JP2004247057A - Proton conductor and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proton conductor made of a fullerene as a mother material, capable of being appropriately used as the proton conductor having equal or better proton conductivity than hydrogen sulfate ester of poly(fullerene hydroxide) well known heretofore, and to provide a manufacturing method of the same. <P>SOLUTION: The proton conductor is made of a poly cyclosulfate of fullerene expressed by general formula (I) C<SB>n</SB>(OSO<SB>3</SB>)<SB>X</SB>, wherein, C<SB>n</SB>denotes a fullerene, and x denotes a number ranging from 5 to 30. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a proton conductor made of polycyclosulfated fullerene, which can be suitably used as a proton conductor in a fuel cell, and a method for producing the same.
[0002]
[Prior art]
In recent years, carbon clusters, that is, aggregates of carbon atoms consisting of closed-shell molecules consisting only of carbon atoms such as fullerenes and tube-like molecules such as carbon nanotubes, are representative materials in nanotechnology (ultrafine technology). Therefore, application to a wide range of fields such as electronic materials, medical uses, and mechanical uses is expected.
[0003]
In particular, recently, the synthesis of carbon clusters having a proton conductive group such as a hydroxyl group or a hydrogen sulfate ester group in the carbon cluster, that is, polyfullerene hydroxide or its hydrogen sulfate ester, has been reported (Non-Patent Document 1). Patent Documents 1 and 2), and the use of such a compound as a proton conductor in fuel cells has also been proposed (see Patent Documents 1 and 2).
[0004]
In general, as a proton conductor, polyhydroxy fullerene hydrogen sulfate having a high proton dissociating hydrogen sulfate ester group is more advantageous than polyhydroxy fullerene having a hydroxyl group, and moreover, more in the molecule. Polyhydroxy fullerene hydrogen sulfate having a hydrogen sulfate ester group is more advantageous.
[0005]
Conventionally, such a polyhydroxylated fullerene hydrogen sulfate is obtained by first treating fullerene with fuming sulfuric acid and then reacting with water to obtain a polyhydroxylated fullerene. To replace the hydroxyl group with a hydrogen sulfate group. However, since poly (hydroxy fullerene hydrogen sulfate) is conventionally produced by performing a three-step reaction starting from fullerene, the overall yield is low, and therefore, the product price must be high. There is a problem that cannot be obtained.
[0006]
[Patent Document 1] WO 01/06519 A1 [Patent Document 2] JP-A-2002-063917 [Non-Patent Document 1] Y. Chiang et al. , J. et al. Chem. Soc. Chem., Chem. Commun. , 1992, 1791
[Non-Patent Document 2] L. Y. Chaing et al. , J. et al. Org. Chem. , 1994, 59, 3960
[0007]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-described problems in the conventional proton conductor derived from fullerene, and a polycyclosulfated fullerene obtained by treating fullerene with fuming sulfuric acid has been conventionally known. The present invention has been found to have a proton conductivity equal to or higher than that of polyhydroxylated fullerene hydrogen sulfate and has led to the present invention. Accordingly, the present invention relates to a proton conductor made of polycyclosulfated fullerene, which can be suitably used as a proton conductor in a fuel cell, and a method for producing the same.
[0008]
[Means for Solving the Problems]
According to the present invention, general formula (I)
C _n (OSO ₃ ) _x
(Wherein, _{C n} represents a fullerene, x is a number ranging from 5 to 30.)
The proton conductor which consists of polycyclosulfated fullerene represented by these is provided.
[0009]
Further, according to the present invention, there is provided a proton conductor comprising polycyclosulfated fullerene, wherein fullerene is reacted with fuming sulfuric acid of 30% or more in an inert gas atmosphere at a reaction temperature in a range of 15 to 135 ° C. A manufacturing method is provided. In particular, according to the present invention, the reaction temperature is preferably in the range of 70 to 130C.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, fullerene used as a starting material does not need to have a single composition.First, the number of carbon atoms forming fullerene may be an integer capable of forming fullerene. as is known, when describing the fullerene _{C n,} n may be, for example, at least one selected from the like 60,70,76,78,80,82,84. However, according to the present invention, particularly, fullerene having 60 carbon atoms, fullerene having 70 carbon atoms, or a mixture thereof is preferably used as the fullerene.
[0011]
According to the present invention, such a fullerene is charged into fuming sulfuric acid in an inert gas atmosphere and stirred, and the inert gas is not particularly limited here. Preferably, fuming sulfuric acid is used as fuming sulfuric acid in an amount of 30% or more. In particular, according to the invention, more preferably at least 40%, especially preferably at least 50%, most preferably at least 60% of fuming sulfuric acid is used.
[0012]
The reaction time with fuming sulfuric acid is usually at least 10 hours, preferably at least 70 hours. However, it need not exceed 120 hours. The fuming sulfuric acid is generally used in an amount of 10 parts by weight or more, preferably 15 to 50 parts by weight, based on 1 part by weight of fullerene.
[0013]
The method for producing a proton conductor according to the present invention will be described in more detail. First, fullerene is reacted with fuming sulfuric acid at a temperature in the range of 15 to 135 ° C. Next, an organic solvent that does not hydrolyze the hydrogen sulfate ester group, for example, diethyl ether is cooled in advance, and the reaction mixture obtained by the above reaction is dispersed in the diethyl ether to obtain a precipitate. Next, the precipitate is separated by, for example, centrifugation, and the precipitate is washed with diethyl ether or a mixed solvent of diethyl ether-acetonitrile, and dried to obtain a polycyclosulfated compound represented by the general formula (I). A proton conductor composed of fullerene can be obtained as a powder.
[0014]
In particular, according to the present invention, the processing temperature of fullerene and fuming sulfuric acid, that is, the reaction temperature is preferably in the range of 70 to 130 ° C., and by treating fullerene at such a temperature range, a preferred embodiment is achieved. For example, a fullerene neutral sulfate having 7 or more OSO ₃ groups per molecule of fullerene and having high proton conductivity of 5 × 10 ⁻² S / cm or more can be obtained. Such polycyclosulfated fullerenes have higher proton conductivity than conventionally known polyfullerenol hydrogen sulfate.
[0015]
The polycyclosulfated fullerene thus obtained is already known in the above-mentioned literature (Non-Patent Document 2), has no hydroxyl group in the molecule, has only OSO ₃ groups, and therefore has proton conductivity. In terms of properties, it is superior to conventionally known polyhydroxy fullerene hydrogen sulfate and can be suitably used as, for example, a proton conductor in a fuel cell.
[0016]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
[0017]
Reference Example 1
(Synthesis of polyhydroxylated fullerene)
Under a nitrogen atmosphere, 20 g of a mixture of fullerenes C ₆₀ and C ₇₀ (C ₆₀ : C ₇₀ = 0.8: 0.2) is uniformly dispersed in 500 g of 60% fuming sulfuric acid, and then stirred at 60 ° C. for 72 hours. did. The obtained reaction mixture was dispersed in cooled diethyl ether, and the formed precipitate was separated by centrifugation, washed with diethyl ether and acetonitrile, and dried under reduced pressure. The obtained powder was dried under a nitrogen atmosphere, uniformly dispersed in 1 L of ion-exchanged water, and then stirred at 80 ° C. for 10 hours. The mixture was separated by centrifugation, washed with ion-exchanged water, centrifuged repeatedly, and dried under reduced pressure.
[0018]
The FT-IR spectrum of the polyhydroxylated fullerene (sample) thus obtained is shown in FIG. 1, and the polyhydroxylated fullerene (C ₆₀ (OH)) described in the literature (Non-Patent Document 1) is shown. ₁₂ ) The spectrum almost coincided with that of the above. As a result of elemental analysis, the sample had a composition of C ₆₀ / C ₇₀ (OH) ₁₅ (C ₆₀ : C ₇₀ = 0.8: 0.2).
[0019]
Further, 300 mg of the sample is sandwiched between platinum disks, formed into a disk-shaped pellet having a diameter of 16 mm at a pressure of about 1 T / cm ² , and the impedance of the pellet is measured at 1 kHz to determine the proton conductivity of the sample. As a result, it was 2.8 × 10 ⁻⁶ S / cm.
[0020]
Comparative Example 1
(Synthesis of polyhydroxy fullerene hydrogen sulfate)
In a nitrogen atmosphere, 15 g of the polyhydroxylated fullerene obtained in Reference Example 1 was uniformly dispersed in 500 g of 60% fuming sulfuric acid, and the mixture was stirred at a reaction temperature of 25 ° C. for 72 hours. The obtained reaction mixture was dispersed in cooled diethyl ether, and the formed precipitate was separated by centrifugation, washed with diethyl ether and acetonitrile, and dried under reduced pressure.
[0021]
The FT-IR spectrum of the thus obtained poly (hydroxy fullerene hydrogen sulfate) (sample) is shown in FIG. Approximately matched the spectrum. As a result of elemental analysis, the sample had a composition of C ₆₀ / C ₇₀ (OH) ₁₁ (OSO ₃ H) ₄ (C ₆₀ : C ₇₀ = 0.8: 0.2). Further, the proton conductivity of the sample was determined in the same manner as in Reference Example 1, and found to be 4.9 × 10 ⁻⁴ S / cm.
[0022]
Example 1
Under a nitrogen atmosphere, 20 g of a mixture of fullerenes C ₆₀ and C ₇₀ (C ₆₀ : C ₇₀ = 0.8: 0.2) was uniformly dispersed in 500 g of 60% fuming sulfuric acid. Stirred for hours. The obtained reaction mixture was dispersed in cooled diethyl ether, and the formed precipitate was separated by centrifugation, washed with diethyl ether and acetonitrile, and dried under reduced pressure.
[0023]
The FT-IR spectrum of the polycyclosulfated fullerene (sample) thus obtained almost coincided with the spectrum of the polycyclosulfated fullerene described in the literature (Non-Patent Document 2). As a result of elemental analysis, the sample had a composition of C ₆₀ / C ₇₀ (OSO ₃ ) _5.4 (C ₆₀ : C ₇₀ = 0.8: 0.2). Further, the proton conductivity of the sample was determined in the same manner as in Reference Example 1, and it was 9.5 × 10 ⁻⁴ S / cm.
[0024]
Example 2
A polycyclo having a composition of C ₆₀ / C ₇₀ (OSO ₃ ) _6.5 (C ₆₀ : C ₇₀ = 0.8: 0.2) in the same manner as in Example 1 except that the reaction temperature was set to 40 ° C. A sulfated fullerene (sample) was obtained. The FT-IR spectrum of the polycyclosulfated fullerene (sample) obtained in this manner also almost coincided with the spectrum of the polycyclosulfated fullerene described in the above-mentioned document (Non-Patent Document 2). Further, the proton conductivity of the sample was determined in the same manner as in Reference Example 1, and it was 1.9 × 10 ⁻³ S / cm.
[0025]
Example 3
Fullerene having a composition of C ₆₀ / C ₇₀ (OSO ₃ ) _6.5 (C ₆₀ : C ₇₀ = 0.8: 0.2) in the same manner as in Example 1 except that the reaction temperature was 60 ° C. (Sample) was obtained. The FT-IR spectrum of the neutral sulfate ester (sample) of the fullerene thus obtained almost coincided with the spectrum of the polycyclosulfuric acid oxide of fullerene described in the above-mentioned reference (Non-Patent Document 2). Further, the proton conductivity of the sample was determined in the same manner as in Reference Example 1, and found to be 5.7 × 10 ⁻³ S / cm.
[0026]
Example 4
A polycyclo having a composition of C ₆₀ / C ₇₀ (OSO ₃ ) _7.5 (C ₆₀ : C ₇₀ = 0.8: 0.2) in the same manner as in Example 1 except that the reaction temperature was 80 ° C. A sulfated fullerene (sample) was obtained. The FT-IR spectrum of the polycyclosulfated fullerene (sample) obtained in this manner also almost coincided with the spectrum of the polycyclosulfated fullerene described in the above-mentioned document (Non-Patent Document 2). The proton conductivity of the sample was determined in the same manner as in Reference Example 1, and found to be 5.0 × 10 ⁻² S / cm.
[0027]
Example 5
A polycyclo having a composition of C ₆₀ / C ₇₀ (OSO ₃ ) _6.8 (C ₆₀ : C ₇₀ = 0.8: 0.2) in the same manner as in Example 1 except that the reaction temperature was set to 120 ° C. A sulfated fullerene (sample) was obtained. The FT-IR spectrum of the polycyclosulfated fullerene (sample) obtained in this manner also almost coincided with the spectrum of the polycyclosulfated fullerene described in the above-mentioned document (Non-Patent Document 2). Further, the proton conductivity of the sample was determined in the same manner as in Reference Example 1, and it was 3.0 × 10 ⁻³ S / cm.
[0028]
【The invention's effect】
As described above, the polycyclosulfated fullerene according to the present invention has a proton conductor equivalent to or higher than conventionally known polyhydroxy fullerene hydrogen sulfate, and is suitably used as a proton conductor in a fuel cell. be able to. Further, according to the method of the present invention, a proton conductor having high proton conductivity can be obtained by a one-step reaction using fullerene as a starting material. Can be obtained in good yield and at low production cost.
[Brief description of the drawings]
FIG. 1 is an FT-IR spectrum of polyhydroxylated fullerene.
FIG. 2 is an FT-IR spectrum of polyhydroxy fullerene hydrogen sulfate obtained by treating polyhydroxy fullerene with fuming sulfuric acid at room temperature.
FIG. 3 is an FT-IR spectrum of the polycyclosulfated fullerene obtained according to the present invention.

Claims (3)

General formula (I)
C _n (OSO ₃ ) _x
(Wherein, _{C n} represents a fullerene, x is a number ranging from 5 to 30.)
A proton conductor comprising a polycyclosulfated fullerene represented by the formula: A method for producing a proton conductor made of polycyclosulfated fullerene, characterized by reacting fullerene with fuming sulfuric acid of 30% or more in an inert gas atmosphere at a reaction temperature in the range of 15 to 135 ° C. The method according to claim 2, wherein the reaction temperature is 70 to 130 ° C.

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