Noble metal particle-containing electrolyte membrane, membrane electrode assembly, electrochemical cell, stack, and electrolytic device

Abstract

Embodiments provide an electrolyte membrane that reduces hydrogen leakage or crossover.SOLUTION: A method for producing a noble metal particle-containing electrolyte membrane according to an embodiment includes a step of spraying a solution containing cationic noble metal complex ions onto a cation exchange membrane and performing a drying treatment to impregnate the cationic noble metal complex ions into a first region on one surface of the cation exchange membrane, and a step of performing a reduction treatment on the cation exchange membrane impregnated with the cationic noble metal complex ions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a method for producing a precious metal particle-containing electrolyte membrane, a precious metal particle-containing electrolyte membrane, a membrane electrode assembly, an electrochemical cell, a stack, and an electrolysis device. [Background technology]

[0002] In recent years, electrochemical cells have been the subject of intensive research. For example, polymer electrolyte membrane electrolysis cells (PEMEC) are expected to be used to generate hydrogen in large-scale energy storage systems. To ensure sufficient durability and electrolytic properties, platinum (Pt) nanoparticle catalysts are generally used in the cathode of PEMEC, and precious metal catalysts such as iridium (Ir) nanoparticle catalysts are generally used in the anode. Methods for obtaining hydrogen from ammonia are also being investigated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-23748 Summary of the Invention [Problem to be solved by the invention]

[0004] Embodiments provide an electrolyte membrane that reduces hydrogen leakage or crossover. [Means for solving the problem]

[0005] A method for producing a precious metal particle-containing electrolyte membrane according to an embodiment includes the steps of spraying a solution containing cationic precious metal complex ions onto a cation exchange membrane and drying the solution to impregnate a first region on one side of the cation exchange membrane with the cationic precious metal complex ions, and performing a reduction treatment on the cation exchange membrane impregnated with the cationic precious metal complex ions. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a schematic cross-sectional view of a precious metal-containing electrolyte membrane according to an embodiment. [Figure 2] 2 is a flowchart of a method for producing a precious metal-containing electrolyte membrane according to an embodiment. [Figure 3] 1 is a schematic diagram of a spray device according to an embodiment. [Figure 4] 1 is a schematic diagram of a membrane electrode assembly (MEA) according to an embodiment. [Figure 5] 1 is a schematic diagram of an electrochemical cell according to an embodiment. [Figure 6] FIG. 2 is a schematic diagram of a stack according to an embodiment. [Figure 7] 1 is a conceptual diagram of an electrolysis device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same components will be denoted by the same reference numerals, and the description of components that have already been described will be omitted as appropriate.

[0008] The physical properties in this specification are values ​​at a temperature of 25°C and a pressure of 1 atom. The thickness of each component is the average value of the distance in the stacking direction.

[0009] (First embodiment) The first embodiment relates to a precious metal particle-containing electrolyte membrane and a method for manufacturing the same. FIG. 1 shows a schematic cross-sectional view of a precious metal particle-containing electrolyte membrane 100 according to one embodiment of the present invention. The precious metal particle-containing electrolyte membrane 100 includes a cation exchange membrane 1 and precious metal particles 2. The region 1A enclosed by a dashed line on the first surface A, which is the main surface of the cation exchange membrane 1, is the first region 1A. The size of the first region 1A varies among precious metal particle-containing electrolyte membranes 100, and is indicated by the multiple dashed lines. The cation exchange membrane 1 contains precious metal particles 2, for example, on the first surface A side, excluding the outer periphery. The precious metal particle-containing electrolyte membrane is preferably used as an electrolyte membrane for a membrane electrode assembly (MEA) in a hydrogen generation device. The description of the precious metal particle-dispersed electrolyte membrane 100 also applies to the description of the method for manufacturing the precious metal particle-dispersed electrolyte membrane 100.

[0010] The cation exchange membrane 1 is a proton-conductive membrane that is electrically insulated from the first surface A side toward the second surface B side. The cation exchange membrane 1 is preferably a fluoropolymer or aromatic hydrocarbon polymer having one or more groups selected from the group consisting of sulfonic acid groups, sulfonimide groups, and sulfate groups. The cation exchange membrane 1 is preferably a fluoropolymer having sulfonic acid groups. Examples of fluoropolymers having sulfonic acid groups that can be used include Nafion (trademark, manufactured by DuPont), Flemion (trademark, manufactured by Asahi Kasei Corporation), Selemion (trademark, manufactured by Asahi Kasei Corporation), Aquivion (trademark; Solvay Specialty Polymers), and Aciplex (trademark, manufactured by Asahi Glass Co., Ltd.).

[0011] The thickness of the cation exchange membrane 1 can be appropriately determined taking into consideration the membrane's properties such as permeability and durability. From the viewpoints of strength, dissolution resistance, and MEA output properties, the thickness of the cation exchange membrane 1 is preferably 20 μm to 500 μm, more preferably 50 μm to 300 μm, and even more preferably 80 μm to 200 μm.

[0012] The precious metal particles 2 are contained in the cation exchange membrane 1. The precious metal particles 2 are preferably particles of one or more precious metals selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. The precious metal particles 2 may include particles of an alloy containing one or more precious metals selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. The precious metal particles 2 are preferably particles of one precious metal selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. The precious metal particles are preferably Pt particles. The precious metal particles are preferably Re particles. The precious metal particles are preferably Rh particles. The precious metal particles are preferably Ir particles. The precious metal particles are preferably Pd particles. The precious metal particles are preferably Ru particles.

[0013] In an MEA using a cation exchange membrane 1, if hydrogen crosses over from the cathode side to the anode side of the cation exchange membrane 1, the hydrogen concentration increases, potentially exceeding the lower explosive limit of 4%. When a precious metal particle-containing electrolyte membrane 100 is used, hydrogen attempting to permeate the membrane comes into contact with oxygen crossing over from the anode side and the precious metal particles 2, whereupon the hydrogen is oxidized to produce water. The precious metal particles 2 act as an oxidation catalyst, enabling the hydrogen to be removed even if it crosses over. The precious metal particle-containing electrolyte membrane 100 can also oxidize hydrogen that has bypassed the membrane and leaked. The precious metal particle-containing electrolyte membrane 100 prevents hydrogen crossover and oxidizes the crossed-over hydrogen, thereby efficiently reducing the hydrogen concentration within the device.

[0014] The average circumscribing circle diameter of the precious metal particles 2 is preferably 0.2 nm or more and 1000 nm or less, more preferably 0.5 nm or more and 300 nm or less, and even more preferably 1 nm or more and 30 nm or less. If the precious metal particles 2 are small, on the order of sub-nanometers, the hydrogen oxidation efficiency decreases due to quantum effects, so more precious metal particles 2 are required. If the precious metal particles 2 are large, more precious metal particles 2 are required to efficiently oxidize hydrogen. The average circumscribing circle diameter of the precious metal particles 2 can be determined by observing a cross section, such as that shown in Figure 1, with a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0015] The precious metal particles 2 are preferably unevenly distributed in the first region 1A of the cation exchange membrane 1 at a depth of less than 50% of the membrane thickness from the surface. Furthermore, it is preferable that the precious metal particles 2 are unevenly distributed at a depth of 30% of the membrane thickness from the surface. The first region 1A (anode side) is the region extending from the first surface A (starting point; anode electrode) of the cation exchange membrane 1 toward the second surface B to a depth of less than 50% of the membrane thickness (end point). For example, if the first region 1A is narrow, the region enclosed by the small dashed line in FIG. 1 corresponds to the first region 1A. For example, if the first region 1A is wide, the region of the large sailboat in FIG. 1 corresponds to the first region 1A. The precious metal particles 2 are preferably contained within the membrane near the surface of the cation exchange membrane 1.

[0016] In FIG. 1 , the first region 1A does not include the outer periphery of the cation exchange membrane 1. The outer periphery of an electrolyte membrane used in an MEA, not limited to the precious metal particle-containing electrolyte membrane 100, may not be in contact with an electrode. For example, hydrogen crossover is unlikely to occur at the surface where the electrolyte membrane contacts a gasket. Therefore, even in the precious metal particle-containing electrolyte membrane 100, the outer periphery of the cation exchange membrane 1 may be excluded from the first region 1A. The outer periphery of the cation exchange membrane 1 where no precious metal particles 2 are present is excluded from the first region 1A. For example, a square cation exchange membrane 1 with sides of 5 cm will be used as an example. The precious metal particles 2 are present in a region 4000 μm inward from the outer periphery of the cation exchange membrane 1 toward the center. The first region 1A is then within a 4 cm × 4 cm area at the center of the cation exchange membrane 1, and extends from the first surface A to the second surface B to a depth of 30% of the membrane thickness. When precious metal particles 2 are present entirely on the first surface A side, the first region 1A is a region within a 5 [cm] x 5 [cm] range at the center of the cation exchange membrane 1, and extending from the first surface A (anode side) to the second surface B side to a depth of 30% of the membrane thickness.

[0017] Preferably, 80 wt% to 100 wt% of the precious metal particles 2 contained in the cation exchange membrane 1 are contained in the first region 1A, more preferably 90 wt% to 100 wt%, and even more preferably 95 wt% to 100 wt%. If the precious metal particles 2 are distributed throughout the membrane, non-crossover hydrogen is likely to be oxidized. To selectively oxidize leaking hydrogen, the precious metal particles 2 are preferably biased toward the first surface A (anode side).

[0018] The amount of precious metal particles 2 contained in the cation exchange membrane 1 is 0.01 [mg / cm 2 ] or more 1[mg / cm 2 ] or less, and 0.05 [mg / cm 2 ] or more 0.2[mg / cm 2 ] or less is more preferable.

[0019] The precious metal particles 2 in the first region 1A are preferably uniformly dispersed. By producing the precious metal particle-containing electrolyte membrane 100 using the manufacturing method of this embodiment, the precious metal particles 2 are concentrated in the narrow first region 1A, resulting in high dispersion of the precious metal particles 2. Regarding the dispersion of the precious metal particles 2, a cross section such as that shown in FIG. 1 is observed using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). A cross section parallel to the long sides of the cation exchange membrane 1 and passing through the center of the cation exchange membrane 1 is observed, and the precious metal particles 2 in the first region 1A are mapped. An energy dispersive spectroscopy (EDX) can be used for the mapping. A polygon (Voronoi polygon) formed by connecting the lines passing through the center between two adjacent precious metal particles 2 is then defined. The Voronoi polygons of all the precious metal particles 2 in the observed cross section are then defined. The standard deviation of the areas of the defined Voronoi polygons is then calculated. When the standard deviation calculated from the area of ​​the Voronoi polygon falls within a predetermined range, the noble metal particles 2 in the first region 1A are considered to be uniformly dispersed.

[0020] A method for manufacturing the precious metal particle-containing electrolyte membrane 100 will now be described. Fig. 2 shows a flowchart of the method for manufacturing the precious metal particle-containing electrolyte membrane 100 of this embodiment. The method for manufacturing the precious metal particle-containing electrolyte membrane 100 includes a step (S01) of spraying a solution containing cationic precious metal complex ions onto the cation exchange membrane 1 and drying the solution to impregnate the first region 1A on one side of the cation exchange membrane 1 with the cationic precious metal complex ions, and a step (S02) of performing a reduction treatment on the cation exchange membrane 1 impregnated with the cationic precious metal complex ions.

[0021] The step (S01) of spraying a solution containing cationic noble metal complex ions onto the cation exchange membrane 1 and drying the solution to impregnate the first region 1A on one side of the cation exchange membrane 1 with the cationic noble metal complex ions will be described.

[0022] The solution containing cationic noble metal complex ions is a solution in which a cationic noble metal complex salt is dissolved in water and / or a mixed solvent of water and a water-soluble organic solvent.

[0023] The cationic noble metal complex salt is ionized in solution into cationic noble metal complex ions and counter ions. The cationic noble metal complex ions include ions of one or more noble metals selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru, and neutral molecules.

[0024] The cationic noble metal complex salt is [MA1 x ] a ·[A2 y b ]. When the cationic noble metal complex salt contains water molecules, the water molecules are ignored in the description of the embodiments. M is one or more noble metals selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru. A1 is a neutral molecule such as NH3 or an amine. A2 is a counter ion (anion) such as a halogen. a is the ionic valence of the cationic noble metal complex ion. a is preferably an integer of +2 or more and +6 or less. b is the ionic valence of the counter ion. b is preferably 1 or more and 2 or less.

[0025] Specific examples of the cationic noble metal complex salt include, but are not limited to, one or more selected from the group consisting of [Pt(NH3)4]Cl2, [Pt(NH3)6]Cl4, [Pd(NH3)4]Cl2, [Pd(NH3)4]Br2, [Pd(C2H8N2)2]Cl2, [Ru(NH3)6]Cl3, [Ir(NH3)6]Cl3, [Ir(NH3)5]Cl2, [Ru(NH3)6]Cl3 and [Rh(NH3)6]Cl3, and preferably one or more selected from the group consisting of ammine complexes and amine complexes.

[0026] The water-soluble organic solvent is preferably one or more selected from the group consisting of alcohols and aprotic polar solvents. Specific examples of alcohols include, but are not limited to, methanol, ethanol, isopropanol, 1-propanol, ethylene glycol, and propylene glycol. Specific examples of aprotic polar solvents include, but are not limited to, dimethylformamide, dimethyl sulfoxide, acetone, acetonitrile, and N-methylpyrrolidone. On the other hand, cationic noble metal complex salts are poorly soluble in water-soluble organic solvents, and adding a large amount of water-soluble organic solvent will cause the complex salt to precipitate. Therefore, it is preferable to add an appropriate amount of water-soluble organic solvent depending on the type of added solvent.

[0027] The cationic noble metal complex ion concentration of the solution containing the cationic noble metal complex ions (concentration of the cationic noble metal complex salt dissolved in the solvent) is preferably 0.05 [wt %] or more and 5 [wt %] or less.

[0028] If the cation exchange membrane 1 is sprayed continuously, impregnation into the surface of the cation exchange membrane 1 may be insufficient. Therefore, in an embodiment, it is preferable to alternately spray and dry the solution containing cationic precious metal complex ions onto the cation exchange membrane 1 multiple times. If the entire amount is sprayed at once, the dispersibility of the precious metal particles 2 after the reduction treatment may be low. Therefore, it is preferable to alternately spray and dry. By spraying a small amount at a time and drying after each spray, the precious metal complex ions can be impregnated without being concentrated in a narrow area. It is also preferable to repeat spraying and drying multiple times.

[0029] There are various types of spray coating devices and methods. Here, as a specific example, we will use a spray device equipped with a rotating drum (with an electrolyte membrane fixed thereto) and a spray nozzle that can move back and forth parallel to the rotating drum. However, this method is not limited to this. From the viewpoint of alternately repeating spraying and drying multiple times, it is preferable to mount the cation exchange membrane 1 on a rotating drum 11 and rotate the cation exchange membrane 1, as shown in the schematic diagram of the spray device in Figure 3. The solution containing cationic precious metal complex ions is sprayed onto the rotating cation exchange membrane 1 from a spray device 12 (the spray nozzle moves back and forth from the right end to the left end of the drum while the spray is being applied). The cation exchange membrane 1 is then dried by applying warm air from a dryer 13 located separately from the spray device 12.

[0030] The temperature of the hot air is preferably 30°C or higher and 120°C or lower, and more preferably 40°C or higher and 80°C or lower. If the temperature is too low, the drying is insufficient and the surface of the cation exchange membrane 1 is sprayed again while it is still wet, which tends to further reduce the drying. If the temperature is too high, the electrolyte membrane dries out, making it difficult for the liquid to penetrate the membrane, which is undesirable.

[0031] The surface temperature of the cation exchange membrane 1 heated by the hot air is, for example, 30° C. or more and 60° C. or less.

[0032] The surface of the rotating drum 11 can be heated to heat the cation exchange membrane 1. By heating the cation exchange membrane 1 from both sides, the surface of the cation exchange membrane 1 can be efficiently impregnated with cationic noble metal complex ions by spraying.

[0033] After spraying and drying, the amount of precious metal ions (converted to precious metal atoms) on the surface of the cation exchange membrane 1 on which the solution containing cationic precious metal complex ions was applied was 0.01 mg / cm 2 ] or more 1[mg / cm 2 ] or less, and 0.05 [mg / cm 2 ] or more 0.2[mg / cm 2 ] or less is more preferable.

[0034] When the cation exchange membrane 1 is impregnated with a solution containing cationic precious metal complex ions, the protons of the cation exchange membrane 1 are exchanged with the cationic precious metal complex ions. Repeated ion exchange, spraying, and drying result in the cationic precious metal complex ions being uniformly impregnated into the surface of the cation exchange membrane 1. The cationic precious metal complex ions ionically bond with, for example, sulfonic acid groups of the cation exchange membrane 1, resulting in good dispersibility. Due to the good dispersibility, the particle size of the precious metal particles 2 formed after reduction varies little, resulting in good dispersibility. Repeated small amounts of spraying and drying, combined with the cation exchange, result in the precious metal particles 2 being unevenly distributed in the first region 1A, improving their dispersibility.

[0035] By providing a mask on the cation exchange membrane 1 placed on the rotating drum 11 and spraying the solution, it is possible to form a region that is not (is difficult to) impregnated with the solution containing cationic noble metal complex ions.

[0036] If the entire cation exchange membrane 1 is immersed in a solution containing cationic precious metal complex ions, a membrane with a different ratio of precious metal particles 2 will be obtained unless the concentration of the cationic precious metal complex ions is adjusted each time. Obtaining membranes with different properties is undesirable because it reduces reliability. Furthermore, if the entire cation exchange membrane 1 is immersed in a solution containing cationic precious metal complex ions, it is difficult to locally immerse the cation exchange membrane 1 in the solution containing cationic precious metal complex ions. Considering the distribution and dispersibility of the cation exchange membrane 1 in the cation exchange membrane 1, a method of repeatedly spraying and drying is preferred.

[0037] The step (S02) of performing a reduction treatment on the cation exchange membrane 1 impregnated with cationic noble metal complex ions will be described below. By performing the reduction treatment, the cationic noble metal complex ions are reduced and noble metal particles 2 are formed.

[0038] The reduction method includes a method of contacting the cation exchange membrane 1 impregnated with cationic noble metal complex ions with a reducing solution, and a method of treating the cation exchange membrane 1 impregnated with cationic noble metal complex ions in a reducing gas atmosphere.

[0039] When the precious metal particle-containing electrolyte membrane 100 is produced by the method of the embodiment, most of the precious metal used in the spraying is present on the surface of the cation exchange membrane 1 as precious metal particles 2. The loading rate of the precious metal particles 2 ([abundance of the precious metal particles 2 in the first region 1A [mg / cm 2 ]] / [amount of precious metal in the precious metal complex sprayed onto the first region 1A [mg / cm 2 When an anionic precious metal complex salt is used for the cation exchange membrane 1, the loading rate is very low, so the spray coating of the embodiment and the combination of the cation exchange membrane 1 and the cationic precious metal complex ion contribute to the formation of highly dispersed precious metal particles 2 selectively in the first region 1A.

[0040] The reducing agent contained in the reducing solution is preferably one or more selected from the group consisting of hydrazine salts, ammonia, NaBH4, LiAlH, hypophosphites, formalin, sulfites, and ascorbate. The reducing agent contained in the reducing solution is preferably one or more selected from the group consisting of hydrazine salts, ammonia, NaBH4, hypophosphites, formalin, sulfites, and ascorbate.

[0041] When the cation exchange membrane 1 impregnated with cationic noble metal complex ions is brought into contact with a reducing solution, it is preferable to immerse the cation exchange membrane 1 impregnated with cationic noble metal complex ions in the reducing solution. When immersing, it is appropriate to fix the cation exchange membrane 1 to a frame and adjust the angle so that the first surface A and the liquid level of the reducing solution are perpendicular or nearly perpendicular. When the first surface A and the liquid level of the reducing solution are perpendicular or nearly perpendicular, hydrogen generated during reduction is less likely to remain on the surface of the cation exchange membrane 1, and therefore reduction is more likely to be sufficient. It is also preferable to stir the reducing solution.

[0042] After immersion in the reducing solution, the membrane is washed with ion-exchanged water or the like. After reduction, the cations (e.g., Na) of the reducing solution are absorbed into, for example, sulfonic acid groups of the cation exchange membrane 1. + ) are bonded to the cation exchange membrane 1. After washing, the membrane is immersed in acid to exchange cations (for example, to exchange Na+ with protons). The membrane may be heated during this acid immersion. Further washing with ion-exchanged water or the like yields a precious metal particle-containing electrolyte membrane 100.

[0043] When treating the cation exchange membrane 1 impregnated with cationic precious metal complex ions in a reducing gas atmosphere, the cation exchange membrane 1 impregnated with cationic precious metal complex ions is placed in a container filled with a reducing gas (e.g., hydrogen gas) atmosphere and subjected to reduction treatment. The reducing gas is preferably heated above room temperature (25°C), and the temperature inside the container is preferably 30°C or higher and 80°C or lower. When reduction treatment is performed using a reducing gas, a precious metal particle-containing electrolyte membrane 100 can be produced without immersing the entire cation exchange membrane 1 in a liquid.

[0044] (Second embodiment) The second embodiment relates to a membrane electrode assembly (MEA). A cross-sectional schematic diagram of an MEA 200 is shown in FIG.

[0045] The MEA 200 includes a first electrode 21, a second electrode 22, and an electrolyte membrane 23 disposed between the first electrode 21 and the second electrode 22. The MEA 200 can be used in a hydrogen generation device such as for water electrolysis. The first electrode 21 includes a substrate 21A and a first catalyst layer 21B. The second electrode 22 includes a substrate 22A and a second catalyst layer 22B.

[0046] The membrane electrode assembly 200 of the embodiment can also be used for electrolytic generation of ammonia. The membrane electrode assembly 200 of the embodiment can be used as a membrane electrode assembly in an electrolysis device for ammonia synthesis. In the second embodiment and other embodiments below, water electrolysis will be described as an example, but the membrane electrode assembly can also be used as a membrane electrode assembly used in electrolysis for ammonia synthesis, in which ultrapure water is supplied to the anode, the water is decomposed at the anode to generate protons and oxygen, the generated protons pass through the electrolyte membrane, and nitrogen supplied to the cathode is combined with the protons and electrons to generate ammonia. The membrane electrode assembly 200 of the embodiment can also be used as a membrane electrode assembly that electrolyzes ammonia to generate hydrogen. The membrane electrode assembly of the embodiment can be used in a hydrogen generation device. In the second embodiment and other embodiments, water electrolysis will be described as an example below. However, the membrane electrode assembly 200 of the embodiment can also be used as a membrane electrode assembly used for electrolysis for ammonia decomposition, in which ammonia is supplied to a cathode, the ammonia is decomposed at the cathode to generate protons and nitrogen, the generated protons pass through an electrolyte membrane, and the protons and electrons combine at the anode to generate hydrogen.

[0047] The first electrode 21 is, for example, an anode. The first catalyst layer 21B of the first electrode 21 contains, for example, an oxide containing Ir and / or Ru.

[0048] The second electrode 22 is, for example, a cathode electrode. The second catalyst layer 22B of the second electrode 22 contains, for example, Pt.

[0049] A precious metal particle-containing electrolyte membrane 100 is used as the electrolyte membrane 23. For example, it is preferable that the first surface A of the precious metal particle-containing electrolyte membrane 100 is located on the side of the first electrode 21, which is the anode electrode.

[0050] The first electrode 21 is adjacent to one surface of the electrolyte membrane 23 and includes a catalyst layer 24 adjacent to the electrolyte membrane 23, and a substrate adjacent to the catalyst layer.

[0051] The second electrode 22 is adjacent to the other surface of the electrolyte membrane 23 and includes a catalyst layer adjacent to the electrolyte membrane 23 and a substrate adjacent to the catalyst layer.

[0052] The MEA using the precious metal particle-containing electrolyte membrane 100 can suppress hydrogen leakage.

[0053] (Third embodiment) The third embodiment relates to an electrochemical cell. Figure 5 shows a cross-sectional view of an electrochemical cell 300 according to the third embodiment.

[0054] As shown in FIG. 4 , the electrochemical cell 300 of the third embodiment includes a first electrode (cathode) 22, a second electrode (anode) 21, an electrolyte membrane 23, a cathode power supply 31, a separator 32, an anode power supply 33, a separator 34, a gasket (seal) 35, and a gasket (seal) 36. For example, the electrolyte membrane 23 may be the precious metal particle-containing electrolyte membrane 100 of the embodiment. The cathode power supply 31 and the anode power supply 33 may be permeable to gas and water. The cathode power supply 31 and the anode power supply 33 may be integrated with the separators 32 and 34. Specifically, the separator may have a flow path for a hydrogen source such as water or a gas, or may have a porous body, but is not limited thereto. The electrochemical cell 300 using the precious metal particle-containing electrolyte membrane 100 of the embodiment suppresses hydrogen leakage and is highly reliable.

[0055] In the electrochemical cell 300 of FIG. 5, electrodes (not shown) are connected to a cathode power supply 31 and an anode power supply 33, and a reaction occurs between the cathode 22 and the anode 21. For example, water is supplied to the anode 21, and the water is decomposed into protons, oxygen, and electrons at the anode electrode 21. The electrode support and power supply are porous, and this porous body functions as a flow path plate. The produced water and unreacted water are discharged, and the protons and electrons are used in the cathode reaction. In the cathode reaction, protons and electrons react to produce hydrogen. Either or both of the produced hydrogen and oxygen are used, for example, as fuel for the fuel cell. The membrane electrode assembly 200 is held in place by separators 32 and 34, and airtightness is maintained by gaskets (seals) 8 and 9.

[0056] (Fourth embodiment) The fourth embodiment relates to a stack. Fig. 6 is a diagram showing a stack of the fourth embodiment. The stack 400 of the fourth embodiment shown in Fig. 6 has a plurality of MEAs 200 or electrochemical cells 300 connected in series. Clamping plates 41 and 42 are attached to both ends of the MEAs or electrochemical cells.

[0057] Because the voltage produced by one MEA 200 or electrochemical cell 300 is low, a high voltage can be obtained by connecting multiple MEAs 200 or electrochemical cells 300 in series to form a stack 400. Because the amount of hydrogen produced by an electrochemical cell 300 made of one MEA 200 is small, a large amount of hydrogen can be produced by connecting multiple electrochemical cells 300 in series to form a stack 400.

[0058] (Fifth embodiment) The fifth embodiment relates to an electrolysis device. Fig. 7 shows a conceptual diagram of the electrolysis device of the fifth embodiment. The electrolysis device 500 uses an electrochemical cell 300 or a stack 400. The electrolysis device of Fig. 7 is a water electrolysis device. The electrolysis device will be described using a water electrolysis device as an example. For example, when generating hydrogen from ammonia, it is preferable to employ a device with a different configuration that uses a precious metal particle-containing electrolyte membrane 100.

[0059] As shown in Figure 7, a water electrolysis stack 400 is constructed by stacking unit cells for water electrolysis in series. A power supply 51 is attached to the water electrolysis stack 400, and a voltage is applied between the anode and cathode. A gas-liquid separator 52, which separates the generated gas from unreacted water, and a mixing tank 53 are connected to the anode side of the water electrolysis stack 400. Water is delivered to the mixing tank 53 by a pump 56 from an ion-exchange water production system 54, and the water passes through a check valve 57 from the gas-liquid separator 52 and into the mixing tank 53, where it is mixed and circulated to the anode. Oxygen generated at the anode passes through the gas-liquid separator 52 to produce oxygen gas. Meanwhile, a hydrogen purifier 59 is connected to the gas-liquid separator 58 on the cathode side to produce high-purity hydrogen. Impurities are discharged via a pathway with a valve 60 connected to the hydrogen purifier 59. To stabilize the operating temperature, the stack and mixing tank can be heated, and the current density during pyrolysis can be controlled.

[0060] Examples of the embodiment will be described below. (Adjustment of coating solution) The coating solution was prepared by preparing a solution of cationic noble metal complex salt, which is the precursor of the noble metal particles, to a predetermined concentration, and then measuring out a predetermined amount of the aqueous solution and adding water and a water-soluble organic solvent (particularly alcohols) to adjust the concentration. The various solutions prepared are shown in Table 1. IPA in Table 1 stands for isopropyl alcohol.

[0061] [Table 1]

[0062] (Spray application of a solution of cationic precious metal complex salts) Nafion 115 (manufactured by DuPont) was set in a spray coating device as a cation exchange membrane, and the prepared solution of cationic precious metal complex salt was sprayed into it. Nafion 115 was placed in a rotating drum, and the rotating drum was rotated. The entire amount of the prepared solution was applied while drying with hot air. The rotating drum had a diameter of 10 cm and was rotated at 450 rpm. After confirming that there were no droplets on the surface of the sprayed cation exchange membrane, the cation exchange membrane was washed with ion-exchange water. The spray conditions are shown in Table 2.

[0063] (reduction to precious metal particles) After washing, the Nafion 115 membrane was immersed in a 1 M NaBH4 aqueous solution at room temperature (25°C) for a predetermined time to reduce the cationic noble metal complex ions to noble metal nanoparticles, resulting in a noble metal nanoparticle-dispersed Nafion 115 membrane. The noble metal nanoparticle-dispersed Nafion 115 membrane was then washed with ion-exchanged water.

[0064] (cation exchange (exchanging sodium ions for protons)) The precious metal nanoparticle-dispersed Nafion115 membrane was immersed in 10% nitric acid heated to 40°C for two hours, removed, and thoroughly washed with ion-exchanged water to produce a precious metal nanoparticle-dispersed Nafion115 membrane. By using this membrane as the electrolyte membrane for the MEA of a water electrolysis device using the spray and dry procedures described in the examples, hydrogen leakage can be suppressed.

[0065] [Table 2]

[0066] In the specification, some elements are represented only by element symbols.

[0067] The technical proposals in the specification are as follows: [Technical proposal 1] a step of spraying a solution containing cationic noble metal complex ions onto a cation exchange membrane and drying the solution to impregnate a first region on one side of the cation exchange membrane with the cationic noble metal complex ions; a step of performing a reduction treatment on the cation exchange membrane impregnated with the cationic noble metal complex ions; The present invention relates to a method for producing an electrolyte membrane containing precious metal particles. [Technical proposal 2] The method for producing an electrolyte membrane containing precious metal particles according to Technical Scheme 1, wherein the spraying and drying processes are repeated. [Technical proposal 3] The method for producing a precious metal particle-containing electrolyte membrane according to Technical Scheme 1 or 2, wherein the cationic precious metal complex ion contains an ion of one or more precious metals selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru, and a neutral molecule as a ligand. [Technical proposal 4] 4. A method for producing an electrolyte membrane containing precious metal particles according to any one of technical solutions 1 to 3, wherein the neutral molecules are NH3 or amines. [Technical proposal 5] 5. A method for producing an electrolyte membrane containing precious metal particles according to any one of Technical Schemes 1 to 4, wherein the spraying and drying are repeated alternately multiple times. [Technical proposal 6] 6. A method for producing a precious metal particle-containing electrolyte membrane according to any one of Technical Schemes 1 to 5, wherein in the step of impregnating the cationic precious metal complex ions, hot air at a temperature of 30°C or higher and 120°C or lower is applied to the cation exchange membrane. [Technical proposal 7] A method for producing a precious metal particle-containing electrolyte membrane according to any one of technical proposals 1 to 6, wherein the concentration of the cationic precious metal complex ions in the solution containing the cationic precious metal complex ions is 0.05 [wt%] or more and 5 [wt%] or less. [Technical proposal 8] In the step of performing the reduction treatment, A method for producing an electrolyte membrane containing precious metal particles according to any one of Technical Schemes 1 to 7, which comprises immersing the membrane in a reducing solution. [Technical proposal 9] 9. The method for producing a precious metal particle-containing electrolyte membrane according to any one of Technical Schemes 1 to 8, wherein in the step of performing the reduction treatment, the cation exchange membrane impregnated with the cationic precious metal complex ions is treated in a heated hydrogen gas atmosphere. [Technical proposal 10] a cation exchange membrane having a first surface as a main surface; a precious metal particle dispersed electrolyte membrane containing precious metal particles on the first surface side of the cation exchange membrane excluding the outer peripheral side thereof; [Technical proposal 11] the noble metal particles are metal particles containing one or more metals selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru, The average circumscribed circle diameter of the noble metal particles is 0.5 [nm] or more and 1000 [nm] The amount of noble metal particles on the first surface side is 0.01 mg / cm 2 ] or more 1[mg / cm 2 ] The precious metal particle-containing electrolyte membrane according to Technical Scheme 10, which is as follows: [Technical proposal 12] 12. The precious metal particle-containing electrolyte membrane according to Technical Scheme 10 or 11, wherein the cation exchange membrane has a sulfonic acid group. [Technical proposal 13] a first electrode having a first substrate and a first catalyst layer provided on the first substrate; a second electrode having a second substrate and a second catalyst layer provided on the second substrate; A membrane electrode assembly using the precious metal particle-containing electrolyte membrane according to any one of Technical Schemes 10 to 12. [Technical proposal 14] An electrochemical cell using the membrane electrode assembly described in Technical Proposal 13. [Technical proposal 15] A stack using the membrane electrode assembly described in Technical Proposal 13. [Technical proposal 16] An electrolysis device using the electrochemical cell according to Technical Scheme 14 or the stack according to Technical Scheme 15.

[0068] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. Although a PEMEC has been described as a water electrolysis cell, the present invention can be similarly applied to other electrolysis cells. These novel embodiments described above can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit and scope of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the invention and its equivalents as defined in the accompanying claims. [Explanation of symbols]

[0069] 1: Cation exchange membrane 1A: 1st area 2: Precious metal particles 11: Rotating drum 12: Spray device 13:Drying equipment 21: 1st electrode 21A: Base material 21B: 1st catalyst layer 22: 2nd electrode 22A: Base material 22B: 2nd catalyst layer 23: Electrolyte membrane 24:Catalyst layer 31: Cathode power supply 32: Separator 33: Anode power supply 34: Separator 41: Clamping plate 42: Clamping plate 51: Power supply 52: Gas-liquid separation equipment 53: Mixing tank 54: Ion exchange water production equipment 56: Pump 57: Check valve 58: Gas-liquid separation equipment 59: Hydrogen purification equipment 60: Valve 100: Electrolyte membrane containing noble metal particles 200: Membrane electrode assembly 300: Electrochemical cell 400: Stack 500: Electrolyzer

Claims

1. a cation exchange membrane having a first surface as a main surface; a precious metal particle-containing electrolyte membrane containing precious metal particles on the first surface side of the cation exchange membrane excluding the outer peripheral side;

2. the noble metal particles are metal particles containing one or more metals selected from the group consisting of Pt, Re, Rh, Ir, Pd, and Ru, The noble metal particles have an average circumscribed circle diameter of 0.5 nm to 1000 nm, The amount of noble metal particles on the first surface side is 0.01 mg / cm ２ ] or more 1 [mg / cm ２ 2. The precious metal particle-containing electrolyte membrane according to claim 1, wherein the noble metal particle content is 0.01 or less.

3. The precious metal particle-containing electrolyte membrane according to claim 1 , wherein the cation exchange membrane has sulfonic acid groups.

4. a region of the cation exchange membrane excluding an outer peripheral portion where the noble metal particles are not present is defined as a first region; 2. The precious metal particle-containing electrolyte membrane according to claim 1, wherein the first region is a region extending from the first surface toward a second surface opposite the first surface to a depth of less than 50% of a thickness of the cation exchange membrane.

5. a first electrode having a first substrate and a first catalyst layer provided on the first substrate; a second electrode having a second substrate and a second catalyst layer provided on the second substrate; A membrane electrode assembly using the precious metal particle-containing electrolyte membrane according to claim 1 .

6. An electrochemical cell using the membrane electrode assembly according to claim 5 .

7. A stack using the membrane electrode assembly according to claim 5.

8. An electrolysis device using the stack according to claim 7.

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