KR20210148910A - Multi-layer composite membrane for water electrolysis and method of preparing the membrane - Google Patents

Abstract

The present invention relates to a separator for water electrolysis, and more specifically, to a multilayer composite separator for water electrolysis including: a polymeric porous support; a garter layer including silica formed on one or both surfaces of the porous support; and a selective layer comprising an ionomer formed on the garter layer, and a method for manufacturing the same. The present invention can provide a separator for water electrolysis having high ionic conductivity, low hydrogen permeability, excellent wettability to a hydrophilic aqueous solution, and thermochemical stability.

Description

Multi-layer composite membrane for water electrolysis and method of preparing the same

The present invention relates to a separation membrane for water electrolysis, and more particularly, to a porous polymer support; a garter layer comprising silica formed on one or both surfaces of the porous support; And it relates to a multilayer composite separator for water electrolysis comprising a selective layer made of an ionomer formed on the garter layer and a manufacturing method thereof, for water electrolysis having high ionic conductivity, low hydrogen permeability, excellent wettability to hydrophilic aqueous solution and thermochemical stability. A separator may be provided.

A water electrolysis system uses electric energy to electrolyze water to produce high-purity hydrogen with oxygen. Polymer electrolyte membrane (PEM) water electrolysis, alkaline water electrolysis (AWE), high temperature It is divided into high temperature steam water electrolysis.

Alkaline water electrolysis uses KOH/NaOH aqueous solution as an electrolyte ^{to move OH -} ions to induce a water electrolysis reaction to produce hydrogen. It is composed of an electrode, an electrolyte, and a separator. 1 is a schematic diagram of the configuration of an alkaline water electrolysis system and reaction schemes at the anode and cathode. As shown in FIG. 1, in the reduction tank, electrons supplied from an external power source and H ₂ O react to generate hydrogen gas and OH ⁻ and this OH ⁻ moves to the oxidation tank through the separation membrane to _{generate H 2} O and oxygen gas. create Alkaline water electrolysis is a technology that has been proven to be practical for large-capacity manufacturing because it is easy to secure relatively fast OER kinetics and electrochemical stability, and it is possible to use a low-cost non-platinum catalyst. However, the selection of the separator has a significant effect on the performance and durability of the system due to the harsh water electrolysis operation conditions such as strong alkaline conditions, electron transfer, radical generation, temperature rise, and pressurization.

Alkaline water electrolysis polymer membranes can be classified into non-ion conductive porous membranes and anion conductive ionomer membranes. A diaphragm such as asbestos has been used as a traditional alkaline water electrolysis membrane, but due to environmental issues, AGFA's Zirfon ^ⓡ membrane, an organic/inorganic composite non-ion conductive porous membrane, has been widely used.

The membrane material located between the cathode reservoir and the anode reservoir must have stable chemical resistance in a strong base (30% KOH) environment, and must be able to quickly move ^{OH - ions to secure high electrochemical performance.} do. In addition, in order to prevent an explosion problem that occurs when the hydrogen concentration in oxygen exceeds 4% in the load operation region, it must have excellent barrier properties against hydrogen dissolved in the KOH solution.

^{Zirfon ⓡ} membrane of AGFA (Velier), which is currently commercially available, is a porous organic-inorganic porous organic-inorganic membrane obtained by coating a slurry in which _{ZrO 2} nanoparticles are dispersed in an NMP solvent together with a polysulfone polymer binder on a porous PPS (Polyphenylene sulfide) polymer matrix support. It is manufactured in the form of a composite membrane.

Zirofon ^ⓡ membrane thickness is 500 ± 50 μm, porosity is 50 ± 20%, pore size is 0.15 ± 0.05 μm, bubble point pressure is 3 ± 1 bar, membrane resistance is 0.3 in 30 °C, 30% KOH solution Ω·cm ² or less.

Zirofon ^ⓡ film alkaline Susan's, but is widely used as a separator, a hydrophobic polymer, PSS material is low, the wettability of the alkaline solution, it is complemented by the massive addition of expensive ZrO ₂ about 30 wt%, and acts as a price rise factors, OH ^{- It} has the disadvantage of not having selectivity for ions. In addition, there is a problem in terms of safety due to the hydrogen crossover problem due to the porous structure.

On the other hand, the anion conductive ionomer membrane has a non-porous structure, so it can secure high barrier properties against hydrogen/oxygen, which is the product, and can increase faradaic efficiency compared to porous membranes. While it has the advantage of being able to use it under conditions, it has been optimized for alkaline water electrolysis so far due to several problems including relatively low ionic conductivity, processability problems due to low solubility, thick film thickness, and weak chemical resistance in alkaline conditions. It is difficult to find commercialized examples.

Republic of Korea Patent Publication No. 10-2019-0135273 Republic of Korea Patent Publication No. 10-159132

The object of the present invention is to have excellent wettability to alkaline solution, high chemical resistance, ^{high selectivity to OH -} ions, low resistance because it can be manufactured in a thin thickness, and a faucet that can be manufactured at a relatively low cost An object of the present invention is to provide a dissolving separation membrane and a method for manufacturing the same.

In order to solve the above problems, the present invention is a polymeric porous support; a garter layer comprising silica formed on one or both surfaces of the porous support; and a selective layer made of an ionomer formed on the garter layer.

In addition, the present invention comprises the steps of: i) coating a mixture of silica and a binder on a porous polymer support and drying the coating to form a garter layer; and ii) coating the ionomer dispersion on the garter layer and drying to form a selective layer.

The multilayer composite separator for water electrolysis according to the present invention has a thin thickness causing excellent wettability and high chemical resistance to alkaline solutions, ^{high selectivity to OH -} ions, and low resistance, and can be manufactured at a relatively low cost. Economical.

In addition, the separation membrane according to the present invention can be applied as a separation membrane for polyelectrolyte (PEM) water electrolysis and water treatment, for example, a separation membrane for nanofiltration and reverse osmosis systems, in addition to the alkaline water electrolysis membrane.

However, the effects of the invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a schematic diagram showing the configuration of a system for alkaline water electrolysis and reaction formulas at the anode and cathode.
2 is a schematic diagram showing the structure and thickness of each layer of a multilayer composite separator for alkaline water electrolysis according to an embodiment of the present invention.
3 is a schematic diagram showing the structure of a multilayer composite separator for alkaline water electrolysis according to another embodiment of the present invention.
^{4 is a graph showing OH-} ion conductivity measurement results of separation membranes according to Examples and Comparative Examples of the present invention.
5 is a graph showing evaluation results of voltage load characteristics according to current density of separators according to Examples and Comparative Examples of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the drawings and examples.

The multilayer composite separator for water electrolysis according to the present invention includes: a polymeric porous support; a garter layer comprising silica formed on one or both surfaces of the porous support; and a selective layer made of an ionomer formed on the garter layer.

FIG. 2 illustrates a multilayer composite separator for water electrolysis according to an embodiment of the present invention, in which an ionomer selective layer is formed on the garter layer having a garter layer formed on one surface of a porous support.

FIG. 3 illustrates a multilayer composite separator for water electrolysis according to another embodiment of the present invention, in which garter layers are formed on both sides of a porous support, and ionomer selection layers are respectively formed on both sides of the garter layer.

In addition, the manufacturing method of the multilayer composite separator according to the present invention is

i) forming a garter layer by coating a mixture of silica and a binder on the polymer porous support and drying; and

ii) coating the ionomer dispersion on the garter layer and drying to form a selective layer.

In addition, the selective layer forming step in the present invention preferably further comprises a high-temperature heat treatment step of 80 to 150 ℃ after the ionomer dispersion coating and drying.

In the present invention, the thickness of the porous support layer is preferably in the range of 25 to 300 µm, the garter layer is 0.5 to 10 µm, and the optional layer is 0.5 to 2 µm. Compared to the thickness of the commercially available Zirfon film, which usually induces a high resistance of about 500 μm, the present invention has the advantage that the entire thickness of the separator can be made thin, so that the resistance can be lowered.

The porous support usable in the present invention may include a polyolefin (polyethylene, polypropylene, etc.) or polytetrafluoroethylene-based polymer having high chemical resistance, and preferably has a porosity of 50% or more. In the present invention, the porous support serves to increase mechanical strength and water permeability.

The present invention is characterized in that a garter layer is formed on one or both surfaces of the porous support. In general, when forming a multilayer film, the lowermost layer consists of a layer having the largest pores. If a coating film is formed directly on it, the coating solution permeates into the pores and some sections are formed in which the pores are blocked, and thus the ion permeability is lowered. In addition, in the case of alkaline water electrolysis, there is a problem in that the water permeability is also reduced because ions are combined with water to pass through. In the present invention, in order to solve this problem, a garter layer was introduced on a porous support as a base layer, and an ionomer coating layer was formed thereon. The garter layer is a layer having pores smaller than the pores of the underlying porous support, and it is possible to minimize penetration of the coating layer.

Therefore, in the present invention, the pores of the garter layer are characterized in that the size is smaller than that of the porous polymer support, the pores of the porous polymer support have an average diameter in the range of 30 nm to 0.8 μm, and the pores of the garter layer have an average diameter of 1 nm to 0.1 μm.

In the present invention, a garter layer is formed using silica, and various shapes such as a spherical shape and a polygonal shape of the silica can be used. It is important to control the pore size of the garter layer. Since silica melts and forms pores in an alkaline environment, the pore size can be controlled to a nano size according to the size of the silica used. On the other hand, in an environment in which silica does not dissolve, water permeability can be improved by using silica having a hydrophilic functional group to increase hygroscopicity in water. Examples of the hydrophilic silica include, but are not limited to, those in which a hydrophilic functional group such as a hydroxyl group, an amine group, a carboxyl group, and a sulfonic acid group is bonded to the end of the silica.

In addition, since the porous support, which is a hydrophobic material, has very low wettability with an electrolyte, using silica to which a hydrophilic functional group is bound to introduce a garter layer in this way improves hydrophilicity and wettability of the electrolyte, and it is useful because it can reduce manufacturing cost.

In addition, in forming the garter layer, glycerin, glycerol, polyethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, etc. having a polyol-based structure may be used as a binder material, and the content of silica is the binder. It is preferable that it is 0.01 to 10% by weight based on the material.

In addition, an ionomer selective layer having conductivity with respect to a specific ion is formed on the garter layer, and it is useful in that a desired functional group is introduced into the selective layer to control the properties of the separator and secure the interface properties. The ionomer used in the present invention may be a perfluorine-based, partially-fluorinated, or hydrocarbon-based ionomer. However, it is preferable to use a perfluorinated ionomer with a more hydrophilic-hydrophobic fine-phase separation structure through rapid ion transport structure formation. It is preferable in that conductivity can be ensured.

For alkaline water electrolysis, an ionomer having an anion conductive functional group may be used, for example, an ammonium group, a phosphonium group, an imidazolium group, a pyridium group, a guanidinium group, or a sulfonium group. it is not Since alkaline water electrolysis moves OH ^- ions to cause water electrolysis, it is advantageous to improve the performance of water electrolysis by using an anion conductive ionomer ^{to improve the movement speed of OH-ions.}

On the other hand, when the multilayer composite separator according to the present invention is applied to PEM water electrolysis, etc., a selective layer can be formed using a cation conductive ionomer. In this case, examples of the cation conductive functional group include, but are not limited to, a hydroxyl group, a sulfonic acid group, a phosphoric acid group, a carboxyl group, and the like.

In the present invention, the selective layer is formed on the garter layer using the ionomer dispersion. Although it is possible to form a selective layer using a general ionomer dispersion, the anion conductive ionomer is not well dispersed under normal temperature / atmospheric pressure conditions. It is more preferable because it is easy to manufacture a film|membrane. In this case, when water and alcohol are used as co-solvents and the ionomer is nano-dispersed using supercritical conditions, the dispersion characteristics of the ionomer can be controlled. The temperature of the supercritical conditions applied to the ionomer nanodispersion of the present invention is in the range of 80 to 300 ° C., and the pressure is preferably in the range of 0.1 to 20 MPa. can If the selective layer is prepared using the ionomer nanodispersion with such a controlled dispersion property, the thickness of the selective layer can be easily controlled, and the arrangement of the anion conductive functional groups is advantageously formed for ion transport behavior through the control of the dispersion property, resulting in electrochemical properties This excellent multilayer composite separator can be obtained.

Polymeric porous support according to the present invention; a garter layer comprising silica formed on one or both surfaces of the porous support; And the multilayer composite separator for water electrolysis comprising a selective layer made of an ionomer formed on the garter layer has ^{a thin thickness that induces excellent wettability and high chemical resistance to alkaline solution, high selectivity to OH -} ions, and low resistance, It is economical because the separation membrane can be manufactured at a relatively low cost.

In addition, the separation membrane according to the present invention can be applied to various fields such as polyelectrolyte water electrolysis in addition to the alkaline water electrolysis membrane.

The present invention will be described in more detail by way of examples below. However, the following examples are provided by way of illustration to help the understanding of the present invention, and the scope of the present invention should not be construed as being limited thereto.

<Example 1>

1-1. Preparation of anion conductive ionomers

The anion conductive ionomer is prepared in two steps (step 1: amination reaction (-F → -O-NH-C ₆ H ₅ ), step 2: _{using a perfluorinated polymer intermediate (PSF) having a -SO 2 F end group):} It was prepared through chemical modification of alkali treatment (-NH → -NH ₂ ^{+ )).} In the first-step amination reaction, ^{2-diethylaminoethanol was added in a nitrogen atmosphere at 100 o} C in a weight ratio of PSF:2-diethylaminoethanol = 5:1, and then a solution containing 0.5 M NaOH aqueous solution was prepared and 200 The PSF was reacted for 7 hours while stirring at a speed of rpm, washed with ultrapure water for 3 hours, dried in a ^{convection oven at 60 o} C for 4 hours, and then prepared by drying in a convection oven at 50 ^o C in the next two steps of alkalinization reaction at 50 o C The M-concentration LiOH solution was stirred at a speed of 200 rpm, and the amination-treated PSF was reacted for 4 hours, washed with ultrapure water for 6 hours, and then dried in a 60 ^o C convection oven for 4 hours. According to this reforming process, a perfluorinated ionomer having an ammonium group as an anion conductive functional group was prepared.

1-2. Preparation of anionically conductive ionomer nanodispersion

The anion conductive ionomer synthesized in Example 1-1 was used as an ionomer for the preparation of the nano-dispersion prior to the preparation of the multilayer composite separator. A water-alcohol mixed solvent was used as a dispersion solvent, and normal propanol (NPA, purity: 95.0 to 98.0 %) used as an alcohol solvent was purchased from Aldrich Chemical Co. in the United States and used without further purification.

The anion-conducting ionomer (weight, 22.5 g) was added to a glass liner containing 123.7 g of NPA and 101.2 g of ultrapure water (weight ratio 55:45). A high pressure/high temperature reactor (4560 Mini-Bench Reactor System, PARR, USA) was equipped with a glass liner, and the reaction mixture in the reactor was heated to 290 °C ^{at a heating rate of 4.25 °C min -1 , and the pressure reached 6.5 MPa.} when the reaction was maintained for 1 hour. After cooling slowly under atmospheric pressure (101.3 kPa), a nanodispersion was obtained. Finally, the nano-dispersion was filtered using filter paper having an average pore size of 5 to 10 μm.

1-3. Manufacture of multi-layer reinforced composite separator

In this example, polytetrafluoroethylene (thickness: 30 μm, porosity: 70%) was used as a porous support, and hydrophilic silica AEROSIL ^® 380 (Evonik Industries AG., Germany) was used to form a garter layer on the support. 5% by weight of polyethylene glycol (0.6 kDa, Aldrich Chemical Co., USA) used as a binder was mixed and coated, and then ^{dried in a convection oven at 50 o} C for 1 hour. Then, to form a selective layer, the anion conductive nanodispersion prepared through the nanodispersion preparation step was coated on the garter layer ^{, dried in a convection oven at 60 o} C for 1 hour, and then ^{heat treated at 150 o} C for 1 hour, resulting in porosity A multilayer composite separator including a garter layer and a selective layer on both sides of the support was prepared.

<Example 2>

A multilayer composite separator was prepared in the same manner as in Example 1, except that a selective layer was formed using a nano-dispersion of an anion conductive ionomer modified with a phosphonium group.

<Example 3>

A multilayer composite separator was prepared in the same manner as in Example 1, except that a selective layer was formed using a nano-dispersion solution of an ionomer having an imidazolium group.

<Example 4>

To form a garter layer on a support, AEROSIL ^® 380 (Evonik Industries AG., Germany), a hydrophilic silica, was mixed at 5 wt% compared to polyethylene glycol (0.6 kDa, Aldrich Chemical Co., USA) used as a binder and coated on only one side After that, it ^{was dried at 50 o} C for 1 hour in a convection oven. Then, to form a selective layer, the anion conductive nano-dispersion prepared through the nano-dispersion preparation step in the same manner as in Example 1 was coated on the garter layer formed on only one side ^{, and then dried in a convection oven at 60 o} C for 1 hour, then 150 ^{o A} multilayer composite separator was prepared in the same manner as in Example 1, except that a garter layer/selective layer was formed only on one side of the porous support after heat treatment at o C for 1 hour.

<Comparative Example 1>

^{A commercially available Neosepta ®} AHA separator (Astom, Japan), which is an anion conductive ionomer separator, was prepared.

<Comparative Example 2>

^{A commercially available Zirfon ®} PERL separator (Agfa, Belgium), which is a non-ion conductive porous separator, was prepared.

<Experimental Example 1> Ion conductivity evaluation

^{For the separator of Comparative Example 1 (AHA) and Example 1 according to the present invention, OH-} ion conductivity according to temperature under water condition was measured to compare the ionic conductivity of the material itself excluding the effect of electrolyte. As a result, as the temperature increased, the ionic conductivity was improved due to the improvement of ion mobility, and the separator of Example 1 according to the present invention exhibited better ionic conductivity than the separator of Comparative Example 1. This is judged to be a complex effect due to the thin thickness (~50 μm) that induces low resistance along with the improvement of wettability through introduction of hydrophilic silica. It can contribute to performance improvement by accelerating the ion transfer rate by reducing the resistance due to the thin thickness. In addition, since it is possible to manufacture a separator with a thin thickness, it is possible to secure economic feasibility through cost reduction when manufacturing a separator. The separators of Examples 1 to 3 according to the present invention ^{exhibited superior OH-} ion conductivity than the separator of Comparative Example 1, and although there was a slight difference depending on the functional group, Example 1 having an ammonium group as an anion conductive functional group was the best.

<Experimental Example 2> Hydrogen gas permeability evaluation

In order to check the hydrogen gas permeability of the material itself, as ^{a result of evaluating the hydrogen gas permeability in the dry state at 80 o} C temperature condition through the time-lag method, in the case of Comparative Example 2 (Zirfon), a non-ion conductive porous separator, porous characteristics For this reason, hydrogen gas permeated as it was and measurement was impossible, and in the case of Comparative Example 1 (AHA), the mechanical properties were very weakened after drying, making it impossible to measure the hydrogen gas permeability. In the case of Example 1 in the present invention, it was confirmed that the low hydrogen gas permeability was 7.74 Barrer even with a relatively thin thickness, which is the hydrogen gas permeability level of the Nafion 212 (DuPont, USA) membrane used as a commercial cation exchange membrane of the same thickness. was similar to This characteristic can contribute to the improvement of stability due to low hydrogen gas permeability when applied to a water electrolysis device in the future, and is expected to help extend the physical lifespan characteristics due to the effect of strengthening the mechanical properties of the support.

Comparative Example 1 Comparative Example 2 Example 1 thickness [㎛] 198 500 50 Hydrogen gas permeability@
80 ^o C [Barrer] not measurable
(weakened mechanical properties) not measurable
(porous) 7.74 ± 0.04

<Experimental Example 3> Voltage load characteristic evaluation

For the separators according to Comparative Example 1 (Zirfon) and Comparative Example 2 (AHA), the voltage load according to the current density under the conditions of ^{80 o C and 5 M KOH was measured using a Ni-based alloy electrode.} In the case of the multilayer composite separators of Examples 1 and 4, the voltage load according to the current density was measured in the same manner except for a lower concentration (3 M KOH). As a result, compared to Comparative Examples 1 and 2, Examples 1 and 4 according to the present invention exhibited the lowest voltage load at the same current density even though they were driven under a KOH condition of a lower concentration. This means it can be operated even with lower power. These results are judged to be performance improvements due to the complex effects of improving wettability to alkaline solutions through the introduction of hydrophilic silica in the garter layer, introducing anion conductive ionomers in the selective layer, and reducing resistance by reducing the thickness of the resulting separator. do. On the other hand, Example 1, in which the garter layer/selective layer was formed in a single side, showed a lower voltage load at the same current density than Example 4 in which the garter layer/selection layer was formed as a single side. This is judged to be the effect of introducing an additional anion conductive ionomer into the selective layer, as the garter layer and the selective layer are formed on both sides, and the wettability to the alkaline solution is improved compared to the single side.

Claims (23)

Polymeric porous support;
a garter layer comprising silica formed on one or both surfaces of the porous support; and
A multilayer composite separator for water electrolysis comprising a selective layer made of an ionomer formed on the garter layer. According to claim 1,
The multilayer composite separator for water electrolysis, characterized in that the pores of the garter layer are smaller in size than the pores of the porous polymer support. 3. The method of claim 2,
The multilayer composite separator for water electrolysis, characterized in that the pores of the polymeric porous support have an average diameter in the range of 30 nm to 0.8 μm. 3. The method of claim 2,
The pores of the garter layer have an average diameter in the range of 1 nm to 0.1 μm. According to claim 1,
The porous polymer support is a multilayer composite separator for water electrolysis, characterized in that it is selected from polyolefin-based or polytetrafluoroethylene-based polymers. According to claim 1,
The silica is a multilayer composite separator for water electrolysis, characterized in that it is a hydrophilic silica in which a functional group selected from a hydroxyl group, an amine group, a carboxyl group, and a sulfonic acid group is bonded to the terminal. According to claim 1,
The ionomer of the selective layer is a multilayer composite separator for water electrolysis, characterized in that it is selected from perfluorine-based, partially-fluorinated, or hydrocarbon-based ionomers. According to claim 1,
The ionomer is an ionomer into which an anion conductive functional group or a cation conductive functional group is introduced. 9. The method of claim 8,
The anion-conducting functional group is an ammonium group, a phosphonium group, an imidazolium group, a pyridium group, a guanidinium group, or a sulfonium group. 9. The method of claim 8,
The cation conductive functional group is a multilayer composite separator for water electrolysis, characterized in that it is selected from a hydroxyl group, a sulfonic acid group, a phosphoric acid group, and a carboxyl group. According to claim 1,
The multilayer composite separator for water electrolysis, characterized in that the thickness of the porous support layer is in the range of 25 to 300 ㎛. According to claim 1,
The thickness of the garter layer is a multilayer composite separator for water electrolysis, characterized in that in the range of 0.5 to 10 ㎛. According to claim 1,
The thickness of the selective layer is a multilayer composite separator for water electrolysis, characterized in that in the range of 0.5 to 2 ㎛. i) forming a garter layer by coating a mixture of silica and a binder on the polymer porous support and drying; and
ii) coating and drying the ionomer dispersion on the garter layer to form a selective layer. 15. The method of claim 14,
The selective layer forming step is a method of manufacturing a multilayer composite separator, characterized in that it further comprises a high temperature heat treatment step of 80 to 150 ℃ after drying. 15. The method of claim 14,
The method for producing a multilayer composite separator, characterized in that the polymeric porous support is selected from polyolefin or polytetrafluoroethylene-based polymer. 15. The method of claim 14,
The method of manufacturing a multilayer composite separator, characterized in that the silica is a hydrophilic silica in which a functional group selected from a hydroxyl group, an amine group, a carboxyl group, and a sulfonic acid group is bonded to the terminal. 15. The method of claim 14,
The binder is a method of manufacturing a multilayer composite separator, characterized in that at least one selected from the group consisting of glycerin, glycerol, polyethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and the like. 15. The method of claim 14,
The content of the silica is a method of manufacturing a multilayer composite separator, characterized in that 0.01 to 10% by weight relative to the binder. 15. The method of claim 14,
The ionomer is a method of manufacturing a multilayer composite separator for water electrolysis, characterized in that the ionomer is an anion conductive functional group or a cation conductive functional group is introduced. 21. The method of claim 20,
Wherein the anion conductive functional group is selected from an ammonium group, a phosphonium group, an imidazolium group, a pyridium group, a guanidinium group, or a sulfonium group. 21. The method of claim 20,
The cation conductive functional group is a method of manufacturing a multilayer composite separator for water electrolysis, characterized in that selected from a hydroxyl group, a sulfonic acid group, a phosphoric acid group, and a carboxyl group. 15. The method of claim 14,
The ionomer dispersion is a method for manufacturing a multilayer composite separator, characterized in that the ionomer is nano-dispersed in a mixed solution of water and alcohol under supercritical conditions.

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