Water electrolysis cell, water electrolysis stack, water electrolysis device, and system for capturing carbon dioxide gas

Abstract

This water electrolysis cell is used for releasing carbon dioxide from an anode-side solution. The water electrolysis cell comprises a vessel, a partition, an anode, a cathode, and an electricity supply part. The partition separates a space inside the water electrolysis cell into an anode-side solution chamber and a cathode-side solution chamber. The anode can be in contact with an anode-side solution placed in the anode-side solution chamber and comprising sodium ions, hydrogen carbonate ions, carbonate ions, chloride ions, and water. The cathode can be in contact with a cathode-side solution placed in the cathode-side solution chamber and comprising water. The partition is made of a sodium-ion conductor.

Description

Water electrolysis cell, water electrolysis stack, water electrolysis device and carbon dioxide gas recovery system

[0001] The present invention relates to a water electrolysis cell, a water electrolysis stack, a water electrolysis device, and a carbon dioxide gas recovery system. This application claims priority to Japanese Application No. 2024-153359, filed September 5, 2024, and incorporates the entire contents of said Japanese application by reference.

[0002] Technologies for capturing carbon dioxide gas from the atmosphere have been developed to achieve carbon neutrality. In recent years, a technology for capturing carbon dioxide dissolved in seawater has been developed for the purpose of capturing carbon dioxide gas from the atmosphere (see Patent Document 1 below). This technology takes advantage of the fact that the carbon dioxide gas concentrations in seawater and the atmosphere are in equilibrium, and reduces the carbon dioxide gas concentration in the atmosphere by releasing and capturing carbon dioxide gas from seawater, which dissolves an equal amount of carbon dioxide gas from the atmosphere into seawater.

[0003] The technology described in Patent Document 1 uses a bipolar membrane (BPM) to generate hydrogen ions from seawater and supply them to the seawater in the cathode vessel. Sodium ions are also removed from the seawater in the cathode vessel using a monovalent cation exchange membrane (M-CEM). This method acidifies the seawater in the cathode vessel, converting bicarbonate ions, carbonate ions, carbon dioxide, or carbon dioxide dissolved in the seawater into carbon dioxide gas and recovering it.

[0004] US 2022 / 0144673

[0005] In the above technology, it is required to increase the efficiency of releasing carbon dioxide gas into seawater.

[0006] The present disclosure provides a water electrolysis cell, a water electrolysis stack, a water electrolysis device, and a carbon dioxide gas recovery system that can increase the efficiency of carbon dioxide gas release from the anode-side solution.

[0007] The water electrolysis cell disclosed herein releases carbon dioxide from an anode-side solution. The water electrolysis cell includes a partition, an anode, and a cathode. The partition separates the space within the water electrolysis cell into an anode-side solution chamber and a cathode-side solution chamber. The anode is disposed in the anode-side solution chamber and is capable of contacting an anode-side solution containing sodium ions, bicarbonate ions, carbonate ions, chloride ions, and water. The cathode is disposed in the cathode-side solution chamber and is capable of contacting a cathode-side solution containing water. The partition is made of a sodium ion conductor.

[0008] FIG. 1 is a graph showing the relationship between the amount of bicarbonate ions and carbonate ions present and the carbon dioxide gas release efficiency. FIG. 2 is a schematic diagram of a first specific example of a carbon dioxide gas recovery system. FIG. 3 is a schematic diagram of a second specific example of a carbon dioxide gas recovery system. FIG. 4 is a schematic diagram of a third specific example of a carbon dioxide gas recovery system. FIG. 5 is an exploded perspective view of a water electrolysis stack of a fourth specific example. FIG. 6 is a perspective view of a water electrolysis stack of a fourth specific example. FIG. 7 is a perspective view of a water electrolysis cell of a fifth specific example. FIG. 8 is a schematic diagram of a carbon dioxide gas recovery system of a sixth specific example. FIG. 9 is a schematic diagram of a carbon dioxide gas recovery system of Example 1. FIG. 10 is a graph showing the relationship between the pH of the anode-side solution and the time of water electrolysis in Example 1 and Comparative Example 1. FIG. 11 is a graph showing the relationship between the concentration of carbon dioxide gas inside the carbon dioxide gas measuring unit and the time of water electrolysis in Example 1 and Comparative Example 1.

[0009] [Summary of the embodiment] A water electrolysis cell according to the present disclosure (1) releases carbon dioxide from an anode-side solution. The water electrolysis cell includes a partition, an anode, and a cathode. The partition separates an anode-side solution chamber from a cathode-side solution chamber. The anode is disposed in the anode-side solution chamber and is capable of contacting an anode-side solution containing sodium ions, bicarbonate ions, carbonate ions, chloride ions, and water. The cathode is disposed in the cathode-side solution chamber and is capable of contacting a cathode-side solution containing water. The partition is made of a sodium ion conductor.

[0010] In this water electrolysis cell, only sodium ions are conducted within the partition. That is, in this water electrolysis cell, only sodium ions are transferred from the anode-side solution to the cathode-side solution without the transfer of hydrogen ions. As a result, the anode-side solution becomes acidic (pH decreases) and the cathode-side solution becomes alkaline (pH increases) due to the electrolysis of the anode-side solution and the cathode-side solution. Therefore, as can be seen from FIG. 1 , as the pH of the anode-side solution (e.g., seawater) decreases, carbon dioxide gas (CO ) is released from the anode-side solution. ２ ) can be released more efficiently.

[0011] (2) In the above (1), the sodium ion conductor constituting the partition may be NASICON. If the sodium ion conductor constituting the partition is NASICON, the transfer of hydrogen ions from the anode solution to the cathode solution can be reliably suppressed while maintaining high sodium ion conduction efficiency.

[0012] (3) In the above-described (1), the cathode solution may further contain sodium ions, bicarbonate ions, carbonate ions, and chloride ions. In this configuration, the anode solution and the cathode solution each contain sodium ions, bicarbonate ions, carbonate ions, chloride ions, and water. This allows the anode solution and the cathode solution to have the same composition. This simplifies the configuration.

[0013] (4) In the above (1), the anode-side solution and the cathode-side solution may be seawater. In this water electrolysis cell, seawater can be used as both the anode-side solution and the cathode-side solution.

[0014] (5) In the water electrolysis cell described above in (1), the partition, the anode, and the cathode may each have a flat plate shape, and the partition, the anode, and the cathode may be arranged so that their respective main planes are parallel to each other. In this water electrolysis cell, the partition, the anode, and the cathode can be arranged compactly.

[0015] (6) In the above-mentioned (1), the partition may have a cylindrical shape having a first axis as a central axis. The anode may have a cylindrical shape having a second axis as a central axis in common with the first axis, overlap with the partition as viewed in the radial direction, and have a diameter different from that of the partition. The cathode may have a cylindrical shape having a third axis as a central axis in common with the first axis, overlap with the partition as viewed in the radial direction, and have a diameter different from that of the partition. The anode, the partition, and the cathode may be arranged in this order as viewed in the radial direction. In this water electrolysis cell, the anode, the partition, and the cathode can be compactly arranged in the first direction. With this water electrolysis cell, the anode-side solution or the cathode-side solution can flow inside the partition along the first direction.

[0016] (7) A water electrolysis stack according to the present disclosure includes a plurality of water electrolysis cells according to any one of (1) to (6) arranged side by side, and a separator separating adjacent water electrolysis cells. Because the water electrolysis stack includes a plurality of water electrolysis cells, the amounts of anode-side solution and cathode-side solution that can be used for water electrolysis can be increased, thereby improving the efficiency of carbon dioxide gas release.

[0017] (8) A water electrolysis device according to the present disclosure includes the water electrolysis stack according to (7) above, and a power source electrically connected to one anode and one cathode.

[0018] (9) In the above-mentioned (8), the separator may be made of a conductive material, and adjacent cells may be connected in series. In this water electrolysis device, the carbon dioxide gas recovery efficiency per volume density can be increased.

[0019] A carbon dioxide gas recovery system according to the present disclosure (10) includes the water electrolysis cell according to the above (8) and a recovery unit communicating with the anode solution chamber for recovering carbon dioxide gas. According to this carbon dioxide gas recovery system, the carbon dioxide gas can be recovered in the recovery unit.

[0020] (11) The system of (10) above further includes a concentration / removal device. The concentration / removal device is connected to the anode-side solution chamber and the cathode-side solution chamber of the water electrolysis apparatus. Seawater concentrated by the concentration / removal device may be supplied to the anode-side solution chamber, and removed water from which seawater components have been removed or partially removed may be supplied to the cathode-side solution chamber. In this carbon dioxide gas recovery system, the amount of seawater components flowing into the cathode-side solution chamber can be reduced or eliminated.

[0021] [Specific Examples of Embodiments] [First Specific Example] A first specific example of a water electrolysis cell and a carbon dioxide gas recovery system according to the present disclosure will be described with reference to Fig. 2. Fig. 2 is a schematic diagram of the first specific example of the carbon dioxide gas recovery system.

[0022] [Carbon dioxide gas recovery system 1] The carbon dioxide gas recovery system 1 includes a filter 2, a water electrolysis cell 3, a power source 70, a carbon dioxide gas recovery unit 4 as an example of a recovery unit, and a hydrogen gas recovery unit 5. The carbon dioxide gas recovery system 1 may further include a pump (not shown). In the carbon dioxide gas recovery system 1, an anode side solution 38 and a cathode side solution 39 (described below) flow through the water electrolysis cell 3 based on the drive of the pump. Hereinafter, the upstream side and downstream side of the flow direction of the anode side solution 38 and the cathode side solution 39 will simply be referred to as the upstream side and the downstream side, respectively. The filter 2 is disposed upstream of the water electrolysis cell 3. The filter 2 removes solid matter from the anode side solution 38 and the cathode side solution 39.

[0023] [Water Electrolysis Cell 3] The water electrolysis cell 3 is used to release carbon dioxide gas. In a first specific example, the water electrolysis cell 3 is used to release carbon dioxide gas and hydrogen gas. The water electrolysis cell 3 includes an anode-side solution chamber inlet 311, an anode-side solution chamber outlet 312, a cathode-side solution chamber inlet 313, a cathode-side solution chamber outlet 314, a partition 32, an anode 33, and a cathode 34.

[0024] [Anode side solution chamber inlet 311, anode side solution chamber outlet 312, cathode side solution chamber inlet 313, and cathode side solution chamber outlet 314] The anode side solution 38 flows into the water electrolysis cell 3 through the anode side solution chamber inlet 311. The anode side solution chamber outlet 312 is located downstream of the anode side solution chamber inlet 311. The cathode side solution 39 flows into the water electrolysis cell 3 through the cathode side solution chamber inlet 313. The cathode side solution chamber outlet 314 is located downstream of the cathode side solution chamber inlet 313. The anode side solution chamber outlet 312 and the cathode side solution chamber outlet 314 are configured to prevent cross-leakage (mixing) between carbon dioxide gas released from the anode side solution 38 and hydrogen gas released from the cathode side solution 39.

[0025] [Divider 32] The divider 32 is disposed within the water electrolysis cell 3. The divider 32 divides the space 315 within the water electrolysis cell 3 into an anode-side solution chamber 36 and a cathode-side solution chamber 37. The anode-side solution chamber 36 and the cathode-side solution chamber 37 are separated by the divider 32. In a first specific example, the divider 32 has a plate, sheet, or membrane shape. The divider 32 extends along the flow direction of at least the anode-side solution 38 and the cathode-side solution 39. The thickness of the divider 32 is 1 μm or more and 5 mm or less.

[0026] The partition 32 is made of a sodium ion conductor. The sodium ion conductor is capable of conducting at least sodium ions. The sodium ion conductor does not conduct hydrogen ions or the conduction of hydrogen ions is suppressed. In a first specific example, the sodium ion conductor may conduct alkali metal ions (other than sodium ions) in addition to sodium ions.

[0027] On the other hand, M-CEM (monovalent cation exchange membrane) is commonly used as a membrane that allows sodium ions to pass through (see, for example, Patent Document 1). However, M-CEM generally also allows hydrogen ions, which are monovalent cations, to pass through. In contrast, the sodium ion conductor (NASICON, described below) in the present disclosure does not allow hydrogen ions to pass through, or the amount of hydrogen ions that pass through is suppressed compared to that of sodium ions.

[0028] The sodium ion conductor constituting the partition 32 is an inorganic or organic material, and is preferably NASICON. NASICON is represented by the following formula: Na １＋ｘ Zr ２ (SiO ４ ) ｘ (P.O. ４ ) ３－ｘ In the above formula, 0≦x≦3 is satisfied, and from the viewpoint of sodium ion conductivity, 1.8≦x≦2.2 is preferably satisfied.

[0029] [Anode 33] The anode 33 is disposed in the anode-side solution chamber 36. In a first specific example, the anode 33 has a flat plate shape. In the first specific example, the anode 33 faces the partition 32. The anode 33 is located away from the partition 32. The anode 33 can be in contact with the anode-side solution 38. Specifically, the anode 33 is in contact with the anode-side solution 38. The anode 33 is made of a conductive material. An example of a conductive material that makes up the anode 33 is carbon.

[0030] [Anode Side Solution 38] The anode side solution 38 contains sodium ions, bicarbonate ions (HCO ３ － ), carbonate ions (CO ３ ２－ ), chloride ions (Cl － ) and water. In the anode-side solution 38, sodium ions, bicarbonate ions, carbonate ions, and chloride ions are dissolved in the water. The bicarbonate ions and carbonate ions are present in the anode-side solution 38 due to carbon dioxide gas in the air dissolving in the water. When the anode-side solution 38 is seawater, the sodium ions and chloride ions are inevitably present in the anode-side solution 38. The anode-side solution 38 may be seawater. Seawater contains alkali metal ions other than sodium ions in addition to sodium ions, bicarbonate ions, carbonate ions, chloride ions, and water.

[0031] [Cathode 34] The cathode 34 is disposed in the cathode-side solution chamber 37. In a first specific example, the cathode 34 has a flat plate shape. In a first specific example, the cathode 34 faces the partition 32. In a first specific example, the cathode 34 is located away from the partition 32. The cathode 34 and the anode 33 sandwich the partition 32. The cathode 34 can come into contact with the cathode-side solution 39. Specifically, the cathode 34 is in contact with the cathode-side solution 39. The cathode 34 is made of a conductive material. An example of a conductive material that makes up the cathode 34 is a Ni—Fe alloy.

[0032] [Cathode-side solution 39] The cathode-side solution 39 contains water. Preferably, the cathode-side solution 39 further contains sodium ions. In addition to water and sodium ions, the cathode-side solution 39 may further contain bicarbonate ions, carbonate ions, and chloride ions. The cathode-side solution 39 may be seawater. When both the anode-side solution 38 and the cathode-side solution 39 are seawater, the water electrolysis cell 3 functions as a "seawater electrolysis cell."

[0033] [Power supply 70] The power supply 70 is electrically connected to each of the anode 33 and the cathode 34. The power supply 70 and the water electrolysis cell 3 constitute a water electrolysis apparatus 100. When both the anode-side solution 38 and the cathode-side solution 39 are seawater, the water electrolysis apparatus 100 is a seawater electrolysis apparatus and also an apparatus for acidifying the anode-side solution 38.

[0034] [Carbon dioxide gas recovery unit 4] The carbon dioxide gas recovery unit 4 communicates with the anode-side solution chamber 36. The carbon dioxide gas recovery unit 4 is connected to the anode-side solution chamber outlet 312. The carbon dioxide gas recovery unit 4 recovers carbon dioxide gas released from the anode-side solution 38 that has been acidified by water electrolysis. Examples of the carbon dioxide gas recovery unit 4 include a gas-liquid separator that uses gravity, a gas-liquid separation filter, or a combination thereof.

[0035] [Hydrogen Gas Recovery Unit 5] The hydrogen gas recovery unit 5 is connected to the cathode side solution chamber 37 via the cathode side solution chamber outlet 314. The hydrogen gas recovery unit 5 recovers hydrogen gas generated from the cathode side solution 39 by water electrolysis and releases the hydrogen gas.

[0036] [Recovery of Carbon Dioxide Gas and Generation of Hydrogen Gas Using Carbon Dioxide Gas Recovery System 1] The anode side solution 38 and the cathode side solution 39 each pass through the filter 2 and are then contained in the anode side solution chamber 36 and the cathode side solution chamber 37, respectively.

[0037] When the power supply 70 is driven, sodium ions are conducted through the partition 32 to form an electric circuit, and a water electrolysis reaction occurs between the anode side solution 38 and the cathode side solution 39 .

[0038] In the anode side solution 38, hydrogen ions increase as shown in the following formula (1): ２ O → 4H ＋ +O ２ +4e － (1) Due to an increase in hydrogen ions in the anode side solution 38, the anode side solution 38 becomes acidic (the pH decreases). As a result, carbon dioxide gas is generated from the anode side solution 38 containing bicarbonate ions and carbonate ions, as shown in formulas (2) and (3). HCO ３ － +H ＋ →CO ２ +H ２ O (2) CO ３ ２－ +2H ＋ →CO ２ +H ２ O (3)

[0039] In the cathode solution 39, hydrogen is generated as shown in the following formula (4): ２ O+4e － →2H ２ +4OH － (4)

[0040] In a conventional configuration using a cation exchange membrane, hydrogen ions, which are monovalent cations like the sodium ions that move through the partition 32, migrate (leak) from the anode-side solution 38 through the partition 32 into the cathode-side solution 39. When hydrogen ions leak into the cathode-side solution 39, the hydrogen ion concentration in the anode-side solution 38 decreases. This prevents the anode-side solution 38 from becoming acidic (preventing a decrease in pH). As a result, as can be seen from FIG. 1 , the amount of carbon dioxide gas released according to equations (2) and (3) decreases.

[0041] However, in the present disclosure, by using a sodium ion conductor that does not conduct hydrogen ions or has suppressed hydrogen ion conduction as the material of the partition 32, migration (leakage) of hydrogen ions in the anode-side solution 38 to the cathode-side solution 39 through the partition 32, as in the conventional configuration, is eliminated or suppressed. Therefore, as described above, the hydrogen ion concentration in the anode-side solution 38 does not decrease. The anode-side solution 38 becomes acidic (the pH decreases). Then, as can be seen from FIG. 1 , carbon dioxide gas (CO ) is released according to the above formulas (2) and (3). ２ ) can be released more efficiently.

[0042] [Modification of the First Specific Example] In the carbon dioxide gas recovery system 1 of the first specific example, the anode side solution 38 and the cathode side solution 39 (seawater) are continuously flowed through the water electrolysis cell 3 by driving a pump. In other words, the water electrolysis cell 3 of the first specific example is of a continuous type. On the other hand, in the carbon dioxide gas recovery system 1 of the modification, the driving of the pump and the introduction of the anode side solution 38 and the cathode side solution 39 may be temporarily stopped to implement an operation method similar to that of a batch type.

[0043] [Second Specific Example] A second specific example of the water electrolysis cell and carbon dioxide gas recovery system according to the present disclosure will be described with reference to Fig. 3. The second specific example is a modification of the first specific example. Fig. 3 is a schematic diagram of the second specific example of the carbon dioxide gas recovery system.

[0044] In the second specific example, the anode-side solution 38 and the cathode-side solution 39 are concentrated water 381 and removed water 391, respectively. The concentrated water 381 is sometimes called salt water. The removed water 391 is sometimes called fresh water. The concentrated water 381 and the removed water 391 will be described later.

[0045] The carbon dioxide gas recovery system 1 further includes a concentration / removal device 7. The concentration / removal device 7 is connected to the anode-side solution chamber 36 and the cathode-side solution chamber 37. The concentration / removal device 7 is disposed between the filter 2 and the anode-side solution chamber 36 in the flow direction of the anode-side solution 38. The concentration / removal device 7 is disposed between the filter 2 and the cathode-side solution chamber 37 in the flow direction of the cathode-side solution 39. In a second specific example, the concentration / removal device 7 may be, for example, a reverse osmosis membrane device. The concentration / removal device 7 concentrates seawater to produce concentrated water 381 and supplies the concentrated water 381 to the anode-side solution chamber 36. The concentration / removal device 7 supplies removed water 391, from which seawater components have been removed or partially removed, to the cathode-side solution chamber 37.

[0046] [Third Specific Example] A third specific example of the water electrolysis cell and carbon dioxide gas recovery system according to the present disclosure will be described with reference to Fig. 4. The third specific example is a modification of the first specific example. Fig. 4 is a schematic diagram of the third specific example of the carbon dioxide gas recovery system.

[0047] The anode 33 and the cathode 34 are each in contact with the partition 32. The anode 33 is a mesh that can supply an anode-side solution 38 to the surface of the partition 32. The cathode 34 is a mesh that can supply a cathode-side solution 39 to the surface of the partition 32.

[0048] [Fourth Specific Example] A fourth specific example of a water electrolysis stack and a carbon dioxide gas recovery system according to the present disclosure will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is an exploded perspective view of a water electrolysis stack according to the fourth specific example. Fig. 6 is a perspective view of a water electrolysis stack according to the fourth specific example.

[0049] The water electrolysis stack 10 includes multiple water electrolysis cells 3A, 3B, and 3C and multiple separators 9A and 9B. In the water electrolysis stack 10, the multiple water electrolysis cells 3 (3A, 3B, and 3C) and the multiple separators 9 (9A and 9B) are arranged alternately. In other words, the multiple water electrolysis cells 3A, 3B, and 3C are arranged side by side. The water electrolysis cells 3A, 3B, and 3C are connected in series. The separator 9A separates adjacent water electrolysis cells 3A and 3B. The separator 9B separates adjacent water electrolysis cells 3B and 3C. Because the water electrolysis stack 10 includes multiple stacked water electrolysis cells 3A, 3B, and 3C, it is sometimes referred to as a water electrolysis stack module. The water electrolysis stack 10 and the power source 70 constitute a water electrolysis device 100.

[0050] Each of the separators 9A, 9B has a plate shape. Each of the separators 9A, 9B has a first main surface 91 and a second main surface 92. The first main surface 91 and the second main surface 92 each extend along a plane perpendicular to the arrangement direction AD. The arrangement direction AD is the direction in which the multiple water electrolysis cells 3A, 3B, 3C are arranged. The arrangement direction AD is synonymous with the stacking direction.

[0051] The first main surface 91 of the separator 9A faces the partition 32 of the water electrolysis cell 3A. The cathode 34 of the water electrolysis cell 3A is sandwiched between the separator 9A and the partition 32 of the water electrolysis cell 3A. The cathode 34 is not directly connected to the power source 70. A plurality of grooves 911 are formed in the first main surface 91. The grooves 911 and the partition 32 form a cathode-side solution chamber 37 (see FIG. 6 ). The grooves 911 are spaced apart from one another. Each of the grooves 911 extends in the second direction D2. A first end and a second end of each groove 911 in the second direction D2 correspond to the cathode-side solution chamber inlet 313 and the cathode-side solution chamber outlet 314, respectively. The second end is located opposite the first end. When viewed in the arrangement direction AD, the separator 9A and the partition 32 are larger than the cathode 34. To prevent hydrogen gas generated from the cathode-side solution 39 and the cathode-side solution 39 from leaking to the periphery of the cell, the peripheral region of the first main surface 91 of the separator 9A, other than the grooves 911, is in contact (close contact) with the partition 32 via an airtight material (not shown). The separator 9A is made of a conductive material.

[0052] The second main surface 92 of the separator 9A faces the partition 32 of the water electrolysis cell 3B. The anode 33 of the water electrolysis cell 3B is sandwiched between the separator 9A and the partition 32 of the water electrolysis cell 3B. The anode 33 is not directly connected to the power source 70. Grooves 921 are formed in the second main surface 92. The grooves 921 are spaced apart from one another. Each of the grooves 921 extends in the third direction D3. The third direction D3 is perpendicular to the alignment direction AD and the second direction D2. The third and fourth ends of the groove 921 in the third direction D3 are the anode-side solution chamber inlet 311 (see the dashed line in FIG. 5 ) and the anode-side solution chamber outlet 312, respectively. The fourth end is located opposite the third end. When viewed in the alignment direction AD, the separator 9A and the partition 32 are larger than the anode 33. In order to prevent the carbon dioxide gas generated from the anode side solution 38 and the anode side solution 38 from leaking to the periphery of the cell, the peripheral region of the second main surface 92 of the separator 9A, other than the groove 921, is in contact (closely adhered) with the partition portion 32 via an airtight material (not shown).

[0053] The water electrolysis cell 3A includes a first end plate 81. The water electrolysis cell 3C includes a second end plate 83. The first end plate 81 is disposed on the anode 33 side of the water electrolysis cell 3A. The first end plate 81 is electrically connected to the power source 70. The first end plate 81 is in contact with and electrically connected to the separator 9A. The first end plate 81 has a third main surface 811. The third main surface 811 faces the anode 33 of the water electrolysis cell 3A. A plurality of grooves 812 are formed in the third main surface 811. The plurality of grooves 812, together with the partition 32 of the water electrolysis cell 3A, form the anode-side solution chamber 36 (see FIG. 6 ) of the water electrolysis cell 3A.

[0054] The second end plate 83 is disposed on the cathode 34 side of the water electrolysis cell 3C. The second end plate 83 is electrically connected to the power source 70. The second end plate 83 is in contact with and electrically connected to the separator 9B. The second end plate 83 has a fourth main surface 831. The fourth main surface 831 faces the cathode 34 of the water electrolysis cell 3C. A plurality of grooves 832 are formed in the fourth main surface 831. The plurality of grooves 832, together with the partition 32 of the water electrolysis cell 3C, form a cathode-side solution chamber 37 (see FIG. 6 ) of the water electrolysis cell 3C.

[0055] [Fifth Specific Example] A fifth specific example of a water electrolysis cell according to the present disclosure will be described with reference to Fig. 7. The fifth specific example is a modification of the first specific example. Fig. 7 is a perspective view of the water electrolysis cell according to the fifth specific example.

[0056] In the water electrolysis cell 3 of the fifth specific example, the partition 32 has a cylindrical shape. The cylinder of the partition 32 has a first axis A1, which is the central axis. The first axis A1 is aligned with the first direction D1. The partition 32 has a fifth end 321 and a sixth end 322. The fifth end 321 is an anode-side solution inlet. The sixth end 322 is an anode-side solution outlet. The sixth end 322 is located on the opposite side of the fifth end 321 in the first direction D1.

[0057] The anode 33 has a cylindrical shape. The cylinder of the anode 33 has a second axis A2, which is the central axis. The second axis A2 is common to the first axis A1. The anode 33 overlaps with the partition portion 32 when viewed in the radial direction. The anode 33 has a diameter different from that of the partition portion 32. In a fifth specific example, the anode 33 has a diameter smaller than that of the partition portion 32. The anode 33 is located on the inner circumferential side of the partition portion 32. The anode 33 may contact the inner circumferential surface of the partition portion 32.

[0058] The cathode 34 has a cylindrical shape. The cylinder of the cathode 34 has a third axis A3, which is the central axis. The third axis A3 is common to the first axis A1. The cathode 34 overlaps with the partition 32 when viewed in the radial direction. The cathode 34 has a diameter different from that of the partition 32. In a fifth specific example, the cathode 34 has a diameter larger than that of the partition 32. The cathode 34 is located on the outer periphery of the partition 32. The cathode 34 may be in contact with the outer periphery of the partition 32. When viewed in the radial direction, the anode 33, the partition 32, and the cathode 34 are aligned. In the fifth specific example, the anode 33, the partition 32, and the cathode 34 are aligned in this order toward the outside in the radial direction.

[0059] In the fifth specific example, the anode side solution 38 (see FIG. 2) flows along the first direction D1 inside the partition part 32. The cathode side solution 39 (see FIG. 2) flows outside the partition part 32.

[0060] [Modification of the Fifth Specific Example] The cathode 34, the partition 32, and the anode 33 may be arranged in this order toward the outside in the radial direction.

[0061] [Sixth Specific Example] A sixth specific example of the water electrolysis cell, water electrolysis stack, and carbon dioxide gas recovery system according to the present disclosure will be described with reference to Fig. 8. Fig. 8 is a schematic diagram of the carbon dioxide gas recovery system according to the sixth specific example. In Fig. 8, some cells are depicted in cross section.

[0062] The carbon dioxide gas recovery system 1 includes a housing 310 , a water electrolysis stack 10 , a power source 70 , a separator 9 , a carbon dioxide gas recovery unit 4 , and a hydrogen gas recovery unit 5 .

[0063] The housing 310 includes an electrolytic container 3101 and a collection container 3102. The electrolytic container 3101 includes a first side wall 331, a second side wall 332, a support wall 333, an opposing wall 334, and a separator 9. A cathode-side solution chamber inlet 313 is formed in the first side wall 331. The second side wall 332 is located downstream of the first side wall 331. An anode-side solution chamber outlet 312 and a cathode-side solution chamber outlet 314 are formed in the second side wall 332. The support wall 333 connects the first side wall 331 and the second side wall 332. A plurality of anode-side solution chamber inlets 311 are fixed to the support wall 333. The peripheries of the plurality of anode-side solution chamber inlets 311 (fifth end 321) are sealed. The opposing wall 334 faces the support wall 333. The opposing wall 334 is positioned away from the support wall 333. The separator 9 is positioned between the support wall 333 and the opposing wall 334. The separator 9 is connected to the first side wall 331 and the second side wall 332. The sixth ends 322 of the plurality of partitions 32 are fixed to the separator 9. The peripheries of the plurality of sixth ends 322 are sealed. The support wall 333 and the separator 9 fix each of the plurality of partitions 32. The separator 9 may be made of an insulating material.

[0064] A plurality of first regions 41 are formed inside the plurality of partitions 32, respectively. A second region 42 is formed between the opposing wall 334 and the separator 9. The second region 42 is in communication with the plurality of first regions 41. The plurality of first regions 41 and the one second region 42 are included in the anode-side solution chamber 36. In other words, the plurality of first regions 41 and the one second region 42 constitute the anode-side solution chamber 36. A single cathode-side solution chamber 37 is formed outside the plurality of partitions 32, between the first side wall 331, the second side wall 332, the support wall 333, the opposing wall 334, and the separator 9. The second region 42, which is part of the anode-side solution chamber 36, and the cathode-side solution chamber 37 are separated by the separator 9.

[0065] The recovery container 3102 is formed with a first flow path 351, a second flow path 361, and a mixing flow path 371. The first flow path 351 communicates with the second region 42 (part of the anode-side solution chamber 36) via the anode-side solution chamber outlet 312. A carbon dioxide gas recovery unit 4 is disposed midway along the first flow path 351. The second flow path 361 communicates with the cathode-side solution chamber 37 via the cathode-side solution chamber outlet 314. A hydrogen gas recovery unit 5 is disposed midway along the second section 72. The mixing flow path 371 communicates with the first flow path 351 and the second flow path 361. The mixing flow path 371 communicates with the outside of the container via an outlet 372.

[0066] The water electrolysis stack 10 is disposed in an electrolysis vessel 3101. The water electrolysis stack 10 includes a plurality of water electrolysis cells 3A, 3B, 3C, and 3D. The water electrolysis cells 3A, 3B, 3C, and 3D are arranged in parallel along a plane perpendicular to the first direction D1. The water electrolysis cells 3A, 3B, 3C, and 3D are spaced apart from one another along the plane perpendicular to the first direction D1. Each of the fifth ends 321 is supported by a support wall 333. The sixth ends 322 are supported by a single separator 9. The anodes 33 and the cathodes 34 form a series circuit. The anode 33 (33A) (not shown in FIG. 8 ) of the water electrolysis cell 3A located at the seventh end of the series circuit and the cathode 34 (34D) of the water electrolysis cell 3D located at the eighth end of the series circuit are each electrically connected to a power source 70. The cathode 34 (e.g., 34A) of the first water electrolysis cell 3 (e.g., 3A) and the anode 33 (e.g., 33B) of the second water electrolysis cell 3 (e.g., 3B) adjacent to the adjacent first water electrolysis cell 3 in the series circuit are electrically connected to each other. Although not shown, the anodes 33 and cathodes 34 of multiple water electrolysis cells 3A, 3B, 3C, and 3D may form a parallel circuit. The water electrolysis stack 10 and the power source 70 constitute a water electrolysis apparatus 100.

[0067] In this sixth example, when the power supply 70 is driven, a voltage is applied to the water electrolysis cells 3A, 3B, 3C, and 3D. As a result, water electrolysis occurs in the anode solution 38 on the inner periphery of each of the water electrolysis cells 3A, 3B, 3C, and 3D, and in the cathode solution 39 on the outer periphery of each of the water electrolysis cells 3A, 3B, 3C, and 3D (on the outer periphery of the cell).

[0068] In the multiple first regions 41 in the anode-side solution chamber 36, the anode-side solution 38 becomes acidic and generates carbon dioxide gas (see formulas (1) to (3)), and is collected from the first regions 41 to the second regions 42. The anode-side solution 38 then enters the carbon dioxide gas recovery unit 4. In the carbon dioxide gas recovery unit 4, the carbon dioxide gas is separated from the anode-side solution 38 and recovered.

[0069] In the cathode solution chamber 37, the cathode solution 39 becomes alkaline and generates hydrogen gas (see formula (4)). The cathode solution 39 enters the hydrogen gas recovery unit 5. In the hydrogen gas recovery unit 5, the hydrogen gas is separated from the cathode solution 39 and recovered.

[0070] The acidic anode side solution 38 from which carbon dioxide gas has been recovered and the alkaline cathode side solution 39 from which hydrogen gas has been recovered are mixed and neutralized in the mixing flow path 371, and then discharged outside the housing 310 through the outlet 372.

[0071] [Example 1] A carbon dioxide gas recovery system 1 was prepared according to the first specific example described above, as shown in Fig. 9. Fig. 9 is a schematic diagram of the carbon dioxide gas recovery system of Example 1.

[0072] The carbon dioxide gas recovery system 1 is provided with a carbon dioxide gas measurement unit 40 instead of the carbon dioxide gas recovery unit 4. The carbon dioxide gas measurement unit 40 includes a first container 46, a first fan 47, and a carbon dioxide gas measurement instrument 43. The partition 32 is made of a sodium ion conductor, Na ３ Zr ２ PSi ２ O １２ (An example of NASICON) was used. A pH meter 45 was also placed in the anode-side solution chamber 36.

[0073] The carbon dioxide gas recovery system 1 was operated. The pH of the anode side solution 38 and the concentration of carbon dioxide gas inside the carbon dioxide gas measuring unit 40 were measured. The electrolysis conditions are described below.

[0074] Anode side solution 38: Pb ２＋ Simulated seawater (ASTM-D: 1141-98 (2003)) Cathode side solution 39: Pb ２＋ Simulated seawater (ASTM-D: 1141-98 (2003)) from which the anode solution chamber 36 has been removed: 1.25 L; the cathode solution chamber 37: 1.25 L; the first container 46: 25 L; the power supply voltage: 2.0 V; the power supply operating time: 70 hours.

[0075] Comparative Example 1 The carbon dioxide gas recovery system 1 was operated in the same manner as in Example 1, and the pH of the anode side solution 38 and the concentration of carbon dioxide gas inside the carbon dioxide gas measuring unit 40 were measured. However, in Comparative Example 1, the partition unit 32 was made of a monovalent cation exchange membrane.

[0076] The results are shown in Figures 10 and 11. Figure 10 is a graph showing the relationship between the pH of the anode solution and the time of water electrolysis for Example 1 and Comparative Example 1. Figure 11 is a graph showing the relationship between the concentration of carbon dioxide gas inside the carbon dioxide gas measuring unit and the time of water electrolysis for Example 1 and Comparative Example 1.

[0077] (Discussion) As can be seen from Fig. 10 , in both Comparative Example 1 and Example 1, the pH of the anode side solution 38 decreased for 18 hours from the start of water electrolysis. However, 19 hours after the start of water electrolysis, the pH of the anode side solution 38 in Comparative Example 1 increased. In contrast to Comparative Example 1, the pH of the anode side solution 38 in Example 1 continued to decrease even 19 hours after the start of water electrolysis. As can be seen from Fig. 11 , in Example 1, the carbon dioxide concentration in the first container 46 was higher than that in Comparative Example 1 from the start to the end of power supply drive.

[0078] It should be understood that the embodiments disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present disclosure is defined not by the above description but by the scope of the claims, and it is intended to include all modifications within the meaning and scope of the claims.

[0079] REFERENCE SIGNS LIST 1 Carbon dioxide gas recovery system, 2 Filter, 3 Water electrolysis cell, 4 Carbon dioxide gas recovery section, 5 Hydrogen gas recovery section, 6 Hydrogen gas recovery section, 7 Concentration and removal device, 3A, 3B, 3C, 3D Cell, 9, 9A, 9B Separator, 10 Water electrolysis stack, 32 Partition section, 33, 33B Anode, 34, 34A Cathode, 36 Anode side solution chamber, 37 Cathode side solution chamber, 38 Anode side solution, 39 Cathode side solution, 41 First region, 42 Second region, 43 Carbon dioxide gas measuring instrument, 45 pH meter, 46 First container, 47 First fan, 50 Hydrogen gas measuring section, 51 Second container, 52 Second fan, 70 Power supply, 81 First end plate, 83 Second end plate, 91 First main surface, 92 Second main surface, 100 Water electrolysis device, 310 Housing, 311 Anode side solution chamber inlet, 312 Anode side solution chamber outlet, 313 Cathode side solution chamber inlet, 314 Cathode side solution chamber outlet, 315 Space, 321 Fifth end, 322 Sixth end, 331 First side wall, 332 Second side wall, 333 Support wall, 334 Opposing wall, 335 Partition wall, 351 First flow path, 361 Second flow path, 372 Outlet, 381 Concentrated water, 391 Removed water, 811 Third main surface, 831 Fourth main surface, 812, 832, 911, 921 Groove, 3101 Electrolytic container, 3102 Recovery container, A1 First axis, A2 Second axis, A3 Third axis, AD Arrangement direction, D1 First direction, D2 Second direction, D3 Third direction.

Claims

1. A water electrolysis cell for releasing carbon dioxide from an anode-side solution, comprising: a partition that separates the space within the water electrolysis cell into an anode-side solution chamber and a cathode-side solution chamber; an anode that is disposed in the anode-side solution chamber and is capable of contacting the anode-side solution containing sodium ions, bicarbonate ions, carbonate ions, chloride ions, and water; and a cathode that is disposed in the cathode-side solution chamber and is capable of contacting the cathode-side solution containing water, wherein the partition is made of a sodium ion conductor.

2. The water electrolysis cell according to claim 1, wherein the sodium ion conductor constituting the partition is NASICON.

3. The water electrolysis cell according to claim 1, wherein the cathode solution further contains sodium ions, bicarbonate ions, carbonate ions, and chloride ions.

4. The water electrolysis cell according to claim 1, wherein the anode side solution and the cathode side solution are seawater.

5. The water electrolysis cell according to claim 1, wherein the partition, the anode, and the cathode each have a flat plate shape, and the partition, the anode, and the cathode are arranged so that their respective main planes are parallel to each other.

6. The water electrolysis cell according to claim 1, wherein the partition section has a cylindrical shape having a first axis which is a central axis; the anode has a cylindrical shape having a second axis which is a central axis in common with the first axis, overlaps with the partition section when viewed in the radial direction, and has a different diameter from the partition section; the cathode has a cylindrical shape having a third axis which is a central axis in common with the first axis, overlaps with the partition section when viewed in the radial direction, and has a different diameter from the partition section; and the anode, the partition section, and the cathode are arranged in this order when viewed in the radial direction.

7. A water electrolysis stack comprising: a plurality of water electrolysis cells according to any one of claims 1 to 6 arranged side by side; and a separator separating adjacent water electrolysis cells.

8. A water electrolysis device comprising: the water electrolysis stack according to claim 7; and a power source electrically connected to one of the anodes and one of the cathodes.

9. The water electrolysis apparatus according to claim 8, wherein the separator is made of a conductive material, and adjacent cells are connected in series.

10. A carbon dioxide gas recovery system comprising: the water electrolysis device according to claim 8; and a recovery section communicating with the anode-side solution chamber for recovering carbon dioxide gas.

11. A carbon dioxide gas recovery system as described in claim 10, further comprising a concentration / removal device connected to the anode side solution chamber and the cathode side solution chamber in the water electrolysis device, wherein seawater concentrated by the concentration / removal device is supplied to the anode side solution chamber, and removed water from which seawater components have been removed or partially removed is supplied to the cathode side solution chamber.

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