Separator, electrolysis cell comprising same, and electrolysis device

Abstract

The present invention relates to a separator which comprises a porous substrate and a mesh substrate laminated on one surface of the porous substrate, and which solves the problem of pinholes occurring in a conventional commercial separator by specifying the porosity of the porous substrate and also has high chemical / mechanical strength while maintaining the pore characteristics of the porous substrate and, simultaneously, can maintain a high level of electrolysis efficiency.

Description

Membrane, electrolytic cell and electrolytic device including same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0098801, filed July 25, 2024, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to a separator, an electrolytic cell including the same, and an electrolytic device.

[0006]

[0007] Carbon dioxide is a greenhouse gas that causes global warming and must be reduced. Known methods for reducing carbon dioxide include capture, chemical conversion, and electrochemical conversion. Among these, electrochemical conversion allows for precise control of the composition of other synthetic gases, offering greater economic benefits than simply removing carbon dioxide. Furthermore, electrolysis of carbon dioxide with water can yield carbon monoxide, ethylene, methane, formic acid, formate, various hydrocarbons, and organic compounds such as aldehydes and alcohols.

[0008] The electrochemical decomposition or reduction of carbon dioxide is categorized by ion exchange method. When using a cation exchange membrane, water is supplied to the anode and an electric current is applied. This causes the water to decompose at the anode, generating oxygen, electrons, and hydrogen ions. These hydrogen ions then migrate to the cathode through the cation exchange membrane. 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, resulting in a reduction reaction and conversion into another substance.

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

[0010] Through the above process, the electrochemical decomposition reaction of carbon dioxide is completed. At this time, the water supplied together with the carbon dioxide reacts with the electrons transferred separately from the carbon monoxide production reaction, undergoing electrolysis to produce hydroxide ions and simultaneously generate hydrogen gas. This reaction between water and electrons can be said to be a competitive reaction with the carbon monoxide production reaction. Since the above reactions are electrochemical reactions, 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 and porous membranes used in carbon dioxide electrolysis cells have low mechanical strength, and when evaluating large-area stacks, the mesh on the anode side causes the membrane to be pressed, creating pinholes. From the moment the pinholes are created, the membrane cannot separate the anode and cathode, so the reactants and products mix, and the anode and cathode come into contact, causing a short circuit, which prevents the electrolysis cell itself from operating. In addition, when the thickness of the membrane does not reach a certain level, the electrolyte on the anode side flows over to the cathode side, causing a problem of reduced electrolysis efficiency.

[0012] (Patent Document 001) KR 1358940 B1

[0013]

[0014] The problem to be solved by the present invention is to provide a separator that can solve the problem of pinholes occurring in conventional commercial separators, while maintaining the pore characteristics of a porous substrate, while having high chemical / mechanical strength and maintaining a high level of electrolysis efficiency, and an electrolysis cell and electrolysis device including the same.

[0015]

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

[0017] (1) The present invention provides a separation membrane comprising a porous substrate and a mesh substrate laminated on one surface of the porous substrate, wherein the porosity of the porous substrate is 20% by volume or more and 95% by volume or less.

[0018] (2) The present invention provides a separation membrane in which the average particle diameter of the pores of the porous substrate in the above (1) is 10 nm or more and 5 μm or less.

[0019] (3) The present invention provides a separation membrane according to (1) or (2), wherein the porous substrate comprises at least one material selected from the group consisting of polyethersulfone, hydrophilized polytetrafluoroethylene, polytetrafluoroethylene, polyvinylidene fluoride, cellulose acetate, polyamide, and polyethersulfone.

[0020] (4) The present invention provides a separation membrane in which the mesh substrate comprises at least one material selected from the group consisting of polyethylene terephthalate, polyether ether ketone, polyamide, nylon, carbon-coated polyethylene terephthalate, polyacrylonitrile, polypropylene, polyethylene, ethylene tetrafluoroethylene, and ethylene-chlorotrifluoroethylene in any one of the above (1) to (3).

[0021] (5) The present invention provides a separation membrane according to any one of the above (1) to (4), wherein the thickness of the porous substrate is 10 ㎛ or more and 500 ㎛ or less.

[0022] (6) The present invention provides a separation membrane according to any one of the above (1) to (5), wherein the thickness of the mesh substrate is 5 ㎛ or more and 150 ㎛ or less.

[0023] (7) The present invention provides a separation membrane according to any one of the above (1) to (6), which does not include a binder or adhesive between the porous substrate and the mesh substrate.

[0024] (8) The present invention provides a separation membrane in which the mesh substrate has a void ratio of 30% or more and 80% or less in any one of the above (1) to (7).

[0025] (9) The present invention provides a separation membrane in the above (2), wherein the porous substrates each independently have an average pore diameter of 100 nm or more and 500 nm or less.

[0026] (10) The present invention provides a separation membrane according to any one of the above (1) to (9), wherein the porous substrate and the mesh substrate do not contain an ion exchange material inside the pores.

[0027] (11) The present invention provides an electrolytic cell comprising an anode; a cathode; and a separator disposed between the cathode and the anode, wherein the separator is a separator according to any one of (1) to (10).

[0028] (12) The present invention provides an electrochemical cell in which one side of the mesh substrate of the separator is in contact with the anode, and one side of the porous substrate is in contact with the cathode in the above (11).

[0029] (13) The present invention provides an electrochemical cell that converts carbon dioxide in any one of the above (11) or (12).

[0030] (14) The present invention provides an electrolytic device including a plurality of separators and an electrolytic cell according to any one of (11) to (13) positioned between the plurality of separators.

[0031]

[0032] The separation membrane of the present invention can have high durability and electrolysis efficiency by improving mechanical strength and chemical properties by laminating a mesh substrate on one side of a porous substrate.

[0033] In addition, it is possible to overcome the problems of the conventional solid anode electrode being pressed against the separator, causing pinholes, resulting in poor electrolyte transport, mixing of products and reactants, and short circuits between the anode and cathode.

[0034] By suppressing the pressing phenomenon by the mesh on the anode side, the transport of electrolyte and ion exchange are smoothly performed, and thus low overvoltage, high conversion rate, and faradaic efficiency can be achieved.

[0035] In addition, by laminating a heterogeneous or homogeneous porous substrate and a mesh substrate without a separate binder or adhesive, it is possible to have low electrical resistance and prevent the anode-side electrolyte from flowing over to the cathode side.

[0036]

[0037] Figure 1 shows a cross-section of the separation membrane of Comparative Example 1.

[0038] Figure 2 shows the surface of the separation membrane of Comparative Example 1.

[0039] Figure 3 shows a cross-section of the separation membrane of Example 1.

[0040] Figure 4 shows the surface of the separation membrane of Example 1.

[0041]

[0042] Hereinafter, the present invention will be described in more detail to facilitate understanding. The terms and words used in this specification and claims should not be interpreted based on their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0043] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0044] In this specification, it should be understood that terms such as “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0045] 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 as a sample in a closed container, injecting mercury into the porous substrate at high pressure, and calculating the ratio of the volume occupied by pores to the total volume of the porous substrate.

[0046] In this specification, the term "porous substrate" refers to a substrate having a plurality of pores formed therein, through which gas or liquid can pass. The pores refer to regions within the porous substrate where no constituent material of the porous substrate exists, and the shape of the pores may be not only spherical, but also polyhedral or amorphous, having length, width, and height determined by intersection of straight or curved elements. For example, the porous substrate may be in the form of a sheet, and an electrolyte containing ions can pass through the pores of the porous substrate.

[0047]

[0048] membrane

[0049] The present invention provides a separation membrane comprising a porous substrate and a mesh substrate laminated on one surface of the porous substrate, wherein the porosity of the porous substrate is 20% by volume or more and 95% by volume or less.

[0050] The separator of the present invention comprises a porous substrate and a mesh substrate laminated on one surface of the porous substrate. In the case of conventional commercial exchange membranes such as anion exchange membranes, sustain ion exchange membranes, AEMION exchange membranes, PiperION exchange membranes, and porous substrates, when manufacturing an electrolysis cell by positioning and fastening them between the cathode and the anode, pressure is applied by the mesh on the anode side, causing a pressing phenomenon. This pressing phenomenon occurs numerous times over the entire area of ​​the separator, and the pressing phenomenon creates pinholes. Here, a pinhole refers to a microscopic hole formed when the pressed portion is burned during electrolysis. FIGS. 1 and 2 are cross-sections and surface views taken after using a conventional separator of a comparative example. Referring to FIGS. 1 and 2, it can be seen that the membrane is dented and burned to form holes compared to the original thickness. For example, in the case of a separator having a thickness of approximately 150 ㎛, it is depressed by pressure from an anode mesh, etc., to the extent that a thickness of approximately 30 ㎛ remains, and this depressed portion burns during electrolysis operation to form a microscopic hole, i.e., a pinhole. If such a pinhole is formed, ion exchange between the cathode and the anode does not occur smoothly, and the reactants and products of the cathode and the anode are mixed, lowering the electrolysis efficiency. In addition, the anode and cathode may come into contact, causing a short circuit within the electrolysis cell, which may cause the carbon dioxide electrolysis reaction to stop.

[0051] Accordingly, the inventor of the present invention used a mesh substrate as a separator by laminating it on one surface of a porous substrate to improve mechanical strength and physical durability, thereby suppressing the pinhole phenomenon, and further, by using a porous substrate having a porosity above a certain range, enabled smooth ion exchange to occur.

[0052] Fig. 3 shows a cross-section of the separator of Example 1, and Fig. 4 shows the surface of the separator of Example 1. Fig. 3 shows a cross-section of the separator of Example 1, and more specifically, it shows a cross-section of the porous substrate after the electrolysis cell was operated after applying the mesh substrate. Compared to Fig. 1, it can be confirmed that the degree of compression by the mesh substrate was significantly alleviated. Fig. 4 also shows the surface of the separator, and no anode electrode shape was visible at all on the surface.

[0053] The porosity of the above porous substrate is 20% by volume or more and 95% by volume or less, and for example, the porosity may be 20% by volume or more, 25% by volume or more, 30% by volume or more, 35% by volume or more, 40% by volume or more, 45% by volume or more, 50% by volume or more, 55% by volume or more, 55.1% by volume or more, 95% by volume or less, 90% by volume or less, 85% by volume or less, 80% by volume or less, 75% by volume or less, 70% by volume or less, 65% by volume or less, or 60% by volume or less. More specifically, the porosity of the above porous substrate may be 50% by volume or more and 95% by volume or 50% by volume or more and 65% by volume. The above 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 is less than the lower limit of the above range, pores in the porous substrate are not sufficiently present, and ions cannot smoothly move through the pores, so the performance of the electrochemical cell including the separator may deteriorate. In addition, if the porosity of the porous substrate is less than the upper limit of the above range, the mechanical properties of the separator may deteriorate, resulting in lower durability. In addition, a crossover phenomenon of reactants and products may occur, which may cause a problem in that the electrochemical cell including the separator cannot be stably operated.

[0054] According to one embodiment of the present invention, the porous substrate and the mesh substrate may not contain an ion exchange material inside the pores. Here, the ion exchange material refers to a material such as a polymer or ionomer that can transport ions between the cathode and the anode. In the case of a conventional separator in which the pores of a porous support are filled with an ion exchange material, the movement of ions occurs through the ion exchange material, but the pores of the porous support are substantially blocked, resulting in a significantly low porosity. Therefore, although the mechanical strength may be excellent, the problem of reduced electrolysis efficiency in terms of ion permeability may occur. On the other hand, in the case of the separator of the present invention, by using a mesh substrate laminated on a porous substrate without a separate ion exchange material, the phenomenon of the ion exchange material being impregnated into the pores and affecting the porosity can be prevented, and the operation stability can be maintained for a long time due to an excellent level of durability.

[0055] In addition, in the case of the separation membrane of the present invention, if more than two sheets of porous substrates or mesh substrates of the same or different types are laminated, the electrical resistance may rapidly increase due to excessive thickness increase, which may cause a problem of reduced electrolysis efficiency.

[0056] According to one embodiment of the present invention, the average particle diameter of the pores of the porous substrate may be 10 nm or more and 5 μm 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 an irregular shape, such as a sphere, an ellipsoid, or a rod shape. For example, the porous substrate has an average pore diameter of 10 nm or more, 20 nm or more, 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, 5000 nm or less, 4000 nm or less, 3000 nm or less, 2000 nm or less, 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, 500 nm or less, 450 nm or less, 430 nm or less, 410 nm or less, 400 nm or less, 390 nm or less, 370 nm or less, 350 nm or less, 330 nm or less, It may be 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, or 200 nm or less, and specifically, the average particle size of the pores may be 30 nm or more and 450 nm or less, or 100 nm or more and 200 nm or less. When the average particle size of the pores of the porous substrate satisfies the above range, ions generated at the cathode can smoothly move through the pores of the separator. Therefore, the carbon dioxide conversion rate of the electrochemical cell including the separator increases, so that the performance of the electrochemical cell can be improved. In addition, when the average particle size of the pores satisfies the above range, the mechanical properties of the separator are superior compared to when the pore size is excessively large, so that the electrochemical cell including the separator can be stably operated.

[0057] The average particle size of the above pores can be measured by measuring the surface of the sample at 6,000 times magnification using a scanning electron microscope (FE-SEM) (ZEISS MINI300 Scanning Electron Microscope), and then measuring the major axis length of the surface pores confirmed in a randomly sampled range (10 μm or more in width and 15 μm or more in length) within the measured image. The number of measurements should be at least 10 or more, and the average and maximum / minimum values ​​of the pore sizes obtained after the measurement can be obtained.

[0058] According to one embodiment of the present invention, the porous substrate may include one or more materials selected from the group consisting of polyethersulfone, hydrophilized polytetrafluoroethylene, polytetrafluoroethylene, polyvinylidene fluoride, cellulose acetate, polyamide, and polyethersulfone. For example, the porous substrate may include polyethersulfone or a hydrophilized polytetrafluoroethylene material. The polyethersulfone has sufficient pores within the substrate, and thus, due to its hydrophilic nature, the electrolyte can sufficiently wet between the pores, thereby having lower resistance and higher efficiency compared to other porous substrates.

[0059] These pores facilitate smooth ion exchange between the anode and cathode, and their low electrical resistance compared to other materials enhances electrolysis efficiency. Furthermore, polyethersulfone offers the advantage of being less costly than commercially available exchange membranes such as Nafion and Sustainion, making it suitable for mass production.

[0060] Furthermore, hydrophilic polytetrafluoroethylene exhibits higher chemical resistance than other materials, making it highly stable under conditions such as high pH levels encountered during electrochemical reactions. Therefore, when hydrophilic polytetrafluoroethylene or polyethersulfone is incorporated into the porous substrate, low resistance and high electrolysis efficiency can be achieved, enabling stable electrochemical reactions to occur.

[0061]

[0062] According to one embodiment of the present invention, the mesh substrate may include one or more materials selected from the group consisting of polyethylene terephthalate, polyether ether ketone, polyamide, nylon, carbon-coated polyethylene terephthalate, polyacrylonitrile, polypropylene, polyethylene, ethylene tetrafluoroethylene, and ethylene-chlorotrifluoroethylene, and specifically, may include polyethylene terephthalate or polyether ether ketone. When the mesh substrate includes a polyethylene terephthalate or polyether ether ketone material, the electrochemical reaction may proceed stably due to high chemical resistance and heat resistance.

[0063] According to one embodiment of the present invention, the thickness of the porous substrate may be 10 ㎛ or more and 500 ㎛ or less, and for example, the thickness of the porous substrate may be 10 ㎛ or more, 20 ㎛ or more, 30 ㎛ or more, 40 ㎛ or more, 50 ㎛ or more, 500 ㎛ or less, 450 ㎛ or less, 400 ㎛ or less, 350 ㎛ or less, 300 ㎛ or less, 250 ㎛ or less, 200 ㎛ or less, 190 ㎛ or less, 180 ㎛ or less, 170 ㎛ or less, 160 ㎛ or less, or 150 ㎛ or less. More specifically, the thickness of the porous substrate may be 30 ㎛ or more and 200 ㎛ or less, or 50 ㎛ or more and 150 ㎛ or less. When the thickness of the porous substrate satisfies the above range, the resistance of the separator is lowered compared to when the separator is excessively thick, thereby improving electrode performance. Furthermore, compared to when the separator is excessively thin, the mechanical properties of the separator are superior, allowing for stable operation of an electrochemical cell including the separator.

[0064] According to one embodiment of the present invention, the thickness of the mesh substrate may be 5 ㎛ or more and 150 ㎛ or less. For example, the thickness of the mesh substrate may be 5 ㎛ or more, 10 ㎛ or more, 15 ㎛ or more, 20 ㎛ or more, 25 ㎛ or more, 30 ㎛ or more, 35 ㎛ or more, 40 ㎛ or more, 45 ㎛ or more, 50 ㎛ or more, 55 ㎛ or more, 60 ㎛ or more, 65 ㎛ or more, 70 ㎛ or more, 150 ㎛ or less, 145 ㎛ or less, 140 ㎛ or less, 135 ㎛ or less, 130 ㎛ or less, 125 ㎛ or less, 120 ㎛ or less, 115 ㎛ or less, 110 ㎛ or less, 105 ㎛ or less, 100 ㎛ or less, 95 ㎛ or less, 90 ㎛ or less, 85 ㎛ or less, 80 ㎛ or less, 75 ㎛ or less, and specifically, the thickness of the mesh substrate may be 20 It may be ㎛ or more and 95 ㎛ or less, or 40 ㎛ or more and 90 ㎛ or less. When the thickness of the mesh substrate satisfies the above thickness range, the electrical resistance derived from the thickness is reduced, but the mesh substrate has an excellent level of mechanical strength, so that the pressing phenomenon occurring from the anode side is suppressed, and the mesh substrate can be operated for a long time when connected to an electrolysis cell.

[0065] In addition, according to one embodiment of the present invention, the thickness of the porous substrate and the mesh substrate may be the same or different from each other. For example, when the porous substrate includes hydrophilized polyethersulfone and the mesh substrate includes polyethylene terephthalate or polyether ether ketone, the thickness of the mesh substrate may be thinner than the thickness of the porous substrate. The mesh substrate including polyethylene terephthalate or polyether ether ketone may serve as a kind of support that improves the mechanical strength of the separator. In this case, as the thickness of the mesh substrate becomes thicker than that of the porous substrate, the mechanical strength may be improved, but the electrical resistance may increase, which may lower the electrolysis efficiency.

[0066] Additionally, according to one embodiment of the present invention, the space ratio of the mesh substrate may be 30% or more and 80% or less. The space ratio refers to the ratio of the space between parallel longitudinal and transverse lines within the mesh, and can be calculated according to Equation 1 below.

[0067] [Formula 1]

[0068] Space ratio (%) = {(tree) / (tree + line diameter)} 2 x 100

[0069] In the above equation 1, the opening refers to the vertical distance between the inner surfaces of two adjacent parallel lines, and the wire diameter refers to the thickness or diameter of the wires that make up the mesh. Even for the same mesh, the opening and space ratio may vary depending on differences in wire diameter.

[0070] The void ratio of the mesh substrate of the present invention may be, for example, 30% or more, 31% or more, 33% or more, 33.5% or more, 35% or more, 37% or more, 37.5% or more, 39% or more, 80% or less, 79% or less, 75% or less, 73% or less, 70% or less, 67% or less, 65% or less, 63% or less, 60% or less, 57% or less, 55% or less, 53% or less, 51% or less, 50% or less, 49% or less, 47% or less, 45% or less, 44.5% or less, 43% or less, 41% or less, 40% or less, and specifically, the void ratio of the mesh substrate may be 33.5% or more and 70% or less. When the void ratio of the mesh substrate satisfies the above range, it is possible to maintain a high level of ion permeability while maintaining an excellent level of mechanical strength, and to improve electrolysis efficiency.

[0071] According to one embodiment of the present invention, a separator is provided that does not include a binder or adhesive between the porous substrate and the mesh substrate. Specifically, the separator of the present invention is manufactured by laminating porous substrates or mesh substrates having hydrophilic properties without using a binder, and thus, a thinner separator can be manufactured compared to separators manufactured using existing binders or adhesives. Furthermore, when manufacturing the separator of the present invention, due to the moisture present in the porous substrate and the fastening pressure applied during the process of fastening the electrolysis cell, the two separators can maintain a zero-gap state without a very small gap, and the porous substrates can be fixed so as not to move between each other. Therefore, the manufacturing time of the separator according to the present invention can be shortened compared to the manufacturing time of a separator through conventional heat treatment or separate pretreatment. Furthermore, since the separator is manufactured by laminating and bonding porous substrates without using a separate binder or adhesive, side reactions caused by the binder or adhesive can be prevented, thereby reducing electrical resistance and preventing a decrease in efficiency.

[0072] On the other hand, when using a method such as coating or heat treatment using a binder or adhesive, even if a very small amount of binder or adhesive is used, a layer may be formed between the porous substrates, affecting the thickness, thereby reducing the electrical resistance, and there is a concern that the porous substrate may be thermally deformed due to the coating or heat treatment.

[0073]

[0074] electrolysis cell

[0075] The electrochemical conversion 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.

[0076] According to another embodiment of the present invention, the electrochemical cell can be utilized in all electrochemical conversion devices, and the electrochemical conversion devices can include devices capable of producing useful chemical substances through electrochemical conversion, such as fuel cells and water electrolysis, and devices capable of reducing and converting carbon dioxide and NOx. More specifically, the electrochemical conversion cell can be an electrochemical conversion cell included in an electrolysis device that converts carbon dioxide into carbon monoxide.

[0077] According to one embodiment of the present invention, the electrochemical cell may be a cell that converts carbon dioxide into carbon monoxide by injecting it, and may include an anode, a cathode, an electrolyte, and a separator. Electrolysis refers to decomposing a substance through a redox reaction by applying a direct current voltage to a decomposition reaction that does not occur spontaneously. The anode serves as an oxidation electrode that oxidizes water to generate oxygen, and at this time, hydrogen ions are generated. The hydrogen ions generated at the anode are transferred to the cathode through the electrolyte, and the cathode serves as a reduction electrode in which reactants input to the cathode can react with electrons and hydrogen ions moved from the anode to generate products. In addition, the separator may be disposed 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 may provide a path for ions to move between the anode and the cathode and may serve to isolate physical contact between the anode and the cathode.

[0078] In addition, the anode and the cathode of the electrochemical cell of the present invention may each include a catalyst layer. In addition, water vapor supplied together with carbon dioxide within the cathode region generates a reduction product through an electroreduction reaction on the cathode surface. Therefore, the cathode may include a gas diffusion layer to evenly supply humidified carbon dioxide gas to the cathode region. When 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. In addition, the hydrophobic gas diffusion layer effectively prevents moisture condensation, thereby ensuring a continuous and uniform supply of carbon dioxide and allowing the electrolysis reaction to proceed smoothly. In addition, the catalyst layer may have a surface such as a porous structure so as to exhibit good gas permeability characteristics on the surface.

[0079] According to one embodiment of the present invention, the anode may include a catalyst active in the electrolysis of water, and the catalyst layer of the anode may include at least one 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, for an oxygen generation reaction. Specifically, the anode in the carbon dioxide electrolysis device of the present invention may include a Ti mesh (Ti-mesh) coated with iridium oxide (IrO2).

[0080] In addition, since the carbon dioxide reduction reaction occurring at the cathode competes with the hydrogen evolution reaction, a catalyst that requires a high voltage for the hydrogen evolution reaction and is active in the carbon dioxide reduction reaction may be included. The catalyst layer of the cathode may include at least one selected from the group consisting of Sn, a Sn alloy, Al, Au, Ag, C, Cd, Co, Cr, Cu, a Cu alloy, Ga, Hg, In, Mo, Nb, Ni, NiCo2O4, a Ni alloy, a Ni-Fe alloy, Pb, Rh, Ti, V, W, Zn, and mixtures thereof for the hydrogen evolution reaction. Specifically, the cathode in the carbon dioxide electrolysis device of the present invention may include silver (Ag).

[0081] In addition, the separator may be a separator according to the present invention described above. The separator may include a porous substrate and a mesh substrate, and one side of the mesh substrate may be in contact with the anode, and one side of the porous substrate may be in contact with the cathode.

[0082] In addition, the electrolyte may be Cs2CO3, CsOH, KHCO3, K2CO3, KOH, KCl, KClO4, K2SiO3, Na2SO4, NaNO3, NaCl, NaF, NaClO4, CaCl2, guanidinium cation, H + A cation, an alkali metal cation, an ammonium cation, an alkylammonium cation, a halide ion, an alkyl amine, a borate, a carbonate, a guanidinium derivative, a nitrite, a nitrate, a phosphate, a polyphosphate, a perchlorate, a silicate, a sulfate, a tetraalkyl ammonium salt, or a mixture thereof may be used. The electrolyte of the carbon dioxide electrolysis device of the present invention may include Cs2CO3.

[0083] In addition, the gas diffusion layer may use a porous body using a carbon material such as carbon fiber cloth, carbon fiber felt, or carbon fiber paper, or a metal porous 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.

[0084] According to one embodiment of the present invention, the electrolysis device can be used in all fields requiring electrochemical conversion, and in particular, can electrochemically decompose carbon dioxide to obtain a desired product, and specifically, the electrolysis device can electrolyze carbon dioxide to produce one or more selected from the group consisting of carbon monoxide, ethylene, methane, formic acid, hydrocarbons, aldehydes, and alcohols.

[0085]

[0086] electrolysis device

[0087] The present invention provides an electrolysis device comprising a plurality of separators and an electrolysis cell according to the present invention positioned between the plurality of separators. Specifically, the electrolysis device of the present invention may include a membrane electrode assembly in which an anode, a separator, a cathode, and a gas diffusion layer are sequentially arranged; and a separator according to the present invention positioned between a plurality of the membrane electrode assemblies. The separator may be positioned on at least one side of the membrane electrode assembly, and specifically, may be included between the membrane electrode assemblies. In addition, the membrane electrode assembly including a separator between the anode and the cathode may form an electrolysis unit cell by closely arranging the separator on one or both sides of the membrane electrode assembly. The separator included in the carbon dioxide electrolysis device of the present invention may not only be responsible for supplying or separating a reaction gas, but may also serve to physically support the membrane electrode assembly and the gas diffusion layer when the cell is fastened, and may also serve to discharge products through electrical conduction and electrochemical reaction and manage heat within the cell.

[0088]

[0089] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0090]

[0091] Example 1

[0092] One sheet of a porous substrate (pore size: 200 nm, thickness: 150 ㎛, porosity: 55.1% by volume) made of PES (polyethersulfone) and one sheet of a mesh substrate (space ratio: 44.5%, thickness: 45 ㎛) made of polyethylene terephthalate were prepared. The surfaces of the porous substrate and the mesh substrate were sufficiently wetted with DI water, and after the porous substrate and the mesh substrate were brought into contact, a constant pressure was applied to sufficiently bond the interfaces to manufacture a separation membrane.

[0093]

[0094] Example 2

[0095] In Example 1, a separation membrane was manufactured in the same manner as in Example 1, except that instead of preparing one sheet of mesh substrate (void ratio: 44.5%, thickness: 45 ㎛) made of polyethylene terephthalate, one sheet of mesh substrate (void ratio: 70%, thickness: 45 ㎛) made of polyether ether ketone was prepared.

[0096]

[0097] Comparative Example 1

[0098] A porous substrate (pore size: 200 nm, thickness: 150 ㎛, porosity: 55.1% by volume) made of PES (polyethersulfone) was prepared and used as a separation membrane.

[0099]

[0100] Comparative Example 2

[0101] A porous substrate (pore size: 200 nm, thickness: 75 ㎛, porosity: 18% by volume) made of PES (polyethersulfone) was prepared and used as a separation membrane.

[0102]

[0103] Comparative Example 3

[0104] In Example 1, a separation membrane was manufactured in the same manner as in Example 1, except that one sheet of a porous substrate (pore size: 200 nm, thickness: 100 ㎛, porosity: 18% by volume) made of PES (polyethersulfone) was prepared instead of the porous substrate of Example 1.

[0105]

[0106] Experimental Example 1 - Measurement of electrolysis efficiency

[0107] Carbon dioxide electrolysis was performed by adjusting the operating conditions of the carbon dioxide electrolysis device as follows using the membranes manufactured in the examples and comparative examples. One side of the mesh substrate of the membrane was connected to the anode, and one side of the porous substrate was connected to the cathode.

[0108] Reaction current density: 100 mA / cm 2 , 200 mA / cm 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 cm 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 conversion rate of carbon dioxide (%), carbon monoxide Faraday efficiency (CO Faraday efficiency, %), hydrogen Faraday efficiency (H2Faraday efficiency, %), and overvoltage were measured, and the results are shown in Table 1 below.

[0119]

[0120] * measurement method

[0121] (1) Carbon dioxide conversion rate (%)

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

[0123]

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

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

[0126] [Mathematical Formula 1]

[0127]

[0128] In the above mathematical expression 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. The 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 ) is the 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 carbon monoxide Faraday efficiency (2).

[0132]

[0133] (4) Voltage (V)

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

[0135]

[0136] Experimental Example 2 - Long-term Performance Characteristics

[0137] For the membranes of Example 1 and Comparative Example 1, the current density was 500 mA / cm 2 Except for the conditions, it was operated for 100 hours under the same conditions as Experimental Example 1. During the 100-hour operation, the conversion rate of carbon dioxide (%), carbon monoxide Faraday efficiency (CO Faraday efficiency, %), hydrogen Faraday efficiency (H2Faraday efficiency, %), and overvoltage were measured, and the results are shown in Table 2 below.

[0138]

[0139] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 100 mA / cm 2Overvoltage (V) -2.631-2.778-2.767-2.743-2.878Carbon monoxide Faraday efficiency (%) 100.00100.0099.3599.298.4Hydrogen Faraday efficiency (%) 0.230.370.380.470.55Carbon dioxide conversion rate (%) 9.609.599.509.449.55200 mA / cm 2 Overvoltage (V) -3.034-3.078-2.985-2.983-3.043Carbon monoxide Faraday efficiency (%) 98.6798.3297.8296.9496.71Hydrogen Faraday efficiency (%) 0.230.260.260.320.31Carbon dioxide conversion rate (%) 18.5718.6118.7218.4518.43300 mA / cm 2 Overvoltage (V) -3.259-3.270-3.132-3.16-3.368Carbon monoxide Faraday efficiency (%) 96.6896.5795.7694.392.93Hydrogen Faraday efficiency (%) 0.200.210.220.240.77Carbon dioxide conversion rate (%) 27.3027.4127.4926.9226.55

[0140] Current density 500 mA / cm 2 Operating time (Hr) Overvoltage (V) Carbon monoxide Faraday efficiency (%) Hydrogen Faraday efficiency (%) Carbon dioxide conversion rate (%) Example 10.5-3.493.360.08724.483-3.4592.360.08624.224-3.4792.920.10124.3717-3.5691.410.31723.9721-3.5591.060.34723.8824.5-3.5690.810.38023.8189.5-3.6290.060.80723.6294-3.6190.210.62823.6697-3.6490.180.63823.65100-3.6190.960.68023.85Comparative example 10.5-3.27093.390.2024.531.5-3.3393.250.1924.4937-3.6128.626.917.4437.5----

[0141] Referring to Tables 1 and 2, it can be confirmed that the separators of Examples 1 and 2 include a mesh substrate, which increases the overvoltage. However, when compared to Comparative Examples 1 and 2, which do not include a mesh substrate, it can be confirmed that they have overvoltage and electrolysis efficiency at the same or higher level. However, when a long-term operation test was conducted at a high current density, Example 1, which includes a mesh substrate, showed a small increase in overvoltage and a very small decrease in electrolysis efficiency when operated for 100 hours, confirming that it has excellent long-term durability. On the other hand, in the case of Comparative Example 1, which does not include a mesh substrate, when operated at a high current density, the electrolysis efficiency rapidly decreased after about 37 hours, so it is predicted that the separator was pressed down by the anode mesh, and pinholes were formed thereafter, preventing the electrolysis cell from operating.

[0142] Through this, it can be confirmed that the separator of the present invention includes a mesh substrate and can maintain excellent levels of overvoltage and electrolysis efficiency for a long period of time.

[0143] In addition, Comparative Example 3 uses a porous substrate that does not satisfy the porosity range of the porous substrate of the present invention, and it can be confirmed that the overvoltage is higher and the carbon monoxide Faraday efficiency is poor compared to the examples.

Claims

1. A porous substrate; and a mesh substrate laminated on one surface of the porous substrate, A separation membrane in which the porosity of the above porous substrate is 20% by volume or more and 95% by volume or less.

2. In claim 1, A separation membrane having an average particle diameter of pores of the porous substrate of 10 nm or more and 5 μm or less.

3. In claim 1, A membrane in which the porous substrate comprises at least one material selected from the group consisting of hydrophilic polytetrafluoroethylene, polytetrafluoroethylene, polyvinylidene fluoride, cellulose acetate, polyamide, and polyethersulfone.

4. In claim 1, A membrane in which the mesh substrate comprises at least one material selected from the group consisting of polyethylene terephthalate, polyether ether ketone, polyamide, nylon, carbon-coated polyethylene terephthalate, polyacrylonitrile, polypropylene, polyethylene, ethylene tetrafluoroethylene, and ethylene-chlorotrifluoroethylene.

5. In claim 1, A separation membrane wherein the thickness of the porous substrate is 10 ㎛ or more and 500 ㎛ or less.

6. In claim 1, A separation membrane having a thickness of the above mesh substrate of 5 ㎛ or more and 150 ㎛ or less.

7. In claim 1, A separator that does not contain a binder or adhesive between the porous substrate and the mesh substrate.

8. In claim 1, The above mesh substrate is a separation membrane having a void ratio of 30% or more and 80% or less.

9. In claim 1, The above porous substrate is a separation membrane having an average pore diameter of 10 nm or more and 500 nm or less.

10. In claim 1, A separation membrane in which the porous substrate and the mesh substrate do not contain an ion exchange material inside the pores.

11. Anode; Cathode; and A separator disposed between the cathode and the anode, An electrolysis cell wherein the above separator is a separator according to claim 1.

12. In claim 11, An electrochemical cell wherein one side of the mesh substrate of the above separator is in contact with the anode, and one side of the porous substrate is in contact with the cathode.

13. In claim 11, The above electrochemical cell is an electrochemical cell that converts carbon dioxide.

14. An electrolytic device comprising a plurality of separators and an electrolytic cell according to claim 11 positioned between the plurality of separators.

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