A choline chloride / urea deep eutectic solvent modified ZIF-8 high-temperature proton exchange membrane and its preparation method and application

Abstract

The present invention provides a choline chloride: urea deep eutectic solvent modified ZIF-8 high-temperature proton exchange membrane and a preparation method and application thereof, belonging to the technical field of fuel cells and proton exchange membrane preparation. The present invention in situ composites a deep eutectic solvent with a zinc hydroxide nanowire membrane by a suction filtration method, thereby preparing a deep eutectic solvent-modified ZIF-8 high-temperature proton exchange membrane; in the ZIF-8 high-temperature proton exchange membrane, the zinc hydroxide nanowire membrane carries the choline chloride: urea deep eutectic solvent, so that the choline chloride: urea deep eutectic solvent is in situ composited into the pores of ZIF-8, thereby achieving the effect of blocking the choline chloride: urea deep eutectic solvent inside the ZIF-8 film and modifying the inner wall; the preparation method is simple to operate, low in energy consumption, and pollution-free, and the prepared ZIF-8 high-temperature proton exchange membrane can have extremely high proton conductivity while maintaining stability, and has good practicality.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells and proton exchange membrane preparation, and specifically relates to a choline chloride:urea deep eutectic solvent-modified ZIF-8 high-temperature proton exchange membrane, a preparation method thereof, and applications thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) convert chemical energy from fuel into electricity without combustion. Their high energy conversion efficiency and near-zero emissions make them an ideal clean energy source. PEMFCs primarily consist of a gas diffusion layer, a catalyst layer, a proton exchange membrane, and bipolar plates. PEMFCs can be categorized as either low-temperature or high-temperature. Compared to low-temperature PEMFCs, high-temperature PEMFCs offer advantages such as higher carbon monoxide tolerance and a simpler water and heat management system, making them a popular choice for research and development.

[0003] Currently, high-temperature proton exchange membranes are typically prepared by doping polymers with solid or organic acids. However, this method suffers from issues such as acid molecule loss, making it difficult to maintain long-term stability and high conductivity, limiting its practical application. Therefore, there is an urgent need to develop a high-temperature proton exchange membrane that can maintain long-term stability while improving proton conductivity to promote the development and application of high-temperature proton exchange membrane fuel cells. Summary of the Invention

[0004] In response to some deficiencies in the prior art, the present invention provides a ZIF-8 high-temperature proton exchange membrane modified with a choline chloride:urea deep eutectic solvent, and a preparation method and application thereof. The present invention in situ composites the deep eutectic solvent with a zinc hydroxide nanowire membrane by a filtration method to prepare a ZIF-8 high-temperature proton exchange membrane modified with a deep eutectic solvent. In the ZIF-8 high-temperature proton exchange membrane, the zinc hydroxide nanowire membrane carries the choline chloride:urea deep eutectic solvent, so that the choline chloride:urea deep eutectic solvent is in situ composited into the pores of the ZIF-8, thereby achieving the effect of blocking the choline chloride:urea deep eutectic solvent inside the ZIF-8 film and modifying the inner wall. The preparation method is simple to operate, low in energy consumption, and pollution-free, and the prepared ZIF-8 high-temperature proton exchange membrane can have extremely high proton conductivity while maintaining stability, and has good practicality.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical means:

[0006] The present invention first provides a ZIF-8 high-temperature proton exchange membrane modified with a choline chloride:urea deep eutectic solvent. The ZIF-8 high-temperature proton exchange membrane is mainly composed of a dense ZIF-8 membrane with nanopores inside the ZIF-8 membrane. The choline chloride:urea deep eutectic solvent is uniformly loaded inside the nanopores of the ZIF-8 membrane to modify the interior of the ZIF-8 membrane. The proton donor groups and proton acceptor groups in the choline chloride:urea deep eutectic solvent interact with each other to establish a continuous hydrogen bond network in the ZIF-8 nanopores.

[0007] The present invention also provides a method for preparing the above-mentioned choline chloride:urea deep eutectic solvent-modified ZIF-8 high-temperature proton exchange membrane, comprising:

[0008] (1) mixing choline chloride and urea and heating them to form a choline chloride:urea deep eutectic solvent;

[0009] vacuum filtering the zinc hydroxide nanowires to obtain a zinc hydroxide nanowire film;

[0010] (2) introducing the choline chloride:urea deep eutectic solvent into the zinc hydroxide nanowire film in situ by vacuum filtration to obtain a zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite film;

[0011] (3) The zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite membrane was reacted in situ in the high temperature vapor of 2-methylimidazole to prepare the ZIF-8 / choline chloride:urea deep eutectic solvent high temperature proton exchange membrane.

[0012] Preferably, in step (1), the molar ratio of choline chloride to urea is 1:2; and the heating temperature is 55-65°C.

[0013] Preferably, in step (1), the preparation method of the zinc hydroxide nanowires is: adding an ethanolamine solution to an equal volume of zinc nitrate solution, stirring evenly, and standing at room temperature to obtain the zinc hydroxide nanowires.

[0014] Preferably, the solvent of the zinc nitrate solution and the ethanolamine solution is a mixture of water and ethanol, and the volume ratio of ethanol to water is 3:2;

[0015] The concentration of the ethanolamine solution is 1-2 mmol / L, and the concentration of the zinc nitrate solution is 3-5 mmol / L;

[0016] The room temperature standing time is 0.5 to 2 hours.

[0017] Preferably, in step (2), the preparation method of the zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite film comprises: placing the choline chloride:urea deep eutectic solvent on the surface of the zinc hydroxide nanowire film, vacuum filtering at 0.05-0.08 MPa until the choline chloride:urea deep eutectic solvent passes through the zinc hydroxide nanowire film, removing the residual choline chloride:urea deep eutectic solvent, and obtaining the zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite film.

[0018] Preferably, in step (3), the in-situ reaction conditions are: reacting in 2-methylimidazole high-temperature steam at 100-140° C. for 18-30 hours.

[0019] Preferably, in the ZIF-8 / choline chloride:urea deep eutectic solvent high temperature proton exchange membrane, the loading amount of the choline chloride:urea deep eutectic solvent is 11-13 wt %.

[0020] The present invention also provides the use of the above-mentioned ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane in the preparation of a high-temperature fuel cell.

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

[0022] The present invention is the first to in situ composite a choline chloride:urea deep eutectic solvent on a zinc hydroxide nanowire membrane through vacuum filtration and introduce it into the pores of the ZIF-8 film to block the choline chloride:urea deep eutectic solvent, thereby changing the proton conductivity of the ZIF-8 film. Compared with other metal-organic framework modification methods, this method avoids the complex organic synthesis steps of ligand modification, has the advantages of simplicity, high efficiency, low energy consumption and pollution-free, and can maintain the stability of the guest molecule and extremely high proton conductivity under high temperature conditions.

[0023] The present invention's ZIF-8 / choline chloride: urea deep eutectic solvent high temperature proton exchange membrane uses dense ZIF-8 membrane as the main body of high temperature proton exchange membrane, providing nanoscale transmission channel; Choline chloride: urea deep eutectic solvent is uniformly loaded in ZIF-8 nanopore, and the physicochemical environment of ZIF-8 nanopore is modified, choline chloride: the proton donor group and the proton acceptor group in the urea deep eutectic solvent interact, and a continuous hydrogen bond network is established in ZIF-8 nanopore, realizing rapid proton transmission. Because of the structural characteristics of choline chloride: urea deep eutectic solvent, proton transmission in the hydrogen bond network it constructs has lower activation energy, which is conducive to achieving higher proton conductivity. In addition, the urea molecule in the choline chloride: urea deep eutectic solvent used in the present invention does not have a delocalized π bond. Compared with other raw materials with delocalized π bonds, it has a weaker electron donation ability and is more stable when forming a hydrogen bond network with choline chloride. The activation energy of proton transmission in this hydrogen bond network is lower, which is conducive to obtaining higher proton conductivity.

[0024] Compared to the ZIF-8 / choline chloride:urea deep eutectic solvent composite materials in the prior art, the ZIF-8 film prepared by the method of the present invention has a dense structure itself, and there is no need to adjust the morphology by choline chloride:urea deep eutectic solvent to obtain a dense structure. The role of the choline chloride:urea deep eutectic solvent is to modify the ZIF-8 nanopores and build a continuous hydrogen bond network for proton transport. Compared to the prior art, the choline chloride:urea deep eutectic solvent described in the present invention plays a role in proton transport, and the prepared ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane has a high proton conductivity in a high-temperature anhydrous environment and can be applied to the field of fuel cells. In addition, the choline chloride:urea deep eutectic solvent is not easy to volatilize under high temperature environment, and its structure contains a large number of proton donor groups and proton acceptor groups. These characteristics enable it to form a continuous hydrogen bond network in the ZIF-8 nanopores as a proton transfer channel, and this hydrogen bond network can exist stably in a high-temperature anhydrous environment, so that the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane obtains higher proton conductivity in a high-temperature anhydrous environment.

[0025] Compared with other in-situ composite methods, the present invention performs in-situ composite by vacuum filtration. When composited by vacuum filtration, the deep eutectic solvent can diffuse from the upper surface to the lower surface of the zinc hydroxide nanowire film under air pressure driving. The air pressure driving force is greater than the capillary force, so that the deep eutectic solvent can be evenly loaded in the zinc hydroxide nanowire film, which is more beneficial to improve the high-temperature proton conductivity. The ZIF-8 / choline chloride: urea deep eutectic solvent high-temperature proton exchange membrane in the present invention is compared with the ZIF-8 composite film prepared by other methods, and the high-temperature proton conductivity is improved by 1 to 2 orders of magnitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an SEM image of the surface of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Example 1.

[0027] Figure 2 This is the XRD pattern of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Example 1.

[0028] Figure 3 This is the impedance diagram of the high-temperature proton exchange membrane of ZIF-8 / choline chloride:urea deep eutectic solvent in Example 1.

[0029] Figure 4 This is an SEM image of the surface of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Example 2.

[0030] Figure 5 This is the XRD pattern of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Example 2.

[0031] Figure 6 This is an SEM image of the surface of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Example 3.

[0032] Figure 7 This is the XRD pattern of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Example 3.

[0033] Figure 8 This is the polarization curve of the H2 / O2 fuel cell assembled using the high-temperature proton exchange membrane of ZIF-8 / choline chloride:urea deep eutectic solvent in Example 4.

[0034] Figure 9 This is an SEM image of the surface of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Comparative Example 1.

[0035] Figure 10 This is the XRD pattern of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Comparative Example 1.

[0036] Figure 11 This is the impedance diagram of the high-temperature proton exchange membrane of ZIF-8 / choline chloride:urea deep eutectic solvent in Comparative Example 1. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0038] Example 1: Preparation of high-temperature proton exchange membrane using ZIF-8 / choline chloride:urea deep eutectic solvent

[0039] (1) Choline chloride and urea in a molar ratio of 1:2 were mixed and heated at 60°C to form a colorless clear liquid to obtain a choline chloride:urea deep eutectic solvent.

[0040] Dissolve ethanolamine and zinc nitrate in a mixture of ethanol and water (V 乙醇 :V 水 =2:3) to prepare a 1.6 mmol / L ethanolamine solution and a 2.4 mmol / L zinc nitrate solution for later use. The ethanolamine solution and the zinc nitrate solution were mixed in a 1:1 volume ratio and stirred thoroughly to obtain a mixed solution. The mixed solution was sealed and reacted at room temperature for 0.5 h to obtain a zinc hydroxide nanowire solution. The zinc hydroxide nanowires were vacuum filtered to obtain a zinc hydroxide nanowire film.

[0041] (2) The choline chloride: urea deep eutectic solvent was composited onto the zinc hydroxide nanowire film by filtration, wherein the volume of the choline chloride: urea deep eutectic solvent was 5 μL, to obtain a zinc hydroxide nanowire / choline chloride: urea deep eutectic solvent composite film.

[0042] (3) The zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite membrane was reacted in situ in 2-methylimidazole high-temperature steam at 120°C for 24 hours. After the reaction, a ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane was obtained. The mass fraction of the choline chloride:urea deep eutectic solvent in the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane was 11.5 wt%.

[0043] Figure 1 This is a SEM image of the surface of a ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane. The image shows that the membrane is a polycrystalline film with well-grown grains that conform to the morphological characteristics of ZIF-8 grains. The grain size ranges from 200 nm to 1 μm, and the grains are densely interwoven. The film has no obvious cracks and is continuous and dense.

[0044] Figure 2 The XRD pattern of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane shows that the peak structure of the modified ZIF-8 is well maintained. This demonstrates the successful synthesis of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane.

[0045] The electrochemical impedance spectroscopy (EIS) test was performed on the ZIF-8 / choline chloride:urea deep eutectic solvent high temperature proton exchange membrane prepared above. During the EIS test, the AC frequency range was 1 Hz to 1 MHz. The test results were as follows: Figure 3 As shown. Figure 3 It can be seen that the ZIF-8 / choline chloride:urea deep eutectic solvent high temperature proton exchange membrane of the present invention has a strong proton conductivity. At 160 ° C, the conductivity reaches 1.12×10 -2 S cm -1 .

[0046] Example 2: Preparation of high-temperature proton exchange membrane using ZIF-8 / choline chloride:urea deep eutectic solvent

[0047] (1) Choline chloride and urea in a molar ratio of 1:2 were mixed and heated at 60°C to form a colorless clear liquid to obtain a choline chloride:urea deep eutectic solvent.

[0048] Dissolve ethanolamine and zinc nitrate in a mixture of ethanol and water (V 乙醇 :V 水 =2:3), prepare a 2 mmol / L ethanolamine solution and a 5 mmol / L zinc nitrate solution for later use. The ethanolamine solution and the zinc nitrate solution are mixed in a 1:1 volume ratio and stirred thoroughly to obtain a mixed solution. The mixed solution is sealed and reacted at room temperature for 1 hour to obtain a zinc hydroxide nanowire solution. The zinc hydroxide nanowires are vacuum filtered to obtain a zinc hydroxide nanowire film.

[0049] (2) The choline chloride: urea deep eutectic solvent was composited onto the zinc hydroxide nanowire film by filtration, wherein the volume of the choline chloride: urea deep eutectic solvent was 3 μL, to obtain a zinc hydroxide nanowire / choline chloride: urea deep eutectic solvent composite film.

[0050] (3) The zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite membrane is reacted in situ in 2-methylimidazole high-temperature steam at 140°C for 18 hours. After the reaction, a ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane is obtained, wherein the mass fraction of the choline chloride:urea deep eutectic solvent in the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane is 10 wt%.

[0051] Figure 4 This is an SEM photograph of the surface of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane. It can be seen from the figure that the ZIF-8 high-temperature proton exchange membrane modified with the choline chloride:urea deep eutectic solvent has good grain intergrowth and the film is continuous without cracks.

[0052] Figure 5The XRD pattern of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane shows that the peak structure of the modified ZIF-8 is well maintained. This demonstrates the successful synthesis of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane.

[0053] Example 3: Preparation of high-temperature proton exchange membrane using ZIF-8 / choline chloride:urea deep eutectic solvent

[0054] (1) Choline chloride and urea in a molar ratio of 1:2 were mixed and heated at 70°C to form a colorless clear liquid to obtain a choline chloride:urea deep eutectic solvent.

[0055] Dissolve ethanolamine and zinc nitrate in a mixture of ethanol and water (V 乙醇 :V 水 =2:3), prepare a 1 mmol / L ethanolamine solution and a 3 mmol / L zinc nitrate solution for later use. The ethanolamine solution and the zinc nitrate solution are mixed in a 1:1 volume ratio and stirred thoroughly to obtain a mixed solution. The mixed solution is sealed and reacted at room temperature for 1 hour to obtain a zinc hydroxide nanowire solution. The zinc hydroxide nanowires are vacuum filtered to obtain a zinc hydroxide nanowire film.

[0056] (2) The choline chloride: urea deep eutectic solvent was composited onto the zinc hydroxide nanowire film by filtration, wherein the volume of the choline chloride: urea deep eutectic solvent was 10 μL, to obtain a zinc hydroxide nanowire / choline chloride: urea deep eutectic solvent composite film.

[0057] (3) The zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite membrane was reacted in situ in 2-methylimidazole high-temperature steam at 130°C for 30 hours. After the reaction, a ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane was obtained. The mass fraction of the choline chloride:urea deep eutectic solvent in the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane was 11.9 wt%.

[0058] Figure 6 This is an SEM photograph of the surface of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane. As can be seen from the figure, the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane is a polycrystalline thin film with well-grown grains, which conforms to the morphological characteristics of ZIF-8 grains. The grain size is between 200nm and 1μm, the grains are densely intergrown, there are no obvious cracks in the film, and it is continuous and dense.

[0059] Figure 7The XRD pattern of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane shows that the peak structure of the modified ZIF-8 is well maintained. This demonstrates the successful synthesis of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane.

[0060] Example 4:

[0061] In order to verify the applicability of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane in fuel cells, it was loaded into a warm proton exchange membrane fuel cell for testing. The steps were as follows: platinum carbon catalyst was coated on both sides of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Example 1. The amount of platinum carbon catalyst was 0.5 mg cm -2 , placed between two pieces of carbon cloth, and hot pressed at 125℃ and 6.4Mpa pressure to prepare a fuel cell membrane electrode. Under anhydrous conditions at 150℃, H2 and O2 were introduced into both sides of the fuel cell membrane electrode, and its polarization curve was tested and the output power density was calculated, such as Figure 8 shown.

[0062] from Figure 8 It can be seen that the fuel cell equipped with ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane has an output power density of 35.2mW / cm 2 , proving that the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane not only has good high-temperature proton conductivity, but also has good practical application potential.

[0063] Comparative Example 1:

[0064] (1) Choline chloride and urea in a molar ratio of 1:2 were mixed and heated at 60°C to form a colorless clear liquid to obtain a choline chloride:urea deep eutectic solvent.

[0065] Dissolve ethanolamine and zinc nitrate in a mixture of ethanol and water (V 乙醇 :V 水 =2:3) to prepare a 1.6 mmol / L ethanolamine solution and a 2.4 mmol / L zinc nitrate solution for later use. The ethanolamine solution and the zinc nitrate solution were mixed in a 1:1 volume ratio and stirred thoroughly to obtain a mixed solution. The mixed solution was sealed and reacted at room temperature for 0.5 h to obtain a zinc hydroxide nanowire solution. The zinc hydroxide nanowires were vacuum filtered to obtain a zinc hydroxide nanowire film.

[0066] (2) Choline chloride: urea deep eutectic solvent was composited onto the zinc hydroxide nanowire film by spin coating, wherein the volume of choline chloride: urea deep eutectic solvent was 5 μL, which was dropped onto the upper surface of the zinc hydroxide nanowire film, first rotated at a low speed of 150 rpm for 10 seconds, and then rotated at a high speed of 3000 rpm for 30 seconds to obtain a zinc hydroxide nanowire / choline chloride: urea deep eutectic solvent composite film.

[0067] (3) The zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite membrane was reacted in situ in 2-methylimidazole high-temperature steam at 120°C for 24 hours. After the reaction, a ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane was obtained. The mass fraction of the choline chloride:urea deep eutectic solvent in the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane was 11.5 wt%.

[0068] Figure 9 This is an SEM photograph of the surface of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane. As can be seen from the figure, the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane is a polycrystalline thin film with well-grown grains, which conforms to the morphological characteristics of ZIF-8 grains. The grain size is between 200nm and 1μm, the grains are densely intergrown, there are no obvious cracks in the film, and it is continuous and dense.

[0069] Figure 10 The XRD pattern of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane shows that the peak structure of the modified ZIF-8 is well maintained. This demonstrates the successful synthesis of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane.

[0070] The electrochemical impedance spectroscopy (EIS) test was performed on the ZIF-8 / choline chloride:urea deep eutectic solvent high temperature proton exchange membrane prepared above. During the EIS test, the AC frequency range was 1 Hz to 1 MHz. The test results were as follows: Figure 11 As shown. Figure 11 It can be seen that the proton conductivity of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared by the spin coating method is lower than that of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared in Example 1. At 160°C, the conductivity is only 2.76×10 -3 S cm -1 Therefore, the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane prepared by the vacuum filtration method of the present invention has higher proton conductivity and can be applied in the field of fuel cells.

[0071] In summary, the present invention uses a suction filtration method to in situ compound the deep eutectic solvent and the zinc hydroxide nanowire film to prepare a deep eutectic solvent-modified ZIF-8 high-temperature proton exchange membrane; in the ZIF-8 high-temperature proton exchange membrane, the zinc hydroxide nanowire film carries the choline chloride: urea deep eutectic solvent, so that the choline chloride: urea deep eutectic solvent is in situ compounded into the pores of ZIF-8, thereby achieving the effect of blocking the choline chloride: urea deep eutectic solvent inside the ZIF-8 film and modifying the inner wall; the preparation method is simple to operate, low in energy consumption, and pollution-free, and the prepared ZIF-8 high-temperature proton exchange membrane can have extremely high proton conductivity while maintaining stability, and has good application in high-temperature fuel cells.

[0072] The embodiments described are preferred implementations of the present invention, but the present invention is not limited to the above implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing a choline chloride:urea deep eutectic solvent-modified ZIF-8 high-temperature proton exchange membrane, characterized in that: include: (1) mixing choline chloride and urea and heating them to form a eutectic solvent to obtain a choline chloride:urea deep eutectic solvent; the molar ratio of choline chloride to urea is 1:2; and the heating temperature is 55-65°C; vacuum filtering the zinc hydroxide nanowires to obtain a zinc hydroxide nanowire film; (2) Introducing the choline chloride:urea deep eutectic solvent into the zinc hydroxide nanowire film in situ by vacuum filtration to obtain a zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite film; The preparation method of the zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite film comprises: placing a choline chloride:urea deep eutectic solvent on the surface of the zinc hydroxide nanowire film, vacuum filtering at 0.05-0.08 MPa until the choline chloride:urea deep eutectic solvent passes through the zinc hydroxide nanowire film, removing the residual choline chloride:urea deep eutectic solvent, and obtaining the zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite film; (3) The zinc hydroxide nanowire / choline chloride:urea deep eutectic solvent composite membrane was reacted in situ in the high temperature vapor of 2-methylimidazole to prepare the ZIF-8 / choline chloride:urea deep eutectic solvent high temperature proton exchange membrane.

2. The method for preparing a ZIF-8 high temperature proton exchange membrane modified with a choline chloride: urea deep eutectic solvent according to claim 1, wherein In step (1), the preparation method of the zinc hydroxide nanowires is: adding an ethanolamine solution to an equal volume of zinc nitrate solution, stirring evenly, and standing at room temperature to obtain the zinc hydroxide nanowires.

3. The method for preparing a ZIF-8 high temperature proton exchange membrane modified with a choline chloride: urea deep eutectic solvent according to claim 2, wherein The solvent of the zinc nitrate solution and the ethanolamine solution is a mixture of water and ethanol, and the volume ratio of ethanol to water is 3:2; The concentration of the ethanolamine solution is 1-2 mmol / L, and the concentration of the zinc nitrate solution is 3-5 mmol / L; The room temperature standing time is 0.5 to 2 hours.

4. The method for preparing a ZIF-8 high temperature proton exchange membrane modified with a choline chloride: urea deep eutectic solvent according to claim 1, wherein In step (3), the in-situ reaction conditions are: reacting in 2-methylimidazole high-temperature steam at 100-140° C. for 18-30 hours.

5. the preparation method of the ZIF-8 high temperature proton exchange membrane modified by choline chloride according to claim 1: urea deep eutectic solvent, is characterized in that, In the ZIF-8 / choline chloride:urea deep eutectic solvent high temperature proton exchange membrane, the loading amount of the choline chloride:urea deep eutectic solvent is 11-13 wt %.

6. Choline chloride: urea deep eutectic solvent-modified ZIF-8 high temperature proton exchange membrane prepared by the method according to any one of claims 1 to 5, characterized in that The ZIF-8 high-temperature proton exchange membrane is mainly composed of a dense ZIF-8 membrane with nanopores inside the ZIF-8 membrane; the choline chloride:urea deep eutectic solvent is uniformly loaded inside the nanopores of the ZIF-8 membrane to modify the interior of the ZIF-8 membrane; the proton donor groups and proton acceptor groups in the choline chloride:urea deep eutectic solvent interact with each other to establish a continuous hydrogen bond network in the ZIF-8 nanopores; in the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane, the loading amount of the choline chloride:urea deep eutectic solvent is 11-13wt%.

7. Use of the ZIF-8 / choline chloride:urea deep eutectic solvent high-temperature proton exchange membrane according to claim 6 in the preparation of a high-temperature fuel cell.

Images