JP2001073178A - Electrode film joined body and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode film joined body of a low cost which is good in an adhesive property and lessens an increase of electrolytic voltage even if electrolysis is continued for a long time regardless of electrolytic temperature and a process for producing the same. SOLUTION: A gaseous oxygen-containing atmosphere is generated in a magnetron sputtering device. An electrode of iridium is formed as a cathode 1 and an electrode of a Nafion film as an anode 2 and a magnetic field is formed in parallel with the cathode surface. A high frequency is oscillated by using a high-frequency generator 4 in a direction orthogonal with the magnetic field, by which the particles of the iridium are jumped out of the cathode 1 and an iridium oxide layer is formed on the Nafion film of the anode 2. Platinum ions are then adsorbed by an ion exchange on the Nafion film and thereafter, the platinum ions are reduced by using a reducing agent, by which the platinum is deposited on the iridium oxide layer and the platinum layer and the iridium oxide layer are laminated on a solid-state high-polymer electrolytic film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode membrane assembly which can be used in a solid polymer electrolyte type water electrolysis device and the like, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, attention has been paid to highly efficient water electrolysis using a solid polymer electrolyte membrane. This water electrolysis method using a solid polymer is characterized by using an electrode membrane assembly in which catalyst electrodes are joined to both sides of a solid polymer electrolyte membrane, and a method for producing an electrode membrane assembly includes a metal or a compound thereof. There has been proposed a method of forming a catalyst electrode on the surface of an ion exchange membrane using a plating solution containing the same. For example, JP-A-10-330979 discloses that a cation exchange resin membrane is subjected to ion exchange adsorption of platinum ions, and then a platinum metal layer is deposited on the membrane surface using a reducing agent, and then at least one of the membrane surfaces is deposited. (Hereinafter referred to as "plating method") is disclosed in which a metal layer made of iridium or platinum-iridium is grown on a surface by electrolytic plating.

[0003]

However, since iridium has a low oxygen overvoltage, it is advantageous in terms of electrolysis to use iridium as a component of an electrode film as in the above plating method, but iridium lacks chemical stability. However, when electrolysis is performed for a long time, iridium is eluted, and the electrolysis voltage increases. Since the tendency of increasing the electrolysis voltage is accelerated when the electrolysis temperature is low (room temperature to about 50 ° C.), it is necessary to maintain the electrolysis temperature at a high temperature of about 60 ° C. or more, and for that, a heater is required. is there.

Further, in the solid polymer type water electrolysis, since pure water having a specific resistance of 1 Mohm or more is used, an ion exchange resin is installed in a pure water circulation line in order to maintain the specific resistance of the pure water. Or high-grade steel (for example, titanium, SUS304, SUS316) having excellent corrosion resistance so that impurity ions (particularly metal ions) do not elute in pure water is used as a pure water piping material to maintain the purity of pure water. be able to. However, when ion exchange resin is used,
Generally, since the upper limit of the continuous use temperature of the ion exchange resin is about 60 ° C., if the electrolytic temperature is to be increased and the electrolysis is to be performed, the pure water is once cooled before passing through the ion exchange resin,
Thereafter, a complicated process of raising the temperature of the pure water to a predetermined electrolysis temperature again by using the heater is required. Further, since a cooling device and a heating device are required, the device becomes expensive.

On the other hand, if the current density is reduced, the electrolysis voltage is reduced.
It is possible to carry out electrolysis for a long time. However, reducing the current density requires increasing the electrolysis area required to generate the same amount of gas by water electrolysis,
The scale of the electrolysis apparatus is increased, and the cost of the apparatus is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object the purpose of achieving good adhesion and maintaining electrolysis even when electrolysis is continued for a long time regardless of the electrolysis temperature. An object of the present invention is to provide a low-cost electrode membrane assembly with a small rise in voltage and a method for manufacturing the same.

[0007]

In order to achieve the above object, the present invention employs a method in which an iridium oxide layer is formed on a solid polymer electrolyte membrane by a magnetron sputtering method, and a platinum layer is formed by an adsorption reduction method. As a result, all disadvantages found in the conventional method are improved, the adhesion is good, and a low-cost electrode membrane assembly with a small increase in electrolysis voltage even when electrolysis is continued for a long time regardless of the electrolysis temperature. Can be provided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS That is, according to the present invention, a magnetron sputtering apparatus is provided with an oxygen gas-containing atmosphere, an iridium electrode is used as a cathode, a solid polymer electrolyte membrane electrode is used as an anode, and a magnetic field is formed parallel to the cathode surface. Then, by applying a predetermined voltage or oscillating a high frequency in a direction orthogonal to this magnetic field, iridium particles are ejected from the cathode to form an iridium oxide layer on the solid polymer electrolyte membrane as the anode, and then After the platinum ions are ion-exchanged and adsorbed on the solid polymer electrolyte membrane, the platinum ions are reduced using a reducing agent to deposit platinum on the inside of the iridium oxide layer. A method for manufacturing an electrode membrane assembly comprising laminating a platinum layer and an iridium oxide layer on a solid polymer electrolyte membrane according to the first invention. After the ion-exchange adsorption of the platinum ion, the platinum ion is reduced using a reducing agent to deposit platinum inside the iridium oxide layer, thereby forming a platinum layer on the solid polymer electrolyte membrane. The inside of the magnetron sputtering apparatus is set to an atmosphere containing oxygen gas, the iridium electrode is used as a cathode, the solid polymer electrolyte membrane electrode is used as an anode, and a magnetic field is formed in parallel with the cathode surface, and a predetermined voltage is applied in a direction orthogonal to the magnetic field. By applying or oscillating a high frequency, the iridium particles are ejected from the cathode to form an iridium oxide layer on the solid polymer electrolyte membrane serving as the anode, thereby forming a platinum layer and iridium oxide on the solid polymer electrolyte membrane. The second invention is a method for producing an electrode membrane assembly characterized by laminating layers, and in the first or second invention, the surface is blasted in advance. The third invention is a method for manufacturing an electrode membrane assembly, characterized by using a solid polymer electrolyte membrane formed in an uneven shape by the method, wherein in the first, second or third invention, magnetron sputtering is performed. The method for manufacturing an electrode membrane assembly characterized by performing intermittently is referred to as a fourth invention, and a fifth embodiment is an electrode membrane assembly having a platinum layer and an iridium oxide layer laminated on the surface of a solid polymer electrolyte membrane. In the fifth invention,
A sixth aspect of the present invention is an electrode film assembly, wherein the platinum layer is formed by an adsorption reduction method, and the iridium oxide layer is formed by a magnetron sputtering method.

According to the first aspect of the present invention, a magnetic field is formed parallel to the cathode surface, and a predetermined voltage (100 to 400 V) is applied in a direction orthogonal to the magnetic field or a high frequency is oscillated. By doing so, the electrons perform high-speed cyclone motion on the cathode surface due to the Lorentz force acting on the electrons, so that the gas near the cathode is ionized and glow discharge plasma is generated to generate a large amount of ions. Thus, the iridium particles that jumped out of the cathode by sputtering with many ions accelerated at high speed reach the anode side while performing cyclone motion in an oxygen gas-containing atmosphere by Lorentz force, and thus, the solid state magnetism is reduced by the magnetron sputtering method. An iridium oxide layer is formed on the molecular electrolyte membrane.

Next, platinum ions are ion-exchanged and adsorbed on the solid polymer electrolyte membrane. The form of the platinum ion is not particularly limited, but is preferably adsorbed in the form of an ammine complex ion.

Subsequent to the adsorption step, a reduction step of reducing platinum ions with a reducing agent is performed. In order to form the platinum layer on the surface of the solid polymer electrolyte membrane, it is preferable to gradually reduce the liquid phase under mild conditions. For example, as the reducing agent, a borohydride aqueous solution is preferable. Examples of the aqueous borohydride solution solution include, for example, sodium borohydride, potassium borohydride, ammonium borohydride, and the like. Thus, an electrode membrane assembly in which the platinum layer and the iridium oxide layer are laminated on the solid polymer electrolyte membrane can be manufactured.

[0012] Instead of the first invention, as in the second invention,
First, a platinum layer is formed on the solid polymer electrolyte membrane by the adsorption reduction method, and then the electrode of the solid polymer electrolyte membrane is used as an anode, the iridium electrode is used as a cathode, and the magnetron sputtering method is used to form a platinum layer on the platinum layer. An electrode film assembly in which an iridium oxide layer is stacked can be manufactured.

Further, by using a solid polymer electrolyte membrane whose surface has been previously formed into an uneven shape by blasting, the area of the bonding interface between the solid polymer electrolyte membrane and the electrode catalyst is increased, and the electrolytic performance is improved.

Further, if the magnetron sputtering is performed intermittently, the iridium oxide layer can be formed smoothly without excessively heating the solid polymer electrolyte membrane.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a magnetron sputtering apparatus. The outer diameter D is 1.0 m and the length L is 1.7.
m. In FIG. 1, reference numeral 1 denotes a cathode made of iridium;
Is the anode of a solid polymer electrolyte membrane made of Nafion 117, and the distance between the cathode 1 and the anode 2 was 75 mm. The iridium cathode 1 has an outer diameter of 120 mm and a thickness of 5 mm.
And a purity of 99.9%. Nafion 117 membrane (DuPont fluororesin sulfonic acid cation exchange membrane, hereinafter referred to as "Nafion membrane")
The anode 2 made of a Nafion film was masked on both sides with a thin steel plate 3 such that a square having a size of 125 mm on one side and a thickness of 180 μm was exposed at the center and a circular portion having a diameter of 80 mm was exposed. In addition, as the Nafion membrane,
Prior to magnetron sputtering, the portion coated with a thin film of iridium oxide (the above-described circular portion having a diameter of 80 mm) is blasted with glass beads to roughen the surface so that an uneven portion is formed, and then subjected to ultrasonic cleaning. , Boiling with hydrochloric acid and boiling with pure water,
What was air-dried at room temperature in a desiccator was used. Reference numeral 4 denotes a high-frequency oscillator, 5a denotes a discharge gas inlet / outlet, and 5b denotes an exhaust outlet.

An experiment was conducted in which an iridium oxide thin film was formed on a Nafion film using the magnetron sputtering apparatus configured as described above, and a platinum layer was formed on the inner surface of the iridium oxide layer formed of the iridium oxide thin film. Therefore, it will be described below.

In this embodiment, an iridium cathode having the above dimensions and an anode made of a Nafion 117 film are used. However, the present invention is not limited to these dimensions. (1) Example 1 The atmosphere in the apparatus was a mixed atmosphere of argon gas and oxygen,
The internal pressure of the apparatus was maintained at 2 × 10 ⁻³ torr, and the oxygen partial pressure was 20% of the total pressure. Then, a magnetic field having a magnitude of 500 Gauss is formed in parallel with the cathode surface, and an output 40
A high frequency of 0 W was intermittently oscillated between the cathode 1 and the anode 2 for 20 minutes. As a result, the iridium particles jumped out of the cathode by the glow plasma generated near the cathode reached the anode while performing cyclone motion by Lorentz force, and a thin film 6 of iridium oxide was formed on the anode (Nafion film) 2. When the cross section of the resulting Nafion film was observed with a scanning electron microscope, as shown in FIG. 2, the iridium particles 9 penetrated into the concave portions 8 on the surface of the Nafion film 7 roughened by blasting, so-called anchor effect. It was observed that the iridium oxide thin film 6 having a thickness of about 1 μm was firmly fixed to the Nafion film 7.
However, no iridium particles were found inside the Nafion film 7.

Next, as shown in FIG. 3A, a Nafion film 7 in which a thin film 6 of iridium oxide is formed on one surface.
After immersion in pure water, boil hydrochloric acid and boil with pure water,
The Nafion membrane 7 was hydrated. Thereafter, platinum ion 10 was ion-exchanged and adsorbed at room temperature until the saturated adsorption amount was reached using a platinum ammine complex solution (FIG. 3 (b)).

Next, the Nafion membrane on which the platinum ions have been adsorbed is washed with pure water, and then a reduction treatment is started with sodium borohydride at a temperature of 40 ° C., while the temperature is gradually raised and sodium borohydride is added. Finally, the temperature was raised to 60 ° C. and a reduction treatment was performed for 1 to 1.5 hours. As shown in FIG. 3C, on one side of the Nafion film 7, an iridium oxide layer formed of a thin film of iridium oxide was formed. Platinum was deposited inside 11, a platinum layer 12 and an iridium oxide layer 11 were laminated on the Nafion film 7, and platinum was deposited on the other surface to obtain an electrode membrane assembly 13 in which the platinum layer 12 was formed. (2) Example 2 In Example 1, after forming an iridium oxide layer formed of a thin film of iridium oxide on a Nafion film by magnetron sputtering, a platinum layer was formed inside the iridium oxide layer by adsorption reduction. In Example 2, a method was first performed in which a platinum layer was formed on a Nafion film by an adsorption reduction method, and then an iridium oxide layer composed of a thin film of iridium oxide was formed on the platinum layer by magnetron sputtering.

That is, a portion to be coated with a thin film of iridium oxide is previously blasted with glass beads to roughen the surface so as to form an uneven portion, and is subjected to ultrasonic cleaning, followed by boiling with hydrochloric acid and boiling with pure water. As shown in FIG. 4A, the Nafion membrane was adsorbed with platinum ions 10 in the Nafion membrane 7 by the ion exchange adsorption treatment.

Next, the Nafion film on which the platinum ions have been adsorbed is washed with pure water, and then subjected to a reduction treatment to deposit platinum on the surface of the Nafion film 7 as shown in FIG. A platinum layer 12 was formed.

Further, the Nafion film on which platinum was deposited on the surface by the above reduction treatment was washed with pure water, and then naturally dried at room temperature in a desiccator, and used as an anode of a magnetron sputtering apparatus shown in FIG. Thereby, as shown in FIG. 4C, the electrode film assembly 14 in which the platinum layer 12 and the iridium oxide layer 11 are laminated on one surface of the Nafion film 7 and the platinum layer 12 is formed on the other surface is formed. I got it.

In both the first and second embodiments, the iridium oxide layer 11 was formed on one surface of the Nafion film 7 because:
Forming iridium oxide on the anode side that can lower the oxygen overvoltage has the effect of lowering the electrolysis voltage,
In addition, the amount of iridium oxide used can be reduced. However, the present invention is not limited to this, and the iridium oxide layers 11 may be formed on both surfaces of the Nafion film 7. (3) Description of Application Example of the Present Invention The electrode membrane assembly of the present invention is, for example, as shown in FIG.
It can be used for a solid polymer electrolyte type water electrolysis device. In FIG. 5, an electrolysis cell 15 is formed by arranging a large number of solid polymer electrolyte membrane units 16 in parallel, and is provided with end electrode plates 17 for current supply at both ends. The solid polymer electrolyte membrane unit 16 mainly includes a solid polymer electrolyte membrane 18, porous feeders 19, 19 provided on both surfaces of the solid polymer electrolyte membrane 18, and the porous feeder 1.
And bipolar electrode plates 20, 20 disposed outside of the electrodes 9, 19. The solid polymer electrolyte membrane 18 is a polymer membrane made of a proton conductive material. Bipolar electrode plate 20
Is such that one side becomes a cathode and the other side becomes an anode by energization. If one bipolar electrode plate 20 is taken, it is composed of the solid polymer electrolyte membrane units 1 on both the left and right sides.
These components are common to the components 6 and 16.

FIG. 6 is an exploded sectional view of one solid polymer electrolyte membrane unit 16, and a porous metal thin film 21 made of a platinum group metal is provided on both surfaces of the solid polymer electrolyte membrane 18. Solid polymer electrolyte membrane 18 and metal thin film 21
Are equivalent to the electrode membrane assembly of the present invention. On both sides of the solid polymer electrolyte membrane 18, there are formed sealed spaces surrounded by the solid polymer electrolyte membrane 18, the bipolar electrode plates 20, 20, and the annular gasket 22, which will be described later. The cathode chamber A and the anode chamber B (FIG. 6)
(Shown by a two-dot chain line). A porous power supply 19 is accommodated in each of the cathode chamber A and the anode chamber B. As the solid polymer electrolyte membrane, a cation exchange membrane as described in the above examples (for example, a fluororesin sulfonic acid cation exchange membrane, “Nafion 11” manufactured by DuPont)
7 "and" Nafion 115 ").

Therefore, as shown in FIG.
When a current is applied between the electrodes 7 and 17 so that the left side in FIG. 5 becomes an anode and the right side becomes a cathode, each bipolar electrode plate 20 generates a cathode on the left side and an anode on the right side. For this reason, one bipolar electrode plate 20 becomes a constituent member on the cathode side 23 in the solid polymer electrolyte membrane unit 16 on the left side in the figure of the bipolar electrode plate, and the solid polymer electrolyte membrane unit 16 on the right side in the figure. Then, it becomes a constituent member on the anode side 24. Thus, as shown in FIG. 6, a cathode chamber A on the right side of the solid polymer electrolyte membrane 18 and an anode chamber B on the left side of the solid polymer electrolyte membrane 18 are formed in one solid polymer electrolyte membrane unit 16. .

In this state, the pure water supply path 25 (see FIG. 5)
When pure water is supplied to the anode chamber B through the reaction chamber, a reaction of 2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ occurs in the anode chamber B, and oxygen gas is generated. The protons generated in the anode chamber B move in the proton-conductive solid polymer electrolyte membrane 18 with a small amount of water, and reach the cathode chamber A. In the cathode chamber A, a reaction of 4H ⁺ + 4e ⁻ → 2H ₂ occurs with the reached protons, and hydrogen gas is generated. (4) Electrolysis test The diameter 80 mm (electrolysis area 50 cm) produced as described above
^Using the electrode membrane assembly ² ), water electrolysis of pure water (current density 1.4 A / cm ² ) was actually performed. For comparison, as described in Japanese Patent Application Laid-Open No. H10-330979, platinum ions are ion-exchanged and adsorbed on a cation exchange resin membrane (Nafion membrane). After depositing a platinum metal layer, using an electrode membrane assembly in which an iridium metal layer is grown on the membrane surface by an electroless plating method, using a device having one solid polymer electrolyte membrane unit to actually purify pure water Water electrolysis (current density 1.4
A / cm ² ). The electrolysis temperature was 30 ° C and 80 ° C.
C. was performed.

As a result, when the electrolysis temperature was 80 ° C., the cell voltage changed as shown in FIG. 7, and when the electrolysis temperature was 30 ° C., the cell voltage changed as shown in FIG. In each of the figures, the cell according to the example of the present invention hardly increased the cell voltage and was stable, while the cell according to the comparative example was 80%.
In the case of ° C, the cell voltage gradually increased, and in the case of 30 ° C, the cell voltage rapidly increased immediately after electrolysis.

As described above, by performing electrolysis using the electrode membrane assembly according to the present invention, it is possible to stably perform water electrolysis at a low voltage for a long time without increasing the cell voltage.

The magnetron sputtering apparatus used in the above embodiment uses a high-frequency AC power supply, but is not limited to this, and may use a DC power supply.

As a method for producing an electrode membrane assembly other than the plating method, there is a hot press method. However, the production method according to the present invention has a stronger bonding between the solid polymer electrolyte membrane and the electrode catalyst, and the electrolytic Sometimes the catalyst does not fall off. Further, the thickness of the electrolytic catalyst layer can be reduced, which is economical.

[0031]

Since the present invention is constituted as described above, the low-cost electrode membrane assembly having good adhesion and little increase in electrolysis voltage even when electrolysis is continued for a long time regardless of electrolysis temperature. The manufacturing method can be provided.

In particular, according to the third aspect of the present invention, it is possible to improve the adhesion between the solid polymer electrolyte membrane and the iridium oxide layer and the electrolytic performance by increasing the area of the bonding interface.

In particular, according to the fourth aspect of the invention, the iridium oxide layer can be formed smoothly.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of a magnetron sputtering apparatus.

FIG. 2 is a cross-sectional view showing an example in which a metal thin film is formed on a solid polymer electrolyte membrane.

FIG. 3 is a diagram schematically illustrating an example of a manufacturing process of an electrode membrane assembly.

FIG. 4 is a view schematically showing another example of the manufacturing process of the electrode membrane assembly.

FIG. 5 is a cross-sectional view showing an example of an electrolytic cell used in a solid polymer electrolyte type water electrolysis device.

6 is an exploded cross-sectional view of the solid polymer electrolyte membrane unit of the electrolytic cell shown in FIG.

FIG. 7 is a diagram showing an example of a transition of a cell voltage in water electrolysis.

FIG. 8 is a diagram showing another example of the transition of the cell voltage in water electrolysis.

DESCRIPTION OF SYMBOLS 1 ... Cathode 2 ... Anode 4 ... High frequency oscillator 6 ... Iridium oxide thin film 7 ... Nafion film 9 ... Iridium particles 10 ... Platinum ion 11 ... Iridium oxide layer 12 ... Platinum layer 13 ... Electrode film assembly 14 ... Electrode membrane assembly 15 ... Electrolysis cell 16 ... Solid polymer electrolyte membrane unit 18 ... Solid polymer electrolyte membrane A ... Cathode chamber B ... Anode chamber

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Manabu Toshima 3-38-3 6104-6104 Shirakawadai, Suma-ku, Kobe-shi, Hyogo Inventor Tsutomu Tai 658-6 Nishioka, Uozumi-cho, Akashi-shi, Hyogo F-term (reference) 4K011 AA31 AA32 BA01 BA07 DA01 4K029 AA11 AA24 BA43 BC00 BD00 CA06 FA02 FA07 GA03

Claims (6)

[Claims] An oxygen gas-containing atmosphere in the magnetron sputtering apparatus, an iridium electrode as a cathode,
The solid polymer electrolyte membrane electrode is used as an anode, a magnetic field is formed parallel to the cathode surface, and a predetermined voltage is applied in a direction orthogonal to the magnetic field or high frequency is oscillated to cause iridium particles to fly out of the cathode. To form an iridium oxide layer on the solid polymer electrolyte membrane as the anode, and then ion-exchange adsorption of platinum ions on the solid polymer electrolyte membrane, and then reduce the platinum ions using a reducing agent, A method for producing an electrode membrane assembly, comprising depositing platinum inside an iridium oxide layer to laminate a platinum layer and an iridium oxide layer on a solid polymer electrolyte membrane. 2. The solid polymer electrolyte membrane, wherein platinum ions are ion-exchanged and adsorbed, and the platinum ions are reduced using a reducing agent to deposit platinum inside the iridium oxide layer. A platinum layer is formed on the electrolyte membrane, and then the inside of the magnetron sputtering apparatus is set to an oxygen gas-containing atmosphere, the iridium electrode is used as a cathode, the solid polymer electrolyte membrane electrode is used as an anode, and a magnetic field is formed parallel to the cathode surface. Then, by applying a predetermined voltage or oscillating a high frequency in a direction orthogonal to the magnetic field, by ejecting iridium particles from the cathode to form an iridium oxide layer on the solid polymer electrolyte membrane as the anode, A method for producing an electrode membrane assembly, comprising laminating a platinum layer and an iridium oxide layer on a solid polymer electrolyte membrane. 3. The method for producing an electrode membrane assembly according to claim 1, wherein a solid polymer electrolyte membrane having a surface formed in advance into an uneven shape by blasting is used. 4. The method according to claim 1, wherein magnetron sputtering is performed intermittently. 5. An electrode membrane assembly in which a platinum layer and an iridium oxide layer are laminated on the surface of a solid polymer electrolyte membrane. 6. The electrode film assembly according to claim 5, wherein the platinum layer is formed by an adsorption reduction method, and the iridium oxide layer is formed by a magnetron sputtering method.