JP2013103151A - Method for coating surface of porous structure with coating material, and method for producing electrode catalyst layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an electrode catalyst layer capable of efficiently coating an electrolyte resin on a surface of a conductive porous structure carrying a catalyst.SOLUTION: The method for producing an electrode catalyst layer for coating an electrolyte resin on the conductive porous structure 3 carrying a catalyst by using a supercritical fluid in a pressure vessel 1 includes: a preparation step of arranging an electrolyte resin dissolved solution dissolving the electrolyte resin and the conductive porous structure carrying a catalyst in the pressure vessel 1; a step of exposing the conductive porous structure 3 carrying a catalyst to an electrolyte resin solution 6 including the electrolyte resin and a solvent in a liquid state at less than the critical temperature and at more than the critical pressure; a step of heating the conductive porous structure to more than the critical temperature of the solvent while exposing the conductive porous structure to the electrolyte resin solution after the exposure step; and a step of depositing the electrolyte resin on the surface of the conductive porous structure by changing the state of the solvent in a supercritical state after the heating step.

Description

  The present invention relates to a method for coating the surface of a porous structure with a coating material, and a method for producing an electrode catalyst layer in which a surface of a conductive porous structure carrying a catalyst is coated with an electrolyte resin.

  A fuel cell directly converts chemical energy into electrical energy by supplying fuel and an oxidant to two electrically connected electrodes and causing the fuel to be oxidized electrochemically. Unlike thermal power generation, fuel cells are not subject to the Carnot cycle, and thus exhibit high energy conversion efficiency. A fuel cell is usually formed by laminating a plurality of single cells having a basic structure of a membrane / electrode assembly in which an electrolyte membrane is sandwiched between a pair of electrodes.

  An electrode of a fuel cell generally includes an electrode catalyst layer containing a catalyst and an electrolyte resin supported on a conductive carrier. In such a fuel cell catalyst layer, the electrode reaction proceeds at the so-called three-phase interface where the conductive carrier, the electrolyte resin, and the reactive gas are in contact, so it is important to efficiently form the three-phase interface. is there. Therefore, it is required to coat the surface of the conductive support carrying the catalyst with the electrolyte resin without unevenness.

For example, Patent Document 1 discloses that by enclosing a conductive carrier carrying a catalyst, a substrate, an electrolyte resin, and a supercritical fluid in a sealed container, and changing the temperature of the substrate, A method for producing an electrode catalyst layer is disclosed in which an electrode catalyst layer comprising a conductive carrier carrying a catalyst and the electrolyte resin is formed on the substrate. In Patent Document 1, as a specific manufacturing method, an electrolyte resin dissolved in a supercritical fluid is heated by heating a substrate in which carbon nanotubes are vertically aligned in a supercritical fluid in which an electrolyte resin is dissolved. A method of depositing around carbon nanotubes is described.
On the other hand, although not an electrolytic resin coating method, Patent Documents 2 and 3 disclose a technique using a supercritical fluid as a method for supporting a metal on the surface.

JP 2010-003531 A JP 2000-17442 A JP 2006-273613 A

  Since the conductive support carrying the catalyst usually has a fine porous structure, it has been difficult to coat the surface of the porous structure of the conductive support with a desired amount of electrolyte resin. Construction of a method for efficiently covering the surface of a conductive carrier is demanded. In particular, when a plurality of carbon nanotubes oriented substantially perpendicularly on a substrate are used as a conductive carrier, it is difficult to distribute the electrolyte resin in the fine gaps between the carbon nanotubes. It was difficult to coat with a sufficient amount of electrolyte resin.

  As in Patent Document 1, it is possible to infiltrate the electrolyte resin into the gaps between the carbon nanotubes by using a supercritical fluid in which the electrolyte resin is dissolved. However, in the method described in Patent Document 1, in the supercritical fluid, There is a problem in that the electrolyte resin concentration is low and it takes time to coat a sufficient amount of the electrolyte resin. Furthermore, the method described in Patent Document 1 also has a problem that it is necessary to use a large amount of electrolyte resin in order to coat a sufficient amount of electrolyte resin.

  The present invention has been accomplished in view of the above-mentioned actual situation, and an object of the present invention is a method capable of efficiently coating a coating material on the surface of a porous structure having a fine porous structure. In particular, it is to provide a method for producing an electrode catalyst layer capable of efficiently coating an electrolyte resin on the surface of a conductive porous structure carrying a catalyst.

The coating method of the present invention is a method of coating the surface of a porous structure with a coating material using a supercritical fluid in a pressure vessel,
A preparatory step of disposing the covering material dissolving solution in which the covering material is dissolved and the porous structure in the pressure vessel;
Exposing the porous structure to a coating solution containing the coating material and a solvent in a liquid state below the critical temperature and above the critical pressure;
After the exposing step, heating the porous structure to a temperature equal to or higher than the critical temperature of the solvent while being exposed to the coating material solution;
After the heating step, changing the state of the solvent in a supercritical state, and depositing the coating material on the surface of the porous structure,
It is characterized by having.

  In the coating method of the present invention, the porous structure is once exposed to a coating material solution containing the coating material and a solvent in a liquid state below the critical temperature and above the critical pressure, thereby bringing the solvent into a supercritical state. In the heating step, since many coating materials can be present in the vicinity of the porous structure, many coating materials can be infiltrated into the pore structure of the porous structure. As a result, in the transition step, the coating material can be efficiently deposited on the surface of the porous structure to coat the porous structure. Further, the porous structure is heated and the solvent existing in the vicinity of the porous structure is brought into a supercritical state, thereby bringing the porous structure into contact with the supercritical fluid containing the coating material at a high concentration. be able to. Furthermore, by heating only the porous structure, it is possible to reduce the energy required to bring the solvent into a supercritical state, thereby reducing the cost of the coating process.

The coating method of the present invention comprises:
In the exposure step, the pressure vessel is pressurized to a pressure higher than the critical pressure of the solvent by introducing the solvent in a gaseous state under a temperature condition lower than the critical temperature of the solvent, and the solvent is transferred to a liquid state, Raising the liquid level of the coating material solution containing the coating material and the liquid solvent, exposing the porous structure to the coating material solution,
In the preparation step, the position of the porous structure is such that the liquid level of the coating material solution in the exposure step rises from the lower end portion of the porous structure to the upper end portion of the porous structure. Preferably it is a position.
This is because the amount of coating material used can be reduced while securing the coating amount of the coating material.

  In the coating method of the present invention, it is preferable that the ambient temperature in the pressure vessel is lower than the critical temperature of the solvent in the heating step. This is because the coating material can be coated more effectively and efficiently.

  In the coating method of the present invention, in the precipitation step, the solvent is preferably transferred from the supercritical state to the gas state without passing through the liquid state. This is because it is possible to suppress the aggregation of the coating material and the change in the porous structure of the porous structure in the precipitation step.

The method for producing an electrode catalyst layer of the present invention is a method for producing an electrode catalyst layer in which a surface of a conductive porous structure carrying a catalyst is coated with an electrolyte resin using a supercritical fluid in a pressure vessel. ,
A preparatory step of disposing an electrolyte resin solution in which the electrolyte resin is dissolved and a conductive porous structure carrying the catalyst in the pressure vessel;
Exposing the conductive porous structure carrying the catalyst to an electrolyte resin solution containing the electrolyte resin and a solvent in a liquid state below a critical temperature and above a critical pressure;
After the exposing step, heating the conductive porous structure to a temperature equal to or higher than the critical temperature of the solvent while being exposed to the electrolyte resin solution;
After the heating step, the state of the solvent in a supercritical state is changed, and the electrolyte resin is deposited on the surface of the conductive porous structure.
It is characterized by having.

  In the method for producing an electrode catalyst layer according to the present invention, as in the coating method according to the present invention, the conductive porous structure once contains an electrolyte resin and a solvent in a liquid state below the critical temperature and above the critical pressure. In the heating step of bringing the solvent into a supercritical state by exposing it to a large amount of electrolyte resin in the vicinity of the conductive porous structure, the pore structure of the conductive porous structure Many electrolyte resins can penetrate into the inside. As a result, in the transition step, the electrolyte resin can be efficiently deposited on the surface of the conductive porous structure, and the conductive porous structure can be covered with the electrolyte resin. In addition, the conductive porous structure is heated and the solvent existing in the vicinity of the conductive porous structure is brought into a supercritical state, so that the conductive porous structure is superconducted containing the electrolyte resin at a high concentration. It can be contacted with a critical fluid. Furthermore, by heating only the conductive porous structure, it is possible to reduce the energy required to bring the solvent into a supercritical state, thereby reducing the production cost of the electrode catalyst layer.

The method for producing the electrode catalyst layer of the present invention comprises:
In the exposure step, the pressure vessel is pressurized to a pressure higher than the critical pressure of the solvent by introducing the solvent in a gaseous state under a temperature condition lower than the critical temperature of the solvent, and the solvent is transferred to a liquid state, By raising the liquid level of the electrolyte solution containing an electrolyte resin and the solvent in a liquid state, the conductive porous structure is exposed to the electrolyte resin solution,
In the preparation step, the conductive porous structure is disposed at a position where the liquid level of the electrolyte resin solution in the exposure step is lower than the lower end of the conductive porous structure. It is preferable that the position be higher than the upper end. This is because the amount of electrolyte resin used can be reduced while securing the amount of electrolyte resin coating on the surface of the conductive porous structure.

  In the method for producing an electrode catalyst layer of the present invention, in the heating step, it is preferable that the ambient temperature in the pressure vessel is lower than the critical temperature of the solvent. This is because the surface of the conductive porous structure can be coated with the electrolyte resin more effectively and efficiently.

  In the method for producing an electrode catalyst layer of the present invention, in the precipitation step, the solvent is preferably transferred from a supercritical state to a gas state without passing through a liquid state. This is because the aggregation of the electrolyte resin and the change in the porous structure of the conductive porous structure can be suppressed in the precipitation step.

  In the method for producing an electrode catalyst layer of the present invention, when the conductive porous structure is supported on a substrate, in the heating step, the substrate is heated to a temperature higher than the critical temperature of the solvent. The conductive porous structure can be heated above the critical temperature of the solvent.

  In the method for producing an electrode catalyst layer of the present invention, the conductive porous structure preferably includes carbon nanotubes that are substantially vertically aligned on the substrate. This is because the substantially vertically aligned carbon nanotubes can form an electrode catalyst layer excellent in gas diffusibility and electron conductivity.

  In the method for producing an electrode catalyst layer of the present invention, examples of the electrode catalyst layer include a fuel cell electrode catalyst layer.

  According to the coating method and the electrode catalyst layer manufacturing method of the present invention, the surface of the porous structure or conductive porous structure, which is the object to be treated, can be efficiently coated with the coating material or the electrolyte resin. . Therefore, according to the present invention, it is possible to reduce the amount of the coating material or the electrolyte resin used and to shorten the coating processing time while securing the coating amount of the coating material or the electrolyte resin.

It is a cross-sectional schematic diagram which shows the mode in the pressure vessel in the exposure process of the coating method and manufacturing method of this invention. It is a cross-sectional schematic diagram explaining the arrangement | positioning position of the electroconductive porous structure (CNT board | substrate) in the pressure vessel used by the Example and the comparative example. It is a figure which shows the relationship between the pressure in the pressure vessel shown in FIG. 2, and the liquid level of an electrolyte resin solution. And state change CHF _3, is a diagram showing a typical example of temperature changes and pressure changes (Example 1) of the coating method and the atmosphere in the production process environment and the conductive porous structure environment of the present invention. And state change CHF _3, is a diagram showing a temperature change and a pressure change in the atmospheric environment and the conductive porous structure environment in Comparative Example 1. And state change CHF _3, is a diagram showing a temperature change and a pressure change in the atmospheric environment and the conductive porous structure environment in Comparative Example 2. And state change CHF _3, is a diagram showing a temperature change and a pressure change in the atmospheric environment and the conductive porous structure environment in Comparative Example 3. It is a figure which shows the relationship between the amount of electrolyte resin solution solutions of an Example and a comparative example, and the amount of electrolyte resin. It is a figure which shows the relationship between the supercritical fluid processing time of an Example and a comparative example, and the fabric weight of electrolyte resin. It is a figure which shows the fabric weight of the electrolyte resin of Example 4, the comparative example 1, and the comparative example 6. FIG.

The coating method of the present invention is a method of coating the surface of a porous structure with a coating material using a supercritical fluid in a pressure vessel,
A preparatory step of disposing the covering material dissolving solution in which the covering material is dissolved and the porous structure in the pressure vessel;
Exposing the porous structure to a coating solution containing the coating material and a solvent in a liquid state below the critical temperature and above the critical pressure;
After the exposing step, heating the porous structure to a temperature equal to or higher than the critical temperature of the solvent while being exposed to the coating material solution;
After the heating step, changing the state of the solvent in a supercritical state, and depositing the coating material on the surface of the porous structure,
It is characterized by having.

The method for producing an electrode catalyst layer according to the present invention is a method for producing an electrode catalyst layer, in which a surface of a conductive porous structure carrying a catalyst is coated with an electrolyte resin using a supercritical fluid in a pressure vessel. There,
A preparatory step of disposing an electrolyte resin solution in which the electrolyte resin is dissolved and a conductive porous structure carrying the catalyst in the pressure vessel;
Exposing the conductive porous structure carrying the catalyst to an electrolyte resin solution containing the electrolyte resin and a solvent in a liquid state below a critical temperature and above a critical pressure;
After the exposing step, heating the conductive porous structure to a temperature equal to or higher than the critical temperature of the solvent while being exposed to the electrolyte resin solution;
After the heating step, the state of the solvent in a supercritical state is changed, and the electrolyte resin is deposited on the surface of the conductive porous structure.
It is characterized by having.

The present inventor has studied to coat the surface of carbon nanotubes (CNTs) substantially vertically aligned on the substrate with an electrolyte resin. In the method described in Patent Document 1, the electrolyte resin is efficiently converted into carbon nanotubes. The knowledge that it cannot be made to coat on the surface of was obtained.
Specifically, in Patent Document 1, CHF ₃ gas is introduced into a pressure vessel containing a substrate (CNT substrate) in which a plurality of CNTs are substantially vertically aligned (CNT substrate) and an electrolyte resin solution to increase the pressure, and CHF ₃ After changing the gas state from the gas state to the supercritical state, the CNT substrate is cooled, and the CHF ₃ in the vicinity of the CNT substrate is changed to the gas state through the liquid state, thereby depositing the electrolyte resin. Further, in Patent Document 1, CHF ₃ gas is introduced into a pressure vessel containing a CNT substrate and an electrolyte resin solution to increase the pressure, and CHF ₃ is changed from a gas state to a supercritical state. The electrolyte resin is deposited by heating and reducing the solubility of the CHF ₃ electrolyte resin in the vicinity of the CNT substrate.
As described above, when CHF ₃ is changed from a gas state to a supercritical state as described in Patent Document 1, since the electrolyte resin is dispersed throughout the pressure vessel, the electrolyte resin concentration in the supercritical fluid is low, The electrolyte resin concentration is lowered. Therefore, it takes time to coat the CNT with a sufficient amount of electrolyte resin (see Comparative Example 1 and Comparative Example 5 and FIG. 9). Moreover, in order to ensure the electrolyte resin concentration in the supercritical fluid existing in the vicinity of the CNT substrate and to coat the CNT with a sufficient amount of electrolyte resin, it is necessary to use a large amount of electrolyte resin (Comparative Example 1 and Comparative Example 1). Example 4, see FIG. 8).

As a result of intensive studies, the inventor first changed a solvent to be in a supercritical state such as CHF ₃ (hereinafter sometimes referred to as a supercritical solvent) into a liquid state, and then the supercritical solvent in the liquid state. And the electrolyte resin solution containing the electrolyte resin, the CNT substrate is exposed, and then the CNT substrate is heated to bring the supercritical solvent near the CNT substrate into a supercritical state, thereby containing the electrolyte resin at a high concentration. It has been found that it is possible to treat a CNT substrate with a supercritical fluid, which can improve the coating amount of the electrolyte resin, reduce the amount of electrolyte resin used, and shorten the treatment time.

This will be specifically described with reference to FIG. FIG. 4 shows the change in the state of CHF ₃ , and the temperature change and pressure change in the environment of the CNT substrate (conductive porous structure) of Example 1 using CHF ₃ as a supercritical solvent ( It is a figure which shows the temperature change and pressure change (solid line arrow) of atmospheric environment.
CHF ₃ has a critical temperature of 25.65 ° C. and a critical pressure of 4.87 MPa, and, as shown in FIG. 4, becomes a supercritical state under conditions of a critical point (25.65 ° C., 4.87 MPa) or higher. . A supercritical fluid has both a gas property (diffusibility) and a solution property (solubility).

Here, the CNT substrate environment is an environment where the CNT substrate is exposed, the temperature of the CNT substrate environment means the temperature of the CNT substrate, and the pressure of the CNT substrate environment means the pressure of the environment where the CNT substrate is exposed. . The environmental temperature of the CNT substrate can be controlled directly or indirectly by a heater or the like that adjusts the temperature of the CNT. In this specification, the porous structure environment and the conductive porous structure environment are also environments to which the respective structures are exposed, and the temperature of each structure environment means the temperature of each structure, The pressure of each structure environment means the pressure of the environment to which each structure is exposed.
In this specification, the temperature and pressure of the atmospheric environment mean the temperature and pressure of the electrolyte resin solution when the supercritical solvent is in a liquid state and a supercritical state in the pressure vessel. When the solvent is in the gaseous state, it means the temperature and pressure of the supercritical solvent in the gaseous state containing the electrolyte resin. The method for controlling the temperature of the atmospheric environment is not particularly limited, and can be controlled by, for example, a temperature controller that can heat and cool the wall of the pressure vessel. The pressure of the atmospheric environment can typically be controlled by the amount of supercritical solvent introduced into the pressure vessel. The pressure of the CNT substrate, the porous structure, and the conductive porous structure can also typically be controlled by the amount of the supercritical solvent in the pressure vessel, and is usually approximately the same as the pressure in the ambient environment.

With the electrolyte resin (electrolyte resin solution) and the CNT substrate placed in the pressure vessel, as shown in FIG. 4, first, the CNT substrate environment and the atmosphere environment are maintained under CHF ₃ below the critical temperature of CHF _{3. 3} or higher so that CHF ₃ in the pressure vessel is in a liquid state ((1) in FIG. 4). At this time, the CNTs are immersed in the electrolyte resin solution in which the electrolyte resin is dispersed and dissolved in the CHF ₃ in a liquid state. Next, with the CNT immersed in the electrolyte resin solution, the temperature of the CNT substrate environment is raised to a temperature higher than or equal to the critical temperature of the CHF ₃ to bring the CHF ₃ near the CNT substrate into a supercritical state (in FIG. 2)). Due to the solubility and diffusibility of the supercritical fluid, the concentration of the electrolyte resin can be locally increased in the vicinity of the CNT substrate, and the electrolyte resin can permeate between the plurality of CNTs on the CNT substrate. Subsequently, by making the pressure of the CNT substrate environment equal to or lower than the critical pressure of CHF ₃ ((3) in FIG. 4), the dissolved electrolyte resin can be deposited and coated on the CNT surface.

  The present inventor has not only applied the method for coating an electrolyte resin to the CNT surface as described above, but also a method for producing an electrode catalyst layer using a CNT substrate, as well as an electrode catalyst layer containing a conductive porous material other than the CNT substrate. It has been found that the present invention can be applied to a production method and a method of coating a porous structure having a fine pore structure such as a CNT substrate with a coating material. In a substrate in which a plurality of CNTs are oriented substantially vertically, a sufficient amount of electrolyte resin can be coated even in the minute gaps between the CNTs. Therefore, as with the CNT substrate, the porous structure having a fine pore structure is used. This is because it has been found that the surface can be efficiently coated with a coating material.

Hereinafter, the coating method and the production method of the electrode catalyst layer of the present invention will be described.
The coating method of the present invention is a method of coating the surface of a porous structure with a coating material using a supercritical fluid in a pressure vessel. The method for producing an electrode catalyst layer of the present invention is a coating method of the present invention. In this method, a conductive porous structure carrying a catalyst is used as the porous structure, and an electrolyte resin is used as the coating material, and the surface of the conductive porous structure is coated with the electrolyte resin. Here, the coating method of the present invention will be described as appropriate while mainly explaining the method for producing the electrode catalyst layer.
In the present specification, the supercritical fluid refers not only to the supercritical fluid itself but also to a supercritical fluid containing an electrolyte resin and other components (for example, a solvent of an electrolyte resin solution). Moreover, in this specification, the covering includes a form covering a part of the surface of the coating target and a form covering the entire surface of the coating target.

[Preparation process]
The preparation step is a step of placing an electrolyte resin solution (coating material solution) in which an electrolyte resin (coating material) is dissolved and a conductive porous structure (porous structure) in a pressure vessel.

The electrolyte resin is not particularly limited as long as it has desired ionic conductivity and can be dissolved in a supercritical fluid. For example, examples of the electrolyte resin having proton conductivity include a fluorine-based polymer electrolyte and a hydrocarbon-based electrolyte. Examples include polymer electrolytes.
Here, the fluoropolymer electrolyte is a perfluorocarbon sulfonic acid resin represented by Nafion (trade name, manufactured by DuPont), Aciplex (trade name, manufactured by Asahi Kasei), Flemion (trade name, manufactured by Asahi Glass), Protonic acids such as sulfonic acid groups, sulfonimide groups, carboxylic acid groups, phosphoric acid groups, phosphonic acid groups, and phenolic hydroxyl groups on copolymers of fluorocarbon vinyl monomers and hydrocarbon vinyl monomers and polymers of difluorovinyl monomers Fluorine-containing polymer electrolytes such as partially fluorinated polymer electrolytes such as those having a group (proton conductive group) introduced.
The hydrocarbon-based polymer electrolyte is a polymer electrolyte that does not contain fluorine. Specifically, polyether ether ketone, polyether ketone, polyether sulfone, polyphenylene sulfide, polyphenylene ether, polyparaphenylene, etc. General purpose plastics such as engineering plastics, polyethylene terephthalate, polyethylene, polypropylene, polystyrene, and proton acid groups (proton conductive groups such as sulfonic acid groups, sulfonimide groups, carboxylic acid groups, phosphoric acid groups, phosphonic acid groups, phenolic hydroxyl groups) ) Or a copolymer thereof.

  The coating material is not particularly limited as long as it can be dissolved in the supercritical fluid, and examples thereof include the above electrolyte resin.

  The electrolyte resin (coating material) can be easily dissolved in the supercritical solvent by introducing the electrolyte resin (coating material) into the pressure vessel as an electrolyte resin dissolving solution (coating material dissolving solution) dissolved in a solvent. The electrolyte resin solution contains an electrolyte resin solution and a supercritical solvent in a liquid state. The solvent in the electrolyte resin solution is not particularly limited as long as the electrolyte resin can be dissolved, and can be appropriately selected. For example, organic solvents, such as alcohol, such as ethanol, are mentioned.

The conductive porous structure is not particularly limited in material and shape as long as it has conductivity and a porous structure.
In the present specification, the porous structure means one having a fine pore structure on the surface. For example, a structure in which a plurality of constituent fibers are regularly arranged (for example, a mesh structure), and a plurality of constituent fibers are random. Non-woven fabric structure arranged in a three-dimensional structure, a three-dimensional network structure having independent holes and connecting holes, a structure in which a plurality of constituent particles are connected, and the like. In addition, CNTs oriented substantially vertically on the substrate are also included in the porous structure.
Here, the CNT oriented substantially perpendicularly on the substrate means that the angle formed by the surface direction of the substrate and the tube length direction of the CNT is in a range of 90 ° ± 30 °. If it is in the range of 90 ° ± 30 °, the same effect as in the case of being oriented vertically (90 °) can be obtained. There are two types of CNT, straight and non-linear. In the case of non-linear CNT, the direction of the straight line connecting the centers of both end faces in the tube length direction is the tube length direction. To do.

  As a constituent material of the conductive porous structure, for example, carbon nanotube (CNT), carbon nanofiber, carbon black, glassy carbon, acetylene black, carbon felt, carbon cloth, carbon nanohorn (CNH), carbon nanowall (CNW) ) And the like, and metals such as titanium, silicon, tin, copper, titania, silica, tin oxide, and metal oxides. These constituent materials may be used alone or in combination of two or more.

  Among them, CNT is preferable as a constituent material of the electrode for the fuel cell from the viewpoint of the diffusibility of the reaction gas in the electrode of the fuel cell, the electronic conductivity, the specific surface area, and the like, and in particular, CNT oriented substantially vertically on the substrate is preferable. . In addition, conductive porous structures containing CNTs, in particular, CNTs oriented substantially perpendicularly on the substrate, are difficult to cover the surface of the CNTs with a sufficient amount of electrolyte resin, and thus the effects obtained by the present invention are particularly high. It can be said.

A catalyst is supported on the conductive porous structure. The catalyst is not particularly limited as long as it can accelerate the electrode reaction. For example, the catalyst for the fuel cell electrode is platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt. And metals such as nickel, manganese, vanadium, molybdenum, gallium, and aluminum, and alloys of these metals.
The method for supporting the catalyst on the conductive porous structure is not particularly limited, and a wet method or a dry method can be employed. For example, a catalytic metal salt solution (for example, a platinum salt solution) is applied to the surface of the conductive porous structure, dried, calcined and reduced, and the conductive porous structure is exposed to a supercritical fluid of the metal catalyst salt. And a method of firing and reducing the metal catalyst salt after precipitation.

  As the porous structure to be covered with the covering material, the specific shape and constituent materials are not particularly limited as long as the porous structure has the above-described porous structure. As a constituent material, the constituent material of the said electroconductive porous structure etc. can be mentioned, for example.

  In the preparation step, the arrangement of the conductive porous structure and the electrolyte resin solution in the pressure vessel is not particularly limited. A preferable arrangement position of the conductive porous structure will be described in [Exposure Step] described later, from the relationship with the liquid level of the electrolyte resin solution in the exposure step.

[Exposure process]
In the exposure process, a conductive porous structure (porous) carrying a catalyst in an electrolyte resin solution (coating material) and an electrolyte resin solution (coating material solution) containing a supercritical solvent in a liquid state below the critical temperature and above the critical pressure. Is the step of exposing the structure).

The electrolyte resin solution contains at least the electrolyte resin and a supercritical solvent in a liquid state that is less than the critical temperature and higher than the critical pressure.
In the subsequent heating step, the supercritical solvent is one that is heated to a critical temperature or higher while maintaining a critical pressure or higher, and is referred to as a supercritical solvent in this specification. is there. The supercritical solvent refers to a solvent used in a supercritical state in the heating step, and includes a solvent in a gas state or a liquid state.

Examples of the supercritical solvent include trifluoromethane (CHF ₃ ), CO ₂ , tetrafluoroethylene (CF ₂ ═CF ₂ ), 1,1,2,2-tetrafluoroethane (CHF ₂ CHF ₂ ), pentafluoro Examples include ethane (CF ₃ CHF ₂ ), water, ethanol, methanol, and the like. These solvents may be used alone or in combination of two or more.

As the supercritical solvent, trifluoromethane (CHF ₃ ) and CO ₂ are particularly preferable. Since CHF ₃ is excellent in solubility of the electrolyte resin, there is an advantage that it is easy to ensure the coating amount of the electrolyte resin on the conductive porous structure. On the other hand, CO ₂ has the advantages of a low global warming potential and low cost. Furthermore, since CO ₂ can be used as a supercritical fluid when CO ₂ is used as a supercritical fluid in the catalyst loading process on the conductive porous structure, the production cost of the electrode catalyst layer can be further reduced. There is also a merit. Since CO ₂ has a lower solubility of the electrolyte resin than CHF ₃ , the coating amount of the electrolyte resin with respect to the conductive porous structure is very large in the conventional coating method of the electrolyte resin using the supercritical fluid. Although there were few, according to this invention, a fabric weight can be improved significantly (refer Example 4, Comparative Examples 1 and 6, FIG. 10).

  In the exposure step, the supercritical solvent is in a liquid state below the critical temperature and above the critical pressure. The method for bringing the supercritical solvent into such a liquid state is not particularly limited. For example, while maintaining the temperature below the critical temperature in the pressure vessel, the supercritical solvent in a gaseous state is introduced and the pressure in the pressure vessel is increased, so that the supercritical solvent is transferred to the liquid state and the critical state is changed. It can be over pressure. At this time, the liquid level of the electrolyte resin solution rises due to the state change of the supercritical solvent to the liquid state.

  In the exposure step, the amount of the supercritical solvent and the position of the conductive porous structure in the pressure vessel are not particularly limited as long as the electrolyte resin solution can be brought into contact with the conductive porous structure and exposed. . However, since the conductive porous body can be treated with a supercritical fluid containing a higher concentration electrolyte resin in the heating step, the position of the conductive porous structure in the preparation step and the electrolyte resin solution in the exposure step It is preferable to control the liquid level height.

Hereinafter, the arrangement position of the conductive porous structure in the preparation process and the liquid level of the electrolyte resin in the exposure process will be described with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing the inside of the pressure vessel in the exposure process. In FIG. 1, an electrolyte resin solution 2 in which an electrolyte resin is dissolved and a CNT substrate 3 are disposed in a pressure vessel 1. A heater 4 capable of heating the CNT substrate is attached to the CNT substrate. The pressure vessel 1 is provided with a temperature adjuster 5 around the pressure vessel 1 so that the ambient temperature in the pressure vessel can be adjusted. Further, the pressure vessel 1 discharges the supply valve 7 for supplying the supercritical solvent into the pressure vessel, and the supercritical solvent in a gas state in the pressure vessel to the outside of the pressure vessel and can be opened to the atmosphere. A valve 8 is provided.

As described above, in the exposure step, the pressure vessel 1 is pressurized above the critical pressure of the supercritical solvent by introducing the supercritical solvent in a gaseous state under a temperature condition lower than the critical temperature of the supercritical solvent. The conductive porous structure 3 can be immersed (exposed) in the electrolyte resin solution 6 by shifting the supercritical solvent to a liquid state and raising the liquid level of the electrolyte resin solution 6.
At this time, it is preferable to arrange the conductive porous structure in the preparation step as follows. That is, as shown in FIG. 1, in the pressure vessel 1, the conductive porous structure 3 is made of the electrolyte solution 6 positioned below the lower end portion 3 b of the conductive porous structure 3 by pressurization in the exposure process. It is preferable that the liquid surface is disposed so as to rise above the upper end portion 3 a of the conductive porous structure 3.

Thus, the electrolyte resin concentration of the electrolyte resin solution to which the conductive porous structure is exposed can be increased by adjusting the position of the conductive porous structure and the position of the liquid surface of the electrolyte resin solution 6. it can. As a result, the electrolyte resin can be deposited more efficiently on the conductive porous structure, and used for the production of the electrode catalyst layer while ensuring the amount of the electrolyte resin that covers the surface of the conductive porous structure. The amount of electrolyte resin to be reduced can be reduced, and furthermore, the time required for the coating process can be shortened.
Here, the lower end portion and the upper end portion of the conductive porous structure mean the lower end portion in the gravitational direction and the upper end portion in the gravitational direction of the conductive porous structure disposed in the pressure vessel, and the rising electrolyte resin solution The lower end is the first contact with the liquid surface, and the upper end is the last contact.

  If the liquid level of the electrolyte resin solution is equal to or higher than the upper end of the conductive porous structure, the entire conductive porous body can be brought into contact with the electrolyte resin solution and exposed. Since the electrolyte resin concentration of the electrolyte resin solution can be increased with a small amount of electrolyte resin used, it is preferable that the level of the liquid surface of the electrolyte resin solution is minimized. In the case where the electrolyte resin is coated only on a desired region of the conductive porous structure, it is not necessary to bring the entire conductive porous structure into contact with the electrolyte resin solution.

  The liquid level of the electrolyte resin solution can be adjusted, for example, by the pressure in the pressure vessel, the amount of the supercritical solvent, etc. By adjusting the amount of the solvent, the pressure in the pressure vessel can be adjusted, and the liquid level can be controlled. By examining the relationship between the pressure in the pressure vessel and the level of the electrolyte resin solution by introducing a supercritical solvent in the gaseous state in advance, the level of the electrolyte resin solution in the exposure process can be easily And it can control appropriately (refer FIG. 3).

The ambient environment temperature and the conductive porous environment temperature in the exposure step are not particularly limited as long as they are both lower than the critical temperature of the supercritical solvent. For example, the critical temperature of the supercritical solvent is preferably −5 ° C. or lower.
In the exposure step, the time for maintaining the pressurized state and exposing the conductive porous structure to the electrolyte resin solution is not particularly limited, and it depends on the electrolyte resin concentration of the electrolyte resin solution, the structure of the porous structure, etc. What is necessary is just to set suitably according to. For example, it can be about 5 to 60 minutes.

[Heating process]
In the heating step, after the exposure step, the supercritical pressure of the supercritical solvent is maintained, and the conductive porous structure (porous structure) is exposed to the electrolyte resin solution (coating material solution) while the solvent is exposed. It is the process of heating above the critical temperature.
In the heating process, the supercritical solvent in the vicinity of the conductive porous structure can be transferred from the liquid state to the supercritical state, and the supercritical fluid in which the electrolyte resin is dissolved is transferred into the porous structure of the conductive porous structure. Can diffuse.

  The method for heating the conductive porous structure is not particularly limited. For example, a heater capable of heating the conductive porous structure is attached to the conductive porous structure, and the conductive porous structure is directly applied by the heater. Can be heated. When the conductive porous structure is supported on the substrate, the conductive porous structure can be heated indirectly or higher than the critical temperature of the supercritical solvent by heating the substrate. Good. In the case of heating the substrate, for example, a heater that can heat the substrate may be attached to the substrate.

  By heating only the conductive porous structure locally in the heating step, only the supercritical solvent existing in the vicinity of the conductive porous structure can be brought into a supercritical state. As a result, since the electrolyte resin concentration can be locally increased in the vicinity of the conductive porous structure in the pressure vessel, it is possible to reduce the amount used and the processing time while securing the amount of electrolyte resin coating. Is possible. In addition, the energy required for heating can be reduced as compared with the case where the entire supercritical solvent in the pressure vessel is brought into a supercritical state.

  The heating temperature of the conductive porous structure is not particularly limited as long as it is equal to or higher than the critical temperature of the supercritical solvent. For example, the temperature is preferably in the range of the critical temperature to the critical temperature + 100 ° C., particularly the critical temperature +10 The range of from ° C to critical temperature + 60 ° C is preferred.

In order to form a supercritical state locally in the vicinity of the conductive porous structure, it is preferable that the atmospheric environment temperature in the pressure vessel is lower than the critical temperature of the supercritical solvent in the heating step. The specific atmospheric environment temperature in the heating step is preferably, for example, in the range of less than the critical temperature of the supercritical solvent to the critical temperature of −30 ° C., and particularly, the critical temperature of the supercritical solvent of −5 ° C. to the critical temperature of −10 ° C. The range of is preferable.
The method for controlling the ambient temperature in the heating step is not particularly limited, and examples thereof include a method using a temperature controller as described above.

  In the heating step, the heating time of the conductive porous structure is not particularly limited, and may be set as appropriate according to the electrolyte resin concentration of the electrolyte resin solution, the structure of the porous structure, and the like. For example, it is preferably 1 to 60 minutes, and a sufficient amount of coating can be secured even for 1 to 10 minutes.

[Precipitation process]
The deposition step is a step of changing the state of the supercritical solvent in the supercritical state after the heating step to deposit the electrolyte resin (coating material) on the surface of the conductive porous structure (porous structure).
In the deposition step, the electrolyte resin (coating material) dissolved in the supercritical fluid is in the vicinity of the conductive porous structure (porous structure), and the electrolyte resin (coating material) accompanying the change in the state of the supercritical solvent. And the surface of the conductive porous structure (porous structure) is covered with the electrolyte resin (coating material).

The state change of the supercritical solvent in the precipitation process may be a transition from the supercritical state to the liquid state, a transition from the supercritical state to the gas state, or a liquid state from the supercritical state to the liquid state. However, it is preferable to shift directly from the supercritical state to the gas state without passing through the liquid state. When passing through the liquid state, the surface tension causes aggregation of the electrolyte resin and aggregation of the material constituting the conductive porous structure such as CNT, so that uniform coating of the electrolyte resin or conductive porous structure This is because it may be difficult to maintain the porous structure.
As a method for transferring the supercritical solvent in the supercritical state near the conductive porous structure from the supercritical state to the gas state without passing through the liquid state, for example, the temperature of the conductive porous structure is set to the critical temperature. There is a method of reducing the pressure of the conductive porous structure environment to a critical pressure or less while maintaining the above.
Specifically, in FIG. 1, there is a method in which the inside of the pressure vessel is opened to the atmosphere by opening the opening 8 of the pressure vessel 1 while the CNT substrate is heated to a supercritical temperature or higher by the heater 4. As a result, as shown in FIG. 4 (3), the conductive porous structure environment can be made higher than the critical temperature and lower than the critical pressure of the supercritical solvent. The gas state can be directly transferred. When the pressure vessel is opened to the atmosphere, the pressure of the atmospheric environment is reduced from the critical pressure to less than the critical pressure, and the supercritical solvent in the liquid state also shifts to the gas state (see FIG. 4 (4)).

  In the precipitation step, the specific conditions for changing the state of the supercritical solvent are not particularly limited. For example, while maintaining the conductive porous structure at a critical temperature or higher as described above, the pressure vessel is evacuated to the atmosphere. In the case of opening, it is preferable to prevent the temperature of the conductive porous structure from decreasing due to exhaust, for example, by adjusting the temperature of a heater capable of heating the conductive porous structure.

  The electrode catalyst layer provided by the method for producing an electrode catalyst layer according to the present invention is superior to conventional electrode catalyst layers because the surface of the conductive porous structure is coated with many electrolyte resins, so that excellent ion Conductivity can be developed. The application of the electrode catalyst layer provided by the present invention is not particularly limited and can be used in a wide variety of fields and fields, but is particularly suitable as a fuel cell electrode catalyst layer.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples.

Example 1
First, a Si substrate (hereinafter referred to as a CNT substrate) in which carbon nanotubes carrying platinum on the surface are substantially vertically aligned was prepared and accommodated in a pressure vessel having a height of 260 mm from the bottom surface and a volume of 500 cm ³ . A heater for heating the CNT substrate was attached to the CNT substrate. The pressure vessel was equipped with a temperature controller for controlling the ambient temperature in the pressure vessel.
In addition, the arrangement | positioning of the CNT board | substrate in a pressure vessel was arrange | positioned so that the position of the upper end part of the CNT board | substrate 3 might become 70 mm from the bottom face of the pressure vessel 1, as shown in FIG. This position is a position that is equal to or lower than the liquid surface (80 cm) of the electrolyte resin solution 6 when pressurized with CHF ₃ gas, which will be described later, and was calculated from the pressure, the ambient environment temperature, and the volume of the pressure vessel. The calculation results are shown in FIG.

  In the pressure vessel, 5 ml of an electrolyte resin solution (solution in which the electrolyte resin was diluted to 3 wt% with ethanol) was charged. The lower end portion of the CNT substrate disposed at a position where the upper end portion is 70 mm from the bottom surface of the pressure vessel 1 was not in contact with the electrolyte resin solution.

Subsequently, as shown in FIG. 4, while maintaining the atmospheric environment temperature and the CNT substrate temperature in the pressure vessel at 20 ° C., CHF ₃ gas was introduced to pressurize the pressure vessel to liquefy CHF ₃ (FIG. 4). 4 (1)). Pressurization with CHF ₃ gas is performed so that the pressure in the pressure vessel is 9 MPa so that the liquid level of the electrolyte resin solution, which is a mixed solution of the electrolyte resin solution and liquefied CHF ₃ , is positioned 80 mm from the bottom of the pressure vessel. I went until. While maintaining the atmospheric environment temperature in the pressure vessel and the CNT substrate temperature at 20 ° C., the pressurized state was maintained for 30 minutes, and the CNT substrate was immersed in the electrolyte resin solution to be exposed.
In addition, even if the pressure in the pressure vessel is 10 MPa as shown in FIG. 3, the entire surface of the CNT substrate can be placed below the surface of the electrolyte resin solution, but the volume of the electrolyte resin solution is smaller, and the electrolyte resin Since the electrolyte resin concentration in the solution can be increased, the pressure was set to 9 MPa.

Subsequently, while maintaining the atmospheric temperature in the pressure vessel at 20 ° C., the CNT substrate was heated to 60 ° C. with a heater, and the liquefied CHF ₃ in the vicinity of the CNT substrate was brought into a supercritical state ((2 in FIG. 4). )). The state where the atmospheric environment temperature in the pressure vessel was 20 ° C. and the CNT substrate temperature was 60 ° C. was maintained for 30 minutes.

Thereafter, while maintaining the atmospheric temperature in the pressure vessel at 20 ° C. and the CNT substrate temperature at 60 ° C., the pressure vessel was opened to the atmosphere to return the pressure vessel pressure to atmospheric pressure ((3) and FIG. 4). (4)). As a result, the supercritical CHF ₃ in the vicinity of the substrate was changed to a gas state without passing through the liquid state, and the electrolyte resin dissolved in the supercritical CHF ₃ was deposited on the CNT surface. At this time, CHF _{3 in} a liquid state of the atmospheric environment was also in a gas state.

When the basis weight of the electrolyte resin per unit area of the CNT substrate was calculated based on the following formula, it was 0.78 mg / cm ² . The results are shown in Table 1. In the following formula, the weight of the CNT substrate before deposition is the weight of the CNT substrate before being installed in the pressure vessel.

(Comparative Example 1)
First, in the same manner as in Example 1, the CNT substrate was accommodated in the pressure vessel, a heater was attached to the CNT substrate, and a temperature controller was attached to the pressure vessel.
Further, 5 ml of an electrolyte resin solution (solution obtained by diluting the electrolyte resin with ethanol to 3 wt%) was put into the pressure vessel.

Subsequently, as shown in FIG. 5, while maintaining the atmospheric temperature and the CNT substrate temperature in the pressure vessel at 30 ° C., CHF ₃ gas is introduced to pressurize the pressure vessel to 9 MPa, and CHF ₃ is in a supercritical state. I made it. While maintaining the atmospheric environment temperature and the CNT substrate temperature in the pressure vessel at 30 ° C., the pressurized state was maintained for 30 minutes.

  Subsequently, as shown in FIG. 5, the CNT substrate was heated to 60 ° C. with a heater while maintaining the ambient temperature in the pressure vessel at 30 ° C. The state where the atmospheric environment temperature in the pressure vessel was 30 ° C. and the CNT substrate temperature was 60 ° C. was maintained for 30 minutes.

  Thereafter, as shown in FIG. 5, while maintaining the atmospheric environment temperature in the pressure vessel at 30 ° C. and the CNT substrate temperature at 60 ° C., the pressure vessel was opened to the atmosphere to return the pressure vessel pressure to atmospheric pressure.

When the basis weight of the electrolyte resin per unit area of the CNT substrate was calculated in the same manner as in Example 1, it was 0.03 mg / cm ² . The results are shown in Table 1.

(Comparative Example 2)
First, in the same manner as in Example 1, the CNT substrate was accommodated in the pressure vessel, a heater was attached to the CNT substrate, and a temperature controller was attached to the pressure vessel.
Further, 5 ml of an electrolyte resin solution (solution obtained by diluting the electrolyte resin with ethanol to 3 wt%) was put into the pressure vessel.

Subsequently, as shown in FIG. 6, while maintaining the atmospheric temperature and the CNT substrate temperature in the pressure vessel at 20 ° C., CHF ₃ gas was introduced and the pressure vessel was pressurized to 9 MPa to liquefy CHF ₃ . While maintaining the atmospheric environment temperature and the CNT substrate temperature in the pressure vessel at 20 ° C., the pressurized state was maintained for 30 minutes.

  Subsequently, as shown in FIG. 6, while maintaining the atmospheric environment temperature in the pressure vessel and the temperature of the CNT substrate at 20 ° C., the pressure vessel was opened to the atmosphere to return the pressure vessel pressure to atmospheric pressure.

When the basis weight of the electrolyte resin per unit area of the CNT substrate was calculated in the same manner as in Example 1, it was 0.02 mg / cm ² . The results are shown in Table 1.

(Comparative Example 3)
First, in the same manner as in Example 1, the CNT substrate was accommodated in the pressure vessel, a heater was attached to the CNT substrate, and a temperature controller was attached to the pressure vessel.
Further, 5 ml of an electrolyte resin solution (solution obtained by diluting the electrolyte resin with ethanol to 3 wt%) was put into the pressure vessel.

Subsequently, as shown in FIG. 7, while maintaining the atmospheric environment temperature and the CNT substrate temperature in the pressure vessel at 30 ° C., CHF ₃ gas is introduced to pressurize the pressure vessel to 9 MPa, and CHF ₃ is supercritical. It was in a state. While maintaining the atmospheric environment temperature and the CNT substrate temperature in the pressure vessel at 30 ° C., the pressurized state was maintained for 30 minutes.

  Subsequently, as shown in FIG. 7, the atmospheric pressure in the pressure vessel and the temperature of the CNT substrate were maintained at 30 ° C., and the pressure vessel was opened to the atmosphere to return the pressure vessel pressure to atmospheric pressure.

When the basis weight of the electrolyte resin per unit area of the CNT substrate was calculated in the same manner as in Example 1, it was 0.02 mg / cm ² . The results are shown in Table 1.

As shown in Table 1, the basis weight of the electrolyte resin of Example 1 is 0.78 mg / cm ^2. Compared with Comparative Examples 1 to 3, the CNT can be covered with about 25 to 40 times the electrolyte resin. did it.

[Amount of electrolyte resin solution and amount of electrolyte resin]
(Example 2)
In Example 1, the electrolyte resin was dissolved in CNT in the same manner except that the amount of the electrolyte resin solution (solution obtained by diluting the electrolyte resin with ethanol to 3 wt%) charged into the pressure vessel was changed from 5 ml to 2.5 ml. The resin was coated, and the basis weight of the electrolyte resin was calculated. The results are shown in FIG. In addition, in FIG. 8, the result of Example 1 is also shown collectively.

(Comparative Example 4)
In Comparative Example 1, the same except that the amount of the electrolyte resin solution (solution obtained by diluting the electrolyte resin to 3 wt% with ethanol) was changed from 5 ml to 2.5 ml, 15 ml, and 20 ml in the pressure vessel. Thus, the electrolyte resin was coated on the CNTs, and the basis weight of the electrolyte resin was calculated. The results are shown in FIG. FIG. 8 also shows the result of Comparative Example 1.
Also shown.

As shown in FIG. 8, according to the present invention, it was confirmed that the amount of electrolyte resin to be used can be greatly reduced. Specifically, the amount of the electrolyte resin used for securing the basis weight of the electrolyte resin of about 0.8 g / cm ² can be set to a quarter or less of the comparative example.

[Supercritical processing time and electrolyte resin weight]

(Example 3)
In Example 1, it is the same except that the atmospheric environment temperature in the pressure vessel is 20 ° C. and the time for maintaining the CNT substrate temperature at 60 ° C. (supercritical fluid processing time) is changed from 30 minutes to 5 minutes at 9 MPa. Thus, the electrolyte resin was coated on the CNTs, and the basis weight of the electrolyte resin was calculated. The results are shown in FIG. In addition, in FIG. 9, the result of Example 1 is also shown collectively.

(Comparative Example 5)
The same as in Comparative Example 1, except that the atmospheric environment temperature in the pressure vessel was 30 ° C. and the time for maintaining the CNT substrate temperature at 60 ° C. (supercritical fluid processing time) was changed from 30 minutes to 100 minutes at 9 MPa. Thus, the CNT was coated with an electrolyte resin, and the basis weight of the electrolyte resin was calculated. The results are shown in FIG. In FIG. 9, the result of Comparative Example 1 is also shown.

  As shown in FIG. 9, according to the present invention, the weight of the electrolyte resin can be remarkably increased, and the processing time of the CNT substrate by the supercritical fluid containing the electrolyte resin can be greatly shortened. It was confirmed that.

Example 4
Instead of CHF ₃ gas, CO ₂ gas (CO ₂ critical temperature 31 ° C., critical pressure 7.3 MPa) was used, and CNT was coated with an electrolyte resin in the same process as in Example 1 as follows.
First, in the same manner as in Example 1, the CNT substrate was accommodated in the pressure vessel, a heater was attached to the CNT substrate, and a temperature controller was attached to the pressure vessel. Further, 5 ml of an electrolyte resin solution (solution obtained by diluting the electrolyte resin with ethanol to 3 wt%) was put into the pressure vessel.

Subsequently, while maintaining the atmospheric environment temperature and the CNT substrate temperature in the pressure vessel at 25 ° C., CO ₂ gas was introduced to pressurize the pressure vessel to liquefy CO ₂ . The pressurization with CO ₂ gas is such that the pressure in the pressure vessel is 9 MPa so that the liquid level of the electrolyte resin solution, which is a mixed solution of the electrolyte resin solution and liquefied CO ₂ , is 80 mm from the bottom of the pressure vessel. I went until. While maintaining the atmospheric environment temperature in the pressure vessel and the CNT substrate temperature at 25 ° C., the pressurized state was maintained for 30 minutes, and the CNT substrate was immersed in the electrolyte resin solution to be exposed.

Subsequently, while maintaining the ambient temperature in the pressure vessel at 25 ° C., the CNT substrate was heated to 60 ° C. with a heater, and the liquefied CO ₂ near the CNT substrate was brought into a supercritical state. The state where the atmospheric environment temperature in the pressure vessel was 25 ° C. and the CNT substrate temperature was 60 ° C. was maintained for 30 minutes.

Thereafter, while maintaining the atmospheric temperature in the pressure vessel at 25 ° C. and the CNT substrate temperature at 60 ° C., the pressure vessel was opened to the atmosphere to return the pressure vessel pressure to atmospheric pressure. Thus, the supercritical CO ₂ in the vicinity of the substrate was changed to a gas state without passing through the liquid state, and the electrolyte resin dissolved in the supercritical CO ₂ was deposited on the CNT surface. In addition, the liquid CO ₂ in the atmospheric environment was also in a gaseous state.
In the same manner as in Example 1, the basis weight of the electrolyte resin was calculated. The results are shown in FIG.

(Comparative Example 6)
Using CO ₂ gas instead of CHF ₃ gas, CNT was coated with an electrolyte resin by the same process as in Comparative Example 1 as follows.
First, in the same manner as in Example 1, the CNT substrate was accommodated in the pressure vessel, a heater was attached to the CNT substrate, and a temperature controller was attached to the pressure vessel. Further, 5 ml of an electrolyte resin solution (solution obtained by diluting the electrolyte resin with ethanol to 3 wt%) was put into the pressure vessel.
Subsequently, while maintaining the atmospheric temperature in the pressure vessel and the CNT substrate temperature at 35 ° C., CO ₂ gas was introduced to pressurize the pressure vessel to 10 MPa to bring CO ₂ into a supercritical state. While maintaining the atmospheric environment temperature and the CNT substrate temperature in the pressure vessel at 35 ° C., the pressurized state was maintained for 30 minutes.
Subsequently, the CNT substrate was heated to 60 ° C. with a heater while maintaining the ambient temperature in the pressure vessel at 35 ° C. The state where the ambient temperature in the pressure vessel was 35 ° C. and the CNT substrate temperature was 60 ° C. was maintained for 30 minutes.
Thereafter, while maintaining the atmospheric environment temperature in the pressure vessel at 35 ° C. and the CNT substrate temperature at 60 ° C., the pressure vessel was opened to the atmosphere to return the pressure vessel pressure to atmospheric pressure.
In the same manner as in Example 1, the basis weight of the electrolyte resin was calculated. The results are shown in FIG. In FIG. 10, the results of Comparative Example 1 are also shown.

As shown in FIG. 10, in Example 4, similarly to Comparative Example 6 using CO ₂ gas, 10 times or more electrolyte resin could be coated on CNT. Furthermore, even when compared with Comparative Example 1 using CHF _3, which has a higher dielectric constant than CO _{2 and} higher solubility of the electrolyte resin, Example 4 has a significantly higher amount of electrolyte resin. This is because, in the manufacturing method of the present invention, the concentration of the electrolyte resin in the vicinity of the CNT substrate can be increased as compared with Comparative Example 1 and Comparative Example 6 even if CO ₂ having low solubility of the electrolyte resin is used. It is.

DESCRIPTION OF SYMBOLS 1 ... Pressure vessel 2 ... Electrolyte resin solution 3 ... CNT board | substrate 4 ... Heater 5 ... Temperature controller 6 ... Electrolyte resin solution 7 ... Supply valve 8 ... Discharge valve

Claims (12)

A method of coating a surface of a porous structure with a coating material using a supercritical fluid in a pressure vessel,
A preparatory step of disposing the covering material dissolving solution in which the covering material is dissolved and the porous structure in the pressure vessel;
Exposing the porous structure to a coating solution containing the coating material and a solvent in a liquid state below the critical temperature and above the critical pressure;
After the exposing step, heating the porous structure to a temperature equal to or higher than the critical temperature of the solvent while being exposed to the coating material solution;
After the heating step, changing the state of the solvent in a supercritical state, and depositing the coating material on the surface of the porous structure,
A coating method characterized by comprising: In the exposure step, the pressure vessel is pressurized to a pressure higher than the critical pressure of the solvent by introducing the solvent in a gaseous state under a temperature condition lower than the critical temperature of the solvent, and the solvent is transferred to a liquid state, Raising the liquid level of the coating material solution containing the coating material and the liquid solvent, exposing the porous structure to the coating material solution,
In the preparation step, the position of the porous structure is determined by the pressure in the exposure step so that the liquid surface of the coating material solution positioned below the lower end of the porous structure has the porous structure. The coating method according to claim 1, wherein the coating method is a position located above the upper end.   The coating method according to claim 1 or 2, wherein, in the heating step, an atmospheric environment temperature in the pressure vessel is made lower than a critical temperature of the solvent.   The coating method according to any one of claims 1 to 3, wherein, in the precipitation step, the solvent is transferred from a supercritical state to a gas state without passing through a liquid state. A method for producing an electrode catalyst layer, wherein a surface of a conductive porous structure carrying a catalyst is coated with an electrolyte resin using a supercritical fluid in a pressure vessel,
A preparatory step of disposing an electrolyte resin solution in which the electrolyte resin is dissolved and a conductive porous structure carrying the catalyst in the pressure vessel;
Exposing the conductive porous structure carrying the catalyst to an electrolyte resin solution containing the electrolyte resin and a solvent in a liquid state below a critical temperature and above a critical pressure;
After the exposing step, heating the conductive porous structure to a temperature equal to or higher than the critical temperature of the solvent while being exposed to the electrolyte resin solution;
After the heating step, the state of the solvent in a supercritical state is changed, and the electrolyte resin is deposited on the surface of the conductive porous structure.
The manufacturing method characterized by having. In the exposure step, the pressure vessel is pressurized to a pressure higher than the critical pressure of the solvent by introducing the solvent in a gaseous state under a temperature condition lower than the critical temperature of the solvent, and the solvent is transferred to a liquid state, By raising the liquid level of the electrolyte solution containing an electrolyte resin and the solvent in a liquid state, the conductive porous structure is exposed to the electrolyte resin solution,
In the preparation step, the conductive porous structure is disposed at a position where the liquid surface of the electrolyte solution positioned below the lower end of the conductive porous structure is electrically conductive by the pressurization in the exposure step. The manufacturing method of Claim 5 which is a position located above the upper end part of a porous structure.   The manufacturing method of Claim 5 or 6 which makes the atmospheric environmental temperature in the said pressure vessel lower than the critical temperature of the said solvent in the said heating process.   The manufacturing method according to claim 5, wherein, in the precipitation step, the solvent is shifted from a supercritical state to a gas state without passing through a liquid state.   The manufacturing method according to claim 5, wherein in the preparation step, an electrolyte solution in which the electrolyte resin is dissolved is disposed in the pressure vessel. The conductive porous structure is supported on a substrate,
The heating process according to any one of claims 5 to 9, wherein in the heating step, the conductive porous structure is heated to a temperature equal to or higher than a critical temperature of the solvent by heating the base material to a temperature equal to or higher than a critical temperature of the solvent. Production method.   The manufacturing method according to claim 10, wherein the conductive porous structure includes carbon nanotubes substantially vertically aligned on the base material.   The manufacturing method according to claim 5, wherein the electrode catalyst layer is a fuel cell electrode catalyst layer.

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