JP7664879B2 - Electrolysis device and method for operating the electrolysis device - Google Patents

Description

The invention of the embodiment relates to an electrolysis device and a method for driving the electrolysis device.

In recent years, from the perspective of both energy and environmental issues, there is a demand not only for converting renewable energy such as solar power generation into electrical energy for use, but also for converting it into a form that can be stored and transported. In response to this demand, research and development is being conducted into artificial photosynthesis technology that uses sunlight to produce chemical substances, like photosynthesis by plants. This technology may make it possible to store renewable energy as storable fuel, and is also expected to create value by producing chemical substances that can be used as industrial raw materials.

As an apparatus for producing chemical substances using renewable energy such as solar power generation, an electrochemical reaction apparatus is known that includes a cathode for reducing carbon dioxide (CO ₂ ) generated, for example, from a power plant or a waste treatment plant, and an anode for oxidizing water (H ₂ O). At the cathode, for example, carbon dioxide is reduced to produce carbon compounds such as carbon monoxide (CO). When such an electrochemical reaction apparatus is realized in a cell form (also called an electrolysis cell), it is considered effective to realize it in a form similar to a fuel cell such as a Polymer Electric Fuel Cell (PEFC). By directly supplying carbon dioxide to the catalyst layer of the cathode, it is possible to rapidly proceed with the carbon dioxide reduction reaction.

However, this type of cell configuration creates problems similar to those faced by PEFCs. In other words, to realize an electrolytic cell that is durable and less prone to breakdowns, it is necessary to keep the resistance of the electrolytic cell low.

JP 2022-42280 A

The problem that this invention aims to solve is to simplify the configuration of the electrolysis device.

The electrolysis device of the embodiment includes an electrolysis cell having a cathode, an anode, a cathode flow path facing the cathode, and an anode flow path facing the anode, a first storage unit, a second storage unit, and an opening connecting the first storage unit and the second storage unit, the first storage unit and the second storage unit being capable of storing a liquid containing at least one ion, a tank that transfers ions contained in the liquid from the first storage unit to the second storage unit through the opening by forming a height difference between the first liquid level and the second liquid level such that the height of the first liquid level of the liquid stored in the first storage unit relative to the lower part of the second storage unit is higher than the height of the second liquid level of the liquid stored in the second storage unit relative to the lower part of the second storage unit, a first flow path connecting the outlet of the cathode flow path and the first storage unit, and a second flow path connecting the second storage unit and the outlet of the anode flow path.

FIG. 1 is a schematic diagram showing a configuration example of an electrolysis device 1. 2 is a schematic diagram showing an example of the structure of a tank 200. FIG. 10 is a schematic diagram showing another example of the structure of the tank 200. FIG. 10 is a schematic diagram showing another example of the structure of the tank 200. FIG.

The following describes the embodiments with reference to the drawings. Note that the drawings are schematic, and for example, the dimensions of each component, such as the thickness and width, may differ from the actual dimensions of the components. In addition, in the embodiments, substantially identical components may be given the same reference numerals, and descriptions thereof may be omitted.

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

Figure 1 is a schematic diagram showing an example of the configuration of an electrolysis device. The electrolysis device shown in Figure 1 is a carbon dioxide electrolysis device.

The electrolysis device 1 shown in FIG. 1 includes an electrolysis cell 100, a power source 150, a tank 200, a cathode supply unit 301, and an anode supply unit 401.

The electrolysis cell 100 includes an anode 111, an anode flow path 112, an anode current collector 113, a cathode 121, a cathode flow path 122, a cathode current collector 123, and a separator 131. The electrolysis cell 100 includes these components sandwiched between a pair of support plates (not shown) and further fastened with bolts or the like.

The anode 111 is provided between and in contact with the separator 131 and the anode flow path 112. The anode 111 is an electrode for oxidizing water (H ₂ O) in the anode solution to produce oxygen (O ₂ ) and hydrogen ions (H ⁺ ), or an electrode for oxidizing hydroxide ions (OH ⁻ ) generated by the reduction reaction of carbon dioxide at the cathode 121 to produce oxygen and water.

The anode 111 preferably contains a catalytic material (anode catalytic material) capable of reducing the overvoltage of the oxidation reaction. Such catalytic materials include, for example, metals such as platinum (Pt), palladium (Pd), and nickel (Ni), alloys and intermetallic compounds containing these metals, binary metal oxides such as manganese oxide (Mn-O), iridium oxide (Ir-O), nickel oxide (Ni-O), cobalt oxide (Co-O), iron oxide (Fe-O), tin oxide (Sn-O), indium oxide (In-O), ruthenium oxide (Ru-O), lithium oxide (Li-O), and lanthanum oxide (La-O), ternary metal oxides such as Ni-Co-O, Ni-Fe-O, La-Co-O, Ni-La-O, and Sr-Fe-O, quaternary metal oxides such as Pb-Ru-Ir-O and La-Sr-Co-O, and metal complexes such as Ru complexes and Fe complexes.

The anode 111 is provided with a substrate having a structure capable of transferring liquid or ions between the separator 131 and the anode flow path 112, for example, a porous structure such as a mesh material, a punching material, a porous body, or a sintered metal fiber body. The substrate may be made of a metal material such as titanium (Ti), nickel (Ni), or iron (Fe), or an alloy containing at least one of these metals (e.g., SUS), or may be made of the above-mentioned anode catalyst material. When an oxide is used as the anode catalyst material, it is preferable to form a catalyst layer by attaching or laminating the anode catalyst material to the surface of a substrate made of the above-mentioned metal material. The anode catalyst material preferably has nanoparticles, nanostructures, nanowires, etc. in order to enhance the oxidation reaction. A nanostructure is a structure in which nanoscale unevenness is formed on the surface of a catalyst material. In addition, it is not necessary to provide an oxidation catalyst on the anode 111. An oxidation catalyst layer provided other than the anode 111 may be electrically connected to the anode 111.

The cathode 121 is in contact with the separator 131. The cathode 121 is supplied with an anode solution and ions from the separator 131, and with carbon dioxide gas from the cathode flow path 122. The cathode 121 is an electrode (reduction electrode) for generating a reduction reaction of carbon dioxide and a reduction reaction of a reduction product to generate a carbon compound. Examples of the carbon compound include carbon monoxide (CO), methane (CH ₄ ), and ethane (C ₂ H ₆ ). The reduction reaction at the cathode 121 may include a side reaction of generating hydrogen (H ₂ ) by generating a reduction reaction of water in addition to the reduction reaction of carbon dioxide.

The cathode 121 has a gas diffusion layer and a cathode catalyst layer provided on the gas diffusion layer. A porous layer denser than the gas diffusion layer may be disposed between the gas diffusion layer and the cathode catalyst layer. The gas diffusion layer is disposed on the cathode flow channel 122 side, and the cathode catalyst layer is disposed on the separator 131 side. The cathode catalyst layer may be embedded in the gas diffusion layer. The cathode catalyst layer preferably has catalyst nanoparticles or catalyst nanostructures. The gas diffusion layer is made of, for example, carbon paper or carbon cloth, and may be treated to be water repellent. The porous layer is made of a porous body with a smaller pore size than the carbon paper or carbon cloth.

By applying an appropriate water-repellent treatment to the gas diffusion layer, carbon dioxide gas reaches the cathode catalyst layer mainly through gas diffusion. The reduction reaction of carbon dioxide and the resulting carbon compounds occurs near the boundary between the gas diffusion layer and the cathode catalyst layer, or near the cathode catalyst layer that has penetrated into the gas diffusion layer.

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

The cathode catalyst material constituting the cathode catalyst layer preferably has nanoparticles of the above-mentioned metal material, nanostructures of the metal material, nanowires of the metal material, or a composite in which nanoparticles of the above-mentioned metal material are supported on a carbon material such as carbon particles, carbon nanotubes, or graphene. By using catalyst nanoparticles, catalyst nanostructures, catalyst nanowires, catalyst nanosupport structures, etc. as the cathode catalyst material, the reaction efficiency of the carbon dioxide reduction reaction in the cathode 121 can be increased.

The anode 111 and the cathode 121 can be connected to a power source 150. Examples of the power source 150 are not limited to a normal system power source or a battery, and may include a power source that supplies electricity generated by renewable energy such as solar cells or wind power generation. The use of renewable energy is environmentally preferable in terms of the effective use of carbon dioxide. The power source 150 may further include a power controller that adjusts the output of the power source to control the voltage between the anode 111 and the cathode 121. The power source 150 may be provided outside the electrolysis device 1.

The anode flow path 112 faces the anode 111. The anode flow path 112 has the function of supplying the anode solution to the anode 111.

The anode solution preferably contains at least water (H ₂ O). Carbon dioxide (CO ₂ ) is supplied from the cathode flow channel 122, so the liquid may or may not contain carbon dioxide (CO ₂ ).

The anode solution may be an aqueous solution (electrolyte) containing metal ions. Examples of the aqueous solution include aqueous solutions containing phosphate ions (PO ₄ ^2- ), borate ions (BO ₃ ^3- ), sodium ions (Na ⁺ ), potassium ions (K ⁺ ), calcium ions (Ca ²⁺ ), lithium ions (Li ⁺ ), cesium ions (Cs ⁺ ), magnesium ions (Mg ²⁺ ), chloride ions (Cl ^- ), and bicarbonate ions (HCO ₃ ^- ). In addition, aqueous solutions containing LiHCO ₃ , NaHCO ₃ , KHCO ₃ , CsHCO ₃ , phosphoric acid, boric acid, and the like may be used.

The anode flow path 112 is provided on the surface of the flow path plate 114. The flow path plate 114 supplies the anode solution, which is an electrolyte, to the anode 111, and has a groove (recess) on the surface that forms the anode flow path 112. It is preferable to use a material that has low chemical reactivity and high conductivity for the material of the flow path plate 114. Examples of such materials include metal materials such as Ti and SUS, and carbon. The anode flow path 112 may be provided on the anode current collector 113. The material of the flow path plate 114 includes, for example, a material that has low chemical reactivity and no conductivity. Examples of such materials include insulating resin materials such as acrylic resin, polyether ether ketone (PEEK), and fluororesin. The flow path plate 114 has an inlet and an outlet for the anode flow path 112, which are not shown, and screw holes for tightening.

The flow path plate 114 is mainly formed from one material, but may be formed from different materials and stacked together. Furthermore, a surface treatment may be applied to a portion or the entire surface to impart hydrophilic or water-repellent properties.

The anode flow path 112 has an inlet and an outlet, and the anode solution is supplied from the anode supply unit 401 through the inlet and discharged through the outlet. The anode solution flows through the anode flow path 112 so as to come into contact with the anode 111.

The anode current collector 113 is electrically connected to the anode 111. The anode current collector 113 is in contact with the surface of the flow path plate 114 opposite the anode flow path 112. The anode current collector 113 preferably contains a material that has low chemical reactivity and high conductivity. Such materials include metal materials such as Ti and SUS, and carbon.

The cathode flow path 122 faces the cathode 121. The cathode flow path 122 has a function of supplying a fluid (cathode gas) containing carbon dioxide to the cathode 121. The fluid containing carbon dioxide may contain steam due to humidification. Compounds generated by the reduction reaction are mainly discharged from the cathode flow path 122. The compounds generated by the reduction reaction differ depending on the type of reduction catalyst, etc. Along with such gas products, steam, or moisture obtained by condensation of steam contained in the humidified carbon dioxide gas, is discharged from the cathode flow path 122.

The cathode flow path 122 is provided on the surface of the flow path plate 124. The flow path plate 124 has a groove (recess) on the surface that forms the cathode flow path 122. The material of the flow path plate 124 is preferably a material that has low chemical reactivity and high conductivity. Examples of such materials include metal materials such as Ti and SUS, and carbon. The material of the flow path plate 124 also includes a material that has low chemical reactivity and no conductivity. Examples of such materials include insulating resin materials such as acrylic resin, polyether ether ketone (PEEK), and fluororesin. The flow path plate 124 has screw holes for tightening (not shown). In addition, packing (not shown) is sandwiched in front and behind each flow path plate as necessary. The cathode flow path 122 may be provided on the cathode current collector 123.

The cathode flow path 122 has an inlet and an outlet. A cathode gas such as carbon dioxide is supplied from the cathode supply unit 301 through the inlet, and a fluid containing the cathode gas is discharged through the outlet. The cathode gas flows through the cathode flow path 122 so as to come into contact with the cathode 121.

The cathode flow channel 122 may have a land that contacts the cathode 121 for electrical contact with the cathode 121. The shape of the cathode flow channel 122 is not particularly limited as long as it is continuously connected, and examples include a serpentine structure in which a long and thin flow channel is bent. This is preferable because it allows the cathode gas to flow uniformly on the surface of the cathode 121, allowing a uniform reaction to occur at the cathode 121.

The cathode gas may be supplied in a dry state. When the cathode gas is carbon dioxide gas, the carbon dioxide concentration of the cathode gas supplied from the cathode supply unit 301 to the cathode flow path 122 does not have to be 100%. It is also possible to use gas containing carbon dioxide discharged from various facilities as the cathode gas.

The flow path plate 124 is mainly formed from one material, but may be formed from different materials and stacked together. Furthermore, a surface treatment may be applied to a portion or the entire surface to impart hydrophilic or water-repellent properties.

The cathode current collector 123 is electrically connected to the cathode 121 of the electrolysis cell 100. The cathode current collector 123 preferably contains a material that has low chemical reactivity and high conductivity. Such materials include metal materials such as Ti and SUS, and carbon.

The separator 131 is disposed so as to separate the anode 111 and the cathode 121. The separator 131 includes an ion exchange membrane capable of transferring ions between the anode 111 and the cathode 121 and separating the anode 111 and the cathode 121. Examples of the ion exchange membrane include a cation exchange membrane such as Nafion or Flemion, and an anion exchange membrane such as Neoceptor, Selemion, or Sustenion. When an alkaline solution is used as the electrolyte and mainly OH ⁻ is assumed to transfer, the separator 131 is preferably composed of an anion exchange membrane. The ion exchange membrane may also be composed of a membrane having a basic skeleton of a hydrocarbon or a membrane having an amine group. However, other than the ion exchange membrane, a salt bridge, a glass filter, a porous polymer membrane, a porous insulating material, or the like may be applied to the separator 131 as long as it is a material capable of transferring ions between the anode 111 and the cathode 121. However, if gas flows between the anode 111 and the cathode 121, a circulation reaction due to reoxidation of the reduction product may occur. For this reason, it is preferable to reduce the gas exchange between the anode 111 and the cathode 121. For this reason, care must be taken when using a porous thin film as the separator 131.

Next, an example of a method for driving the electrolysis cell 100 will be described. Here, the case where carbon monoxide is generated as a carbon compound will be mainly described, but the carbon compound as a reduction product of carbon dioxide is not limited to carbon monoxide.

First, the reaction process in which water (H ₂ O) is oxidized to generate hydrogen ions (H ⁺ ) will be described. When a current is supplied from the power source 150 between the anode 111 and the cathode 121, an oxidation reaction of water (H ₂ O) occurs at the anode 111 in contact with the anode solution. Specifically, as shown in the following formula (1), H ₂ O contained in the anode solution is oxidized to generate oxygen (O ₂ ) and hydrogen ions (H ⁺ ).

2H ₂ O → 4H ⁺ +O ₂ +4e ^-... (1)

The H ⁺ generated at the anode 111 moves through the electrolyte and separator 131 present in the anode flow path 112, and reaches the vicinity of the cathode 121. A reduction reaction of carbon dioxide occurs due to electrons (e ⁻ ) based on the current supplied from the power source 150 to the cathode 121 and the H ⁺ that has moved to the vicinity of the cathode 121. Specifically, as shown in the following formula (2), carbon dioxide supplied from the cathode flow path 122 to the cathode 121 is reduced to generate carbon monoxide. Furthermore, hydrogen ions receive electrons as shown in the following formula (3), generating hydrogen. At this time, hydrogen may be generated simultaneously with carbon monoxide.

CO ₂ +2H ⁺ +2e ^- → CO+H ₂ O...(2)
2H ⁺ +2e ^- → H ₂ ...(3)

Next, a reaction process in which carbon dioxide (CO ₂ ) is reduced to generate hydroxide ions (OH ⁻ ) will be described. When a current is supplied from the power source 150 between the anode 111 and the cathode 121, water (H ₂ O) and carbon dioxide (CO ₂ ) are reduced near the cathode 121 to generate carbon monoxide (CO) and hydroxide ions (OH ⁻ ), as shown in the following formula (4). Furthermore, hydrogen is generated by water receiving electrons, as shown in the following formula (5). At this time, hydrogen may be generated simultaneously with carbon monoxide. The hydroxide ions (OH ⁻ ) generated by these reactions diffuse near the anode 111, and as shown in the following formula (6), the hydroxide ions (OH ⁻ ) are oxidized to generate oxygen (O ₂ ).

2CO ₂ +2H ₂ O+4e ^- → 2CO+4OH ^-... (4)
2H ₂ O+2e ^- → H ₂ +2OH ^-... (5)
4OH ^- → 2H ₂ O+O ₂ +4e ^-... (6)

The electrolysis cell 100 is not limited to being specialized for the reduction of carbon dioxide, but can also produce reduction products and hydrogen in any ratio, such as producing carbon monoxide and hydrogen in a 1:2 ratio, followed by a chemical reaction to produce methanol.

Hydrogen is a cheap and easily available raw material from water electrolysis and fossil fuels, so the ratio of hydrogen does not need to be high. From these perspectives, it is economically and environmentally preferable for the ratio of carbon monoxide to hydrogen to be at least 1, and preferably 1.5 or more.

The electrolysis device of the embodiment is not limited to a carbon dioxide electrolysis device, and may be, for example, a nitrogen electrolysis device. In the case of a nitrogen electrolysis device, ammonia can be generated by reducing nitrogen (N ₂ ) gas by the cathode 121. The configuration of the carbon dioxide electrolysis device can be appropriately applied to other configurations of the nitrogen electrolysis device.

In the electrolysis cell 100, a phenomenon is known in which potassium (K ⁺ ) ions in the electrolyte circulating on the anode flow path 112 side move to the cathode flow path 122 side, and the K ⁺ ions flow out of the cell from the outlet of the cathode flow path 122 together with steam and moisture generated in the cathode 121, resulting in a decrease in the electrolyte concentration. If the electrolyte concentration circulating on the anode 111 side decreases, the resistance of the electrolysis cell 100 increases, leading to problems such as performance degradation during long-term continuous operation of the electrolysis cell 100. In response to this, it is possible to return the liquid accumulated in a cathode discharge liquid recovery bottle called a trap on the outlet side of the cathode flow path 122 to an electrolyte tank that stores the electrolyte connected to the anode flow path 112 using a pump. This allows the K ⁺ ions contained in the cathode discharge liquid to be returned to the electrolyte with a reduced concentration, thereby suppressing the decrease in the electrolyte concentration.

However, when using a trap, a trap and a pump for moving the liquid from the trap to the electrolyte tank are required, and the system around the electrolytic cell 100 becomes complicated, and power is also required to drive the pump. Furthermore, since the discharge rate of the liquid discharged from the cathode flow path 122 is slower than the electrolyte circulation rate on the anode flow path 112 side, the timing of moving the liquid accumulated in the trap to the electrolyte tank by pumping becomes intermittent. In addition, it is known that the K ⁺ ion concentration of the cathode discharge liquid is higher than the K ⁺ ion concentration of the electrolyte. Therefore, since a high concentration of K ⁺ ion-containing liquid is intermittently dropped into the electrolyte tank, in this case, it takes time for the K ⁺ ions to diffuse in the electrolyte tank and the K ⁺ ion concentration to become uniform. It is preferable to perform the mechanism for avoiding such a decrease in the concentration of the electrolyte more efficiently.

In contrast, the electrolysis device 1 of the embodiment includes a tank 200, but does not include a trap or a pump for moving liquid from the trap to the electrolyte tank. FIG. 2 is a schematic diagram showing an example of the structure of the tank 200. The tank 200 includes a storage section 201, a storage section 202, a supply flow path 204, a discharge flow path 205, a supply flow path 206, a discharge flow path 207, and a discharge flow path 208.

The container 201 and the container 202 can contain a liquid including an anode solution. The container forming the container 201 and the container 202 may be made of glass, resin, metal, or the like. This container is a container that has high airtightness between gas and liquid. If the container is made of metal, it is preferable that an insulating coating is applied to the inside in order to avoid leakage current due to electrical conduction through the anode solution. The insulating coating may be resin, glass, or rubber, and is preferably highly durable. The container may be provided with a water level sensor at one or several places in the container to measure the height of the liquid level contained therein. In addition, the container may be provided with a sensor at one or several places in the container to measure the ion concentration or electrical conductivity of the liquid. In addition, the container may be provided with a sensor at one or several places in the container to measure the pressure or temperature inside the container. The operation of the electrolysis device 1 may be controlled by a controller or the like while referring to the values detected by these sensors.

The volume of the container is preferably large enough to hold the anode solution and condensed water required to operate the electrolysis device 1, and may be, for example, 1 L to 100 L, but is not limited to this range. The shape of the container is not particularly limited, but may be, for example, spherical, cylindrical, or rectangular.

At least one further storage section may be provided between storage section 201 and storage section 202. It is preferable that the height of the lower parts of these storage sections is gradually decreased. It is further preferable that the anode solution is constantly present in all of these storage sections.

In addition, a pipe for recovering gas may be connected to each of the upper parts of the multiple storage sections. This makes it difficult for the gas from the cathode flow path 122 and the gas from the anode flow path 112 to mix even if the total amount of liquid in the container decreases or increases for some reason, and allows the gas product to be recovered while maintaining a safe condition.

The partition 203 is provided between the storage section 201 and the storage section 202, and separates the storage section 201 from the storage section 202. The partition 203 has at least one opening 203a connecting the storage section 201 and the storage section 202. No pump is formed in the middle of the opening 203a. The material of the partition 203 may be a semipermeable membrane, polymer membrane, liquid junction, or porous material that allows liquid to pass but does not allow gas to pass easily, for example, a glass filter impregnated with liquid. An ion exchange membrane may also be used, for example, a cation exchange membrane such as Nafion or Flemion. The liquid junction may be, for example, a semipermeable membrane of animal origin such as a sintered glass layer, a cellulose layer, pulp, absorbent cotton, or fish skin, an ion exchange membrane, a solution having a condensed structure such as agar or gelatin, or the like. The opening 203a may be multiple.

The opening 203a allows liquid to pass through but not gas. This makes it possible to spatially separate gas components (e.g., CO, _CO2 , and hydrogen ( _H2 ) gas) that come out together with the fluid discharged from the outlet of the cathode flow channel 122 from gas components (e.g., oxygen ( _O2 ) and _CO2 gas) that come out together with the electrolytic solution discharged from the outlet of the anode flow channel 112. This allows valuable products (e.g., CO and _H2 gas) that are the products of the carbon dioxide electrolysis cell to be separated from the liquid and recovered, and further prevents the _H2 gas and _O2 gas from mixing, which is effective in terms of safety.

The storage section 201 and the storage section 202 may be asymmetrical with respect to the partition wall 203. The two spaces formed by the walls inside the container may have the same shape and volume, or may have different shapes and volumes. The volume of the storage section 201 is preferably smaller than the volume of the storage section 202, and further, the upper part 201a of the storage section 201 may be higher relative to the lower part 202b of the storage section 202 than the upper part 202a of the storage section 202. The lower part 201b of the storage section 201 may be inclined so as to be lower toward the storage section 202 in order to promote the movement of liquid from the storage section 201 to the storage section 202.

The supply flow path 204 connects the storage unit 201 and the outlet of the cathode flow path 122. The electrolysis device 1 can supply a fluid containing a cathode gas supplied from the cathode flow path 122 to the storage unit 201 via the supply flow path 204. It is preferable that the supply flow path 204 is provided at a position closer to the upper part 201a than to the lower part 201b of the storage unit 201. As a result, the liquid from the cathode flow path 122 accumulates in the lower part of the container, and the gas product from the cathode flow path 122 accumulates in the upper part of the container. FIG. 2 shows the supply flow path 204 provided in the upper part 201a as an example.

The discharge flow path 205 is connected to the storage unit 201. The electrolysis device 1 can discharge the gaseous reduction product in the storage unit 201 from the storage unit 201 via the discharge flow path 205. The discharge flow path 205 is preferably provided at a position closer to the upper part 201a of the storage unit 201 than to the lower part 201b. FIG. 2 shows, as an example, the discharge flow path 205 provided in the upper part 201a.

The supply flow path 206 connects the storage unit 202 to the outlet of the anode flow path 112. The electrolysis device 1 can supply a fluid containing an anode solution supplied from the anode flow path 112 to the storage unit 202 via the supply flow path 206. The supply flow path 206 may be provided at a position closer to the upper portion 202a of the storage unit 202 than to the lower portion 202b. FIG. 2 shows, as an example, the supply flow path 206 provided in the upper portion 202a.

The discharge flow path 207 is connected to the storage unit 202. The electrolysis device 1 can discharge the gaseous oxidation product supplied into the storage unit 202 through the discharge flow path 207 from the storage unit 202. The discharge flow path 207 may be provided at a position closer to the upper part 202a than to the lower part 202b of the storage unit 202, or closer to the lower part 202b than to the upper part 202a of the storage unit 202. FIG. 2 shows, as an example, the discharge flow path 207 provided in the upper part 202a.

The discharge flow path 208 connects the storage unit 202 and the anode supply unit 401. The electrolysis device 1 can discharge the liquid containing the anode solution in the storage unit 202 from the storage unit 202 to the anode supply unit 401 via the discharge flow path 208. It is preferable that the discharge flow path 208 is provided at a position closer to the lower part 202b than to the upper part 202a of the storage unit 202. FIG. 2 shows, as an example, the discharge flow path 208 provided on the side part 202c of the storage unit 202.

Each of the supply flow path 204, the discharge flow path 205, the supply flow path 206, the discharge flow path 207, and the discharge flow path 208 is a pipe. The pipe is formed, for example, using a material that can be applied to the container.

The cathode supply unit 301 is connected to the inlet of the cathode flow path 122. The cathode supply unit 301 can supply a cathode gas to the cathode flow path 122. In the case of a carbon dioxide electrolysis device, the cathode supply unit 301 can supply a cathode gas containing carbon dioxide gas to the cathode flow path 122. In the case of a nitrogen electrolysis device, the cathode supply unit 301 can supply a cathode gas containing nitrogen to the cathode flow path 122. The cathode supply unit 301 includes, for example, a tank that contains the cathode gas and a mass flow controller that adjusts the flow rate of the cathode gas supplied from the tank to the cathode flow path 122. The supply of the cathode gas by the cathode supply unit 301 may be controlled by a controller or the like in accordance with detection signals from a water level sensor, a pressure sensor, a temperature sensor, or a sensor that measures the ion concentration or conductivity of the liquid, which are provided in the container that forms the storage unit 201 and the storage unit 202.

The anode supply unit 401 connects the discharge flow path 208 and the inlet of the anode flow path 112. The anode supply unit 401 can supply the fluid containing the anode solution discharged from the discharge flow path 208 to the anode flow path 112. This allows the anode solution to be circulated. The anode supply unit 401 includes, for example, a pump. The flow rate of the liquid containing the anode solution supplied to the anode 111 by the pump can be adjusted. The supply of liquid by the anode supply unit 401 may be controlled by a controller or the like according to detection signals from a water level sensor, a pressure sensor, a temperature sensor, or a sensor that measures the ion concentration or conductivity of the liquid, which are provided in the containers that form the storage unit 201 and the storage unit 202.

Next, an example of a method for driving the tank 200 will be described. When the electrolyte solution that has moved from the supply flow path 204 to the cathode flow path 122 side together with the cathode gas is supplied, the fluid containing the liquid and gas generated on the cathode 121 side is pushed by the pressure of the raw material gas supplied to the cathode 121 side and accumulates below the storage section 201. In the storage section 201, gas-liquid separation occurs due to the effect of gravity, etc. The separated liquid generated on the cathode 121 side containing metal ions accumulates below the storage section 201. Meanwhile, the storage section 202 is made to contain liquid at a substantially constant water level. When a fluid containing an anode solution is supplied from the supply flow path 206 to the storage unit 202, and the electrolyte solution that has moved from the supply flow path 204 to the cathode flow path 122 side together with the cathode gas is supplied to the storage unit 201, the electrolysis device 1 is driven to form a height difference between the liquid levels 211 and 212 so that the height of the liquid level 211 of the liquid contained in the storage unit 201 relative to the lower part 202b of the storage unit 202 is higher than the height of the liquid level 212 of the liquid contained in the storage unit 202 relative to the lower part 202b of the storage unit 202. As a result, ions such as K ⁺ ions contained in the electrolyte solution move from the storage unit 201 to the storage unit 202 through the opening 203a.

As a result, for example, the liquid with a high K ⁺ ion concentration discharged from the outlet of the cathode flow path 122 and the electrolyte circulating on the anode flow path 112 side are mixed through the opening 203a. As a result, since the K ⁺ ions diffuse in the electrolyte, a large concentration gradient does not occur, the time until the K ⁺ ion concentration becomes uniform can be significantly shortened, and the electrolyte in the storage section 202 can be maintained at a high concentration. In addition, since the device configuration can be simplified, the installation area of the device can be made smaller, and further, since the configuration of the tank 200 does not require a trap or a pump for moving the liquid from the trap to the electrolyte tank, the power required to operate the pump can be reduced.

The structure of the tank 200 is not limited to the example structure shown in FIG. 2. FIGS. 3 and 4 are schematic diagrams showing other example structures of the tank 200.

The tank 200 shown in FIG. 3 differs from the tank 200 shown in FIG. 2 in that the opening 203a is formed using a pipe 231. The pipe 231 connects the storage section 201 and the storage section 202. The pipe 231 may be formed using, for example, a material that can be used for a container.

A valve controlled by an external signal may be provided in the pipe 231. The opening and closing of the valve is controlled by a controller or the like in accordance with detection signals from a water level sensor, a pressure sensor, a temperature sensor, or a sensor that measures the ion concentration or electrical conductivity of the liquid provided in the container.

Furthermore, the tank 200 shown in FIG. 3 differs from the tank 200 shown in FIG. 2 in that the height of the lower portion 201b relative to the lower portion 202b is made higher than that of the lower portion 202b, thereby forming a height difference between the liquid level 211 and the liquid level 212.

The tank 200 shown in FIG. 4 differs from the tank 200 shown in FIG. 2 in that the opening 203a is formed in a partition 232 that does not allow liquid and gas to pass through. The material of the partition 232 may be, for example, glass, resin, or metal. When the material of the partition 232 is metal, it is preferable that the partition 232 is electrically insulated from the outside of the container. The thickness of the partition 232 is not particularly limited as long as it is strong enough to withstand the pressure difference in the internal space of the container, and may be, for example, 1 mm to 50 cm, but is not limited to this range.

The opening 203a shown in FIG. 4 is provided at a position closer to the lower portion 201b of the storage portion 201 and the lower portion 202b of the storage portion 202 than to the upper portion 201a of the storage portion 201 and the upper portion 202a of the storage portion 202, respectively. The opening 203a may have a polygonal shape such as a triangle or a circle, or may be a combination of these. The shape of the opening 203a is preferably one that does not impede the movement of liquid, but the periphery of the opening 203a may be flat or may have protrusions.

The size of the opening 203a is preferably large enough not to impede the movement of liquid, and may be, for example, 1 mm to 10 cm, but is not limited to this range.

The number of openings 203a per unit area is preferably a value that does not impede the movement of liquid, and more preferably a value that maintains the strength of the partition wall 203.

The above embodiment is presented as an example and is not intended to limit the scope of the invention. The above embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. The above embodiment and its variations are included in the scope and gist of the invention, as well as in the scope of the invention and its equivalents described in the claims.

1...electrolysis device, 100...electrolysis cell, 111...anode, 112...anode flow path, 113...anode current collector, 114...flow path plate, 121...cathode, 122...cathode flow path, 123...cathode current collector, 124...flow path plate, 131...separator, 150...power source, 200...tank, 201...accommodation section, 201a...upper section, 201b...lower section, 202...accommodation section, 202a...upper section, 202b...lower section, 202c...side section, 203...partition wall, 203a...opening, 204...supply flow path, 205...discharge flow path, 206...supply flow path, 207...discharge flow path, 208...discharge flow path, 211...liquid level, 212...liquid level, 231...piping, 232...partition wall, 301...cathode supply section, 401...anode supply section.

Claims (14)

an electrolysis cell comprising a cathode, an anode, a cathode flow passage facing the cathode, and an anode flow passage facing the anode;
a tank having a first storage unit, a second storage unit, and an opening connecting the first storage unit and the second storage unit, the first storage unit and the second storage unit being capable of storing a liquid containing at least one ion, and forming a height difference between the first liquid level and the second liquid level such that a height of a first liquid level of the liquid stored in the first storage unit relative to a lower part of the second storage unit is higher than a height of a second liquid level of the liquid stored in the second storage unit relative to the lower part of the second storage unit, thereby transferring ions contained in the liquid from the first storage unit to the second storage unit via the opening;
a first flow path connecting an outlet of the cathode flow path and the first container;
a second flow passage connecting the second container and an outlet of the anode flow passage;
5. An electrolysis apparatus comprising: a) a first electrolysis tank; b) a first electrolysis tank; c) a second electrolysis tank; d) a first electrolysis tank; d) a second electrolysis tank; The electrolysis device according to claim 1, wherein the tank has a partition wall provided between the first storage section and the second storage section and having the opening. The electrolysis device according to claim 1 or 2, wherein the tank has a pipe having the opening. The electrolysis device according to claim 1 , wherein a lower portion of the first storage portion is provided at a higher position than a lower portion of the second storage portion. 5. The electrolysis device according to claim 1 , wherein the cathode is capable of reducing carbon dioxide to produce a carbon compound. 5. The electrolysis device according to claim 1 , wherein the cathode is capable of reducing nitrogen to produce ammonia. 7. The electrolysis device according to claim 1 , wherein the at least one ion comprises a potassium ion. A method for operating an electrolysis device, comprising the steps of:
The electrolysis device comprises:
an electrolysis cell comprising a cathode, an anode, a cathode flow passage facing the cathode, and an anode flow passage facing the anode;
a tank having a first storage section, a second storage section, and an opening connecting the first storage section and the second storage section, the first storage section and the second storage section being capable of storing a liquid containing at least one ion;
a first flow path connecting an outlet of the cathode flow path and the first container;
a second flow passage connecting the second container and an inlet of the anode flow passage;
and no trap and no pump for moving the liquid from the trap to the tank;
The driving method includes:
A method for driving an electrolytic device, comprising: forming a height difference between the first liquid level and the second liquid level such that a height of a first liquid level of the liquid contained in the first storage unit relative to a lower part of the second storage unit is higher than a height of a second liquid level of the liquid contained in the second storage unit relative to the lower part of the second storage unit, thereby transferring ions contained in the liquid from the first storage unit to the second storage unit through the opening. The driving method according to claim 8 , wherein the tank has a partition wall provided between the first container portion and the second container portion and having the opening. The driving method according to claim 8 or 9 , wherein the tank has a pipe having the opening. 11. The driving method according to claim 8 , wherein a lower portion of the first housing portion is provided at a higher position than a lower portion of the second housing portion. The driving method according to claim 8 , wherein the cathode reduces carbon dioxide to produce a carbon compound. The driving method according to claim 8 , wherein the cathode reduces nitrogen to produce ammonia. The method according to claim 8 , wherein the at least one ion includes a potassium ion.

Images