JP2006294306A - Proton conductive material and fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proton conductor that exhibits high proton conductivity in a low-humidity environment and to provide a high-performance fuel cell using the proton conductor as an electrolyte. <P>SOLUTION: This invention provides a proton conductive material in which a solid acid is carried by a porous carrier having a penetrating hole and including a hydrophilic group, and a fuel cell using the proton conductive material as an electrolyte. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a proton conductor in which a solid acid is supported on a porous carrier, and further to a fuel cell using the proton conductor as an electrolyte.

The proton conductivity of the electrolyte used in the fuel cell is preferably as high as possible. As the electrolyte plate used in the fuel cell using the solid polymer electrolyte, a proton conductive ion exchange resin is usually used. In particular, ion exchange membranes made of perfluorocarbon polymers having sulfonic acid groups have been widely studied.
However, such an ion exchange membrane is very expensive, and there is a problem that durability under high temperature conditions is insufficient, or good proton conductivity is not exhibited unless the membrane is sufficiently hydrated. That is, good proton conductivity cannot be obtained in a dry state or at a temperature exceeding the boiling point of water.

For this purpose, a system for managing water that is not directly involved in the electrochemical reaction is required, and it has been difficult to operate at a temperature higher than the boiling point of water. Thus, a proton conductor using a porous carrier is known as a proton conductor that exhibits good proton conductivity in a low-cost and lower humidity environment.
Non-Patent Document 1 describes a proton conductor of mesoporous ethane silica containing propylsulfonic acid in the skeleton. However, the proton conductors prepared by this method are only examples showing proton conduction exceeding 10 ⁻² S / cm for the first time when the water content is 200% or more.

Non-Patent Document 2 describes a proton conductor of mesoporous ethane silica containing arenesulfonic acid in the skeleton. However, there are only examples that exceed 10 ⁻² S / cm for the first time at a moisture content of 100% or more.
That is, according to these techniques, in order to obtain good proton conductivity, it is necessary to maintain a high water content, and therefore good proton conductivity can be obtained unless the humidity is high (relative humidity of 100% or more). It cannot be maintained.
Micropor. Mesopor. Mater. 59, 195 (2003) Micropor. Mesopor. Mater. 71, 17 (2004)

As described above, a proton conductor using a porous carrier having sufficient performance for practical use of a fuel cell in a low humidity environment has not been developed yet.
Therefore, the present invention provides a proton conductor that exhibits high proton conductivity in a low-humidity environment, and further provides a high-performance fuel cell that uses this proton conductor as an electrolyte.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have shown that protons exhibiting higher proton conductivity in a lower humidity atmosphere than conventional by loading a solid acid on a porous carrier subjected to hydrophilic treatment. The inventors have found that a conductive material can be obtained, and have completed the present invention.
That is, the gist of the present invention resides in a proton conductive material in which a solid acid is supported on a porous carrier having a through hole and having a hydrophilic group. Furthermore, the present invention resides in a fuel cell including the proton conducting material.

The proton conductor of the present invention has higher ionic conductivity at a lower humidity than before. For example, it exhibits a proton conductivity of 10 ⁻² S / cm or more under conditions of a temperature of 80 ° C. and a relative humidity of 30%. And the proton conductor of this invention can be preferably used for electrolytes, such as a fuel cell.

Hereinafter, the present invention will be described in detail.
1. Porous carrier having a through hole and a hydrophilic group (1) Through hole The through hole in the present invention is, for example, J. Org. Electron Microsc. 48, 795 (1999) and Nature, 408, 449 (2000), and the three-dimensional structure reproduced by electron crystallography combining high-resolution TEM and electron diffraction. Refers to a hole having a different outlet. A porous carrier having a through hole is very preferable in that it has many proton conduction paths in addition to the particle surface.

(2) Porous carrier The porous carrier in the present invention is a carrier having many pores having a diameter of 1 nm or more. The pore diameter is usually 50 nm or less. Since the porous carrier of the present invention is used as an electrolyte, it needs to be insulative. Here, the insulating property means that the specific volume resistance value is 10 ³ Ωm or more.

Hereinafter, preferred physical properties of the porous carrier will be described.
Specific surface area The specific surface area of the porous carrier according to the proton conductor of the present invention (hereinafter appropriately referred to as the porous carrier used in the present invention) is not particularly limited, but is usually 400 m ² / g or more, preferably 900 m ² / g or more, preferably a is 1000 m ² / g or more, and usually 2000 m ² / g or less. Since a large number of hydrophilic groups can be introduced, a larger specific surface area is preferable. If the specific surface area is small, it tends to be difficult to impart sufficient hydrophilicity to the porous carrier. Moreover, when the specific surface area is large, the strength tends to decrease.
In addition, although the measuring method of a specific surface area is arbitrary, it can measure by BET method etc. by nitrogen gas adsorption / desorption, for example.

-Mode pore diameter The mode diameter Dmax of the porous carrier used in the present invention is usually 1 nm or more, preferably 2 nm or more, more preferably 2.5 nm or more, and usually 50 nm or less, preferably 20 nm or less, more preferably Is 10 nm or less. When the mode maximum pore diameter Dmax is small, it tends to be difficult to impart sufficient hydrophilicity to the porous carrier, and it is difficult to introduce a solid acid into the pores. Moreover, when the most frequent maximum hole diameter Dmax is large, the solid acid introduced into the hole tends to be easily removed.

In addition, although the measuring method of the mode pore diameter Dmax is arbitrary, for example, it can measure by BJH method etc. by nitrogen gas adsorption / desorption.
Further, the porous carrier having through-holes used in the present invention has a pore volume having a diameter within a range of ± 20% of the value of the most frequent pore diameter Dmax, relative to the volume of pores having a diameter of 1 nm or more. Thus, it is usually 70% or more, preferably 75% or more, more preferably 80% or more. This means that the diameter of the porous carrier having through-holes used in the present invention is uniform in the vicinity of the most frequent pore diameter Dmax, that is, the pore diameter distribution is extremely narrow (sharp). The upper limit of the ratio value is not particularly limited, but is usually 99% or less. When the pore size distribution is small, the structure of the porous carrier having through-holes used in the present invention becomes uniform, and the inside of the pores can be used effectively.

-Pore volume The pore volume of the porous carrier having through-holes used in the present invention is usually 0.4 ml / g or more, preferably 0.8 ml / g or more, more preferably 1.0 ml / g or more, and usually It is 3.0 ml / g or less, preferably 2.5 ml / g or less, more preferably 2.0 ml / g or less. If the pore volume is small, it tends to be difficult to impart sufficient hydrophilicity to the porous carrier. Moreover, when the pore volume is larger than the above range, the strength tends to decrease.

-Particle size The particle size of the porous support | carrier which has a through-hole used for this invention is about several dozen micrometers normally. When used as an electrolyte for a fuel cell, it is preferably pulverized to a submicron order, that is, a particle size of less than 1 μm. By making the particle size on the order of submicron, it is possible to obtain a thin electrolyte, whereby the voltage drop due to the electrolyte is reduced, and the efficiency as a fuel cell becomes closer to the theoretical value. The pulverization method is not particularly limited, and a commercially available pulverizer can be used.

  Specific examples of the porous carrier having a through-hole used in the present invention include mesoporous metal oxides such as mesoporous silica and non-silica niobium, titanium, and tantalum. Among them, mesoporous silica has the above-mentioned preferable characteristics. It is suitable because it satisfies a good balance.

-Mesoporous silica Mesoporous silica as a porous carrier having a through-hole used in the present invention (hereinafter, appropriately referred to as mesoporous silica used in the present invention) is described in, for example, page 13 of "Science and Engineering of Zeolite" (Kodansha 2000). It is mesoporous silica exemplified as one of mesoporous materials.
However, mesoporous silica generally refers to silica having pores having a pore diameter of 2 nm to 50 nm, but mesoporous silica in the present invention refers to silica having pores of 1 nm to 50 nm. In the present invention, silica refers to silicic anhydride and is represented by the chemical formula of SiO ₂ .

-Constituent element of mesoporous silica The mesoporous silica having a through-hole used in the present invention preferably contains an element other than oxygen and silicon. When many elements other than oxygen and silicon are contained, the mesoporous silica used in the present invention is usually hydrophilic.
The element other than oxygen and silicon (hereinafter, this element is represented by “M”) is preferably an element from group 4 to group 14 in the periodic table. Specifically, group 4 elements such as titanium and zirconium, group 5 elements such as vanadium and niobium, group 12 elements such as zinc, group 13 elements such as aluminum, boron and gallium, iron, manganese, cobalt, and tin Among these, aluminum, boron, gallium, titanium, zinc, and iron are more preferable.

Further, the molar ratio (Si / M) of silicon and M in the skeleton of the mesoporous silica having through-holes used in the present invention is usually 100 or less, usually 1 or more, preferably 10 or more, more preferably 50 or more. It is. The higher the M content, the higher the hydrophilicity, but the lower the crystallinity, so the above range is preferable.

Specific Examples of Mesoporous Silica Specific examples of mesoporous silica used in the present invention include mesoporous silica described in Microporous Materials, Vol. 2, Item 17 (1993), that is, FSM-16, MCM-41, MCM. -48, MCM-50, SBA-1, SBA-2, SBA-3, HMS, MSU-1, MSU-2, SBA-11, SBA-12, MSU-V, MSU-3, SBA-15, SBA -16.

(3) Hydrophilic group Among the porous carriers having the above water vapor adsorption amount, those having a hydrophilic group are preferable.

Examples of the hydrophilic group include a hydroxy group, an amino group which may be substituted with a hydrocarbon group having 1 to 20 carbon atoms, a carboxy group, a phosphonic acid group, a sulfonic acid group, and an imidazolidine group. A phosphonic acid group and a sulfonic acid group are preferable.
The amount of the hydrophilic group is usually 0.1 mmol or more, preferably 0.5 mmol or more, more preferably 1.0 mmol or more, and usually 50 mmol or less, preferably 40 mmol or less, more preferably 30 mmol / g or less per 1 g of the porous carrier. It is.

When the hydrophilic group is an acidic group (proton-donating group), strong alkali such as sodium hydroxide, and when the hydrophilic group is a basic group (proton-accepting group), sulfuric acid, hydrochloric acid, etc. The amount of hydrophilic groups can be measured by neutralization titration with a strong acid.
The porous carrier having a through hole used in the present invention preferably has high hydrophilicity. Specifically, the water vapor adsorption amount per gram of porous carrier at a temperature of 80 ° C. and a relative humidity of 30% is preferably 50 mg or more, more preferably 70 mg or more, and further preferably 90 mg or more. Usually, it is 2000 mg or less, preferably 1500 mg or less, more preferably 1000 mg or less.

The amount of water vapor adsorption in the present invention is calculated from the difference between the mass after vacuum drying at 150 ° C. for 2 hours and the mass after holding at 80 ° C. and 30% relative humidity for 2 hours after vacuum drying.
In the proton conducting material of the present invention, it is considered that protons are hydrated at low humidity and are conducted as oxonium ions. Further, the porous carrier having hydrophilicity has the ability to retain moisture even at low humidity. Therefore, when a porous carrier having a through hole subjected to hydrophilic treatment is used as a proton conductive material, proton conductivity at low humidity is improved.

-Hydrophilic treatment In the present invention, the above porous carrier can be used as it is, but it is preferable to perform a hydrophilic treatment.
When hydrophilic treatment is performed on the porous carrier having through-holes used in the present invention, the method is not particularly limited, and a known method can be used. For example, the method of providing the said hydrophilic functional group is mentioned preferably.
Hereinafter, as a specific example of the hydrophilic treatment, a case where mesoporous silica is used as the porous carrier will be described.

  A silane coupler having a hydrophilic group or a functional group that can be converted into a hydrophilic group is modified to mesoporous silica. The silane coupler may be mixed with a precursor of the base material when producing mesoporous silica, or may be modified to mesoporous silica after the mesoporous silica is produced. However, in order to obtain a controlled pore structure, it is preferable to modify the silane coupler after producing mesoporous silica.

The method for modifying the silane coupler is not particularly limited, and various known methods can be selected and used. For example, (1) dispersing and refluxing mesoporous silica in water,
Recovered by filtration after hydration, and modified by refluxing with the silane coupler in an organic solvent such as toluene, (2) Dispersing mesoporous silica in water adjusted to ammonia basic, stirring, time Any known method such as a method of slowly dropping the silane coupler and modifying it may be used. In addition, examples of the functional group that can be converted into a hydrophilic group include an alkoxy group, an epoxy group, an amide group, a cyano group, a phosphino group, and a mercapto group. These functional groups can be converted into hydrophilic groups by hydration or oxidation.

2. Solid acid The solid acid used in the present invention is a Bronsted acid and is preferably one capable of holding water at a temperature higher than 100 ° C. by thermal analysis such as TG-DTA. Specific examples include various heteropolyacids, cesium salts such as CsHSO ₄ and Cs ₂ (HSO ₄ ) (H ₂ PO ₄ ), rubidium salts such as Rb ₃ H (SeO ₄ ) ₂ , (NH ₄ ) ₃ H ammonium salts such as _{(sO 4) 2, K 3} H (sO 4) bisulfate salts such as ₂ include hydrogen phosphate salts such as HZr ₂ (PO _{4) 3.} The amount of the solid acid is usually 0.1 mmol or more, preferably 0.3 mmol or more, more preferably 0.5 mmol or more, per 1 g of the porous carrier carrying the solid acid as the proton acid amount. Moreover, it is 50 mmol or less normally, Preferably it is 40 mmol or less, More preferably, it is 30 mmol or less.

In addition, in this specification, heteropoly acid is the concept containing a free acid and an acidic salt. Here, the acid salt means a salt of a heteropoly acid in which some of hydrogen ions are replaced with a basic cation, for example, an alkali metal cation. The heteropolyacids may be used as the solid acid of the present invention, 12-tungstophosphoric acid _{(H 3 [PW 12 O 40} ] xH 2 O), 12- molybdophosphoric acid _{(H 3 [PMo 12 O 40} ] xH 2 O) 12-silicotungstic acid (H ₄ [SiW ₁₂ O ₄₀ ] xH ₂ O), 12-silicotungstic acid monosodium (H ₃ Na [SiW ₁₂ O ₄₀ ] x
H ₂ O), 12- silicomolybdic acid _{(H 4 [SiMo 12 O 40} ] xH 2 O), diphosphorus - ammonium molybdate _{((NH 4) 6 [P} 2 Mo 18 O 62] xH 2 O), two Cobalt-ammonium molybdate ((NH ₄ ) [Co ₂ Mo ₁₀ O ₃₆ ] xH ₂ O), cesium hydrogen tungstophosphate (Cs _2.5 H _0.5 [PW ₁₂ O ₄₀ ] xH ₂ O), cesium hydrogen silicotungstate ( Cs ₃
H [SiW ₁₂ O ₄₀ ] xH ₂ O).

In addition, the polyvalent oxidation state and hydration state of the heteropolyacid described above with reference to specific examples are not limited to the actual state of the electrolyte for a fuel cell using such a proton conductor, particularly before being supported on the porous carrier of the present invention. This is a state before being subjected to power generation conditions.
The oxidation state and hydration state of the metal in the hydrated / heteropolyacid introduced into the pores of the porous support may change, for example, under the power generation conditions of the fuel cell, and for example, depending on the method of introducing the heteropolyacid. Therefore, it is considered that the oxidation state and hydration state of the heteropolyacid after use may change from the oxidation state and hydration state of the heteropolyacid before being supported on the porous carrier. The hydration state of the heteropolyacid affects the acidic state of the proton conductor and thus the proton conductivity.

3. Method of supporting solid acid on porous carrier The method of supporting the solid acid on the porous carrier is not particularly limited, and various known methods can be selected and used. For example, the impregnation method <absorption method, pore-filling method, “incipient wetness”, which is well known as a method for supporting various compounds on solids
"Method, evaporation to dryness method, spray method, etc.", precipitation method <coprecipitation method, precipitation method, kneading method, etc.>, ion exchange Any known method such as an exchange method may be used.

Among these methods, as a method for supporting a solid acid, a method in which more solid acid is contained in the pores of the porous carrier is preferable. Specifically, the impregnation method is preferable, and the pore-filling method is more preferable.
It is considered that the performance as a proton conductor is improved by containing a solid acid in the pores.
In order to contain a larger amount of the solid acid in the pores of the porous carrier, for example, the porous carrier is sufficiently dried by vacuum drying or the like to reduce adsorbed water in the pores as much as possible. The solid acid may be dissolved in a solvent having an amount equal to or less than the total pore volume, and the solid acid may be supported in small portions.

  The solvent used at this time is not particularly limited as long as it dissolves the solid acid. However, when there is a concern that the structure of the porous carrier is broken by the acid, it is preferable that the solvent be supported by dissolving in an organic solvent. Further, when it is necessary to remove the solvent after loading, it is preferable to use a volatile solvent. Specific examples of the organic solvent suitable for use include diethyl ether, acetone, alcohols and the like.

The presence of a solid acid in the pores can be confirmed, for example, by measuring the pore volume by nitrogen gas adsorption / desorption and comparing the pore volumes before and after loading.
4). Proton conductivity The powdered proton conductive material thus obtained is obtained. The proton conductive material of the present invention usually has a proton conductivity of 1.0 × 10 ⁻² [s at 80 ° C. and a relative humidity of 30%. / Cm] or more. The proton conductivity at 120 ° C. and a relative humidity of 50% is 1.0 × 10 ⁻³ [s / cm] or more, more preferably 1.0 × 10 ⁻⁴ [s / cm] or more. The upper limit is usually 10 [s / cm] or less.

  In order to measure proton conductivity in the present invention, a powder of proton transmission material is filled in an evaluation cell made of a stainless steel electrode plated with gold and a Teflon (registered trademark) mold, and tightened with a torque of 3 Nm, The proton conductivity is measured by an AC impedance method (measurement frequency: 0.1 Hz to 5 MHz) while maintaining a predetermined temperature and humidity in a constant temperature and humidity chamber.

5. Forming Method There is no limitation on the method for forming a powder in which a solid acid is introduced into the pores of a porous carrier having through holes.
For example, as a method for forming a thin film, a known thin film forming method such as spin coating or dipping can be used by dispersing the powder in a solvent. At this time, binders such as PTFE (polytetrafluoroethylene) and PVDF (polyvinylidene fluoride), and molding agents such as alkoxysilanes and silane couplers may be used together with the solvent.
On the other hand, a molded body can be obtained by pelletizing the powder with a tablet molding machine. Further, by including the above molding aid, molding of the molded body can be facilitated, and physical properties of the molded body, that is, proton conductivity, strength and the like can be controlled.

6). Fuel Cell Electrolyte A proton conductive material in which a solid acid is introduced into the pores of a porous carrier having a through hole of the present invention is particularly preferably used as an electrolyte for a fuel cell. The electrolyte of the present invention can be used in the same manner as a known electrolyte as a fuel cell electrolyte. Hereinafter, the case of using a porous carrier in which a solid acid is introduced into pores having through holes of the present invention will be described.

The shape of the electrolyte of the fuel cell is not particularly limited, but is usually a film, a film, or a sheet, and the thickness is usually 1 μm or more and 20 mm or less. In order to lower the electrical resistance, it is preferable to make it thinner. That is, 1 mm or less is preferable, and 500 μm or less is more preferable.
Moreover, even if the electrolyte itself does not maintain its shape alone, it is thinned to about 0.001 to 20 mm on a support such as a fuel electrode, an air electrode, or carbon paper, carbon cloth, a graphite plate, Or you may laminate. As a general method at this time, a known thinning technique such as a dipping method or a spin coating method, or a coating technique can be used. In this case, a binder or a molding agent such as PTFE or PVDF may be used.

  An electrolyte using a porous carrier in which a solid acid is introduced into a through-hole that has been subjected to the hydrophilic treatment of the present invention is used, and an electromotive part in which the electrolyte is sandwiched between a fuel electrode (anode) and an air electrode (cathode) By configuring, a fuel cell can be formed. The electrolyte at this time is preferably formed into a shape (usually a sheet shape) used as a fuel cell. This means that it is preferable to have a shape-retaining property that can maintain a certain shape during the assembly operation of the fuel cell and during operation after assembly.

(Anode / Cathode)
The fuel electrode (anode) of a fuel cell usually contains an electrode catalyst such as platinum for electrochemically oxidizing hydrogen or methanol to generate protons and electrons. The air electrode (cathode) contains an electrode catalyst such as platinum for oxidizing protons conducted from the anode into the electrolyte into water. A part of platinum used as an electrode catalyst may be replaced by another noble metal such as palladium or ruthenium or alloyed as necessary.
The anode and cathode contain an electrically conductive compound for current collection.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not restrict | limited to a following example, unless it exceeds the summary, It can implement in various deformation | transformation.
Example 1
<Synthesis of porous carrier having through holes>
(Mesoporous silica Al-MCM-48 (Si / Al = 80))
To 83.3 ml of distilled water at 50 ° C., 28 g of n-hexadecyltrimethylammonium bromide was gradually added and dissolved while stirring with a stirrer. To this, 41.7 ml of 1 mol / l NaOH was added, and after stirring for 5 minutes, 0.125 g of Al (OH) ₃ was dissolved. Next, 26.7 g of tetraethoxysilane was slowly added and stirred for 1 hour. This solution was transferred to a 200 ml Teflon (registered trademark) container and placed in a constant temperature bath at 110 ° C. Two days later, the product was taken out from the thermostatic chamber, allowed to cool at room temperature, and then filtered. The obtained solid was thoroughly washed with distilled water and ethanol. Finally, the white solid obtained by filtration was baked in air at 540 ° C. for 10 hours to obtain Al-MCM-48 (Si / Al = 80). The Al-MCM-48 thus obtained
(Si / Al = 80) has a through hole, and the structure was confirmed by XRD.
From the results of nitrogen adsorption, the BET specific surface area was 1249 m ² / g, the most frequent pore diameter Dmax determined by the BJH method was 2.8 nm, and the pore volume was 1.356 cc / g. The most frequent pore diameter D
The volume of pores having a diameter within a range of 20% of the value of max was 80% or more with respect to the entire volume of pores having a diameter of 1 nm or more.

<Hydrophilic treatment (modification of sulfonic acid group)>
1 g of Al-MCM-48 was suspended in a water-methanol mixture (water 0.4 g, methanol 18 ml, 28% aqueous ammonia 0.16 g) adjusted to be ammonia basic, and 3-mercaptopropyltrimethoxysilane (3-Mercapto 0.85 g of propyl trimethoxy silane (hereinafter referred to as MPTMS) was added dropwise over 6 hours and stirred at room temperature for 20 hours. Solid-liquid separation was performed by filtration, and the particles were washed with methanol. The resulting product was suspended in a mixed solution of 31% hydrogen peroxide solution (1.71 g) and methanol (8.75 g), heated to 60 ° C., stirred for 30 hours, and then filtered. After washing with distilled water and ethanol, drying was performed to obtain Al-MCM-48 having a modified propylsulfonic acid group. The water vapor adsorption amount per gram of the Al-MCM-48 at a temperature of 80 ° C. and a relative humidity of 30% was 106.6 mg.

From the results of nitrogen adsorption, the BET specific surface area was 1179 m ² / g, the most frequent pore diameter Dmax determined by the BJH method was 2.2 nm, and the pore volume was 0.9935 cc / g.
Further, the volume of the pores having a diameter within the range of 20% of the value of the mode pore diameter Dmax was 80% or more with respect to the volume of the pores having a diameter of 1 nm or more.
After dispersing 0.1 g of Al-MCM-48 introduced with sulfonic acid groups in 30 ml of saturated saline, the protons in the sulfonic acid groups were exchanged with sodium ions in the sodium chloride by stirring at room temperature for 15 minutes. . The filtrate obtained by filtering the mixture was neutralized and titrated with a 0.025 N aqueous sodium hydroxide solution. As a result, the amount of sulfonic acid groups contained in Al-MCM-48 into which sulfonic acid groups had been introduced was 1 Calculated as .22 mmol / g.

<Introduction of 12-tungstophosphoric acid into porous carrier pores>
0.5 g of Al-MCM-48 modified with a sulfonic acid group was placed in 50 ml of a screw tube, vacuum-dried at 150 ° C. for 3 hours, cooled to room temperature, and a stir bar was added. To this, a solution obtained by dissolving 0.462 g of 12-tungstophosphoric acid in diethyl ether (0.255 g) having the same volume as the pore volume was dropped, and shaking was repeated many times. Finally, the sulfonic acid group-modified Al-MCM-48 in which 12-tungstophosphoric acid was introduced into the mesopores by drying at 100 ° C. for a whole day and night was obtained.

From the results of nitrogen adsorption, the BET specific surface area was 86.81 m ² / g, the most frequent pore diameter Dmax determined by the BJH method was 2.4 nm, and the pore volume was 0.06235 cc / g. Further, the volume of the pores having a diameter within the range of 20% of the value of the mode pore diameter Dmax was 80% or more with respect to the volume of the pores having a diameter of 1 nm or more.
After 0.1 g of Al-MCM-48 supporting sulfonic acid groups and 12-tungstophosphoric acid was dispersed in 30 ml of saturated saline, the mixture was stirred at room temperature for 15 minutes to give sulfonic acid groups and 12-tungstophosphoric acid. Were exchanged for sodium ions in sodium chloride. The filtrate obtained by filtering the mixture was subjected to neutralization titration with an aqueous 0.025 N sodium hydroxide solution. As a result, protons contained in Al-MCM-48 carrying sulfonic acid groups and 12-tungstophosphoric acid were obtained. The acid amount was calculated to be 1.94 mmol / g.

<Measurement of proton conductivity>
The obtained powder was filled in an evaluation cell consisting of a gold-plated stainless steel electrode and a Teflon (registered trademark) mold, and tightened with a torque of 3 Nm, and the AC impedance method (an LCR high tester manufactured by Hioki Electric, measuring frequency 0. 1 Hz to 5 MHz), the relative humidity dependence (30% to 90%) of proton conductivity at 80 ° C. in a constant temperature and humidity chamber was measured (FIG. 1).
(Comparative Example 1)
In Example 1, it carried out like Example 1 except not having introduce | transduced 12-tungstophosphoric acid into a mesopore. The relative humidity dependence of the conductivity obtained is shown in FIG.
(Comparative Example 2)
In Example, it carried out like Example 1 except not having introduce | transduced the propylsulfonic acid group. At a temperature of 80 ° C. and a relative humidity of 30%, the water vapor adsorption amount per 1 g of the Al-MCM-48 into which no propylsulfonic acid group was introduced was 15.9 mg.

  After dispersing 0.1 g of Al-MCM-48 in which 12-tungstophosphoric acid was introduced into the mesopores in 30 ml of saturated saline, the protons in 12-tungstophosphoric acid were dissolved in sodium chloride by stirring at room temperature for 15 minutes. Of sodium ions. The filtrate obtained by filtering the mixture was subjected to neutralization titration with a 0.025 N aqueous sodium hydroxide solution, and as a result, the protonic acid contained in Al-MCM-48 in which 12-tungstophosphoric acid was introduced into the mesopores. The amount was calculated as 1.70 mmol / g.

The relative humidity dependence of the conductivity obtained is shown in FIG.
The results of Examples and Comparative Examples are shown in Table 1 below. Note that the water vapor adsorption amount is a hydrophilic index.

From the above results, it can be seen that the porous carrier having a through-hole exhibits excellent proton conductivity under low humidity conditions by having a specific hydrophilicity and supporting a solid acid.
That is, by comparing Example 1 with Comparative Example 1, even a porous carrier having a through hole having the same hydrophilicity (water vapor adsorption amount) has a low humidity for the first time by carrying a solid acid. It can be seen that the proton conductivity is excellent under the environment.

Further, by comparing Example 1 and Comparative Example 2, if the porous carrier is not subjected to hydrophilic treatment and the hydrophilicity (water vapor adsorption amount) of the porous carrier is low, even if a solid acid is supported. It can be seen that it does not have good proton conductivity.
Therefore, even when a porous carrier in which a solid acid is introduced into pores whose surfaces are subjected to hydrophilic treatment on the surface of the example is used as an electrolyte of a fuel cell, higher power generation efficiency can be obtained compared to the comparative example. Is clear.

It is the relative humidity dependence of the proton conductivity of the proton conductive material of Example 1 and Comparative Examples 1 and 2.

Claims (5)

  A proton conducting material having a solid acid supported on a porous carrier having a through-hole and a hydrophilic group.   2. The proton conductive material according to claim 1, wherein the porous carrier is a porous carrier having a water vapor adsorption amount of 1 mg / g of porous carrier of 50 mg or more at a temperature of 80 ° C. and a relative humidity of 30%. The proton conductive material according to claim 1 or 2, wherein the amount of the hydrophilic group is 0.1 mmol or more per 1 g of the porous carrier.   A fuel cell using the proton conductive material according to claim 1 as an electrolyte.   A method for producing a proton conducting material, comprising adding a hydrophilic group to a porous carrier having a through-hole and then supporting a solid acid.

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