JP2020136216A - Method of manufacturing catalytic ink - Google Patents

Abstract

To provide a method of manufacturing a catalytic ink capable of easily manufacturing a catalytic ink having a viscosity comparable to that of a conventional one.SOLUTION: The method for manufacturing a catalytic ink includes: a step of preparing a catalyst dispersion containing catalyst-supported particles, a highly oxygen-permeable ionomer, and a solvent; and a step of applying a shear treatment to the catalyst dispersion using a centrifugal disc-type high-speed agitator.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a method for producing a catalyst ink for a fuel cell electrode.

A solid polymer fuel cell is attracting attention as an energy source as a fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas. In a polymer electrolyte fuel cell, a membrane electrode assembly (“fuel electrode-”” generally formed by bonding electrodes (air electrode and fuel electrode) composed of a catalyst layer to both sides of a solid polymer electrolyte, which is an electrolyte membrane, respectively. A solid polymer electrolyte membrane-air electrode ") (also called MEA) is arranged.

Each electrode is formed from a catalyst layer, and the catalyst layer is a layer for causing an electrode reaction by an electrode catalyst contained in the catalyst layer. The catalyst layer generally includes a catalyst and an electrolyte because a three-phase interface in which the three phases of the electrolyte, the catalyst and the reaction gas coexist is required to allow the electrode reaction to proceed.

In the membrane electrode assembly, each electrode is formed by applying a catalyst ink to the surface of the electrolyte membrane and drying it. The catalyst ink generally contains a catalyst, a proton (H ⁺ ) conductive electrolyte, and a dispersion solvent that disperses the catalyst and the electrolyte.

For example, Patent Document 1 describes a method for producing a catalyst ink used for forming a catalyst electrode.
(A) A step of dispersing catalyst-supported particles, which are conductive particles on which a catalyst is supported, in a solvent to generate a catalyst dispersion liquid.
(B) A step of mixing an ionomer and a volatile solvent to prepare a gel body, and
(C) A manufacturing method including a step of stirring and mixing the catalyst dispersion liquid and the gel body to prepare a catalyst ink is described.

International Publication No. 2013/031060

Patent Document 1 describes that according to the above method, it is possible to provide a catalyst ink capable of improving the performance of the catalyst electrode. However, the method of Patent Document 1 requires a gelling step for gelling the ionomer, and such a step leads to an expansion of the manufacturing space and an increase in cost. Therefore, a complicated step such as a gelling step is not required, and a method for producing a catalyst ink having the same viscosity as the conventional one is required.

Therefore, an object of the present disclosure is to provide a method for producing a catalyst ink, which can easily produce a catalyst ink having the same viscosity as the conventional one.

An example of the embodiment of this embodiment is as follows.

(1) A step of preparing a catalyst dispersion containing catalyst-supporting particles, a highly oxygen-permeable ionomer, and a solvent.
The process of preparing the catalyst ink by shearing the catalyst dispersion using a centrifugal disk type high-speed stirrer.
A method for producing a catalytic ink, including.
(2) The method for producing a catalyst ink according to (1), wherein the shear rate in the shearing treatment is 1.0 × 10 ^{5 to} 5.5 × 10 ⁵ [1 / s].
(3) The method for producing a catalyst ink according to (1) or (2), wherein the obtained catalyst ink has a shear viscosity of 35 to 110 [mPa · s].
(4) The method for producing a catalyst ink according to any one of (1) to (3), wherein the clearance in the shearing treatment is 0.3 mm or less.
(5) The oxygen permeability coefficient of the high oxygen permeable ionomer measured by the high vacuum method at a temperature of 100 ° C. is 1 × 10 ^-12 [cm ³ (Normal) · cm / cm ² · s · Pa] or more. The method for producing a catalyst ink according to any one of (1) to (4), which is a polymer having an oxygen / nitrogen separation coefficient at 100 ° C. of 2.5 or more.
(6) The catalyst ink according to any one of (1) to (5), wherein a catalyst dispersion is prepared by adding a high oxygen permeable ionomer to a solution in which catalyst-supporting particles are dispersed in a solvent. Manufacturing method.
(7) The method for producing a catalyst ink according to any one of (1) to (6), which comprises a filtration treatment and / or a defoaming treatment after the shearing treatment.

The present disclosure can provide a method for producing a catalyst ink, which can easily produce a catalyst ink having the same viscosity as the conventional one.

It is a schematic diagram for demonstrating the process of the manufacturing method which concerns on this Embodiment. It is a schematic schematic diagram for demonstrating the structural example of the centrifugal disk type high-speed stirrer used in the manufacturing method which concerns on this embodiment. It is a graph which shows the result of Example 1. FIG. It is a graph which shows the result of Examples 2-5.

The method for producing the catalyst ink according to the present embodiment is a step of preparing a catalyst dispersion containing catalyst-supporting particles, a high oxygen permeable ionomer, and a solvent, and using a centrifugal disk type high-speed stirrer to prepare the catalyst dispersion. Includes a step of shearing and preparing a catalytic ink.

FIG. 1 is a schematic diagram for explaining the process of the manufacturing method according to the present embodiment. First, the catalyst-supported particles, the highly oxygen-permeable ionomer, and the solvent are mixed to prepare a catalyst dispersion. Then, the obtained catalyst dispersion is sheared using a centrifugal disk type high-speed stirrer to prepare a catalyst ink. By this shearing treatment, the shear viscosity of the catalyst dispersion can be increased. Therefore, according to the method for producing a catalyst ink according to the present embodiment, a catalyst ink having the same viscosity as the conventional one can be easily produced.

Hereinafter, the present embodiment will be described.

(1) Catalyst dispersion preparation step The production method according to the present embodiment includes a step of preparing a catalyst dispersion containing catalyst-supporting particles, a highly oxygen-permeable ionomer, and a solvent (catalyst dispersion preparation step).

The catalyst-supported particles are conductive particles on which a catalyst is supported. As the carrier (conductive particles) of the catalyst-supported particles, a carrier known in the art can be used, and the carrier is not limited, but is, for example, a carbon material such as carbon black, carbon nanotube, or carbon nanofiber. , Or a carbon compound such as silicon carbide can be used. Examples of the carbon black include acetylene black-based carbon black (Gepanzerter Manns, etc.), furnace black-based carbon black (Vulcan, etc.) and the like. As the carrier, acetylene black-based carbon black is preferable.

The catalyst supported on the carrier is the reaction at the electrode of MEA. Air electrode (cathode): O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O
Fuel electrode (anode): 2H ₂ → 4H ⁺ + 4e ⁻
The metal catalyst known in the art can be used without limitation as long as it exhibits a catalytic action. As the catalyst, for example, platinum, platinum alloy, palladium, rhodium, gold, silver, osmium, iridium and the like can be used without limitation. Examples of platinum alloys include platinum and aluminum, chromium, manganese, iron, cobalt, nickel, gallium, zirconium, molybdenum, ruthenium, rhodium, palladium, vanadium, tungsten, rhenium, osmium, iridium, titanium, and lead. An alloy with at least one of them, for example, platinum cobalt and the like can be mentioned. Platinum is preferable as the catalyst.

Preferred examples of the catalyst-supported particles include platinum-supported carbon particles, platinum / ruthenium-supported carbon particles, and nickel-supported carbon particles.

The catalyst-supported particles can be produced by a method known in the art.

The content of the catalyst is usually 1% by mass to 60% by mass, preferably 10% by mass to 50% by mass, based on the total mass of the catalyst-supporting particles.

The content of the catalyst-supported particles is usually 3% by mass to 20% by mass, preferably 5% by mass to 15% by mass, based on the total mass of the catalyst dispersion.

In this embodiment, a highly oxygen permeable ionomer is used as the polymer having ionic conductivity. The high oxygen permeable ionomer preferably has an oxygen permeability coefficient of 1 × 10 ^-12 [cm ³ (Normal) · cm / cm ² · s · Pa] or more measured under the condition of a temperature of 100 ° C. by a high vacuum method. It is a polymer having an oxygen / nitrogen separation coefficient of 2.5 or more at 100 ° C. When the oxygen permeability coefficient of the highly oxygen permeable ionomer is 1 × ^10-12 [cm ³ (Normal) · cm / cm ² · s · Pa] or more, the oxygen concentration in the reaction field becomes high and the reaction easily proceeds. Become. The upper limit of the oxygen permeability coefficient of the highly oxygen permeable ionomer is not particularly limited, but is usually less than 5 × ^10-11 [cm ³ (Normal) · cm / cm ² · s · Pa]. Further, when the oxygen / nitrogen separation coefficient of the high oxygen permeable ionomer at 100 ° C. is 2.5 or more, the oxygen concentration in the reaction field is sufficiently increased and the power generation characteristics are improved.

The oxygen permeability coefficient of the high oxygen permeability ionomer is the oxygen permeability coefficient of the cast membrane measured at a temperature of 100 ° C. based on the high vacuum method by setting a cast membrane made from a solid polymer electrolyte polymer in a gas permeability measuring device. Is.

The oxygen / nitrogen separation coefficient of the high oxygen permeable ionomer at 100 ° C is obtained by setting a cast membrane made of a solid polymer electrolyte polymer in a gas permeation measuring device and measuring the cast at a temperature of 100 ° C based on the high vacuum method. It is the ratio of the oxygen permeation coefficient and the nitrogen permeation coefficient of the membrane.

The weight average molecular weight of the high oxygen permeability ionomer is preferably ^{1 × 10 4 ~1 × 10 7} , more preferably an ^{5 × 10 4 ~5 × 10 6} , more preferably 1 × ¹⁰ 5 ~3 × 10 is a ^6.

The content of the highly oxygen permeable ionomer is usually 3% by mass to 20% by mass, preferably 5% by mass to 15% by mass, based on the total mass of the catalyst dispersion.

Examples of the solvent include water, alcohol and the like. Examples of the alcohol include aliphatic alcohols (for example, methanol, ethanol, 1-propanol, 2-propanol) and the like. As the solvent, one type may be used alone, or two or more types may be used in combination. As the solvent, a mixed solvent of water and alcohol (particularly 1-propanol) is preferable. In the mixed solvent of water and alcohol, the mixing ratio of water and alcohol (water: alcohol) is usually 40:60 to 95: 5, preferably 60:40 to 80:20 in terms of mass ratio.

The materials required for producing other inks can be determined according to a conventional method according to the viscosity and concentration of the target ink.

In the catalyst dispersion preparation step, specifically, a catalyst dispersion can be prepared by adding a high oxygen permeable ionomer to a solution in which catalyst-supporting particles are dispersed in a solvent.

Each material is well mixed and evenly dispersed. For mixing the materials, for example, a continuous twin-screw kneader, a batch kneader, a pressure homogenizer, a bead mill, an ultrasonic vibration device, or the like can be used.

(2) Shearing Step The manufacturing method according to the present embodiment includes a step (shearing step) of preparing a catalyst ink by subjecting the catalyst dispersion to a shearing treatment using a centrifugal disk type high-speed stirrer.

In the shearing process, the above-mentioned catalyst dispersion is sheared using a centrifugal disk type high-speed stirrer. By using the centrifugal disk type high-speed stirrer, a high shearing force due to the centrifugal disk, pressure collision, thin film swirling, etc. can be applied to the catalyst dispersion, and the shear viscosity of the slurry can be increased. Further, by applying a high shearing force, a high oxygen permeable ionomer can be entangled with the catalyst-supported particles.

FIG. 2 is a schematic view showing a configuration example of a centrifugal disc type high-speed stirrer. The stirring device 100 includes a container 110 and a disk 120. On the upper wall surface 111 inside the container 110, a supply port 130 for supplying the catalyst dispersion liquid to be sheared into the container 110 is arranged. Further, a discharge port 140 is arranged at the bottom of the container 110. By connecting the discharge port 140 to the supply pipe 130, it is possible to continuously process the catalyst dispersion liquid.

The disk 120 is rotated at high speed by the drive motor 160 via the rotating shaft 150. A clearance is provided between the disk 120 and the upper wall surface 111 inside the container 110, and the narrower the clearance, the greater the shearing force. Further, the higher the rotation speed of the disk, the larger the shearing force.

The centrifugal disk type high-speed stirrer gives a uniform and high shearing force by stirring a hollow swirling thin film using centrifugal force, and examples thereof include the trade name "Disparizer" (manufactured by Shinto Kogyo Co., Ltd.).

The target shear viscosity of the catalyst ink is preferably 35 mPa · s to 110 mPa · s when measured under the condition that the shear rate is 562 [1 / s]. From the viewpoint of obtaining this shear viscosity, it is preferable to set the shear rate to 1.0 × 10 ^{5 to} 5.5 × 10 ⁵ [1 / s], and 1.1 × 10 ^{5 to} 5.2 × 10 ⁵ [ It is more preferable to set it to [1 / s], and it is further preferable to set it to 1.2 × 10 ^{5 to} 5.0 × 10 ⁵ [1 / s]. If the shear rate is less than ^{1.0 × 10 5 [1 / s} ], there are cases where the viscosity does not rise to the shear viscosity of the aim. Further, if the shear rate exceeds ^{5.5 × 10 5 [1 / s} ], there are cases where the viscosity exceeding the shear viscosity of the aim obtained which causes the coating defect.

The rotation speed of the disc can be appropriately selected in consideration of the desired shear rate and clearance. Specifically, the rotation speed of the disc can be appropriately selected from, for example, 1,000 to 36,000 rpm. As a reference, when the clearance is 0.05 mm, the shear viscosity of the obtained catalyst ink is 35 mPa · s to 110 mPa · s (562 [1 / s]) by setting the rotation speed to 1,000 to 5,000 rpm. It has been confirmed that it falls within the range of. When the clearance is 0.3 mm, the shear viscosity of the obtained catalyst ink is 35 mPa · s to 110 mPa · s (562 [1 / s]) by setting the rotation speed to 8,000 to 36,000 rpm. It has been confirmed that it falls within the range.

The clearance is preferably 0.3 mm or less. If the clearance exceeds 0.3 mm, it becomes difficult to crush the agglomeration of the catalyst-supported particles, and the power generation performance may vary.

After the shearing treatment, a filtration treatment and / or a defoaming treatment may be included.

Using the catalyst ink obtained in the above steps, the catalyst layer for a fuel cell electrode can be produced by a method known in the art, for example, as follows. The catalyst ink is applied to the electrolyte film to a certain thickness by a coating method such as a doctor blade method, a spray method, a screen printing method, a gravure coating method, a die coating method, or an inkjet method, and dried.

The obtained catalyst layer for fuel cell electrodes can be used as an air electrode and / or a fuel electrode contained in the MEA of various electrochemical devices such as polymer electrolyte fuel cells.

Hereinafter, this embodiment will be described with reference to Examples. The present embodiment is not limited to the following examples.

[Example]
A highly oxygen-permeable ionomer-containing solution was added to a solution in which catalyst-supported particles (platinum-supported carbon) were dispersed in a solvent (mixed solvent of water and ethanol) and mixed to prepare a catalyst dispersion. The shear viscosity of the catalyst dispersion was 20 [mPa · s] (562 [1 / s]).

Next, using a centrifugal disk type high-speed stirrer "Disparizer" (manufactured by Shinto Kogyo Co., Ltd., model: CDMX-150TH, disk diameter: 80 mm), the above catalyst dispersion was charged under the conditions shown in Table 1 below. Shear force was applied. The shear viscosities of the obtained catalyst ink are also shown in Table 1 below.

Further, FIG. 3 shows a graph showing the shear viscosity of the catalyst dispersion (before treatment) and the shear viscosity of the catalyst ink obtained in Example 1 (after treatment). Further, FIG. 4 shows a graph in which the number of revolutions is plotted on the vertical axis and the clearance is plotted on the horizontal axis for Examples 2 to 5.

From these examples, it can be seen that the catalyst ink having the same viscosity as the conventional one (35 mPa · s to 110 mPa · s) can be easily produced by the configuration of the present embodiment. Further, from the viewpoint of obtaining a catalyst ink having a shear viscosity of 35 mPa · s to 110 mPa · s (standard range), the shear rate should be set to 1.0 × 10 ^{5 to} 5.5 × 10 ⁵ [1 / s]. Is preferable.

100 Centrifugal disk type high-speed agitator 110 Container 111 Upper wall surface 120 Disk 130 Supply port 140 Discharge port 150 Rotating shaft 160 Drive motor

Claims (1)

A step of preparing a catalyst dispersion containing catalyst-supported particles, a highly oxygen-permeable ionomer, and a solvent, and
The process of preparing the catalyst ink by shearing the catalyst dispersion using a centrifugal disk type high-speed stirrer.
A method for producing a catalytic ink, including.