JP2010053400A - Method for manufacturing porous conductor for electrolyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a porous conductor for an electrolyzer, by which the thickness is made thin effectively while sustaining high strength, and the porosity is enhanced satisfactorily. <P>SOLUTION: The method for manufacturing a porous conductor includes a step S1 for forming a spherical titanium powder sintered compact by sintering a spherical titanium powder and a step S2 for forming a spherical titanium powder thermally sprayed layer which is brought into contact with an electrolyte. To at least the spherical titanium powder thermally sprayed layer, an etching treatment S4 is applied after grinding or cutting processing, and then a plating treatment S5 is applied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a porous conductor for an electrolytic device that is in contact with an electrolyte membrane and used as a power feeding body for electrolysis.

  For example, an electrolyte membrane / electrode structure in which an anode electrode and a cathode electrode each having an electrode catalyst layer and a gas diffusion layer are disposed on both sides of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched by separators. Solid polymer fuel cells are known.

  In this type of fuel cell, fuel gas (mainly containing hydrogen) is supplied to the anode side electrode, while oxidant gas (mainly oxygen-containing gas, for example, air) is supplied to the cathode side electrode. As a result, DC electric energy is obtained.

  In general, a water electrolysis apparatus is employed to produce hydrogen as a fuel. This water electrolysis apparatus uses a solid polymer electrolyte membrane in order to decompose water and generate hydrogen (and oxygen). Electrode catalyst layers are provided on both sides of the solid polymer electrolyte membrane to form an electrolyte membrane / electrode structure, and a power feeder is provided on both sides of the electrolyte membrane / electrode structure. It is configured. That is, the unit is configured substantially in the same manner as the above fuel cell.

  Therefore, in a state where a plurality of units are stacked, a voltage is applied to both ends in the stacking direction, and water is supplied to the anode-side power feeding body. For this reason, water is decomposed and hydrogen ions (protons) are generated on the anode side of the electrolyte membrane / electrode structure, and the hydrogen ions permeate the solid polymer electrolyte membrane and move to the cathode side to bond with electrons. Thus, hydrogen is produced. On the other hand, on the anode side, oxygen produced together with hydrogen is discharged from the unit with excess water.

  As said electric power feeder, as disclosed by patent document 1, for example, it is the electric power feeder for water electrolysis cells used by arranging on both sides of a membrane electrode assembly, and titanium is used in an inert gas atmosphere. There has been known one made of a titanium fiber sintered plate in which the surface in contact with the membrane electrode assembly is smoothed by plasma spraying.

Japanese Patent Application Laid-Open No. 11-302891

  By the way, the porosity and the shape of the titanium material are extremely different between the titanium fiber sintered plate and the plasma sprayed layer on the surface thereof. For this reason, there is a problem in that the electrical resistance increases at the joint interface between the two, and the electrical resistance as a power supply becomes higher than the apparent porosity, resulting in a large loss voltage. Furthermore, there is a possibility that liquid permeability and air permeability may be reduced due to a large change in the porosity at the joint interface between the two.

  The present invention solves this type of problem, and provides a method for producing a porous conductor for an electrolytic device capable of effectively reducing the thickness while maintaining high strength and improving the porosity. The purpose is to provide.

  The present invention relates to a method for producing a porous conductor for an electrolytic device that is in contact with an electrolyte membrane and used as a power feeding body for electrolysis. This manufacturing method includes a step of sintering a spherical titanium powder to form a spherical titanium powder sintered body, and a spherical titanium powder finer than the spherical titanium powder sintered body in the spherical titanium powder sintered body. A step of forming a spherical titanium powder sprayed layer in contact with the electrolyte membrane.

  Moreover, it is preferable that thermal spraying is a low pressure plasma spraying.

  Further, it is preferable that at least the spherical titanium powder sprayed layer is plated.

  According to the present invention, since the spherical titanium powder is thermally sprayed on the spherical titanium powder sintered body, it is possible to form a spherical titanium powder sprayed layer which is a thin and dense porous sprayed layer. Therefore, the spherical titanium powder sprayed layer can ensure high strength, maintain gas and water permeability, and improve the retention of the electrolyte membrane.

  Further, by spraying the spherical titanium powder, the dense spherical titanium powder sprayed layer can be thinned, and the porosity of the spherical titanium powder sprayed layer can be controlled by changing the melting degree and the spraying speed. For this reason, the thickness can be accurately and easily controlled to an arbitrary thickness, and the porosity can be set according to the base layer.

  In addition, the spherical titanium powder sintered body as the base layer is not sintered again, and it is possible to prevent the porosity from changing as much as possible. That is, in the laminated structure of the base layer and the spherical titanium powder sprayed layer, the porosity can be made uniform, and the permeability (liquid permeability) of the electrolytic solution is not affected.

  FIG. 1 is a perspective explanatory view of a water electrolysis apparatus 10 to which a porous conductor for an electrolysis apparatus manufactured by a manufacturing method according to an embodiment of the present invention is applied, and FIG. FIG.

  The water electrolysis apparatus 10 includes a stacked body 14 in which a plurality of unit cells 12 are stacked in the horizontal direction (arrow A direction). At one end in the stacking direction of the stacked body 14, a terminal plate 16a, an insulating plate 18a, and an end plate 20a are sequentially disposed outward. Similarly, a terminal plate 16b, an insulating plate 18b, and an end plate 20b are sequentially disposed on the other end in the stacking direction of the stacked body 14 toward the outside.

  The water electrolysis apparatus 10 integrally clamps and holds between the end plates 20a and 20b via a plurality of tie rods 22 extending in the direction of arrow A, for example. The water electrolysis apparatus 10 may employ a configuration in which the water electrolysis apparatus 10 is integrally held by a box-like casing (not shown) including end plates 20a and 20b configured as squares as end plates. Moreover, the water electrolysis apparatus 10 can be set to various shapes such as a cylindrical shape in addition to a cubic shape.

  As shown in FIG. 1, terminal portions 24a and 24b are provided on the side portions of the terminal plates 16a and 16b so as to protrude outward. The terminal portions 24a and 24b are electrically connected to the power source 28 via the wirings 26a and 26b. The terminal part 24 a on the anode (anode) side is connected to the positive pole of the power supply 28, while the terminal part 24 b on the cathode (cathode) side is connected to the negative pole of the power supply 28.

  As shown in FIGS. 2 and 3, the unit cell 12 includes an electrolyte membrane / electrode structure 32, and an anode separator 34 and a cathode separator 36 that sandwich the electrolyte membrane / electrode structure 32. The anode side separator 34 and the cathode side separator 36 are made of, for example, a carbon member or the like, or a steel plate, a stainless steel plate, a titanium plate, an aluminum plate, a plated steel plate, or a metal surface thereof is subjected to a surface treatment for corrosion prevention. The metal plate is formed by press-forming or cutting and then performing anticorrosion surface treatment.

  The electrolyte membrane / electrode structure 32 includes, for example, a solid polymer electrolyte membrane 38 in which a perfluorosulfonic acid thin film (about 50 μm) is impregnated with water, and the solid polymer electrolyte membrane 38 sandwiched between the solid polymer electrolyte membrane 38 and the solid polymer electrolyte membrane 38. An anode-side power feeding body (electrolytic device porous conductor) 40 and a cathode-side power feeding body (electrolytic device porous conductor) 42 are provided to reinforce the electrolyte membrane 38.

  An anode electrode catalyst layer 44 a and a cathode electrode catalyst layer 44 b are formed on both surfaces of the solid polymer electrolyte membrane 38. The anode electrode catalyst layer 44a uses, for example, a Ru (ruthenium) -based catalyst, while the cathode electrode catalyst layer 44b uses, for example, a platinum catalyst.

  At one end edge of the unit cell 12 in the arrow B direction (horizontal direction in FIG. 3), there is a supply communication hole 46 that communicates with each other in the arrow A direction that is the stacking direction and supplies water (pure water). Provided. The other end edge of the unit cell 12 in the direction of arrow B communicates with each other in the direction of arrow A, and a discharge communication hole 48 for discharging oxygen generated by the reaction and used water, and is generated by the reaction. Hydrogen flow communication holes 50 for flowing hydrogen are arranged in the direction of arrow C.

  As shown in FIG. 4, for example, a first flow path 52 extending in the direction of arrow B is provided on the surface 34 a of the anode separator 34 facing the electrolyte membrane / electrode structure 32. The first flow path 52 is provided in a range corresponding to the surface area of the anode-side power feeding body 40 and communicates with the supply communication hole 46 and the discharge communication hole 48. The other surface 34b of the anode side separator 34 is configured to be flat.

  As shown in FIG. 3, for example, a second flow path 54 extending in the direction of arrow B is formed on the surface 36 a of the cathode separator 36 facing the electrolyte membrane / electrode structure 32. The second flow path 54 is provided in a range corresponding to the surface area of the cathode-side power feeding body 42 and communicates with the hydrogen flow communication hole 50. The other surface 36b of the cathode side separator 36 is configured to be flat.

  The seal members 56a and 56b are integrated with each other around the outer peripheral ends of the anode side separator 34 and the cathode side separator 36. The seal members 56a and 56b include, for example, EPDM, NBR, fluorine rubber, silicone rubber, fluorosilicone rubber, butyl rubber, natural rubber, styrene rubber, chloroplane, acrylic rubber, or other seal materials, cushion materials, or packing materials. Used.

  As shown in FIG. 1, pipes 58 a, 58 b and 58 c communicating with the supply communication hole 46, the discharge communication hole 48 and the hydrogen flow communication hole 50 are connected to the end plate 20 a.

  Next, an operation for manufacturing the anode-side power feeder 40 constituting the electrolyte membrane / electrode structure 32 will be described with reference to the flowchart shown in FIG.

  In addition, since the cathode side electric power feeding body 42 is manufactured similarly to the anode side electric power feeding body 40, the detailed description is abbreviate | omitted. The cathode side power supply 42 is provided as necessary, and in particular, an anode side power supply that requires strength to hold the solid polymer electrolyte membrane 38 against high-pressure hydrogen generated on the cathode side. Only 40 may be provided.

  First, as shown in FIG. 6, a spherical gas atomized titanium powder 60 having a predetermined average particle diameter (a particle diameter equal to or larger than the film thickness of the solid polymer electrolyte membrane 38, for example, 45 μm to 150 μm) is made of high-density alumina. The dish-shaped sintering container 62 is filled without pressure.

  In the sintering container 62, the spherical gas atomized titanium powder 60 is vacuum-sintered without applying pressure (step S1), whereby a thin plate-like spherical titanium powder sintered body 64 is manufactured (see FIG. 7). The spherical titanium powder sintered body 64 has a porosity in the range of 10% to 50%. The sintering temperature is lower than the melting point of titanium, and is preferably in the range of 800 ° C to 1300 ° C, for example.

  Next, the process proceeds to step S2, and the spherical titanium powder 66 having a finer particle size than the spherical titanium powder sintered body 64 is sprayed onto the spherical titanium powder sintered body 64, thereby contacting the solid polymer electrolyte membrane 38 with a spherical shape. A titanium powder sprayed layer 68 is formed (see FIG. 8). The spherical titanium powder 66 is pure titanium particles or titanium alloy particles, and the average particle size is set to a particle size equal to or less than the film thickness of the solid polymer electrolyte membrane 38, for example, 45 μm or less.

  This thermal spraying process is a low-pressure plasma spraying process. Specifically, as shown in FIG. 9, a spherical titanium powder sintered body 64 is disposed in the vacuum chamber 70, and in this vacuum chamber 70, a thermal spray gun 72 is provided. Faces the spherical titanium powder sintered body 64. The spray gun 72 is provided with a powder material inlet 74, a working gas inlet 76, a cooling water inlet 78a and a cooling water outlet 78b.

  Therefore, in the vacuum chamber 70, the spherical titanium powder 66 is supplied from the powder material inlet 74 of the thermal spray gun 72, and an inert gas such as argon or helium is supplied from the working gas inlet 76. In this state, a plasma jet is generated, and the spherical titanium powder 66 is put therein, whereby the molten particles of the spherical titanium powder 66 are sprayed onto the spherical titanium powder sintered body 64.

  At this time, since plasma spraying is performed in a vacuum or in an inert gas, an oxide film is not formed on the surface of the titanium particles. Therefore, film formation is performed in a low melting state, and the porous spherical titanium powder sprayed layer 68 having a porosity set within a range of 10% to 50% is reliably formed.

  Furthermore, it progresses to step S3 and the smoothing process by grinding or cutting is given to the surface of the spherical titanium powder sprayed layer 68 and the surface of the spherical titanium powder sintered compact 64 (refer FIG. 10). In this smoothing process, clogging occurs due to grinding or the like, and an etching process is performed after the smoothing process (step S4).

  For example, as an etching solution, a mixed solution of 10 ml of nitric acid, 10 ml of 10% hydrofluoric acid and 180 ml of pure water is used, and etching is performed at room temperature with an etching time of 90 seconds. Note that the smoothing process and the etching process may be performed as necessary, and may be deleted.

  Next, after the cleaning and activation processes are performed, the process proceeds to step S5, and at least the spherical titanium powder sprayed layer 68 is subjected to a plating process using, for example, platinum (Pt).

  As a result, the anode-side power feeding body 40 is manufactured, and the anode-side power feeding body 40 is disposed on one side of the solid polymer electrolyte membrane 38, and the cathode-side power feeding body 42 processed in the same manner is The molecular electrolyte membrane 38 is disposed in the other direction. Therefore, the electrolyte membrane / electrode structure 32 is obtained.

  The operation of the water electrolysis apparatus 10 configured as described above will be described below.

  As shown in FIG. 1, water is supplied from a pipe 58a to the supply communication hole 46 of the water electrolysis apparatus 10, and via a power source 28 electrically connected to the terminal portions 24a and 24b of the terminal plates 16a and 16b. Voltage is applied. For this reason, as shown in FIG. 3, in each unit cell 12, water is supplied from the supply communication hole 46 to the first flow path 52 formed between the anode separator 34 and the anode power feeder 40. Water moves along the anode-side power feeder 40.

  Accordingly, water is decomposed by electricity in the anode electrode catalyst layer 44a, and hydrogen ions, electrons, and oxygen are generated. Hydrogen ions generated by this anodic reaction permeate the solid polymer electrolyte membrane 38 and move to the cathode electrode catalyst layer 44b side, and combine with electrons to obtain high-pressure hydrogen.

  For this reason, hydrogen flows along the second flow path 54 formed between the cathode side separator 36 and the cathode side power supply body 42, and this hydrogen flows through the hydrogen flow communication hole 50 to form the water electrolysis device 10. It can be taken out to the outside. On the other hand, oxygen generated by the reaction and used water flow in the first flow path 52, and these are discharged to the outside of the water electrolysis apparatus 10 along the discharge communication hole 48.

  In this case, in the present embodiment, at least the anode-side power supply body 40 of the anode-side power supply body 40 and the cathode-side power supply body 42 constituting the electrolyte membrane / electrode structure 32 is sintered with a spherical titanium powder by a sintering process. After the body 64 is formed, the spherical titanium powder 66 is thermally sprayed on the spherical titanium powder sintered body 64 by the low pressure plasma spraying process to form the spherical titanium powder sprayed layer 68.

  Accordingly, since the spherical titanium powder 66 having a small particle diameter is sprayed on the spherical titanium powder sintered body 64, the spherical titanium powder sprayed layer 68 which is a thin and dense porous sprayed layer can be formed. Therefore, the spherical titanium powder sprayed layer 68 ensures high strength and improves the holding power of the solid polymer electrolyte membrane 38 against high-pressure hydrogen generated on the cathode side, and also has good gas and water permeability. The effect that it becomes possible to maintain is acquired.

  Furthermore, since the fine spherical titanium powder 66 is thermally sprayed, the dense spherical titanium powder sprayed layer 68 can be thinned and, for example, accurately and easily controlled to an arbitrary thickness in units of several tens of micrometers. Can do. Moreover, the spherical titanium powder sintered body 64 that is the base layer is not sintered again, and it is possible to prevent the porosity from changing as much as possible. Thereby, there exists an advantage that a water electrolysis process can be performed favorably.

  In addition, although this embodiment demonstrated using the water electrolysis apparatus 10, it is not limited to this, It can apply to various electrolysis apparatuses.

It is a perspective explanatory view of a water electrolysis device to which a porous conductor for electrolysis devices manufactured by a manufacturing method concerning an embodiment of the present invention is applied. It is a partial cross section side view of the water electrolysis device. It is a disassembled perspective explanatory drawing of the unit cell which comprises the said water electrolysis apparatus. It is front explanatory drawing of the anode side separator which comprises the said unit cell. It is a flowchart explaining the said manufacturing method. It is explanatory drawing of a sintering process. It is a partially expanded explanatory view of a spherical titanium powder sintered body. It is a partially expanded explanatory view of a state in which a spherical titanium powder sprayed layer is formed on the spherical titanium powder sintered body. It is explanatory drawing of a thermal spraying process. It is explanatory drawing of a smoothing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Water electrolysis apparatus 12 ... Unit cell 14 ... Laminated body 16a, 16b ... Terminal plate 18a, 18a ... Insulating plate 20a, 20b ... End plate 24a, 24b ... Terminal part 28 ... Power supply 32 ... Electrolyte membrane and electrode structure 34 ... Anode-side separator 36... Cathode-side separator 38... Solid polymer electrolyte membrane 40... Anode-side power feeding body 42... Cathode-side power feeding body 44 a ... Anode electrode catalyst layer 44 b. ... Hydrogen flow communication holes 52, 54 ... Flow path 60 ... Spherical gas atomized titanium powder 62 ... Sintering vessel 64 ... Spherical titanium powder sintered body 66 ... Spherical titanium powder 68 ... Spherical titanium powder sprayed layer 72 ... Spray gun

Claims (3)

A method for producing a porous conductor for an electrolysis device that is in contact with an electrolyte membrane and is used as a power feeding body for electrolysis,
A step of sintering spherical titanium powder to form a spherical titanium powder sintered body;
Forming a spherical titanium powder sprayed layer in contact with the electrolyte membrane by spraying the spherical titanium powder sintered body with a finer spherical titanium powder than the spherical titanium powder sintered body;
A method for producing a porous conductor for an electrolytic device, comprising:   The manufacturing method according to claim 1, wherein the thermal spraying is low-pressure plasma spraying.   3. The method according to claim 1, wherein at least the spherical titanium powder sprayed layer is plated.

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