Water electrolysis apparatus, hydrogen production system, and water electrolysis method

Abstract

To provide a water electrolysis apparatus capable of reducing overvoltage in water electrolysis without heating a water electrolysis cell.SOLUTION: A water electrolysis apparatus 1 comprises an anode-side supply line La1 for supplying degassed water Wa1 from which dissolved oxygen has been removed to the anode side (anode 12 and separator 14) of a water electrolysis cell 10, an anode-side discharge line La2 for discharging water Wa2 containing oxygen gas released from the anode side of the water electrolysis cell 10 to the outside of the water electrolysis cell 10, and a cathode-side discharge line Lc2 for discharging water Wc2 containing hydrogen gas released from the cathode side of the water electrolysis cell 10 to the outside of the water electrolysis cell 10. A DC power source is connected to the anode 12 and the cathode 13 of the water electrolysis cell 10 to electrolyze water and generate oxygen gas on the anode side and hydrogen gas on the cathode side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a water electrolysis device, a hydrogen production system, and a water electrolysis method. [Background technology]

[0002] A hydrogen energy system that contributes to the efficient use of renewable energy consists of technologies for hydrogen production, storage and transportation, and hydrogen utilization. Of these, hydrogen production by water electrolysis is the most expensive, which is hindering the social implementation of hydrogen energy systems. A known water electrolysis device is a polymer electrolyte membrane water electrolysis device (PEMWE) that includes a water electrolysis cell that electrolyzes water using a solid polymer electrolyte membrane to generate oxygen at the anode and hydrogen at the cathode (for example, Patent Documents 1 and 2). Compared to other water electrolysis devices, solid polymer water electrolysis devices are superior in terms of high current density operation, responsiveness, and compactness, but are expensive because they use rare metals such as iridium and platinum as electrode catalysts.To date, efforts to reduce the cost of water electrolysis cells in water electrolysis devices have been made by replacing expensive catalytic precious metals with non-precious metals, or by optimizing operating conditions and water electrolysis cell design to enable high current density operation and reduce electrode area.

[0003] In a solid polymer water electrolysis system, water supplied to the anode side is converted into 2H2O → O2 + 4H + +4e - It is decomposed by the reaction of H + moves through the solid polymer electrolyte membrane and remains on the cathode side for 4 hours. + +4e - →Hydrogen gas is generated by the reaction of 2H2. In order to generate hydrogen gas and oxygen gas highly efficiently by electrolyzing water, it is necessary to apply a voltage between the anode and cathode that is higher than the theoretical decomposition voltage of water (1.23 V) by the amount of the water electrolysis overvoltage, but it is desirable for the electrolysis voltage to be as small as possible. Non-Patent Document 1 discloses a water electrolysis device in which water near its boiling point is supplied to an anode and a water electrolysis reaction is carried out under boiling conditions. The water electrolysis device disclosed in Non-Patent Document 1 can heat a water electrolysis cell to the boiling point of 100°C or higher. At this time, the supplied water boils near the anode, generating water vapor bubbles. This reduces the oxygen partial pressure and dissolved oxygen concentration in the oxygen bubbles generated by water electrolysis on the anode surface, thereby reducing the overvoltage. By superimposing boiling in this way, water electrolysis can be carried out with high efficiency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-228292 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-147562 [Non-patent literature]

[0005] [Non-Patent Document 1] I. Li and K. Ito et al., Int. J. Hydrogen Energy, 47(2022)25499-25510 Summary of the Invention [Problem to be solved by the invention]

[0006] In the water electrolysis device disclosed in Non-Patent Document 1, which performs a water electrolysis reaction under boiling conditions, the cell itself is heated to 100°C or higher, which causes the deterioration of constituent materials (especially the solid polymer electrolyte membrane). Under these circumstances, an object of the present invention is to provide a water electrolysis device that can reduce the anode overvoltage during water electrolysis without heating the water electrolyzer, and a hydrogen production system including the water electrolysis device. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the present inventors found that anode overvoltage can be reduced without heating the water electrolysis apparatus by using degassed water with a reduced dissolved oxygen concentration as water to be supplied to the anode, and completed the present invention.

[0008] That is, the present invention relates to the following inventions. <1> a water electrolysis cell including a solid polymer electrolyte membrane, an anode provided in contact with one surface of the solid polymer electrolyte membrane, and a cathode provided in contact with the other surface of the solid polymer electrolyte membrane; an anode-side supply line that supplies deaerated water obtained by removing dissolved oxygen from water to the anode of the water electrolysis cell; an anode-side discharge line for discharging the oxygen-containing water discharged from the anode side of the water electrolysis cell to the outside of the water electrolysis cell; a cathode-side discharge line for discharging the hydrogen gas-containing water discharged from the cathode side of the water electrolysis cell to the outside of the water electrolysis cell; A water electrolysis device comprising: <2> <1> A hydrogen production system including the water electrolysis apparatus according to claim 1, a water storage tank for storing water; a purification device for purifying the water transferred from the water storage tank to produce purified water; a degassing device that removes dissolved oxygen from the purified water transferred from the purification device to produce degassed water, The degassed water is supplied to the anode of the water electrolyzer via the anode-side supply line. <3> The degassing device is a membrane degassing device. <2> The hydrogen production system according to claim 1 <4> The purification device comprises a first purification device that purifies the water transferred from the water storage tank, and a second purification device that further purifies the purified water supplied from the first purification device. <2> or <3> The hydrogen production system according to claim 1. <5> a circulation flow path for circulating water containing oxygen gas released from the anode side of the water electrolysis cell to the degassing device; <2> from <4> The hydrogen production system according to any one of the above. <6> The circulation flow path is connected to the purification device. <5> The hydrogen production system according to claim 1. <7> A water electrolysis method using a water electrolysis cell including a solid polymer electrolyte membrane, an anode provided in contact with one surface of the solid polymer electrolyte membrane, and a cathode provided in contact with the other surface of the solid polymer electrolyte membrane, The water electrolysis method, wherein the water supplied to the anode is degassed water from which dissolved oxygen has been removed. <8> The degassed water is purified water from which dissolved oxygen has been removed. <7> The water electrolysis method according to claim 1. [Effects of the Invention]

[0009] According to the present invention, there are provided a water electrolysis device capable of reducing the overvoltage of water electrolysis without heating the water electrolyzer, and a hydrogen production system including the water electrolysis device. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating a hydrogen production system according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating a water electrolysis device according to an embodiment of the present invention. [Figure 3] FIG. 1 is a schematic cross-sectional view of a water electrolysis cell (single cell) according to an embodiment of the present invention. [Figure 4] FIG. 2 is a plan view of an anode separator (interdigitated flow channels) according to an embodiment of the present invention. [Figure 5] FIG. 10 is an explanatory diagram of oxygen gas discharge through an interdigitated flow channel. [Figure 6] FIG. 1 is a schematic diagram of a water electrolysis cell (single cell) used in the examples. [Figure 7] FIG. 1 is a schematic diagram of a degassing device used in the examples. [Figure 8] FIG. 2 shows the IV characteristics of the water electrolysis cell used in the examples ((a) without degassing, (b) with degassing). DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below using examples, etc., but the present invention is not limited to the examples below and can be practiced with any modifications within the scope of the gist of the present invention. In this specification, the symbol "to" is used as an expression including the numerical values ​​or physical quantities before and after it. In addition, in this specification, the expression "A and / or B" includes "A only," "B only," and "both A and B."

[0012] The water electrolysis device of the present invention comprises: a water electrolysis cell including a solid polymer electrolyte membrane, an anode provided in contact with one surface of the solid polymer electrolyte membrane, and a cathode provided in contact with the other surface of the solid polymer electrolyte membrane; an anode-side supply line that supplies degassed water, obtained by removing dissolved oxygen from water, to the anode of the water electrolysis cell; an anode-side discharge line that discharges water containing oxygen gas released from the anode side of the water electrolysis cell to the outside of the water electrolysis cell; and a cathode-side discharge line that discharges water containing hydrogen gas released from the cathode side of the water electrolysis cell to the outside of the water electrolysis cell.

[0013] The present invention also provides a water electrolysis method using a water electrolysis cell including a solid polymer electrolyte membrane, an anode provided in contact with one surface of the solid polymer electrolyte membrane, and a cathode provided in contact with the other surface of the solid polymer electrolyte membrane, wherein the water supplied to the anode is degassed water from which dissolved oxygen has been removed.

[0014] With this configuration, the water electrolysis device of the present invention supplies degassed water, from which dissolved oxygen has been removed, to water to be electrolyzed on the anode side, thereby reducing anode overvoltage, thereby improving the efficiency of water electrolysis without heating the water electrolytic cell.

[0015] Furthermore, a hydrogen production system of the present invention includes the water electrolysis device of the present invention described above, and includes a water storage tank for storing water, a purification device that purifies water transferred from the water storage tank to produce purified water, and a degassing device that produces degassed water by degassing dissolved oxygen from the purified water transferred from the purification device, and the degassed water is supplied to the anode of the water electrolysis cell via the anode-side supply line.

[0016] The hydrogen production system of the present invention includes the water electrolysis device of the present invention described above, and therefore is capable of producing hydrogen with high efficiency.

[0017] In the present invention, "deaerated water from which dissolved oxygen has been removed" (hereinafter simply referred to as "deaerated water") refers to water whose dissolved oxygen concentration has been reduced below the saturated dissolved oxygen concentration by deaeration treatment. The details of why the use of degassed water as water supplied to the anode reduces the anode overvoltage in water electrolysis are not completely clear. However, it is presumed that the use of degassed water with a reduced dissolved oxygen concentration reduces the oxygen activity at the anode, which contributes to the reduction in the concentration overvoltage of the anode.

[0018] The degree of degassing in degassed water (the ratio of the dissolved oxygen concentration to the saturated dissolved oxygen concentration) is not limited as long as the anodic concentration overpotential is significantly reduced. The degassing degree is, for example, 0.30 or less, 0.20 or less, 0.15 or less, or 0.10 or less, where the saturated dissolved oxygen concentration is 1. Since the saturated dissolved oxygen concentration of water (1 atmosphere, 25°C) is 8.5 mg / L, a degassing degree of 0.10 results in a dissolved oxygen concentration of 0.85 mg / L (1 atmosphere, 25°C).

[0019] Any method can be used to remove dissolved oxygen from water as long as it can produce degassed water with a desired degree of degassing, and known degassing devices such as a membrane degasser, vacuum degasser, or heating device can be used.

[0020] The water used to produce degassed water is not limited as long as it does not impair the object of the present invention, but purified water is preferred. "Purified water" refers to water that has been treated to remove impurities (but does not include degassing treatment). In the present invention, water purified by a known method can be used, for example, water purified by a known purification device such as ion exchange, distillation, reverse osmosis membrane, ultrafiltration membrane, or microfiltration membrane, or a combination of these methods.

[0021] Embodiments of a water electrolysis apparatus and a hydrogen production system according to the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and can be modified as desired without departing from the spirit and scope of the present invention. The dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In all drawings, like components are designated by like reference numerals, and descriptions thereof will be omitted where appropriate.

[0022] In this specification, the term "line" is a general term for a line such as a flow path, a passage, or a conduit through which a fluid can flow.

[0023] Fig. 1 shows a hydrogen production system equipped with a water electrolysis apparatus according to an embodiment of the present invention, and Fig. 2 shows a schematic diagram of the configuration of the water electrolysis apparatus according to an embodiment of the present invention.

[0024] In FIG. 1 , the hydrogen production system 100 is mainly composed of a water electrolysis apparatus 1 including a water electrolysis cell 10 and a degassing apparatus 20, a water storage tank 30 connected to a raw water line L1, a first purification apparatus 41 connected to the water storage tank 30 via a line L2, a second purification apparatus 42 connected to the first purification apparatus 41 via a line L3, a gas-liquid separator 51 connected to the anode side of the water electrolysis apparatus 1 via a line La2, a gas-liquid separator 52 connected to the cathode side of the water electrolysis apparatus 1 via a line Lc2, and a circulation flow path 60 that circulates the water from which oxygen gas has been removed, discharged from the gas-liquid separator 51, to the second purification apparatus 42.

[0025] As shown in Figures 1 and 2, the water electrolysis apparatus 1 includes an anode-side supply line La1 that supplies degassed water Wa1 degassed in the degassing device 20 to the anode side (anode 12 and separator 14) of the water electrolysis cell 10, an anode-side discharge line La2 that discharges water Wa2 containing oxygen gas released from the anode side of the water electrolysis cell 10 to the outside of the water electrolysis cell 10, a cathode-side supply line Lc1 that supplies cathode-side supply water Wc1 to the cathode side (cathode 13 and separator 15) of the water electrolysis cell, and a cathode-side discharge line Lc2 that discharges water Wc2 containing hydrogen gas released from the cathode side of the water electrolysis cell 10 to the outside of the water electrolysis cell 10.

[0026] Although one water electrolytic cell 10 is shown in FIG. 1, two or more water electrolytic cells 10 may be arranged in series or in parallel (or a combination of series and parallel).

[0027] The water storage tank 30 is a tank for storing raw water W1 supplied via a raw water line L1. The upstream end of the raw water line L1 is connected to a supply source (not shown) of the raw water W1. The raw water W1 may be any type as long as it does not impair the objectives of the present invention, and is typically tap water or groundwater.

[0028] The water storage tank 30 is connected to the first refinery device 41 via a line L2. A liquid feed pump P1 is provided on the line L2. The liquid feed pump P1 pressure-feeds raw water W2, such as tap water or groundwater, stored in the water storage tank 30 toward the first refinery device 41. The operation (driving and stopping) of the liquid feed pump P1 is controlled by a control unit (not shown).

[0029] The raw water W2 transferred from the water storage tank 30 is pre-filtered in a pre-filter (not shown) to remove solid matter, and then the impurity ions in the water are removed in a first purification device 41 to produce purified water W3 of a predetermined purity, and then the water is purified in a second purification device 42 to produce purified water W4 of a predetermined purity.

[0030] The first purification device 41 and the second purification device 42 are not particularly limited as long as they can produce purified water W3, W4 of the desired purity, and are selected appropriately taking into consideration the types and concentrations of impurities contained in the raw water W2. The first purification device 41 is used for roughly purifying the raw water W2, and may be, for example, a membrane filtration device. The second purification device 42 is used for highly purifying the purified water W3 from the first purification device 41, and may be, for example, an electrodeionized water production device or an ion exchange resin purification device.

[0031] In the present embodiment shown in Fig. 1, two purifiers, a first purifier 41 and a second purifier 42, are arranged in series, but there are no particular limitations as long as they can supply water of the desired purity to the degassing device 20. For example, a single purifier may be used, or two or more purifiers may be arranged in series or in parallel (or a combination of series and parallel). When two or more purifiers are used, any purifier may be used as long as it can supply water of the desired purity.

[0032] The second refiner 42 is connected to the degassing device 20 via a line L4. In this embodiment, a membrane degassing device is used as the degassing device 20, and purified water W4 supplied from the second refiner 42 is passed through one side of a gas-liquid separation membrane, and a vacuum pump is connected to the other side to reduce the pressure, thereby removing dissolved gases (particularly dissolved oxygen) from the flow path side to the reduced pressure side where the gas partial pressure is lower, thereby degassing the purified water W4 and producing degassed water Wa1. The degassed water Wa1 degassed by the degassing device 20 is supplied to the anode side (anode 12 and separator 14) of the water electrolysis cell 10 via the anode side supply line La1.

[0033] The degassed water Wa1 is water from which dissolved oxygen has been removed by degassing. The degassing degree of the degassed water Wa1 is 0.30 or less, 0.20 or less, 0.15 or less, or 0.10 or less, where the saturated dissolved oxygen concentration is 1.

[0034] In this embodiment, a membrane degassing device is used as the degassing device 20, but this is not limited to this, and other degassing devices such as a vacuum degassing device or a heating degassing device can be used as long as they can produce the desired degassed water. 1 shows one degassing device 20, two or more degassing devices may be arranged in series or in parallel (or a combination of series and parallel). When two or more degassing devices are used, any degassing device may be used as long as it can supply degassed water with the desired degree of degassing.

[0035] The water electrolytic cell 10 will be described below with reference to FIGS. FIG. 3 is a cross-sectional schematic diagram of a water electrolysis cell 10 (single cell), and FIG. 4 is a plan view of an anode separator according to an embodiment of the present invention. Although Figures 2 and 3 show a single water electrolysis cell (single cell) as the water electrolysis cell 10, the water electrolysis cell 10 may also be a water electrolysis stack in which multiple single cells are stacked in series and / or in parallel.

[0036] The water electrolytic cell 10 is a so-called solid polymer water electrolytic cell, which comprises a solid polymer electrolyte membrane 11, and an anode 12 and a cathode 13 arranged to sandwich the solid polymer electrolyte membrane 11 therebetween.

[0037] A DC power supply (not shown) is connected to the anode 12 and cathode 13 of the water electrolytic cell 10, and the power required for water electrolysis is supplied from the DC power supply to the water electrolytic cell 10. At the anode 12 of the water electrolytic cell 10, degassed water Wa1 degassed in the degassing device 20 is electrolyzed using water supplied via the anode-side supply line La1 to generate oxygen gas on the anode side and hydrogen gas on the cathode side. Note that the water electrolysis apparatus 1 of this embodiment has a cathode-side supply line Lc1 for supplying water Wc1 to the cathode side, but the cathode-side supply line Lc1 need not be provided if it is not necessary to replenish water to the cathode side.

[0038] The operating conditions of the water electrolytic cell 10 (applied voltage, temperature, water supply rate, etc.) may be set in accordance with the operating conditions of known water electrolytic cells, and are appropriately determined taking into consideration conditions such as the target water electrolysis rate (hydrogen generation rate), the types of components constituting the water electrolytic cell, and the reaction areas of the electrodes (anode, cathode).

[0039] The operating temperature can be, for example, 70°C to 100°C.

[0040] The applied voltage is set so that water electrolysis proceeds at a desired rate at a predetermined operating temperature, and is usually set to 1.3 V or higher, taking into account overvoltage (especially anode overvoltage) over the theoretical electrolysis voltage of water (1.23 V (25°C), 1.18 V (80°C)). In the water electrolysis apparatus of the present invention, degassed water, from which dissolved oxygen has been removed, is supplied to the anode as water to be used for water electrolysis, thereby reducing anode overvoltage and enabling the applied voltage to be reduced compared to when degassed water is not used. The degree of reduction in anode overvoltage depends on the concentration of dissolved oxygen contained in the degassed water, and by reducing the dissolved oxygen concentration through degassing treatment, the reduced overvoltage can be, for example, 3 mV or more, 5 mV or more, 10 mV or more, or 15 mV or more.

[0041] In the water electrolysis cell 10 (single cell), the anode 12 is composed of an anode catalyst layer 121 and a porous transport layer 122 , and the cathode 13 is composed of a cathode catalyst layer 131 and a porous transport layer 132 . The components of the water electrolytic cell 10 (single cell) are similar to those of known water electrolytic cells (single cells), and therefore detailed description will be omitted and only a brief description will be given.

[0042] The solid polymer electrolyte membrane 11 is a known proton-conductive solid polymer electrolyte membrane, such as a fluorine-based electrolyte material or a hydrocarbon-based electrolyte material. An electrolyte membrane made of a fluorine-based electrolyte material is particularly preferred because of its excellent heat resistance and chemical stability. Specific examples of suitable materials include Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.).

[0043] 3, in the water electrolysis cell 10 (single cell), an anode catalyst layer 121 is provided on one side of an electrolyte membrane 11, and a porous transport layer 122 is laminated on the anode catalyst layer 121. A cathode catalyst layer 131 is provided on the opposite side of the electrolyte membrane 11, and a porous transport layer 132 is laminated on the cathode catalyst layer 131.

[0044] The anode 12 (anode catalyst layer 121 and porous transport layer 122) can be a conventionally known anode catalyst layer and porous transport layer used in a water electrolysis cell, and can be appropriately selected depending on the type of solid polymer electrolyte membrane 11. Typically, the anode catalyst layer 121 contains catalyst noble metal particles (e.g., iridium oxide) and an electrolyte material, and has a porous structure. The porous transport layer 122 can be made of a material (e.g., titanium fiber) that has gas diffusivity and electrical conductivity.

[0045] The cathode 13 (cathode catalyst layer 131 and porous transport layer 132) can be a conventionally known cathode catalyst layer and porous transport layer used in a water electrolysis cell, and can be appropriately selected depending on the type of solid polymer electrolyte membrane. Typically, the cathode catalyst layer 131 contains a carbon material (graphite, carbon black, activated carbon, etc.) carrying catalytic noble metal particles (e.g., platinum) and an electrolyte material. The porous transport layer 132 can be made of a material (e.g., carbon fiber) that has gas diffusivity and electrical conductivity.

[0046] 3, anode separator 14 and cathode separator 15 are arranged to sandwich anode 12 and cathode 13. More specifically, anode separator 14 is arranged so that the surface on which ribs 141 are formed contacts porous transport layer 122 of anode 12, and cathode separator 15 is arranged so that the surface on which ribs 151 are formed contacts porous transport layer 132 of cathode 13.

[0047] The materials of the anode separator 14 and the cathode separator 15 are not limited, but may be made of carbon or metal, for example.

[0048] The anode separator 14 has ribs 141 on one side thereof, and a water supply channel Li1 and a water discharge channel Li2 are formed between the ribs 141. The channel structure of the channels is not limited to an interdigitated type (comb type), a serpentine type, or the like, but in this embodiment, an interdigitated type channel is formed. The cathode separator 15 has ribs 151 on one side thereof, and water flow paths Ls are formed between the ribs 151. The structure of the flow paths Ls is not limited to a specific flow path structure, and may be an interdigitated type (comb type) or a serpentine type, but in this embodiment, a serpentine type flow path is formed.

[0049] 4, an interdigitated flow path is formed in the anode separator 14. The interdigitated flow path is a flow path in which water supply flow paths Li1 and water discharge flow paths Li2 are alternately arranged with ribs 141 interposed therebetween.

[0050] The water supply flow path Li1 is a flow path with an open water inlet side and a closed water outlet side, and the water discharge flow path Li2 is a flow path with a closed water inlet side and an open water outlet side. Water supplied from the anode-side supply port Li1in flows through the water supply flow path Li1. Water flowing through the water discharge flow path Li2 is discharged from the anode-side discharge port Li2out.

[0051] FIG. 5 shows an explanatory diagram of oxygen gas discharge through an interdigitated flow channel. Degassed water supplied from the anode-side supply port Li1in first flows through the water supply flow path Li1, permeates the porous transport layer 122, reaches the water discharge flow path Li2, and is discharged from the anode-side discharge port Li2out. In this way, water is forced to pass through the porous transport layer 122, which promotes the discharge of oxygen gas generated at the anode by water electrolysis.

[0052] Water Wa2 containing oxygen gas generated on the anode side of the water electrolysis tank 10 is separated into oxygen gas and water (containing dissolved oxygen) by a gas-liquid separator 51 connected via a line La2. The oxygen is recovered as gas, and the separated water W5 (containing dissolved oxygen) is transferred to the second purification device 42 via a circulation flow path 60. The water W5 containing dissolved oxygen is purified in the second purification device 42, then degassed again in the degassing device 20, and then supplied to the anode 12 of the water electrolysis cell 20.

[0053] The circulation flow path 60 may be provided with a filter (not shown). During water electrolysis in the water electrolysis cell 20, solid matter originating from the anode 12 (anode catalyst layer 121) may be mixed in and may clog the equipment that constitutes the hydrogen production system 100. However, if the solid matter can be removed using a filter, such problems can be prevented.

[0054] In this embodiment, the second purification device 42, line L4, degassing device 20, line La1, water electrolysis cell 10 (anode 12 and separator 14), line La2, gas-liquid separator 51, and circulation flow path 60 constitute a degassed water circulation path, but this configuration is not limited to this. The water discharged from the gas-liquid separator 51 may be discarded as it is, or may be used for other purposes without being circulated for producing degassed water. Also, when circulating to produce degassed water, the water (including dissolved oxygen) discharged from the gas-liquid separator 51 can be circulated upstream of the degassing device 20, and a circulation flow path 60 can be arranged so that the water is transported to the water storage tank 30 or the first purification device 41.

[0055] Furthermore, water Wc2 containing hydrogen gas generated on the cathode side of the water electrolyzer 10 is separated into hydrogen gas and water by a gas-liquid separator 52 connected via a line Lc2. Because the hydrogen gas after gas-liquid separation contains a large amount of moisture, the hydrogen gas after gas-liquid separation is usually recovered after being dehumidified. On the other hand, the water after gas-liquid separation is recovered or discarded depending on the purpose.

[0056] Although the embodiments of the water electrolysis apparatus and hydrogen production system of the present invention have been described above with reference to the drawings, the embodiments disclosed herein are illustrative in all respects and are not limiting. In particular, in the embodiments disclosed herein, matters not explicitly disclosed, such as operating conditions, various parameters, dimensions, weights, and volumes of components, do not deviate from the scope of ordinary practice by a person skilled in the art, and values ​​that can be easily assumed by a person skilled in the art are used. [Example]

[0057] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0058] 1. Preparation of evaluation cell (single cell) Using the JARI standard cell from the Japan Automobile Research Institute (JARI), a water electrolysis cell for evaluation was fabricated in accordance with Figures 3 and 4.

[0059] A catalyst-coated membrane (CCM) was prepared by coating the anode catalyst and cathode catalyst on each side of a solid polymer electrolyte membrane using the following procedure. The solid polymer electrolyte membrane (PEM) used was Aquivion E87-12S (Solvay, membrane thickness 117 μm). The anode catalyst was IrO2 (Tokuriki Honten, TYPE IV, loading 1.5 mg / cm). 2 The cathode catalyst was Pt / C (Tanaka Kikinzoku Co., Ltd., model number TEC10E50E). The catalyst solution was prepared by mixing the catalyst metal, ionomer, ethanol, and pure water. The ionomer used was Aquivion D83-06A from Sigma-Aldrich. The solution was applied to the PEM using a spray printer for fuel cell research manufactured by Nordson Corporation. The catalyst loading on the anode and cathode sides was 1.5 mg / cm. 2 _IrO2, 0.5mg / cm 2The catalyst was then hot-pressed for 360 seconds using a Shinto Kogyo high-precision desktop digital press CYP-T at a temperature of 155°C and a surface pressure of 3.1 MPa to obtain the desired catalyst-coated membrane (CCM).

[0060] Figure 6 shows the components of the evaluation water electrolysis cell. The cell components are as follows: Solid polymer electrolyte (PEM): Aquivion E87-12S (Solvay, film thickness 117 μm) Anode catalyst layer: IrO2 (loading amount 1.5 mg / cm 2 ) Anode porous transport layer (PTL): Platinum-plated titanium mesh (Nikko Techno, NKT-2001-05) Anode separator: Platinum-plated titanium (Interdigitated flow path) Cathode catalyst layer: Pt / C (46 wt%, loading 0.5 mg / cm 2 ) Cathode porous transport layer (PTL): Carbon paper (SGL Carbon, SGL 34AA) Cathode separator: Carbon (Serpentine-type flow path) Gasket: Polytetrafluoroethylene (PTFE)

[0061] Table 1 shows the specifications of the cell components, and Table 2 shows the configurations of the anode catalyst layer and cathode catalyst layer in the catalyst coated membrane (CCM).

[0062] [Table 1]

[0063] [Table 2]

[0064] 2. Evaluation Using the prepared water electrolysis cell for evaluation, water electrolysis was evaluated with and without degassing. The water supplied to the anode was Takasugi Pharmaceutical's industrial purified water (pH 5.0-7.5, electrical conductivity: 5 μS / cm or less (25°C)), and was supplied to the anode using a continuous supply water pump (TACMINA, Q-100-VE-PS). A degasser and a dissolved oxygen meter were installed between the water pump and the anode supply pipe. The degassing device is a membrane type degassing device, 3M TM Liqui-Cell TM A separation membrane module (MM-0.5 x 1) was used. Figure 7 shows a schematic diagram of the membrane degassing device used. As shown in Figure 7, a tube (hollow fiber) with countless small holes that only allow gas to pass through is installed in the direction of vacuuming, and the piping in the liquid phase direction and the piping in the vacuuming direction are independent. A Xylem Analytics Multi 9310 IDS was used as the dissolved oxygen measuring device. The flow rate of oxygen gas generated at the anode by water electrolysis was measured with a mass flow meter through a back pressure valve (KOFLOC, 6800a), a gas-liquid separator, and a gas dryer. Similarly, the flow rate of hydrogen generated at the cathode was measured with a mass flow meter through a back pressure valve (KOFLOC, 6800a), a gas-liquid separator, and a gas dryer.

[0065] The water supplied to the anode side was degassed using the membrane degassing device, and the ratio of the saturated dissolved oxygen concentration to the dissolved oxygen concentration of the degassed water was calculated from the value of the dissolved oxygen meter. In this experimental system, when the water flow rate to the anode side was 10.0 cc / min, the degassing rate was 0.14.

[0066] Figure 8 shows the results of a comparison of the IV characteristics of water electrolysis when the water supplied to the anode side was (a) not degassed and (b) degassed (water flow rate: 10.0 cc / min, cell temperature: 80°C). As shown in Figure 8, regardless of the current density, the applied voltage was lower for (b) with degassing treatment than for (a) without degassing treatment. This result confirmed that the electrolysis voltage of water is reduced by reducing the dissolved oxygen concentration through degassing treatment. [Industrial Applicability]

[0067] According to the present invention, the efficiency of water electrolysis is increased by the degassing treatment, and hydrogen can be produced with high efficiency, which is industrially promising. [Explanation of symbols]

[0068] 1 Water electrolysis device 10 Water electrolyzer 11 Solid polymer electrolyte membrane 12 anodes 121 Catalyst layer 122 Porous transport layer 13 Cathode 131 Catalyst layer 132 Porous transport layer 14 Separator (anode side) 15 Separator (cathode side) 20 Degassing device 30 Water Tank 41 Refining device (first refining device) 42 Refining equipment (second refining equipment) 51 Gas-liquid separator (anode side) 52 Gas-liquid separator (cathode side) 60 Circulation flow path 100 Hydrogen Production System L1~L4, water transfer lines La1 Anode side supply line La2 anode side emission line Li1 Water supply channel Li1in anode side supply port Lc1 Cathode side supply line Lc2 Cathode side discharge line Li2 water discharge channel Li2out Anode side outlet P1, P2 pumps W1, W2 raw water W3, W4 purified water Wa1 degassed water Wa2 Water containing oxygen gas Wc1 water (not degassed) Wc2 Water containing hydrogen gas

Claims

1. a water electrolysis cell including a solid polymer electrolyte membrane, an anode provided in contact with one surface of the solid polymer electrolyte membrane, and a cathode provided in contact with the other surface of the solid polymer electrolyte membrane; an anode-side supply line that supplies deaerated water obtained by removing dissolved oxygen from water to the anode of the water electrolysis cell; an anode-side discharge line for discharging the oxygen-containing water discharged from the anode side of the water electrolysis cell to the outside of the water electrolysis cell; a cathode-side discharge line for discharging the hydrogen gas-containing water discharged from the cathode side of the water electrolysis cell to the outside of the water electrolysis cell; A water electrolysis device comprising:

2. A hydrogen production system including the water electrolysis device according to claim 1, a water storage tank for storing water; a purification device for purifying the water transferred from the water storage tank to produce purified water; a degassing device that removes dissolved oxygen from the purified water transferred from the purification device to produce degassed water, The hydrogen production system is characterized in that the degassed water is supplied to the anode of the water electrolysis cell via the anode-side supply line.

3. The hydrogen production system according to claim 2 , wherein the degassing device is a membrane degassing device.

4. 3. The hydrogen production system according to claim 2, wherein the purification device comprises a first purification device that purifies the water transferred from the water storage tank, and a second purification device that further purifies the purified water supplied from the first purification device.

5. 5. The hydrogen production system according to claim 2, further comprising a circulation flow path for circulating water containing oxygen gas, which is released from the anode side of the water electrolysis cell, to the degassing device.

6. The hydrogen production system according to claim 5 , wherein the circulation flow path is connected to the purification device.

7. A water electrolysis method using a water electrolysis cell including a solid polymer electrolyte membrane, an anode provided in contact with one surface of the solid polymer electrolyte membrane, and a cathode provided in contact with the other surface of the solid polymer electrolyte membrane, 10. The method for water electrolysis, wherein the water supplied to the anode is degassed water from which dissolved oxygen has been removed.

8. The method for water electrolysis according to claim 7, wherein the degassed water is degassed water obtained by removing dissolved oxygen from purified water.

Images