Electrolysis cell and manufacturing method therefor

Abstract

The present invention relates to an electrolysis cell comprising, in order to have low interfacial resistance and obtain high electric conversion efficiency, a gas diffusion layer, a cathode, an anode, an electrolytic solution, and a separator positioned between the cathode and the anode, wherein the separator includes a porous substrate and a coating layer disposed on at least one surface of the porous substrate, the coating layer includes an anion exchange ionomer, and the anion exchange ionomer is not included within pores of the porous substrate.

Description

Electrolysis cell and method for manufacturing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0112690, filed August 28, 2023, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to an electrolytic cell for electrolyzing carbon dioxide and a method for manufacturing the same.

[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 process of electrochemically decomposing carbon dioxide is similar to the electrolysis technology of water, but since the activity of the electrochemical reaction improves in a strongly alkaline atmosphere, a KOH aqueous solution of a certain concentration is generally used as an electrolyte. When water is supplied to the anode and current is applied, the water is decomposed into hydrogen ions and electrons along with the generation of oxygen gas. The electrons move to the cathode through an external conductor, and the hydrogen ions move to the cathode through an ion-selective membrane. At this time, the moved electrons react with the carbon dioxide and water supplied to the cathode to produce carbon monoxide and hydroxide ions (OH). -) is decomposed into hydrogen ions (H ) of the anode, and the generated hydroxide ions are converted into hydrogen ions (H ) of the anode. + ) reacts with the electrons to produce water, thereby becoming electrically neutral. 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 and is electrolyzed to produce hydrogen gas and simultaneously produce hydroxide ions. This reaction of 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 controlling the voltage.

[0009] Meanwhile, the electrolysis cell includes a cathode, an anode, an electrolyte, and a separator, and conventionally, an anion exchange membrane that is generally available on the market is used as the separator, and in particular, Sustainion from Dioxide Materials Co. is the most widely used anion exchange membrane, but this is expensive, which may be an economical cost issue to use, and mass supply is impossible, and since it may crack and crumble in a dry state due to its low mechanical strength, the work process was very low when the Sustainion anion exchange membrane was attached to the electrolysis cell. Accordingly, research on a porous substrate that can replace the Sustainion anion exchange membrane is in progress, but such a porous substrate still has poor mechanical strength due to its porosity, and has a problem in that cations from the electrolyte on the anode side cross over to the cathode side due to the porosity, which lowers the electrolysis efficiency.

[0010] Accordingly, there is a need for research on a membrane that can be mass-produced at low cost, has high durability and mechanical strength, and has carbon dioxide conversion efficiency equivalent to or higher than the above-mentioned Sustainion anion exchange membrane or can improve the porous substrate.

[0011] (Patent Document 1) KR 2019-0125822 A

[0012]

[0013] The problem to be solved by the present invention is to provide a separation membrane that improves electrolysis efficiency by maintaining the pore characteristics of a porous substrate while also having the ion selectivity of an ionic polymer separation membrane, and an electrolysis cell including the same.

[0014] In addition, the problem to be solved by the present invention is to provide a separation membrane that can be used on a large area instead of a commercial anion exchange separation membrane attached to an existing electrolysis cell and has high chemical and mechanical strength, and a method for manufacturing an electrolysis cell including the same.

[0015]

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

[0017] (1) The present invention provides an electrolysis cell comprising a gas diffusion layer, a cathode, an anode, an electrolyte, and a separator positioned between the cathode and the anode, wherein the separator comprises a porous substrate and a coating layer disposed on at least one surface of the porous substrate, the coating layer comprising an anion exchange ionomer, and wherein the anion exchange ionomer is not included inside the pores of the porous substrate.

[0018] (2) The present invention provides an electrolytic cell in the above (1), wherein the coating layer is disposed on a surface of the porous substrate facing the cathode.

[0019] (3) The present invention provides an electrolysis cell according to (1) or (2), wherein the porous substrate includes at least one selected from the group consisting of polyethersulfone, polyvinylidene difluoride, cellulose acetate, polytetrafluoroethylene, and polyimide.

[0020] (4) The present invention provides an electrolysis cell according to any one of the above (1) to (3), wherein the anion exchange ionomer is a hydrocarbon ionomer or a perfluorinated ionomer.

[0021] (5) The present invention provides an electrolytic cell in any one of the above (1) to (4), wherein the electrolytic cell is a zero-gap membrane electrode assembly cell in which the gas diffusion layer, the cathode, the separator, and the anode having an anode fluid path formed therein are sequentially laminated without gaps.

[0022] (6) The present invention provides an electrolysis cell in which the ratio of the thickness of the coating layer and the thickness of the porous substrate is 1:10 to 200 in any one of the above (1) to (5).

[0023] (7) The present invention provides an electrolysis cell according to any one of the above (1) to (6), wherein the thickness of the coating layer is 1.0 ㎛ or more and 10.0 ㎛ or less.

[0024] (8) The present invention provides an electrolysis cell according to any one of the above (1) to (7), wherein the thickness of the porous substrate is 5.0 ㎛ or more and 250.0 ㎛ or less.

[0025] (9) The present invention provides an electrolysis cell in which the average particle diameter of the pores of the porous substrate is 10.0 nm or more and 450.0 nm or less in any one of the above (1) to (8).

[0026] (10) The present invention provides an electrolytic cell that electrolyzes carbon dioxide in any one of the above (1) to (9).

[0027] (11) The present invention provides an electrolytic cell according to any one of the above (1) to (10), wherein the electrolytic cell produces at least one product selected from the group consisting of carbon monoxide, ethylene, methane, formic acid, hydrocarbons, aldehydes, and alcohols.

[0028] (12) The present invention provides a method for manufacturing an electrolysis cell, comprising the steps of: manufacturing a separator having a coating layer disposed on one surface (S10); installing a cathode on one surface of the separator having the coating layer disposed on the other surface (S20); and installing a separator on the outside of the cathode and the anode, respectively (S30); wherein the step of manufacturing the separator (S10) comprises: preparing a coating composition comprising an anion exchange ionomer and an organic solvent; and a porous substrate (S1); forming a coating layer by applying the coating composition to one surface of the porous substrate (S2); and drying the coating layer to manufacture the separator (S3).

[0029] (13) The present invention provides a method for manufacturing an electrolysis cell, wherein, in the above (12), the coating composition comprises 1 wt% or more and 10 wt% or less of the anion exchange ionomer.

[0030] (14) The present invention provides a method for manufacturing an electrolysis cell, wherein, in step S30, the coating layer is formed to a thickness of 1.0 ㎛ or more and 10.0 ㎛ or less in the above (12) or (13).

[0031]

[0032] According to the electrolysis cell of the present invention, the carbon dioxide conversion efficiency of the electrolysis cell can be increased by fastening the separator of the present invention having high chemical and mechanical strength and improved ion selectivity.

[0033] In addition, according to the electrolysis cell according to the present invention, the contact between the cathode and the separator is increased, thereby reducing the interfacial resistance and lowering the overvoltage.

[0034]

[0035] Figure 1 (a) is a surface SEM photograph before coating of Example 2 of the present invention, and (b) is a surface SEM photograph after coating of Example 2 of the present invention.

[0036] Figure 2 is a surface SEM photograph showing that the pores of the porous substrate are blocked by the coating layer of Comparative Example 8.

[0037]

[0038] 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.

[0039] 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.

[0040] In this specification, it should be understood that the terms “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.

[0041]

[0042] electrolysis cell

[0043] The present invention provides an electrolysis cell comprising a gas diffusion layer, a cathode, an anode, an electrolyte, and a separator positioned between the cathode and the anode, wherein the separator comprises a porous substrate and a coating layer disposed on at least one surface of the porous substrate, the coating layer comprising an anion exchange ionomer, and wherein the anion exchange ionomer is not included within the pores of the porous substrate.

[0044]

[0045] In the case of commercial anion exchange membranes used in conventional electrolysis cells, they cannot be used on a large area, and they crumble in a dry state without moisture, so the workability when assembling the electrolysis cell was very low. To replace them, porous substrates were used, but it was difficult to significantly improve the mechanical strength due to the porosity, and cations (Cs) from the electrolyte on the anode side + , K + The problem occurred that the carbon dioxide conversion efficiency was reduced because the porous substrate passed through the porosity and passed to the cathode side, generating salt. In addition, the porous substrate had poor contact with the electrode, which increased the interfacial resistance, and as a result, the problem of increased overvoltage also occurred.

[0046]

[0047] Accordingly, the inventor of the present invention conducted research on a separator that can increase ion selectivity to prevent cations from passing from the anode to the cathode side, increase the mechanical strength of the porous substrate, and increase the contact between the separator and the electrode to reduce the interfacial resistance, and developed the electrolysis cell of the present invention.

[0048] The electrolytic cell of the present invention comprises a gas diffusion layer, a cathode, an anode electrolyte, and a separator positioned between the cathode and the anode, wherein the separator comprises a porous substrate and a coating layer disposed on at least one surface of the porous substrate, wherein the coating layer comprises the anion exchange ionomer. The anion exchange ionomer has a positive charge and can form anion transport channels, and can smoothly transport anions through the anion transport channels, while inhibiting the transport of cations. That is, the anion exchange ionomer can prevent cations from being transported from the anode through the pores of the porous substrate to the cathode. Consequently, by disposing a coating layer comprising the anion exchange ionomer on at least one surface of the porous substrate, the ion selectivity of the porous substrate can be improved.

[0049] Fig. 1 is a SEM photograph of the surface before coating of Example 2 of the present invention (a), and a SEM photograph of the surface after coating of Example 2 of the present invention (b). Specifically, these are photographs before and after coating showing that the pore size of the porous substrate is maintained even after a coating layer is formed on the porous substrate. The anion exchange ionomer is not impregnated or included in the pores of the porous substrate, but is included only in the coating layer. By controlling the concentration of the anion exchange ionomer and the thickness of the coating layer formed during the coating process on the surface of the porous substrate, it is possible to control whether the anion exchange ionomer is impregnated or not in the pores of the porous substrate, so that the pore size of the porous substrate is not affected, and the pore size before coating can be maintained as it is. That is, by maintaining the pore size of the porous substrate even after coating, the ion exchange performance of the original porous substrate is not lowered, but rather the ion selectivity can be increased, so that when the separator is connected to an electrolysis cell and operated, the electrolysis efficiency can be further improved. Meanwhile, whether the membrane is impregnated or included inside the pores of the porous substrate can be controlled depending on the concentration of the anion exchange ionomer included in the coating composition, the thickness of the formed coating layer, the material of the porous substrate, the pore size, etc.

[0050] Meanwhile, if the coating layer includes a cation exchange ionomer rather than an anion exchange ionomer, it is difficult to prevent cations from being transferred from the anode to the cathode, so the ion selectivity is significantly reduced, and the overvoltage increases during operation of the electrolysis cell, which may lower the electrolysis efficiency.

[0051] According to one embodiment of the present invention, the coating layer may be disposed on a side of the porous substrate that faces the cathode. The two sides of the porous substrate may face the anode and the cathode, respectively, and the coating layer may be disposed on a side of the separator that faces the cathode. In this case, anion exchange can occur more smoothly, and cation transport can be prevented more effectively. In particular, in the case of a cell having a zero-gap membrane-active junction structure described below, since the anode side is in contact with the anolyte, the anolyte can sufficiently permeate into the pores of the porous substrate. Therefore, even if a coating layer is present on the side that faces the anode, it may be difficult to achieve a significant effect because ion movement is easy. However, on the cathode side, although the porous substrate wetted with the anode solution and the cathode catalyst are in contact, there is no medium that can connect the porous substrate and the cathode catalyst, so ion movement is not easy. At this time, the anion exchange ionomer of the coating layer can act as a passage that can move ions between the cathode catalyst layer and the surface of the porous substrate. Here, the ion is OH generated in the process of converting CO2 to CO. - It could be.

[0052] Meanwhile, in the case of a cell having a zero-gap membrane electrode assembly structure to be described later, the separator and the cathode can form a structure in which they are laminated without a gap therebetween, in which case the coating layer improves the adhesion between the separator and the cathode, thereby reducing the interfacial resistance, and consequently improving the electrolysis efficiency. On the other hand, in the zero-gap membrane electrode assembly structure, if the coating layer is disposed on one of the two sides of the porous substrate facing the anode, the electrolyte flows between the separator and the anode, so the adhesion between the separator and the anode is reduced, and it is difficult for the adhesion improving function of the coating layer to be properly exerted, so the electrolysis efficiency may be lowered compared to the case where the coating layer is disposed on the side of the separator facing the cathode.

[0053]

[0054] According to one embodiment of the present invention, the ratio of the coating layer thickness and the porous substrate thickness may be 1:10 to 200. For example, the ratio may be 1:10 or more, 1:20 or more, 1:30 or more, 1:40 or more, 1:50 or more, 1:60 or more, 1:70 or more, 1:80 or more, 1:90 or more, 1:200 or less, 1:190 or less, 1:180 or less, 1:170 or less, 1:160 or less, 1:150 or less, 1:140 or less, 1:130 or less, 1:120 or less, 1:110 or less, 1:100 or less. Specifically, the ratio of the coating layer thickness and the porous substrate thickness may be 1:20 to 100. When the ratio of the thickness of the coating layer and the thickness of the porous substrate satisfies the above numerical range, ion selectivity can be increased without increasing the resistance of the separation membrane due to the thickness, and electrolysis efficiency can be improved.

[0055]

[0056] According to one embodiment of the present invention, the porous substrate may include at least one selected from the group consisting of polyethersulfone, polyvinylidene difluoride, cellulose acetate, polytetrafluoroethylene, polyimide, polyamide, polyacrylate, polycarbonate, and polyolefin, and specific examples thereof include polyethylene, polypropylene, polybutylene, polypentene, polymethylpentene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, and nylon. Specifically, the porous substrate may include polyethersulfone. When the porous substrate includes the polyethersulfone, the ion permeability and ion selectivity are excellent, and thus, when the porous substrate is fastened as a separator to an electrolysis cell, the electrolysis efficiency may be improved.

[0057] Additionally, the thickness of the porous substrate may be 5.0 ㎛ or more and 250.0 ㎛ or less. For example, the thickness of the porous substrate may be 5.0 ㎛ or more, 10.0 ㎛ or more, 20.0 ㎛ or more, 30.0 ㎛ or more, 40.0 ㎛ or more, 50.0 ㎛ or more, 60.0 ㎛ or more, 70.0 ㎛ or more, 80.0 ㎛ or more, 90.0 ㎛ or more, 100.0 ㎛ or more, 110.0 ㎛ or more, 120.0 ㎛ or more, 130.0 ㎛ or more, 140.0 ㎛ or more, 150.0 ㎛ or more, 250.0 ㎛ or less, 230.0 ㎛ or less, 210.0 ㎛ or less, 200.0 ㎛ or less, 190.0 ㎛ or less, 180.0 ㎛ or less, 170.0 ㎛ or less, or 160.0 ㎛ or less. Specifically, the thickness of the porous substrate may be 100.0 ㎛ or more and 170.0 ㎛ or less, and when the porous substrate satisfies the thickness, the crossover phenomenon in which cations of the electrolyte pass through the porous substrate can be reduced, a short circuit can be prevented by separating the regions of the anode and cathode, and the performance of the electrolysis cell can be improved by lowering the overvoltage.

[0058]

[0059] Additionally, the average particle diameter of the pores of the porous substrate may be 10.0 nm or more and 450.0 nm or less. For example, the average particle diameter of the pores of the porous substrate is 10.0 nm or more, 20.0 nm or more, 30.0 nm or more, 40.0 nm or more, 50.0 nm or more, 60.0 nm or more, 70.0 nm or more, 80.0 nm or more, 90.0 nm or more, 100.0 nm or more, 110.0 nm or more, 120.0 nm or more, 130.0 nm or more, 450.0 nm or less, 425.0 nm or less, 400.0 nm or less, 375.0 nm or less, 350.0 nm or less, 275.0 nm or less, 250.0 nm or less, 240.0 nm or less, 230.0 nm or less, 220.0 nm or less, 210.0 nm or less, 200.0 nm or less, 190.0 nm or less, It may be 180.0 nm or less, 170.0 nm or less, 160.0 nm or less, 150.0 nm or less, or 140.0 nm or less. Specifically, the average particle diameter of the pores of the porous substrate may be 100.0 nm or more and 200.0 nm or less, and when the pores of the porous substrate satisfy the average particle diameter, smooth ion transport can be achieved, resistance inside the porous substrate can be reduced, and excellent mechanical strength and durability can be maintained.

[0060] 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.

[0061] According to one embodiment of the present invention, the anion exchange ionomer may be a hydrocarbon-based ionomer or a fluorine-based ionomer. For example, the anion exchange ionomer may be a fluorine-based or hydrocarbon-based anionic ionomer containing alkylammonium, guanidinium, imidazolium, piperidinium, and derivatives thereof in the side chain, and specifically, the anion exchange ionomer may be at least one selected from the group consisting of a sustain ionomer, a polybenzimidazole (polybenzimidazole-based anion exchange membrane (AEM)), an Aemion ionomer, an Orion ionomer, a functionalized imidazolium, a functionalized piperidinium, a functionalized quaternary ammonium, a functionalized guanidinium, a polystyrene, a polyfluoroolefin, and a polyallyl. Preferably, the anion exchange ionomer may be a sustain ionomer.

[0062] In addition, the thickness of the coating layer may be 1.0 ㎛ or more and 10.0 ㎛ or less. For example, the thickness of the coating layer may be 1.0 ㎛ or more, 1.5 ㎛ or more, 2.0 ㎛ or more, 2.5 ㎛ or more, 3.0 ㎛ or more, 3.5 ㎛ or more, 4.0 ㎛ or more, 4.5 ㎛ or more, 10.0 ㎛ or less, 9.5 ㎛ or less, 9.0 ㎛ or less, 8.5 ㎛ or less, 8.0 ㎛ or less, 7.5 ㎛ or less, 7.0 ㎛ or less, 6.5 ㎛ or less, 6.0 ㎛ or less, 5.5 ㎛ or less, 5.0 ㎛ or less, and specifically, the thickness of the coating layer may be 1.0 ㎛ or more and 5.0 ㎛ or less. When the coating layer satisfies the above thickness, a separate layer can be formed on the surface of the porous substrate, and since the material of the anion exchange ionomer is not impregnated or included inside the pores of the porous substrate, the pore size of the porous substrate can be maintained, thereby improving ion selectivity and maintaining excellent electrolysis efficiency.

[0063]

[0064] According to one embodiment of the present invention, the electrolytic cell is provided as a zero-gap membrane electrode assembly cell in which the gas diffusion layer, the cathode, the separator, and the anode having an anode fluid path formed therein are sequentially laminated without gaps. Specifically, the zero-gap membrane electrode assembly may be formed in the form of a very thin plate by sequentially laminating the gas diffusion layer, the cathode, the separator, and the anode having an anode fluid path formed therein in order to increase driving voltage and current efficiency.

[0065] Conventional electrolysis cells have a gap structure in which the electrodes and the separator are spaced apart by a few millimeters, but the zero gap is a sandwich-type electrolysis cell in which the cathode electrode and the anode negative electrode are in contact with each other with the separator in between, thereby eliminating the gap between the electrodes and the separator. The zero gap-type electrolysis cell can reduce the solution ion resistance due to the presence of an electrolyte and reduce the increase in mass transfer resistance due to the generated gas when implementing a large-area electrode.

[0066] Specifically, the electrolyte flowing toward the cathode is called catholyte, and the electrolyte flowing toward the anode is called anolyte. The zero-gap membrane electrode assembly may not include the catholyte, but may only include the anolyte. The electrolysis cell having the zero-gap membrane electrode assembly structure has a structure in which the electrolyte does not flow in the front part of the cathode, but only in the front part of the anode, thereby minimizing the gap between the cathode, the anode, and the separator, thereby enabling rapid ion transport, increasing current efficiency, and solving the additional problem of voltage increase during the electrolysis reaction, thereby having the advantage of lowering the overvoltage. In addition, in this case, separators may be arranged on both sides of the zero-gap membrane electrode assembly to form one cell.

[0067] When the separator of the present invention is fastened within an electrolytic cell having the zero-gap membrane electrode assembly structure, the coating layer may be disposed between the porous substrate and the cathode. In this case, the coating layer may improve the adhesion between the separator and the cathode, thereby reducing the interfacial resistance, thereby reducing the overvoltage and increasing the electrolysis efficiency.

[0068]

[0069] Hereinafter, the decomposition principle of the electrolysis device and each component of the electrolysis device will be described.

[0070] The above 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 acts as an oxidation electrode, oxidizing 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 acts as a reduction electrode, so that reactants introduced to the cathode can react with electrons and hydrogen ions transferred 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 serve to isolate physical contact between the anode and the cathode.

[0071] In addition, the anode and the cathode of the electrolysis device of the present invention may each include a catalyst layer. In addition, water vapor supplied together with carbon dioxide in 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.

[0072] 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 evolution reaction. Specifically, the anode in the electrolysis device of the present invention may include titanium (Ti) coated with iridium oxide (IrO2).

[0073] In addition, since the carbon dioxide reduction reaction occurring at the cathode competes with the hydrogen evolution reaction, a catalyst that is active in the carbon dioxide reduction reaction and requires a high voltage for the hydrogen evolution 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 electrolysis device of the present invention may include silver (Ag).

[0074] Additionally, the separator may include a coating layer including a porous substrate and an anion exchange ionomer, as described above.

[0075] In addition, the electrolyte solution is KHCO3, K2CO3, KOH, KCl, KClO4, K2SiO3, Na2SO4, NaNO3, NaCl, NaF, NaClO4, CaCl2, Cs2CO3, H3PO4, KHPO4, guanidinium cation, H + At least one electrolyte 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, tetraalkyl ammonium salts, or mixtures thereof may be used, and specifically, the electrolyte of the carbon dioxide electrolysis cell of the present invention may include an aqueous solution containing at least one selected from the group consisting of KOH, KHCO3, Cs2CO3, H3PO4, or a mixture of H3PO4 and KHPO4.

[0076] 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 electrolysis device of the present invention, the gas diffusion layer may use carbon fiber cloth.

[0077] 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.

[0078]

[0079] Electrolysis cell manufacturing method

[0080] The present invention provides a method for manufacturing an electrolysis cell, comprising the steps of: (S10) manufacturing a separator having a coating layer disposed on one surface; (S20) installing a cathode on one surface of the separator having the coating layer disposed on the other surface; and (S30) installing a separator plate on the outside of the cathode and the anode, respectively; and wherein the step of manufacturing the separator (S10) comprises: (S1) preparing a coating composition comprising an anion exchange ionomer and an organic solvent; and (S2) forming a coating layer by applying the coating composition to one surface of the porous substrate; and (S3) drying the coating layer to manufacture the separator.

[0081] The cathode and anode may be the cathode and anode described in the electrolysis cell, and the separator manufactured by the step of manufacturing the separator may be the separator described in the electrolysis cell. The separator plate may be installed on the outside of the cathode and the anode, respectively, and the separator plate installed on the outside of the cathode may be provided with an inlet and an outlet through which a supplied material and a produced material are introduced and discharged. In addition, the separator plate installed on the outside of the anode may be provided with an inlet and an outlet through which an electrolyte may be introduced and discharged.

[0082] According to one embodiment of the present invention, the coating composition may include 1 wt% or more and 10 wt% or less of the anion exchange ionomer. For example, the coating composition may include 1.0 wt% or more, 2.0 wt% or more, 3.0 wt% or more, 4.0 wt% or more, 10.0 wt% or less, 9.0 wt% or less, 8.0 wt% or less, 7.0 wt% or less, 6.0 wt% or less, or 5.0 wt% or less of the anion exchange ionomer. Specifically, the coating composition may include 1.0 wt% or more and 5.0 wt% or less of the anion exchange ionomer, and when the coating composition includes the anion exchange ionomer in the above content range, the material of the anion exchange ionomer may not be impregnated into the pores of the porous substrate, but may be included only in the coating layer. In this case, since the material of the anion exchange ionomer does not affect the pore size of the porous substrate, the phenomenon of cation crossover can be prevented, while excellent ion selectivity can be achieved and high electrolysis efficiency can be obtained.

[0083] In addition, the ionomer coating composition may further include an organic solvent. Specifically, the coating composition may be one in which the anion exchange ionomer is dissociated in the organic solvent. The organic solvent may include at least one selected from the group consisting of ethanol, n-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), dipropylene glycol (DPG), ethylene glycol (EG), propylene glycol (PG), and isopropyl alcohol (IPA). The content of the organic solvent may be the remainder of the ionomer coating composition after excluding the content of the anion exchange ionomer.

[0084] In addition, according to one embodiment of the present invention, in the step S30, the coating layer may be formed to a thickness of 1.0 ㎛ or more and 10.0 ㎛ or less. For example, the coating layer may be 1.0 ㎛ or more, 2.0 ㎛ or more, 3.0 ㎛ or more, 4.0 ㎛ or more, 10.0 ㎛ or less, 9.0 ㎛ or less, 8.0 ㎛ or less, 7.0 ㎛ or less, 6.0 ㎛ or less, or 5.0 ㎛ or less. Specifically, the coating layer may be 1.0 ㎛ or more and 5.0 ㎛ or less, and when the coating layer satisfies the thickness, the material of the anion-exchanging ionomer may not be impregnated into the pores of the porous substrate, but may be included only in the coating layer.

[0085] In addition, according to one embodiment of the present invention, the coating method for forming the coating layer may be performed by a method such as bar coating, dip coating, spin coating, and spray coating, and preferably may be performed by a bar coating method. The bar coating may be performed by applying the coating composition onto one surface of the porous substrate using various methods such as a Meyer bar, a doctor blade, a slot die, a comma bar, and a spin coat.

[0086] In addition, according to one embodiment of the present invention, through the step (S13) of drying the coating layer to manufacture a separator, the remaining organic solvent can be removed to form a solid coating layer. Specifically, the drying step can be performed at 50°C to 150°C for 30 minutes to 8 hours. If the drying step is performed at a temperature lower than 50°C or for a time shorter than 30 minutes, the organic solvent may not be sufficiently removed, which may affect the properties of the coating layer. In addition, if the drying step is performed at a temperature higher than 150°C or for a time longer than 8 hours, it may cause denaturation of the porous substrate, resulting in a deterioration of the properties of the separator.

[0087]

[0088] 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.

[0089]

[0090] <Manufacturing and Use of Membranes>

[0091] Example 1

[0092] A porous filter (pore size: 200 nm, thickness: 150 ㎛) made of PES (polyethersulfone) was placed on a bar coater, and a 200 ㎛ bar was used to coat the Sustainment dispersion solution (5 wt%, EtOH) only on the side of the porous filter that would face the cathode to form a coating layer. Thereafter, the ethanol was dried for 10 minutes under conditions of 50 °C, and the coated porous filter was additionally placed in a circulation oven and further dried at 80 °C for 1 to 8 hours to manufacture a separation membrane.

[0093]

[0094] Example 2

[0095] A separation membrane was manufactured in the same manner as in Example 1, except that a porous filter (pore size: 100 nm, thickness: 150 ㎛) made of PES (polyethersulfone) was used.

[0096]

[0097] Comparative Example 1

[0098] The same porous filter as in Example 1 was used as a separator without any coating work.

[0099]

[0100] Comparative Example 2

[0101] A separator was manufactured in the same manner as in Example 1, except that only the surface facing the anode among the two sides of the porous filter identical to Example 1 was coated.

[0102]

[0103] Comparative Example 3

[0104] The same porous filter as in Example 2 was used as a separator without any coating work.

[0105]

[0106] Comparative Example 4

[0107] A separator was manufactured in the same manner as in Example 1, except that only the surface facing the anode among the two sides of the porous filter identical to Example 2 was coated.

[0108]

[0109] Comparative Example 5

[0110] SustainionX37-50 Grade RT Membrane anion exchange membrane from Dioxide Materials Co. was purchased, and the anion exchange membrane was used after being immersed in a 1 M KOH aqueous solution for 1 day.

[0111]

[0112] Comparative Example 6

[0113] A separation membrane was manufactured in the same manner as in Example 1, except that Nafion dispersion solution (5 wt%, EtOH) was used instead of Sustainion dispersion solution (5 wt%, EtOH).

[0114]

[0115] Comparative Example 7

[0116] A separation membrane was manufactured in the same manner as in Example 1, except that Sustainion dispersion solution (15 wt%, EtOH) was used instead of Sustainion dispersion solution (5 wt%, EtOH).

[0117]

[0118] Comparative Example 8

[0119] A separation membrane was manufactured in the same manner as in Example 1, except that Nafion dispersion solution (15 wt%, EtOH) was used instead of Sustainion dispersion solution (5 wt%, EtOH).

[0120]

[0121] Comparative Example 9

[0122] A porous filter made of the same PES (polyethersulfone) as in Example 1 was used as a separation membrane without any coating process.

[0123] However, instead of forming a coating layer on the porous filter, a coating layer was formed directly on the gas diffusion layer coated with a Ag catalyst applied as a cathode. Specifically, the gas diffusion layer (GDL) coated with a Ag catalyst applied as a cathode was placed on a bar coater, and a Nafion dispersion solution (15 wt%, EtOH) was coated only on the side facing the membrane using a 200 μm bar to form a coating layer. Thereafter, the ethanol was dried for 10 minutes under temperature conditions of 50 °C, and the coated gas diffusion layer was additionally placed in a circulation oven and further dried at 80 °C for 1 to 8 hours to prepare a gas diffusion layer. The gas diffusion layer and the membrane were used in the experimental examples below.

[0124]

[0125] Experimental example

[0126] A carbon dioxide electrolysis unit cell including a zero-gap structure membrane electrode assembly in which an anode, an anode electrolyte, a separator manufactured by Examples and Comparative Examples, a cathode, and a gas diffusion layer are sequentially laminated was operated under the operating conditions described below.

[0127] Reaction current density: 100 mA / cm 2 , 200 mA / cm 2 , 300 mA / cm 2 , 400 mA / cm 2 , (Constant current operation)

[0128] Reaction voltage: 1~4 V

[0129] Reaction temperature: 40 ℃

[0130] Reaction pressure: 1 atm (atmospheric pressure)

[0131] Anode catalyst: IrO2on Ti mesh

[0132] Cathode catalyst: Ag powder

[0133] Electrode area: 25 cm 2

[0134] Gas diffusion layer: Sigracet 39BB, JNTG

[0135] Anode electrolyte: 0.25 M Cs2CO3 (25 ml / min)

[0136] Cathode reactant: 40 ℃ Humidified CO2 gas (25 ccm)

[0137]

[0138] Electrolysis was performed under the above operating conditions using the above carbon dioxide electrolysis unit cell, and the conversion rate (%) of carbon monoxide, carbon monoxide Faraday efficiency (CO Faraday efficiency, %), hydrogen Faraday efficiency (H2Faraday efficiency, %), voltage, and impedance were measured, and the measured results are shown in Table 1.

[0139]

[0140] * measurement method

[0141] (1) Conversion rate of carbon monoxide (%)

[0142] The conversion rate (%) was calculated as the ratio of carbon monoxide (CO) produced to the amount of carbon dioxide (CO2) gas injected per hour.

[0143]

[0144] (2) Carbon monoxide Faraday efficiency (CO Faraday efficiency, %)

[0145] The composition of the gas discharged from the above carbon dioxide electrolysis device was measured through GC (Gas Chromatography) analysis. In addition, the Faraday efficiency was calculated using the following equation.

[0146] [Mathematical Formula 1]

[0147]

[0148] In the above mathematical expression 1, Q is the flow rate in the path that discharges the product outside the carbon dioxide electrolysis device, 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.

[0149]

[0150] (3) Hydrogen Faraday efficiency (H2 Faraday efficiency, %)

[0151] The above hydrogen Faraday efficiency was measured and calculated in the same manner as the carbon monoxide Faraday efficiency (2) above.

[0152]

[0153] (4) Voltage (V)

[0154] 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 , 400 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.

[0155]

[0156] (5) Impedance (mΩ)

[0157] Ohmic resistance was measured at 0.2 V and frequencies of 100 KHz-10 Hz using a VSP potentiostat from BioLogic.

[0158]

[0159] ClassificationExample 1Example 2Comparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Comparative Example 5Comparative Example 6Comparative Example 7Comparative Example 8Comparative Example 9Porous substrate type / pore size (nm)PES / 200PES / 100PES / 200PES / 200PES / 100PES / 100SustainionX37-50PES / 200PES / 200PES / 200PES / 200Coating materialSustainion (5 wt%, EtOH)Sustainion (5 wt%, EtOH)NoneSustainion (5 wt%, EtOH)NoneSustainion (5 wt%, EtOH)NoneNafion (5 wt%, EtOH)Sustainion (15 wt%, EtOH)Nafion (15 wt%, EtOH)Nafion (15 wt%, EtOH)Coating location (one side of the membrane facing a specific electrode)CathodeCathode-Anode-Anode-CathodeCathodeCathodeCathodeCathodeDirect coating thickness (㎛)Porous substrate15012515015012515050150150150150150Coating layer33-4-2-3>10>105Current density100 mA / cm 2 Voltage (V) - 2.792 - 2.857 - 2.901 - 2.883 - 2.840 - 2.666 - 3.022 - 3.471 N.A - 4.0 - 2.932 CO Faraday efficiency (%) 100.009 9.74 100.001 00.009 9.009 8.009 5.88 4.93 N.AN.A 97.32 H2 Faraday efficiency (%) 0.33 0.37 0.38 0.43 0.25 0.38 - N.AN.A 0.67 Carbon dioxide conversion rate (%) 9.83 9.5 49.849 849 9.9 69.70 9.16 8.17 N.AN.A 9.21 Current density 200 mA / cm 2Voltage (V) - 3.105 - 3.094 - 3.180 - 3.154 - 3.111 - 3.032 - 3.297 - 3.749 N.AN.A - 3.190 CO Faraday efficiency (%) 96.16 97.66 95.36 95.22 95.46 94.44 93.27 8.44 N.AN.A 90.82 H2 Faraday efficiency (%) 0.28 0.32 0.39 0.42 0.23 0.36 - N.AN.A 0.56 Carbon dioxide conversion rate (%) 18.8 1 18.69 18.66 18.74 19.22 18.69 17.83 15.09 N.AN.A 17.19 Current density 300 mA / cm 2 Voltage (V) - 3.304 - 3.264 - 3.387 - 3.355 - 3.301 - 3.232 - 3.473 - 3.812 N.AN.A - 3.348 CO Faraday efficiency (%) 9 1.87 9 3.229 0.429 0.069 2.559 1.40 8 8.78 7 0.73 N.AN.A 8 4.49 H2 Faraday efficiency (%) 0.33 0.31 1.30 1.48 0.36 0.36 - N.AN.A 0.65 Carbon dioxide conversion rate (%) 26.96 26.75 26.54 26.58 27.95 27.13 25.48 20.41 N.AN.A 23.99 Current density 400 mA / cm 2 Voltage (V) - 3.460 - 3.413 - 3.571 - 3.496 - 3.465 - 3.367 - 3.65 - 4.050 N.AN.A - 3.560 CO Faraday efficiency (%) 87.86 88.65 83.94 84.27 89.86 85.72 81.21 42.76 N.AN.A 82.27 H2 Faraday efficiency (%) 0.5 11.65 2.84 2.68 0.64 2.08 - N.AN.A 1.75 Carbon dioxide conversion rate (%) 34.38 33.93 32.84 33.16 36.18 33.92 31.08 20.57 N.AN.A 33.50

[0160]

[0161] Referring to Table 1 above, in Example 1, where the surface facing the cathode of the PES porous substrate (200 nm) was coated with Sustainion (5 wt%, EtOH), it was confirmed that the overall performance was superior in terms of overvoltage, carbon monoxide Faradaic efficiency, hydrogen Faradaic efficiency, and carbon dioxide conversion rate compared to Comparative Examples 1 and 2, where no coating was performed or the surface facing the anode was coated. In particular, the current density was 300 mA / cm 2 , 400 mA / cm 2 You can see that the performance difference becomes larger as you go up.

[0162] In addition, in the case of Example 2, in which the surface facing the cathode of the PES porous substrate (100 nm) was coated with Sustainion (5 wt%, EtOH), it was confirmed that the overall performance was excellent in terms of overvoltage, carbon monoxide Faradaic efficiency, hydrogen Faradaic efficiency, and carbon dioxide conversion rate, compared to Comparative Examples 3 and 4, in which the surface facing the anode was coated or not coated. Similarly, the current density was 300 mA / cm 2 , 400 mA / cm 2 You can also see that the performance difference becomes larger as you go up.

[0163] In addition, in the case of Comparative Example 5 using SustainionX37-50 as a conventionally used anion exchange membrane, it can be confirmed that all electrolysis efficiencies are inferior to those of the examples, and in the case of Comparative Example 6 using a cationic ionomer, it can be confirmed that the overvoltage is also very inferior.

[0164] In addition, Comparative Example 7 used Sustainion (15%, EtOH) as a coating material. In this case, a coating layer thickness of about 10 ㎛ or more was formed. However, Sustainion itself cracked and crumbled during the drying stage, making it impossible to manufacture the film itself.

[0165] In addition, Comparative Example 8 was coated using powder-form Nafion (15 wt%, EtOH). In this case, the pores on the surface were immediately blocked, and when evaluating the performance, the current density was 100 mA / cm. 2 The performance measurement was not possible because the overvoltage exceeded -4.0 V. The surface SEM image of the film manufactured in Comparative Example 8 is shown in Fig. 2. Fig. 2 is a surface SEM image showing that the pores of the porous substrate were blocked by the coating layer of Comparative Example 8.

[0166] In addition, Comparative Example 9 is a case where a coating layer is formed directly on the cathode, rather than coating Nafion (15 wt%, EtOH) on a porous substrate. In Examples 1 and 2, the Nafion ionomer coating layer is coated on a PES porous substrate in a porous form, so there is no problem with material transfer. On the other hand, in the case of Comparative Example 9, since the coating is performed directly on the cathode, the coating is formed in a film form, and since it is difficult for substances such as ions and H2O of the electrolyte required for carbon dioxide conversion to come into contact with the catalyst, it can be confirmed that the electrical resistance and overvoltage are high compared to the Examples, and thus the electrical efficiency is inferior.

Claims

1. A gas diffusion layer comprising: a cathode; an anode; an electrolyte; and a separator positioned between the cathode and the anode. The above separator comprises a porous substrate and a coating layer disposed on at least one surface of the porous substrate, The above coating layer comprises an anion exchange ionomer, An electrolysis cell in which the anion exchange ionomer is not included within the pores of the porous substrate.

2. In claim 1, An electrolysis cell wherein the coating layer is disposed on one side of the porous substrate facing the cathode.

3. In claim 1, An electrolysis cell wherein the porous substrate comprises at least one selected from the group consisting of polyethersulfone, polyvinylidene difluoride, cellulose acetate, polytetrafluoroethylene, and polyimide.

4. In claim 1, An electrolysis cell wherein the above anion exchange ionomer is a hydrocarbon ionomer or a perfluoro ionomer.

5. In claim 1, The above electrolytic cell is an electrolytic cell in which the gas diffusion layer, the cathode, the separator, and the anode having an anode fluid path are sequentially laminated without gaps.

6. In claim 1, An electrolysis cell wherein the ratio of the thickness of the coating layer and the thickness of the porous substrate is 1:10 to 200.

7. In claim 1, An electrolysis cell wherein the thickness of the coating layer is 1.0 ㎛ or more and 10.0 ㎛ or less.

8. In claim 1, An electrolysis cell wherein the thickness of the porous substrate is 5.0 ㎛ or more and 250.0 ㎛ or less.

9. In claim 1, An electrolysis cell wherein the average particle diameter of the pores of the porous substrate is 10.0 nm or more and 450.0 nm or less.

10. In claim 1, The above electrolysis cell is an electrolysis cell that electrolyzes carbon dioxide.

11. In claim 1, The electrolytic cell is an electrolytic cell that produces one or more products selected from the group consisting of carbon monoxide, ethylene, methane, formic acid, hydrocarbons, aldehydes, and alcohols.

12. Step of manufacturing a separator having a coating layer disposed on one side (S10); Step (S20) of installing a cathode on one side of the above-mentioned separator where the coating layer is disposed, and installing an anode on the other side; and Including a step (S30) of installing a separator on the outside of the cathode and anode, respectively; The step (S10) of manufacturing the above separation membrane is as follows: A coating composition comprising an anion exchange ionomer and an organic solvent; and a step of preparing a porous substrate (S1); Step (S2) of forming a coating layer by applying the coating composition to one surface of a porous substrate; and A method for manufacturing an electrolysis cell, comprising a step (S3) of manufacturing a separator by drying the coating layer.

13. In claim 12, A method for manufacturing an electrolysis cell, wherein the coating composition comprises 1 wt% or more and 10 wt% or less of the anion exchange ionomer.

14. In claim 12, A method for manufacturing an electrolysis cell, wherein the coating layer is formed to a thickness of 1.0 ㎛ or more and 10.0 ㎛ or less in the above step S30.

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