Electrolysis device

Abstract

The present invention relates to an electrolysis device comprising: an electrolysis cell including a gas diffusion layer, a cathode, a cation separator, an anode, and an electrolyte; and a storage tank connected to the outside of the electrolysis cell through a discharge channel for discharging a product from the cathode, wherein an acidic solution included in the storage tank and the electrolyte included in the electrolysis cell are the same kind of solution.

Description

electrolysis device

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0077537, filed June 16, 2023, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present invention relates to an electrolytic device that electrochemically reduces carbon dioxide.

[0006]

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

[0008] The process of electrochemically decomposing carbon dioxide is similar to the electrolysis technology of water, but since the activity of the electrochemical reaction improves in a strongly alkaline atmosphere, a KOH aqueous solution of a certain concentration is generally used as an electrolyte. When water is supplied to the anode and current is applied, the water is decomposed into hydrogen ions and electrons along with the generation of oxygen gas. The electrons move to the cathode through an external conductor, and the hydrogen ions move to the cathode through an ion-selective membrane. At this time, the moved electrons react with the carbon dioxide and water supplied to the cathode to produce carbon monoxide and hydroxide ions (OH). -) is decomposed into hydrogen ions (H ) of the anode, and the generated hydroxide ions are converted into hydrogen ions (H ) of the anode. + ) reacts with the electrons to produce water, thereby becoming electrically neutral. Through the above process, the electrochemical decomposition reaction of carbon dioxide is completed. At this time, the water supplied together with the carbon dioxide reacts with the electrons transferred separately from the carbon monoxide production reaction and is electrolyzed to produce hydrogen gas and simultaneously produce hydroxide ions. This reaction of water and electrons can be said to be a competitive reaction with the carbon monoxide production reaction. Since the above reactions are electrochemical reactions, the amount of carbon monoxide produced and the hydrogen / carbon dioxide ratio can be easily controlled by controlling the voltage.

[0009] Meanwhile, in the conventional electrolysis device, OH is generated by a side reaction at the cathode during the carbon dioxide electrolysis process. - is generated, and the above OH - It reacts again with the supplied carbon dioxide to form carbonate (HCO3 - ) occurs. Therefore, the conventional electrolysis device had a problem in that the supplied carbon dioxide was not converted into the desired product and instead generated carbonate, resulting in a loss of carbon dioxide. In addition, the conventional electrolysis device had a problem in that the efficiency of the electrolysis was reduced because the carbonate passed through the anion exchange membrane and diffused to the anode, and carbon dioxide was generated through an oxidation reaction at the anode.

[0010] (Patent Document 001) KR 10-2018-0133688 A

[0011]

[0012] The problem to be solved by the present invention is to provide an electrolysis device that can prevent the loss of carbon dioxide converted into carbonate and improve the yield of the product by separating carbon dioxide again from carbonate generated by a side reaction during carbon dioxide electrolysis, and can control the overall ion balance of the electrolysis device to operate for a long time.

[0013]

[0014] The present invention provides an electrolysis device.

[0015] (1) The present invention provides an electrolysis device comprising an electrolysis cell including a gas diffusion layer, a cathode, a cation separation membrane, an anode, and an electrolyte, and a storage tank connected to a discharge path for discharging a product from the cathode outside the electrolysis cell, wherein the acid solution contained in the storage tank and the electrolyte contained in the electrolysis cell are homogeneous solutions.

[0016] (2) The present invention provides an electrolysis device comprising, in the above (1), an aqueous solution containing at least one selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid, citric acid, and oxalic acid; and a salt containing at least one selected from the group consisting of cesium, potassium, and sodium.

[0017] (3) The present invention provides an electrolysis device in the above (2), wherein the salt includes at least one selected from the group consisting of Cs2CO3, CsHCO3, Cs2SO4, CsCl, CsNO3, K2CO3, KHCO3, K2SO4, K3PO4, KCl, KNO3, Na2CO3, NaHCO3, Na2SO4, Na3PO4, NaCl and NaNO3.

[0018] (4) The present invention provides an electrolysis device in which, in any one of the above (1) to (3), the storage tank includes an acid solution storage unit and an electrolyte storage unit connected thereto, and the electrolyte storage unit is connected to the anode through a solution exchange path.

[0019] (5) The present invention provides an electrolysis device according to (4), wherein the solution exchange path includes a first solution exchange path for transferring an acidic solution from the electrolyte storage unit to the anode and a second solution exchange path for transferring an electrolyte from the anode to the electrolyte storage unit.

[0020] (6) The present invention provides an electrolytic device in which, in any one of the above (1) to (5), the electrolytic cell is a zero-gap membrane electrode assembly cell in which the gas diffusion layer, the cathode, the separator, and the anode having an anode liquid path formed therein are sequentially stacked.

[0021] (7) The present invention provides an electrolysis device in which a product generated by an electrolytic reaction at the cathode in any one of the above (1) to (6) is transferred to the storage tank through the discharge path, and the product includes carbon monoxide, water vapor, and salt.

[0022] (8) The present invention provides an electrolysis device in which carbon dioxide generated from the salt in the storage tank is supplied to the electrolysis cell in the above (7).

[0023] (9) The present invention provides an electrolysis device according to (7) or (8), wherein the salt is a carbonate.

[0024] (10) The present invention provides an electrolysis device that electrolyzes carbon dioxide in any one of the above (1) to (9).

[0025] (11) The present invention provides an electrolysis device in which, in the above (10), the carbon dioxide is supplied to the electrolysis cell in a state including water vapor.

[0026] (12) The present invention provides an electrolytic device in any one of the above (1) to (11), wherein the electrolytic device electrolyzes carbon dioxide to produce at least one selected from the group consisting of carbon monoxide, ethylene, methane, formic acid, hydrocarbons, aldehydes, and alcohols.

[0027]

[0028] The electrolysis device of the present invention can prevent the loss of carbon dioxide by connecting a storage tank containing an acid solution to an electrolysis cell to separate carbon dioxide from a salt generated by a side reaction.

[0029] In addition, the electrolysis device of the present invention can improve the electrolysis efficiency of carbon dioxide by reducing the loss of carbon dioxide, thereby increasing the yield of the product.

[0030] In addition, the electrolysis device of the present invention uses the same solution for the electrolyte in the electrolysis cell and the acid solution in the storage tank, and transfers or circulates each solution through a path connecting the electrolysis cell and the storage tank, thereby suppressing changes in the pH of the storage tank and the electrolyte, and at the same time, cations are constantly replenished to the electrolyte to maintain ion balance, so that the electrolysis device can be operated for a long period of time.

[0031]

[0032] Figure 1 is a schematic diagram of a carbon dioxide electrolysis device according to the present invention.

[0033] Figure 2 is a schematic diagram of a conventional carbon dioxide electrolysis device.

[0034] Figure 3 (a) is a graph showing the pH change of the electrolyte over time in Example 1, Comparative Example 1, and Comparative Example 3, and (b) is a graph showing the pH change of the electrolyte over time in Example 2, Comparative Example 2, and Comparative Example 4.

[0035] Figure 4 (a) is a graph showing changes in ionic conductivity of the electrolyte over time in Example 1, Comparative Example 1, and Comparative Example 3, and (b) is a graph showing changes in ionic conductivity of the electrolyte over time in Example 2, Comparative Example 2, and Comparative Example 4.

[0036]

[0037] Hereinafter, the present invention will be described in more detail to facilitate understanding. The terms and words used in this specification and claims should not be interpreted based on their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0038] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0039] In this specification, it should be understood that the terms “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0040]

[0041] The present invention provides an electrolysis device comprising an electrolysis cell including a gas diffusion layer, a cathode (13), a cation separation membrane (15), an anode (11), and an electrolyte, and a storage tank (2) connected to a discharge path (30) for discharging a product from the cathode outside the electrolysis cell, wherein the acid solution contained in the storage tank (2) and the electrolyte are homogeneous solutions.

[0042] According to one embodiment of the present invention, the electrolysis device can be utilized in all fields of electrochemical conversion, and the electrolysis device can be a device capable of producing useful chemical substances through electrochemical conversion such as carbon dioxide electrolysis or water electrolysis, and a device capable of being utilized for reducing and converting carbon dioxide and NOx. Specifically, the electrolysis device can be an electrochemical conversion device that converts carbon dioxide into carbon monoxide and ethylene.

[0043]

[0044] As described in the background technology above, a conventional electrolysis cell having a structure in which an electrolyte flows through the front surface of a conventional cathode generates OH by a side reaction during the reduction process of carbon dioxide. - It reacts again with carbon dioxide to form carbonate (HCO3 -) and thus had a problem of carbon dioxide loss, and the problem could be solved by flowing an acidic electrolyte over the front of the cathode, but in this case, the resistance increased due to the acidic electrolyte, which caused an additional problem of voltage increase when the conventional electrolysis cell was operated. In addition, an anion exchange membrane was mainly used as a separator included in the conventional electrolysis cell, but the anion exchange membrane has excellent carbon dioxide conversion efficiency due to fast ion transfer, but has very low mechanical strength, and has a problem of lowering the efficiency of the electrolysis because the carbonate passes through the anion exchange membrane and diffuses to the anode and generates carbon dioxide through an oxidation reaction at the anode. Therefore, the inventor of the present invention developed an electrolysis device capable of reducing the loss of supplied carbon dioxide by separating carbon dioxide again from the carbonate without diffusing the generated carbonate to the anode.

[0045]

[0046] According to one embodiment of the present invention, the electrolysis device according to the present invention includes an electrolysis cell and a storage tank (2) connected to a discharge path (30) outside the electrolysis cell. The electrolysis cell includes a cathode (13) and an anode (11), and a gas diffusion layer may be disposed in close contact with the cathode (13), and may include a separation membrane (15) and an electrolyte disposed between the cathode (13) and the anode (11). In addition, the separation membrane (15) is a cation exchange membrane, and when the separation membrane (15) is a cation exchange membrane, the carbonate produced can be prevented from being transferred to the anode (11).

[0047]

[0048] According to one embodiment of the present invention, the cathode (13) is connected to a supply conduit through which a reactant is supplied, and a discharge conduit (30) through which a product generated after electrolysis is discharged. The reactant may be carbon dioxide, and the carbon dioxide may be in a gaseous state and may include water vapor at about 40 to 60°C. In addition, the product is generated by electrolysis of the carbon dioxide, and may be at least one selected from the group consisting of carbon monoxide, ethylene, methane, formic acid, hydrocarbons, aldehydes, and alcohols. Unreacted carbon dioxide, water vapor, and carbonates generated by side reactions may be further discharged together with the product discharged from the discharge conduit (30).

[0049]

[0050] The storage tank (2) may be disposed outside the electrolysis cell and may be connected to the discharge path (30). In addition, the storage tank (2) may contain an acidic solution. The acidic solution may include an aqueous solution containing at least one selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid, citric acid, and oxalic acid; and a salt containing at least one selected from the group consisting of cesium, potassium, and sodium. For example, the acidic solution may be a mixed solution containing sulfuric acid (H2SO4) and cesium sulfate (Cs2SO4). In addition, the salt may include at least one selected from the group consisting of Cs2CO3, CsHCO3, Cs2SO4, CsCl, CsNO3, K2CO3, KHCO3, K2SO4, K3PO4, KCl, KNO3, Na2CO3, NaHCO3, Na2SO4, Na3PO4, NaCl and NaNO3. Carbon dioxide can be separated again from the carbonate by the acidic solution filled in the storage tank (2). That is, the acidic solution can play a role in generating carbon dioxide by reacting with the generated carbonate, and specifically, the hydrogen ion (H) of the acidic solution + ) and carbonate (HCO3- ) can react to produce water and carbon dioxide.

[0051] Additionally, according to one embodiment of the present invention, the acidic solution of the present invention may be a solution of the same type as the electrolyte. In this case, the acidic solution and the electrolyte may be a mixed solution containing, for example, sulfuric acid (H2SO4) and cesium sulfate (Cs2SO4).

[0052]

[0053] Fig. 2 is a schematic diagram of a conventional carbon dioxide electrolysis device. Referring to Fig. 2, a conventional carbon dioxide electrolysis device is connected to a discharge path (30-1) of a cathode (13-1) and an acid solution storage tank (20-1). Water and carbon dioxide can be separated from the carbonate by the acid solution of the acid solution storage tank (20-1). However, in this case, since the acid solution is continuously consumed, it is difficult for the reaction between the carbonate and the hydrogen ions of the acid solution to proceed for a long period of time, and as a result, it may be difficult to continuously operate while maintaining high electrolysis efficiency. Accordingly, the present invention forms a structure in which the acid solution is a solution of the same type as the electrolyte and the solutions are circulated with each other, thereby supplying the acid solution from the electrolyte and allowing a continuous carbonate reaction to occur in the acid solution storage tank.

[0054]

[0055] In addition, according to one embodiment of the present invention, the storage tank (2) of the present invention may include the acid solution storage unit (20) and the electrolyte storage unit (22) connected thereto, and the electrolyte storage unit (22) may be connected to the anode (11) through a solution exchange path. The electrolyte storage unit (22) may be spaced apart from the acid solution storage unit (20) and may be connected to each other through a connection unit (21). There is a risk that gaseous products transported from the cathode, such as carbon monoxide and ethylene, may be mixed with the acid solution in the storage tank (2) and not be completely discharged to the outside, and there is a concern that the yield of the products may be reduced. To prevent this, the electrolysis device of the present invention includes the storage tank (2) divided into an acid solution storage unit (20) and an electrolyte storage unit (22), and allows the acid solution to move between the acid solution storage unit (20) and the electrolyte storage unit (22) through a connection unit (21), thereby obtaining a desired level of product yield and allowing the acid solution to be smoothly transferred to the anode through the solution exchange path. The solution contained in the electrolyte storage unit (22) may be the same solution as the acid solution contained in the acid solution storage unit (20) and the electrolyte.

[0056]

[0057] Fig. 1 is a schematic diagram of a carbon dioxide electrolysis device according to the present invention. Referring to Fig. 1, the acid solution storage unit (20) is connected to the cathode (13) through a discharge path (30), and the acid solution storage unit (20) can be connected to the electrolyte storage unit (22) through a connection unit (21) and be spaced apart from each other. In addition, the electrolyte storage unit (22) can be connected to the anode (11) through a solution exchange path. In the acid solution storage unit (20), the carbonate transported from the cathode (13) through the discharge path (30) and the hydrogen ions of the acid solution react, and the carbon dioxide separated through this and the unreacted carbon dioxide can be introduced back into the electrolysis cell through the supply path of the cathode (13). In addition, the product transferred from the cathode (13) to the acid solution storage unit (20) through the discharge path (30) can be obtained by being discharged to the outside of the electrolysis device through the product discharge unit in the acid solution storage unit (20). At this time, there is a concern that the separated carbon dioxide, unreacted carbon dioxide, and product may be mixed with the acid solution as gaseous substances and may not be discharged to the outside of the storage tank (2) but may flow into the electrolyte storage unit (22). To prevent this, the product discharge unit through which the product is discharged to the outside is set higher than the position of the connection unit (21), and the acid solution is filled up to the upper side of the connection unit (21), so that the gaseous substances can be efficiently discharged to the outside. The above product discharge unit can serve to discharge the gaseous substance inside the acid solution storage unit (20) to the outside, and the connection unit (21) can serve to connect the acid solution storage unit (20) and the electrolytic cell storage unit (22) to transport the acid solution. For example, as shown in FIG. 1, the acid solution storage unit (20), the connection unit (21), and the electrolyte storage unit (22) can be arranged in an “H” shape.

[0058] In addition, according to one embodiment of the present invention, the solution exchange path may include a first solution exchange path (40) for transferring the acid solution from the electrolyte storage unit (22) to the anode (11); and a second solution exchange path (50) for transferring the electrolyte from the anode (11) to the electrolyte storage unit (22).

[0059]

[0060] The acid solution contained in the electrolytic cell storage unit (22) can be transported to the anode (11) through the solution exchange first flow path (40). In the case of a conventional electrolysis device, as the electrolysis reaction progresses, one or more cations selected from the group consisting of cesium, potassium, and sodium contained in the electrolyte move toward the cathode due to the voltage applied to the electrolysis cell, and as a result, the cations of the electrolyte may be continuously consumed. In addition, the concentration of hydrogen ions relative to the cations of the electrolyte increases, lowering the pH of the electrolyte. In this case, the hydrogen production reaction, which is a competing reaction with the carbon dioxide production reaction, becomes more active, lowering the carbon dioxide production efficiency and making it impossible to operate the electrolysis device for a long period of time. In the case of the electrolytic device of the present invention, since the acidic solution and the electrolyte correspond to the same type of solution, the cations are supplied to the anode (11) through the first solution exchange path (40), and the pH and ionic conductivity of the electrolyte are maintained at a level similar to that at the beginning of operation, thereby enabling continuous operation of the electrolytic device.

[0061] In addition, the electrolyte from the anode (11) can be transferred to the electrolyte storage unit (22) through the second solution exchange passage (50). As described above, the acidic solution in the acidic solution storage tank reacts with carbonate to separate carbon dioxide, and thus the acidic solution is continuously consumed, so the pH in the acidic solution storage tank gradually increases, and when a certain operating time elapses, the acidic solution storage tank cannot perform its function. In the case of the electrolysis device of the present invention, since the acidic solution and the electrolyte correspond to the same solution, the electrolyte is supplied from the anode to the electrolyte storage unit (22) through the second solution exchange passage (50), and the electrolyte is transferred from the electrolyte storage unit to the acidic solution storage unit, thereby maintaining the pH of the acidic solution in the storage tank (2), thereby enabling continuous operation. In this case, since the material transferred through the second solution exchange path from the anode (11) may include not only the electrolyte but also oxygen gas resulting from an oxidation reaction, a gas-liquid separator (60) may be further included in the second solution exchange path (50), and the gaseous material may be separated through the gas-liquid separator, and only the electrolyte may be transferred.

[0062] That is, the electrolysis device of the present invention uses the electrolyte in the electrolysis cell and the acid solution in the acid solution storage tank as the same solution, and at the same time, configures the solutions to be transferred or circulated to each other through the solution exchange path, thereby maintaining the overall ion balance of the electrolysis device at the same level as at the beginning of operation, and operating the electrolysis device for a long period of time without deterioration in electrolysis efficiency.

[0063] According to one embodiment of the present invention, the electrolyte comprises one or more cations (Na) selected from the group consisting of cesium, potassium and sodium. + , K + , Cs +) may be an aqueous solution. For example, the electrolyte may be an aqueous solution including at least one selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid, citric acid, and oxalic acid; and at least one selected from the group consisting of Cs2CO3, CsHCO3, Cs2SO4, CsCl, CsNO3, K2CO3, KHCO3, K2SO4, K3PO4, KCl, KNO3, Na2CO3, NaHCO3, Na2SO4, Na3PO4, NaCl, and NaNO3. In addition, as described above, the electrolyte and the acidic solution in the acidic solution storage tank (20) may be solutions of the same kind.

[0064]

[0065] According to one embodiment of the present invention, the separation membrane (15) may be a cation exchange membrane, and specifically, a Nafion separation membrane (15). The cation separation membrane (15) may serve to prevent the carbonate generated at the cathode (13) from diffusing toward the anode (11). On the other hand, when the separation membrane (15) is an anion exchange membrane, since the carbonate is diffused toward the anode, the transport of the carbonate to the acid solution storage tank is not smooth, which may lower the overall electrolysis efficiency and increase the loss of the supplied carbon dioxide.

[0066]

[0067] According to one embodiment of the present invention, the electrolysis cell may be a zero-gap membrane electrode assembly cell in which the gas diffusion layer, the cathode (13), the separator (15), and the anode (11) having an anode (11) liquid path are sequentially laminated. Specifically, the zero-gap membrane electrode assembly may be formed in the form of a very thin plate film in which the gas diffusion layer, the cathode (13), the separator (15), and the anode (11) having an anode (11) liquid path are sequentially laminated in order to increase driving voltage and current efficiency.

[0068] Conventional electrolysis cells have a gap structure in which the electrodes and the separator are spaced apart by a few millimeters, but the zero gap is a sandwich-type electrolysis cell in which the cathode electrode and the anode negative electrode are in contact with each other with the separator in between, thereby eliminating the gap between the electrodes and the separator. The zero gap-type electrolysis cell can reduce the solution ion resistance due to the presence of an electrolyte and reduce the increase in mass transfer resistance due to the generated gas when implementing a large-area electrode.

[0069] Specifically, the electrolyte flowing toward the cathode (13) side is called cathode (13) solution, and the electrolyte flowing toward the anode (11) side is called anode (11) solution. The zero-gap membrane electrode assembly may not include the cathode (13) solution, but may only include the anode (11) solution. The electrolysis cell having the zero-gap membrane electrode assembly structure has a structure in which the electrolyte does not flow in the front portion of the cathode (13) and only flows in the front portion of the anode (11), thereby minimizing the gap between the cathode (13), the anode (11), and the separator (15), thereby enabling rapid ion transport, increasing current efficiency, and solving the additional problem of voltage increase during the electrolysis reaction, thereby having the advantage of lowering the overvoltage. In addition, in this case, separators may be arranged on both sides of the zero-gap membrane electrode assembly to form one cell.

[0070]

[0071] According to one embodiment of the present invention, the product generated by the electrolytic reaction in the cathode (13) can be transported to the storage tank (2) through the discharge path (30), and the product can include carbon monoxide, water vapor, and a salt. The salt can be a carbonate. Carbon dioxide can be separated from the carbonate in the acid solution storage tank (20), and the regenerated carbon dioxide can be resupplied to the cathode (13) through the supply path. The electrolysis device of the present invention separates carbon dioxide from the carbonate by the storage tank (2) and circulates the carbon dioxide to the electrolysis cell, thereby reducing the loss of carbon dioxide and increasing the electrolysis efficiency. In addition, by using the acid solution and the electrolyte as the same solution, supplying the electrolyte to the storage tank (2), and supplying the cations of the storage tank (2) to the electrolyte, it is possible to operate for a long period of time and maintain high electrolysis efficiency.

[0072]

[0073] Hereinafter, the decomposition principle of the electrolysis device and each component of the electrolysis device will be described.

[0074] The above electrolysis refers to decomposing a substance through a redox reaction by applying a direct current voltage to a decomposition reaction that does not occur spontaneously. The anode acts as an oxidation electrode, oxidizing water to generate oxygen, and at this time, hydrogen ions are generated. The hydrogen ions generated at the anode are transferred to the cathode through the electrolyte, and the cathode acts as a reduction electrode, so that reactants introduced to the cathode can react with electrons and hydrogen ions transferred from the anode to generate products. In addition, the separator may be disposed between the anode and the cathode. The separator may be composed of an inert material that does not participate in the electrochemical reaction itself, but may provide a path for ions to move between the anode and the cathode and serve to isolate physical contact between the anode and the cathode.

[0075] In addition, the anode and the cathode of the electrolysis device of the present invention may each include a catalyst layer. In addition, water vapor supplied together with carbon dioxide in the cathode region generates a reduction product through an electroreduction reaction on the cathode surface. Therefore, the cathode may include a gas diffusion layer to evenly supply humidified carbon dioxide gas to the cathode region. When the cathode includes a hydrophobic gas diffusion layer, the supplied carbon dioxide can be smoothly diffused, distributed, and supplied to the catalyst layer of the cathode. In addition, the hydrophobic gas diffusion layer effectively prevents moisture condensation, thereby ensuring a continuous and uniform supply of carbon dioxide and allowing the electrolysis reaction to proceed smoothly. In addition, the catalyst layer may have a surface such as a porous structure so as to exhibit good gas permeability characteristics on the surface.

[0076] According to one embodiment of the present invention, the anode may include a catalyst active in the electrolysis of water, and the catalyst layer of the anode may include at least one selected from the group consisting of Pt, Au, Pd, Ir, Ag, Rh, Ru, Ni, Al, Mo, Cr, Cu, Ti, W, alloys thereof, or mixed metal oxides, such as Ta2O5, IrO2, for an oxygen evolution reaction. Specifically, the anode in the electrolysis device of the present invention may include titanium (Ti) coated with iridium oxide (IrO2).

[0077] In addition, since the carbon dioxide reduction reaction occurring at the cathode competes with the hydrogen evolution reaction, a catalyst that is active in the carbon dioxide reduction reaction and requires a high voltage for the hydrogen evolution reaction may be included. The catalyst layer of the cathode may include at least one selected from the group consisting of Sn, a Sn alloy, Al, Au, Ag, C, Cd, Co, Cr, Cu, a Cu alloy, Ga, Hg, In, Mo, Nb, Ni, NiCo2O4, a Ni alloy, a Ni-Fe alloy, Pb, Rh, Ti, V, W, Zn, and mixtures thereof for the hydrogen evolution reaction. Specifically, the cathode in the electrolysis device of the present invention may include silver (Ag).

[0078] In addition, as described above, the separation membrane may include a cation exchange membrane (CEM), and specifically, may be a Nafion exchange membrane. In the case of the cation exchange membrane, it may act as a bonding membrane that prevents the reducing substance generated at the cathode through catalytic action from moving to the anode and being oxidized, and may be a separation phase that inhibits the permeation of anions and allows cations such as hydrogen ions (H+) to pass through.

[0079] In addition, the electrolyte may be an electrolyte according to the present invention as described above, and specifically, may be an acidic electrolyte, and more specifically, may be an aqueous solution containing cesium sulfate. The electrolyte composition may contain the electrolyte in an amount of 0.1 to 15.0 M, preferably 0.25 to 10.0 M. The concentration of the electrolyte is related to the generation efficiency of the product (the generation efficiency of the target product relative to the applied current density) and the voltage. The higher the concentration of the electrolyte, the lower the generation voltage, required voltage, or overvoltage. However, the above-described conditions are preferable in order to minimize the increase in manufacturing cost and the generation of additional products due to side reactions.

[0080] In addition, the gas diffusion layer may use a porous body using a carbon material such as carbon fiber cloth, carbon fiber felt, or carbon fiber paper, or a metal porous body made of a thin metal plate with a mesh structure such as expanded metal or metal mesh, and in the electrolysis device of the present invention, the gas diffusion layer may use carbon fiber cloth.

[0081] According to one embodiment of the present invention, the electrolysis device can be used in all fields requiring electrochemical conversion, and in particular, can electrochemically decompose carbon dioxide to obtain a desired product, and specifically, the electrolysis device can electrolyze carbon dioxide to produce one or more selected from the group consisting of carbon monoxide, ethylene, methane, formic acid, hydrocarbons, aldehydes, and alcohols.

[0082]

[0083] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0084]

[0085] Example 1

[0086] The carbon dioxide electrolysis device shown in the schematic diagram of Fig. 1 was operated under the operating conditions described below. The carbon dioxide electrolysis device was operated by including a membrane electrode assembly having a zero-gap structure in which an anode, a cation separation membrane (type: Nafion®212), a cathode, and a gas diffusion layer were sequentially laminated, and an acid solution storage tank connected to the outside of the cathode and the membrane electrode assembly and filled with an acid solution (0.5 M Cs2SO4 pH adjusted to 2~3 by H2SO4). The first and second solution exchange channels were installed to allow the acid solution and the electrolyte to circulate.

[0087] Reaction current density: 100 mA / cm 2 (Constant current operation)

[0088] Reaction voltage: 1~4 V

[0089] Reaction temperature: 40 ℃

[0090] Reaction pressure: 1 atm (atmospheric pressure)

[0091] Anode catalyst: IrO2on Ti mesh

[0092] Cathode catalyst: Ag powder

[0093] Electrode area: 25 cm 2

[0094] Gas diffusion layer: Sigracet 39BB

[0095] Anode electrolyte: 0.5 M Cs2SO4 pH adjusted to 2~3 by H2SO4 (25 ml / min)

[0096] Cathode reactant: 40 ℃ Humidified CO2 gas (200 ccm)

[0097] 40 ℃ Humidified CO2 gas supply flow rate: 200 ml / min

[0098]

[0099] Example 2

[0100] The reaction current density is 200 mA / cm 2 The carbon dioxide electrolysis device was operated under the same conditions as in Example 1, except that it was performed as described above.

[0101]

[0102] Comparative Example 1

[0103] A carbon dioxide electrolysis device was operated under the same conditions as in Example 1, except that an acid solution storage tank was not included (see Table 1).

[0104]

[0105] Comparative Example 2

[0106] The carbon dioxide electrolysis device was operated under the same conditions as Example 2 except that the acid solution storage tank was not included (see Table 1).

[0107]

[0108] Comparative Example 3

[0109] The carbon dioxide electrolysis device was operated under the same conditions as in Example 1, except that the carbon dioxide electrolysis device shown in the schematic diagram of Fig. 2 was used instead of the carbon dioxide electrolysis device shown in the schematic diagram of Fig. 1, and the conditions were changed to those in Table 1.

[0110]

[0111] Comparative Example 4

[0112] The carbon dioxide electrolysis device was operated under the same conditions as in Example 2, except that the carbon dioxide electrolysis device shown in the schematic diagram of Fig. 2 was used instead of the carbon dioxide electrolysis device shown in the schematic diagram of Fig. 1 and the conditions were changed to those in Table 1.

[0113]

[0114] The conditions of the above examples and comparative examples are shown in Table 1 below.

[0115] Current density (mA / cm) 2) Whether acid solution storage tank is included (O / X) Whether acid solution and electrolyte are circulated (O / X) Acid solution Electrolyte Example 1100OOCs2SO4+ H2SO4Cs2SO4+ H2SO4Example 2200OOCs2SO4+ H2SO4Cs2SO4+ H2SO4Comparative Example 1100XXXCs2SO4+ H2SO4Comparative Example 2200XXXCs2SO4+ H2SO4Comparative Example 3100OXH2SO4Cs2SO4Comparative Example 4200OXH2SO4Cs2SO4

[0116] Experimental Example 1 - Measuring pH changes in electrolyte

[0117] The carbon dioxide electrolysis device according to the above examples and comparative examples was operated for 8 hours, and the pH was measured over time from before the operation of the electrolysis device to 8 hours after the operation, and the values ​​are shown in Table 2. In addition, the change in the initial pH value and the pH value after 8 hours are shown in Table 2.

[0118]

[0119] Experimental Example 2 - Measurement of electrolyte ionic conductivity

[0120] The carbon dioxide electrolysis device according to the above examples and comparative examples was operated for 8 hours, and the ionic conductivity of the electrolyte was measured over time from before the operation of the electrolysis device to 8 hours after the operation. The measured values ​​are shown in Table 3. In addition, the change in the initial ionic conductivity value and the ionic conductivity value after 8 hours is shown in Table 3.

[0121]

[0122] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Time (min) pH Time (min) pH Time (min) pH Time (min) pH Time (min) pH 0 (Initial) 2.580 (Initial) 30 (Initial) 2.580 (Initial) 30 (Initial) 2.580 (Initial) 3452.47253.09802.1602.37152.5602.431602.511353.061401.981202.18652.141802.162502.522403.022001.932102.112 52.142402.083202.513003.07480(Final)1.87480(Final)2.081802.143102.113902.563903.13----2402.123602.114402.58480(Final)3.09----480(Final)2.054202.11480(Final)2.6--------480(Final)2.09Change0.02Change0.09Change0.71Change0.92Change0.53Change0.91

[0123] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Time (min) Ionic Conductivity (μS / cm) Time (min) Ionic Conductivity (μS / cm) Time (min) Ionic Conductivity (μS / cm) Time (min) Ionic Conductivity (μS / cm) Time (min) Ionic Conductivity (μS / cm) Time (min) Ionic Conductivity (μS / cm) 0 (Initial) 1132820 (Initial) 90521.50 (Initial) 1132820 (Initial) 90521.50 (Initial) 1132820 (Initial) 90521.545122190251027278015978360129660151189316011820516011429413593052.5140204074120205340125168608180257599250113527240102685200275420210293306180242995240305934 320117769300101824480(Final)347643480(Final)356944240300728310314021390117752239097303.4----480(Final)372262360342573440117033480(Final)91940.6------420365359480(Final)116565--------480(Final)382393Change3283Change1419.1Change234361Change266422.5Change258980Change291871.5

[0124] Referring to Table 2, Table 3, Figures 3, and 4 above, it can be confirmed that Examples 1 and 2 driven by the electrolysis device according to the present invention have very small changes in the pH of the electrolyte and the ionic conductivity compared to the comparative example. That is, it can be confirmed that Examples 1 and 2 use the solution and the electrolyte contained in the acid solution storage tank as the same solution and circulate the solution, thereby maintaining the overall ion balance within the electrolysis device at a certain level.

[0125] Since the cesium ions contained in the electrolyte move to the cathode side and relatively many hydrogen ions remain, the pH of the electrolyte decreases over time, and the ionic conductivity of the electrolyte also increases due to the hydrogen ions having higher ionic conductivity than the cesium ions. However, when the pH of the electrolyte decreases and the balance between the cesium ions and the hydrogen ions is broken, the hydrogen production reaction, which is a competing reaction with the carbon dioxide production reaction, becomes more active, lowering the carbon dioxide production efficiency and making long-term operation impossible. Compared to Example 1, which has the same current density, it can be confirmed that in Comparative Examples 1 and 3, the pH drops rapidly after 8 hours, and the change in the ionic conductivity of the electrolyte is also significantly large. In addition, it can be confirmed that in Comparative Examples 2 and 4, the change in pH and ionic conductivity after 8 hours is also large compared to Example 2. In other words, Comparative Examples 1 to 4 have very large changes in the pH and ionic conductivity of the electrolyte, and the ionic balance is broken, so the hydrogen production reaction occurs more actively, making long-term operation difficult.

[0126] 2: Storage tank

[0127] 11: Anode

[0128] 13: Cathode

[0129] 15: Membrane

[0130] 20: Acid solution storage compartment

[0131] 21: Connection

[0132] 22: Electrolyte storage compartment

[0133] 30: Emission Euro

[0134] 40: Solution exchange 1st euro

[0135] 50: Solution exchange 2nd Euro

[0136] 60: Gas-liquid separator

[0137] 11-1: Anode of a conventional device

[0138] 13-1: Cathode of a conventional device

[0139] 15-1: Separator of conventional device

[0140] 20-1: Acid solution storage tank of conventional device

[0141] 30-1: Exhaust path of conventional device

[0142] 60-1: Gas-liquid separator of conventional device

Claims

1. An electrolysis cell comprising a gas diffusion layer, a cathode, a cation separator, an anode, and an electrolyte; and A storage tank is included outside the electrolysis cell, and is connected to a discharge path for discharging the product from the cathode, An electrolysis device wherein the acid solution contained in the storage tank and the electrolyte contained in the electrolysis cell are homogeneous solutions.

2. In claim 1, An electrolysis device comprising an aqueous solution comprising at least one selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, acetic acid, citric acid, and oxalic acid; and a salt comprising at least one selected from the group consisting of cesium, potassium, and sodium.

3. In claim 2, An electrolysis device wherein the salt comprises at least one selected from the group consisting of Cs2CO3, CsHCO3, Cs2SO4, CsCl, CsNO3, K2CO3, KHCO3, K2SO4, K3PO4, KCl, KNO3, Na2CO3, NaHCO3, Na2SO4, Na3PO4, NaCl and NaNO3.

4. In claim 1, The above storage tank includes an acid solution storage unit and an electrolyte storage unit connected thereto, An electrolysis device in which the electrolyte storage unit is connected to the anode through a solution exchange path.

5. In claim 4, The above solution exchange path is a first solution exchange path that transfers an acid solution from the electrolyte storage unit to the anode; and An electrolysis device comprising a second solution exchange path for transferring electrolyte from the anode to the electrolyte storage unit.

6. In claim 1, An electrolysis device in which the above electrolysis cell is a zero-gap membrane electrode assembly cell in which the gas diffusion layer, the cathode, the separator, and the anode having an anode liquid path formed therein are sequentially stacked.

7. In claim 1, The product generated by the electrolytic reaction at the cathode is transported to the storage tank through the discharge path, An electrolytic device wherein the above products include carbon monoxide, water vapor and salt.

8. In claim 7, An electrolysis device in which carbon dioxide generated from the salt in the storage tank is supplied to the electrolysis cell.

9. In claim 7, An electrolytic device wherein the above salt is a carbonate.

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

11. In claim 10, An electrolysis device in which the carbon dioxide is supplied to the electrolysis cell in a state including water vapor.

12. In claim 1, The above electrolysis device is an electrolysis device that electrolyzes carbon dioxide to produce at least one selected from the group consisting of carbon monoxide, ethylene, methane, formic acid, hydrocarbons, aldehydes, and alcohols.

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