersion solvent is 1-5 mg / mL, and the coating method is any one of scraping and spraying.

2. The method for preparing a large-area Prussian blue thin film according to claim 1, characterized in that, In step (1), the conductive substrate is any one of a transparent tin-doped indium oxide substrate, a fluorine-doped tin oxide substrate, an aluminum-doped zinc oxide substrate, a silver nanowire transparent conductive substrate, or an opaque carbon nanotube substrate, a graphene substrate or a metal foil electrode material, and the size of the conductive substrate is not limited.

3. The method for preparing a large-area Prussian blue thin film according to claim 1, characterized in that, In step (2), the ferricyanide is one or more of potassium ferricyanide and sodium ferricyanide, and the molar concentration is 2-50 mmol / L; The ferric salt is one or more of ferric chloride, ferric nitrate and ferric sulfate, and the molar concentration is 2-50 mmol / L; The potassium salt is one or more of potassium chloride, potassium sulfate and potassium nitrate, and the molar concentration is 2-100 mmol / L.

4. The method for preparing a large-area Prussian blue thin film according to claim 1, characterized in that, The total soaking time in step (3) is 30-200 s, and the soaking is divided into one-time soaking or multiple times of soaking, and Ti3C2T x MXene nanoplatelet dispersion.

5. The method for preparing a large-area Prussian blue thin film according to claim 1, characterized in that, In step (1), the Ti3C2T x MXene nanosheets were prepared by in-situ etching of Ti3AlC2MAX phase from a mixed solution of lithium fluoride and concentrated hydrochloric acid.

6. A large area Prussian blue film, characterized in that, The large-area Prussian blue film is prepared by the method of any one of claims 1-5.

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