TW202118904A - Porous substrate with catalyst supported thereon for water electrolysis, electrode for water electrolysis, gas diffusion layer, stack cell for water electrolysis, and cell module for water electrolysis - Google Patents

Abstract

An objective of the present invention is to provide a porous substrate with catalyst supported thereon having a new configuration (form), which is excellent in water electrolysis performance and durability thereof in a water electrolysis cell, an electrode for water electrolysis, and a stack cell for water electrolysis using the same.

As a solution, the present invention provides a porous substrate with catalyst supported thereon 3, an electrode for water electrolysis 2, a gas diffusion layer using the same, a single cell for water electrolysis 1, a stack cell for water electrolysis 9, and a cell module for water electrolysis 10. The porous substrate with catalyst supported thereon 3 is a porous substrate 3p on which a catalyst 3c is supported, which sandwiches a PEM and forms a cathode or an anode in contact with the PEM and also functions as a gas diffusion layer.

The catalyst 3c is supported on a side surface of the pores of the porous substrate 3p or a side surface of a fiber 3q forming the porous substrate 3p, and is present from the surface to the inside of the porous substrate 3p itself.

The ionomer 4 is in contact with the catalyst 3c and such filled that it has a concentration gradient in the thickness direction of the porous substrate 3p from the surface of the porous substrate 3p toward the inside.

Description

Porous substrate with catalyst for water electrolysis, electrode for water electrolysis, gas diffusion layer, stacked unit for water electrolysis, and unit module for water electrolysis

The present invention relates to a porous substrate supporting a catalyst for water electrolysis and an electrode for water electrolysis. More specifically, it relates to the use of a polymer electrolyte membrane (PEM: Polymer Electrolyte Membrane) for water electrolysis. In addition, the porous substrate for supporting the catalyst, the electrode for water electrolysis, and the gas for water electrolysis are characterized by the supporting type of the catalyst and the ionic polymer contacting the catalyst and its existence type (filling type). Diffusion layer, stacked unit for water electrolysis, and unit module for water electrolysis.

The membrane electrode assembly (MEA) used in fuel cells or "water electrolysis cells for hydrogen generators" has: an electrode formed with a catalyst layer, and a polymer sandwiched between the anode and the cathode Electrolyte membrane (PEM membrane).

In addition, in the conventional membrane electrode assembly (MEA), for example, as shown in Figure 1 (b), Figure 2 (b) and Figure 2 (c), the catalyst system forms a layer and exists, that is, as a catalyst The layer is present in the membrane electrode assembly (MEA). In addition, the gas diffusion layer contacts the catalyst layer to capture the generated gas.

The invention described in Patent Document 1 relates to a method for producing a membrane electrode assembly (MEA) that is judged to be a good product when the amount of sulfuric acid ions contained in the electrode catalyst layer is less than a predetermined value. A membrane electrode assembly with an electrode catalyst layer formed on the surface of an electrolyte membrane and its manufacturing method.

The manufacturing steps in this manufacturing method are described below. Prepare the electrolyte membrane and prepare the electrode catalyst layer, use the prepared electrolyte membrane and electrode catalyst layer to make the catalyst layer forming membrane, then prepare the gas diffusion layer, and use the produced catalyst layer to form the membrane and the prepared gas The diffusion layer is used to produce a membrane electrode assembly (MEA).

However, the membrane electrode assembly (MEA) of Patent Document 1 except for fuel cell users, the electrode catalyst layer of the membrane electrode assembly (MEA) is a continuous printing ink containing an ionic polymer and a catalyst. It is produced by coating on the surface of the substrate or electrolyte membrane and drying it (thereby reducing the amount of sulfate ions).

Patent Document 2 discloses a method for manufacturing a durable membrane electrode assembly that is not heat-molded on a membrane with a "diffusion medium deposited with a catalyst layer". In this patent document 2, a catalyst layer is deposited on a diffusion medium layer, and then an ionic polymer layer is provided on the surface of the catalyst layer to produce a membrane electrode assembly (MEA) for a fuel cell.

However, in the membrane electrode assembly (MEA) of Patent Document 2, in addition to fuel cell users, the catalyst is formed on the diffusion medium in the form of a catalyst layer, and the ionic polymer is also sprayed on the catalyst. Comprehensive on the layer. In addition, regarding the manufacturing method of the catalyst layer of the membrane electrode assembly (MEA) The method is to continuously transfer the catalyst layer in the form of slurry or coat it on the diffusion medium layer to form. Once the catalyst is coated on the transfer substrate, it is transferred to the film by heating and molding.

In recent years, as the demand for hydrogen has expanded, it is an electrolysis technology that requires excellent water. However, there are still shortcomings in the prior art, and more excellent technology is still required for the performance or durability of the water electrolysis unit.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent No. 6128099

[Patent Document 2] Japanese Patent No. 4738350

The present invention was made in view of the above circumstances. The subject is to provide a unit for water electrolysis (including a single unit for water electrolysis, a stacked unit for water electrolysis, etc.) that has excellent water electrolysis performance or durability, and has a difference from the past. The new structure (type) of the porous matrix that holds the catalyst.

In other words, it is to provide an electrode for water electrolysis with excellent water electrolysis performance or durability, and a porous substrate supporting a catalyst used in the electrode for water electrolysis.

The inventors of the present invention conducted intensive studies to solve the above-mentioned problems. As a result, they found that the water electrolysis performance and the type of the catalyst layer are not provided on the (porous) substrate without the concept of the so-called "catalyst layer". Its durability is excellent.

It has been found that if the catalyst is supported in the pores constituting the porous matrix or the fibers forming the porous matrix, the water electrolysis performance or durability is excellent.

In addition, it has been found that if the catalyst is supported and the polymer electrolyte membrane (PEM: Polymer Electrolyte Membrane) is sandwiched by the obtained porous matrix supporting the catalyst as described above, it is not easy to cause gas lift ( Gas Lift) caused by the separation of the catalyst, it becomes less likely to cause performance degradation.

Furthermore, it has been discovered that by filling the ionic polymer in a specific state (state) from the electrode surface contacting the polymer electrolyte membrane, that is, the surface of the porous matrix holding the catalyst to the inside, it is possible to obtain The cell voltage (electrolysis voltage) is reduced, and the porous substrate for the water electrolysis with excellent water electrolysis performance and durability, which supports the catalyst, has completed the present invention.

That is, the present invention provides a porous substrate that holds a catalyst, which has the following structure: it exists in a single unit for water electrolysis by sandwiching a polymer electrolyte membrane (PEM) and contacts the polymer Electrolyte membrane (PEM) constitutes a cathode or anode, and also functions as a gas diffusion layer,

The catalyst is supported on the side surface of the pores of the porous matrix or the side surface of the fiber forming the porous matrix, and exists in a manner of covering from the surface of the porous matrix itself to the inside, and

The ionic polymer contacts the catalyst and is filled with a concentration gradient in the thickness direction of the porous substrate from the surface of the porous substrate toward the inside.

In addition, the present invention provides the porous substrate supporting the catalyst obtained by the following steps: attaching a metal catalyst or a metal catalyst precursor to the side surface of the pores of the porous substrate before firing or forming The side faces of the fibers of the porous matrix before firing are then fired.

In addition, the present invention provides the above-mentioned porous substrate supporting the catalyst, wherein the film thickness or particle size of the above-mentioned catalyst is smaller than the "void formed by the above-mentioned pores and/or "the gap between the above-mentioned fibers"". The average caliber is long.

In other words, the porous substrate for supporting the catalyst is provided, wherein the thickness of the film when the catalyst is supported by a film or the particle size when the catalyst is supported by particles is less than "" The size of the "hole" and/or "the gap between the above-mentioned fibers".

In addition, the present invention provides the above-mentioned porous substrate supporting the catalyst, wherein the material of the above-mentioned porous substrate is titanium (Ti) or titanium (Ti) alloy or carbon (C).

In addition, the present invention provides an electrode for water electrolysis, which is the above-mentioned porous substrate supporting a catalyst.

In addition, the present invention provides a gas diffusion layer, which is the porous substrate supporting the catalyst.

In addition, the present invention provides a single unit for water electrolysis, which has a structure in which a polymer electrolyte membrane (PEM) is sandwiched by the porous substrate supporting the catalyst.

In addition, the present invention provides a stacked unit for water electrolysis. When a structure in which a polymer electrolyte membrane (PEM) is sandwiched by a porous matrix supporting a catalyst is used as a single unit for water electrolysis, It is formed by stacking two or more single cells for water electrolysis.

In addition, the present invention provides a unit module for water electrolysis in which the above-mentioned stacked units for water electrolysis are arranged two-dimensionally or three-dimensionally.

According to the present invention, it is possible to provide a solution to the aforementioned problems and the aforementioned problems, for example, due to the excellent water electrolysis performance of maintaining a constant (low) value and stability of the cell voltage, and the support of the catalyst It is strong and has good contact, so it can provide an electrode for water electrolysis with excellent durability. In addition, a single unit for water electrolysis or a stacked unit for water electrolysis using the electrode for water electrolysis can be provided.

Specifically, by supporting the catalyst on the porous substrate in a specific shape or pattern, the catalyst can be integrated with the porous substrate. Specifically, the catalyst is supported on "the surface of the pores or fibers constituting the porous carbon matrix" by catalyst particles or a catalyst film, thereby accumulating in the form of a catalyst layer (porous) Compared with the shape of the upper surface (or lower surface) of the substrate, it can have more excellent water electrolysis performance and durability.

Specifically, for example, in the conventional method of depositing a catalyst on a substrate in the form of a layer, the catalyst layer may potentially peel off from the substrate due to gas lift. However, according to the present invention, a method can be provided. A porous substrate or electrode for water electrolysis for water electrolysis that prevents the catalyst from peeling from the porous substrate or the catalyst is peeled from the material constituting the porous substrate.

In addition, a single unit for water electrolysis or a stacked unit for water electrolysis using the porous substrate (electrode for water electrolysis) supporting the catalyst can be provided.

Furthermore, by allowing the ionic polymer to have a concentration gradient in the thickness direction (or filling) in the porous matrix supporting the catalyst, a stable low value of the unit voltage (applied voltage) can be brought about. In addition, , It can provide an electrode for water electrolysis that is less likely to cause the separation of the catalyst or the separation of the catalyst caused by gas lift.

This kind of "catalyst (film or particle) detachment" can especially be achieved by the aforementioned "support of the catalyst in a specific type to the porous matrix" and the aforementioned "existence of an ionic polymer layer in a specific type" The synergistic effect of the anti-corrosion system can effectively prevent and suppress.

The porous substrate supporting the catalyst of the present invention is used as an electrode for water electrolysis, and a single unit of water electrolysis having a cathode for water electrolysis, a polymer electrolyte membrane (PEM), and an anode for water electrolysis in sequence, Water electrolysis can be performed at a low electrolysis voltage without peeling or detachment of the catalyst film or catalyst particles, so the durability is extremely high.

In addition, even if the unit voltage (applied voltage) is low, the single cell will operate. Therefore, a stack of two or more "single cells for water electrolysis using the porous substrate supporting the catalyst" is stacked for water electrolysis. The unit will operate even if the applied voltage is low. That is, in the case of stacking two or more single cells for water electrolysis, the effect of "low voltage operation" can be achieved, and more hydrogen (and oxygen) can be obtained with less electricity.

1: Single unit for water electrolysis

2: Electrode for water electrolysis

3: Porous matrix that holds the catalyst

3c: Metal catalyst, metal oxide catalyst, catalyst

3p: porous matrix

3q: Fibers and fibers forming a porous matrix

4: ionic polymer

5: Polymer electrolyte membrane (PEM)

6: Power supply

7: Resin tank

8: Bipolar plate

9: Stacking unit for water electrolysis

10: Unit module for water electrolysis

Fig. 1 is a schematic exploded perspective view of a unit for water electrolysis having a single unit for water electrolysis. (a) is a schematic development perspective view of a porous substrate (electrode for water electrolysis, gas diffusion layer) using the catalyst of the present invention, and (b) is a schematic development perspective view of a conventional unit for water electrolysis.

Fig. 2 is a schematic cross-sectional view of a single unit for water electrolysis showing the presence of a catalyst. (a) is a schematic cross-sectional view showing the "supporting state of the catalyst to the porous substrate" in the porous substrate holding the catalyst of the present invention, (b) and (c) are showing the historical catalyst A schematic cross-sectional view of the existence pattern of.

Fig. 3 is a schematic enlarged cross-sectional view of the porous substrate supporting the catalyst of the present invention.

4 is an enlarged cross-sectional view showing that the ionic polymer and the contact catalyst are filled with a concentration gradient from the surface of the porous substrate toward the inside in the porous substrate supporting the catalyst of the present invention. (a) is a schematic enlarged cross-sectional view corresponding to FIG. 3, and (b) is an SEM photograph showing a cross-section of the actual porous substrate supporting the catalyst.

Figure 5 is a porous substrate (which can be an electrode for water electrolysis or a gas diffusion layer) of the present invention that holds a catalyst for sandwiching a polymer electrolyte membrane (PEM) of the single unit for water electrolysis of the present invention The cross-sectional view is roughly enlarged.

Fig. 6 is a schematic enlarged cross-sectional view showing an example of a state in which an ion polymer is filled with a concentration gradient in the thickness direction from the surface of the electrode for water electrolysis (the porous substrate supporting the catalyst) toward the inside. (a) is a state in which ionic polymer is filled with a concentration gradient from the surface (that is, from both sides) on the side contacting the polymer electrolyte membrane (PEM) and the power supply body toward the inside, and (b) is the state in which the contact is high The surface on the side of the molecular electrolyte membrane (PEM) is filled with an ionic polymer in a state with a concentration gradient toward the inside.

Fig. 7 is a schematic exploded perspective view of the stacked unit for water electrolysis of the present invention in which two single units for water electrolysis of the present invention are stacked.

Fig. 8 is a schematic view of the stack unit for water electrolysis of the present invention. (a) is a perspective view of the stack unit connected with wiring and piping, (b) is a schematic cross-sectional view showing the "hydrogen outlet" on the cathode side and the "water inlet" and "water outlet and oxygen outlet" on the anode side, (c ) Is a perspective view of the stacking unit without wiring and piping.

Fig. 9 is a schematic perspective view of a unit module for water electrolysis in which the stacked units for water electrolysis of the present invention are arranged three-dimensionally.

The following is an explanation of the present invention, but the present invention is not limited to the following specific forms, and can be arbitrarily modified within the scope of technical ideas.

<Porous substrate holding catalyst>

The porous substrate supporting the catalyst of the present invention is a porous substrate supporting the catalyst having the following structure: a polymer electrolyte membrane (PEM (Polymer Electrolyte Membrane)), and contact the polymer electrolyte membrane (PEM) to form a cathode or anode, and also play the function of a gas diffusion layer.

The catalyst is supported on the side surface of the pores of the porous matrix or the side surface of the fiber forming the porous matrix, and exists in a manner of covering from the surface of the porous matrix itself to the inside, and

The ionic polymer contacts the catalyst and is filled with a concentration gradient in the thickness direction of the porous substrate from the surface of the porous substrate toward the inside.

The porous base system supporting the catalyst of the present invention is used in "single unit for water electrolysis" or "stacked unit for water electrolysis formed by stacking two or more single units for water electrolysis" (hereinafter sometimes two These are collectively referred to as "units for water electrolysis").

As shown in Fig. 1(a), Fig. 2(a), Fig. 5, etc., the porous substrate 3 supporting the catalyst of the present invention is in the single unit 1 for water electrolysis to sandwich the polymer electrolyte membrane ( PEM) 5 exists, and contacts the polymer electrolyte membrane (PEM) 5 to constitute the electrode 2 (cathode or anode) for water electrolysis.

In the present invention, the cathode or anode of the single unit 1 for water electrolysis must be composed of the porous substrate 3 supporting the catalyst of the present invention. Preferably, both the cathode and the anode are composed of the porous substrate 3 supporting the catalyst of the present invention. The matrix 3 constitutes.

However, the type or type of the actual catalyst 3c, porous substrate 3p, etc., and even the manufacturing method in the cathode and anode can be different in the cathode and anode according to their respective polarities.

The porous substrate 3 supporting the catalyst of the present invention has a structure that functions as the electrode 2 for water electrolysis and also functions as a gas diffusion layer. Therefore, the porous substrate 3 supporting the catalyst of the present invention is also a gas diffusion layer.

As shown in the cross-sectional views of Figures 3, 4(a), (b) and Figure 5, the porous substrate 3 for supporting the catalyst of the present invention is supported on a porous supporting body capable of gas diffusion. Hold the catalyst. That is, Yu Dan holds a catalyst The gas system generated in the vicinity of the catalyst of the porous substrate 3, since the porous substrate holding the catalyst itself also functions as a gas diffusion layer, moves (diffuses) the gas to be extracted to the outside.

"Porous Matrix"

In the present invention, the term "porous" means (has) a structure (property) capable of supporting the catalyst to the inside, and is not limited to the type where openings are formed only on the plane (upper surface), and It is a state that is roughened by chemical or physical etching, sputtering, etc.; a porous state; a form that has a space state, etc.; a fibrous aggregate; a state of knitted fabric, fabric, non-woven fabric, etc. By. The above-mentioned "pores" or "voids formed by the fibrous ones constituting aggregates" may also form irregular voids in the thickness direction. In addition, "porous" can also be referred to as a state or property with air permeability.

Fig. 3 is a schematic cross-sectional view before the ionic polymer 4 is provided. The left image is before the catalyst is provided, and the right image is after the catalyst is provided. However, the porous substrate 3p of the present invention can not only support externally, but also support contact. The space up to the inside of the medium is sufficient, and it can be one with so-called through holes (but it does not exclude the existence of independent holes), one with woven fibers or non-woven fabric, etc. For example, an aggregate of fibers such as non-woven fabrics also has pores in the gaps between the fibers, so in the present invention, it is referred to as a "porous matrix" in a broad sense.

As shown in Figures 3 to 5, the present invention is characterized in that the catalyst (catalyst particles or catalyst film) is present in a manner that covers the surface of the porous substrate 3p itself to the inside, and is characterized by the ionic polymer 4 Since the porous substrate 3p itself exists from the surface to the inside, the porous substrate 3p of the present invention must have voids through which the catalyst or the ionic polymer 4 can enter (can be provided to) the inside.

The material of the porous substrate 3p of the present invention is not particularly limited as long as it is conductive, and it is preferably electronically conductive, resistant to corrosion (oxidation, etc.), and resistant to various chemical reactions or For properties such as electrochemical reaction and high strength, specifically, a titanium group metal, an alloy of a titanium group metal, a compound of a titanium group metal, or carbon (C) is preferable.

The so-called "titanium group metal" here means titanium, zirconium or hafnium. That is, the matrix of the titanium group includes a titanium matrix, a zirconium matrix, a hafnium matrix, a titanium alloy matrix, a zirconium alloy matrix, or a hafnium alloy matrix.

In addition, "compounds of titanium group metals" include, for example, titanium nitride (titanium nitride (TiN)), titanium carbide (titanium carbide (TiC)), and titanium diboride (titanium diboride (TiB ₂ ) )Wait.

From the viewpoint of low cell voltage and better prevention of catalyst particles from detaching from the electrode substrate, the metal or alloy of the titanium group is particularly preferably titanium or a titanium alloy, and particularly preferably titanium.

In addition, carbon (C) preferably has a graphite structure (graphene structure).

The porous matrix 3p of the present invention is particularly preferably an aggregate of titanium fibers or titanium alloy fibers, or an aggregate of carbon fibers.

"catalyst"

In the present invention, the catalyst is present so as to cover from the surface of the porous substrate 3p itself to the inside as described above. Specifically, the catalyst is supported on the side surfaces or the pores of the porous substrate 3p. It is the side surface of the fiber 3q that forms the porous substrate 3p, and it exists so as to cover the inside from the surface of the porous substrate 3p itself (FIGS. 3 to 5).

Fig. 5 is a schematic cross-sectional view of the porous substrate 3 supporting the catalyst of the present invention. Fibers 3q such as carbon fibers and titanium fibers constitute the porous substrate 3p, and not only the surface of the fibers 3q on the surface of the porous substrate 3p itself , The catalyst particles are also supported to the surface of the fibers 3q inside the porous matrix 3p itself.

The above-mentioned "surface of the porous substrate itself" is a term relative to the "inside of the porous substrate itself." Therefore, the above-mentioned "surface of the porous substrate itself" does not mean the side surface of the pores of the porous substrate 3p or The surface of the material (fiber, etc.) constituting the porous matrix 3p.

In the present invention, it is preferable that the catalyst is not only deposited on the surface of the porous substrate 3p itself as a catalyst layer, but is supported on the sides of the pores of the porous substrate 3p or forms the porous substrate 3p. The side surfaces of the fibers 3q of the matrix 3p exist so as to cover from the surface of the porous matrix 3p itself to the inside (FIGS. 3 to 5 ).

The catalyst is in the form of a catalyst layer, in other words, the catalyst is only present (formed or accumulated) on the surface of the polymer electrolyte membrane (PEM) 5 as shown in Figure 2(b), or As shown in Figure 2(c), when only (formed or deposited) on the surface of the porous substrate 3p itself, the contact area between the catalyst and the porous substrate 3p becomes smaller. In addition, the catalyst and the polymer electrolyte membrane (PEM ) The contact area of 5 becomes smaller, so the aforementioned excellent effects of the present invention cannot be obtained.

The porous substrate 3 supporting the catalyst of the present invention preferably has the following structure, that is, by attaching a metal catalyst or a metal catalyst precursor to the side surface or the hole of the porous substrate 3p before firing It is a structure obtained by the step of forming the side surfaces of the fibers 3q of the porous matrix 3p before firing and firing them.

In the above-mentioned preferred aspect of the present invention, the type and composition of the catalyst formed on the porous matrix 3p or the type of catalyst particles supported, etc., whether directly specified or parameterized It is impossible or impractical to wait for those who are specifically designated. Therefore, the above-mentioned preferable configuration (aspect) can only be specified by the manufacturing method.

Specifically, the catalyst of the present invention is preferably to apply a coating solution in which "metal catalyst or metal catalyst precursor" is dissolved or finely dispersed on the porous substrate 3p, and then this is fired to thereby Form and get.

That is, the catalyst of the present invention is particularly preferred to attach the "metal catalyst or metal catalyst precursor" to the side surface of the hole of the porous substrate 3p or the side surface of the fiber 3q by coating and drying the coating liquid. It is obtained by firing.

Here, the coating method is not particularly limited, and examples include spray coating via a sprayer, dip coating, brush coating, brush coating, and screen printing coating. After coating, it can be dried according to common methods as needed to distill off the coating solvent.

The "baking" performed after the attachment means a general heat treatment in a broad sense. The firing temperature depends on the type of catalyst (precursor) and is not particularly limited. It is preferably 160°C or higher and 800°C or lower, particularly preferably 230°C or higher and 750°C or lower, and particularly preferably 300°C or higher and 700°C or lower.

The roasting time (heat treatment time) is not particularly limited as long as it can achieve the catalytic effect. It is preferably 10 minutes or more and 8 hours or less, particularly preferably 30 minutes or more and 5 hours or less, and particularly preferably 1 hour or more and 3 hours or less .

When the calcination time is above the above lower limit, the same effect as when the above calcination temperature is above the above lower limit can be obtained. When the calcination time is below the above upper limit, the same effect can be obtained as when the above calcination temperature is below the above upper limit. Support the catalyst well.

As shown in Figure 2 (b), when the catalyst is present on the polymer electrolyte membrane (PEM) 5, when the catalyst is to be supported by firing, due to the polymer electrolyte membrane (PEM) 5 It has poor heat resistance, so it melts or deteriorates at the above-mentioned firing temperature. Therefore, in the case of the type shown in Figure 2(b), the catalyst cannot be generated by firing.

According to the present invention, since a metal catalyst or a metal catalyst precursor can be attached to the porous substrate 3p (generally having a tendency to be stronger in heat resistance) and fired to obtain a catalyst (supported thereon), Therefore, compared with the case where only coating, drying and firing are performed, the adhesion to the porous substrate 3p is increased, a catalyst with an excellent shape and composition can be used, and the range of catalysts that can be used is wider.

In the present invention, the volume of the pores constituting the porous matrix 3p may be changed due to firing to increase the pores, or the thickness of the fibers 3q constituting the porous matrix 3p may become thinner. On the contrary, when this phenomenon is caused, the catalyst is easily supported on "the side of the pores of the porous matrix or the side of the fiber 3q forming the porous matrix." In the case of particles, the size of the catalyst It can become more abundant and the catalyst can exist (support) slowly (uniformly) so as to cover from the surface of the porous base 3p itself to the inside easily.

In addition, the ionic polymer 4 described later may be easily filled with a concentration gradient in the thickness direction of the porous substrate 3p from the surface to the inside of the porous substrate 3p.

The porous substrate 3 supporting the catalyst of the present invention is preferably obtained by attaching a metal catalyst or a metal catalyst precursor to the porous substrate 3p and baking it. Among the metal catalyst or metal catalyst precursor The metal is not particularly limited as long as it is a catalyst particle or a catalyst film formed by firing that functions as a catalyst. Among them, from the viewpoint of high catalytic effect, it is preferably selected from the group consisting of platinum (Pt), ruthenium (Ru), iridium (Ir), palladium (Pd), tantalum (Ta) and nickel (Ni) In the metal. The above-mentioned metals may be used singly or in combination of two or more kinds. In addition, it can also be used in combination with metals other than the above.

In other words, the catalyst of the present invention is preferably one selected from the group consisting of platinum (Pt), ruthenium (Ru), iridium (Ir), palladium (Pd), tantalum (Ta) and nickel (Ni) The above metals or metal-containing compounds.

The metal compound in the metal catalyst/metal catalyst precursor that is the raw material of the catalyst is not limited to those shown below. Specifically, for example, chloroplatin (IV) acid n hydrate, chloroplatin (IV) ) Ammonium acid, dinitrodiammine platinum (II), platinum dichloride (II), platinum tetrachloride (IV), tetraammine platinum (II) n hydrate, tetraammine platinum (II) , Hexahydroxyplatinum(IV) acid and other platinum-containing compounds; ruthenium(III) chloride hydrate, ruthenium(III) nitrate, ruthenium(IV) oxide hydrate and other ruthenium-containing compounds; chloroiridium(IV) acid n-hydrate, Iridium(III) chloride n hydrate, iridium(III) chloride anhydrate, iridium(IV) nitrate, ammonium chloride(IV) ammonium, hexaamine iridium(III) hydroxide and other iridium-containing compounds; Palladium chloride( II), palladium nitrate (II), dinitrodiamine palladium (II), palladium acetate (II), tetraammonium palladium (II) and other palladium compounds; nickel chloride (II) anhydrous, chlorinated Nickel-containing compounds such as nickel (II) hexahydrate and nickel nitrate (II) hexahydrate; tantalum pentachloride, tantalum alkoxide, etc.

The metal catalyst precursor is not particularly limited. Specifically, for example, an alcohol coordinated to the above-mentioned metal compound can be mentioned. It is particularly preferred to dissolve the above-mentioned metal compound in an alcohol solvent to prepare a metal catalyst precursor, and then apply a coating solution containing the metal catalyst precursor to the porous substrate 3p, dry it, and then calcinate to convert In order to support the catalyst together, a porous substrate 3 that supports the catalyst is prepared.

In the case of attaching a metal catalyst or a metal catalyst precursor to the porous substrate 3p by coating, "the solvent (dispersion medium) used in the coating liquid for the coating" and/or the above-mentioned "coating on the metal The "alcohol of the compound" preferably includes methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, cyclohexanol, and the like.

In the case of adhesion to the porous carbon substrate by coating, the coating method of the coating liquid is not limited, but preferred methods include: brushing method, spray method, spray coating method, Impregnation method, etc.

In addition, for example, as shown in Figures 3 and 4, the catalyst can be supported on the side of the hole or the side of the fiber 3q in the form of a membrane, or, for example, as shown in Figure 5, it can be supported on the side of the hole or in the state of particles. It is the side of fiber 3q.

Generally, iridium (Ir), tantalum (Ta), etc. are supported on the side of the hole or fiber 3q in the form of a film, and platinum (Pt) is supported on the side of the hole or fiber 3q in the form of particles, etc. .

The average particle size of the catalyst particles differs depending on the type of the catalyst and is not particularly limited. The number average particle size is preferably 300 μm or less, particularly preferably 200 μm or less, and particularly preferably 100 μm or less. The number-average particle size of the present invention can be observed by scanning electron microscope (SEM: Scanning Electron Microscope) to observe the cross section of the porous material holding the catalyst obtained after firing, and 20 catalyst particles are randomly selected and obtained The average value of the diameter is then defined by the average value of the diameter thus obtained.

When the average particle size of the catalyst particles is too large, the catalyst effect is reduced, which may increase the cell voltage or detach from the electrode substrate.

Furthermore, in addition to this, in the case of the present invention, as described later, in particular, it is difficult for the catalyst particles to enter the inside of the porous base 3p, and sometimes it is difficult to support the inside of the porous base 3p.

On the other hand, if the average particle size is too small, it may infiltrate from the side surface of the pores of the porous matrix 3p or the side surface of the fiber 3q to the microscopic deep part. However, if the surface area of the catalyst can be increased by adjoining and bonding a plurality of fine particles, it does not necessarily need to be in the above-mentioned particle size range.

The so-called "cell voltage" refers to the electrolysis voltage applied between the cathode and anode of a water electrolysis cell for the electrolysis of water.

In the case where the catalyst is supported on the side surface of the pores of the porous substrate 3p or the side surface of the fiber 3q in the form of a membrane, the average thickness of the membrane varies depending on the type of catalyst and is not particularly limited. However, it is preferably 50 μm or less, particularly preferably 40 μm or less, and particularly preferably 30 μm or less. The average film thickness can be obtained by observing the cross-section of the porous material holding the catalyst obtained after sintering with a scanning electron microscope (SEM), and then it can be defined as such.

"Ionic Polymer"

The porous substrate 3 supporting the catalyst of the present invention preferably has an ionomer 4 on the side adjacent to the polymer electrolyte membrane (PEM) 5.

Here, "ionic polymer" is also referred to as a cation exchange polymer, a polymer having a strong acid group in the side chain, a proton conductive polymer, an ion conductive polymer, etc. The so-called "ionic polymer" means having the above Polymers of chemical structure or physical properties.

For example, the upper surface of the porous matrix 3p of aggregates of carbon fibers, titanium fibers, etc. is originally not flat (Figure 2(a), Figures 3 to 5), so the contact with the polymer electrolyte membrane (PEM) 5 sometimes Therefore, the contact between the catalyst and the polymer electrolyte membrane (PEM) is sometimes insufficient.

In addition, in the present invention, since the catalyst also exists inside the porous substrate 3p, a large amount of catalyst also exists inside the porous substrate 3p. If there is no ionic polymer 4, the catalyst and polymer Electrolyte membrane (PEM) contact will become more inadequate.

According to the present invention, in the configuration shown in Fig. 2(a) and Figs. 3 to 6, due to the presence of the ionic polymer 4, it is present in the porous matrix 3p itself and the porous matrix 3p and the polymer electrolyte The gaps between the membranes (PEM) are filled, so that the contact between them is good, and the contact between the ionic polymer 4 and the catalyst and the contact between the polymer electrolyte membrane (PEM) 5 and the catalyst are good.

In the porous substrate supporting the catalyst of the present invention, the ionic polymer 4 is in contact with the supported catalyst, and has the thickness direction of the porous substrate 3p from the surface of the porous substrate 3p toward the inside. The state of the concentration gradient is filled (refer to Figure 2(a), Figure 4 to Figure 6).

The direction in which the concentration of the ionic polymer is high is the side of the porous matrix supporting the catalyst that is in contact with the polymer electrolyte membrane (PEM) 5 (Figure 6(b)). In addition, it is also preferable to The opposite side, that is, with the power supply body 6 The concentration on the contact side is also high, and it is filled with a concentration gradient in the thickness direction of the porous substrate 3p from the surface to the inside (FIG. 6(a)).

In view of the necessity of contact, it is important in the present invention to surround the catalyst film or the catalyst particles with the ionic polymer 4. In addition, the ionic polymer 4 is filled in a state having a concentration gradient in the thickness direction of the porous matrix 3p.

As shown in Fig. 6(b), near the deep part of the porous substrate 3p (that is, the side in contact with the polymer electrolyte membrane (PEM) 5 is the opposite side), the ion polymerization The substance 4 may be absent or less, and furthermore, from the point of view of penetrability, it is preferable to have a part where the ionic polymer 4 is absent or a less part.

In addition, as shown in FIG. 6(a), in the vicinity of the deep portion (that is, the portion away from the contact surface with the PEM5 and the power supply body 6) of the porous substrate 3p (holding the catalyst), the ionic polymer 4 may not Exist or less, and furthermore, from the point of view of penetrability, it is preferable to have a part where the ionic polymer 4 is not present or a part where there is less.

As mentioned above, firing is performed to prepare the catalyst, but when the fibers 3q constituting the porous matrix 3p become thinner, it becomes more difficult to contact. For example, as shown in Fig. 5, the ionic polymer 4 contacts the catalyst 3c. And when it exists in a state with a concentration gradient from the surface of the porous substrate 3p toward the inside, the contact between the porous substrate supporting the catalyst (the catalyst 3c) and the polymer electrolyte membrane (PEM) 5 becomes extremely good.

That is, the ionic polymer 4 has the function of conducting "hydrogen ions (protons) to the cathode side", and is adjacent to the polymer electrolyte membrane (PEM) by being present in the porous substrate 3 supporting the catalyst. On the side of 5, the resistance when protons are conducted from the polymer electrolyte membrane (PEM) 5 to the surface of the catalyst can be greatly reduced.

Therefore, by filling the ionic polymer 4 toward the inside of the porous matrix 3 that supports the catalyst, it is possible to remove the power supply and/or resin tank that cannot directly contact with the polymer electrolyte membrane (PEM). The protons generated in the "side catalyst" are conducted to the cathode side, which improves the utilization efficiency of the catalyst.

As a result, when the ionic polymer 4 is filled in the above-mentioned aspect of the present invention and operated under a constant current value, even if the cell voltage (electrolysis voltage) is low, the water electrolysis cell is operated, and the damage caused by The detachment of catalyst particles caused by the generated gas.

The amount of the ionic polymer 4 varies depending on the thickness or porosity of the porous substrate 3 that supports the catalyst, and the usage conditions of the water electrolysis unit, such as the amount of hydrogen generated per unit time, and is not particularly Limited, only gas is generated along with water electrolysis and the gas needs to be extracted to the outside. Therefore, it is better not to coat the entire surface of the catalyst thickly by the ionic polymer 4, but to make the surface of the catalyst microscopically Partially exposed, macroscopically, it is better not to fill all the voids of the porous substrate 3 holding the catalyst by the ionic polymer 4, but to use the porous substrate 3 holding the catalyst. It is filled with a concentration gradient in the thickness direction, and the generated gas is discharged.

Since it is necessary to extract the generated gas from the side of the power supply 6 and/or the resin tank 7, in order to extract the gas more efficiently, it is better to use "Polymer Electrolyte Membrane (PEM)" and "Power Supply 6 and/ Or between the resin tanks 7″, the amount of the ionomer 4 has a slope.

Therefore, although not particularly limited, in the void volume of the porous matrix 3 supporting the catalyst, the ratio of the volume of the void filled by the ionic polymer 4 (hereinafter sometimes referred to as "filling rate ") Preferably it is 10 volume% or more and 90 volume% or less, more preferably 20 volume% or more and 80 volume% or less, particularly preferably 30 volume% or more and 70 volume% or less.

That is, the present invention is also: the ionic polymer 4 is injected into the voids of the porous substrate 3 supporting the catalyst, and the void volume of the porous substrate 3 supporting the catalyst Among them, the porous substrate 3 supporting the catalyst in which the ratio of filling the voids by the ionic polymer 4 is 10% by volume or more and 90% by volume or less.

The above-mentioned effects of the ionic polymer 4 can be better achieved regardless of whether it is a cathode for water electrolysis or an anode for water electrolysis (refer to FIG. 5).

The filling of the ionic polymer 4 can be formed by, for example, coating an ionic polymer dispersion or an ionic polymer solution on the porous substrate 3p supporting the catalyst.

The present invention is also: after the catalyst is supported on the porous substrate 3p, the solution of the ionic polymer 4 is applied and dried to have a concentration gradient from the surface of the porous substrate 3p to the inside The porous matrix 3 supporting the catalyst obtained by filling the ionic polymer 4.

It can be coated from the side in contact with the polymer electrolyte membrane (PEM) 5 to obtain a catalyst-supporting porous substrate 3 with a concentration gradient as shown in Figure 6(b), or further after that , It is also coated from the side in contact with the power supply 6 to obtain a porous substrate 3 supporting the catalyst with a concentration gradient on both sides as shown in Figure 6(a).

In a preferred aspect of the present invention, the quality and type of the ionic polymer 4 is filled in the porous matrix 3p, or the type of contact with the catalyst, etc., whether directly specified or by parameters, etc. It is impossible or almost impractical to specify. Therefore, the above-mentioned preferred aspect (configuration) can only be specified by the manufacturing method.

Examples of the coating method include a brushing method, a spray method, and a spray coating method.

After coating the ionic polymer dispersion (ionic polymer solution), volatilize the solvent (dispersion medium) at about 60°C, preferably above 120°C and below 250°C, particularly preferably above 140°C and below 200°C, and more The heat treatment is preferably carried out in 1 minute or more and 1 hour or less, and particularly preferably in 3 minutes or more and 30 minutes or less.

"Chemical Structure of Ionomers"

The above-mentioned ionic polymer 4 is not particularly limited as long as it has ion conductivity, especially proton conductivity, and can be used in the single unit 1 for water electrolysis. That is, the "ionic polymer" in the present invention means a proton conductive polymer.

The ionic polymer 4 is not particularly limited, and may be a fluorine-based ionic polymer 4 having fluorine atoms in the molecule, or a non-fluorine-based ionic polymer 4 having no fluorine atoms in the molecule.

Although not particularly limited, fluorine-based ionic polymers are preferred, and ion-conducting polymers having a perfluorovinyl ether skeleton having a polyvinyl fluoride skeleton as the main chain and a sulfonic acid group as a side chain at the end are particularly preferable.物(Proton Conductive Polymer).

Although not particularly limited, examples of particularly preferred ionic polymers 4 used in the present invention are shown below.

In this formula (1), m is a natural number.

In this formula (2), p is a natural number.

In this formula (3), n is a natural number.

The ionic polymer represented by formula (1) is a polymer composed of a polytetrafluoroethylene (PTFE: Polytetrafluoroethylene) skeleton as the main chain and a perfluoroether pendant side chain having a sulfonic acid group at the end. Because the side chain is relatively long, it is also called long-side-chain (LSC: long-side-chain) ionic polymer.

The equivalent weight (EW: equivalent weight) of the ionic polymer represented by formula (1) (the weight of the polymer required to supply 1 mol of proton) is not limited, and is particularly preferably 900g/mol to 1200g/mol . The preferable range of m in formula (1) is a range that can be calculated from the equivalent mass.

The long side chain (LSC) ionic polymer represented by the formula (1) is not limited, and commercially available products can be preferably used, and examples include Nafion (registered trademark) manufactured by Du Pont Co., Ltd. and the like.

The long side chain (LSC) ionic polymer represented by the formula (1) is preferably Nafion (registered trademark) (EW=1100 g/mol, m=6.6 in the formula (1)) and the like.

The ionic polymer represented by formula (2) or formula (3) is a polymer composed of a polytetrafluoroethylene (PTFE) skeleton as the main chain and a perfluoro pendant side chain with a sulfonic acid group at the end . Because the side chain is relatively short, it is also called short-side-chain (SSC: short-side-chain) ionic polymer.

The equivalent mass (EW) of the ionic polymer represented by formula (2) or formula (3) is not limited, and is particularly preferably 700 g/mol to 950 g/mol. The preferable range of p in formula (2) and the preferable range of n in formula (3) are ranges that can be calculated from the equivalent mass.

The short side chain (SSC) ionic polymer represented by formula (2) or formula (3) is not limited, and commercially available products can be preferably used. For example, 3M ionic polymer manufactured by 3M Corporation can be cited.

"The relationship between "the film thickness or particle size of the catalyst" and "the voids of the porous matrix">

In the porous substrate 3 supporting the catalyst of the present invention, the film thickness or particle size of the catalyst supported on the porous substrate 3p is preferably smaller than the gap formed by the pores and/or the gaps between the fibers. The average caliber is long. In larger cases, it is sometimes difficult for the catalyst to better support the material constituting the porous matrix 3p.

In addition, although the above-mentioned voids are voids of the porous substrate 3p after supporting the catalyst by baking or the like, the voids of the porous substrate 3p before supporting the catalyst by baking or the like are preferably also It is larger than the size (film thickness or particle size) of the catalyst obtained. In smaller cases, the "metal catalyst or metal catalyst precursor" dissolved or micro-dispersed in the catalyst coating liquid is sometimes difficult to enter the porous interior. As a result, sometimes the catalyst cannot be removed from the porous body. The porous substrate 3p exists in such a way that the surface itself covers the inside.

In addition, in the porous matrix supporting the catalyst of the present invention, the porous matrix 3 excluding the ionic polymer 4, and the porosity expressed by the following definition formula (1), is preferably 3 volumes % Above 80% by volume.

Porosity (volume %)=100×[volume of the void of the porous substrate holding the catalyst]/[volume of the porous substrate holding the catalyst] (1)

Since the so-called "porous matrix supporting the catalyst" means the one that already holds the catalyst, when the catalyst is supported by firing, the "void" of the above-mentioned "void ratio" means The voids of the porous matrix 3p after firing.

Since the volume of the catalyst particles (catalyst film) is very small compared to the volume of the above-mentioned voids, the "voids of the porous substrate" are almost equal to the "voids of the porous substrate holding the catalyst".

The molecule of the above definition formula (1) can be used to measure the weight and volume of the porous substrate 3 that holds the catalyst, and use the true specific gravity of the material (Ti, C, etc.) to calculate, and since the denominator is also easy to determine, the void The rate can be obtained as such and defined in terms of those who obtain it as such.

The void ratio is preferably measured before the ionic polymer 4 is imparted (filled).

The void ratio is particularly preferably from 5 vol% to 70 vol%, and particularly preferably from 10 vol% to 60 vol%.

If the porosity is too small, it is difficult to support the catalyst, and sometimes it cannot be supported to the inside of the porous substrate 3p. In addition, it is difficult for the ionic polymer solution/dispersion to flow into the porous substrate 3p, and sometimes the ionic polymer 4 cannot be filled into the porous substrate 3p, or it may not have a concentration in the thickness direction of the porous substrate 3p. The state of the gradient is filled, etc. In addition, the diffusibility of gas is deteriorated, and the function as a gas diffusion layer may be deteriorated.

On the other hand, when the porosity is too large, the strength of the porous substrate 3 supporting the catalyst may decrease, or the conductivity may decrease.

In the porous substrate 3 supporting the catalyst of the present invention, the sum of "the microscopic area of the "catalyst that exists so as to cover from the surface of the porous substrate itself" to the above-mentioned ionic polymer" is preferably "The macroscopic area of the surface of the porous substrate 3 holding the catalyst that contacts the above-mentioned polymer electrolyte membrane (PEM) 5" is more than twice as large. The above-mentioned magnification is called "contact area magnification".

The above-mentioned microscopic area is observed by scanning electron microscope (SEM) to observe the cross section of the porous matrix 3 which is filled with the ionic polymer, and the cross section of the catalyst can be calculated (calculated) from the cross section of the catalyst. As for the surface area, the surface (volume) of the catalyst inside the porous matrix 3 that is not filled with the ionic polymer 4 to support the catalyst is excluded from the microscopic area.

The above-mentioned macroscopic area can be obtained by multiplying the vertical length and the horizontal length, for example, when the porous substrate 3 supporting the catalyst is rectangular.

The above-mentioned "contact area magnification" is obtained by dividing the above-mentioned microscopic area by the above-mentioned macroscopic area, so it can be defined by the value obtained in this way.

The contact area magnification is particularly preferably 3 times or more, more preferably 4 times or more and 300 times or less, and particularly preferably 5 times or more and 100 times or less.

If the contact area ratio is too small, the aforementioned various "(filling) effects of the ionic polymer 4" may not be obtained, and when it is too large, it may be difficult to produce the porous substrate 3 supporting the catalyst.

<Electrode for Water Electrolysis>

As described above, the present invention is also an electrode 2 for water electrolysis, which is characterized by the porous substrate 3 supporting the catalyst of the present invention.

In addition, as described above, the present invention is also a gas diffusion layer, which is characterized by the porous substrate 3 supporting the catalyst of the present invention.

That is, as described above, in view of the type and function of the porous substrate 3 supporting the catalyst of the present invention, the porous substrate 3 supporting the catalyst of the present invention can also function as an electrode for water electrolysis. The function of 2 is used. In addition, the porous substrate 3 supporting the catalyst of the present invention can also be used as a function of a gas diffusion layer.

〈Single unit for water electrolysis〉

The present invention is also a single unit 1 for water electrolysis, which is characterized by a structure in which a polymer electrolyte membrane (PEM) 5 is sandwiched by the porous substrate 3 supporting the catalyst of the present invention.

As shown in Figure 1(a) as an example, the single unit 1 for water electrolysis of the present invention has a polymer electrolyte membrane (PEM) 5 sandwiched by a porous substrate 3 supporting a catalyst of the present invention. It has a structure, and more specifically, it is sandwiched by a gasket, a power supply body 6, a resin tank body 7, and the like. In addition, the single unit 1 for water electrolysis of the present invention is formed by sandwiching a porous substrate 3 (electrode for water electrolysis) supporting a catalyst as shown in FIG. 5 by the above-mentioned structure.

The structure of the power supply body 6, the resin tank body 7 and the like is not particularly limited, and generally known ones can be used.

Fig. 7 shows a stack unit 9 for water electrolysis that connects two single units for water electrolysis of the present invention, and the right and left sides of which are the single unit 1 for water electrolysis, respectively.

The invention of the single unit 1 for water electrolysis of the present invention does not exclude the use (combined use) of other layers or other members/structures in addition to the above or those shown in the drawings.

<Stacking unit for water electrolysis>

The present invention is also a stacked unit 9 for water electrolysis, which is used when a structure in which a polymer electrolyte membrane (PEM) 5 is sandwiched by a porous substrate 3 supporting a catalyst is used as a single unit 1 for water electrolysis , It is formed by stacking two or more single cells 1 for water electrolysis.

Fig. 7 shows the outline of the stack unit 9 for water electrolysis of the present invention. As shown in FIG. 7, the stack unit 9 for water electrolysis of the present invention is constructed by sandwiching the bipolar plate 8 by the single unit 1 for water electrolysis of the present invention described above.

The stacked unit 9 for water electrolysis of the present invention is formed by stacking 2 or more single units for water electrolysis of the present invention, preferably 3 or more and 10 or less, and particularly preferably 4 or more and 6 or less. to make.

When the number of layers is too small, the water electrolysis efficiency (hydrogen generation efficiency) may deteriorate. On the other hand, when the number of layers is too large, the voltage required for water electrolysis may increase.

As mentioned above, the single cell 1 for water electrolysis using the porous substrate 3 of the present invention is characterized by a low cell voltage, so even if a plurality of single cells 1 for water electrolysis are connected in series, the water electrolysis can be reduced. The electrolysis voltage between the cathode and the anode of the stacked unit 9 is used.

The invention of the stack unit 9 for water electrolysis of the present invention does not exclude the use (combined use) of other layers or other members/structures in addition to the above or those shown in the drawings.

8(a) and (b) show that the stack unit 9 for water electrolysis of the present invention is further provided with cathode wiring, anode wiring, water inlet, water outlet, hydrogen discharge piping (hydrogen outlet), and oxygen discharge piping (oxygen). Conceptual diagram of export), etc. The water outlet and the oxygen discharge pipe (oxygen outlet) can be the same (shared).

〈Unit module for water electrolysis〉

The present invention is also a unit module 10 for water electrolysis, which is characterized by arranging the above-mentioned stacked units 9 for water electrolysis in a two-dimensional or three-dimensional arrangement.

FIG. 9 is a schematic perspective view showing the unit module 10 for water electrolysis in which the stack units 9 for water electrolysis of the present invention are arranged in a three-dimensional manner.

By being configured as the unit module 10 for water electrolysis, a large amount of water can be efficiently electrolyzed to obtain a large amount of hydrogen or oxygen.

In addition, as shown in FIG. 9, a setting board may be installed, and only a part of the stack unit 9 for water electrolysis may be drawn out for replacement or maintenance, or the power supply may be stopped (setting the power outage period), so that the efficiency of operation can be improved.

The invention of the unit module 10 for water electrolysis of the present invention does not exclude the use (combined use) of other components added to these, in addition to the above or those shown in the drawings.

[Example]

The following series of examples and comparative examples will illustrate the present invention more specifically, but the present invention is not limited to these examples without departing from the spirit thereof.

Below, unless otherwise stated, the value related to ratio or% is mass ratio or mass %.

Example 1

<Manufacturing of porous substrates that hold catalysts and electrodes for water electrolysis>

Using a sprayer, apply an alcohol-based coating solution containing chloroiridium (IV) acid hexahydrate as a metal catalyst (metal precursor) to a titanium fiber with a fiber diameter of 50μm in a manner that does not cause unevenness. The porous substrate 3p aggregated like a flat plate serves as a catalyst.

At this time, it was confirmed that the coating liquid penetrated into the inside from the surface of the porous substrate 3p itself.

Next, in order to volatilize the solvent of the coating liquid, the porous substrate was heated at 70°C for 30 minutes to dry it. In order to improve the adhesion between the metal catalyst 3c and the surface of the porous substrate (the side surface of the fiber), the heat treatment is performed by heating at 600°C, which is a higher temperature than the above-mentioned drying temperature, for 2 hours.

Observed by scanning electron microscope (SEM) the "porous matrix supporting the catalyst before ionic polymer filling", as shown in Figures 2 to 4, the iridium catalyst is supported in the formation The side surface of the titanium fiber of the porous substrate 3p is present in a jacket shape so as to cover the titanium fiber from the surface of the porous substrate 3p itself to the inside. The film thickness of the catalyst is 0.3 μm to 10 μm.

Using a sprayer, a dispersion liquid of an ionic polymer (Nafion (registered trademark) manufactured by Du Pont) was applied to the porous substrate 3p supporting the metal catalyst 3c from the side in contact with the PEM.

At this time, it was confirmed that the dispersion liquid penetrated into the inside from the surface of the porous substrate 3 holding the catalyst.

Next, in order to volatilize the dispersion medium of the ionic polymer dispersion, the porous substrate 3 supporting the catalyst was heated at 100° C. for 30 minutes to be dried.

Observed by scanning electron microscope (SEM), the obtained "porous matrix supporting catalyst after ionomer filling" is shown in Figures 4 and 5. It can be confirmed that the ionic polymer 4 is in contact with each other. Iridium, which is a catalyst, is filled with a concentration gradient in the thickness direction from the surface of the porous substrate 3p toward the inside (see, in particular, Figs. 4(b) and 6(b)).

The porosity of the obtained "porous matrix supporting the catalyst filled with ionic polymer" has a porosity of 40% by volume and a contact area ratio of 10 times. "It is formed by the gaps between the fibers constituting the porous matrix. The average aperture length of the voids is 25 μm to 50 μm.

Example 2

In Example 1, except that a porous matrix 3p composed of carbon fibers was used instead of the porous matrix 3p composed of titanium fibers, it was the same as in Example 1 to obtain a porous matrix 3 supporting a catalyst. (Electrode 2 for water electrolysis).

On the way, it was confirmed that the coating liquid of the catalyst penetrated into the inside from the surface of the porous substrate 3p itself.

In addition, it was confirmed that the ionic polymer dispersion liquid penetrated into the inside from the surface of the porous substrate 3 supporting the catalyst.

Observing the obtained porous substrate 3 holding the catalyst by scanning electron microscope (SEM), it can be seen that the iridium catalyst is supported on the side surface of the carbon fiber forming the porous substrate 3p, and the porous substrate 3 The surface of the matrix 3p itself exists in such a way that it covers the inside.

In addition, it was confirmed that the ionic polymer 4 was in contact with the catalyst and was filled in a state having a concentration gradient in the thickness direction from the surface of the porous substrate 3p toward the inside (refer to FIGS. 4(b) and 6(b) in particular).

Example 3

In Example 1, except that a platinum catalyst was used instead of the iridium catalyst, the porous substrate 3 (electrode 2 for water electrolysis) supporting the catalyst was obtained in the same manner as in Example 1.

On the way, it was confirmed that the coating liquid of the catalyst penetrated into the inside from the surface of the porous substrate 3p itself.

In addition, it was confirmed that the ionic polymer dispersion liquid penetrated into the inside from the surface of the porous substrate 3 supporting the catalyst.

Observing the obtained porous substrate 3 holding the catalyst by scanning electron microscope (SEM), it can be seen that the platinum catalyst is supported on the side surface of the titanium fiber forming the porous substrate 3p, and from the The porous substrate 3p exists in such a way that the surface itself covers the inside.

In addition, it was confirmed that the ionic polymer 4 was in contact with the catalyst and was filled in a state having a concentration gradient in the thickness direction from the surface of the porous substrate 3p toward the inside (especially FIGS. 5 and 6(b)).

Comparative example 1

In Example 1, except that a matrix composed of titanium fibers with a porosity of 1% by volume was used as a (porous) matrix, the same as in Example 1 was used to obtain an electrode 2 for water electrolysis (catalyst layer forming matrix). ).

As a (porous) substrate, a substrate composed of titanium fibers with a porosity of 1% by volume. Since the pores (voids) are smaller than metal catalyst particles, it is difficult for the catalyst coating liquid to escape from the porous substrate 3p itself. The surface penetrates into the interior.

Observing the obtained electrode 2 for water electrolysis with a scanning electron microscope (SEM), it can be seen that the catalyst does not exist in the porous substrate 3p itself, but a catalyst layer is formed on the (porous) substrate . It becomes the layer composition of "porous matrix\metal catalyst layer\ion polymer layer".

Comparative example 2

In Example 1, except that the ionic polymer 4 is not filled, that is, the dispersion liquid of the ionic polymer 4 is not coated, the others are the same as in Example 1 to obtain the porous matrix 3 supporting the catalyst.

Observing the obtained porous substrate 3 holding the catalyst with a scanning electron microscope (SEM), it can be seen that although the catalyst exists in the porous substrate 3p itself, it is not filled with the ionic polymer 4, So the catalyst is isolated.

Comparative example 3

A conventional membrane electrode assembly (MEA) was used as an electrode for water electrolysis.

The membrane electrode assembly (MEA) used is coated with carbon particles and "catalyst platinum particles" on one side of the PEM, and "catalyst iridium oxide particles" are coated on the other side. Dry to fix.

Evaluation example 1

<Assembly of a single unit for water electrolysis>

The single unit 1 for water electrolysis is assembled with the configuration shown in Fig. 1(a).

Specifically, a polymer electrolyte membrane (PEM) is placed in the center, and the porous matrix that has a metal catalyst 3c and an ionic polymer 4, which is obtained in the above-mentioned embodiment, is placed on the two outer sides. 3 (Electrode for water electrolysis 2)" or the electrode for water electrolysis obtained in the comparative example.

Furthermore, after disposing the power supply body 6 on the two sides and further disposing the resin tank body 7 on the outer sides of the two sides, the two ends are locked by bolts to sandwich each structure, and the single unit 1 for water electrolysis is assembled.

<Initial performance evaluation based on water electrolysis test>

The pure water at a temperature of 20°C was circulated in the single unit 1 for water electrolysis obtained in the above examples and comparative examples by a pump, the pure water for electrolysis was supplied to the anode side of the unit for water electrolysis, and a DC power supply was used To record the value of the cell voltage during water electrolysis at a given current density.

The initial cell voltage (V) at a current density of 100A/dm ^{2 is shown in Table 1 below.}

<Durability evaluation of a single unit for water electrolysis based on the water electrolysis test>

As in the initial performance evaluation described above, pure water was circulated and supplied to the single cell 1 for water electrolysis, a DC power supply was ^{used to set the current value so that the current density became 100 A/dm 2} , electrolysis was continuously performed, and the cell voltage was recorded.

The cell voltage [V] after 500 hours is shown in Table 2 below.

Evaluation example 2

<Assembly of stack unit for water electrolysis>

The single unit 1 for water electrolysis is stacked in the configuration shown in FIG. 7 to assemble the stacked unit 9 for water electrolysis.

Specifically, "Porous substrate supporting catalyst (anode)/Polymer electrolyte membrane (PEM)/Porous substrate supporting catalyst (cathode)" is used as a single unit 1 for water electrolysis, Five of these single units are stacked (stacked) with the bipolar plate 8 interposed therebetween to constitute one stacked unit 9 for water electrolysis. In Fig. 7, 2 single units are overlapped, and in Evaluation Example 2, 5 are overlapped.

〈Initial performance evaluation of stacking unit for water electrolysis〉

The pure water at a temperature of 20°C was circulated by a pump in the stacked unit 9 for water electrolysis after 5 "single units for water electrolysis obtained in the foregoing Examples and Comparative Examples" were stacked as described above, and the pure water for electrolysis Water is supplied to the anode side of the water electrolysis cell (refer to FIG. 8), and a DC power supply is used to record the value of the stacked cell voltage during water electrolysis at a predetermined current density.

The initial stack cell voltage at a current density of 100A/dm ^{2 is shown in Table 3 below.}

<Durability Evaluation of Stacked Units for Water Electrolysis>

Using the stacked unit 9 for water electrolysis obtained by stacking the porous substrate 3 (electrode 2 for water electrolysis) obtained in Example 1 with the catalyst obtained in Example 1 as in Evaluation Example 2, under the condition that the current value is constant The electrolysis of water was continuously performed, and the change in the voltage of the stacked unit was recorded.

The stack cell voltage after 500 hours has risen slightly compared to the initial stack cell voltage, but the single cell corresponds to the level in Table 2, so there is no particular problem.

Initial performance evaluation of a single cell for water electrolysis (initial cell voltage)

[Table 1]

Durability evaluation of a single cell for water electrolysis (cell voltage after 500 hours)

[Table 2]

Initial performance evaluation of stack unit 9 for water electrolysis (initial stack unit voltage)

[table 3]

From Tables 1 to 3, it can be seen that the electrode 2, the single unit 1 for water electrolysis, and the stacked unit 9 for water electrolysis using the porous substrate 3 of the present invention that hold the catalyst are used in water electrolysis. At the beginning, the cell voltage (necessary applied voltage) is a stable low value.

In addition, this value can be maintained after the endurance test.

On the other hand, the electrode 2 for water electrolysis of the comparative example, the single unit 1 for water electrolysis, and the stacked unit 9 for water electrolysis have high cell voltage (necessary applied voltage) at the start of water electrolysis, and are also high after the endurance test. .

Even if the porous substrate 3 supporting the catalyst obtained in Examples 2 and 3 is used, it is the same as in Example 1, and the cell voltage is a stable low value. That is, the initial cell voltage, the cell voltage after 500 hours, the initial stacked cell voltage, and the stacked cell voltage after 500 hours are almost the same as the results in Table 1 to Table 3 of Example 1, and the voltage is lower.

[Industrial Applicability]

The porous substrate 3 supporting the catalyst of the present invention has excellent characteristics as an electrode for water electrolysis or a gas diffusion layer, and the cell voltage of a single cell for water electrolysis using it or a stacked cell 9 for water electrolysis in which the single cell is stacked It is low, prevents the catalyst from detaching from the electrode substrate, and is excellent in manufacturability and durability, so it is widely used in all fields that require hydrogen or oxygen.

2: Electrode for water electrolysis

3: Porous matrix that holds the catalyst

3c: Metal catalyst or metal oxide catalyst

3q: Fiber forming a porous matrix

Claims (17)

A porous matrix that holds a catalyst, which has the following structure: it exists in a single unit for water electrolysis by sandwiching a polymer electrolyte membrane (PEM: Polymer Electrolyte Membrane), and contacts the polymer electrolyte membrane ( PEM) to form a cathode or anode, and also play the function of the gas diffusion layer, The catalyst is supported on the side surface of the pores of the porous matrix or the side surface of the fiber forming the porous matrix, and exists in a manner of covering from the surface of the porous matrix itself to the inside, and The ionic polymer contacts the catalyst and is filled with a concentration gradient in the thickness direction of the porous substrate from the surface of the porous substrate toward the inside. The porous substrate supporting the catalyst as described in claim 1, which is obtained by the following steps: attaching a metal catalyst or a metal catalyst precursor to the side surface or the hole of the porous substrate before firing It is a step of forming the sides of the fibers of the porous matrix before firing and firing them. The porous substrate supporting the catalyst according to claim 1, wherein the film thickness or particle size of the catalyst is smaller than the average diameter of the "voids formed by the pores and/or the gaps between the fibers" long. The porous substrate supporting a catalyst according to claim 1, wherein the catalyst is not only deposited on the surface of the porous substrate itself as a catalyst layer, but is supported in the pores of the porous substrate The side surface of or the side surface of the fiber forming the porous matrix, and it exists in a manner of covering from the surface of the porous matrix itself to the inside. The porous matrix supporting the catalyst as described in claim 1, wherein the porous matrix supporting the catalyst after excluding the ionic polymer has a porosity expressed by the following definition formula (1) of 3% by volume Above 80% by volume, Porosity (volume %)=100×[volume of void of porous substrate holding catalyst]/[volume of porous substrate holding catalyst] (1). The porous substrate for supporting a catalyst according to claim 1, wherein the ionic polymer is filled in the voids of the porous substrate for supporting the catalyst, relative to the porous substrate for supporting the catalyst The total volume of the voids of the porous matrix, and the ratio of the volume of the voids filled by the ionic polymer is 10% by volume or more and 90% by volume or less. The porous substrate supporting the catalyst as described in claim 1, wherein "the above-mentioned catalyst existing in such a way as to cover from the surface of the above-mentioned porous substrate itself to the inside" is the sum of the microscopic areas in contact with the above-mentioned ionic polymer, It is more than 2 times the macroscopic area of the surface of the porous substrate holding the catalyst that contacts the above-mentioned polymer electrolyte membrane (PEM). The porous substrate for supporting a catalyst according to claim 1, wherein the ionic polymer is obtained by applying a solution or dispersion of the ionic polymer after the catalyst is supported on the porous substrate. The drying is obtained by filling in a state with a concentration gradient from the surface of the porous substrate toward the inside. The porous substrate supporting a catalyst according to claim 1, wherein the catalyst is selected from platinum (Pt), ruthenium (Ru), iridium (Ir), palladium (Pd), tantalum (Ta), and nickel (Ni) One or more metals or metal-containing compounds in the group consisting of (Ni). The porous substrate supporting the catalyst according to claim 1, wherein the material of the porous substrate is titanium (Ti) or titanium (Ti) alloy or carbon (C). The porous matrix supporting a catalyst according to claim 1, wherein the porous matrix is titanium fiber or titanium alloy fiber or an aggregate of carbon fiber. The porous matrix supporting a catalyst according to claim 1, wherein the ionic polymer is a proton conductive polymer. An electrode for water electrolysis, which is a porous substrate supporting a catalyst according to any one of claims 1 to 12. A gas diffusion layer, which is a porous substrate supporting a catalyst according to any one of claims 1 to 12. A single unit for water electrolysis, which has a structure in which a polymer electrolyte membrane (PEM) is sandwiched by a porous matrix supporting a catalyst as described in any one of claims 1 to 12. A stacked unit for water electrolysis, which is a structure in which a polymer electrolyte membrane (PEM) is sandwiched by a porous substrate supporting a catalyst as a single unit for water electrolysis, and two or more are stacked The water electrolysis described in claim 15 is made up of a single unit. A unit module for water electrolysis, which is formed by arranging the stacked units for water electrolysis described in claim 16 in two or three dimensions.

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