Hydrogen ion conducting multilayer composite membrane

Abstract

To provide a hydrogen ion conductive multi-layer composite membrane having excellent durability, ion conductivity, and hydrogen permeation reduction effect.SOLUTION: The present invention provides a hydrogen ion conductive multilayer composite membrane comprising: inner reinforced membranes comprising a porous PTFE layer impregnated with an ionomer composition and outer reinforced membranes positioned on both sides of the inner reinforced membrane, wherein the outer reinforced membranes comprise a porous PTFE layer impregnated with an ionomer composition.SELECTED DRAWING: Figure 1

Description

Detailed Description of the Invention

[0001] [Technical Field]

[0002] The present invention relates to a proton-conducting multilayer composite membrane. [Background technology]

[0003] Water electrolysis is a technology that produces hydrogen by electrolyzing water, and is environmentally friendly. Types of water electrolysis include proton exchange membrane (PEM), anion exchange membrane (AEM), alkaline, and solid oxide.

[0004] Meanwhile, fuel cells are a highly efficient power generation device that is more efficient than existing internal combustion engines, consumes less fuel, and is a pollution-free energy source that does not produce environmental pollutants such as SOx, NOx, or VOCs.Furthermore, fuel cells have the added advantage of requiring less land area for production facilities and a shorter construction period, and are applicable in a variety of fields, from mobile power sources for portable devices and other transportation, to distributed power generation for homes and power businesses.

[0005] Fuel cells are broadly classified into five types based on their operating temperature and electrolyte: alkaline fuel cells (AFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), polymer electrolyte membrane fuel cells (PEMFC), and direct methanol fuel cells (DMFC). Among these, polymer electrolyte fuel cells (PEFCs) have attracted considerable attention due to their excellent mobility.

[0006] The electrolyte membranes used in cation exchange membrane water electrolysis and polymer electrolyte fuel cells are mainly fluorinated carbon electrolyte membranes, and a representative example is Nafion, a perfluorinated hydrogen ion exchange membrane developed by DuPont in the United States in the early 1960s. In addition to Nafion, other similar perfluorinated polymer electrolyte commercial membranes include Asahi Kasei's Aciplex-S membrane, Dow Chemicals' Dow membrane, and Asahi Glass' Flemion membrane.

[0007] This single membrane (casting membrane) is composed only of ion-conducting electrolyte, making it easy to manufacture and widely used in experimental and mass-produced products. However, under the operating conditions of water electrolysis systems and fuel cell systems, material fatigue accumulates due to volume changes, resulting in durability issues. In addition, as the membrane becomes thicker, membrane resistance increases and electrochemical performance deteriorates, while reducing the membrane thickness reduces performance due to issues with hydrogen permeation and durability. Therefore, there is a need for an improvement to the above problem. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a hydrogen ion conductive multilayer composite membrane that is excellent in durability, ion conductivity, and hydrogen permeation reducing effect. Another object of the present invention is to provide a water electrolysis system and a fuel cell that use a hydrogen ion conductive multilayer composite membrane as a separation membrane. However, the object of the present invention is not limited to the above object, and other objects not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0009] As a means for solving the above problem, The present invention provides a proton-conducting multilayer composite membrane comprising an inner reinforcement membrane comprising a porous PTFE layer impregnated with an ionomer composition, and outer reinforcement membranes positioned on both sides of the inner reinforcement membrane, wherein the outer reinforcement membrane comprises a porous PTFE layer impregnated with an ionomer composition.

[0010] Additionally, the average pore size and porosity of the porous PTFE layer of the outer reinforcing membrane may be smaller than the average pore size and porosity of the PTFE of the inner reinforcing membrane.

[0011] The PTFE of the outer reinforcement membrane may have an average pore size in the range of 0.1 μm to 0.2 μm and a porosity in the range of 70% to 80%, and the PTFE of the inner reinforcement membrane may have an average pore size in the range of 0.2 μm to 0.4 μm and a porosity in the range of 80% to 90%. In addition, the number of the inner reinforcing membranes may be one or two to five.

[0012] In addition, the outer reinforced membrane may include a PTFE layer impregnated with an ionomer, a surface-modified layer formed by plasma surface treatment on one or both outer surfaces of the PTFE layer, and an ionomer layer coated on the surface-modified layer. The inner reinforced membrane may include a PTFE layer impregnated with an ionomer, a surface-modified layer formed by plasma surface treatment on one or both outer surfaces of the PTFE layer, and an ionomer layer coated on the surface-modified layer.

[0013] In addition, the viscosity and ionomer concentration of the ionomer composition used when coating the ionomer layer on the surface modification layer may be higher than the viscosity and ionomer concentration of the ionomer composition used when impregnating the ionomer inside the PTFE layer. The viscosity difference may be in the range of 10 cp to 100 cp from 25° C., and the concentration difference may be in the range of 30% to 80% by weight. In addition, one or more of the inner and outer reinforcing membranes may be treated with an acid to reduce voids.

[0014] In addition, before bonding the inner and outer reinforced membranes, the surfaces to be bonded may be pretreated with plasma and coated with an ionomer composition, and then the membranes may be bonded together, so that a separate ionomer coating layer may be present between the inner and outer reinforced membranes. In addition, a catalyst mesh layer may be interposed between the at least one outer reinforced membrane and the at least one inner reinforced membrane, thereby forming a catalyst layer. The present invention also provides a water electrolysis system and a fuel cell comprising the proton-conductive multilayer composite membrane as a separation membrane. [Effects of the Invention]

[0015] The proton-conductive multilayer composite membrane of the present invention is excellent in durability, ion conductivity, and hydrogen permeation reducing effect, and can be usefully used as a separation membrane in water electrolysis systems and fuel cells. The above effects and additional effects are described in detail below. [Brief explanation of the drawings]

[0016] 1 and 2 are schematic diagrams showing the structure and manufacturing process of a proton-conducting multilayer composite membrane according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Before describing the present invention in detail below, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art, unless otherwise defined.

[0018] Throughout this specification and claims, unless otherwise stated, the term "comprising" is used to mean the inclusion of a referenced item, step or group of items and steps, and is not used to mean the exclusion of any other item, step or group of items or groups of steps. On the contrary, various embodiments of the present invention may be combined with any other embodiment unless expressly stated to the contrary.

[0019] The present invention will now be described in more detail. A proton-conductive multilayer composite membrane according to an embodiment of the present invention includes an inner reinforcing membrane including a porous PTFE layer impregnated with an ionomer composition, and outer reinforcing membranes positioned on both sides of the inner reinforcing membrane and including porous PTFE layers impregnated with an ionomer composition. The inner reinforcing membrane may be one, or two or more, as shown in FIG. 1. Preferably, two to five membranes may be stacked. The thickness of the proton-conductive multilayer composite membrane may be in the range of 20 μm to 100 μm, and considering factors such as thinness, durability, proton conductivity, and reduced hydrogen permeation, the thickness may be in the range of 30 μm to 60 μm.

[0020] The porous PTFE layer may be a PTFE membrane having porosity due to expansion. The porous PTFE membrane may be a commercially available product that meets the required performance, or may be directly produced.

[0021] The porous PTFE membrane may be manufactured by a publicly known method. For example, the porous PTFE membrane may be manufactured through the following steps: First, tritetrafluoroethylene powder and a lubricant are mixed, followed by primary molding to obtain a preform, which is then extruded to obtain a rod-shaped primary molded body, which is then processed into a sheet to obtain a secondary molded body, which is dried to remove the lubricant, and then stretched in the transverse and longitudinal directions. A PTFE membrane with desired properties can be manufactured by controlling the type and content of the powder used and the stretching process conditions.

[0022] The porous PTFE layer of the outer reinforcement membrane and the PTFE layer of the inner reinforcement membrane may be the same PTFE membrane. More preferably, the average pore size and porosity of the porous PTFE layer of the outer reinforcement membrane may be smaller than the average pore size and porosity of the PTFE layer of the inner reinforcement membrane. By using a PTFE layer of the outer reinforcement membrane with a relatively small pore size and porosity, it is possible to block hydrogen that can infiltrate from the outside, thereby reducing hydrogen permeability and improving durability. By using a PTFE layer of the inner reinforcement membrane with a relatively large pore size and porosity, it is possible to increase the impregnation of ionomer and impregnate the ionomer at a high content, thereby improving proton conductivity. Specifically, the PTFE layer of the outer reinforcing membrane may have an average pore size of 0.1 to 0.2 μm and a porosity of 70% to 80%, and the PTFE of the inner reinforcing membrane may have an average pore size of 0.2 to 0.4 μm and a porosity of 80% to 90%. The difference in average pore size between the two PTFE layers may be in the range of 0.05 to 0.3 μm, and the difference in porosity may be in the range of 5% to 20%.

[0023] The ionomer composition may include a conductive ionomer, a solvent, and a surfactant, and may optionally further include a radical scavenger.

[0024] Any hydrogen ion conductive polymer can be used as the conductive ionomer, for example, a polymer resin having a cation exchanger, i.e., a hydrogen ion conductive group, selected from the group consisting of sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, phosphonic acid groups, and derivatives thereof, in its side chain.

[0025] For example, the material may include one or more proton-conducting polymers selected from a fluoride-based polymer, a benzimidazole-based polymer, a polyimide-based polymer, a polyphenylene sulfide-based polymer, a polysulfone-based polymer, a polyether ketone-based polymer, a polyether-ether ketone-based polymer, or a polyphenylquinoxaline-based polymer.

[0026] Preferably, a perfluorinated sulfonated ionomer is used as the conductive ionomer. Specifically, polyperfluorosulfonate (trade names: Nafion, Dupont) can be used as the perfluorinated sulfonated ionomer. In addition, commercial products such as Aciplex (Asahi Kasei Chemical), Flemion (Asahi Glass), and Fumion (Fumatech) can also be used. As the solvent, a commonly used solvent such as N-methylpyrrolidone, isopropyl alcohol, or normal propyl alcohol can be used.

[0027] Considering both the compatibility with PTFE and environmental issues, the surfactant should preferably contain a hydrophobic group in which hydrocarbon hydrogen is partially substituted with fluorine, and the hydrophilic group of the surfactant should preferably be a hydrophilic group having compatibility with the ionomer having a sulfonic acid group.

[0028] Known surfactants can be used, including, for example, DuPont's Zonyl series, 3M's Novec series, or a mixture thereof. Specifically, Zonyl surfactants include ZonylTBS (RfCH2CH2SO3X (X = H or NH4), Rf = F(CF2CF2)3-8), ZonylFSN (RfCH2CHO(CH2CH20)xH), and ZonylFSP (RfCHO)P(O)(ONH4). Novec surfactants include Novec 4200 (Ammonium Fluoroalkylsulfonamide), Novec 4300 (Ammonium Fluoroalkylsulfonate), Novec 4430 (Polymeric Fluorochemical Active), and Novec 4432 (Polymeric Fluor).

[0029] The method for impregnating the porous PTFE with the ionomer composition is not limited, and examples thereof include coating the porous PTFE with the ionomer composition, immersing the PTFE in the ionomer composition, etc. By impregnation, the ionomer composition penetrates into the interior of the porous PTFE and can also remain on the surface of the PTFE.

[0030] Prior to the impregnation step, the porous PTFE can be plasma pretreated to further enhance the impregnation of the ionomer composition. The plasma treatment can be performed on one or both sides of the PTFE.

[0031] Surface modification technology using plasma treatment applies various types of energy and particles to the surface, applying physical impact to the surface to increase roughness, breaking polymer chains, and forming new chemical bonds, resulting in an increase in hydrophilic functional groups.

[0032] There are two types of plasma: low-pressure plasma, which generates plasma by discharging at low pressure, and atomic pressure plasma, which generates plasma by discharging at normal pressure. The room temperature, atomic pressure plasma method is superior in terms of its advantages. Atmospheric pressure plasma technology can generate efficient, stable, and uniform plasma discharge at normal pressure, i.e., atmospheric pressure (760 Torr), without using a costly vacuum system, improving economy and productivity.

[0033] After impregnation, it is recommended to apply heat to the support to perform a two-stage heat treatment to allow the ionomer to crystallize. If the gas generated during the heat treatment is not removed in stages, cracks may occur after the heat treatment, causing problems with hydrogen permeability and durability. Specifically, the first heat treatment is performed using hot air at 150-210°C, and the second heat treatment is performed using near-infrared (NIR) light at 50-100°C.

[0034] On the other hand, the PTFE-impregnated membrane impregnated with ionomer can be plasma-treated again to form a surface-modified layer, and then coated with an ionomer layer again, thereby further improving durability and hydrogen permeability reduction performance.

[0035] Specifically, as shown in FIG. 2, the outer reinforced membrane may include a PTFE layer impregnated with an ionomer, a surface-modified layer formed on the outer surface or both surfaces of the PTFE layer by plasma surface treatment followed by heat treatment, and an ionomer layer coated on the surface-modified layer formed on the outer surface or both surfaces (a drawing in which both surfaces are treated is omitted).

[0036] Similarly, the internal reinforced membrane may also include a PTFE layer impregnated with an ionomer, a surface-modified layer formed on the outer surface or both surfaces of the PTFE layer by plasma surface treatment followed by heat treatment, and an ionomer layer coated on the surface-modified layer formed on the outer surface or both surfaces.

[0037] Here, the viscosity and ionomer concentration of the ionomer composition used to coat the ionomer layer on the surface modification layer may be higher than the viscosity and ionomer concentration of the ionomer composition used to impregnate the PTFE layer with the ionomer. Because the PTFE is already impregnated with the ionomer, the ionomer composition used to coat the surface modification layer can have a relatively high viscosity and ionomer concentration to ensure coatability and coating film stability and uniformity rather than impregnation.

[0038] The viscosity difference between the two ionomer compositions may be within the range of 10 cp to 100 cp at 25° C., and the concentration difference may be within the range of 30% to 80% by weight. Specifically, the low-viscosity ionomer composition may have a viscosity of 10 cp to 30 cp at 25° C., and the high-viscosity ionomer composition may have a viscosity of 40 cp to 110 cp at 25° C. Additionally, the low-concentration ionomer composition may have a concentration of 5% to 25% by weight, and the high-concentration ionomer composition may have a concentration of 40 to 85% by weight.

[0039] One or more of the internally reinforced membrane and the externally reinforced membrane thus fabricated can be post-treated with an acid to reduce voids that hinder ion conduction and increase hydrogen permeation. The acid solution is not limited, and commonly used acids such as sulfuric acid, hydrochloric acid, and nitric acid can be used. The acid solution concentration can be within the range of 0.01 to 5 mol. The acid treatment can be performed by applying the acid solution to the reinforced membrane or immersing the reinforced membrane in the acid solution, and is not limited. After the acid treatment, the membrane is washed with deionized water, and pressure is applied to the reinforced membrane to fabricate a reinforced membrane with a thickness of 10 to 15 μm. The reinforced membrane can then be heat-treated to fabricate the reinforced membrane.

[0040] The inner and outer reinforced membranes thus prepared can be bonded together to form a proton-conducting multilayer composite membrane, as shown in Figure 1. Prior to bonding, the surfaces of the reinforced membranes to be bonded can be pretreated with plasma, and the pretreated surfaces can be coated with an ionomer composition before bonding. In this case, a separate ionomer coating layer can be present between the inner and outer reinforced membranes. This separate ionomer coating layer can form an interface distinct from the plasma-pretreated surface. During ionomer coating, the ionomer composition can penetrate the interface and part of the interior of the reinforced membrane, making the interface invisible to the naked eye. As will be seen in the examples below, the proton-conducting multilayer composite membrane may further include a catalyst layer therein, and may optionally further include other functional layers.

[0041] The proton-conductive multilayer composite membrane according to the present invention may have an outer reinforcement layer of 15% to 40% of the thickness and an inner reinforcement layer of 60 to 85% of the thickness, which may provide excellent durability, ion conductivity, and hydrogen permeation reduction effects. The proton-conductive multilayer composite membrane of the present invention can be very useful as a separator in a water electrolysis system and a separator in a fuel cell.

[0042] The types and structures of water electrolysis systems and fuel cells to which the proton-conductive multilayer composite membrane of the present invention is applied as a separation membrane may be applied without limitation as long as protons are conducted through a separation membrane, and detailed descriptions thereof will be omitted as they have been disclosed. [Example]

[0043] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to the following examples.

[0044] Production Example 1-1: Production of ionomer composition A The conductive ionomer used was polyperfluorosulfonate (trade name Nafion, Dupont) as a perfluorinated sulfonated ionomer, and isopropyl alcohol (IPA) was used as the solvent, with the ionomer being 12 wt% of the total composition. To improve impregnation, a surfactant was added at 0.5 wt% of the total composition.

[0045] The ionomer composition was dispersed using a shear stress device at 1000-2000 rpm for 1 hour, and then a secondary dispersion was performed using an Ultra-Sonic device at an amplitude of 30-50% for 1 hour to ensure that the ionomer molecules were uniformly distributed within the composition. This was done to adjust the size of the chemical particles and facilitate their impregnation into the pores of the PTFE membrane. The final viscosity of the ionomer composition was measured at 25°C to be 20 cp.

[0046] Production Example 1-2: Production of Ionomer Composition B The same procedure as in Preparation Example 1-1 was carried out, except that the ionomer was used in an amount of 60% by weight based on the total solution. The viscosity of the ionomer was measured at 25° C. to be 68 cp.

[0047] Manufacturing Example 2-1: Manufacturing of PTFE / ionomer-impregnated membrane A Expanded porous PTFEA was prepared. The average pore size of the porous PTFEA was 0.15 μm, and the porosity was 75%. First, a primary plasma treatment was performed on porous PTFEA using room temperature and atmospheric pressure plasma at 220 V and 2-10 A. Then, the surface of the PTFEA, which had been surface-modified by the primary plasma treatment, was impregnated into the support with a solution of ionomer composition A prepared in Preparation Example 1-1. After impregnation, the support was heat-treated to crystallize the ionomer. The heat treatment was performed by passing hot air at 100-150°C to produce PTFE / ionomer-impregnated membrane A.

[0048] Manufacturing Example 2-2: Manufacturing of PTFE / ionomer-impregnated membrane B Expanded porous PTFE B was prepared. The average pore size of porous PTFE B was 0.30 μm, and the porosity was 85%. A PTFE / ionomer-impregnated membrane B was produced in the same manner as in Preparation Example 2-1, except that porous PTFE B was used instead of porous PTFE A.

[0049] Manufacturing Example 3-1: Manufacturing of PTFE / ionomer reinforced membrane A The upper surface of the impregnated membrane A of Preparation Example 2-1 was subjected to a secondary plasma treatment at room temperature and atmospheric pressure under conditions of 220 V and 1 to 4 A to modify the surface. Then, the ionomer composition B prepared in Preparation Example 1-2 was coated on the newly formed surface-modified layer. After coating, a dual heat treatment was performed using hot air at 150 to 210°C and near-infrared (NIR) radiation at 0 to 100°C. Thereafter, the opposite side of the impregnated membrane A was subjected to plasma surface modification layer formation treatment, coating with ionomer composition B, and heat treatment under the same conditions as above to produce a PTFE / ionomer reinforced membrane A.

[0050] Manufacturing Example 3-2: Manufacturing of PTFE / ionomer reinforced membrane B PTFE / ionomer reinforced membrane B was produced in the same manner as in Preparation Example 3-1, except that impregnated membrane B of Preparation Example 2-2 was used instead of impregnated membrane A of Preparation Example 2-1.

[0051] Manufacturing Example 3-1-1: Post-treatment of PTFE / ionomer reinforced membrane A The reinforced membrane A of Preparation Example 3-1 was treated with acid for post-treatment. A 1.0M sulfuric acid solution was used as the acid solution for the reinforced membrane A, and the membrane was washed with deionized water to reduce voids that may have formed during the impregnation and drying processes. The reinforced membrane was then pressed to produce a reinforced membrane A with a thickness of 8 μm, which was then heat-treated at 180-200°C.

[0052] Manufacturing Example 3-2-1: Post-treatment of PTFE / ionomer reinforced membrane B The same procedure as in Preparation Example 3-1-1 was carried out, but Reinforced Membrane B of Preparation Example 3-2 was used instead of Reinforced Membrane A of Preparation Example 3-1, and the same post-treatment was carried out to produce Reinforced Membrane B with a thickness of 15 μm.

[0053] Manufacturing Example 4-1: Manufacturing of PTFE / ionomer multilayer composite membrane A One surface of the PTFE / ionomer reinforced membrane A of Production Example 3-1-1 was subjected to a plasma treatment at room temperature and atmospheric pressure under conditions of 220 V and 2 to 10 A to modify the surface. Meanwhile, one side of the PTFE / ionomer reinforced membrane B of Production Example 3-2-1 was subjected to plasma treatment under the same conditions as above to modify the surface. Next, the plasma-treated surface of PTFE / ionomer reinforced membrane A was coated with ionomer composition B from Preparation Example 1-2, and the plasma-treated surface of PTFE / ionomer reinforced membrane B was brought into contact with the coating layer of ionomer composition B, followed by thermal bonding to produce a PTFE / ionomer multilayer composite membrane containing two PTFEs. This was then heat-treated at 150-210°C using hot air, and the NIR was heat-treated at 50-100°C.

[0054] Two PTFE / ionomer multilayer composite membranes containing two PTFE layers were prepared as described above, and the exposed surface of each PTFE / ionomer reinforced membrane B was plasma-treated in the same manner as described above to modify the surface. The plasma-treated surface of one of the reinforced membranes B was then coated with ionomer composition B from Preparation Example 1-2 and thermally bonded in the same manner as described above to produce a PTFE / ionomer multilayer composite membrane containing four PTFE layers. This was then heat-treated in the same manner as described above to produce a final PTFE / ionomer multilayer composite membrane containing four PTFE layers. The thickness of the multilayer composite membrane was measured to be approximately 50 μm.

[0055] Manufacturing Example 4-2: Manufacturing of PTFE / ionomer multilayer composite film B Plasma treatment, ionomer coating, and thermal bonding were performed in the same manner as in Preparation Example 4-1, but the layers were laminated and thermally bonded in a reinforced membrane A / reinforced membrane B / reinforced membrane A structure to produce a PTFE / ionomer multilayer composite membrane B containing three PTFE layers and one inner reinforced membrane B. The thickness of the multilayer composite membrane was measured to be approximately 35 μm.

[0056] Manufacturing Example 4-3: Manufacturing of PTFE / ionomer multilayer composite film C Plasma treatment, ionomer coating, and thermal bonding were performed in the same manner as in Preparation Example 4-1, but the structure of reinforced membrane A / catalyst layer / reinforced membrane B / reinforced membrane B / reinforced membrane A was laminated and thermally bonded to produce PTFE / ionomer multilayer composite membrane C, which had three PTFE layers. The thickness of the multilayer composite membrane was measured to be approximately 53 μm. The catalyst layer is composed of a mesh layer coated with cerium oxide, and was laminated between reinforced membrane A and reinforced membrane B in Manufacturing Example 4-1 before thermal bonding. The catalyst layer prevents side reactions caused by gas crossover that may occur during operation, thereby improving drive performance and durability.

[0057] Manufacturing Example 4-4: Manufacturing of PTFE / ionomer multilayer composite film D Plasma treatment, ionomer coating, and thermal bonding were performed in the same manner as in Preparation Example 4-1, but the membranes were laminated and thermally bonded in a reinforced membrane A / reinforced membrane A / reinforced membrane A / reinforced membrane A structure to produce PTFE / ionomer multilayer composite membrane D, which had four PTFE layers. The thickness of the multilayer composite membrane was measured to be approximately 50 μm.

[0058] Manufacturing Example 4-5: Manufacturing of PTFE / ionomer multilayer composite film E The plasma treatment, ionomer coating, and thermal bonding were carried out in the same manner as in Preparation Example 4-1, but the membranes were laminated and thermally bonded in a reinforced membrane B / reinforced membrane B / reinforced membrane B / reinforced membrane B structure to produce a PTFE / ionomer multilayer composite membrane E having four PTFE layers. The thickness of the multilayer composite film was measured to be about 50 μm.

[0059] Experimental example 1: Tensile strength evaluation Samples of the products manufactured in the manufacturing examples were prepared so that the horizontal and vertical lengths were 1cm x 10cm in the MD (Machine Direction) and TD (Transverse Direction) directions, respectively, and the samples were fixed to a universal material testing machine jig with a distance of 5cm between the upper and lower jigs to evaluate the tensile strength. The results are shown in Table 1.

[0060] Experimental Example 2: Ion Conductivity Evaluation The composite membrane manufactured in the manufacturing example was prepared to a size of 4cm x 1cm, and the sample was attached to an ion conductivity jig. The measurement environment was maintained at a temperature of 80°C and a humidity of 95% in a thermo-hygrostat, and measurements were made using an impedance analyzer in the measurement range of 0.001Hz to 100,000Hz (through-plane standard). The results are shown in Table 1.

[0061] Experimental example 3: Evaluation of hydrogen permeability through impregnated membranes The hydrogen permeability of the products manufactured in the manufacturing examples was measured using a bubble flow meter at 60°C and 9 bar, and the results are shown in Table 1.

[0062] Experimental example 4: Accelerated durability evaluation test After the product manufactured in the manufacturing example was manufactured in an MEA, the OCV was monitored. The cell temperature was set to 90°C, and the relative humidity was set to 0% (dry, 30 seconds) - 100% (wet, 45 seconds), and approximately 10,000 cycles were performed. The results are shown in Table 2.

[0063] [Table 1]

[0064] As can be seen from Table 1 above, the reinforced membranes of Preparation Examples 3-1 and 3-2 exhibited significantly reduced hydrogen permeability compared to the impregnated membranes of Preparation Examples 2-1 and 2-2. In addition, when post-treatment was performed using an acid solution as in Preparation Examples 3-1-1 and 3-2-1, it was confirmed that the voids were reduced, improving ionic conductivity and reducing hydrogen permeability.

[0065] In addition, as can be seen from Preparation Examples 4-1 to 4-5, the PTFE used in the outer multilayer composite membrane has a small pore size and porosity, while the PTFE used in the inner multilayer composite membrane has a relatively large pore size and porosity, which confirms that ion conductivity, durability, and hydrogen permeability can be simultaneously achieved.

[0066] [Table 2] Furthermore, as can be seen from Production Example 4-3, it can be confirmed that the use of a catalyst layer further improves the durability of the membrane and provides excellent driving performance.

Claims

1. an inner reinforcement membrane comprising a porous PTFE layer impregnated with an ionomer composition; and outer reinforcement membranes positioned on opposite sides of the inner reinforcement membrane and including porous PTFE layers impregnated with an ionomer composition; the average pore size and porosity of the porous PTFE layer of the outer reinforcing membrane are smaller than the average pore size and porosity of the PTFE of the inner reinforcing membrane; The average pore size of the PTFE of the outer reinforcement membrane is 0.1 to 0.2 μm, and the porosity is within the range of 70% to 80%; The average pore size of the PTFE of the inner reinforcing membrane is 0.2 to 0.4 μm, and the porosity is in the range of 80% to 90%; a catalyst layer is present between the at least one outer reinforcement membrane and the at least one inner reinforcement membrane, the catalyst layer being composed of a catalyst mesh layer coated with cerium oxide; Hydrogen ion conducting multilayer composite membrane.

2. 2. The proton-conducting multilayer composite membrane of claim 1, wherein the internal reinforcement membrane is one or in the range of two to five layers.

3. The outer reinforced membrane is PTFE layer with ionomer impregnated inside; a surface-modified layer formed by plasma surface treatment on the outer surface or both surfaces of the PTFE layer; and 10. The proton-conducting multilayer composite membrane of claim 1, further comprising: an ionomer layer coated on the surface modification layer formed on the outer surface or both surfaces.

4. The internal reinforcement membrane is PTFE layer with ionomer impregnated inside; a surface-modified layer formed by plasma surface treatment on the outer surface or both surfaces of the PTFE layer; and 10. The proton-conducting multilayer composite membrane of claim 1, further comprising: an ionomer layer coated on the surface modification layer formed on the outer surface or both surfaces.

5. The inner reinforced membrane and the outer reinforced membrane are bonded after the surfaces to be bonded are pretreated with plasma and coated with an ionomer composition, and a separate ionomer coating layer is present between the inner reinforced membrane and the outer reinforced membrane, according to claim 1. Hydrogen ion conducting multilayer composite membrane.

6. A water electrolysis system comprising the hydrogen ion conductive multilayer composite membrane of claim 1 as a separation membrane.

7. A fuel cell comprising the hydrogen ion conductive multilayer composite membrane of claim 1 as a separation membrane.

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