Seawater electrolysis apparatus

Abstract

Provided is a seawater electrolysis apparatus for electrolyzing sea water at sea, in which pH reduction around an anode is eliminated and generation of chlorine is suppressed. A seawater electrolysis apparatus (1) for electrolyzing seawater at sea comprises: a cathode (20); an anode (10) disposed facing the cathode (20); a diaphragm (21) disposed between the cathode (20) and the anode (10); a power supply (30) for applying a voltage between the cathode (20) and the anode (10); and a control device (40) for controlling application of the voltage from the power source (30) between the cathode (20) and the anode (10). The control device (40) stops voltage application when a first predetermined period has elapsed after the start of voltage application, and resumes voltage application when a second predetermined period has elapsed after the stop of voltage application.

Description

seawater electrolyzer

[0001] The present invention relates to a seawater electrolysis apparatus for electrolyzing seawater at sea.

[0002] Demand for green hydrogen is increasing. To meet this demand, hydrogen production by seawater electrolysis is the optimal method in terms of both cost and production scale. However, when electrolyzing a chlorine-containing solution such as seawater, chlorine gas is also generated from the anode during electrolysis, which has an environmental impact.

[0003] Patent Document 1 describes that in an electrolysis device that produces slightly acidic electrolyzed water by electrolysis of a chlorine-containing composition, chlorine gas may be liberated when the hydrogen ion concentration is pH 4 or less.

[0004] Various types of anodes have been developed to prevent the generation of chlorine gas. For example, Patent Document 2 describes the use of an anticorrosion electrode to which manganese dioxide is attached by electrodeposition to keep the chlorine generation rate extremely low.

[0005] Non-Patent Document 1 describes that by providing a manganese dioxide membrane with intercalated sodium ions on a fluorine-doped tin oxide (FTO) electrode, the selectivity of the oxygen evolution reaction (OER) over the chlorine evolution reaction (CER) is increased.

[0006] International Publication No. 2011 / 158279 Japanese Patent Publication No. 11-100686

[0007] Hikaru Abe, Ai Murakami, Shun Tsunekawa, Takuya Okada, Toru Wakabayashi, Masaaki Yoshida, and Masaharu Nakayama, “Selective Catalyst for Oxygen Evolution in Neutral Brine Electrolysis: An Oxygen-Deficient Manganese Oxide Film”, ACS Catal. 2021,11,11, pp.6390-6397<URL: https: / / doi.org / 10.1021 / acscatal.0c05496>

[0008] Around the anode, oxygen (O ２ ), the hydrogen ion concentration increases and the pH decreases. Even if a coating is provided on the surface of the anode as described in Patent Document 2 and Non-Patent Document 1, the decrease in pH due to water electrolysis cannot be avoided. If the pH around the anode decreases too much, the selectivity of the chlorine evolution reaction (CER) increases, making it easier for chlorine to be generated.

[0009] The objective of the present invention is to continuously generate hydrogen while suppressing the generation of chlorine by eliminating excessive drops in pH around the anode in a hydrogen generation device that generates hydrogen by electrolyzing seawater at sea.

[0010] One aspect of the present invention is a seawater electrolysis apparatus for electrolyzing seawater at sea, comprising: a cathode; an anode disposed opposite the cathode; a diaphragm disposed between the cathode and the anode; a power supply that applies a voltage between the cathode and the anode; and a control device that controls the application of the voltage from the power supply to between the cathode and the anode, wherein the control device stops the application of the voltage when a first predetermined period has elapsed since the start of the application of the voltage, and resumes the application of the voltage when a second predetermined period has elapsed since the application of the voltage was stopped.

[0011] According to the present invention, in a seawater electrolysis device that electrolyzes seawater at sea, the application of voltage from the power source between the cathode and anode is stopped after a first predetermined period has elapsed, thereby eliminating the decrease in pH around the anode, and then the application of voltage is resumed once the pH has increased, thereby making it possible to continuously produce hydrogen while suppressing the generation of chlorine.

[0012] 1 is a circuit diagram of a seawater electrolysis system 1 that generates hydrogen by electrolyzing seawater at sea. FIG. 2 is a schematic plan view of the seawater electrolysis system 1. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. FIG. 4 is a schematic view of a hydrogen recovery system 70. FIG. 5 is a timing chart showing the relationship between the timing of applying a voltage between the anode 10 and the cathode 20 and the pH around the anode 10. FIG. 6 is a schematic view showing the configuration of the device in Experiment 1. FIG. 7 is a schematic view showing the configuration of the device in Experiment 2. FIG. 8 is a diagram showing the relationship between the amount of chlorine generated and the electrolysis time in Experiments 1 and 2. FIG. 9 is a diagram showing the relationship between the oxygen generation rate and the electrolysis time in Experiments 1 and 2. FIG. 10 is a diagram showing the relationship between the pH and the electrolysis time in Experiments 1 and 2.

[0013] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the term "sea" includes water bodies containing chlorine-containing compositions, such as brackish water areas at the mouth of an river, brackish lakes, salt lakes, and salt lakes. In this specification, the term "seawater" includes brackish water, which is a mixture of freshwater and seawater. In this specification, the term "water current" includes river currents, tidal currents, and ocean currents.

[0014] [First embodiment] Fig. 1 is a circuit diagram of a seawater electrolysis system 1 according to this embodiment, which electrolyzes seawater at sea. As shown in Fig. 1, the seawater electrolysis system 1 includes an anode 10, a cathode 20, a power supply 30, and a control device 40. Although not shown in Fig. 1, a diaphragm 21 is provided between the anode 10 and the cathode 20, as shown in Figs. 2 and 3.

[0015] The anode 10 and the cathode 20 are disposed facing each other in the sea. When a voltage is applied between the anode 10 and the cathode 20 from the power supply 30, oxygen is produced by an oxidation reaction at the anode 10, and hydrogen is produced by a reduction reaction at the cathode. The power supply 30 applies a voltage between the anode 10 and the cathode 20 while the anode 10 and the cathode 20 are immersed in seawater. Electric power is supplied to the power supply 30 from an external power source, such as an offshore wind power generator or solar power generator.

[0016] The control device 40 includes a processor, a storage device that stores software (programs, firmware, etc.) executed by the processor, and the like. The control device 40 controls the application of a voltage between the anode 10 and the cathode 20 from the power source 30. Furthermore, as will be described later, when a moving mechanism 60 is provided, the control device 40 controls the moving mechanism 60. Furthermore, as will be described later, when a pH sensor 41 is provided around the anode 10, a signal from the pH sensor 41 is input to the control device 40. In this case, the control device 40 may control the power source 30 and the moving mechanism 60 in accordance with the output of the pH sensor 41.

[0017] Fig. 2 is a schematic plan view of the seawater electrolysis apparatus 1, and Fig. 3 is an elevation view taken along the line III-III in Fig. 2. Although Figs. 1 to 3 show the seawater electrolysis apparatus 1 having three pairs of anodes 10 and cathodes 20, the number of pairs of anodes 10 and cathodes 20 is arbitrary. Although not shown, it is preferable to provide a net or the like around the seawater electrolysis apparatus 1 to prevent the intrusion of fish, seaweed, and the like.

[0018] 2 and 3, a spacer 11 is provided on the top of the anode 10. The spacer 11 is made of an insulator or is covered with an insulating film. The anode 10 may be in the form of a flat plate, or in the form of a mesh such as a punched mesh or expanded metal.

[0019] A catalyst layer is provided on the surface of the anode 10 to enhance the selectivity of the oxygen evolution reaction (OER) over the chlorine evolution reaction (CER) when seawater is electrolyzed. Specifically, a manganese dioxide (MnO ２ The anode 10 is formed by providing a layer of titanium (Ti), an alloy of titanium and tantalum (TiTa), an alloy of iridium and tantalum (IrTa), an alloy of TiTa and IrTa (TIR), or the like, as the conductive base material used for the anode 10. Alternatively, a layer of an oxide of an alloy of iridium and tantalum (IrTaO) formed on titanium may be used as the conductive base material.

[0020] The conductive substrate was prepared by adding manganese sulfate (MnSO４ ) and sulfuric acid (H ２ SO ４ ) in an aqueous solution to form a manganese dioxide (MnO ２ A layer of manganese dioxide (MnO ２ For example, a layer of manganese dioxide doped with vanadium (V) (Mn-VO) may be formed on a conductive substrate by electrodeposition of a layer of manganese dioxide. ４ ), sodium orthovanadate (Na ３ VO ４ ) and sulfuric acid (H ２ SO ４ ) in an aqueous solution, a Mn—V—O layer can be formed on the manganese dioxide layer.

[0021] As shown in Figures 2 and 3, a cover 22 is provided on top of the cathode 20. The cover 22 is made of an insulator or is covered with an insulating film. The cathode 20 may be in the form of a flat plate, or in the form of a mesh such as a punched mesh or expanded metal. When the seawater electrolysis apparatus 1 is placed on the sea, the cathode 20 is suspended from a support rod 51 and placed vertically.

[0022] The upper end of the diaphragm 21 is disposed above the sea level S, and as shown in Fig. 2, surrounds the outer periphery of the cover 22 and is held between the spacer 11 and the cover 22. Therefore, the diaphragm 21 is disposed so as to surround the entire periphery of the cathode 20 in the horizontal direction. The lower part of the diaphragm 21 may be open.

[0023] The vertical length of the diaphragm 21 is preferably longer than the vertical length of the cathode 20. That is, as shown in FIG. 3, the diaphragm 21 is preferably disposed so that its lower end is lower than the lower end of the cathode 20. The width of the diaphragm 21 is preferably greater than the width of the opposing surface of the cathode 20 and the anode 10. The diaphragm 21 may have openings below the sea level S at both widthwise ends of the cathode 20 (the left and right ends in FIG. 2). That is, the diaphragm 21 does not need to surround the entire horizontal periphery of the cathode 20, as long as the diaphragm 21 is disposed between the cathode 20 and the anode 10. In this case, the width of the diaphragm 21 needs to be sufficient to prevent the gases generated at the anode 10 and the cathode 20 from mixing in the seawater, and is preferably, for example, at least twice the width of the opposing surface of the cathode 20 and the anode 10.

[0024] A hydrogen collection nozzle 23 is provided on the top of the cover 22. The hydrogen collection nozzle 23 is connected to a hydrogen recovery device 70 (see FIG. 4). The hydrogen gas (H ２ ) rises toward the sea surface S inside the diaphragm 21 and is collected in the space surrounded by the sea surface S, the diaphragm 21, and the cover 22. ２ ) is taken out from the hydrogen collection nozzle 23 and sent to the hydrogen recovery device 70.

[0025] 4 is a schematic diagram of the hydrogen recovery device 70. The hydrogen recovery device 70 includes a water seal tank 71, a hydrogen purifier 72, etc. The hydrogen gas extracted from the hydrogen collection nozzle 23 is transferred to the next process via the water seal tank 71, the hydrogen purifier 72, etc.

[0026] The seawater electrolysis apparatus 1 includes a holder 50 that holds the anode 10 and the cathode 20. The holder 50 holds the anode 10 and the cathode 20 with a space therebetween through which seawater can flow. For example, the holder 50 includes a support rod 51 and a float 52. The support rod 51 supports the anode 10 and the cathode 20 while being insulated from the anode 10 and the cathode 20. Specifically, as shown in FIGS. 2 and 3 , the spacer 11, the cover 22, and the diaphragm 21 are sandwiched between a spacer 11 provided on the top of the anode 10 and a cover 22 provided on the top of the cathode 20, and the spacer 11, the cover 22, and the diaphragm 21 are supported by the support rod 51 and fastened together with a fastener (not shown). As a result, the anode 10 and the cathode 20 are spaced a predetermined distance apart, and the diaphragm 21 is disposed between the anode 10 and the cathode 20. Both ends of the support rod 51 are fixed to floats 52. The floats 52 allow the seawater electrolysis apparatus 1 to be placed on the sea.

[0027] As described above, a catalyst layer is provided on the surface of the anode 10 to increase the selectivity of the oxygen evolution reaction (OER) over the chlorine evolution reaction (CER) when seawater is electrolyzed. However, around the anode 10, oxygen (O ２ ) is generated, the hydrogen ion concentration increases and the pH decreases. ２ O → O ２ +4H ＋ +4e － (4OH － →2H ２ O+O ２ +4e － ) ... (1) When the pH decreases, the selectivity of the chlorine evolution reaction (CER) increases, and chlorine gas is more likely to be generated.

[0028] In this embodiment, the application of voltage between the anode 10 and the cathode 20 from the power supply 30 is turned on and off at predetermined time intervals to stop electrolysis while the pH around the anode 10 is decreasing. Fig. 5 is a timing chart showing the relationship between the timing of applying a voltage between the anode 10 and the cathode 20 and the pH around the anode 10. As shown in the upper part of Fig. 5, application of a voltage between the anode 10 and the cathode 20 for a predetermined application period T1 and stopping application of the voltage between the anode 10 and the cathode 20 for a predetermined stop period T2 are repeated.

[0029] 5, the application period T1 is set to be the time from when the application of voltage between the anode 10 and the cathode 20 begins until the pH around the anode 10 drops to a predetermined value pHβ (e.g., pH=4) or shorter. The application period T1 is set appropriately depending on the shape of the anode 10, the distance between the anode 10 and the cathode 20, the surface areas of the anode 10 and the cathode 20, the amount of current, the seawater temperature, the speed of the water current, etc. Therefore, the application period T1 may differ for each setting.

[0030] The stop period T2 is set so that it is long enough for the pH around the anode 10 to rise to a predetermined value pHα (e.g., pH = 6) after the electrolysis of seawater is stopped. The stop period T2 is set appropriately depending on the shape of the anode 10, the distance between the anode 10 and the cathode 20, the surface areas of the anode 10 and the cathode 20, the seawater temperature, the water flow speed, etc. Therefore, the stop period T2 may differ for each setting.

[0031] The increase in pH around the anode 10 during the stop period T2 is caused by replacement of the seawater around the anode 10. The replacement of the seawater around the anode 10 is caused by, for example, a water current causing seawater to flow around the anode 10. In this case, the stop period T2 may be set to a value greater than the value obtained by dividing the width of the anode 10 by the speed of the water current.

[0032] For example, the application period T1 may be set to 5 minutes, the stop period T2 may be set to 1 minute, and the application of voltage from the power supply 30 between the anode 10 and the cathode 20 may be turned on and off in a 6-minute cycle. By turning on and off the application of voltage from the power supply 30 between the anode 10 and the cathode 20 at predetermined time intervals in this manner, an excessive decrease in pH around the anode 10 can be suppressed, and chlorine gas liberation can be prevented.

[0033] Alternatively, the control device 40 may provide a pH sensor 41 on or around the anode 10, and control the power supply 30 to stop applying a voltage between the anode 10 and the cathode 20 when the pH of the seawater on the surface of the anode 10 reaches a predetermined lower limit pHβ, and to start applying a voltage between the anode 10 and the cathode 20 when the pH of the seawater on the surface of the anode 10 reaches a predetermined upper limit pHα. Here, the "pH of the seawater on the surface of the anode 10" may be the pH of the seawater between the anode 10 and the diaphragm 21. The "predetermined lower limit pHβ" may be set to a value (e.g., pH = 4) higher than the pH value at which chlorine is liberated by electrolysis of seawater. If chlorine generation is tolerable to a certain extent, a pH value set according to that level may be used as the "pH value at which chlorine is liberated." Furthermore, the "predetermined upper limit pHα" may be set to a pH value (e.g., pH = 6) high enough to increase the selectivity of the oxygen evolution reaction (OER) over the chlorine evolution reaction (CER) during seawater electrolysis by the anode 10. The values ​​of α and β may be measured values ​​of the pH sensor 41, or may be values ​​calculated based on the measured values ​​of the pH sensor 41. In particular, although the present embodiment illustrates the case where one pH sensor 41 is used, multiple pH sensors 41 may be provided in appropriate positions depending on the size of the seawater electrolysis system 1, the conditions of the installation location, etc. In this case, the values ​​of α and β may be calculated as appropriate based on the measured values ​​of each pH sensor 41. This calculation is performed by the control device 40, which serves as calculation means.

[0034] The seawater electrolysis apparatus 1 may include a moving mechanism 60 that moves the anode 10, the cathode 20, and the diaphragm 21 in a direction intersecting the direction in which the anode 10 faces the cathode 20 (the vertical direction in FIG. 1 ). Moving the anode 10, the cathode 20, and the diaphragm 21 allows the seawater around the anode 10 to be replaced. This allows the anode 10 and the like to be moved to a position where the pH of the surrounding seawater is sufficiently high, and seawater electrolysis can be resumed, without waiting for the surrounding seawater to be replaced by a water flow. The control device 40 may control the moving mechanism 60 to move the anode 10, the cathode 20, and the diaphragm in the width direction of the surface of the anode 10 facing the cathode 20 (the horizontal direction in FIG. 2 ).

[0035] The movement mechanism 60 may be, for example, a slide rail provided in the width direction (horizontal direction in FIG. 1 ) of the surface of the anode 10 facing the cathode 20. The float 52 may also be moved along the slide rail. Alternatively, a rope (not shown) may be attached to the float 52, and the entire seawater electrolysis apparatus 1 may be moved by pulling the rope from the outside. The float 52 may also be provided with a propeller such as a screw, and the seawater electrolysis apparatus 1 may be moved by self-propelling.

[0036] The anode 10 needs to be moved to a position where the pH of the surrounding seawater is sufficiently high, and therefore the movement distance of the anode 10 is preferably equal to or greater than the width of the surface of the anode 10 facing the cathode 20 (the width in the lateral direction in FIG. 1 ). The movement mechanism 60 moves the anode 10, the cathode 20, and the diaphragm 21. For example, the entire seawater electrolysis apparatus 1 may be moved by moving the float 52 in the lateral direction in FIG. 2 .

[0037] The movement mechanism 60 preferably moves the anode 10, the cathode 20, and the diaphragm 21 during the stop period T2. In this case, the movement speed is preferably equal to or greater than the value obtained by dividing the movement distance of the anode 10 by the stop period T2. Alternatively, the movement of the anode 10, the cathode 20, and the diaphragm 21 may be performed during the application period T1, not limited to the stop period T2.

[0038] Alternatively, a pH sensor 41 may be provided around the anode 10, and when the pH measured by the pH sensor 41 reaches a predetermined lower limit, the control device 40 may start moving the anode 10 using the moving mechanism 60. When the pH measured by the pH sensor 41 reaches a predetermined upper limit, the control device 40 may stop moving the anode 10 using the moving mechanism 60. The method for setting the "predetermined lower limit" and "predetermined upper limit" is as described above. The predetermined upper and lower limits of pH may be values ​​measured by the pH sensor 41 or may be values ​​calculated based on the measurements of the pH sensor 41, as described above. Instead of controlling the movement of the anode 10 based on the pH value, the movement distance may be calculated in advance. For example, the movement distance to a position where the pH of the seawater around the anode 10 is sufficiently high may be calculated in advance depending on the size of the seawater electrolysis apparatus 1, the conditions of the installation location, and the like. Furthermore, the previously calculated movement distance may be corrected based on the measurements of the pH sensor 41.

[0039] Hereinafter, the relationship between the decrease in pH due to electrolysis and the generation of chlorine at the anode will be described based on an experiment on the electrolysis of a sodium chloride aqueous solution. [Experiment 1] An electrolytic cell as shown in Figure 6 was created, and electrolysis was performed while circulating a sodium chloride aqueous solution. An anode chamber 110 containing an anode 101, a cathode chamber 120 containing a cathode 102, a diaphragm 103, and a spacer 104 were arranged in this order as shown in Figure 6, and then fastened together to form an electrolytic cell.

[0040] The anode 101 was made of a titanium conductive substrate and a manganese dioxide (MnO ２ The cathode 102 was made of a conductive substrate made of nickel. The diaphragm 103 was made of an alkali-resistant anion exchange membrane (AHA, manufactured by Astom Corporation). The thickness of the spacer 104 (the horizontal length in FIG. 6) was 15 mm.

[0041] The anolyte was circulated by supplying it from an anolyte tank 111 provided outside the electrolytic cell to the anode chamber 110 using a liquid feed pump 112 and recovering it from the anode chamber 110 to the anolyte tank 111. The anolyte was an aqueous sodium chloride solution, and its initial concentration was 30 g / L. The liquid feed rate by the liquid feed pump 112 was 104 mL / min, and the linear flow velocity in the anode chamber 110 was 0.5 cm / sec.

[0042] The cathode fluid was circulated by supplying it from a cathode fluid tank 121 provided outside the electrolytic cell to the cathode chamber 120 using the liquid supply pump 112 and recovering it from the cathode chamber 120 to the cathode fluid tank 121. The cathode fluid was an aqueous sodium chloride solution, and its initial concentration was 30 g / L. The liquid supply rate by the liquid supply pump 122 was 104 mL / min, and the linear flow velocity in the cathode chamber 120 was 0.5 cm / sec.

[0043] While circulating the anolyte and catholyte, a voltage was applied between the anode 101 and the cathode 102 from the power supply 130 to perform electrolysis. A DC power supply (PMC35-2A, manufactured by Kikusui Electronics Co., Ltd.) was used as the power supply 130. The current value was 0.1 A / cm2 relative to the surface area of ​​the anode 101 and the cathode 102. ２ It was set to be.

[0044] While the electrolysis was carried out for 30 minutes, a portion of the anolyte was withdrawn from the anolyte tank 111 every 5 minutes to measure the amount of chlorine generated and the pH. The amount of chlorine generated was measured by the diethylparaphenylenediamine method (DPD method). The pH was measured using pH test paper.

[0045] The oxygen generation rate was calculated based on the amount of chlorine generated and the electron equivalent that flowed. Here, the oxygen generation in the anode chamber is expressed by the following formula (1), while the chlorine generation is expressed by the following formula (2). 2H ２ O → O ２ +4H ＋ +4e － (4OH － →2H ２ O+O ２ +4e －) ... (1) 2Cl － →Cl ２ +2e － ...(2) If the amount of oxygen generated in equation (1) is n_O2 and the amount of chlorine generated in equation (2) is n_Cl2, the electrons generated in equation (1) are 4 × n_O2 and the electrons generated in equation (2) are 2 × n_Cl2. The total amount of electrons generated in equations (1) and (2) is the electron equivalent n_e － Then, the following equation holds: 4 × n_O2 + 2 × n_Cl2 = n_e － Therefore, the amount of oxygen generated is expressed by the following formula: n_O2 = (n_e － The oxygen generation rate was calculated using the following formula: Oxygen generation rate = 4 × n_O2 / n_e － = (n_e － -2 × n_Cl2) / n_e － Therefore, the electron equivalent (n_e － The oxygen generation rate can be calculated from the amount of chlorine generated (n_Cl2) measured by the DPD method.

[0046] [Experiment 2] An electrolytic cell as shown in Fig. 7 was prepared, and electrolysis was performed while circulating an aqueous sodium chloride solution. An anode chamber 110 containing an anode 101, a cathode chamber 120 containing a cathode 102, and a diaphragm 103 were arranged in this order as shown in Fig. 7, and then fastened together to form an electrolytic cell. The only difference from the electrolytic cell of Experiment 1 shown in Fig. 7 is that the spacer 104 was not present.

[0047] The relationship between the amount of chlorine generated and electrolysis time in Experiments 1 and 2 is shown in Figure 8 , the relationship between the oxygen generation rate and electrolysis time in Figure 9 , and the relationship between pH and electrolysis time in Figure 10 . As shown in Figures 8 and 9 , chlorine was not detected until 5 minutes after the start of electrolysis in both Experiments 1 and 2. On the other hand, as shown in Figure 10 , the pH was 6 before the start of electrolysis, but dropped to 4 5 minutes after the start of electrolysis. As shown in Figures 8 and 9 , chlorine was detected 10 minutes after the start of electrolysis in both Experiments 1 and 2. As shown in Figure 10 , the pH dropped to 3 10 minutes after the start of electrolysis. Thereafter, as shown in Figure 8 , the amount of chlorine generated increased with increasing electrolysis time. As shown in Figure 9 , the oxygen generation rate remained at just under 80% 15 minutes after the start of electrolysis. As shown in Figure 10 , the pH was 3 from 10 to 25 minutes after the start of electrolysis, but dropped to 2 30 minutes after the start of electrolysis.

[0048] The results of Experiments 1 and 2 demonstrate that oxygen can be generated without generating chlorine until the pH of the anolyte drops to a predetermined value. This demonstrates that chlorine generation can be suppressed by preventing a decrease in pH around the anode. Experiments 1 and 2 were conducted using salt water. However, even in the electrolysis of seawater, chlorine generation can be suppressed by preventing an excessive decrease in pH around the anode. Therefore, even in a seawater electrolysis device, by appropriately setting the application period for applying a voltage between the anode and cathode and the stop period for stopping the application of voltage between the anode and cathode, depending on the size of the cathode and anode, the distance between the cathode and anode, the voltage, the current, the seawater temperature, the water flow rate, etc., and alternately applying and stopping the voltage application, hydrogen can be continuously generated while suppressing chlorine generation. This application claims priority to Japanese Patent Application No. 2024-050672, filed March 27, 2024.

Claims

1. A seawater electrolysis apparatus for electrolyzing seawater at sea, comprising: a cathode; an anode disposed opposite the cathode; a diaphragm disposed between the cathode and the anode; a power supply that applies a voltage between the cathode and the anode; and a control device that controls the application of the voltage from the power supply to between the cathode and the anode, wherein the control device stops the application of the voltage when a first predetermined period has elapsed since the start of the application of the voltage, and resumes the application of the voltage when a second predetermined period has elapsed since the application of the voltage was stopped.

2. The seawater electrolysis apparatus according to claim 1, further comprising a movement mechanism that moves the anode, the cathode, and the diaphragm within the second predetermined period.

3. The seawater electrolysis apparatus according to claim 2, wherein the direction of movement of the anode by the movement mechanism is the width direction of the surface of the anode facing the cathode, and the movement distance of the anode is equal to or greater than the width of the facing surface.

4. The seawater electrolysis apparatus according to claim 1, further comprising: a cover disposed above the cathode and connected to an upper end of the diaphragm; and a hydrogen collection nozzle that collects hydrogen generated from the cathode by electrolysis of seawater.

5. The seawater electrolysis apparatus according to claim 1, wherein the width of the diaphragm is greater than the width of the surface of the cathode facing the anode.

6. The seawater electrolysis apparatus according to claim 1, wherein the vertical height of the diaphragm is greater than the vertical height of the cathode.

7. The seawater electrolysis system according to claim 4, further comprising a recovery device for recovering the hydrogen collected by the hydrogen collection nozzle.

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