Preparation method and application of attapulgite-based fluid composite basic polyelectrolyte membrane

Abstract

The application relates to the technical field of fuel cells, and particularly discloses a preparation method of an attapulgite fluid composite alkaline polyelectrolyte membrane, which comprises the following steps: (1) preparing an attapulgite fluid; (2) dissolving quaternary ammonium chitosan and polyvinyl alcohol to obtain a mixed casting solution; and (3) filling the attapulgite fluid into the mixed casting solution, and taking glutaraldehyde as a crosslinking agent to obtain the attapulgite fluid composite alkaline polyelectrolyte membrane. When the molecular structure of the attapulgite fluid is designed, a cation layer with anion exchange function is grafted on the outer layer, the cation activity of the cation layer on the outer layer of the attapulgite fluid is stronger, a more continuous channel is constructed for the transmission of hydroxyl ions, and the transmission capacity of the composite membrane for anions is significantly improved. The composite membrane has high ion conductivity and excellent mechanical properties, and has a wide application prospect in the field of fuel cell alkaline anion exchange membranes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cells, in particular to a preparation method of a palygorskite-based fluid composite alkaline polyelectrolyte membrane and application thereof. BACKGROUND

[0002] Due to the non-renewable nature of fossil fuels and the atmospheric pollution caused by their combustion, finding green, clean and efficient new energy to replace traditional fossil fuels has become a research hotspot. Fuel cells have the advantages of low environmental pollution, high power density and wide fuel sources, and are considered as one of the most promising new chemical energy technologies. As the core component of fuel cells, ion exchange membranes play a dual role of conducting H + or OH - and separating fuel and oxidant, and their performance directly affects the working performance of fuel cells. According to the different polyelectrolytes, there are two categories of acid proton exchange membranes (PEM) and alkaline anion exchange membranes (AEM). In order to meet the application requirements of fuel cells, ion exchange membranes must have high ionic conductivity and mechanical properties. Traditional PEMs must be used in acidic environments, and the electrode catalysts of the cell are mainly precious metals such as platinum, which greatly limits their application due to the high price and scarcity of resources. Therefore, AEMs using non-precious metal catalysts have become a new research hotspot. However, there is no commercial AEM that can fully meet the requirements of fuel cells, and designing AEMs with high ionic conductivity and high mechanical strength is the key to the high performance of fuel cells.

[0003] AEMs mainly consist of a polymer backbone and cationic functional groups, and the cationic functional groups are used for anion exchange, while the polymer backbone mainly determines the mechanical properties and chemical stability of the membrane. Compared with synthetic polymers, natural polymers have a wide range of sources and are environmentally friendly, so they have attracted more and more attention from researchers to solve the increasingly serious problems of petrochemical raw material crisis and environmental pollution. Chitosan is the only natural polysaccharide containing free amino groups and is a green energy material with great potential for anion exchange function. However, the strong hydrogen bonds between its molecules limit the transport of ions. In addition, the high hydrophilicity of chitosan leads to a decrease in its mechanical strength in aqueous solution, further hindering its application as an ion exchange membrane.

[0004] Attapulgite is a natural clay with chain-layered structure, containing abundant water and hydroxyl groups, and rich in surface charge, which can be ion-exchanged. Attapulgite is an ideal filler for modifying chitosan-based anion exchange membranes, because it can improve the mechanical properties and ionic conductivity of chitosan, and is easy to operate and mass production. However, the process of compounding attapulgite with chitosan matrix is prone to agglomeration, which cannot fully exert its characteristics and advantages. The common method to solve the problem of agglomeration and dispersion is to modify the surface of attapulgite to improve its compatibility with chitosan matrix. In Chinese patent application

Application No. 201910093149.1

Application No. 201910094052.2

Advanced Materials, 2005, 17: 234-237

Carbon, 2012, 50: 2056-2060

Application No. 200610124454.5

Application No. 201410605875.4

Application No. CN201410446024.X

[0005] In view of the above problems of the prior art, the present application aims to provide a preparation method of a palygorskite fluid composite alkaline polyelectrolyte membrane and its application in fuel cells.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A preparation method of a palygorskite fluid composite alkaline polyelectrolyte membrane, comprising the following steps:

[0008] A palygorskite fluid with an anion layer on the inner layer and a cation layer on the outer layer is prepared by a two-step method using natural palygorskite as the "core": first, a sulfonic acid silane coupling agent is grafted to the palygorskite, and then the obtained palygorskite grafted with the sulfonic acid silane coupling agent is subjected to ion exchange with a polyether amine or a polyether quaternary ammonium salt to form a cation outer layer with flexible long chains, thereby obtaining the palygorskite fluid with an anion on the inner layer and a cation on the outer layer.

[0009] Quaternized chitosan and polyvinyl alcohol are dissolved to obtain a mixed casting solution;

[0010] The palygorskite fluid is filled into the mixed casting solution, and a crosslinking reaction occurs under the action of a crosslinking agent to construct a quaternized chitosan / polyvinyl alcohol interpenetrating polymer network as a membrane matrix, thereby obtaining the palygorskite fluid composite alkaline polyelectrolyte membrane.

[0011] Further, the palygorskite is purified before modification, specifically: the palygorskite is added to a sodium hexametaphosphate aqueous solution, ultrasonically dispersed, and then allowed to stand and separate into layers, and the upper layer of the suspension is centrifuged and dried to obtain the purified palygorskite.

[0012] Further, the sulfonic acid silane coupling agent is one of 3-(methoxysilyl)-propane sulfonic acid, 3-(trihydroxysilyl)-propane sulfonic acid, and 2(2-trihydroxysilyl)ethyl benzene sulfonic acid.

[0013] Further, the sulfonic acid silane coupling agent is grafted to the palygorskite under the following reaction conditions: the mass ratio of the sulfonic acid silane coupling agent to the palygorskite is 1-10:1, the pH value of the reaction solution is 4-6, the reaction temperature is 60-80℃, and the reaction time is 8-24h.

[0014] Further, the polyether amine or polyether quaternary ammonium salt is one of cocoalkylamine polyoxyethylene ether, nonylphenol polyoxyethylene propyltrimethyl ammonium chloride, octyl polyoxyethylene octadecyl ammonium chloride.

[0015] Further, the mass ratio of the quaternized chitosan to polyvinyl alcohol in the mixed casting solution is 1:1 to 9:1.

[0016] Further, the quaternization degree of the quaternized chitosan is 40% to 60%.

[0017] Further, the filling mass fraction of the attapulgite-based fluid is 1% to 30% of the polymer matrix, preferably 10% to 30%, and more preferably 20%.

[0018] Further, the crosslinking agent is glutaraldehyde, and the amount is 1% to 10% of the mass of the casting solution.

[0019] Further, a preparation method of an attapulgite-based fluid composite basic polyelectrolyte membrane, the method comprising the following steps:

[0020] (1) Attapulgite is added to a sodium hexametaphosphate aqueous solution, and after ultrasonic dispersion, it is left to stand and separate into layers. The upper layer of the suspension is centrifuged, dried, and then ground to obtain purified attapulgite, which is ready for use;

[0021] (2) The purified attapulgite superfine powder is added to deionized water and ultrasonically dispersed. A sulfonic acid-based silane coupling agent aqueous solution is added to the attapulgite water dispersion, and a sodium hydroxide aqueous solution is slowly added dropwise until the pH value of the mixed dispersion is adjusted to between 4 and 6. The reaction is carried out under strong mechanical stirring and heating. The obtained white sol is centrifuged, and the product is repeatedly washed with deionized water until no foam is generated. After drying, the sulfonic acid-based silane coupling agent grafted attapulgite is obtained, which is ground and ready for use;

[0022] (3) The sulfonic acid-based silane coupling agent grafted attapulgite powder obtained in the previous step is prepared into an aqueous solution with a mass-volume fraction of 0.1 g / mL. The polyether amine or polyether quaternary ammonium salt aqueous solution is added dropwise. The H + of the sulfonic acid group is ion-exchanged with the N + of the quaternary ammonium salt to form a cationic outer layer with a polyether long chain. The pH value is carefully monitored to be neutral during the process. Slow vacuum is applied under heating to remove excess water to obtain an attapulgite-based fluid with an anion inner layer and a cationic outer layer structure.

[0023] (4) dissolving quaternary ammonium chitosan in 0.5-2% acetic acid aqueous solution to form quaternary ammonium chitosan aqueous solution with mass percentage concentration of 1-15%, the quaternary ammonium chitosan has quaternary ammonium substitution degree of 40-60%; meanwhile, dissolving a certain amount of polyvinyl alcohol in water at 90℃ to obtain polyvinyl alcohol aqueous solution with mass percentage concentration of 1-5%; mixing the above two solutions uniformly to obtain quaternary ammonium chitosan-polyvinyl alcohol casting solution;

[0024] (5) filling attapulgite fluid obtained in step (3) into casting solution obtained in step (4), adding a certain amount of glutaraldehyde, and then performing crosslinking, drying, cooling, membrane stripping and ion exchange to obtain attapulgite fluid composite basic polyelectrolyte membrane;

[0025] Preferably, the sulfonic silane coupling agent in step (2) is one of 3-(methoxysilyl)-propane sulfonic acid, 3-(trihydroxysilyl)-propane sulfonic acid and 2(2-trihydroxysilyl) ethyl benzene sulfonic acid, the mass-volume fraction of the aqueous solution thereof is 0.4-0.6 g / mL, the mass ratio of the sulfonic silane coupling agent to attapulgite is 1-10:1, and the reaction temperature is 60-80℃, and the reaction time is 8-24 h.

[0026] Preferably, the polyether amine or polyether quaternary ammonium salt in step (3) is one of coconut alkyl amine polyoxyethylene ether, nonylphenol polyoxyethylene propyl trimethyl ammonium chloride and octane polyoxyethylene octadecyl ammonium chloride, the mass-volume fraction of the aqueous solution thereof is 0.1-0.3 g / mL, and the heating temperature during vacuum extraction is 40-60℃.

[0027] Preferably, the mass ratio of quaternary ammonium chitosan to polyvinyl alcohol in the mixed casting solution in step (4) is 1:1-9:1.

[0028] Preferably, the filling mass fraction of attapulgite fluid in step (5) is 1-30% of the polymer matrix (i.e. the sum of the mass of quaternary ammonium chitosan and polyvinyl alcohol), and the mass fraction of crosslinking agent glutaraldehyde is 1-10% of the mass of the casting solution obtained in step (4).

[0029] Preferably, the attapulgite fluid obtained in step (3) is filled into the quaternary ammonium chitosan-polyvinyl alcohol casting solution obtained in step (4), and glutaraldehyde crosslinking agent is added, and then the mixture is poured onto a glass film forming plate after uniform mixing, and then defoaming, crosslinking, drying, cooling, membrane stripping and ion exchange are performed to obtain an attapulgite fluid composite basic polyelectrolyte membrane.

[0030] The present application introduces an organic double molecular layer on the surface of the attapulgite, and a sulfonic acid group silane coupling agent "inner crown" is anchored on the attapulgite "core" by forming a covalent bond through the reaction of the hydroxyl group on the silane coupling agent and the hydroxyl group on the surface of the attapulgite, and the flexible long chain of the polyether amine or polyether quaternary ammonium salt "outer crown" can provide a "flowing medium", so that the attapulgite has room temperature fluidity, and the self-agglomeration tendency of the attapulgite is greatly reduced, and the advantages of the one-dimensional nanometer structure of the rod-shaped attapulgite are fully utilized.

[0031] The attapulgite fluid composite basic polyelectrolyte membrane prepared in the present application (see attached Figure 1 ) compared with the polyelectrolyte membrane obtained by directly compounding the unmodified attapulgite with the polymer matrix (see attached Figure 3 ), avoids the agglomeration of the attapulgite nanorods in the matrix, improves the dispersibility of the attapulgite nanorods in the matrix and the compatibility of the attapulgite nanorods with the matrix, fully utilizes the reinforcing and toughening effect of the one-dimensional rod-shaped attapulgite on the polymer matrix, and greatly improves the mechanical properties of the membrane.

[0032] The attapulgite fluid composite basic polyelectrolyte membrane prepared in the present application, since the cationic layer with anion exchange function is grafted on the outer layer when the molecular structure of the attapulgite fluid is designed, the cation activity of the outer layer of the attapulgite fluid is stronger, and a more continuous channel is constructed for the transmission of hydroxyl ions, and the ion conduction capacity of the composite membrane for anions is significantly improved.

[0033] Compared with the "shell" "core" structure strategy adopted in the traditional inorganic particle modification, the "shell" of the "shell" "core" structure adopted in the present application is an organic double molecular layer, which can significantly improve the compatibility of the inorganic particles with the organic polymer matrix, and in the process of constructing the organic double molecular shell, a large number of ions are introduced and the cationic layer with anion exchange function is grafted on the outer layer, so that a more continuous anion transmission channel is constructed in the matrix, which not only enhances and toughens the membrane, but also improves the ion conductivity of the membrane.

[0034] The natural attapulgite selected in the present application is abundant in source, has room temperature fluidity after modification, and greatly reduces the use of volatile solvents in the compounding process with the polymer matrix, and the quaternary ammonium chitosan and polyvinyl alcohol are dissolved in aqueous solution, so the membrane preparation process is more friendly to the environment, and meets the requirements of green chemistry and sustainable development.

[0035] In summary, the attapulgite fluid composite basic polyelectrolyte membrane prepared in the present application is expected to be widely applied in the field of basic polyelectrolyte fuel cells. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a scanning electron microscope graph of the cross section of the attapulgite fluid composite basic polyelectrolyte membrane prepared in Example 1.

[0037] Figure 2 Figure 2 is a cross-sectional scanning electron microscope image of the quaternary ammonium chitosan-polyvinyl alcohol polymer basic polyelectrolyte membrane prepared in Comparative Example 1.

[0038] Figure 3 Figure 4 is a cross-sectional scanning electron microscope image of the attapulgite composite basic polyelectrolyte membrane prepared in Comparative Example 2. DETAILED DESCRIPTION

[0039] The following applicants further describe the technical solutions of the present application in combination with specific examples and drawings, but the scope of protection requested by the present application is not limited to these examples.

[0040] Attapulgite (purchased from Dehang Mining Products Co., Ltd., particle size 200 mesh); 3-(trihydroxysilyl)-propane sulfonic acid was purchased from Shanghai Yuan Ye Biological Technology Co., Ltd.; 3-(methoxysilyl)-propane sulfonic acid and 2(2-trihydroxysilyl) ethyl benzene sulfonic acid were purchased from Hubei Nuona Technology Co., Ltd.; cocoyl amine polyoxyethylene ether was purchased from Hubei Xingyan New Material Technology Co., Ltd.; nonylphenol polyoxyethylene propyltrimethylammonium chloride and octyl polyoxyethylene octadecyl ammonium chloride were purchased from Wuhan Shuer Biological Technology Co., Ltd.; polyvinyl alcohol (purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd., Mw = 80000); quaternary ammonium chitosan was self-made according to the following method: 10 g of chitosan (purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd., deacetylation degree 80-95%, viscosity 50-800 mPa·s) was dissolved in 600 mL of 2 vol.% acetic acid aqueous solution, then 500 mL of 1 M NaOH aqueous solution was added, soaked for 6 hours, and then washed with deionized water until neutral. The above-mentioned alkalized chitosan was added to a three-necked flask, 500 mL of 40 vol.% isopropanol aqueous solution was added, and mechanical stirring was performed for 2 h. The temperature was raised to 65°C, 15.3 g of 2,3-epoxypropyltrimethylammonium chloride was added, and constant temperature reaction was performed for 6 hours. After the reaction was completed, the stirring was stopped, the solvent was removed by centrifugation, and the unreacted quaternary ammonium reagent was washed away with anhydrous ethanol, and the product was freeze-dried to obtain quaternary ammonium chitosan. The quaternary ammonium substitution degree of the obtained quaternary ammonium chitosan was tested by conductometric titration method, which was 40%.

[0041] Example 1 A method for preparing an attapulgite composite basic polyelectrolyte membrane, the steps of which are as follows:

[0042] (1) 10 g of attapulgite was added to 500 mL of 0.3% sodium hexametaphosphate aqueous solution, ultrasonic dispersion was performed for 6 h, and then it was left to stand for 24 h to separate the layers. The upper layer suspension was centrifuged, dried at 80°C for 24 h, and then ground to obtain purified attapulgite, which was used for further experiments.

[0043] (2) Take 3 g of purified attapulgite superfine powder, add 100 mL of deionized water, and ultrasonically disperse for 10 min. Then add 7.5 mL of 0.4 g / mL 3-(methoxysilyl)-propane sulfonic acid aqueous solution to the attapulgite water dispersion, slowly add sodium hydroxide aqueous solution until the pH value of the mixed dispersion is adjusted to 5, and mechanically stir at 80°C for 12 h. The obtained white sol is centrifuged, washed repeatedly with deionized water until no foam is generated, and the product is vacuum dried at 60°C for 24 h to obtain 3-(methoxysilyl)-propane sulfonic acid grafted attapulgite, which is ground and used.

[0044] (3) Take the 3-(methoxysilyl)-propane sulfonic acid grafted attapulgite obtained in step (2) to prepare a 0.1 g / mL aqueous solution, slowly add a 0.1 g / mL aqueous solution of coconut alkyl amine polyoxyethylene ether, and carefully monitor the pH value until the solution is neutral. Slowly vacuum at 50°C to remove excess water to obtain an attapulgite-based fluid with an anion inner layer and a cation outer layer structure.

[0045] (4) Dissolve 8 g of quaternized chitosan (quaternization degree of 40%) in 1 vol.% acetic acid aqueous solution to form a 10 wt.% quaternized chitosan aqueous solution; at the same time, dissolve 2 g of polyvinyl alcohol in water at 90°C to obtain a 5 wt.% polyvinyl alcohol aqueous solution; mix the two solutions uniformly to obtain a quaternized chitosan-polyvinyl alcohol casting solution.

[0046] (5) Take 2 g of the attapulgite-based fluid prepared in step (3) and fill it into the casting solution obtained in step (4), and add 1 wt.% glutaraldehyde to the casting solution obtained in step (4), and then crosslink, dry, cool, and peel off the membrane to obtain an attapulgite-based fluid composite basic polyelectrolyte membrane. The quaternized chitosan matrix in the composite membrane contains Cl - , which is immersed in a 2M KOH solution for 36 h for ion exchange (Cl - → OH - ), and the composite membrane is repeatedly immersed and washed with deionized water until the washing liquid is neutral, and then vacuum dried at 60°C to obtain an attapulgite-based fluid composite basic polyelectrolyte membrane containing OH - . The scanning electron microscope image of the cross section is shown in Figure 1 .

[0047] Comparative Example 1, 8 g of quaternary ammonium chitosan (quaternary ammonium substitution degree of 40%) was dissolved in 1 vol.% acetic acid aqueous solution to form a 10 wt.% quaternary ammonium chitosan aqueous solution; at the same time, 2 g of polyvinyl alcohol was dissolved in water at 90 °C to obtain a 5 wt.% polyvinyl alcohol aqueous solution; the above two solutions were mixed uniformly to obtain a quaternary ammonium chitosan-polyvinyl alcohol casting solution. 1 wt.% glutaraldehyde was added to the casting solution, cross-linked, dried, cooled, peeled off, and ion exchanged to obtain a quaternary ammonium chitosan-polyvinyl alcohol polymer basic polyelectrolyte membrane, and the scanning electron microscope picture of the cross section thereof is shown in Figure 2 .

[0048] Comparative Example 2, 8 g of quaternary ammonium chitosan (quaternary ammonium substitution degree of 40%) was dissolved in 1 vol.% acetic acid aqueous solution to form a 10 wt.% quaternary ammonium chitosan aqueous solution; at the same time, 2 g of polyvinyl alcohol was dissolved in water at 90 °C to obtain a 5 wt.% polyvinyl alcohol aqueous solution; the above two solutions were mixed uniformly to obtain a quaternary ammonium chitosan-polyvinyl alcohol casting solution. 2 g of purified attapulgite in step (1) was filled into the casting solution, 1 wt.% glutaraldehyde was added to the casting solution, cross-linked, dried, cooled, peeled off, and ion exchanged to obtain an attapulgite composite basic polyelectrolyte membrane, and the scanning electron microscope picture of the cross section thereof is shown in Figure 3 .

[0049] Comparative Example 3: 3 g of purified attapulgite superfine powder was added to 100 mL of deionized water, and after ultrasonic dispersion, the pH value was adjusted to 10. Then 7.5 mL of 0.4 g / mL dimethyl octadecyl [3-(trimethoxysilyl) propyl] ammonium chloride methanol solution was added to the attapulgite water dispersion with adjusted pH value, and the mixture was aged at room temperature for 24 h with intermittent oscillation. The obtained white sol was centrifuged, and washed repeatedly with deionized water and methanol until no foam was generated. The product was dried at 60 °C under vacuum for 24 h to obtain dimethyl octadecyl [3-(trimethoxysilyl) propyl] ammonium chloride grafted attapulgite, which was ground and used as needed. 1 g of the dimethyl octadecyl [3-(trimethoxysilyl) propyl] ammonium chloride grafted attapulgite obtained in the above step was added to 50 mL of anhydrous ethanol, and after ultrasonic dispersion, the mixture was poured into a three-necked flask. Then 10 mL of 0.1 g / mL nonylphenol polyoxyethylene ether sodium sulfate aqueous solution was added, and the mixture was subjected to strong mechanical stirring at 70 °C under reflux for 24 h. The solvent was removed by centrifugation, and the obtained product was washed repeatedly with deionized water and methanol until no foam was generated. The product was first dried at 60 °C for 48 h, and then dried at room temperature under vacuum for 24 h to obtain attapulgite-based fluid with a cationic inner layer and an anionic outer layer. 8 g of quaternized chitosan (quaternization degree of 40%) was dissolved in 1 vol.% acetic acid aqueous solution to form a 10 wt.% quaternized chitosan aqueous solution; at the same time, 2 g of polyvinyl alcohol was dissolved in water at 90 °C to obtain a 5 wt.% polyvinyl alcohol aqueous solution; and the two solutions were mixed to obtain a quaternized chitosan-polyvinyl alcohol casting solution. 2 g of the attapulgite-based fluid obtained in the above step was filled into the casting solution, and 1 wt.% of glutaraldehyde was added. After crosslinking, drying, cooling, membrane stripping and ion exchange, an attapulgite-based fluid composite basic polyelectrolyte membrane was obtained.

[0050] The performance test results of the polyelectrolyte membranes prepared in Example 1 and Comparative Examples 1-3 are shown in Table 1.

[0051] Table 1

[0052]

[0053] From the results of Table 1, it can be seen that the polyelectrolyte membrane obtained in Comparative Example 2 has slightly higher ionic conductivity and certain improvement in tensile strength compared with Comparative Example 1, but the elongation at break decreases, indicating that the unmodified attapulgite has certain reinforcing effect on the quaternary ammonium chitosan-polyvinyl alcohol polymer matrix, but increases the brittleness of the matrix; compared with Comparative Example 1, the ionic conductivity, tensile strength and elongation at break of the polyelectrolyte membrane obtained in Comparative Example 3 are greatly improved, indicating that the attapulgite-based fluid has good reinforcing and toughening effect on the matrix and is beneficial to improving the ionic conductivity of the composite membrane; compared with Comparative Example 3, the tensile strength and elongation at break of the attapulgite-based fluid composite basic polyelectrolyte membrane prepared in Example 1 are not much different, but the room temperature ionic conductivity and ionic conductivity at 80℃ are further improved. It is shown that the structure of the inner ion layer of the attapulgite-based fluid has great influence on the ion transmission capacity of the composite membrane, and the molecular design of the inner layer being anion and the outer layer being cation is confirmed to be more beneficial to the transmission of anions by the composite membrane. The attapulgite-based fluid composite electrolyte membrane prepared in this embodiment has cations with anion exchange function grafted on the outer layer, which further improves the ionic conductivity of the quaternary ammonium chitosan-polyvinyl alcohol polymer matrix, and has a synergistic effect of simultaneously reinforcing and toughening the matrix.

[0054] Figure 1 、 Figure 2 、 Figure 3 are the scanning electron microscope images of the cross sections of the attapulgite-based fluid composite basic polyelectrolyte membrane prepared in Example 1, the quaternary ammonium chitosan-polyvinyl alcohol polymer basic polyelectrolyte membrane prepared in Comparative Example 1 and the attapulgite composite basic polyelectrolyte membrane prepared in Comparative Example 2, respectively. Figure 2 and Figure 3 It can be seen that the unmodified attapulgite has obvious agglomeration in the polymer matrix; while Figure 1 , the modified attapulgite-based fluid is uniformly dispersed in the matrix, and no agglomerates and microphase separation phenomena are observed, indicating that the attapulgite-based fluid has good compatibility with the polymer matrix and the interface is tightly combined. This dense composite system is beneficial to improving the mechanical properties and ionic conductivity of the composite membrane.

[0055] Example 2 A preparation method of an attapulgite-based fluid composite basic polyelectrolyte membrane, the steps of which are as follows:

[0056] (1) 10 g of attapulgite was added to 500 mL of 0.3% sodium hexametaphosphate aqueous solution, ultrasonically dispersed for 6 h, and then statically layered for 24 h. The upper layer suspension was centrifuged, and dried at 80℃ for 24 h to obtain purified attapulgite, which was ground and used.

[0057] (2) Take 1.5 g purified attapulgite superfine powder, add 100 mL deionized water, and ultrasonically disperse for 10 min. Then add 5 mL 0.6 g / mL 3-(trihydroxysilyl)-propane sulfonic acid aqueous solution to the attapulgite water dispersion, slowly add sodium hydroxide aqueous solution until the pH value of the mixed dispersion is adjusted to 4, and react at 70°C under strong mechanical stirring for 24 h. The obtained white sol is centrifuged, washed repeatedly with deionized water until no foam is generated, and the product is vacuum dried at 60°C for 24 h to obtain 3-(trihydroxysilyl)-propane sulfonic acid grafted attapulgite, which is ground and used.

[0058] (3) The 3-(trihydroxysilyl)-propane sulfonic acid grafted attapulgite powder obtained in step (2) is prepared into an aqueous solution with a mass / volume fraction of 0.1 g / mL, and a nonylphenol polyoxyethylene propyltrimethyl ammonium chloride aqueous solution with a mass / volume fraction of 0.2 g / mL is slowly added, with careful monitoring of the pH value until the solution is neutral. Slowly vacuumize at 60°C to remove excess water to obtain an attapulgite-based fluid with an anion inner layer and a cation outer layer structure.

[0059] (4) Dissolve 9 g of quaternized chitosan (quaternized substitution degree of 60%) in 2 vol.% acetic acid aqueous solution to form a 15 wt.% quaternized chitosan aqueous solution; at the same time, dissolve 1 g of polyvinyl alcohol in water at 90°C to obtain a 3 wt.% polyvinyl alcohol aqueous solution; mix the two solutions uniformly to obtain a quaternized chitosan-polyvinyl alcohol casting solution.

[0060] (5) Take 0.1 g of the attapulgite-based fluid prepared in step (3) and fill it into the casting solution obtained in step (4), and add 2 wt.% of glutaraldehyde based on the mass of the casting solution obtained in step (4), and then crosslink, dry, cool, and peel off the film to obtain an attapulgite-based fluid composite basic polyelectrolyte membrane. Soak it in 2M KOH solution for 36 h for ion exchange, repeatedly soak and clean the composite membrane with deionized water until the washing liquid is neutral, and then vacuum dry at 60°C to obtain an attapulgite-based fluid composite basic polyelectrolyte membrane containing OH - .

[0061] Example 3 A method for preparing an attapulgite-based fluid composite basic polyelectrolyte membrane, the steps of which are as follows:

[0062] (1) Take 10 g of attapulgite and add it to 500 mL of 0.3% sodium hexametaphosphate aqueous solution, ultrasonically disperse for 6 h, and stand for 24 h to separate the layers. Take the upper layer of the suspension, centrifuge, and dry at 80°C for 24 h to obtain purified attapulgite, which is ground and used.

[0063] (2) Take 5 g of purified attapulgite superfine powder, add 200 mL of deionized water, and ultrasonically disperse for 10 min. Then add 25 mL of 0.6 g / mL 2-(2-trihydroxysilyl) ethyl benzene sulfonic acid aqueous solution to the attapulgite water dispersion, slowly add sodium hydroxide aqueous solution until the pH value of the mixed dispersion is adjusted to 5, and react at 60°C under strong mechanical stirring for 24 h. The obtained white sol is centrifuged, washed repeatedly with deionized water until no foam is generated, and the product is vacuum dried at 60°C for 24 h to obtain 2-(2-trihydroxysilyl) ethyl benzene sulfonic acid grafted attapulgite, which is ground and used.

[0064] (3) The 2-(2-trihydroxysilyl) ethyl benzene sulfonic acid grafted attapulgite powder obtained in step (2) is prepared into an aqueous solution with a mass fraction of 0.1 g / mL, and a 0.3 g / mL octyl polyoxyethylene octadecyl ammonium chloride aqueous solution is slowly added dropwise, with the pH value being carefully monitored until the solution is neutral. Slowly vacuumize at 40°C to remove excess water to obtain attapulgite fluid with an anion inner layer and a cation outer layer structure.

[0065] (4) Dissolve 7 g of quaternary ammonium chitosan (quaternary ammonium substitution degree of 60%) in 2 vol.% acetic acid aqueous solution to form a 2 wt.% quaternary ammonium chitosan aqueous solution; at the same time, dissolve 3 g of polyvinyl alcohol in water at 90°C to obtain a 1 wt.% polyvinyl alcohol aqueous solution; and mix the two solutions to obtain a quaternary ammonium chitosan-polyvinyl alcohol casting solution.

[0066] (5) Take 0.5 g of the attapulgite fluid prepared in step (3) and fill it into the casting solution obtained in step (4), and add 3 wt.% glutaraldehyde based on the mass of the casting solution obtained in step (4), and then crosslink, dry, cool, and peel off the film to obtain an attapulgite fluid composite basic polyelectrolyte membrane. Soak it in 2M KOH solution for 36 h for ion exchange, repeatedly soak and clean the composite membrane with deionized water until the washing liquid is neutral, and then vacuum dry at 60°C to obtain an attapulgite fluid composite basic polyelectrolyte membrane containing OH - .

[0067] Example 4 A method for preparing an attapulgite fluid composite basic polyelectrolyte membrane, the steps of which are as follows:

[0068] (1) Take 10 g of attapulgite and add it to 500 mL of 0.3% sodium hexametaphosphate aqueous solution, ultrasonically disperse for 6 h, and stand for 24 h to separate the layers. Take the upper layer of the suspension, centrifuge, and dry at 80°C for 24 h to obtain purified attapulgite, which is ground and used.

[0069] (2) Take 0.5 g purified attapulgite superfine powder, add 50 mL deionized water, and ultrasonic dispersion for 10 min. Then add 6.25 mL 0.4 g / mL 3-(trihydroxysilyl)-propane sulfonic acid aqueous solution to the attapulgite water dispersion, slowly drop the sodium hydroxide aqueous solution until the pH value of the mixed dispersion is adjusted to 6, and react at 70°C under strong mechanical stirring for 10 h. The obtained white sol is centrifuged, washed repeatedly with deionized water until no foam is generated, and the product is vacuum dried at 60°C for 24 h to obtain 3-(trihydroxysilyl)-propane sulfonic acid grafted attapulgite, which is ground and used.

[0070] (3) The 3-(trihydroxysilyl)-propane sulfonic acid grafted attapulgite powder obtained in step (2) is prepared into an aqueous solution with a mass-volume fraction of 0.1 g / mL, and a 0.1 g / mL aqueous solution of coconut alkyl amine polyoxyethylene ether is added dropwise. The excess water is removed by slow vacuum extraction at 50°C to obtain an attapulgite fluid with an anion inner layer and a cation outer layer structure.

[0071] (4) Dissolve 6 g of quaternized chitosan (quaternization degree of substitution is 50%) in 2 vol.% acetic acid aqueous solution to form a 10 wt.% quaternized chitosan aqueous solution; at the same time, dissolve 4 g of polyvinyl alcohol in water at 90°C to obtain a 5 wt.% polyvinyl alcohol aqueous solution; mix the above two solutions uniformly to obtain a quaternized chitosan-polyvinyl alcohol casting solution.

[0072] (5) Take 3 g of the attapulgite fluid prepared in step (3) and fill it into the casting solution obtained in step (4), and add 5 wt.% of glutaraldehyde based on the mass of the casting solution obtained in step (4). After crosslinking, drying, cooling, and membrane stripping, an attapulgite fluid composite basic polyelectrolyte membrane is obtained. It is immersed in 2M KOH solution for 36 h for ion exchange, and the composite membrane is repeatedly immersed and washed with deionized water until the washing liquid is neutral. After vacuum drying at 60°C, an attapulgite fluid composite basic polyelectrolyte membrane containing OH - is obtained.

[0073] Example 5 A method for preparing an attapulgite fluid composite basic polyelectrolyte membrane, the steps of which are as follows:

[0074] (1) Take 10 g of attapulgite and add it to 500 mL of 0.3% sodium hexametaphosphate aqueous solution, ultrasonic dispersion for 6 h, and stand for 24 h to separate the layers. Take the upper layer suspension, centrifuge, and dry at 80°C for 24 h to obtain purified attapulgite, which is ground and used.

[0075] (2) Take 0.2 g of purified attapulgite superfine powder, add 50 mL of deionized water, and ultrasonically disperse for 10 min. Then add 5 mL of 0.4 g / mL 3-(methoxysilyl)-propane sulfonic acid aqueous solution to the attapulgite water dispersion, slowly drop the sodium hydroxide aqueous solution until the pH value of the mixed dispersion is adjusted to 4, and mechanically stir at 80°C for 8 h. The obtained white sol is centrifuged, washed repeatedly with deionized water until no foam is generated, and the product is vacuum dried at 60°C for 24 h to obtain 3-(methoxysilyl)-propane sulfonic acid grafted attapulgite, which is ground and used.

[0076] (3) The 3-(methoxysilyl)-propane sulfonic acid grafted attapulgite powder obtained in step (2) is prepared into an aqueous solution with a mass fraction of 0.1 g / mL, and a 0.1 g / mL octyl polyoxyethylene octadecyl ammonium chloride aqueous solution is added dropwise, and the excess water is removed by slow vacuum extraction at 60°C to obtain an attapulgite-based fluid with an anion inner layer and a cation outer layer structure.

[0077] (4) Dissolve 5 g of quaternized chitosan (quaternary ammonium substitution degree of 40%) in 2 vol.% acetic acid aqueous solution to form a 5 wt.% quaternary ammonium chitosan aqueous solution; at the same time, dissolve 5 g of polyvinyl alcohol in water at 90°C to obtain a 1 wt.% polyvinyl alcohol aqueous solution; mix the two solutions uniformly to obtain a quaternary ammonium chitosan-polyvinyl alcohol casting solution.

[0078] (5) Take 1 g of the attapulgite-based fluid prepared in step (3) and fill it into the casting solution obtained in step (4), and add 10 wt.% glutaraldehyde to the casting solution obtained in step (4), and then crosslink, dry, cool, and peel off the film to obtain an attapulgite-based fluid composite basic polyelectrolyte membrane. It is immersed in 2M KOH solution for 36 h for ion exchange, and the composite membrane is repeatedly immersed and washed with deionized water until the washing liquid is neutral, and then vacuum dried at 60°C to obtain an attapulgite-based fluid composite basic polyelectrolyte membrane containing OH - .

[0079] Table 2 lists the performance index data of the attapulgite-based fluid composite basic polyelectrolyte membranes prepared in Examples 2-5. As can be seen from Table 2, the ion conductivity of the composite basic polyelectrolyte membrane at 80°C is ≥56 mS / cm, and the tensile strength is maintained at a high level (≥52 MPa), and the elongation at break is ≥162%. In Example 4, the addition amount of the attapulgite-based fluid in the preparation of the attapulgite-based fluid composite basic polyelectrolyte membrane reaches 30 wt.%, and the ion conductivity of the prepared polyelectrolyte membrane is high (69 mS / cm), and the mechanical properties are good (tensile strength 65 MPa, elongation at break 256%).

[0080] Table 2

[0081] Performance indicators Example 2 Example 3 Example 4 Example 5 Ionic conductivity (mS / cm, 80°C) 56 61 69 62 Tensile strength (MPa) 52 56 65 70 Elongation at break (%) 162 158 256 261

[0082] The performance of the films prepared in the above examples was tested by the following methods:

[0083] (1) Ionic conductivity: The ionic conductivity of the films was tested by two-electrode AC impedance method on a frequency response analyzer, with a frequency scanning range of 1-10 6 Hz and an AC signal amplitude of 50 mV. The cut films (3 cm long and 2 cm wide) were immersed in room temperature deionized water before the test until the water absorption reached saturation. The ionic conductivity σ (S / cm) of the film was calculated by the following formula:

[0084]

[0085] In the formula, L is the distance between the two electrodes (cm); A is the effective cross-sectional area of the film to be tested between the two electrodes (cm 2 ); and R is the resistance of the film to be tested (Ω), which is obtained by Nyquist plot.

[0086] (2) Tensile strength and elongation at break: The film was cut into a rectangular strip with a length of 4 cm and a width of 1 cm, and tested on an electronic tensile machine at a tensile speed of 1 mm / min.

Claims

1. A method for preparing an attapulgite-based fluid composite basic polyelectrolyte membrane, characterized in that, The method comprises the following steps: The preparation of the attapulgite fluid comprises the following steps: grafting a sulfonic silane coupling agent to attapulgite, ion exchanging the obtained sulfonic silane coupling agent grafted attapulgite with a polyether amine or a polyether quaternary ammonium salt to form a cationic outer layer with flexible long chains, and obtaining an attapulgite fluid with an anion inner layer and a cation outer layer; Dissolving the quaternized chitosan and polyvinyl alcohol to obtain a mixed casting solution; The attapulgite fluid is filled into the mixed casting solution, and crosslinking occurs under the action of a crosslinking agent to obtain an attapulgite fluid composite basic polyelectrolyte membrane. The filling mass fraction of the attapulgite fluid is 1-30% of the polymer matrix.

2. The production method according to claim 1, characterized by, The sulfonic silane coupling agent is one of 3-(methoxysilyl)-propane sulfonic acid, 3-(trihydroxysilyl)-propane sulfonic acid and 2(2-trihydroxysilyl) ethyl benzene sulfonic acid; and / or The polyether amine is a coconut alkyl amine polyoxyethylene ether, and the polyether quaternary ammonium salt is one of a nonylphenol polyoxyethylene propyl trimethyl ammonium chloride and an octyl polyoxyethylene octadecyl ammonium chloride.

3. The preparation method according to claim 2, characterized in that, The grafting reaction of the sulfonic silane coupling agent and the attapulgite is carried out under the following conditions: the mass ratio of the sulfonic silane coupling agent to the attapulgite is 1-10:1, the pH value of the reaction solution is 4-6, the reaction temperature is 60-80°C, and the reaction time is 8-24 h.

4. The method of claim 1, wherein, The quaternization substitution degree of the quaternized chitosan is 40-60%, and the mass ratio of the quaternized chitosan to the polyvinyl alcohol in the mixed casting solution is 1:1-9:

1.

5. The production method according to any one of claims 1 to 4, characterized by, The preparation method comprises the following steps: (1) The attapulgite is added to a sodium hexametaphosphate aqueous solution, ultrasonically dispersed, and then allowed to stand and separate into layers. The upper layer of the suspension is centrifuged, dried, and then ground to obtain purified attapulgite, which is ready for use; (2) The purified attapulgite superfine powder is added to deionized water and ultrasonically dispersed. A sulfonic silane coupling agent aqueous solution is added to the attapulgite water dispersion, and a sodium hydroxide aqueous solution is slowly added dropwise until the pH value of the mixed dispersion is adjusted to 4-6. The reaction is carried out under strong mechanical stirring and heating. The obtained white sol is centrifuged, and the product is repeatedly washed with deionized water until no foam is generated. After drying, the sulfonic silane coupling agent grafted attapulgite is obtained, which is ready for use after being ground; (3) The sulfonic silane coupling agent grafted attapulgite powder obtained in the above step is prepared into an aqueous solution with a mass-volume fraction of 0.1 g / mL. A polyether amine or polyether quaternary ammonium salt aqueous solution with a mass-volume fraction of 0.1-0.3 g / mL is added dropwise. The pH value is carefully monitored to be neutral during the process. The solution is slowly vacuumed under heating to remove excess water, and an attapulgite fluid with an anion inner layer and a cation outer layer is obtained. (4) Dissolve quaternary ammonium chitosan in 0.5-2% acetic acid aqueous solution to form a quaternary ammonium chitosan aqueous solution with a mass percentage concentration of 1-15%, and the quaternary ammonium substitution degree of the quaternary ammonium chitosan is 40-60%; meanwhile, dissolve a certain amount of polyvinyl alcohol in water at 90°C to obtain a polyvinyl alcohol aqueous solution with a mass percentage concentration of 1-5%; mix the above two solutions uniformly to obtain a quaternary ammonium chitosan-polyvinyl alcohol casting solution; (5) Fill the attapulgite fluid obtained in step (3) into the casting solution obtained in step (4), add 1-10% glutaraldehyde based on the mass of the casting solution, and then perform crosslinking, drying, cooling, membrane stripping, and ion exchange to obtain an attapulgite fluid composite basic polyelectrolyte membrane.

6. Application of the attapulgite fluid composite basic polyelectrolyte membrane prepared by the preparation method of any one of claims 1-5 to a fuel cell.

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