Paper-based diaphragm for alkaline water electrolysis and preparation method thereof

Abstract

The invention discloses a paper-based diaphragm for alkaline water electrolysis and a preparation method of the paper-based diaphragm. A PPS / aramid fiber porous base material is prepared by adopting a wet non-woven process, a PVA-polymer quaternary ammonium salt blending layer is constructed on one side of the base material, OH <-> conduction is promoted by utilizing a quaternary ammonium group of polymer quaternary ammonium salt, and a three-dimensional network is formed through glutaraldehyde crosslinking. According to the paper-based diaphragm prepared through the method, when the porosity is 60.4%, the strength still reaches 8.98 MPa, the surface resistance of the diaphragm is greatly reduced to 68 m omega.cm < 2 >, the ionic conductivity synchronously jumps to 515 mS.cm <-1 >, the electrolytic current density is promoted to reach 1474 mA under the polarization voltage of 2.0 V, the vertical swelling rate of the diaphragm is stabilized at 12% through the cross-linked functional layer, and the paper-based diaphragm has the advantages that the paper-based diaphragm can be applied to the field of lithium ion batteries. The diaphragm achieves an optimal balance in key indexes such as aperture, strength, ionic conductivity and alkali liquor stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of paper-based diaphragm for alkaline water electrolysis and its preparation method.Belongs to diaphragm technical field. BACKGROUND

[0002] Currently, more than 80% of energy supply in global energy consumption still relies on fossil fuels such as oil, natural gas and coal. However, this dependence is facing severe challenges, not only because these resources are gradually depleted and subject to geographical distribution and mining difficulty, but also because the combustion of fossil fuels releases a large amount of greenhouse gases such as carbon dioxide, exacerbating the trend of global warming. Therefore, promoting global energy transformation and accelerating the development of clean, efficient and sustainable renewable energy has become the consensus of the international community. In the field of renewable energy, hydrogen energy is considered as the most potential zero-carbon energy carrier to replace fossil fuels in the future due to its high energy density and wide source. The widespread application of hydrogen energy not only can address the dual crisis of global warming and energy shortage, but also can meet the growing energy demand of mankind and provide power for the sustainable development of society. Therefore, vigorously developing hydrogen energy industry has become an important strategy for the global response to environmental and energy challenges.

[0003] Hydrogen energy has outstanding advantages such as high energy density, high heat value and high conversion efficiency, and has become the focus of attention on the world energy stage. Realizing large-scale and low-cost production of hydrogen is a key step for the development and utilization of hydrogen energy. Alkaline water electrolysis technology stands out among various hydrogen production methods due to its high maturity, simple operation and relatively low cost, and has become one of the dominant technologies for large-scale hydrogen production in industry.

[0004] Alkaline electrolysis water diaphragm as a key material plays a crucial role in promoting hydrogen energy technology development and promoting energy structure transformation and upgrading. In the process of alkaline water electrolysis, the role of diaphragm cannot be underestimated. It not only needs to separate the anode and cathode to prevent the mixing of dangerous hydrogen and oxygen, but also needs to allow the passage of ions to maintain the progress of the electrolysis reaction. Therefore, the performance of the diaphragm is directly related to the efficiency, safety and service life of the electrolytic cell. From the early asbestos diaphragm to the modern organic fiber diaphragm such as polyphenylene sulfide (PPS), to the composite diaphragm being developed, the progress of material science has made it possible to improve the performance of the diaphragm. However, existing diaphragm materials still face technical challenges in terms of chemical stability, hydrophilicity, etc. Especially in high temperature and strong alkaline environment, the high ionic conductivity of the diaphragm is a key problem. For example, the preparation method of alkaline water electrolysis composite diaphragm modified by polyvinyl alcohol composite hydrophilic thin layer disclosed in CN117230484A, the composite diaphragm is composed of a porous substrate and a surface skin layer. On the one hand, the porous substrate provides high electrolyte flux; on the other hand, through the construction of the surface skin layer, the gas barrier performance of the diaphragm can be effectively increased; the preparation method of a composite diaphragm for ultra-thin alkaline water electrolysis disclosed in CN115896863B, the composite diaphragm is composed of a porous support layer and a dense skin layer formed on the outer surface of the porous support layer, the porous support layer and the dense skin layer are prepared from the same composition of slurry, the slurry includes nanofibers, inorganic nanoparticles, organic polymer and binder, the mass percentage content S% of the nanofiber in the slurry and the length L and diameter D of the nanofiber satisfy: S = K * sqrt(L / D); the preparation method of an ultra-hydrophilic polyphenylene sulfide diaphragm for alkaline water electrolysis cell disclosed in CN118852708A, the preparation method of the diaphragm includes the following steps: first, the PPS diaphragm is cleaned, dried and subjected to surface plasma treatment; then placed in a 70°C deoxygenated acrylic acid aqueous solution for heat preservation to carry out grafting reaction; after the reaction is completed, it is cleaned and dried to obtain an ultra-hydrophilic polyphenylene sulfide diaphragm. However, the ionic conductivity of the composite diaphragm obtained by these methods needs to be improved when applied to alkaline water electrolysis.

[0005] In recent years, researchers have been working to develop new diaphragm materials to overcome the shortcomings of traditional diaphragms. Building a thin film composite (TFC) may be the most promising solution. The TFC concept is derived from ultrafiltration and nanofiltration technology, which is the core solution for the next generation of seawater desalination and water purification. Its structure is usually composed of a high-flux support layer and a high-selectivity functional layer. For AWE technology, existing researches mostly use porous polyethylene (PE), porous polypropylene (PP) or polyphenylene sulfide (PPS) as the support material, and construct the selective functional layer by quaternary ammonium membrane or cross-linked polyvinyl alcohol (PVA).

[0006] Current support layer materials mainly use dry non-woven technology (such as needle punching, spun-bonding, etc.) materials and fabrics. Compared with substrates prepared by wet non-woven technology, they have complex process, poor wettability, high thickness, large pore size, uneven pore size distribution, and low local air tightness. Short fiber-based separators have grown rapidly in recent years, and their wet laying process is simple, low in cost, excellent in wettability, high in porosity, and pore size can be accurately controlled by fiber ratio and post-treatment. It has great application value in the field of alkaline water electrolysis. However, the short fiber-based separator still has problems such as insufficient mechanical strength and uneven pore size distribution. SUMMARY

[0007] [TECHNICAL PROBLEM]

[0008] The technical problem to be solved by the present application is to overcome the defects of insufficient ion conductivity of the existing alkaline water electrolysis separator in a high-temperature strong alkali environment, and to provide a paper-based separator with high porosity, low swelling rate and high ion conductivity, and a preparation method thereof. The separator is designed to effectively reduce the ohmic loss of the electrolysis process and improve the hydrogen production efficiency and current density.

[0009] [TECHNICAL SCHEME]

[0010] To solve the above technical problems, the present application adopts the following technical scheme:

[0011] The first object of the present application is to provide a preparation method of a paper-based separator for alkaline water electrolysis, comprising the following steps:

[0012] S1, according to the mass percentage, 50-80% of the chopped fiber is mixed with 20-50% of the aramid pulp, and 0.3-0.8% of the dispersing agent is added, and the slurry is obtained by stirring and dispersing;

[0013] S2, the slurry obtained in step S1 is papered to obtain a wet paper web, and the separator substrate is obtained by drying;

[0014] S3, the polyvinyl alcohol solution and the chitosan quaternary ammonium salt solution are blended at a volume ratio of 1:0.67-4, and are coated on one side of the substrate, and are dried to obtain the dried separator;

[0015] S4, the dried separator is crosslinked in a solution containing a crosslinking agent, and the paper-based separator for alkaline water electrolysis is obtained after crosslinking, cleaning and drying.

[0016] The core of the technical solution includes two parts. The first is the preparation of the substrate: a PPS / aramid porous substrate is prepared by a wet non-woven process, and by adjusting the fiber ratio (PPS chopped fiber 50-80%, aramid 1313 pulp 20-50%), a high-strength substrate with a porosity >80% and a thickness ≤350μm is obtained. The second is the design of the functional layer: a PVA-polymer quaternary ammonium salt blended layer is constructed on one side of the substrate, the quaternary ammonium groups of the polymer quaternary ammonium salt are used to promote OH- conduction, and a three-dimensional network is formed by glutaraldehyde crosslinking, which not only maintains the pore structure but also inhibits swelling. By combining the porous structure of the substrate with the ion selectivity of the functional layer, a surface resistance ≤100mΩ·cm 2 , and an ionic conductivity ≥500mS·cm -1 .

[0017] In an embodiment of the present application, the chopped fiber is one of polypropylene, polyethylene, polysulfone, polyether sulfone, polyphenyl sulfone, polyphenylene sulfide, polysulfone, and polyether ether ketone.

[0018] In an embodiment of the present application, the aramid pulp is aramid 1313 pulp with a beating degree of 40°SR-80°SR.

[0019] In an embodiment of the present application, the chopped fiber is cleaned with a sodium alkyl benzene sulfonate solution before mixing, and the chopped fiber slurry is obtained by beating after cleaning, wherein the concentration of the sodium alkyl benzene sulfonate solution is 1.0×10 2 -1.5×10 2 mol / L.

[0020] In an embodiment of the present application, in the S1 step, the dispersant is one or a combination of polyethylene oxide, polyacrylamide, polyvinyl alcohol, or hydroxymethyl cellulose.

[0021] In an embodiment of the present application, in the S1 step, the dispersion is carried out in an aqueous solution at 2000-3000rpm for 10-20 minutes.

[0022] In an embodiment of the present application, the basis weight of the wet paper web is 40-120g / m 2 .

[0023] In an embodiment of the present application, in the S2 step, the drying temperature is 105℃-120℃, and the drying time is 5-15min.

[0024] In an embodiment of the present application, the concentration of the polyvinyl alcohol solution is 8%-12%, and the concentration of the chitosan quaternary ammonium salt solution is 1%-5%.

[0025] In one embodiment of the present application, the proportion of the polyvinyl alcohol solution in the total volume of the polyvinyl alcohol solution and the chitosan quaternary ammonium salt solution is 20% to 60%.

[0026] In one embodiment of the present application, the volume ratio of the polyvinyl alcohol solution to the chitosan quaternary ammonium salt solution is one of 60:40, 50:50, 40:60, 30:70 or 20:80.

[0027] In one embodiment of the present application, in the S3 step, the drying is performed at 50 to 70°C for 10 to 15 hours.

[0028] In one embodiment of the present application, after drying, the membrane is crosslinked in a methanol solution containing 0.12% to 2% HCl and 5% to 15% glutaraldehyde at 40 to 80°C for 5 to 15 minutes.

[0029] The second object of the present application is to provide a paper-based membrane for alkaline water electrolysis prepared by the method.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] (1) The present application provides a preparation method of a paper-based membrane for alkaline water electrolysis, which uses wet non-woven material as the membrane substrate. By adjusting the content of aramid pulp, the membrane has high porosity (> 60%) and good mechanical properties (such as tensile strength of 8.98-9.14 MPa), solving the contradiction between high porosity and mechanical properties of traditional membranes; at the same time, the pore size distribution of the base paper is more uniform, and the average pore size is reduced to below 3 μm, thereby more effectively inhibiting gas permeation and improving the gas barrier performance of the membrane.

[0032] (2) The membrane has a double-effect conduction mechanism, the porous structure of the substrate promotes electrolyte infiltration, and the QCS quaternary ammonium group conducts OH- in a directional manner, and the ionic conductivity of the membrane is as high as 515 mS·cm -1 (Example 3), which is significantly higher than that of existing PPS membranes.

[0033] (3) The three-dimensional network structure formed inside the membrane by glutaraldehyde crosslinking treatment effectively inhibits the swelling of the alkaline solution while maintaining porosity. The vertical swelling rate of the membrane after seven days of alkaline solution immersion is reduced from 20% for the uncrosslinked membrane to 12% for the crosslinked membrane, ensuring long-term operation reliability. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The electron micrograph of the present application; (a) base paper (b) surface layer of the membrane of Example 3.

[0035] Figure 2 The pore size distribution graph of the base paper of the present application.

[0036] Figure 3 For the swelling rate graph of the present application, (a) Comparative Example 3 (b) Example 3. DETAILED DESCRIPTION

[0037] The following describes preferred embodiments of the present application, and it should be understood that the embodiments are for better explaining the present application and are not intended to limit the present application.

[0038] Test method:

[0039] 1. Porosity

[0040] The porosity of the separator was measured by the weighing method. A 5 cm x 5 cm piece of the film was cut out, the film area (S) was recorded, the film was wetted with deionized water, the film surface was wiped with filter paper, and the thickness d and weight (Mwet) of the film in the wet state were measured. After vacuum drying at 80°C, the dry weight (Mdry) was measured, and the porosity C was calculated according to formula (1).

[0041]

[0042] In the formula, C is the porosity, %; Mwet is the wet film mass, g; Mdry is the dry film mass, g; p is the deionized water density, g / cm3; S is the film area, cm2; and d is the film thickness, cm. wet dry

[0043] 2. Pore size distribution

[0044] The pore size distribution of the base paper was tested using a porous material pore size analyzer (CFP-1100AX).

[0045] 3. Electrochemical performance

[0046] The electrochemical performance of the separator was tested by an electrochemical workstation using a three-electrode system. Among them, the foamed nickel was the working electrode and the counter electrode, the area was 1 x 1 cm2, the saturated Hg / HgO was the reference electrode, and the electrolyte was a 30% KOH solution. The electrochemical impedance was set to constant current test, the current density was 200 mA / cm2, and the frequency was 10-2-105 Hz. The test results were fitted using ZView2 software. The polarization curve measurement was set to a voltage of -0.8 V to 2.5 V and an amplitude of 10 mV.

[0047] The resistance R1 when the film was clamped and the resistance R0 when the film was not clamped were obtained from the impedance spectrum, formula (2) was used to calculate the ionic conductivity σ of the film, and formula (3) was used to calculate the surface resistance Rs of the film:

[0048]

[0049] Rs = (R1 - R0) x A (3)​​

[0050] where σ is the conductivity, mS-crn1; δ is the thickness of the membrane, cm; Rs is the areal resistance of the membrane, mΩ-cm2; R1 is the resistance measured with the membrane clamped, mΩ; R0 is the solution resistance measured without the membrane, A is the active membrane area, cm2, which in this experiment was 0.5625 cm2.

[0051] 4. Base stability and base uptake

[0052] The size scale method was used to determine the swelling ratio of the membranes. First, the membrane to be tested was dried in a vacuum oven at 80 °C for 24 h. The completely dried membrane to be tested was cut into a rectangular sample of about 5 cm x 4 cm. The length of the long side of the membrane sample was measured with a ruler, the thickness of the sample was measured with a digital thickness gauge, and the mass of the membrane sample was measured with an analytical balance. Then, the membrane sample was completely immersed in a sealed glass petri dish filled with KOH solution and placed in a constant temperature water bath. Fresh base was replaced every 1 day and the sample membrane was removed. The liquid adhering to the surface of the membrane was quickly wiped off with filter paper, and the length of the long side of the wet membrane, the thickness, and the mass were measured. The base uptake and the swelling ratio of the membrane were calculated from equations (5), (5), and (6).

[0053]

[0054] where Ww and Wd are the mass of the sample membrane in wet and dry states, respectively, g; is the horizontal swelling ratio, %; is the vertical swelling ratio, %; Lw and Ld are the length of the long side of the sample membrane in wet and dry states, cm; Tw and Td are the thickness of the sample membrane in wet and dry states, cm2.

[0055] 5. Mechanical properties

[0056] Ten points were randomly selected on the paper sample, and the thickness of the paper sample was measured using a thickness gauge according to GB / T 451.3-2002, and the average value was taken. A material tensile strength tester was used, and the sample was cut into 100 mm x 15 mm according to GB / T 453-2002, and the tensile strength of the sample was tested at a test speed of 5 mm min1. Each sample was tested 5 times, and the average value was taken.

[0057] Raw materials used in the examples:

[0058] Polyphenylene sulfide short fibers (6 mm) were treated by beating, and the beating degree was 22°SR. Anionic polyacrylamide (APAM, number average molecular weight about 4 million), polyethylene oxide (PEO, number average molecular weight about 4 million) were purchased from Lianyungang Fiber New Material Research Institute Co., Ltd. Aramid pulp (aramid 1313, beating degree 34°SR) was purchased from Sinopec Yizheng Chemical Fibre Co., Ltd.

[0059] Polyvinyl alcohol (PVA, alcoholysis degree 95%) and chitosan quaternary ammonium salt (QCS, hydroxypropyl trimethyl ammonium chloride chitosan, degree of substitution 95%) were purchased from Shanghai Melin Biochemical Science and Technology Co., Ltd. Glutaraldehyde (analytical pure, 25%), concentrated hydrochloric acid (analytical pure, 37%), and anhydrous methanol (analytical pure) were from Shanghai Rongyao Chemical Reagent Co., Ltd. Deionized water was purchased from Shanghai Maier Biochemical Technology Co., Ltd.

[0060] Example 1:

[0061] S1, polyphenylene sulfide short fiber pretreatment: cleaning and dispersion of polyphenylene sulfide short fibers, the fibers were cleaned after being immersed in 1.2 x 10 2 mo1 / L LAS solution and then dried for standby, and then the cleaned polyphenylene sulfide short fibers were beaten with a beater to disperse uniformly.

[0062] S2, slurry preparation: mixing 70% polyphenylene sulfide short fibers and 30% aramid 1313 pulp with a beating degree of 45°SR; adding 0.5wt% of polyethylene oxide and 0.6wt% of anionic polyacrylamide based on the dry pulp, and dispersing in an aqueous solution at 2500 rpm for 10 minutes.

[0063] S3, wet forming: forming a wet paper web with a basis weight of 100 g / m 2 , using a paper sample dryer to dry, the drying temperature is 105°C, and the drying time is 5 min, until the moisture content is less than 8%.

[0064] S4, functional layer coating: blending 10% PVA solution with 2% QCS solution at a volume ratio of 50:50, and coating on one side of the substrate, and drying at 60°C for 12h.

[0065] S5, crosslinking treatment: crosslinking the dried separator in a methanol solution containing 0.12% HC1 and 10% glutaraldehyde at 60°C for 10 min.

[0066] S6, post-treatment: washing the crosslinked separator with deionized water and vacuum drying at 60°C to obtain the finished product.

[0067] Example 2:

[0068] S1, polyphenylene sulfide short fiber pretreatment: cleaning and dispersion of polyphenylene sulfide short fibers, the fibers were cleaned after being immersed in 1.2 x 10 2 mo1 / L LAS solution and then dried for standby, and then the cleaned polyphenylene sulfide short fibers were beaten with a beater to disperse uniformly.

[0069] S2, slurry preparation: mixing polyphenylene sulfide short fibers 60%, aramid 1313 pulp with beating degree of 45°SR 40%; adding polyethylene oxide with absolute dry pulp mass ratio of 0.5wt% and anionic polyacrylamide with absolute dry pulp mass ratio of 0.6%, dispersing in aqueous solution for 10 minutes at 2500 rpm.

[0070] S3, wet forming: forming a wet paper web with basis weight of 100 g / m 2 , drying using a paper-like dryer, drying temperature is 105℃, drying time is 5 min, until the moisture content is less than 8%.

[0071] S4, functional layer coating: blending 10% PVA solution and 2% QCS solution at a volume ratio of 50:50, blade coating on one side of the substrate, drying at 60℃ for 12h.

[0072] S5, cross-linking treatment: cross-linking the dried separator in a methanol solution containing 0.12% HC1 and 10% glutaraldehyde at 60℃ for 10 min.

[0073] S6, post-treatment: washing the cross-linked separator with deionized water, vacuum drying at 60℃ to obtain the finished product.

[0074] Example 3:

[0075] S1, polyphenylene sulfide short fiber pretreatment: cleaning and dispersing polyphenylene sulfide short fibers, cleaning the fibers by immersing them in a LAS solution with a concentration of 1.2 x 10 2 mo1 / L, then drying for standby, then using a beater to beat the cleaned polyphenylene sulfide short fibers for uniform dispersion.

[0076] S2, slurry preparation: mixing polyphenylene sulfide short fibers 50%, aramid 1313 pulp with beating degree of 45°SR 50%; adding polyethylene oxide with absolute dry pulp mass ratio of 0.5wt% and anionic polyacrylamide with absolute dry pulp mass ratio of 0.6%, dispersing in aqueous solution for 10 minutes at 2500 rpm.

[0077] S3, wet forming: forming a wet paper web with basis weight of 100 g / m 2 , drying using a paper-like dryer, drying temperature is 105℃, drying time is 5 min, until the moisture content is less than 8%.

[0078] S4, functional layer coating: blending 10% PVA solution and 2% QCS solution at a volume ratio of 20:80, blade coating on one side of the substrate, drying at 60℃ for 12h.

[0079] S5, cross-linking treatment: cross-linking the dried separator in a methanol solution containing 0.12% HC1 and 10% glutaraldehyde at 60℃ for 10 min.

[0080] S6, Post-treatment: The cross-linked membrane was washed with deionized water and dried at 60°C under vacuum to obtain the finished product.

[0081] Example 4:

[0082] S1, PPS short fiber pretreatment: The PPS short fiber was cleaned and dispersed, and then immersed in a LAS solution with a concentration of 1.2 x 10 2 moL / L for cleaning and drying. Then, the cleaned PPS short fiber was beaten with a beater to disperse uniformly.

[0083] S2, Slurry preparation: 50% PPS short fiber and 50% aramid 1313 pulp with a beating degree of 45°SR were mixed. 0.5wt% polyethylene oxide and 0.6wt% anionic polyacrylamide were added to the dry pulp, and dispersed in an aqueous solution at 2500 rpm for 10 minutes.

[0084] S3, Wet forming: A wet paper web with a basis weight of 100 g / m 2 was made, and dried using a paper dryer at a temperature of 105°C for 5 minutes until the moisture content was less than 8%.

[0085] S4, Functional layer coating: 10% PVA solution and 2% QCS solution were blended at a volume ratio of 50:50, and then coated on one side of the substrate, and dried at 60°C for 12 hours.

[0086] S5, Cross-linking treatment: The dried membrane was cross-linked in a methanol solution containing 0.12% HCl and 10% glutaraldehyde at 60°C for 10 minutes.

[0087] S6, Post-treatment: The cross-linked membrane was washed with deionized water and dried at 60°C under vacuum to obtain the finished product.

[0088] Comparative Example 1:

[0089] S1, PPS short fiber pretreatment: The PPS short fiber was cleaned and dispersed, and then immersed in a LAS solution with a concentration of 1.2 x 10 2 moL / L for cleaning and drying. Then, the cleaned PPS short fiber was beaten with a beater to disperse uniformly.

[0090] S2, Slurry preparation: 50% PPS short fiber and 50% aramid 1313 pulp with a beating degree of 45°SR were mixed. 0.5wt% polyethylene oxide and 0.6wt% anionic polyacrylamide were added to the dry pulp, and dispersed in an aqueous solution at 2500 rpm for 10 minutes.

[0091] S3, wet forming: a wet paper web with a basis weight of 100 g / m2was formed, dried using a paper-like dryer, the drying temperature was 105°C, the drying time was 5 min, until the moisture content was less than 8%. 2

[0092] S4, functional layer coating: a 10% PVA solution was coated on one side of the substrate by blade coating, dried at 60°C for 12 h.

[0093] S5, cross-linking treatment: the dried separator was cross-linked in a methanol solution containing 0.12% HC1 and 10% glutaraldehyde at 60°C for 10 min.

[0094] Comparative Example 2:

[0095] S1, polyphenylene sulfide short fiber pretreatment: the polyphenylene sulfide short fiber was cleaned and dispersed, and the fiber was immersed in a 1.2 x 10 2 mo1 / L LAS solution for cleaning, then dried for standby, and then the cleaned polyphenylene sulfide short fiber was beaten by a beater to disperse uniformly.

[0096] S2, pulp preparation: 50% polyphenylene sulfide short fiber and 50% aramid 1313 pulp with a beating degree of 45°SR were mixed; 0.5wt% of polyethylene oxide and 0.6wt% of anionic polyacrylamide were added to the absolutely dry pulp, and dispersed in an aqueous solution at 2500 rpm for 10 minutes.

[0097] S3, wet forming: a wet paper web with a basis weight of 100 g / m2was formed, dried using a paper-like dryer, the drying temperature was 105°C, the drying time was 5 min, until the moisture content was less than 8%. 2

[0098] S4, functional layer coating: a 10% PVA solution and a 2% QCS solution were blended at a volume ratio of 80:20, coated on one side of the substrate by blade coating, and dried at 60°C for 12 h.

[0099] S5, cross-linking treatment: the dried separator was cross-linked in a methanol solution containing 0.12% HC1 and 10% glutaraldehyde at 60°C for 10 min.

[0100] S6, post-treatment: the cross-linked separator was washed with deionized water, and vacuum dried at 60°C to obtain a finished product.

[0101] Comparative Example 3:

[0102] S1, polyphenylene sulfide short fiber pretreatment: the polyphenylene sulfide short fiber was cleaned and dispersed, and the fiber was immersed in a 1.2 x 10 2 ​​After washing in a mol / L LAS solution and drying, the cleaned polyphenylene sulfide chopped fibers are then pulped using a pulping machine to ensure uniform dispersion.

[0103] S2. Slurry preparation: Mix 50% of polyphenylene sulfide chopped fibers and 50% of aramid 1313 pulp with a freeness of 45°SR; add 0.5 wt% of oven-dried ethylene oxide and 0.6 wt% of oven-dried anionic polyacrylamide, and disperse in an aqueous solution at 2500 rpm for 10 minutes.

[0104] S3, Wet forming: The sheet forming quantity is 100g / m³ 2 The wet paper web is dried using a paper pattern dryer at a temperature of 105°C for 5 minutes until the moisture content is below 8%.

[0105] S4. Functional layer coating: Mix 10% PVA solution and 2% QCS solution at a volume ratio of 10:90, apply to one side of the substrate by scraping, and dry at 60℃ for 12h.

[0106] S5. Crosslinking treatment: Crosslink the dried diaphragm in a methanol solution containing 0.12% HCl and 10% glutaraldehyde at 60°C for 10 min.

[0107] S6. Post-treatment: The cross-linked membrane is washed with deionized water and dried under vacuum at 60°C to obtain the finished product.

[0108] Comparative Example 4:

[0109] S1. Pretreatment of polyphenylene sulfide chopped fibers: Cleaning and dispersing of polyphenylene sulfide chopped fibers, immersing the fibers in 1.2×10⁻⁶ water. 2 After washing in a mol / L LAS solution and drying, the cleaned polyphenylene sulfide chopped fibers are then pulped using a pulping machine to ensure uniform dispersion.

[0110] S2. Slurry preparation: Mix 50% of polyphenylene sulfide chopped fibers and 50% of aramid 1313 pulp with a freeness of 45°SR; add 0.5 wt% of oven-dried ethylene oxide and 0.6 wt% of oven-dried anionic polyacrylamide, and disperse in an aqueous solution at 2500 rpm for 10 minutes.

[0111] S3, Wet forming: The sheet forming quantity is 100g / m³ 2 The wet paper web is dried using a paper pattern dryer at a temperature of 105°C for 5 minutes until the moisture content is below 8%.

[0112] S4, functional layer coating: 10% PVA solution and 2% QCS solution were blended at a volume ratio of 20:80, and then were coated on one side of the substrate. After drying at 60°C for 12h, the finished product was obtained.

[0113] S5, post-treatment: the cross-linked membrane was washed with deionized water and vacuum dried at 60°C to obtain the finished product.

[0114] Table 1: comprehensive performance of paper of each example

[0115]

[0116] Test results

[0117] The base paper prepared by blending aramid pulp and PPS short fibers has a high uniformity of pore size distribution. The membrane prepared by using the base paper as the substrate has excellent mechanical properties (tensile strength 8.16-9.14MPa) and high porosity (60.4%-75.4%).

[0118] Compared with examples 1 and 2, the aramid pulp content in the paper-based substrate used in examples 3 and 4 is higher, which leads to an increase in tensile strength but a decrease in porosity, and the ion conductivity of the membrane decreases under the same functional layer. In example 3, the introduction of QCS and glutaraldehyde cross-linking greatly reduces the membrane surface resistance to 68mΩ·cm 2 Compared with example 3, the QCS content in example 4 is low, which results in fewer quaternary ammonium groups as OH- surface hopping carriers in the functional layer, so the ion conductivity is also lower.

[0119] The strength of the base paper in example 3 is still 8.98MPa at a porosity of 60.4%. In the functional layer modification, the introduction of QCS and glutaraldehyde cross-linking greatly reduces the membrane surface resistance to 68mΩ·cm 2 (Example 3), which is 86% lower than that of comparative example 1 (482mΩ·cm 2 ) without QCS. The ion conductivity also jumps to 515mS·cm -1, pushing the electrolysis current density to 1474 mA at 2.0 V polarization voltage, which is 160% higher than that of Comparative Example 1 (567 mA). The long-term alkaline stability test (80℃, 30% KOH, 7 days) further verifies that the cross-linked functional layer stabilizes the vertical swelling rate of the separator at 12%, which is much lower than that of Comparative Example 1 (19.5%) and Comparative Example 4 (about 20%) of the uncross-linked separator. While the addition amount of chitosan quaternary ammonium salt in Comparative Example 2 is insufficient to form a dense and continuous OH-transport network, and the addition amount of chitosan quaternary ammonium salt in Comparative Example 3 is too much that the quaternary ammonium groups will aggregate to form a local high charge density area. Such aggregation hinders the directional hopping conduction of OH- and reduces the ionic conductivity. In summary, the separator of Example 3 achieves an optimal balance in key indicators such as pore size, strength, ionic conductivity, and alkaline stability.

[0120] Although the present application has been disclosed with reference to the preferred embodiments, it is not intended to limit the application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the application. Therefore, the scope of protection of the present application should be defined by the claims.

Claims

1. A method for the preparation of a paper-based separator for alkaline water electrolysis, characterized by, The method comprises the following steps: S1, mixing 50-80% short fibers and 20-50% aramid pulp according to mass percentage, and adding 0.3-0.8% dispersant, and stirring and dispersing to obtain a slurry; S2, the slurry obtained in step S1 is used to make a wet paper web, and the wet paper web is dried to obtain a separator substrate; S3, polyvinyl alcohol solution and chitosan quaternary ammonium salt solution are blended at a volume ratio of 1:0.67-4, and are coated on one side of the substrate by doctor blade, and are dried to obtain a dried separator; S4, the dried separator is crosslinked in a solution containing a crosslinking agent, and is washed and dried after crosslinking to obtain the paper-based separator for alkaline water electrolysis.

2. The method of claim 1, wherein, The short fibers are one of polypropylene, polyethylene, polysulfone, polyether sulfone, polyphenyl sulfone, polyphenylene sulfide, polysulfone and polyether ether ketone.

3. The method of claim 1, wherein, The aramid pulp is aramid 1313 pulp, and the beating degree is 40°SR-80°SR.

4. The method according to claim 1 or 2, characterized in that, The short cut fibers are cleaned with a sodium alkyl benzene sulfonate solution before mixing, and a uniformly dispersed short cut fiber slurry is obtained after beating, wherein the concentration of the sodium alkyl benzene sulfonate solution is 1.0×10 2 ~1.5×10 2 mol / L.

5. The method of claim 1, wherein, In step S1, the dispersant is one or a combination of polyethylene oxide, polyacrylamide, polyvinyl alcohol or hydroxymethyl cellulose.

6. The method of claim 1, wherein, The basis weight of the wet paper web is 40 to 120 g / m 2 .

7. The method of claim 1, wherein, The concentration of the polyvinyl alcohol solution is 8%-12%, and the concentration of the chitosan quaternary ammonium salt solution is 1%-5%.

8. The method of claim 7, wherein, The proportion of the polyvinyl alcohol solution in the total volume of the polyvinyl alcohol solution and the chitosan quaternary ammonium salt solution is 20%-60%.

9. The method of claim 1, wherein, The dried separator is crosslinked in a methanol solution containing 0.12%-2% HCl and 5%-15% glutaraldehyde at 40-80°C for 5-15 min.

10. A paper-based separator for alkaline water electrolysis prepared by the method of any one of claims 1-9.

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