JP5110835B2 - Catalyst electrode for fuel cell, membrane / electrode assembly using the same, and fuel cell - Google Patents

Description

The present invention relates to a catalyst electrode for a fuel cell, a membrane / electrode assembly using the catalyst electrode, and a fuel cell, which are useful as a battery for in-vehicle use, household use or portable equipment.

A fuel cell using hydrogen and oxygen has been attracting attention as a power generation system in which the reaction product is in principle only water and has almost no adverse effects on the environment. In recent years, a polymer electrolyte fuel cell using an ion exchange membrane having hydrogen ion conductivity as an electrolyte among fuel cells has a low operating temperature, a high output density, and can be easily downsized. It is expected to be used for in-vehicle power sources and household stationary power sources.

FIG. 7 is an exploded perspective view showing a configuration example of a single cell of the polymer electrolyte fuel cell. The polymer electrolyte fuel cell is configured by stacking a large number of single cells 60. The single cell 60 is configured by laminating an anode-side separator 61, an anode-side catalyst electrode 62, a solid polymer electrolyte membrane 63 that conducts hydrogen ions, a cathode-side catalyst electrode 64, and a cathode-side separator 65 in this order. Has been. The anode-side catalyst electrode 62 includes an electrode base material 62a and a catalyst layer 62b laminated on the surface of the electrode base material 62a. The cathode-side catalyst electrode 64 includes an electrode base material 64a and an electrode base material. And a catalyst layer 64b laminated on the surface of 64a. Each of the anode side electrode base material 62a and the cathode side electrode base material 64a is composed of a member having gas diffusion capacity, electronic conductivity, and mechanical strength, such as carbon paper or carbon cloth. Is being used. The anode side catalyst layer 62b and the cathode side catalyst layer 64b are composed of carbon fine particles carrying a platinum group catalyst or porous activated carbon, and are connected to the upper and lower surfaces of the solid polymer electrolyte membrane 63 that conducts hydrogen ions, respectively. Has been.
The anode-side separator 61 is provided with a reaction gas channel 61a to supply hydrogen gas. On the other hand, the cathode-side separator 65 is provided with a reaction gas channel 65a for supplying oxygen gas. The hydrogen gas is decomposed into hydrogen ions and electrons by the catalytic action of the platinum group catalyst of the anode side catalyst layer 62b (anode electrode reaction), the hydrogen ions are conducted through the solid polymer electrolyte membrane 63, and the electrons pass through the load circuit. The external electric circuit is conducted to reach the cathode side catalyst layer 64b. Oxygen, hydrogen ions, and electrons react to generate water (cathode electrode reaction) by the catalytic action of the platinum group catalyst of the cathode side electrode catalyst layer 64b (cathode electrode reaction). At this time, between the anode side catalyst electrode 62 and the cathode side catalyst electrode 64 Electric power is generated by the electron flow flowing through the.

As the hydrogen gas supplied to the anode, it is also possible to use a reformed gas obtained by steam reforming methane, methanol or the like. For example, when methanol is used, methanol is reacted stepwise as shown in the following formulas (1) and (2) using a catalyst such as a Cu—Zn system at a temperature of 250 to 300 ° C.
CH ₃ OH = 2H ₂ + CO-90 kJ / mol (1)
CO + H ₂ O = H ₂ + CO ₂ +40 kJ / mol (2)
That is, methanol is decomposed into hydrogen and carbon monoxide (CO) in a reformer, and the produced CO is reacted with water vapor to produce a reformed gas composed of hydrogen gas and carbon dioxide (CO ₂ ). The reformed gas is supplied to the anode as a fuel gas.

In order to increase the power generation capacity of the fuel cell, it is necessary to increase the electrode reaction rate per unit surface area of the catalyst layer. That is, the catalyst layer needs to be able to diffuse a sufficient gas, have a large catalyst surface area in contact with the gas, and have a high catalyst reaction rate. In addition, the catalyst layer has a thickness that allows electrons to conduct, and that the generated hydrogen ions are easily taken into the polymer electrolyte membrane, or that the hydrogen ions in the solid polymer electrolyte membrane can be easily taken in. Must be below a certain value.
In addition, the reserves of platinum group elements are limited, and in order to supply fuel cells at low cost, it is preferable to use a low-cost catalyst instead of the platinum group catalyst.

Conventionally, as a catalyst layer of a fuel cell, there is a layer using conductive spherical carbon particles such as carbon black as a catalyst carrier. In this catalyst layer, a platinum group element is supported on the surface of carbon particles by vapor deposition, impregnation, electroless plating, alcohol reduction, or the like, and the carbon particles are laminated to form a catalyst layer. Gas diffuses through voids between the laminated carbon particles, and this gas comes into contact with the platinum group catalyst supported on the surface of the carbon particles to cause a catalytic reaction.
Conventionally, there is a catalyst layer using activated carbon instead of the carbon particles. Since activated carbon has fine pores, gas can be diffused through these pores.

Further, in recent years, a fuel cell catalyst layer in which a carbon nanotube powder is synthesized by an arc discharge method or a chemical vapor deposition method, a platinum group catalyst is supported on the powder, and the powder is laminated on an electrode substrate (see Patent Document 1). It has been known. Carbon nanotubes have electronic conductivity and have a nano-sized elongated shape, so the specific surface area is extremely large. If used as a catalyst carrier, the catalyst surface area of the catalyst layer can be increased, and the carbon nanotubes are supported on the carbon nanotubes. Since the particle size of the platinum group catalyst is nanosized in proportion to the diameter of the carbon nanotube, the catalytic reaction rate per unit amount of the platinum group catalyst is increased, and the amount of the platinum group catalyst used can be reduced.
JP 2006-12832 A JP 2005-335968 A JP 2004-277241 A

However, since all of the above fuel cell catalyst layers use a high-cost platinum group catalyst, there is a problem that the cost of the fuel cell is high.
The inventors have a catalytic action (anode electrode reaction) in which a nanocarbon composite material composed of diamond fine particles and a plurality of nanocarbon materials having one end fixed to the diamond fine particles decomposes hydrogen into hydrogen ions and electrons, And it discovered that it had a catalytic action (cathode electrode reaction) which oxygen, a hydrogen ion, and an electron react and produce water, and it came to this invention.

  In view of the above problems, an object of the present invention is to provide a catalyst electrode for a fuel cell that does not use a platinum group catalyst, a membrane / electrode assembly using the catalyst electrode, and a fuel cell.

  In order to achieve the above object, a catalyst electrode for a fuel cell according to the present invention is a catalyst electrode for a fuel cell comprising an electrode substrate and a catalyst layer laminated on the electrode substrate surface. A nanocarbon composite material comprising a plurality of nanocarbon materials to which is fixed is used as a catalyst.

According to this configuration, a nanocarbon composite material composed of diamond fine particles and a plurality of nanocarbon materials fixed at one end to the diamond fine particles has a catalytic action for decomposing hydrogen into hydrogen ions and electrons, and oxygen and hydrogen. Since it has a catalytic action in which ions and electrons react to generate water, it can be used as a fuel cell catalyst electrode.

The nanocarbon material may be any one of carbon nanotubes, carbon nanofilaments, carbon nanofibers, or carbon nanocoils, or a combination thereof.

The nanocarbon composite material is preferably marimo-like carbon in which a plurality of nanocarbon materials are fixed in a spherical shape with diamond fine particles as nuclei. According to this configuration, since a large number of nanocarbon materials exist uniformly in the three-dimensional direction, the catalyst layer using marimo-like carbon has a uniform gas diffusion capacity and catalytic reaction rate throughout the catalyst layer. Therefore, the power generation capacity can be further improved.

The nanocarbon composite material is preferably synthesized by heating diamond fine particles carrying transition metal fine particles in a hydrocarbon gas.
The marimo-like carbon, which is the above-mentioned nanocarbon composite material, is preferably synthesized by suspending and stirring diamond fine particles carrying transition metal fine particles in a hydrocarbon gas and heating them.

The fuel cell membrane / electrode assembly of the present invention comprises the above fuel cell catalyst electrode and a hydrogen ion conductive polymer electrolyte membrane joined to the fuel cell catalyst electrode.
By using the fuel cell membrane / electrode assembly having this configuration for the anode side electrode, the cathode side electrode, or both, a low-cost fuel cell can be realized.

  The fuel cell of the present invention is a low-cost fuel cell characterized in that the above-described fuel cell catalyst electrode is used for the anode side electrode, the cathode side electrode, or both.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, the same member is demonstrated using the same code | symbol.
First, the catalyst electrode for a fuel cell of the present invention will be described.
FIG. 1 is a diagram showing a configuration of a fuel cell catalyst electrode of the present invention, (a) a schematic cross-sectional view of a fuel cell catalyst electrode, and (b) a schematic view of a nanocarbon composite material. FIG.
(A) As shown to a figure, the catalyst electrode 1 for fuel cells of this invention consists of the catalyst layer 3 laminated | stacked on the surface of the electrode base material 2 and the electrode base material 2. FIG. The catalyst layer 3 is configured by laminating nanocarbon composite materials 4. The electrode base material 2 may be a member having gas diffusibility, electronic conductivity, and mechanical strength, and is, for example, carbon paper or carbon cloth.
(B) As shown in the figure, the nanocarbon composite material 4 has a structure in which a plurality of nanocarbon materials 7 are grown from diamond fine particles 6 with one end fixed. The type of the nanocarbon material 7 may be any of carbon nanotubes, carbon nanofilaments, carbon nanofibers, or carbon nanocoils, or a combination thereof. As described below, the nanocarbon composite material 4 can be selected depending on the type of catalyst used in the synthesis. In addition, although a display is abbreviate | omitted in the figure, a small amount of binder for bonding the nanocarbon composite material 4 to each other may exist.

FIG. 2 is a view showing another configuration of the catalyst electrode for a fuel cell of the present invention, (a) is a schematic cross-sectional view of the catalyst electrode for fuel cell, and (b) is one of the nanocarbon composite materials. It is a figure which shows the marimo-like carbon which is one.
(A) As shown to a figure, the catalyst electrode 8 for fuel cells of this invention consists of the electrode base material 2 and the catalyst layer 9 laminated | stacked on the surface of the electrode base material 2. FIG. The catalyst layer 9 is configured by laminating marimo-like carbon 10. Marimo-like carbon is a kind of nanocarbon composite material, and a plurality of nanocarbon materials grow in a spherical shape with diamond fine particles as the core and have a structure similar to that of plant algae. (Refer to Patent Document 2). The electrode base material 2 may be a member having gas diffusibility, electronic conductivity, and mechanical strength, and is, for example, carbon paper or carbon cloth.
(B) As shown in the figure, the marimo-like carbon 10 has a configuration in which a plurality of nanocarbon materials 7 are grown in a spherical shape from diamond fine particles 6 with the diamond fine particles as nuclei. The type of the nanocarbon material 7 may be any of carbon nanotubes, carbon nanofilaments, carbon nanofibers, or carbon nanocoils, or a combination thereof. As described below, it can be selected depending on the type of catalyst used when synthesizing the marimo-like carbon. Although not shown in the figure, there may be a small amount of binder for bonding the marimo-like carbons 10 to each other. The catalyst layer 9 using the marimo-like carbon 10 has a uniform gas diffusion capacity and catalytic reaction rate over the entire catalyst layer 9, and can further improve the power generation capacity.

Next, the membrane / electrode assembly for a fuel cell of the present invention will be described.
FIG. 3 is a schematic cross-sectional view showing the configuration of the fuel cell membrane-electrode assembly of the present invention. In the drawing, the nanocarbon composite material of the catalyst layer is the marimo-like carbon shown in FIG. 2, but the same applies to the nanocarbon composite material shown in FIG.
(A) As shown in the figure, the fuel cell membrane / electrode assembly 21 of the present invention comprises the fuel cell catalyst electrode 8 of the present invention shown in FIG. 2 and hydrogen ions bonded to the fuel cell catalyst electrode 8. It consists of a conductive solid electrolyte membrane 22. The hydrogen ion conductive solid electrolyte membrane 22 is preferably a Nafion membrane (manufactured by DuPont, registered trademark), for example. The fuel cell membrane / electrode assembly 21 may be used only on the anode side, or may be used only on the cathode side. Also, as shown in FIG. A fuel cell membrane / electrode assembly 23 having a structure in which a catalyst layer 9 is bonded to each of both surfaces, and an electrode base material 2 is bonded to each of the catalyst layers 9 and used on both the anode side and the cathode side. Also good.

Next, a fuel cell using the fuel cell catalyst electrode of the present invention will be described.
FIG. 4 is a schematic cross-sectional view showing the configuration of a single cell of the fuel cell of the present invention. FIG. 4A is a single cell of the fuel cell of the present invention using the fuel cell catalyst electrode 8 of the present invention on the anode side. 31, (b) shows the single cell 32 of the fuel cell of the present invention using the fuel cell catalyst electrode 8 of the present invention on the cathode side, and (c) shows the anode of the fuel cell catalyst electrode 8 of the present invention as the anode. The single cell 33 of the fuel cell of this invention used for the side and cathode side is shown.
Compared with the prior art fuel cell shown in FIG. 7, the single cells 31, 32, and 33 of the fuel cell of the present invention have a catalyst electrode for a fuel cell and the fuel cell of the present invention shown in FIG. The only difference is the use of the catalyst electrode, and the rest of the configuration is the same, so the description is omitted.

Next, the manufacturing method of the catalyst electrode for fuel cells of this invention is demonstrated.
First, a nanocarbon composite material is synthesized by the following method (see Patent Document 3).
As the diamond fine particles used as a nucleus, those commercially available for polishing can be used, and those having a particle size of 1 μm or less are preferable. Since the surface of commercially available diamond fine particles is oxidized unevenly, it is preferable to use the diamond fine particles after heating the diamond fine particles in an oxidizing atmosphere to make the surface uniform.
Next, the transition metal catalyst fine particles for growing the nanocarbon material are supported on the diamond fine particles to produce the diamond catalyst fine particles. For example, diamond fine particles are immersed in an aqueous solution of a transition metal salt and allowed to stand overnight, the excess water is evaporated, dried, and fired in air at 400 to 500 ° C. to cause decomposition and oxidation of the metal salt to form the metal salt. If converted into an oxide and reduced in a reducing atmosphere, diamond catalyst fine particles can be produced (see Patent Document 3). At this time, the diameter of the transition metal catalyst fine particles and the interval between the transition metal catalyst fine particles can be selected by selecting the diameter of the diamond fine particles and the concentration of the transition metal salt. Alternatively, a transition metal thin film may be deposited on the nanocarbon material, heated in a reducing atmosphere, and the transition metal liquid fine particles may be distributed in an island shape on the diamond fine particles to carry the transition metal catalyst fine particles. At this time, the diameter of the transition metal catalyst fine particles and the interval between the transition metal catalyst fine particles can be selected by selecting the diameter of the diamond fine particles and the thickness of the transition metal thin film. By selecting the diameter of the transition metal catalyst fine particles supported on the diamond fine particles and the interval between the transition metal catalyst fine particles, the voids between the nanocarbon materials of the nanocarbon composite material can be selected. Moreover, the kind of nanocarbon material can be selected by selecting the kind of transition metal catalyst. For example, if Ni or Co is selected, the nanocarbon material becomes a carbon nanotube, and if Pd is selected, the nanocarbon material becomes carbon nanographite (a kind of carbon nanofiber) (see Patent Document 2).

  Next, by heating the diamond catalyst fine particles in a hydrocarbon gas, the hydrocarbon is decomposed by the catalytic action of the transition metal catalytic fine particles, and the nano particles proportional to the diameter of the transition metal catalytic fine particles are obtained using the transition metal catalytic fine particles as nuclei. Carbon material grows. Further, since the carrier of the transition metal catalyst fine particles is diamond, even at a high temperature at which the hydrocarbon is decomposed, the transition metal catalyst fine particles are not bonded to each other to form a large diameter transition metal catalyst fine particle. Nanocarbon materials with small size can be grown. The length of the nanocarbon material is proportional to the heating time in the hydrocarbon gas. According to the above method, a nanocarbon composite material composed of diamond fine particles and a plurality of nanocarbon materials having one ends fixed to the diamond fine particles can be synthesized.

By the way, the above synthesis is performed by using a fixed bed flow type synthesizer, placing diamond catalyst fine particles in a reaction tube in a container, and heating the hydrocarbon gas to the decomposition temperature while flowing the hydrocarbon gas through the reaction tube. And do it. However, there is a difference in the flow rate of the supplied hydrocarbon gas between the surface of the diamond catalyst fine particle on the side close to the container where the diamond catalyst fine particles are arranged and the surface on the far side, so that the three-dimensional Nanocarbon material does not grow uniformly in the direction.
On the other hand, marimo-like carbon, which is a nanocarbon composite material in which a plurality of nanocarbon materials 7 are grown in a spherical shape with diamond fine particles as nuclei, can be synthesized as follows.
FIG. 5 is a diagram showing a configuration of a fluidized gas phase synthesis apparatus for producing marimo-like carbon.
In the figure, a fluidized gas phase synthesis production apparatus 41 includes a vertically disposed reaction tank 43 containing diamond catalyst fine particles 42 and a gas 44 made of hydrocarbons provided respectively in the lower and upper parts of the reaction tank 43. From the introduction port 45 to introduce, the discharge port 46 to discharge the gas 45, the heating device 47 disposed so as to surround the reaction layer 43, and the filter 48 through which the diamond catalyst fine particles 42 do not pass and the gas 42 passes. It is configured. In addition, a mixing device 50 for mixing the reaction auxiliary gas and the dilution gas 49 with the gas 44 made of hydrocarbon is provided.
Using the fluidized gas phase synthesizer 41, marimo-like carbon is synthesized as follows (see Patent Document 2). That is, the diamond catalyst fine particles 42 are disposed on the filter 48. A gas 44 made of hydrocarbons is introduced from the introduction port 45 at a predetermined flow rate and discharged from the discharge port 46. The predetermined flow rate of the gas 46 is a flow rate at which the diamond catalyst fine particles 42 float in the reaction tank 43 and is stirred. If the reaction tank 43 is made of fused quartz, the state is confirmed with the naked eye. Set the flow rate. For example, it is preferable that the flow rate is such that the diamond catalyst fine particles 42 float in the reaction tank 43 and are stirred so as not to jump out from the discharge port 46.
According to this method, since the diamond catalyst fine particles 42 float and are stirred in the reaction tank 43, the catalytic reaction occurs evenly over the entire surface of the diamond catalyst fine particles. As a result, a plurality of nanocarbon materials are converted into diamond. Marimo-like carbon grown spherically with fine particles as nuclei can be synthesized. In addition, the length of the nanocarbon material is increased in proportion to the time to float and stir at a predetermined temperature, and the diameter of the produced marimo-like carbon increases, so the time to float and stir at the predetermined temperature is selected. By doing so, marimo-like carbon having a desired diameter can be synthesized.

  Next, the nanocarbon composite material is dispersed in a solvent to form a paste, which is applied to a porous electrode substrate such as carbon paper or carbon cloth, and fired to produce the fuel cell catalyst electrode of the present invention. To do.

Next, the manufacturing method of the membrane-electrode assembly for fuel cells of this invention is demonstrated.
The fuel cell membrane / electrode assembly of the present invention is obtained by overlapping the fuel cell catalyst electrode of the present invention and the hydrogen ion conductive polymer electrolyte membrane shown in FIG. To manufacture.
Further, as shown in FIG. 3B, when the fuel cell catalyst electrode of the present invention is used as an anode side catalyst electrode and a cathode side catalyst electrode, the present invention is provided on both sides of the hydrogen ion conductive solid electrolyte membrane, respectively. The catalyst layer surfaces of the catalyst electrode for a fuel cell of the invention are overlapped and joined by hot pressing.

Next, the manufacturing method of the fuel cell of this invention is demonstrated.
As shown in FIG. 4A, when the fuel cell catalyst electrode of the present invention is used as an anode side catalyst electrode, the hydrogen ion conductive polymer electrolyte membrane side of the fuel cell membrane / electrode assembly of the present invention is used. A conventional cathode-side catalyst electrode is joined to each other, separators are joined to the upper and lower surfaces of the joined body to form a single cell, and a plurality of the single cells are joined in series to produce the fuel cell of the present invention.
In addition, as shown in FIG. 4B, when the fuel cell catalyst electrode of the present invention is used as a cathode side catalyst electrode, the hydrogen ion conductive polymer electrolyte of the fuel cell membrane / electrode assembly of the present invention is used. A conventional anode-side catalyst electrode is joined to the membrane, a separator is joined to the upper and lower surfaces of the joined body to form a single cell, and a plurality of the single cells are joined in series to produce the fuel cell of the present invention.
As shown in FIG. 4C, when the fuel cell catalyst electrode of the present invention is used as an anode side catalyst electrode and a cathode side catalyst electrode, the upper and lower surfaces of the fuel cell membrane / electrode assembly of the present invention are used. Each of the separators is joined to form a single cell, and a plurality of the single cells are joined in series to produce the fuel cell of the present invention.

Example 1
Diamond catalyst fine particles were prepared by supporting 5 wt% of Co on diamond fine particles having a particle diameter of 15 to 100 nm, and the diamond catalyst fine particles were placed in a fixed bed flow type synthesizer. The synthesis temperature was 600 ° C., the methane gas flow rate was 20 ml / min, The synthesis was performed in a synthesis time of 60 minutes to obtain a nanocarbon composite material in which the nanocarbon material is a carbon nanotube.
Next, in a mixed solvent consisting of 4.8 g of this nanocarbon composite material, 11.4 g of a commercially available hydrogen ion conductive polymer electrolyte 21 wt% Nafion solution (registered trademark), 6.4 g of water, and 10.0 g of isopropanol A catalyst paste was prepared by stirring for 30 minutes using an ultrasonic homogenizer. This catalyst paste is referred to as catalyst paste A.
Moreover, the catalyst paste by a prior art was produced as follows. That is, 2.0 g of a commercially available platinum-supported carbon catalyst in which 30 wt% of a platinum catalyst is supported on carbon black fine particles having a particle diameter of about 10 nm, 5.0 g of a commercially available hydrogen ion conductive polymer electrolyte 21 wt% solution Nafion solution (registered trademark), A catalyst paste was prepared by stirring for 30 minutes using an ultrasonic homogenizer in a mixed solvent consisting of 11.0 g of water and 16.0 g of isopropanol. This catalyst paste is referred to as catalyst paste B.
Next, the prepared catalyst paste A was applied onto carbon paper (manufactured by E-Tek) at a thickness of 3 μm and fired to produce a fuel cell catalyst electrode of the present invention. This catalyst electrode for a fuel cell is referred to as catalyst electrode A. Further, the prepared catalyst paste B was applied onto carbon paper (manufactured by E-Tek) at a thickness of 3 μm and fired to produce a catalyst electrode for a comparative fuel cell of the prior art. This catalyst electrode for a fuel cell is referred to as catalyst electrode B.
Next, the catalyst electrode A and the catalyst electrode B are cut into the same area, and each of these catalyst electrodes is joined to a hydrogen ion conductive polymer electrolyte membrane (Nafion membrane, registered trademark) manufactured by DuPont. A battery membrane / electrode assembly was prepared. The joining was performed using a hot press under conditions of 140 ° C., 50 kg / cm ² , and 5 minutes. The membrane / electrode assembly for fuel cell using the catalyst electrode A is referred to as membrane / electrode assembly A, and the membrane / electrode assembly for fuel cell using the catalyst electrode B is referred to as membrane / electrode assembly B.
Next, the catalyst electrode B is joined to the solid electrolyte membrane side of the membrane / electrode assembly A, separators are joined to the upper and lower surfaces of the joined body, the fuel cell catalyst electrode A of the present invention is used on the anode side, and the cathode On the side, a fuel cell having a configuration using the catalyst electrode B of the prior art was prepared. This fuel cell is referred to as a fuel cell A.

(Example 2)
Only the catalyst electrode A was joined to the solid electrolyte membrane side of the membrane-electrode assembly B, the catalyst electrode A for the fuel cell of the present invention was used on the cathode side, and the conventional catalyst electrode B was used on the anode side. A fuel cell having a configuration different from that of Example 1 was prepared. This fuel cell is referred to as a fuel cell B.

(Example 3)
A fuel cell having a configuration different from that of Example 1 only in that the catalyst electrode A is joined to the solid electrolyte membrane side of the membrane-electrode assembly A, and the catalyst electrode A for the fuel cell of the present invention is used on both the anode side and the cathode side. It was created. This fuel cell is referred to as a fuel cell C.

Next, the power generation capacities of the fuel cells A, B, and C were measured. The power generation capacity was measured by supplying hydrogen gas that was humidified and heated at 80 ° C. so that the hydrogen flow rate was 1000 ml / min and the oxygen flow rate was 1000 ml / min, and the reaction was performed by supplying oxygen gas. The measurement was made by comparing the generated current per unit surface area of the catalyst layer when the load resistance was selected so that the electromotive force was 0.5 volt, that is, the generated current density.
FIG. 6 is a diagram illustrating measurement results of the power generation capacities of the fuel cells A, B, and C.
From the figure, it can be seen that the fuel cell C using the catalyst electrode A for fuel cells of the present invention on both the anode side and the cathode side has a power generation current density of 9 mA / cm ² , and the power generation current density of the fuel cell. Is limited by the smaller power generation current density on the anode side or on the cathode side, the anode side fuel cell catalyst electrode A of the present invention and the cathode side fuel cell catalyst electrode A of the present invention are respectively It can be seen that it has a generated current density of at least 9 mA / cm ² .
Also, from the figure, the power generation current density of the fuel cell A using the fuel cell catalyst electrode A of the present invention on the anode side and the prior art catalyst electrode B on the cathode side is larger than the power generation current density of the fuel cell C. Therefore, it can be seen that the power generation current density of the fuel cell C is limited by the anode side fuel cell catalyst electrode A of the present invention, and the size thereof is 20 mA / cm ² .
Also, from the figure, the power generation current density of the fuel cell B using the fuel cell catalyst electrode A of the present invention on the cathode side and the prior art catalyst electrode B on the anode side is smaller than the power generation current density of the fuel cell C. Therefore, it can be seen that the generated current density of the fuel cell B is limited by the cathode-side fuel cell catalyst electrode A of the present invention, and the size thereof is 10 mA / cm ² .
Thus, it can be seen that the catalyst electrode for a fuel cell of the present invention has a power generation capability on both the anode side and the cathode side, although no platinum catalyst is used. This result shows that a catalyst layer made of a nanocarbon composite material composed of diamond fine particles and a plurality of nanocarbon materials fixed at one end to the diamond fine particles has a catalytic action that decomposes hydrogen into hydrogen ions and electrons, and oxygen This is because it has a catalytic action in which water reacts with hydrogen ions and electrons to generate water.

As understood from the above description, the catalyst electrode for a fuel cell, the membrane / electrode assembly, and the fuel cell of the present invention have diamond fine particles used for the electrode catalyst layer and one end fixed to the diamond fine particles. A nanocarbon composite material composed of a plurality of nanocarbon materials has a catalytic action of decomposing hydrogen into hydrogen ions and electrons, and a catalytic action of reacting oxygen, hydrogen ions, and electrons to generate water. It can be used as a catalyst electrode for a battery or a membrane / electrode assembly.
Moreover, since a high-cost platinum group catalyst is not used, a low-cost fuel cell can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structure of the catalyst electrode for fuel cells of this invention, (a) A figure is a schematic cross section of a catalyst electrode for fuel cells, (b) A figure is a figure which shows a nano carbon composite material typically. . FIG. 5 is a diagram showing another configuration of the catalyst electrode for a fuel cell of the present invention, (a) a schematic cross-sectional view of the catalyst electrode for a fuel cell, and (b) a marimo which is one of the nanocarbon composite materials. It is a figure which shows a carbon-like carbon typically. It is a schematic cross section which shows the structure of the membrane electrode assembly for fuel cells of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing the configuration of a single cell of a fuel cell according to the present invention, wherein FIG. Is a single cell of the fuel cell of the present invention using the catalyst electrode for the fuel cell of the present invention on the cathode side, and (c) is the present invention of using the catalyst electrode for the fuel cell of the present invention on the anode side and the cathode side. 1 shows a single cell of the fuel cell. It is a figure which shows the structure of the apparatus for manufacturing a marimo-like carbon. It is a figure which shows the measurement result of the electric power generation capability of the fuel cell of this invention. It is a disassembled perspective view which shows the structural example of the single cell of a polymer electrolyte fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Catalyst electrode 2 for fuel cells of this invention Electrode base material 3 Catalyst layer 4 Nanocarbon composite material 6 Diamond fine particle 7 Nanocarbon material 7a The space | gap 8 between nanocarbon materials 9 Fuel electrode catalyst electrode 9 of the other structure of this invention Catalyst Layer 10 of Other Configuration of Invention Invention Marimo-like Carbon 21 Fuel Cell Membrane / Electrode Assembly 22 of the Present Invention Hydrogen Ion Conductive Solid Electrolyte Membrane 23 Fuel Cell Membrane / Electrode Assembly 31 Fuel Cell 32 of the Present Invention Fuel cell 33 of the present invention Fuel cell 41 of the present invention Fluidized gas phase synthesis device 42 Diamond catalyst fine particle 43 Reaction tank 44 Hydrocarbon gas 45 Inlet port 46 Outlet port 47 Heating device 48 Filter 49 Reaction auxiliary gas or dilution gas 50 Mixing device 60 Single cell 61 Anode separator 61a
62 Anode side catalyst electrode 62a Electrode base material 62b Catalyst layer 63 Hydrogen ion conductive solid electrolyte membrane 64 Cathode side catalyst electrode 64a Electrode base material 64b Catalyst layer 65 Cathode side separator 65a Reaction gas flow path

Claims (3)

A fuel cell catalyst electrode comprising an electrode substrate and a catalyst layer laminated on the electrode substrate surface, comprising diamond fine particles having a particle size of 1 μm or less and a plurality of nanocarbon materials having one ends fixed to the diamond fine particles A nanocarbon composite material is used as a catalyst, and a platinum group catalyst is not used, and the nanocarbon material of the nanocarbon composite material is any one of a carbon nanotube, a carbon nanofilament, a carbon nanofiber, and a carbon nanocoil, or The nanocarbon composite material is characterized in that a plurality of nanocarbon materials are marimo-like carbon fixed in a spherical shape with diamond fine particles as nuclei, and the nanocarbon composite material comprises: Diamond particles carrying transition metal particles distributed in islands on diamond particles Is synthesized by heating in a hydrocarbon gas, and the nanocarbon composite material is synthesized by floating and stirring diamond fine particles supporting transition metal fine particles in a hydrocarbon gas and heating them. The catalyst electrode for fuel cells characterized by these.   A fuel cell membrane / electrode assembly comprising the catalyst electrode for a fuel cell according to claim 1 and a hydrogen ion conductive solid polymer electrolyte membrane. A fuel cell comprising the fuel cell catalyst electrode according to claim 1.

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