Separator, method for manufacturing same, electrolysis cell comprising same, and electrolysis apparatus

Abstract

The present invention relates to a separator and to an electrolysis cell comprising same, the separator having high chemical and mechanical strength while maintaining pore characteristics of a porous substrate by controlling air permeability, thickness, and tensile strength of the porous substrate, and at the same time, able to maintain a high level of electrolysis efficiency.

Description

Separator, method of manufacturing the same, electrolysis cell and electrolysis device including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0174744 filed November 29, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a separator, a method for manufacturing the same, an electrolysis cell including the same, and an electrolysis device.

[0006]

[0007] Carbon dioxide is a greenhouse gas that causes global warming and is a target that must be reduced. Methods for reducing carbon dioxide include carbon capture, chemical conversion, and electrochemical conversion. Among these, the electrochemical conversion method allows for precise control of components to produce other synthetic gases, thereby providing economic benefits compared to simply removing carbon dioxide. Additionally, carbon dioxide can be electrolyzed with water to obtain carbon monoxide, ethylene, methane, formic acid, formate, various hydrocarbons, and organic substances such as aldehydes or alcohols.

[0008] The process of electrochemically decomposing or reducing carbon dioxide is classified according to the ion exchange method. In the case where a cation exchange membrane is used, water is supplied to the anode and an electric current is applied, causing the water at the anode to decompose to generate oxygen, electrons, and hydrogen ions, and the hydrogen ions move through the cation exchange membrane to the cathode. At the cathode, carbon dioxide reacts with the electrons generated at the anode and the hydrogen ions that have passed through the cation exchange membrane to undergo a reduction reaction and is converted into other substances.

[0009] In addition, when using an anion exchange membrane (AEM), an aqueous KOH solution of a certain concentration is generally used as the electrolyte because the activity of the electrochemical reaction improves in a strong basic atmosphere. When carbon dioxide and water are supplied together to the cathode and an electric current is applied, hydroxide ions (OH - ) occurs, and the hydroxide ions pass through the anion exchange membrane and move to the anode. The moved hydroxide ions are converted into water and oxygen at the anode, and electrons are generated in this process. The electrons move along the wire to the cathode, and the moved electrons react with carbon dioxide and water at the cathode to decompose into carbon monoxide and hydroxide ions.

[0010] The electrochemical decomposition reaction of carbon dioxide is completed through the above process. At this time, the water supplied along with the carbon dioxide reacts with the electrons that have moved separately from the carbon monoxide generation reaction to undergo electrolysis, generating hydroxide ions and simultaneously producing hydrogen gas. This reaction between water and electrons can be described as a competitive reaction with the carbon monoxide generation reaction. Since these reactions are electrochemical, the amount of carbon monoxide produced and the hydrogen / carbon dioxide ratio can be easily controlled by adjusting the voltage.

[0011] Meanwhile, commercial anion exchange membranes (e.g., Dioxide Material, Sustainion) used as conventional membranes in carbon dioxide electrolysis cells are expensive, posing a significant economic burden, and have low mechanical strength. Consequently, during large-area stack evaluations, the membrane is compressed by the mesh on the anode side, causing pinholes to form. Since the membrane can no longer function to separate the anode and cathode from the moment these pinholes form, reactants and products mix, and the anode and cathode come into contact, causing a short circuit and preventing the electrolysis cell itself from operating. Furthermore, if the thickness, air permeability, porosity, and tensile strength of the membrane do not meet certain standards, the electrolyte on the anode side leaks to the cathode side, resulting in a decrease in electrolysis efficiency.

[0012] (Patent Document 001) KR 1358940 B1

[0013]

[0014] The problem to be solved by the present invention is to provide a membrane that can maintain high chemical / mechanical strength while maintaining high levels of electrolysis efficiency, and an electrolysis cell including the same, in order to solve the above problems when using conventional commercial anion exchange membranes.

[0015]

[0016] The present invention provides a separator, an electrolytic cell including the same, and a method for manufacturing a separator.

[0017] (1) The present invention provides a separator comprising a porous substrate, wherein the thickness of the porous substrate is 60 μm or more and 150 μm or less, the air permeability of the porous substrate is 40 s / 100cc or more and 90 s / 100cc or less, and the tensile strength of the porous substrate according to the following measurement method is 1 MPa or more and 20 MPa or less.

[0018] [measurement method]

[0019] A specimen of a porous substrate cut to a width of 10 mm and a length of 30 mm was fixed to a tensile strength measuring device, and the force at the point of breakage was measured while tensile testing the specimen at a speed of 5 mm per minute.

[0020] (2) The present invention provides a separation membrane according to (1), wherein the porous substrate comprises one or more selected from the group consisting of polyether sulfone, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, nylon and polyolefin.

[0021] (3) The present invention provides a separation membrane in which, in (1) or (2), the porosity of the porous substrate is 10 volume% or more and 55 volume% or less.

[0022] (4) The present invention provides a separation membrane in which, in any one of (1) to (3), the porous substrate is nonionic.

[0023] (5) The present invention provides a separation membrane in any one of (1) to (4), wherein the porous substrate does not contain an ion exchange material inside the pores.

[0024] (6) The present invention provides a separation membrane in which, in any one of (1) to (5), the average pore size of the porous substrate is 30.0 nm or more and 350.0 nm or less.

[0025] (7) The present invention provides a separation membrane in which, in any one of (1) to (6), the thickness of the porous substrate is 60 μm or more and 80 μm or less.

[0026] (8) The present invention provides an electrolytic cell comprising a separator according to any one of (1) to (7); an anode; and a cathode.

[0027] (9) The present invention provides an electrolytic cell in which the electrolytic cell converts carbon dioxide, in the above (8).

[0028] (10) The present invention provides a method for manufacturing a separation membrane comprising the step of pressurizing a porous substrate at a temperature of 100°C or higher and 170°C or lower under a pressure of 1 ton or higher and 5 ton or lower.

[0029] (11) The present invention provides a method for manufacturing a separation membrane in which, in (10) above, the pressurizing step is performed for 1 minute or more and 10 minutes or less.

[0030]

[0031] The separator of the present invention is manufactured by pressurizing a porous substrate at a specific temperature and pressure, and has excellent mechanical strength and chemical properties, thereby possessing high durability and electrolysis efficiency.

[0032] In addition, the problem of the separator being pressed from the conventional rigid anode electrode, causing pinholes, which hinders the smooth transfer of the electrolyte and mixes the products and reactants, and causes a short circuit between the anode and cathode, can be overcome.

[0033]

[0034] Hereinafter, the present invention will be described in more detail to aid in understanding the invention. In this case, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0035] The terms used in this specification are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0036] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0037] In this specification, "porosity" refers to porosity measured using the principle of mercury intrusion porosimetry (MIP). The porosity of a porous substrate can be measured by placing the porous substrate sample into a closed container, injecting mercury into the porous substrate under high pressure, and calculating the ratio of the volume occupied by the pores to the total volume of the porous substrate.

[0038] In this specification, "porous substrate" refers to a substrate having a plurality of pores formed therein, and refers to a substrate through which gas or liquid can permeate. The pores refer to regions within the porous substrate where the constituent material of the porous substrate is not present, and the shape of the pores may be not only spherical but also polyhedral or amorphous, having length, width, and height formed by the intersection of straight or curved elements. For example, the porous substrate may be in the form of a sheet, and an electrolyte containing ions may permeate through the pores of the porous substrate.

[0039] In this specification, the average pore size can be measured using a scanning electron microscope. Specifically, the sample surface can be measured by magnifying it 6,000 times using a scanning electron microscope (FE-SEM, ZEISS MINI300 Scanning Electron Microscope), and then the pore size can be measured by the length of the major axis among the surface pores identified within a randomly sampled range (width 10.0 μm or more, height 15.0 μm or more) in the measured image. The number of measurements can be at least 10, and the average value of the measured pore sizes can be calculated.

[0040]

[0041] Separator

[0042] The present invention provides a separation membrane comprising a porous substrate, wherein the thickness of the porous substrate is 60 μm or more and 150 μm or less, the air permeability of the porous substrate is 40 s / 100cc or more and 90 s / 100cc or less, and the tensile strength of the porous substrate according to the following measurement method is 1 MPa or more and 20 MPa or less.

[0043] [measurement method]

[0044] A specimen of a porous substrate cut to a width of 10 mm and a length of 30 mm was fixed to a tensile strength measuring device, and the force at the point of breakage was measured while tensile testing the specimen at a speed of 5 mm per minute.

[0045] The separator of the present invention comprises a porous substrate. When manufacturing an electrolysis cell by positioning and connecting a conventional commercial anion exchange membrane, such as a sustain ion exchange membrane, between a cathode and an anode, pressure is applied by a mesh or the like on the anode side, causing a compression phenomenon. This compression phenomenon occurs in multiple places across the entire area of ​​the separator, and the compression phenomenon creates pinholes. Here, a pinhole refers to a micro-hole formed when the compressed part burns out during electrolysis operation. If such pinholes are formed, it is difficult for ion exchange between the cathode and the anode to proceed smoothly, and the reactants and products on the cathode and anode sides are mixed, thereby reducing electrolysis efficiency. In particular, the anode and cathode come into contact, causing a short circuit within the electrolysis cell, which may result in the cessation of the carbon dioxide electrolysis reaction.

[0046] Accordingly, the inventor of the present invention used a porous substrate as a separator that improves mechanical strength and physical durability while simultaneously possessing a certain level of porosity and air permeability, thereby suppressing the pinhole phenomenon and enabling smooth ion exchange.

[0047] The thickness of the porous substrate is 60 μm or more and 150 μm or less. For example, the thickness of the porous substrate may be 60 μm or more, 65 μm or more, 70 μm or more, 75 μm or more, 80 μm or more, 85 μm or more, 90 μm or more, 150 μm or less, 145 μm or less, 140 μm or less, 135 μm or less, 130 μm or less, 125 μm or less, 120 μm or less, 115 μm or less, 110 μm or less, 105 μm or less, 100 μm or less, and 95 μm or less. Specifically, the thickness of the porous substrate may each be independently 60 μm or more and 80 μm or less. Here, the thickness of the porous substrate can be measured using a digital high-precision thickness gauge (547-401A) from Mitutoyo. If the thickness of the porous substrate does not satisfy the above range, that is, if the thickness of the porous substrate is excessively thick, the electrical resistance may be high when connected to an electrolysis cell and used, which may degrade the performance of the electrode. In addition, if the thickness of the separator is excessively thin, the mechanical properties of the porous substrate are inferior, making it difficult to stably operate the electrolysis cell.

[0048] In addition, the air permeability of the porous substrate of the present invention is 40 s / 100cc or more and 90 s / 100cc or less. The air permeability refers to the time it takes for a certain volume of gas (e.g., air) to pass through a certain area at a certain pressure when a certain volume of gas (100 cc) is passed through it, and the higher the air permeability, the faster the same amount of gas passes through the membrane. For example, the air permeability of the porous substrate is 10 s / 100cc or more, 11 s / 100cc or more, 13 s / 100cc or more, 15 s / 100cc or more, 17 s / 100cc or more, 19 s / 100cc or more, 20 s / 100cc or more, 21 s / 100cc or more, 23 s / 100cc or more, 25 s / 100cc or more, 27 s / 100cc or more, 29 s / 100cc or more, 30 s / 100cc or more, 31 s / 100cc or more, 33 s / 100cc or more, 35 s / 100cc or more, 37 s / 100cc or more, 39 s / 100cc or more, 40 s / 100cc or more, 41 s / 100cc or more, 43 s / 100cc or more, 45 s / 100cc or more, 47 s / 100cc or more, 49 s / 100cc or more, 50 s / 100cc or more, 120 s / 100cc or less, 115 s / 100cc or less, 110 s / 100cc or less, 105 s / 100cc or less, 100 s / 100cc or less, 95 s / 100cc or less, 90 s / 100cc or less, 87 s / 100cc or less, 85 s / 100cc or less, 80 s / 100cc or less, 75 s / 100cc or less, 70 s / 100cc or less, 69 s / 100cc or less, 67 s / 100cc or less, 65 It may be s / 100cc or less, 63 s / 100cc or less, 61 s / 100cc or less, 60 s / 100cc or less, 59 s / 100cc or less, 57 s / 100cc or less, 55 s / 100cc or less, or 54 s / 100cc or less. More specifically, the air permeability of the porous substrate may be 40 s / 100cc or more and 90 s / 100cc or less.If the permeability of the porous substrate exceeds the upper limit of its numerical range, the movement of ions becomes inefficient when an electric circuit is formed through the separator membrane. This leads to increased resistance, which may result in a decrease in the reaction rate or an increase in the energy consumption required for the reaction. Furthermore, since material transport is not efficient, the transfer of water molecules or ions necessary for the carbon dioxide reduction reaction slows down, which may reduce the efficiency of product formation. On the other hand, if the permeability of the porous substrate exceeds the lower limit of its numerical range, material transport proceeds too easily, potentially causing a crossover phenomenon where the carbon dioxide gas flowing on the cathode side and the electrolyte flowing on the anode side mix across the separator membrane. If this crossover phenomenon occurs, a problem may arise where the electrolysis efficiency drops sharply.

[0049] At this time, air permeability can be measured by the ASTM D726-94 method. Specifically, the air permeability value is 1 in of a porous substrate when 100 cc of air is applied under a pressure of 12.2 inH2O. 2 It is expressed as the time (in seconds) taken to pass through the cross-section, i.e., the air passage time.

[0050] In addition, the tensile strength of the porous substrate according to the following measurement method is 1 MPa or more and 20 MPa or less.

[0051] [measurement method]

[0052] A specimen of a porous substrate cut to a width of 10 mm and a length of 30 mm was fixed to a tensile strength measuring device, and the force at which the specimen broke was measured while tensile testing the specimen at a speed of 5 mm per minute.

[0053] Specifically, the porous substrate was tested using static Materials Testing Machines from ZwickiLine. Specifically, a specimen cut to a width of 10 mm and a length of 30 mm was fixed to the measuring machine, and the force at the moment of breakage was measured while tensile testing the specimen at a speed of 5 mm per minute. Tensile strength refers to the value obtained by dividing the force at which deformation or fracture occurs by the cross-sectional area of ​​the specimen before deformation occurs. The tensile strength of the porous substrate of the present invention may be 1 MPa or more, 3 MPa or more, 5 MPa or more, 7 MPa or more, 9 MPa or more, 10 MPa or more, 10.8 MPa or more, 11 MPa or more, 12 MPa or more, 12.1 MPa or more, 20 MPa or less, 19 MPa or less, 18 MPa or less, 17 MPa or less, 15 MPa or less, 13 MPa or less, and 12.5 MPa or less. High tensile strength means that the material can withstand a high maximum tensile stress before permanent deformation. Generally, since separators are placed within cells with a structure prone to deformation under pressure from electrodes, it is desirable for them to have a high tensile stress to withstand before deformation occurs. Accordingly, if the tensile strength of the porous substrate does not satisfy the above range, it is difficult to secure excellent mechanical strength and durability. Consequently, permanent deformation of the separator may occur, leading to cell short circuits or material crossover phenomena. At the same time, electrical resistance increases, and the electrolysis cell efficiency may be inferior.

[0054]

[0055] According to one embodiment of the present invention, the porous substrate may comprise one or more selected from the group consisting of polyether sulfone, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, nylon, and polyolefin. For example, the porous substrate may comprise polyether sulfone. The polyether sulfone contains sufficient pores within the substrate, and due to its hydrophilic properties, the electrolyte can be sufficiently soaked between the pores, thereby having lower resistance and higher efficiency compared to other porous substrates. Furthermore, ion exchange between the anode and cathode can be smoothly carried out through the pores, and the electrolysis efficiency can be increased due to the low electrical resistance characteristics compared to other materials. Additionally, polyether sulfone has the advantage of being suitable for mass production due to the lower economic burden compared to commercial exchange membranes such as Nafion and Sustainion.

[0056] Additionally, as an example, the porous substrate may include a hydrophilized polytetrafluoroethylene material. Hydrophilized polytetrafluoroethylene has higher chemical resistance compared to other materials and can be very stable against high pH and other conditions that occur during electrochemical reactions.

[0057]

[0058] In addition, according to one embodiment of the present invention, the porosity of the porous substrate may be 10 volume% or more and 60 volume% or less. For example, the above porosity is 10 vol% or more, 11 vol% or more, 13 vol% or more, 13.4 vol% or more, 15 vol% or more, 17 vol% or more, 19 vol% or more, 19.1 vol% or more, 20 vol% or more, 21 vol% or more, 21.8 vol% or more, 22.0 vol% or more, 25 vol% or more, 27 vol% or more, 29 vol% or more, 30 vol% or more, 31 vol% or more, 33 vol% or more, 35 vol% or more, 60 vol% or less, 59 vol% or less, 57 vol% or less, 55 vol% or less, 53 vol% or less, 51 vol% or less, 50 vol% or less, 49 vol% or less, 47 vol% or less, 45 vol% or less, 43 vol% or less, 41 vol% or less, 40 vol% or less, 39 vol% The volume may be 37% or less. Specifically, the porosity of the porous substrate may be 10% or more and 20% or less. The porosity refers to the ratio of the volume of pores to the total volume of the porous substrate. If the porosity of the porous substrate does not exceed the lower limit of the above range, there may not be enough pores within the porous substrate to allow ions to move smoothly through the pores, which may lead to a decrease in the performance of the electrolysis cell containing the separator (porous substrate). Furthermore, if the porosity of the porous substrate exceeds the upper limit of the above range, the mechanical properties of the porous substrate deteriorate, resulting in reduced durability. Additionally, a crossover phenomenon between reactants and products may occur, causing a problem where the electrolysis cell containing the separator (porous substrate) cannot be operated stably. Here, the porosity of the porous substrate can be measured using the principle of Mercury Intrusion Porosimetry (MIP).

[0059]

[0060] According to one embodiment of the present invention, the porous substrate may be nonionic. The porous substrate is nonionic. When the porous substrate is used as a separator, it may have excellent price competitiveness without degrading the performance of the electrochemical carbon dioxide conversion system.

[0061] On the other hand, if the substrate included in the separator is nonporous and non-ionic, it is impossible to operate the electrochemical carbon dioxide conversion system because there are no 'pathways for ion movement,' such as ionic channels. Furthermore, if the substrate included in the separator is nonporous and anionic, although the carbon dioxide conversion rate is good, it is not suitable because it dries out easily at room temperature and may crumble or break. Additionally, if the substrate included in the separator is nonporous and cationic, it is not suitable for use in an electrochemical carbon dioxide conversion system operated under basic conditions. Furthermore, if the current density applied to the electrochemical carbon dioxide conversion system is high, operation is not possible.

[0062] Furthermore, unlike porous substrates with formed pores, conventionally used ion exchange membranes are composed in the form of sheets manufactured using ionic materials. Since the purpose is to facilitate the exchange of desired ions while preventing the movement of fluids other than the ions, it is difficult to form pores in conventionally used ion exchange membranes. Consequently, in the case of such ion exchange membranes, it is difficult to derive the ranges of porosity and air permeability of the porous substrate of the present invention described above.

[0063]

[0064] According to one embodiment of the present invention, the porous substrate may not contain an ion exchange material within the pores. Here, the ion exchange material refers to a material such as a polymer or an ionomer capable of transporting ions between a cathode and an anode. In the case of a conventional separator in which an ion exchange material is filled into the pores of a porous support, ion movement occurs through the ion exchange material; however, since the pores of the porous support are substantially blocked, the porosity is significantly low, and while mechanical strength may be excellent, a problem may arise in which the electrolysis efficiency is reduced in terms of ion permeability. On the other hand, the separator of the present invention uses a porous substrate that does not contain a separate ion exchange material, thereby preventing the phenomenon in which the ion exchange material is impregnated into the pores and affects the porosity, and can maintain operational stability for a long time due to an excellent level of durability.

[0065]

[0066] According to one embodiment of the present invention, the average pore size of the porous substrate may be 30.0 nm or more and 350.0 nm or less. The porous substrate refers to a substrate having numerous holes, i.e., pores, on the surface or inside of the material. The pores may have irregular shapes such as spherical, ellipsoidal, or rod-shaped. For example, the porous substrate may have an average particle size of pores of 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, 100 nm or more, 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more, 350 nm or less, 330 nm or less, 310 nm or less, 300 nm or less, 290 nm or less, 270 nm or less, 250 nm or less, 230 nm or less, 210 nm or less, and specifically, the average particle size of pores may be 100 nm or more and 200 nm or less. When the average particle size of pores of the porous substrate satisfies the above range, ions generated at the cathode can move smoothly through the pores of the separation membrane. Therefore, the carbon dioxide conversion rate of the electrolysis cell including the above-mentioned membrane can be increased, thereby improving the performance of the electrolysis cell. In addition, when the average particle size of the pores satisfies the above range, the mechanical properties of the membrane are superior compared to when the pore particle size is excessively large, so the electrolysis cell including the membrane can be operated stably.

[0067] The average particle size of the above pores can be measured by magnifying the sample surface 6,000 times using a scanning electron microscope (FE-SEM) (ZEISS MINI300 Scanning Electron Microscope), and then determining the pore size by measuring the major axis length of the surface pores identified within a randomly sampled range (width 10 µm or more, height 15 µm or more) in the measured image. The number of measurements is set to at least 10, and the average and maximum / minimum values ​​of the pore sizes obtained after measurement can be calculated.

[0068]

[0069] Method for manufacturing a separation membrane

[0070] The present invention provides a method for manufacturing a separation membrane comprising the step of pressurizing a porous substrate under a temperature condition of 100°C or higher and 170°C or lower and a pressure condition of 1 ton or higher and 5 ton or lower.

[0071] In the case of conventional anion exchange membranes, the mechanical strength was so poor that it crumbled upon drying, making it impossible to measure tensile strength, and the cost was a significant burden, making it impossible to manufacture large-scale separation membranes. Accordingly, porous substrates were used as a means to replace the anion exchange membranes and improve mechanical strength; however, even porous substrates lacked sufficient mechanical strength for long-term operation. Accordingly, the inventor of the present invention developed a method for manufacturing a separation membrane that can improve mechanical strength while maintaining an excellent level of electrolysis efficiency by applying pressure to a porous substrate under specific temperature and pressure conditions.

[0072] The porous substrate may comprise one or more selected from the group consisting of polyether sulfone, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, nylon, and polyolefin. For example, the porous substrate may comprise polyether sulfone and polytetrafluoroethylene.

[0073] In addition, the temperature condition of the pressurizing step is 100 ℃ or higher and 170 ℃ or lower. For example, it may be 100 ℃ or higher, 105 ℃ or higher, 110 ℃ or higher, 115 ℃ or higher, 120 ℃ or higher, 125 ℃ or higher, 130 ℃ or higher, 170 ℃ or lower, 165 ℃ or lower, 160 ℃ or lower, 155 ℃ or lower, 150 ℃ or lower, 145 ℃ or lower, 140 ℃ or lower, and more specifically, it may be 130 ℃ or higher and 150 ℃ or lower. In addition, the pressure condition of the pressurizing step may be 1 ton or higher and 5 ton or lower. For example, the pressure conditions may be 1.0 ton or more, 1.3 ton or more, 1.5 ton or more, 1.7 ton or more, 2.0 ton or more, 2.3 ton or more, 2.5 ton or more, 5.0 ton or less, 4.7 ton or less, 4.5 ton or less, 4.3 ton or less, 4.0 ton or less, 3.7 ton or less, 3.5 ton or less, 3.3 ton or less, 3.0 ton or less, and 2.7 ton or less. When the porous substrate is pressurized under the above temperature and pressure conditions, the thickness and porosity of the porous substrate decrease, and the air permeability and tensile strength increase, thereby improving mechanical strength while suppressing the phenomenon of crossover between reactants and products, and maintaining a high level of electrolysis efficiency.

[0074] In addition, according to an embodiment of the present invention, the pressurizing step may be performed for 1 minute or more and 10 minutes or less. For example, the pressurizing step may be 1 minute or more, 2 minutes or more, 3 minutes or more, 4 minutes or more, 5 minutes or more, 10 minutes or less, 9 minutes or less, 8 minutes or less, 7 minutes or less, and 6 minutes or less. When the pressurizing step is performed satisfying the above range, mechanical strength can be improved more effectively while maintaining an excellent level of electrolysis efficiency.

[0075]

[0076] electrolysis cell

[0077] The electrolytic cell of the present invention may include an anode, a cathode, an electrolyte, and a separator disposed between the cathode and the anode. The separator includes the separator according to the present invention described above.

[0078] According to another embodiment of the present invention, the electrolysis cell can be utilized in an electrochemical conversion device, and the electrochemical conversion device may include a device capable of producing useful chemical substances through electrochemical conversion such as a fuel cell or water electrolysis, and a device capable of being utilized for the reduction and conversion of carbon dioxide and NOx. More specifically, the electrolysis cell may be an electrolysis cell included in an electrolysis device that converts carbon dioxide into carbon monoxide.

[0079] According to one embodiment of the present invention, the electrolysis cell may be a cell that converts carbon dioxide into carbon monoxide by introducing it, and may include an anode, a cathode, an electrolyte, and a separator. Electrolysis refers to the process of decomposing a substance through a redox reaction by applying a direct current voltage to a decomposition reaction that does not occur spontaneously. The anode acts as an oxidation electrode, oxidizing water to generate oxygen, thereby producing hydrogen ions. The hydrogen ions generated at the anode are transferred to the cathode through the electrolyte, and the cathode acts as a reduction electrode, allowing reactants introduced into the cathode to react with electrons and hydrogen ions transferred from the anode to produce a product. Additionally, the separator may be placed between the anode and the cathode. The separator may be composed of an inert material that does not participate in the electrochemical reaction itself, but it may provide a pathway for ions to move between the anode and the cathode and serve to separate physical contact between the anode and the cathode.

[0080] In addition, the anode and the cathode of the electrolysis cell of the present invention may each include a catalyst layer. Furthermore, water vapor supplied along with carbon dioxide within the cathode region generates a reduction product through an electroreduction reaction on the cathode surface. Accordingly, the cathode may include a gas diffusion layer to evenly supply humidified carbon dioxide gas to the cathode region. If the cathode includes a hydrophobic gas diffusion layer, the supplied carbon dioxide can be smoothly diffused, distributed, and supplied to the catalyst layer of the cathode. Additionally, the hydrophobic gas diffusion layer effectively prevents moisture condensation, thereby ensuring a continuous and uniform supply of carbon dioxide while allowing the electrolysis reaction to proceed smoothly. Furthermore, the catalyst layer may have a surface, such as a porous structure, to effectively exhibit gas permeability characteristics on its surface.

[0081] According to one embodiment of the present invention, the anode may include a catalyst active for the electrolysis of water, and the catalyst layer of the anode may include one or more selected from the group consisting of Pt, Au, Pd, Ir, Ag, Rh, Ru, Ni, Al, Mo, Cr, Cu, Ti, W, alloys thereof, or mixed metal oxides, such as Ta2O5, IrO2, etc., for an oxygen generation reaction. Specifically, the anode in the carbon dioxide electrolysis apparatus of the present invention may include a Ti mesh coated with iridium oxide (IrO2).

[0082] In addition, since the carbon dioxide reduction reaction occurring at the cathode competes with the hydrogen generation reaction, it may include a catalyst that exhibits activity in the carbon dioxide reduction reaction while having a high voltage required for the hydrogen generation reaction. The catalyst layer of the cathode may include one or more selected from the group consisting of Sn, Sn alloy, Al, Au, Ag, C, Cd, Co, Cr, Cu, Cu alloy, Ga, Hg, In, Mo, Nb, Ni, NiCo2O4, Ni alloy, Ni-Fe alloy, Pb, Rh, Ti, V, W, Zn, and mixtures thereof for the hydrogen generation reaction. Specifically, the cathode in the carbon dioxide electrolysis device of the present invention may include silver (Ag).

[0083] In addition, the above-described separator may be a separator according to the present invention. The separator may include a porous substrate.

[0084] In addition, the above electrolyte is Cs2CO3, CsOH, KHCO3, K2CO3, KOH, KCl, KClO4, K2SiO3, Na2SO4, NaNO3, NaCl, NaF, NaClO4, CaCl2, guanidinium cation, H + Selected from the group consisting of aqueous solutions containing cations, alkali metal cations, ammonium cations, alkylammonium cations, halide ions, alkyl amines, borates, carbonates, guanidinium derivatives, nitrites, nitrates, phosphates, polyphosphates, perchlorates, silicates, sulfates, tetraalkylammonium salts, or mixtures thereof may be used, and the electrolyte of the carbon dioxide electrolysis device of the present invention may include Cs2CO3.

[0085] In addition, the gas diffusion layer may use a porous body made of carbon material such as carbon fiber cloth, carbon fiber felt, or carbon fiber paper, or a porous metal body made of a thin metal plate with a mesh structure such as expanded metal or metal mesh, and in the carbon dioxide electrolysis device of the present invention, the gas diffusion layer may use carbon fiber paper.

[0086] According to one embodiment of the present invention, the electrolysis device can be utilized in all fields requiring electrochemical conversion, and in particular, can obtain a desired product by electrochemically decomposing carbon dioxide. Specifically, the electrolysis device can produce one or more selected from the group consisting of carbon monoxide, ethylene, methane, formic acid, hydrocarbons, aldehydes, and alcohols by electrolyzing carbon dioxide.

[0087]

[0088] electrolysis device

[0089] The present invention provides an electrolysis apparatus comprising a plurality of separator plates and an electrolysis cell according to the present invention located between the plurality of separator plates. Specifically, the electrolysis apparatus of the present invention may include a membrane electrode assembly in which an anode, a separator, a cathode, and a gas diffusion layer are arranged in sequence; and a separator plate according to the present invention located between the plurality of membrane electrode assemblies. The separator plate may be located on at least one side of the membrane electrode assembly, and specifically, may be included between the membrane electrode assemblies. Furthermore, a membrane electrode assembly including a separator between the anode and the cathode may form an electrolysis unit cell by closely placing the separator plate on one side or both sides of the membrane electrode assembly. The separator plate included in the carbon dioxide electrolysis apparatus of the present invention not only handles the supply or separation of reaction gases but also serves to physically support the membrane electrode assembly and the gas diffusion layer when the cell is connected. Additionally, it may perform functions such as discharging products and managing heat inside the cell through electrical conduction and electrochemical reactions.

[0090]

[0091] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0092]

[0093] Example 1

[0094] A porous substrate made of polyethersulfone (PES) (pore size: 200 nm, thickness: 150 μm, porosity: 55.1 vol%, air permeability: 20 s / 100 cc) was prepared, and the porous substrate was pressurized for 5 minutes at a pressure of 3 ton at a temperature of 130 ℃ using a Carver 4122 press machine. Subsequently, a separation membrane was prepared by sufficiently wetting the surface of the pressurized porous substrate with DI water. The thickness of the prepared separation membrane was 80 μm, the porosity was 19.1 vol%, and the air permeability was 43 s / 100 cc.

[0095]

[0096] Example 2

[0097] A separator was prepared by carrying out the porous substrate of Example 1 in the same manner as Example 1, except for the pressurization point at a temperature of 150 ℃ and a pressure of 5 ton for 5 minutes. The thickness of the prepared separator was 70 μm, the porosity was 13.4 volume%, and the air permeability was 87 s / 100cc.

[0098]

[0099] Comparative Example 1

[0100] The porous substrate of Example 1 above was used as is without a pressurizing process. The thickness of the porous substrate was 150 μm, the porosity was 55.1 volume%, and the air permeability was 20 s / 100cc.

[0101]

[0102] Comparative Example 2

[0103] A separator was prepared by carrying out the porous substrate of Example 1 in the same manner as Example 1, except for the pressurization point at a temperature of 170°C and a pressure of 5 ton for 5 minutes. The thickness of the prepared separator was 48 μm, the porosity was 9.4 volume%, and the air permeability was 113 s / 100cc.

[0104]

[0105] Experimental Example 1

[0106] Carbon dioxide electrolysis was performed by adjusting the operating conditions of a carbon dioxide electrolysis device including a separation membrane prepared according to the examples and comparative examples as follows. In the case of a separation membrane composed of heterogeneous porous substrates, one side of the porous substrate (B) was connected to the anode, and one side of the porous substrate (A) was connected to the cathode.

[0107]

[0108] Reaction current density: 200 mA / cm² 2 , 300 mA / cm 2 (Constant current operation)

[0109] Reaction voltage: 1~4 V

[0110] Reaction temperature: 40 ℃

[0111] Reaction pressure: 1 atm (atmospheric pressure)

[0112] Anode catalyst: IrO2 on Ti mesh

[0113] Cathode catalyst: Ag powder

[0114] Electrode area: 25 cm² 2

[0115] Gas diffusion layer: Sigracet 39BB, JNTG

[0116] Anode electrolyte: 0.25 M Cs2CO3 (25 ml / min)

[0117] Cathode reactant: 40 ℃ Humidified CO2 gas (25 ccm)

[0118] During the above electrolysis, the carbon dioxide conversion rate (%), carbon monoxide Faraday efficiency (CO Faraday efficiency, %), and voltage were measured, and the results are shown in Table 1 below.

[0119]

[0120] * measurement method

[0121] (1) CO2 conversion rate (%)

[0122] The conversion rate (%) was calculated as the ratio of carbon monoxide (CO) produced to the amount of carbon dioxide (CO2) gas input per hour.

[0123]

[0124] (2) Carbon monoxide Faraday efficiency (CO Faraday efficiency, %)

[0125] The gas composition in the exhaust line was measured through GC (Gas-Chromatography) analysis. In addition, the Faraday efficiency was calculated using the following equation.

[0126] [Mathematical Formula 1]

[0127]

[0128] In the above mathematical equation 1, Q is the flow rate in the discharge line, F is the Faraday constant, p is the pressure, T is the measured temperature, and R is the ideal gas constant. Total current (total current, i total ) is the value of the total current applied over time, and the current for the product (i product ) is the volume of gas measured through GC analysis (V product It is a value calculated from ).

[0129]

[0130] (3) Hydrogen Faraday efficiency (H2 Faraday efficiency, %)

[0131] The above hydrogen Faraday efficiency was calculated by analyzing hydrogen gas through GC analysis and measuring it in the same way as the above (2) carbon monoxide Faraday efficiency.

[0132]

[0133] (4) Voltage (V)

[0134] Current application and voltage measurement were performed using a BioLogic VSP potentiostat. An 80 A booster was installed to apply current corresponding to a large area. The applied current was 100 mA / cm². 2 , 200 mA / cm 2 , 300 mA / cm 2 After maintaining the steps for a certain period of time, the voltage was recorded at the point when 30 minutes had elapsed. At this time, Gas Chromatography (GC) analysis was also performed simultaneously.

[0135]

[0136] Experimental Example 2 - Tensile Strength

[0137] The porous substrates of the examples and comparative examples were tested using static Materials Testing Machines from ZwickiLine. Specifically, a specimen cut to a width of 10 mm and a length of 30 mm was fixed to the measuring machine, and the force at the moment of fracture was measured while tensile testing the specimen at a speed of 5 mm per minute. Tensile strength refers to the value obtained by dividing the force at which deformation or fracture occurs by the cross-sectional area of ​​the specimen before deformation occurs.

[0138] Classification Example 1 Example 2 Comparative Example 1 Comparative Example 2 Tensile Strength 10.08 12.15.67 12.68 200 mA / cm 2 Overpotential (V) -2.983 -3.031 -3.18 -3.268 Carbon Monoxide Faraday Efficiency (%) 96.94 95.78 95.36 92.96 Hydrogen Faraday Efficiency (%) 0.32 0.29 0.39 0.77 300 mA / cm² 2 Overvoltage (V) -3.160 -3.227 -3.39 -3.476 Carbon Monoxide Faraday Efficiency (%) 94.30 93.15 90.42 89.82 Hydrogen Faraday Efficiency (%) 0.24 0.26 1.3 1.47

[0139] Referring to Table 1, Examples 1 and 2 are porous substrates that satisfy all the thickness, air permeability, and tensile strength of the present invention, and it can be confirmed that they have low overpotential and high electrical efficiency. On the other hand, Comparative Example 1 does not satisfy the range of the present invention in terms of air permeability and also has a high porosity, resulting in high overpotential and an electrolysis efficiency that is inferior to that of the examples. In addition, Comparative Example 2 has thickness, air permeability, and porosity outside the range of the present invention, and it can be confirmed that it has significantly high overpotential and hydrogen Faraday efficiency, and an electrolysis efficiency that is significantly inferior to that of the examples.

Claims

1. Includes a porous substrate, The thickness of the above porous substrate is 60 μm or more and 150 μm or less, and The air permeability of the above porous substrate is 40 s / 100cc or more and 90 s / 100cc or less, and A separator having a tensile strength of 1 MPa or more and 20 MPa or less according to the following measurement method of the porous substrate. [measurement method] A specimen of a porous substrate cut to a width of 10 mm and a length of 30 mm was fixed to a tensile strength measuring device, and the force at the point of breakage was measured while tensile testing the specimen at a speed of 5 mm per minute.

2. In Claim 1, The above porous substrate is a separator comprising one or more selected from the group consisting of polyether sulfone, cellulose acetate, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, nylon, and polyolefin.

3. In Claim 1, A separation membrane having a porosity of 10 volume% or more and 55 volume% or less of the porous substrate.

4. In Claim 1, The above porous substrate is a nonionic separation membrane.

5. In Claim 1, The above porous substrate is a separation membrane that does not contain an ion exchange material inside the pores.

6. In Claim 1, A separation membrane having a pore average particle size of 30.0 nm or more and 350.0 nm or less of the above porous substrate.

7. In Claim 1, A separation membrane having a thickness of 60 μm or more and 80 μm or less of the porous substrate.

8. An electrolytic cell comprising a separator according to claim 1; an anode; and a cathode.

9. In Claim 8, The above electrolysis cell is an electrolysis cell that converts carbon dioxide.

10. A method for manufacturing a separation membrane comprising the step of pressurizing a porous substrate under a pressure condition of 1 ton or more and 5 ton or less under a temperature condition of 100 ℃ or more and 170 ℃ or less.

11. In Claim 10, A method for manufacturing a separation membrane in which the above-mentioned pressurizing step is performed for 1 minute or more and 10 minutes or less.

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