Composite proton exchange membrane with humidity adjusting function as well as preparation method and application of composite proton exchange membrane

Abstract

The invention belongs to the field of hydrogen energy, and particularly relates to a composite proton exchange membrane with a humidity adjusting function and a preparation method and application thereof. The proton exchange membrane comprises a perfluorosulfonic acid nanofiber network substrate layer and a water-containing gel filling layer in a network of the perfluorosulfonic acid nanofiber network substrate layer. Wherein the perfluorosulfonic acid nanofiber network substrate layer is prepared from a precursor solution containing a doping substance in an electrostatic spinning mode, and the doping substance is a hydrogel component; the hydrogel filling layer is formed by a hydrogel component, or is formed by a hydrogel component containing a doping substance, and the doping substance is a precursor solution for preparing the perfluorosulfonic acid nanofiber network substrate layer in a doping manner. According to the prepared composite membrane, the dosage of perfluorosulfonic acid is remarkably reduced, and the membrane preparation cost is greatly reduced. The method can be widely applied to the fields of hydrogen energy fuel cells, alcohol fuel cells and the like.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy, specifically a composite proton exchange membrane with humidity regulation function, its preparation method and application. Background Technology

[0002] Hydrogen energy, as a clean, efficient, and renewable energy source for the future, is becoming a key technological direction for the global energy structure transformation. With the accelerated development of hydrogen energy technology applications, especially in transportation, energy storage, and industry, fuel cell technology is regarded as an important support for realizing a green and low-carbon energy system.

[0003] Proton exchange membrane fuel cells (PEMFCs) are widely used in new energy vehicles, distributed energy, aerospace, and portable power sources due to their high energy conversion efficiency, zero emissions, and rapid response capabilities. The proton exchange membrane (PEM) is the core component of a PEMFC, directly affecting the overall efficiency, durability, and operating cost of the fuel cell. Currently, the mainstream proton exchange membrane material on the market is perfluorosulfonic acid (PFSA), such as Nafion, which is widely used due to its excellent chemical stability and high proton conductivity. However, proton transport in PFSA membranes relies on a hydrogen bond network formed by moisture. In high-temperature and low-humidity environments, moisture evaporation leads to a significant decrease in proton conductivity, affecting the stable operation of the fuel cell. Furthermore, the high manufacturing cost of PFSA membranes (approximately $500-1000 / m²) further limits the commercialization of fuel cells. Therefore, improving the performance of proton exchange membranes in high-temperature and low-humidity environments while reducing their cost has become a key issue in fuel cell technology research.

[0004] To improve the high-temperature and low-humidity adaptability of perfluorosulfonic acid (PFSA) membranes, researchers have employed various modification methods, such as inorganic filling and phosphoric acid doping. For example, introducing hydrophilic mineral fibers, layered inorganic minerals with silicate functional groups, graphene oxide quantum dots, and sulfonated graphene into PFSA membranes enhances their moisture retention. However, this approach suffers from several drawbacks: low doping levels result in poor water retention, while high doping levels lead to poor nanomaterial fractionation, impaired membrane density, and low proton conductivity (200710052392.6, 200610019182.2, 200710025569.3, 201710893273.7). Furthermore, incorporating proton conductors such as phosphoric acid into polybenzimidazole (PBX) membranes can also improve their high-temperature proton conductivity, but phosphoric acid leaching can cause long-term membrane stability issues (202411330047.4). Compared to the aforementioned materials, hydrogels exhibit better water absorption. Researchers have already improved the intramembrane water environment of proton exchange membranes by incorporating highly hydrophilic hydrogels (202310375439.1, 201911289784.3). However, the amount of hydrogel incorporation is limited, and its introduction can, to some extent, disrupt the hydrophilic ion domain structure formed by the self-phase separation of the perfluorosulfonic acid membrane, affecting proton conduction. Therefore, developing a composite proton exchange membrane with humidity regulation capabilities, constructing continuous proton transport channels within the membrane, and simultaneously improving the membrane's moisture retention, proton conductivity, and reducing fabrication costs remains one of the core challenges in current hydrogen fuel cell technology. Summary of the Invention

[0005] The purpose of this invention is to provide a composite proton exchange membrane with humidity regulation function, its preparation method and application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A composite proton exchange membrane with humidity regulation function, wherein the composite proton exchange membrane is a perfluorosulfonic acid nanofiber network substrate layer and a hydrogel filling layer in the network; wherein the perfluorosulfonic acid nanofiber network substrate layer is obtained by electrospinning a precursor liquid containing dopant, and the dopant is a hydrogel component.

[0008] The hydrogel filling layer is formed from hydrogel components or hydrogel components containing dopants, wherein the dopants are precursor solutions used to prepare the perfluorosulfonic acid nanofiber network substrate.

[0009] The perfluorosulfonic acid nanofiber network substrate and hydrogel filling layer are prepared by doping materials.

[0010] The hydrogel is composed of one or more substances selected from polyvinyl alcohol (PVA), polyacrylamide (PAM), polyacrylic acid (PAA), and polyacrylamide (PAAm) prepared by solvent preparation; the amount of dopant added to the hydrogel is 2-50 wt%.

[0011] The precursor solution is a perfluorosulfonic acid solution, wherein the concentration of perfluorosulfonic acid is 3-15 wt%; the final concentration of the dopant in the precursor solution is 0.5-5 wt%.

[0012] A method for preparing the aforementioned composite proton exchange membrane with humidity regulation function.

[0013] (1) Prepare a perfluorosulfonic acid solution with a concentration of 3-15wt% as a precursor solution, or add hydrogel components to the precursor solution so that the final concentration of the hydrogel components in the precursor solution is 0.5-5wt%, and then use electrospinning to form a perfluorosulfonic acid nanofiber network substrate layer.

[0014] (2) Prepare a hydrogel solution as a hydrogel component, or add a precursor solution to the hydrogel component so that the final concentration of the precursor solution in the hydrogel component is 2-50wt%, and then add a crosslinking agent to the solution and mix well before uniformly coating it on the surface of the perfluorosulfonic acid nanofiber network substrate layer formed in step (1) above.

[0015] (3) The hydrogel is uniformly filled into the nanofiber network of the substrate layer by solvent evaporation or freeze drying to form a composite proton exchange membrane.

[0016] The parameters of the electrospinning process include:

[0017] Spinning voltage: 15-25kV

[0018] Spinning rate: 0.2-1.5 mL / h

[0019] Collection distance: 10-20cm

[0020] Relative humidity: 30-50%.

[0021] The perfluorosulfonic acid solution is an alcoholic solution coordinated with perfluorosulfonic acid powder (concentration 3-15wt%), or a commercially available perfluorosulfonic acid solution.

[0022] The hydrogel is composed of one or more substances selected from polyvinyl alcohol (PVA), polyacrylamide (PAM), polyacrylic acid (PAA), and polyacrylamide (PAAm) that are prepared into a solution by solvent, and the solid content in the solution is 2-15 wt%.

[0023] The solvents used include ethanol, propanol, isopropanol, N,N-dimethylformamide, N,N-dimethylacetamide, and mixed alcohol solutions.

[0024] The crosslinking agent is glutaraldehyde, polyethylene glycol diglycidyl ether, or a phosphate crosslinking agent;

[0025] The thickness of the hydrogel layer is consistent with the thickness of the perfluorosulfonic acid nanofiber substrate, wherein the thickness of the nanofiber substrate layer is 15-50 μm; that is, when the hydrogel layer penetrates the substrate layer grid and the two layers have the same thickness, the conductivity and water regulation can be guaranteed.

[0026] The perfluorosulfonic acid nanofiber network substrate has a fiber diameter ranging from 50 nm to 500 nm, a fiber network pore size ranging from 100 nm to 2000 nm, and a porosity of 40% to 80%, in order to optimize the proton transport path and improve the water absorption capacity of the membrane.

[0027] An application of the composite proton exchange membrane with humidity regulation function, wherein the composite proton exchange membrane is used in hydrogen fuel cells, alcohol fuel cells and water electrolysis for hydrogen production.

[0028] The present invention has the following advantages:

[0029] 1. This invention uses electrospinning technology to prepare perfluorosulfonic acid nanofiber substrates. Subsequently, an aqueous solution of hydrogel containing a crosslinking agent or perfluorosulfonic acid and a crosslinking agent is poured onto the surface of the nanofiber substrate, allowing the solution to enter the fiber pores. After solvent evaporation and crosslinking by the crosslinking agent, a composite proton exchange membrane with humidity regulation capability dominated by an interpenetrating nanofiber network is obtained.

[0030] 2. The composite membrane of this invention has humidity regulation capability and can maintain high proton conductivity under low humidity: The composite membrane is prepared by combining perfluorosulfonic acid nanofibers with hydrogel. In this membrane, the interpenetrating network of perfluorosulfonic acid nanofibers serves as the main pathway for proton transport. The hydrogel provides a stable water content for the perfluorosulfonic acid nanofibers through dynamic water absorption and release, which helps to ensure stable proton conduction, broadens its humidity application range, and improves the adaptability and reliability of fuel cells. In addition, by adjusting the thickness of the nanofiber network layer to be consistent with the thickness of the hydrogel, the availability of proton transport channels and effective humidity regulation function can be ensured simultaneously, thereby improving proton transport performance.

[0031] 3. The composite membrane of the present invention has a continuous proton transport channel, which promotes efficient proton transport: the perfluorosulfonic acid nanofibers constructed by electrospinning technology have a three-dimensional interpenetrating network structure, which can serve as a proton transport channel, effectively reducing transport resistance and improving the conductivity of the membrane.

[0032] 4. Reduced perfluorosulfonic acid usage and lower production costs: Compared to commercial perfluorosulfonic acid homogenized membranes, the composite membrane involved in this invention significantly reduces the amount of perfluorosulfonic acid used by utilizing a perfluorosulfonic acid nanofiber network as a proton transport channel, which is beneficial to reducing membrane manufacturing costs. Attached Figure Description

[0033] Figure 1 The surface SEM image of the perfluorosulfonic acid nanofiber network substrate layer provided by the present invention.

[0034] Figure 2 The images show surface and cross-sectional SEM images of the hydrogel / perfluorosulfonic acid-filled nanofiber composite membrane provided in this embodiment of the invention; wherein, A is the surface morphology structure image and B is the cross-sectional morphology structure image.

[0035] Figure 3 A comparison of the proton conductivity of the perfluorosulfonic acid nanofiber network substrate and the hydrogel / perfluorosulfonic acid filled nanofiber composite membrane provided in the embodiments of the present invention.

[0036] Figure 4 A comparison of the proton conductivity of the hydrogel / perfluorosulfonic acid filled nanofiber composite membrane and the hydrogel filled nanofiber composite membrane provided in the embodiments of the present invention.

[0037] Figure 5 Comparison diagram of hydrogel / perfluorosulfonic acid filled nanofiber composite membrane and hydrogel / perfluorosulfonic acid composite membrane provided in the embodiments of the present invention.

[0038] Figure 6 This is a comparison chart showing the effect of different hydrogel concentrations on proton conductivity, provided in an embodiment of the present invention.

[0039] Figure 7 The conductivity cycle test diagram of the hydrogel / perfluorosulfonic acid filled nanofiber composite membrane provided in the embodiment of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0041] This invention relates to a composite proton exchange membrane with humidity regulation capabilities, dominated by an interpenetrating nanofiber network. The membrane comprises a perfluorosulfonic acid nanofiber network substrate layer prepared using electrospinning technology, containing highly interpenetrating three-dimensional conductive channels to improve proton transport efficiency. A hydrogel filling layer, uniformly distributed within the nanofiber network of the substrate layer, exhibits dynamic water absorption and release capabilities to maintain stable proton conductivity and enhance membrane durability and mechanical properties. To improve the interfacial compatibility between the perfluorosulfonic acid nanofibers and the hydrogel, at least one layer of the composite proton exchange membrane incorporates a dopant material; specifically, a small amount of hydrogel component can be added to the substrate layer, and a small amount of perfluorosulfonic acid can be added to the hydrogel filling layer. Furthermore, the thickness of the hydrogel layer should be consistent with the thickness of the perfluorosulfonic acid nanofiber substrate layer, ensuring efficient proton conduction and humidity regulation capabilities, thus broadening its humidity application range. Consequently, this invention's composite proton exchange membrane possesses excellent mechanical properties and cycling stability, maintaining relatively stable proton conductivity during multiple cycles of humidity changes. Meanwhile, the composite proton exchange membrane of this invention reduces the amount of perfluorosulfonic acid used compared to the traditional perfluorosulfonic acid homogeneous membrane, thereby reducing production costs, improving economic feasibility, and making it suitable for large-scale production and widely applicable to fields such as hydrogen fuel cells and alcohol fuel cells.

[0042] Example 1

[0043] Preparation of perfluorosulfonic acid nanofiber network substrate

[0044] Perfluorosulfonic acid nanofiber membranes were prepared using electrospinning technology. A 5 wt% perfluorosulfonic acid alcohol solution was prepared by dissolving perfluorosulfonic acid powder in methanol as a precursor solution. To increase the interfacial compatibility between the nanofibers and the hydrogel, 5 wt% polyvinyl alcohol was added to the above solution, and the solution was stirred evenly using a magnetic stirrer. The mixed solution was then transferred to an ultrasonic bath for defoaming. Subsequently, a perfluorosulfonic acid nanofiber network substrate was prepared using electrospinning technology, with the ambient temperature maintained at 30-35℃ and the relative humidity at 30-40%; the voltage was adjusted to 20 kV, the spinning rate was 0.3 mL / h, and the collection distance was 15 cm.

[0045] After spinning, the prepared perfluorosulfonic acid nanofiber network substrate is removed from the rotating drum and placed in a desiccator for drying to remove residual solvent and moisture, thus successfully preparing the perfluorosulfonic acid nanofiber network substrate (PNF) (see [link to documentation]). Figure 1 ).

[0046] The surface morphology of the above nanofiber substrate was characterized:

[0047] The morphology of the nanofiber substrate was analyzed using scanning electron microscopy, among which... Figure 1The results showed that the substrate consisted of an interwoven network of fibers with a diameter of approximately 240 nm.

[0048] Example 2

[0049] Preparation of hydrogel / perfluorosulfonic acid filled nanofiber composite membrane

[0050] To prepare a 5 wt% polyvinyl alcohol aqueous solution, polyvinyl alcohol was added to water and stirred until a homogeneous aqueous solution was formed, which served as the hydrogel component. Then, a 5 wt% perfluorosulfonic acid alcohol solution was added to the solution, along with glutaraldehyde at a concentration of 5 phr relative to polyvinyl alcohol as a crosslinking agent. The mixture was stirred until homogeneous. Subsequently, the solution was poured onto the surface of the perfluorosulfonic acid nanofiber network substrate layer obtained in Example 1. After filling, the layer was left at room temperature for 8 hours to allow the hydrogel to fill the fiber network. After the solvent evaporated, a hydrogel / perfluorosulfonic acid uniformly filled nanofiber composite proton exchange membrane (PNF / PVA-5 wt%) was formed.

[0051] The surface and cross-sectional morphology of the above-mentioned composite proton exchange membrane were characterized:

[0052] The morphology of the composite film was analyzed using scanning electron microscopy, among which... Figure 2 The results showed that the surface of the composite membrane became smooth and flat, and the fiber network structure could be seen. Combined with the cross-sectional morphology, it can be seen that the hydrogel successfully filled the pores of the fiber network, and the membrane thickness was about 32 μm.

[0053] The proton conductivity of the two composite membranes in Examples 1 and 2 was tested.

[0054] The conductivity of the two membranes prepared in Example 1 and Example 2 was tested at a temperature of 80°C and a relative humidity of 60-98%.

[0055] from Figure 3 As can be seen, at a humidity of 60%, the conductivity of the composite membrane reaches ~65 mS / cm, significantly higher than that of the nanofiber membrane (~15 mS / cm); when the humidity is 98%, the conductivity of the composite membrane increases to ~110 mS / cm, also higher than that of the nanofiber membrane. Furthermore, when the humidity varies between 60% and 98%, the conductivity of the composite membrane fluctuates relatively gently, indicating that the hydrogel has a certain humidity regulation capability.

[0056] Comparative Example 1

[0057] Preparation of hydrogel-filled nanofiber composite membranes

[0058] According to the above embodiments, a 5 wt% polyvinyl alcohol aqueous solution was prepared as the hydrogel component, and then glutaraldehyde at a concentration of 5 phr relative to polyvinyl alcohol was added as a crosslinking agent. The solution was stirred until it was uniformly mixed. Subsequently, the above solution was poured onto the surface of the perfluorosulfonic acid nanofiber network substrate layer obtained in Example 1 above. After filling, it was placed at room temperature for 8 hours to allow the hydrogel to fill into the fiber network. After the solvent evaporated, a nanofiber composite membrane (PNF / PVA-0) with uniform hydrogel filling was formed.

[0059] The proton conductivity of the two composite films described above was tested.

[0060] Following the testing method described in Example 2, the proton conductivity of the two composite films prepared in Example 2 and Comparative Example 1 was tested. Figure 4 It can be seen that the introduction of hydrogel fillers can reduce the fluctuation of proton conductivity with humidity to a certain extent. However, the composite membrane has higher proton conductivity after the introduction of perfluorosulfonic acid into the hydrogel filler. This is mainly due to the formation of multi-level nano-transmission channels in the membrane, which increases the continuity of the transmission channels.

[0061] Comparative Example 2

[0062] Preparation of hydrogel / perfluorosulfonic acid composite membrane

[0063] Prepare a 5 wt% polyvinyl alcohol aqueous solution, add a 5 wt% perfluorosulfonic acid alcohol solution to it, and simultaneously add glutaraldehyde at a concentration of 5 phr relative to polyvinyl alcohol as a crosslinking agent. Stir until the solution is uniformly mixed. Then, pour the above solution into a mold, and after the solvent evaporates, a hydrogel and perfluorosulfonic acid composite film (PVA / PFSA) is formed.

[0064] The proton conductivity of the two composite films from Example 2 and Comparative Example 2 was tested:

[0065] Following the test method described in Example 2, the proton conductivity of the two composite films from Example 2 and Comparative Example 2 was tested. Figure 5 It can be seen that the hydrogel and perfluorosulfonic acid composite membrane has the lowest proton conductivity, while the proton conductivity is significantly improved after the introduction of perfluorosulfonic acid nanofibers, which indicates that the nanofiber network is the main channel for proton transport.

[0066] Example 3

[0067] Preparation of hydrogel / perfluorosulfonic acid filled nanofiber composite membrane

[0068] Prepared according to the method described in Example 2, except that when preparing the perfluorosulfonic acid nanofiber network substrate layer according to Example 1, the concentration of polyvinyl alcohol was adjusted to 3 wt% and 7 wt% to prepare the hydrogel / perfluorosulfonic acid filled nanofiber composite membrane.

[0069] The composite films prepared in Examples 2 and 3 were subjected to proton conductivity tests:

[0070] According to the test method described in Example 2, from Figure 6 It can be seen that, compared with the composite membranes with hydrogel concentrations of 3 wt% and 5 wt%, the proton conductivity decreased when the hydrogel concentration was 7 wt%. This may be because when the hydrogel concentration is high, a layer of hydrogel covers the membrane surface, and its poor proton conductivity affects proton transport.

[0071] Then, the composite film prepared in Example 2 was subjected to a humidity cycling test.

[0072] The ambient humidity of the membrane was increased from 60% to 98% and then decreased to 60% to complete one cycle. The change in proton conductivity of the composite membrane was tested during the three-cycle test.

[0073] like Figure 7 Test results show that the proton conductivity of the composite membrane remained relatively stable during three consecutive cycles of testing, indicating that the composite membrane has humidity control capabilities and excellent stability.

[0074] In summary, the composite proton exchange membrane of this invention utilizes electrospinning technology to prepare a highly conductive perfluorosulfonic acid nanofiber substrate, followed by solvent evaporation to fill the nanofiber network with polyvinyl alcohol hydrogel, thereby forming a composite proton exchange membrane with an interpenetrating network structure. Based on the rapid proton conductivity of the nanofibers and the excellent water regulation capability of the hydrogel, this composite membrane maintains high proton conductivity even under high temperature and low humidity environments. Furthermore, the composite membrane prepared by this invention significantly reduces the amount of perfluorosulfonic acid used, greatly reducing membrane fabrication costs. It can be widely applied in hydrogen fuel cells, alcohol fuel cells, and other fields.

[0075] The specific embodiments described above are only used to illustrate the spirit of the present invention. The scope of protection of the present invention is not limited thereto. Modifications made by those skilled in the art under the guidance of the present invention and within the scope of the spirit of the present invention are still within the scope of protection of the present invention.

Claims

1. A composite proton exchange membrane with humidity regulation function, characterized in that, The composite proton exchange membrane is a perfluorosulfonic acid nanofiber network substrate layer and a hydrogel-filled layer in the network; wherein, the perfluorosulfonic acid nanofiber network substrate layer is obtained by electrospinning a precursor liquid containing dopant, and the dopant is a hydrogel component. The hydrogel filling layer is formed from hydrogel components or hydrogel components containing dopants, wherein the dopants are precursor solutions for preparing perfluorosulfonic acid nanofiber network substrates.

2. The composite proton exchange membrane with humidity regulation function according to claim 1, characterized in that, The perfluorosulfonic acid nanofiber network substrate and hydrogel filling layer are prepared by doping materials.

3. The composite proton exchange membrane with humidity regulation function according to claim 1 or 2, characterized in that, The hydrogel is composed of one or more substances selected from polyvinyl alcohol (PVA), polyacrylamide (PAM), polyacrylic acid (PAA), and polyacrylamide (PAAm) prepared by solvent preparation; the amount of dopant added to the hydrogel is 2-50 wt%.

4. The composite proton exchange membrane with humidity regulation function according to claim 1 or 2, characterized in that, The precursor solution is a perfluorosulfonic acid solution, wherein the concentration of perfluorosulfonic acid is 3-15 wt%; the final concentration of the dopant in the precursor solution is 0.5-5 wt%.

5. A method for preparing a composite proton exchange membrane with humidity regulation function as described in claim 1, characterized in that, (1) Prepare a perfluorosulfonic acid solution with a concentration of 3-15wt% as a precursor solution, or add hydrogel components to the precursor solution so that the final concentration of the hydrogel components in the precursor solution is 0.5-5wt%, and then use electrospinning to form a perfluorosulfonic acid nanofiber network substrate layer. (2) Prepare a hydrogel solution as a hydrogel component, or add a precursor solution to the hydrogel component so that the final concentration of the precursor solution in the hydrogel component is 2-50wt%, and then add a crosslinking agent to the solution and mix well before uniformly coating it on the surface of the perfluorosulfonic acid nanofiber network substrate layer formed in step (1) above. (3) The hydrogel is uniformly filled into the nanofiber network of the substrate layer by solvent evaporation or freeze drying to form a composite proton exchange membrane.

6. The method for preparing the composite proton exchange membrane with humidity regulation function according to claim 5, characterized in that, The parameters of the electrospinning process include: Spinning voltage: 15-25kV Spinning rate: 0.2-1.5 mL / h Collection distance: 10-20cm Relative humidity: 30-50%.

7. The method for preparing the composite proton exchange membrane with humidity regulation function according to claim 5, characterized in that, The hydrogel is composed of one or more substances selected from polyvinyl alcohol (PVA), polyacrylamide (PAM), polyacrylic acid (PAA), and polyacrylamide (PAAm) that are prepared into a solution by solvent, and the solid content in the solution is 2-15 wt%.

8. The method for preparing a composite proton exchange membrane with humidity regulation function according to claim 5 or 7, characterized in that, The solvents used include ethanol, propanol, isopropanol, N,N-dimethylformamide, N,N-dimethylacetamide, and mixed alcohol solutions.

9. The method for preparing the composite proton exchange membrane with humidity regulation function according to claim 5, characterized in that, The thickness of the hydrogel layer is consistent with the thickness of the perfluorosulfonic acid nanofiber substrate, wherein the thickness of the nanofiber substrate layer is 15-50 μm.

10. An application of the composite proton exchange membrane with humidity regulation function as described in claim 1, characterized in that, Applications of the composite proton exchange membrane in hydrogen fuel cells, alcohol fuel cells, and hydrogen production via water electrolysis.

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