Separator and electrochemical conversion cell including same

Abstract

The present invention relates to a separator comprising a base membrane and a hydrophilic porous structure layer or a hydrophobic porous structure layer laminated on at least one surface of the base membrane, wherein the base membrane is an anion exchange membrane, a cation exchange membrane or an amphoteric ion exchange membrane.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0049687 filed on April 21, 2022 and Korean Patent Application No. 10-2023-0050853 filed on April 18, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated by reference into this specification.

[0002] The present invention relates to a separator and an electrochemical conversion cell including the same. [Background technology]

[0003] Carbon dioxide is a greenhouse gas that causes global warming and must be reduced. Methods for reducing carbon dioxide include collection, chemical conversion, and electrochemical conversion. Among these, the electrochemical conversion method allows precise control of the components to produce other synthetic gases, and can be more economically beneficial than simply removing carbon dioxide.

[0004] The process by which carbon dioxide is electrochemically decomposed is similar to that of water electrolysis technology, but since the activity of electrochemical reactions is improved in a strong alkaline atmosphere, a KOH aqueous solution of a certain concentration is generally used as the electrolyte. When a current is applied while water is supplied to the anode, the water is decomposed into hydrogen ions and electrons with the generation of oxygen gas. The electrons move to the cathode via an external conductor, and the hydrogen ions move to the cathode via an ion-selective separator. Here, the transferred electrons react with the carbon dioxide and water supplied to the cathode to produce carbon monoxide and hydroxide ions (OH - ) and the hydroxide ions that are generated are transported to the anode via hydrogen ions (H +) to produce water, thereby achieving an electrically neutral state. Through this process, the electrochemical decomposition reaction of carbon dioxide is completed. Here, the water supplied together with carbon dioxide reacts with the transferred electrons and is electrolyzed to generate hydrogen gas and hydroxide ions, separately from the carbon monoxide production reaction. It can be said that this reaction between water and electrons is in a competitive relationship with the carbon monoxide production reaction. Since the reaction is an electrochemical reaction, the amount of carbon monoxide produced and the hydrogen / carbon dioxide ratio can be easily adjusted by adjusting the voltage.

[0005] Meanwhile, when an anion exchange membrane is used as the ion-selective separator, the carbon dioxide electrolysis reaction can show an excellent carbon dioxide conversion rate. However, in general, the anion exchange membrane is prone to drying and deformation in a room temperature environment, and in order to prevent such a risk, the anion exchange membrane can be stored in an environment with sufficient moisture. However, when the anion exchange membrane is exposed to room temperature in order to assemble an electrochemical conversion cell or stack in a room temperature environment, the anion exchange membrane can dry out and be broken or damaged in a short time, and there is a problem that the processability of the assembly work is reduced due to such poor mechanical properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] KR10-2019-0125822A Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to improve the mechanical properties at room temperature by constantly having a predetermined amount of moisture in the separator.

[0008] That is, the present invention aims to provide a separator having a structure in which a porous structure layer having hydrophilic or hydrophobic properties is laminated on the surface of an ion exchange membrane, thereby maintaining a predetermined amount of moisture on the surface of the ion exchange membrane, thereby maintaining the performance of the ion exchange membrane at the same level, and improving the mechanical properties at room temperature, and an electrochemical conversion cell including the same. [Means for solving the problem]

[0009] The present invention provides a separator and an electrochemical conversion cell including the same.

[0010] (1) The present invention provides a separator comprising a base membrane and a hydrophilic porous structure layer or a hydrophobic porous structure layer laminated on at least one surface of the base membrane, wherein the base membrane is an anion exchange membrane, a cation exchange membrane or an amphoteric ion exchange membrane.

[0011] (2) The present invention provides the separator according to the above (1), wherein the hydrophilic porous structure layer contains a hydrophilic polymer.

[0012] (3) The present invention provides a separator according to the above (1) or (2), wherein the hydrophilic porous structure layer contains polytetrafluoroethylene (PTFE) whose surface has been hydrophilically treated.

[0013] (4) The present invention provides the separator according to any one of the above (1) to (3), wherein the average particle size of the pores in the hydrophilic porous structure layer is 0.2 to 0.45 μm.

[0014] (5) The present invention provides the separator according to any one of the above (1) to (4), wherein the hydrophilic porous structure layer is laminated on one surface of the base membrane.

[0015] (6) The present invention provides the separator according to any one of the above (1) to (5), wherein the separator does not contain a binder between the base membrane and the hydrophilic porous structure layer.

[0016] (7) The present invention provides a separator according to any one of (1) to (6), wherein the hydrophobic porous structure layer is one or more selected from the group consisting of PTFE, PVDF, nylon, CA (Cellulose acetate), and PES (Polyethylene sulfide).

[0017] (8) The present invention provides an electrochemical conversion cell comprising a cathode, an anode, an electrolyte, and a separator according to any one of (1) to (7) above, disposed between the cathode and the anode.

[0018] (9) The present invention provides, in the above (8), an electrochemical conversion cell that converts carbon dioxide into carbon monoxide. Effect of the Invention

[0019] The separator of the present invention has a structure in which a porous structure layer having hydrophilic or hydrophobic properties is laminated on the surface of an ion exchange membrane, so that the moisture content of the ion exchange membrane can be maintained at a predetermined level even when left at room temperature for a long period of time, and the mechanical properties of the exchange membrane can be improved.

[0020] In addition, the separator of the present invention maintains its wettability even in a room temperature environment, thereby preventing the separator from drying out and becoming damaged or crumbling, and improving poor processability that may occur due to the damage when assembling a cell or stack in a room temperature environment.

[0021] In addition, the electrochemical conversion cell including the separator of the present invention not only has improved mechanical properties by including a separator that can maintain wettability even at room temperature, but also has the same or higher levels in terms of the Faraday efficiency of carbon monoxide, the carbon dioxide conversion rate, and the voltage of the electrochemical conversion cell. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a side view showing the structure of a separator according to the present invention. [Diagram 2] 1 is a photograph showing the state of a conventional anion exchange membrane after being exposed to air at room temperature for two hours. [Diagram 3] 4 is a photograph showing the state of the separator according to the present invention after being exposed to air at room temperature for two hours. [Figure 4] FIG. 2 is a graph showing the carbon dioxide conversion rate, the carbon monoxide Faraday efficiency, and the voltage in Examples 1 to 5 and Comparative Examples 1 and 2. [Diagram 5] 1 is a SEM image showing the shape of a porous structure layer according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be described in more detail below to aid in understanding the present invention. In this regard, the terms and words used in the specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that are consistent with the technical ideas of the present invention, in accordance with the principle that the inventors can appropriately define the concepts of terms in order to best describe their inventions.

[0024] Separator The separator of the present invention includes a base membrane and a hydrophilic porous structure layer or a hydrophobic porous structure layer laminated on at least one surface of the base membrane, and the base membrane can be an anion exchange membrane, a cation exchange membrane, or an amphoteric ion exchange membrane.

[0025] According to an embodiment of the present invention, the separator may include a base membrane and a porous structure layer, and the porous structure layer may be laminated on at least one surface of the base membrane. The base membrane may be an ion-selective exchange membrane, and the base membrane may include an anion exchange membrane, a cation exchange membrane, or an amphoteric ion exchange membrane. Specifically, the separator of the present invention may be an anion exchange membrane.

[0026] In addition, the porous structure layer may have hydrophilic or hydrophobic properties. The porous structure layer may be laminated on at least one surface of the base membrane to maintain a predetermined moisture content of the base membrane.

[0027] In addition, the porous structure layer has a porous structure, and the porous structure means a structure having a large number of holes, i.e., pores, on the surface or inside of a material. The pores may have an irregular shape such as a sphere, an ellipsoid, or a rod, and the average diameter of the pores may be 0.2 μm to 0.45 μm, as described below. The average diameter of the pores can be measured as the length of the major axis of the surface pores observed in an arbitrarily sampled range (10 μm or more horizontally and 15 μm or more vertically) in a photograph measured using a field emission scanning electron microscope (FE-SEM). The porous structure layer of the present invention has a porous structure, and thus has a light weight and excellent mechanical strength, and has a low resistance, so that the transfer of materials can be smoothly performed through the pores.

[0028] Meanwhile, an anion exchange membrane is generally used as a separator of an electrochemical conversion device. When an anion exchange membrane is used as a separator of the electrochemical conversion device, the electrochemical conversion rate of the electrochemical conversion device is excellent. However, the anion exchange membrane is easily dried when exposed to room temperature, and when fastened to a cell or stack of an electrochemical conversion device at room temperature, the anion exchange membrane is easily dried, and therefore, the moisture content cannot be maintained, and the anion exchange membrane may be broken or damaged. Specifically, the anion exchange membrane can be stored with water or fluid having sufficient moisture, and since the fastening process of the cell or stack is performed in a room temperature environment, when the anion exchange membrane is exposed to a room temperature environment, even though the anion exchange membrane is stored in water having sufficient moisture, the moisture of the anion exchange membrane is easily evaporated, and the anion exchange membrane may be damaged. Therefore, the conventional anion exchange membrane may cause considerable problems in terms of workability due to its poor mechanical properties in a room temperature environment. Therefore, in order to improve or maintain such mechanical properties and workability of the anion exchange membrane, a certain amount of moisture must always be present in the anion exchange membrane and the wettability of the moisture must be maintained.

[0029] The separator of the present invention has the effect of improving the poor mechanical properties and poor workability, which are problems of the conventional separator, while maintaining the same or higher level of performance as the conventional separator. Specifically, the separator of the present invention has a porous structure layer having hydrophilic or hydrophobic properties laminated on at least one surface of the base membrane, so that the moisture content of the separator can be maintained at a predetermined level even when left at room temperature for a long period of time, thereby improving the poor mechanical properties and poor workability.

[0030] Fig. 2 shows the appearance of a conventional hydrophilically coated anion exchange membrane when exposed to the air for 2 hours at room temperature, and Fig. 3 shows the appearance of a separator having a hydrophilic porous structure layer laminated on the surface of the anion exchange membrane of the present invention when exposed to the air for 2 hours at the same room temperature. Fig. 3(a) shows the application of PTFE with a hydrophilic or hydrophobic surface treatment, and Fig. 3(b) shows the application of PVDF with a hydrophilic or hydrophobic surface treatment.

[0031] According to an embodiment of the present invention, the separator may not be deformed from its initial shape when exposed to air at room temperature for more than 2 hours.

[0032] Specifically, referring to FIG. 2, when the separator of the present invention and the conventional separator are exposed to the air at room temperature in the same manner, the conventional separator undergoes water evaporation after 1 to 2 hours, and is broken or mechanically distorted.

[0033] In contrast, referring to Fig. 3, the separator of the present invention can maintain its initial shape without cracking or breaking even after 1 to 2 hours. The separator of the present invention has a structure in which a porous structure layer having hydrophilic or hydrophobic properties is laminated on the surface of a base membrane, and therefore has the advantage of having a higher moisture content and being able to maintain the moisture content for a long period of time compared to a single separator that is simply treated to be hydrophilic.

[0034] This allows the initial shape of the separator to be maintained without deformation due to the moisture, and improves poor mechanical properties and workability caused by a room temperature environment. In addition, the separator of the present invention can maintain a weight of 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of its initial weight even when exposed to air at room temperature for 2 hours or more. In addition, when the separator is exposed to air at room temperature for 2 hours or more, the shrinkage rate of the separator can be 15% or less, 13% or less, 11% or less, 9% or less, 7% or less, 5% or less, or 3% or less. The shrinkage rate can be calculated by (initial length of separator - length of separator after shrinking at 25°C / 2hr) / (initial length of separator) x 100.

[0035] In addition, the manufacturing process of the separator of the present invention is simpler and less complicated than the process of simply subjecting one separator to hydrophilic treatment. Specifically, the process of coating one separator with a hydrophilic material can be performed at a high temperature of 100° C. or more, in which case the separator may deform, shrink, or melt. In addition, the coating process is not performed well depending on the moisture present in the separator, and is possible when a water-based binder is used or a dry environment is provided, and the conventional process of hydrophilizing or coating the surface of the separator is complicated in terms of process conditions and may take a long process time. In addition, in the case of a coating method using water as a solvent, it is difficult to uniformly coat the internal pores due to the high viscosity and surface tension of water, and the hydrophilic coating material may dissolve in water and be detached from the separator, resulting in a disadvantage in that hydrophilicity is lost. In addition, the use of a binder increases the thickness of the separator, reducing the energy density, and increasing the manufacturing cost, thereby reducing efficiency.

[0036] According to an embodiment of the present invention, the separator may not include a binder between the base membrane and the hydrophilic porous structure layer. In particular, the separator of the present invention can be manufactured by stacking a porous structure layer having hydrophilic properties without using a binder, thereby making it possible to manufacture a separator with a thinner thickness. In addition, in the manufacturing process of the separator of the present invention, the adhesion of the stacked porous structure layer is increased due to the moisture present in the ion-selective exchange membrane and the porous structure layer, so that the porous structure layer can be quickly fixed to the ion-selective exchange membrane. Therefore, when manufacturing the separator according to the present invention, the manufacturing time can be shortened compared to the manufacturing time of a separator using a conventional hydrophilic treatment.

[0037] According to an embodiment of the present invention, the hydrophilic porous structure layer may include at least one selected from the group consisting of hydrophilic polymers, hydrophilic metals, ceramics, and cellulose.

[0038] The hydrophilic porous structure layer included in the separator of the present invention may include a hydrophilic polymer. Specifically, the hydrophilic polymer may be a polymer prepared by polymerizing a monomer containing at least one hydrophilic group selected from the group consisting of a hydroxyl functional group (-OH), a carboxyl acid functional group (-COOH), an alkylene oxide functional group (-RO-), and an amine functional group (-NH2). In addition, the hydrophilic polymer may include at least one selected from the group consisting of polypyrolidone, polyethylene glycol, and polyvinyl alcohol. The hydrophilic polymer may be one or more hydrophobic polymers selected from the group consisting of polyethylene (PE), polypropylene (PP), polycarbonate (PC), polyimide, polyether imide (PEI), polysulfone (PSF), polyether sulfone (PES), polyvinyledene difluoride (PVDF), and polytetrafluoroethylene (PTFE) that have been hydrophilically treated. More specifically, the hydrophilic polymer that can be used in the hydrophilic porous structure layer of the present invention may be polytetrafluoroethylene (PTFE) that has been hydrophilically treated.

[0039] The hydrophilic porous structure layer may also include a hydrophilic metal, and most metals and metal oxides have hydrophilic properties due to their high surface energy. The hydrophilic metal may refer to a metal or metal oxide whose surface is completely wetted by water and has a contact angle with water of less than 90 degrees. The metal may include at least one selected from the group consisting of Ni, Cu, Al, Fe, stainless steel, Fe-Ni alloys, Fe-Ni-Cr alloys, and Fe-Ni-SiC alloys, and the metal oxide may include at least one selected from the group consisting of titanium butoxide, zirconium butoxide, MgO, hydrophilic zeolite A, and ETS-based porous materials as hydrophilic metal oxides.

[0040] The hydrophilic porous structure layer may include ceramic, and the ceramic may include one or more selected from the group consisting of ZrO2, Al2O3, and SiO2.

[0041] Also, the hydrophilic porous structure layer may contain cellulose, and the cellulose may include cellulose acetate and cellulose nitrate.

[0042] According to an embodiment of the present invention, the hydrophilic porous structure layer may include polytetrafluoroethylene (PTFE) whose surface has been hydrophilically treated.

[0043] The polytetrafluoroethylene (PTFE) is a polymeric compound consisting of carbon and fluorine, and is a crystalline material having excellent electrical resistance, high thermal stability, acid resistance, chemical resistance, melting point and dimensional stability. However, the polytetrafluoroethylene exhibits excellent sliding properties and non-adhesive properties, and is essentially hydrophobic because it is a polymeric compound consisting only of carbon and fluorine.

[0044] Therefore, the polytetrafluoroethylene usable for the hydrophilic porous structure layer of the present invention is a polytetrafluoroethylene that has been hydrophilically treated, and the hydrophilically treated polytetrafluoroethylene can have the same or higher mechanical strength and dimensional stability as the conventional polytetrafluoroethylene, and can have improved adhesion and hydrophilicity. Therefore, the hydrophilic porous structure layer containing the hydrophilically treated polytetrafluoroethylene has improved adhesion to the anion exchange membrane, and can be fixed after lamination without a separate binder.

[0045] In contrast, hydrocarbon polymers such as polyethylene have the disadvantages of low mechanical strength, increased brittleness when dry, and poor dimensional stability due to expansion when wet. In addition, the porous structure layer containing the polyethylene has poor adhesion to the anion exchange membrane, requiring a separate binder, and the thickness of the entire separator increases, which can result in poor energy density and resistance.

[0046] The method for hydrophilizing polytetrafluoroethylene aims to reduce the contact angle of water with the surface of the polymer material to make it hydrophilic, and methods such as high voltage corona discharge and direct current plasma discharge can be used to change the contact angle.

[0047] According to an embodiment of the present invention, the average diameter of the pores of the hydrophilic porous structure layer may be 0.2 μm to 0.45 μm. More specifically, the average diameter of the pores of the hydrophilic porous structure layer may be 0.2 μm or more, 0.22 μm or more, 0.24 μm or more, 0.26 μm or more, 0.28 μm or more, and may be 0.45 μm or less, 0.43 μm or less, 0.41 μm or less, 0.4 μm or less, or 0.37 μm or less. When the average diameter of the pores of the hydrophilic porous structure layer of the present invention satisfies the above range, the resistance of the hydrophilic porous structure layer is reduced, the electrolyte permeability is improved, and the mechanical strength is excellent.

[0048] Fig. 5 is an SEM photograph of the porous structure layer containing PTFE of the present invention. The average particle size of the pores can be measured by using a scanning electron microscope (FE-SEM) (Hitachi S-4800 Scanning Electron Microscope) to measure the surface of the sample at 2,500 times magnification, and then measuring the length of the major axis of the surface pores observed in an arbitrarily sampled range (10 μm or more horizontally and 15 μm or more vertically) in the measured photograph as the pore diameter. The number of measurements is a minimum of 10 or more, and the average and maximum pore diameters obtained after the measurement can be obtained.

[0049] According to an embodiment of the present invention, the hydrophilic porous structure layer may be laminated on any one side of the base membrane. The hydrophilic porous structure layer may be laminated on at least one side of the base membrane, and more specifically, the hydrophilic porous structure layer may be laminated on only one side of the base membrane. Even if the separator has the hydrophilic porous structure layer laminated on only one side of the base membrane, the separator can maintain a moisture content at the same level as a separator laminated on both sides of the base membrane, thereby ensuring sufficient mechanical strength and workability for fastening a cell or stack. In addition, the separator of the present invention, in which the hydrophilic porous structure layer is laminated on only one side of the base membrane, has a reduced overall thickness of the separator, has high ionic conductivity, and reduces resistance, thereby obtaining high performance and conversion rate.

[0050] On the other hand, in the case of a structure in which a hydrophilically treated porous structure layer is impregnated with an anion exchange membrane or an ion-conductive polymer material, the porous structure layer cannot retain moisture in the exchange membrane, and thus the wettability of the separator to moisture may be significantly reduced compared to a separator having a laminated structure.

[0051] In addition, in the separator having the impregnated structure, the entire area of ​​the anion exchange membrane cannot form a single layer, and since the anion exchange membrane is impregnated into each pore of the porous structure layer, ion transport cannot be performed uniformly over the entire area of ​​the anion exchange membrane, which can reduce the faradaic efficiency of carbon monoxide.

[0052] According to one embodiment of the present invention, the separator of the present invention may include a base membrane and a hydrophobic porous structure layer on at least one surface of the base membrane.

[0053] The hydrophobic porous structure layer can prevent the moisture contained in the ion selective exchange membrane from evaporating or escaping to the outside during storage due to its hydrophobicity. The material usable for the hydrophobic porous structure layer can include at least one selected from the group consisting of PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), nylon, CA (cellulose acetate), and PES (polyethylene sulfide), and specifically, the hydrophobic porous structure layer of the present invention can include PVDF.

[0054] Electrochemical Conversion Cell The electrochemical conversion cell of the present invention can include an anode, a cathode, an electrolyte, and a separator disposed between the cathode and the anode, the separator including the separator of the present invention described above.

[0055] According to another embodiment of the present invention, the electrochemical conversion cell can be used in any electrochemical conversion device, and the electrochemical conversion device can include a device capable of producing useful chemicals by electrochemical conversion such as a fuel cell or water electrolysis, and a device capable of reducing and converting carbon dioxide and NOx. Specifically, the electrochemical conversion cell can be an electrochemical conversion cell included in an electrolysis device that converts carbon dioxide into carbon monoxide.

[0056] According to an embodiment of the present invention, the electrochemical conversion cell may be a cell that converts carbon dioxide into carbon monoxide by inputting carbon dioxide, and may include an anode, a cathode, an electrolyte, and a separator. Electrolysis means that a decomposition reaction that does not occur by itself is performed by applying a direct current voltage to decompose a material through an oxidation-reduction reaction. The anode is an oxidation electrode that oxidizes water to generate oxygen, and hydrogen ions are generated at this time. The hydrogen ions generated from the anode are transferred to the cathode via the electrolyte, and the cathode is a reduction electrode that can generate products by reacting reactants input to the cathode with electrons and hydrogen ions transferred from the anode. The separator may be disposed between the anode and the cathode. The separator may be made of an inert material that does not participate in an electrochemical reaction by itself, but may provide a path through which ions can move between the anode and the cathode, and may play a role in isolating the physical contact between the anode and the cathode.

[0057] In addition, the anode and the cathode of the electrochemical conversion cell 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 by an electric reduction reaction on the surface of the cathode. Therefore, the cathode may include a gas diffusion layer to uniformly supply humidified carbon dioxide gas to the cathode region side. 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 condensation of moisture, thereby allowing the supply of carbon dioxide to be continuous and uniform, and allowing the electrolysis reaction to be smoothly performed. In addition, the catalyst layer may have a surface such as a porous structure so that the gas permeability is well exhibited on the surface.

[0058] According to one embodiment of the present invention, the anode may include a catalyst active in water electrolysis, and the catalytic 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, etc., for the oxygen evolution reaction. Specifically, the anode in the carbon dioxide electrolysis device of the present invention may include nickel (Ni) coated with ruthenium oxide (RuO2) and cerium oxide (CeO2).

[0059] In addition, since the carbon dioxide reduction reaction occurring at the cathode competes with the hydrogen generation reaction, a large voltage is required for the hydrogen generation reaction, and a catalyst showing activity in the carbon dioxide reduction reaction may be included. The catalyst layer of the cathode may contain one or more selected from the group consisting of Sn, Sn alloy, Al, Au, Ag, C, Cd, Co, Cr, Cu, Cu alloy, Ga, Hg, In, Mo, Nb, Ni, NiCo2O4, Ni alloy, Ni-Fe alloy, Pb, Rh, Ti, V, W, Zn, and mixtures thereof for the hydrogen generation reaction. Specifically, the cathode in the carbon dioxide electrolysis device of the present invention may contain silver (Ag).

[0060] The separator may include a cation exchange membrane (CEM) or an anion exchange membrane (AEM).

[0061] The electrolyte may be KHCO3, K2CO3, KOH, KCl, KClO4, K2SiO3, Na2SO4, NaNO3, NaCl, NaF, NaClO4, CaCl2, guanidine cation, H + A solution containing an ion, an alkali metal cation, an ammonium cation, an alkylammonium cation, a halide ion, an alkylamine, a borate, a carbonate, a guanidine derivative, a nitrite, a nitrate, a phosphate, a polyphosphate, a perchlorate, a silicate, a sulfate, a tetraalkylammonium salt, or a mixture thereof, may be used, and the electrolyte of the carbon dioxide electrolysis device of the present invention may include KOH.

[0062] In addition, the gas diffusion layer may be 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. In the carbon dioxide electrolysis device of the present invention, the gas diffusion layer may be a carbon fiber cloth.

[0063] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to exemplary embodiments thereof, so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0064] Example 1 As shown in Fig. 1, a separator including an anion exchange membrane and a hydrophilic porous structure layer laminated on one side of the anion exchange membrane was manufactured. The manufacturing process of the separator is as follows.

[0065] An anion exchange membrane (Sustainion X37, Dioxide Materials) was prepared as the base membrane, and a surface-hydrophilized polytetrafluoroethylene (PTFE) (Hyundai Micro) with a pore size of 0.2 μm was prepared as the porous structure layer. The surface of the surface-hydrophilized PTFE porous structure layer was thoroughly wetted with ultrapure water (DI water), and then laminated on the anion exchange membrane, and a certain pressure was applied to thoroughly bond the interface to manufacture the device.

[0066] Example 2 A laminated separator was manufactured in the same manner as in Example 1, except that a hydrophilically treated PVDF (Hyundai Micro) porous structure layer was used instead of the hydrophilically treated PTFE (Hyundai Micro) porous structure layer.

[0067] Example 3 A separator was manufactured in the same manner as in Example 1, except that only the PTFE porous structure layer whose surface had been hydrophilically treated was used without the anion exchange membrane.

[0068] Example 4 A separator having a laminated structure was manufactured in the same manner as in Example 1, except that a PTFE porous structure layer having a pore size of 0.4 μm and having been subjected to a surface hydrophilic treatment was used.

[0069] Example 5 A laminated separator was manufactured in the same manner as in Example 1, except that a porous structure layer containing cellulose acetate was used instead of the hydrophilic PTFE (Hyundai Micro).

[0070] Example 6 A laminated separator was manufactured in the same manner as in Example 1, except that a porous structure layer containing polyethylene sulfide was used instead of the hydrophilic PTFE (Hyundai Micro).

[0071] Comparative Example 1 A separator was produced in the same manner as in Example 1, except that the separator did not include a porous structure layer and included only an anion exchange membrane.

[0072] Comparative Example 2 A separator having a laminated structure was produced in the same manner as in Example 1, except that a porous structure layer containing polyethylene (PE) was used.

[0073] Comparative Example 3 As the porous structure layer, surface-hydrophilized polytetrafluoroethylene (PTFE) (Hyundai Micro) with a pore size of 0.2 μm was prepared. The polytetrafluoroethylene was fixed to a 10 cm x 10 cm frame, and the PTFE frame was thoroughly immersed in a DI water bath and maintained at 60 ° C for 12 hours. An aqueous solution containing 30 wt % ethanolamine (Ethanolamine, Sigma-Aldrich>98%) was prepared, and the PTFE frame was placed in it and reacted at 80 ° C for a day while stirring. The PTFE frame was then washed several times with distilled water to remove the remaining ethanolamine, and vacuum dried at room temperature for a day. A separator was manufactured by placing PTFE, the surface and inside of which were substituted with ionic functional groups fixed to the frame, on an anion exchange membrane (Sustainion X37, Dioxide Materials), and leaving it for 1 hour so that the anion exchange membrane was impregnated.

[0074] Experimental Example 1 The separators prepared according to the examples and comparative examples were exposed to the outside air at room temperature for 2 hours, and the moisture evaporation phenomenon and state of the separator were observed. The results of the state of the separator are shown in Table 1 below.

[0075] [Table 1]

[0076] Experimental Example 2 Carbon dioxide electrolysis was carried out by adjusting the operating conditions of the carbon dioxide electrolysis apparatus including the separators prepared according to the examples and comparative examples as follows.

[0077] Reaction current density: 100mA / cm 2 (Constant current operation) Reaction voltage: 3~3.5V Reaction temperature: 40℃ Reaction pressure: 1 atm (normal pressure) Anode catalyst: RuO2+CeO2on Ni mesh Cathode catalyst: Ag powder Electrode area: 25cm 2 Gas diffusion layer: Sigracet 39BB Anode electrolyte: 0.5M KHCO3 (25 ml / min) Cathode reactant: 40℃ humidified CO2 gas (25 ccm)

[0078] During the electrolysis, the carbon dioxide conversion rate (%), the carbon monoxide Faraday efficiency (CO Faraday efficiency, %), and the voltage were measured, and the results are shown in Table 2 below and are graphed in FIG. 4.

[0079] *Measurement method (1) Carbon dioxide conversion rate (%) The conversion rate (%) was calculated as the ratio of carbon monoxide (CO) produced to the amount of carbon dioxide (CO2) gas input per hour.

[0080] (2) Faraday efficiency of carbon monoxide (%) The gas composition was measured by GC (Gas Chromatography) analysis at the exhaust line, and the Faraday efficiency was calculated by the following formula.

[0081]

number

[0082] In the above mathematical formula 1, Q is the flow rate in the exhaust line, F is the Faraday constant, p is the pressure, T is the measured temperature, and R is the ideal gas constant. total ) is the value of the total current applied over time, and the current to the product (i product ) is the volume of gas measured by GC analysis (V product ) is the value calculated from

[0083] (3) Voltage (V) The application of current and the measurement of voltage were carried out using a VSP potentiostat manufactured by BioLogic. An 80 A booster was attached, and a current corresponding to a large area was applied. The current application was 100 mA / cm. 2 , 200mA / cm 2 , 300mA / cm 2 After maintaining each step for a predetermined time, the voltage at the time when 10 minutes had elapsed was recorded. At this time, GC (Gas Chromatography) analysis was also performed at the same time.

[0084] [Table 2]

[0085] Referring to Tables 1 and 2, it can be seen that in Examples 1 to 6 using separators including a porous structure layer according to the present invention, the separators are in good condition without any change even when exposed to the outside air for 2 hours at room temperature, and this is because the porous structure layer maintains the moisture wettability of the separator and contains a certain level of moisture. In contrast, in the case of Comparative Example 1, which does not include a porous structure layer and uses only an anion exchange membrane, it can be seen that the separator is entirely crushed and cracked when exposed to the outside air for 2 hours at room temperature.

[0086] In addition, it can be confirmed that Examples 1 to 6 maintain the wettability of water, and thus improve the workability, as well as have excellent effects in terms of the carbon dioxide conversion rate, the faradaic efficiency of CO, and the overvoltage. On the other hand, it can be confirmed that Comparative Example 2, which uses a separator including a porous structure layer containing polyethylene (PE), maintains the wettability of water, but generates an overvoltage of 6V or more when used in an electrochemical conversion cell, and thus shows very poor effects in terms of the carbon dioxide conversion rate and the faradaic efficiency of CO.

[0087] In addition, in the case of Comparative Example 3, the anion exchange membrane is impregnated in the porous structure layer, and in the case of Comparative Example 3, the anion exchange membrane having ion conductivity cannot be formed into a single layer, but is impregnated in each pore and arranged unevenly, so that the porous structure layer that maintains the wettability of water cannot perform its original role, and the separator is broken after 1-2 hours. In addition, it can be confirmed that the separator of Comparative Example 3 cannot uniformly transfer ions over the entire area of ​​the anion exchange membrane, and therefore the faradaic efficiency of carbon monoxide is reduced. [Explanation of symbols]

[0088] 100 Anion exchange membrane 200 porous structure layer

Claims

1. A base membrane; A hydrophilic porous structure layer or a hydrophobic porous structure layer laminated on at least one surface of the base membrane, The separator, wherein the base membrane is an anion exchange membrane, a cation exchange membrane, or an amphoteric ion exchange membrane.

2. The separator according to claim 1 , wherein the hydrophilic porous structure layer comprises a hydrophilic polymer.

3. The separator according to claim 1 , wherein the hydrophilic porous structure layer comprises polytetrafluoroethylene (PTFE) whose surface has been treated to be hydrophilic.

4. 2. The separator according to claim 1, wherein the average particle size of the pores in the hydrophilic porous structure layer is 0.2 to 0.45 μm.

5. The separator according to claim 1 , wherein the hydrophilic porous structure layer is laminated on one side of the base membrane.

6. The separator of claim 1 , wherein the separator does not include a binder between the base membrane and the hydrophilic porous structural layer.

7. The separator according to claim 1 , wherein the hydrophobic porous structure layer is at least one selected from the group consisting of PTFE, PVDF, nylon, CA (Cellulose acetate), and PES (Polyethylene sulfide).

8. a cathode, an anode, and an electrolyte; 8. An electrochemical conversion cell comprising: a separator according to claim 1 disposed between the cathode and the anode.

9. 9. The electrochemical conversion cell of claim 8, wherein the electrochemical conversion cell converts carbon dioxide to carbon monoxide.

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