JP2004031173A - Proton exchange film and its forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proton exchange film having high proton conductivity at room temperature, enabled to be manufactured at a low cost. <P>SOLUTION: The proton exchange film has high proton conductivity by forming layers of coordination polymer metal complex R<SB>2</SB>dtoaM (here, M is metal) so as to absorb a water molecule between them. The coordination polymer metal complex may have hydrogen coordinated H<SB>2</SB>dtoaCu, (C<SB>2</SB>H<SB>4</SB>OH)<SB>2</SB>dtoaCu, (C<SB>3</SB>H<SB>6</SB>OH)<SB>2</SB>dtoaCu or the like at the position of an alkyl group R. The proton exchange film of H<SB>2</SB>dtoaCu has a high proton conductivity of 10<SP>-2</SP>S×cm<SP>-1</SP>equivalent to Naphyon at room temperature, and capable of operating at a temperature ranging up to 150°C. Further, a manufacturing method of the proton exchange film is provided. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a proton exchange membrane used, for example, as an electrolyte of a polymer electrolyte fuel cell, and a method for producing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, regarding environmental issues, fuel cells have been receiving attention as so-called clean energy sources. Such fuel cells are highly efficient and can use a variety of fuels such as natural gas and methanol. Therefore, they are expected to contribute to promoting the substitution of petroleum and have an environmental conservation effect. I have. In particular, polymer electrolyte fuel cells are expected to be widely used as home and portable power supplies because of their features such as high output density and low-temperature operation.
[0003]
By the way, as an electrolyte of a polymer electrolyte fuel cell, from the viewpoint of chemical, thermal and mechanical stability, conventionally, a film-shaped conductive ion exchange membrane (proton exchange membrane) made of a fluorine resin, for example, Nafion is used. ) Is used.
[0004]
[Problems to be solved by the invention]
However, such a proton exchange membrane is limited to a fluorinated resin in terms of strength, and its performance improvement has reached its limit.
Further, a proton exchange membrane using a fluorine-based resin, particularly Nafion, is relatively expensive.
[0005]
In view of the above, an object of the present invention is to provide a proton exchange membrane and a method for producing the same, which have high proton conductivity at room temperature and can be produced at low cost.
[0006]
[Means for Solving the Problems]
The object is, according to the first configuration of the present invention, characterized in that the proton exchange membrane is composed of a thin film of a coordination polymer metal complex R ₂ dtoaM (where M is a metal).
[0007]
In the present invention, the proton exchange membrane has high proton conductivity at room temperature by absorbing water molecules between layers of the coordination polymer metal complex R ₂ dtoa.
[0008]
In the present invention, in the proton exchange membrane, the metal M of the coordination polymer metal complex R ₂ dtoaM is a transition metal.
[0009]
In the present invention, in the proton exchange membrane, the transition metal is one of copper (Cu), nickel (Ni), iron (Fe), and cobalt (Co).
[0010]
In the present invention, in the proton exchange membrane, hydrogen (H) is coordinated at the position of the alkyl group R of the coordinated polymer metal complex R ₂ dtoaM.
[0011]
In the proton exchange membrane according to the present invention, the alkyl group R of the coordination polymer metal complex R ₂ dtoaM is (C ₂ H ₄ OH).
[0012]
In the proton exchange membrane according to the present invention, the alkyl group R of the coordination polymer metal complex R ₂ dtaoM is (C ₃ H ₆ OH).
[0013]
According to the first configuration, the proton exchange membrane is composed of the coordination polymer metal complex R ₂ dtoaM (where M is a metal).
Further, the proton exchange membrane of the present invention is characterized by having high proton conductivity at room temperature by absorbing water molecules between the layers of the coordination polymer metal complex R ₂ dtoaM. The metal is in particular a transition metal, preferably one of copper (Cu), nickel (Ni), iron (Fe) or cobalt (Co).
According to the above configuration, since the coordination polymer metal complex contains water molecules between layers in order to increase proton conductivity, the proton conductivity is very high at room temperature, and Conductivity is very low and is almost the same as insulator.
Therefore, the coordination polymer metal complex R ₂ dtoaM has high proton conductivity at room temperature and has no electron conduction, so that it is used as an electrolyte of a polymer electrolyte fuel cell, that is, as a proton exchange membrane. Thereby, the same proton conductivity as that of a conventional proton exchange membrane made of a fluorine-based resin can be obtained.
[0014]
Further, the coordination polymer metal complex R ₂ dtoaM has a thermal durability up to about 150 ° C., and thus can sufficiently withstand use.
[0015]
According to the second configuration of the present invention, a step of forming a coordination polymer metal complex R ₂ dtoaM (where M is a metal) into a thin film by pressure molding; And forming a proton exchange membrane by the step of storing ozone.
[0016]
Further, according to the method for producing a proton exchange membrane of the present invention, the coordination polymer metal complex R ₂ dtoaM is such that H (hydrogen) is coordinated at the position of the alkyl group R, and H _{2 where} M is Cu. dtoaCu.
[0017]
According to the second configuration of the method for producing a proton exchange membrane of the present invention, a proton exchange membrane made of a thin film of a copper coordination polymer complex (R) ₂ dtoaCu can be produced easily and at low cost using an inexpensive material. Will be done. Therefore, it can be manufactured at a lower cost as compared with a conventional fluorine resin such as Nafion.
[0018]
Since the proton exchange membrane is composed of a coordination polymer metal complex, that is, a polymer, it can be easily thinned, and the proton conductivity and durability can be further improved by improving the alkyl group R as a side chain. It is possible.
[0019]
When H (hydrogen) is coordinated at the position of the alkyl group R of the coordination polymer metal complex R ₂ dtoaM, the coordination polymer metal complex can be easily produced from dithiooxamide. .
In this case, since the side chain extending between the layers of the coordination polymer metal complex H ₂ dtoaM is small, the molecular weight of water in the molecule is relatively large, and higher proton conductivity can be obtained.
[0020]
Furthermore, according to the third configuration of the method for producing a proton exchange membrane of the present invention, a step of reacting dithiooxamide with propanolamine, and mixing the reaction product of dithiooxamide and propanolamine in an aqueous ethanol solution together with copper sulfate. Through the steps, a copper coordination polymer complex (C ₃ H ₆ OH) ₂ dtoCu is generated, and then the copper coordination polymer complex (C ₃ H ₆ OH) ₂ dtoCu is formed into a thin film by pressure molding. It is characterized in that a proton exchange membrane is produced by passing through a step and a step of absorbing water molecules in the thinned copper coordination polymer complex (C ₃ H ₆ OH) ₂ dtoCu.
[0021]
According to the third configuration, a proton exchange membrane formed of a thin film of a copper coordination polymer complex (C ₃ H ₆ OH) ₂ dtoaCu can be easily and inexpensively manufactured from an inexpensive material. Therefore, it can be manufactured at low cost as compared with a conventional fluorine resin such as Nafion.
[0022]
Thus, according to the present invention, for example, a proton exchange membrane used as an electrolyte of a polymer electrolyte fuel cell is constituted by a thin film of a coordination polymer metal complex R ₂ dtoaM containing water molecules between layers. Accordingly, a proton exchange membrane having high proton conductivity at room temperature can be provided at low cost.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 shows a configuration of one embodiment of a proton exchange membrane according to the present invention. In FIG. 1, a proton exchange membrane 10 is a thin film of a coordination polymer metal complex R ₂ dtoaM. The thin film of the coordination polymer metal complex R ₂ dtoaM has a multilayer structure, and has high proton (H ⁺ : hydrogen ion) conductivity at room temperature by absorbing water molecules between the layers. ing.
[0024]
Here, R ₂ dtoa (dithiooxamide) has a structure in which the alkyl group R is (C ₂ H ₄ OH) or (C ₃ H ₆ OH), and hydrogen (H) is coordinated at the position of the alkyl group R. It is a molecule, that is, a polymer material, and is represented by the structural formula shown in FIG.
[0025]
Hereinafter, a case where M is a transition metal copper (Cu) in the coordination polymer metal complex (C ₂ H ₄ OH) ₂ dtoaM (where M is a metal) will be described as an example.
The copper coordination polymer complex R ₂ dtoaCu has a layered molecular structure in which transition metal Cu is bonded to R ₂ dtoa as shown in FIG. 3, has a distance d between each layer, and has a layered structure. It is a molecular complex.
_{Here, H 2 toaCu, (C 2} H 4 OH) 2 dtoaCu, (C 3 H 6 OH) 2 dtoaCu of d, respectively, 5.7 Å, 9.95A, is 11.82A.
[0026]
The copper coordination polymer complex R ₂ dtoaCu exhibits proton conduction due to occlusion of water molecules. On the other hand, the copper coordination polymer complex R ₂ dtoaCu is reduced as a result of absorbing hydrogen, and causes electron conduction. Therefore, it is not preferable as a proton exchange membrane for conducting only protons.
Therefore, the copper coordination polymer complex R ₂ dtoaCu is in a state where hydrogen is not occluded, that is, it is in a sufficiently oxidized state and an insulator state having a small electron conductivity. Keep it large.
[0027]
Next, a method for measuring the proton conductivity of the proton exchange membrane of the present invention will be described. In the copper coordination polymer complex R ₂ dtoaCu, electron conduction occurs when hydrogen is absorbed, and proton conduction occurs when moisture is absorbed. Therefore, in a mixed state in which both hydrogen and water molecules are occluded, both electron conduction and proton conduction occur. Therefore, the proton conductivity was determined as follows.
[0028]
When the conductivity of the copper coordination polymer complex R ₂ dtoaCu is measured by direct current, proton is not supplied from the direct current power source, so proton conduction occurs immediately after application of direct current but disappears immediately, and only conduction by electrons occurs. Thus, the electronic conductivity is immediately obtained from the measurement of the DC conductivity.
Further, by measuring the complex conductance of alternating current of the copper coordination polymer complex R ₂ dtoaCu, it is possible to measure the conductivity contributed to both proton conduction and electron conduction. Therefore, the proton conductivity can be calculated as the difference between the complex conductance measurement and the DC conductivity measurement.
[0029]
FIG. 4 is a diagram showing the proton conductivity and the relative humidity of the proton exchange membrane of the present invention. In FIG. 4, the horizontal axis is relative humidity (RH), and the vertical axis is proton conductivity σ _p (S · cm ⁻¹ ). Here, the relative humidity (RH) is the humidity when the copper coordination polymer complex R ₂ dtoaCu absorbs water molecules.
In the figure, ●, □, and Δ represent the proton conductivity of H ₂ dtoaCu, (C ₂ H ₄ OH) ₂ dtoaCu, and (C ₃ H ₆ OH) ₂ dtoaCu, respectively. The figure shows the change in proton conductivity when the relative humidity RH is about 15% to 100%.
It can be seen that the proton conductivity of any of the copper coordination polymer complexes R ₂ dtoaCu is maximized when the relative humidity RH is 100%.
At this time, the proton conductivity of H ₂ dtoaCu, (C ₂ H ₄ OH) ₂ dtoaCu, and (C ₃ H ₆ OH) ₂ dtoaCu is 10 ⁻² S · cm ⁻¹ and 3 × 10 ⁻⁴ S · cm ⁻¹ , 5 × 10 ⁻⁶ S · cm ⁻¹ . At this time, the ion transport number is almost 1.
The proton conductivity of H ₂ dtoaCu, 10 ⁻² S · cm ^−1, is a value comparable to a Nafion membrane practically used in a polymer electrolyte fuel cell.
[0030]
It can be seen that, when the relative humidity RH decreases, the proton conductivity of any of the copper coordination polymer complexes R ₂ dtoaCu decreases.
As described above, if the water molecules are not occluded sufficiently, the proton conductivity is so low that it does not operate as a proton exchange membrane.
[0031]
Therefore, it is inferred that the proton conduction mechanism of the copper coordination polymer complex (R) ₂ dtoaCu is similar to the proton conduction mechanism of Nafion conventionally used as an electrolyte of a fuel cell.
[0032]
FIG. 5 is a table showing the number of water molecules per dimer of the copper coordination polymer complex R ₂ dtoaCu which is the proton exchange membrane of the present invention. The value of the number of water molecules was measured by thermogravimetric analysis. Under the condition where the relative humidity RH for absorbing water molecules of the proton exchange membrane of the present invention is 100%, H ₂ dtoaCu, (C ₂ H ₄ OH) ₂ dtoaCu, and (C ₃ H ₆ OH) ₂ dtoaCu per dimer The number of water molecules is 9.0, 3.3, and 3.3, respectively.
From this, as shown in FIG. 5, it can be seen that H ₂ dtoaCu having a large proton conductivity has the largest number of water molecules per dimer.
[0033]
At a relative humidity RH of 75%, the number of water molecules per dimer of the copper coordination polymer complex R ² dtoaCu decreases to 2.8, 1.8, and 2.2, respectively. . For this reason, it is preferable that the proton exchange membrane of the present invention be hermetically sealed so that water molecules of R ₂ dtoaCu are not reduced.
[0034]
FIG. 6 is a diagram showing the thermal durability of the copper coordination polymer complex H ₂ dtoaCu which is the proton exchange membrane of the present invention. In the figure, the horizontal axis is the ambient temperature (° C.), and the vertical axis is the weight loss (%). Weight loss values were determined by thermogravimetric analysis.
The cases where the relative humidity RH is 0%, 75%, and 100% are shown. The proton exchange membrane of the present invention having a relative humidity RH of 100% has a weight loss of about 9% from 20 ° C. to 50 ° C., but from 50 ° C. to 150 ° C., the weight loss does not change with temperature and is almost constant. It is about 10%. Then, at 150 ° C. or higher, the weight loss increases again.
This indicates that H ₂ dtoaCu, which is the proton exchange membrane of the present invention, can be used up to 150 ° C.
[0035]
The weight loss of (C ₂ H ₄ OH) ₂ dtoaCu, (C ₃ H ₆ OH) ₂ dtoaCu also shows the same temperature characteristics as the above-mentioned weight loss of R ₂ dtoaCu, and can be used up to 150 ° C.
[0036]
The proton exchange membrane 10 according to the present invention is configured as described above and operates as follows.
That is, as described above, the proton exchange membrane 10 exhibits a high proton conductivity at room temperature through water molecules contained in the molecules of the copper coordination polymer complex R ₂ dtoaCu. In particular, in the case of H ₂ dtoaCu, the number of water molecules in the molecule is 9 per dimer, and shows an extremely high proton conductivity comparable to a Nafion membrane.
[0037]
Therefore, the proton exchange membrane 10 of the present invention has a proton conductivity substantially equal to that of a proton exchange membrane made of a fluorine-based resin conventionally used as an electrolyte of a polymer electrolyte fuel cell, and is easily manufactured using inexpensive materials. Therefore, it can be manufactured at low cost and has thermal durability up to about 150 ° C., so that it can be practically used.
Further, since the copper coordination polymer complex, H ₂ dtoaCu, (C ₂ H ₄ OH) ₂ dtoaCu, and (C ₃ H ₆ OH) ₂ dtoaCu, are polymers, they can be easily formed as a thin film. .
[0038]
Thus, a thin film in which water molecules are occluded in H ₂ dtoaCu, (C ₂ H ₄ OH) ₂ dtoaCu, and (C ₃ H ₆ OH) ₂ dtoaCu, which are copper coordination polymer complexes containing water molecules. The resulting proton exchange membrane 10 of the present invention has high proton conductivity at room temperature and can be manufactured at low cost.
[0039]
Next, an embodiment of the method for producing a proton exchange membrane of the present invention will be described. First, since the copper coordination polymer complex (C ₃ H ₆ OH) ₂ dtoaCu is a novel material, its manufacturing method will be described.
FIG. 7 shows a method for producing a proton exchange membrane composed of a thin film of a copper coordination polymer complex (C ₃ H ₆ OH) ₂ dtoaCu.
First, in FIG. 7A, when dithiooxamide and propanolamine are mixed, N, N′-bis (3-hydroxypropyl) dithiooxamide, which is an intermediate substance, and ammonia gas are generated.
[0040]
Next, as shown in FIG. 7 (B), the above-mentioned intermediate substance is taken out and put into a 5% ethanol aqueous solution at 60 ° C. together with copper sulfate to obtain N, N′-bis (3-hydroxypropyl). Dithiooxamidato copper (II), that is, the above-mentioned copper coordination polymer complex (HOC ₃ H ₆ ) ₂ dtoaCu is produced.
[0041]
When H (hydrogen) is coordinated at the position of the alkyl group R of the coordination polymer metal complex R ₂ dtoaM, the coordination polymer metal complex itself can be easily produced from dithiooxamide. .
In this case, since the side chain extending between the layers of the coordination polymer metal complex R ₂ dtoaM is small, the molecular weight of water in the molecule is increased, and higher proton conductivity can be obtained.
[0042]
When the alkyl group R of the coordination polymer metal complex R ₂ dtoaM is (C ₂ H ₄ OH), the coordination polymer metal complex itself can be easily produced from dithiooxamide.
[0043]
The copper coordination polymer complex (H) ₂ dtoaCu, (C ₂ H ₄ OH) ₂ dtoaCu, and (C ₃ H ₆ OH) ₂ dtoaCu thus formed are preferably subjected to pressure molding. To form a sheet-like thin film having a thickness of
[0044]
Next, it is checked that the sheet-like thin film is in a reduced state and no electron conduction is caused by hydrogen absorption. If hydrogen is stored, oxidation is performed.
In order to measure the reduced state, as described above, it is possible to determine and determine the electron conductivity due to hydrogen occlusion by direct current conductance measurement.
[0045]
Next, the sheet-like thin film in the reduced state is immersed in water to absorb water molecules and reform the state to have a high proton conductivity, thereby producing a proton exchange membrane.
Thereby, the proton exchange membrane 10 of a sheet-like thin film having a desired thickness suitable for the electrolyte of the polymer electrolyte fuel cell can be formed. In this case, since each material is inexpensive and a large-sized heating device is not required, the copper coordination polymer complex (R) ₂ dtoaCu can be easily manufactured at low cost.
[0046]
The present invention is not limited to the above embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that they are also included in the scope of the present invention. For example, in the above-described embodiment, the proton exchange membrane 10 is made of a copper coordination polymer complex R ₂ dtoaCu, wherein H ₂ dtoaCu in which hydrogen is coordinated at the position of the alkyl group R or the alkyl group R is (C ₂ H ₄ OH) or _(although C ₃ H 6 OH) copper coordination and a polymer complex _R 2 _dtoaCu is not limited to this, other alkyl groups R, met for example _(CH 2 OH) Of course, it may be possible.
[0047]
Further, in the above-described embodiment, the case of the copper coordination polymer complex R ₂ dtoaCu having copper as a central metal has been described. Alternatively, it goes without saying that a transition metal such as cobalt (Co) may be used.
[0048]
【The invention's effect】
As described above, according to the present invention, the coordination polymer metal complex R ₂ dtoaM of R ₂ dtoa (dithiooxamide) constituting the proton exchange membrane has extremely low electron conductivity at room temperature and is almost the same as an insulator. However, the proton conductivity is very high.
Therefore, since the above-mentioned coordination polymer metal complex R ₂ dtoaM has high proton conductivity at room temperature, it can be used as an electrolyte of a polymer electrolyte fuel cell, that is, by using it as a proton exchange membrane to obtain the conventional fluorine. It is possible to obtain the same proton conductivity as that of a proton exchange membrane made of a resin.
[0049]
Further, the coordination polymer metal complex R ₂ dtoaM has a thermal durability up to about 150 ° C., and thus can be sufficiently used.
In addition, the coordination polymer metal complex R ₂ dtoaM can be easily synthesized from an inexpensive material, and thus can be manufactured at a lower cost than conventional fluorine resins such as Nafion.
Further, since the proton exchange membrane is composed of a coordination polymer metal complex, that is, a polymer, the membrane can be easily thinned, and the proton conductivity and durability can be further improved by improving the alkyl group R as a side chain. It is also possible to improve.
As described above, according to the present invention, an extremely excellent proton exchange membrane having high proton conductivity at room temperature and capable of being manufactured at low cost is provided.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a configuration of one embodiment of a proton exchange membrane according to the present invention.
FIG. 2 is a structural formula of R ₂ dtoa (dithiooxamide).
FIG. 3 is a schematic perspective view showing the molecular structure of a copper coordination polymer complex.
FIG. 4 is a graph showing the relationship between the relative humidity and the proton conductivity of the copper coordination polymer complex constituting the proton exchange membrane of the present invention.
FIG. 5 is a graph showing the number of water molecules contained in the copper coordination polymer complex constituting the proton exchange membrane of the present invention at relative humidity.
FIG. 6 is a view showing the thermal durability of a copper coordination polymer complex H ₂ dtoaCu which is a proton exchange membrane of the present invention.
FIG. 7 is a diagram showing an example of a method for producing a proton exchange membrane according to the present invention.
[Explanation of symbols]
10. Proton exchange membrane

Claims (10)

A proton exchange membrane comprising a coordination polymer metal complex R ₂ dtoaM (where M is a metal). _2. The proton exchange membrane according to claim 1, wherein water molecules are occluded between layers of the coordination polymer metal complex R ₂ dtoaM to provide high proton conductivity at room temperature. 3. The proton exchange membrane according to claim 1, wherein the metal M of the coordination polymer metal complex R ₂ dtoaM is a transition metal. The proton exchange membrane according to claim 3, wherein the transition metal is one of copper (Cu), nickel (Ni), iron (Fe), and cobalt (Co). 5. The proton exchange membrane according to claim 1, wherein H (hydrogen) is coordinated at the position of the alkyl group R of the coordination polymer metal complex R ₂ dtoaM. The proton exchange membrane according to any one of claims 1 to 4, wherein the alkyl group R of the coordination polymer metal complex R ₂ dtoaM is (C ₂ H ₄ OH). The proton exchange membrane according to any one of claims 1 to 4, wherein the alkyl group R of the coordination polymer metal complex R ₂ dtaoM is (C ₃ H ₆ OH). Pressure-forming a coordination polymer metal complex R ₂ dtoaM (where M is a metal) to form a thin film;
Causing the coordination polymer metal complex to absorb water molecules,
A method for producing a proton exchange membrane, comprising: 9. The coordination polymer metal complex R ₂ dtoaM is H ₂ dtoaCu in which H (hydrogen) is coordinated at the position of the alkyl group R and M is Cu. 10. A method for producing a proton exchange membrane. The step of reacting dithiooxamide with propanolamine and the step of mixing the reaction product of dithiooxamide and propanolamine together with copper sulfate in an aqueous ethanol solution form copper coordination polymer complex (C ₃ H ₆ OH) ₂ dtoaCu. Generate
Next, pressure-molding the copper coordination polymer complex (C ₃ H ₆ OH) ₂ dtoCu to form a thin film,
Causing the thinned copper coordination polymer complex (C ₃ H ₆ OH) ₂ dtoCu to absorb water molecules;
A method for producing a proton exchange membrane, comprising:

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