Water electrolysis device

Abstract

It prevents deterioration of electrolysis performance even after the electrolysis time has elapsed. [Solution] The water electrolysis apparatus according to the present disclosure comprises a water electrolysis cell to which an electrolyte solution, which is an alkaline aqueous solution, is supplied; an oxygen gas liquid separator in which the electrolyte solution is stored; and an electrolyte supply line, which is a pipe connecting the oxygen gas liquid separator in which the electrolyte solution is stored and flowing from the oxygen gas liquid separator in which the electrolyte solution is stored toward the positive electrode side of the water electrolysis cell. The electrolyte supply line has an alkali-resistant layer formed on its inner surface in at least a portion of the section from the connection point with the oxygen gas liquid separator in which it is connected to the positive electrode side of the water electrolysis cell.

Description

[Technical Field]

[0001] This disclosure relates to a water electrolysis apparatus. [Background technology]

[0002] A water electrolysis device produces hydrogen gas and oxygen gas by electrolyzing an aqueous solution. The water electrolysis cell consists of an ion exchange membrane with a negative electrode catalyst layer and a positive electrode catalyst layer on either side. Power supply units are positioned outside these, and separators are positioned outside each power supply unit. Aqueous solution is then supplied to both separators.

[0003] For example, Patent Document 1 discloses a water electrolysis method and a water electrolysis apparatus in which water is supplied to the cathode side of an electrolytic membrane including a solid polymer membrane having a catalyst layer on its surface, and a potential difference is applied to both sides of the electrolytic membrane to electrolyze the water, wherein the pressure difference between both sides of the electrolytic membrane is controlled to 50 kPa or less, and temperature-controlled water is supplied only to the cathode side of the electrolytic membrane. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6332792 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In such water electrolysis devices, the water electrolysis voltage would increase, leading to a decrease in electrolysis efficiency and a deterioration in durability.

[0006] In view of the above issues, this disclosure aims to provide a water electrolysis apparatus that can prevent deterioration of electrolysis performance even after an elapsed electrolysis time. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the water electrolysis apparatus according to this disclosure comprises a water electrolysis cell to which an electrolyte solution, which is an alkaline aqueous solution, is supplied; a gas-liquid separator for oxygen gas in which the electrolyte solution is stored; and an electrolyte supply line, which is a pipe connecting the gas-liquid separator for oxygen gas in which the electrolyte solution is stored, to which the electrolyte solution flows from the gas-liquid separator for oxygen gas in which the electrolyte solution flows toward the positive electrode side of the water electrolysis cell. The electrolyte supply line has an alkali-resistant layer formed on its inner surface in at least a portion of the section from the connection point with the gas-liquid separator for oxygen gas in which it is connected to the positive electrode side of the water electrolysis cell. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a water electrolysis apparatus that can prevent deterioration of electrolysis performance even after an elapsed electrolysis time. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a diagram illustrating the overview of the water electrolysis system related to this disclosure. [Figure 2] Figure 2 is a schematic diagram showing an example of the configuration of a water electrolysis cell according to this disclosure. [Figure 3] Figure 3 is an exploded perspective view of the water electrolysis cell relating to this disclosure. [Figure 4] Figure 4 is a cross-sectional view showing an example of the configuration of a film electrode assembly according to this disclosure. [Figure 5A] Figure 5A is a schematic diagram showing the configuration of the electrolyte supply unit according to this disclosure. [Figure 5B] Figure 5B is a schematic cross-sectional view showing the configuration of the electrolyte supply line. [Figure 6] Figure 6 is a graph showing the current-voltage characteristics for each electrolyte supply method of the water electrolysis system according to this disclosure. [Figure 7] Figure 7 is a graph showing the change in electrolysis voltage over time for each electrolyte supply method of the water electrolysis system according to this disclosure. [Figure 8] Figure 8 is a schematic diagram showing the configuration of the electrolyte supply unit according to this disclosure. [Figure 9] FIG. 9 is a graph showing changes in electrolysis voltage with the lapse of energization time for each presence or absence of an alkali-resistant layer in the water electrolysis system according to the present disclosure. [Figure 10] FIG. 10 is a graph showing changes in electrolysis voltage with the lapse of energization time for each presence or absence of an alkali-resistant layer in the water electrolysis system according to the present disclosure. [Figure 11] FIG. 11 is a diagram showing a configuration example of a descaling unit of the water electrolysis system according to the present disclosure. MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the embodiments described below.

[0011] (About Water Electrolysis Apparatus) First, a water electrolysis system 1 according to the present disclosure will be described with reference to FIG. 1. FIG. 1 is a diagram for explaining the outline of the water electrolysis system according to the present disclosure. As shown in FIG. 1, the water electrolysis system 1 according to the present disclosure includes a power generator 40, a gas-liquid separator 62 for oxygen gas, a gas-liquid separator 64 for hydrogen gas, and a water electrolysis apparatus 100. That is, the water electrolysis system 1 uses the electric power generated by the power generator 40 to electrolyze water by the water electrolysis apparatus 100 to generate hydrogen and oxygen, supplies oxygen to the gas-liquid separator 62 for oxygen gas, and supplies hydrogen to the gas-liquid separator 64 for hydrogen gas.

[0012] The power generator 40 is, for example, an apparatus that generates power using renewable energy. The power generator 40 may be, for example, a solar power generation apparatus, a solar thermal power generation apparatus, a wind power generation apparatus, a hydroelectric power generation apparatus, a geothermal power generation apparatus, or the like. In power generation using these renewable energies, since output fluctuations are large due to weather conditions and the like, conversion into stable energy is required. The power generator 40 is not limited to a power generator using renewable energy, and may be another thermal power generator or a nuclear power generator.

[0013] The water electrolysis device 100 generates hydrogen by electrolyzing water using electricity. As shown in Figure 1, the water electrolysis device 100 is electrically connected to the power generation device 40, and the electricity generated in the power generation device 40 is rectified into DC by a rectifier 50 and then supplied as DC electricity. Therefore, if the power generation device 40 is a renewable energy power generation device, the water electrolysis system 1 generates green hydrogen, which means hydrogen generated by renewable energy.

[0014] However, the water electrolysis device 100 does not have to be provided in the water electrolysis system 1 including the power generator 40, nor does it have to operate using the electricity generated by the power generator 40.

[0015] (Regarding water electrolysis equipment) Next, the water electrolysis apparatus 100 according to this disclosure will be described. Figure 2 is a schematic diagram showing an example of the configuration of the water electrolysis apparatus according to this disclosure. The water electrolysis apparatus 100 is a device that generates hydrogen (H2) and oxygen (O2) by electrolyzing water (H2O) contained in an electrolyte. The water electrolysis apparatus 100 may be, for example, a device using an anion exchange membrane (AEM). However, the water electrolysis apparatus 100 may also be, for example, a device using a proton exchange membrane (PEM: Polymer Electrolyte Membrane).

[0016] As shown in Figure 2, the water electrolysis apparatus 100 comprises, for example, a water electrolysis cell 10, a power supply unit 14, and an electrolyte supply unit 16. In Figure 2, the water electrolysis apparatus 100 is configured to have one water electrolysis cell 10, but instead of one water electrolysis cell 10, it may be configured to have a cell stack which is an assembly of multiple water electrolysis cells 10.

[0017] The power supply unit 14 is a DC power supply device that applies voltage to the water electrolysis cell 10. The power supply unit 14 applies the DC voltage necessary for the electrolysis of the electrolyte between the negative electrode and the positive electrode of the water electrolysis cell 10. The power supply unit 14 can be any power source. For example, as shown in Figure 1, if the water electrolysis device 100 is provided in a water electrolysis system 1 that includes a power generator 40, then the power generator 40 and the rectifier 50 can be said to correspond to the power supply unit 14.

[0018] The electrolyte supply unit 16 supplies electrolyte to the water electrolysis cell 10. The electrolyte may be, for example, pure water or an alkaline aqueous solution. Examples of alkaline aqueous solutions include potassium hydroxide (KOH) and sodium hydroxide (NaOH).

[0019] In this embodiment, the electrolyte supply unit 16 includes a negative electrode side supply unit 16A that supplies electrolyte to the negative electrode side of the water electrolysis cell 10, and a positive electrode side supply unit 16B that supplies electrolyte to the positive electrode side of the water electrolysis cell 10. The configurations of the negative electrode side supply unit 16A and the positive electrode side supply unit 16B will be described below, but this is just one example, and the negative electrode side supply unit 16A and the positive electrode side supply unit 16B may have any configuration that can supply electrolyte to the negative electrode side and the positive electrode side.

[0020] The negative electrode side supply unit 16A includes an electrolyte supply line L1 (electrolyte supply channel), an electrolyte discharge line L2 (electrolyte discharge channel), a hydrogen gas gas-liquid separator 64, and a pump 72. The hydrogen gas gas-liquid separator 64 is a tank that stores electrolyte and separates hydrogen from the electrolyte. The electrolyte supply line L1 is a pipe through which the electrolyte flows and is connected to the hydrogen gas gas-liquid separator 64 and the negative electrode side of the water electrolysis cell 10. The electrolyte discharge line L2 is a pipe through which the electrolyte flows and is connected to the negative electrode side of the water electrolysis cell 10 and the hydrogen gas gas-liquid separator 64. The pump 72 is a pump that supplies the electrolyte in the hydrogen gas gas-liquid separator 64 to the negative electrode side of the water electrolysis cell 10 and is provided, for example, in the electrolyte supply line L1. In the negative electrode supply unit 16A, when the pump 72 is driven, the electrolyte in the hydrogen gas gas-liquid separator 64 is supplied to the negative electrode side of the water electrolysis cell 10 through the electrolyte supply line L1. The electrolyte supplied to the negative electrode side of the water electrolysis cell 10 is returned to the hydrogen gas gas-liquid separator 64 through the electrolyte discharge line L2.

[0021] The positive electrode side supply unit 16B includes an electrolyte supply line L3 (electrolyte supply channel), an electrolyte discharge line L4 (electrolyte discharge channel), an oxygen gas liquid separator 62, and a pump 70. The oxygen gas liquid separator 62 is a tank that stores the electrolyte and separates the oxygen from the electrolyte. The electrolyte supply line L3 is a pipe through which the electrolyte flows and is connected to the oxygen gas liquid separator 62 and the positive electrode side of the water electrolysis cell 10. The electrolyte discharge line L4 is a pipe through which the electrolyte flows and is connected to the positive electrode side of the water electrolysis cell 10 and the oxygen gas liquid separator 62. The pump 70 is a pump that supplies the electrolyte in the oxygen gas liquid separator 62 to the positive electrode side of the water electrolysis cell 10 and is provided, for example, in the electrolyte supply line L3. In the positive electrode supply unit 16B, when the pump 70 is driven, the electrolyte in the gas-liquid separator for oxygen gas 62 is supplied to the positive electrode side of the water electrolysis cell 10 through the electrolyte supply line L3. The electrolyte supplied to the positive electrode side of the water electrolysis cell 10 is returned to the gas-liquid separator for oxygen gas 62 through the electrolyte discharge line L4.

[0022] Thus, the electrolyte supply unit 16 may be a so-called bipolar feed type having both a negative electrode side supply unit 16A and a positive electrode side supply unit 16B, but is not limited thereto. For example, the electrolyte supply unit 16 may be a so-called anode feed type having a positive electrode side supply unit 16B and no negative electrode side supply unit 16A. The electrolyte supply unit 16 is preferably a bipolar feed type or an anode feed type, but may also be a so-called cathode feed type having a negative electrode side supply unit 16A and no positive electrode side supply unit 16B.

[0023] The detailed configuration of the electrolyte supply unit 16 will be described later.

[0024] (Regarding water electrolysis cells) Next, the main components of the water electrolysis cell 10 of the water electrolysis apparatus 100 according to this disclosure will be described with reference to Figure 2. The water electrolysis cell 10 is a component of the cell stack and generates hydrogen and oxygen by causing the electrolysis of water contained in the electrolyte solution using electrical energy input from the outside. The water electrolysis cell 10 electrolyzes water when the electrolyte solution is supplied from the electrolyte supply unit 16 and a voltage is applied from the power supply unit 14. As shown in Figure 2, the water electrolysis cell 10 has as its main components a negative electrode separator 11, a positive electrode separator 12, and a membrane electrode assembly 13. These components will be described in order below.

[0025] (Negative electrode separator) The negative electrode separator 11 is a component that defines one side of the housing space of the water electrolysis cell 10. The negative electrode separator 11 may be, for example, a rectangular, or in other words, square, plate-shaped component. The negative electrode separator 11 may be made of a conductive material. A negative voltage is applied to the negative electrode separator 11 from the power supply unit 14 via a power supply unit 33 (see Figure 3), which will be described later. As shown in Figure 2, the electrolyte supply line L1 is connected to one end of the negative electrode separator 11. The electrolyte discharge line L2 is connected to the other end of the negative electrode separator 11. In the case of an anode feed type, the negative electrode side of the water electrolysis cell 10 (in this case, the negative electrode separator 11) is not connected to the electrolyte supply line L1, and no electrolyte is supplied to it.

[0026] (Positive electrode separator) The positive electrode separator 12 is a component that defines the other side of the housing space of the water electrolysis cell 10. The positive electrode separator 12 may be, for example, a rectangular, or in other words, square, plate. The positive electrode separator 12 may be made of a conductive material. A positive voltage is applied to the positive electrode separator 12 from the power supply unit 14 via the power supply unit 34 (see Figure 3), which will be described later. As shown in Figure 2, the electrolyte supply line L3 is connected to one end of the positive electrode separator 12. The electrolyte discharge line L4 is connected to the other end of the positive electrode separator 12. In the case of a cathode feed type, the positive electrode side of the water electrolysis cell 10 (in this case, the positive electrode separator 12) is not connected to the electrolyte supply line L3, and therefore no electrolyte is supplied.

[0027] (Configuration of the membrane electrode assembly) The membrane electrode assembly (MEA) 13 is a structure assembled by combining an ion exchange membrane, a catalyst, and a power supply. The membrane electrode assembly 13 is positioned between the negative electrode separator 11 and the positive electrode separator 12 described above, and is located in the housing space of the water electrolysis cell 10.

[0028] As shown in Figure 2, the membrane electrode assembly 13 comprises an ion exchange membrane 21, a negative electrode side catalyst layer 22, a positive electrode side catalyst layer 23, a negative electrode side power supply 24, a positive electrode side power supply 25, and protective films 26 and 27. Of the components of the membrane electrode assembly 13, the negative electrode side catalyst layer 22 and the negative electrode side power supply 24 constitute the negative electrode, and the positive electrode side catalyst layer 23 and the positive electrode side power supply 25 constitute the positive electrode. These components will be described in order below. The protective films 26 and 27 will be described in detail later.

[0029] (Regarding ion exchange membranes) The ion exchange membrane 21 is a membrane that selectively allows ions to pass through. The ion exchange membrane 21 is, for example, a solid polymer electrolyte membrane. Specifically, the ion exchange membrane 21 is a membrane that allows hydroxide ions (OH) to pass through. - ) may be a conductive anion exchange membrane (AEM). An anion exchange membrane (AEM) is obtained by adding ion exchange groups consisting of ammonium or imidazolium cations to a hydrocarbon main chain skeleton such as polystyrene, polyethersulfone, polyphenylene, or copolymer polymer to impart anionic conductivity. However, the ion exchange membrane 21 is not limited to anion exchange membranes, and may be, for example, a proton exchange membrane (PEM) of a different type from an anion exchange membrane.

[0030] The ion exchange membrane 21 may be, for example, a rectangular sheet and has flexibility, meaning it can bend easily under external force. The ion exchange membrane 21 may be formed with an external size smaller than the external size of the negative electrode separator 11 or the positive electrode separator 12. As shown in Figure 2, the ion exchange membrane 21 is positioned between the negative electrode separator 11 and the positive electrode separator 12 and is located in the housing space of the water electrolysis cell 10.

[0031] When a voltage is applied to the water electrolysis cell 10 by the power supply unit 14, the ion exchange membrane 21 undergoes the chemical reaction shown below on the negative electrode side, generating hydrogen from the electrolyte. The generated hydroxide ions move from the negative electrode side through the membrane electrode assembly 13 to the positive electrode side. 2H2O + 2e -→H2+2OH -

[0032] When a voltage is applied to the water electrolysis cell 10 by the power supply unit 14, the ion exchange membrane 21 undergoes the following chemical reaction on the positive electrode side, releasing hydroxide ions (OH) contained in the electrolyte. - Oxygen is produced from ). 2OH - → 1 / 2O2 + H2O + 2e -

[0033] As a result, the following chemical reactions occur when considering the water electrolysis cell 10 as a whole. H2O → H2 + 1 / 2O2

[0034] The ion exchange membrane 21 may contain a polyphenylene-based or tetraphenyl-based composition in its main chain and an imidazolium group or a quaternary ammonium group in its side chain, as an example of a membrane with relatively high ionic conductivity. Alternatively, the ion exchange membrane 21 may contain a polysulfone-based or bromobutylstyrene-based composition, as an example of a membrane with relatively high oxidation resistance.

[0035] (Regarding the negative electrode catalyst layer) The negative electrode side catalyst layer 22 is a layer (electrode side catalyst layer) that promotes the chemical reaction of water electrolysis. The negative electrode side catalyst layer 22 may be formed in the shape of a rectangular sheet, for example. The external dimensions of the negative electrode side catalyst layer 22 may be smaller than, for example, the external dimensions of the ion exchange membrane 21. As shown in Figure 2, the negative electrode side catalyst layer 22 is provided on the side of the protective membrane 26 opposite to the side in contact with the ion exchange membrane 21. The negative electrode side power supply 24 is connected to the side of the negative electrode side catalyst layer 22 opposite to the side in contact with the protective membrane 26. A negative voltage is applied to the negative electrode side catalyst layer 22 from the power supply unit 14 via the negative electrode side separator 11 and the negative electrode side power supply 24, and it functions as part of the negative electrode of the water electrolysis cell 10.

[0036] The negative electrode catalyst layer 22 may be made of a material that promotes chemical reactions, and various materials are available. For example, the negative electrode catalyst layer 22 may contain at least one of the following: nickel, nickel alloy, cerium oxide, lanthanum oxide, and platinum (Pt). In addition to the materials mentioned above, the negative electrode catalyst layer 22 may also contain other materials such as carbon.

[0037] (Regarding the positive electrode catalyst layer) The positive electrode side catalyst layer 23 is a layer (electrode side catalyst layer) that promotes the chemical reaction of water electrolysis. The positive electrode side catalyst layer 23 may be, for example, a rectangular, or in other words, square, sheet. The positive electrode side catalyst layer 23 may contain at least one of the following: Ni, Ni alloy, Cu-Co alloy, PbRu oxide, Ir oxide, etc. Also, its external size may be smaller than, for example, the external size of the ion exchange membrane 21. As shown in Figure 2, the positive electrode side power supply 25 is connected to the positive electrode side catalyst layer 23 on the side opposite to the side of the protective membrane 27 that is in contact with the ion exchange membrane 21. The positive electrode side catalyst layer 23 functions as part of the positive electrode of the water electrolysis cell 10 when a positive voltage is applied from the power supply unit 14 via the positive electrode side separator 12 and the positive electrode side power supply 25.

[0038] (Regarding the negative electrode power supply) The negative electrode side power supply member 24 is an electrical connecting member that transmits the voltage applied to the negative electrode side separator 11 to the negative electrode side catalyst layer 22. That is, the negative electrode side power supply member 24 is made of a conductive material. As shown in Figure 2, the negative electrode side power supply member 24 is located between the negative electrode side separator 11 and the negative electrode side catalyst layer 22, with one side in contact with the negative electrode side separator 11 and the other side in contact with the negative electrode side catalyst layer 22.

[0039] The negative electrode side power supply 24, which is not shown in Figure 2, is formed in such a way that the electrolyte and the hydrogen gas generated by the reaction can pass through its interior. Specifically, the negative electrode side power supply 24 is formed from a porous material such as a metal mesh structure, a sintered body, fibers, a conductive carbon fiber mesh structure, or a nonwoven fabric. In other words, the negative electrode side power supply 24 is formed from a material having a predetermined porosity. In terms of shape, the negative electrode side power supply 24 may have the same external dimensions as the negative electrode side catalyst layer 22. The negative electrode side catalyst layer 22 and the negative electrode side power supply 24 constitute the negative electrode of the water electrolysis cell 10.

[0040] (Regarding the positive electrode power supply) The positive electrode side power supply member 25 is an electrical connecting member that transmits the voltage applied to the positive electrode side separator 12 to the positive electrode side catalyst layer 23. That is, the positive electrode side power supply member 25 is made of a conductive material. The positive electrode side power supply member 25 is located between the positive electrode side separator 12 and the positive electrode side catalyst layer 23, with one side in contact with the positive electrode side separator 12 and the other side in contact with the positive electrode side catalyst layer 23.

[0041] The structure of the positive electrode side power supply 25, which is not shown in Figure 2, is formed such that the electrolyte and oxygen gas generated by the reaction can pass through its interior. Specifically, the positive electrode side power supply 25 may be formed from a porous material such as a metal mesh structure, a sintered body, a fiber, or a nonwoven fabric. In other words, the positive electrode side power supply 25 can be said to be formed from a material having a predetermined porosity. For example, the positive electrode side power supply 25 may have the same porosity as the negative electrode side power supply 24. In terms of shape, the positive electrode side power supply 25 may have the same external dimensions as the positive electrode side catalyst layer 23. The positive electrode side catalyst layer 23 and the positive electrode side power supply 25 constitute the positive electrode of the water electrolysis cell 10.

[0042] (Detailed configuration of the water electrolysis cell) Next, the detailed configuration of the water electrolysis cell 10 according to this disclosure will be described with reference to Figure 3. Figure 3 is an exploded perspective view of the water electrolysis cell according to this disclosure. In addition to the negative electrode separator 11, positive electrode separator 12, and membrane electrode assembly 13 described above, the water electrolysis cell 10 includes, for example, insulators 31, 32, power supply units 33, 34, insulating materials 35, 36, and end plates 37, 38. These configurations will be described in order below.

[0043] The insulators 31 and 32 are components that insulate the outer periphery of the negative electrode separator 11 from the outer periphery of the positive electrode separator 12. The insulators 31 and 32 are not particularly limited in material as long as they are insulating materials, and may be, for example, sheet resins such as PTFE (Poly Tetra Fluoro Ethylene).

[0044] As shown in Figure 3, the insulator 31 positioned on the negative electrode side may be a frame-shaped sheet member whose outer shape is slightly larger than the outer shape of the negative electrode side separator 11. Similarly, as shown in Figure 3, the insulator 31 is in contact with the negative electrode side separator 11 and, although not shown, covers the negative electrode side header (the piping section for electrolyte inlet and outlet).

[0045] As shown in Figure 3, the insulator 32 positioned on the positive electrode side may be a frame-shaped sheet member whose outer shape is slightly larger than the outer shape of the positive electrode side separator 12. As shown in Figure 3, the insulator 32 is in contact with the positive electrode side separator 12 and, although not shown, covers the positive electrode side header (the piping section for electrolyte inlet and outlet).

[0046] The power supply members 33 and 34 are electrical connecting members that transmit the negative voltage and positive voltage applied from the power supply unit 14 to the negative electrode separator 11 and the positive electrode separator 12, respectively. The power supply members 33 and 34 may be made of a conductive material, for example, a metal plate member (for example, a copper plate).

[0047] As shown in Figure 3, the power supply unit 33, which is positioned on the negative electrode side, is in contact with the negative electrode separator 11 from the opposite side of the housing space of the water electrolysis cell 10, and is electrically connected to the negative electrode separator 11. A negative voltage necessary for electrolysis in the water electrolysis cell 10 is applied to the power supply unit 33 from the power supply unit 14.

[0048] As shown in Figure 3, the power supply unit 34 is connected to the positive electrode separator 12 from the opposite side of the housing space of the water electrolysis cell 10, and is electrically connected to the positive electrode separator 12. A positive voltage necessary for electrolysis in the water electrolysis cell 10 is applied to the power supply unit 33 from the power supply unit 14.

[0049] The insulating material 35 is an insulating component located on the outside of the power supply body 33. The insulating material 35 may be formed to have an external size that is, for example, the same as or larger than the external size of the power supply body 33. The insulating material 36 is located on the outside of the power supply body 34. The insulating material 36 may have an external size that is, for example, the same as or larger than the external size of the power supply body 34. The insulating material 35 may be formed from, for example, polyacetal.

[0050] The end plates 37 and 38 are components that form the ends of the water electrolysis cell 10. The outer dimensions of the end plate 37 may be the same as, for example, the outer dimensions of the insulating materials 35 and 36, or larger than the outer dimensions of the insulating materials 35 and 36. The end plates 37 and 38 are formed from, for example, metal plate members (for example, stainless steel plates such as SUS304). Although not shown in Figure 3, the end plates 37 and 38 may have multiple bolt holes, and the surface pressure of the electrolysis surface can be appropriately set by applying pressure with bolts or jacks.

[0051] As shown in Figure 3, the negative electrode end plate 37 is located on the opposite side from the insulating material 35 with respect to the housing space of the water electrolysis cell 10.

[0052] As shown in Figure 3, the positive electrode end plate 38 is located on the opposite side from the insulating material 36 with respect to the housing space of the water electrolysis cell 10.

[0053] The water electrolysis cell 10 is not limited to the configuration described above. For example, the water electrolysis cell 10 may be a combination of a negative electrode separator 11, a positive electrode separator 12, and a membrane electrode assembly 13, with multiple membrane electrode assemblies stacked in layers.

[0054] (Regarding the structure of the membrane electrode assembly) Next, an example of the configuration of the membrane electrode assembly according to this disclosure will be described with reference to Figure 4. Figure 4 is a cross-sectional view showing an example of the configuration of the membrane electrode assembly according to this disclosure.

[0055] As shown in Figure 4, the membrane electrode assembly 13 has a protective film 26, a negative electrode side catalyst layer 22, a negative electrode side power supply 24, and a positive electrode side power supply 25 stacked in that order on one side of the ion exchange membrane 21. On the other side of the ion exchange membrane 21, the membrane electrode assembly 13 has a protective film 27, a positive electrode side catalyst layer 23, and a positive electrode side power supply 25 stacked in that order.

[0056] As shown in Figure 4, an electrolyte (in this example, water (H2O) in which potassium hydroxide (KOH) is dissolved) is supplied to the negative electrode power supply 24 to generate a reduction reaction of water and an anode reaction, thereby generating hydrogen (H2). Similarly, an electrolyte (in this example, water (H2O) in which potassium hydroxide (KOH) is dissolved) is supplied to the positive electrode power supply 25 to generate hydroxide ions (OH) in the opposite direction to the negative electrode side. - This causes an oxidation reaction, producing water (H2O) and oxygen (O2).

[0057] (Regarding the electrolyte supply unit) Next, the detailed configuration of the electrolyte supply unit 16 according to this disclosure will be described using Figure 5A. Figure 5A is a schematic diagram showing the configuration of the electrolyte supply unit according to this disclosure. In the following description, a so-called anode feed type configuration will be described, which has a positive electrode side supply unit 16B and does not have a negative electrode side supply unit 16A.

[0058] (Positive electrode supply unit) In this embodiment, the positive electrode supply unit 16B supplies an alkaline aqueous solution to the water electrolysis cell 10 as the electrolyte. The positive electrode supply unit 16B includes an electrolyte supply line L3 and an electrolyte discharge line L4, an oxygen gas liquid separation device 62, a pump 70, and a scale removal unit 80.

[0059] As described above, the gas-liquid separator 62 for oxygen gas is a tank for storing the electrolyte. The gas-liquid separator 62 for oxygen gas may also have the function of a gas-liquid separator, which separates the gaseous component oxygen contained in the electrolyte from the liquid component of the electrolyte.

[0060] The electrolyte supply line L3 is a pipe through which the electrolyte flows and is connected to the oxygen gas liquid separator 62 and the positive electrode side of the water electrolysis cell 10. Hereafter, the point where the electrolyte supply line L3 is connected to the oxygen gas liquid separator 62 will be referred to as connection point L3A, and the point where the electrolyte supply line L3 is connected to the positive electrode side of the water electrolysis cell 10 will be referred to as connection point L3B.

[0061] The electrolyte discharge line L4 is a pipe through which the electrolyte flows and is connected to the positive electrode side of the water electrolysis cell 10 and the gas-liquid separator 62 for oxygen gas.

[0062] Pump 70 draws electrolyte from the oxygen gas liquid separator 62, sends it to the electrolyte supply line L3, and supplies the electrolyte to the positive electrode side of the water electrolysis cell 10 via the electrolyte supply line L3. Pump 70 may be implemented as a diaphragm pump or a centrifugal pump, etc. Pump 70 may also be connected to a control device equipped with a CPU (Central Processing Unit) as a computing device and ROM (Read Only Memory), RAM (Ramdom Access Memory), etc. as storage devices, to control the flow rate discharged from pump 70.

[0063] The scale removal unit 80 removes metal scale and scale components contained in the electrolyte. Scale refers to a substance formed when metal ions in an aqueous solution precipitate as a solid. Scale components refer to metal ions dissolved in the electrolyte at concentrations below saturation. Specifically, the scale removal unit 80 selectively removes specific metal ions contained in the electrolyte. In other words, the scale removal unit 80 is capable of removing specific metal ions dissolved in the electrolyte at concentrations below saturation.

[0064] The scale removal unit 80 may be provided at any location within the positive electrode supply unit 16B that is in contact with the electrolyte, but in this embodiment, it is provided in the electrolyte supply line L3. More specifically, in this embodiment, the scale removal unit 80 is provided in the electrolyte supply line L3 between connection point L3A and connection point L3B. Alternatively, the scale removal unit 80 may be provided within the oxygen gas gas-liquid separator 62. In this case, a pipe connected to the scale removal unit 80 is provided within the oxygen gas gas-liquid separator 62, the electrolyte is supplied to the scale removal unit 80 through this pipe, and the electrolyte from which the scale has been removed in the scale removal unit 80 is returned to the oxygen gas gas-liquid separator 62 through this pipe. The detailed configuration of the scale removal unit 80 will be described later.

[0065] In the configuration described above, the water electrolysis system 1 receives potassium hydroxide solution from the oxygen gas liquid separator 62 to the positive electrode side of the water electrolysis cell 10, and hydroxide ions (OH) are produced at the positive electrode side. - An oxidation reaction takes place, and the generated oxygen (O2) is returned to the gas-liquid separator 62 for oxygen gas. Meanwhile, on the negative electrode side, a reduction reaction of water takes place, and the generated hydrogen is supplied to the gas-liquid separator 64 for hydrogen gas.

[0066] (Electrolyte supply line) Figure 5B is a schematic cross-sectional view showing the configuration of the electrolyte supply line. Since the electrolyte is an alkaline aqueous solution, metal ions may leach from the inner surface of the piping through which the electrolyte flows, forming scale, which can increase the water electrolysis voltage and reduce the electrolysis efficiency. In contrast, in this embodiment, the electrolyte supply line L3 has an alkali-resistant layer F2 formed on its inner surface in at least a portion of the section from connection point L3A to connection point L3B. This suppresses the leaching of metal ions from the electrolyte supply line L3 and prevents a decrease in electrolysis efficiency. Furthermore, since the electrolyte supply line L3 is the part that supplies the electrolyte to the water electrolysis cell 10, suppressing the leaching of metal ions from the electrolyte supply line L3 can particularly effectively suppress a decrease in the electrolysis efficiency of the water electrolysis cell 10.

[0067] More specifically, as shown in Figure 5B, the electrolyte supply line L3 has a base material F1 and an alkali-resistant layer F2. The base material F1 is a cylindrical member and is the base material portion of the piping of the electrolyte supply line L3. The base material F1 is preferably made of metal, and more preferably of stainless steel. The alkali-resistant layer F2 is a layer formed on the inner circumferential surface of the base material F1. In the section where the alkali-resistant layer F2 is formed, the entire inner circumferential surface of the base material F1 is covered by the alkali-resistant layer F2, so that the inner circumferential surface of the base material F1 is not exposed and does not come into contact with the electrolyte flowing inside.

[0068] The alkali-resistant layer F2 may be composed of any material that has alkali resistance (i.e., is poorly soluble or insoluble in alkaline aqueous solutions). For example, the alkali-resistant layer F2 may be made of nickel. In this case, for example, the nickel alkali-resistant layer F2 may be formed by nickel plating the inner circumferential surface of the base material F1.

[0069] Furthermore, the alkali-resistant layer F2 may be composed of an alkali-resistant resin. Polyethylene (PE) is an example of an alkali-resistant resin. Other alkali-resistant resins include polypropylene (PP), ABS (Acrylonitrile Butadiene Styrene) resin (acrylonitrile-butadiene-styrene copolymer resin), polyetheretherketone (PEEK), polyvinyl chloride (PVC), and polymethyl methacrylate (PMMA).

[0070] The alkali-resistant layer F2 may be provided in any section of the electrolyte supply line L3 from connection point L3A to connection point L3B, but in this embodiment, as shown in Figure 5B, it is provided in the section between the location where the scale removal unit 80 is provided and the connection point L3B connected to the water electrolysis cell 10. This suppresses the formation of scale in the electrolyte from which scale has been removed by the scale removal unit 80 until it reaches the water electrolysis cell 10, and thus can particularly effectively suppress the decrease in the electrolysis efficiency of the water electrolysis cell 10.

[0071] Furthermore, the alkali-resistant layer F2 may be provided throughout the entire section from connection point L3A to connection point L3B. This allows for a more effective suppression of the decrease in the electrolysis efficiency of the water electrolysis cell 10.

[0072] Furthermore, in this embodiment, no alkali-resistant layer F2 is formed on the electrolyte discharge line L4. That is, the electrolyte discharge line L4 is made of base material F1, and no alkali-resistant layer F2 is formed on the inner surface of the base material F1 throughout its entire length. The electrolyte that passes through the electrolyte discharge line L4 passes through the scale removal section 80 before reaching the water electrolysis cell 10, and scale can be removed at this time. Therefore, even without forming an alkali-resistant layer F2 on the electrolyte discharge line L4, the decrease in the electrolysis efficiency of the water electrolysis cell 10 can be suppressed. Moreover, by not forming an alkali-resistant layer F2 on the electrolyte discharge line L4, the increase in cost can also be suppressed. However, an alkali-resistant layer F2 may also be formed on the inner surface of the electrolyte discharge line L4. This will further appropriately suppress the decrease in the electrolysis efficiency of the water electrolysis cell 10.

[0073] Furthermore, the alkali-resistant layer F2 may be provided on metal components of the water electrolysis apparatus 100 other than the electrolyte supply line L3, at locations that come into contact with the electrolyte. For example, the alkali-resistant layer F2 may be provided on the part of the water electrolysis cell 10 that comes into contact with the electrolyte, i.e., on the inner surface of the positive electrode separator 12. Alternatively, the alkali-resistant layer F2 may be provided on the part of the pump 70 that comes into contact with the electrolyte. This further effectively suppresses the decrease in the electrolysis efficiency of the water electrolysis cell 10.

[0074] (Regarding performance for each electrolyte supply method) Next, the performance of the anode feed of the water electrolysis system 1 according to this disclosure will be explained using Figure 6. Figure 6 is a graph showing the current-voltage characteristics for each electrolyte supply mode of the water electrolysis system according to this disclosure.

[0075] In FIG. 6, line T1 shows the relationship between current density and cell voltage in cathode feed, line T2 shows the relationship between current density and cell voltage in anode feed, and line T3 shows the relationship between current density and cell voltage in bipolar feed. As shown in lines T2 and T3, anode feed and bipolar feed have an equivalent relationship of electrolytic voltage with respect to current. This means that the two have substantially equivalent electrolytic performance. On the other hand, as shown in line T1, in the case of cathode feed, the results show that no extreme voltage rise is observed with respect to anode feed and bipolar feed.

[0076] As a result of analysis, it was suggested that the activation voltage of cathode feed is large. This is because on the anode side where the oxygen evolution reaction with high resistance occurs, between the anion exchange membrane via the potassium hydroxide solution and the anode electrode catalyst, hydroxide ion (OH - -) has no migration path, which is presumed to result in a reduced reaction field. Therefore, it can be said that the anode feed type is more advantageous.

[0077] As described above, compared with the bipolar feed configuration in which the electrolyte is supplied to both electrodes, the anode feed configuration eliminates the need for the negative electrode side supply unit 16A. Therefore, since the number of parts of the water electrolysis cell 10 can be reduced, the manufacturing cost of the water electrolysis cell 10 and the procurement cost of parts can be reduced. In addition, by providing the scale removing unit 80 only on the anode side, it is also possible to suppress an increase in water electrolysis voltage, that is, a decrease in electrolysis efficiency.

[0078] (Regarding temporal changes in performance for each electrolyte supply configuration) Next, the transition of water electrolysis performance over time for the anode feed of the water electrolysis system 1 according to the present disclosure will be described with reference to FIG. 7. FIG. 7 is a graph showing the transition of electrolysis voltage along with the elapse of energization time for each electrolyte supply configuration of the water electrolysis system according to the present disclosure.

[0079] In Figure 7, line T4 shows the relationship between energization time and cell voltage in the cathode feed, line T5 shows the relationship between energization time and cell voltage in the anode feed, and line T6 shows the relationship between energization time and cell voltage in the bipolar feed. As shown by lines T5 and T6, when water electrolysis was performed by energizing the anode feed for 16 hours, no significant increase in electrolysis voltage was observed even after 16 hours, and it was found to be equivalent to the electrolysis voltage at the start of energization. Furthermore, the electrolysis voltage of the bipolar feed and the anode feed were equivalent after 16 hours, indicating that the electrolysis voltage of the anode feed is not significantly different from that of the bipolar feed.

[0080] Based on the above, the anode feed configuration of the water electrolysis system 1 according to this disclosure can suppress the rise in electrolysis voltage as the energizing time elapses. Therefore, it is possible to provide a water electrolysis system 1 that can suppress costs and prevent deterioration of electrolysis performance even as the electrolysis time elapses.

[0081] In the above description, the electrolyte is supplied only to the positive electrode side in an anode-feed type, and the negative electrode side supply unit 16A is not provided. In the following, preferred configurations of the negative electrode side supply unit 16A in cases where the negative electrode side supply unit 16A is provided, such as in a bipolar-feed type, will be described. Figure 8 is a schematic diagram showing the configuration of the electrolyte supply unit according to this disclosure.

[0082] (Negative electrode supply unit) In this embodiment, the negative electrode supply unit 16A supplies an alkaline aqueous solution to the water electrolysis cell 10 as the electrolyte. The negative electrode supply unit 16A includes an electrolyte supply line L1 and an electrolyte discharge line L2, a gas-liquid separator 64 for hydrogen gas, a pump 72, and a scale removal unit 80.

[0083] As described above, the hydrogen gas gas-liquid separator 64 is a tank for storing the electrolyte. The hydrogen gas gas-liquid separator 64 may also have the function of a gas-liquid separator, which separates hydrogen, which is the gaseous component contained in the electrolyte, from the electrolyte, which is the liquid component.

[0084] The electrolyte supply line L1 is a pipe through which the electrolyte flows and is connected to the hydrogen gas gas-liquid separator 64 and the negative electrode side of the water electrolysis cell 10. Hereafter, the point where the electrolyte supply line L1 is connected to the hydrogen gas gas-liquid separator 64 will be referred to as connection point L1A, and the point where the electrolyte supply line L1 is connected to the negative electrode side of the water electrolysis cell 10 will be referred to as connection point L1B (see Figure 8).

[0085] The electrolyte discharge line L2 is a pipe through which the electrolyte flows, and is connected to the negative electrode side of the water electrolysis cell 10 and the gas-liquid separator 64 for hydrogen gas.

[0086] Pump 72 draws electrolyte from the hydrogen gas liquid separator 64, sends it to the electrolyte supply line L1, and supplies the electrolyte to the negative electrode side of the water electrolysis cell 10 via the electrolyte supply line L1. The configuration of pump 72 may be the same as that of pump 70.

[0087] The scale removal unit 80 removes metal scale contained in the electrolyte. The scale removal unit 80 may be provided at any location in the negative electrode supply unit 16A that is in contact with the electrolyte, but in this embodiment, it is provided in the electrolyte supply line L1. More specifically, in this embodiment, the scale removal unit 80 is provided in the electrolyte supply line L1 between connection point L1A and connection point L1B. Alternatively, the scale removal unit 80 may be provided in the hydrogen gas gas-liquid separator 64. In this case, a pipe connected to the scale removal unit 80 is provided in the hydrogen gas gas-liquid separator 64, the electrolyte is supplied to the scale removal unit 80 through that pipe, and the electrolyte from which the scale has been removed in the scale removal unit 80 is returned to the hydrogen gas gas-liquid separator 64 through that pipe.

[0088] The electrolyte supply line L1 is provided with an alkali-resistant layer F2 on its inner surface in at least a portion of the section from connection point L1A to connection point L1B.

[0089] More specifically, the electrolyte supply line L1, like the electrolyte supply line L3, has a base material F1 and an alkali-resistant layer F2. The alkali-resistant layer F2 may be provided in any section of the electrolyte supply line L1 from connection point L1A to connection point L1B, but in this embodiment, it is provided in the section between the location where the scale removal unit 80 is provided and the connection point L1B connected to the water electrolysis cell 10. The alkali-resistant layer F2 may also be provided in the entire section from connection point L1A to connection point L1B.

[0090] Furthermore, in this embodiment, no alkali-resistant layer F2 is formed on the electrolyte discharge line L2. That is, the electrolyte discharge line L2 is made of the base material F1, and no alkali-resistant layer F2 is formed on the inner surface of the base material F1 throughout its entire length. However, an alkali-resistant layer F2 may also be formed on the inner surface of the electrolyte discharge line L2.

[0091] Furthermore, the alkali-resistant layer F2 may be provided not only in the electrolyte supply line L1, but also in other locations of the metal components constituting the water electrolysis apparatus 100 that come into contact with the electrolyte. For example, the alkali-resistant layer F2 may be provided in the location of the water electrolysis cell 10 that comes into contact with the electrolyte, i.e., on the inner surface of the negative electrode separator 11. Alternatively, the alkali-resistant layer F2 may be provided in the location of the pump 72 that comes into contact with the electrolyte.

[0092] (Regarding the change in performance over time due to the presence or absence of an alkali-resistant layer) Next, the change in electrolysis voltage over time, depending on the presence or absence of the alkali-resistant layer F2 on the inner surface of the piping of the water electrolysis system 1 according to this disclosure, will be explained using Figure 9. Figure 9 is a graph showing the change in electrolysis voltage over time with and without the alkali-resistant layer of the water electrolysis system according to this disclosure. Figure 9 explains the case with and without nickel plating as the alkali-resistant layer. Line T9 in Figure 9 shows the relationship between the energizing time and the water electrolysis voltage when nickel plating is not provided, and line T10 shows the relationship between the energizing time and the water electrolysis voltage when nickel plating is provided. As shown by lines T9 and T10, it is shown that when an alkali-resistant layer is provided, the rise in the water electrolysis voltage is suppressed even as the energizing time elapses, compared to when an alkali-resistant layer is not provided. Therefore, it is possible to suppress the decrease in the efficiency of water electrolysis as the energizing time of the water electrolysis cell 10 elapses.

[0093] As explained above, by providing an alkali-resistant layer F2 such as nickel plating on the inner surface of the electrolyte supply line L3, iron ions (Fe) from the surface of the piping can be prevented. 3+ ) and chromium ions (Cr 3+ This minimizes the elution of trace amounts of metal ions, such as ) and other metal ions. As a result, it is possible to suppress the deposition of scale on the water electrolysis cell 10, thereby suppressing the rise in water electrolysis voltage as the energizing time progresses and suppressing the deterioration of water electrolysis efficiency as the energizing time progresses. Therefore, it is possible to provide a water electrolysis system 1 that can prevent deterioration of electrolysis performance even as the electrolysis time progresses while keeping costs down.

[0094] Next, the change in electrolysis voltage over time with and without a resin coating on the inner surface of the piping of the water electrolysis system 1 according to this disclosure will be explained using Figure 10. Figure 10 is a graph showing the change in electrolysis voltage over time with and without an alkali-resistant layer in the water electrolysis system according to this disclosure. Figure 10 explains the case with and without a resin coating as an alkali-resistant layer. Line T10 in Figure 10 shows the relationship between the energizing time and the water electrolysis voltage when no resin coating is provided, and line T11 shows the relationship between the energizing time and the water electrolysis voltage when a resin coating is provided. As shown in Figure 10, compared to the case without a resin coating, the rise in the water electrolysis voltage is suppressed even as the energizing time elapses when a resin coating is provided. Therefore, it is possible to suppress the decrease in the efficiency of water electrolysis as the energizing time of the water electrolysis cell 10 elapses.

[0095] (Regarding the scale removal section) Next, the configuration of the scale removal unit 80 of the water electrolysis system 1 according to this disclosure will be explained with reference to Figure 11. Figure 11 is a diagram showing an example of the configuration of the scale removal unit of the water electrolysis system according to this disclosure. As shown in Figure 11, the scale removal unit 80 according to this disclosure comprises a filter unit 82, an anion exchange resin unit 84, and a chelate resin unit 86. As shown in Figure 11, the electrolyte is supplied in the order of filter unit 82, anion exchange resin unit 84, and chelate resin unit 86.

[0096] The filter section 82 filters out solid particles from the electrolyte. The filter section 82 may be implemented as, for example, a mesh filter. A mesh filter is a filter having a mesh structure made by weaving together linear members such as metal or plastic. The size of the mesh openings determines the size of the solid particles that are filtered out. The diameter of the pores in the mesh of the mesh filter may be, for example, 1 micrometer. Furthermore, it is desirable that the filter section 82 be made of an alkali-resistant material, for example, polyethersulfone.

[0097] The anion exchange resin section 84 is a resin that has positively charged fixed ions inside. This allows the anion exchange resin section 84 to selectively permeate negatively charged ions. Specifically, the anion exchange resin section 84 allows hydroxide ions (OH) to pass through. - ) It may be a conductive anion exchange membrane (AEM). An anion exchange membrane (AEM) is obtained by adding ion exchange groups consisting of ammonium or imidazolium cations to a hydrocarbon main chain skeleton such as polystyrene, polyethersulfone, polyphenylene, or copolymer polymer to impart anionic conductivity.

[0098] The chelate resin section 86 selectively extracts specific ions from the electrolyte using the chelate resin. The chelate resin section 86 extracts trace amounts of iron ions (Fe) that leach from the surface of the stainless steel pipe. 2+ Fe 3+ ) and chromium ions (Cr 2+ 、 Cr 3+ The chelate resin portion 86 may be formed from a chelate resin that is particularly good at capturing iron ions (Fe 2+ 、 Fe 3+ ) and nickel ions (Ni 2+ Ni 3+ ) and may be formed by a polyamine-type chelate resin, which is a chelate resin that easily captures ). That is, the chelate resin portion 86 includes a resin material having at least one of iminodiacetic acid, aminophosphoric acid, and type I quaternary ammonium as a functional group.

[0099] As a result, the electrolyte supplied to the scale removal unit 80 has solid particles such as metal with a particle size larger than the diameter of the filter pores removed by the filter unit 82. Then, the anion exchange resin unit 84 allows negative ions in the electrolyte to pass through. Finally, the chelate resin unit 86 captures specific metal ions in the electrolyte that could become scale. Therefore, scale components that could degrade the performance of the anion exchange membrane of the water electrolysis cell 10 can be appropriately removed from the electrolyte.

[0100] (Structure and effect) The water electrolysis apparatus 100 according to the first embodiment includes a water electrolysis cell 10 to which an electrolyte solution, which is an alkaline aqueous solution, is supplied; an oxygen gas liquid separator 62 in which the electrolyte solution is stored; and an electrolyte supply line L3 which is a pipe connecting the oxygen gas liquid separator 62 to the positive electrode side of the water electrolysis cell 10, and through which the electrolyte solution flows from the oxygen gas liquid separator 62 to the positive electrode side of the water electrolysis cell 10. In at least a portion of the electrolyte supply line L3, from the connection point L3A with the oxygen gas liquid separator 62 to the connection point L3B with the positive electrode side of the water electrolysis cell 10, an alkali-resistant layer F2 having alkali resistance is formed on the inner surface.

[0101] This configuration suppresses the elution of metal ions from the surface of the electrolyte supply line L3, thereby suppressing the deposition of scale on the water electrolysis cell 10. This suppresses the rise in water electrolysis voltage over time and reduces the deterioration of water electrolysis efficiency over time. Therefore, it is possible to provide a water electrolysis apparatus 100 that can prevent deterioration of electrolysis performance even after a long electrolysis period.

[0102] The water electrolysis apparatus 100 according to the second embodiment is the same as the water electrolysis apparatus 100 according to the first embodiment, wherein the alkali-resistant layer is made of nickel or an alkali-resistant resin.

[0103] This configuration makes it possible to provide a water electrolysis apparatus 100 that can appropriately suppress the elution of metal ions from the surface of the electrolyte supply line L3, thereby preventing deterioration of electrolysis performance even after an elapsed electrolysis time.

[0104] The water electrolysis apparatus 100 according to the third embodiment is the water electrolysis apparatus 100 according to the first or second embodiment, wherein the electrolyte supply line L3 is provided with a scale removal section 80 for removing scale components between the connection point L3A with the gas-liquid separator 62 for oxygen gas and the connection point L3B with the positive electrode side of the water electrolysis cell 10, and the alkali-resistant layer F2 is formed in the section of the electrolyte supply line L3 between the location where the scale removal section 80 is provided and the connection point L3B with the positive electrode side of the water electrolysis cell 10.

[0105] This configuration makes it possible to provide a water electrolysis apparatus 100 that can appropriately suppress the elution of metal ions from the surface of the electrolyte supply line L3, thereby preventing deterioration of electrolysis performance even after an elapsed electrolysis time.

[0106] The water electrolysis apparatus 100 according to the fourth embodiment is the water electrolysis apparatus 100 according to the third embodiment, wherein the scale removal unit 80 comprises a filter unit 82 that captures particles of a predetermined diameter contained in the electrolyte, an anion exchange resin unit 84 that selectively allows ions of the electrolyte to pass through, and a chelate resin unit 86 formed of a chelate resin that selectively captures metal ions of the electrolyte, the chelate resin comprising a resin material having at least one of iminodiacetic acid, aminophosphoric acid, and type I quaternary ammonium as a functional group.

[0107] With this configuration, the electrolyte supplied to the scale removal unit 80 has solid particles such as metal with a particle size larger than the diameter of the filter pores removed by the filter unit 82, the anion exchange resin unit 84 allows negative ions in the electrolyte to pass through, and the chelate resin unit 86 can capture specific metal ions that can become scale in the electrolyte. Therefore, scale components that may degrade the performance of the anion exchange membrane of the water electrolysis cell 10 can be appropriately removed from the electrolyte. Thus, a water electrolysis device 100 can be provided that prevents deterioration of electrolysis performance even after the electrolysis time has elapsed.

[0108] The water electrolysis apparatus 100 according to the fifth embodiment is a water electrolysis apparatus 100 according to any one of the first to fourth embodiments, wherein electrolyte is not supplied to the negative electrode side of the water electrolysis cell 10.

[0109] This anode feed configuration eliminates the need for the cathode-side electrolyte supply line and scale removal unit compared to a bipolar feed configuration that supplies electrolyte to both electrodes. As a result, the number of parts in the water electrolysis system 1 can be reduced, thereby lowering the manufacturing cost and parts procurement cost of the water electrolysis device 100. Consequently, it is possible to provide a water electrolysis device 100 that can suppress costs while preventing deterioration of electrolysis performance even after an elapsed electrolysis time.

[0110] Although embodiments of the present disclosure have been described above, the embodiments are not limited to those described herein. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the gist of the embodiments described above. [Explanation of symbols]

[0111] 1. Water electrolysis system 10 Water electrolysis cell 11. Negative electrode separator 12 Positive electrode separator 13 Membrane electrode assembly 14 Power supply section 16 Electrolyte supply section 16A Negative side supply section 16B Positive electrode side supply section 21 Ion exchange membrane 22 Negative electrode side catalyst layer 23 Positive electrode side catalyst layer 24 Negative electrode power supply 25 Positive electrode power supply 26,27 Protective film 31,32 Insulator 33,34 Power feeder 35,36 Insulating material 37, 38 End Plates 40 Power generation equipment 50 rectifier 62. Gas-liquid separation device for oxygen gas 64. Gas-liquid separation device for hydrogen gas 70, 72 pumps 80 Scale removal section 82 Filter section 84 Anion exchange resin part 86 Chelate resin part 100 Water electrolysis equipment

Claims

1. A water electrolysis cell is supplied with an alkaline aqueous electrolyte, A gas-liquid separator for oxygen gas in which the aforementioned electrolyte is stored, An electrolyte supply line is a pipe through which the electrolyte flows from the oxygen gas gas-liquid separator to the positive electrode side of the water electrolysis cell, connecting the oxygen gas gas-liquid separator and the positive electrode side of the water electrolysis cell. It has, The electrolyte supply line has an alkali-resistant layer formed on its inner surface in at least a portion of the section from the connection point with the gas-liquid separator for oxygen gas to the connection point with the positive electrode side of the water electrolysis cell. Water electrolysis equipment.

2. The alkali-resistant layer is composed of nickel or an alkali-resistant resin. The water electrolysis apparatus according to claim 1.

3. The electrolyte supply line is provided with a scale removal section between the connection point to the gas-liquid separation device for oxygen gas and the connection point to the positive electrode side of the water electrolysis cell, for removing scale components. The alkali-resistant layer is formed in the section of the electrolyte supply line between the location where the scale removal section is provided and the connection point to the positive electrode side of the water electrolysis cell. A water electrolysis apparatus according to claim 1 or claim 2.

4. The scale removal unit is A filter unit that captures particles of a predetermined diameter contained in the electrolyte, An anion exchange resin portion that selectively allows ions of the electrolyte to pass through, The device comprises a chelate resin portion formed by a chelate resin that selectively captures metal ions in the electrolyte, The chelate resin comprises a resin material having at least one of iminodiacetic acid, aminophosphate, and type I quaternary ammonium as a functional group. The water electrolysis apparatus according to claim 3.

5. The electrolyte is not supplied to the negative electrode side of the water electrolysis cell. A water electrolysis apparatus according to claim 1 or claim 2.

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