Electrochemical reactor and method for manufacturing an electrochemical reactor

Abstract

To extend the lifespan of electrochemical reactors. [Solution] The electrochemical reaction apparatus comprises an electrochemical reaction structure having a cathode, an anode, a diaphragm having a first surface facing the cathode and a second surface facing the anode, a cathode channel facing the cathode, and an anode channel facing the anode; a first channel through which a first fluid containing the substance to be reduced flows, supplied to the cathode channel; a second channel through which a second fluid containing water flows, supplied to the anode channel; a third channel through which a third fluid containing reduction products flows, discharged from the cathode channel; and a fourth channel through which a fourth fluid containing water and oxygen flows, discharged from the anode channel. The diaphragm has a concentration gradient in which the concentration of chemical species that decompose, capture, or inactivate reactive oxygen species decreases from the second surface to the first surface.

Description

[Technical Field]

[0001] Embodiments of the present invention relate to an electrochemical reactor and a method for manufacturing an electrochemical reactor. [Background technology]

[0002] In recent years, concerns about the depletion of fossil fuels such as oil and coal have led to increased expectations for sustainably usable renewable energy. From the perspective of such energy and environmental issues, the development of Power to Chemicals (P2C) technology is progressing, which uses renewable energy such as solar power to electrochemically reduce carbon dioxide and create a storable chemical energy source. Electrochemical reactors, such as carbon dioxide reactors that realize P2C technology, include an anode that oxidizes water (H2O) to produce oxygen (O2) and a cathode that reduces carbon dioxide (CO2) to produce carbon compounds. The anode and cathode of the carbon dioxide reactor are connected to a power source derived from renewable energy such as solar power, hydroelectric power, wind power, and geothermal power.

[0003] The cathode of a carbon dioxide reactor is positioned to be immersed in water containing dissolved carbon dioxide, for example, or to be in contact with carbon dioxide flowing through a channel. The cathode reduces carbon dioxide by obtaining a reduction potential from a power source derived from renewable energy, producing carbon compounds such as carbon monoxide (CO), formic acid (HCOOH), methanol (CH3OH), methane (CH4), ethanol (C2H5OH), ethane (C2H6), ethylene (C2H4), formaldehyde (HCHO), ethylene glycol (C2H6O2), acetic acid (CH3COOH), and propanol (C3H7OH). The anode is positioned to be in contact with an electrolyte containing water, and reacts with oxygen and hydrogen ions (H + ) generates. In such carbon dioxide reactors, there is a need to improve the utilization efficiency of carbon dioxide, as well as the utilization efficiency and utility value of the carbon dioxide reduction products. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2024 / 058177 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] The problem to be solved by the embodiments of the present invention is to extend the life of an electrochemical reaction device. [Means for Solving the Problems]

[0006] The electrochemical reaction device of the embodiment includes a cathode having a reduction catalyst that promotes a reduction reaction for reducing a reduction target substance, which is carbon dioxide or nitrogen, to produce a reduction product; an anode having an oxidation catalyst that promotes an oxidation reaction for oxidizing water to produce oxygen; a diaphragm having a first surface facing the cathode and a second surface facing the anode; a cathode flow path facing the cathode; and an anode flow path facing the anode. The electrochemical reaction structure includes a first flow path connected to the inlet of the cathode flow path, through which a first fluid containing the reduction target substance flows while being supplied to the cathode flow path; a second flow path connected to the inlet of the anode flow path, through which a second fluid containing water flows while being supplied to the anode flow path; a third flow path connected to the outlet of the cathode flow path, through which a third fluid containing the reduction product flows while being discharged from the cathode flow path; and a fourth flow path connected to the outlet of the anode flow path, through which a fourth fluid containing water and oxygen flows while being discharged from the anode flow path. The diaphragm has a concentration gradient in which the concentration of a chemical species that decomposes, captures, or inactivates reactive oxygen species decreases from the second surface toward the first surface. [Brief Description of the Drawings]

[0007] [Figure 1] It is a schematic diagram showing a configuration example of an electrochemical reaction device. [Figure 2] It is a schematic diagram showing a structural example of a diaphragm.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments will be described with reference to the drawings. In each of the embodiments shown below, substantially the same constituent parts are 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] In this specification, "connect" includes not only directly connecting but also indirectly connecting in some cases, unless otherwise specified.

[0010] FIG. 1 is a schematic diagram showing a configuration example of an electrochemical reaction apparatus. FIG. 1 shows an electrochemical reaction apparatus 1. The electrochemical reaction apparatus 1 has an electrochemical reaction structure 10, a flow path P1, a flow path P2, a flow path P3, and a flow path P4.

[0011] The electrochemical reaction structure 10 has a cathode 11, an anode 12, a diaphragm 13, a flow path plate 14, a flow path plate 15, a current collector 16, and a current collector 17.

[0012] The cathode 11 is, for example, a reduction electrode for performing a reduction reaction of at least one reduction target (substance to be reduced). Examples of the reduction target include, for example, nitrogen and carbon dioxide. A reduction product can be generated by reducing the reduction target.

[0013] The cathode 11 reduces, for example, carbon dioxide supplied as a gas of the reduction target or carbon dioxide contained in the first electrolytic solution (cathode solution) to generate a carbon compound as a reduction product. Examples of the carbon compound include carbon monoxide, formic acid, methanol, methane, ethanol, ethane, ethylene, formaldehyde, ethylene glycol, acetic acid, propanol, etc. The cathode 11 may cause a side reaction of generating hydrogen by a reduction reaction of water together with the reduction reaction of carbon dioxide. The cathode 11 may reduce, for example, nitrogen supplied as a gas of the reduction target to generate ammonia as a reduction product.

[0014] Cathode 11 has, for example, a reduction catalyst that promotes a reduction reaction to reduce a target substance and produce a reduction product. The reduction catalyst can be formed using, for example, a material that reduces the activation energy required to reduce the target substance. In other words, the reduction catalyst can be formed using, for example, a material that lowers the overpotential when a reduction product is produced by the reduction reaction of the target substance.

[0015] The cathode 11 can be formed using, for example, a metallic material or a carbon material. Examples of metallic materials include metals such as gold, aluminum, copper, silver, platinum, palladium, zinc, mercury, indium, nickel, and titanium, as well as alloys containing such metals. Examples of carbon materials include graphene, carbon nanotubes (CNTs), fullerenes, and Ketjenblack. However, the cathode 11 is not limited to these materials and may be formed using, for example, a metallic complex such as a Ru complex or a Re complex, or an organic molecule having an imidazole skeleton or a pyridine skeleton. The cathode 11 may also be formed using a mixture of multiple materials. The cathode 11 may have a structure in which a reduction catalyst in the shape of, for example, a thin film, a lattice, particulate, or wire is placed on a conductive substrate. The type of reduction product produced by the reduction reaction also differs depending on the type of reduction catalyst.

[0016] Anode 12 is an oxidation electrode for carrying out an oxidation reaction of at least one oxidizing agent (substance to be oxidized). Examples of oxidizing agents include water. Anode 12 oxidizes oxidizing agents such as substances or ions in the second electrolyte (anodic solution) to produce oxygen.

[0017] Anode 12 has an oxidation catalyst that promotes oxidation reactions, for example, by oxidizing water to produce oxygen. The oxidation catalyst can be formed using, for example, a material that reduces the activation energy when oxidizing the substance to be oxidized, in other words, a material that lowers the reaction overpotential. Examples of oxidation reactions at anode 12 include the oxidation of water to produce oxygen or hydrogen peroxide, and the oxidation of chloride ions (Cl -This includes reactions that oxidize ) to produce chlorine, and reactions that oxidize carbonate ions or bicarbonate ions to produce carbon dioxide.

[0018] Examples of oxidation catalysts include metallic materials. Examples of metallic materials include ruthenium, iridium, platinum, cobalt, nickel, iron, manganese, tantalum, zirconium, and tin. Furthermore, examples of metallic materials include binary metal oxides, ternary metal oxides, and quaternary metal oxides. Examples of binary metal oxides include 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), and ruthenium oxide (Ru-O). Examples of ternary metal oxides include nickel-iron oxide (Ni-Fe-O), nickel-cobalt oxide (Ni-Co-O), lanthanum-cobalt oxide (La-Co-O), nickel-lanthanum oxide (Ni-La-O), and strontium-iron oxide (Sr-Fe-O). Examples of quaternary metal oxides include lead-ruthenium-iridium oxide (Pb-Ru-Ir-O) and lanthanum-strontium-cobalt oxide (La-Sr-Co-O). However, the oxidation catalyst is not limited to these materials; it may also be formed using metal hydroxides containing metals such as cobalt, nickel, iron, and manganese, or metal complexes such as ruthenium complexes and iron complexes. Furthermore, the oxidation catalyst may be formed by mixing multiple materials.

[0019] The anode 12 may be formed using a composite material that includes both an oxidation catalyst and a conductive material. Examples of conductive materials include carbon materials such as carbon black, activated carbon, fullerene, carbon nanotubes, graphene, Ketjenblack, and diamond; transparent conductive oxides such as indium tin oxide (ITO), zinc oxide (ZnO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), and antimony-doped tin oxide (ATO); metals such as copper, aluminum, titanium, nickel, silver, tungsten, cobalt, and gold; and alloys containing at least one of these metals. The anode 12 may include a structure having an oxidation catalyst on a conductive substrate, for example, in the form of a thin film, lattice, particulate, or wire. The conductive substrate can be formed using a metallic material, for example, titanium, a titanium alloy, or stainless steel.

[0020] The diaphragm 13 is provided between the cathode 11 and the anode 12. The diaphragm 13 can separate the cathode chamber 140 and the anode chamber 150. The diaphragm 13 contains hydrogen ions (H + ) and hydroxide ions (OH - ), bicarbonate ions (HCO3) - ), carbonate ions (CO3 2- Ions such as ) can be moved. The diaphragm 13 allows for the formation of an electrochemical reaction cell having a two-chamber structure. The diaphragm 13 may be provided in contact with the cathode 11 and the anode 12.

[0021] The diaphragm 13 can be formed using, for example, a membrane that allows anions or cations to flow selectively. This makes it possible to make the composition of the second electrolyte in contact with the anode 12 different from the composition of the first electrolyte in contact with the cathode 11, and further, differences in ionic strength, pH, etc., can promote reduction or oxidation reactions. The diaphragm 13 may also have the function of allowing some ions contained in the electrolyte in which the cathode 11 and anode 12 are immersed to pass through, that is, the function of shielding one or more types of ions contained in the electrolyte. This makes it possible to make the pH, etc., different between the two electrolytes. Furthermore, regarding ion shielding, the diaphragm may not completely shield some ions, but rather exert an effect that limits the amount of movement by ion species.

[0022] The diaphragm 13 can be formed using, for example, ion exchange membranes such as Neosepta® from Astom Corporation, Celemion® and Aciplex® from Asahi Glass Co., Ltd., Fumasep® and fumapem® from Fumatech Corporation, Nafion®, a fluororesin produced by sulfonating and polymerizing tetrafluoroethylene from DuPont Corporation, Lewabrane® from LANXESS Corporation, IONSEP® from IONTECH Corporation, Mustang® from PALL Corporation, ralex® from mega Corporation, Gore-Tex® from Gore-Tex Corporation, Sustainion® from DIOXIDEMATERIALS Corporation, and PiperION® from Versogen Corporation. The ion exchange membrane may be formed using, for example, a membrane with a hydrocarbon as its basic skeleton. The anion exchange membrane may be formed using, for example, a membrane having an amine group. If there is a pH difference between the first electrolyte and the second electrolyte, a diaphragm 13 can be formed using a bipolar membrane in which a cation exchange membrane and an anion exchange membrane are stacked, thereby allowing the pH of each electrolyte to be stably maintained during use.

[0023] The diaphragm 13 may be formed using materials such as silicone resin, perfluoroalkoxyalkane (PFA), perfluoroethylenepropene copolymer (FEP), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyethersulfone (PES), or other fluorine-based resins, porous ceramic membranes, fillers filled with glass filters or agar, or insulating porous materials such as zeolites or oxides. In particular, hydrophilic porous membranes are preferred as materials for the diaphragm 13 because they can suppress clogging by air bubbles.

[0024] The cathode 11, anode 12, and diaphragm 13 are stacked to form an electrochemical reaction cell. The electrochemical reaction structure 10 may have a cell stack formed by stacking multiple electrochemical reaction cells. By forming a cell stack, the amount of carbon dioxide reacted per unit area increases, thus increasing the amount of reduction product produced. The number of stacked electrochemical reaction cells is preferably, for example, 10 to 150.

[0025] The flow channel plate 14 forms a cathode chamber 140. The cathode chamber 140 is provided on the surface of the flow channel plate 14 facing the cathode 11, and can form a cathode flow channel. The cathode chamber 140 has an inlet for supplying fluid to the cathode chamber 140 and an outlet for discharging fluid from the cathode chamber 140. The surface shape of the cathode flow channel is not particularly limited, but for example, it is serpentine. The flow channel plate 14 can be formed using a conductive material such as a metal material or a carbon material.

[0026] The flow channel plate 15 forms an anode chamber 150. The anode chamber 150 is provided on the surface of the flow channel plate 15 facing the anode 12, and can form an anode flow channel. The anode chamber 150 has an inlet for supplying fluid to the anode chamber 150 and an outlet for discharging fluid from the anode chamber 150. The surface shape of the anode flow channel is not particularly limited, but for example, it is serpentine. The flow channel plate 15 can be formed using a conductive material such as a metal material or a carbon material.

[0027] The current collector 16 is electrically connected to the cathode 11. The current collector 16 may be provided, for example, on the opposite side of the flow channel plate 14 from the cathode 11 and electrically connected to the cathode 11 via the flow channel plate 14. The current collector 17 is electrically connected to the anode 12. The current collector 17 may be provided, for example, on the opposite side of the flow channel plate 15 from the anode 12 and electrically connected to the anode 12 via the flow channel plate 15. The current collectors 16 and 17 can be formed using a conductive material containing a metallic element such as titanium.

[0028] Current collectors 16 and 17 may be connected to a power supply 20. The power supply 20 can, for example, supply power to the electrochemical reaction structure 10. The power supply 20 can supply voltage and current to the electrochemical reaction structure 10 to cause electrolytic reactions such as oxidation and reduction reactions, and is electrically connected to the cathode 11 and anode 12. Using the electrical energy supplied from the power supply 20, the reduction reaction at the cathode 11 and the oxidation reaction at the anode 12 are carried out. The power supply 20 and the current collector 16, and the power supply 20 and the current collector 17 are connected, for example, by wiring. Electrical equipment such as inverters, converters, and batteries may be installed between the electrochemical reaction structure 10 and the power supply 20 as needed. The driving method for the electrochemical reaction structure 10 may be a constant voltage method or a constant current method.

[0029] The power source 20 may be a normal commercial power source or a battery, or it may be a power source that converts renewable energy into electrical energy and supplies it. Examples of such power sources include power sources that convert kinetic energy or potential energy such as wind power, hydropower, geothermal energy, and tidal power into electrical energy; power sources such as solar cells that have a photoelectric conversion element that converts light energy into electrical energy; power sources such as fuel cells and storage batteries that convert chemical energy into electrical energy; and power sources such as devices that convert vibration energy such as sound into electrical energy. The photoelectric conversion element has the function of separating charges using the energy of light such as irradiated sunlight. Examples of photoelectric conversion elements include pin junction solar cells, pn junction solar cells, amorphous silicon solar cells, multi-junction solar cells, monocrystalline silicon solar cells, polycrystalline silicon solar cells, dye-sensitized solar cells, and organic thin-film solar cells. Furthermore, the photoelectric conversion element may be stacked with at least one of the cathode 11 and anode 12 inside the electrochemical reaction structure 10.

[0030] The power supply 20 can, for example, adjust the current or voltage supplied to the electrochemical reaction structure 10. The power supply 20 may have, for example, a power controller that adjusts the current or voltage supplied to the electrochemical reaction structure 10. The power supply 20 may have a function to adjust the pressure in the cathode chamber 140 or the anode chamber 150 by adjusting the current or voltage supplied to the electrochemical reaction structure 10. The power supply 20 may be located outside the electrochemical reactor 1.

[0031] Electrolytic reactions such as oxidation and reduction reactions by the electrochemical reaction structure 10 are preferably carried out at a temperature between room temperature (e.g., 25°C) and 100°C, where the electrolyte does not vaporize. The above temperature is preferably between 60°C and 95°C, and more preferably between 60°C and 80°C. Lowering the temperature below room temperature would require a cooling device such as a chiller, which may reduce the overall energy efficiency of the system. At temperatures above 100°C, the water in the electrolyte vaporizes, increasing resistance and potentially reducing the electrolytic efficiency.

[0032] The current density of the cathode 11 is not particularly limited, but in order to increase the production amount of the reduction product per unit area, a higher current density is preferable. The current density is preferably 100 mA / cm 2 or more and 1.5 A / cm 2 or less, more preferably 300 mA / cm 2 or more and 700 mA / cm 2 or less. If it is less than 100 mA / cm 2 , the production amount of the reduction product per unit area is low, and a large area is required. If it exceeds 1.5 A / cm 2 , the side reaction of hydrogen generation increases, and the concentration of the reduction product decreases.

[0033] When the Joule heat also increases by increasing the current density and rises above an appropriate temperature, a cooling mechanism may be provided in or near the electrochemical reaction structure 10. The cooling mechanism may be water cooling or air cooling. Even when the temperature of the electrochemical reaction structure 10 is higher than room temperature, if it is 100 °C or lower, it may be left at that temperature.

[0034] The flow path P1 is connected to the inlet of the cathode chamber 140. The flow path P1 allows the cathode supply fluid supplied to the cathode chamber 140 to flow. The cathode supply fluid contains a reduction target such as carbon dioxide. The cathode supply fluid may be a gas containing a gaseous reduction target or a first electrolytic solution containing a reduction target.

[0035] The flow path P1 may be connected to a reduction target supply source. The reduction target supply source may have a reduction target separation and recovery device and may be connected to the reduction target separation and recovery device. The reduction target gas from the reduction target separation and recovery device can be supplied to the flow path P1, for example, directly or after being stored once. Examples of the reduction target supply source include facilities having various incinerators and combustion furnaces such as thermal power plants and garbage incinerators, steel mills, facilities having blast furnaces, etc. The reduction target supply source is not limited to these facilities and may be other factories that generate a reduction target.

[0036] The channel P2 is connected to the inlet of the anode chamber 150. The anode supply fluid supplied to the anode chamber 150 can flow through channel P2. The anode supply fluid includes water or a second electrolyte. Channel P2 may be connected to an anode solution supply source. The anode solution supply source can supply, for example, a second electrolyte used in the anode supply fluid.

[0037] The flow path P3 is connected to the outlet of the cathode chamber 140. The flow path P3 can carry the cathode discharge fluid discharged from the cathode chamber 140. The cathode discharge fluid includes carbon compounds and hydrogen, which are examples of reduction products produced by the reduction reaction in the cathode 11, and a portion of the reduced substance gas contained in the cathode supply fluid or a portion of the first electrolyte.

[0038] The flow path P4 is connected to the outlet of the anode chamber 150. The flow path P4 can carry the anode discharge fluid discharged from the anode chamber 150. The anode discharge fluid includes, for example, gaseous oxygen produced by the oxidation reaction at the anode 12, a substance to be reduced that moves from the cathode chamber 140 or the electrolyte, and water or a portion of the second electrolyte contained in the anode supply fluid.

[0039] The flow path P3 may be connected to a valuable substance production apparatus. Examples of valuable substance production apparatus include chemical synthesis apparatuses that produce valuable substances through chemical synthesis using raw materials such as carbon monoxide. Examples of valuable substances include methanol produced by a methanol production apparatus, hydrocarbons produced by a Fischer-Tropsch reactor, synthetic gasoline, diesel fuel, jet fuel, and olefin compounds produced by an olefin production apparatus. By providing a valuable substance production apparatus downstream of the electrochemical reaction structure 10, valuable substances with high added value can be produced from the products of the electrochemical reaction structure 10.

[0040] The type of chemical synthesis apparatus is not particularly limited, as long as it can react and synthesize other substances from the reduction products generated in cathode 11. Examples of reactions using reduction products from a chemical synthesis apparatus include chemical reactions, electrochemical reactions, and biological transformation reactions using organisms such as algae, enzymes, yeast, and bacteria.

[0041] The flow path P3 may be connected to a product separator instead of a valuable materials production device. The product separator can separate carbon compounds such as carbon monoxide, which are products, by separating excess carbon dioxide from the cathode discharge fluid or by removing water from the cathode discharge fluid. For example, when carbon monoxide gas is produced in the electrochemical reaction structure 10 by formula (2) above, methanol can be produced by methanol synthesis, or jet fuel or diesel fuel can be produced by Fischer-Tropsch synthesis, by using a mixed gas containing the produced carbon monoxide gas and hydrogen gas as a byproduct of the reduction reaction as a raw material. However, the flow path P3 may be connected to a tank that stores gas containing carbon compounds such as carbon monoxide instead of a valuable materials production device.

[0042] The first electrolyte is preferably a solution with a high absorption rate of the substance to be reduced. The form in which the substance to be reduced exists in the first electrolyte is not necessarily limited to a dissolved state; the substance to be reduced may be present as bubbles mixed in the first electrolyte. Examples of electrolytes containing the substance to be reduced include aqueous solutions containing bicarbonates and carbonates such as lithium bicarbonate (LiHCO3), sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), cesium bicarbonate (CsHCO3), sodium carbonate (Na2CO3), and potassium carbonate (K2CO3), as well as phosphoric acid and boric acid. The electrolyte containing the substance to be reduced may also contain alcohols such as methanol and ethanol, or ketones such as acetone, or it may be an alcohol solution or a ketone solution. The first electrolyte may also contain a substance absorbent that lowers the reduction potential of the substance to be reduced, has high ionic conductivity, and absorbs the substance to be reduced.

[0043] The electrolytes, such as the first and second electrolytes, can be solutions containing water, for example, aqueous solutions containing any electrolyte. Preferably, this solution is an aqueous solution that promotes the oxidation reaction of water. Examples of aqueous solutions containing electrolytes include phosphate ions (PO4). 2- ), borate ions (BO33- ), sodium ions (Na + ), potassium ions (K + ), calcium ions (Ca 2+ ), lithium ion (Li + ), cesium ions (Cs + ), magnesium ions (Mg 2+ ), chloride ions (Cl - ), bicarbonate ions (HCO3) - ), carbonate ions (CO3 - ), hydroxide ion (OH - Examples include aqueous solutions containing ) and the like.

[0044] The electrolytes mentioned above include, 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 in a liquid state over a wide temperature range, can be used. Furthermore, other electrolytes 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 electrolytes may have high ionic conductivity, the property of absorbing the substance to be reduced, and the characteristic of lowering the reduction energy.

[0045] 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.

[0046] 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.

[0047] Examples of tertiary amines include trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trimethanolamine, triethanolamine, trippropanolamine, tributanolamine, trihexanolamine, methyldiethylamine, and methyldipropylamine.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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, may also be used. A buffer solution such as potassium phosphate solution may be supplied to the anode chamber 150.

[0052] The second electrolyte contains water as the oxidizing agent. By changing the amount of water and electrolyte components in the first and second electrolytes, the reactivity can be altered, thereby changing the selectivity of the reducing agent and the proportion of the generated substances. The first and second electrolytes may contain redox pairs as needed. Examples of redox pairs include Fe. 3+ / Fe 2+ ya IO 3- / I - These are some examples.

[0053] Next, an example of the operation method of the electrochemical reactor 1 will be described. Here, we will describe the case in which carbon dioxide is reduced to mainly carbon monoxide and water is oxidized to produce oxygen. When a cathode supply fluid containing carbon dioxide is supplied to the cathode chamber 140, and an anode supply fluid containing a second electrolyte is supplied to the anode chamber 150, and a voltage greater than the electrolysis voltage is applied between the cathode 11 and anode 12 by power supply from the power supply 20, an oxidation reaction of water occurs near the anode 12 in contact with the second electrolyte. As shown in equation (1) below, an oxidation reaction of water contained in the second electrolyte occurs, electrons are lost, and oxygen and hydrogen ions are produced. Some of the generated hydrogen ions move to the cathode chamber 140 via the diaphragm 13. 2H2O → 4H + +O2+4e- …(1)

[0054] Hydrogen ions (H) generated on the anode 12 side + As the electrons reach the vicinity of cathode 11, electrons (e) are sent from the power supply 20 to cathode 11. - When ) is supplied, a reduction reaction of carbon dioxide occurs. As shown in equation (2) below, hydrogen ions (H) move to the vicinity of cathode 11. + ) and electrons (e) supplied from power supply 20 - ) reduces carbon dioxide, producing carbon monoxide. 2CO2 + 4H + +4e - → 2CO + 2H2O …(2)

[0055] The gaseous component contained in the anode discharge fluid from the anode chamber 150 is mainly oxygen gas, as shown in equation (1) above. In the reactions at cathode 11 and anode 12, most of the carbon dioxide contained in the cathode supply fluid supplied to cathode chamber 140 is reduced at cathode 11, but some is reduced as carbon dioxide or carbonate ions (CO3 2- ) and bicarbonate ions (HCO3) - These ions flow into the anode 12 side. When the pH of the anode solution (second electrolyte) becomes, for example, 6 or less, the carbonate ions and bicarbonate ions that have moved to the anode 12 side come into existence as carbon dioxide through a chemical equilibrium reaction, and some of them remain dissolved in the anode solution. The carbon dioxide gas that cannot be dissolved in the anode solution is included along with oxygen gas in the anode discharge fluid discharged from the anode chamber 150. Under typical operating conditions of the electrochemical reaction structure 10, the ratio of carbon dioxide gas to oxygen gas in the anode discharge fluid may rise to, for example, 2:1.

[0056] The reduction product may contain carbon dioxide, carbon monoxide, and hydrogen produced by the electrolysis of water. The hydrogen concentration can be adjusted as needed depending on the application. When using hydrogen in a chemical synthesis apparatus, carbon dioxide may be separated from the cathode discharge fluid to use a mixture of carbon monoxide and hydrogen. If hydrogen is not used, only carbon monoxide is separated from the cathode discharge fluid. When producing methanol, the hydrogen produced in cathode 11 can be used as a valuable material by adjusting the number of moles of hydrogen to approximately twice the number of moles of carbon monoxide. On the other hand, by suppressing hydrogen side reactions in cathode 11 depending on the reaction conditions, the concentration of hydrogen in the reduction product can be adjusted to a range of 0.1% to 5% by volume. This allows the electrochemical reactor to be used as a carbon monoxide production apparatus to produce high concentrations of carbon monoxide.

[0057] Here, we will further explain an example of the structure of the diaphragm 13. Figure 2 is a schematic cross-sectional diagram illustrating an example of the diaphragm structure. Figure 2 shows the cathode 11, the anode 12, the diaphragm 13, the flow channel plate 14, and the flow channel plate 15.

[0058] The membrane 13 contains chemical species (also called quenchers or inhibitors) that decompose, capture (retain), or inactivate reactive oxygen species generated by the electrochemical reaction structure 10. Reactive oxygen species are highly reactive oxygen species such as hydrogen peroxide, superoxide anion radical, hydroxyl radical, and singlet oxygen.

[0059] The chemical species are metals, metal oxides, or metal hydroxides containing at least one metallic element from the following: cerium (Ce), manganese (Mn), cobalt (Co), platinum (Pt), ruthenium (Ru), tungsten (W), and tin (Sn), iridium (Ir), cesium (Cs), silver (Ag), iron (Fe), and aluminum (Al). Preferred examples of metals are Ce, Mn, Co, Pt, Ru, W, or Sn, with particularly preferred examples being Ce, Mn, or Co. Examples of metal oxides include MnO, Mn3O4, MnO2, MnO3, Mn2O7, CoO, Co2O3, Co3O4, and CeO2. Examples of metal hydroxides include Mn(OH)2, MnO(OH), MnO(OH)2, and Ce(OH)4. The chemical species may, for example, be attached to the surface of the material constituting the membrane 13.

[0060] The decomposition of reactive oxygen species occurs, for example, by converting reactive oxygen species into water or oxygen through radical reactions.

[0061] Reactive oxygen species are captured by reacting with them, for example, stable radical compounds, and converting them into inert reactants.

[0062] Inactivation of reactive oxygen species is achieved, for example, by suppressing the radicals generated from reactive oxygen species.

[0063] The membrane 13 has a surface 13a facing the cathode 11 and a surface 13b facing the anode 12. The membrane 13 has a concentration gradient in which the concentration of the above chemical species decreases from surface 13b toward surface 13a. The above chemical species are abundant in region R2 on the surface 13b side (near the anode 12) of the membrane 13, and less abundant in region R1 on the surface 13a side (near the cathode 11) of the membrane 13. This is because hydrogen, a byproduct of the electrolysis of the substance to be reduced generated on the cathode 11 side, diffuses through the membrane 13, is oxidized on the anode 12 side, and reacts with reactive oxygen species such as hydrogen peroxide. Since the concentration of the chemical species is highest in region R2, decomposition reactions by reactive oxygen species occur in the membrane 13 from surface 13b.

[0064] Region R1 includes surface 13a and has a first thickness of 0.1 to 0.003 times the thickness of the diaphragm 13 from surface 13a. Region R2 includes surface 13b and has a second thickness of 0.1 to 0.003 times the thickness of the diaphragm 13 from surface 13b.

[0065] On the other hand, if the above chemical species are also present in large quantities in region R1, they may function as a reduction catalyst for cathode 11. When the above chemical species are present in contact with cathode 11, they may cause hydrogen production through the reduction of hydrogen ions generated from water, rather than the reduction reaction of the target substance.

[0066] Furthermore, if the membrane 13 contains the above chemical species, it may inhibit the ion diffusion of the second electrolyte in the membrane 13. If the above chemical species is also present in large quantities in region R1, the effect of ion diffusion will be significant, so the inhibition of ion diffusion can be suppressed by increasing the concentration of the above chemical species in region R2.

[0067] It is important that the above chemical species are directly contained in the membrane 13 to prevent deterioration of the membrane 13. It is known that metals such as platinum, which are effective in decomposing, retaining, and inactivating reactive oxygen species, are used as oxidation catalysts for the anode 12. However, the presence of the above metal in the membrane 13 allows for the decomposition, capture, or inactivation of reactive oxygen species before the decomposition reaction of the membrane 13 by reactive oxygen species dissolved in the second electrolyte can proceed.

[0068] When the diaphragm 13 is formed using the above resin material, the diaphragm 13 has carbon contained in the resin material and metal elements contained in the chemical species. The ratio of metal atoms to 100 carbon atoms in region R2 is preferably 3 or more and 24 or less, preferably 4 or more and 18 or less. That is, the atomic ratio of metal elements to carbon in region R2 (second atomic ratio) is preferably 0.03 or more and 0.24 or less, preferably 0.04 or more and 0.18 or less. If it is less than 3 (0.03), the effect of decomposing, retaining, and inactivating the reactive oxygen species of the chemical species decreases, and if it is more than 24 (0.24), ion diffusion of the electrolyte in the diaphragm 13 is inhibited. The ratio of metal atoms to 100 carbon atoms in region R1 is preferably smaller than the ratio of metal atoms to 100 carbon atoms in region R2, and is preferably 0 or more and 6 or less, preferably 1 or more and 3 or less. In other words, the atomic ratio of the metal element to carbon in region R1 (the first atomic ratio) is preferably smaller than the second atomic ratio, and is preferably 0 to 0.06, and more preferably 0.01 to 0.03.

[0069] Carbon atoms and metal atoms in regions R1 and R2 can be observed, for example, by observing five or more observation points on the surfaces of 13a and 13b of the diaphragm using X-ray photoelectron spectroscopy. The first and second atomic ratios can then be calculated from the average number of atoms of each atom in these observation areas.

[0070] If the diaphragm 13 is an inorganic material film containing metallic elements of chemical species but no carbon, it may not be possible to adjust the mass based on carbon atoms. Therefore, the amount of chemical species can be adjusted within an appropriate range in mass percentage. In this case, the concentration of metallic elements in region R2 (second concentration) is preferably 4.5% by mass or more and 36% by mass or less, preferably 6% by mass or more and 27% by mass or less. The concentration of metallic elements in region R1 (first concentration) is preferably lower than the second concentration. The first concentration is preferably 0% by mass or more and 9% by mass or less, preferably 1% by mass or more and 5% by mass or less.

[0071] In the electrochemical reactor 1, a concentration gradient is formed in which the concentration of the above chemical species decreases from the anode 12 side to the cathode 11 side of the diaphragm 13. This allows for a high Faraday efficiency of the reduction product and improved durability in the electrochemical reactor 1, thereby extending the lifespan of the electrochemical reactor 1.

[0072] Preferably, the above chemical species are deposited on the surface or inside the anode 12 by an electrochemical reaction after incorporating a precursor substance into the anode 12, and then a voltage is applied between the cathode 11 and the anode 12 to precipitate the species on the surface or inside the diaphragm 13. This allows for the formation of a concentration gradient of the above chemical species in the diaphragm 13, with a higher concentration in region R2 and a lower concentration in region R1. Examples of precursors to be incorporated into the anode 12 include metal oxides, hydroxides, chlorides, and complexes. [Examples]

[0073] Electrochemical reactors for Examples 1, 2, 3, and 4, and Comparative Example 1 were fabricated. Furthermore, to evaluate the durability and electrolysis efficiency characteristics, a cathode supply fluid containing carbon dioxide was supplied to the cathode channel, and an anode supply fluid containing potassium bicarbonate at a concentration of 0.1 mol / L as the electrolyte was supplied to the anode channel, at a rate of 700 mA / cm². 2 Each electrochemical reactor was operated under the following conditions with the following current density: By controlling the voltage with power supply 20, the current density between cathode 11 and anode 12 was set to 700 mA / cm². 2 An electric current was passed through the cathode 11 to reduce carbon dioxide and produce carbon monoxide, and the anode 12 to oxidize water and produce oxygen. Furthermore, the cathode discharge fluid discharged from the cathode channel was collected and analyzed to calculate the carbon monoxide production Faraday efficiency.

[0074] Each electrochemical reactor was evaluated as follows based on the change in carbon monoxide production Faraday efficiency. Electrochemical reactors with a carbon monoxide production Faraday efficiency of 80% or higher were marked with ○ (FE: Good), and those with an efficiency of less than 80% were marked with × (FE: Bad). Furthermore, electrochemical reactors where the time until the carbon monoxide production Faraday efficiency decreased by 10% from the start of operation was less than 100 hours were marked with × (Durability: Bad), electrochemical reactors where this time was 100 hours or more were marked with ○ (Durability: Good), and electrochemical reactors where this time was less than 100 hours were marked with × (Durability: Bad).

[0075] (Comparative Example 1) A 0.5 mol / L cobalt chloride solution was prepared by mixing ethanol and water in a 9:1 ratio. A porous resin diaphragm, to be used as diaphragm 13, was immersed in this solution, removed, and dried. It was then dried in a 60°C oven for 5 hours. An electrochemical reactor, as shown in Figure 1, was constructed using this diaphragm. The evaluation results for the electrochemical reactor in Comparative Example 1 were × (FE: Bad), ○ (Durability: Good). X-ray photoelectron spectroscopy measurements confirmed that cobalt atoms were uniformly deposited on both the anode 12 and cathode 11 sides. This indicates that no concentration gradient was formed. The presence of cobalt atoms in diaphragm 13 inhibited ion diffusion of the electrolyte within diaphragm 13, resulting in a decrease in electrolysis efficiency. These results are shown in Table 1.

[0076] (Example 1) An iridium-coated titanium porous body, to be used as anode 12, was immersed in a cobalt chloride solution similar to that used in Comparative Example 1, removed, and dried. Then, the porous body was sintered in an electric furnace at 450°C for 1 hour to produce anode 12. An electrochemical reactor, as shown in Figure 1, was constructed using this anode 12. A preliminary run was then performed for 1 hour under the above operating conditions to transfer chemical species that decompose, capture, or inactivate reactive oxygen species to the diaphragm 13. The electrochemical reactor was disassembled, the diaphragm 13 was removed, and the amounts of carbon atoms and metal atoms (cobalt atoms) were compared using X-ray photoelectron spectroscopy. The anode 12 side contained 12 cobalt atoms for every 100 carbon atoms, while the cathode 11 side contained less than 0.1 cobalt atoms, making them almost undetectable. Specifically, the atomic ratio of the metal element (cobalt) to carbon in region R2 (M / C) was 0.12, and the atomic ratio of cobalt to carbon in region R1 was 0.001 or less. Furthermore, an electrochemical reactor was fabricated again using the same process. Upon evaluation, the electrochemical reactor of Example 1 was evaluated as ○ (FE: Good) and ○ (Durability: Good). These results are shown in Table 1.

[0077] (Example 2) Anode 12 was prepared by coating a titanium nonwoven fabric with ruthenium, cobalt, and tin oxides as catalysts. The elemental ratio of the prepared ruthenium, cobalt, and tin was 10:10:3. An electrochemical reactor, as shown in Figure 1, was prepared in the same manner as in Example 1, except that this anode 12 was used. Subsequently, a preliminary operation was performed for 1 hour under the above operating conditions to transfer chemical species that decompose, capture, or inactivate reactive oxygen species to the diaphragm 13. The electrochemical reactor was disassembled, the diaphragm 13 was removed, and the amounts of carbon atoms and cobalt atoms were compared by X-ray photoelectron spectroscopy. It was found that on the anode 12 side, chemical species that decompose, capture, or inactivate reactive oxygen species were present at a ratio of 15 cobalt atoms to 100 carbon atoms, while on the cathode 11 side, the amount of cobalt atoms was less than 0.1 and almost undetectable. Specifically, the atomic ratio of the metal element (cobalt) to carbon in region R2 (M / C) was 0.15, and the atomic ratio of cobalt to carbon in region R1 was 0.001 or less. Furthermore, an electrochemical reactor was fabricated again using the same process. Upon evaluation, the carbon dioxide reduction apparatus of Example 2 was evaluated as ○ (FE: Good) and ○ (Durability: Good). These results are shown in Table 1.

[0078] (Example 3) A 0.5 mol / L manganese chloride solution was prepared by mixing ethanol and water in a 9:1 ratio. An iridium-coated titanium porous body to be used as anode 12 was immersed in this solution, removed, and dried. Then, the porous body was sintered in an electric furnace at 600°C for 2 hours to produce anode 12. An electrochemical reactor, as shown in Figure 1, was prepared in the same manner as in Example 1, except that anode 12 was used. Then, a preliminary operation was performed for 1 hour under the above operating conditions to transfer chemical species that decompose, capture, or inactivate reactive oxygen species to the diaphragm 13. The electrochemical reactor was disassembled, the diaphragm 13 was removed, and the amounts of carbon atoms and manganese atoms were compared by X-ray photoelectron spectroscopy. It was found that on the anode 12 side, manganese atoms were present in a ratio of 8 to 100 carbon atoms, while on the cathode 11 side, manganese atoms were less than 0.1 and hardly detectable. Specifically, the atomic ratio of the metal element (manganese) to carbon in region R2 (M / C) was 0.08, and the atomic ratio of manganese to carbon in region R1 was 0.001 or less. Furthermore, an electrochemical reactor was fabricated again using the same process. Upon evaluation, the carbon dioxide reduction apparatus of Example 3 was evaluated as ○ (FE: Good) and ○ (Durability: Good). These results are shown in Table 1.

[0079] (Example 4) A 0.05 mol / L bis(acetylacetonate)platinum solution was prepared using acetone. An iridium-coated titanium porous body to be used as anode 12 was immersed in this solution, removed, and dried. Then, the porous body was sintered in an electric furnace at 450°C for 1 hour to produce anode 12. An electrochemical reactor, as shown in Figure 1, was prepared in the same manner as in Example 1, except that anode 12 was used. Then, a preliminary operation was performed for 1 hour under the above operating conditions to transfer chemical species that decompose, capture, or inactivate reactive oxygen species to the diaphragm 13. The electrochemical reactor was disassembled, the diaphragm 13 was removed, and the amounts of carbon atoms and platinum atoms were compared by X-ray photoelectron spectroscopy. It was found that on the anode 12 side, platinum atoms were present in a ratio of 5 to 100 carbon atoms, while on the cathode 11 side, the amount of platinum atoms was less than 0.1 and almost undetectable. Specifically, the atomic ratio of the metal element (platinum) to carbon in region R2 (M / C) was 0.05, and the atomic ratio of platinum to carbon in region R1 was 0.001 or less. Furthermore, an electrochemical reactor was fabricated again using the same process. Upon evaluation, the carbon dioxide reduction apparatus of Example 4 was evaluated as ○ (FE: Good) and ○ (Durability: Good). These results are shown in Table 1.

[0080] [Table 1]

[0081] Table 1 shows that by forming a concentration gradient of the above chemical species from the anode 12 side to the cathode 11 side of the diaphragm 13, a high Faraday efficiency of the reduction product can be achieved in the electrochemical reactor, and durability can be improved, thereby extending the lifespan of the electrochemical reactor.

[0082] 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.

[0083] The above embodiments can be summarized in the following technical proposal. (Technical proposal 1) An electrochemical reaction structure comprising: a cathode having a reduction catalyst that promotes a reduction reaction to reduce a target substance, which is carbon dioxide or nitrogen, and produce a reduction product; an anode having an oxidation catalyst that promotes an oxidation reaction to oxidize water and produce oxygen; a diaphragm having a first surface facing the cathode and a second surface facing the anode; a cathode channel facing the cathode; and an anode channel facing the anode. A first channel is connected to the inlet of the cathode channel and through which a first fluid containing the object to be reduced flows, which is supplied to the cathode channel. A second channel is connected to the inlet of the anode channel and through which a second fluid containing the water is supplied to the anode channel, A third channel is connected to the outlet of the cathode channel, through which a third fluid containing the reduction product flows, which is discharged from the cathode channel. A fourth channel is connected to the outlet of the anode channel, through which a fourth fluid containing the water and oxygen flows, which is discharged from the anode channel. It is equipped with, The above-mentioned diaphragm has a concentration gradient in which the concentration of chemical species that decompose, capture, or inactivate reactive oxygen species decreases from the second surface to the first surface. Electrochemical reactor. (Technical proposal 2) The above diaphragm has carbon and a metal element, The above diaphragm is, A first region including the first surface and having a first atomic ratio of the metal element to the carbon, A second region including the second surface and having a second atomic ratio of the metal element to the carbon, It has, The above second atomic ratio is 0.03 or more and 0.24 or less, The first atomic ratio described above is smaller than the second atomic ratio described above. The electrochemical reaction apparatus described in Technical Proposal 1. (Technical proposal 3) The above first atomic ratio is between 0 and 0.06. The electrochemical reaction apparatus described in Technical Proposal 2. (Technical proposal 4) The above diaphragm contains a metallic element and does not contain carbon. The above diaphragm is, A first region including the first surface and having a first concentration of the metal element, A second region including the second surface and having a second concentration of the metal element, It has, The second concentration mentioned above is 4.5% by mass or more and 36% by mass or less. The first concentration described above is lower than the second concentration described above. The electrochemical reaction apparatus described in Technical Proposal 1. (Technical proposal 5) The first concentration mentioned above is between 0% by mass and 9% by mass. The electrochemical reaction apparatus described in Technical Proposal 4. (Technical proposal 6) The above chemical species is a metal, metal oxide, or metal hydroxide containing at least one metallic element selected from the group consisting of cerium, manganese, cobalt, platinum, ruthenium, tungsten, and tin. An electrochemical reaction apparatus as described in any one of Technical Proposal 1 to Technical Proposal 5. (Technical proposal 7) The above-mentioned reactive oxygen species are hydrogen peroxide, superoxide anion radical, hydroxyl radical, or singlet oxygen. An electrochemical reaction apparatus as described in any one of Technical Proposals 1 through 6. (Technical proposal 8) The above reduction catalyst promotes a chemical reaction that reduces carbon dioxide to produce carbon compounds. An electrochemical reaction apparatus as described in any one of Technical Proposal 1 to Technical Proposal 7. (Technical proposal 9) The above reduction catalyst promotes the chemical reaction that reduces the above nitrogen to produce ammonia. An electrochemical reaction apparatus as described in any one of Technical Proposal 1 to Technical Proposal 7. (Technical proposal 10) A method for manufacturing an electrochemical reaction apparatus, The above electrochemical reaction apparatus is A cathode having a reduction catalyst that promotes a reduction reaction to reduce a target substance, which is carbon dioxide or nitrogen, and produce a reduction product, An anode having an oxidation catalyst that promotes an oxidation reaction that oxidizes water to produce oxygen, A diaphragm having a first surface facing the cathode and a second surface facing the anode, The cathode chamber facing the cathode mentioned above, The anode chamber facing the above anode, It is equipped with, The above manufacturing method is A precursor of a chemical species that decomposes, captures, or inactivates reactive oxygen species is formed on the above anode. By applying a voltage between the cathode and the anode to move the precursor to the diaphragm, a concentration gradient is formed in which the concentration of the chemical species in the diaphragm decreases from the second surface to the first surface. A method for manufacturing an electrochemical reaction apparatus. [Explanation of Symbols]

[0084] 1...Electrochemical reactor, 10...Electrochemical reaction structure, 11...Cathode, 12...Anode, 13...Diaphragm, 13a...Surface, 13b...Surface, 14...Flow channel plate, 15...Flow channel plate, 16...Current collector, 17...Current collector, 20...Power supply, 140...Cathode chamber, 150...Anode chamber, P1...Flow channel, P2...Flow channel, P3...Flow channel, P4...Flow channel, R1...Region, R2...Region.

Claims

1. An electrochemical reaction structure comprising: a cathode having a reduction catalyst that promotes a reduction reaction to reduce a target substance, which is carbon dioxide or nitrogen, and produce a reduction product; an anode having an oxidation catalyst that promotes an oxidation reaction to oxidize water and produce oxygen; a diaphragm having a first surface facing the cathode and a second surface facing the anode; a cathode channel facing the cathode; and an anode channel facing the anode. A first channel is connected to the inlet of the cathode channel, through which a first fluid containing the object to be reduced flows, which is supplied to the cathode channel. A second channel is connected to the inlet of the anode channel and through which a second fluid containing water flows, which is supplied to the anode channel. A third channel is connected to the outlet of the cathode channel, through which a third fluid containing the reduction product flows, which is discharged from the cathode channel. A fourth channel is connected to the outlet of the anode channel, through which a fourth fluid containing water and oxygen flows, which is discharged from the anode channel. It is equipped with, The diaphragm has a concentration gradient in which the concentration of chemical species that decompose, capture, or inactivate reactive oxygen species decreases from the second surface to the first surface. Electrochemical reactor.

2. The aforementioned diaphragm has carbon and a metal element, The aforementioned diaphragm is A first region including the first surface and having a first atomic ratio of the metal element to the carbon, A second region including the second surface and having a second atomic ratio of the metal element to the carbon, It has, The second atomic ratio is 0.03 or more and 0.24 or less. The first atomic ratio is smaller than the second atomic ratio. The electrochemical reaction apparatus according to claim 1.

3. The first atomic ratio is 0 or greater and 0.06 or less. The electrochemical reaction apparatus according to claim 2.

4. The aforementioned diaphragm contains a metallic element and does not contain carbon. The aforementioned diaphragm is A first region including the first surface and having a first concentration of the metal element, A second region including the second surface and having a second concentration of the metal element, It has, The second concentration is 4.5% by mass or more and 36% by mass or less. The first concentration is lower than the second concentration. The electrochemical reaction apparatus according to claim 1.

5. The first concentration is 0% by mass or more and 9% by mass or less. The electrochemical reaction apparatus according to claim 4.

6. The aforementioned chemical species is a metal, metal oxide, or metal hydroxide containing at least one metallic element selected from the group consisting of cerium, manganese, cobalt, platinum, ruthenium, tungsten, and tin. The electrochemical reaction apparatus according to claim 1.

7. The reactive oxygen species is hydrogen peroxide, superoxide anion radical, hydroxyl radical, or singlet oxygen. The electrochemical reaction apparatus according to claim 1.

8. The reduction catalyst promotes a chemical reaction that reduces carbon dioxide to produce a carbon compound. The electrochemical reaction apparatus according to claim 1.

9. The reduction catalyst promotes a chemical reaction that reduces nitrogen to produce ammonia. The electrochemical reaction apparatus according to claim 1.

10. A method for manufacturing an electrochemical reaction apparatus, The electrochemical reaction apparatus is, A cathode having a reduction catalyst that promotes a reduction reaction to reduce a target substance, which is carbon dioxide or nitrogen, and produce a reduction product, An anode having an oxidation catalyst that promotes an oxidation reaction that oxidizes water to produce oxygen, A diaphragm having a first surface facing the cathode and a second surface facing the anode, A cathode chamber facing the aforementioned cathode, an anode chamber facing the anode, It is equipped with, The aforementioned manufacturing method is A precursor of a chemical species that decomposes, captures, or inactivates reactive oxygen species is formed on the anode. By applying a voltage between the cathode and the anode to move the precursor to the diaphragm, a concentration gradient is formed in which the concentration of the chemical species in the diaphragm decreases from the second surface to the first surface. A method for manufacturing an electrochemical reaction apparatus.

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