JP7424134B2 - Composite titanium parts, electrodes for water electrolysis, and water electrolysis equipment - Google Patents

Description

The present invention relates to a flexible composite titanium member, a water electrolysis electrode, and a water electrolysis device made of the composite titanium member.

In recent years, the demand for hydrogen is expected to increase as the movement towards realizing a hydrogen society for a _CO2- free society is accelerating, and technology to produce hydrogen cheaply and efficiently using renewable energy is needed. development is required.
Water electrolysis devices are attracting attention as a candidate for hydrogen production technology, and there are several types such as solid oxide water electrolysis devices (SOEC) and alkaline water electrolysis devices. Among these, solid polymer type (PEM type) water electrolysis equipment has the advantage of being able to operate at around 100°C, and having high electrolysis efficiency and high hydrogen purity during generation.

The internal structure and members of a solid polymer water electrolysis cell are, for example, from the cathode side: current collector plate (Au plated SUS plate, etc.) / gas diffusion layer (electrode): carbon porous body / catalyst layer (Pt/C + ionomer). ) / ion exchange membrane (polymer material) / catalyst layer (Ir particles + ionomer) / gas diffusion layer (electrode): titanium porous body / current collector plate (Au plated SUS plate, etc.).

The above-mentioned gas diffusion layer is often called a GDL (gas diffusion layer), but it is also called an electrode because it plays the role of transmitting current to the catalyst layer, which is the reaction site of the water electrolysis reaction.
The properties required of the gas diffusion layer (electrode) on the anode side are (1) the need to diffuse raw material liquid water and oxygen gas after water electrolysis, and (2) the need to be able to withstand the harsh corrosive environment during electrolysis. It does not corrode. Therefore, a titanium material with excellent corrosion resistance is used for the gas diffusion layer (electrode) on the anode side.
For example, Patent Document 1 proposes a gas diffusion layer using a sintered body of titanium fibers.

However, in the sintered body of titanium fibers as shown in Patent Document 1, the ends of the fibers are exposed on the surface, and the surface is likely to have irregularities. Here, the gas diffusion layer (electrode) mentioned above is used sandwiched between two members of different hardness (the soft catalyst layer and the hard current collector plate), so the contact surface of the gas diffusion layer (electrode) When unevenness occurs, extreme stress concentration tends to occur and damages the soft catalyst layer, making it unsuitable for use as an electrode.

Therefore, for example, Patent Document 2 proposes a method in which a noble metal layer is formed on the surface of a punching metal made of titanium, and the surface roughness (Ra) is set to 0.5 μm or less.
Furthermore, Patent Document 3 describes a machine that uses a titanium fiber sintered body for a titanium porous electrode and can maintain a thickness of 0.3 to 0.7 mm even under stress of 20 to 150 kgf/ ^cm2 . A system with physical strength and flexibility has been proposed.
Further, Patent Document 4 proposes a method in which an ion exchange membrane and an electrode are brought into close contact with each other by using a disc spring or a coil spring behind the electrode on the cathode side.

Japanese Patent Application Publication No. 2004-259457 Japanese Patent Application Publication No. 2019-137891 Japanese Patent Application Publication No. 2018-156798 Japanese Patent Application Publication No. 2006-070322

By the way, in Patent Document 2, punching metal made of titanium is used and does not have a three-dimensional network structure, so there is a possibility that liquid water as a raw material and oxygen gas after water electrolysis cannot be sufficiently diffused. was there. Furthermore, since a noble metal layer is formed, there is a problem in that the cost increases significantly.
Further, in Patent Document 3, the membrane is made of a sintered body of titanium fibers, and there is a risk of damaging the ion exchange membrane in which the titanium fibers come into contact with each other.

Further, in Patent Document 4, since a disc spring or a coil spring is used, it is possible to arrange it on the cathode side, but it is not possible to arrange it on the anode side where oxygen gas is generated.
In addition, on the anode side, since oxygen gas is generated as mentioned above, the gas diffusion layer (electrode) and other components such as the catalyst layer are likely to separate due to volume fluctuation. ) and other members are required to be improved.

The present invention has been made against the background of the above-mentioned circumstances, and is aimed at making it possible to sufficiently contact other adjacent members and to allow fluids such as liquids and gases to circulate and diffuse well. The object of the present invention is to provide a composite titanium member that can perform the following, as well as a water electrolysis electrode and a water electrolysis device made of the composite titanium member.

In order to solve these problems and achieve the above object, the composite titanium member of the present invention comprises a titanium sintered member that is made of a sintered body of titanium or titanium alloy particles and has a three-dimensional network structure; A bellows member is bonded to one surface of the titanium sintered member and has a structure in which a titanium plate is bent into a bellows shape, and the porosity of the titanium sintered member is within a range of 52% or more and 95% or less. , the thickness (folded height) of the bellows member is within a range of 0.3 mm or more and 2.7 mm or less .

According to the composite titanium member having this configuration, since the titanium sintered member having a three-dimensional network structure is provided, fluids such as liquids and gases can be circulated and diffused well.
The titanium sintered member is bonded to one surface of the titanium sintered member, and is provided with a bellows member having a structure in which a titanium plate is bent into a bellows shape (a structure in which mountain folds and valley folds are repeated). It can be pressed toward other adjacent members, and it is possible to improve the adhesion with the other adjacent members.

In addition, in the composite titanium member of the present invention, since the porosity of the titanium sintered member is within the range of 52% to 95%, fluids such as liquids and gases can be more effectively distributed and diffused. It becomes possible to do so.
Furthermore, since the thickness (folded height) of the bellows member is within the range of 0.3 mm or more and 2.7 mm or less, its elastic force sufficiently presses the titanium sintered member toward the adjacent member. can do.

Further, in the composite titanium member of the present invention, it is preferable that the bellows member has communicating holes and has a porosity in the range of 10% to 60%.
In this case , since the porosity is within the range of 10% or more and 60% or less, this bellows material also allows fluids such as liquids and gases to more effectively circulate and diffuse.

Moreover, in the composite titanium member of the present invention, it is preferable that the titanium plate constituting the bellows member is expanded titanium or punched titanium.
In this case, since the titanium plate constituting the bellows material is made of expanded titanium or punched titanium, this bellows material also allows fluids such as liquids and gases to circulate and diffuse better. . Further, the elastic force of the bellows member allows the titanium sintered member to be sufficiently pressed toward the adjacent member.

The water electrolysis electrode of the present invention is characterized by being made of the above-mentioned composite titanium member.
According to the electrode for water electrolysis having this structure, since it is made of the above-mentioned composite titanium member, it has excellent flowability of liquid and gas, and excellent contact with other members. Contact resistance with components (ion exchange membrane, catalyst layer, current collector plate) can be reduced, and water can be electrolyzed efficiently and stably.

The water electrolysis device of the present invention is characterized by being equipped with the above-mentioned water electrolysis electrode.
According to the electrode for water electrolysis having this structure, since the electrode for water electrolysis is made of the above-mentioned composite titanium member, it has excellent flowability of liquid and gas, and excellent contactability with other members. This makes it possible to reduce contact resistance with other adjacent members (ion exchange membrane, catalyst layer, current collector plate), and to perform water electrolysis efficiently and stably.

According to the present invention, there is provided a composite titanium member that can be brought into sufficient contact with other adjacent members and that can circulate and diffuse fluids such as liquids and gases well, and this composite titanium member. It becomes possible to provide a water electrolysis electrode and a water electrolysis device consisting of the following.

It is an explanatory view showing an example of a composite titanium member which is an embodiment of the present invention. FIG. 2 is an explanatory diagram of a titanium sintered member constituting the composite titanium member shown in FIG. 1. FIG. FIG. 1 is a flow diagram showing a method for manufacturing a composite titanium member according to an embodiment of the present invention. 1 is a schematic explanatory diagram of a water electrolysis device that is an embodiment of the present invention.

EMBODIMENT OF THE INVENTION Below, the composite titanium member, the electrode for water electrolysis, and the water electrolysis apparatus which are embodiment of this invention are demonstrated with reference to the attached drawing.

The composite titanium member 1 of this embodiment is used as a current-carrying member such as a cathode electrode of a polymer electrolyte fuel cell (PEFC), an anode electrode of a water electrolysis device, an electrode material for a lithium ion battery or a lithium ion capacitor, etc. It is something that
In this embodiment, as will be described later, it is used as an electrode constituting a gas diffusion layer (GDL) of a water electrolysis device (water electrolysis device) shown in FIG.

As shown in FIG. 1, the composite titanium member 1 of this embodiment includes a titanium sintered member 10 that is made of a sintered body of titanium or titanium alloy particles and has a three-dimensional network structure; and a bellows member 20 having a structure in which a titanium plate is bent into a bellows shape.

As shown in FIG. 2, the titanium sintered member 10 is a porous body, and includes a skeleton part 12 having a three-dimensional network structure and a pore part 13 surrounded by the skeleton part 12. There is.
Further, the pore portions 13 surrounded by the skeleton portion 12 communicate with each other and have communicating holes that open toward the outside of the titanium sintered member 10 .
This titanium sintered member 10 is constructed by, for example, sintering titanium sintering raw material powder containing titanium.

Moreover, in this embodiment, it is preferable that the porosity P of the titanium sintered member 10 is within the range of 50% or more and 95% or less. Note that the porosity P of the titanium sintered member 10 is calculated using the following formula.
P (%) = (1-(W/(V×D _T )))×100
W: Mass (g) of titanium sintered member 10
V: Volume of titanium sintered member 10 (cm ³ )
D _T : True density (g/cm ³ ) of titanium or titanium alloy constituting the titanium sintered member 10

Here, in this embodiment, when the porosity P of the titanium sintered member 10 is 50% or more, the flow of gas and liquid is not inhibited, and it becomes possible to sufficiently diffuse them. On the other hand, when the porosity P of the titanium sintered member 10 is 95% or less, strength is ensured and breakage during handling or use can be suppressed.
In addition, in order to further promote the flow of gas and liquid, the lower limit of the porosity P of the titanium sintered member 10 is preferably set to 70% or more, and more preferably 80% or more. On the other hand, in order to further ensure the strength of the titanium sintered member 10, the upper limit of the porosity P of the titanium sintered member 10 is preferably 93% or less, more preferably 90% or less.

Furthermore, in this embodiment, it is preferable that the average pore diameter R of the titanium sintered member 10 is within the range of 50 μm or more and 600 μm or less. Note that the average pore diameter R of the titanium sintered member 10 was determined as the equivalent circle diameter (diameter) determined from the cross-sectional area of the pore portion 13 by observing the cross section.

Here, in this embodiment, when the average pore diameter R of the titanium sintered member 10 is 50 μm or more, the flow of gas and liquid is not hindered and it becomes possible to sufficiently diffuse them. On the other hand, when the average pore diameter R of the titanium sintered member 10 is 600 μm or less, contact points with other members are secured, and the contact resistance can be sufficiently reduced.
In order to further promote the flow of gas and liquid, the lower limit of the average pore diameter R of the titanium sintered member 10 is preferably 100 μm or more, and more preferably 150 μm or more. On the other hand, in order to further ensure contact points with other members, the upper limit of the average pore diameter R of the titanium sintered member 10 is preferably 550 μm or less, more preferably 500 μm or less.

The bellows member 20 has a structure in which a titanium plate is bent into a bellows shape, and its elastic force makes it possible to press the titanium sintered member 10. Note that as the titanium plate, expanded titanium, punched titanium, etc. can be used. Alternatively, it may be a titanium plate with holes formed therein.

Here, in this embodiment, as shown in FIG. 1, the thickness D (folded height) of the bellows member 20 is preferably within a range of 0.3 mm or more and 2.7 mm or less.
In this embodiment, when the thickness D of the bellows member 20 is 0.3 mm or more, sufficient elastic force is ensured, and it is possible to sufficiently press the titanium sintered member 10 toward another adjacent member. Become. On the other hand, when the thickness D of the bellows member 20 is 2.7 mm or less, the thickness of the composite titanium member 1 can be prevented from becoming thicker than necessary.
In addition, in order to further ensure elasticity, the lower limit of the thickness D of the bellows member 20 is preferably 0.5 mm or more, more preferably 0.7 mm or more. On the other hand, in order to further reduce the thickness of the composite titanium member 1, the upper limit of the thickness D of the bellows member 20 is preferably 2.5 mm or less, more preferably 2.3 mm or less.

Further, in the present embodiment, the bellows member 20 has communicating holes, and preferably has a porosity in the range of 10% to 60%.
In this embodiment, when the porosity of the bellows member 20 is 10% or more, the flow of gas and liquid is not inhibited and it becomes possible to sufficiently diffuse them. On the other hand, when the porosity of the bellows member 20 is 60% or less, strength is ensured, sufficient elastic force can be obtained, and the titanium sintered member 10 can be sufficiently pressed against other adjacent members. becomes possible.
In order to further promote the flow of gas and liquid, the lower limit of the porosity of the bellows member 20 is preferably 15% or more, more preferably 20% or more. On the other hand, in order to obtain more sufficient elastic force, the upper limit of the porosity of the bellows member 20 is preferably 55% or less, more preferably 50% or less.

Next, a method for manufacturing the composite titanium member 1 according to the present embodiment will be described with reference to the flowchart in FIG. 3.

The method for manufacturing the composite titanium member 1 according to this embodiment includes a titanium sintered member forming step S01, a bellows member forming step S02, and a joining step S03.
Here, as shown in FIG. 3, the titanium sintered member forming step S01 includes a titanium-containing slurry forming step S11, a molded body forming step S12, a foaming step S13, a degreasing step S14, and a sintering step S15. .

(Titanium-containing slurry forming step S11)
First, titanium powder made of titanium or a titanium alloy is prepared as a raw material powder. In this embodiment, titanium hydride powder or pure titanium powder produced by dehydrogenating titanium hydride powder was prepared.
A titanium-containing slurry is prepared by mixing a water-soluble resin binder, an organic solvent, a plasticizer, water as a solvent, and in some cases a surfactant with this raw material powder.

(Molding process S12)
Next, the titanium-containing slurry described above is formed into a sheet shape by a doctor blade method or the like to form a molded body.

(Foaming step S13)
Next, the above molded body is foamed to produce a spongy green molded body.

(Degreasing step S14)
Next, the above-mentioned sponge-like green molded body is placed on a zirconia plate and heated in a vacuum atmosphere to perform a degreasing treatment to obtain a degreased body.

(Sintering step S15)
Next, the above-described degreased body is cooled to 50° C. or lower in a vacuum atmosphere, or sintered in a vacuum atmosphere without cooling, to produce a titanium sintered member.

(Accordion part material forming process S02)
On the other hand, a titanium plate made of expanded titanium or the like in which holes are formed is prepared, and the bellows member 20 is obtained by bending this titanium plate.

(Joining process S03)
The titanium sintered member 10 obtained as described above and the bellows member 20 are joined. There are no particular restrictions on the joining method, and existing methods such as welding can be applied. Further, the titanium sintered member 10 and the bellows member 20 may be integrated by sintering.

In the manner described above, the composite titanium member 1 of this embodiment is manufactured.

Next, FIG. 4 shows a schematic diagram of the water electrolysis electrode and water electrolysis device according to this embodiment. Note that the water electrolysis device of this embodiment is a solid polymer type water splitting device that has high electrolysis efficiency and high hydrogen purity during generation.

As shown in FIG. 4, the water electrolysis device 30 of this embodiment includes an anode 32 and a cathode 33 that are arranged opposite each other, and an ion permeable membrane 34 that is arranged between the anode 32 and the cathode 33. A water electrolysis cell 31 is provided. Note that catalyst layers 35 and 36 are formed on both surfaces of the ion permeable membrane 34 (the contact surface with the anode electrode 32 and the contact surface with the cathode electrode 33), respectively.
Here, as for the cathode 33, the ion permeable membrane 34, and the catalyst layers 35 and 36, those used in conventional general solid polymer water electrolysis devices can be applied.

The above-mentioned anode electrode 32 is an electrode for water electrolysis according to this embodiment. This anode electrode 32 (electrode for water electrolysis) is composed of the composite titanium member 1 of this embodiment described above.

In the water electrolysis device 30 (water electrolysis cell 31) described above, as shown in FIG. 4, water (H ₂ O) is supplied from the anode 32 side, and electricity is applied to the anode 32 and cathode 33 . Then, oxygen (O ₂ ) generated by water electrolysis is discharged from the anode 32 and hydrogen (H ₂ ) is discharged from the cathode 33.
Here, in the anode electrode 32, as mentioned above, water (liquid) and oxygen (gas) will flow, so in order to stably flow these liquids and gas, it is necessary to have a high porosity. is preferred. Furthermore, since the anode electrode 32 is exposed to oxygen, it is required to have excellent corrosion resistance. Therefore, the water electrolysis electrode made of the composite titanium member 1 of this embodiment is particularly suitable as the anode electrode 32.

According to the composite titanium member 1 of this embodiment configured as described above, since it includes the titanium sintered member 10 having a three-dimensional network structure, fluids such as liquids and gases can be circulated well. It becomes possible to spread.
Since the bellows member 20 is bonded to one side of the titanium sintered member 10 and has a structure in which a titanium plate is bent into a bellows shape, the bellows member 20 allows the titanium sintered member 10 to be directed toward an adjacent member. It can be pressed, and it is possible to improve the adhesion with other adjacent members.

Here, in this embodiment, if the porosity P of the titanium sintered member 10 is within the range of 50% or more and 95% or less, fluids such as liquids and gases can be more effectively distributed and diffused. In addition, the strength of the titanium sintered member 10 itself can be ensured, and the ease of handling can be improved.

In addition, in this embodiment, when the thickness D (folding height) of the bellows member 20 is within the range of 0.3 mm or more and 2.7 mm or less, the titanium sintered member 10 is connected to the adjacent titanium sintered member 10 by its elastic force. The composite titanium member 1 (electrode for water electrolysis) can be prevented from becoming thicker than necessary.
Furthermore, in the present embodiment, when the porosity of the bellows part material 20 is within the range of 10% to 60%, this bellows part material 20 also allows fluids such as liquids and gases to circulate better. The titanium sintered member 10 can be sufficiently pressed against the adjacent member by ensuring strength.

In addition, in this embodiment, when the titanium plate constituting the bellows member 20 is made of expanded titanium, fluids such as liquids and gases can be more effectively distributed and diffused in the bellows member 20 as well. It becomes possible. Furthermore, the elastic force of the bellows member 20 can sufficiently press the titanium sintered member 10 toward the adjacent member.

Furthermore, since the water electrolysis electrode of this embodiment is composed of the above-described composite titanium member 1 and is used as the anode electrode 32, it has excellent flowability of liquid and gas, and has excellent contact with other members. It has excellent properties and can reduce contact resistance with the adjacent ion permeable membrane 34 and catalyst layer 35, making it possible to perform water electrolysis efficiently and stably.

In the water electrolysis device 30 of this embodiment, since the water electrolysis electrode made of the composite titanium member 1 described above is used as the anode electrode 32, it has excellent fluidity and gas flowability, and also The contact resistance with the adjacent ion permeable membrane 34 and catalyst layer 35 can be reduced, and water electrolysis can be carried out efficiently and stably.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical idea of the invention.
For example, in this embodiment, the water electrolysis device (water electrolysis cell) having the structure shown in FIG. A water electrolysis device (water electrolysis cell) having another structure may be used as long as it includes an electrode for electrolysis.
Further, the composite titanium member of the present invention may be used for purposes other than water electrolysis devices.

Below, the results of a confirmation experiment conducted to confirm the effects of the present invention will be explained.
First, in Inventive Example 1-5, a titanium sintered member (width 35 mm x A sample having a length of 15 mm and a thickness as shown in Table 1 was obtained.
In Comparative Examples 1 and 2, a titanium plate (width 35 mm x length 15 mm) having the thickness shown in Table 1 was prepared instead of the titanium sintered member.

In addition, titanium plates having the porosity, pore diameter, and pore shape shown in Table 1 were bent and formed to have the thickness (folding height) shown in Table 1 as bellows material.
In Example 1-5 of the present invention, a bellows member was bonded to one surface of the titanium sintered member described above to form a composite titanium member.
In Comparative Example 1, only a titanium plate was used.
In Comparative Example 2, the bellows material shown in Table 1 was bonded to the titanium plate.

The contact resistance of the composite titanium members of Inventive Examples 1-5 and Comparative Examples 1 and 2 was evaluated as follows.
The composite titanium members of Inventive Examples 1-5 and Comparative Examples 1 and 2 were brought into contact with carbon paper, and these were sandwiched between two copper plates. With a load of 0.2 MPa applied to the copper plate in the stacking direction, a direct current of 1 A was passed between the carbon paper and the composite titanium member, and the contact resistance was measured. The evaluation results are shown in Table 1.

In Comparative Example 1, which was composed of only a titanium plate, the contact resistance was as high as 190 mΩ·cm ² .
In Comparative Example 2, which had a configuration in which a bellows member was bonded to a titanium plate, the contact resistance was as large as 240 mΩ·cm ² .

On the other hand, in Example 1-5 of the present invention, which has a structure in which a bellows member is attached to a titanium sintered member forming a three-dimensional network structure, the contact resistance is 130 mΩ・cm ² or less, and the carbon paper and the composite titanium member are sufficiently bonded. I was able to get it in close contact with.

From the above, it was confirmed that according to the examples of the present invention, it is possible to provide a composite titanium member that can make sufficient contact with other members.

1 Composite titanium member 10 Titanium sintered member 20 Bellows member 30 Water electrolysis device 32 Anode electrode (electrode for water electrolysis)

Claims (5)

A titanium sintered member made of a sintered body of titanium or titanium alloy particles and has a three-dimensional network structure; a bellows member joined to one surface of the titanium sintered member and having a structure in which a titanium plate is bent into a bellows shape; It is equipped with
The porosity of the titanium sintered member is within the range of 52% or more and 95% or less,
A composite titanium member characterized in that the thickness (folded height) of the bellows member is within a range of 0.3 mm or more and 2.7 mm or less . The composite titanium member according to claim 1 , wherein the bellows member has communication holes and has a porosity in a range of 10% to 60%. 3. The composite titanium member according to claim 1 , wherein the titanium plate constituting the bellows member is expanded titanium or punched titanium. An electrode for water electrolysis, comprising the composite titanium member according to any one of claims 1 to 3 . A water electrolysis device comprising the water electrolysis electrode according to claim 4 .

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