JP2002110178A - Method for fabricating gas-diffusion electrode and method for fabricating electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a catalyst layer having a high gas permeability on the surface of a gas-diffusion electrode comprising carbon sheets. SOLUTION: A catalyst layer is formed on the surface of the carbon sheets by applying a dispersion liquid containing a catalyst and fibrous carbon to the carbon sheets by means of the spray-dry method, dropping method, or the like. Herewith, a catalyst layer of high gas permeability is formed, so that the energy efficiency of an electrochemical device using such a gas-diffusion electrode can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a gas diffusion electrode and a method for manufacturing an electrochemical device.
A method for forming a catalyst layer having high gas permeability on the surface of an electrode substrate of a gas diffusion electrode made of a carbon sheet, and manufacturing an electrochemical device such as a fuel cell or an air cell using such a gas diffusion electrode. On how to do it.

[0002]

2. Description of the Related Art Since the industrial revolution, fossil fuels such as gasoline and light oil have been widely used not only as energy sources for automobiles but also as energy sources for electric power production. The use of fossil fuels has enabled humankind to enjoy such dramatic improvements in living standards and the development of industry, but on the other hand, the planet has been threatened with serious environmental destruction, There is a possibility that fuel will be depleted, and a long-term stable supply will be questioned.

[0003] Therefore, hydrogen is contained in water, is inexhaustibly present on the earth, has a large amount of chemical energy per substance, and when used as an energy source, harmful substances and earth. Because it does not emit greenhouse gases, it is a clean alternative to fossil fuels, and
In recent years, it has attracted great attention as an inexhaustible energy source.

[0004] In particular, in recent years, research and development of an electric energy generator capable of extracting electric energy from hydrogen energy has been actively carried out. From large-scale electric power generation to on-site in-house electric power generation, and further for automobiles, The application as a power supply is expected.

[0005] An electric energy generator for extracting electric energy from hydrogen energy, that is, a fuel cell has a hydrogen electrode to which hydrogen is supplied and an oxygen electrode to which oxygen is supplied. Hydrogen supplied to the hydrogen electrode is
By the action of the catalyst, protons (protons) and electrons are dissociated, and the electrons are collected by the current collector of the hydrogen electrode, while the protons are carried to the oxygen electrode. The electrons collected at the hydrogen electrode are transferred to the oxygen electrode via a load. On the other hand, oxygen supplied to the oxygen electrode combines with protons and electrons carried from the hydrogen electrode by the action of a catalyst to generate water. In this way, an electromotive force is generated between the hydrogen electrode and the oxygen electrode, and a current flows to the load.

[0006]

As described above, in a fuel cell that extracts electric energy from hydrogen energy, in order to generate an electromotive force between the hydrogen electrode and the oxygen electrode, hydrogen is converted into protons at the hydrogen electrode. It is necessary to dissociate into (protons) and electrons. On the other hand, in an oxygen electrode, it is necessary to react protons, electrons and oxygen to produce water. Therefore, a catalyst layer for promoting the dissociation of protons and electrons of hydrogen is required in the hydrogen electrode, and a catalyst layer for promoting the binding of protons, electrons and oxygen is required in the oxygen electrode.

Here, in order for the catalyst layer to efficiently promote the dissociation of protons and electrons of hydrogen and the bond between protons, electrons and oxygen, the catalyst layer must have good gas permeability. Can be That is, if the gas permeability of the catalyst layer is low, the ratio of the hydrogen gas or oxygen gas reaching the catalyst layer becomes low, and the efficiency of generating electric energy is reduced.

However, the conventional method for forming a catalyst layer is to simply apply a powdery catalyst with a binder to the surface of an electrode substrate for a hydrogen electrode and an oxygen electrode. Therefore, there is a problem that the efficiency of generating electric energy is low. For this reason, conventionally, a method capable of forming a catalyst layer having high gas permeability on an electrode substrate of a hydrogen electrode and an oxygen electrode has been desired.

[0009] Such a problem has arisen not only in hydrogen electrodes and oxygen electrodes for fuel cells, but also in electrodes used in other electrochemical devices such as air cells.

Accordingly, an object of the present invention is to provide a method for forming a catalyst layer having high gas permeability on an electrode substrate of a gas diffusion electrode, and a method for forming a fuel cell or an air cell using a pole by such gas diffusion. It is an object of the present invention to provide a method for manufacturing an electrochemical device, thereby increasing the energy efficiency of the electrochemical device.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
This is achieved by a method for producing a gas diffusion electrode, wherein a catalyst layer is formed on the surface of a carbon sheet by applying a dispersion containing a catalyst and fibrous carbon to the carbon sheet.

It is another object of the present invention to provide a gas diffusion electrode having a catalyst layer formed on the surface of a carbon sheet by applying a dispersion containing a catalyst and fibrous carbon to the carbon sheet. And a step of attaching an electrolyte membrane to the catalyst layer of the gas diffusion electrode.

According to the present invention, since the catalyst layer is formed on the surface of the carbon sheet by using a dispersion containing the catalyst and fibrous carbon, the catalyst is applied to the carbon sheet. The gas permeability can be maintained at a high level while being reliably held on the surface. Accordingly, if an electrochemical device such as a fuel cell or an air cell is configured using the gas diffusion electrode manufactured by the method, the energy efficiency can be sufficiently increased.

In a preferred embodiment of the present invention, the fibrous carbon is at least one of a carbon nanotube and acicular graphite.

According to a preferred embodiment of the present invention, the use of carbon nanotubes as the fibrous carbon makes it possible to enhance the adhesion of the formed catalyst layer. It is possible to further enhance the gas permeability of the layer.

In a further preferred aspect of the present invention, the fibrous carbon is both the carbon nanotube and the acicular graphite.

According to a further preferred embodiment of the present invention, since both carbon nanotubes having high adhesion and acicular graphite having high gas permeability are used as the fibrous carbon, high adhesion and high gas permeability are obtained. It is possible to balance the properties.

In a further preferred embodiment of the present invention, the catalyst is supported on a carbon material.

In a further preferred aspect of the present invention, the catalyst is supported on the carbon nanotube.

According to a further preferred embodiment of the present invention, since the catalyst is supported on the carbon nanotube itself, it is not necessary to use the catalyst-supporting carbon separately from the carbon nanotube which is the fibrous carbon.

In a further preferred embodiment of the present invention, the dispersion further contains a proton conductive material.

According to a further preferred embodiment of the present invention, since the dispersion further contains a proton conductive material, it is possible to efficiently conduct protons dissociated by the catalyst.

In a further preferred embodiment of the present invention, the proton conductive material is formed of a carbonaceous material containing carbon as a main component, into which a proton dissociable group is introduced.

In a further preferred embodiment of the present invention, the coating is performed by a spray drying method.

In another preferred embodiment of the present invention, the coating is performed by a dropping method.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a schematic configuration of a fuel cell to be manufactured according to a preferred embodiment of the present invention.

As shown in FIG. 1, the fuel cell according to the present embodiment comprises an oxygen electrode 1, a hydrogen electrode 2 as a fuel electrode, and a proton conductor 3 sandwiched between the oxygen electrode 1 and the hydrogen electrode 2. And The oxygen electrode 1 is composed of an electrode substrate 4 made of a carbon sheet and a catalyst layer 5 formed on the surface thereof. Similarly, the hydrogen electrode 2 is composed of an electrode substrate 6 made of a carbon sheet and a catalyst layer formed on the surface thereof. 7. A positive electrode lead 8 extends from the electrode substrate 4 of the oxygen electrode 1, and a negative electrode lead 9 extends from the electrode substrate 6 of the hydrogen electrode 2. These positive electrode lead 8 and negative electrode lead 9 are connected to a load (not shown). Connected. On the oxygen electrode 1 side, the air 10 is configured to be supplied from the inlet 11 to the flow channel 12 and discharged from the outlet 13, and on the hydrogen electrode 2 side, supplied from the hydrogen supply source 14. The hydrogen 15 is configured to be supplied to the flow path 17 from the inlet 16 and discharged from the outlet 18.

The hydrogen 15 supplied from the inlet 16 to the flow path 17 reaches the catalyst layer 7 formed on the surface of the hydrogen layer 15 through the electrode base 6 made of a carbon sheet, and is dissociated into protons and electrons by the catalytic action. You. Among them, electrons move to the negative electrode lead 9 via the electrode base 6 and are supplied to a load (not shown), and protons move to the oxygen electrode 1 side via the proton conductor 3. On the other hand, the oxygen 10 supplied to the flow channel 12 from the inlet 11 reaches the catalyst layer 5 formed on the surface through the electrode substrate 4 made of a carbon sheet, and is supplied from the proton conductor portion 3 by the catalytic action. The protons and the electrons supplied from the load via the positive electrode lead 8 combine to form water. In this way, a desired electromotive force is extracted.

Here, the proton conductor 3 is made of hydrogen 15
Is a membrane that prevents permeation and allows the passage of protons, and the material is not particularly limited, and a carbonaceous material containing carbon as a main component is used as a base material, and a material into which a proton dissociable group is introduced is used. Is preferred. here,
The “proton dissociable group” means a “functional group from which a proton can be eliminated by ionization”.

As the carbonaceous material serving as the base of the proton conductor portion 3, any material can be used as long as it contains carbon as a main component. It is necessary that ionic conductivity is greater than electronic conductivity. Here, specific examples of the carbonaceous material serving as a base include a carbon cluster, which is an aggregate of carbon atoms, and a carbon tube.

There are various types of carbon clusters, and preferred are fullerenes, those having an open end in at least a part of the fullerene structure, those having a diamond structure, and the like. Of course, the invention is not limited thereto, and any material may be used as long as the ion conductivity after introduction of the proton dissociating group is higher than the electron conductivity.

It is preferable to select fullerene as the carbonaceous material serving as a base material of the proton conductor portion 3, and to add a proton dissociating group such as —OH group or —OSO ₃
H group, -COOH group, -SO ₃ H group, -OPO (OH)
It is preferable to use a material into which _two groups have been introduced as the material of the proton conductor portion 3.

However, a material other than the above-described material having a carbonaceous material containing carbon as a main component, such as a perfluorosulfonic acid resin, may be used as the material of the proton conductor portion 3.

As the hydrogen supply source 14, a hydrogen cylinder, a hydrogen storage alloy or a carbonaceous hydrogen storage material can be used. As the carbonaceous hydrogen storage material, fullerene, carbon nanofiber, carbon nanotube,
Examples include carbon soot, nanocapsules, bucky onions, and carbon fibers.

Next, a method of manufacturing the fuel cell according to this embodiment will be described.

First, a carbon sheet having a predetermined area and a dispersion mixed with catalyst-supporting carbon and fibrous carbon are prepared. As the dispersion liquid, a mixed liquid in which a trace amount of sodium hydroxide is added to a mixed liquid of water, alcohols such as methanol and ethanol, and toluene may be used. Here, sodium hydroxide plays a role in preventing aggregation of fibrous carbon.

Here, the carbon sheet is a sheet composed of a collection of graphite fibers, and constitutes the electrode bases 4 and 6 of the oxygen electrode 1 and the hydrogen electrode 2. Also,
The catalyst-supporting carbon refers to graphite particles on which a catalyst substance is supported, and the supported catalyst includes platinum, a platinum alloy, palladium, magnesium, titanium, manganese,
There are lanthanum, vanadium, zirconium, nickel-lanthanum alloy, titanium-iron alloy, iridium, rhodium, gold and the like, and preferred are platinum and platinum alloy. Further, fibrous carbon refers to carbon nanotubes (CNT), carbon nanofibers (CNF), acicular graphite, and the like, and one or more of these can be selected and used.

The carbon nanotube is a tubular carbonaceous material having a diameter of about several nanometers or less, typically about 1.2 to 1.7 nanometers, and is a single-walled carbon nanotube composed of a single-layer tube. (S
WCNT) and multi-wall carbon nanotubes (MWCNT) in which two or more layers are concentrically overlapped are known. The length is not particularly limited, but is typically about several micrometers. Further, the carbon nanofiber refers to a carbon nanotube having a particularly large diameter among carbon nanotubes. Typically, the diameter is several nanometers or more.
Reach micrometer. In the following description, “carbon nanotube” includes carbon nanofibers. In addition, acicular graphite typically refers to acicular graphite having a diameter of about 200 nanometers and a length of about several micrometers.

Next, a dispersion in which the catalyst-supporting carbon and the fibrous carbon are mixed is sprayed onto the surface of the carbon sheet by a spray drying method. At this time, the catalyst-supporting carbon sprayed on the carbon sheet is held on the surface of the carbon sheet by being entangled with the fibrous carbon sprayed at the same time.

Here, when carbon nanotubes are selected as the fibrous carbon, since they are very fine fibrous substances, they have a high ability to entangle and adhere the catalyst-supporting carbon to the carbon sheet. If the carbon sheet is formed at a high density, the gas permeability of the carbon sheet may be impaired. On the other hand, if acicular graphite is selected as the fibrous carbon, the acicular graphite is a fibrous (acicular) substance that is thicker than carbon nanotubes. Although there is no possibility of impairing the carbonaceous material, the ability to entangle the catalyst-supporting carbon on the carbon sheet and bring it into close contact is not so high. Therefore, it is preferable to mix carbon nanotubes and acicular graphite as the fibrous carbon in the dispersion. If the carbon nanotubes and the acicular graphite are mixed, the catalyst-carrying carbon can be effectively adhered to the carbon sheet while maintaining high gas permeability of the carbon sheet. However, in the present embodiment, it is not essential to mix carbon nanotubes and acicular graphite in the dispersion liquid, as long as the gas permeability of the carbon sheet is ensured, only carbon nanotubes may be used, Conversely, as long as the adhesion of the catalyst-carrying carbon to the carbon sheet is ensured, only the acicular graphite may be used.

The carbon nanotubes can be generated by an arc discharge method using a graphite rod.

The carbon sheet on which the catalyst layer has been formed becomes the oxygen electrode 1 and the hydrogen electrode 2.

Next, the oxygen electrode 1 thus completed
The proton conductor 3 is sandwiched between the hydrogen electrode 2 and the oxygen electrode 1, and an inlet 11 for air 10, a flow path 12 and an outlet 13 are provided on the oxygen electrode 1 side, and an inlet for hydrogen 15 is provided on the hydrogen electrode 2 side. 1
6, the fuel cell according to the present embodiment is completed by providing the flow path 17 and the discharge port 18.

As described above, according to the present embodiment, the dispersion containing the catalyst-carrying carbon and the fibrous carbon mixed therein is sprayed onto the surface of the carbon sheet by the spray-dry method, whereby the oxygen electrode 1 and the hydrogen electrode 1 of the fuel cell are sprayed. 2, that is, since the electrode bases 4 and 6 on which the catalyst layers 5 and 7 are respectively formed are manufactured, the catalyst layer having high gas permeability is formed on the carbon sheet as the electrode base by a very simple method. can do. Therefore, a fuel cell using the electrode manufactured as described above has high energy generation efficiency.

In particular, when both carbon nanotubes and acicular graphite are selected as the fibrous carbon to be introduced into the dispersion liquid, when both are mixed, high gas permeability and high adhesion are both achieved. Becomes possible. Therefore, a fuel cell using the electrode manufactured as described above has a very high energy generation efficiency.

Next, another preferred embodiment of the present invention will be described.

The configuration of the fuel cell to be manufactured according to this embodiment is as shown in FIG. 1 and has been described above.

In this embodiment, first, a carbon sheet having a predetermined area, and a dispersion in which carbon nanotubes supporting a catalyst and acicular graphite are mixed are prepared. As described above, the type of the catalyst includes platinum, platinum alloy, palladium, magnesium, titanium, manganese, lanthanum, vanadium, zirconium, nickel-lanthanum alloy, titanium-iron alloy, iridium, rhodium, gold, and the like. Preferred are platinum and platinum alloys.

The method for supporting the catalyst on the carbon nanotubes is not particularly limited, but a chemical supporting method using a solution containing a platinum complex (liquid layer chemical supporting method) or an arc discharge method using a carbon-based electrode containing platinum. Should be applied.

In the former chemical loading method (liquid layer chemical loading method), for example, an aqueous solution of chloroplatinic acid is treated with sodium hydrogen sulfite or hydrogen peroxide, and then carbon nanotubes are mixed into the solution and stirred. Thereby, a catalyst-supporting carbon nanotube can be obtained. In the latter arc discharge method, platinum or a platinum alloy is partially incorporated in the electrode portion of the arc discharge, and this is evaporated by arc discharge, and adhered to the carbonaceous material contained in the chamber. Thus, a catalyst-carrying carbon nanotube can be obtained.

As another method for supporting the catalyst on the carbon nanotubes, the carbon nanotubes may be introduced into a sputtering chamber, and the catalyst may be supported on the carbon nanotubes by a sputtering method. At this time, if sputtering is performed while oscillating the carbon nanotube, a catalyst can be formed over a wider area of the carbon nanotube. Further, the carbon nanotubes are introduced into the dispersion liquid, filtered using a filter to form the carbon nanotubes into a sheet shape, and then the catalyst is sputtered, and thereafter, the sheets are entangled with each other by applying ultrasonic waves. The solidified carbon nanotubes may be physically separated into individual carbon nanotubes. In this way, once the carbon nanotubes are formed into a sheet and then the catalyst is formed, and then physically separated into individual carbon nanotubes, the handling of the carbon nanotubes becomes easy.

Next, a dispersion in which the catalyst-supporting carbon nanotubes and the acicular graphite are mixed is sprayed on the surface of the carbon sheet by a spray drying method. At this time, since the catalyst-carrying carbon nanotube and the acicular graphite are both fibrous substances, they are entangled and held on the surface of the carbon sheet.

Here, since carbon nanotubes are very fine fibrous substances, they have a high ability to entangle and adhere to the carbon sheet, but if they are formed at an excessively high density, the gas permeability of the carbon sheet may be impaired. is there. On the other hand, needle-like graphite is a fibrous (needle-like) substance that is thicker than carbon nanotubes. Therefore, by forming this on the carbon sheet simultaneously with the carbon nanotubes, it is possible to maintain high gas permeability of the carbon sheet. It becomes possible. However, in the present embodiment, it is not essential to mix the catalyst-supporting carbon nanotubes and the acicular graphite in the dispersion liquid, as long as the gas permeability of the carbon sheet is ensured, using only the catalyst-supporting carbon nanotubes. Is also good.

The carbon sheet on which the catalyst layer has been formed as described above becomes the oxygen electrode 1 and the hydrogen electrode 2.

Next, the oxygen electrode 1 thus completed
The proton conductor 3 is sandwiched between the hydrogen electrode 2 and the oxygen electrode 1, and an inlet 11 for air 10, a flow path 12 and an outlet 13 are provided on the oxygen electrode 1 side, and an inlet for hydrogen 15 is provided on the hydrogen electrode 2 side. 1
6, the fuel cell according to the present embodiment is completed by providing the flow path 17 and the discharge port 18.

As described above, according to this embodiment, the oxygen electrode 1 and the hydrogen electrode 2 of the fuel cell are manufactured by spraying the solution having at least the catalyst-supported carbon nanotubes onto the surface of the carbon sheet by spray drying. Therefore, the catalyst layer having high gas permeability can be formed on the carbon sheet as the electrode substrate by a very simple method. Therefore, a fuel cell using the electrode manufactured as described above has high energy generation efficiency.

In this embodiment, since the acicular graphite is further introduced into the solution, it is possible to achieve both high gas permeability and high adhesion. Therefore, a fuel cell using the electrode manufactured as described above has a very high energy generation efficiency.

Next, still another preferred embodiment of the present invention will be described.

The configuration of the fuel cell to be manufactured according to this embodiment is as shown in FIG. 1 and has been described above.

In the present embodiment, first, a carbon sheet having a predetermined area, and a dispersion mixed with catalyst-supporting carbon, fibrous carbon, and a proton conductive material are prepared. The proton conductive material is not particularly limited, but it is preferable to use the same material as the material used for the proton conductor 3. For example, the proton conductor 3
When a material (fullerenol) in which fullerene is introduced with -OH group, which is a proton-dissociable group, is used as fullerene, it is preferable to use fullerenol as the proton conductive material to be mixed into the dispersion.

Next, a dispersion containing the catalyst-carrying carbon, fibrous carbon, and proton conductive material is sprayed onto the surface of the carbon sheet by a spray drying method. At this time, the catalyst-supporting carbon sprayed on the carbon sheet is held on the surface of the carbon sheet by being entangled with the fibrous carbon sprayed at the same time. Further, since a proton conductive material is introduced into the solution, the proton conductive material is disposed near the catalyst-carrying carbon held on the surface of the carbon sheet.

As the fibrous carbon to be mixed into the dispersion, carbon nanotubes and acicular graphite can be used. As described above, while keeping the gas permeability of the carbon sheet high, the catalyst-carrying carbon can be used. In order to effectively adhere to the carbon sheet, it is preferable to mix carbon nanotubes and acicular graphite. However, also in the present embodiment, it is not essential to mix the carbon nanotubes and the acicular graphite in the dispersion, as long as the gas permeability of the carbon sheet is ensured.
Only carbon nanotubes may be used, and conversely, only needle graphite may be used as long as the adhesion of the catalyst-supporting carbon to the carbon sheet is ensured.

The carbon sheet on which the catalyst layer has been formed becomes the oxygen electrode 1 and the hydrogen electrode 2.

Next, the oxygen electrode 1 thus completed
The proton conductor 3 is sandwiched between the hydrogen electrode 2 and the oxygen electrode 1, and an inlet 11 for air 10, a flow path 12 and an outlet 13 are provided on the oxygen electrode 1 side, and an inlet for hydrogen 15 is provided on the hydrogen electrode 2 side. 1
6, the fuel cell according to the present embodiment is completed by providing the flow path 17 and the discharge port 18.

According to this embodiment, since the proton conductive material is mixed in the catalyst layer, the proton dissociated from the hydrogen 15 by the catalytic action is efficiently supplied to the proton conductor 3 on the hydrogen electrode 2 side. At the same time, on the oxygen electrode 2 side, protons supplied from the proton conductor 3 can be efficiently supplied to the catalyst. Thereby, the fuel cell manufactured by the method according to the present embodiment has high energy generation efficiency.

Further, according to this embodiment, since the proton conductive material is mixed in the catalyst layer, the adhesion between the oxygen electrode 1 and the proton conductor 3 and the hydrogen electrode 2 and the proton conductor 3 The effect of improving the adhesiveness with the adhesive is also obtained.

Next, still another preferred embodiment of the present invention will be described.

FIG. 2 is a diagram showing a schematic configuration of an air battery to be manufactured according to still another preferred embodiment of the present invention.

As shown in FIG. 2, the air battery (air-zinc battery) manufactured according to this embodiment is
, A negative electrode 22, and an electrolyte 23 sandwiched between the air electrode 21 and the negative electrode 22. The air electrode 21 is composed of an electrode substrate made of a carbon sheet and a catalyst layer formed on the surface thereof, and the negative electrode 22 is composed of a zinc plate having a thickness of 100 micrometers. Further, a positive electrode lead 24 is led out from the electrode base of the air electrode 21,
A negative electrode lead 25 extends from the negative electrode 22, and these positive electrode lead 24 and negative electrode lead 25 are connected to a load (not shown). The air electrode 21, the negative electrode 22, and the electrolyte 23 sandwiched therebetween are sandwiched between Teflon (registered trademark) plates 26a and 26b having a thickness of 3 mm.
a and 27b. Further, a plurality of air holes 28 for supplying air to the air electrode 21 are formed in the Teflon plate 26b. The diameter of the air hole 28 is 1.5 mm.

The air battery having such a configuration can be manufactured by the following method.

First, by the method according to each of the above embodiments,
The air electrode 21 is produced by forming a catalyst layer on the surface of the carbon sheet. A gel of an aqueous solution of zinc chloride as the electrolyte 23 is applied to the catalyst layer of the air electrode 21 to a thickness of about 50 micrometers,
2 are joined. Then, both sides of this joined body are firmly sandwiched between Teflon plates 26a and 26b, and bolts 27a
And 27b. Thereby, the air battery is completed.

In the air battery thus manufactured, the reaction represented by the formula (1) proceeds at the air electrode 21,
In the negative electrode 22, the reaction represented by the formula (2) proceeds.

O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻・ ・ ・ Equation (1) Zn + 2OH ⁻ → Zn (OH) ₂ + 2e ⁻・ ・ ・ Equation (2) Therefore, the reaction represented by the equation (3) as a whole is As a result, a predetermined electromotive force can be obtained.

_1/2 O ₂ + Zn + H ₂ O → Zn (OH) ₂ ... (3) FIG. 3 is a graph showing the discharge characteristics of an air battery to be manufactured according to still another preferred embodiment of the present invention. is there.

FIG. 3 shows changes in output voltage (load characteristics) when the current density is changed for each of the air battery according to the present embodiment and the conventional air battery.

Referring to FIG. 3, the open-circuit voltage (when the current value is zero) is almost the same, but as the current density increases, the air battery according to the present embodiment is different from the conventional air battery. It can be seen that the output voltage is maintained higher. From these results, it is understood that the output characteristics of the air battery using the gas diffusion electrode manufactured by the method of the present invention for the air electrode 21 are improved.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. It goes without saying that it is a thing.

For example, in each of the above embodiments, the dispersion containing the catalyst and the fibrous carbon is applied to the surface of the carbon sheet by the spray drying method, but the application method is limited to the spray drying method. However, the coating may be performed by another method, for example, a dropping method.

In the third embodiment, the proton conductive material is mixed in the dispersion. However, the application of the proton conductive material may not be performed simultaneously with the formation of the catalyst layer.
After forming the catalyst layer on the surface of the carbon sheet according to the first embodiment, a proton conductive material may be applied.

Further, in the third embodiment,
As the dispersion to be applied, a dispersion in which catalyst-supporting carbon, fibrous carbon, and a proton conductive material are mixed is used, but a dispersion in which catalyst-supporting carbon nanotubes and a proton conductive material are mixed may be used. . In this case, as described in the second embodiment, in order to increase gas permeability, it is preferable to further mix acicular graphite into the dispersion.

In each of the above embodiments, a mixture of water, a mixture of alcohols such as methanol and ethanol and toluene and a small amount of sodium hydroxide is used as the dispersion. The components of the liquid are not limited to these, and a dispersion composed of other components may be used.

Further, in the above embodiment, hydrogen gas is used as the fuel gas of the fuel cell manufactured. However, the fuel gas is not limited to hydrogen gas, and other fuel gas, for example, methanol is vaporized. You may use the gas made to have. In this case, the reaction represented by the formula (4) proceeds in the negative electrode to which the gas obtained by vaporizing methanol is supplied, and the reaction represented by the formula (5) in the oxygen electrode 1 (the positive electrode) to which air is supplied. Progresses.

[0084] _{CH 3 OH + H 2 O →} CO 2 + 6H + + 6e - ··· Equation _{^{(4) 6H + + 3 /}} 2O 2 + 6e - → 3H 2 O ··· (5) Thus, as a whole the formula (6) The reaction shown in (1) proceeds, and a predetermined electromotive force can be obtained.

CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O Formula (6) However, when a gas obtained by vaporizing methanol is used as the fuel gas, carbon dioxide is generated in addition to water.

[0086]

As described above, according to the present invention,
Since a catalyst layer having high gas permeability can be formed on the surface of the electrode substrate of the gas diffusion electrode made of a carbon sheet, it is possible to form an electrochemical device such as a fuel cell or an air battery using such a gas diffusion electrode. Energy efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a fuel cell to be manufactured according to a preferred embodiment of the present invention.

FIG. 2 is a view showing a schematic configuration of an air battery to be manufactured according to still another preferred embodiment of the present invention.

FIG. 3 is a graph showing a discharge characteristic of an air battery to be manufactured according to still another preferred embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oxygen electrode 2 Hydrogen electrode 3 Proton conductor part 4, 6 Electrode substrate 5, 7 Catalyst layer 8 Positive electrode lead 9 Negative electrode lead 10 Air 11 Inlet 12 Flow path 13 Outlet 14 Hydrogen supply source 15 Hydrogen 16 Inlet 17 Flow path 18 Discharge port 21 Air electrode 22 Negative electrode 23 Electrolyte 24 Positive electrode lead 25 Negative electrode lead 26a, 26b Teflon plate 27a, 27b Bolt 28 Air hole

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B05D 1/02 B05D 1/02 Z 1/30 1/30 (72) Inventor Minehisa Imazato Shinagawa, Tokyo 6-7-35 Kita-Shinagawa, Ward Sony Corporation F-term (reference) 4D075 AA01 AC02 DA04 DB01 DC19 DC22 EA02 EB01 EC22 4K011 AA12 AA23 AA31 AA52 AA58 AA68 DA11 5H018 AA02 AA10 BB06 BB08 BB12 DD05 EE05 BB05 BB08 CX02 EE05 EE06

Claims (20)

[Claims] 1. A method for manufacturing a gas diffusion electrode, comprising applying a dispersion containing a catalyst and fibrous carbon to a carbon sheet to form a catalyst layer on the surface of the carbon sheet. 2. The method according to claim 1, wherein the fibrous carbon is at least one of carbon nanotubes and acicular graphite. 3. The method according to claim 2, wherein the fibrous carbon is both the carbon nanotube and the acicular graphite. 4. The method according to claim 1, wherein the catalyst is supported on a carbon material. 5. The method for producing a gas diffusion electrode according to claim 2, wherein the catalyst is supported on the carbon nanotube. 6. The method according to claim 1, wherein the dispersion further contains a proton conductive material. 7. The gas diffusion electrode according to claim 6, wherein the proton conductive material is made of a carbonaceous material containing carbon as a main component, into which a proton dissociable group is introduced. Manufacturing method. 8. The method according to claim 1, wherein the coating is performed by a spray drying method. 9. The method according to claim 1, wherein the application is performed by a dropping method. 10. A step of applying a dispersion containing a catalyst and fibrous carbon to a carbon sheet to produce a gas diffusion electrode having a catalyst layer formed on the surface of the carbon sheet; Attaching an electrolyte membrane to the catalyst layer. 11. The method according to claim 10, wherein the electrochemical device is a fuel cell. 12. The method according to claim 10, wherein the electrochemical device is an air battery. 13. The method according to claim 10, wherein the fibrous carbon is at least one of a carbon nanotube and acicular graphite. 14. The method according to claim 13, wherein the fibrous carbon is both the carbon nanotube and the acicular graphite. 15. The method according to claim 10, wherein the catalyst is supported on a carbon material. 16. The method according to claim 13, wherein the catalyst is carried on the carbon nanotube. 17. The electrolyte membrane according to claim 1, wherein a carbonaceous material containing carbon as a main component is used as a base material, and a proton conductive material having a proton-dissociable group introduced therein is contained therein. 12. The method for producing an electrochemical device according to item 11. 18. The method according to claim 17, wherein the dispersion further includes the proton conductive material. 19. The method for manufacturing an electrochemical device according to claim 10, wherein the application is performed by a spray drying method. 20. The method according to claim 10, wherein the application is performed by a dropping method.