Electrochemical carbon dioxide conversion system

Abstract

The present invention relates to an electrochemical carbon dioxide conversion system, which includes: a first electrode; a second electrode; and a separator membrane positioned between the first electrode and the second electrode, being porous and comprising a first layer and a second layer having different average pore sizes.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2024-0058752, filed on May 2, 2024, and Korean Patent Application No. 10-2025-0051392, filed on April 21, 2025, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This invention relates to an electrochemical carbon dioxide conversion system. Background Technology

[0004] With industrialization, fossil fuels have been overused, resulting in excessive carbon dioxide production and causing problems such as climate anomalies and global warming. As the economic and social problems arising from these issues become more apparent, international discussions on reducing carbon dioxide emissions are expanding. Consequently, technologies for converting carbon dioxide (a major cause of global warming) into useful compounds have attracted considerable interest. Among these technologies, electrochemical conversion can transform carbon dioxide into useful substances, such as high-value fuels or platform compounds used in the synthesis of petrochemical products. Furthermore, its importance is increasing due to its potential use as a renewable energy storage technology. However, to realize this technology and apply it industrially for profit, various systems and materials need to be developed.

[0005] Meanwhile, while anion exchange membranes offer good carbon dioxide conversion efficiency when used as separators in electrochemical carbon dioxide conversion systems, they are prone to drying at room temperature and may therefore crack or be damaged. Furthermore, cation exchange membranes increase manufacturing costs due to their high price and are difficult to apply to electrochemical carbon dioxide conversion systems operating under alkaline conditions because they must be used under acidic conditions. Additionally, when porous substrates are used as separators, carbon dioxide gas circulating around the reduction electrode moves towards it, potentially degrading the performance of the electrochemical carbon dioxide conversion system.

[0006] [Related Technical Documents]

[0007] [Patent Literature]

[0008] (Patent Document 1) WO2022-264007A Summary of the Invention

[0009] Technical issues

[0010] The present invention aims to provide an electrochemical carbon dioxide conversion system that exhibits improved CO Faradaic efficiency, improved CO2 conversion rate and reduced overpotential by enabling good circulation of the electrolyte composition and preventing carbon dioxide circulating around the reducing electrode from moving to the oxidizing electrode.

[0011] Technical solution

[0012] To achieve the above objectives, 1) the present invention provides an electrochemical carbon dioxide conversion system comprising: a first electrode; a second electrode; and a separator membrane positioned between the first electrode and the second electrode, being porous and comprising a first layer and a second layer having different average pore sizes.

[0013] 2) The present invention can provide an electrochemical carbon dioxide conversion system according to 1), wherein the ratio of the average pore size of the first layer to the average pore size of the second layer is from 100:0.1 to 65.0.

[0014] 3) The present invention can provide an electrochemical carbon dioxide conversion system according to 1) or 2), wherein the average pore size of the first layer is 20 nm to 4,970 nm larger than the average pore size of the second layer.

[0015] 4) The present invention can provide an electrochemical carbon dioxide conversion system according to 2), wherein the average pore size of the first layer is 30 nm to 5,000 nm.

[0016] 5) The present invention can provide an electrochemical carbon dioxide conversion system according to 2), wherein the average pore size of the second layer is 30 nm to 5,000 nm.

[0017] 6) The present invention can provide an electrochemical carbon dioxide conversion system according to any one of 1) to 5), wherein the average thickness of the first layer is from 10.0 μm to 500.0 μm.

[0018] 7) The present invention can provide an electrochemical carbon dioxide conversion system according to any one of 1) to 6), wherein the average thickness of the second layer is from 10.0 μm to 500.0 μm.

[0019] 8) The present invention can provide an electrochemical carbon dioxide conversion system according to any one of 1) to 7), wherein the first electrode is an oxidation electrode, and the first layer of the separator is oriented toward the first electrode.

[0020] 9) The present invention can provide an electrochemical carbon dioxide conversion system according to any one of 1) to 8), wherein the second electrode is a reduction electrode and the second layer of the separator is an oriented second electrode.

[0021] 10) The present invention may provide an electrochemical carbon dioxide conversion system according to any one of 1) to 9), wherein the separator membrane comprises one or more selected from polyethersulfone, polytetrafluoroethylene, cellulose acetate, polyvinylidene fluoride, polyethylene, polypropylene, polyvinyl alcohol, polyacrylonitrile, Nafion and nylon.

[0022] Beneficial effects

[0023] The electrochemical carbon dioxide conversion system according to the invention enables good circulation of the electrolyte composition and prevents carbon dioxide circulating around the reducing electrode from moving to the oxidizing electrode, thereby improving CO Faraday efficiency and CO2 conversion rate, and reducing overpotential. Detailed Implementation

[0024] The invention will be described in further detail below to aid in understanding it.

[0025] The terms and phrases used in this specification and claims should not be construed as limited to their common or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical scope of the invention, based on the principle that the inventors may appropriately define the concepts of terms in order to best describe the invention.

[0026] In this invention, the average aperture can be measured using a scanning electron microscope. Specifically, after measuring the sample surface using a field emission scanning electron microscope (FE-SEM, ZEISS MINI300 scanning electron microscope) at 6,000x magnification, the length of the major axis of the aperture in the surface determined within a randomly sampled area (10 μm or more in width and 15 μm or more in length) in the obtained photograph can be measured as the aperture size. The number of measurements should be at least 10, and the average value of the measured aperture can be calculated.

[0027] In this invention, the average thickness of the first and second layers of the separator can be measured using a digital high-precision thickness gauge (Mitutoyo Corporation, commercially available 547-401A).

[0028] In this invention, porosity can be measured using the mercury intrusion porosity determination method. Specifically, it can be measured using a porosity measuring instrument (manufacturer: Micromeritics Instrument Corporation, instrument name: AutoPore V) via the mercury intrusion porosity determination method.

[0029] Electrochemical carbon dioxide conversion system

[0030] An electrochemical carbon dioxide conversion system according to one embodiment of the present invention includes: a first electrode; a second electrode; and a separator membrane positioned between the first electrode and the second electrode, the separator membrane being porous and comprising a first layer and a second layer having different average pore sizes.

[0031] Furthermore, an electrochemical carbon dioxide conversion system according to one embodiment of the present invention may comprise an electrolyte composition.

[0032] According to one embodiment of the present invention, the electrochemical carbon dioxide conversion system can be a membrane electrode assembly type electrolyzer or a flow electrolyzer.

[0033] Here, a membrane electrode assembly (MEA) type electrolyzer refers to a structure in which a first electrode, a separator membrane, and a second electrode are sequentially positioned. Furthermore, the MEA type electrolyzer can be operated by supplying an electrolyte composition to the first electrode and carbon dioxide to the second electrode. In this case, the first electrode can be an oxidation electrode, and the second electrode can be a reduction electrode.

[0034] A flow-through electrolyzer refers to a structure in which a separator membrane is positioned between a first electrode and a second electrode, an electrolyte composition is positioned between the first electrode and the separator membrane, and an electrolyte composition is positioned between the second electrode and the separator membrane. In this case, the first electrode can be an oxidation electrode, and the second electrode can be a reduction electrode.

[0035] The components of an electrochemical carbon dioxide conversion system according to one embodiment of the present invention will be described in detail below.

[0036] 1) First electrode

[0037] The first electrode can be an oxidation electrode. When the electrolyte composition is neutral or alkaline, OH... - It can be oxidized at the oxidation electrode to produce oxygen, water, and electrons (e). - Furthermore, water and electrons can move to the reduction electrode to initiate the carbon dioxide reduction reaction.

[0038] Furthermore, when the electrolyte composition is acidic, water molecules can be oxidized at the oxidation electrode to generate oxygen and hydrogen ions (H+). + ) and electrons (e - Hydrogen ions and electrons can move to the reduction electrode via a separator membrane and an external circuit, respectively. The hydrogen ions and electrons moving from the oxidation electrode encounter carbon dioxide to initiate a reduction reaction, and various conversion products can be generated depending on the number of electrons and hydrogen ions involved in the reaction.

[0039]

[0040]

[0041]

[0042]

[0043]

[0044] The oxide electrode may contain oxides selected from one or more of Ru, Ir, Pt, Co, Ni, Fe and Cu.

[0045] 2) Second electrode

[0046] The second electrode can be a reduction electrode. At the reduction electrode, water and electrons moving from the oxidation electrode can meet carbon dioxide to initiate a reduction reaction, or hydrogen ions and electrons moving from the oxidation electrode can meet carbon dioxide to initiate a reduction reaction.

[0047] The reduction electrode may include a gas diffusion layer and a catalyst layer positioned on the gas diffusion layer.

[0048] The gas diffusion layer may include one or more of a gas diffusion medium and a microporous layer.

[0049] The gas diffusion medium has pores with a size larger than the pore size in the microporous layer, and may include one or more of nonwoven carbon paper, carbon felt, nickel foam, titanium foam, and insulating mesh.

[0050] The microporous layer may contain one or more of a material selected from carbon powder and thermally expandable graphite.

[0051] When the gas diffusion layer includes both a gas diffusion medium and a microporous layer, the gas diffusion layer may include a gas diffusion medium, a microporous layer positioned on the gas diffusion medium, and a catalyst layer positioned on the microporous layer.

[0052] The catalyst layer may contain one or more of In, Sn, Hg, Pb, Zn, Au, Ag, and Cu, which are active in the carbon dioxide conversion reaction, and one or more of fluorine-based polymers and anionic polymers. The fluorine-based polymer may be polytetrafluoroethylene.

[0053] 3) Separator membrane

[0054] The separator membrane separates the first electrode and the second electrode and can act as a channel for ions generated at the first electrode to move to the second electrode.

[0055] The separator membrane is positioned between the first electrode and the second electrode, is porous, and comprises a first layer and a second layer with different average pore sizes. Specifically, the separator membrane may comprise a first layer and a second layer in a laminated state.

[0056] When the separator membrane has the above-described structure, the positions of the first and second layers of the separator membrane can be adjusted according to the type of electrode, thereby improving the performance of the electrochemical carbon dioxide conversion system. For example, when the positions are adjusted so that the reducing electrode, which supplies carbon dioxide, faces the layer of the separator membrane with a small average pore size, and the oxidizing electrode, which supplies the electrolyte composition, faces the layer of the separator membrane with a large average pore size, carbon dioxide movement towards the oxidizing electrode can be prevented as much as possible, and the electrolyte composition supplied to the oxidizing electrode can circulate well within the electrochemical carbon dioxide conversion system.

[0057] The average pore size of the first layer can be larger than that of the second layer, and the ratio of the average pore size of the first layer to that of the second layer can be from 100:0.1 to 65.0, preferably from 100:0.3 to 60.0, more preferably from 100:0.5 to 55.0, and most preferably from 100:0.6 to 50.0. When the above conditions are met, even when the separator membrane is squeezed by the electrode, pore blockage can be prevented, allowing the electrolyte composition to flow smoothly. Furthermore, it can prevent a decrease in the efficiency of the electrochemical carbon dioxide conversion system and a rapid increase in overpotential. Specifically, when the first layer faces the oxidation electrode, the shape of the oxidation electrode can mitigate the phenomenon of partial compression of the separator membrane therein, and the large average pore size of the first layer can prevent pore blockage. As a result, the electrolyte composition can flow smoothly within the electrochemical carbon dioxide conversion system, and the movement of carbon dioxide supplied to the reduction electrode toward the oxidation electrode can be prevented as much as possible.

[0058] The average pore size of the first layer can be 20 nm to 4,970 nm larger than that of the second layer, preferably 100 nm to 4,970 nm, more preferably 250 nm to 4,800 nm, and most preferably 250 nm to 450 nm. When the above conditions are met, even when the separator membrane is squeezed by the electrode, pore blockage can be prevented, allowing the electrolyte composition to flow smoothly. Furthermore, it can prevent a decrease in the efficiency of the electrochemical carbon dioxide conversion system and a rapid increase in overpotential. Specifically, when the first layer faces the oxidation electrode, the shape of the oxidation electrode can mitigate the phenomenon of partial compression of the separator membrane therein, and the large average pore size of the first layer can prevent pore blockage. As a result, the electrolyte composition can flow smoothly within the electrochemical carbon dioxide conversion system, and the movement of carbon dioxide supplied to the reduction electrode toward the oxidation electrode can be prevented as much as possible.

[0059] The average pore size of the first layer can be from 30 nm to 5,000 nm, preferably from 100 nm to 5,000 nm, more preferably from 200 nm to 850 nm, and most preferably from 200 nm to 450 nm. When the above conditions are met, even when the separator is squeezed by the electrode, the pores can be prevented from becoming blocked, allowing the electrolyte composition to flow smoothly.

[0060] The average pore size of the second layer can be from 30 nm to 1,000 nm, preferably from 30 nm to 850 nm, more preferably from 50 nm to 450 nm, and most preferably from 100 nm to 200 nm. When the above conditions are met, even when the separator is squeezed by the electrode, the squeezing of the second layer can be minimized due to the first layer. As a result, the efficiency reduction and rapid increase of overpotential in the electrochemical carbon dioxide conversion system can be prevented. Furthermore, the migration of carbon dioxide supplied to the reduction electrode toward the oxidation electrode can be prevented as much as possible.

[0061] The average thickness of the first layer can be from 10.0 μm to 500.0 μm, preferably from 50.0 μm to 200.0 μm, more preferably from 50.0 μm to 150.0 μm, and most preferably from 100.0 μm to 150.0 μm. When the above conditions are met, the compression of the second layer can be minimized even when the separator is compressed by the electrode. In addition, the first layer can prevent the increase of overpotential in the electrochemical carbon dioxide conversion system due to increased resistance and prevent performance degradation (i.e., prevent increased hydrogen generation).

[0062] The average thickness of the second layer can be from 10.0 μm to 500.0 μm, preferably from 50.0 to 200.0 μm, more preferably from 50.0 μm to 150.0 μm, and most preferably from 100.0 μm to 150.0 μm. When the above conditions are met, the second layer can prevent the increase of overpotential in the electrochemical carbon dioxide conversion system due to increased resistance and prevent performance degradation (i.e., prevent increased hydrogen generation).

[0063] The first and second layers can have the same or different porosities, and the porosities can each independently be from 33.0% to 99.0%, preferably from 40.0% to 90.0%, and more preferably from 50.0% to 85.0%. When the above conditions are met, the separator membrane can be sufficiently wetted by the electrolyte composition, and thus ions can move smoothly, thereby minimizing overpotential. Furthermore, preventing the movement of carbon dioxide supplied to the reduction electrode toward the oxidation electrode, or preventing the movement of the electrolyte composition supplied to the oxidation electrode toward the reduction electrode, can prevent a decrease in the efficiency of the electrochemical carbon dioxide conversion system.

[0064] When the first electrode is an oxidation electrode, it is preferable that the first layer of the separator faces the first electrode. When the oxidation electrode to which the electrolyte composition is supplied and the first layer of the separator having a large average pore size are positioned facing each other, the electrolyte composition supplied to the oxidation electrode can circulate well within the electrochemical carbon dioxide conversion system.

[0065] When the second electrode is a reduction electrode, it is preferable that the second layer of the separator faces the second electrode. When the reduction electrode supplied with carbon dioxide and the second layer of the separator, which has a small average pore size, are positioned facing each other, the movement of carbon dioxide toward the oxidation electrode can be prevented as much as possible.

[0066] The separator may comprise one or more of polyethersulfone, polytetrafluoroethylene, cellulose acetate, polyvinylidene fluoride, polyethylene, polypropylene, polyvinyl alcohol, polyacrylonitrile, Nafion, and nylon. Of those listed above, the separator is preferably polyethersulfone or polytetrafluoroethylene, which allows the electrolyte composition of a hydrophilic material to adequately fill the pores of the separator and allows for the smooth movement of ions. Polytetrafluoroethylene is preferably treated to be hydrophilic.

[0067] 4) Electrolyte composition

[0068] The electrolyte composition may contain one or more electrolytes selected from KOH, KHCO3, K2CO3, NaOH, NaHCO3, Na2CO3, LiOH, LiHCO3, Li2CO3, CsOH, CsHCO3 and Cs2CO3, wherein Cs2CO3 is preferred.

[0069] In addition, the electrolyte composition may contain an aqueous solvent. The aqueous solvent may be water, and specifically may be one or more selected from pure water, ion-exchanged water, and distilled water.

[0070] The electrolyte composition may contain an electrolyte at a concentration of 0.1 M to 15.0 M, and preferably 0.25 M to 10.0 M. The electrolyte concentration is related to the product formation efficiency (target product formation efficiency relative to the applied current density) and voltage. Higher electrolyte concentrations result in lower generated voltages, required voltages, or overpotentials. However, the above conditions are preferred to minimize increases in manufacturing costs and the formation of additional products due to side reactions.

[0071] Preferred embodiments of the invention will be presented below to aid in understanding the invention. However, it will be apparent to those skilled in the art that the descriptions presented herein are merely preferred embodiments for illustrative purposes only, and various changes and modifications can be made without departing from the scope and spirit of the invention, and the invention covers all such changes and modifications provided they fall within the scope of the appended claims and their equivalents.

[0072] Example 1

[0073] <Manufacturing of the separator membrane>

[0074] A first layer with an average pore size of 450 nm (material: polyethersulfone, porosity: 77.8%, average thickness: 110.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES045200A) and a second layer with an average pore size of 200 nm (material: polyethersulfone, porosity: 55.1%, average thickness: 150.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES020200A) were laminated to fabricate a separator membrane.

[0075] <Manufacturing of an Electrochemical Carbon Dioxide Conversion System>

[0076] A membrane electrode assembly type electrolyzer (active area: 25 cm²) in which the oxidation electrode (a titanium mesh with IrO₂ dispersed) and the reduction electrode (a gas diffusion layer with Ag catalyst dispersed, manufacturer: SGL Carbon, product name: Sigrracet 39 BB) are separated by a separator membrane. 2 An electrochemical carbon dioxide conversion system is described. Here, the first layer of the separator is positioned facing the oxidation electrode, and the second layer of the separator is positioned facing the reduction electrode. As the electrolyte composition, a 0.25M aqueous solution of Cs2CO3 obtained by dissolving Cs2CO3 in pure water is used.

[0077] In addition, the electrolyte composition is supplied to the oxidation electrode at 25 ml / min, and carbon dioxide humidified at 40°C is supplied to the reduction electrode at 200 ml / min.

[0078] Example 2

[0079] <Manufacturing of the separator membrane>

[0080] A first layer with an average pore size of 450 nm (material: polyethersulfone, porosity: 77.8%, average thickness: 110.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES045200A) and a second layer with an average pore size of 100 nm (material: polyethersulfone, porosity: 64.2%, average thickness: 145.8 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES045200A) were laminated to fabricate a separator membrane.

[0081] <Manufacturing of an Electrochemical Carbon Dioxide Conversion System>

[0082] An electrochemical carbon dioxide conversion system was manufactured in the same manner as in Example 1, except that the separator membrane manufactured above was used instead of the separator membrane manufactured in Example 1.

[0083] Example 3

[0084] <Manufacturing of the separator membrane>

[0085] A first layer with an average pore size of 200 nm (material: polyethersulfone, porosity: 55.1%, average thickness: 150.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES045200A) and a second layer with an average pore size of 30 nm (material: polyethersulfone, porosity: 55.1%, average thickness: 125.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES003200A) were laminated to fabricate a separator membrane.

[0086] <Manufacturing of an Electrochemical Carbon Dioxide Conversion System>

[0087] An electrochemical carbon dioxide conversion system was manufactured in the same manner as in Example 1, except that the separator membrane manufactured above was used instead of the separator membrane manufactured in Example 1.

[0088] Example 4

[0089] <Manufacturing of the separator membrane>

[0090] A first layer with an average pore size of 800 nm (material: polyethersulfone, porosity: 50.0% to 70.0%, average thickness: 130.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES080200A) and a second layer with an average pore size of 50 nm (material: polyethersulfone, porosity: 50.0% to 70.0%, average thickness: 134.7 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES005200A) are laminated to fabricate a separator membrane.

[0091] <Manufacturing of an Electrochemical Carbon Dioxide Conversion System>

[0092] An electrochemical carbon dioxide conversion system was manufactured in the same manner as in Example 1, except that the separator membrane manufactured above was used instead of the separator membrane manufactured in Example 1.

[0093] Example 5

[0094] <Manufacturing of the separator membrane>

[0095] A first layer with an average pore size of 5,000 nm (material: polyethersulfone, porosity: 47.4%, average thickness: 130.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES500200A) and a second layer with an average pore size of 30 nm (material: polyethersulfone, porosity: 55.1%, average thickness: 125.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES003200A) were laminated to fabricate a separator membrane.

[0096] <Manufacturing of an Electrochemical Carbon Dioxide Conversion System>

[0097] An electrochemical carbon dioxide conversion system was manufactured in the same manner as in Example 1, except that the separator membrane manufactured above was used instead of the separator membrane manufactured in Example 1.

[0098] Example 6

[0099] <Manufacturing of the separator membrane>

[0100] A first layer with an average pore size of 450 nm (material: polytetrafluoroethylene (PTFE), porosity: 85.0%, average thickness: 50.0 μm, manufacturer: Cobbeter, and product name: PTFE HH-0.45-A4) and a second layer with an average pore size of 200 nm (material: polyethersulfone, porosity: 55.1%, average thickness: 150.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES020200A) were laminated to fabricate a separator membrane.

[0101] <Manufacturing of an Electrochemical Carbon Dioxide Conversion System>

[0102] An electrochemical carbon dioxide conversion system was manufactured in the same manner as in Example 1, except that the separator membrane manufactured above was used instead of the separator membrane manufactured in Example 1.

[0103] Example 7

[0104] <Manufacturing of the separator membrane>

[0105] A first layer with an average pore size of 200 nm (material: polyethersulfone, porosity: 55.1%, average thickness: 150.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES045200A) and a second layer with an average pore size of 100 nm (material: polyethersulfone, porosity: 64.2%, average thickness: 145.8 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES045200A) were laminated to fabricate a separator membrane.

[0106] <Manufacturing of an Electrochemical Carbon Dioxide Conversion System>

[0107] An electrochemical carbon dioxide conversion system was manufactured in the same manner as in Example 1, except that the separator membrane manufactured above was used instead of the separator membrane manufactured in Example 1.

[0108] Comparative Example 1

[0109] <Manufacturing of the separator membrane>

[0110] Two polyethersulfone layers with an average pore size of 200 nm (porosity: 55.1%, average thickness: 150.0 μm, manufacturer: Hyundai Micro Co., Ltd., and product name: PES020200A) were laminated to manufacture a separator membrane.

[0111] <Manufacturing of an Electrochemical Carbon Dioxide Conversion System>

[0112] An electrochemical carbon dioxide conversion system was manufactured in the same manner as in Example 1, except that the separator membrane manufactured above was used instead of the separator membrane manufactured in Example 1.

[0113] Experimental Example 1

[0114] Carbon dioxide reduction was carried out using the carbon dioxide conversion systems of the examples and comparative examples. A 300 mA / cm² pressure was applied to the electrochemical carbon dioxide conversion system. 2 The current was applied for 60 minutes. Thirty minutes after the current was applied, the overpotential applied to the carbon dioxide conversion system was measured three times, and the average values ​​are shown in Tables 1 and 2 below.

[0115] Experiment Example 2

[0116] During the overpotential measurement in Experimental Example 1, the composition of the gas released from the reduction electrode was measured every 5 minutes in the last 15 minutes by gas chromatography. H2, CO, and CO2 were separated and quantitatively analyzed using He carrier gas. The number of electrons used was obtained from the number of moles of CO, and the CO Faraday efficiency was calculated. The results are shown in Tables 1 and 2 below.

[0117] In addition, the CO2 conversion rate was calculated by substituting the number of moles of CO generated relative to the number of moles of CO2 supplied into the following equation, and the results are shown in Tables 1 and 2 below.

[0118] CO2 conversion rate = (number of moles of CO produced) / (number of moles of CO2 supplied) × 100

[0119] [Table 1]

[0120]

[0121] [Table 2]

[0122]

[0123] Referring to Tables 1 and 2, it was determined that Examples 1 to 7 exhibited lower overpotential, higher CO Faradaic efficiency, and higher CO2 conversion rate compared to Comparative Example 1. Specifically, when comparing Examples 1 and 2, which used the same first layer but had different average pore sizes in the second layer, it was determined that Example 1, which had a larger average pore size and lower porosity in the second layer, exhibited higher overpotential, lower CO2 conversion rate, and higher CO Faradaic efficiency compared to Example 2, which had a smaller average pore size and higher porosity in the second layer. When comparing Examples 1 and 6, which used the same second layer, it was determined that Example 1, which used polyethersulfone as the first layer material, exhibited lower overpotential, lower CO Faradaic efficiency, and lower CO2 conversion rate compared to Example 6, which used PTFE as the first layer material.

[0124] When comparing Examples 2 and 7, which use the same second layer, it was determined that Example 2, which has a larger average pore size in the first layer, exhibited lower overpotential, lower CO Faradaic efficiency, and equivalent CO2 conversion rate compared to Example 7, in which the second layer has a smaller average pore size.

[0125] When comparing Examples 3 and 5, which use the same second layer, it was determined that Example 3, which has a smaller average pore size in the first layer, exhibited higher overpotential, lower CO Faradaic efficiency, and lower CO2 conversion rate compared to Example 5, in which the first layer has a larger average pore size.

[0126] When comparing Examples 3 and 7, which use the same first layer, it was determined that Example 3, which has a smaller average pore size in the second layer, exhibited higher overpotential, lower CO Faradaic efficiency, and lower CO2 conversion rate compared to Example 7, in which the second layer has a larger average pore size.

[0127] When comparing Example 7, in which the first and second layers have similar thicknesses, with Comparative Example 1, it was determined that Example 7, in which the first and second layers have different average pore sizes, exhibited lower overpotential, higher CO Faradaic efficiency, and higher CO2 conversion rate compared to Comparative Example 1, in which the first and second layers have the same average pore size.

Claims

1. An electrochemical carbon dioxide conversion system, comprising: First electrode; Second electrode; as well as A separator membrane, positioned between the first electrode and the second electrode, is porous and comprises a first layer and a second layer with different average pore sizes.

2. The electrochemical carbon dioxide conversion system according to claim 1, wherein the ratio of the average pore size of the first layer to the average pore size of the second layer is from 100:0.1 to 65.

0.

3. The electrochemical carbon dioxide conversion system according to claim 1, wherein the average pore size of the first layer is 20 nm to 4,970 nm larger than the average pore size of the second layer.

4. The electrochemical carbon dioxide conversion system according to claim 2, wherein the average pore size of the first layer is 30 nm to 5,000 nm.

5. The electrochemical carbon dioxide conversion system according to claim 2, wherein the average pore size of the second layer is from 30 nm to 5,000 nm.

6. The electrochemical carbon dioxide conversion system according to claim 1, wherein the average thickness of the first layer is from 10.0 μm to 500.0 μm.

7. The electrochemical carbon dioxide conversion system according to claim 1, wherein the average thickness of the second layer is from 10.0 μm to 500.0 μm.

8. The electrochemical carbon dioxide conversion system according to claim 1, wherein the first electrode is an oxidation electrode, and the first layer of the separator membrane faces the first electrode.

9. The electrochemical carbon dioxide conversion system according to claim 1, wherein the second electrode is a reduction electrode, and the second layer of the separator membrane faces the second electrode.

10. The electrochemical carbon dioxide conversion system of claim 1, wherein the separator membrane comprises one or more selected from polyethersulfone, polytetrafluoroethylene, cellulose acetate, polyvinylidene fluoride, polyethylene, polypropylene, polyvinyl alcohol, polyacrylonitrile, Nafion, and nylon.

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