JPH11217688A - Solid polymer electrolyte-catalyst composite electrode, water electrolyzing device and fuel battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slid polymer electrolyte-catalyst composite electrode with high electronic conductivity, furthermore to provide a water electrolytic cell improved in energy efficiency and to improve a fuel battery improved in working voltage characteristics. SOLUTION: The structure in which electronically conductive substance is carried on an ion conducting region in a solid polymer electrolyte domain of a porous solid polymer electrolyte-calalyst composite electrode contg. solid polymer electrolytes 2 and catalytic grains 3 is made. In the water electrolytic cell and a fuel battery, this electrode is used, and the structure in which a feeding body (collecting body) is in contact with the surface of the electrode is made.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte-catalyst composite electrode, a water electrolysis tank and a fuel cell using the same.

2. Description of the Related Art A solid polymer electrolyte-catalyst composite electrode used for a water electrolyzer, a fuel cell, and the like includes a solid polymer electrolyte and catalyst particles, and the catalyst particles are three-dimensionally distributed and a plurality of catalyst particles are contained therein. Is a porous electrode in which pores are formed, for example, water as a raw material of a water electrolysis tank, oxygen as an active material of a fuel cell, and hydrogen are mainly supplied into the electrode through the pores, The reaction proceeds with the three-layer interface formed by the catalyst and the solid polymer electrolyte in the electrode with the feed material or the active material. Such a solid polymer electrolyte-catalyst composite electrode includes, for example, a type consisting only of a solid polymer electrolyte 22 and catalyst particles 23 as shown in a sectional structural view of FIG. There is a type in which the PTFE particles 25 are further added thereto. Usually, in the former type, the pores 24 occupy about 10% or more of the electrode volume, and in the latter type, The ratio is getting bigger. For the type consisting of the solid polymer electrolyte and the catalyst particles only, for example, a paste in which the catalyst particles and the solid polymer electrolyte solution are kneaded is prepared and formed into a film (thickness: 3 to 30 μm) on the polymer film.
m), and then dried naturally. In this type, the solid polymer electrolyte also serves as a binder. Further, a type in which PTFE particles are added is, for example, a catalyst particle and a PT particle having a particle diameter of about 0.23 μm.
A paste is prepared by kneading the FE particle dispersion solution, and is formed into a film (thickness: 3 to 30 μm) on a polymer film.
It is manufactured by heating and drying so that the E particles work as a binder, further impregnating the membrane with a solid polymer electrolyte solution, and naturally drying, and PTFE particles mainly play a role as a binder. In any of the above cases, a solid polymer electrolyte solution obtained by dissolving a liquid having the same composition as the ion exchange membrane to be bonded later with an alcohol or the like is used, and as the catalyst particles, Metal or metal oxide catalyst particles, carbon particles, catalyst-carrying carbon and the like are used, and particles having a particle diameter of about 0.05 to 10 μm are often used.

Such a solid polymer electrolyte-catalyst composite electrode is formed as an ion exchange membrane-catalyst electrode assembly by, for example, bonding to both surfaces of an ion exchange membrane which is a solid polymer electrolyte membrane by a hot press method. Further, a power supply for power supply and current collection for the electrode (in the case of a fuel cell, a current collector for forming a gas diffusion layer, hereinafter referred to only as a current collector) is applied to the electrode surface. It is used as an electrode for a polymer electrolyte water electrolyzer and a polymer electrolyte fuel cell by being in contact with and being incorporated into a water electrolyzer and a fuel cell holder. In the case of a water electrolysis tank, the power supply (current collector) is used to supply power to the electrodes and at the same time to have a role of securing a flow path for raw water and generated oxygen and hydrogen. In order to have a role of securing a flow path for oxygen and hydrogen as active materials at the same time as transferring electrons with the electrodes, titanium,
A porous body made of a material such as carbon is often used.

[0003]

The solid polymer electrolyte-catalyst composite electrode can obtain good characteristics in a water electrolyzer and a fuel cell by: 1) having a wide electrode / electrolyte interface; Smooth supply of active material at the electrolyte interface and discharge of adult organisms 3) Good ion conduction to the electrode / electrolyte interface, especially good proton conduction 4) Good electron conduction to the electrode / electrolyte interface. Required. In particular, items 3) and 4) are very important items that greatly contribute to the internal resistance of the water electrolyzer and the fuel cell. In other words, proton conductivity,
If the electron conductivity is poor, the electrolysis voltage increases in the water electrolyzer, and the energy conversion efficiency decreases in the fuel cell, such as a decrease in its output. The formation of continuous solid electrolyte passages (electrolyte channels) in the electrode is essential for good proton conduction, and the formation of continuous catalyst particle passages (electron conduction channels) in the electrode is essential for good electron conduction. .

On the other hand, in the case of the type comprising only the solid polymer electrolyte and the catalyst particles, since the electrode is composed only of the solid polymer electrolyte and the catalyst particles, a sufficient amount of the solid is contained in the electrode. An electrolyte and a sufficient amount of catalyst particles can be filled, and good proton conduction and good electron conduction are expected. However, in practice, high proton conductivity is obtained, but electron conductivity is low. This is because when a paste is prepared by kneading the catalyst particles and the solid polymer electrolyte solution, a solid electrolyte film having no electron conduction is formed on the catalyst particles, and even when the film is formed, contact between the catalyst particles and the catalyst particles occurs. This is because the solid electrolyte remains at the interface and a continuous solid electrolyte passage (electrolyte channel) is formed, but the formation of a continuous catalyst particle passage (electron conduction channel) is hindered.

On the other hand, in the case of a type in which PTFE particles are added, a paste composed of catalyst particles and PTFE particles is formed into a film and then impregnated with a solid polymer electrolyte solution. Thus, the presence of the solid electrolyte can be prevented, and high electron conductivity can be expected by forming continuous catalyst particle passages (electron conduction channels). However, in practice, the expected electron conductivity cannot be obtained. This is because the particle size of PTFE, which functions as a binder, is often larger than the catalyst particle size, occupies a large volume in the electrode, and the electrode is not sufficiently filled with the catalyst particle, and This is because the absolute number of conduction channels is insufficient.

Therefore, in general, a solid polymer electrolyte-catalyst composite electrode is used as an ion exchange membrane-catalyst electrode assembly, and when used in a water electrolysis tank or a fuel cell, a dense and porous power feeder (current collector) is used. Use sintered titanium or fired carbon. These power supply bodies (current collectors) are made of titanium fibers or carbon fibers, and therefore have moderate irregularities due to these fibers on the surface. The fibers partially enter the inside of the electrode to form a macroscopic electron conduction channel, thereby improving the electron conductivity of the solid polymer electrolyte-catalyst composite electrode.

FIG. 14 is a cross-sectional view for explaining the structure of a solid polymer electrolyte-catalyst composite electrode in contact with a feeder made of sintered titanium made of titanium fiber, and FIG. FIG. 2B is a partially enlarged view of a cross section. As shown in the figure, this structure is composed of catalyst particles 23, PT
The feeder 27 is constituted by the FE particles 25 and the solid polymer electrolyte 22, and a feeder 27 is brought into contact with the electrode surface having a plurality of pores 24 by heating and pressing.
When a part of the fiber 28 constituting the electrode 7 enters the inside of the electrode, an electron conductive portion is formed by the feeder fiber 28 to the inside of the electrode, and the macro electron conductivity in the electrode is maintained. However, microscopically, electron conductivity is not sufficient due to the presence of the pores (voids) generated between the catalyst particles and the solid polymer electrolyte as described above, and the specific resistance of the electrode alone is, for example, 4.5 ×. 10 ⁴ mΩ · cm, and even if a macro electron conduction channel is formed by the feeder as described above, the actual specific resistance of the electrode as a whole is 2 ×.
It is only 10 ⁴ mΩ · cm, which is considerably larger than that of the solid polymer membrane (10 mΩ · cm). Therefore, when such an electrode is used in a water electrolysis device or a fuel cell, the water electrolysis device The resistance of this electrode occupies a considerable part of the internal resistance of fuel cells and fuel cells.

In view of the above, the present invention provides a solid polymer electrolyte-catalyst composite electrode having high electron conductivity, and a water electrolysis apparatus having improved energy efficiency and a fuel cell having improved operating voltage characteristics. The purpose is to provide.

[0009]

The solid polymer electrolyte-catalyst composite electrode of the present invention is a porous solid polymer electrolyte-catalyst composite electrode comprising a solid polymer electrolyte and catalyst particles, and comprises: It is characterized in that an electron conductive substance is supported in an ion conductive region in a polymer electrolyte layer. Conventionally, a solid electrolyte that has only played a role of forming an ion conductive passage (electrolyte channel) is used. The present invention is intended to solve the above-mentioned problems of the conventional solid polymer electrolyte-catalyst composite electrode by simultaneously having a role of an electron conduction channel (electron conduction channel). That is, by supporting an electron conductive substance in the ion conductive region in the solid polymer electrolyte layer, the solid polymer electrolyte is provided with ion conductivity and electron conductivity at the same time. Improve conductivity.

The solid polymer electrolyte is preferably made of an ion-exchange resin, and among them, a cation-type polymer electrolyte having a low internal resistance is preferable. Particularly, when the solid polymer electrolyte is used for a water electrolysis apparatus or a fuel cell, For example, proton type ones such as perfluorosulfonic acid type solid polymer electrolyte and styrene-divinylbenzene type sulfonic acid type solid polymer electrolyte are more preferable.

[0011] Further, the water electrolysis tank of the present invention comprises a porous solid polymer electrolyte-catalyst composite electrode comprising a solid polymer electrolyte in which an ion conductive region carries an electron conductive substance and catalyst particles; And a power supply body in contact with the surface of the electrode.

Further, the fuel cell of the present invention comprises a porous solid polymer electrolyte-catalyst composite electrode comprising a solid polymer electrolyte in which an ion conductive region carries an electron conductive substance and catalyst particles; A current collector for forming a gas diffusion layer in contact with the surface of the electrode.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The solid polymer electrolyte-catalyst composite electrode of the present invention comprises a solid polymer electrolyte and catalyst particles as main components. It is distributed with a dimensional spread and further has a large number of pores in the electrode, and an electron conductive substance is supported in the ion conductive region in the solid polymer electrolyte layer. After preparing a porous solid polymer electrolyte-catalyst composite electrode body comprising a solid polymer electrolyte and catalyst particles by a conventional method in the form of a film, it is present in the solid polymer electrolyte layer in the electrode body. Electron conductive material is applied to the ion conduction region by electroless plating (for example, Eiichi Toriyo, Japanese Patent Publication No. 58-47471, Raymond Liu, J. Electroch
em. Soc., 139, 15 (1992)). As described above, the method of supporting the electron conductive substance after the production of the electrode main body is simple and preferable. In addition, at the time of carrying the electron conductive substance, it is also possible to simultaneously carry the electron conductive substance on the surface inside the electrode pores, or to form a layer made of the electron conductive substance on the surface of the electrode body, It is preferable that the electron conductive material is also carried on the surface in the electrode pores, so that the electron conductivity is further improved. Further, it is also preferable to form a layer made of the electron conductive material on the surface of the electrode body, so that the power supply and distribution properties are good. Is more preferable.

In the case where the solid polymer electrolyte is a perfluorosulfonic acid type solid polymer electrolyte, the proton conduction shows a spherical (about 40 Å diameter) cluster in which hydrophilic exchange groups are assembled together with water. It is believed that they are dispersed in a hydrophobic fluorocarbon matrix, and are formed through a three-dimensionally formed cluster network connected by channels of about 10 angstroms. (For example, research on ionic conduction and the like has been performed for a long time, and SCYeo and A. Eisenberg. J. App.
y.Polym.Sci., 21,875 (1997), TDGierk.Paper 483
presented at The Electrochemical Society Meetin
g, Atlanta, Georgia, October 9-14, 1997 and HLYeger and
A.Steck, J. Electrochem. Soc., 128, 1880 (1981) and Z.
Ogumi and T. Kuroe, J. Electrochem. Soc., 132, 2601 (19
85). From this fact, the electron conductive substance is supported in the solid polymer electrolyte cluster network of the solid polymer electrolyte-catalyst composite electrode, thereby forming a microscopic, three-dimensional electron conduction channel in the electrode. As a result, the electron conductivity of the electrode is greatly improved, and good results are obtained.

As the electron conductive substance, various substances such as metals, conductive metal oxides, and conductive polymers can be used, and preferably, they have excellent corrosion resistance and can function as a catalyst. Pt, Ir, Ru, Rh, Pd
Platinum group metals such as IrO ₂ , Ir ₂ O ₃ , RuO ₂ , Ru ₂
It is preferable to use a platinum group metal oxide such as O ₃ , RhO ₂ , Rh ₂ O ₃ , and PdO. Further, gold or a carbon material may be used because of its excellent corrosion resistance. These substances can be carried by, for example, an adsorption reduction method in which metal ions to be electron conductive substances are adsorbed to a solid polymer electrolyte and then reduced. In the case of the platinum group metal, the concentration of the boron borohydride solution is increased by using an electroless plating method in which the platinum group metal ion is adsorbed on the solid polymer electrolyte and then treated with an aqueous borohydride solution. Alternatively, a larger amount of platinum group metal ions adsorbed on the solid polymer electrolyte can be supported on the cluster network portion of the solid polymer electrolyte while leaving the metal as a metal (for example, P. Millet, J. Appl. Electrochem., 25, 233). (199
5) Reference). In this case, in particular, the concentration of the borohydride aqueous solution is set to 2
When the content is at least 10 ^-1 mol / l, most of the platinum group metal can be deposited on the cluster network portion, and it works more effectively by improving the microscopic electron conductivity of the electrode. As the catalyst particles contained in the electrode, carbon particles, platinum group metal particles such as palladium, platinum and ruthenium, platinum group metal oxide particles, carbon particles carrying a catalyst element, and the like can be used. Further, if necessary, auxiliary components such as polytetrafluoroethylene (PTFE) particles may be added.

The solid polymer electrolyte-catalyst composite electrode of the present invention can be used for a salt electrolysis apparatus, a water electrolyzer, a fuel cell, and the like. Are abutted. For example, the electrode of the present invention is joined to both sides of an ion exchange membrane which is a solid polymer electrolyte membrane, and a power feeder is brought into contact with the electrode surface.
In this case, the power supply body used may be a porous one so as not to hinder the supply of the reactant, for example, a conventionally used porous sintered titanium, calcined carbon, etc. The one having the above opening diameter is preferable, and the one in contact with the electrode surface is preferably flat so that a pinhole is not formed by the unevenness of the power supply body.The material is titanium, platinum-plated or gold-plated stainless steel, Titanium and the like are preferred.

In the case where a layer made of an electron conductive material is formed on the electrode surface, an electron conductive material layer is formed on both surfaces of the electrode film, and not only on the contact surface of the power feeder but also on the above-mentioned ion exchange membrane. An electron conductive material layer may be provided on the surface. The electron conductive material layer may be formed only on the contact surface with the ion exchange membrane. When used as a water electrolyzer, platinum, iridium, platinum-iridium alloy, ruthenium, platinum-
Ruthenium alloys are preferred.

When the electrode of the present invention is used in a fuel cell, a current collector for forming a gas diffusion layer is brought into contact with the electrode surface of the present invention in the same manner as described above. For example, the electrode of the present invention is joined to both sides of an ion exchange membrane which is a solid polymer electrolyte membrane, and a current collector is brought into contact with the electrode surface.
In this case, the current collector used may be a porous current collector that does not hinder the supply of the reactants, such as conventionally used porous sintered titanium and calcined carbon. The one having an opening diameter of 100 μm or more is preferable, and the one in contact with the electrode surface is preferably flat so that a pinhole is not formed by the unevenness of the current collector, and the material is titanium, platinum plating or gold plating. Stainless steel, titanium and the like are preferred. Also,
When forming a layer made of an electron conductive material on the electrode surface,
An electron conductive material layer may be formed on both surfaces of the electrode film so that the electron conductive material layer is provided not only on the contact surface of the current collector but also on the bonding surface with the ion exchange membrane. The electron conductive material layer may be formed only on the contact surface with the ion exchange membrane. When used as a fuel cell, the catalyst material is preferably platinum or a platinum-ruthenium alloy.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Example 1 A solid polymer electrolyte-catalyst composite electrode and a water electrolysis tank using the same were produced by the following procedure.

Iridium particles and a solid polymer electrolyte solution (Nafion solution, manufactured by Aldrich) are kneaded to form a paste, and then a film is formed on a film of ethylene tetrafluoride-6-propylene copolymer (FEP). And dried naturally. In this state, the weight ratio of the iridium particles to the solid polymer electrolyte solution is 8:92.

Next, the catalyst layer formed on the FEP film was immersed in a [Pd (NH ₃ ) ₄ ] Cl ₂ solution for 2 hours to be adsorbed on the cluster network portion of the solid polymer electrolyte. Hydrogen reduction was performed at 〜120 ° C. under a pressure of 30 kg / cm 2, and palladium (Pd) was supported on the cluster network. The supported amount of palladium was about 2 mg per 1 g of the solid polymer electrolyte solution. [See Tetsuo Sakai, Kei Takenaka, Osaka Institute of Technology, 36, 10 (1985)].

The solid polymer electrolyte-catalyst composite electrode obtained by the above operation is joined to both surfaces of a perfluorosulfonic acid type ion exchange membrane (Nafion-115, manufactured by DuPont) by hot pressing at 130 ° C. Thus, an ion exchange membrane-catalyst electrode assembly was obtained. This ion exchange membrane-catalyst electrode assembly was mounted on a water electrolysis tank holder. For comparison, the same structure as the ion-exchange membrane-catalyst electrode assembly of this example was attached to the same water electrolysis tank holder except that the operation of supporting palladium on the cluster network was not performed. The IV characteristics of the water electrolysis tank were measured. The result is shown in FIG.

From the figure, it can be seen that the characteristics of the water electrolyzer using the solid polymer electrolyte-catalyst composite electrode obtained by the present invention are much superior to those of the conventional one, and the main factor is that
From the slope of the −V curve, it can be seen that this is due to the reduction of the internal resistance inside the electrode.

(Example 2) Example electrode A: After kneading iridium particles and a solid polymer electrolyte solution (Nafion solution, manufactured by Altrich Co., Ltd.) to form a paste,
A film was formed on an EP (ethylene tetrafluoride / propylene hexafluoride copolymer) film and air-dried, thereby producing a solid polymer electrolyte-catalyst composite electrode body. The electrode plane shape is 32
mm × 32 mm square, 10 μm thick, the weight ratio of iridium particles to solid polymer electrolyte in this state is 75:25, and the iridium content per unit area is 1.5 mg / cm ^{2 of} electrode. Met. Then, the solid polymer electrolyte-catalyst composite electrode body formed on the FEP film is immersed in a [Pd (NH ₃ ) ₄ ] Cl ₂ solution for 2 hours, and [Pd ( NH ₃ ) ₄ ] ²⁺
This is reduced with hydrogen at 00 to 120 ° C. under a pressure of 30 kg / cm 2, and palladium (P
d) was carried. The supported amount of palladium was about 5 mg per 1 g of the solid polymer electrolyte.

The electrode manufactured by the above steps is referred to as an example electrode A.

FIG. 1 is a sectional view for explaining the structure of the electrode A of the embodiment. As shown in the figure, the electrode of this embodiment has a pore 4 (having a pore diameter of approximately 10 μm to 20 μm) including a solid polymer electrolyte 2 and catalyst particles 3 (average particle diameter of 5 μm) which are iridium particles. A porous solid polymer electrolyte-catalyst composite electrode having a large number of palladium particles in a cluster network inside the solid polymer electrolyte 2 (channel diameter). (About 50 angstroms).

Example Electrode B First, iridium particles and a solid polymer electrolyte solution (Nafion solution, manufactured by Altrich Co., Ltd.) were kneaded to form a paste.
A film was formed on an FEP film and air-dried, thereby producing a solid polymer electrolyte-catalyst composite electrode body. The electrode plane shape is a square of 32 mm × 32 mm, the thickness is 10 μm,
In this state, the weight ratio of the iridium particles to the solid polymer electrolyte was 75:25, and the iridium content per unit area was 1.5 mg per 1 cm ² of the electrode.

Next, this solid polymer electrolyte-catalyst composite electrode body formed on the FEP film was
[Pt (NH ₃ ) ₄ ] Cl ₂ solution 1 containing mg of Pt
Immersion for 12 hours in the polymer electrolyte part [Pt
(NH ₃ ) ₄ ] After adsorbing ²⁺ ions, 60 ° C., 4 × 1
It was reduced to at NaBH ₄ aqueous solution 0 ^-1 mol / l.

Further, the solid polymer electrolyte-catalyst composite electrode main body was placed on both surfaces of a perfluorosulfonic acid type ion exchange membrane (Nafion-112, manufactured by DuPont).
Bonding was performed by hot pressing at 0 ° C. to produce an ion exchange membrane-catalyst electrode assembly, and this ion exchange membrane-catalyst electrode body assembly was mounted on a holder shown in FIG.
5% H ₂ PtCl ₆ aqueous solution _{1ml, 0.75% N 2 H 4} · 2
A Pt plating solution consisting of 1 ml of an aqueous HCl solution and 8 ml of water was put therein, and left standing for 12 hours in an aqueous solution at 40 ° C., whereby the solid polymer electrolyte-catalyst composite electrode according to the present invention and the ion exchange membrane were joined. A membrane-catalyst electrode assembly was prepared. This electrode is referred to as Example electrode B. In addition,
In FIG. 15, 29 indicates an ion exchange membrane catalyst electrode assembly, 30 indicates a holder tank, and 31 indicates packing.
The electrode manufactured through the above steps is referred to as an example electrode B.

FIG. 2 is a sectional view for explaining the structure of the electrode B of the embodiment. As shown in the figure, the electrode of this embodiment has a pore 4 (having a pore diameter of approximately 10 μm to 20 μm) including a solid polymer electrolyte 2 and catalyst particles 3 (average particle diameter of 5 μm) which are iridium particles. A solid-state polymer electrolyte-catalyst composite electrode having a large number of platinum-conducting channels formed in the solid polymer electrolyte 2 by supporting platinum in a cluster network.
(A channel diameter of about 50 angstroms) and a platinum layer 6 formed on the inner surface of the pores 4 in the electrode and on the surface of the electrode to have a structure in which platinum, which is an electron conductive substance, is supported. This electrode is joined to the ion exchange membrane 7. The platinum layer 6 has a thickness of about 0.5
It is a porous film consisting of a collection of fine platinum particles of μm. In addition, the platinum layer 6 is formed on the electrode surface and the inner surface of the pores 4.
It is also formed on the surface.

In the present electrode, the macroscopic electron conductivity of the electrode is ensured by the platinum layer 6 even if the feeder does not enter the electrode as in the conventional case. Channels are formed, and the connection on the electron conduction between the catalyst particles, which was conventionally weak in electrical connection, is improved.

Comparative electrode C: Iridium particles and a solid polymer electrolyte solution (Nafion solution, manufactured by Altrich Co., Ltd.) were kneaded to form a paste.
A film was formed on an EP film and air-dried, whereby a solid polymer electrolyte-catalyst composite electrode was prepared. This electrode is referred to as reference electrode C. The planar shape of the comparative electrode C is 32 mm x 32 m
m, the thickness is 10 μm, the weight ratio of iridium particles to the solid polymer electrolyte in this state is 75:25, and the iridium content per unit area is the electrode 1c.
1.5 mg per m ² . The comparative electrode C has the same structure as the example electrodes A and B except that no platinum or palladium electron conduction channel is formed.

When the film resistances of the electrodes A and B and the comparative electrode C were measured, the electrode A of the example was 0.4 × 10 ⁴ mΩ ·
cm, Example electrode B: 0.2 × 10 ⁴ mΩ · cm, Comparative electrode C: 4.5 × 10 ⁴ mΩ · cm.

Water Electrolyzer A water electrolyzer having the following structure was prepared using the electrodes A and B and the comparative electrode C. Example electrode A and comparative electrode C
These were placed on both surfaces of a perfluorosulfonic acid type ion exchange membrane (Dafon, Nafion-112).
After bonding by a hot press at 0 ° C. to produce an ion exchange membrane-catalyst electrode assembly, the assembly was used in a water electrolysis cell. Example electrode B was assembled in a water electrolysis tank using an ion exchange membrane-catalyst electrode assembly in which the above example electrode B and the ion exchange membrane were joined.

FIG. 3 is a schematic structural view showing the structure of this water electrolysis tank. As shown in the figure, in the present water electrolysis tank, a feeder 9 is brought into contact with an electrode 8 of an ion-exchange membrane-catalyst electrode assembly in which electrodes 8 are joined to both surfaces of an ion-exchange membrane 7. And a titanium anode plate 10 and a titanium cathode plate 11 are pressed against them. The power supply 9 is composed of a titanium plate (dotted line in the figure) and expanded titanium (triangular wave-shaped line in the figure). The titanium plate is a 0.15 mm-thick titanium flat plate as shown in FIG. .7 × 0.95P × 60 ° staggered hole processing by photo-etching (opening ratio 49%), both sides plated with 0.15μm platinum, on which two expanded titanium layers are laminated. It is a thing. In this structure, the titanium plate having a flat surface is configured to contact the surface of the electrode 8 bonded to the ion exchange membrane 7, so that the electrode contact surface of the power feeder is flat and has no irregularities, which is different from the conventional structure. Little penetration of the feeder into the electrodes as would occur.

FIG. 5 shows the current-voltage characteristics of these water electrolysis tanks. In the figure, the curve A is the one using the example electrode A, B is the one using the example electrode B, C is the one using the comparison electrode C, D is the one using the comparison electrode C, and the feeder is porous. This shows what was made of sintered titanium. The titanium fiber sintered plate has a fiber diameter of about 50 μm, a pore diameter of about 50 μm to 100 μm, and a porosity of about 7 μm.
0% and a thickness of about 1 mm were used.

As can be seen from FIG.
It is superior to the characteristics of a water electrolysis tank using a comparative electrode C using the same flat photo-etching feeder, and has a low electrolysis voltage and good energy conversion efficiency. In addition, the characteristics are the same as those of D using a sintered plate of titanium fiber. this is,
The specific resistance of the electrode is reduced by the Pd micro-electron conduction channel formed in the cluster network portion in the electrode according to the present embodiment, and even if a feeder having a flat contact surface with the electrode is used, electrons can reach inside the electrode. This is because the exchange was performed and the resistance of the entire water electrolysis tank was kept low.

Further, the electrode using the electrode B of the embodiment is superior to the electrode D using the sintered plate of titanium fiber, and has a low electrolytic voltage and good energy conversion efficiency.
This is because not only the above-mentioned enhancement of the micro-electron conduction of the electrode (in this case, by the micro-electron conduction channel of Pt), but also the macro-electron conduction of the electrode by the platinum layer formed on the electrode surface layer and the inner surface of the pores. This is due to a synergistic effect due to the improvement in microelectronic conduction.

Example 3 A solid polymer electrolyte-catalyst composite electrode and a fuel cell using the same were produced by the following procedure.

After kneading a carbon powder carrying 30 wt% of platinum and a PTFE dispersion solution to form a paste,
After forming a film on a P film, it was dried by heating at 120 ° C. for 2 hours.

After natural cooling, a perfluorosulfonic acid type polymer electrolyte (Nafion solution, manufactured by Aldrich) was sprayed, impregnated, and air-dried. In this state, the weight ratio of platinum-supported carbon, PTFE, and solid polymer electrolyte is
60:22:18.

The catalyst layer formed on the FEP film was immersed in a [Pd (NH ₃ ) ₄ ] Cl ₂ solution for 2 hours to be adsorbed on the cluster network portion of the solid polymer electrolyte. Under a pressure of 30 kg / cm
After hydrogen reduction, palladium (Pd) was supported on the cluster network. The supported amount of palladium was about 2 mg per 1 g of the solid polymer electrolyte solution.

The solid polymer electrolyte-catalyst composite electrode obtained by the above operation was joined to both surfaces of a perfluorosulfonic acid type ion exchange membrane (Nafion-115, manufactured by DuPont) by hot pressing at 130 ° C. Thus, an ion exchange membrane-catalyst electrode assembly was obtained. Porous carbon paper, which had been subjected to a water-repellent treatment to serve as a gas diffusion layer, was joined to both outer surfaces of the ion-exchange membrane-catalyst electrode assembly by a hot press in the same manner, and mounted on a fuel cell holder. Also, for comparison,
The same structure as the ion-exchange membrane-catalyst electrode assembly of this example was mounted on a similar fuel cell holder except that the palladium loading operation on the cluster network was not performed, and the IV characteristics of both fuel cells were measured. Was measured. The result is shown in FIG.

As can be seen from the figure, the characteristics of the fuel cell using the solid polymer electrolyte-catalyst composite electrode obtained by the present invention are much superior to those of the conventional fuel cell.
From the slope of the −V curve, it can be seen that this is due to the reduction of the internal resistance inside the electrode.

(Example 4) Example electrode E First, carbon powder carrying 30 wt% of platinum and PTF
The E particle dispersion was kneaded to form a paste, and then formed on a tetrafluoroethylene-6-fluorofluoropropylene copolymer (FEP) film, followed by heating and drying at 120 ° C for 2 hours. Then, after natural cooling, a perfluorosulfonic acid type polymer electrolyte (Aldrich, N
afion solution) was sprinkled, impregnated, and air-dried to prepare a solid polymer electrolyte-catalyst composite electrode body.
The electrode has a square shape of 32 mm × 32 mm and a thickness of 10 μm. In this state, platinum-supported carbon, PTFE,
The weight ratio of the solid polymer electrolyte was 60:22:18, and the platinum content per unit area was 0.1 mg / cm ² of the electrode.

Then, the solid polymer electrolyte-catalyst composite electrode body formed on the FEP film was replaced with [Pd (N
H _{3) 4]} Cl ₂ solution was immersed for 2 hours, after which the solid polymer in the cluster network of electrolyte [Pd (NH _{3) 4]} ²⁺ was adsorbed, 100 to 120 ° C., a pressure of 30kg / C〓 This was hydrogen-reduced below, and palladium (Pd) was supported on the cluster network. The supported amount of palladium was about 5 mg per 1 g of the solid polymer electrolyte.

The electrode manufactured by the above steps is referred to as an example electrode E.

FIG. 6 is a sectional view for explaining the structure of the electrode E of the embodiment. As shown in the figure, the electrode of the present embodiment is composed of a solid polymer electrolyte 2 and catalyst particles 13 (particle diameter 0.21 μm or less) composed of platinum-supported carbon powder and PTFE.
Pores 4 comprising particles 14 (average particle diameter 0.5 μm)
A porous solid polymer electrolyte-catalyst composite electrode having a large number of pores (having a pore diameter in a range of approximately 5 μm to 20 μm), wherein palladium is formed by supporting palladium in a cluster network inside the solid polymer electrolyte 2. The electron conduction channel 1 (having a channel diameter of about 50 Å) is formed.

Example electrode F The example electrode E was used as an electrode matrix, and was used as a perfluorosulfonic acid type ion exchange membrane (Nafio, manufactured by DuPont).
n-112) by hot pressing at 130 ° C. to produce an ion-exchange membrane-catalyst electrode matrix assembly, and mounting the ion-exchange membrane-catalyst electrode matrix assembly on the holder shown in FIG. A Pt plating solution consisting of 1 ml of a 2.5% H ₂ PtCl ₆ aqueous solution, 1 ml of a 0.75% N ₂ H ₄ .2HCl aqueous solution and 8 ml of water was put on both sides thereof, and left standing at 40 ° C. aqueous solution for 12 hours. Then, an ion exchange membrane-catalyst electrode assembly in which the solid polymer electrolyte-catalyst composite electrode according to the present invention and the ion exchange membrane were bonded was produced. This electrode is referred to as Example electrode F.

FIG. 7 is a sectional view for explaining the structure of the ion-exchange membrane-catalyst electrode assembly of the present example in which the electrode F of the embodiment and the ion-exchange membrane are joined. As shown in the figure, the electrode of this embodiment is composed of a solid polymer electrolyte 2 and catalyst particles 13 (particle diameter 0.21 μm or less) composed of platinum-supporting carbon powder and PTFE particles 14 (average particle diameter 0.5 μm). A solid polymer electrolyte-catalyst composite electrode having a large number of pores having a pore diameter in the range of approximately 5 μm to 20 μm, wherein platinum is contained in the solid polymer electrolyte 2 in the cluster network. An electron conduction channel 1 (channel diameter of about 50 angstroms) of platinum formed by being carried is formed, and a platinum layer 1 is formed on the inner surface of the pores 4 in the electrode and on the surface of the electrode.
By forming No. 5, a structure in which platinum which is an electron conductive substance is supported is obtained. The platinum layer 15 is a porous film having a thickness of about 1 μm and formed by collecting fine platinum particles. The platinum layer 15 is formed between the electrode surface and the pores 4.
It is formed on the inner surface and is formed not only on the surface of the solid polymer electrolyte 2 but also on the surface of the catalyst particles 13. This electrode is joined to the ion exchange membrane 7.

Comparative electrode G A carbon powder carrying 30 wt% of platinum and a PTFE dispersion were kneaded to form a paste, and then a film was formed on an ethylene tetrafluoride-6-fluorofluoropropylene copolymer (FEP) film. After that, 120
It was dried by heating at ℃ for 2 hours. Then, after natural cooling, a perfluorosulfonic acid type polymer electrolyte (Alfrich, Nafion solution)
Was sprayed, impregnated, and air-dried, thereby producing a solid polymer electrolyte-catalyst composite electrode body. The planar shape of the electrode is a square of 32 mm × 32 mm, the thickness is 10 μm, and the weight ratio of platinum-supported carbon, PTFE, and solid polymer electrolyte in this state is 60:22:18, and the platinum content per unit area Is 0.1 mg per cm ^{2 of} electrode
Met. The comparative electrode G has the same structure as the example electrodes E and F, except that no platinum or palladium electron conduction channel is formed.

When the film resistances of the electrodes E and F and the comparative electrode G were measured, the electrode E of the example was 2.5 × 10 ⁴ mΩ ·
cm, Example electrode F: 2.0 × 10 ⁴ mΩ · cm, Comparative electrode G: 7.5 × 10 ⁴ mΩ · cm.

Fuel Cell A fuel cell having the following structure was manufactured using the electrodes E and F and the comparative electrode G. Example electrode E and comparative electrode G were bonded to both surfaces of a perfluorosulfonic acid-type ion exchange membrane (Nafion-112, manufactured by DuPont) by hot pressing at 130 ° C. to obtain an ion exchange membrane-catalyst electrode. After the assembly was manufactured, it was used in a fuel cell. Example electrode F was assembled in a fuel cell using an ion exchange membrane-catalyst electrode assembly in which the above example electrode F and the ion exchange membrane were bonded.

FIG. 8 is a schematic structural view showing the structure of this fuel cell. As shown in the figure, the present fuel cell includes a current collector 18 which forms a gas diffusion layer on an electrode 17 of an ion exchange membrane-catalyst electrode assembly in which electrodes 17 are bonded to both surfaces of an ion exchange membrane 16. And a packing 21 is disposed around the graphite positive electrode plate 19 and the graphite negative electrode plate 20 under pressure. Current collector 1
Numeral 8 is composed of a titanium plate (dotted line in the figure) and expanded titanium (triangular wave-shaped line in the figure). The titanium plate is a 0.15 mm-thick titanium plate as shown in FIG.
0.7 × 0.95P × 60 ° zigzag processing with Photo Etching
(Opening ratio: 49%) Platinum plating of 0.15 μm on both surfaces, on which two expanded titanium layers are laminated. In this structure, the titanium plate having a flat surface is configured to be in contact with the surface of the electrode 17 bonded to the ion-exchange membrane 16, so that the electrode contact surface of the current collector is flat and has no irregularities. Little penetration of the current collector into the electrode as can be seen.

FIG. 9 shows current-voltage characteristics of these fuel cells. In the figure, the curve E is the one using the example electrode E, F is the one using the example electrode F, G is the one using the comparison electrode G, H is the one using the comparison electrode G, and the current collector is made water-repellent. A baked carbon paper treated and joined by hot pressing is shown. The calcined carbon paper used had a fiber diameter of about 10 μm, a pore diameter of about 50 μm to 100 μm, a porosity of about 70%, and a thickness of about 1 mm.

As can be seen from the figure, the electrode using the embodiment electrode E is
It is superior to the characteristics of a fuel cell using a comparative electrode G using the same flat photo-etched current collector, has a small decrease in operating voltage, and uses fired carbon paper H
It is equivalent to the characteristic of This is because palladium (Pd) formed in the cluster network portion in the electrode of the present embodiment
The micro-electron conduction channel reduces the specific resistance of the electrode, and even if a current collector with a flat contact surface with the electrode is used, electrons can be transferred even inside the electrode, keeping the overall resistance of the water electrolysis tank low. It depends.

Further, the electrode using the electrode F of the embodiment is superior to the electrode H using the fired carbon paper, and the operating voltage is hardly reduced. This is due not only to the improvement in the microelectron conduction of the electrode described above, but also to the synergistic effect due to the improvement in macroelectron conduction and micro-electron proper electron conduction of the electrode due to the platinum layer formed on the electrode surface layer and on the inner surface of the pores. It is due to.

[0059]

According to the solid polymer electrolyte-catalyst composite electrode of the present invention, a solid polymer electrolyte-catalyst composite electrode having high electron conductivity and low resistance can be obtained. It is possible to reduce the electrolysis voltage and improve the energy efficiency, and it is possible to increase the extraction current while suppressing the decrease in the operating voltage by using the fuel cell. Furthermore, since a sufficient power supply can be performed using a power supply (current collector) such as sintered titanium or calcined carbon without penetrating the power supply (current collector) into the electrode, a power supply (collector) having a flat surface is provided. This makes it possible to prevent the occurrence of pinholes when the ion exchange membrane is made thinner, thereby improving energy conversion efficiency and greatly improving safety. Further, sufficient power supply is possible without using a power supply body (current collector) having a dense structure.

According to the water electrolysis tank of the present invention, the electrolysis voltage can be reduced and the energy conversion efficiency can be improved. In addition, for example, when porous sintered titanium having a dense structure or the like is used as a power feeder, a high water pressure is required to supply water to the electrodes, and a device for supplying water such as a high-pressure pump becomes large-scale. Although there was a problem, in the water electrolysis tank of the present invention,
By using a coarse power feeder such as coarse expanded Ti or photo-etched Ti as a power feeder, the pressure of water supplied to the electrodes in the water electrolysis tank can be reduced, and a small system as a whole can be constructed without using a high-pressure pump. .

According to the fuel cell of the present invention, the current can be increased while suppressing the decrease in the operating voltage, and the output can be increased. In addition, for example, when porous calcined carbon having a dense structure is used as a current collector, the thickness of the current collector is usually 0.5 mm to 1.0 mm, so that diffusion of oxygen or hydrogen of the supplied fuel to the electrode is smooth. In addition, there is a problem that water of the product stays in the current collector, further inhibiting the diffusion of the supplied fuel to the electrode. By using a coarse current collector such as expanded Ti or photo-etched Ti,
The gas can be smoothly diffused in the fuel cell, the product water can be prevented from staying, and the energy conversion efficiency can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of an example electrode A.

FIG. 2 is a cross-sectional view illustrating a structure of an ion-exchange membrane-catalyst electrode assembly of the present example in which an electrode B of an example and an ion-exchange membrane are joined.

FIG. 3 is a schematic structural view showing a structure of a water electrolysis tank.

FIG. 4 is a diagram showing a zigzag hole processing of the titanium plate 4;

FIG. 5 is a diagram showing current-voltage characteristics of a water electrolysis tank.

FIG. 6 is a cross-sectional view illustrating a structure of an example electrode E.

FIG. 7 is a cross-sectional view illustrating the structure of an ion-exchange membrane-catalyst electrode assembly of the present example in which the electrode F of the example and the ion-exchange membrane are joined.

FIG. 8 is a schematic structural view showing the structure of a fuel cell.

FIG. 9 is a diagram showing current-voltage characteristics of a fuel cell.

FIG. 10 is a diagram showing current-voltage characteristics of a water electrolysis tank.

FIG. 11 is a diagram showing current-voltage characteristics of a fuel cell.

FIG. 12 is a sectional structural view of a conventional electrode.

FIG. 13 is a sectional structural view of a conventional electrode.

FIG. 14 is a cross-sectional view illustrating the structure of a solid polymer electrolyte-catalyst composite electrode in contact with a feeder made of sintered titanium.

FIG. 15 is a structural view of a holder for plating.

[Explanation of symbols]

 1,5 Electron conduction channel 2,22 Solid polymer electrolyte 3,13,23 Catalyst particles 4,24 Pores 6,15 Platinum layer 7,16 Ion exchange membrane 8,17,26 Electrode 9 Feeder 18 Current collector 10 Anode plate 11 Cathode plate 11 Platinum-supported carbon particles 14, 25 PTFE particles 19 Positive plate 20 Negative plate

Claims (4)

[Claims] 1. A porous solid polymer electrolyte-catalyst composite electrode comprising a solid polymer electrolyte and catalyst particles,
A solid polymer electrolyte-catalyst composite electrode, wherein an electron conductive substance is supported in an ion conductive region in the solid polymer electrolyte layer. 2. The solid polymer electrolyte is a perfluorosulfonic acid type solid polymer electrolyte, wherein an electron conductive substance is supported on a cluster network portion in the solid polymer electrolyte layer. The polymer electrolyte according to claim 1,
Catalyst composite electrode. 3. A porous solid polymer electrolyte-catalyst composite electrode comprising a solid polymer electrolyte in which an electron conductive substance is supported in an ion conduction region and catalyst particles; A water electrolysis tank, comprising: 4. A porous solid polymer electrolyte-catalyst composite electrode comprising a solid polymer electrolyte in which an ion conductive region carries an electron conductive substance and catalyst particles, and a porous solid polymer electrolyte-catalyst composite electrode which is in contact with the surface of the electrode. And a current collector forming a gas diffusion layer.