JP2935183B1 - Manufacturing method of gas diffusion electrode - Google Patents

Abstract

The present invention provides a method for manufacturing a gas diffusion electrode, in which a manufacturing process is simplified, a productivity is high, and a reaction layer of a gas diffusion electrode having high oxygen reduction performance can be manufactured. SOLUTION: In a method for manufacturing a gas diffusion electrode, a reaction layer raw material and / or a gas supply layer raw material are each dispersed in an aqueous solution, and a self-organizing agent is mixed with these dispersions to disperse them before self-organization. A method for producing a gas diffusion electrode, comprising spraying a liquid to form a coating. Primary particle size 0.5
Hydrophobic carbon black fine particles of less than micron, hydrophilic carbon black fine particles, surfactant,
A dispersion with a PTFE dispersion of 5 microns or less is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a gas diffusion electrode, and more particularly to a method for manufacturing a gas diffusion electrode in which a gas supply layer and / or a reaction layer can be easily formed by spraying.

[0002]

2. Description of the Related Art A gas diffusion electrode usually has a structure comprising a gas supply layer and a reaction layer, and its application is, for example, fuel cell or electrolysis of an alkali chloride solution. In electrolysis of an alkali chloride solution by an ion exchange membrane method, a gas diffusion electrode is used as an oxygen cathode as the cathode. Normally, ion exchange membrane electrolysis is performed in an electrolytic cell partitioned into an anode chamber and a cathode chamber by an ion exchange membrane which is a cation exchange membrane.In this electrolytic tank, an aqueous sodium chloride solution is placed in an anode chamber having an anode, A cathode portion having a cathode contains an aqueous solution of caustic soda. Among these, in the electrolytic cell of the type using a gas diffusion electrode as a cathode, the cathode part is a catholyte chamber containing an aqueous solution of caustic soda between the ion exchange membrane and the gas diffusion electrode, a reaction layer and a gas supply. It has a structure composed of a gas diffusion electrode composed of layers and an oxygen gas chamber. In the electrolytic cell having such a configuration, when electricity is supplied between both the anode and the cathode gas diffusion electrode for electrolysis, an oxygen reduction reaction occurs on the gas diffusion electrode, and the cathode potential increases. Is significantly reduced.

In a conventional method for producing a reaction layer of a gas diffusion electrode, a surfactant is added to and dispersed in hydrophilic carbon black to form polytetrafluoroethylene (PT).
FE) The dispersion is mixed and frozen, and the hydrophobic
The surfactant was added to Bon Black, dispersed, mixed with PTFE dispersion, frozen, thawed and mixed. Carbon black and PTFE dispersion coagulate by these freezing and thawing operations,
Agglomerates of a hydrophilic part and a hydrophobic part were formed, and these were mixed to form a mixed state of fine hydrophilic parts and hydrophobic parts that function as a reaction layer.

However, in such a conventional method for producing a reaction layer of a gas diffusion electrode, the operation of freezing and thawing for coagulating a PTFE dispersion or the like takes a long time, so that the electrode production cost is high. Moreover, there is a problem that the mixed state of the hydrophilic part and the hydrophobic part is not always desirable for obtaining a good performance, and the control is difficult. Therefore, there has been a need for a method of manufacturing a gas diffusion electrode that simplifies a manufacturing process, shortens a manufacturing time, and can manufacture a reaction layer of a gas diffusion electrode having high oxygen reduction performance.

[0005]

SUMMARY OF THE INVENTION In order to easily manufacture a gas diffusion electrode, the present inventor has made it easy to form a gas diffusion layer by forming a gas supply layer and a reaction layer on a conductive substrate. Considering the manufacturing method, we applied for a patent earlier. Furthermore, for the method, in order to make the gas supply layer and the reaction layer easier to form, for example, a self-organizing agent such as alcohol is added to a dispersion of hydrophilic carbon black or polytetrafluoroethylene (PTFE). When added
Since the dispersion coagulates and self-organizes, it becomes a paste, so it was confirmed that it could be obtained by applying it on a conductive substrate, drying it, and heating it. . By the way, when manufactured by the above-mentioned method, the self-organized one formed with alcohol has a large cohesive force of PTFE, so that it becomes rice cake-like and cannot be formed unless it is applied with a spatula. In this method, the film forming method involving the operation of rubbing with a spatula the cake that has been self-assembled with alcohol into a rice cake form has the disadvantage that the process is complicated and requires skill. For this reason, there has been a demand for simplifying a method for forming such a gas diffusion electrode.

[0006]

Means for Solving the Problems The present inventor has studied various means for achieving the above object. According to the above-mentioned method, what has been self-organized with a self-organizing agent such as alcohol becomes rice cake-like over time. Because it is difficult to form a film,
We thought that spraying would be possible if we controlled the speed of self-assembly, and conceived that it would be good to finally form a self-assembled film with alcohol. The present invention has been reached by studying means for performing the above.

[0007] The present invention has solved the above-mentioned problems by the following means. (1) In the method for producing a gas diffusion electrode, the reaction layer raw material or
Characterized in that the gas supply layer material dispersed in water solution, and mixed self-assembled into the dispersion, by spraying the mixture to form a reaction layer or gas feed layer by coating of A method for producing a gas diffusion electrode. (2) a primary particle size of 0.5 microns or less hydrophobic carbon black fine particles, and dispersion of the surfactant and below the PTFE Disupajo down primary particle size of 0.5 microns, a two-liquid self structuring fluid line The method for producing a gas diffusion electrode according to the above (1), wherein the gas supply layer is formed by supplying the mixture, mixing and mixing, spraying, and forming a film.

(3) Fine particles of hydrophilic carbon black having a primary particle size of 0.5 μm or less, fine particles of hydrophobic carbon black having a primary particle size of 0.5 μm or less, a surfactant, and PTFE having a primary particle size of 0.5 μm or less Disupajo down
And two liquids, a self-organizing liquid and a dispersion liquid of
The method for producing a gas diffusion electrode according to (1), wherein the reaction layer is formed by mixing and mixing, spraying, and forming a coating film. (4) primary particle size of 0.5 microns or less PTFE dispersion, two-liquid dispersion and self-organization for solution of a surfactant and a primary particle size of 0.5 micron or less of the catalyst fine particles was piped, (1) wherein the reaction layer is formed by mixing and mixing, spraying, and forming a coating film.
A method for producing the gas diffusion electrode according to the above.

[0009] (5) a primary particle size of 0.5 microns or less carbon black fine, the dispersion of a surfactant and a primary particle size of 0.5 micron or less of the catalyst fine particles, the PTFE dispersion and self-structuring solution Are sprayed into the same gas stream to form a reaction layer, whereby a reaction layer is formed. (6) Forming a coating film of the gas supply layer raw material dispersion by spraying on the substrate of the gas diffusion electrode, and forming a coating film of the reaction layer raw material dispersion by spraying continuously on the coating; Alternatively, the method of manufacturing a gas diffusion electrode according to any one of (1) to (5), wherein the order of forming the coating films is reversed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the manufacturing method of the present invention, either one of the reaction layer and the gas supply layer of the gas diffusion electrode may be performed, or both may be performed. In the case where the gas diffusion electrode mainly forms only the reaction layer and the gas supply layer does not particularly need to be formed in a self-organized manner, the reaction layer alone may be manufactured according to the present invention. The reaction layer can be formed in several ways.
For example, in a method in which a catalyst is supported after forming a layer to form a reaction layer, first, a hydrophilic carbon black and a hydrophobic carbon black are dispersed with a surfactant, for example, Triton, and then the reaction is performed by adding a PTFE dispersion. A layer dispersion is obtained. In the case of a method in which a reaction layer containing catalyst fine particles is formed in a single operation, a liquid dispersion such as a mixture of silver fine particles and PTFE dispersion is self-assembled with alcohol such as ethanol. It can be achieved by self-organizing with an agent and spraying immediately. After mixing, the dispersion liquid is self-assembled, so that when spraying, this self-assembled one is sprayed, but after mixing, it hardens into a rice cake shape after a certain time, making it impossible to spray There are cases. Therefore, it is better to spray as soon as possible after mixing. However, when the concentration is low, the whole does not solidify in a rice cake shape, and in that case, spraying can be performed depending on conditions.

For example, the case of spraying the reaction layer dispersion will be described in detail with reference to the drawings.
The reaction layer dispersion liquid 5 is introduced from the introduction pipe 1 connected to the spray nozzle, ethanol 6 is introduced from the introduction pipe 2, both liquids are merged in the merge passage 3, and are discharged from the tip of the nozzle 4. When the high-pressure gas 8 is ejected from the ejection gas pipe 7, the escaping liquid is blown off to form a spray 9,
A coating film can be formed by applying the spray 9 toward the electrode substrate.

In the method for producing a gas diffusion electrode of the present invention, for example, the preparation of a reaction layer dispersion liquid will be described in detail. First, a surfactant is added to a catalyst, for example, silver fine particles or hydrophilic carbon black. After ultrasonic dispersion, a PTFE dispersion is added, mixed and dispersed. The dispersion obtained at this time is such that the fine particles of silver or hydrophilic carbon black and PTFE form a micellar structure by the action of a surfactant and maintain a highly dispersed state stably in the form of fine particles. Is what it is. The dispersion state is such that the diameter of the particles in which the primary particles are aggregated during the dispersion is 5 μm or less in average. The fine particles of the catalyst and the fine particles of hydrophilic carbon black preferably have primary particles having an average particle diameter of 1 μm or less, particularly preferably 0.5 μm or less. It is better to be fine due to problems such as nozzle clogging in relation to spraying. Similarly, hydrophobic carbon black or the like can be dispersed as a constituent material.

That is, after adding hydrophilic carbon black and hydrophobic carbon black to water and a surfactant, dispersing them and mixing PTFE fine particles, the ability of the surfactant is controlled, whereby the hydrophilic property is controlled. Carbon black and PTF
A reaction layer dispersion in which E fine particles, hydrophobic carbon black and PTFE fine particles are dispersed can be prepared. In the case of silver fine particles and PTFE fine particles, a surfactant,
For example, it is better to disperse by Triton.

The main constituent material of the reaction layer is a catalyst made of a noble metal such as platinum, a mixture of fine particles of hydrophilic carbon and fine particles of water-repellent carbon, a small amount of fine particles of fluororesin, and if necessary, these fine particles. These are the binder particles to be connected. Catalysts include, but are not limited to, alkali-resistant noble metals such as platinum, other white metal, gold, silver and alloys of these noble metals. But,
Considering both performance and cost, silver can be said to be a preferable catalyst. These noble metals are used in the form of fine particles.
The main constituent materials of the gas supply layer are water-repellent carbon fine particles and fluororesin fine particles and, if necessary, binder particles connecting these fine particles.

In the production of the gas diffusion electrode of the present invention, any of anionic surfactants, cationic surfactants, nonionic surfactants and amphoteric surfactants is used as a surfactant for dispersion. Can be used, but a nonionic surfactant is preferred because it is not affected by salts or ions. Examples of the fluorine resin include tetrafluoroethylene (tetrafluoroethylene) resin, ethylene trifluoride chloride (chlorotrifluoroethylene) resin, ethylene tetrafluoride / propylene hexafluoride (ethylene fluoride propylene) resin, and vinylidene fluoride resin However, tetrafluoroethylene resin (PTFE) is particularly preferred. The PTFE dispersion is an aqueous dispersion of PTFE fine particles, and the dispersion contains a surfactant for dispersion. As described above, the surfactant is a nonionic surfactant. Is desirable.

The self-organizing agent added to the dispersion has an action of destroying the dispersed micelles, and thus can be referred to as a "micelle destroying agent". Organic solvents such as methyl alcohol
And alcohols such as ethyl alcohol, isopropyl alcohol and ketones such as acetone.
The amount of use of these micelle-disrupting agents may be any amount as long as the micelle structure of the aggregate of surfactant molecules is broken into a fractal state.
You may use it in the ratio before and after that. Alcohol is added to this dispersion.
By adding the particles, the micelle structure that enables the dispersion of each fine particle is broken, and the fine particles are aggregated. At that time, the aggregation becomes a fractal state, thereby forming a hydrophilic layer in a fractal state. The above-mentioned alcohol acts as a micelle breaking agent.

In a dispersion in which hydrophobic carbon black or the like is dispersed as a constituent material, a hydrophobic portion is also agglomerated by alcohol, but in this case, the aggregated state is smaller than a hydrophilic portion. When the thus obtained hydrophilic layer and the hydrophobic part are mixed, the hydrophobic part aggregates in the range of 5 to 100 microns enter around the hydrophilic part aggregates having a fractal structure in the range of 5 to 100 microns, In addition, the area of the interface of the hydrophilic portion becomes huge. In addition, in a normal case, the size of the hydrophilic part aggregate is larger than the size of the hydrophobic part aggregate. As a result, the performance is improved and the electrode life is also increased. In the case of silver fine particles and PTFE fine particles, the fine particles are dispersed with a surfactant, for example, Triton, and added with ethanol to form silver fine particles and PTFE fine particles.
The TFE fine particles are each aggregated in a fractal form of about several microns, and these are secondarily aggregated.

[0018]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited to these examples.

Example 1 A solution prepared by dispersing 20 g of zirconia fine particles having an average particle diameter of 0.15 micron in 1 liter of an aqueous solution by adding 100 ml of 20% triton, 70 ml of 35% formalin, and 35 g of silver nitrate dissolved in water while cooling. 250 ml was added dropwise over 1 hour, and the pH was adjusted to 9 by adding caustic soda, whereby silver was supported on the zirconia fine particles. 1 part of Triton and 9 parts of water are added to 4 parts (by weight) of silver-supported zirconia fine particles, and dispersed by an ultrasonic dispersing machine. To this, 1 part of PTFE dispersion D-1 (manufactured by Daikin Industries, Ltd.) is added, and the mixture is stirred and mixed to prepare a reaction layer dispersion. The reaction layer dispersion was introduced from one tube for spraying, and ethanol was sent from the other tube to join and mix in one passage. Immediately after mixing, the silver-plated foamed nickel body (12 × 28m square), 0.3m
m. This is pressed at a pressure of 10 kg / cm ² and pressed into the inside to form a reaction layer.

Further, from the backside, a paste made by adding ethanol to a dispersion of PTFE dispersion D-1 (manufactured by Daikin Industries, Ltd.) is pressed into a gas diffusion layer. This is dried at 80 ° C. for 3 hours, and pressed at room temperature at 40 kg.
An electrode was obtained by heat treatment at a pressure of / cm ² for 60 seconds and 250 ° C. for 10 minutes, followed by cooling. When the oxygen reduction performance of this electrode was measured, a high performance of 0.80 V (vs. RHE) was obtained at a current density of 30 A / dm ² .

Example 2 2.5 parts of hydrophilic carbon black (AB-12, average particle size 400 °, prototype, manufactured by Denki Kagaku Kogyo KK) carrying 10% (by weight) of silver and PTFE dispersion D-1
1 part (manufactured by Daikin Industries, Ltd.) is dispersed. 50 parts of isopropyl alcohol is added to this dispersion to allow self-organization. Separately, 20% was added to 2 parts of hydrophobic carbon black (No. 6, average particle size 500 mm, prototype, manufactured by Denki Kagaku Kogyo KK).
20 parts of Triton and PTFE dispersion D-
1 part (manufactured by Daikin Industries, Ltd.) is dispersed. The dispersion and isopropyl alcohol are combined to form a self-organized structure.

This is sprayed on a silver-plated nickel foam body of 50 ppi to a thickness of 200 μm from above, and rolled together with a 1 mm-thick silicon sheet.
Press into the reaction layer inside the foamed nickel body. 2 parts of hydrophobic carbon black (No. 6, average particle size 500 mm, prototype, manufactured by Denki Kagaku Kogyo) and PTF from the back of the nickel foam body
A gas supply layer dispersion prepared from 1 part of E dispersion D-1 (manufactured by Daikin Industries, Ltd.) was mixed with isopropyl alcohol and sprayed to form a gas supply layer.
After drying at 80 ° C. for 3 hours, the surfactant is removed with an ethanol extractor. After drying, 380 ° C. at 50 kg / cm ² ,
An electrode was obtained by pressing for 60 seconds. When the oxygen reduction performance of this electrode was measured, a high performance of 0.81 V (vs. RHE) was obtained at a current density of 30 A / dm ² . Its performance was superior to that of an electrode prepared by coagulating a dispersion by freezing, which is a conventional method, by 20 mV.

Example 3 Silver fine particles (manufactured by Mitsui Kinzoku Mining Co., Ltd., average particle size Ag-303)
0) 2 parts of PTFE dispersion D-1 (manufactured by Daikin Industries, Ltd.) was added to 5 parts, and the reaction layer dispersion obtained by stirring and mixing was mixed with ethanol to form a silver-plated foamed nickel body (12 × 28 cm square). ) And spray to a thickness of 0.5 mm. This is pressed at a pressure of 10 kg / cm ² and pushed into the silver-plated nickel foam body to form a reaction layer. Further, PTFE dispersion D-1 (manufactured by Daikin Industries, Ltd.) and ethanol are simultaneously sprayed from the back of the foamed nickel body to form a gas supply layer.

After drying at 80 ° C. for 3 hours and removing the surfactant by an extractor using ethanol, drying at 100 ° C. for 2 hours, a silicon resin sheet was placed on the gas supply layer side, and the room temperature was 40 kg / cm. ² was pressed for 60 seconds, heat-treated at 250 ° C. without pressure for 10 minutes, and cooled to obtain an electrode. A salt electrolyzer with zero gap between the electrode and the ion exchange membrane was assembled and operated continuously. As a result, an electrolytic cell voltage of 2.01 V was obtained under the conditions of a current density of 30 A / dm ² , a temperature of 90 ° C., an obtained caustic soda concentration of 32% NaOH, and an oxygen supply of twice the theoretical value. Operation can be performed without voltage fluctuation for 40 days, and electrolysis is ongoing.

Example 4 Hydrophobic carbon black (No. 6, average particle diameter 500)
(2) 20 parts of Triton (20 parts) were dispersed in 2 parts of a prototype, manufactured by Denki Kagaku Kogyo Co., Ltd., and then dispersed by adding 1.2 parts of PTFE dispersion D-1 (Daikin Industries Co., Ltd.). The dispersion and the two liquids of acetone were combined, mixed and self-assembled, and sprayed on the way to form a gas supply layer having a thickness of 400 microns on a 50-mesh silver mesh. Further, silver was converted to hydrophilic carbon black (AB-1).
2, average particle size 400 mm, prototype, manufactured by Denki Kagaku Kogyo) 3
Part and hydrophobic carbon black (No. 6, average particle diameter 50)
0%, prototype, manufactured by Denki Kagaku Kogyo Co., Ltd.) 2 parts, 20 parts of 20% triton and PTFE dispersion D-1
3 parts (manufactured by Daikin Industries, Ltd.) are dispersed.

The dispersion and the two liquids of acetone were mixed and mixed at the same flow rate through a pipe, self-assembled, and sprayed to a thickness of 200 μm on the gas supply layer to form a reaction layer. The nitrogen gas for spraying was heated to 120 ° C. 8
After drying at 0 ° C. for 3 hours, the surfactant was removed with an extractor for ethanol over 6 hours. After drying, put in a jig, 50
An electrode was obtained by pressing at kg / cm ² at 380 ° C. for 60 seconds. The reaction layer was loaded with 0.5 mg / cm ^{2 of} platinum by suction coating a chloroplatinic acid solution. When the oxygen reduction performance of this electrode was measured, a high performance of 0.82 V (vs. RHE) was obtained at 30 A / dm ² . A platinum-supported gas diffusion electrode produced by coagulating a dispersion by freezing, which is a conventional method, was produced at the same time, but the results were almost the same or slightly better.

[0027]

According to the present invention, since a dispersion such as a reaction layer dispersion can be directly sprayed, the reaction layer and / or the gas supply layer of the gas diffusion electrode can be easily manufactured. , The process was simplified and the productivity was improved. The present invention can be manufactured without a complicated manufacturing process and without skill. In addition, in the present invention, a simple operation of simply spraying can provide a coating layer in which a dispersion of the reaction layer raw material or the gas supply layer raw material is self-organized with a self-organizing agent. A strong reaction layer and / or gas supply layer can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view of forming a spray according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 introduction pipe 2 introduction pipe 3 merge passage 4 nozzle 5 reaction layer dispersion 6 ethanol 7 jet gas pipe 8 high-pressure gas 9 spray

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-337249 (JP, A) JP-A-4-75260 (JP, A) JP-A-8-302492 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C25B 11/20 C25B 11/12

Claims (6)

(57) [Claims] The manufacturing method of claim 1 a gas diffusion electrode, a reaction layer material or gas feed layer material was dispersed in water solution, and mixed self-assembled into the dispersion, by spraying the mixture, coating To form a reaction layer or gas supply layer
A method for producing a gas diffusion electrode. 2. Hydrophobic carbon black fine particles having a primary particle size of 0.5 μm or less, a surfactant and a primary particle size of 0.5
The dispersion of the following PTFE Disupajo down microns,
2. The method for producing a gas diffusion electrode according to claim 1, wherein a gas supply layer is formed by supplying two liquids of the self-organizing liquid via a pipe, mixing and mixing, spraying, and forming a film. . 3. A hydrophilic carbon black fine particle having a primary particle size of 0.5 μm or less, a hydrophobic carbon black fine particle having a primary particle size of 0.5 μm or less, a surfactant, and a PTFE disperser having a primary particle size of 0.5 μm or less. and minutes <br/> dispersion liquid of the job down, the two solutions of the self-assembled liquid for supplying a pipe, is combined mixture is sprayed, and forming a reaction layer by coating of A method for manufacturing a gas diffusion electrode according to claim 1. 4. PTFE having a primary particle size of 0.5 micron or less.
Dispersion, the dispersion and two solutions of self-organization for solution of a surfactant and a primary particle size of 0.5 micron or less of the catalyst fine particles is supplied in the pipe, is combined mixture is sprayed to the coating film of it The method for producing a gas diffusion electrode according to claim 1, wherein the reaction layer is formed by: 5. The primary particle size of 0.5 microns or less carbon black fine, the dispersion of a surfactant and a primary particle size of 0.5 micron or less of the catalyst fine particles, and a PTFE dispersion and self-structuring solution 2. The method for producing a gas diffusion electrode according to claim 1, wherein the reaction layer is formed by spraying into the same gas stream to form a coating film. 6. A coating of a gas supply layer raw material dispersion is formed on a substrate of a gas diffusion electrode by spraying, and a coating of a reaction layer raw material dispersion is formed on the coating by continuous spraying. The method for producing a gas diffusion electrode according to any one of claims 1 to 5, wherein the order of forming the coating film is reversed.