KR102643968B1 - Membrane-electrode assembly prepared from cation exchange membnrane for producing hydrogen water and method for preparing membrane-electrode assembly - Google Patents

Abstract

The present invention relates to a method of manufacturing a membrane-electrode assembly for efficient hydrogen water production and to the membrane-electrode assembly. Impregnating a porous polymer film with a mixed solution of a monomer, a cross-linking agent and an initiator to fill the pores, subjecting the mixed solution filled in the pores of the porous polymer film to a cross-linking polymerization reaction, and placing the cross-polymerized polymer film in a cation exchanger. Preparing a pore-filling cation exchange membrane by introducing a cation exchanger into a polymer film by impregnating it with a solution having a cation exchange membrane, impregnating the pore-filling cation exchange membrane in a solution containing platinum ions to ion-exchange the platinum ion-exchanged pore-filling cation exchanger. Provided is a method for manufacturing a membrane-electrode assembly comprising the step of impregnating a membrane in an aqueous alkaline solution to reduce platinum ions to form an electrode layer, comprising a porous polymer film having a thickness of 25 ㎛ or less and applying an electrode metal to the surface of the porous polymer film. It provides a membrane-electrode assembly for generating hydrogen water, including an electrode layer, wherein the pores of the porous polymer film are filled with a cation exchange resin and the electrode metal is present.

Description

Membrane-electrode assembly and method of manufacturing a membrane-electrode assembly based on a pore-filling cation exchange membrane for efficient hydrogen water generation

The present invention relates to a method of manufacturing a membrane-electrode assembly for efficient hydrogen water production and to the membrane-electrode assembly.

An ion exchange membrane refers to a synthetic resin membrane that selects cations and anions and allows only one ion to pass through. There are cation exchange membranes and anion exchange membranes.

The cation exchange membrane has a negative charge, so it repels negative ions and allows only positive ions to pass through. On the other hand, the anion exchange membrane has a positive charge and has the property of allowing only negative ions to pass through. Representative ion exchange membranes include cation exchange membranes with sulfone groups and anion exchange membranes with quaternary ammonium groups.

These ion exchange membranes are widely used in fields such as fuel cells, diffusion dialysis, redox flow batteries, water treatment, and seawater desalination. They must have high selectivity, so they have low permeability of solvents and non-ionic solutes, and diffusion of selected permeable ions. It requires low resistance to heat, high mechanical strength and chemical resistance.

As a technology for ion exchange membranes, Korean Patent Publication No. 2012-0074365 discloses that a solution containing a polymer with ion exchange ability is prepared, a cross-linking agent is added to the solution to form a film, and then an ion exchange membrane is manufactured through cross-linking. A method for manufacturing an ion exchange membrane consisting of heat treatment steps is disclosed. However, the technology disclosed in the above patent document requires the use of a reinforcing material due to limitations in the mechanical properties of the ion exchange resin.

Meanwhile, an anion exchange membrane is generally created by casting a monomer paste onto a non-woven fabric made of PVC or PE, creating a base membrane through thermal or light polymerization, and then performing quaternary ammonation or sulfonation. Alternatively, a cation exchange membrane is manufactured. However, in this case, in order to obtain mechanical properties above a certain level, the thickness of the ion exchange membrane becomes thicker than 150㎛, and the manufacturing cost increases because a continuous manufacturing process is impossible.

Therefore, research has been conducted on a method of manufacturing an ion exchange membrane that can exhibit sufficient mechanical properties for ion exchange while reducing the thickness of the ion exchange membrane. In this regard, Korean Patent Publication No. 2012-0059585 describes a porous substrate. A method of manufacturing a thin-thick ion exchange membrane by using it as a base membrane is disclosed.

Meanwhile, research on hydrogen water has been actively conducted since the late 1990s, especially in Japan, and commercialization began in earnest in 1997 when related research results were covered in the American biology journal 'BBRC'. Currently, hydrogen water is known to account for more than 10% of the total drinking water market in Japan.

Hydrogen water is known to increase immunity by removing oxygen radicals and is effective in preventing aging and adult diseases. For example, according to a study by Okayama University, when changes in periodontal tissue of rats were observed in an experiment using hydrogen water, it was confirmed that drinking hydrogen water had a significant antioxidant effect [T. Tomofuji et al., Scientific Report, 4, Article number: 5534 (2014)].

Hydrogen water production methods can be broadly divided into four types: hydrogen gas injection type, stick type, reagent addition type, and electrolysis type.

Among these, the polymer electrolyte membrane water electrolysis method, which corresponds to the electrolysis method, is a method of electrolyzing water using a membrane-electrode assembly (MEA) in which an electrode catalyst is bonded to both sides of a polymer electrolyte, even at high current densities. It has the advantage of being able to perform electrolysis with high efficiency, producing high purity hydrogen from pure water, and also having high electrolysis efficiency.

The most important part of the hydrogen water production method using MEA is the performance of the MEA. Therefore, it is generally required to have excellent chemical stability and high hydrogen ion conductivity, and for this reason, Nafion is commonly used to manufacture MEA.

However, Nafion is very expensive, which has the problem of greatly increasing the manufacturing cost of MEA. Therefore, in order to produce hydrogen water efficiently and economically, there is a need to develop a hydrogen ion exchange membrane with excellent chemical stability, high hydrogen ion conductivity, and low manufacturing cost, and a high-efficiency MEA based on it.

The present invention seeks to provide a method for manufacturing a membrane-electrode assembly for efficient and economical hydrogen water production and an electrochemical hydrogen water production device using the same.

The present invention relates to a method for manufacturing a membrane-electrode assembly, which includes filling pores by impregnating a porous polymer film with a mixed solution of a monomer, a cross-linker, and an initiator, and cross-polymerizing the mixed solution filled in the pores of the porous polymer film. reacting, impregnating the cross-polymerized polymer film with a solution containing a cation exchanger to introduce a cation exchanger into the polymer film to produce a pore-filling cation exchange membrane, impregnating the pore-filling cation exchange membrane with a solution containing platinum ions to produce ions It includes a step of exchanging and impregnating the platinum ion exchanged pore-filling cation exchange membrane with an aqueous alkaline solution to reduce platinum ions to form a catalyst layer.

The cation exchange group includes a sulfonic acid group (-SO ₃ H), a carboxyl group (-COOH), a phosphonic group (-PO ₃ H ₂ ), a phosphinic group (-HPO ₂ H), and an asonic group (-AsO ₃ H ₂ ). and a selinonic group (-SeO ₃ H).

The monomers include styrene, N-Phenylacrylamide, N-(Triphenylmethyl)methacrylamide, Ethylene glycol phenyl ether acrylate, 2 -Hydroxy-3-phenoxypropyl acrylate, 2-sulfoethyl methacrylate and 3-sulfopropyl methacrylate It may be at least one selected from the group consisting of.

The crosslinking agent is divinylbenzene, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, hydroxypivalic acid neo. Pentyl glycol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, tricyclodecane dimethanol diacrylate, trimethylolpropane triacrylate, glycerin triacrylate, trimethyl It may be at least one selected from the group consisting of all-propane triacrylate and tris(2-hydroxyethyl)isocyanurate triacrylate.

It is preferable to use two or more crosslinking agents having different molecular weights.

The crosslinking agent is a mixture of divinylbenzene, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, and 1,6-hexanediol dimethacrylate, and contains 60 to 90% divinylbenzene based on 100% by weight of the crosslinking agent. Weight percent, may include in the range of 3 to 15% by weight of ethylene glycol dimethacrylate, 3 to 15% by weight of 1,3-butanediol dimethacrylate, and 3 to 15% by weight of 1,6-hexanediol dimethacrylate. You can.

The crosslinking polymerization reaction may be performed by photo-crosslinking or thermal crosslinking.

The initiator may be at least one photoinitiator selected from the group consisting of benzophenone, benzyldimethylketal, 1,2-diphenyl ethanedione, hydroxyldimethylacetopone, and α-hydroxycyclohexylphenylmethanone.

The initiator may be at least one thermal initiator selected from the group consisting of benzoyl peroxide, benzoyl peroxide, azobisisobutyronitrile, azomethane, and azoisopropane.

The crosslinking agent is preferably contained in an amount of 10 to 30% by weight based on a total of 100% by weight of the monomer and crosslinking agent.

The initiator is preferably included in an amount of 1 to 5 parts by weight based on 100 parts by weight of monomer.

The step of ion-exchanging with metal ions for forming the electrode layer includes impregnating the pore-filling cation exchange membrane in an aqueous sulfuric acid solution for 1 to 15 hours and then washing it with water, dissolving the metal ion-containing precursor for forming the electrode layer in methanol or a mixed solvent of ethanol and water. This can be performed by a process including preparing a solution containing platinum ions and impregnating the cleaned pore-filling cation exchange membrane with a precursor solution containing metal ions for forming an electrode layer.

The sulfuric acid aqueous solution may have a concentration of 0.5 to 2M.

The mixed solvent of methanol or ethanol and water preferably has a volume ratio of methanol or ethanol and water of 1:2 to 1:5.

The precursor solution containing the metal ion for forming the electrode layer preferably has a concentration of 0.1 to 0.7mM of the metal ion for forming the electrode layer.

The step of ion exchange with metal ions for forming the electrode layer is preferably performed for 20 minutes to 1 hour.

The reduction is performed by impregnating the pore-filling cation exchange membrane, which has been ion-exchanged with metal ions for forming the electrode layer, in a reducing solution in which at least one selected from the group consisting of NaBH ₄ and LiAlH ₄ is dissolved in an aqueous alkaline solution of pH 11 to 14. desirable.

Impregnation in the reducing solution is preferably performed for 30 minutes to 5 hours.

The reducing solution may be one in which NaBH ₄ is dissolved in an aqueous alkaline solution at a concentration of 0.6 to 0.9 M.

The metal ion for forming the electrode layer may be platinum, ruthenium, or a mixed metal ion thereof.

The alkaline aqueous solution preferably has a temperature of 25 to 60°C.

The porous polymer film may have a thickness of 25 ㎛ or less (excluding 0 ㎛).

The porous polymer film is from the group consisting of LLDPE (Linear Low Density Polyethylene), LDPE (Low Density Polyethylene), PE (Polyethylene)-based copolymer, PP (Polypropylene), EVA (Ethylene Vinyl Alcohol), and EOR (Ethylene Octene Rubber). You can use whatever you choose.

It may further include washing the porous polymer film in a solvent for 30 minutes to 5 hours and then drying it.

The solvent may be selected from the group consisting of acetone, dimethylacetamide (DMAc), dimethylformamide (DMF), acetonitrile, methanol, and ethanol.

It may further include impregnating the membrane-electrode assembly obtained in the step of reducing the platinum ions with an aqueous sulfuric acid solution for 30 minutes to 5 hours and then washing it with water.

The present invention provides a membrane-electrode assembly, wherein the pores of a porous polymer film having a thickness of 25㎛ or less are filled with a cation exchange resin, platinum is present in the cation exchange resin, and the porous A catalyst layer made of platinum is included on the surface of the polymer film.

The cation exchange resin may be produced by polymerization of a monomer, a crosslinking agent, and a photoinitiator or thermal initiator.

The porous polymer film is from the group consisting of LLDPE (Linear Low Density Polyethylene), LDPE (Low Density Polyethylene), PE (Polyethylene)-based copolymer, PP (Polypropylene), EVA (Ethylene Vinyl Alcohol), and EOR (Ethylene Octene Rubber). It may be chosen.

The monomers include styrene, N-phenylacrylamide, N-(Triphenylmethyl)methacrylamide, ethylene glycol phenyl ether acrylate, and 2-hydroxy. -From the group consisting of 2-Hydroxy-3-phenoxypropyl acrylate, 2-sulfoethyl methacrylate and 3-sulfopropyl methacrylate There may be at least one selected.

The crosslinking agent is divinylbenzene, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, hydroxypivalic acid neo. Pentyl glycol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, tricyclodecane dimethanol diacrylate, trimethylolpropane triacrylate, glycerin triacrylate, trimethyl It may include two or more compounds having different molecular weights selected from the group consisting of all-propane triacrylate and tris(2-hydroxyethyl)isocyanurate triacrylate.

The crosslinking agent may include divinylbenzene, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, and 1,6-hexanediol dimethacrylate.

The photoinitiator may be at least one selected from the group consisting of benzophenone, benzyldimethylketal, 1,2-diphenyl ethanedione, hydroxyldimethylacetopone, and α-hydroxycyclohexylphenylmethanone.

The thermal initiator may be at least one selected from the group consisting of benzoyl peroxide, benzoyl peroxide, azobisisobutyronitrile, azomethane, and azoisopropane.

The membrane-electrode assembly of the present invention is manufactured based on a pore-filling cation exchange membrane that is thin and has excellent electrical performance and strong physical strength, so the manufacturing cost is very low and at the same level as that of the conventional Nafion-based membrane-electrode assembly. performance can be obtained.

The membrane-electrode assembly of the present invention can be manufactured by using a porous polymer film with a thickness of 25㎛ or less as a substrate and filling the pores with a cation exchange resin, allowing continuous production by roll-to-roll method. It is possible to improve productivity.

In addition, the porous polymer film used as a substrate has excellent mechanical strength, so by reducing the thickness, the electrical resistance can be significantly lowered, while sufficient mechanical properties can be secured.

Furthermore, cross-linking density can be increased by mixing two or more cross-linking agents with different molecular weights, thereby greatly improving chemical and physical stability.

Additionally, the durability of the hydrocarbon-based cation exchange membrane can be improved by spraying and coating the Nafion solution on the surface.

Figure 1 is a graph showing the results of measuring the change in hydrogen concentration under constant current conditions.
Figure 2 is a graph showing the voltage change during hydrogen water production under constant current conditions.

The present invention seeks to provide a method for manufacturing a membrane-electrode assembly using a pore-filling cation exchange membrane and a membrane-electrode assembly produced thereby.

The membrane-electrode assembly provided by the present invention can be manufactured by manufacturing a pore-filling cation exchange membrane and introducing a catalyst into its surface and pores. Hereinafter, the present invention will be described in more detail.

First, the manufacturing method of the pore-filling cation exchange membrane of the present invention will be described.

The pore-filling cation exchange membrane of the present invention uses a porous polymer film as a substrate. By using a porous polymer film as a substrate, a pore-filling cation exchange membrane can be manufactured by a roll-to-roll method, which is preferable because it can improve productivity.

The porous polymer film is not particularly limited, and any film that is used to manufacture an ion exchange membrane can be suitably used in the present invention.

The porous polymer film includes, for example, LLDPE (Linear Low Density Polyethylene), LDPE (Low Density Polyethylene), PE (Polyethylene)-based copolymer, PP (Polypropylene), EVA (Ethylene Vinyl Alcohol), and EOR (Ethylene Octene Rubber). ) can be mentioned.

The porous polymer film is not necessarily limited to this, but may have a thickness of 25㎛ or less. Even if a thin film is used in this way, the porous polymer film used as a substrate can provide sufficient mechanical properties and function effectively as a membrane-electrode assembly of the present invention. In addition, because the thickness is thin, the amount of material used in manufacturing the membrane-electrode assembly can be reduced, which is also desirable for reducing manufacturing costs.

If the thickness of the porous polymer film exceeds 25㎛, a problem may occur in which the electrical resistance of the membrane increases.

The thickness of the porous polymer film is not particularly limited as long as it is a thin film of 25 ㎛ or less, but preferably has a thickness of 5 ㎛ or more, for example, 7 ㎛ or more, 8 ㎛ or more, or 10 ㎛ or more.

The porous polymer film can be used after being washed with a solvent. The washing can be performed for 30 minutes to 5 hours. The washing is to remove impurities on the surface of the porous polymer film, and it is desirable to remove impurities that affect pore penetration of monomers. The solvent that can be used for such cleaning is not particularly limited, and polar solvents can be used, such as acetone, dimethylacetamide (DMAc), dimethylformamide (DMF), acetonitrile, and methanol ( methanol), ethanol, etc. Among these, acetone is most suitable considering its volatility and polarity.

The washing time is not particularly limited as long as it is 30 minutes or more, but is preferably performed for 5 hours or less from the viewpoint of process economy. More preferably, it may be 30 minutes to 3 hours. After the washing, the porous polymer film is dried.

In the present invention, a cation exchange resin is filled in the pores of the porous polymer film. In order to fill the cation exchange resin, the method includes the step of supporting the porous polymer film in a raw material solution for polymerization of the cation exchange resin and filling the raw material solution into the pores.

The raw material solution is a mixed solution containing a monomer, a cross-linking agent, and an initiator. The mixed solution is impregnated with the porous polymer film to fill the pore material raw material solution, and then subjected to a cross-linking polymerization reaction to fill the pores with a cation exchange resin.

The monomer is the main material for forming a cation exchange resin by polymerization, and includes styrene, N-phenylacrylamide, N-(triphenylmethyl)methacrylamide, and ethylene glycol phenyl. Ethylene glycol phenyl ether acrylate, 2-Hydroxy-3-phenoxypropyl acrylate, 2-sulfoethyl methacrylate and 3- Examples include sulfopropyl methacrylate (3-sulfopropyl methacrylate), which can be used alone or in combination of two or more.

The crosslinking agent is divinylbenzene, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,6-hexanediol diacrylate, hydroxypivalic acid neo. Pentyl glycol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, tricyclodecane dimethanol diacrylate, trimethylolpropane triacrylate, glycerin triacrylate, trimethyl Allpropane triacrylate and tris(2-hydroxyethyl)isocyanurate triacrylate can be used.

At this time, it is preferable to use a mixture of two or more crosslinking agents to improve the chemical and physical durability of the membrane-electrode assembly. More preferably, the use of two or more crosslinking agents with different molecular weights provides the effect of reducing ion transfer resistance by appropriately controlling the distance and free volume between polymer chains.

For example, as a crosslinking agent, divinylbenzene (weight average molecular weight 130.19), ethylene glycol dimethacrylate (weight average molecular weight 198.22), 1,3-butanediol dimethacrylate (weight average molecular weight 226.27), 1,6- When a mixture of four types of hexanediol dimethacrylate (weight average molecular weight 254.32) is used, the crosslinked structure is as follows.

In this way, by using a mixture of two or more crosslinking agents with different molecular weights, the crosslinking density of the polymer can be formed more densely. In other words, it increases the crosslinking density by effectively crosslinking both long and short polymer chains at the same time, and also has the effect of widening the spacing between polymer chains, thereby improving ionic conductivity.

As an example, in the case of using the four types of crosslinking agents as described above, but not limited to this, 60 to 90% by weight of divinylbenzene and 3 to 15% by weight of ethylene glycol dimethacrylate based on 100% by weight of the total crosslinking agent. , can be used by mixing 1,3-butanediol dimethacrylate in an amount of 3 to 15% by weight and 1,6-hexanediol dimethacrylate in an amount of 3 to 15% by weight.

The crosslinking agent may be included in an amount of 10 to 30% by weight based on 100% of the total weight of the monomer and crosslinking agent. If it is contained in less than 10% by weight, there is a problem that physical and chemical durability is reduced, and if it is contained in more than 30% by weight, there is a problem such as a decrease in ionic conductivity.

The crosslinking polymerization reaction between the monomer and the crosslinking agent can be performed by photoinitiation or thermal initiation. For this purpose, a reaction initiator is included, and the reaction initiator may be a photoinitiator or a thermal initiator.

The photoinitiators include benzophenone, benzyldimethylketal, 1,2-diphenyl ethanedione, hydroxydimethylacetopone, and α-hydroxycyclohexylphenylmethanone, which can be used alone or in a mixture of two or more types. You can also use it.

Meanwhile, the thermal initiator includes benzoyl peroxide, benzoyl peroxide, azobisisobutyronitrile, azomethane, and azoisopropane, and these may be used alone or in combination of two or more.

The reaction initiator can be used in an amount of 1 to 5% by weight based on 100 parts by weight of monomer. If it is less than 1% by weight, there is a problem that the polymerization reaction does not sufficiently occur, and if it is more than 5% by weight, there are problems such as reduced initiation efficiency and residual unreacted initiator.

As described above, a pore-filling cation exchange membrane can be manufactured by impregnating and filling a porous polymer film with the mixed solution and then subjecting it to a cross-linking polymerization reaction. Specifically, but not limited to this, after filling the porous polymer film with a monomer, the porous polymer film is sandwiched between two release films and brought into close contact through rolling, and after removing the excess monomer, the porous polymer film is formed using two sheets of glass. After clamping, light or heat polymerization can be performed.

The conditions for the photopolymerization and thermal polymerization are not particularly limited, but photopolymerization can be performed at room temperature for 1 to 10 minutes based on a 1kW UV light source, and thermal polymerization is performed for 1 to 5 hours at a temperature range of 60 to 90°C. can do.

In the polymerization, it is preferable to seal the edges of the release film and glass plate on both sides of the porous polymer film with Kapton tape or the like to prevent contact with oxygen and loss of monomers.

As a result, a porous polymer film filled with polymers in the pores can be obtained, and includes the step of introducing a cation exchange group into the polymer filled in the pores of the porous polymer film.

The cation exchange group is introduced for the production of hydrogen water, and the cation exchange group is not particularly limited, for example, a sulfonic acid group (-SO ₃ H), a carboxyl group (-COOH), a phosphonic group (-PO ₃ H ₂ ), phosphinic group (-HPO ₂ H), asonic group (-AsO ₃ H ₂ ), selinonic group (-SeO ₃ H), etc. These cation exchange groups may be any one, as well as two or more types.

The cation exchange group can be introduced into the polymer by dissolving the compound having the cation exchange group in an organic solvent and then impregnating the pores with a porous polymer film filled with the polymer. The introduction reaction of the cation exchange group is not particularly limited, but can be performed, for example, by impregnation at a temperature of 30 to 60°C for 3 to 15 hours.

As a result, it is possible to obtain a pore-filling cation exchange membrane in which a cation exchange resin is introduced into the pores. For the pore-filling cation exchange membrane, Nafion solution can be sprayed on the surface as needed. As a result, the durability of the hydrocarbon-based cation exchange membrane can be further improved.

It includes the step of introducing a metal into the pore-filling cation exchange membrane to form an electrode layer on the surface. The electrode layer can be formed by slurry coating or electrolytic plating, but in the present invention, it is preferable to form the electrode layer by applying electroless plating, especially non-equilibrium-impregnation/reduction method. When forming an electrode layer by the non-equilibrium-impregnation/reduction method, metal is introduced into the surface of the cation exchange membrane as well as into the pores of the porous polymer film to improve electrochemical properties, thereby improving hydrogen water generation efficiency. It is desirable because it can be done.

This first involves impregnating the pore-filling cation exchange membrane with an aqueous sulfuric acid solution, washing it with distilled water, and drying it. The step of immersing in the sulfuric acid aqueous solution is not particularly limited, but the pore-filling cation exchange membrane is immersed in an aqueous sulfuric acid solution of 0.5M or more, more preferably 1M or more, and 2M or less, more preferably 1.5M or less, for 1 hour or more. This can be performed by impregnating for at least 6 hours, preferably for 15 hours or less, 12 hours or less, and more preferably for 10 hours or less.

Thereafter, metal ions can be introduced by impregnating the pore-filling cation exchange membrane with the precursor solution containing the metal component for forming the electrode layer. The electrode layer can introduce metal ions by impregnating the pore-filling cation exchange membrane with a precursor solution containing the metal component. The metal ion is introduced into the surface and pores of the cation exchange membrane, and the metal ion is introduced by being replaced by a cation exchange group of the cation exchange membrane.

The metal precursor for forming the electrode layer is dissolved in a mixed solvent of methanol and water, preferably methanol or ethanol and water of 1:2 to 1:5, more preferably 1:2 to 1:3. Includes steps. The metal precursor for forming the electrode layer is preferably dissolved at a concentration of 0.1 to 0.7mM, more preferably 0.1 to 0.5mM, and even more preferably 0.2 to 0.5mM.

The metal for forming the electrode layer is not limited to this, and any metal that can function as an electrode can be suitably used. Examples include platinum, ruthenium, and mixed metals of platinum and ruthenium, and it is more preferable to use platinum.

The pore-filling cation exchange membrane is preferably impregnated with the metal precursor solution for forming the electrode layer for 20 minutes to 1 hour, more preferably 30 minutes to 1 hour. Through this impregnation, the metal for forming the electrode layer diffuses and ion-exchanges into the pore-filling ion exchange membrane.

If the metal concentration and impregnation time of the solution impregnating the pore-filling ion exchange membrane are less than the above range, water decomposition does not occur sufficiently and the efficiency of hydrogen water production decreases, and if it is excessive, resistance increases, which is not desirable.

A catalyst layer can be formed by reducing metal ions introduced into the cation exchange membrane. The reduction can be performed by impregnating the cation exchange membrane into which metal ions are introduced with a reducing agent solution. Specifically, the substituted metal ion on the surface of the cation exchange membrane first contacts a reducing agent and is reduced by chemical reduction, and then penetrates into the pores of the cation exchange membrane, and the substituted metal ion forms a metal crystal nucleation point within the pore and becomes non-electrolytic. It is reduced by reduction.

For the reduction, NaBH ₄ is added to an aqueous alkaline solution of pH 11 to 14, more preferably pH 12 to 14, with a temperature range of room temperature (25°C) to 60°C, more preferably 30 to 50°C. and LiAlH ₄ to prepare a reducing solution, and impregnating the reducing solution with a pore-filling ion exchange membrane introduced with the metal ion.

The immersion time in the reducing solution is not limited to this, but can be, for example, 30 minutes to 10 hours, 30 minutes to 7 hours, 30 minutes to 5 hours, or 45 minutes to 3 hours. If the impregnation is less than 30 minutes, the reduction of the introduced metal ions is not sufficient, and if the impregnation is more than 10 hours, no additional reduction effect can be obtained.

As a result, a membrane-electrode assembly with a metal electrode layer can be obtained. Afterwards, the membrane-electrode assembly is additionally soaked in an aqueous sulfuric acid solution for at least 30 minutes, preferably at least 1 hour, and at most 5 hours, more preferably at least 3 hours. The step of impregnating for less than an hour and then washing with distilled water may be further included.

For example, when the metal for forming the electrode layer is Pt and the reducing agent is NaBH ₄ , when the cation exchange membrane into which Pt cations are introduced is impregnated with a reducing agent solution, the Pt ions substituted on the surface of the cation exchange membrane are chemically reduced as shown in the following reaction formula: It is reduced by reaction.

BH ₄ ^- + 8OH ^- + 4Pt(II) → H ₂ BO ₃ ^- + 5H ₂ O + 4Pt(0)

Subsequently, the substituted Pt ions in the pores of the cation exchange membrane are reduced by the following reaction.

BH ₄ ^- + 8OH ^- → H ₂ BO ₃ ^- + 5H ₂ O + 8e ^-

8e ^- + 4Pt(II) → 4Pt (0)

By this non-equilibrium-impregnation/reduction method, electrodes can be introduced to the surface of the cation exchange membrane, thereby producing a membrane-electrode assembly. The membrane electrode assembly obtained by the present invention can be suitably used for hydrogen water production.

The membrane-electrode assembly provided by the present invention is thin yet has strong physical strength, and can provide excellent electrical performance due to its thin thickness. In addition, compared to the conventional Nafion-based membrane-electrode assembly, the manufacturing cost can be significantly reduced while providing equivalent performance.

Example

Hereinafter, the present invention will be described in more detail through examples. The implementation provided below is a specific example of carrying out the present invention, and is not intended to limit the present invention.

Examples 1 to 5

1. Preparation of pore-filling cation exchange membrane

As a porous polymer film, a polyethylene porous film (thickness: 25㎛, W-Scope Korea Co. Ltd.) was washed in acetone solvent for 3 hours and dried in an oven.

As a monomer for polymerization, 80 parts by weight of styrene (Sty) and 20 parts by weight of crosslinking agent were mixed and used. The crosslinking agents include divinylbenzene (DVB), ethylene glycol dimethacrylate (EGDMA), 1,3-butanediol dimethacrylate (BDDMA), and 1,6-hexanediol dimethacrylate (HDDMA) with different molecular weights. were used at different weight ratios as shown in Table 1.

As a polymerization initiator, benzoyl peroxide (BPO) thermal polymerization initiator was used in an amount of 2 parts by weight based on the weight of the monomer.

A monomer solution was prepared by mixing the monomer, cross-linking agent, and photoinitiator.

The washed porous film was impregnated with the monomer solution to fill the pores of the porous film with monomer.

The porous film filled with monomers in the pores was sandwiched between two sheets of release film, brought into close contact through rolling, and excess monomer was removed.

Afterwards, the porous film filled with monomers in the pores was inserted between two glass plates, sealed with Kapton tape to prevent contact with oxygen and loss of monomers, and thermal polymerization was performed at 80°C for 3 hours.

After the thermal polymerization, the porous film was impregnated in a solution of 20 parts by weight of chlorosulfonic acid dissolved in dichlorobenzene at 35°C, and the sulfonation reaction was performed for 12 hours.

Finally, pore-filling cation exchange membranes (ion exchange membranes 1 to 5) were prepared by sequentially washing them with dichlorobenzene and distilled water, and then impregnated with 0.5 M NaCl solution and stored.

The prepared cation exchange membranes 1 to 5 were immersed in 1M sulfuric acid aqueous solution for 6 hours, then washed with distilled water and dried.

Afterwards, Pt(II)(NH ₃ ) ₄ Cl ₂ (tetra-amine platinum chloride hydrate, 98%) was added to a solvent mixed with methanol and water at a volume ratio of 1:3 at a concentration of 0.3mM. After making a solution by dissolving it, the cleaned cation exchange membrane was impregnated in the solution for 40 minutes to allow platinum ions to diffuse and ion exchange into the inside of the cation exchange membrane.

Next, a reducing solution was prepared by dissolving NaBH ₄ at a concentration of 0.8M in an alkaline aqueous solution of pH 13 preheated to 50°C.

A membrane-electrode assembly was prepared by impregnating the cation exchange membrane substituted with platinum ions in the reducing solution and then reducing it to platinum through a reduction reaction for 2 hours to form an electrode layer.

The prepared membrane-electrode assembly was immersed in a 0.5 M aqueous sulfuric acid solution for 2 hours and then washed with distilled water (Membrane-electrode assemblies 1 to 5).

Example 6

After the pore-filling cation exchange membrane of Example 5 was brought into close contact with a hot plate heated to 80°C, 5% by weight of Nafion (in IPA, D521, DuPont) solution was sprayed at a loading amount of 1 mg/cm2 using a spray gun. Nafion was coated on the surface of the pore-filling cation exchange membrane to prepare a pore-filling cation exchange membrane (ion exchange membrane 6).

The Nafion-coated pore-filling cation exchange membrane was dried in a drying oven at 80°C for 1 hour.

Afterwards, after one side was dried, Nafion coating was performed on the other side under the same conditions.

Next, a membrane-electrode assembly was prepared for the cation exchange membrane by the same method as Example 1 (membrane-electrode assembly 6).

Comparative Example 1

A membrane-electrode assembly was prepared by forming an electrode layer of platinum on Nafion 117 from DuPont, a commercial cation exchange membrane, in the same manner as in Example 1 (membrane-electrode assembly 7).

Experiment example

1. Evaluation method

(1) Evaluation of membrane properties

The ion-exchange capacity ( IEC ) of the cation exchange membrane was measured through traditional acid-base titration and calculated using the following equation (1).

(1)

(One)

In the above equation, W _{dry memb} is the mass of the dried membrane, C is the concentration of the titrant solution, and V is the volume of the solution used for the titration.

The water content (water uptake, WU ) was calculated by measuring the wet weight ( W _wet ) and dry weight ( W _dry ) of the membrane and using equation (2).

(2)

(2)

Membrane electrical resistance ( MER ) and ion conductivity (σ) were measured using alternating current impedance measurement as follows.

After the membrane was sufficiently immersed in 0.5M NaCl or 0.5M HCl electrolyte solution, a potentiostat containing a 2-point probe clip cell and an impedance analyzer was used. Electrical resistance was measured by connecting a galvanostat, and MER and ionic conductivity were calculated from the following equations (3) and (4), respectively.

(3)

(3)

(4)

(4)

In the above equation (3), R ₁ represents the sum of the resistance of the electrolyte and the membrane, R ₂ represents the resistance of the electrolyte solution, Area represents the effective area of the membrane and electrode, and L represents the thickness of the membrane.

In addition, the ion transport number ( E _m ) is calculated by emf using a 2-compartment diffusion cell. method and calculated using the following equations (5) and (6).

(5)

(5)

(6)

(6)

In the above equation, E _m represents the measured cell potential, R is the gas constant, T is the absolute temperature, and F is the Faraday constant. Additionally, C _L and C _H are the concentrations of the NaCl solution, which were tested at 1mM and 5mM, respectively. The cell potential ( E _m ) was measured by connecting a pair of Ag/AgCl electrodes to a digital voltmeter.

The tensile strength of the manufactured cation exchange membrane was measured according to ASTM method D-882-79 under dry and wet conditions using a universal testing machine (5567 model, Instron).

The chemical durability of the ion exchange membrane was evaluated through the following Fenton oxidation test.

After preparing Fenton's reagent, which is an aqueous solution containing 3% by weight H ₂ O ₂ and 2 ppm FeSO ₄ , the temperature was maintained at 80°C. After measuring the initial weight of the cation exchange membrane, the cation exchange membrane was impregnated with the Fenton reagent. The weight of the cation exchange membrane was measured over time, and the weight reduction rate before and after the Fenton oxidation reaction was determined.

(2) Evaluation of water electrolysis characteristics (generation of hydrogen water)

To evaluate the water electrolysis characteristics, the concentration of hydrogen produced at the anode was measured under room temperature and constant current conditions using a dissolved hydrogen measuring device attached to the cell. Titanium electrodes were used for both the cathode and anode, and the current density was fixed at 0.02A/cm2. Table 2 shows the water electrolysis characteristics evaluation conditions.

2. Evaluation of membrane properties

The electrochemical properties of membrane-electrode assemblies 1 to 6 prepared in Examples 1 to 6 and membrane-electrode assemblies 7 prepared in Comparative Example 1 were measured in the same manner as described above, and the results are shown in Table 3.

As can be seen from Table 3, the membrane-electrode assembly 1 obtained in Example 1 showed inferior ionic conductivity compared to the membrane-electrode assembly 7 using Nafion in Comparative Example 1. However, it was found that the membrane-electrode assemblies 1 to 6 of Examples 1 to 6 exhibited very low electrical resistance due to their thin thickness and large ion exchange capacity.

In addition, despite the high ion exchange capacity of the membrane-electrode assemblies 1 to 6 of Examples 1 to 6, the water content was not high compared to the commercial membrane, which is due to the fact that the polyolefin porous polymer film as a support was physically filled with the ionomer in the pores. This is thought to be because it prevents excessive swelling and also has a high degree of cross-linking.

On the other hand, compared to membrane-electrode assembly 1 of Example 1 in which a single cross-linking agent (DVB) was used, the electrical properties of the membrane in membrane-electrode assemblies 2 to 6 of Examples 2 to 6 when a cross-linking agent with a relatively large molecular weight was mixed were used. Resistance was reduced, and at the same time, the ion transport number (ion-sensitive permeability) of the membrane was maintained.

On the other hand, as the content of the cross-linking agent increases, the moisture content increases, albeit slightly. This can be interpreted as the fact that the free volume of the membrane increases as the content of the cross-linking agent with a large molecular weight increases, and the free volume increases. As a result, the electrical resistance of the membrane tended to decrease, and at the same time, it was confirmed that the permeability of the ion exchange membrane was maintained due to optimization of the cross-linking structure.

Meanwhile, in the case of membrane-electrode assembly 6 of Example 6 with Nafion spray coating, the thickness increased due to the introduction of the Nafion coating layer, which resulted in lower electrical performance in NaCl solution compared to membrane-electrode assembly 5 of Example 5. The resistance tended to increase somewhat, but despite the increase in thickness, the electrical resistance in the HCl solution was at the same level as that of membrane-electrode assembly 5 of Example 5. This can be interpreted as the characteristic of Nafion, which has high conductivity for hydrogen ions, being expressed through surface coating.

The mechanical strength characteristics of membrane-electrode assemblies 1 to 6 prepared in Examples 1 to 6 and membrane-electrode assemblies 7 prepared in Comparative Example 1 were measured, and the results are shown in Table 4.

As can be seen from Table 4, the membrane-electrode assemblies 1 to 5 of Examples 1 to 5 are similar to the membrane-electrode assemblies 7 of Comparative Example 1 due to the strong physical properties and high degree of cross-linking of the support despite the thin film thickness. In comparison, it showed an excellent tensile strength of more than 4 times.

Additionally, compared to membrane-electrode assembly 1 of Example 1 using DVB alone as a cross-linking agent, it can be seen that membrane-electrode assemblies 2 to 5 of Examples 2 to 5 using a mixed cross-linking agent showed higher tensile strength values. This means that the crosslinking degree was improved by using a mixed crosslinking agent. However, it can be seen that as the cross-linking agent content increases, the tensile strength tends to decrease slightly.

Membrane-electrode assemblies 5 and 6 prepared in Examples 5 and 6 and membrane-electrode assemblies 7 prepared in Comparative Example 1 were evaluated for chemical stability through the Fenton oxidation experiment as described above, and the results are shown in Table 5. indicated.

As can be seen from Table 5, membrane-electrode assembly 5 of Example 5 is a hydrocarbon-based substrate, and showed a weight reduction rate of more than twice that of membrane-electrode assembly 7 prepared by Comparative Example 1. However, as shown in Table 5 above, this weight reduction rate is significantly lower than that of Astom's commercially available CMX product, which shows a weight reduction rate of more than 10%.

In addition, it can be seen that the membrane-electrode assembly 6 of Example 6, whose surface was coated with Nafion, had an increased oxidation stability and had a weight loss rate value close to the level of membrane-electrode assembly 7 of Comparative Example 1. That is, even in the case of the membrane-electrode assembly of Example 5 without Nafion coating, it can provide sufficient chemical stability for practical applications due to its high crosslinking density, but by additionally coating the surface with Nafion, the membrane-electrode assembly of Comparative Example 1 It can be seen that chemical stability approaching 7 can be achieved.

3. Evaluation of water electrolysis characteristics

Membrane-electrode assemblies 1 to 6 prepared in Examples 1 to 6 and membrane-electrode assemblies prepared in Comparative Example 1 were evaluated for hydrogen water production performance in the same manner as described above, and the results are shown in FIGS. 3 and 4 shown in

As can be seen from Figure 3, the hydrogen production by each membrane-electrode assembly showed results that were not significantly different. Since this is a constant current condition, this result is consistent with the theoretical assumption that hydrogen production will not be different. If hydrogen production is low, it can be determined that this is due to a defect in the ion exchange membrane or the effect of low ion selectivity.

Additionally, it can be seen from Figure 4 that the voltage maintains a constant value without change. This means that a stable water decomposition reaction is occurring. If the hydrogen gas produced inside the membrane-electrode assembly does not escape smoothly, or if the catalyst in the electrode layer does not function, a rapid increase in voltage can be observed. However, it can be confirmed that the voltage is stably maintained in all membrane-electrode assemblies of Examples 1 to 6.

On the other hand, it can be seen that as the content of the cross-linking agent increases, the water decomposition voltage tends to decrease. This result is consistent with the electrical resistance of the ion exchange membrane described previously. In particular, it can be seen that the membrane-electrode assembly 5 of Example 5 and the membrane-electrode assembly of Example 6 exhibit water decomposition voltages at the same level as the Nafion-based membrane-electrode assembly of Comparative Example 1.

Claims (35)

Filling the pores by impregnating a porous polymer film in a mixed solution of a monomer, a crosslinker, and an initiator;
Cross-polymerizing the mixed solution filled in the pores of the porous polymer film;
Preparing a pore-filling cation exchange membrane by impregnating the cross-polymerized polymer film in a solution having a cation exchange group to introduce a cation exchange group into the polymer film;
Impregnating the pore-filling cation exchange membrane in a solution containing metal ions for forming an electrode layer to ion-exchange the metal for forming an electrode layer; and
Impregnating the pore-filling cation exchange membrane exchanged with the metal ion for forming the electrode layer in an aqueous alkaline solution to reduce the metal ion for forming the electrode layer to form an electrode layer.
Membrane-electrode assembly manufacturing method comprising. The method of claim 1, wherein the cation exchange group is a sulfonic acid group (-SO ₃ H), a carboxyl group (-COOH), a phosphonic group (-PO ₃ H ₂ ), a phosphinic group (-HPO ₂ H), an asonic group ( -AsO ₃ H ₂ ) and a selinonic group (-SeO ₃ H). A method of manufacturing a membrane-electrode assembly that is at least one selected from the group consisting of. The method of claim 1, wherein the monomer is styrene, N-phenylacrylamide, N-(Triphenylmethyl)methacrylamide, and ethylene glycol phenyl ether acrylate. phenyl ether acrylate), 2-Hydroxy-3-phenoxypropyl acrylate, 2-sulfoethyl methacrylate and 3-sulfopropyl methacrylate ( A method of manufacturing at least one membrane-electrode assembly selected from the group consisting of 3-sulfopropyl methacrylate). The method of claim 1, wherein the crosslinking agent is divinylbenzene, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, and 1,6-hexanediol diacrylate. , hydroxypivalic acid neopentyl glycol diacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, tricyclodecane dimethanol diacrylate, trimethylolpropane triacrylate, A method of producing a membrane-electrode assembly comprising at least two selected from the group consisting of glycerin triacrylate, trimethylolpropane triacrylate, and tris(2-hydroxyethyl)isocyanurate triacrylate. The method of claim 4, wherein the crosslinking agent uses two or more different molecular weights. The method of claim 1, wherein the crosslinking agent is a mixture of divinylbenzene, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, and 1,6-hexanediol dimethacrylate, based on 100% by weight of the crosslinking agent. 60 to 90% by weight of divinylbenzene, 3 to 15% by weight of ethylene glycol dimethacrylate, 3 to 15% by weight of 1,3-butanediol dimethacrylate, and 3 to 15% by weight of 1,6-hexanediol dimethacrylate. % Membrane-electrode assembly manufacturing method. The method of claim 1, wherein the crosslinking polymerization reaction is performed by photo-crosslinking or thermal crosslinking. The method of claim 1, wherein the initiator is at least one photoinitiator selected from the group consisting of benzophenone, benzyldimethylketal, 1,2-diphenyl ethanedione, hydroxyldimethylacetopone, and α-hydroxycyclohexylphenylmethanone. Method for manufacturing phosphorus membrane-electrode assembly. The method of claim 1, wherein the initiator is at least one thermal initiator selected from the group consisting of benzoyl peroxide, benzoyl peroxide, azobisisobutyronitrile, azomethane, and azoisopropane. The method of claim 1, wherein the crosslinking agent is contained in an amount of 10 to 30% by weight based on a total of 100% by weight of the monomer and the crosslinking agent. The method of claim 1, wherein the initiator is included in an amount of 1 to 5 parts by weight based on 100 parts by weight of the monomer. The method of claim 1, wherein the step of ion exchanging with metal ions for forming the electrode layer,
Impregnating the pore-filling cation exchange membrane in an aqueous sulfuric acid solution for 1 to 15 hours and then washing it with water;
Preparing a platinum ion-containing solution by dissolving a metal ion-containing precursor for forming an electrode layer in methanol or a mixed solvent of ethanol and water; and
Impregnating the cleaned pore-filling cation exchange membrane with a precursor solution containing metal ions for forming an electrode layer.
A method of manufacturing a membrane-electrode assembly carried out by a process comprising. The method of claim 12, wherein the aqueous sulfuric acid solution has a concentration of 0.5 to 2M. The method of claim 12, wherein the mixed solvent of methanol or ethanol and water has a volume ratio of methanol or ethanol and water of 1:2 to 1:5. The method of claim 1, wherein the precursor solution containing metal ions for forming the electrode layer has a concentration of 0.1 to 0.7mM of the metal ions for forming the electrode layer. The method of manufacturing a membrane-electrode assembly according to claim 1, wherein the step of ion exchange with metal ions for forming the electrode layer is performed for 20 minutes to 1 hour. The method of claim 1, wherein the reduction is performed by using a reducing solution in which at least one selected from the group consisting of NaBH ₄ and LiAlH ₄ is dissolved in an alkaline aqueous solution having a pH of 11 to 14 by ion-exchanging the pore-filling cation exchange membrane with metal ions for forming the electrode layer. A method of manufacturing a membrane-electrode assembly performed by impregnating. The method of claim 1, wherein the impregnation with the reducing solution is performed for 30 minutes to 5 hours. The method of claim 18, wherein the reducing solution is NaBH ₄ or LiAlH ₄ dissolved in an aqueous alkaline solution at a concentration of 0.6 to 0.9 M. The method of claim 1, wherein the metal ion for forming the electrode layer is an ion of platinum, ruthenium, or a mixed metal thereof. The method of claim 17, wherein the aqueous alkaline solution has a temperature of 20 to 60°C. The method of claim 1, wherein the porous polymer film has a thickness of 25 ㎛ or less (excluding 0 ㎛). The method of claim 1, wherein the porous polymer film is LLDPE (Linear Low Density Polyethylene), LDPE (Low Density Polyethylene), PE (Polyethylene)-based copolymer, PP (Polypropylene), EVA (Ethylene Vinyl Alcohol), and EOR (Ethylene Octene). A method of manufacturing a membrane-electrode assembly selected from the group consisting of Rubber. The method of claim 1, further comprising washing the porous polymer film in acetone solvent for 30 minutes to 5 hours and then drying it. The method of claim 1, further comprising impregnating the membrane-electrode assembly obtained in the step of reducing the metal ions with an aqueous sulfuric acid solution for 30 minutes to 5 hours and then washing it with water. The method of manufacturing a membrane-electrode assembly according to any one of claims 1 to 25, further comprising coating the pore-filling cation exchange membrane by spraying a Nafion solution on the surface. delete delete delete delete delete delete delete delete delete