Electrolytic apparatus, electrolytic system, and operating method for electrolytic apparatus

Abstract

To suppress the consumption of unnecessary current in an electrolytic reaction of an electrolytic apparatus.SOLUTION: An electrolytic apparatus comprises: a first electrolytic cell for reducing a reducible object and oxidizing an oxidizable object; a second electrolytic cell for reducing a reducible object and oxidizing an oxidizable object; a first source for supplying a first fluid containing a reducible object gas to the first and second electrolytic cells; a second source for supplying a second fluid containing an oxidizable object liquid to the first and second electrolytic cells; and at least one power supply that supplies a first power supply current to the first electrolytic cell and a second power supply current to the second electrolytic cell. The at least one power source sets the values of the first power supply current and the second power supply current so that the current density of the current flowing through the second electrolytic cell when reducing the reducible object is higher than the current density of the current flowing through the first electrolytic cell when reducing the reducible object.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE Embodiments of the present invention relate to electrolysis devices and systems. [Background technology]

[0002] In recent years, from the viewpoints of both energy and environmental issues, it is desired not only to convert renewable energy such as solar power generation into electrical energy for use, but also to convert it into a state that can be stored and transported. In response to this demand, research and development of artificial photosynthesis technology that produces chemical substances using sunlight, like photosynthesis by plants, is being carried out. This technology is expected to make it possible to store renewable energy as storable fuel, and to create value by producing chemical substances that can be used as industrial raw materials.

[0003] As a device for producing chemical substances using renewable energy such as solar power generation, electrolysis devices (electrochemical reaction devices) such as carbon dioxide electrolysis devices equipped with a cathode that reduces carbon dioxide (CO2) generated from power plants and waste treatment plants, and an anode that oxidizes water (H2O), are known. At the cathode, for example, carbon dioxide is reduced to produce carbon compounds such as carbon monoxide (CO). When realizing such an electrolysis device in a cell form (also called an electrolysis cell), it is considered effective to realize it in a form similar to a fuel cell such as a Polymer Electric Fuel Cell (PEFC). By directly supplying carbon dioxide to the catalyst layer of the cathode, it is possible to quickly proceed with the reduction reaction of carbon dioxide. Furthermore, by forming a stack structure in which electrolysis cells are stacked, it is possible to efficiently proceed with the reduction reaction in a small space. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2011 / 0256463 [Patent Document 2] U.S. Patent No. 7,147,953 [Patent Document 3] Patent Publication No. 2022-42280 [Non-patent literature]

[0005] [Non-Patent Document 1] ACS Energy Lett. 2019, 4, 1770-1777 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to suppress unnecessary current consumption in the electrolytic reaction of an electrolytic device. [Means for solving the problem]

[0007] The electrolysis device of the embodiment includes a first electrolysis cell that reduces a substance to be reduced and oxidizes a substance to be oxidized, a second electrolysis cell that reduces a substance to be reduced and oxidizes a substance to be oxidized, a first supply source that supplies a first fluid containing a gas of the substance to be reduced to the first electrolysis cell and the second electrolysis cell, a second supply source that supplies a second fluid containing a liquid of the substance to be oxidized to the first electrolysis cell and the second electrolysis cell, and at least one power source that supplies a first power source current to the first electrolysis cell and a second power source current to the second electrolysis cell. The at least one power source sets a value of the first power source current and a value of the second power source current so that the current density of the current flowing through the second electrolysis cell when the substance to be reduced is higher than the current density of the current flowing through the first electrolysis cell when the substance to be reduced is reduced. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a configuration example of an electrolysis device according to an embodiment. [Diagram 2] 1 is a schematic perspective view showing a structural example of a cell structure 100. FIG. [Diagram 3]FIG. 2 is a schematic diagram showing a structural example of a membrane electrode assembly MEA. [Figure 4] 3 is a schematic diagram showing an example of the structure of a cathode flow path plate 14. FIG. [Diagram 5] 2 is a schematic diagram showing an example of the structure of an anode flow path plate 15. FIG. [Figure 6] 2 is a schematic diagram showing an example of the structure of a cathode current collector 16. FIG. [Figure 7] 2 is a schematic diagram showing an example of the structure of an anode current collector 17. FIG. [Figure 8] 2 is a schematic diagram showing an example of the structure of an insulating layer 18. FIG. [Figure 9] 2 is a schematic diagram for explaining the flow of a cathode fluid and the flow of an anode fluid in the cell structure 100. FIG. [Figure 10] 1 is a schematic perspective view showing a structural example of a cell structure 100. FIG. [Figure 11] FIG. 2 is a schematic diagram showing how impurities and substances to be reduced in a cathode fluid flow in series through each electrolysis cell 10. [Figure 12] FIG. 2 is a diagram showing an example of a graph showing the relationship between the current density flowing through the electrolysis cell 10 and the cell voltage and the Faraday efficiency. [Figure 13] FIG. 2 is a schematic diagram showing another example of an electrolysis device according to an embodiment. [Figure 14] FIG. 2 is a schematic diagram showing another example of an electrolysis device according to an embodiment. [Figure 15] FIG. 2 is a schematic diagram showing another example of an electrolysis device according to an embodiment. [Figure 16] FIG. 2 is a schematic diagram showing another example of an electrolysis device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an electrolysis device according to an embodiment will be described with reference to the drawings. In each embodiment shown below, substantially the same components are denoted by the same reference numerals, and some of the descriptions thereof may be omitted. The drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each part, etc. may differ from the actual ones.

[0010] In this specification, "connect" includes not only direct connection but also indirect connection unless otherwise specified. Furthermore, in this specification, "connect" includes not only physical connection but also electrical connection unless otherwise specified.

[0011] Fig. 1 is a schematic diagram showing a configuration example of an electrolysis device of an embodiment. Fig. 1 shows a configuration example of an electrolysis device 1. The electrolysis device 1 includes an electrolysis cell 10 in which an electrolysis reaction takes place, a cathode supply source 20 that supplies a cathode fluid, an anode supply source 30 that supplies an anode fluid, and a power source 40 that supplies power to the electrolysis cell 10. Fig. 1 shows an X-axis, a Y-axis, and a Z-axis. The X-axis, the Y-axis, and the Z-axis perpendicularly intersect with each other. The Z-axis is along the thickness direction of the electrolysis cell 10. Fig. 1 shows a part of an XZ cross section including the X-axis and the Z-axis.

[0012] The electrolysis cell 10 includes a cathode 11, an anode 12, a membrane (separator) 13, a cathode flow path plate 14 having a cathode flow path 140, an anode flow path plate 15 having an anode flow path 150, a cathode current collector 16, and an anode current collector 17. The cathode 11, the anode 12, and the membrane 13 may be stacked to form a membrane electrode assembly MEA. The stacking order of the components of the electrolysis cell 10 is not limited to that shown in FIG. 1, and may be reversed to that shown in FIG. 1, for example.

[0013] The electrolysis device 1 has a plurality of electrolytic cells 10. The plurality of electrolytic cells 10 are, for example, stacked with an insulating layer 18 interposed therebetween to form a cell structure 100 such as a cell stack. FIG. 2 is a schematic perspective view showing a structural example of the cell structure 100. The cell structure 100 further has an insulating layer 18 between two stacked electrolytic cells 10. The stacked electrolytic cells 10 may be sandwiched between a pair of support plates and further fastened with bolts or the like. Although FIGS. 1 and 2 show electrolytic cells 10_1, 10_2, and 10_3 as the plurality of electrolytic cells 10, the number of electrolytic cells 10 may be two or more and is not limited to the number shown in FIGS. 1 and 2.

[0014] The cathode 11 is, for example, an electrode (reduction electrode) for inducing a reduction reaction of at least one reduction target (substance to be reduced) and generating a reduction product. The at least one reduction target includes, for example, carbon dioxide or nitrogen. The cathode 11 is in contact with the diaphragm 13. The cathode 11 is an electrode (reduction electrode) for inducing a reduction reaction of a reduction target and generating a reduction product. Examples of the reduction target include carbon dioxide, nitrogen, hydrogen, oxygen, reduction products, etc. Examples of the reduction products include carbon compounds, ammonia, etc. Examples of the carbon compounds include carbon monoxide (CO), methane (CH4), ethane (C2H6), etc. The reduction reaction at the cathode 11 may include a side reaction of inducing a reduction reaction of water to generate hydrogen (H2). The reduction reaction at the cathode 11 may also include a side reaction of inducing a reduction reaction of oxygen to generate water (H2O) in addition to the reduction reaction of carbon dioxide.

[0015] The cathode 11 is supplied with an anode fluid and ions from the membrane 13, and is supplied with a cathode fluid from the cathode flow path 140. The cathode 11 may have a gas diffusion layer and a cathode catalyst layer provided on the gas diffusion layer. The cathode 11 may further have a porous layer denser than the gas diffusion layer between the gas diffusion layer and the cathode catalyst layer. The gas diffusion layer is disposed on the cathode flow path 140 side, and the cathode catalyst layer is disposed on the membrane 13 side. The cathode catalyst layer may be embedded in the gas diffusion layer. The cathode catalyst layer preferably has catalyst nanoparticles or catalyst nanostructures. The gas diffusion layer is made of, for example, carbon paper or carbon cloth, and may be subjected to a water repellent treatment. The porous layer is made of a porous body having a smaller pore size than the carbon paper or carbon cloth.

[0016] By applying an appropriate water-repellent treatment to the gas diffusion layer, carbon dioxide gas reaches the cathode catalyst layer mainly by gas diffusion. The reduction reaction of carbon dioxide and the reduction reaction of the carbon compounds generated by the carbon dioxide occur near the boundary between the gas diffusion layer and the cathode catalyst layer, or near the cathode catalyst layer that has penetrated into the gas diffusion layer.

[0017] The cathode catalyst layer preferably contains a catalyst material (cathode catalyst material) capable of reducing the overvoltage of the reduction reaction. Examples of such materials include metals such as gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), titanium (Ti), cadmium (Cd), zinc (Zn), indium (In), gallium (Ga), lead (Pb), and tin (Sn), metal materials such as alloys and intermetallic compounds containing at least one of these metals, carbon materials such as carbon (C), graphene, CNT (carbon nanotube), fullerene, and Ketjen Black, and metal complexes such as Ru complexes and Re complexes. The cathode catalyst layer can be applied in various shapes such as a plate, mesh, wire, particle, porous, thin film, and island shape.

[0018] The cathode catalyst material constituting the cathode catalyst layer preferably has nanoparticles of the above-mentioned metal material, nanostructures of the metal material, nanowires of the metal material, or a composite in which nanoparticles of the above-mentioned metal material are supported on a carbon material such as carbon particles, carbon nanotubes, graphene, etc. By using catalyst nanoparticles, catalyst nanostructures, catalyst nanowires, catalyst nanosupport structures, etc. as the cathode catalyst material, the reaction efficiency of the carbon dioxide reduction reaction in the cathode 11 can be increased.

[0019] The anode 12 is provided between the diaphragm 13 and the anode flow path 150 and is in contact with them. The anode 12 oxidizes water (HO) in the anode solution contained in the anode fluid to produce oxygen (O) and hydrogen ions (H + ) at the cathode 11, or hydroxide ions (OH - ) to produce oxygen and water.

[0020] The anode 12 preferably contains a catalytic material (anode catalytic material) capable of reducing the overvoltage of the oxidation reaction. Examples of such catalytic materials include metals such as platinum (Pt), palladium (Pd), and nickel (Ni), alloys and intermetallic compounds containing these metals, binary metal oxides such as manganese oxide (Mn-O), iridium oxide (Ir-O), nickel oxide (Ni-O), cobalt oxide (Co-O), iron oxide (Fe-O), tin oxide (Sn-O), indium oxide (In-O), ruthenium oxide (Ru-O), lithium oxide (Li-O), and lanthanum oxide (La-O), ternary metal oxides such as Ni-Co-O, Ni-Fe-O, La-Co-O, Ni-La-O, and Sr-Fe-O, quaternary metal oxides such as Pb-Ru-Ir-O and La-Sr-Co-O, and metal complexes such as Ru complexes and Fe complexes.

[0021] The anode 12 is provided with a substrate having a structure capable of transferring liquid or ions between the diaphragm 13 and the anode flow passage 150, for example, a porous structure such as a mesh material, a punching material, a porous body, or a sintered metal fiber body. The substrate may be made of a metal material such as titanium (Ti), nickel (Ni), iron (Fe), or an alloy containing at least one of these metals (for example, SUS), or may be made of the above-mentioned anode catalyst material. When an oxide is used as the anode catalyst material, it is preferable to form a catalyst layer by attaching or laminating the anode catalyst material on the surface of a substrate made of the above-mentioned metal material. The anode catalyst material preferably has nanoparticles, nanostructures, nanowires, etc. in order to enhance the oxidation reaction. A nanostructure is a structure in which nanoscale unevenness is formed on the surface of a catalyst material. In addition, it is not necessary to provide an oxidation catalyst on the anode 12. An oxidation catalyst layer provided other than on the anode 12 may be electrically connected to the anode 12.

[0022] The diaphragm 13 is provided between the cathode 11 and the anode 12. The diaphragm 13 is arranged so as to separate the cathode 11 and the anode 12. The diaphragm 13 includes an ion exchange membrane capable of transferring ions between the cathode 11 and the anode 12 and separating the cathode 11 and the anode 12. Examples of the ion exchange membrane include a cation exchange membrane such as Nafion or Flemion, and an anion exchange membrane such as Neosepta, Selemion, or Sustenion. An alkaline solution is used as the electrolyte, and mainly OH - In the case where the movement of ions is assumed, the diaphragm 13 is preferably made of an anion exchange membrane. The ion exchange membrane may be made of a membrane having a basic skeleton of a hydrocarbon or a membrane having an amine group. However, other than the ion exchange membrane, a salt bridge, a glass filter, a porous polymer membrane, a porous insulating material, or the like may be used for the diaphragm 13 as long as it is a material capable of moving ions between the cathode 11 and the anode 12. However, if gas flows between the cathode 11 and the anode 12, a circulation reaction due to reoxidation of the reduction product may occur. For this reason, it is preferable that the gas exchange between the cathode 11 and the anode 12 is small. For this reason, care must be taken when using a thin porous film as the diaphragm 13.

[0023] The cathode flow channel plate 14 has a cathode flow channel 140. The cathode flow channel 140 faces the cathode 11. A cathode fluid that is supplied to the cathode 11 and contains a substance to be reduced can flow through the cathode flow channel 140. The cathode fluid may contain water vapor by being humidified. The reduction products are mainly discharged from the cathode flow channel 140 as contained in the cathode fluid. The reduction products differ depending on the type of reduction catalyst, etc. Together with such gas products, steam, or moisture obtained by condensation of steam contained in the humidified carbon dioxide gas, is discharged from the cathode flow channel 140.

[0024] The reduction products also vary depending on the composition of the cathode fluid. When the cathode fluid contains carbon dioxide gas or humidified carbon dioxide gas, the reduction products produced are primarily carbon monoxide gas and hydrogen as a by-product. When the cathode fluid contains nitrogen gas, the reduction products produced are primarily ammonia. When the cathode fluid contains impurity gases such as oxygen, the oxygen is reduced to produce water as a reduction product.

[0025] The cathode flow path 140 is provided on the surface of the cathode flow path plate 14. The cathode flow path plate 14 has a groove (recess) on the surface that forms the cathode flow path 140. The cathode flow path plate 14 is preferably formed using a material that has low chemical reactivity and high conductivity. Examples of such materials include metal materials such as Ti and SUS, and carbon. The material of the flow path plate includes, for example, a material that has low chemical reactivity and no conductivity. Examples of such materials include insulating resin materials such as acrylic resin, polyether ether ketone (PEEK), and fluororesin. The cathode flow path plate 14 has screw holes for fastening (not shown). In addition, packing (not shown) may be sandwiched in front and behind each cathode flow path plate 14 as necessary. The cathode flow path 140 may be provided in the cathode current collector 16.

[0026] The cathode flow channel 140 has an inlet and an outlet, and a cathode fluid is supplied from the cathode supply source 20 via the inlet, and a cathode fluid containing unreacted substances to be reduced and reduction products is discharged via the outlet. The cathode fluid flows through the cathode flow channel 140 so as to come into contact with the cathode 11. The cathode fluid discharged from the cathode flow channel 140 may contain unreacted substances to be reduced and reduction products.

[0027] The cathode flow channel 140 may have a land that contacts the cathode 11 for electrical connection with the cathode 11. The shape of the cathode flow channel 140 is not particularly limited as long as it is continuously connected, and may be, for example, a serpentine structure in which a long and thin flow channel is bent. This is preferable because the cathode fluid flows uniformly on the surface of the cathode 11, allowing a uniform reaction to occur in the cathode 11.

[0028] The cathode fluid may be supplied in a dry state. When the cathode fluid contains carbon dioxide gas, the carbon dioxide concentration of the cathode fluid supplied from the cathode supply source 20 to the cathode flow path 140 may not be 100%. Fluids containing carbon dioxide gas discharged from various facilities may also be used as the cathode fluid. In this case, the cathode fluid may contain impurity gas. If the first gas contained in the cathode fluid is carbon dioxide gas, the second gas is a substance different from carbon dioxide, such as oxygen or nitrogen. The concentration of the second gas is lower than the concentration of the first gas, and is preferably, for example, 1 ppm or more and 100,000 ppm or less.

[0029] The cathode flow path plate 14 is mainly formed of one material, but may be formed of a plurality of different materials and stacked together. Furthermore, a surface treatment may be applied to a part or the entire surface to impart hydrophilic or water-repellent properties.

[0030] The anode flow channel plate 15 has an anode flow channel 150. The anode flow channel 150 faces the anode 12. The anode flow channel 150 allows an anode fluid to flow therethrough, the anode fluid being supplied to the anode 12. The anode fluid includes a liquid such as, for example, an anode solution.

[0031] The anode solution preferably contains at least water (H2O). For example, when the substance to be reduced is carbon dioxide, the carbon dioxide is supplied from the cathode flow channel 140, so the anode solution may or may not contain carbon dioxide.

[0032] The anode solution can be an aqueous solution (electrolyte) containing metal ions. The aqueous solution can contain, for example, phosphate ions (PO4 2- ), borate ion (BO3 3- ), sodium ion (Na + ), potassium ion (K + ), calcium ion (Ca 2+ ), lithium ion (Li + ), Cesium ion (Cs + ), magnesium ion (Mg 2+ ), chloride ion (Cl - ), hydrogen carbonate ion (HCO3 - ) and the like. In addition, aqueous solutions containing lithium hydrogen carbonate (LiHCO3), sodium hydrogen carbonate (NaHCO3), potassium hydrogen carbonate (KHCO3), cesium hydrogen carbonate (CsHCO3), phosphoric acid, boric acid, and the like may also be used.

[0033] The anode flow path 150 is provided on the surface of the anode flow path plate 15. The anode flow path plate 15 is for supplying an anode fluid to the anode 12, and has a groove (recess) on the surface that forms the anode flow path 150. The anode flow path plate 15 is preferably formed using a material that has low chemical reactivity and high conductivity. Examples of such materials include metal materials such as Ti and SUS, and carbon. The anode flow path 150 may be provided on the anode current collector 17. The material of the anode flow path plate 15 includes, for example, a material that has low chemical reactivity and no conductivity. Examples of such materials include insulating resin materials such as acrylic resin, polyether ether ketone (PEEK), and fluororesin. The anode flow path plate 15 has screw holes for fastening (not shown).

[0034] The anode flow path plate 15 is mainly formed of one material, but may be formed of a plurality of different materials and stacked together. Furthermore, a surface treatment may be applied to a part or the entire surface to impart hydrophilic or water-repellent properties.

[0035] The anode flow channel 150 has an inlet and an outlet, and the anode fluid is supplied from the anode supply source 30 via the inlet and discharged via the outlet. The anode fluid flows through the anode flow channel 150 so as to come into contact with the anode 12. The anode fluid discharged from the anode flow channel 150 may contain unreacted substances to be oxidized, an electrolyte, oxidation products, etc.

[0036] The anode flow channel 150 may have a land that contacts the anode 12 for electrical connection with the anode 12. The shape of the anode flow channel 150 is not particularly limited as long as it is continuously connected, and examples of the shape include a serpentine structure in which a long and thin flow channel is bent. This is preferable because the anode fluid flows uniformly on the surface of the anode 12, allowing a uniform reaction to occur on the anode 12.

[0037] The cathode current collector 16 is electrically connected to the cathode 11. The cathode current collector 16 is in contact with the surface of the cathode flow path plate 14 opposite to the cathode flow path 140. The cathode current collector 16 preferably contains a material that has low chemical reactivity and high conductivity. Examples of such materials include metal materials such as Ti and SUS, and carbon.

[0038] The anode current collector 17 is electrically connected to the anode 12. The anode current collector 17 is in contact with the surface of the anode flow path plate 15 opposite to the anode flow path 150. The anode current collector 17 preferably contains a material that has low chemical reactivity and high conductivity. Examples of such materials include metal materials such as Ti and SUS, and carbon.

[0039] The insulating layer 18 is provided between the two electrolysis cells 10. The insulating layer 18 is formed using a material, for example, a material coated with a fluororesin such as silicone or polytetrafluoroethylene (PTFE), an insulating resin material such as acrylic resin, polyether ether ketone (PEEK), or a fluororesin. The electrolysis device 1 may have a plurality of insulating layers 18.

[0040] The cathode supply source 20 can, for example, supply a cathode fluid to the electrolysis cell 10. The cathode supply source 20 is connected to the cathode flow passage 140 of the electrolysis cell 10_1 via, for example, piping.

[0041] The anode supply source 30 can, for example, supply an anode fluid to the electrolysis cell 10. The anode supply source 30 is connected to the anode flow passage 150 of the electrolysis cell 10_1 via, for example, piping.

[0042] The power source 40 can, for example, supply a power source current to each of the multiple electrolytic cells 10. The power source 40 is, for example, electrically connected to the cathode current collectors 16 of each of the multiple electrolytic cells 10 via wiring. The multiple cathode current collectors 16 may be electrically connected to each other in a parallel connection. The power source 40 is, for example, electrically connected to the anode current collectors 17 of each of the multiple electrolytic cells 10 via wiring. The multiple anode current collectors 17 may be electrically connected to each other in a parallel connection.

[0043] Examples of the power source 40 are not limited to a normal system power source or a battery, and may include a power source that supplies power generated by renewable energy such as solar cells or wind power generation. The use of renewable energy is environmentally preferable in terms of effective use of the substance to be reduced. The power source 40 may further include a power controller that adjusts the output of the power source 40 to control the voltage between the cathode 11 and the anode 12. The power source 40 may be provided outside the electrolysis device 1. The power source 40 can realize optimal operation of the electrolysis cell 10 by controlling the current or voltage supplied to each electrolysis cell 10, and can increase the reaction efficiency of the reduction reaction of the substance to be reduced in the cathode 11. In addition, the power source 40 can realize optimal operation of the electrolysis cell 10 by adjusting the current or voltage supplied to each electrolysis cell 10, and can increase the reaction efficiency of the reduction reaction of the substance to be reduced in the cathode 11. An element for monitoring the current, such as a resistor element, may be provided between the power source 40 and the electrolysis cell 10 or the cell structure 100. This makes it possible to control the voltage and achieve optimal operation of the electrolysis cell 10, thereby increasing the reaction efficiency of the reduction reaction at the cathode 11.

[0044] The cathode fluid and the anode fluid can be supplied to the multiple electrolysis cells 10 so as to flow in series or in parallel. When the cathode fluid and the anode fluid are supplied to the multiple electrolysis cells 10 so as to flow in series, the multiple electrolysis cells 10 may be connected in series with multiple cathode flow paths 140 and multiple anode flow paths 150. An example of the structure of each component of the electrolysis cell 10 when multiple cathode flow paths 140 are connected in series and multiple anode flow paths 150 are connected in series is described below.

[0045] FIG. 3 is a schematic diagram showing a structural example of a membrane electrode assembly MEA. FIG. 3 shows an XY plan view. The membrane electrode assembly MEA may be surrounded by a support plate 130. The support plate 130 has, for example, an opening 130a and an opening 131. The opening 130a penetrates the support plate 130 in the Z-axis direction and is a space in which the membrane electrode assembly MEA is disposed. The opening 131 penetrates the support plate 130 in the Z-axis direction and is, for example, a through hole such as a via. The support plate 130 has a plurality of openings 131. The plurality of openings 131 are provided around the opening 130a. A cathode fluid can flow through one of the plurality of openings 131. An anode fluid can flow through the other one of the plurality of openings 131. FIG. 3 shows an opening 131_1 and an opening 131_2 as the plurality of openings 131, but the number of openings 131 may be two or more and is not limited to the number shown in FIG. 3. The opening 131_1 allows the cathode fluid to flow. The opening 131_2 allows the anode fluid to flow. The support plate 130 is preferably formed using, for example, an insulating material. Note that the above configuration is merely an example, and the multiple openings 131 may be provided in another member, such as the cathode 11 or the anode 12, instead of the support plate 130, as long as the cathode fluid and the anode fluid can pass through the layer including the membrane electrode assembly MEA without leaking.

[0046] FIG. 4 is a schematic diagram showing a structural example of the cathode flow path plate 14. FIG. 4 shows an XY plan view. The cathode flow path plate 14 has, for example, a cathode flow path 140 and an opening 141. The cathode flow path 140 is provided on the membrane electrode assembly MEA side of the cathode flow path plate 14, and may be formed in a serpentine shape along the XY plane as shown in FIG. 4, or may have another shape. The opening 141 penetrates the cathode flow path plate 14 in the Z-axis direction, and is, for example, a through hole such as a via. The cathode flow path plate 14 has a plurality of openings 141. A cathode fluid can flow through one of the plurality of openings 141. An anode fluid can flow through the other one of the plurality of openings 141. FIG. 4 shows openings 141_1, 141_2, and 141_3 as the plurality of openings 141, but the number of openings 141 may be two or more and is not limited to the number shown in FIG. 4. The cathode flow channel 140 is connected to the opening 131_1. The opening 141_1 is provided, for example, on the surface opposite to the surface on which the cathode flow channel 140 is formed, overlaps one end of the cathode flow channel 140, and is connected to the cathode flow channel 140. The opening 141_2 is connected, for example, to the opening 131_2. The other end of the cathode flow channel 140 overlaps, for example, with the opening 131_1. A cathode fluid can flow through the opening 141_1. An anode fluid can flow through the opening 141_2.

[0047] FIG. 5 is a schematic diagram showing a structural example of the anode flow plate 15. FIG. 5 shows an XY plan view. The anode flow plate 15 has, for example, an anode flow channel 150 and an opening 151. The anode flow channel 150 may be formed in a serpentine shape along the XY plane as shown in FIG. 5, or may have another shape. The opening 151 is, for example, a through hole such as a via that penetrates the anode flow plate 15 in the Z-axis direction. The anode flow plate 15 has a plurality of openings 151. One of the plurality of openings 151 can allow the cathode fluid to flow. The other one of the plurality of openings 151 can allow the anode fluid to flow. FIG. 5 shows openings 151_1 and 151_2 as the plurality of openings 151, but the number of openings 151 may be two or more and is not limited to the number shown in FIG. 5. The opening 151_1 is connected to, for example, the opening 131_1. The opening 151_2 is provided on the surface opposite to the surface on which the anode flow channel 150 is formed, overlaps one end of the anode flow channel 150, and is connected to, for example, the opening 131_2. The opening 151_1 allows the cathode fluid to flow. The opening 151_2 allows the anode fluid to flow.

[0048] FIG. 6 is a schematic diagram showing a structural example of the cathode current collector 16. FIG. 6 shows an XY plan view. The cathode current collector 16 has, for example, an opening 161. The opening 161 penetrates the cathode current collector 16 in the Z-axis direction and is, for example, a through hole such as a via. The cathode current collector 16 has a plurality of openings 161. One of the plurality of openings 161 can allow a cathode fluid to flow. The other one of the plurality of openings 161 can allow an anode fluid to flow. FIG. 6 shows openings 161_1 and opening 161_2 as the plurality of openings 161, but the number of openings 161 may be two or more and is not limited to the number shown in FIG. 6. The opening 161_1 is connected to, for example, opening 141_1. The opening 161_2 is connected to, for example, opening 141_2. The opening 161_1 can allow a cathode fluid to flow. The opening 161_2 can allow an anode fluid to flow.

[0049] FIG. 7 is a schematic diagram showing a structural example of the anode current collector 17. FIG. 7 shows an XY plan view. The anode current collector 17 has, for example, an opening 171. The opening 171 penetrates the anode current collector 17 in the Z-axis direction and is, for example, a through hole such as a via. The anode current collector 17 has a plurality of openings 171. One of the plurality of openings 171 can allow a cathode fluid to flow. The other one of the plurality of openings 171 can allow an anode fluid to flow. FIG. 7 shows openings 171_1 and 171_2 as the plurality of openings 171, but the number of openings 171 may be two or more and is not limited to the number shown in FIG. 7. The opening 171_1 is connected to, for example, opening 151_1. The opening 171_2 is connected to, for example, opening 151_2. The opening 171_1 can allow a cathode fluid to flow. The opening 171_2 can allow an anode fluid to flow.

[0050] FIG. 8 is a schematic diagram showing a structural example of the insulating layer 18. FIG. 8 shows an XY plan view. The insulating layer 18 has, for example, an opening 181. The opening 181 penetrates the insulating layer 18 in the Z-axis direction and is, for example, a through hole such as a via. The insulating layer 18 has a plurality of openings 181. One of the plurality of openings 181 can allow a cathode fluid to flow. The other one of the plurality of openings 181 can allow an anode fluid to flow. FIG. 8 shows openings 181_1 and 181_2 as the plurality of openings 181, but the number of openings 181 may be two or more and is not limited to the number shown in FIG. 8. The opening 181_1 is connected to, for example, opening 171_1. The opening 181_2 is connected to, for example, opening 171_2. The opening 181_1 can allow a cathode fluid to flow. The opening 181_2 can allow an anode fluid to flow.

[0051] When multiple electrolytic cells 10 are stacked with an insulating layer 18 sandwiched between them, the positions of the multiple openings 131, the multiple openings 141, the multiple openings 151, the multiple openings 161, the multiple openings 171, and the multiple openings 181 may be different between an odd-numbered electrolytic cell 10_2n-1 (n is a natural number) such as electrolytic cell 10_1 and an even-numbered electrolytic cell 10_2n (n is a natural number) such as electrolytic cell 10_2. For example, between an odd-numbered electrolytic cell 10_2n-1 (n is a natural number) and an even-numbered electrolytic cell 10_2n (n is a natural number), the positions of openings 131_1 and 131_2, openings 141_1 and 141_2, openings 151_1 and 151_2, openings 161_1 and 161_2, openings 171_1 and 171_2, and openings 181_1 and 181_2 may each have a symmetrical relationship. Depending on the shape of the flow path, the positions of the openings 131_1 and 131_2, the positions of the openings 141_1 and 141_2, the positions of the openings 151_1 and 151_2, the positions of the openings 161_1 and 161_2, the positions of the openings 171_1 and 171_2, and the positions of the openings 181_1 and 181_2 may be asymmetric between the odd-numbered electrolytic cell 10_2n-1 (n is a natural number) and the even-numbered electrolytic cell 10_2n (n is a natural number). When a packing is provided, a plurality of openings may also be formed in the packing to allow the cathode fluid and the anode fluid to pass therethrough.

[0052] The flow of the cathode fluid and the anode fluid in each electrolysis cell 10 when the cathode fluid and the anode fluid are supplied to a plurality of electrolysis cells 10 so as to flow in series will be described with reference to Figures 9 and 10. Figures 9 and 10 are schematic diagrams for explaining the flow of the cathode fluid and the anode fluid in each electrolysis cell 10. The solid arrows in Figures 9 and 10 indicate the flow of the cathode fluid. The solid arrows in Figures 9 and 10 indicate the flow of the anode fluid.

[0053] In the electrolytic cell 10_2n-1 of the odd-numbered stages, such as the first stage electrolytic cell 10_1, the cathode fluid can move to the next stage electrolytic cell 10 by passing through the opening 161_1, passing through the opening 141_1, moving from one end of the cathode flow path 140 to the other end, passing through the opening 131_1, passing through the opening 151_1, passing through the opening 171_1, and passing through the opening 181_1, as shown in FIG. 9.

[0054] In the odd-numbered electrolytic cell 10_2n-1, as shown in FIG. 9, the anode fluid can move to the next electrolytic cell 10 by passing through opening 161_2, opening 141_2, opening 131_2, moving from one end of the anode flow path 150 to the other end, passing through opening 151_2, opening 171_2, and opening 181_2.

[0055] In the electrolytic cell 10_2n of an even-numbered stage, such as the second stage electrolytic cell 10_1, the cathode fluid can move to the next stage electrolytic cell 10 by passing through the opening 161_1, passing through the opening 141_1, moving from one end of the cathode flow path 140 to the other end, passing through the opening 131_1, passing through the opening 151_1, passing through the opening 171_1, and passing through the opening 181_1, as shown in FIG. 10 .

[0056] In the odd-numbered electrolytic cell 10_2n-1, as shown in FIG. 9, the anode fluid can move to the next electrolytic cell 10 by passing through opening 161_2, opening 141_2, opening 131_2, moving from one end of the anode flow path 150 to the other end, passing through opening 151_2, opening 171_2, and opening 181_2.

[0057] Next, a description will be given of an example of a method for operating the electrolysis device 1. Here, the case where carbon monoxide is produced as a carbon compound will be mainly described, but the reduction product of carbon dioxide is not limited to carbon compounds.

[0058] First, water (HO) is oxidized to produce hydrogen ions (H +The reaction process for producing hydrogen ions (H2O) will be described. When a cathode fluid is supplied from a cathode supply source 20 to the cathode flow path 140, an anode fluid is supplied from an anode supply source 30 to the anode flow path 150, and a current is supplied from a power source 40 between the cathode 11 and the anode 12, an oxidation reaction of water (H2O) occurs at the anode 12 in contact with the anode solution. Specifically, as shown in the following formula (1), the H2O contained in the anode solution is oxidized to oxygen (O2) and hydrogen ions (H + ) is generated.

[0059] 2H2O → 4H + +O2+4e - (1)

[0060] H generated at anode 12 + The electrons (e - ) and H that migrated near cathode 11 + This causes a reduction reaction of carbon dioxide. Specifically, as shown in the following formula (2), carbon dioxide supplied from the cathode 11 flow path to the cathode 11 is reduced to generate carbon monoxide. Also, as shown in the following formula (3), hydrogen ions receive electrons to generate hydrogen. At this time, hydrogen may be generated simultaneously with carbon monoxide.

[0061] CO2+2H + +2e - → CO+H2O (2)

[0062] 2H + +2e - → H2···(3)

[0063] Next, carbon dioxide (CO2) is mainly reduced to hydroxide ions (OH -When a current is supplied from a power source between the cathode 11 and the anode 12, water (H2O) and carbon dioxide (CO2) are reduced near the cathode 11 to produce carbon monoxide (CO) and hydroxide ions (OH - ) is produced. In addition, hydrogen is produced when water accepts electrons as shown in the following formula (5). In this case, hydrogen may be produced simultaneously with carbon monoxide. The hydroxide ions (OH - ) diffuses near the anode 12 and converts into hydroxide ions (OH - ) is oxidized to produce oxygen (O2).

[0064] 2CO2+2H2O+4e - → 2CO+4OH - (4)

[0065] 2H2O+2e - → H2+2OH - (5)

[0066] 4OH - → 2H2O+O2+4e - (6)

[0067] In this way, the electrolysis cell 10 can be specialized not only for the reduction of carbon dioxide, but also for producing reduction products and hydrogen in any ratio, such as producing carbon monoxide and hydrogen in a 1:2 ratio, followed by a chemical reaction to produce methanol.

[0068] Hydrogen is a cheap and easily available raw material from water electrolysis and fossil fuels, so the ratio of hydrogen does not need to be high. From these perspectives, it is preferable from the standpoint of economic efficiency and the environment that the ratio of carbon monoxide to hydrogen is at least 1, and preferably 1.5 or more.

[0069] Next, we will describe the reaction process when oxygen (O2) is reduced to produce water (H2O). When a current is supplied from a power source between the cathode 11 and the anode 12, oxygen (O2) is reduced near the cathode 11 to produce water (H2O), as shown in the following formula (7). At this time, water may be produced simultaneously with carbon monoxide and hydrogen, but due to differences in reduction potential, it is believed that the reduction of oxygen mainly proceeds. As shown in the following formula (8), water in the electrolyte is oxidized to produce oxygen (O2) and protons (H + ) is generated, and the proton (H + ) diffuses from the vicinity of the anode 12. Hydrogen peroxide (H2O2) may also be generated as an intermediate product or product. The oxygen reduction reaction may be a two-electron reduction or a four-electron reduction, and may occur in both acidic and alkaline environments.

[0070] O2+4H + +4e - → 2H2O ···(7)

[0071] 2H2O → O2+4H + +4e - (8)

[0072] Such an electrolysis cell 10 is not only specialized for reducing carbon dioxide, but is also capable of reducing impurity gases such as oxygen and nitrogen even if they are mixed in.

[0073] In the case of the nitrogen electrolysis device, ammonia can be produced by reducing nitrogen by the cathode 11. For other configurations of the nitrogen electrolysis device, the configurations of the electrolysis device 1 can be appropriately applied. In this case, the impurity gas of the cathode fluid is not nitrogen.

[0074] When the cathode fluid is supplied from the cathode supply source 20 to the cell structure 100 to reduce the target substance in the electrolysis cell 10 to generate a reduction product, if the cathode fluid contains a gas of the target substance such as carbon dioxide or nitrogen and an impurity gas such as oxygen, current is consumed to reduce the impurity gas, resulting in a wasteful consumption of current. Furthermore, the current for reducing the target substance is reduced accordingly, the amount of carbon dioxide reduced is reduced, and the Faraday efficiency of the reduction product such as carbon compounds and ammonia may decrease. In conventional electrolysis devices, the cathode fluid, the anode fluid, and the power supply current are supplied so as to flow in series in the cell stack, making it difficult to control the current supply amount of the first-stage electrolysis cell where the reduction of the impurity gas mainly occurs. In addition, in order to realize an electrolysis device with high electrolysis efficiency, it is necessary to make the electrolysis device operable with low power consumption.

[0075] In contrast, the electrolytic device of the embodiment supplies a first power supply current to the electrolytic cells 10 of a first group including the electrolytic cells 10 in the first stage, and supplies a second power supply current to the electrolytic cells 10 of a second group including at least one of the electrolytic cells 10 in the next stage or later. In the electrolytic device 1 shown in FIG. 1, a current can be supplied individually to each electrolytic cell 10 by connecting a plurality of electrolytic cells 10 in parallel to a power supply 40. Without being limited thereto, a first power supply current may be supplied to the electrolytic cells 10 of the first group including the electrolytic cells 10 in the first stage to the Xth stage (X is a natural number of 2 or more), and a second power supply current may be supplied to the electrolytic cells 10 of the second group including at least one of the electrolytic cells 10 in the X+1th stage or later.

[0076] FIG. 11 is a schematic diagram showing how impurities such as oxygen and substances to be reduced such as carbon dioxide in the cathode fluid flow in series through each electrolysis cell 10. FIG. 12 is a diagram showing an example of a graph showing the relationship between the current density flowing through the electrolysis cell 10 and the cell voltage and the Faraday efficiency. The solid curve shown in FIG. 12 represents the relationship between the cell voltage of the electrolysis cell 10 to which a mixed gas containing carbon dioxide gas and oxygen gas is supplied and the current density of the current flowing through the electrolysis cell 10. The dotted curve shown in FIG. 12 represents the relationship between the cell voltage of the electrolysis cell 10 to which a simple carbon dioxide gas is supplied and the current density of the current flowing through the electrolysis cell 10. The dashed-dotted curve shown in FIG. 12 represents the relationship between the Faraday efficiency of carbon monoxide of the electrolysis cell 10 to which a simple carbon dioxide gas is supplied and the current density of the current flowing through the electrolysis cell 10. The two-dot-dash curve shown in FIG. 12 represents the relationship between the Faraday efficiency of carbon monoxide of the electrolysis cell 10 to which a mixed gas containing carbon dioxide gas and oxygen gas is supplied and the current density of the current flowing through the electrolysis cell 10.

[0077] When the current density of the current flowing through the electrolysis cell 10 is low, the current is consumed mainly for water production by oxygen reduction, and the production of carbon monoxide by carbon dioxide reduction does not progress. On the other hand, when the current density of the current flowing through the electrolysis cell 10 is high, the current is consumed mainly for carbon monoxide production, and carbon monoxide production progresses. This is thought to be because oxygen is preferentially reduced near the inlet of the cathode flow channel 140 of the electrolysis cell 10, resulting in a low oxygen concentration, while the environment is favorable for carbon dioxide reduction from the middle stage of the cathode flow channel 140 onwards. As shown in Figures 11 and 12, at 100 mA / cm 2 In the range of low current densities below this (range A in Fig. 12), the reduction of oxygen takes precedence, and the current is consumed mainly for the production of water by oxygen reduction, and the production of carbon monoxide by the reduction of carbon dioxide does not proceed. 2 In the above-mentioned range of high current density (range B in FIG. 12), the reduction of carbon dioxide takes precedence, and current is consumed mainly in the production of carbon monoxide by the reduction of carbon dioxide.

[0078] Therefore, a first power supply current is supplied so that the current flowing through the first stage electrolytic cell 10 (electrolytic cell 10_1) has a low current density. The current density at this time is, for example, 1 mA / cm 2 More than 150mA / cm 2 As a result, oxygen reduction is preferentially performed in the first-stage electrolytic cell 10. As a result, most of the impurities in the cathode fluid are reduced in the first-stage electrolytic cell 10, and the composition of the cathode fluid flowing through the electrolytic cells 10 in the subsequent stages and thereafter is mainly composed of only gas to be reduced. Here, the area of ​​the first-stage electrolytic cell 10 and the area of ​​the electrolytic cells 10 in the subsequent stages and thereafter are the same, but the areas of the multiple electrolytic cells 10 do not necessarily have to be the same. The area of ​​the electrolytic cell 10 includes, for example, the area of ​​the overlapping portion between the cathode 11 and the cathode flow channel 140 and the area of ​​the overlapping portion between the anode 12 and the anode flow channel 150, etc.

[0079] Furthermore, a second power supply current is supplied so that the current flowing through the electrolytic cells 10 at the next stage and thereafter has a high current density. The current density at this time is, for example, 150 mA / cm 2 The upper limit of the current density is not particularly limited, but is, for example, 1000 mA / cm 2 As a result, more substances to be reduced can be reduced in the electrolytic cells 10 at the next stage or later, and the composition of the cathode fluid supplied to the electrolytic cells 10 at the next stage or later can be composed of gases of substances to be reduced. Therefore, the electrolytic cells 10 that consume current for the reduction of impurities can be limited to the electrolytic cells 10 at the first stage, and unnecessary current consumption in electrolytic reactions such as the reduction reaction of impurities can be suppressed. As a result, an electrolytic device that operates with low power consumption can be provided. Impurity gas such as oxygen may also be supplied to the electrolytic cells 10 at the second stage or later. In this case, in the electrolytic device of the embodiment, a power source current can be supplied from the power source 40 so that the current density of the current flowing through each of the electrolytic cells 10 of the second group including at least one of the electrolytic cells 10 at the next stage or later is higher than the current density of the current flowing through each of the electrolytic cells 10 of the first group including the electrolytic cell 10_1 at the first stage and at least one of the electrolytic cells 10 at the second stage or later. In addition, as shown in FIG. 12, the reduction potential of carbon dioxide gas is higher than the reduction potential of oxygen gas.

[0080] FIG. 13 is a schematic diagram showing another example of the electrolysis device of the embodiment. FIG. 13 shows another configuration example of the electrolysis device 1. As shown in FIG. 13, the electrolysis device 1 may share one cathode current collector 16 and one anode current collector 17 for a plurality of electrolysis cells 10. FIG. 13 shows an example in which the electrolysis cell 10_2 and the electrolysis cell 10_3 are provided between the one cathode current collector 16 and the one anode current collector 17, and the anode flow path plate 15 in the electrolysis cell 10_2 is electrically connected to the cathode flow path plate 14 in the electrolysis cell 10_3. With the above configuration, the number of the cathode current collectors 16 and the anode current collectors 17 can be reduced, thereby suppressing the manufacturing cost and thickness of the cell structure 100.

[0081] Fig. 14 is a schematic diagram showing another example of the electrolysis device of the embodiment. Fig. 14 shows another configuration example of the electrolysis device 1. As shown in Fig. 14, the electrolysis device 1 may have a power supply 41 and a power supply 42.

[0082] The power supply 41 is electrically connected to the first group of electrolytic cells 10 including the first stage electrolytic cell 10. The power supply 41 can supply a first power supply current to the first stage electrolytic cell 10. The rest of the description of the power supply 41 can be appropriately cited from the description of the power supply 40.

[0083] The power supply 42 is electrically connected to a second group of electrolytic cells 10 including at least one of the electrolytic cells 10 next to the first group of electrolytic cells 10. The power supply 42 can supply a second power supply current to the next or subsequent electrolytic cells 10. The rest of the description of the power supply 42 can be appropriately cited from the description of the power supply 40.

[0084] The values ​​of the first power supply current and the second power supply current are adjusted by the power supplies 41 and 42 so that, when the above-mentioned area of ​​the electrolytic cells 10 of the first group is the same as the above-mentioned area of ​​the electrolytic cells 10 of the second group, the current density of the current flowing through the electrolytic cells 10 of the second group is higher than the current density of the current flowing through the electrolytic cells 10 of the first group. With the above-mentioned configuration, for example, the first power supply current and the second power supply current can be individually set and supplied so as to provide an optimal current density according to the cell voltage of each of the electrolytic cells 10 of the first group and the electrolytic cells 10 of the second group. In this case, if it is difficult to predict the voltage, the optimal current density can be adjusted by providing a resistor between the electrolytic cells 10 of the first group and the electrolytic cells 10 of the second group or by connecting a current monitor to each electrolytic cell 10. Alternatively, the cell voltage of each electrolytic cell 10 may be controlled to supply a current. Alternatively, the reduction product may be selectively changed by controlling the voltage or current of the electrolytic cells 10 of the second group. Here, the area of ​​the electrolytic cells 10 in the first group is the same as the area of ​​the electrolytic cells 10 in the second group, but the areas of the electrolytic cells do not necessarily have to be the same. In this case, the respective values ​​of the current density of the first power source current and the current density of the second power source current are adjusted by the power sources 41 and 42 so that the current density flowing through the electrolytic cells 10 in the second group is higher than the current density flowing through the electrolytic cells 10 in the first group.

[0085] Fig. 15 is a schematic diagram showing another example of the electrolysis device of the embodiment. Fig. 15 shows another configuration example of the electrolysis device 1. As shown in Fig. 15, the electrolysis device 1 may have a power supply 41 and a power supply 42, separate the electrolysis cells 10 of the first group from the electrolysis cells 10 of the second group, and have a pipe 19a for supplying a cathode fluid from the electrolysis cells 10 of the first group to the electrolysis cells 10 of the second group, and a pipe 19b for supplying a cathode fluid from the electrolysis cells 10 of the first group to the electrolysis cells 10 of the second group.

[0086] The pipe 19a connects the cathode flow path 140 of the electrolytic cell 10 in the final stage of the first group to the cathode flow path 140 of the electrolytic cell 10 in the first stage of the second group. The pipe 19b connects the anode flow path 150 of the electrolytic cell 10 in the final stage of the first group to the anode flow path 150 of the electrolytic cell 10 in the first stage of the second group. The pipes 19a and 19b can be formed using, for example, a metal material or an insulating material. With the above configuration, the electrolytic cells 10 in the first group can be spaced apart from the electrolytic cells 10 in the second group. This allows, for example, efficient use of space even in a narrow installation space.

[0087] FIG. 16 is a schematic diagram showing another example of the electrolysis device of the embodiment. FIG. 16 shows another configuration example of the electrolysis device 1. As shown in FIG. 16, the electrolysis device 1 has a power source 41 and a power source 42, and may supply a cathode fluid from a cathode supply source 20 to a plurality of electrolysis cells 10 so as to flow in parallel, and may supply an anode fluid from an anode supply source 30 to a plurality of electrolysis cells 10 so as to flow in parallel. The cathode flow path 140 of the electrolysis cells 10 of the first group and the cathode flow path 140 of the electrolysis cells 10 of the second group may be connected in parallel, for example. The anode flow path 150 of the electrolysis cells 10 of the first group and the anode flow path 150 of the electrolysis cells 10 of the second group may be connected in parallel, for example. With the above configuration, the optimal current, gas composition, and gas flow rate can be set and flowed individually according to the cell voltage of each of the electrolysis cells 10 of the first group and the electrolysis cells 10 of the second group. In this case, if it is difficult to predict the voltage, the optimal current density can be adjusted by providing a resistor between the electrolytic cells 10 of the first group and the electrolytic cells 10 of the second group, or by connecting a current monitor to each electrolytic cell 10. Alternatively, the cell voltage of each electrolytic cell 10 may be controlled to supply current. Alternatively, the reduction product may be selectively changed by controlling the voltage or current of the electrolytic cells 10 of the second group.

[0088] When the cathode fluid includes a first gas that is a target for reduction and a second gas that is an impurity, and the second gas is nitrogen, the first group of electrolytic cells 10 may reduce the nitrogen to produce ammonia, and the second group of electrolytic cells 10 may reduce a target for reduction, such as carbon dioxide, to produce a reduction product, such as a carbon compound.

[0089] The cathodes 11 in the electrolysis cells 10 of the first group may have a first catalyst, and the cathodes 11 in the electrolysis cells 10 of the second group may have a second catalyst. The first catalyst is different from the second catalyst. An example of the first catalyst is platinum or an alloy thereof. An example of the second catalyst is gold. By selecting an optimal catalyst for each electrolysis cell 10 according to the main product, the electrolysis efficiency of the electrolysis device can be further improved.

[0090] The electrolysis device 1 may be applied to, for example, an electrolysis system. The electrolysis system may further include, for example, a control device. The control device may control, for example, a power supply voltage or a power supply current from the power supply 40. The control device may also control, for example, a flow rate of a cathode fluid from the cathode supply source 20. The control device may also control, for example, a flow rate of an anode fluid from the anode supply source 30. The control device may include, for example, hardware having a calculation device such as a processor. Note that each operation may be stored as an operation program in a computer-readable recording medium such as a memory, and each operation may be executed by appropriately reading out the operation program stored in the recording medium by the hardware.

[0091] The above-mentioned configuration examples of the electrolysis device 1 can be combined as appropriate.

[0092] The configurations of the above-mentioned embodiments can be applied in combination with each other, and some of them can be replaced. Although several embodiments of the present invention have been described here, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the scope of the invention and its equivalents described in the claims.

[0093] The above embodiments can be summarized in the following technical solutions. (Technical proposal 1) a first electrolysis cell for reducing a substance to be reduced and oxidizing a substance to be oxidized; a second electrolysis cell for reducing the substance to be reduced and oxidizing the substance to be oxidized; a first supply source that supplies a first fluid containing a gas of the substance to be reduced to the first electrolysis cell and the second electrolysis cell; a second supply source that supplies a second fluid containing a liquid of the object to be oxidized to the first electrolytic cell and the second electrolytic cell; at least one power supply providing a first power supply current to the first electrolytic cell and a second power supply current to the second electrolytic cell; Equipped with the at least one power source sets a value of the first power source current and a value of the second power source current such that a current density of a current flowing through the second electrolytic cell when the substance to be reduced is higher than a current density of a current flowing through the first electrolytic cell when the substance to be reduced is reduced; Electrolyzer. (Technical proposal 2) The first electrolysis cell comprises: a first membrane electrode assembly having a first cathode, a first anode, and a first diaphragm between the first cathode and the first anode; a first cathode flow channel plate having a first cathode flow channel facing the first cathode; a first anode flow channel plate having a first anode flow channel facing the first anode; having The second electrolysis cell comprises: a second membrane electrode assembly having a second cathode, a second anode, and a second diaphragm between the second cathode and the second anode; a second cathode flow channel plate having a second cathode flow channel facing the second cathode; a second anode flow channel plate having a second anode flow channel facing the second anode; having The electrolysis device comprises: a first cathode current collector electrically connected to the first cathode and to the at least one power source; a first anode current collector electrically connected to the first anode and to the at least one power source; a second cathode current collector electrically connected to the second cathode and to the at least one power source; a second anode current collector electrically connected to the second anode and to the at least one power source; Further comprising: Electrolysis equipment as described in Technical Proposal 1. (Technical proposal 3) The second cathode flow path is connected in series to the first cathode flow path. Electrolysis equipment as described in Technical Proposal 2. (Technical proposal 4) The second cathode flow path is connected in parallel to the first cathode flow path. Electrolysis equipment as described in Technical Proposal 2. (Technical proposal 5) a power source that supplies the first power source current to the first electrolytic cell via the first cathode current collector and the first anode current collector and supplies the second power source current to the second electrolytic cell via the second cathode current collector and the second anode current collector; the first cathode current collector, the first anode current collector, the second cathode current collector, and the second anode current collector are electrically connected to the at least one power source. An electrolysis apparatus according to any one of technical proposals 2 to 4. (Technical proposal 6) The at least one power source a first power supply that supplies the first power supply current to the first electrolysis cell via the first cathode current collector and the first anode current collector; a second power supply that supplies the second power supply current to the second electrolysis cell through the second cathode current collector and the second anode current collector; Including, An electrolysis apparatus according to any one of technical proposals 2 to 4. (Technical proposal 7) The first fluid includes a first gas and a second gas, The first gas is carbon dioxide gas, the second gas is a gas of a substance different from the carbon dioxide, the first electrolytic cell and the second electrolytic cell reduce the carbon dioxide and reduce the substance; The reduction potential of the carbon dioxide is higher than the reduction potential of the substance; An electrolysis apparatus according to any one of technical proposals 1 to 6. (Technical proposal 8) The substance is oxygen. Electrolysis device as described in technical proposal 7. (Technical proposal 9) The substance is nitrogen. Electrolysis device as described in technical proposal 7. (Technical proposal 10) The concentration of the second gas in the first fluid is 1 ppm or more and 100,000 ppm or less. An electrolysis device according to any one of technical proposals 7 to 9. (Technical proposal 11) further comprising a third electrolytic cell between the second cathode current collector and the second anode current collector; The third electrolytic cell comprises: A third cathode; and a third anode; and a third diaphragm between the third cathode and the third anode; a third cathode flow channel plate having a third cathode flow channel facing the third cathode; a fourth anode flow channel plate having a third anode flow channel facing the third anode; having The third cathode is electrically connected to the second anode, or the third anode is electrically connected to the second cathode; An electrolysis apparatus according to any one of technical proposals 2 to 6. (Technical proposal 12) a first pipe connecting the first electrolysis cell and the second electrolysis cell and supplying the first fluid from the first cathode flow path to the second cathode flow path; a second pipe connecting the first electrolysis cell and the second electrolysis cell and supplying the second fluid from the first anode flow path to the second anode flow path; Further comprising: An electrolysis apparatus according to any one of technical proposals 2 to 7. (Technical proposal 13) the first cathode having a first catalyst; the second cathode having a second catalyst; the first catalyst is different from the second catalyst; An electrolysis apparatus according to any one of technical proposals 2 to 6 and technical proposal 12. (Technical proposal 14) the first fluid comprises carbon dioxide gas; The first electrolysis cell reduces carbon dioxide at the first cathode to produce carbon compounds; The second electrolysis cell reduces carbon dioxide at the second cathode to produce the carbon compound. An electrolysis apparatus according to any one of technical proposals 2 to 6, technical proposal 12, and technical proposal 13. (Technical proposal 15) The first fluid comprises nitrogen gas; the first electrolysis cell reduces nitrogen to produce ammonia at the first cathode; the second electrolysis cell reduces nitrogen to produce ammonia at the second cathode; The electrolysis apparatus according to any one of technical proposals 2 to 6, technical proposal 12, and technical proposal 13. (Technical proposal 16) The first electrolysis cell comprises: a first membrane electrode assembly having the first cathode, the first anode, and the first diaphragm; a first support plate surrounding the first membrane electrode assembly and having a first opening and a second opening; a first cathode flow path plate having the first cathode flow path connected to the first opening, a third opening connected to the first cathode flow path, and a fourth opening connected to the second opening; a first anode flow path plate having the first anode flow path connected to the second opening, a fifth opening connected to the first opening, and a sixth opening connected to the first anode flow path; the first cathode current collector having a seventh opening connected to the third opening and an eighth opening connected to the fourth opening; the first anode current collector having a ninth opening connected to the fifth opening and a tenth opening connected to the sixth opening; Equipped with The second electrolysis cell comprises: a second membrane electrode assembly having the second cathode, the second anode, and the second diaphragm; a second support plate surrounding the second membrane electrode assembly and having an eleventh opening and a twelfth opening; a second cathode flow path plate having the second cathode flow path connected to the eleventh opening, a thirteenth opening connected to the second cathode flow path, and a fourteenth opening connected to the twelfth opening; a second anode flow path plate having the second anode flow path connected to the twelfth opening, a fifteenth opening connected to the eleventh opening, and a sixteenth opening connected to the second anode flow path; the second cathode current collector having a seventeenth opening connected to the thirteenth opening and an eighteenth opening connected to the fourteenth opening; the second anode current collector having a nineteenth opening connected to the fifteenth opening and a twentieth opening connected to the sixteenth opening; Equipped with An electrolysis apparatus according to any one of technical proposals 2 to 6 and technical proposals 12 to 15. (Technical proposal 17) further comprising an insulating layer provided between the first electrolytic cell and the second electrolytic cell, the insulating layer having a 21st opening connecting the 9th opening and the 14th opening, and a 22nd opening connecting the 10th opening and the 13th opening; Electrolysis device as described in Technical Proposal 16. (Technical proposal 18) An electrolysis system comprising an electrolysis device according to any one of technical proposals 1 to 17. (Technical proposal 19) 1. A method for operating an electrolysis apparatus, comprising the steps of: The electrolysis device comprises: a first electrolysis cell for reducing a substance to be reduced and oxidizing a substance to be oxidized; a second electrolysis cell for reducing the substance to be reduced and oxidizing the substance to be oxidized; a first supply source that supplies a first fluid containing a gas of the substance to be reduced to the first electrolysis cell and the second electrolysis cell; a second supply source that supplies a second fluid containing a liquid of the object to be oxidized to the first electrolytic cell and the second electrolytic cell; at least one power supply providing a first power supply current to the first electrolytic cell and a second power supply current to the second electrolytic cell; Equipped with The above operation method is supplying a first fluid containing a gas of the object to be reduced to the first electrolysis cell and the second electrolysis cell, and supplying a second fluid containing a liquid of the object to be oxidized to the first electrolysis cell and the second electrolysis cell; supplying the first power supply current to the first electrolytic cell to reduce the substance to be reduced, and supplying the second power supply current to the second electrolytic cell to reduce the substance to be reduced; a current density of a current flowing through the second electrolytic cell when the substance to be reduced is reduced is higher than a current density of a current flowing through the first electrolytic cell when the substance to be reduced is reduced; A method for operating an electrolysis device. [Explanation of symbols]

[0094] DESCRIPTION OF THE REFERENCE NUMERALS 1...electrolysis device, 10...electrolysis cell, 11...cathode, 12...anode, 13...diaphragm, 14...cathode flow path plate, 15...anode flow path plate, 16...cathode current collector, 17...anode current collector, 18...insulating layer, 19...piping, 20...cathode supply source, 30...anode supply source, 40...power source, 41...power source, 42...power source, 100...cell structure, 130...support plate, 130a...opening, 131...opening, 140...cathode flow path, 141...opening, 150...anode flow path, 151...opening, 161...opening, 171...opening, 181...opening, MEA...membrane electrode assembly.

Claims

1. a first electrolysis cell for reducing a substance to be reduced and oxidizing a substance to be oxidized; a second electrolysis cell for reducing the substance to be reduced and oxidizing the substance to be oxidized; a first supply source that supplies a first fluid containing a gas of the substance to be reduced to the first electrolysis cell and the second electrolysis cell; a second supply source that supplies a second fluid containing a liquid of the object to be oxidized to the first electrolytic cell and the second electrolytic cell; at least one power source providing a first power source current to the first electrolytic cell and a second power source current to the second electrolytic cell; Equipped with the at least one power source sets a value of the first power source current and a value of the second power source current such that a current density of a current flowing through the second electrolytic cell when the substance to be reduced is higher than a current density of a current flowing through the first electrolytic cell when the substance to be reduced is reduced; Electrolyzer.

2. The first electrolysis cell comprises: a first membrane electrode assembly having a first cathode, a first anode, and a first diaphragm between the first cathode and the first anode; a first cathode flow channel plate having a first cathode flow channel facing the first cathode; a first anode flow channel plate having a first anode flow channel facing the first anode; having The second electrolysis cell comprises: a second membrane electrode assembly having a second cathode, a second anode, and a second diaphragm between the second cathode and the second anode; a second cathode flow channel plate having a second cathode flow channel facing the second cathode; a second anode flow channel plate having a second anode flow channel facing the second anode; having The electrolysis device comprises: a first cathode current collector electrically connected to the first cathode and to the at least one power source; a first anode current collector electrically connected to the first anode and to the at least one power source; a second cathode current collector electrically connected to the second cathode and to the at least one power source; a second anode current collector electrically connected to the second anode and to the at least one power source; Further comprising:

2. The electrolysis device according to claim 1.

3. the second cathode flow path is connected in series to the first cathode flow path; 3. The electrolysis device according to claim 2.

4. The second cathode flow path is connected in parallel to the first cathode flow path.

3. The electrolysis device according to claim 2.

5. The at least one power source a power source that supplies the first power source current to the first electrolytic cell via the first cathode current collector and the first anode current collector and that supplies the second power source current to the second electrolytic cell via the second cathode current collector and the second anode current collector; the first cathode current collector, the first anode current collector, the second cathode current collector, and the second anode current collector are electrically connected to the power source.

3. The electrolysis device according to claim 2.

6. The at least one power source a first power supply that supplies the first power supply current to the first electrolytic cell through the first cathode current collector and the first anode current collector; a second power supply that supplies the second power supply current to the second electrolytic cell through the second cathode current collector and the second anode current collector; Including, 3. The electrolysis device according to claim 2.

7. The first fluid includes a first gas and a second gas, The first gas is carbon dioxide gas, the second gas is a gas of a substance different from the carbon dioxide, the first electrolytic cell and the second electrolytic cell reduce the carbon dioxide and reduce the substance; The reduction potential of the carbon dioxide is higher than the reduction potential of the substance; 2. The electrolysis device according to claim 1.

8. The substance is oxygen.

8. The electrolysis device according to claim 7.

9. The substance is nitrogen.

8. The electrolysis device according to claim 7.

10. The concentration of the second gas in the first fluid is 1 ppm or more and 100,000 ppm or less.

8. The electrolysis device according to claim 7.

11. further comprising a third electrolytic cell between the second cathode current collector and the second anode current collector; The third electrolysis cell comprises: A third cathode; and a third anode; and a third diaphragm between the third cathode and the third anode; a third cathode flow channel plate having a third cathode flow channel facing the third cathode; a fourth anode flow plate having a third anode flow channel facing the third anode; having the third cathode is electrically connected to the second anode, or the third anode is electrically connected to the second cathode; 3. The electrolysis device according to claim 2.

12. a first pipe connecting the first electrolytic cell and the second electrolytic cell and supplying the first fluid from the first cathode flow path to the second cathode flow path; a second pipe connecting the first electrolysis cell and the second electrolysis cell and supplying the second fluid from the first anode flow path to the second anode flow path; Further comprising:

3. The electrolysis device according to claim 2.

13. the first cathode having a first catalyst; the second cathode having a second catalyst; the first catalyst is different from the second catalyst; 3. The electrolysis device according to claim 2.

14. the first fluid comprises carbon dioxide gas; The first electrolysis cell reduces carbon dioxide at the first cathode to produce carbon compounds; the second electrolysis cell reduces the carbon dioxide at the second cathode to produce the carbon compound; 3. The electrolysis device according to claim 2.

15. the first fluid comprises nitrogen gas; the first electrolytic cell reduces nitrogen to produce ammonia at the first cathode; the second electrolysis cell reduces the nitrogen at the second cathode to produce the ammonia; 3. The electrolysis device according to claim 2.

16. The first electrolysis cell comprises: a first membrane electrode assembly having the first cathode, the first anode, and the first diaphragm; a first support plate surrounding the first membrane electrode assembly and having a first opening and a second opening; a first cathode flow channel plate having the first cathode flow channel connected to the first opening, a third opening connected to the first cathode flow channel, and a fourth opening connected to the second opening; a first anode flow channel plate having the first anode flow channel connected to the second opening, a fifth opening connected to the first opening, and a sixth opening connected to the first anode flow channel; the first cathode current collector having a seventh opening connected to the third opening and an eighth opening connected to the fourth opening; the first anode current collector having a ninth opening connected to the fifth opening and a tenth opening connected to the sixth opening; Equipped with The second electrolysis cell comprises: a second membrane electrode assembly having the second cathode, the second anode, and the second diaphragm; a second support plate surrounding the second membrane electrode assembly and having an eleventh opening and a twelfth opening; a second cathode flow channel plate having the second cathode flow channel connected to the eleventh opening, a thirteenth opening connected to the second cathode flow channel, and a fourteenth opening connected to the twelfth opening; a second anode flow channel plate having the second anode flow channel connected to the twelfth opening, a fifteenth opening connected to the eleventh opening, and a sixteenth opening connected to the second anode flow channel; the second cathode current collector having a seventeenth opening connected to the thirteenth opening and an eighteenth opening connected to the fourteenth opening; the second anode current collector having a nineteenth opening connected to the fifteenth opening and a twentieth opening connected to the sixteenth opening; Equipped with 3. The electrolysis device according to claim 2.

17. The electrolytic cell further includes an insulating layer provided between the first electrolytic cell and the second electrolytic cell, the insulating layer having a 21st opening connecting the 9th opening and the 14th opening, and a 22nd opening connecting the 10th opening and the 13th opening.

17. The electrolysis device of claim 16.

18. An electrolysis system comprising the electrolysis device according to any one of claims 1 to 17.

19. 1. A method for operating an electrolysis apparatus, comprising the steps of: The electrolysis device comprises: a first electrolysis cell for reducing a substance to be reduced and oxidizing a substance to be oxidized; a second electrolysis cell for reducing the substance to be reduced and oxidizing the substance to be oxidized; a first supply source that supplies a first fluid containing a gas of the substance to be reduced to the first electrolysis cell and the second electrolysis cell; a second supply source that supplies a second fluid containing a liquid of the object to be oxidized to the first electrolytic cell and the second electrolytic cell; at least one power source that supplies a first power source current to the first electrolytic cell and a second power source current to the second electrolytic cell; Equipped with The operating method includes: A first fluid containing a gas of the object to be reduced is supplied to the first electrolysis cell and the second electrolysis cell, and a second fluid containing a liquid of the object to be oxidized is supplied to the first electrolysis cell and the second electrolysis cell; supplying the first power supply current to the first electrolytic cell to reduce the substance to be reduced, and supplying the second power supply current to the second electrolytic cell to reduce the substance to be reduced; a current density of a current flowing through the second electrolytic cell when the substance to be reduced is higher than a current density of a current flowing through the first electrolytic cell when the substance to be reduced is reduced; A method for operating an electrolysis device.

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