JP2003151583A - Solid high polymer electrolyte film and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid high polymer electrolyte that can provide a fuel cell, which can maintain high voltage also in long-term operation or high temperature operation and has excellent stability. SOLUTION: It consists of an organic resin and hydrate oxide antimony particles expressed with a formula Sb2 O5 .nH2 O (n=0.1 to 5). Average particle diameter of this particles is in the range of 5 to 50 nm, and the content of hydrate oxide antimony particles is in the range of 5 to 80 weight % by converting it to the oxide (Sb2 O5 ).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid polymer electrolyte membrane and a fuel cell using the solid polymer electrolyte membrane. More specifically, the present invention relates to a solid polymer electrolyte membrane fuel cell having excellent stability capable of maintaining high voltage even during long-term operation or high temperature operation.

[0002]

BACKGROUND OF THE INVENTION In recent years, fuel cells have been attracting attention as a power generation system that uses clean hydrogen as an energy source and that does not generate greenhouse gases such as CO ₂ with high efficiency and no pollution. Such fuel cells are under full-scale development research for the purpose of use in fixed facilities such as homes and businesses, and mobile facilities such as automobiles.

Fuel cells are classified according to the electrolyte membrane used, and are classified into alkaline electrolyte membrane type, solid polymer electrolyte membrane type, phosphoric acid type, molten carbonate type, and solid electrolyte membrane type.
At this time, in the solid polymer electrolyte membrane type and the phosphoric acid type, the charge transfer body is a proton, and it is also called a proton type fuel cell. The fuel used in this fuel cell is natural gas, L
Hydrocarbon-based fuels such as P gas, city gas, alcohol, gasoline, kerosene, and light oil are included.

First, such a hydrocarbon fuel is converted into hydrogen gas and CO gas by reactions such as steam reforming and partial oxidation, and CO gas is removed to obtain hydrogen gas. This hydrogen is supplied to the anode and dissociated into protons (hydrogen ions) and electrons by the metal catalyst of the anode, the electrons flow to the cathode while working through the circuit, and the protons (hydrogen ions) diffuse through the electrolyte membrane and form the cathode. And then becomes water from the electrons and hydrogen ions at the cathode and oxygen supplied to the cathode and diffuses into the electrolyte membrane. That is, it is a mechanism for extracting an electric current in the process of supplying oxygen and hydrogen derived from fuel gas to generate water.

As an electrolyte membrane used in such a fuel cell, a polystyrene type cation exchange membrane having a sulfonic acid group, a mixed membrane of fluorocarbon sulfonic acid and polyvinylidene fluoride, and a fluorocarbon matrix grafted with trifluoroethylene. The film used is a perfluorocarbon sulfonic acid film or the like. However, the movement of protons in the electrolyte membrane made of such an organic resin membrane, that is, the ionic conductivity of the membrane, depends on the water content in the membrane, and is about 80% after long-term operation.
When it is operated at a high temperature of ℃ or higher, the water content in the membrane is lowered, and as a result, the ionic conductivity is lowered and the generated voltage and voltage are lowered.

For this reason, in JP-A-6-103983, a compound having a phosphoric acid group is contained in a polymer film to allow the polymer film to exhibit a good water retention performance, whereby 80 ° C. or A solid polymer electrolyte membrane fuel cell that can be suitably used at operating temperatures higher than that has also been proposed. Further, Japanese Patent Laid-Open No. 2001-143723 discloses that
As an electrolyte membrane for a fuel cell, which can be suitably used at an operating temperature of 80 ° C. or higher, there is disclosed a membrane made of an amorphous silica molded body containing phosphorus pentoxide.

However, when these proposed solid polymer electrolyte membranes are used at a high temperature of 100 ° C. or higher for a long period of time, the voltage still drops and the battery performance deteriorates. Therefore, as a result of diligent studies on means for improving battery performance by long-term use under such high temperature conditions, the present inventors have found that antimony oxide particles have high proton conductivity and high water retention at high temperatures. Therefore, by using these antimony oxide particles as a solid polymer electrolyte membrane together with an organic resin, it was found that a fuel cell having high cell performance can be obtained even when used at high temperature for a long time, and the present invention is completed. Came to.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solid polymer electrolyte capable of providing a fuel cell excellent in stability capable of maintaining a high voltage even in long-term operation or high temperature operation.

[0009]

SUMMARY OF THE INVENTION A solid polymer electrolyte membrane according to the present invention comprises an organic resin and hydrated antimony oxide particles represented by the following formula (1), and the average particle diameter of the particles is in the range of 5 to 50 nm. It is characterized in that the content of the hydrated antimony oxide particles is in the range of 5 to 80% by weight in terms of oxide (Sb ₂ O ₅ ).

Sb ₂ O ₅ .nH ₂ O (1) n = 0.1 to 5 The organic resin is a polystyrene cation exchange resin having a sulfonic acid group, a mixture of fluorocarbon sulfonic acid and polyvinylidene fluoride, a fluorocarbon. Graft copolymer grafted with trifluoroethylene on the matrix, perfluorocarbon sulfonic acid resin, vinylidene fluoride resin, 2-dichloroethylene resin, polyethylene resin, vinyl chloride resin, ABS resin,
At least one selected from the group consisting of AS resin, polycarbonate resin, polyamide resin, polyimide resin, and methacrylic resin is preferable.

A polymer electrolyte membrane fuel cell according to the present invention comprises the above solid polymer electrolyte membrane.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The solid polymer electrolyte membrane fuel cell according to the present invention will be described below. Solid Polymer Electrolyte Membrane The solid polymer electrolyte membrane according to the present invention comprises an organic resin and hydrated antimony oxide particles represented by the following formula (1).

[Organic Resin] The organic resin is not particularly limited as long as it can be used as a solid electrolyte membrane. For example, a polystyrene cation exchange resin having a sulfonic acid group, a mixture of fluorocarbon sulfonic acid and polyvinylidene fluoride, Graft copolymer obtained by grafting trifluoroethylene on a fluorocarbon matrix, perfluorocarbon sulfonic acid resin, vinylidene fluoride resin, 2-dichloroethylene resin, polyethylene resin, vinyl chloride resin, ABS resin, AS resin, polycarbonate resin, polyamide resin, Polyimide resin,
At least one selected from the group consisting of methacrylic resins is preferable.

These organic resins are disclosed, for example, in JP-A-6-
275301, JP 10-199559, JP 10-4073
It is possible to use the materials exemplified in JP-A No. 7 and JP-A No. 6-103983. [Hydrated antimony oxide particles] The hydrated antimony oxide particles used in the present invention are antimony oxide hydrates and are represented by the following formula. (Except for mere adhering water, which is not water of crystallization) Sb ₂ O ₅ · nH ₂ O (1) n = 0.1 to 5 Antimony oxide particles have proton conductivity,
It is added to enhance the conductivity of the solid polymer electrolyte membrane.

The average particle size of such hydrated antimony oxide particles is preferably 5 to 50 nm, more preferably 5 to 25 nm. When the average particle size is less than 5 nm, the powder resistance (volume resistance value) may exceed 10 ¹⁰ Ω · cm, which results in low cation conductivity, and thus a sufficient output voltage cannot be obtained. Sometimes. If the average particle diameter exceeds the upper limit range, depending on the method for producing a solid polymer electrolyte membrane, it may not be possible to sufficiently introduce hydrated antimony oxide particles into the electrolyte membrane, and even if it can be introduced, it is solid. The strength of the polymer electrolyte membrane may be insufficient.

The water content of the hydrated antimony oxide particles is the water content when dried at 100 ° C. for 1 hour,
It is preferably in the range of approximately 0.5 to 22% by weight, more preferably 2 to 22% by weight. Further, preferably 200
The water content after drying at ℃ is 0.25 to 10% by weight,
Further, it is desirable to be in the range of 0.5 to 10% by weight.

When the water content of the hydrated antimony oxide particles after drying at 200 ° C. is less than 0.25% by weight, the effect of using the hydrated antimony oxide particles as the inorganic proton conductive particles cannot be obtained. During high temperature operation and long term operation, the voltage drops and the battery performance tends to decrease. 20
It is difficult to obtain a product having a water content of more than 10% by weight after drying at 0 ° C.

The hydrated antimony oxide particles used in the present invention do not need to be in the above water content range when used for preparing a solid polymer electrolyte membrane, and after the solid polymer electrolyte membrane is prepared, it is subjected to humidification treatment or the like. It can also be used as the water content range. The hydrated antimony oxide particles used in the present invention preferably have a powder resistance (volume resistance value) of less than 10 ¹⁰ Ω · cm, and more preferably less than 10 ⁷ Ω · cm.

If the volume resistance value of the conductive oxide particles exceeds the above upper limit, the effect of keeping the electric resistance low is insufficient, but a sufficient output voltage is obtained, although it depends on the content in the solid polymer electrolyte membrane. Sometimes I can't. [Solid Polymer Electrolyte Membrane] The solid polymer electrolyte membrane according to the present invention is composed of the organic resin and the hydrated antimony oxide particles.

Hydrated antimony oxide in solid polymer electrolyte membrane
The content of particles is oxide (Sb₂O _Five) As 5-80
%, Or even 10 to 50% by weight
preferable. The content of hydrated antimony oxide particles is in the above range
If it is inside, the proton conductivity of the solid polymer electrolyte membrane is high.
In addition, it has high water retention at high temperature and can be used at high temperature for a long time.
A fuel cell with high cell performance can be obtained even when used under
It In addition, hydrated antimony oxide particles in an amount less than the above lower limit
Even if it contains, the effect of using particles will be insufficient.
And the content of hydrated antimony oxide particles exceeds the above upper limit.
It is difficult to manufacture anything that exceeds this amount, and even if it could be made,
The strength of the solid polymer electrolyte membrane may be insufficient.

In the solid polymer electrolyte membrane according to the present invention, substantially hydrated antimony oxide particles are attached (supported) or introduced into the membrane body made of the above-mentioned organic resin. Therefore, the organic resin film body is preferably porous and has a porosity of 5% or more, preferably 10% or more. The method for producing a solid polymer electrolyte membrane according to the present invention is not particularly limited as long as hydrated antimony oxide particles can be attached (supported) or introduced into an organic resin film body. It can be obtained by immersing the resin film, introducing hydrated antimony oxide particles into the pores of the organic resin film, and then drying. In addition, the amount of hydrated antimony oxide particles introduced can be increased by repeating this dipping and drying, if necessary.

When a sol in which hydrated antimony oxide particles are stably dispersed is used as the dispersion liquid, a solid polymer electrolyte membrane in which hydrated antimony oxide particles are uniformly dispersed can be obtained. When a mixed solvent of water and alcohol is used as the dispersion medium of the sol, the affinity with the resin is increased, and it is possible to obtain a solid polymer electrolyte membrane in which the inorganic proton conductive oxide particles are more uniformly dispersed in the membrane. it can. As a result, even if the formed fuel cell is operated at a high temperature for a long time, the decrease in proton conductivity is small and a high output voltage can be maintained.

Further, after immersing in the above dispersion liquid, taking out, drying and then heating at a temperature near the softening point of the organic resin used, the hydrated antimony oxide particles can be strongly fixed to the organic resin film. Alternatively, the solid polymer electrolyte membrane after drying can be sandwiched between two electrode membranes and fixed during hot pressing. It can also be obtained by previously dispersing hydrated antimony oxide particles in a resin monomer and polymerizing it when the organic resin film is manufactured. In addition, the solid polymer electrolyte membrane according to the present invention can be manufactured by once dissolving the organic resin, mixing the hydrated antimony oxide particles, and molding the membrane by a known molding method.

In the present invention, a method of immersing and drying the organic resin film body in a dispersion liquid of hydrated antimony oxide particles is preferable from the viewpoint of strength of the film to be obtained and ease of production. Fuel Cell The fuel cell according to the present invention is characterized by using the above-mentioned solid polymer electrolyte membrane.

Specifically, the solid polymer electrolyte membrane is composed of the above-mentioned solid polymer electrolyte membrane and a pair of gas diffusion electrodes (fuel electrode and oxidizing electrode) arranged on both sides of the membrane. A unit cell is formed by sandwiching a molecular electrolyte membrane and arranging a current collector with a groove that forms a fuel chamber and an oxidant chamber on both sides of the both electrodes. It is configured by stacking layers.

The gas diffusion electrode usually comprises a porous sheet in which a conductive material carrying catalyst particles is held by a hydrophobic resin binder such as PTFE. Also, conductive material and PTFE
A catalyst particle layer may be provided on the contact surface of the solid polymer electrolyte membrane of a porous sheet made of a hydrophobic resin binder such as A solid polymer electrolyte membrane is sandwiched between a pair of such gas diffusion electrodes, and they are crimped by a known crimping means such as hot pressing.

Any catalyst may be used as long as it has a catalytic action on hydrogen oxidation reaction and oxygen reduction reaction, such as platinum,
It can be selected from metals such as ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum or alloys thereof.

Any electrically conductive material may be used as the electrically conductive material. For example, carbon black such as furnace black, channel black, and acetylene black known as carbon materials, activated carbon, graphite, and various metals can be used. . Examples of the hydrophobic resin binder include various resins containing fluorine, such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and perfluorosulfonic acid.

A proton conductive polymer may be used as the hydrophobic resin binder, and this polymer also has a function as a binder in the polymer itself, and in the catalyst layer, the catalyst particles and the conductive particles are contained. It is possible to form a matrix having sufficient stability with Further, a gas diffusion layer made of the hydrophobic resin binder may be provided on the opposite surface in contact with the solid polymer electrolyte membrane.

The supported amount of the catalyst is 0.01 to 5 mg / cm ² in the state where the catalyst layer sheet is formed, and more preferably 0.1 to 1 mg / cm ² . The electrically conductive porous material has a specific surface area of 100 to 2000 m ² /
A value of g is preferable for obtaining sufficient permeability. The average pore diameter of the gas diffusion electrode is preferably 0.01 to 1 μm.

Further, in the present invention, a proton conductive polymer layer formed at the interface where at least one of the catalyst layers and the solid polymer electrolyte membrane are in contact may be formed. In the fuel cell according to the present invention, hydrogen is supplied to the fuel chamber, air (oxygen) is supplied to the oxidant chamber, and electricity is generated by the following electrode reaction. A fuel electrode ^{_{(anode): H 2 → 2H + +}} 2e - oxygen electrode ^{(cathode): 2H + + 1 / 2O} 2 + 2e - →
In the antimony oxide particles in the 2H ₂ O solid polymer electrolyte membrane, hydrogen is bonded to oxygen of the antimony oxide skeleton, exists in the state of water, or is a proton (H ⁺ ) or hydronium ion (H ₃ O ^+). ) It is thought that it exists in the state of.

Gaseous water and condensed water produced by the cell reaction quickly pass through the oxygen electrode through a layer having higher water repellency and fine pores by a capillary phenomenon.

[0033]

EFFECTS OF THE INVENTION According to the present invention, the solid polymer electrolyte membrane is composed of an organic resin membrane and inorganic proton conductive oxide particles excellent in high-temperature water retention performance and conductivity, so long-term operation, 100 It is possible to provide a solid polymer electrolyte membrane fuel cell that can stably maintain a high output voltage even when it is operated at a high temperature of ℃ or higher.

[0034]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0035]

EXAMPLE 1 Inorganic proton conductive oxide particles as antimony pentoxide particles (average particle diameter _{10nm, Sb 2 O 5 · 2} .
5H ₂ O) was used to prepare a mixed solvent dispersion having a concentration of Sb ₂ O ₅ of 30% by weight of ethyl alcohol: water = 50: 50. As an organic resin film, a perfluorocarbon sulfonic acid film (A) (manufactured by Du Pont: Nafion film N-11)
(7, film thickness 183 μm) was immersed at 50 ° C. for 12 hours, taken out, and dried at 100 ° C. for 12 hours to obtain a solid polymer electrolyte membrane (A). The content of antimony pentoxide particles in the solid polymer electrolyte membrane (A) was 20% by weight calculated from the weight increase.

The platinum content is 40% by weight as Pt.
Of platinum-supported carbon particles in ethyl alcohol: water = 5
A 0:50 mixed solvent was added to form a paste, and two carbon papers (manufactured by Toray Industries, Inc.) treated with tetrafluoroethylene for water repellency were used.
Apply to a density of mg / cm ² and apply at 100 ° C for 1
After drying for 2 hours, two gas diffusion electrodes (A) were prepared.

Two gas diffusion electrodes (A) were used as a positive electrode and a negative electrode, and the solid polymer electrolyte membrane (A) was sandwiched between these electrodes, and hot pressed at 100 ° C. for 5 minutes under a pressure of 150 kg / cm ^2. A unit cell (A) in which the gas diffusion electrode (A) and the solid polymer electrolyte membrane (A) were joined was prepared. Evaluation The unit cell (A) was humidified at 80 ° C. and 30% relative humidity for 2 hours. Then, under normal pressure, 80 ℃, 100 ℃, 140
At each temperature of ° C, the device was operated at a current density of 0.5 A / cm ² for 50 hours, and the output voltage at each temperature was measured.

The results are shown in Table 1.

[0039]

Example 2 The solid polymer electrolyte membrane (A) obtained in the same manner as in Example 1 was again added to the antimony pentoxide particle dispersion liquid at 50 ° C.
Soak for 12 hours at 100 ° C for 12 hours
It was dried for an hour to obtain a solid polymer electrolyte membrane (B). The content of antimony pentoxide particles in the solid polymer electrolyte membrane (B) was 35% by weight due to the weight increase.

Evaluation A unit cell (B) was prepared in the same manner as in Example 1 except that the solid polymer electrolyte membrane (B) was used, and the output voltage was measured. The results are shown in Table 1.

[0041]

Example 3 The solid polymer electrolyte membrane (B) obtained in the same manner as in Example 2 was again added to the antimony pentoxide particle dispersion liquid at 50 ° C.
Soak for 12 hours at 100 ° C for 12 hours
It was dried for an hour to obtain a solid polymer electrolyte membrane (C). The content of antimony pentoxide particles in the solid polymer electrolyte membrane (C) was 45% by weight due to the weight increase.

Evaluation A unit cell (C) was prepared in the same manner as in Example 1 except that the solid polymer electrolyte membrane (C) was used, and the output voltage was measured. The results are shown in Table 1.

[0043]

Example 4 Antimony Pentoxide Particles (Average Particle Diameter 40n
m, Sb ₂ O ₅ .2.5H ₂ O) was used to obtain a solid polymer electrolyte membrane (D) in the same manner as in Example 1. The content of antimony pentoxide particles in the solid polymer electrolyte membrane (D) was 15% by weight due to the weight increase.

Evaluation A unit cell (D) was prepared in the same manner as in Example 1 except that the solid polymer electrolyte membrane (D) was used, and the output voltage was measured. The results are shown in Table 1.

[0045]

[Example 5] Perfluorocarbon sulfonic acid film (B) as an organic resin film (manufactured by DuPont: Nafion film N-11)
5, a solid polymer electrolyte membrane (E) was obtained in the same manner as in Example 1 except that the thickness was 127 μm). The content of antimony pentoxide particles in the solid polymer electrolyte membrane (E) was 25% by weight due to the weight increase.

Evaluation A unit cell (E) was prepared in the same manner as in Example 1 except that the solid polymer electrolyte membrane (E) was used, and the output voltage was measured. The results are shown in Table 1.

[0047]

[Example 6] Perfluorocarbon sulfonic acid film (C) as an organic resin film (manufactured by DuPont: Nafion film NE-11)
35, film thickness 51 μm) was used to obtain a solid polymer electrolyte membrane (F) in the same manner as in Example 1. The content of antimony pentoxide particles in the solid polymer electrolyte membrane (F) was 15% by weight due to the weight increase.

Evaluation A unit cell (F) was prepared in the same manner as in Example 1 except that the solid polymer electrolyte membrane (F) was used, and the output voltage was measured. The results are shown in Table 1.

[0049]

COMPARATIVE EXAMPLE 1 A unit cell (G) was prepared in the same manner as in Example 1 except that the perfluorocarbon sulfonic acid membrane (A) was used as the solid polymer electrolyte membrane (G) without introducing antimony pentoxide particles. Then, the output voltage was measured. The results are shown in Table 1.

[0050]

[Comparative Example 2] A unit cell (H) was prepared in the same manner as in Example 1 except that the perfluorocarbon sulfonic acid membrane (B) was used as the solid polymer electrolyte membrane (H) without introducing antimony pentoxide particles. Then, the output voltage was measured. The results are shown in Table 1.

[0051]

Comparative Example 3 A unit cell (I) was prepared in the same manner as in Example 1 except that the perfluorocarbon sulfonic acid membrane (C) was used as the solid polymer electrolyte membrane (I) without introducing antimony pentoxide particles. Then, the output voltage was measured. The results are shown in Table 1.

[0052]

[Table 1]

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[Procedure amendment]

[Submission Date] November 13, 2002 (2002.11.
13)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

As an electrolyte membrane used in such a fuel cell, a polystyrene type cation exchange membrane having a sulfonic acid group, a mixed membrane of fluorocarbon sulfonic acid and polyvinylidene fluoride, and a fluorocarbon matrix grafted with trifluoroethylene. The film used is a perfluorocarbon sulfonic acid film or the like. However, the movement of protons in the electrolyte membrane made of such an organic resin membrane, that is, the ionic conductivity of the membrane, depends on the water content in the membrane, and is about 80% after long-term operation.
When ℃ high temperature operation above, the water content is reduced in the membrane, resulting in reduced ion conductivity, there are problems such as causing a decrease in the generation voltage.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

Two gas diffusion electrodes (A) were used as a positive electrode and a negative electrode, and the solid polymer electrolyte membrane (A) was sandwiched between these electrodes, and hot pressed at 100 ° C. for 5 minutes under a pressure of 150 kg / cm ^2. A unit cell (A) in which the gas diffusion electrode (A) and the solid polymer electrolyte membrane (A) were joined was prepared. Evaluation The unit cell (A) was humidified at 80 ° C. and 30% relative humidity for 2 hours. Then, under normal pressure, 80 ° C, 100 ° C, 120
Current density of 0.5 A / cm ² at each temperature of ℃ and 140 ℃
Was operated for 50 hours, and the output voltage at each temperature at this time was measured.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiro Komatsu             No. 13-2 Kitaminato-cho, Wakamatsu-ku, Kitakyushu City, Fukuoka Prefecture             Medium Chemical Industry Co., Ltd. Wakamatsu Factory F term (reference) 5H026 AA06 CX05 EE12 EE18 EE19                       HH01 HH05

Claims (3)

[Claims] 1. An organic resin and hydrated antimony oxide particles represented by the following formula (1), wherein the particles have an average particle size of 5:
The solid polymer electrolyte membrane is in the range of ˜50 nm, and the content of the hydrated antimony oxide particles is in the range of 5 to 80% by weight in terms of oxide (Sb ₂ O ₅ ). Sb ₂ O ₅ · nH ₂ O (1) n = 0.1 to 5 2. The organic resin is a polystyrene cation exchange resin, a mixture of fluorocarbon sulfonic acid and polyvinylidene fluoride, a graft copolymer in which trifluoroethylene is grafted on a fluorocarbon matrix, a perfluorocarbon sulfonic acid resin, and a fluorocarbon resin. At least one selected from the group consisting of vinylidene chloride resin, 2-dichloroethylene resin, polyethylene resin, vinyl chloride resin, ABS resin, AS resin, polycarbonate resin, polyamide resin, polyimide resin, and methacrylic resin. Item 2. The solid polymer electrolyte membrane according to item 1. 3. A solid polymer electrolyte membrane fuel cell comprising the solid polymer electrolyte membrane according to claim 1 or 2.