JPS5875774A - Porous catalytic layer of air electrode and manufacturing method - Google Patents

Abstract

PURPOSE:To produce a porous catalytic layer for an air electrode in short time with low cost which is enable of the heavy load discharge while having the excellent liquid-proof performance by bearing one or both metal porphyrin and fluorine solvent having the hydrophilic group or the perfluoro compound on a conductive porous member. CONSTITUTION:A metal porphyrin having the hydrophiric group is solvent in the water where a porous member molded from the conductive powder is immersed then dried thereafter it is sintered in the inert ambient and immersed in the fluorine solvent containing or not containing the perfluoro compound then bound to produce a molded member. Cobalt porphorin or iron porphyrin dimer is perferable as the metal porphorin. As the hydrophilic group, phenyl sulfone acid group or its alkali metal salt is preferably because it will improve the water solubability of the metal porphyrin considerably. As the fluorine solvent, the low polymer of 1-chloro-1,2,2-trifluorosthylene is most preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a porous catalyst layer of an air electrode such as a hydrogen/-elementary fuel cell, a metal/air cell, or a -elementary senna fuel cell, and a method thereof. The present invention relates to a method for forming a porous catalyst layer of an air electrode into sg* in a short time and at low cost, which is capable of sg* and has excellent leakage resistance.

Conventionally, gas diffusion electrodes have been used as various air electrodes. Recently, this gas diffusion electrode is composed of a conductive porous catalyst layer that has the ability to electrochemically reduce oxygen gas, and a water-repellent layer that is integrally attached to the gas side of the catalyst layer. The electrode has a two-layer structure.

In the case of nickel, the catalyst layer includes large tundaste carbides coated with nickel tungstic acid and palladium cobalt, which have low oxygen reduction overpotentials, noble metals such as nickel, silver, platinum, and palladium, and metal oxides such as Tungsten dioxide. A catalyst having an electrochemical reduction ability for oxygen gas, such as a chelate compound such as gold jII7 talocyanine or metal porphyrin, is supported on a base material that is a conductive powder such as activated carbon powder or graphite powder. It is a porous body made by molding powder into a desired shape (for example, a plate shape) with an electrolytic resistant binder such as polytetra 70 ethylene or preethylene. Alternatively, the porous material may be prepared by forming a porous material in advance using conductive powder and a binder, and the above-mentioned catalyst may be supported on this material.

In addition, in order to prevent the electrolyte from leaking from the porous catalyst layer, generally.

For example, it has water repellency (large contact angle with the electrolyte) such as petittrafluoroethylene, I-retetrafluoroethylene-hexafluoropropylene copolymer, polyethylene-tetrafluoroethylene copolymer, and propylene. A predetermined amount of the substance is mixed with the base material carrying the solvent to form an integrated water-repellent layer.Also, a galvanic air electrode used to detect the concentration of dissolved oxygen gas in water. In particular, in cases where electrolyte leakage is not allowed, a water-repellent and oxygen gas permeable thin film made of the above-mentioned material is applied to the air-side surface of the porous catalyst layer by hot melting. Attempts have been made to form an integral water-repellent layer by attaching the water-repellent layer by an appropriate method such as adhesion, pressure bonding, or adhesion.

Now, inside the pores of such a porous catalyst layer,
A two-electron reduction reaction of oxygen as shown in formula (1) proceeds due to the reaction of the supported catalyst.

o2 + n2 o + 2e-, 0, H- + OH'- (1), cobal) porphyrin and #l porphyrin, which are a type of metal porphyrin in the above catalyst group, are known to exist in their respective dimer forms. However, these two
It is presumed that in the case where the mercury is used as a catalyst, a four-electron reduction reaction of oxygen as shown in equation (2) is proceeding.

02+ 2H20+ 4e--40H- (2) Therefore, when a dimer of cobalt porphyrin or a dimer of iron porphyrin is used as a catalyst, compared to the case where the catalyst promotes the reaction of formula (1), A larger current can be extracted. That is, heavy load discharge becomes possible.

However, metalloporphyrins, including these divalent forms, are generally insoluble in water and alcohol, and are only soluble in limited organic solvents such as benzene, pyridine, dimethylformamide (DMF), and tetrahydrofuran (TEHF). .

Moreover, the saturated amount of metal porphyrin dissolved in organic solvents is small at around 1%.

Therefore, when gold jII porphyrin is supported on a base material that is a conductive powder (for example, activated carbon powder) or a porous body thereof, first, the metal porphyrin powder is dissolved in the above organic solvent until it is saturated. The base material is immersed in a solution, which is then extracted and dried, and the residual solvent is evaporated to precipitate metal porphyrin.
It was necessary to repeat several times until approximately 10 weight S of metal porphyrin was loaded on the substrate.

Therefore, in order to support a predetermined amount of metal porphyrin, it was necessary to repeat the process many times and take a lot of time. Furthermore, since the organic solvents used are all substances that are harmful to the human body, it was necessary to install equipment to remove or collect the organic solvents and their vapors in order to ensure the safety and health of workers. .

Furthermore, in the case of a conventional porous catalyst layer, continuous heavy load discharge (for example, more than s o mA/m'') is difficult to achieve. It became necessary to increase the thickness of the catalytic converter, and as a result, the entire electric power station became a military police force.
Continuous discharge of 15+1 layers is possible, but the thickness of the layer is a
, 125 ~ o, s m, and in order to determine this, if the above thin film is attached to the air side surface of the porous catalyst layer, this thickness can be reduced to about 125μ, but In this case, l Q mA/ex? It was difficult to extract this amount of current continuously.

The present inventors have made extensive efforts to solve the above-mentioned production difficulties when using metall-lufirin and its dimer as a catalyst capable of reducing nitrogen gas. Metal porphyrins with hydrophilic groups introduced are not water-soluble, and their solubility is much higher than when organic solvents are used, so metal porphyrins can be easily supported on substrates without using harmful organic solvents. I got the idea that it is possible. Furthermore, in order to improve the heavy load discharge characteristics, particularly the continuous heavy load discharge characteristics, it is effective to co-support either or both of a fluorine solvent and a par-70 compound having an ability to dissolve oxygen gas. I found it.

The present invention is based on the above ideas and facts, and provides a porous catalyst layer for an air electrode that is capable of continuous heavy load discharge and has excellent leakage resistance, and is inexpensive and requires short manufacturing time. The purpose is to provide the Ila method.

The porous catalyst layer of the air electrode of the present invention is composed of a conductive porous body containing a metal porphyrin having a hydrophilic group, a fluorine solvent, and/or a par-70 compound. , and its manufacturing method is to dissolve a metal porphyrin having a parent wood group in water and add a conductive powder or the conductive powder to the aqueous solution and the L number aqueous solution! IL8
After soaking the porous body as a body and extracting the collected conductive powder or the porous body, it is dried or fired in an inert atmosphere if necessary, and then the conductive powder or the porous body is extracted. It is characterized in that it is immersed in a fluorine solvent containing a fluorine solvent or a par-70 compound, and in the case of the conductive powder, it is further bound with a binder to form a molded body.

In the catalyst layer of the present invention, metal porphyrin having a hydrophilic group functions as a catalyst.

The metal lufirin to be used is preferably cobal) lufidan, iron lufirin, or their dimers from the viewpoint of heavy load discharge.

Various parent groups are introduced into these metalloporphyrins. As a result, it becomes water-soluble. The parent group to be introduced may be one that imparts water solubility without impairing the catalytic ability of the metal luphyrin, such as methanesulfonic acid groups such as methanesulfonic acid groups and ethanesulfonic acid groups; And salts of them with alkali metals such as Na, phenylsulfone I! Aromatic sulfone groups such as p-)ruenesulfone groups and their salts with alkali metals such as Na, phenylcardanic acid groups, methylpyridinium groups, methylaminophenyl groups and their combinations with Na,
Among these, phenylsulfonic acid groups or their alkali metal salts can be mentioned. is preferably used because it greatly increases the water solubility of metal melfilin.

Such water-soluble metal lufilin is prepared as follows. For example, in the case of introducing a phenylsulfonic acid group as a hydrophilic group, α8 mol of virol and α8
Dissolve 31 moles of benzaldehyde in 31 moles of propionic acid and heat to reflux for 30 minutes. Cool to room temperature to obtain tetra-7 enylgylfilin, then the tetraphenyl lky
Irin was sulfonated in concentrated sulfuric acid to give α.

Ie'#r-tetotephenyl gulfyrin trisulfonate is obtained.

Now, the catalyst layer of the present invention is manufactured as follows. First, powder of metal porphyrin having a hydrophilic group is dissolved in water. The amount of solubility varies depending on the hydrophilic group, the type of metal porphyrin, etc., but for example, if the hydrophilic group is a phenylsulfonic acid group and the metal luphyrin is a dimer of cobalt and luphyrin, it will be more than loP with respect to 100 F of water. and very large.

In the aqueous solution of metal purphyrin obtained in this way,
The conductive powder or its porous molded body, ie, the base material of the catalyst layer, is immersed. As a result, the metal porphyrin aqueous solution is supported on the surface of the substrate and in its internal pores.

Next, the base material is taken out from the aqueous solution, dried to volatilize the water, and metal porphyrin having a hydrophilic group is precipitated on the surface or in the internal pores of the base material.

In addition, when the base material obtained by the above method is heated and calcined in an inert atmosphere such as nitrogen or argon at a temperature range of 150 to 1300 G, some of the hydrophilic groups of the supported metal lufirin are removed. or all of it is dissipated or disintegrated and decommissioned,
Metalloporphyrins that have lost part or all of the parent wood group remain. The remaining metallurgical bonds as described above have an increased number of conjugated bonds in their structure, increasing their chemical stability. Accordingly, a catalyst layer made of a heated and calcined base material is useful because of its improved storage characteristics (stability).

In the catalyst layer of the present invention, either or both of a fluorine solvent and a par-70 compound are further coexisting in the conductive powder or its porous material in which a metal porphyrin having a parent wood group is supported as described above. carried.

The fluorine solvent used in the present invention only needs to be one that has the ability to dissolve oxygen gas, is liquid at room temperature, has a relatively high boiling point and solubility, and has a relatively low surface tension.
For example, boiling point: 100 to 300 C, oxygen gas dissolution ability: 4 Q vol % or more, surface tension t 30 dy
A value of ne/ms or less is preferable.

For example, l-talol-1.2.2-) low polymer of lifluoroethylene (degree of polymerization 4-8, molecular weight SOO-900),
70
You can open Loetan, Par 70 Lopentane, Par 70 Lothiol, etc. Of these, 1-ri pru 1.
2.2-) The low polymer of 70 ethylene has a high oxygen gas dissolving ability of more than 10 times that of water, and also has excellent alkali resistance and
Since it has excellent acid resistance and heat resistance, it is most preferable for use in the present invention.

Further, the Par 7a-compound used in the present invention has an ability to dissolve oxygen gas, and includes, for example, Par 70 Rothry n-butylamine, Per 70 Rothry propylamine, Per 70 Lodecalin, Per 70 Lomethyldecalin,
Examples include perfluorinated ethers. These compounds have a large oxygen solubility of about 40 VOj% (oxygen solubility of liquid is about 32 vol%) and an oxygen transfer rate of 14 to 26 fileg (90 an-K for hemoglobin in blood). These fluorine solvents and bar 70 related compounds are adsorbed and co-existed on the conductive powder on which metal porphyrin is already supported, or on the surface of the body or on the walls of internal pores. can be easily achieved by immersing a conductive powder or a porous material thereof containing lufilin in the above-mentioned fluorine solvent or a fluorine solvent containing a par-704 compound.

In addition, if the base material is a conductive powder, it is further added to PTFH.
It is kneaded and bound with a binder such as, and formed into a catalyst layer using a predetermined method (for example, using a rolling roll). When the base material is a conductive porous material, it can be applied as the catalyst layer 11.

In the inner pore walls of the catalyst layer obtained in this way, the metal sealant, the fluorine solvent, and/or the Per70 compound coexist. As mentioned above, the metal lufirin performs an electrochemical reduction reaction of oxygen gas. Both the fluorine solvent and the par-70 compound increase the oxygen gas concentration (partial pressure) in the internal pores of the catalyst layer by exhibiting fluorine gas and gas resolving ability, and as a result, they can be used under heavy loads. Making electricity possible. Both the fluorine solvent and the par-70 compound have similar oxygen gas dissolving abilities, but differ in their rate of oxygen gas uptake. That is, the storage time of the fluorine solvent and oxygen gas is long, and on the contrary, the rate of extraction of the par 70 compound is high.

Therefore, when only the fluorine solvent coexists with the metal gilfilin, instantaneous heavy load discharge is possible, but if the heavy load discharge is continued for a long time, the consumption rate of oxygen gas in the internal pores will decrease. Since the fluorine solvent cannot extract the fluorine gas at the following speed, one point of continuous heavy load discharge ore occurs.

On the other hand, when a par 70 compound coexists, the bar 7
Since the oxygen gas intake rate of the zero-mouth compound is high, the internal pores have a heavy responsibility. Since it can sufficiently follow the consumption rate of oxygen gas during discharge, continuous heavy load discharge progresses smoothly.

Therefore, in the catalyst layer of the present invention, in addition to metal melphyrin, either a fluorine solvent or a Par7 four-mouth compound is supported, and quadruple load discharge is possible, but in particular continuous heavy load discharge is possible. In order to make this possible, it is preferred that both the fluorine solvent and the Par70 compound coexist.

The fluorine solvent exerts the above effect when supported in a layer with a weight of α0001 or more relative to the weight of the conductive powder or its porous material, but if it exceeds 30 weight, the internal resistance of the catalyst layer itself increases. As a result, the voltage drop during heavy load discharging becomes a good thing and a bad thing. Further, it is preferable to use the Par 70 compound dissolved in a fluorine solvent, and in this case, the Par 70 compound is preferably in the range of α1 to 10 volumes relative to the solvent volume of the fluorine solvent.

These fluorine solvents and par-70 compounds not only contribute to heavy load discharge of the porous catalyst layer, but also improve the leakage resistance of the resulting catalyst layer based on their own water repellency. There is power in giving.

The conductive powder or porous material thereof constituting the base material of the catalyst layer of the present invention is a powder such as activated carbon powder, graphite powder, or metal nickel powder, or a porous material formed by molding these powders according to a conventional method.

Since the present invention is configured as described above, it is possible to support a necessary amount of a metal porphydan dimer, for example, which is capable of heavy load discharge, on a base material in a single loading operation. Therefore, the manufacturing time of the catalyst layer can be shortened, and the manufacturing cost thereof can be reduced. Furthermore, since no organic solvents harmful to the human body are used, safety and health issues are significantly improved and the method is useful.

Furthermore, since it coexists with either or both of a fluorine solvent and a par-70 compound, it is of great industrial value because it enables even heavier load discharge, especially continuous heavy load discharge.

The following is a description based on embodiments of the present invention.

Example (1) Production of Catalyst Layer Sample 20F of a dimer powder of cobalt methane filin having four 7-ethyl sulfonic acid groups per single molecule was dissolved in 1,507 ml of water at room temperature.

Activated carbon powder 801 having an average particle size of 1 oojI was added to the resulting aqueous solution. Overall exam 1011
After stirring for a while, a layer of activated carbon powder was added. The resulting powder was dried at 120C. When analyzed by the DTA method, it was found that the above-mentioned dimer was deposited on the surface of the activated carbon powder.

1-chloro-1,2゜2-trifluoride containing 6 powders and 5 volumes of par 70 lodecalin.
After suspending in an ethylene (degree of polymerization 4-6, molecular weight 500-700) solution, it was dried in a nitrogen stream at TGOC. One weight of the above fluorine solvent and 45% by weight of the par70 compound were adsorbed on the powder.

In a lie, 10 to 20% by weight of PTPE 60 arc depurge was added to this as a binder, and the material was then rolled out to form a sheet with a thickness of A7. The obtained Retasheet had a porous structure having 60 pores with an average particle size of 4 μm.

%21JI 1 molecule Kobarciborphyrin with benzenesulfonic acid group! Of was dissolved in 90p water at room temperature.

90Fft1m of activated carbon powder having an average particle size of 100μ was added to the resulting aqueous solution. It was confirmed that Copal) and Rufusgan were supported on the surface of the activated carbon powder.

This powder is mixed with 1-talol-1.2.2-trifluoroethylene (polymerization!! 4-6, molecular weight 500-
700) The solution was slightly cloudy and was dried at 180C in a nitrogen stream.

The above fluorine solvent was adsorbed by 10 weight arcs. Ta. Then, measure the thickness in the same way as sample 1. Prepare a sheet of α7m and use it as a sample. It was set as 2.

Sample 31 (copal) llufirin dimer was mixed with pyridine 10
It was dissolved in 0011j. Here, activated carbon powder 180F having an average particle size of 100 mm was turbid, and then the activated carbon powder was separated and dried by heating to 1 soc in an airtight drying chamber equipped with a pyridine recovery device. This operation was repeated 10 times to obtain 79 cobalcivolphyrin dimers.

This powder may also use PTFE as a binder. A sheet having a thickness of α7ss was molded and designated as Sample 3.

(2) Preparation of air electrode Samples 1, 2, 3. Nickel net (
A current collector) was crimped, and a composite thin film of polytesilafluoroethylene (water repellent layer)/fluoroethylene propylene (heat-fusible adhesive layer) with a thickness of 6fi was heat-sealed on the other side at 250C to reduce the overall thickness. The air electrode had a triple structure of approximately αγpeng.

(3) Preparation of air electrodes Using the above three types of air electrodes, mercury amalgamated zinc powder having a weight ratio of 3 arcs and passing through 60 to 150 mesh was mixed with a sodium hydroxide solution as a gelling agent. Three air-zinc batteries were assembled using zinc electrodes dispersed in a gel-like electrolyte dispersed therein and meriad nonwoven fabric used as a separator.

(4) For each sample, the maximum discharge current density at 25C was measured for 3 air batteries with a temperature higher than the comparison level. The results are shown in Table 1 as a ratio based on the value of the battery using the catalyst layer of Sample 3. In addition,
The time and cost required for manufacturing the catalyst layers of Samples 1 and 2 were calculated as a ratio with respect to Sample 3, and these percentages are also listed. In addition, these batteries were stored at 4 BC and a relative humidity of 9°, and the number of days until leakage occurred was measured and recorded.

As is clear from Table 1, No. 111iP, the catalyst layer of the present invention has a higher maximum current density than the conventional (comparative example), and has excellent leakage resistance, resulting in reduced papermaking, manufacturing time, and manufacturing cost. It turned out that stone crabs had an advantage in this respect.

(5) Effect of heating and calcination Catalyst layer 3 that supports 3.0 weight of cobalt dalphyrin dimer having 4 penuzenesulfonic acid groups per monomolecule without supporting fluorine solvent or bar compound. pieces,
30 Or in an argon stream.

It was fired for 20 minutes at each temperature of 450 U and 6 GOr. A fluorine solvent and a bar 70 compound were co-supported on the obtained fired powder in the same manner as in the production of sample 1. An air electrode was prepared from the obtained catalyst layer as described above, and three 8R4411 zinc-air batteries were fabricated by a conventional method.

After storing this battery at 30 U for one year, it was continuously discharged at a current density of 5 mm at a temperature of 25 C.

The drum-shaped duration of each battery is determined by a catalyst layer that supports a fluorine solvent and a par70 compound without being heated or fired.
The ratios are shown in Table 2 based on the case of R4411 battery.

Table 2 As is clear from Table 2, when the catalyst layer is heated and fired,
It turns out that the discharge duration becomes longer.

In the above embodiment, an air-zinc battery using hydroxide as the electrolyte was shown, but other electrolytes such as ammonium chloride, sodium hydroxide, lithium hydroxide,
It goes without saying that the same effect as 1 can be obtained using cesium hydroxide, rubidium hydroxide, etc. Hey, air-
The catalyst layer of the present invention is also applicable to iron batteries.

As described in detail above, according to the present invention, a catalyst layer of an air electrode capable of a heavy load wave type can be manufactured cheaply in gIi-manufacturing time and without causing any harm to the human body. Therefore, its industrial value is great.

Claims (1)

[Claims] t31 A porous catalyst for an air electrode comprising a porous material having a hydrophilic group and a porphyrin having a hydrophilic group, a fluorine solvent, and/or a part-free compound. layer. i゛The gold metal porphyrin, copal) 1 Luphyrin 2
2. The porous catalyst layer of an air electrode according to claim 1, which is either or both of a dimer and a dimer of iron filin. A metal porphyrin having a hydrophilic group is dissolved in water to form an aqueous solution, a conductive powder or a porous body which is a molded body of the conductive powder is immersed in an aqueous solution, and then the conductive powder or the porous body is taken out. After drying or firing in an inert atmosphere if necessary, the conductive powder or porous body is immersed in a fluorine solvent or a fluorine solvent containing a Bar7EIK1 compound. In this case, tie it with a binding material! A method for manufacturing a porous catalyst layer of an air electrode, characterized by forming an IL carved body. 4. The method for producing a porous catalyst layer for an air electrode according to claim 3, wherein the metal porphyrin is a dimer of cobalt porphyrin or a dimer of iron porphyrin.