Carbon dioxide electrolysis device and carbon dioxide electrolysis method

Abstract

To provide a carbon dioxide electrolysis device capable of suppressing clogging of a cathode flow path and suppressing deterioration of an electrolyte membrane.SOLUTION: A carbon dioxide electrolysis device according to an embodiment comprises an electrolysis cell including a cathode electrode to which carbon dioxide gas is supplied, an anode electrode, and an electrolyte membrane interposed between the cathode electrode and the anode electrode, a current supply unit for supplying current to the electrolysis cell, and a control unit. A value obtained by dividing the current supplied to the electrolysis cell by a planar effective area of the electrolysis cell is defined as current density. The control unit controls the current supply unit such that the current density is 10 mA / cm2 to 1000 mA / cm2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments relate to a carbon dioxide electrolysis device and a carbon dioxide electrolysis method. [Background technology]

[0002] In recent years, concerns about the depletion of fossil fuels such as oil and coal have led to growing expectations for sustainable renewable energy sources. Examples include solar cells, which generate electricity using solar energy, and wind power, which generates electricity using wind energy. However, these energy sources face the challenge of providing a stable supply of electricity because their output depends on weather and natural conditions. Therefore, attempts have been made to stabilize the power supply by storing electricity generated by renewable energy sources in storage batteries. However, storage batteries are expensive and suffer from power losses during charging and discharging.

[0003] In response to these issues, a technology is known that uses electricity generated from renewable energy to perform water electrolysis to produce hydrogen (H2) from water. Alternatively, another technology is known that uses electricity generated from renewable energy to electrochemically reduce carbon dioxide (CO2) and convert it into chemical substances (chemical energy) such as carbon compounds, such as carbon monoxide (CO), formic acid (HCOOH), methanol (CH3OH), methane (CH4), acetic acid (CH3COOH), ethanol (C2H5OH), ethane (C2H6), or ethylene (C2H4). Storing these chemical substances in cylinders or tanks has the advantage of lowering energy storage costs and minimizing storage losses compared to storing electricity (electrical energy) in batteries.

[0004] A carbon dioxide electrolysis device that electrochemically reduces carbon dioxide has a stacked structure in which multiple electrolytic cells are stacked. Carbon dioxide gas is supplied to the cathode electrodes of the electrolytic cells, and an electric current is supplied to the electrolytic cells, causing the carbon dioxide to be electrolyzed and reduced to produce carbon monoxide. A cathode flow path that serves as a flow path for carbon dioxide gas is adjacent to the cathode electrode, and the carbon dioxide gas is mixed with an electrolytic solution and flows through the cathode flow path while in contact with the cathode electrode. An anode flow path that serves as a flow path for the electrolytic solution is adjacent to the anode electrode, and the electrolytic solution flows through the anode flow path while in contact with the anode electrode.

[0005] The electrolytic reaction formula at the cathode electrode is expressed by the following formulas (1) and (2). 2CO2+2e - → CO+CO3 2- (1) 2H2O+2e - → H2+2OH - (2)

[0006] Consider the case where the cathode is operated at a current density where the theoretical carbon dioxide gas concentration in the cathode fluid (described later) is 100%. In this case, the electrolytic reaction shown in the above formula (1) can proceed. This results in the formation of carbonate ions (CO3 2- The amount of CO₂ produced increases, and salts may precipitate at the inlet side of the cathode flow channel. The precipitated salts may clog the cathode flow channel.

[0007] On the other hand, when the concentration of carbon dioxide gas in the cathode fluid is low, the operating mode of the carbon dioxide electrolysis device switches to water electrolysis mode. In this case, the electrolysis reaction shown in equation (2) above can proceed. If the hydrogen gas generated in equation (2) cross-leaks to the anode electrode, reactive oxygen species including OH radicals (·OH) are generated. If these reactive oxygen species are, for example, OH radicals, they are generated on the outlet side of the cathode electrode as shown in equation (3) below, and can cause deterioration of the electrolyte membrane. HO → OH+H + +e - (3) [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2022-137607 [Patent Document 2] Japanese Patent Application Publication No. 2023-135261 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the embodiments is to provide a carbon dioxide electrolysis device and a carbon dioxide electrolysis method that can suppress blockage of the cathode flow channel and also suppress deterioration of the electrolyte membrane. [Means for solving the problem]

[0010] The carbon dioxide electrolysis device according to the embodiment is a device that electrolyzes carbon dioxide gas. The carbon dioxide electrolysis device includes an electrolysis cell including a cathode electrode to which carbon dioxide gas is supplied, an anode electrode, and an electrolyte membrane interposed between the cathode electrode and the anode electrode, a current supply unit that supplies current to the electrolysis cell, and a control unit. The value obtained by dividing the current supplied to the electrolysis cell by the planar effective area of ​​the electrolysis cell is defined as the current density. The control unit controls the electrolysis cell so that the current density is 10 mA / cm. 2 ~1000mA / cm 2 The current supply unit is controlled so that

[0011] A carbon dioxide electrolysis device according to an embodiment is a device that electrolyzes carbon dioxide gas. The carbon dioxide electrolysis device includes an electrolysis cell including a cathode electrode to which carbon dioxide gas is supplied, an anode electrode, and an electrolyte membrane interposed between the cathode and anode electrodes; a carbon dioxide gas flow rate regulator that regulates the flow rate of carbon dioxide gas supplied to the cathode electrode; and a control unit. The current density is defined as the current supplied to the electrolysis cell divided by the planar effective area of ​​the electrolysis cell. The theoretical carbon dioxide gas flow rate is defined as the minimum flow rate of carbon dioxide gas when the total amount of electricity per unit time at a given current density is used in the electrolysis reaction from carbon dioxide to carbon monoxide, and the flow rate ratio is defined as the ratio of the supply flow rate of carbon dioxide gas to the theoretical carbon dioxide gas flow rate. The control unit controls the carbon dioxide gas flow rate regulator so that the flow rate ratio is 50% to 500%.

[0012] A carbon dioxide electrolysis method according to an embodiment is a carbon dioxide electrolysis device for electrolyzing carbon dioxide gas, and is a method using a carbon dioxide electrolysis device including an electrolysis cell including a cathode electrode to which carbon dioxide gas is supplied, an anode electrode, and an electrolyte membrane interposed between the cathode and anode electrodes. The carbon dioxide electrolysis method includes the steps of supplying carbon dioxide gas to the cathode electrode, supplying a current to the electrolysis cell, and increasing the output of the carbon dioxide electrolysis device. The current density is defined as the current supplied to the electrolysis cell divided by the planar effective area of ​​the electrolysis cell. In the step of increasing the output, when the current density is 10 mA / cm 2 ~1000mA / cm 2 The current value is adjusted so that

[0013] A carbon dioxide electrolysis method according to an embodiment is a method using a carbon dioxide electrolysis device that performs electrolysis of carbon dioxide gas, the method using a carbon dioxide electrolysis device including an electrolysis cell that includes a cathode electrode to which carbon dioxide gas is supplied, an anode electrode, and an electrolyte membrane interposed between the cathode and anode electrodes. The carbon dioxide electrolysis method includes the steps of supplying carbon dioxide gas to the cathode electrode, supplying a current to the electrolysis cell, and increasing the output of the carbon dioxide electrolysis device. The current density is defined as the current supplied to the electrolysis cell divided by the planar effective area of ​​the electrolysis cell. The theoretical carbon dioxide gas flow rate is defined as the minimum flow rate of carbon dioxide gas when the total amount of electricity per unit time at a given current density is used in the electrolysis reaction from carbon dioxide to carbon monoxide, and the flow rate ratio is defined as the ratio of the supply flow rate of carbon dioxide gas to the theoretical carbon dioxide gas flow rate. In the step of increasing the output, the supply flow rate of carbon dioxide gas is adjusted so that the flow rate ratio is 50% to 500%. [Effects of the Invention]

[0014] According to the embodiment, it is possible to suppress blockage of the cathode flow channel and deterioration of the electrolyte membrane. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing a carbon dioxide electrolysis device according to this embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the carbon dioxide electrolysis unit shown in FIG. [Figure 3] FIG. 3 is a flowchart showing an example of the carbon dioxide electrolysis method according to this embodiment. [Figure 4] FIG. 4 is a graph showing the relationship between cell voltage and current density. [Figure 5] FIG. 5 is a graph showing the relationship between the theoretical flow rate of carbon dioxide and the Faraday efficiency. [Figure 6] FIG. 6 is a schematic diagram showing a modification of the carbon dioxide electrolysis device shown in FIG. [Figure 7]FIG. 7 is a schematic diagram showing another modified example of the carbon dioxide electrolysis device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a carbon dioxide electrolysis device and a carbon dioxide electrolysis method according to the present embodiment will be described with reference to the drawings.

[0017] 1, the carbon dioxide electrolysis device 1 includes a carbon dioxide electrolysis unit 2, an electrolyte solution supply unit 3, a current supply unit 4, a carbon dioxide gas supply unit 5, a carbon dioxide gas flow rate adjustment unit 6, and a control unit 7. The carbon dioxide electrolysis device 1 electrolyzes carbon dioxide gas supplied to a cathode electrode 20, which will be described later.

[0018] As shown in Fig. 2, the carbon dioxide electrolysis unit 2 includes one or more electrolysis cells 10. More specifically, the carbon dioxide electrolysis unit 2 includes a pair of current collector plates 11, a plurality of electrolysis cells 10 stacked between the pair of current collector plates 11, and a plurality of separators 12 stacked alternately with the electrolysis cells 10. The electrolysis cells 10, separators 12, and current collector plates 11 are clamped and pressed by a pair of clamping plates (not shown).

[0019] The electrolysis cell 10 includes a cathode electrode 20, an anode electrode 21, and an electrolyte membrane 22 interposed between the cathode electrode 20 and the anode electrode 21. The cathode electrode 20 is in contact with the electrolyte membrane 22 and a separator 12. A cathode gas and an electrolytic solution may be supplied to the cathode electrode 20. A cathode flow path 23 through which the cathode gas and the electrolytic solution flow is formed on the surface of the separator 12 that is in contact with the cathode electrode 20. The anode electrode 21 is in contact with the electrolyte membrane 22 and the separator 12. The electrolytic solution is supplied to the anode electrode 21. An anode flow path 24 through which the electrolytic solution flows is formed on the surface of the separator 12 that is in contact with the anode electrode 21.

[0020] An electrolyte may be supplied to the cathode electrode 20 and the anode electrode 21 from an electrolyte supply unit 3. The electrolyte may be, for example, an aqueous solution of an electrolyte containing potassium element in its composition. Examples of the electrolyte include an aqueous solution of potassium hydroxide (KOH), an aqueous solution of potassium bicarbonate (KHCO3), and an aqueous solution of potassium carbonate (K2CO3). The electrolyte supplied to the cathode electrode 20 and the electrolyte supplied to the anode electrode 21 may be the same or different. A cathode gas containing carbon dioxide gas is supplied to the cathode electrode 20 from a carbon dioxide gas supply unit 5. That is, the carbon dioxide gas supplied to the cathode electrode 20 is mixed with the electrolyte. However, the electrolyte does not necessarily have to be supplied to the cathode electrode 20.

[0021] The electrolyte membrane 22 is made of an electrolyte material, and may be, for example, an ion exchange membrane or a porous membrane.

[0022] 1, the electrolyte solution supply unit 3 supplies the electrolyte solution to the carbon dioxide electrolysis unit 2. The electrolyte solution supply unit 3 may include, for example, a pump (not shown). By driving the pump, the electrolyte solution stored in a storage unit (not shown) may be supplied to the carbon dioxide electrolysis unit 2.

[0023] The current supply unit 4 supplies a current for carrying out an electrolysis reaction to the carbon dioxide electrolysis unit 2. The current supply unit 4 is also referred to as a power supply unit. The current supply unit 4 may be controlled by the control unit 7, and the current supplied to the carbon dioxide electrolysis unit 2 may be adjusted.

[0024] The carbon dioxide gas supply unit 5 supplies carbon dioxide gas to the cathode electrode 20 of the carbon dioxide electrolysis unit 2. The carbon dioxide gas supply unit 5 may include a carbon dioxide gas cylinder, or may include a tank in which carbon dioxide gas is stored.

[0025] The carbon dioxide gas flow rate adjuster 6 adjusts the supply flow rate of carbon dioxide gas to the cathode electrode 20 of the carbon dioxide electrolysis unit 2. The carbon dioxide gas flow rate adjuster 6 may include, for example, a flow rate adjustment valve (not shown). The supply flow rate of carbon dioxide gas may be adjusted by adjusting the aperture of the flow rate adjustment valve. The carbon dioxide gas flow rate adjuster 6 may be controlled by the control unit 7 to adjust the supply flow rate of carbon dioxide gas.

[0026] The control unit 7 controls the current supply unit 4 and the carbon dioxide gas flow rate adjuster 6 described above.

[0027] For example, the control unit 7 may determine whether the current density of the current supplied to the electrolysis cell 10 is 10 mA / cm 2 ~1000mA / cm 2 The current density is the value obtained by dividing the current supplied to the electrolytic cell 10 by the planar effective area of ​​the electrolytic cell 10. The planar effective area of ​​the electrolytic cell 10 is the planar area of ​​the electrolytic cell 10 in the region of the electrolytic cell 10 through which the current passes, and when the current passes throughout the entire area of ​​the electrolytic cell 10, it is the entire planar area of ​​the electrolytic cell 10. The control unit 7 controls the current density supplied to the electrolytic cell 10 to be 100 mA / cm or less. 2 ~1000mA / cm 2 The current supply unit 4 may be controlled so that:

[0028] For example, the control unit 7 may control the carbon dioxide gas flow rate adjusting unit 6 so that the supply flow rate of carbon dioxide gas is 50% to 500% of the theoretical carbon dioxide gas flow rate. The theoretical carbon dioxide gas flow rate is defined as the minimum flow rate of carbon dioxide gas when the total amount of electricity per unit time at a predetermined current density is used in the electrolytic reaction from carbon dioxide to carbon monoxide. The amount of electricity per unit time is current. The ratio of the supply flow rate of carbon dioxide gas to the theoretical carbon dioxide gas flow rate is defined as the flow rate ratio. The flow rate ratio is expressed as carbon dioxide gas supply flow rate / theoretical carbon dioxide gas flow rate. As an example, when the current density is 1000 mA / cm 2 When the theoretical carbon dioxide gas flow rate is 10 Nm 3 / h, where the current density is 1000mA / cm 2 When the flow rate ratio is 100%, the supply flow rate of carbon dioxide gas is 10 Nm 3 / h, and the supply flow rate of carbon dioxide gas when the flow rate ratio is 200% is 20 Nm 3 / h. The control unit 7 may control the carbon dioxide gas flow rate adjusting unit 6 so that the flow rate ratio is 100% to 200%.

[0029] A carbon dioxide electrolysis method using the carbon dioxide electrolysis device according to this embodiment configured as described above will be described with reference to FIG.

[0030] First, when electrolysis of carbon dioxide gas is performed in the carbon dioxide electrolysis device 1 shown in Figures 1 and 2, the current value to be supplied to the electrolysis cell 10 by the current supply unit 4 is set (step S1). Specifically, the current value is set in the control unit 7 so as to obtain a desired current density. For example, when the current density is 10 mA / cm 2 ~1000mA / cm 2 The current value may be set so that:

[0031] Subsequently, carbon dioxide gas is supplied from the carbon dioxide gas supply unit 5 to the carbon dioxide electrolysis unit 2 (step S2). At this time, the supply flow rate of the carbon dioxide gas may be lower than the supply flow rate of the carbon dioxide gas in step S4, which will be described later.

[0032] Carbon dioxide gas is supplied as a cathode gas to the cathode electrode 20 of the electrolysis cell 10. The cathode gas is mixed with the electrolytic solution and flows through a cathode flow path 23 formed in the separator 12 while contacting the cathode electrode 20. The electrolytic solution supplied to the anode electrode 21 flows through an anode flow path 24 formed in the separator 12 while contacting the anode electrode 21.

[0033] In step S2, the carbon dioxide gas may be mixed with an inert gas. The carbon dioxide gas mixed with the inert gas may be supplied to the cathode electrode 20.

[0034] In step S2, the electrolytic solution is supplied from the electrolytic solution supply unit 3 to the cathode electrode 20 and the anode electrode 21 of the electrolytic cell 10. Also in step S2, after the supply of carbon dioxide gas to the electrolytic cell 10 is started, the concentration and flow rate of the carbon dioxide gas supplied from the carbon dioxide gas supply unit 5 to the electrolytic cell 10 may be measured. A cooling system may be started a predetermined time after the start of the carbon dioxide gas supply. During the period from the start of the carbon dioxide gas supply until the cooling system is started, a warm-up operation may be performed in which carbon dioxide gas is continuously supplied to the electrolytic cell 10.

[0035] Next, current is supplied from the current supply unit 4 to the carbon dioxide electrolysis unit 2 (step S3). The electrolytic reaction shown in the above formula (1) occurs at the cathode electrode 20. The current supply unit 4 supplies current at the current value set in the above step S1. Electrolysis begins when current is supplied to the electrolytic cell 10. After electrolysis begins, it is confirmed that operation is stable. At this time, the current value may be smaller than the current value in step S4, which will be described later.

[0036] Thereafter, the output of the carbon dioxide electrolysis device 1 is increased (step S4). In this case, the supply flow rate of carbon dioxide gas to the carbon dioxide electrolysis unit 2 may be increased. The carbon dioxide gas flow rate adjuster 6 may adjust the supply flow rate of carbon dioxide gas to a desired flow rate using the control unit 7. For example, the supply flow rate of carbon dioxide gas may be adjusted so that the flow rate ratio is 50% to 500%.

[0037] In step S4, the value of the current supplied to the carbon dioxide electrolysis unit 2 may be increased. In this case, the current value may be increased to the value set in step S1 described above. For example, the current value in step S4 is set to a value at a current density of 10 mA / cm 2 ~1000mA / cm 2 It may be adjusted so that

[0038] In step S4, the amount of carbon monoxide produced increases, and the output of the carbon dioxide electrolysis device 1 increases.

[0039] This completes the start-up of the carbon dioxide electrolysis device 1 (step S5). After start-up, operation continues and carbon monoxide production continues.

[0040] When the concentration of carbon dioxide gas in the cathode gas is 100% and the current density is set to 100%, carbonate ions (CO3 2- ) is produced, and salt may precipitate on the inlet side of the cathode flow channel 23. If the electrolytic solution is an aqueous solution of an electrolyte containing potassium element in its composition, potassium carbonate (K2CO3) is produced as a salt. The precipitated salt may clog the cathode flow channel 23.

[0041] On the other hand, when the concentration of carbon dioxide gas in the cathode gas is low and the voltage between the cathode electrode 20 and the anode electrode 21 is high, the electrolytic reaction shown in the above formula (3) proceeds, and active oxygen species including OH radicals may be generated. For example, when the active oxygen species is OH radicals, the OH radicals may be generated on the outlet side of the cathode flow channel 23, but may react with the material of the electrolyte membrane 22, causing deterioration of the electrolyte membrane 22.

[0042] Therefore, in this embodiment, the control unit 7 controls the current supply unit 4 to adjust the current density of the current supplied to the electrolytic cell 10 to within a predetermined range. More specifically, when the current density is 10 mA / cm 2 ~1000mA / cm 2 This allows the current density to be reduced. In this case, the electrolytic reaction at the cathode electrode 20 shown in the above formula (1) can be suppressed, and the carbonate ions (CO 2- ) can be reduced. Therefore, the amount of salt precipitation can be reduced, and clogging of the cathode flow channel 23 can be suppressed.

[0043] More specifically, the current density is set to 1000 mA / cm 2 On the other hand, the amount of salt deposition can be effectively reduced by setting the current density to 10 mA / cm or less. 2By setting the current density to the above, the amount of salt deposition can be reduced while the electrolytic reaction (electrolytic reaction formula (1)) at the cathode electrode 20 can proceed as shown in FIG. 4, and the amount of carbon monoxide produced can be ensured. 2 The cell voltage at this point is called the theoretical voltage. The theoretical voltage is the minimum voltage required for the electrolysis reaction to proceed. The region where the cell voltage is greater than the theoretical voltage is called the overvoltage region.

[0044] 4, by increasing the voltage (cell voltage) between the cathode electrode 20 and the anode electrode 21, the electrolytic reaction formula (1) becomes the main reaction, and the amount of carbon monoxide produced can be increased. 2 When the current density reaches this limit, the amount of carbon monoxide produced does not increase even if the cell voltage is increased further. This current density is called the limiting current density.

[0045] As mentioned above, the current density is 10 mA / cm 2 ~1000mA / cm 2 By adjusting the current density to 1000 mA / cm, the amount of OH radicals produced can be reduced. That is, by reducing the current density, the cell voltage can be reduced, and an increase in overvoltage can be suppressed. Since the amount of OH radicals produced increases as the overvoltage increases, a decrease in the current density can effectively reduce the amount of OH radicals produced. Therefore, deterioration of the electrolyte membrane 22 due to OH radicals can be suppressed. When the current density is 1000 mA / cm, 2 By setting the following, it is possible to effectively prevent the overvoltage from increasing.

[0046] In particular, the current density is set to 10 mA / cm 2 ~1000mA / cm 2 For example, by reducing the current density within the range of 10 mA / cm, it is possible to more effectively prevent the overvoltage from increasing. 2 ~100mA / cm 2 On the other hand, the current density may be set to 10 mA / cm 2By doing so, it is possible to carry out the electrolytic reaction at the cathode electrode 20 while suppressing an increase in overvoltage, and to ensure the amount of carbon monoxide produced.

[0047] On the other hand, when the current density is 10mA / cm 2 ~100mA / cm 2 Range greater than 100mA / cm 2 ~1000mA / cm 2 In order to more effectively suppress the increase in overvoltage, the current density is set to 100 mA / cm. 2 It is desirable to locate it near the

[0048] Furthermore, during operation of the carbon dioxide electrolysis device 1, the control unit 7 controls the carbon dioxide gas flow rate adjuster 6 to adjust the supply flow rate of carbon dioxide gas supplied to the electrolytic cell 10 within a predetermined range. More specifically, the flow rate ratio is adjusted to be 50% to 500%. This allows the supply flow rate of carbon dioxide gas to be appropriately adjusted. In this case, the supply flow rate of carbon dioxide gas flowing through the cathode flow channel 23 is ensured, and salt deposited in the cathode flow channel 23 can be blown away. This makes it possible to prevent clogging of the cathode flow channel 23.

[0049] More specifically, by setting the flow rate ratio to 50% or more, salt deposited in the cathode flow channel 23 can be effectively blown away. On the other hand, by setting the flow rate ratio to 500% or less, salt can be blown away while suppressing the emission of carbon dioxide gas that does not participate in the electrolysis reaction from the cathode flow channel 23. Considering the Faraday efficiency, the flow rate ratio is preferably set to 100% to 200%. As shown in FIG. 5, by setting the flow rate ratio to 100% or more, the electrolysis reaction can be performed in a region with high Faraday efficiency. By setting the flow rate ratio to 200% or less, a decrease in the carbon monoxide production efficiency can be suppressed. In other words, once the flow rate ratio reaches 200%, further increasing the carbon dioxide gas supply flow rate does not increase the Faraday efficiency, and therefore the amount of carbon monoxide produced. Therefore, it is effective to set the flow rate ratio to 200% or less. The Faraday efficiency refers to the ratio of the partial current that contributes to the production of carbon monoxide to the total current. Furthermore, by setting the flow rate ratio to 200% or less, the supply flow rate of carbon dioxide gas can be increased, making it possible to more effectively blow away salt that has precipitated in the cathode flow path 23, and further suppress the emission of carbon dioxide gas that does not undergo an electrolytic reaction from the cathode flow path 23.

[0050] Furthermore, as described above, adjusting the flow rate ratio to 50% to 500% can reduce the amount of OH radicals generated. That is, by appropriately adjusting the supply flow rate of carbon dioxide gas, the supply flow rate of carbon dioxide gas to the cathode electrode 20 can be ensured, and a shortage of carbon dioxide gas at the cathode electrode 20 can be prevented. This reduces the amount of OH radicals generated, and prevents the electrolyte membrane 22 from being deteriorated by OH radicals. By setting the flow rate ratio to 50% or more, the amount of OH radicals generated can be effectively reduced. On the other hand, by setting the flow rate ratio to 500% or less, the amount of carbon dioxide gas that does not undergo electrolytic reaction can be suppressed from being discharged from the cathode flow channel 23 while reducing the amount of OH radicals generated. As described above, when the flow rate ratio is adjusted to 100% to 200%, the supply flow rate of carbon dioxide gas can be increased, which can more effectively reduce the amount of OH radicals generated and can further suppress the amount of carbon dioxide gas that does not undergo electrolytic reaction from being discharged from the cathode flow channel 23.

[0051] In the present embodiment described above, the control unit 7 controls the current density of the current supplied to the electrolytic cell 10 to be 10 mA / cm 2 ~1000mA / cm 2 In the above example, the control unit 7 controls the current supply unit 4 so that the current density of the current supplied to the electrolytic cell 10 is 10 mA / cm and the carbon dioxide gas flow rate adjuster 6 so that the flow rate ratio is 50% to 500%. However, the present embodiment is not limited to this. For example, the control unit 7 may control the current density of the current supplied to the electrolytic cell 10 so that the current density is 10 mA / cm. 2 ~1000mA / cm 2 When the control unit 7 controls the current supply unit 4 so that the flow rate ratio is 50% to 500%, the adjustment range of the flow rate ratio is not limited to 50% to 500%. On the other hand, for example, when the control unit 7 controls the carbon dioxide gas flow rate adjustment unit 6 so that the flow rate ratio is 50% to 500%, the adjustment range of the current density is 10 mA / cm 2 ~1000mA / cm 2 It is not limited to being.

[0052] As shown in FIG. 1 , the carbon dioxide electrolysis device 1 according to this embodiment may further include an input unit 8. The input unit 8 may be configured to input the concentration of carbon dioxide gas in the cathode gas supplied to the cathode electrode 20. The control unit 7 may control the current supply unit 4 based on the concentration of carbon dioxide gas input from the input unit 8. More specifically, the control unit 7 may control the current supply unit 4 to reduce the current density as the concentration of carbon dioxide gas in the cathode gas supplied to the cathode electrode 20 decreases. Controlling the current supply unit 4 based on the carbon dioxide gas concentration makes it possible to set the current density according to the supply flow rate of carbon dioxide gas supplied to the cathode electrode 20, thereby improving the production efficiency of carbon monoxide gas.

[0053] The carbon dioxide gas concentration input to the input unit 8 may be a carbon dioxide gas concentration that has been acquired in advance. The configuration of the input unit 8 is arbitrary as long as it allows the carbon dioxide gas concentration to be input. The input unit 8 may be configured so that an operator can input the carbon dioxide gas concentration, or may be configured so that the carbon dioxide gas concentration is input to the input unit 8 by being transmitted as electronic information from an external device (not shown). The input unit 8 may be configured integrally with the control unit 7 or may be configured separately.

[0054] 6, the carbon dioxide electrolysis device 1 may further include a carbon dioxide gas concentration meter 9 in addition to the input unit 8. The carbon dioxide gas concentration meter 9 measures the concentration of carbon dioxide gas supplied from the carbon dioxide gas supply unit 5 to the cathode electrode 20. In the example shown in FIG. 6, the current supply unit 4 can be controlled based on the concentration of carbon dioxide gas actually supplied to the cathode electrode 20, thereby further improving the efficiency of carbon monoxide production. In the example shown in FIG. 6, the carbon dioxide gas concentration meter 9 measures the concentration of carbon dioxide gas downstream of the carbon dioxide gas flow rate adjuster 6 and upstream of the cathode electrode 20. The concentration of carbon dioxide gas measured by the carbon dioxide gas concentration meter 9 may be transmitted to the input unit 8.

[0055] Moreover, the carbon dioxide electrolysis device 1 in the present embodiment described above may further include an inert gas supply unit 30 and an inert gas flow rate adjustment unit 31, as shown in FIG.

[0056] The inert gas supply unit 30 supplies an inert gas to the cathode electrode 20 of the carbon dioxide electrolysis unit 2. The inert gas may be mixed with carbon dioxide gas from the carbon dioxide gas supply unit 5 and supplied to the cathode electrode 20. The inert gas is a gas that does not affect the electrolysis reaction at the cathode electrode 20. An example of such an inert gas is hydrogen gas. While flowing through the cathode flow channel 23, the hydrogen gas is discharged from the outlet of the cathode flow channel 23 without undergoing an electrolysis reaction. The inert gas supply unit 30 may include a cylinder of inert gas or may include a tank in which the inert gas is stored.

[0057] The inert gas flow rate adjusting unit 31 adjusts the supply flow rate of the inert gas to be mixed with the carbon dioxide gas. The inert gas flow rate adjusting unit 31 may include, for example, a flow rate adjusting valve (not shown). The supply flow rate of the inert gas may be adjusted by adjusting the opening degree of the flow rate adjusting valve. The inert gas flow rate adjusting unit 31 may be controlled by the control unit 7 to adjust the supply flow rate of the inert gas.

[0058] The control unit 7 shown in FIG. 7 may control the inert gas flow rate regulator 31 described above. More specifically, the control unit 7 may control the inert gas flow rate regulator 31 to mix the carbon dioxide gas with the inert gas. When the cathode gas does not contain an inert gas, the control unit 7 may control the inert gas flow rate regulator 31 to block the flow of the inert gas. In this case, the concentration of carbon dioxide gas in the cathode gas becomes 100%. On the other hand, when the cathode gas contains an inert gas, the inert gas flow rate regulator 31 may be controlled to supply the inert gas to the cathode electrode 20. In this case, the concentration of carbon dioxide gas in the cathode gas becomes less than 100%, and the partial pressure of the carbon dioxide gas decreases. As the partial pressure of the carbon dioxide gas decreases, the control unit 7 may control the current supply unit 4 to decrease the current density. This can suppress the electrolytic reaction at the cathode electrode 20 shown in the above-described formula (1), thereby reducing the amount of salt precipitation. This can prevent the cathode flow path 23 from being blocked. The current density is 10 mA / cm. 2 ~1000mA / cm 2 may be selected within the range.

[0059] The flow rate of the inert gas supplied to the cathode electrode 20 may be adjusted as appropriate, thereby adjusting the partial pressure of carbon dioxide gas in the cathode gas as appropriate.

[0060] According to the embodiment described above, it is possible to suppress blockage of the cathode flow channel and deterioration of the electrolyte membrane.

[0061] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, it is of course possible to combine parts of these embodiments as appropriate within the spirit of the invention. [Explanation of symbols]

[0062] 1: carbon dioxide electrolysis device, 4: current supply unit, 6: carbon dioxide gas flow rate adjustment unit, 7: control unit, 8: input unit, 10: electrolysis cell, 20: cathode electrode, 21: anode electrode, 22: electrolyte membrane, 30: inert gas supply unit, 31: inert gas flow rate adjustment unit

Claims

1. A carbon dioxide electrolysis device that performs electrolysis of carbon dioxide gas, an electrolysis cell including a cathode electrode to which the carbon dioxide gas is supplied, an anode electrode, and an electrolyte membrane interposed between the cathode electrode and the anode electrode; a current supply unit that supplies current to the electrolysis cell; A control unit; Equipped with A value obtained by dividing the current supplied to the electrolytic cell by the planar effective area of ​​the electrolytic cell is defined as a current density; The control unit controls the current density to be 10 mA / cm ２ ~1000mA / cm ２ The current supply unit is controlled so as to Carbon dioxide electrolysis device.

2. The control unit controls the current density to be 100 mA / cm ２ ~1000mA / cm ２ 2. The carbon dioxide electrolysis device according to claim 1, wherein the current supply unit is controlled so that:

3. a carbon dioxide gas flow rate adjusting unit that adjusts the supply flow rate of the carbon dioxide gas to the cathode electrode; a theoretical carbon dioxide gas flow rate is defined as the minimum flow rate of carbon dioxide gas when the total amount of electricity per unit time at a predetermined current density is used in the electrolytic reaction from carbon dioxide to carbon monoxide, and a flow rate ratio is defined as the ratio of the supply flow rate of carbon dioxide gas to the theoretical carbon dioxide gas flow rate; the control unit controls the carbon dioxide gas flow rate adjustment unit so that the flow rate ratio is 50% to 500%. The carbon dioxide electrolysis device according to claim 1 .

4. an input unit for inputting the concentration of the carbon dioxide gas to be supplied to the cathode; the control unit controls the current supply unit to adjust the current density based on the concentration of the carbon dioxide gas input to the input unit. The carbon dioxide electrolysis device according to any one of claims 1 to 3.

5. A carbon dioxide electrolysis device that performs electrolysis of carbon dioxide gas, an electrolysis cell including a cathode electrode to which the carbon dioxide gas is supplied, an anode electrode, and an electrolyte membrane interposed between the cathode electrode and the anode electrode; a carbon dioxide gas flow rate adjusting unit that adjusts the supply flow rate of the carbon dioxide gas to the cathode electrode; A control unit; Equipped with A value obtained by dividing the current supplied to the electrolytic cell by the planar effective area of ​​the electrolytic cell is defined as a current density; a theoretical carbon dioxide gas flow rate is defined as the minimum flow rate of carbon dioxide gas when the total amount of electricity per unit time at a predetermined current density is used in the electrolytic reaction from carbon dioxide to carbon monoxide, and a flow rate ratio is defined as the ratio of the supply flow rate of carbon dioxide gas to the theoretical carbon dioxide gas flow rate; the control unit controls the carbon dioxide gas flow rate adjustment unit so that the flow rate ratio is 50% to 500%. Carbon dioxide electrolysis device.

6. the control unit controls the carbon dioxide gas flow rate adjustment unit so that the flow rate ratio is 100% to 200%. The carbon dioxide electrolysis device according to claim 3 or 5.

7. an inert gas supply unit that supplies an inert gas to be mixed with the carbon dioxide gas; an inert gas flow rate adjusting unit that adjusts the supply flow rate of the inert gas to be mixed with the carbon dioxide gas; Further provided with The control unit controls the inert gas flow rate adjustment unit so as to mix the inert gas with the carbon dioxide gas. The carbon dioxide electrolysis device according to claim 3 or 5.

8. A carbon dioxide electrolysis method using a carbon dioxide electrolysis device that performs electrolysis of carbon dioxide gas, the carbon dioxide electrolysis device including an electrolytic cell including a cathode electrode to which the carbon dioxide gas is supplied, an anode electrode, and an electrolyte membrane interposed between the cathode electrode and the anode electrode, supplying the carbon dioxide gas to the cathode electrode; supplying an electric current to the electrolysis cell; increasing the output of the carbon dioxide electrolysis device; Equipped with A value obtained by dividing the current supplied to the electrolytic cell by the planar effective area of ​​the electrolytic cell is defined as a current density; In the step of increasing the output, the current density is 10 mA / cm ２ ~1000mA / cm ２ The current value of the current is adjusted so that A carbon dioxide electrolysis method comprising:

9. In the step of increasing the output, the current density is 100 mA / cm ２ ~1000mA / cm ２ The current value of the current is adjusted so that The carbon dioxide electrolysis method according to claim 8.

10. a theoretical carbon dioxide gas flow rate is defined as the minimum flow rate of carbon dioxide gas when the total amount of electricity per unit time at a predetermined current density is used in the electrolytic reaction from carbon dioxide to carbon monoxide, and a flow rate ratio is defined as the ratio of the supply flow rate of carbon dioxide gas to the theoretical carbon dioxide gas flow rate; In the step of increasing the output, the supply flow rate of the carbon dioxide gas is adjusted so that the flow rate ratio is 50% to 500%. The carbon dioxide electrolysis method according to claim 8.

11. further comprising a step of inputting the concentration of the carbon dioxide gas to be supplied to the cathode electrode; In the step of increasing the output, a current value of the current is adjusted based on a concentration of the carbon dioxide gas. The carbon dioxide electrolysis method according to any one of claims 8 to 10.

12. A carbon dioxide electrolysis method using a carbon dioxide electrolysis device that performs electrolysis of carbon dioxide gas, the carbon dioxide electrolysis device including an electrolytic cell including a cathode electrode to which the carbon dioxide gas is supplied, an anode electrode, and an electrolyte membrane interposed between the cathode electrode and the anode electrode, supplying the carbon dioxide gas to the cathode electrode; supplying an electric current to the electrolysis cell; increasing the output of the carbon dioxide electrolysis device; Equipped with A value obtained by dividing the current supplied to the electrolytic cell by the planar effective area of ​​the electrolytic cell is defined as a current density; a theoretical carbon dioxide gas flow rate is defined as the minimum flow rate of carbon dioxide gas when the total amount of electricity per unit time at a predetermined current density is used in the electrolytic reaction from carbon dioxide to carbon monoxide, and a flow rate ratio is defined as the ratio of the supply flow rate of carbon dioxide gas to the theoretical carbon dioxide gas flow rate; In the step of increasing the output, the supply flow rate of the carbon dioxide gas is adjusted so that the flow rate ratio is 50% to 500%. Carbon dioxide electrolysis method.

13. In the step of increasing the output, the supply flow rate of the carbon dioxide gas is adjusted so that the flow rate ratio is 100% to 200%. The carbon dioxide electrolysis method according to claim 10 or 12.

14. In the step of supplying the carbon dioxide gas, an inert gas is mixed with the carbon dioxide gas. The carbon dioxide electrolysis method according to claim 10 or 12.

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