Electrolysis equipment

Abstract

To provide an electrolytic device capable of increasing the reduction reaction rate of a substance to be reduced, such as CO2, introduced into a gas flow path.SOLUTION: An electrolytic device of an embodiment comprises: an electrolytic cell including a porous cathode 11 in contact with one side of a diaphragm, an anode in contact with the other side of the diaphragm, a cathode flow path 12 in contact with the porous cathode 11, and an anode flow path in contact with the anode; a first supply part for supplying a gas containing a substance to be reduced to the cathode flow path 12; and a second supply part for supplying an electrolytic solution to the anode flow path. The cathode flow path 11 comprises a first region A1 having a gas flow path 121 of a continuous structure having a first gas inlet GI1 connected to the first supply part and a first gas outlet GO1, and a second region A2 having a gas flow path 122 of an interrupted structure having a second gas inlet GI2 connected to the first gas outlet GO1 and a second gas outlet GO2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] Embodiments of the present invention relate to an electrolytic device. [Background technology]

[0002] In recent years, concerns have arisen about the depletion of fossil fuels such as oil and coal, and expectations for sustainably usable renewable energy are rising. From the perspective of such energy and environmental issues, development is underway on power-to-chemical technology, which uses renewable energy such as solar power to electrochemically reduce carbon dioxide and create a storable chemical energy source. An electrolytic device that realizes power-to-chemical technology includes, for example, an anode that oxidizes water (H2O) to produce oxygen (O2) and a cathode that reduces carbon dioxide (CO2) to produce carbon compounds such as carbon monoxide (CO).

[0003] The cathode of an electrolytic device is positioned, for example, to be in contact with CO2 flowing through a gas channel. The cathode obtains the reduction potential of CO2 from a power source derived from renewable energy, etc., and reduces CO2 to produce carbon compounds such as carbon monoxide (CO), formic acid (HCOOH), methanol (CH3OH), methane (CH4), ethanol (C2H5OH), ethane (C2H6), ethylene (C2H4), and ethylene glycol (C2H6O2). When a reduction reaction is induced by flowing CO2 gas through a gas channel, the partial pressure of CO2 in the gas becomes lower at the channel outlet side, making it difficult for the CO2 reduction reaction to proceed. Therefore, the reduction reaction rate of the CO2 introduced into the gas channel tends to decrease at the channel outlet side. Thus, in electrolytic devices, it is necessary to suppress the decrease in the reduction reaction of CO2, the substance to be reduced, due to the gas channel, and to increase the reduction reaction rate of the reduced substance, such as the introduced CO2. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-070936

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide an electrolysis device capable of increasing the reduction reaction rate of a reducible substance introduced into a gas flow path.

Means for Solving the Problems

[0006] The electrolysis device according to the embodiment has a diaphragm, a first surface in contact with one surface of the diaphragm, and a second surface opposite to the first surface, a porous cathode for reducing a reducible substance, an anode disposed so as to be in contact with the other surface of the diaphragm for oxidizing an oxide, a cathode flow path provided on the second surface of the porous cathode for flowing a gas containing a reducible substance so as to supply the reducible substance to the porous cathode, an anode flow path provided so as to be in contact with the anode for flowing the electrolytic solution so as to supply an electrolytic solution containing an oxide to the anode, an electrolytic cell including the anode flow path, a first supply unit for supplying the gas containing the reducible substance to the cathode flow path, and a second supply unit for supplying the electrolytic solution to the anode flow path. In the electrolysis device according to the embodiment, the cathode flow path includes a first region including a gas flow path having a continuous structure having a first gas inlet connected to the first supply unit and a first gas outlet, and a second region including a gas flow path having an intermittent structure having a second gas inlet connected to the first gas outlet and a second gas outlet.

Brief Description of the Drawings

[0007] [Figure 1] It is a cross-sectional view showing the electrolysis device according to the embodiment. [Figure 2] It is a plan view showing the cathode flow path in the electrolytic cell of the electrolysis device shown in FIG. 1. [Figure 3] It is a perspective view showing the cathode flow path in the electrolytic cell of the electrolysis device shown in FIG. 1. [Figure 4]It is a cross-sectional view showing the gas flow in the second region in the electrolytic cell of the electrolytic device shown in FIG. 3.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the electrolytic device of the embodiment will be described with reference to the drawings. In each of the embodiments shown below, substantially the same constituent parts may be denoted by the same reference numerals, and the description thereof may be partially omitted. The drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thicknesses of each part, etc. may be different from the actual ones.

[0009] FIG. 1 is a cross-sectional view showing the electrolytic device 1 of the embodiment, FIG. 2 is a plan view showing the cathode flow path in the electrolytic cell of the electrolytic device shown in FIG. 1, and FIG. 3 is a perspective view showing the cathode flow path in the electrolytic cell of the electrolytic device shown in FIG. 1. Hereinafter, mainly the carbon dioxide electrolytic device will be described, but the electrolytic device of the embodiment is not limited thereto, and for example, an electrolytic device that electrolyzes nitrogen (N2) to generate ammonia (NH3) may be used. The carbon dioxide (CO2) electrolytic device 1 shown in FIGS. 1, 2, and 3 includes an electrolytic cell 2, a carbon dioxide (CO2) supply unit 3 which is a first supply unit for supplying carbon dioxide (CO2) as a substance to be reduced to the electrolytic cell 2, and an electrolytic solution supply system 4 as a second supply unit for supplying an electrolytic solution containing an oxidized substance as an anode solution to the electrolytic cell 2.

[0010] The electrolytic cell 2 comprises a cathode section 10, an anode section 20, and a diaphragm 30. The cathode section 10 includes a porous cathode 11, a cathode channel 12, a cathode channel plate 13, and a cathode current collector plate 14. The anode section 20 includes an anode 21, an anode channel 22, an anode channel plate 23, and an anode current collector plate 24. The diaphragm 30 is positioned to separate the anode section 10 and the cathode section 20. The electrolytic cell 2 is sandwiched between a pair of support plates (not shown) and further tightened with bolts or the like. The porous cathode 11 and anode 21 are connected to a power supply 5 that supplies current to them. The power supply 5 is electrically connected to the porous cathode 11 and anode 21 via a current introduction member or the like. The power supply 5 is not limited to a normal grid power supply or battery, but may also be a power source that supplies electricity generated from renewable energy sources such as solar cells, wind power generation, or geothermal power generation. The electrolytic cell 2 may have a state in which multiple stacked cells are integrated. When multiple cells are arranged as an integrated unit, the amount of carbon dioxide reaction per unit area increases, which can increase the processing capacity, and it is preferable to stack about 10 to 150 cells.

[0011] The CO2 supply unit 3 is connected to the gas inlet of the cathode channel 12 via piping 31 and is configured to supply gas containing CO2 (hereinafter also simply referred to as CO2 gas) to the cathode channel 12. As the CO2 passes through the cathode channel 12, it is converted into carbon compounds such as carbon monoxide (CO) by a reduction reaction. The gas containing CO etc. (exhaust gas) generated by the reduction reaction in the cathode channel 12 is discharged via piping 32 connected to the gas outlet of the cathode channel 12. Although not shown in the figures, a valuable materials manufacturing unit is connected to the piping 32 connected to the gas outlet of the cathode channel 12, for example. The valuable materials manufacturing unit is a chemical synthesis unit that synthesizes valuable materials using CO etc. discharged from the cathode channel 12 as raw materials. The valuable materials manufacturing unit is provided as needed, and instead, a tank for storing exhaust gas containing CO etc. may be used. The cathode channel 12 will be described in detail later.

[0012] The electrolytic solution supply system 4 has a circulation path 41 and a pump 42 that circulate the electrolytic solution as an anode solution via the anode flow path 22. A gas-liquid separation unit 43 is connected to the circulation path 41. In the gas-liquid separation unit 43, the liquid component containing the anode solution and the gas component containing the products are separated, and the liquid component is circulated in the circulation path 41, including the anode flow path 22, by the pump 42. The gas component separated in the gas-liquid separation unit 43 contains oxygen (O2), which is a product of the anode 21. Furthermore, since CO2 supplied to the cathode flow path 12 moves to the anode flow path 22 side, the gas component also contains CO2. The gas component discharge section of the gas-liquid separation unit 43 is connected to the CO2 separation unit 44. The CO2 separated in the CO2 separation unit 44 is returned to the CO2 supply unit 3 as needed.

[0013] The porous cathode 11 is an electrode (reduction electrode) that causes a reduction reaction of carbon dioxide (CO2) to produce carbon compounds such as carbon monoxide (CO), methane (CH4), ethane (C2H6), ethylene (C2H4), methanol (CH3OH), ethanol (C2H5OH), and ethylene glycol (C2H6O2). In the porous cathode 11, a side reaction may occur simultaneously with the reduction reaction of carbon dioxide (CO2), generating hydrogen (H2) through the reduction reaction of water (H2O). The porous cathode 11 has a first surface that is in contact with the diaphragm 30 and a second surface that is in contact with the cathode channel 12. The first surface of the porous cathode 11 is in contact with one surface of the diaphragm 30.

[0014] The cathode channel 12, which is a channel for CO2-containing gas (hereinafter also referred to as CO2 gas), is composed of pits (grooves / recesses) provided in the cathode channel plate 13. It is preferable to use a material with low chemical reactivity and high conductivity for the cathode channel plate 13. Examples of such materials include metallic materials such as Ti and SUS, and carbon materials. The cathode channel plate 13 is provided with a gas inlet and outlet (not shown). CO2 gas is introduced from the CO2 supply unit 3 through the gas inlet or gas outlet. Furthermore, reaction product gases containing CO, H2, etc. are discharged through the gas inlet or gas outlet, and the discharged gas is sent to a valuable product manufacturing unit (not shown) or recovered in a product recovery unit. The cathode channel plate 13 and the cathode channel 12 provided thereon are provided so as to be in contact with a second surface opposite to the first surface that is in contact with the diaphragm 30 of the porous cathode 11.

[0015] The porous cathode 11 has a structure that allows ions to move between the diaphragm 30 and the cathode channel 12, such as a porous structure like a mesh material, a punching material, a porous body, or a metal fiber sintered body. The cathode catalyst material may have nanoparticles, nanostructures, nanowires, etc., to enhance the reduction reaction. A nanostructure is a structure in which nanoscale irregularities are formed on the surface of the catalyst material. The porous cathode 11 has, for example, a porous gas diffusion layer and a porous cathode catalyst layer. A porous layer denser than the gas diffusion layer may be placed between the gas diffusion layer and the cathode catalyst layer. The gas diffusion layer is located on the cathode channel 12 side, and the cathode catalyst layer is located on the diaphragm 30 side. The cathode catalyst layer may be embedded in the gas diffusion layer. In this way, the porous cathode 11 has a porous structure.

[0016] 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 is treated with a water-repellent coating. Electrolytic solution or ions are supplied to the cathode catalyst layer from the anode 21 via a diaphragm 30. In the gas diffusion layer, CO2 gas is supplied from the cathode channel 12, and the products of the CO2 gas reduction reaction are discharged. The CO2 reduction reaction occurs near the boundary between the gas diffusion layer and the cathode catalyst layer, and the gaseous products are discharged from the cathode channel 12.

[0017] The cathode catalyst layer of the porous cathode 11 is preferably composed of a catalyst material (cathode catalyst material) capable of reducing CO2 to produce carbon compounds and reducing the overpotential of such reactions. Examples of cathode catalyst 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), alloys and intermetallic compounds containing at least one of these metals, carbon materials such as carbon (C), graphene, CNT (carbon nanotube), fullerene, and Ketjenblack, and metal complexes such as Ru complexes and Re complexes. Various shapes such as plate-like, mesh-like, wire-like, particulate, porous, thin-film-like, and island-like can be applied to the cathode catalyst layer.

[0018] The anode 21 is an electrode (oxidizing electrode) that causes an oxidation reaction of water (H2O) in the anode solution, which is the electrolytic solution, to produce oxygen (O2). The anode 21 has a first surface that is in contact with the diaphragm 30 and a second surface that is in contact with the anode channel 22. The first surface of the anode 21 is in close contact with the diaphragm 30. The anode channel 22 supplies the anode solution to the anode 21 and is composed of pits (grooves / recesses) provided in the anode channel plate 23. The anode solution flows through the anode channel 22 so as to be in contact with the anode 21. The anode channel plate 23 is provided so as to be in contact with the second surface of the anode 21, which is opposite to the first surface that is in contact with the diaphragm 30.

[0019] It is preferable to use a material with low chemical reactivity and high conductivity for the anode channel plate 23. Examples of such materials include metallic materials such as Ti and SUS, and carbon materials. Multiple lands (protrusions) are provided in the anode channel 22. The lands are provided for mechanical retention and electrical conductivity. It is preferable to provide the lands alternately in order to homogenize the flow of the anode solution. The anode channel 22 is meandering due to these lands. Furthermore, it is preferable to provide the lands alternately in the anode channel 22 in order to properly discharge the anode solution containing oxygen (O2) gas.

[0020] The anode 21 is preferably composed mainly of a catalytic material (anode catalyst material) that is capable of oxidizing water (H2O) to produce oxygen and hydrogen ions and reducing the overpotential of such a reaction. Examples of anode catalyst 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 21 has a porous structure, such as a mesh material, a perforated material, a porous body, or a metal fiber sintered body, that allows the anode solution or ions to move between the diaphragm 30 and the anode channel 22. The anode catalyst material may have nanoparticles, nanostructures, nanowires, etc., to enhance the oxidation reaction. A nanostructure is a structure in which nanoscale irregularities are formed on the surface of the catalyst material.

[0022] The separator 30 is composed of an ion exchange membrane or the like that can move ions and an electrolytic solution between the porous cathode 11 and the anode 21 and can separate the cathode part 10 and the anode part 20. Examples of the ion exchange membrane include Neocepta (registered trademark) of Asahi Kasei Corporation, Selemion (registered trademark) of Asahi Glass Company, Ltd., Aciplex (registered trademark), Fumasep (registered trademark) and fumapem (registered trademark) of Fumatech, Nafion (registered trademark) which is a fluororesin obtained by sulfonating and polymerizing tetrafluoroethylene of DuPont, Lewabrane (registered trademark) of LANXESS, IONSEP (registered trademark) of IONTECH, Mustang (registered trademark) of PALL, Ralex (registered trademark) of Mega, Gore-Tex (registered trademark) of Gore-Tex Corporation, etc. However, as long as it is a material that can move ions between the porous cathode 11 and the anode 21, a glass filter, a porous polymer membrane, a porous insulating material, etc. may be applied to the separator 30 instead of the ion exchange membrane.

[0023] As the electrolytic solution as the anode solution, a solution using water (H2O), for example, an aqueous solution containing an arbitrary electrolyte can be used. This solution is preferably an aqueous solution that promotes the oxidation reaction of water. Examples of the aqueous solution containing an electrolyte include an aqueous solution containing phosphate ions (PO4 2- ), borate ions (BO3 3- ), sodium ions (Na + ), potassium ions (K + ), calcium ions (Ca 2+ ), lithium ions (Li + ), cesium ions (Cs + ), magnesium ions (Mg 2+ ), chloride ions (Cl - ), hydrogen carbonate ions (HCO3 - ), carbonate ions (CO3 - ), hydroxide ions (OH - ), etc.

[0024] As the above-mentioned electrolytic solution, for example, cations such as imidazolium ions and pyridinium ions, and BF4 -PF6 - Ionic liquids or aqueous solutions thereof, which consist of salts with anions such as ethanolamine, and remain liquid over a wide temperature range, can be used. Furthermore, other electrolytic solutions include amine solutions or aqueous solutions thereof, such as ethanolamine, imidazole, and pyridine. Examples of amines include primary amines, secondary amines, and tertiary amines. These electrolytic solutions may have high ionic conductivity, carbon dioxide absorption properties, and properties that reduce reduction energy.

[0025] Examples of primary amines include methylamine, ethylamine, propylamine, butylamine, pentylamine, and hexylamine. The hydrocarbons of the amines may be substituted with alcohols, halogens, etc. Examples of substituted amine hydrocarbons include methanolamine, ethanolamine, and chloromethylamine. Unsaturated bonds may also be present. The same applies to secondary and tertiary amines.

[0026] Examples of secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, dimethanolamine, diethanolamine, and dipropanolamine. The substituted hydrocarbons may be different. This is also true for tertiary amines. For example, examples of amines with different hydrocarbons include methylethylamine and methylpropylamine.

[0027] Examples of tertiary amines include trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trimethanolamine, triethanolamine, trippropanolamine, tributanolamine, trihexanolamine, methyldiethylamine, and methyldipropylamine.

[0028] Examples of cations in ionic liquids include 1-ethyl-3-methylimidazolium ion, 1-methyl-3-propylimidazolium ion, 1-butyl-3-methylimidazole ion, 1-methyl-3-pentylimidazolium ion, and 1-hexyl-3-methylimidazolium ion.

[0029] The 2-position of the imidazolium ion may be substituted. Examples of cations in which the 2-position of the imidazolium ion is substituted include 1-ethyl-2,3-dimethylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, 1-butyl-2,3-dimethylimidazolium ion, 1,2-dimethyl-3-pentylimidazolium ion, and 1-hexyl-2,3-dimethylimidazolium ion.

[0030] Examples of pyridinium ions include methylpyridinium, ethylpyridinium, propylpyridinium, butylpyridinium, pentylpyridinium, and hexylpyridinium. Both the imidazolium ion and the pyridinium ion may be substituted with alkyl groups and may have unsaturated bonds.

[0031] As an anion, fluoride ions (F - ), chloride ions (Cl - ), bromide ions (Br - ), iodide ion (I - ), BF4 - PF6 - CF3COO - CF3SO3 - NO3 - SCN - , (CF3SO2)3C - Examples include bis(trifluoromethoxysulfonyl)imide, bis(trifluoromethoxysulfonyl)imide, and bis(perfluoroethylsulfonyl)imide. Twin ions in which the cation and anion of an ionic liquid are linked by a hydrocarbon are also acceptable. A buffer solution such as potassium phosphate solution may be supplied to the first and second containment tanks 24 and 25.

[0032] The carbon dioxide electrolyzer 1 of this embodiment operates as follows. Here, we describe the case in which CO2 is reduced to mainly carbon monoxide (CO) and H2O is oxidized to produce oxygen. When a voltage greater than the electrolysis voltage is applied between the porous cathode 11 and the anode 21, an oxidation reaction of H2O occurs near the anode 21, which is in contact with the electrolytic solution as the anode solution. As shown in equation (1) below, an oxidation reaction of H2O contained in the electrolytic solution occurs, electrons are lost, and oxygen (O2) and hydrogen ions (H) are produced. + ) and are generated. The generated hydrogen ions (H + A portion of it moves to the cathode channel 12 side via the diaphragm 30. 2H2O → 4H + +O2+4e - …(1)

[0033] Hydrogen ions (H) generated on the anode 21 side + As the electrons reach the vicinity of the porous cathode 11, electrons (e) are sent from the power supply 5 to the cathode 21. - When ) is supplied, a reduction reaction of CO2 occurs. As shown in equation (2) below, hydrogen ions (H) move to the vicinity of the porous cathode 11. + ) and electrons (e) supplied from power supply 5 - ) reduces the CO2 flowing through the cathode channel 12, generating carbon monoxide (CO). 2CO2 + 4H + +4e - → 2CO + 2H2O …(2)

[0034] As shown in equation (1) above, the gas component discharged from the anode channel 22 on the anode 21 side contains oxygen (O2) gas as a product. Furthermore, although the CO2 supplied to the porous cathode 11 side is reduced in the porous cathode 11, a portion of it is reduced as CO2 or carbonate ions (CO3). 2- ) and bicarbonate ions (HCO3) - These then flow into the anode 21 side as carbonate ions (CO3) that have moved to the anode 21 side. 2- ) and bicarbonate ions (HCO3) -The CO2 gas, through a chemical equilibrium reaction, comes into existence as CO2, and some of it dissolves in the anode solution. Any CO2 gas that cannot be dissolved in the anode solution is included in the gas emitted from the anode 21 side, along with the O2 gas.

[0035] As shown in Figures 2 and 3, the cathode flow path 12 comprises a first region A1 having a continuous first gas flow path 121 and a second region A2 having a discontinuous second gas flow path 122. The first gas flow path 121 in the first region A1 has a first gas inlet GI1 and a first gas outlet GO1. The second gas flow path 122 in the second region A2 has a second gas inlet GI2 and a second gas outlet GO2. In the first gas flow path 121, the first gas inlet GI1 is connected to the CO2 supply unit 3 (not shown in Figures 2 and 3), and the first gas outlet GO1 is connected to the second gas inlet GI2 of the second gas flow path 122. The second gas outlet GO2 of the second gas flow path 122 is connected to a valuable material production unit and a product recovery unit (not shown). Thus, the first region A1 of the cathode flow path 12 is located upstream of the CO2 gas flow, and the second region A2 is located downstream of the CO2 gas flow.

[0036] In the first region A1, located upstream of the CO2 gas flow, the partial pressure of CO2 in the gas flowing through the cathode channel 12 remains relatively high. In such a first region A1, as shown in Figures 2 and 3, there is a first gas channel 121 having a continuous structure, for example, in a meandering shape (serpentine shape). That is, the CO2 gas (including products) flowing into the first gas channel 121 flows continuously from the first gas inlet GI1 to the first gas outlet GO2 of the first gas channel 121, which has a continuous structure. The first gas channel 121, which has a continuous structure, is composed of pits (grooves / recesses) provided in the cathode channel plate 13. Specifically, by forming lands 131 of the cathode channel plate 13 on the cathode 13 so that the flow path is continuous, the first gas channel 121 having a meandering shape (serpentine shape) with a continuous structure is formed, for example.

[0037] In the first gas channel 121 having a continuous structure in the first region A1, CO2 gas penetrates from the first gas channel 121 into the porous catalyst layer of the porous cathode 11, similar to a typical electrolytic cell, and the CO2 reduction reaction proceeds. In this case, since the first region A1 is located upstream of the CO2 gas flow, the CO2 partial pressure is relatively high. Therefore, even if the first gas channel 121 is formed by simply arranging the lands 131 of the cathode channel plate 13 on the porous cathode 11 to form a continuous channel, the CO2 reduction reaction can be carried out simply by allowing CO2 gas to penetrate from the first gas channel 121 into the porous catalyst layer of the porous cathode 11.

[0038] In contrast, since the second region A2 is located downstream of the CO2 gas flow, the CO2 partial pressure decreases as the CO2 reduction reaction proceeds in the first region A1. Therefore, if the same gas flow path as the first region A1 is applied to the second region A2, the CO2 reduction reactivity decreases, and the reduction reaction rate of CO2 introduced into the cathode flow path 12 decreases. For this reason, the second region A2, located downstream of the CO2 gas flow, is fitted with a second gas flow path 122 with an intermittent structure, as shown in Figures 2 and 3.

[0039] The discontinuous structure of the second gas channel 122 shown in Figures 2 and 3 has locally provided dead-end sections BP, thereby forming the discontinuous structure. The dead-end sections BP are formed, for example, by arranging the lands 131 of the cathode channel plate 13 in a dead-end shape. The CO2 gas flowing through the second gas channel 122 is blocked by the dead-end sections BP. However, the CO2 gas is subjected to the gas pressure flowing through the second gas channel 122, and furthermore, a porous cathode 11 is present at the bottom of the second gas channel 122. Therefore, as shown in Figure 4, for example, the CO2 gas blocked by the dead-end sections BP of the second gas channel 122 is forcibly passed from the second gas channel 122 through the porous cathode 11 by the gas pressure, and the CO2 reduction reaction proceeds at that time. This makes it possible to improve the reduction reaction rate of the CO2 introduced into the cathode channel 12.

[0040] For example, if the cathode channel 12 is constructed using only the continuous gas channel structure applied to the first region A1, the flow rate is 2.6 sccm / cm². 2 When CO2 is introduced, 1.3 sccm / cm³ flows into the anode channel 22. 2 CO2 moves, and flows from cathode channel 12 at a rate of 0.13 sccm / cm². 2 CO2, 1.17 sccm / cm³ 2 CO, 0.13 sccm / cm³ 2 H2 is emitted. That is, the reduction reaction rate of CO2 is 90%. In contrast, when a cathode channel 12 is applied which is composed of a first region A1 having a continuous structure first gas channel 121 and a second region A2 having an intermittent structure second gas channel 122, so that the overall channel length is the same, the rate is 2.6 sccm / cm 2 When CO2 is introduced, similarly, 1.3 sccm / cm³ is released from the anode channel 22. 2 Although CO2 is emitted, 1.3 sccm / cm³ is emitted from the cathode channel 12. 2 CO, 0.13 sccm / cm³ 2 H2 is emitted. The amount of CO2 in the gas emitted from the second gas flow path 122 is approximately 0 sccm / cm². 2 As a result, the CO2 reduction reaction rate can be made approximately 100%. In this way, by applying a cathode channel 12 composed of a first region A1 with a continuous first gas channel 121 and a second region A2 with an intermittent second gas channel 122, it becomes possible to significantly improve the CO2 reduction reaction rate. By making the CO2 reduction reaction rate 100%, it becomes unnecessary to introduce a CO2 separation device between the piping 32 and the valuable materials manufacturing section.

[0041] The first gas channel 121 in the first region A1 and the second gas channel 122 in the second region A2 may be directly connected, or a dehumidifier to remove water may be placed between them. This allows CO2 gas with reduced moisture content to be supplied from the first gas channel 121 in the first region A1 to the second gas channel 122 in the second region A2. Therefore, the reduction reactivity of CO2 in the second gas channel 122 in the second region A2 can be increased. Examples of dehumidifiers that can be placed between the first gas channel 121 and the second gas channel 122 include compressed air dehumidifiers, cooling dehumidifiers, adsorption dehumidifiers, and heating regeneration dehumidifiers.

[0042] A cell structure comprising a cathode channel 12 having a first region A1 and a second region A2 may have the same configuration in all other respects except for the gas channel shape, or a configuration appropriate to those regions may be applied. For example, it is preferable that the area of ​​the first region A1 be larger than the area of ​​the second region A2. Since the first region A1 has a continuous first gas channel 121, the amount of CO2 flowing and the resulting reaction amount can be increased. In contrast, the second region A2 is a region that forces CO2 gas, which is blocked in a dead end BP in the second gas channel 122, to pass into the porous cathode 11 in order to increase the reduction reaction rate of CO2 in gas with a low CO2 partial pressure. Therefore, by making the area of ​​the first region A1 larger than the area of ​​the second region A2, it is possible to increase the reaction amount of CO2 gas. In other words, by increasing the area of ​​the first region A1, which has a high amount of CO2 flowing and the resulting reaction amount, it is possible to suppress the decrease in the overall reaction amount of CO2 gas in the electrolytic cell 2.

[0043] Regarding the porous cathode 11 of the first region A1 and the porous cathode 11 of the second region A2, it is preferable that the film thickness of the porous cathode 11 of the second region A2 is thicker than that of the porous cathode 11 of the first region A1. This allows the reduction reaction of CO2, which is blocked in the dead end BP of the second gas channel 122, to proceed efficiently when it is forced to pass through the porous cathode 11. Furthermore, it is preferable that the porosity of the porous cathode (including the porous cathode catalyst layer, etc.) 11 of the second region A2 is higher than that of the porous cathode (including the porous cathode catalyst layer, etc.) 11 of the first region A1. This also allows the reduction reaction of CO2, which is forced to pass through the second gas channel 122, to proceed efficiently. Specifically, the porosity of the porous cathode 11 in the second region A2 is preferably 40% to 95%, and the porosity of the porous cathode 11 in the first region A1 is preferably 30% to 80%.

[0044] Regarding the porous cathode catalyst layers of the porous cathode 11 in the first region A1 and the second region A2, it is preferable that the catalyst content of the porous cathode catalyst layer in the second region A2 is greater than that of the porous cathode catalyst layer in the first region A1. Furthermore, it is preferable that the current density applied to the cell portion having the second region A2 is lower than the current density applied to the cell portion having the first region A1. These measures allow the reduction reaction of CO2 to proceed efficiently in the first gas channel 121 and the reduction reaction of the remaining CO2 in the second gas channel 122 to proceed efficiently.

[0045] The first region A1 having a continuous first gas channel 121 and the second region A2 having a discontinuous second gas channel 122 can be arranged in parallel within a single electrolytic cell 2. Alternatively, an electrolytic cell 2 having the first region A1 with a continuous first gas channel 121 and an electrolytic cell 2 having the second region A2 with a discontinuous second gas channel 122 can be stacked, for example. These can also be arranged in parallel. Thus, the first region A1 and the second region A2 only need to be connected in that order, and they can be arranged within a single electrolytic cell 2, or they can be arranged in two separate electrolytic cells to form a stacked structure, etc.

[0046] In the embodiments described above, the CO2 electrolytic apparatus 1 was mainly explained, but the electrolytic apparatus of the embodiment can also be applied to the electrolysis and reduction of N2. In the N2 electrolytic apparatus, gaseous N2 is circulated in the cathode channel so as to be in contact with the cathode (reduction electrode), and an electrolytic solution containing water or water vapor is circulated in the anode channel so as to be in contact with the anode (oxidation electrode). At the cathode, nitrogen (N2) is reduced to produce ammonia (NH3). With such an N2 electrolytic apparatus, it is possible to prevent the reduction of N2 gas from becoming a mixed gas of N2 and NH3, and to produce high-concentration NH3. For the catalysts and other materials of each electrode, catalyst materials suitable for the electrolysis and reduction of N2 are used.

[0047] The configurations of each embodiment described above can be applied in combination, and can also be partially 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, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as described in the claims. [Explanation of symbols]

[0048] 1... Electrolytic device, 2... Electrolytic cell, 3... Carbon dioxide supply unit, 4... Electrolytic solution supply system, 5... Power supply, 10... Cathode section, 11... Cathode, 12... Cathode channel, 13... Cathode channel plate, 14... Cathode current collector plate, 20... Anode section, 21... Anode, 22... Anode channel, 23... Anode channel plate, 24... Anode current collector plate, 30... Diaphragm, 121... First gas channel, 122... Second gas channel, A1... First region, A2... Second region, GI1... First gas inlet, GO1...First gas outlet, GI2...Second gas inlet, GO2...Second gas outlet.

Claims

1. An electrolytic cell comprising: a diaphragm; a porous cathode having a first surface in contact with one surface of the diaphragm and a second surface opposite to the first surface, for reducing a substance to be reduced; an anode disposed in contact with the other surface of the diaphragm for oxidizing an oxide; a cathode channel provided on the second surface of the porous cathode for circulating a gas containing the substance to be reduced to supply the substance to the porous cathode; and an anode channel provided in contact with the anode for circulating an electrolytic solution containing the oxide to supply the electrolytic solution to the anode. A first supply unit that supplies the gas containing the substance to be reduced to the cathode channel, An electrolytic apparatus comprising a second supply unit that supplies the electrolytic solution to the anode channel, The electrolytic apparatus comprises a cathode flow path having a first region with a continuous gas flow path having a first gas inlet and a first gas outlet connected to the first supply unit, and a second region with an intermittent gas flow path having a second gas inlet and a second gas outlet connected to the first gas outlet.

2. The electrolytic apparatus according to claim 1, wherein the area of ​​the first region is greater than the area of ​​the second region.

3. The electrolytic apparatus according to claim 1, wherein the film thickness of the porous cathode in the second region is thicker than the film thickness of the porous cathode in the first region.

4. The electrolytic apparatus according to claim 1, wherein the porosity of the porous cathode in the second region is higher than the porosity of the porous cathode in the first region.

5. The electrolytic apparatus according to claim 1, wherein the catalyst content of the porous cathode in the second region is greater than the catalyst content of the porous cathode in the first region.

6. The electrolytic apparatus according to claim 1, wherein the current density applied to the second region is lower than the current density applied to the first region.

7. The electrolytic apparatus according to claim 1, further comprising a dehumidifier positioned between the first gas outlet of the first region and the second gas inlet of the second region.

8. The electrolytic apparatus according to claim 1, wherein the first region and the second region are arranged within a single electrolytic cell.

9. The electrolytic apparatus according to claim 1, wherein the first region and the second region are arranged in different electrolytic cells.

10. The electrolytic apparatus according to claim 9, wherein the electrolytic cell on which the first region is located and the electrolytic cell on which the second region is located are stacked.

11. The electrolytic apparatus according to claim 1, wherein the electrolytic apparatus is a carbon dioxide electrolytic apparatus.

12. An electrolytic cell comprising a first electrolytic cell and a second electrolytic cell, wherein the first electrolytic cell and the second electrolytic cell each comprise a diaphragm, a porous cathode having a first surface in contact with one surface of the diaphragm and a second surface opposite to the first surface for reducing a substance to be reduced, an anode disposed in contact with the other surface of the diaphragm for oxidizing an oxide, a cathode channel provided on the second surface of the porous cathode for circulating a gas containing a substance to be reduced to supply the substance to be reduced to the porous cathode, and an anode channel provided in contact with the anode for circulating the electrolytic solution containing an oxide to supply the anode. A first supply unit that supplies the gas containing the substance to be reduced to the cathode channel of the first electrolytic cell, An electrolytic apparatus comprising a second supply unit that supplies the electrolytic solution to the anode channel of the first electrolytic cell, The cathode channel of the first electrolytic cell has a first region comprising a gas channel with a continuous structure having a first gas inlet and a first gas outlet connected to the first supply unit, The electrolytic device wherein the cathode channel of the second electrolytic cell has a second region comprising a gas channel with an intermittent structure having a second gas inlet and a second gas outlet connected to the first gas outlet.

13. The electrolytic apparatus according to claim 12, wherein the first electrolytic cell and the second electrolytic cell are stacked.

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