JP7809666B2 - Electrolysis system and method for operating the electrolysis system - Google Patents

Description

An embodiment of the present invention relates to an electrolysis system.

In recent years, concerns have arisen about the depletion of fossil fuels such as oil and coal, leading to growing expectations for renewable energy sources that can be used sustainably. Examples of renewable energy sources include solar cells and wind power. However, these have the challenge of making it difficult to ensure a stable supply of electricity, as the amount of power they generate depends on the weather and natural conditions. For this reason, attempts have been made to stabilize the power supply by storing electricity generated by renewable energy sources in storage batteries. However, storing electricity comes with issues such as the cost of storage batteries and losses that occur during storage.

In view of these circumstances, attention has been drawn to a technology that uses electricity generated from renewable energy to reduce substances to be reduced, such as water (H ₂ O), carbon dioxide (CO ₂ ), and nitrogen (N ₂ ), and convert them into chemical substances (chemical energy) such as carbon compounds and nitrogen compounds. Storing these chemical substances in cylinders or tanks has the advantage of lowering energy storage costs and minimizing storage losses compared to storing electricity (electrical energy) in batteries.

JP 2013-159503 A International Publication No. 2019/176141

The problem that this invention aims to solve is to prevent a decrease in electrolysis efficiency.

The electrolysis system of this embodiment includes an electrolysis cell having an anode that oxidizes a substance to be oxidized to produce an anode product, a cathode that reduces a substance to be reduced to produce a cathode product, a diaphragm disposed between the anode and the cathode, a first flow path plate facing the anode and having an anode flow path through which an anode fluid containing the substance to be reduced flows, and a second flow path plate facing the cathode and having a cathode flow path through which a cathode fluid containing the substance to be reduced flows, with the anode, cathode, diaphragm, first flow path plate, and second flow path plate being stacked in a first direction; a rotation axis disposed on the opposite side of the cathode from the diaphragm and extending along a second direction intersecting the first direction; and a rotary drive device that rotates the electrolysis cell around the rotation axis.

FIG. 1 is a block diagram showing an example of the configuration of an electrolysis system. FIG. 2 is a schematic diagram showing a first structural example of the electrolysis unit 10. FIG. 2 is a schematic diagram showing a first structural example of the electrolysis unit 10. FIG. 1 is a schematic diagram showing an example of the structure of an electrolytic cell stack. FIG. 4 is a schematic diagram showing a second structural example of the electrolysis unit 10. FIG. 10 is a schematic diagram showing a modified example of the electrolysis unit 10.

The following describes the embodiments with reference to the drawings. The relationship between the thickness and planar dimensions of each component, the thickness ratio of each component, etc. shown in the drawings may differ from the actual product. The up-down direction may differ from the up-down direction according to gravitational acceleration. Furthermore, in the embodiments, substantially identical components are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

In this specification, "connection" includes not only physical connection but also electrical connection, and unless otherwise specified, includes not only direct connection but also indirect connection.

Figure 1 is a block diagram showing an example configuration of an electrolysis system. The electrolysis system 1 includes an electrolysis unit 10 that performs electrolysis, a rotational drive unit 20 connected to the electrolysis unit 10, and a control unit 30 connected to the electrolysis unit 10 and the rotational drive unit 20.

(First structural example of electrolysis unit 10)
2 and 3 are schematic diagrams showing a first structural example of the electrolysis unit 10. Figures 2 and 3 show an X-axis, a Y-axis perpendicular to the X-axis, and a Z-axis perpendicular to both the X-axis and the Y-axis. Figure 2 shows a portion of the X-Y cross section. Figure 3 shows a portion of the X-Z cross section.

The electrolysis unit 10 has an electrolysis cell 11, a rotating shaft 12, and a fixed shaft 13.

The electrolysis cell 11 has an anode 101, a cathode 102, a diaphragm 103, a flow path plate 104, and a flow path plate 105. The anode 101, the cathode 102, the diaphragm 103, the flow path plate 104, and the flow path plate 105 extend, for example, in the X-axis direction and are stacked in the Y-axis direction.

The anode 101 oxidizes an object to be oxidized to generate an anode product. Examples of the object to be oxidized include water. Examples of the anode product include oxygen (O ₂ ) and hydrogen ions (H ⁺ ). The anode 101 is connected to the positive (+) terminal of the power source 40 to cause an oxidation reaction in the anode 101. The anode 101 can be in various shapes, such as a plate, mesh, wire, particle, porous, thin film, or island shape.

The anode 101 has an anode conductor 111 and an anode catalyst 112.

The anode conductor 111 is electrically connected to the power source 40 and functions as an electrode for the anode 101. The anode conductor 111 has a structure that allows liquid and ions to move between the diaphragm 103 and the anode flow path 140, such as a porous substrate made of a mesh material, punched material, porous material, or sintered metal fiber material. The substrate may be made of a metal material such as titanium (Ti), nickel (Ni), or iron (Fe), or an alloy containing at least one of these metals (e.g., SUS), or it may be made of an oxidation catalyst material described below. When an oxide is used as the oxidation catalyst material, it is preferable to form a catalyst layer by attaching or laminating the oxidation catalyst material to the surface of a substrate made of one of the above metal materials. The oxidation catalyst material preferably has nanoparticles, nanostructures, nanowires, etc. to enhance the oxidation reaction. A nanostructure is a structure in which nanoscale irregularities are formed on the surface of a catalyst material.

The anode catalyst 112 is preferably composed of a material (oxidation catalyst material) capable of oxidizing an anode target to generate an anode product and reducing the overvoltage of such a reaction. Examples of oxidation 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), and ruthenium oxide (Ru-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. The anode 101 may be a composite electrode in which these materials are layered on a substrate.

The cathode 102 reduces the target substance to be reduced to produce a cathode product. Examples of the target substance to be reduced include water, carbon dioxide, nitrogen, etc. Examples of the cathode product include hydrogen, carbon compounds, nitrogen compounds, etc. Examples of the target substance to be reduced may include hydrogen, carbon compounds, nitrogen compounds, etc. obtained by a reduction reaction. The cathode 102 is connected to the negative (-) terminal of the power source 40 to cause a reduction reaction. The cathode 102 has, at least in part, a site capable of electrically reducing water, carbon dioxide, or nitrogen (hereinafter also referred to as a reduction site).

Examples of carbon compounds are carbon monoxide (CO), formic acid (HCOOH), methane (CH ₄ ), methanol (CH ₃ OH), acetic acid (CH ₃ COOH), ethane (C ₂ H ₆ ), ethylene (C ₂ H ₄ ), ethanol (C ₂ H ₅ OH), formaldehyde (HCHO), acetaldehyde (CH ₃ CHO), ethylene glycol (HOCH ₂ CH ₂ OH), 1-propanol (CH ₃ CH ₂ CH ₂ OH), isopropanol (CH ₃ CHOHCH ₃ ), acetylene (C ₂ H ₂ ), glycerol (C ₃ H ₈ O ₃ ), dihydroxyacetone (C ₃ H ₆ O ₃ ), hydroxypyruvic acid (C ₃ H ₄ O ₄ ), mesoxalic acid (C ₃ H ₂ O ₅ ), and oxalic acid (C 2 H ₆ ). H ₂ O ₄ ), glyceraldehyde (C ₃ H ₆ O ₃ ), glyceric acid (C ₃ H ₆ O ₄ ), tartronic acid (C ₃ H ₄ O ₅ ), glycolic acid (C ₂ H ₄ O ₃ ), glyoxal (C ₂ H ₂ O ₂ ), glycolaldehyde (C ₂ H ₄ O ₂ ), glyoxylic acid (C ₂ H ₂ O ₃ ), etc.

Examples of nitrogen compounds include ammonia, urea, uric acid, amino acids, etc.

The cathode 102 may be immersed in or in contact with the electrolyte. The cathode 102 may be in contact with water vapor, carbon dioxide gas, or nitrogen gas. The cathode 102 may be in contact with water vapor, carbon dioxide gas, or nitrogen gas dissolved in the electrolyte.

The cathode 102 has a cathode conductor 121 and a cathode catalyst 122.

The cathode conductor 121 is electrically connected to the power source 40 and functions as an electrode for the cathode 102. While FIG. 2 shows the cathode conductor 121 directly connected to the cathode catalyst 122, the configuration of the cathode conductor 121 is not limited to this. The cathode conductor 121 may be physically separated from the cathode catalyst 122 and electrically connected to it. The cathode conductor 121 only needs to be able to pass the current supplied from the power source 40 through the cathode catalyst 122. Furthermore, if the cathode catalyst 122 itself has the conductivity required of an electrode, the cathode catalyst 122 can also function as the cathode conductor 121, and the cathode conductor 121 can be omitted.

The cathode conductor 121 can be formed using a metal material containing one of the following metal elements: gold (Au), silver (Ag), copper (Cu), platinum (Pt), nickel (Ni), zinc (Zn), palladium (Pd), aluminum (Al), iron (Fe), manganese (Mn), titanium (Ti), tin (Sn), indium (In), gallium (Ga), and bismuth (Bi). The metal material may be a simple metal element, or an alloy containing the metal element, such as an alloy like SUS or an intermetallic compound. Furthermore, the cathode conductor 121 may be formed using, for example, a translucent and conductive metal oxide such as ITO (indium tin oxide), ZnO (zinc oxide), FTO (fluorine-doped tin oxide), AZO (aluminum-doped zinc oxide), or ATO (antimony-doped tin oxide), a semiconductor such as silicon or germanium, a conductive resin, or a conductive ion exchange membrane. The cathode conductor 121 may also be formed using a carbon material such as carbon black, carbon nanotubes, or fullerene. The cathode conductor 121 may also be, for example, a laminate including a metal material layer and another conductive material layer, or a laminate including a conductive material layer other than a metal material layer and another conductive material layer.

The cathode conductor 121 may have a porous structure including pores that allow the electrolyte to pass through, or a structure with through-holes. The through-holes may be a structure that connects the cathode conductor 121 to the cathode catalyst 122. The porous structure can be obtained, for example, by etching a member to form pores, or by using a porous material. The cathode conductor 121 with a porous structure preferably has a pore distribution of, for example, 1 mm or more and 20 mm or less. The through-holes can be formed, for example, by etching the cathode conductor 121. In a cathode conductor 121 with a porous structure, the interconnected pores can also be considered as through-holes. A cathode conductor 121 with a porous structure or through-holes can ensure high conductivity and a large active surface area while increasing the diffusibility of ions and reactants through the pores or through-holes.

The cathode catalyst 122 has sites (reduction sites) capable of reducing the substance to be reduced. The reduction sites in the cathode catalyst 122 need only be present on the surface, but it is preferable that the reduction sites extend to the interior of the porous body. Examples of cathode catalysts 122 with reduction sites include reduction catalyst materials, i.e., materials that reduce the activation energy required to reduce the substance to be reduced; in other words, materials that reduce the overvoltage that occurs when hydrogen, carbon compounds, and nitrogen compounds are produced by a reduction reaction (materials that constitute the reduction sites/reduction catalyst materials). The cathode catalyst 122 is preferably formed from a material that constitutes the reduction sites (reduction catalyst material).

When the cathode catalyst 122 is formed from a reduction catalyst material, examples of the reduction catalyst material include a metal material containing at least one metal element selected from gold (Au), silver (Ag), copper (Cu), platinum (Pt), nickel (Ni), zinc (Zn), and palladium (Pd). The metal material used as the reduction catalyst material may be any of the above metal elements alone, or an alloy containing the above metal elements.

The cathode catalyst 122 is not limited to being formed entirely of the reduction catalyst material. A cathode catalyst 122 having a reduction site may be formed of a metal material other than the reduction catalyst material, with the reduction catalyst material present on its surface. The reduction catalyst material may also be present inside the cathode catalyst 122. A method for providing the reduction catalyst material in the cathode catalyst 122 includes, but is not limited to, applying fine particles (nanoparticles), a dispersion, or a solution of the reduction catalyst material to the cathode catalyst 122. In such cases, in addition to the metal materials (Au, Ag, Cu, Pt, Ni, Zn, Pd), the reduction catalyst material may also include carbon, graphene, carbon nanotubes, fullerenes, Ketjen black, and other carbon materials, and metal complexes such as Ru complexes and Re complexes. Furthermore, the reduction catalyst material may be a composite material containing two or more of the metal materials, carbon materials, and metal complexes described above, or may contain organic molecules, etc.

The cathode catalyst 122 may be made of a reduction catalyst material capable of reducing nitrogen to produce ammonia. Such materials include molybdenum complexes. Examples include the molybdenum complexes (A) to (D) shown below.

A first example is a molybdenum complex having (A) N,N-bis(dialkylphosphinomethyl)dihydrobenzimidazolidene as the PCP ligand (wherein the two alkyl groups may be the same or different, and at least one hydrogen atom on the benzene ring may be substituted with an alkyl group, an alkoxy group, or a halogen atom).

A second example is a molybdenum complex having (B) 2,6-bis(dialkylphosphinomethyl)pyridine as the PNP ligand (wherein the two alkyl groups may be the same or different, and at least one hydrogen atom on the pyridine ring may be substituted with an alkyl group, alkoxy group, or halogen atom).

A third example is a molybdenum complex having (C) a bis(dialkylphosphinomethyl)arylphosphine (where the two alkyl groups may be the same or different) as the PPP ligand.

A fourth example is a molybdenum complex (D) represented by trans-Mo(N ₂ ) ₂ (R ¹ R ² R ³ P) ₄ (wherein R ¹ , R ² , and R ³ may be the same or different and are alkyl or aryl groups, and two R ^3s may be bonded to each other to form an alkylene chain).

In the molybdenum complexes described above, the alkyl group may be, for example, a linear or branched alkyl group such as methyl, ethyl, propyl, butyl, pentyl, hexyl, or structural isomers thereof, or a cyclic alkyl group such as cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl. The alkyl group preferably contains 1 to 12 carbon atoms, more preferably 1 to 6. The alkoxy group may be, for example, a linear or branched alkoxy group such as methoxy, ethoxy, propoxy, butoxy, pentoxy, hexyloxy, or structural isomers thereof, or a cyclic alkoxy group such as cyclopropoxy, cyclobutoxy, cyclopentoxy, or cyclohexyloxy. The alkoxy group preferably contains 1 to 12 carbon atoms, more preferably 1 to 6. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

Examples of the molybdenum complex (A) include the molybdenum complex represented by the following formula (A1):

(wherein ^R1 and ^R2 are alkyl groups which may be the same or different, X is an iodine atom, a bromine atom, or a chlorine atom, and at least one hydrogen atom on the benzene ring may be substituted with an alkyl group, an alkoxy group, or a halogen atom)

Examples of the alkyl group, alkoxy group, and halogen atom include those already exemplified. ^R1 and ^R2 are preferably bulky alkyl groups (for example, tert-butyl or isopropyl). It is preferred that the hydrogen atoms on the benzene ring are unsubstituted, or that the hydrogen atoms at the 5- and 6-positions are substituted with linear, cyclic, or branched alkyl groups having 1 to 12 carbon atoms.

Examples of the molybdenum complex (B) include molybdenum complexes represented by the following formulas (B1), (B2), and (B3).

(wherein R ¹ and R ² are alkyl groups which may be the same or different; X is an iodine atom, a bromine atom, or a chlorine atom; and at least one hydrogen atom on the pyridine ring may be substituted with an alkyl group, an alkoxy group, or a halogen atom.)

Examples of the alkyl group, alkoxy group, and halogen atom include those already exemplified. ^R1 and ^R2 are preferably bulky alkyl groups (for example, tert-butyl or isopropyl). It is preferred that the hydrogen atom on the pyridine ring is unsubstituted, or that the hydrogen atom at position 4 is substituted with a linear, cyclic, or branched alkyl group having 1 to 12 carbon atoms.

Examples of the molybdenum complex (C) include the molybdenum complex represented by the following formula (C1):

(wherein R ¹ and R ² are alkyl groups which may be the same or different, R ³ is an aryl group, and X is an iodine atom, a bromine atom, or a chlorine atom)

Examples of the alkyl group include the same groups as those already exemplified. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and groups in which at least one of the cyclic hydrogen atoms is substituted with an alkyl group or a halogen atom. Examples of the alkyl group and the halogen atom include the same groups as those already exemplified. ^R1 and ^R2 are preferably bulky alkyl groups (for example, a tert-butyl group or an isopropyl group). For ^R3 , for example, a phenyl group is preferred.

Examples of the molybdenum complex (D) include molybdenum complexes represented by the following formulas (D1) and (D2).

(wherein R ¹ , R ² , and R ³ are alkyl or aryl groups which may be the same or different, and N is 2 or 3).

Examples of the alkyl group and aryl group include the same groups as those already exemplified. In formula (D1), it is preferable that ^R1 and ^R2 are aryl groups (e.g., phenyl groups) and ^R3 is an alkyl group having 1 to 4 carbon atoms (e.g., methyl group), or that ^R1 and ^R2 are alkyl groups having 1 to 4 carbon atoms (e.g., methyl group) and ^R3 is an aryl group (e.g., phenyl group). In formula (D2), it is preferable that ^R1 and ^R2 are aryl groups (e.g., phenyl groups) and N is 2.

The diaphragm 103 is provided between the anode 101 and the cathode 102. The diaphragm 103 is composed of an ion exchange membrane or the like that allows ions to move between the anode 101 and the cathode 102 and separates the anode 101 and the cathode 102. Examples of ion exchange membranes that can be used include cation exchange membranes such as Nafion and Flemion, and anion exchange membranes such as Neoceptor and Selemion. In addition to these, any material that allows ions to move between the anode 101 and the cathode 102 can be used as the diaphragm 103.

The anode 101, cathode 102, and diaphragm 103 form a membrane electrode assembly (MEA). The membrane electrode assembly (MEA) has a conductive structure between the anode 101 and cathode 102 when a voltage is applied, via the diaphragm 103, the electrolyte, or both, and an insulating structure when no voltage is applied.

The flow path plate 104 has an anode flow path 140. The anode flow path 140 faces the anode 101 and the anode conductor 111. An anode fluid containing a substance to be oxidized can flow through the anode flow path 140. The anode fluid includes a solution containing at least water. The inlet of the anode flow path 140 may be connected to an anode supply source that supplies the substance to be oxidized. The outlet of the anode flow path 140 may be connected to an anode fluid collector that collects the anode fluid. The shape of the anode flow path 140 is not particularly limited, but may have a rectangular or serpentine shape in the X-Z cross section, for example.

The water-containing solution may be, for example, an electrolyte solution containing any electrolyte. This solution is preferably an aqueous solution that promotes the oxidation reaction of water. Examples of the electrolyte solution include aqueous solutions containing phosphate ions (PO ₄ ²⁻ ), borate ions (BO ₃ ³⁻ ), bicarbonate ions (HCO ₃ ⁻ ), sodium ions (Na ⁺ ), potassium ions (K ⁺ ), calcium ions (Ca ²⁺ ), lithium ions (Li ⁺ ), cesium ions (Cs ⁺ ), magnesium ions (Mg ²⁺ ), chloride ions (Cl ⁻ ), bromide ions (Br ⁻ ), iodide ions (I ⁻ ), and the like.

The solution containing H ₂ O and CO ₂ is preferably a solution with a high absorption rate of H ₂ O and CO ₂ , and examples thereof include aqueous solutions of LiHCO ₃ , NaHCO ₃ , KHCO ₃ , and CSHCO _3. Alcohols such as methanol, ethanol, and acetone may be used as the solution containing H ₂ O and CO _2. The solution containing H ₂ O, CO ₂ , and N ₂ is preferably a solution containing an H ₂ O, CO ₂ , and N ₂ absorbent that lowers the reduction potential of H ₂ O, CO ₂ , and N ₂ , has high ionic conductivity, and absorbs H ₂ O, CO ₂ , and N _2. Such a solution may be an ionic liquid or an aqueous solution thereof that is composed of a salt of a cation such as an imidazolium ion or a pyridinium ion and an anion such as BF ₄ ^- or PF ₆ ^- and remains in a liquid state over a wide temperature range. Other solutions include solutions of amines such as ethanolamine, imidazole, pyridine, etc., or aqueous solutions thereof. The amine may be any of primary amines, secondary amines, and tertiary amines.

The flow path plate 105 has a cathode flow path 150. The cathode flow path 150 faces the cathode 102 and the cathode conductor 121. A cathode fluid containing a substance to be reduced can flow through the cathode flow path 150. The cathode fluid contains substances to be reduced such as water, carbon dioxide, and nitrogen. The inlet of the cathode flow path 150 may be connected to a cathode supply source that supplies the substance to be reduced. The outlet of the cathode flow path 150 may be connected to a cathode fluid collector that collects the cathode fluid. The shape of the cathode flow path 150 is not particularly limited, but may be, for example, a rectangular or serpentine shape in the X-Z cross section.

Examples of the power supply 40 are not limited to ordinary power grids or batteries, but may also include power sources that supply electricity generated by renewable energy sources such as solar cells or wind power. The power supply 40 may further include a power controller that adjusts the output of the power supply to control the voltage between the anode 101 and the cathode 102. The power supply 40 may also be provided outside the electrolysis unit 10. The power supply 40 may supply power to the anode 101 and the cathode 102 via the flow channel plate 104 and the flow channel plate 105. A conductive member may be provided between the anode 101 and the flow channel plate 104, or between the cathode 102 and the flow channel plate 105.

The rotating shaft 12 can rotate, for example, along the X-Y plane. The rotating shaft 12 is connected to the electrolytic cell 11 via the fixed shaft 13. The fixed shaft 13 is connected, for example, to the opposite side of the anode flow path 140 of the flow path plate 13. The rotating shaft 12 has a rotation center in the Z-axis direction. The rotating shaft 12 is provided, for example, on the opposite side of the diaphragm 103 of the anode 101. The rotating shaft 12 may be included in the flow path plate 104 or may be separate. The rotating shaft 12 is preferably aligned with the direction of gravity.

The rotation drive unit 20 is connected to the rotation shaft 12 and can rotate the electrolytic cell 11 around the rotation shaft 12. The rotation drive unit 20 has, for example, a rotation drive device that rotates the electrolytic cell 11 based on a control signal from the control unit 30.

The control unit 30 can control the rotational operation of the rotational drive unit 20 by controlling the rotary drive device. The control unit 30 can control the electrolysis unit 10 by controlling the electrolysis operation of the electrolytic cell 11. The control unit 30 may be configured using hardware such as a processor. Each operation may be stored as an operation program on a computer-readable recording medium such as memory, and each operation may be executed by the hardware appropriately reading out the operation program stored on the recording medium.

The electrolysis unit 10 may have a stack of multiple electrolysis cells 11. Figure 4 is a schematic diagram showing an example structure of an electrolysis cell stack. The electrolysis cell stack shown in Figure 4 has multiple electrolysis cells 11, stacked in the Y-axis direction. The electrolysis cell stack may have a flow path plate 106 between multiple membrane electrode assemblies MEAs instead of the flow path plate 104 or flow path plate 105. The flow path plate 106 has a first surface having an anode flow path 140 facing the anode 101 and a second surface having a cathode flow path 150 facing the cathode 102. The number of stacked electrolysis cells 11 is not limited to the number shown in Figure 4. For other descriptions of the electrolysis cell stack, the descriptions in Figures 2 and 3 can be used as appropriate.

Next, an example of a method for operating the electrolysis system 1 will be described. In this example, the material to be oxidized is supplied to the anode flow path 140, the material to be reduced is supplied to the cathode flow path 150, and a voltage is applied between the anode 101 and the cathode 102 from the power supply 40 to supply a current between the anode 101 and the cathode 102. This causes the electrolysis cell 11 to perform electrolysis.

When a current is passed through the anode 101 and the cathode 102, an oxidation reaction occurs near the anode 101 and a reduction reaction occurs near the cathode 102, as shown below. Here, a case will be described in which carbon dioxide, the object to be reduced, is reduced to produce carbon monoxide (CO) as the anode product, but the anode product is not limited to carbon monoxide and may be other carbon compounds such as the organic compounds mentioned above or nitrogen compounds. Furthermore, the reaction process in the electrolytic cell may be one that mainly produces hydrogen ions (H ⁺ ) or one that mainly produces hydroxide ions (OH ^- ), but is not limited to either of these reaction processes.

The following describes the reaction process when water ( _H2O ) is oxidized to generate hydrogen ions (H ⁺ ). When a current is supplied between the anode 101 and the cathode 102, a water oxidation reaction occurs at the anode 101, which is in contact with the object to be oxidized flowing through the anode flow path 140. Specifically, as shown in the following formula (1), water contained in the anode fluid is oxidized to generate oxygen ( _O2 ) and hydrogen ions (H ⁺ ).
2H ₂ O → 4H ⁺ +O ₂ +4e ^- …(1)

The H ⁺ generated at the anode 101 moves through the cathode fluid in the cathode flow path 150 via the anode 101 and the diaphragm 103, and reaches the vicinity of the cathode 102. A reduction reaction of carbon dioxide occurs due to electrons (e ⁻ ) based on the current supplied from the power source 40 to the cathode 102 and the H ⁺ that has moved to the vicinity of the cathode 102. Specifically, as shown in the following formula (2), carbon dioxide contained in the reduction target supplied from the cathode flow path 150 to the cathode 102 is reduced to generate carbon monoxide.
2CO ₂ +4H ⁺ +4e ^- → 2CO+2H ₂ O...(2)

Next, we will describe the reaction process when carbon dioxide (CO ₂ ) is reduced to produce hydroxide ions (OH ⁻ ). When a current is supplied between the anode 101 and the cathode 102, water (H ₂ O) and carbon dioxide (CO ₂ ) are reduced near the cathode 102, producing carbon monoxide (CO) and hydroxide ions (OH ⁻ ), as shown in the following formula (3). The hydroxide ions (OH ⁻ ) diffuse to the vicinity of the anode 101, where they are oxidized to produce oxygen (O ₂ ), as shown in the following formula ( ⁴ ):
2CO ₂ +2H ₂ O+4e ^- → 2CO+4OH ^-... (3)
4OH ⁻ → 2H ₂ O+O ₂ +4e ⁻ …(4)

Furthermore, when nitrogen (N ₂ ), which is the object to be reduced, is reduced to produce ammonia (NH ₃ ), which is the anode product, water or hydroxide ions are electrochemically oxidized near the anode 101 based on the following formula (5) or formula (6) to produce oxygen. Near the cathode 102, nitrogen is reduced based on the following formula (7) or formula (8) to produce ammonia.
3H ₂ O → 3/2O ₂ +6H ⁺ +6e ^-... (5)
6OH ⁻ → 3/2O ₂ +3H ₂ O+6e ⁻ …(6)
N ₂ +6H ₂ O+6e ⁻ → 2NH ₃ +6OH ⁻ …(7)
N ₂ +6H ⁺ +6e ^- → 2NH ₃ ...(8)

The cathode fluid containing the cathode product is discharged from the outlet of the cathode flow path 150 and separated into cathode exhaust and cathode effluent using a gas-liquid separator. The cathode exhaust and cathode effluent may be further separated into individual compounds using a separate separation device. This allows the cathode product to be recovered. However, if the cathode product has a high viscosity within the operating temperature range of the electrolytic cell 11, the cathode product may adhere to the cathode 102, making it difficult to remove. The operating temperature range of the electrolytic cell 11 is, for example, 25°C or higher and 200°C or lower.

To activate the reduction reaction, it is preferable to form a microstructure in the cathode catalyst 122. For example, a cathode with a nanoparticle catalyst on the electrode substrate that exhibits high activity in the reduction reaction of carbon dioxide can be used. The reduction reaction can be increased by increasing the amount of catalyst supported. However, some cathode products have high viscosity, making them difficult to remove from the cathode 102, preventing the sequential catalytic reaction from proceeding. This reduces the efficiency of electrolysis. Examples of cathode products with high viscosity include ethylene glycol.

The anode fluid containing the anode products is discharged from the outlet of the anode flow path 140 and separated into anode exhaust and anode waste liquid using a gas-liquid separator. The anode exhaust and anode waste liquid may be further separated into individual compounds using a separate separation device. This allows the anode products to be recovered. However, if the anode products contain gas, an increase in the amount of gas will prevent the liquid contained in the oxidation target from reaching the anode 101. This will result in a decrease in electrolysis efficiency.

In contrast, in the electrolysis system of this embodiment, the control unit 30 controls the rotation drive unit 20 to rotate the electrolysis cell 11 around the rotation axis 12. When the electrolysis cell 11 is rotated, centrifugal force is generated toward the outside of the electrolysis cell 11 (the side opposite the rotation axis 12 of the electrolysis cell 11). The arrow indicates the direction of the centrifugal force.

Centrifugation causes the cathode product to detach from the cathode 102 and flow more easily through the cathode flow path 150. This allows for efficient recovery of the cathode product. Furthermore, if the cathode product contains gas and has a smaller molecular weight than the substances to be reduced, such as carbon dioxide and nitrogen, centrifugation does not hinder the recovery of the cathode product. On the other hand, if the cathode product contains gas and has a larger molecular weight than the substances to be reduced, such as carbon dioxide and nitrogen, adjusting the size and centrifugation speed can assist in the recovery of the cathode product. This prevents a decrease in electrolysis efficiency.

Furthermore, centrifugal separation makes it easier for the material to be oxidized to move outward relative to the anode products, and for the anode products to move inward relative to the material to be oxidized. This is because the material to be oxidized has a greater specific gravity than the anode products. This allows the material to be efficiently supplied to the anode 101 to carry out the oxidation reaction, while the anode products are recovered. This prevents a decrease in electrolysis efficiency.

The rotation operation may be performed after the electrolytic reaction or simultaneously with the electrolytic reaction. For example, a first electrode that can contact the flow path plate 104 and a second electrode that can contact the flow path plate 105 may be provided at the top or bottom of the flow path plate 104 and flow path plate 105 in the Z-axis direction, and the first and second electrodes may be connected to a power source 40. A structure may be formed in which the electrolytic cell 11 rotates on the first and second electrodes, allowing a voltage to be applied between the anode 101 and the cathode 102 and causing the electrolytic cell 11 to rotate. When the rotation operation is performed after the electrolytic reaction, the rotation operation may be performed after stopping the supply of the material to be oxidized, the supply of the material to be reduced, and the supply of current to the anode 101 and the cathode 102.

The cathode fluid may contain a gaseous substance that is not involved in oxidation or reduction. The gaseous substance is supplied, for example, by supplying a mixed gas containing the substance to be reduced and the gaseous substance to the cathode flow channel 150. The gaseous substance can dissolve the cathode products. Within the operating temperature range of the electrolysis cell 11, the viscosity of the gaseous substance is preferably lower than that of the cathode products. Examples of gaseous substances include water vapor, acidic compounds such as hydrogen chloride and nitric acid, basic compounds such as ammonia and hydrazine, and organic solvents such as methanol, ethanol, propanol, hexane, and chloroform. By using a gaseous substance, even highly viscous cathode products can be dissolved in the gaseous substance, allowing for efficient recovery of the cathode products. It is preferable not to liquefy the gaseous substance after introducing it into the cathode flow channel 150. This is because centrifugation causes the liquefied gaseous substance to remain on the flow channel slab 105 side and is less likely to move to the cathode 102 side. However, if a large amount of gaseous material is introduced and liquefied, and the supply of the material to be reduced is blocked, the gaseous material will not remain in the flow path slab 105 but will reach the cathode 102 through centrifugation, allowing the highly viscous cathode product to be dissolved and recovered.

(Second structural example of the electrolysis unit 10)
Fig. 5 is a schematic diagram showing a second structural example of the electrolysis unit 10. Fig. 5 shows an X-axis, a Y-axis perpendicular to the X-axis, and a Z-axis perpendicular to both the X-axis and the Y-axis. Fig. 5 shows a part of the external view.

The second structural example of the electrolysis unit 10 differs from the first structural example in that the electrolysis cells 11 are cylindrical (columnar) and extend in the Z-axis direction. Below, we will explain the differences from the first structural example, and for other parts, the explanation of the first structural example can be used as appropriate.

The membrane electrode assembly MEA surrounds the flow path plate 104 and is surrounded by the flow path plate 105. In this case, the anode 101, cathode 102, and diaphragm 103 are cylindrical and extend in the Z-axis direction. The anode conductor 111 may surround the flow path plate 104. The anode catalyst 112 may surround the anode conductor 112. The diaphragm 103 may surround the anode catalyst 112. The cathode catalyst 122 may surround the diaphragm 103. The cathode conductor 121 may surround the cathode catalyst 122. The flow path plate 105 may surround the anode conductor 121.

The anode flow path 140 and the cathode flow path 150 are preferably strip-shaped extending in the Z-axis direction. In this case, the anode flow path 140 and the cathode flow path 150 may penetrate the flow path plate 104 and the flow path plate 105, respectively, in the Z-axis direction. The anode flow path 140 is provided along the inner periphery of the membrane electrode assembly MEA. The cathode flow path 150 is provided along the outer periphery of the membrane electrode assembly MEA.

The rotation axis 12 extends in the Z-axis direction, for example, along the center of the flow path plate 104. It is preferable that the rotation axis 12 be aligned with the direction of gravity.

In the electrolysis system of the second embodiment, as in the first embodiment, the control unit 30 controls the rotation drive unit 20 to rotate the electrolysis cell 11 around the rotation axis 12. When the electrolysis cell 11 is rotated, centrifugal force is generated toward the outside of the electrolysis cell 11 (the opposite side of the rotation axis 12 of the electrolysis cell 11 (the opposite side of the MEA of the flow path plate 105)). The arrow indicates the direction of the centrifugal force.

Centrifugation causes the cathode product to detach from the cathode 102 and flow more easily through the cathode flow path 150. This allows for efficient recovery of the cathode product. Furthermore, if the cathode product contains gas and has a smaller molecular weight than the substances to be reduced, such as carbon dioxide and nitrogen, centrifugation does not hinder the recovery of the cathode product. On the other hand, if the cathode product contains gas and has a larger molecular weight than the substances to be reduced, such as carbon dioxide and nitrogen, adjusting the size and centrifugation speed can assist in the recovery of the cathode product. This prevents a decrease in electrolysis efficiency.

Furthermore, centrifugal separation makes it easier for the material to be oxidized to move outward relative to the anode products, and for the anode products to move inward relative to the material to be oxidized. This is because the material to be oxidized has a greater specific gravity than the anode products. This allows the material to be efficiently supplied to the anode 101 to carry out the oxidation reaction, while the anode products are recovered. This prevents a decrease in electrolysis efficiency.

The rotation operation may be performed after the electrolytic reaction or simultaneously with the electrolytic reaction. For example, a first electrode that can contact the flow path plate 104 and a second electrode that can contact the flow path plate 105 can be provided at the top or bottom of the flow path plate 104 and flow path plate 105 in the Z-axis direction, respectively. The first and second electrodes can be connected to a power source 40, and a structure can be formed in which the electrolytic cell 11 rotates on the first and second electrodes. This allows a voltage to be applied between the anode 101 and cathode 102, and the electrolytic cell 11 can be rotated.

The cathode product may move downward due to gravity. On the other hand, if the material to be reduced is supplied to the cathode 102 from below the electrolysis cell 11, the unreacted material of the material to be reduced can be recovered from the top of the cathode flow path 150, allowing the unreacted material to be efficiently reused.

Since centrifugal force is proportional to the square of the angular velocity and to the radius of rotation, the faster the rotation speed of the electrolytic cell 11, the better, and the longer the distance from the rotation axis 12 to the anode 101 and the distance from the rotation axis 12 to the cathode 102, the better.

(Modification of the electrolysis unit 10)
FIG. 6 is a schematic diagram showing a modified example of the electrolysis unit 10. The electrolysis unit 10 shown in FIG. 6 differs from the first structural example in that it further includes an anode supply system 200 and a cathode supply system 300. The anode supply system 200 and the cathode supply system 300 may be controlled by a control unit 30. Below, differences from the first structural example will be described, and the description of the first structural example can be used for other parts as appropriate. Note that the present invention is not limited to the first structural example, and the second structural example may also be applied.

The anode supply system 200 has an anode supply source 201, an anode fluid recovery device 202, an anode supply flow path P1, an anode discharge flow path P2, and an anode circulation flow path P3, and is configured so that the material to be oxidized circulates through the anode flow path 140. The anode supply flow path P1 is connected to the inlet of the anode flow path 140. The anode discharge flow path P2 is connected to the outlet of the anode flow path 140. The anode supply flow path P1 and the anode discharge flow path P2 are connected to the anode flow path 140 so as not to interfere with the rotation of the electrolytic cell 11. The anode supply system 200 connects the anode supply flow path P1 and the anode discharge flow path P2 via the anode circulation flow path P3. Valves and pumps may be provided along the anode supply flow path P1, anode discharge flow path P2, or anode circulation flow path P3 to control the pressure of each flow path and the flow rate of the fluid flowing through each flow path.

The anode supply source 201 supplies the material to be oxidized to the inlet of the anode flow path 140. The material to be oxidized is introduced into the anode flow path 140 via the anode supply flow path P1. The pressure in the anode flow path 140 may be controlled by providing a pressure controller in at least one of the anode supply flow path P1, the anode discharge flow path P2, and the anode circulation flow path P3. The anode fluid recovery device 202 includes a tank that recovers the anode fluid discharged from the outlet of the anode flow path 140 via the anode discharge flow path P2, and a gas-liquid separator provided in the tank that separates the anode fluid into an anode effluent containing the material to be oxidized and an anode exhaust containing anode products.

In a modified example of the electrolysis unit 10, an anode fluid recovery device 202 is provided at the outlet of the anode flow path 140, and the anode products can be recovered by separating them from the anode fluid. Furthermore, by separating the material to be oxidized from the anode fluid and returning it to the anode supply source 201, the unreacted material to be oxidized can be reused.

The cathode supply system 300 includes a cathode supply source 301, a cathode fluid recovery device 302, a cathode supply flow path P4, a cathode discharge flow path P5, and a cathode circulation flow path P6, and is configured to circulate the material to be reduced through the cathode flow path 150. The cathode supply flow path P4 is connected to the inlet of the cathode flow path 150. The cathode discharge flow path P5 is connected to the outlet of the cathode flow path 150. The cathode supply flow path P4 and the cathode discharge flow path P5 are connected to the cathode flow path 150 so as not to interfere with the rotation of the electrolysis cell 11. The cathode supply system 300 connects the cathode supply flow path P4 and the cathode discharge flow path P5 via the cathode circulation flow path P6. Valves or pumps may be provided along the cathode supply flow path P4, cathode discharge flow path P5, or cathode circulation flow path P6 to control the pressure of each flow path and the flow rate of the fluid flowing through each flow path.

The cathode supply source 301 supplies the material to be reduced to the inlet of the cathode flow path 150. The material to be reduced is introduced into the cathode flow path 150 via the cathode supply flow path P4. Note that a pressure controller may be installed in at least one of the cathode supply flow path P4, the cathode discharge flow path P5, and the cathode circulation flow path P6 to control the pressure in the cathode flow path 150. The cathode fluid recovery device 302 includes a tank that recovers the cathode fluid discharged from the outlet of the cathode flow path 150 via the cathode discharge flow path P5, and a gas-liquid separator installed in the tank that separates the cathode fluid into a cathode effluent containing unreacted material of the material to be oxidized or reduced, and a cathode exhaust containing cathode products.

In a modified example of the electrolysis unit 10, a cathode fluid recovery device 302 is provided at the outlet of the cathode flow path 150, and the cathode products can be recovered by separating them from the cathode fluid. Furthermore, by separating the material to be reduced from the cathode fluid and returning (resupplying) it to the inlet of the cathode flow path 150 via the cathode supply source 301, the unreacted material of the material to be reduced can be reused. In a modified example of the electrolysis unit 10, an anode fluid recovery device 202 is provided at the outlet of the anode flow path 140, and the anode products can be recovered by separating them from the anode fluid. Furthermore, by separating the material to be oxidized from the anode fluid and returning (resupplying) it to the inlet of the anode flow path 140 via the anode supply source 201, the unreacted material of the material to be oxidized can be reused.

The configurations of the above-described embodiments can be applied in combination with each other, and some parts can be replaced with other parts. While 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 a variety of other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their variations are within the scope and spirit of the invention, as well as the invention and its equivalents as set forth in the claims.

The above embodiments can be summarized in the following technical solutions.
(Technical proposal 1)
an electrolysis cell comprising: an anode that oxidizes a substance to be oxidized to produce an anode product; a cathode that reduces a substance to be reduced to produce a cathode product; a diaphragm provided between the anode and the cathode; a first flow path plate that faces the anode and has an anode flow path through which an anode fluid containing the substance to be reduced flows; and a second flow path plate that faces the cathode and has a cathode flow path through which a cathode fluid containing the substance to be reduced flows, wherein the anode, the cathode, the diaphragm, the first flow path plate, and the second flow path plate are stacked in a first direction;
a rotation axis disposed on the cathode opposite the diaphragm and extending along a second direction intersecting the first direction;
a rotary drive device that rotates the electrolytic cell around the rotation axis;
An electrolysis system comprising:
(Technical proposal 2)
The object to be oxidized contains water,
The electrolysis system according to Technical Solution 1, wherein the anode product comprises oxygen.
(Technical proposal 3)
the substance to be reduced contains carbon dioxide,
The electrolysis system according to the first or second aspect of the present invention, wherein the cathode product comprises a carbon compound.
(Technical proposal 4)
The substance to be reduced contains nitrogen,
The electrolysis system according to the first or second aspect of the present invention, wherein the cathode product comprises a nitrogen compound.
(Technical proposal 5)
The electrolysis system according to any one of Technical Schemes 1 to 4, having a plurality of the electrolysis cells.
(Technical proposal 6)
the cathode fluid includes a gaseous substance that does not participate in the oxidation and the reduction;
The electrolysis system according to any one of Technical Schemes 1 to 5, wherein the cathode product is dissolved in the gaseous substance.
(Technical proposal 7)
The electrolysis system according to any one of technical solutions 1 to 6, wherein the second direction is along the direction of gravity.
(Technical proposal 8)
The electrolysis system according to any one of Technical Schemes 1 to 7, wherein the electrolysis cell is cylindrical.
(Technical proposal 9)
The electrolysis system according to any one of Technical Schemes 1 to 8, further comprising at least one collector selected from the group consisting of a cathode fluid collector connected to an outlet of the cathode flow channel and collecting a cathode fluid containing the cathode product, and an anode fluid collector connected to the outlet of the anode flow channel and collecting an anode fluid containing the anode product.
(Technical proposal 10)
The electrolysis system according to any one of Technical Schemes 1 to 9, further comprising at least one circulation flow path selected from the group consisting of a cathode circulation flow path connected to the outlet of the cathode flow path, through which unreacted material of the object to be reduced is resupplied to the inlet of the cathode flow path, and an anode circulation flow path connected to the outlet of the anode flow path, through which unreacted material of the object to be oxidized is resupplied to the inlet of the anode flow path.
(Technical proposal 11)
1. A method for operating an electrolysis system, comprising:
The electrolysis system comprises:
an electrolysis cell including an anode, a cathode, a diaphragm provided between the anode and the cathode, a first flow path plate facing the anode and having an anode flow path through which an anode fluid containing a substance to be oxidized flows, and a second flow path plate facing the cathode and having a cathode flow path through which a cathode fluid containing a substance to be reduced flows, wherein the anode, the cathode, the diaphragm, the first flow path plate, and the second flow path plate are stacked in a first direction;
The driving method includes:
supplying the substance to be oxidized to the anode, supplying the substance to be reduced to the cathode, and applying a voltage between the anode and the cathode to oxidize the substance to be oxidized to generate an anode product and reduce the substance to be reduced to generate a cathode product;
rotating the electrolytic cell around a rotation axis that is disposed on the opposite side of the cathode from the diaphragm and that extends along a second direction that intersects with the first direction;
How to drive an electrolysis system.
(Technical proposal 12)
The method according to technical proposal 11, wherein the electrolysis cell is rotated after producing the anode product and the cathode product.
(Technical proposal 13)
The method according to technical proposal 11, wherein the electrolysis cell is rotated while producing the anodic product and the cathodic product.

1...Electrolysis system, 10...Electrolysis unit, 11...Electrolysis cell, 12...Rotating shaft, 13...Fixed shaft, 20...Rotation drive unit, 30...Control unit, 40...Power supply, 101...Anode, 102...Cathode, 103...Diaphragm, 104...Flow path plate, 105...Flow path plate, 106...Flow path plate, 111...Anode conductor, 112...Anode catalyst, 121...Cathode conductor, 122...Cathode catalyst, 140...Anode flow path, 150...cathode flow path, 200...anode supply system, 201...anode supply source, 202...anode fluid recovery device, 300...cathode supply system, 301...cathode supply source, 302...cathode fluid recovery device, MEA...membrane electrode assembly, P1...anode supply flow path, P2...anode discharge flow path, P3...anode circulation flow path, P4...cathode supply flow path, P5...cathode discharge flow path, P6...cathode circulation flow path.

Claims (13)

an electrolysis cell comprising: an anode that oxidizes a substance to be oxidized to produce an anode product; a cathode that reduces a substance to be reduced to produce a cathode product; a diaphragm provided between the anode and the cathode; a first flow path plate that faces the anode and has an anode flow path through which an anode fluid containing the substance to be reduced flows; and a second flow path plate that faces the cathode and has a cathode flow path through which a cathode fluid containing the substance to be reduced flows, wherein the anode, the cathode, the diaphragm, the first flow path plate, and the second flow path plate are stacked in a first direction;
a rotation axis disposed on the cathode opposite the diaphragm and extending along a second direction intersecting the first direction;
a rotary drive device that rotates the electrolytic cell around the rotation axis;
An electrolysis system comprising: The object to be oxidized contains water,
10. The electrolysis system of claim 1, wherein the anode products include oxygen. the substance to be reduced contains carbon dioxide,
The electrolysis system of claim 1 , wherein the cathode products include carbon compounds. The substance to be reduced contains nitrogen,
The electrolysis system of claim 1 , wherein the cathode products include nitrogen compounds. The electrolysis system of claim 1, comprising a plurality of the electrolysis cells. the cathode fluid includes a gaseous substance that does not participate in the oxidation and the reduction;
The electrolysis system of claim 1 , wherein the cathode product is dissolved in the gaseous substance. The electrolysis system of claim 1, wherein the second direction is along the direction of gravity. The electrolysis system of claim 1, wherein the electrolysis cell is cylindrical. The electrolysis system of claim 1, further comprising at least one collector selected from the group consisting of a cathode fluid collector connected to the outlet of the cathode flow channel and collecting a cathode fluid containing the cathode product, and an anode fluid collector connected to the outlet of the anode flow channel and collecting an anode fluid containing the anode product. The electrolysis system of claim 1 further comprises at least one circulation flow path selected from the group consisting of a cathode circulation flow path connected to the outlet of the cathode flow path and through which unreacted material to be reduced is resupplied to the inlet of the cathode flow path, and an anode circulation flow path connected to the outlet of the anode flow path and through which unreacted material to be oxidized is resupplied to the inlet of the anode flow path. 1. A method for operating an electrolysis system, comprising:
The electrolysis system comprises:
an electrolysis cell including an anode, a cathode, a diaphragm provided between the anode and the cathode, a first flow path plate facing the anode and having an anode flow path through which an anode fluid containing a substance to be oxidized flows, and a second flow path plate facing the cathode and having a cathode flow path through which a cathode fluid containing a substance to be reduced flows, wherein the anode, the cathode, the diaphragm, the first flow path plate, and the second flow path plate are stacked in a first direction;
The driving method includes:
supplying the substance to be oxidized to the anode, supplying the substance to be reduced to the cathode, and applying a voltage between the anode and the cathode to oxidize the substance to be oxidized to generate an anode product and reduce the substance to be reduced to generate a cathode product;
rotating the electrolytic cell around a rotation axis that is disposed on the opposite side of the cathode from the diaphragm and that extends along a second direction that intersects with the first direction;
How to drive an electrolysis system. The method of claim 11, wherein the electrolysis cell is rotated after producing the anode product and the cathode product. The method of claim 11, wherein the electrolysis cell is rotated while producing the anode product and the cathode product.