KR100668317B1 - Proton conducting electrolyte and fuel cell using the same - Google Patents

Abstract

Provided are a proton conductive membrane having excellent proton conductivity, heat resistance, and mechanical strength, and a fuel cell using the same.

To which the main chain polymer (3) having the hard segment portion (1) and the soft segment portion (2) is added, either or both of the side chain polymer (4) having a proton dissociation group or the side chain polymer (5) made of a dendrimer. A proton conductive electrolyte is adopted.

Description

Proton conducting electrolyte and fuel cell using the same}

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the molecular structure of the proton conductive electrolyte which is embodiment of this invention.

<Explanation of symbols for the main parts of the drawings>

One… Hard segment part

2… Soft segment part

3... Backbone polymer

4… Side chain polymers with proton dissociation groups

5... Side Chain Polymers Made from Dendrimers

The present invention relates to a proton conductive electrolyte and a fuel cell, and more particularly, to a proton conductive electrolyte having excellent heat resistance and proton conductivity.

With the recent deterioration of the global environment, the development of dissemination of clean energy has become a very small task worldwide. For example, in transportation relations, urban air pollution caused by exhaust gas from internal combustion engines such as automobiles has become a problem along with the development of the transportation network and the increase in the number of vehicles. As countermeasures, electric and internal combustion engine vehicles, such as hybrid cars, have been developed. One of them is the use of fuel cells as an energy source that does not pollute the atmosphere for automobiles that are lightweight and easy to handle. In addition, the introduction of fuel cells into the home is the same as the transportation field.

There are various types of fuel cells, such as alkali type, phosphoric acid type, molten carbonate type, solid electrolyte type, and solid polymer type, depending on the type of electrolyte, but they can operate at low temperature, are easy to handle, and have high output density. The older brother is attracting attention as an energy source for electric vehicles and homes.

Proton conductive membranes used in solid polymer fuel cells require high ion conductivity for protons involved in the electrode reaction of the fuel cell. As such a proton conductive film, a film made of a super acidic group-containing fluorine-based polymer is known. However, such a polymer material is very expensive because it is a fluorine-based polymer, and since the proton conductive medium is water, there is a problem that it is necessary to always supply water by humidifying.

The inclusion of ion dissociating groups such as carboxylic acid groups, sulfonic acid groups, and phosphoric acid groups in the aromatic skeleton in order to have proton conductivity is described in Japanese Patent Laid-Open Nos. 2002-280019 and 2002-358978. However, these ion dissociating groups have problems such as low heat resistance, inflexibility in membranes, and low proton conductivity because they are detached at high temperatures.

Japanese Patent Laid-Open No. 8-504293 discloses related articles, but proton conductivity is not disclosed at all.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a proton conductive membrane having excellent proton conductivity, heat resistance and mechanical strength, and a fuel cell using the same.

In order to achieve the above object, the present invention employs the following configurations.

The proton conductive electrolyte of the present invention is characterized in that any one or both of side chain polymers made of side chain polymers or dendrimers having a proton dissociating group or a side chain polymer having a proton dissociation group is added to the main chain polymer having a hard segment portion and a soft segment portion.

According to the above configuration, a proton conductive film having excellent proton conductivity, heat resistance, and mechanical strength can be obtained.

In the proton conductive electrolyte of the present invention, a polyisocyanate having any one of an aromatic ring, a heterocyclic ring, and an alicyclic ring as a proton conductive electrolyte described above, and an acid anhydride, a polyamine compound, and a polyol compound are reacted with each other. And the polyisocyanate and the compound are bonded by a group selected from the group of imide group, urea group and urethane group.

According to the above constitution, a proton conductive film having excellent proton conductivity and flexibility can be obtained.

In addition, the proton conductive electrolyte of the present invention is the proton conductive electrolyte described above, wherein the soft segment portion has a polyoxyalkylene chain and is bonded to the hard segment portion by either or both of a urea group and a urethane group.

According to the above configuration, a proton conductive film having a high proton conductivity can be obtained.

In addition, the proton conductive electrolyte of the present invention is a proton conductive electrolyte described above, wherein the thermal decomposition temperature of the main chain polymer is 220 ° C or higher, and the storage modulus at 200 ° C is in the range of 1 × 10 ⁷ Pa or more and 1 × 10 ⁹ Pa or less. It is characterized by.

According to the said structure, the proton conductive film excellent in heat resistance can be obtained.

In addition, the proton conductive electrolyte of the present invention is the proton conductive electrolyte described above, wherein the proton dissociation group is any one of a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group.

According to the above configuration, a proton conductive film having a high proton conductivity can be obtained.

In addition, the proton conductive electrolyte of the present invention is a proton conductive electrolyte described above, wherein the side chain polymer formed from the dendrimer has at least a polyethylene oxide chain, and has a polyacrylate having at least two of an amino group, a hydroxyl group, and a sulfonic acid group at the terminal of the polyethylene oxide chain. It is characterized by that.

According to the above configuration, a proton conductive film having a high proton conductivity can be obtained.

Next, the fuel cell of the present invention comprises a pair of electrodes and an electrolyte membrane disposed between each electrode, wherein the electrolyte membrane becomes the proton conductive electrolyte according to any one of the above, and a part of the electrode is the proton conductive electrolyte. It is characterized by containing.

According to the above configuration, it is possible to provide a high performance fuel cell having excellent power generation characteristics.

Embodiments of the present invention will be described below with reference to the drawings. 1 schematically shows the structure of a proton conductive electrolyte of the present invention.

As shown in Fig. 1, the proton conductive electrolyte according to the present invention comprises a main chain polymer (3) having a hard segment portion (1) and a soft segment portion (2) from a side chain polymer (4) having a proton dissociation group or a dendrimer. Any one or both of the side chain polymers 5 which were formed are added and comprised.

The hard segment part 1 is formed by reaction with a polyisocyanate, an acid anhydride, a polyamine compound, or a polyol compound. The hard segment portion 1 is coupled to the soft segment portion 2 by either or both of a urea group and a urethane group. The combination of hard and soft segments ranges from 90 to 110 NCO. By providing this hard segment part 1, the heat resistance of a proton conductive electrolyte improves.

The polyisocyanate which comprises the hard segment part 1 has one of an aromatic ring, a heterocyclic ring, and an alicyclic ring. As an aromatic ring, a benzene ring, a naphthalene ring, anthracene ring, a fullerene ring, etc. are mentioned, A benzene ring and a naphthalene ring are especially preferable. Examples of the heterocycle include oxygen, nitrogen, and sulfur, and those having oxygen and nitrogen are particularly preferable.

Examples of the alicyclic ring include conventional ones, and there is no particular limitation.

The acid anhydride, polyamine compound, and polyol compound constituting the hard segment portion 1 react with the polyisocyanate to form imide groups, urea groups, and urethane groups, respectively. That is, the imide group is formed by the reaction of polyisocyanate with polyvalent acid anhydride, and the urea group is formed by reaction of polyisocyanate with polyamine compound and the urethane group is formed by reaction of polyisocyanate with polyol compound.

Examples of the polyisocyanate include the following ones. Tolylene diisocyanate, diphenylmethane diisocyanate (hereinafter abbreviated as MDI), xylene diisocyanate, naphthalene diisocyanate, etc. can be illustrated as a compound which has an aromatic ring. Moreover, isophorone diisocyanate, cyclohexane diisocyanate, etc. can be illustrated as a compound which has an alicyclic ring. Furthermore, hexamethylene diisocyanate, lysine diisocyanate, etc. can be illustrated as an aliphatic compound. Moreover, derivatives of the compounds described in these can also be used. You may use these together as needed. The NCO% of the polyisocyanate is usually 20 to 48%, preferably 25 to 48%. Outside this range, heat resistance and mechanical strength are insufficient.

Moreover, as an example of a polyhydric acid anhydride, a pyromellitic anhydride, a trimethic anhydride benzene tetra carboxylic dianhydride, a naphthalene tetracarboxylic dianhydride, etc. are mentioned.

Examples of the polyamine compound include aliphatic diamines (such as ethylene diamine and propylene diamine), alicyclic diamines (such as isophorone diamine), aromatic diamines ((polytetramethylene oxide-di-P-aminobenzoate), and (4,4'-dia). Mino-3,3'-diethylamino-5,5'-diaminodiphenylmethane), (2,2 ', 3,3'-tetrachloro-4,4'-diaminodiphenylmethane), ( 3,3'-dichloro-4,4'-diaminodiphenylmethane), (trimethylene-bis (4-aminobenzoate)), (3,5-dimethylthiotoluenediamine), etc.] are mentioned. You may mix and use these. Particular preference is given to alicyclic diamines and aromatic diamines among the polyamine compounds. The amine number is usually 250 to 500, preferably 300 to 500. Outside this range, heat resistance and mechanical strength are inferior.

Examples of the polyol compound include aliphatic diols (ethylene glycol, propylene glycol, etc.) and aromatic diols (hydroquinone, bisphenol A, etc.). A hydroxyl value is 250-500 normally, Preferably it is 300-500. Outside this range, heat resistance and mechanical strength are inferior.

Next, the soft segment part 2 has a polyoxyalkylene chain, and is couple | bonded with the hard segment part 1 by either or both of a urea group and a urethane group. By providing this soft segment part 2, flexibility is provided to the main chain polymer 3, and the conductivity of a proton improves.

Examples of the polyoxyalkylene chain constituting the soft segment portion 2 include a polyethylene oxide chain, a polypropylene oxide chain, and a polytetrahydrofuran oxide chain, and in particular, the polyethylene oxide chain and the polytetrahydrofuran oxide chain are proton conductivity. It is preferable from a viewpoint of a mechanical property.

The soft segment part 2 has a polyoxyalkylene chain in a molecule | numerator, and has a hydroxyl group or an amino group at the terminal, specifically, a hydroxyl value is represented by polyoxyalkylene glycol or polyalkylene oxide-di-P-aminobenzoate. Or amine value is 28-200 normally, Preferably it is 28-150. Outside this range, mechanical strength falls.

The main chain polymer 3 preferably has a thermal decomposition temperature of 220 ° C. or higher and a storage modulus at 200 ° C. of 1 × 10 ⁷ Pa or more and 1 × 10 ⁹ Pa or less. Outside of this range, desirable heat resistance and mechanical properties cannot be obtained.

Next, the side chain polymer 4 has a proton dissociation group at its terminal. As a proton dissociation group, one or more things chosen from the group of a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group can be illustrated. Preferred of these are sulfonic acid groups and phosphoric acid groups. Although there is no limitation in particular as a kind of side chain polymer 4, Poly (meth) acrylate is preferable.

As a specific example of the side chain polymer 4, the following can be illustrated. As an example in which a proton dissociation group is a sulfonic acid group, poly (2-acrylamide-2-methylpropanesulfonic acid (it abbreviates to TBAS hereafter), polystyrene sulfonic acid, etc. can be illustrated.

Moreover, polyacrylic acid, poly ((beta) -methacryloyloxyethylhydrogen succinate), poly ((beta)-methacroyloxy ethylhydrogen phthalate), etc. can be illustrated as an example in which a proton dissociation group is a carboxylic acid group.

Furthermore, examples of the proton dissociation group are phosphoric acid groups include poly [mono (2-acryloyloxyethyl) acid phosphate], poly [mono (2-methacryloyloxyethyl) acid phosphate], and the like.

These can be obtained by known methods by radical polymerization or photopolymerization from each monomer.

Next, the side chain polymer (5) made from a dendrimer is a poly (meth) acrylate having at least a polyethylene oxide chain and having at least two of an amino group, a hydroxyl group and a sulfonic acid group. Specifically, an alkylene oxide containing ethylene oxide is added to a compound having three or more hydroxyl groups in a molecule (trimethylolpropane, pentaerythritol, etc.), reacted with methacryl isocyanate, and known by radical polymerization or photopolymerization. The material obtained can be used.

Furthermore, the side chain polymer 4 and the side chain polymer 5 may be polymerized from each monomer in the main chain polymer 5.

Although the ratio of the main chain polymer (3), the side chain polymer (4), and the side chain polymer (5) is not particularly limited, it is usually 0.1 to 1 part by weight of the side chain polymer (4) and the side chain polymer ( It is good to make 5) 0.01-1 weight part. More preferably, the side chain polymer 4 is 0.3 to 1 part by weight and the side chain polymer 5 is 0.01 to 0.5 part by weight based on 1 part by weight of the main chain polymer 3.

Next, a fuel cell according to the present invention will be described in detail. The fuel cell according to the present invention comprises a pair of electrodes and an electrolyte membrane disposed between each electrode, the electrolyte membrane comprising the proton conductive electrolyte according to the present invention, and the proton conductive electrolyte is formed on a part of the electrode. It is comprised.

That is, the fuel cell is composed of an electrolyte membrane made of a proton conductive electrolyte, and an air electrode (electrode) and a fuel electrode (electrode) disposed in contact with both sides of the electrolyte membrane.

In the anode, hydrogen of the fuel is electrochemically oxidized to produce protons and electrons. The produced protons are transported by the electrolyte membrane and move to the air electrode. In addition, electrons generated in the anode flow through the cathode connected to the fuel cell. Oxygen is supplied to the air electrode, and protons, oxygen, and electrons react to produce water.

The fuel electrode and the air electrode constituting the fuel cell are composed of a conductive material, a binder, and a catalyst. Any conductive material may be used as the conductive material, and various metals and carbon materials may be mentioned. For example, carbon black, such as acetylene black, activated carbon, graphite, etc. are mentioned, These are used individually or in mixture.

The catalyst is not particularly limited as long as it promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen. For example, lead, iron, manganese, cobalt, chromium, gallium, vanadium, tungsten, ruthenium, iridium, palladium, platinum, rhodium Or their alloys.

Moreover, it is preferable to use the said proton conductive electrolyte as a binder. In addition to the proton conductive electrolyte, a binder may be used in combination with another resin. In that case, the other resin is preferably a fluorine resin having water repellency. Among the fluororesins, the melting point is more preferably 400 ° C. or lower, and examples thereof include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and the like.

EXAMPLE

Hereinafter, the present invention will be described with reference to the following examples, but the present invention is not limited thereto. In addition, the measurement conditions of the physical property evaluated in the Example are as follows.

Proton Conductivity: An electrode is made by pressing two platinum wires (diameter 0.2 mm) in contact with the surface of a sample formed into a long, thick paper shape at an interval of 5 mm. The resistance when an alternating current (1 kHz) is applied to this electrode is measured by an impedance analyzer. Measured. Proton conductivity was calculated | required by 1 / (R * t * D) from the slope (R) of an electrode space | interval, resistance, sample thickness (t), and sample width (D). The measurement was performed at 80 degreeC and 95% of humidity.

Storage elastic modulus: It carried out using the viscoelasticity measuring apparatus (Rheogel-E4000 by the UMB company) at the temperature increase rate of 2 degree-C / min, the temperature range of 20-230 degreeC, the frequency 100 Hz, and the displacement of 5 micrometers.

(Example 1)

20.8 parts by weight of MDI and 100 parts by weight of polytetramethylene oxide-di-P-aminobenzoate (amine value 89) were mixed, dissolved in 400 parts of tetrahydrofuran, the solution was poured into a fluorine resin chare and tetrahydrofuran By removing the backbone polymer of Example 1 was obtained.

The viscoelasticity measurement was performed on the obtained main chain polymer, and the storage elastic modulus in 200 degreeC was 4 * 10 <^7> Pa, and the thermal decomposition temperature was 250 degreeC.

(Example 2)

25.7 parts by weight of MDI, 50 parts by weight of polytetramethylene oxide-di-P-aminobenzoate (amine number 89), and 50 parts by weight of polytetramethylene oxide-di-P-aminobenzoate (amine value 132) were mixed and The main chain polymer of Example 2 was obtained by dissolving in 400 parts of tetrahydrofuran, inject | pouring the solution into the fluorine resin share, and removing the tetrahydrofuran.

As a result of measuring viscoelasticity with respect to the obtained main chain polymer, the storage elastic modulus in 200 degreeC was 8 * 10 <^7> Pa, and the thermal decomposition temperature was 270 degreeC.

(Example 3)

1 part by weight of the main chain polymer prepared in Example 1, 1 part by weight of TBAS (50% aqueous solution) as the side chain polymer (4), 0.01 part of 2-hydroxy-2-methylpropiophenone as a polymerization initiator, tetra 6 parts of hydrofuran was mixed and degassed, and then irradiated with ultraviolet (400W mercury lamp) for 7 minutes. The product was then washed with hot water (80 ° C.) for 1 hour and then dried. In this way, the proton conductive electrolyte of Example 3 was prepared.

The proton conductivity of the obtained proton conductive electrolyte was 6.1 × 10 ⁻³ S / cm.

Furthermore, the proton conductivity of the main chain polymer of Example 1 was 3 × 10 ^-6 S / cm. Therefore, it can be seen that the proton conductivity can be improved by adding the side chain polymer 4 to the main chain polymer.

(Example 4)

1 part by weight of the main chain polymer prepared in Example 2, 2 parts by weight of TBAS (50% aqueous solution) as the side chain polymer (4), 0.01 part of 2-hydroxy-2-methylpropiophenone as the polymerization initiator, and side chains. Ethylene oxide was added to pendaerythritol as polymer (5), and the hydroxyl value was 545. 10 parts of reactant with 3.7 parts of 2-methacroyloxyethyl isocyanate and 6 parts of tetrahydrofuran were mixed. A proton conductive electrolyte of Example 4 was prepared in the same manner as in Example 3 except for the above.

The proton conductivity of the obtained proton conductive electrolyte was 1 × 10 ⁻³ S / cm.

Furthermore, the proton conductivity of the main chain polymer of Example 1 was 3 × 10 ^-6 S / cm. Therefore, it can be seen that the proton conductivity can be improved by adding the side chain polymer 4 and the side chain polymer 5 to the main chain polymer.

(Example 5)

A fuel cell was constructed using the proton conductive electrolyte in Example 3. As the electrode, a Pt / C catalyst carrying 30% of platinum was used, dispersed in a polymer solution of the catalyst and tetrahydrofuran (solution in Example 3), and the solution was removed to form a catalyst layer. Further, an electrolyte membrane made of the proton conductive electrolyte of Example 3 was disposed between the electrodes. The cell voltage of 0.66 V was obtained at a current density of 0.3 A / cm ² when power was generated at 80 ° C. using air and hydrogen.

According to the proton conductive electrolyte of the present invention, it is possible to improve proton conductivity, heat resistance, and mechanical strength. In addition, according to the fuel cell of the present invention, it is possible to provide a high performance fuel cell having excellent power generation characteristics.

Claims (7)

One or both of side chain polymers made of side chain polymers or dendrimers having sulfonic acid groups or dendrimers are added to the main chain polymer having a hard segment portion and a soft segment portion, and the hard segment portion is reacted with a polyisocyanate having an aromatic ring and a polyamine compound. And the soft segment portion has a polyoxyalkylene chain, and the side chain polymer formed from the dendrimer is a polymer polymerized by adding an alkylene oxide to a compound having three or more hydroxyl groups in a molecule and reacting with methacrylic isocyanate to polymerize it. A proton conductive electrolyte. The proton conductive electrolyte of claim 1, wherein the polyisocyanate and the compound are bonded to a urea group. The proton conductive electrolyte according to claim 1, wherein the soft segment portion is bonded to the hard segment portion by one or both of a urea group and a urethane group. The proton conductive electrolyte according to claim 1, wherein the pyrolysis temperature of the main chain polymer is 220 ° C or higher, and the storage modulus at 200 ° C is 1 × 10 ⁷ Pa or more and 1 × 10 ⁹ Pa or less. delete The proton conductive electrolyte according to claim 1, wherein the side chain polymer formed from the dendrimer is a polyacrylate having at least two of an amino group, a hydroxyl group, and a sulfonic acid group at its terminal. It consists of a pair of electrodes and the electrolyte membrane arrange | positioned between each electrode, Comprising: The said electrolyte membrane becomes the proton conductive electrolyte in any one of Claims 1-4, and 6, The part of the said electrode is a said proton A fuel cell comprising a conductive electrolyte.

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