Chitosan-based dicationic anion exchange membrane and preparation method thereof

Abstract

The present invention discloses a chitosan-based double cationic anion exchange membrane and a preparation method thereof, which comprises first preparing a Cl ‑ or Br ‑ Cationic guanidine salts with negative ions + Ionic liquid ions, chitosan and initiator are then added thereto, and polyguanidine ionic liquid is obtained by heating and polymerization. The polyguanidine ionic liquid is then coated on a glass plate by a coating method and immediately placed in an anti-solvent to obtain a polyguanidine ionic liquid membrane. The membrane is then immersed in Cu 2+ or Zn 2+ The membrane is immersed in a saturated alkaline solution, then washed with ultrapure water for multiple times, and dried to form a membrane to prepare the chitosan-based double cationic anion exchange membrane. The present invention optimizes the anion exchange membrane, and the anion exchange membrane prepared thereby has better OH ‑ Conductivity and alkaline stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell anion exchange membranes, and in particular relates to a chitosan-based dicationic anion exchange membrane and a preparation method thereof. Background Art

[0002] Fuel cell technology is a technology that uses the chemical reaction of hydrogen and oxygen to generate electricity. With the increasing demand for clean energy and the limitations of traditional combustion energy, fuel cell technology has gradually become a highly sought-after energy solution. Fuel cell technology has been making continuous progress in technology, cost, application, infrastructure and policy, and has gradually become an important part of the clean energy field. It is of great significance to achieve sustainable energy development and address climate change. In fuel cell systems, anion exchange membranes (AEMs) are a key technology used to separate the anode and cathode while transferring hydroxide ions (OH - ) and prevent hydrogen ions (H + The development of these AEMs is significant because it can address several issues with traditional proton exchange membrane fuel cells (PEMFCs), such as the high cost of platinum catalysts, the need for pure hydrogen, and catalyst poisoning. Overall, AEMs play a key role in fuel cell systems and are an essential component for achieving efficient fuel cell operation.

[0003] At present, AEMs have OH - The problem of low conductivity and poor alkaline stability is that OH - The volume of H + , so OH - The ion mobility is only H + 57% of the AEMs, which resulted in OH - The ionic conductivity is higher than that of H in proton exchange membranes (PEMs). + The electrical conductivity is much lower. Furthermore, alkaline anion exchange membrane fuel cells (AEMFCs) typically operate at high temperatures (60°C-80°C) and strongly alkaline conditions (pH>14). However, the ion exchange groups and polymer backbones of most AEMs degrade under these conditions due to the strong nucleophilicity of OH-, resulting in a significant decrease in cell output power. Therefore, developing membrane materials that combine high ionic conductivity with high stability is key to the field of polyelectrolyte fuel cells.

[0004] Among the numerous materials, the polymeric form of ionic liquids (ILs) and their potential as emerging polymers have attracted increasing interest. Poly (ionic liquid) s (PILs) are mainly composed of polymers containing ionic groups in the repeating units, which exhibit good solubility, conductivity, thermal stability and chemical stability, and can be used to solve the problems existing in AEMs at this stage. In addition, guanidine, as a kind of organic strong base, has strong alkaline characteristics and structural adjustability. The nitrogen atom in guanidine has a pair of lone pair electrons, which shows strong coordination ability and can coordinate with Cu, Co, Ni, Pd, Cr, Zn, Pt and other metals to form metal complexes. Chitosan, as the only alkaline polysaccharide in natural polysaccharides, has excellent biological functions and can undergo chemical modification reactions, and is considered as a functional biological material with application potential. Chitosan is used in fuel cell anion exchange membranes as a high value-added application, which can also effectively improve the stability of AEMs.

[0005] The present application combines the film-forming property, conductivity, thermal stability and chemical stability of poly (ionic liquid) s with the strong alkalinity and conductivity of guanidine to prepare a novel poly (guanidinium) ionic liquid basic fuel cell anion exchange membrane. At the same time, by adding chitosan which is insoluble in water and has excellent alkali resistance in the membrane, the hydrophilicity of the organic-inorganic composite membrane is improved and the crystallinity is reduced, and the electrical conductivity is improved. In addition, with the strong coordination ability of the nitrogen atom in guanidine, the present application prepares a poly (guanidinium) ionic liquid-Cu 2+ or Zn 2+ dicationic basic fuel cell anion exchange membrane based on the above poly (guanidinium) ionic liquid anion exchange membrane, which further improves the ion conductivity, alkali resistance stability, thermal stability and electrochemical performance. SUMMARY

[0006] The present application aims to overcome the problems existing in the prior art and provide a chitosan-based dicationic anion exchange membrane with excellent electrical conductivity and good alkali stability and a preparation method thereof.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A chitosan-based dicationic anion exchange membrane, and a preparation method thereof, includes the following steps:

[0009] (1) Guanidine is reacted with bromohexane or 1,6-dibromohexane to prepare 1-hexyl guanidine or 1,6-hexyl diguanidine, which is then reacted with p-vinylbenzyl chloride or 4-bromostyrene under alkaline conditions to obtain cationic guanidine salt-N + ionic liquid by extraction or layering;

[0010] (2) The natural polysaccharide is dissolved in the cationic guanidine salt-N +Then, an initiator is added to the ionic liquid to initiate polymerization under heating conditions to prepare a polyguanidine salt ionic liquid;

[0011] (3) coating the polyguanidine ionic liquid prepared in step (2) on a glass plate by a coating method, and immediately placing it in an anti-solvent to obtain a polyguanidine ionic liquid membrane;

[0012] (4) Place Cu or Zn in NaOH solution and stir to dissolve to obtain Cu 2+ or Zn 2+ A saturated alkaline solution is prepared, and the polyguanidine ionic liquid membrane prepared in step (3) is immersed in the alkaline solution, washed with ultrapure water for multiple times, and then dried to obtain the chitosan-based dicationic anion exchange membrane.

[0013] Furthermore, the molar ratio of bromohexane or 1,6-dibromohexane to guanidine used in step (1) is 1:1-1:3, and the reaction time is 3-5 hours.

[0014] Furthermore, the molar ratio of p-vinylbenzyl chloride or 4-bromostyrene to guanidine used in step (1) is 1:(1-3), and the reaction is carried out at pH = 9-11 for 3-5 hours.

[0015] Furthermore, the natural polysaccharide used in step (2) is chitosan, and the amount thereof is cationic guanidine salt-N + 0.80-1.00% by mass of the ionic liquid.

[0016] Furthermore, the initiator used in step (2) is AIBN, and its dosage is cationic guanidine salt-N + 0.1-0.5% of the mass of the ionic liquid.

[0017] Furthermore, the polymerization temperature in step (2) is 60° C.-80° C., and the polymerization time is 3-5 hours.

[0018] Furthermore, the anti-solvent in step (3) includes any one or more of methanol, ethanol, and acetone.

[0019] Furthermore, the mass concentration of the NaOH solution used in step (4) is 0.05-0.10%.

[0020] Furthermore, the soaking time in step (4) is 1-2 hours.

[0021] The present invention utilizes the good film-forming property, electrical conductivity, thermal stability, chemical stability of polyionic liquid and the strong alkalinity and electrical conductivity of guanidine to prepare a polyguanidine salt ionic liquid alkaline fuel cell anion exchange membrane with good ionic conductivity and alkali stability. At the same time, chitosan is added to improve the hydrophilicity of the anion exchange membrane and reduce its crystallinity, thereby improving the electrical conductivity and alkali resistance. The polyguanidine salt ionic liquid membrane containing chitosan is immersed in Cu 2+ or Zn 2+ In saturated alkaline solution, the ionic conductivity, thermal stability, alkali stability and electrochemical performance of the anion exchange membrane were further improved, and the polyguanidine salt ionic liquid coordinated Cu 2+ or Zn 2+ dual cationic anion exchange membrane.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) In terms of type, the present invention proposes for the first time a dual-cationic alkaline fuel cell anion exchange membrane;

[0024] (2) From the perspective of raw materials, chitosan was used for the first time to prepare anion exchange membranes for dual-cationic alkaline fuel cells;

[0025] (3) From the application point of view, the present invention can effectively improve the ionic conductivity and alkaline stability of AEMs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the coordination principle of the dual cationic anion exchange membrane prepared in Example 1.

[0027] Figure 2 This is a sample picture of the dual cationic anion exchange membrane prepared in Example 1.

[0028] Figure 3 The conductivity comparison chart of the anion exchange membranes prepared in Example 1 and the comparative example is shown.

[0029] Figure 4 This is a diagram showing the alkali resistance of the anion exchange membranes prepared in Example 1 and the comparative example. DETAILED DESCRIPTION

[0030] A chitosan-based dicationic anion exchange membrane, the preparation method of which comprises the following steps:

[0031] (1) Hexane bromide or 1,6-dibromohexane is mixed with guanidine in a molar ratio of 1:1-1:3 and reacted for 3-5 hours to obtain 1-hexylguanidine or 1,6-hexyldiguanidine. Then, p-vinylbenzyl chloride or 4-bromostyrene is added in a molar ratio of guanidine to p-vinylbenzyl chloride or 4-bromostyrene of 1:1-3:1, and the mixture is reacted under alkaline conditions of pH = 9-11 for 3-5 hours to obtain cationic guanidine salt-N + Ionic liquid, and drying, dehumidification and solvent removal;

[0032] (2) The cationic guanidine salt-N + Chitosan with a mass of 0.80-1.00% of the ionic liquid is dissolved in the cationic guanidine salt-N prepared in step (1). + The ionic liquid was then added with cationic guanidine salt-N + The initiator AIBN with a concentration of 0.1-0.5% by weight of the ionic liquid is polymerized at 60-80°C for 3-5 hours to prepare a polyguanidine ionic liquid;

[0033] (3) coating the polyguanidine ionic liquid prepared in step (2) on a glass plate by a coating method, and immediately placing it in an anti-solvent such as methanol, ethanol, or acetone to obtain a polyguanidine ionic liquid membrane;

[0034] (4) Place Cu or Zn in a NaOH solution with a mass concentration of 0.05-0.10% and stir to dissolve to obtain Cu 2+ or Zn 2+ A saturated alkaline solution is prepared, and the polyguanidine ionic liquid membrane prepared in step (3) is immersed in the alkaline solution for 1-2 hours, washed with ultrapure water for multiple times, and then the membrane is placed on a glass plate for drying to obtain a chitosan-based dicationic anion exchange membrane.

[0035] In order to make the contents of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0036] Example 1

[0037] Step 1: Guanidine and bromohexane were mixed in a molar ratio of 1:1 and reacted for 4 hours to obtain 1-hexylguanidine. Then, p-vinylbenzyl chloride was added in a molar ratio of guanidine to p-vinylbenzyl chloride of 2:1 and reacted for 4 hours under alkaline conditions of pH = 10 to obtain cationic guanidine salt-N by extraction. + Ionic liquid, and drying, dehumidification and solvent removal;

[0038] Step 2: cationic guanidine salt-N + Chitosan with a mass percentage of 1.00% of the ionic liquid was added to the prepared cationic guanidine salt-N +In the ionic liquid ion, cationic guanidine salt-N + Ionic liquids;

[0039] Step 3: Dissolve the chitosan in cationic guanidine salt-N + Add cationic guanidine salt-N + The initiator AIBN, which is 0.1% by weight of the ionic liquid, is heated at 80°C to initiate polymerization of the ionic liquid for 3 hours to obtain a polyguanidine ionic liquid.

[0040] Step 4: coating the prepared polyguanidine ionic liquid on a glass plate by a coating method and immediately placing it in ethanol to obtain a polyguanidine ionic liquid membrane;

[0041] Step 5: Place Cu in a 0.10% NaOH solution and stir to dissolve it to obtain Cu 2+ A saturated alkaline solution was prepared, and the prepared polyguanidine salt ionic liquid membrane was immersed in the alkaline solution. After soaking for 1 hour, the membrane was taken out and washed with ultrapure water for multiple times. The membrane was then placed on a glass plate and dried to form a membrane.

[0042] Comparative Example

[0043] Step 1: Guanidine and bromohexane were mixed in a molar ratio of 1:1 and reacted for 4 hours to obtain 1-hexylguanidine. Then, p-vinylbenzyl chloride was added in a molar ratio of guanidine to p-vinylbenzyl chloride of 2:1 and reacted for 4 hours under alkaline conditions of pH = 10 to obtain cationic guanidine salt-N by extraction. + ionic liquid, and drying the ionic liquid to dehumidify and remove the solvent;

[0044] Step 2: cationic guanidine salt-N + Chitosan with a mass percentage of 1.00% of the ionic liquid was added to the prepared cationic guanidine salt-N + In the ionic liquid ion, cationic guanidine salt-N + Ionic liquids;

[0045] Step 3: Dissolve the chitosan in cationic guanidine salt-N + Add cationic guanidine salt-N + The initiator AIBN, which is 0.1% by weight of the ionic liquid, is heated at 80°C to initiate polymerization of the ionic liquid for 3 hours to obtain a polyguanidine ionic liquid.

[0046] Step 4: Apply the prepared polyguanidine ionic liquid on a glass plate by a coating method, and immediately place it in ethanol to obtain a polyguanidine ionic liquid membrane.

[0047] The anion exchange membranes prepared in Example 1 and the comparative example were divided into several parts and placed in fuel cells at 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, and 90°C for conductivity test experiments. The results are shown in Table 1. Figure 3 .Depend on Figure 3 As can be seen, the conductivity of the chitosan-based dicationic anion exchange membrane prepared in Example 1 continuously increases as the temperature rises from 30°C to 90°C. At 90°C, its conductivity exceeds 0.06 S / cm, far exceeding the conductivity at 30°C. In contrast, the conductivity of the ionic liquid membrane prepared in the comparative example shows little change with temperature, remaining consistently below 0.02 S / cm. This demonstrates that the chitosan-based dicationic anion exchange membrane prepared in the present invention exhibits excellent conductivity at temperatures between 60°C and 90°C.

[0048] The anion exchange membranes prepared in Example 1 and the comparative example were placed in 1M NaOH aqueous solution at 80°C, and the conductivity changes of the membranes after soaking for different times were measured. The results are as follows: Figure 4 As shown. Figure 4 It can be seen that the conductivity attenuation of the membrane prepared in Example 1 is relatively low, indicating that it has better alkali resistance.

[0049] Example 2

[0050] Step 1: Guanidine and bromohexane were mixed in a molar ratio of 2:1 and reacted for 4 hours to obtain 1-hexylguanidine. Then, p-vinylbenzyl chloride was added in a molar ratio of guanidine to p-vinylbenzyl chloride of 2:1 and reacted for 4 hours under alkaline conditions of pH = 10 to obtain cationic guanidine salt-N by extraction. + ionic liquid, and drying the ionic liquid to dehumidify and remove the solvent;

[0051] Step 2: cationic guanidine salt-N + Chitosan with a mass percentage of 1.00% of the ionic liquid was added to the prepared cationic guanidine salt-N + In the ionic liquid ion, cationic guanidine salt-N + Ionic liquids;

[0052] Step 3: Dissolve the chitosan in cationic guanidine salt-N + Add cationic guanidine salt-N + The initiator AIBN, which is 0.1% by weight of the ionic liquid, is heated at 80°C to initiate polymerization of the ionic liquid for 3 hours to obtain a polyguanidine ionic liquid.

[0053] Step 4: coating the prepared polyguanidine ionic liquid on a glass plate by a coating method, and immediately placing it in ethanol to obtain a polyguanidine ionic liquid membrane;

[0054] Fifth step: Cu is placed in a 0.10% NaOH solution to be stirred and dissolved, and Cu is prepared 2+ The saturated alkaline solution is prepared, and then the prepared polyguanidine ionic liquid film is immersed in the alkaline solution, taken out after soaking for 1 hour, and washed with ultrapure water for multiple times, and then the film is tightly attached to a glass plate to be dried into a film.

[0055] The prepared chitosan-based double-cationic anion exchange film is divided into several parts and placed in fuel cells at 30℃, 40℃, 50℃, 60℃, 70℃, 80℃ and 90℃ respectively for conductivity test experiments. The results show that when the temperature rises from 30℃ to 90℃, the conductivity of the chitosan-based double-cationic anion exchange film prepared in the embodiment continuously rises, and the conductivity at 90℃ exceeds 0.065 s / cm, which is much higher than the conductivity at 30℃, proving that the chitosan-based double-cationic anion exchange film prepared in the application has good conductivity at 60℃-90℃.

[0056] Example 3

[0057] First step: guanidine and bromohexane are mixed according to a molar ratio of 3:1 and reacted for 4 hours to prepare 1-hexyl guanidine, and then p-vinyl benzyl chloride is added according to a molar ratio of guanidine to p-vinyl benzyl chloride of 2:1, and reacted for 4 hours under alkaline conditions with pH = 10, and cationic guanidine salt-N + The ionic liquid is dried, dehumidified and solvent-removed;

[0058] Second step: chitosan with a mass fraction of 1.00% of the ionic liquid is added to the prepared cationic guanidine salt-N + The ionic liquid is dried, dehumidified and solvent-removed; + The ionic liquid is dried, dehumidified and solvent-removed; + The ionic liquid is dried, dehumidified and solvent-removed;

[0059] Third step: initiator AIBN with a mass fraction of 0.1% of the cationic guanidine salt-N + The ionic liquid is dried, dehumidified and solvent-removed; + The ionic liquid is dried, dehumidified and solvent-removed;

[0060] Fourth step: the prepared polyguanidine ionic liquid is coated on a glass plate by coating method, and immediately placed in ethanol to obtain a polyguanidine ionic liquid film;

[0061] Fifth step: Cu is placed in a 0.10% NaOH solution to be stirred and dissolved, and Cu is prepared 2+A saturated alkaline solution was prepared, and the prepared polyguanidine salt ionic liquid membrane was immersed in the alkaline solution. After soaking for 1 hour, the membrane was taken out and washed with ultrapure water for multiple times. The membrane was then placed on a glass plate and dried to form a membrane.

[0062] The prepared chitosan-based dicationic anion exchange membrane was divided into several portions and placed in a fuel cell at 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, and 90°C for conductivity testing. The results showed that the conductivity of the chitosan-based dicationic anion exchange membrane prepared in this example continued to increase as the temperature rose from 30°C to 90°C. At 90°C, its conductivity exceeded 0.07 s / cm, far exceeding the conductivity at 30°C. This demonstrates that the chitosan-based dicationic anion exchange membrane prepared in this embodiment has good conductivity at temperatures between 60°C and 90°C.

[0063] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a chitosan-based dicationic anion exchange membrane, characterized in that: The steps include: (1) Guanidine is reacted with bromohexane or 1,6-dibromohexane to obtain 1-hexylguanidine or 1,6-hexyldiguanidine, which is then reacted with p-vinylbenzyl chloride or 4-bromostyrene under alkaline conditions to obtain cationic guanidine salt-N by extraction or delamination. + Ionic liquids; (2) Dissolve the natural polysaccharide in the cationic guanidine salt prepared in step (1) + Then, an initiator is added to the ionic liquid to initiate polymerization under heating conditions to prepare a polyguanidine salt ionic liquid; (3) coating the polyguanidine ionic liquid prepared in step (2) on a glass plate by a coating method, and immediately placing it in an anti-solvent to obtain a polyguanidine ionic liquid membrane; (4) Place Cu or Zn in NaOH solution and stir to dissolve to obtain Cu 2+ or Zn 2+ a saturated alkaline solution, then immersing the polyguanidine ionic liquid membrane prepared in step (3) in the alkaline solution, washing with ultrapure water, and then drying to obtain the chitosan-based dicationic anion exchange membrane; The natural polysaccharide used in step (2) is chitosan, and the amount used is cationic guanidine salt-N + 0.80-1.00% by mass of the ionic liquid.

2. The method for preparing a chitosan-based dicationic anion exchange membrane according to claim 1, wherein: The molar ratio of bromohexane or 1,6-dibromohexane to guanidine used in step (1) is 1:1-1:3, and the reaction time is 3-5 hours.

3. The method for preparing a chitosan-based dicationic anion exchange membrane according to claim 1, wherein: The molar ratio of p-vinylbenzyl chloride or 4-bromostyrene to guanidine used in step (1) is 1:(1-3), and the reaction is carried out at pH = 9-11 for 3-5 hours.

4. The method for preparing a chitosan-based dicationic anion exchange membrane according to claim 1, wherein: The initiator used in step (2) is AIBN, and its dosage is cationic guanidine salt-N + 0.1-0.5% of the mass of the ionic liquid.

5. The method for preparing a chitosan-based dicationic anion exchange membrane according to claim 1, wherein: The polymerization temperature in step (2) is 60°C-80°C and the time is 3-5 hours.

6. The method for preparing a chitosan-based dicationic anion exchange membrane according to claim 1, wherein: The anti-solvent in step (3) includes any one or more of methanol, ethanol, and acetone.

7. The method for preparing a chitosan-based dicationic anion exchange membrane according to claim 1, wherein: The mass concentration of the NaOH solution used in step (4) is 0.05-0.10%.

8. The method for preparing a chitosan-based dicationic anion exchange membrane according to claim 1, wherein: The soaking time in step (4) is 1-2 hours.

9. A chitosan-based dicationic anion exchange membrane prepared by the method of claim 1.

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