Apparatus and method for electrolysis of carbon dioxide

Abstract

The present invention relates to a carbon dioxide electrolysis device including a carbon dioxide electrolysis cell including an anode, a cathode, an electrolyte, and a separation membrane disposed between the anode and the cathode, a supply line for supplying gaseous carbon dioxide and water vapor to the cathode, and a discharge line for discharging products and water vapor generated by the electrolysis reaction of carbon dioxide inside the carbon dioxide electrolysis cell to the outside of the cell, the discharge line including a condenser for condensing the water vapor discharged from the discharge line.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0007386 dated 18 January 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to an electrolysis apparatus and method for carbon dioxide. [Background technology]

[0003] Carbon dioxide is a greenhouse gas that causes global warming and must be reduced. Methods for reducing carbon dioxide include capture, chemical conversion, and electrochemical conversion. Of these, electrochemical conversion allows for precise control of the composition to produce other synthesis gases, yielding more economic benefits than simply removing carbon dioxide.

[0004] The electrochemical decomposition of carbon dioxide is similar to the electrolysis of water, but a strongly basic atmosphere improves the activity of the electrochemical reaction, so generally, a KOH aqueous solution of a predetermined concentration is used as the electrolyte. When an electric current is applied while water is supplied to the anode, the water is decomposed into hydrogen ions and electrons along with the generation of oxygen gas. The electrons move to the cathode via an external wire, and the hydrogen ions move to the cathode via an ion-selective separation membrane. Here, the moved electrons react with the carbon dioxide and water supplied to the cathode to form carbon monoxide and hydroxide ions (OH). - It is decomposed into ), and the resulting hydroxide ions are hydrogen ions (H) at the anode. +) reacts with the carbon dioxide to produce water, resulting in an electrically neutral state. The electrochemical decomposition reaction of carbon dioxide is completed through the above process. Here, the water supplied along with the carbon dioxide reacts with the electrons that have moved separately from the carbon monoxide production reaction to undergo electrolysis, generating hydrogen gas and hydroxide ions. This reaction between water and electrons can be said to be a competitive reaction with the carbon monoxide production reaction. Since the above 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] On the other hand, when a cationic conductive membrane is used as an ion-selective separation membrane, the K contained in the electrolyte + Ions move to the cathode through the separation membrane, and at this time, K + The ions react with the carbon dioxide in the cathode, and salts such as potassium carbonate (K2CO3) precipitate. Also, when an anion-conducting membrane is used as an ion-selective separation membrane, hydroxide ions mainly move, but K + Some positive ions, such as ions, also move, and in this case, salts are formed in the same way as when using the aforementioned positive ion conductive film.

[0006] The salt generated and precipitated from the cathode accumulates inside the apparatus as the electrolysis of carbon dioxide progresses. This accumulation of salt can clog the inlet and outlet for supplying and discharging carbon dioxide, thereby reducing the productivity and efficiency of the carbon dioxide electrolysis apparatus and making continuous operation over long periods impossible. Furthermore, removing the salt requires additional equipment or work, resulting in inefficiencies in terms of equipment and operation. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Korean Registered Patent Publication No. 10-1793711 [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that this invention aims to solve is to remove the salt generated from the electrolyte during the electrolysis of carbon dioxide by dissolving it in water.

[0009] In other words, the present invention aims to provide a carbon dioxide electrolysis apparatus and method that, during the electrolysis of carbon dioxide, can dissolve and remove the salt produced by a side reaction of the electrolysis by condensing the water vapor supplied along with the carbon dioxide and discharged together with the products of the electrolysis reaction, thereby generating water. [Means for solving the problem]

[0010] The present invention provides an electrolysis apparatus for carbon dioxide and a method for electrolysis of carbon dioxide.

[0011] (1) The present invention provides a carbon dioxide electrolysis apparatus comprising a carbon dioxide electrolysis cell including an anode, a cathode, an electrolyte, and a separation membrane disposed between the anode and the cathode; a supply line for supplying gaseous carbon dioxide and water vapor to the cathode; and a discharge line for discharging products and water vapor generated by the electrolysis reaction of carbon dioxide inside the carbon dioxide electrolysis cell to the outside of the cell, wherein the discharge line includes a condensation section for condensing the water vapor discharged from the discharge line.

[0012] (2) The present invention provides an electrolysis apparatus for carbon dioxide in which the gaseous carbon dioxide is supplied in a state containing water vapor, as described in (1) above.

[0013] (3) The present invention provides a carbon dioxide electrolysis apparatus in which, in (1) or (2) above, the steam supplied in the supply line has a temperature of 40°C to 60°C.

[0014] (4) In any one of the above (1) to (3), the present invention provides an electrolysis apparatus for carbon dioxide in which the condensation part is exposed to the outside of the electrolysis cell for carbon dioxide.

[0015] (5) In any one of the above (1) to (4), the present invention provides an electrolysis apparatus for carbon dioxide in which the condensation part includes a storage part for storing water formed by condensing water vapor discharged from the discharge line.

[0016] (6) In any one of the above (1) to (5), the present invention provides an electrolysis apparatus for carbon dioxide in which the discharge line includes a first line for transferring the product and water vapor discharged from the discharge line from the electrolysis cell for carbon dioxide to the condensation part, and a second line for discharging the product from the condensation part to the outside.

[0017] (7) In the above (6), the present invention provides an electrolysis apparatus for carbon dioxide in which the condensation part is connected such that a step is formed between the first line and the second line.

[0018] (8) In the above (7), the present invention provides an electrolysis apparatus for carbon dioxide in which the second line is arranged higher than the first line by the step.

[0019] (9) The present invention provides a method for electrolyzing carbon dioxide, comprising: a step (S1) of supplying gaseous carbon dioxide and water vapor to a cathode of an electrolysis cell for carbon dioxide including an anode, a cathode, an electrolyte, and a separation membrane; a step (S2) of electrolyzing the carbon dioxide supplied to the cathode in the step (S1); a step (S3) of discharging the product generated by electrolysis in the step (S2) and the water vapor supplied in the step (S1) to the outside of the electrolysis cell for carbon dioxide; and a step (S4) of condensing the water vapor discharged in the step (S3).

[0020] (10) The present invention provides a method for electrolyzing carbon dioxide in which, in step (9), the water formed by the condensation of the water vapor discharged in step (S4) dissolves the salt produced from the electrolyte by electrolysis in step (S2).

[0021] (11) The present invention provides a method for electrolyzing carbon dioxide produced by the reaction of an electrolyte with supplied carbon dioxide, in accordance with (10) above.

[0022] (12) The present invention provides a method for electrolyzing carbon dioxide, wherein the salts in (10) or (11) are KHCO3 and K2CO3. [Effects of the Invention]

[0023] According to the carbon dioxide electrolysis apparatus and method of the present invention, water can be produced by directly utilizing the water vapor supplied along with the carbon dioxide during the electrolysis of carbon dioxide, and salt can be continuously removed using the produced water without the need for a separate salt removal apparatus or salt removal work.

[0024] Furthermore, since the carbon dioxide electrolysis apparatus of the present invention does not require a separate salt removal apparatus or separate salt removal work, it does not require a salt removal apparatus and space for carrying out this work, and the volume of the carbon dioxide electrolysis apparatus can be reduced.

[0025] Furthermore, according to the carbon dioxide electrolysis apparatus and method of the present invention, salt can be continuously removed without the need for a separate salt removal apparatus or salt removal work, and since the inlet and outlet of the carbon dioxide electrolysis apparatus are not blocked by salt, smooth and continuous operation is possible without voltage changes, and the production volume and electrolysis efficiency do not decrease even with continuous operation.

[0026] Furthermore, the carbon dioxide electrolysis apparatus of the present invention, due to the special structure of its discharge line, can easily condense water and dissolve salt, eliminating the need to add another condenser or water spray device, making it easy to install and maintain, and efficient in terms of structure and equipment. [Brief explanation of the drawing]

[0027] [Figure 1] This is a cross-sectional view of a carbon dioxide electrolysis apparatus according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view of a conventional carbon dioxide electrolysis apparatus. [Figure 3] This graph shows the change in voltage over time in Examples 1 and 2. [Figure 4] This graph shows the change in voltage over time in Example 3. [Figure 5] This graph shows the change in voltage over time in Examples 4, 5, 6, and 7. [Figure 6] This graph shows the change in voltage over time in Examples 8 and 9. [Figure 7] This graph shows the change in voltage over time in Comparative Example 1. [Modes for carrying out the invention]

[0028] The present invention will now be described in more detail to facilitate understanding of it. Hereinafter, terms and words used in this specification and in the claims will not be interpreted to be limited to their ordinary or dictionary meanings, but rather to be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0029] Electrolysis apparatus for carbon dioxide Figure 1 is a cross-sectional view illustrating a carbon dioxide electrolysis apparatus according to one embodiment of the present invention.

[0030] Referring to Figure 1, the carbon dioxide electrolysis apparatus of the present invention includes a carbon dioxide electrolysis cell 1000 comprising an anode 100, a cathode 200, an electrolyte 400, and a separation membrane 300 disposed between the anode 100 and the cathode 200; a supply line 500 for supplying gaseous carbon dioxide and water vapor to the cathode 200; and an exhaust line 700 for discharging the products and water vapor generated by the carbon dioxide electrolysis reaction inside the carbon dioxide electrolysis cell 1000 to the outside of the cell, wherein the exhaust line 700 may include a condensation unit 750 for condensing the water vapor discharged from the exhaust line 700.

[0031] According to one embodiment of the present invention, the carbon dioxide electrolysis cell 1000 is a device that takes carbon dioxide and converts it into carbon monoxide, and may include an anode 100, a cathode 200, an electrolyte 400, and a separation membrane 300. Electrolysis means decomposing a substance through a redox reaction by applying a DC voltage, thereby preventing a decomposition reaction that does not occur on its own. The anode 100 acts as an oxidation electrode, oxidizing water to generate oxygen, and in this process, hydrogen ions are produced. The hydrogen ions produced from the anode 100 are transferred to the cathode 200 via the electrolyte 400, and the cathode 200 acts as a reduction electrode, where reactants introduced to the cathode 200 react with electrons and hydrogen ions that have moved from the anode 100 to produce a product. The separation membrane 300 can be placed between the anode 100 and the cathode 200. The separation membrane 300 can be made of an inert material that does not participate in electrochemical reactions itself, but can provide a path through which ions can move between the anode 100 and the cathode 200, and can play a role in separating the physical contact between the anode 100 and the cathode 200.

[0032] Furthermore, the anode 100 and cathode 200 of the carbon dioxide electrolysis cell 1000 of the present invention may each include a catalyst layer. In addition, water vapor supplied together with carbon dioxide within the cathode region generates reduction products by an electro-reduction reaction on the surface of the cathode 200. Therefore, the cathode 200 may include a gas diffusion layer 210 to uniformly supply humidified carbon dioxide gas to the cathode region. When the cathode 200 includes a hydrophobic gas diffusion layer 210, the supplied carbon dioxide can be smoothly diffused, distributed, and supplied to the catalyst layer 230 of the cathode. The hydrophobic gas diffusion layer 210 also effectively prevents the condensation of water, ensuring a continuous and uniform supply of carbon dioxide and allowing the electrolysis reaction to proceed smoothly. The catalyst layer 230 may have a surface such as a porous structure so that its gas permeability characteristics are well exhibited.

[0033] According to one embodiment of the present invention, the anode 100 may contain a catalyst active in the electrolysis of water, and the catalyst layer of the anode 100 may contain one or more selected from the group consisting of Pt, Au, Pd, Ir, Ag, Rh, Ru, Ni, Al, Mo, Cr, Cu, Ti, W, alloys thereof, or mixed metal oxides, such as Ta2O5 and IrO2, for the oxygen evolution reaction. Specifically, the anode 100 in the carbon dioxide electrolysis apparatus of the present invention may contain nickel (Ni) coated with ruthenium oxide (RuO2) and cerium oxide (CeO2).

[0034] Furthermore, since the carbon dioxide reduction reaction occurring in the cathode 200 is a competitive reaction with the hydrogen evolution reaction, the voltage required for the hydrogen evolution reaction is high, and the catalyst can include one that is active in the carbon dioxide reduction reaction. The catalyst layer 230 of the cathode 200 can include one or more selected from the group consisting of Sn, Sn alloys, Al, Au, Ag, C, Cd, Co, Cr, Cu, Cu alloys, Ga, Hg, In, Mo, Nb, Ni, NiCo2O4, Ni alloys, Ni-Fe alloys, Pb, Rh, Ti, V, W, Zn, and mixtures thereof for the hydrogen evolution reaction. Specifically, the cathode 200 in the carbon dioxide electrolysis apparatus of the present invention can include silver (Ag).

[0035] Furthermore, the separation membrane 300 may include a cation exchange membrane (CEM) or an anion exchange membrane (AEM).

[0036] Furthermore, the electrolyte 400 includes KHCO3, K2CO3, KOH, KCl, KClO4, K2SiO3, Na2SO4, NaNO3, NaCl, NaF, NaClO4, CaCl2, guanidinium cation, and H + The electrolyte 400 of the carbon dioxide electrolysis apparatus of the present invention may contain KOH, selected from the group consisting of cations, alkali metal cations, ammonium cations, alkylammonium cations, halide ions, alkylamines, borates, carbonates, guanidinium derivatives, nitrites, phosphates, polyphosphates, perchlorates, silicates, sulfates, tetraalkylammonium salts, or aqueous solutions containing mixtures thereof.

[0037] Furthermore, the gas diffusion layer 210 can be made of a porous material made of carbon material such as carbon fiber cloth, carbon fiber felt, or carbon fiber paper, or a porous metal made of a thin sheet metal with a mesh structure such as expanded metal or metal mesh. In the carbon dioxide electrolysis apparatus of the present invention, the gas diffusion layer can be made of carbon fiber cloth.

[0038] According to one embodiment of the present invention, the carbon dioxide electrolysis apparatus of the present invention may include a supply line 500 for supplying gaseous carbon dioxide and water vapor to the cathode 200, a transfer line 600 for transporting the supplied carbon dioxide and water vapor to the cathode 200 region so that they can participate in the reaction with minimal resistance, and an discharge line 700 for discharging the products and water vapor generated by the reaction to the outside of the cell.

[0039] The supply line 500, transfer line 600, and discharge line 700 are not limited in length, material, or form, as long as they have the function of smoothly transferring carbon dioxide and water vapor. The form of the transfer line 600 may include a parallel structure in which straight lines are arranged parallel to each other, or a serpentine structure having repeated "S" shapes. The supply line and discharge line may be connected to the carbon dioxide electrolysis cell 1000, and the transfer line 600 may be located inside the carbon dioxide electrolysis cell 1000 adjacent to the cathode 200 side. However, as described below, the discharge line 700 may include a condensation section 750 and is preferably located outside the carbon dioxide electrolysis cell 1000 and connected to the carbon dioxide electrolysis cell 1000.

[0040] According to one embodiment of the present invention, the carbon dioxide electrolysis apparatus of the present invention may include a condensation unit 750 in the discharge line 700. The condensation unit 750 can condense the water vapor supplied via the supply line 500 and discharge it from the discharge line 700 via the reaction line to produce water.

[0041] On the other hand, in a carbon dioxide electrolysis apparatus, the electrolyte 400-1 used during the electrolysis reaction exists in the form of cations and anions. When some of the cations move to the cathode region via the separation membrane 300-1, they react with the carbon dioxide supplied to the cathode region to form a salt, which is then precipitated. In conventional carbon dioxide electrolysis apparatuses, this salt cannot be removed and accumulates continuously in the carbon dioxide electrolysis cell, supply line 500-1, and discharge line 700-1, eventually clogging the supply line 500-1 and discharge line 700-1. In this case, the carbon dioxide electrolysis apparatus cannot be driven continuously, which is inconvenient for experiments and research requiring long-term evaluation. Therefore, in order to remove such salt, the carbon dioxide electrolysis apparatus of the present invention has a condensation unit 750 located in the discharge line 700 that converts the supplied water vapor into water and dissolves the salt, thus solving the conventional problems described above.

[0042] According to one embodiment of the present invention, the gaseous carbon dioxide can be supplied in a state containing water vapor. This allows for the supply of a larger quantity than when carbon dioxide is supplied alone, and improves the efficiency of the carbon dioxide electrolysis apparatus. Specifically, the carbon dioxide and water vapor may be bubbled together via another humidifier and supplied in a state containing water vapor, or the carbon dioxide and water vapor may be brought into contact and mixed together via another device and supplied in that state. In this case, the method of supplying humidified carbon dioxide is not limited, as long as the carbon dioxide can be supplied in a humidified state to the cathode 200 region via the supply line 500.

[0043] When the carbon dioxide is supplied in a humidified state, it can be converted into water via the condenser 750 included in the discharge line 700, which has the effect of reducing the volume of the carbon dioxide electrolysis apparatus and simplifying it.

[0044] According to one embodiment of the present invention, the steam supplied in the supply line 500 can have a temperature of 40°C to 60°C. Specifically, the temperature of the supplied steam can be 40°C or higher, 43°C or higher, 46°C or higher, 49°C or higher, and 60°C or lower, 57°C or lower, 54°C or lower, or 51°C or lower. The carbon dioxide electrolysis apparatus can operate while maintaining a temperature of 40°C to 60°C, but the temperature of the apparatus may rise due to heat generation or the temperature of the supplied material within the carbon dioxide electrolysis apparatus. When the carbon dioxide electrolysis apparatus operates within the temperature range, the electrolysis efficiency is maintained and the amount of product produced does not decrease. Therefore, when the temperature of the supplied steam meets the range, it has the effect of maintaining the appropriate temperature of the carbon dioxide electrolysis apparatus, maintaining the amount of product produced, and increasing the electrolysis efficiency.

[0045] According to one embodiment of the present invention, the condensing unit 750 can be exposed to the outside of the carbon dioxide electrolysis cell 1000. As described above, the condensing unit 750 can condense water vapor supplied via the supply line 500 and convert it into water, and the condensing unit 750 can be included in the discharge line 700 connected to the carbon dioxide electrolysis cell 1000. Furthermore, the condensing unit 750 is exposed to the outside of the carbon dioxide electrolysis cell 1000 and in contact with ambient air, allowing the water vapor to condense naturally by ambient air without the need for a separate condenser or heat exchanger. By exposing the condensing unit 750 to the outside of the carbon dioxide electrolysis cell 1000, the carbon dioxide electrolysis apparatus of the present invention has the effect of not requiring a separate condensation device, reducing the volume of the apparatus, and not requiring additional energy.

[0046] According to one embodiment of the present invention, the condensing unit 750 may include a storage unit 770 in which water formed by the condensation of water vapor discharged from the discharge line 700 is stored. The condenser condenses water vapor discharged from the discharge line 700 to form water, and the formed water plays a role in dissolving and removing salt, which will be described later. Therefore, when the formed water is stored in a predetermined space and the salt is discharged through the discharge line 700, a space may be needed for the salt to come into contact with the water and dissolve. However, the carbon dioxide electrolysis apparatus of the present invention includes a storage unit 770 in the condensing unit 750 included in the discharge line 700, thereby allowing the condensed water to be stored and the salt to be dissolved in the storage unit 770.

[0047] According to one embodiment of the present invention, the discharge line 700 may include a first line 710 through which the product and water vapor discharged from the discharge line 700 are transported from the carbon dioxide electrolysis cell 1000 to the condensation section 750, and a second line 730 through which the product is discharged to the outside from the condensation section 750. The condensation section 750 may be included in the discharge line 700 connected to the carbon dioxide electrolysis cell 1000 and may also serve to connect the first line 710 and the second line 730. The first line 710 may serve to transport the product and water vapor generated by the electrochemical reaction from the cathode 200 region to the condensation section 750, and the water vapor may partially participate in the reaction, and a portion of the supplied water vapor may be discharged. The second line 730 may serve to discharge the product and ionic substances generated by the dissolution of the salt from the condensation section 750 to the outside.

[0048] On the other hand, the discharge line 700-1 in conventional carbon dioxide electrolysis apparatuses generally has a simple straight pipe shape and is content with merely serving the role of discharging the products of the electrolysis reaction. In contrast, the discharge line 700 in the carbon dioxide electrolysis apparatus of the present invention has a structure in which a condensation unit 750 is placed and connected between the first line 710 and the second line 730. This eliminates the need to place the condensation unit 750 in a separate space outside the discharge line 700, and not only can the products be discharged to the outside without the need for multiple other discharge lines 700, but it can also remove salts that are produced as by-products during the electrolysis reaction.

[0049] According to one embodiment of the present invention, the condensing section 750 can be connected to the first line 710 and the second line 730 such that a step is formed between them, and the second line 730 can be positioned higher than the first line 710 due to the step. The carbon dioxide electrolysis apparatus of the present invention includes an discharge line 700 having a stepped structure between the first line 710 and the second line 730, thereby allowing the condensing section 750 and the storage section 770 to be included simultaneously without the need to install separate space and equipment in the discharge line 700.

[0050] On the other hand, in the case of the discharge line 700-1 of a conventional carbon dioxide electrolysis apparatus, it is common to have a linear pipe structure in order to discharge the generated gas phase products to the outside. In contrast, the discharge line 700 of the carbon dioxide electrolysis apparatus of the present invention connects the first line 710 connected to the carbon dioxide electrolysis cell 1000 and the second line 730 that discharges the products to the outside with the condensation section 750, and by providing a step so that the second line 730 is positioned higher than the first line 710, it can serve as a kind of filter or inlet. Specifically, the products generated by the electrolysis reaction of carbon dioxide can be carbon monoxide or hydrogen gas, and both the products and unreacted carbon dioxide gas can be discharged. In contrast, the salt produced as a by-product of electrolysis is formed when the cations of the electrolyte 400 react with the carbon dioxide and form ionic bonds, and has a solid phase. Therefore, the gaseous products generated by the electrolysis reaction can be discharged to the outside via the discharge line, while the salt produced as a by-product during the electrolysis reaction cannot be discharged to the outside due to the step, but can be dissolved in contact with the water in the storage section 770. The height of the step may be, but is not limited to, a height that allows the gaseous products to be discharged, stores the water produced by the condensation of the water vapor, and allows it to come into contact with the salt.

[0051] Method of electrolysis of carbon dioxide The present invention provides a method for electrolyzing carbon dioxide, which may include the steps of: (S1) supplying gaseous carbon dioxide and water vapor to the cathode 200 of a carbon dioxide electrolysis cell 1000 comprising an anode 100, a cathode 200, an electrolyte 400, and a separation membrane 300; (S2) electrolyzing the carbon dioxide supplied to the cathode 200 in step (S1); (S3) discharging the products generated by electrolysis in step (S2) and the water vapor supplied in step (S1) to the outside of the carbon dioxide electrolysis cell 1000; and (S4) condensing the water vapor discharged in step (S3).

[0052] According to one embodiment of the present invention, the water formed by the condensation of the water vapor discharged in step (S4) can dissolve the salt produced from the electrolyte 400 by electrolysis in step (S2).

[0053] On the other hand, conventional electrolysis methods for carbon dioxide involve cations contained in the electrolyte 400-1 moving through the separation membrane 300-1 to the cathode region, where they react with supplied carbon dioxide to precipitate salts. These salts exist in solid form in the catalyst layer 230-1 and gas diffusion layer 210-1 of the carbon dioxide electrolysis apparatus and accumulate in the supply line 500-1 and discharge line 700-1. As a result, the efficiency decreases as the experiment or research is conducted for a longer period, which limits the possibility of conducting continuous experiments or research for extended periods and makes it difficult to maintain a constant production volume. Furthermore, it was necessary to install a separate salt removal device or water treatment device, or to use methods such as directly removing the salts, which was inefficient in terms of equipment and could lead to an increase in the volume of the apparatus itself.

[0054] To solve the aforementioned problems, the electrolysis method for carbon dioxide of the present invention effectively removes salt by condensing the water vapor supplied along with the products generated by electrolysis and carbon dioxide, and converting it back into water when the water vapor is discharged.

[0055] The electrolysis method for carbon dioxide of the present invention has the advantage of simplifying the process without the inconvenience of conventional methods that require complex equipment and separate devices, as it can condense the water vapor to produce water and dissolve and remove salt when discharging the product and water vapor. This allows for continuous, long-term experiments and research.

[0056] Furthermore, the electrolysis method for carbon dioxide of the present invention has the effect of increasing the amount of carbon dioxide supplied by supplying both carbon dioxide and water vapor, thereby increasing the amount of carbon monoxide produced. Moreover, since condensation is carried out using the supplied water vapor, there is no need to supply additional water to dissolve the salt when discharging the product and water vapor, thus improving process efficiency.

[0057] According to one embodiment of the present invention, the salt can be produced by the reaction of electrolyte 400 with supplied carbon dioxide, and the salt can be KHCO3 and K2CO3. Specifically, in the electrolysis method of carbon dioxide of the present invention, since KOH is used as the electrolyte, potassium ions can react with carbon dioxide to produce potassium carbonate salt.

[0058] Hereinafter, embodiments of the present invention will be described in detail so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0059] Example 1 As shown in Figure 1, a carbon dioxide electrolysis apparatus was constructed to produce carbon monoxide by electrolyzing carbon dioxide. The carbon dioxide electrolysis apparatus included a condensation unit 750 in the discharge line 700, and the electrolysis of carbon dioxide was carried out by adjusting the operating conditions of the carbon dioxide electrolysis apparatus as follows.

[0060] Reaction current density: 200 mA / cm² 2 (Constant current operation) Reaction voltage: 3~3.5V Reaction temperature: 40℃ Reaction pressure: 1 atm (atmospheric pressure) Separation membrane: Anion exchange membrane (Sustainion X37, dioxide) Anode catalyst: RuO2 + CeO2on Ni mesh Cathode catalyst: Ag powder Electrode area: 100cm2 Gas diffusion layer: Sigracet 39BB Anode electrolyte: 1M KOH (200 ml / min) Cathode reactant: 40°C humidified CO2 gas (800 ccm) Form of transfer line: parallel type Cross-sectional area of transfer line: 0.55 mm 2 The conversion rate (%) of carbon monoxide, the Faraday efficiency of carbon monoxide (CO Faraday efficiency, %), and the voltage during the electrolysis were measured.

[0061] Example 2 The reaction current density was set to 300 mA / cm 2 Except for setting the reaction current density to 300 mA / cm, the electrolysis was carried out in the same manner as in Example 1, and the conversion rate (%) of carbon monoxide, the Faraday efficiency of carbon monoxide (CO Faraday efficiency, %), and the voltage during the electrolysis were measured.

[0062] Example 3 Except for using 1M KHCO3 (200 ml / min) as the anode electrolyte, the electrolysis was carried out in the same manner as in Example 1, and the conversion rate (%) of carbon monoxide, the Faraday efficiency of carbon monoxide (CO Faraday efficiency, %), and the voltage during the electrolysis were measured.

[0063] Example 4 Except for changing the form of the transfer line from the parallel type to the serpentine type with repeated "S" shapes, the electrolysis was carried out in the same manner as in Example 1, and the conversion rate (%) of carbon monoxide, the Faraday efficiency of carbon monoxide (CO Faraday efficiency, %), and the voltage during the electrolysis were measured.

[0064] Example 5 The reaction current density was 300 mA / cm 2Except for the settings, the procedure was carried out in the same manner as in Example 4 above, and the carbon monoxide conversion rate (%), carbon monoxide Faraday efficiency (CO2 Faraday efficiency, %), and voltage during the electrolysis were measured.

[0065] Example 6 The cross-sectional area of ​​the transfer line is 0.75 mm². 2 Except for the change made, the procedure was carried out in the same manner as in Example 1, and the carbon monoxide conversion rate (%), carbon monoxide Faraday efficiency (CO2 Faraday efficiency, %), and voltage during the electrolysis were measured.

[0066] Example 7 The reaction current density is 300 mA / cm². 2 Except for the settings, the procedure was carried out in the same manner as in Example 6 above, and the carbon monoxide conversion rate (%), carbon monoxide Faraday efficiency (CO2 Faraday efficiency, %), and voltage during the electrolysis were measured.

[0067] Example 8 Except for changing the anode catalyst from RuO2+CeO2on Ni mesh to IrO2-Ti mesh, the procedure was carried out in the same manner as in Example 1, and the carbon monoxide conversion rate (%), carbon monoxide Faraday efficiency (CO2 Faraday efficiency, %), and voltage were measured.

[0068] Example 9 The reaction current density is 300 mA / cm². 2 Except for the settings, the procedure was carried out in the same manner as in Example 8, and the carbon monoxide conversion rate (%), carbon monoxide Faraday efficiency (CO2 Faraday efficiency, %), and voltage during the electrolysis were measured.

[0069] Comparative Example 1 Except for not including a condensation section, the procedure was carried out in the same manner as in Example 1, and the carbon monoxide conversion rate (%), carbon monoxide Faraday efficiency (CO2 Faraday efficiency, %), and voltage during the electrolysis were measured.

[0070] *Measurement method (1) Carbon monoxide 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.

[0071] (2) Faraday efficiency of carbon monoxide (%) The gas composition at the discharge line was measured by GC (Gas Chromatography) analysis. Furthermore, the Faraday efficiency (FE) was also measured. product The value was calculated using the following formula.

[0072] [Formula 1] FE product (%)=(i product / i total ) × 100 = [(V product ×Q×(2Fp / RT)) / i total ]×100

[0073] In equation 1 above, Q is the flow rate in the discharge line, F is the Faraday constant, p is the pressure, T is the measured temperature, and R is the ideal gas constant. Total current (i total ) is the value of the total current applied over time, and the current (i) applied to the product. product ) is the volume of gas (V) measured by GC analysis. product This is a value calculated from ).

[0074] (3) Voltage (V) Current application and voltage measurement were performed using a BioLogic VSP potentiostat. An 80A booster was installed, and a current corresponding to a large area was applied. The applied current was 100mA / cm². 2 , 200mA / cm 2 , 300mA / cm 2 The voltage was recorded after maintaining each step for a predetermined time, and then 10 minutes had elapsed. Gas chromatography (GC) analysis was also performed simultaneously.

[0075] [Table 1]

[0076] Referring to Table 1, Comparative Example 1, which does not include a condenser in the discharge line, shows inferior results in terms of carbon monoxide conversion rate, carbon monoxide Faraday efficiency, and voltage compared to Examples 1-6, which include a condenser. In Example 4, the carbon monoxide conversion rate is similar to that of Comparative Example 1, but it was confirmed that it showed even better results in terms of carbon monoxide Faraday efficiency and voltage. Based on these results, it was confirmed that by including a condenser in the discharge line and removing salt, a high carbon monoxide conversion rate and carbon monoxide Faraday efficiency can be maintained without overvoltage.

[0077] Furthermore, Figures 3 to 6 show the voltage changes over time in Examples 1 to 6, and Figure 7 shows the voltage changes over time in Comparative Example 1. Referring to Figures 3 to 7, it was confirmed that in Comparative Example 1, the supply line and discharge line were clogged with salt generated during electrolysis, causing abnormalities in supply and flow, and resulting in a rapid change in voltage over time. In contrast, in each of the examples, it was confirmed that the conversion of carbon monoxide proceeded smoothly with minimal voltage changes over time. [Explanation of Symbols]

[0078] 100 anodes 200 Cathode 210 Gas diffusion layer 230 Catalyst layer 300 Separation membrane 400 Electrolytes 1000 carbon dioxide electrolysis cell 500 supply lines 600 Transfer Line 700 discharge line 710 Line 1 730 Line 2 750 Condensing section 770 Storage section 100-1 Anode of a conventional carbon dioxide electrolysis apparatus 200-1 Cathode of a conventional carbon dioxide electrolysis apparatus 210-1 Gas diffusion layer of a conventional carbon dioxide electrolysis apparatus 230-1 Catalyst layer of a conventional carbon dioxide electrolysis apparatus 300-1 Separation membrane of a conventional carbon dioxide electrolysis apparatus 400-1 Electrolyte of a conventional carbon dioxide electrolysis apparatus 1000-1 Electrolysis cell of a conventional carbon dioxide electrolysis apparatus 500-1 Supply line for conventional carbon dioxide electrolysis equipment 600-1 Transfer line for conventional carbon dioxide electrolysis apparatus 700-1 Conventional discharge line for carbon dioxide electrolysis equipment

Claims

1. A carbon dioxide electrolysis cell comprising an anode, a cathode, an electrolyte, and a separation membrane disposed between the anode and the cathode, A supply line for supplying gaseous carbon dioxide and water vapor to the cathode, The electrolysis cell for carbon dioxide includes an outlet line for discharging the products and water vapor generated by the electrolysis reaction of carbon dioxide inside the cell to the outside of the cell. The temperature of the steam supplied in the aforementioned supply line is 40°C to 60°C. The discharge line includes a condensing section for condensing the water vapor discharged from the discharge line, a first line through which the product and the water vapor discharged from the discharge line are transferred from the carbon dioxide electrolysis cell to the condensing section, and a second line through which the product is discharged to the outside from the condensing section, wherein the condensing section is connected to the first line and the second line such that a step is formed between them, in an electrolysis apparatus for carbon dioxide.

2. The carbon dioxide electrolysis apparatus according to claim 1, wherein the carbon dioxide in the gas phase is supplied in a state containing the water vapor.

3. The carbon dioxide electrolysis apparatus according to claim 1 or 2, wherein the condensing section is exposed to the outside of the carbon dioxide electrolysis cell.

4. The carbon dioxide electrolysis apparatus according to claim 1 or 2, wherein the condensation section includes a storage section in which water formed by the condensation of water vapor discharged from the discharge line is stored.

5. The electrolysis apparatus for carbon dioxide according to claim 1 or 2, wherein the second line is positioned higher than the first line due to the step.

6. Step (S1) of supplying gaseous carbon dioxide and water vapor to the cathode of a carbon dioxide electrolysis cell, which includes an anode, cathode, electrolyte and separation membrane, Step (S2) involves electrolyzing the carbon dioxide supplied to the cathode in step (S1), Step (S3) involves discharging the product generated by electrolysis in step (S2) and the water vapor supplied in step (S1) to the outside of the carbon dioxide electrolysis cell via an exhaust line. The step includes a step (S4) of condensing the water vapor discharged in step (S3), The temperature of the water vapor supplied in step (S1) is 40°C to 60°C. A method for electrolyzing carbon dioxide, wherein the discharge line includes a condensation section for condensing the water vapor discharged from the discharge line, a first line through which the product and the water vapor discharged from the discharge line are transferred from the carbon dioxide electrolysis cell to the condensation section, and a second line through which the product is discharged to the outside from the condensation section, and the condensation section is connected to the first line and the second line such that a step is formed between them.

7. The method for electrolyzing carbon dioxide according to claim 6, wherein the water formed by the condensation of the water vapor discharged in step (S4) dissolves the salt produced from the electrolyte by electrolysis in step (S2).

8. The electrolysis method for carbon dioxide according to claim 7, wherein the salt is produced by the reaction of an electrolyte with supplied carbon dioxide.

9. The aforementioned salt is KHCO ３ and K ２ CO ３ The method for electrolyzing carbon dioxide according to claim 7 or 8.

Images