JP4925091B2 - PROTON CONDUCTIVE COMPOSITE ELECTROLYTE MEMBRANE AND METHOD FOR PRODUCING THE SAME - Google Patents

Description

  The present invention relates to a proton conductive composite electrolyte membrane and a method for producing the same, and more specifically, a fuel cell, water electrolysis, hydrohalic acid electrolysis, salt electrolysis, oxygen electrolysis capable of operating in a higher temperature range. The present invention relates to a proton conductive composite electrolyte membrane used for a concentrator, a humidity sensor, a gas sensor, and the like, and a method for manufacturing the same.

Fuel cells have high power generation efficiency and excellent environmental load control, and are expected to contribute to solving environmental and energy problems that are currently a major issue in countries that consume large amounts of energy. It is a generational energy supply device.
Fuel cells are classified according to the type of electrolyte. Among them, polymer electrolyte fuel cells are small and can provide high output, so that they can be used for small-sized stationary devices, mobile devices, and portable terminals. Research and development is underway for the application of energy as a source of energy.

  In addition, a solid polymer material having a hydrophilic functional group such as a sulfonic acid group or a phosphoric acid group in a polymer chain is used for an electrolyte membrane of a solid polymer fuel cell. Since such a solid polymer material is firmly bonded to specific ions and has a property of selectively transmitting cations or anions, it is formed into particles, fibers or membranes, and electrodialyzed. It is used in various applications such as diffusion dialysis and battery diaphragm.

  Furthermore, solid polymer fuel cells are currently being actively improved as power generation means that can provide high overall energy efficiency. The main components are anode and cathode electrodes, a separator plate that forms a gas flow path, and a solid polymer electrolyte membrane that separates the electrodes. Protons generated on the anode catalyst move through the solid polymer electrolyte membrane, reach the cathode catalyst, and react with oxygen. Therefore, the ionic conduction resistance between the two electrodes greatly affects the battery performance.

  In order to form a fuel cell using the above-mentioned solid polymer electrolyte membrane, it is necessary to join the catalyst of both electrodes and the solid polymer electrolyte membrane by an ion conductive path. For this purpose, a catalyst layer in which a polymer electrolyte solution and catalyst particles are mixed, applied and dried to bond them together is used as an electrode, and the electrode catalyst and the solid polymer electrolyte membrane are pressed under heating. The technique was commonly used.

In general, a polymer in which a sulfonic acid group is introduced into a perfluorocarbon-based main chain is used as a polymer electrolyte responsible for ionic conduction. Specific products include Nafion manufactured by DuPont, Flemion manufactured by Asahi Glass Co., and Aciplex manufactured by Asahi Kasei Co., Ltd., and the like.
A perfluorosulfonic acid polymer electrolyte is composed of a perfluorocarbon main chain and a side chain having a sulfonic acid group, and the polymer electrolyte is a region mainly composed of a sulfonic acid group and a region mainly composed of a perfluorocarbon main chain. It is thought that the sulfonic acid group phase forms a cluster by microphase separation. The site where the perfluorocarbon main chain is aggregated contributes to the chemical stability of the perfluorosulfonic acid electrolyte membrane, and the sulfonic acid groups gather to form a cluster that contributes to ionic conduction. Part.

  As described above, it is difficult to produce a perfluorosulfonic acid electrolyte membrane having both excellent chemical stability and ionic conductivity, and there is a drawback that it is very expensive. Therefore, the use of the perfluorosulfonic acid electrolyte membrane is limited, and it is extremely difficult to apply it to a polymer electrolyte fuel cell which is expected to be a power source for a moving body.

  On the other hand, current polymer electrolyte fuel cells are operated in a relatively low temperature range from room temperature to about 80 ° C. The limitation of this operating temperature is that the perfluorosulfonic acid electrolyte membrane used has a glass transition point in the vicinity of 120 to 130 ° C., and maintains an ion channel structure that contributes to proton conduction at higher temperatures. In practice, it is desirable to use at 100 ° C. or lower, and since water is used as a proton conducting medium, pressurization is required when the boiling point exceeds 100 ° C., which is the boiling point of water. By becoming.

However, the low operating temperature results in low power generation efficiency for the fuel cell and significant poisoning of the catalyst by CO. When the operating temperature is 100 ° C. or higher, the power generation efficiency is improved and the waste heat can be used, so that energy can be used more efficiently.
Also, considering the application to fuel cell vehicles, if the operating temperature can be raised to 120 ° C, not only the efficiency will be improved, but also the radiator load required for exhaust heat will be reduced, and it will be used in current mobile units. The same specifications as the existing radiator can be applied, so the system can be made compact.

  Thus, various studies have been made so far in order to realize operation at higher temperatures. Typically, as an action with a view to reducing the cost of the previous electrolyte membrane, instead of a perfluorosulfonic acid electrolyte membrane, an inexpensive aromatic hydrocarbon polymer material with excellent heat resistance is used. Application to molecular electrolyte membranes is being studied.

For example, a silane compound having one organic group having a reactive terminal per Si is hydrolyzed and dehydrated and condensed to obtain a reaction intermediate. Then, a brainsted acid containing phosphotungstic acid is added to the reaction intermediate to produce protons. There has been proposed a method for producing a good proton conducting membrane by producing a conductor raw material solution, impregnating the polymer porous membrane with this solution and then performing heat treatment (see, for example, Patent Document 1).
JP 2004-241229 A

  However, although the above conventional example shows high ionic conductivity of several tens of mS / cm at a temperature of 100 ° C. or higher, sufficient ionic conductivity is provided in a region where the temperature drops to room temperature to 80 ° C. because phosphotungstic acid is used. It is difficult to secure. Further, in the conventional example, general-purpose polymer porous materials are used for the support, and these can be said to be realistic materials in consideration of industrial technical background. However, there is a high possibility of breakage or the like when a continuous load is applied under high temperature and high humidity while having heat resistance of 100 ° C. or more as material characteristics.

  Instead of phosphotungstic acid, in order to ensure ionic conductivity in a wide temperature range, use of an aromatic hydrocarbon polymer electrolyte excellent in heat resistance is also being studied. However, an electrolyte polymer using such an aromatic hydrocarbon polymer material is an extremely rigid polymer material, and may be damaged when an excessive load is applied by a process such as hot pressing when forming an electrode. There is. Furthermore, these aromatic hydrocarbon polymer materials are modified with acidic functional groups such as sulfonic acid groups and phosphoric acid groups in order to impart proton conductivity, and are water-soluble or water-swellable. In the case of water-solubility, it cannot be applied to a system that generates water such as a fuel cell, and in the case of water-swelling, the electrode is damaged by the stress due to swelling. Can happen.

  Furthermore, in order to realize high ionic conductivity, it is desirable to introduce a large number of acidic functional groups to be introduced into the electrolyte polymer, but the amount introduced is limited in order to maintain the film shape of the polymer material itself. . In an electrolyte membrane using a polymer electrolyte, in order to ensure its dimensional stability and self-supporting property, the support is often impregnated. In any of the electrolyte membranes obtained by impregnation, the electrolyte membrane It causes a decrease in its ionic conductivity.

  In this way, ensuring dimensional stability and self-sustainability as an electrolyte membrane related to fuel cell reliability, and improving ionic conductivity with the aim of improving battery performance, are the sulfonic acid groups and phosphorus introduced into the resin, respectively. It is related to the amount of acid groups and the like, and both characteristics are in a trade-off relationship. Therefore, it is difficult to realize an electrolyte membrane having both characteristics because one improvement reduces the other characteristic.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is excellent in ionic conductivity, high heat resistance, suppression of swelling when containing water, and production at low cost. An object of the present invention is to provide a proton conductive composite electrolyte membrane and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventors have introduced hydrophilic functional groups into the spherical pores of the inorganic porous body in which the spherical pores are regularly and three-dimensionally formed. (Surface modification of the inorganic porous body) It was found that the above problems can be solved by arranging a hydrocarbon electrolyte having high ion conductivity together, and the present invention has been completed.

That is, the proton conductive composite electrolyte membrane of the present invention includes an inorganic porous body having a plurality of spherical pores, and a proton conductive hydrocarbon electrolyte disposed in the spherical pores. The inner diameter is substantially uniform, the adjacent spherical holes communicate with each other, the inner wall surface has a proton-donating functional group, and the spherical holes have an ordered arrangement structure resulting from a close-packed structure, and It is characterized by having a communication port regularly formed between adjacent spherical holes.

  In addition, a preferred embodiment of the proton conductive composite electrolyte membrane of the present invention is characterized in that the inorganic porous body is formed from a suspension obtained by mixing polymer fine particles and an inorganic material.

  Furthermore, another preferred embodiment of the proton conductive composite electrolyte membrane of the present invention is characterized in that the inner diameter of the spherical pore of the inorganic porous body is 20 to 500 nm. Furthermore, it is preferable that the internal diameter of the spherical hole of the said inorganic porous body is 20-200 nm.

  Furthermore, in another preferred embodiment of the proton conductive composite electrolyte membrane of the present invention, the proton donating functional group is in a ratio of 0.2 to 2.8 mmol / g per unit mass of the inorganic porous material. It is included.

  Further, another preferred embodiment of the proton conductive composite electrolyte membrane of the present invention is that the above-mentioned inorganic porous material has an Equivalent Weight (EW) value (dry inorganic porous material weight per equivalent of proton-donating functional group). 350 to 3600 g / eq.

Furthermore, the manufacturing method of the proton conductive composite type electrolyte membrane of the present invention, in manufacturing the proton conductive composite type electrolyte membrane,
1. Mixing an inorganic sol and a spherical organic resin using a solvent;
2. A step of stirring the mixed solution to form a suspension;
3. Filtering the suspension to form a membrane,
4). Removing excess water from the filtration molded membrane;
5. A step of drying the filtration molded membrane,
6). A step of heating and baking the filtration molded membrane to obtain an inorganic porous body,
7). Introducing a proton-donating functional group into the inner wall surface of the spherical pore of the inorganic porous body;
8). Fixing the proton-donating functional group;
9. Impregnating the spherical pores of the inorganic porous body with a hydrocarbon-based electrolyte;
10. Drying and forming a proton conductive composite electrolyte membrane,
It is characterized by performing.

  According to the present invention, a proton conductive composite electrolyte membrane having excellent ionic conductivity, high heat resistance, and suppressing swelling when containing water can be produced at low cost.

  Hereinafter, the proton conductive composite electrolyte membrane of the present invention will be described in detail. In the present specification and claims, “%” indicates a mass percentage unless otherwise specified.

The proton conductive composite electrolyte membrane of the present invention is formed by disposing a hydrocarbon-based electrolyte material in a plurality of spherical holes of an inorganic porous body.
Each of the spherical holes has a substantially uniform inner diameter, exists three-dimensionally inside the porous body, and communicates with adjacent spherical holes via a communication port.
Further, the inner wall surface of the spherical hole is treated so that the proton donating functional group exists.
Further, the hydrocarbon-based electrolyte is disposed (filled) so as to exhibit proton conductivity through the communication port.
FIG. 1 shows a schematic structure and a photograph of the present electrolyte membrane.

In this way, an inorganic porous body having a proton-donating functional group on the pore surface is used as a holding body, and a polymer electrolyte to be impregnated therein is disposed, so that the entire membrane in an electrolyte membrane in which both materials are composited Since the amount of the proton-donating functional group in can be increased, it is possible to obtain an inorganic / organic composite electrolyte membrane in which the decrease in ionic conductivity due to composite formation is suppressed.
Furthermore, since an aromatic hydrocarbon-based electrolyte utilizing an engineering plastic with high heat resistance can be disposed inside, an electrolyte having excellent heat resistance can be obtained.

  In the wet state, the inorganic porous body suppresses the swelling of the hydrocarbon electrolyte. In particular, since the spherical pores existing inside the porous body are configured with a substantially uniform diameter, the porous body receives a homogeneous and dispersed swelling force against the swelling of the electrolyte material when it contains water. Electrolyte damage is suppressed. In other words, since the spherical pores of the inorganic porous body have a three-dimensional regular array structure, the swelling pressure of the electrolyte material is uniformly applied to the inorganic porous body, so that it becomes a support for the electrolyte membrane that swells with water.

Furthermore, since it can be comprised with a cheaper material than a perfluorosulfonic acid type electrolyte, it is cheaper than a conventional product and an electrolyte membrane suitable for popularization can be obtained.
Furthermore, since a proton conductive functional group is interposed at the interface between the inorganic porous support and the hydrocarbon-based electrolyte, compared to a hybrid membrane in which the spherical pores of the inorganic porous support are simply impregnated with an electrolyte solution. Proton conductivity is further improved.

  Here, the inorganic porous body is preferably made of a metal oxide. Since many metal oxides are stable and available at a low cost, a desired electrolyte membrane can be obtained by appropriately selecting them.

  The inorganic porous body is preferably made of a material that forms an inorganic sol. In this case, a sol-gel method, which is a simple inorganic material forming technique, can be applied, and an inorganic porous body can be obtained at a low cost.

  The inorganic sol-forming material is preferably an inorganic colloid. The inorganic colloid is suitable for forming an inorganic porous body using polymer particles as a template, and can form a spherical hole in which a three-dimensional ordered arrangement state is maintained.

  Furthermore, the inorganic porous body preferably includes, for example, those related to silica, titania, alumina, zirconia, or tantalum, and any combination thereof. At this time, it can be an inorganic colloid that can withstand practical use.

The inorganic porous body is obtained from, for example, a suspension obtained by mixing polymer fine particles and an inorganic material.
By applying such a suspension, an inorganic porous body can be obtained using a three-dimensional regular array structure formed by stacking polymer fine particles as a template. In particular, an inorganic porous body having an arbitrary pore size structure can be designed by controlling the particle size and the lamination state of the polymer fine particles. The polymer fine particles in the pores are removed by heat treatment or the like, so that a space for the electrolyte material is secured.
In addition, by using an inorganic porous body having spherical pores regularly arranged three-dimensionally in this way, it functions as a homogeneous support. Therefore, when combined with a polymer electrolyte, the electrolyte contains water. Concentration of swelling force exerted on the support can be suppressed, and damage to the electrolyte membrane can be prevented.
Furthermore, since the spherical pores of the inorganic porous material can be produced so as to ensure a high porosity exceeding 70%, a large amount of hydrocarbon electrolyte can be introduced, and excellent ionic conductivity can be realized.

The inner diameter of the spherical pores of the inorganic porous body is preferably 20 to 500 nm in view of the balance between the amount of the proton conductive functional group and the difficulty in introducing the hydrocarbon electrolyte. At this time, the ionic conductivity of the electrolyte membrane can be improved.
If it exceeds 500 nm, the amount of the proton conductive functional group immobilized per unit weight of the inorganic porous support is small, so that the effect tends to be insufficient. If it is less than 20 nm, formation of a porous material using a spherical resin as a template tends to be difficult.

The inner diameter of the spherical hole is more preferably 20 to 200 nm, and particularly preferably 50 to 150 nm. At this time, the contribution of the surface modification of the proton conductive functional group can be sufficiently exhibited.
That is, when the thickness is 150 nm or less, the amount of proton conductive functional groups immobilized per unit weight of the inorganic porous support increases rapidly, and a sufficient effect can be exhibited. When the thickness is 50 nm or more, formation of a porous body using a spherical resin as a template becomes easier and stable production is possible.

As the proton donating functional group on the inner wall surface of the spherical hole, a Bronsted acid type functional group can be adopted. In this case, a region that promotes proton conduction is formed at the interface between the inorganic support and the organic electrolyte, so that proton conductivity can be improved as compared with the conventional product.
Specifically, a sulfonic acid group, a phosphoric acid group, or a carboxylic acid group, and any combination thereof can be introduced.

The proton-donating functional group differs in the amount of functional group that can be introduced depending on the inner diameter of the spherical pore, but from the viewpoint of improving proton conductivity, 0.2 to 2.8 mmol per unit mass of the inorganic porous material It is preferable to be contained at a ratio of / g.
More preferably, it is contained at a rate of 0.3 to 1.2 mmol / g per unit mass of the inorganic porous material. For example, by setting the proton conductive functional group concentration (about 0.9 to 1.1 mmol / g) present in a Nafion (trademark: DuPont) membrane generally used in PEFC to the same level or more, The effect of higher proton conductivity can be expected.

  In addition, from the same viewpoint, it is preferable that the Equivalent Weight (EW) value of the inorganic porous material is 350 to 3600 g / eq. More preferably, it is 890-2700 g / eq. The EW value is usually defined as the dry polymer weight per equivalent of sulfonic acid groups in an electrolyte membrane typified by Nafion. Here, the target is an inorganic porous material having a proton-donating functional group, The dry weight of the inorganic porous material per equivalent of the donating functional group is shown.

  In this case, since the amount of proton conductive functional groups introduced per unit area increases, the ionic conductivity of the proton conductive composite electrolyte membrane can be increased. Moreover, the amount of proton conductive functional groups contained in the composite electrolyte membrane can also be increased by increasing the inner wall area of the spherical pores per unit membrane weight.

Specifically, the relationship between the pore diameter of the inorganic porous body and the amount of proton conductive functional groups that can be introduced, and the relationship between the pore diameter of the inorganic porous body and the EW value are monovalent that can be introduced per unit surface area of the metal oxide. When calculated based on the proton donating functional group (represented by a sulfonic acid group), the results are shown in FIGS.
Thus, it can be seen that the smaller the pore diameter, the more proton conductive functional groups that can be introduced into the inorganic porous material. Further, when paying attention to EW, it is desirable that the EW value is small because it indicates the unit weight of the inorganic porous material per functional group. FIG. 3 shows that the EW value decreases as the pore diameter decreases.

On the other hand, as the hydrocarbon-based electrolyte disposed in the spherical pores of the inorganic porous body, it is preferable to use a hydrocarbon-based resin provided with a functional group that expresses proton conductivity.
By employing a hydrocarbon resin with excellent heat resistance, an electrolyte membrane with excellent heat resistance can be obtained, and a material cheaper than conventional perfluorosulfonic acid electrolyte materials can be applied.

In addition, the hydrocarbon electrolyte preferably has an ion exchange capacity of at least 1 to 6 meq / g.
In order to set the ion exchange capacity within the above range, for example, the type of the aromatic hydrocarbon electrolyte, the amount of the proton conductive functional group to be imparted, and the like may be appropriately adjusted. At this time, if the amount of the proton conductive functional group introduced into the aromatic hydrocarbon electrolyte is less than 1 meq / g, sufficient proton conductivity cannot be expressed, and if it exceeds 6 meq / g, the electrolyte material is It becomes difficult to maintain a solid state.

  In addition, in the conventional perfluorosulfonic acid electrolyte membrane represented by Nafion (trademark: manufactured by DuPont), those around 1 meq / g are marketed, but those of 2 meq / g or more are difficult. In the present invention, an electrolyte membrane having higher proton conductivity than conventional ones can be designed.

Furthermore, it is preferable to use a polyether polymer as the hydrocarbon electrolyte.
Specifically, as shown in FIG. 4, polyether ether ketone or polyether sulfone obtained by sulfonating a polyether-based substance can be used. Typically, polyether ether sulfone is preferably used.
In this case, an inorganic porous body having a regularly arranged space can be impregnated with more electrolyte materials than a conventional perfluorosulfonic acid electrolyte, and has a higher proton conductivity than a conventional product. An electrolyte can be obtained.

Next, the production method of the proton conductive composite electrolyte membrane of the present invention will be described in detail.
In the production method of the present invention, the following steps:
1. Mixing an inorganic sol and a spherical organic resin using a solvent;
2. A step of stirring the mixed solution to form a suspension;
3. Filtering the suspension to form a membrane,
4). Removing excess water from the filtration molded membrane;
5. A step of drying the filtration molded membrane,
6). A step of heating and baking the filtration molded membrane to obtain an inorganic porous body,
7). Introducing a proton-donating functional group into the inner wall surface of the spherical pore of the inorganic porous body;
8). Fixing the proton-donating functional group;
9. Impregnating the spherical pores of the inorganic porous body with a hydrocarbon-based electrolyte;
10. Drying and forming a proton conductive composite electrolyte membrane,
To produce the proton conductive composite electrolyte membrane described above.
FIG. 5 shows the flow of the manufacturing procedure.

  Here, through steps 1 to 6, an inorganic porous body in which spherical pores are three-dimensionally arranged using a spherical organic resin as a template is obtained.

  In Step 1 and Step 2, the inorganic colloid and the organic resin material can be mixed in a homogeneous state. Thereby, the inorganic porous body comprised with a homogeneous inorganic support body can be obtained.

In Step 3, filtration is suitable as a method of filling the gap with an inorganic sol using a spherical organic resin as a template. Filtration can be performed by appropriately reducing the pressure by about 10 to 60 kPa from the size of the spherical pores and the pore density of the inorganic porous body.
As the spherical organic resin used in step 3, for example, polyethylene of about 20 nm to 1500 nm can be used. Typically, polyolefin resin, polystyrene resin, cross-linked acrylic resin, methyl methacrylate resin, polyamide resin, and the like can be selected as appropriate. If it is smaller than 20 nm, homogeneous impregnation of the electrolyte polymer tends to be difficult. On the other hand, if the thickness exceeds 1500 nm, the homogeneity of the support structure constituting the inorganic support may be disturbed.

Furthermore, in step 4, the drying time in the next drying step can be shortened by previously removing the solvent contained in the filtration membrane.
Furthermore, in step 5, the filtration molded membrane is previously dried at room temperature, thereby facilitating the handling of the membrane in the firing step or the like.

Next, in step 6, the filtration molded membrane is heated and fired, whereby an inorganic support made of inorganic sol is fired and a porous body can be formed by baking and removing the template resin.
At this time, it is preferable to perform temporary baking for removing the organic resin material in the filtration membrane, and then sinter the inorganic porous body.
Temporary baking is performed at a heating rate of 1 to 10 ° C./min, preferably 2 to 5 ° C./min, 400 to 500 ° C., more preferably 430 to 470 ° C., and heat treatment is performed for 30 minutes or longer. Can do.
Baking can be performed, for example, at a temperature of 800 to 900 ° C. or higher for about 30 to 100 minutes. This main baking may be repeated a plurality of times.

Further, in Steps 7 and 8, for example, the silanol groups on the inner wall surface of the spherical pores of the porous silica material are increased by hydrothermal treatment, and the porous silica material is made into a 2 to 3.5% silane coupling agent aqueous solution. It can be immersed for 30 minutes to 24 hours to form a mercapto group, which can be oxidized to a sulfonic acid group (SO ₃ H group).
In addition, as another method, the porous body treated with hydrothermal treatment is impregnated in a toluene solution of 1,3-propane sultone adjusted to 5% concentration and refluxed at 120 ° C. for 24 hours. By performing the step, the SO ₃ H group can be introduced and fixed in a one-step reaction.

  Further, in steps 9 and 10, the obtained porous body is impregnated with an electrolyte and dried to easily obtain the intended inorganic / organic composite electrolyte membrane. In particular, the drying time can be shortened by applying a temperature at which the polymer electrolyte does not break during drying, and a cross-linking agent is used at the same time when the polymer electrolyte is impregnated to promote a crosslinking reaction, thereby obtaining a stronger membrane. You can also.

In Step 9, the hydrocarbon electrolyte may be any one that can be mixed with the following impregnation solvent, and may take any form of powder, beads, gel, or solution.
Examples of the solvent for the impregnation solution include water, methanol, ethanol, linear and branched alcohols typified by n-propanol, isopropanol, and the like, olefins such as n-hexane, cyclohexane, toluene, and xylene. Aromatic solvents, ethers typified by dimethyl ether, etc., ethyl acetate, methyl acetate, acetonitrile, dimethyl sulfoxide (DMSO), dichloroethane (EDC), dioxane, tetrahydrofuran (THF), dimethylformamide (DMF), N-methylpyrrolidone ( NMP) and the like can be selected as appropriate and used.
In addition, the said solvent may be used individually or may be used in mixture suitably selecting multiple.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in full detail, this invention is not limited to these Examples.

Example 1
By using a porous silica as a matrix and introducing a conductive polymer into the pores, a proton conductive composite type electrolyte membrane was produced.

1) Production of silica porous body As an organic resin material for controlling the pore diameter of the silica porous body, polystyrene spherical particles having an average diameter of about 200 nm were used.
The polystyrene spherical particles and colloidal silica having a diameter of 70 to 100 nm were mixed and prepared so that the solute volume contained in the suspension solution had a predetermined film thickness.

  As a procedure, first, a predetermined amount of polystyrene was weighed and added to water. Thereafter, the colloidal silica-containing solution was added to the polystyrene spherical fine particle-containing solution. In addition, a suspension solution in which these particles were uniformly dispersed was obtained by ultrasonic stirring.

The suspension solution was then filtered. The membrane filter was set in a filter holder, the pressure was reduced to a pressure of 10 kPa or less with respect to atmospheric pressure using a manual vacuum pump, and the suspension solution was filtered.
After all of the suspended solution has been filtered, the excess solvent contained in the filter-formed membrane is removed using excess water such as filter paper as a water-absorbing material, and after sufficient drying at room temperature, it is peeled off from the membrane filter. Thus, a film made of a mixture of polystyrene and silica was obtained.

  This mixture film was heat-treated as follows. First, in order to remove polystyrene, the temperature was raised to 450 ° C. at a temperature raising rate of 3 ° C./min, and calcination was performed at that temperature for 60 minutes. Moreover, in order to sinter the silica, a heat treatment was performed at 800 ° C. or higher for about 60 minutes after the preliminary firing. Furthermore, in order to improve mechanical strength, heat treatment was performed at a temperature of 900 ° C. or higher for 15 minutes, and the temperature was slowly returned to room temperature, thereby obtaining a porous silica material.

2) Modification of inner wall of spherical hole of porous body First, the obtained silica porous body was hydrothermally treated at 170 ° C. for 24 hours using an autoclave. The increase in silanol groups (SiOH groups) was confirmed by FT-IR.

  Next, mercapto groups (SH groups) were introduced into the spherical pores of the porous silica material. The porous silica material was immersed in a 2.6% aqueous solution using γ-mercaptopropyltrimethoxysilane (γ-Mercaptopropyltrimethoxysilane) as a silane coupling agent for 20 hours. Then, it was vacuum-dried at 100 ° C. for 10 minutes. The absorption of the mercapto group on the inner wall of the spherical hole was observed by FT-IR.

Thereafter, a 10% hydrogen peroxide solution was used to oxidize the 2 hr mercapto group at 70 ° C. to form a sulfonic acid group. The presence of sulfonic acid groups on the inner wall of the spherical hole was confirmed by observation with ESCA.
The outline of the reaction mechanism in the above sulfonic acid group introduction step is shown in FIG.

The introduced silanol group was measured and confirmed using FT-IR. As shown in FIG. 7, introduction of SiOH groups was confirmed by detecting a peak derived from SiOH groups found at about 3500 to 3700 cm ⁻¹ .
Further, as shown in FIG. 8, the introduced sulfonic acid group (SO ₃ H group) was confirmed by the element ratio of S to Si obtained by measuring the EDS spectrum.

3) Impregnation of hydrocarbon-based electrolyte Using polyetherethersulfone, sulfonation treatment was performed by the following procedure to obtain a polymer electrolyte. The synthesized polymer solution was introduced into the pores to produce a composite electrolyte membrane.
Specifically, sulfonated polyether ether sulfone (S-PEES) is sulfonated using Poly (oxy-1,4-phenylene-1,4-phenylenesulfyl-1,4-phenylene) as a starting material. I got it. In addition, a composite electrolyte membrane was prepared by impregnating a porous silica body with a sulfonated polyether electrolyte aqueous solution adjusted to a predetermined concentration and evaporating water.
FIG. 9 shows a cross-sectional SEM image of the composite film obtained after drying. From this, it was observed that the electrolyte resin (S-PEES) was present in the spherical pores of the porous silica.

Moreover, in the dried composite electrolyte membrane, the amount of sulfonic acid groups per unit weight constituting S-PEES was determined by neutralization titration, and the ion exchange capacity was calculated.
Here, the ion exchange capacity of the composite electrolyte membrane of the present example was 3.2 meq / g. This value is more than three times the ion exchange capacity of Nafion (trademark: manufactured by DuPont), which is a typical perfluorosulfonic acid electrolyte membrane, has a high sulfonic acid group density, and exhibits proton conductivity. It turns out that it works more advantageously.

(Example 2)
In the impregnation step of the hydrocarbon electrolyte, 2-acrylamido-2-methylpropanesulfonic acid, N, N'-methyl-bisacrylamide (crosslinking agent), and ammonium peroxide sulfate (initiator) are polymerized. Except for using the obtained polymer gel (AMPS gel), the same operation as in Example 1 was repeated to obtain an inorganic / organic composite film.
Specifically, a mixed solution obtained by dissolving the above materials in pure water was dropped onto the porous silica material, and vacuum degassing was performed to fill the mixed solution into the spherical pores of the porous silica material. . Subsequently, an inorganic / organic composite film impregnated with the gel electrolyte was obtained by heating and polymerization at 60 ° C. for 1 hr.

(Comparative Examples 1 and 2)
Except that the inner wall of the spherical pore of the porous silica was not modified with a sulfonic acid group, the same operation as in Examples 1 and 2 was repeated to obtain an electrolyte membrane as an example of a conventional product.

(Example 3)
In accordance with Example 1, a proton conductive composite electrolyte membrane was prepared by introducing a conductive polymer into the pores using a porous silica as a matrix.

1) Preparation of a porous silica material According to Example 1, except that polystyrene spherical particles having an average diameter of about 200 nm were changed to polystyrene spherical particles of 470 nm as an organic resin material for controlling the pore diameter of the porous silica material. A porous body was produced.
Using polystyrene spherical particles having different sizes, polystyrene spherical particles and colloidal silica having a diameter of 70 to 100 nm were mixed and prepared so that the solute volume contained in the suspension solution had a predetermined film thickness.

  As a procedure, first, a predetermined amount of polystyrene was weighed and added to water. Thereafter, the colloidal silica-containing solution was added to the polystyrene spherical fine particle-containing solution. In addition, a suspension solution in which these particles were uniformly dispersed was obtained by ultrasonic stirring.

The suspension solution was then filtered. The membrane filter was set in a filter holder, the pressure was reduced to a pressure of 10 kPa or less with respect to atmospheric pressure using a manual vacuum pump, and the suspension solution was filtered.
After all of the suspended solution has been filtered, the excess solvent contained in the filter-formed membrane is removed using excess water such as filter paper as a water-absorbing material, and after sufficient drying at room temperature, it is peeled off from the membrane filter. Thus, a film made of a mixture of polystyrene and silica was obtained.

  This mixture film was heat-treated as follows. First, in order to remove polystyrene, the temperature was raised to 450 ° C. at a temperature raising rate of 3 ° C./min, and calcination was performed at that temperature for 60 minutes. Moreover, in order to sinter the silica, a heat treatment was performed at 800 ° C. or higher for about 60 minutes after the preliminary firing. Furthermore, in order to improve mechanical strength, heat treatment was performed at a temperature of 900 ° C. or higher for 15 minutes, and the temperature was slowly returned to room temperature, thereby obtaining a porous silica material.

2) Modification of inner wall of spherical pore of porous body First, each of the obtained porous silica bodies having different sizes was subjected to hydrothermal treatment at 170 ° C. for 24 hours using an autoclave. The increase in silanol groups (SiOH groups) was confirmed by FT-IR following Example 1.

  Next, mercapto groups (SH groups) were introduced into the spherical pores of the porous silica material. The porous silica material was immersed in a 2.6% aqueous solution using γ-mercaptopropyltrimethoxysilane (γ-Mercaptopropyltrimethoxysilane) as a silane coupling agent for 20 hours. Then, it was vacuum-dried at 100 ° C. for 10 minutes. The absorption of the mercapto group on the inner wall of the spherical hole was observed by FT-IR.

  Thereafter, a 10% hydrogen peroxide solution was used to oxidize the 2 hr mercapto group at 70 ° C. to form a sulfonic acid group. The presence of sulfonic acid groups on the inner wall of the spherical hole was confirmed by observation with ESCA.

3) Impregnation of hydrocarbon-based electrolyte Following Example 2, again in the impregnation step of hydrocarbon-based electrolyte, 2-acrylamido-2-methylpropanesulfonic acid and N, N′-methyl-bisacrylamide (crosslinking agent) And a polymer gel (AMPS gel) obtained by polymerizing ammonium peroxide sulfate (initiator) to obtain an inorganic / organic composite film.
Specifically, a mixed solution obtained by dissolving the above materials in pure water was dropped onto the porous silica material, and vacuum degassing was performed to fill the mixed solution into the spherical pores of the porous silica material. . Subsequently, an inorganic / organic composite film impregnated with the gel electrolyte was obtained by heating and polymerization at 60 ° C. for 1 hr.

(Comparative Example 3)
As in Comparative Examples 1 and 2, the same operation as in Example 3 was repeated except that the inner wall of the spherical pore of the porous silica was not modified with a sulfonic acid group, thereby obtaining an electrolyte membrane as an example of a conventional product. It was.

(Evaluation measurement)
1) Quantification of proton-conducting functional group introduced into composite type electrolyte membrane For the composite type electrolyte membrane obtained in Example 1, the proton conductivity bound to the hydrocarbon electrolyte impregnated in the electrolyte membrane is measured. The compositional element analysis of the sample was carried out using energy dispersive X-ray spectroscopy (EDS method) for the amount of functional group introduced. Note that the EDS method can measure the energy of characteristic X-rays emitted from a sample and perform composition element analysis of the sample. An example of a spectrum obtained by this analysis is shown in FIG.

  As shown in FIG. 8, the Si element constituting the silica porous body and the S element derived from the sulfonic acid group responsible for proton conduction introduced into the hydrocarbon electrolyte are detected in the EDS spectrum. From the peak, the amount of each element was calculated by sensitivity correction, and the element ratio S / Si was obtained. The element ratio largely fluctuated depending on the measurement site, and the element ratio was 5 to 16. From this, the resin impregnation to the inorganic / organic composite electrolyte membrane was confirmed.

2) Evaluation of ion conductivity of composite electrolyte membrane The proton conductivity of the obtained composite electrolyte membrane was measured by applying an AC wave of 100 Hz to 1 MHz with a sample sandwiched between gold electrodes of a predetermined area. And evaluated.
The ionic conductivity here was calculated based on the area in contact with the gold electrode without considering the porosity. The measurement was performed by adjusting the environment of temperature and humidity so that the water vapor partial pressure was saturated.
FIG. 10 shows the evaluation results of Example 1 using S-PEES resin as the electrolyte immobilized in the porous body.
Similarly, FIG. 11 shows the evaluation results of Example 2 (pore diameter 200 nm) and Example 3 (pore diameter 470 nm) using AMPS gel as the electrolyte immobilized in the porous body.

  As a result of the sulfonic acid treatment on the surface, it was revealed that the ionic conductivity was improved in all of Examples 1, 2, and 3. In particular, as shown in FIG. 11, the effect of improving the ionic conductivity at 200 nm having a smaller pore diameter was high. This is presumably because the amount of sulfonic acid groups occupying per unit volume of the electrolyte membrane increased.

3) Power generation evaluation using composite type electrolyte membrane The power generation characteristics of the hydrogen / oxygen fuel cell using the inorganic / organic composite type electrolyte membrane obtained in Example 2 were evaluated by the following procedure. For the evaluation, a graphite cell FC05-01SP (manufactured by Electrochem) was used. For the electrode, a 38% platinum-supported carbon catalyst (Tanaka Kikinzoku), glycerol, water, and Nafion (trademark: DuPont) solution were mixed, and this ink was applied on carbon paper and dried. .
Here, the ink composition is 2 parts by weight of glycerol, 3 parts by weight of water, and 3 parts by weight of a 5% Nafion solution with respect to 1 part by weight of the platinum-supported carbon catalyst. Got. This ink was applied onto carbon paper so that the amount of platinum was 3 mg / cm ^2, and dried at 120 ° C. overnight to produce carbon paper 3 with catalyst layer 2.
A membrane electrode assembly (MEA) as shown in FIG. 12 is arranged by sandwiching both surfaces of the inorganic / organic composite electrolyte membrane 1 obtained in Example 2 with the electrode catalyst-coated carbon paper (2, 3). The MEA was assembled to the test cell described above.

The power generation characteristics were evaluated by flowing hydrogen and oxygen with controlled temperature and humidity into the cell and measuring the cell voltage with respect to the current value flowing between the electrodes located at both ends of the cell.
FIG. 13 shows the power generation characteristics of the cell assembled using the electrolyte membrane of Example 2.

  As shown in FIG. 13, the power generation characteristics of the cell using the inorganic / organic composite electrolyte membrane obtained in Example 2 may greatly exceed the power generation characteristics of the cell using the electrolyte membrane obtained in Comparative Example 2. all right. This difference in power generation characteristics exceeds the performance estimated from the ionic conductivity caused by both electrolyte membranes, so it is considered that the surface treatment greatly contributes to the power generation characteristics.

It is the schematic and SEM photograph which show the structure of the electrolyte membrane of this invention typically. It is a graph which shows the relationship between the internal diameter of a spherical hole, and the amount of sensory devices (concentration). It is a graph which shows the relationship between the internal diameter of a spherical hole, and EW value. 2 is a structural formula showing an example of a polyether-based polymer. It is a flowchart which shows the preparation procedures of a proton conductive composite type electrolyte membrane. It is a flowchart which shows the procedure which fixes a proton donating functional group to the spherical hole inner wall of an inorganic porous body. It is a graph which shows the example of IR measurement after a proton-donating functional group fixed to the spherical hole inner wall of an inorganic porous body. It is a graph which shows the example of a measurement of an EDS spectrum. It is a photograph which shows the cross-sectional SEM image of a composite type electrolyte membrane. It is a graph which shows the ionic conductivity of the composite type electrolyte using S-PEES electrolyte. It is a graph which shows the relationship between ion conductivity and temperature. It is a schematic diagram which shows a membrane electrode junction part. It is a graph which shows the electric power generation test using a sulfonated electrolyte membrane.

Explanation of symbols

1 Composite Electrolyte Membrane 2 Catalyst Layer 3 Carbon Paper

Claims (21)

An inorganic porous body having a plurality of spherical holes, and a proton-conductive hydrocarbon electrolyte disposed in the spherical holes,
The spherical hole has an almost uniform inner diameter, the adjacent spherical holes communicate with each other, and has a proton donating functional group on the inner wall surface,
It said spherical pores have a regular arrangement structure due to the close-packed structure, and proton-conductive composite electrolyte membrane characterized by having regularly formed communicating port between the adjacent spherical pores.   2. The proton conductive composite electrolyte membrane according to claim 1, wherein the inorganic porous body is made of a metal oxide.   3. The proton conductive composite electrolyte membrane according to claim 1, wherein the inorganic porous material is obtained from a material that forms an inorganic sol.   4. The proton conductive composite electrolyte membrane according to claim 3, wherein the inorganic sol-forming material is an inorganic colloid.   5. The proton conductive composite electrolyte membrane according to claim 4, wherein the inorganic colloid includes at least one selected from the group consisting of silica, titania, alumina, zirconia and tantalum.   The proton-conductive composite electrolyte membrane according to any one of claims 1 to 5, wherein the inorganic porous body is formed from a suspension in which polymer fine particles and an inorganic material are mixed.   The proton conductive composite electrolyte membrane according to any one of claims 1 to 6, wherein an inner diameter of the spherical pore of the inorganic porous body is 20 to 500 nm.   The proton conductive composite electrolyte membrane according to any one of claims 1 to 6, wherein an inner diameter of the spherical pore of the inorganic porous body is 20 to 200 nm.   The proton conductive composite electrolyte membrane according to any one of claims 1 to 6, wherein an inner diameter of the spherical pore of the inorganic porous body is 50 to 150 nm.   The proton-conducting composite electrolyte membrane according to any one of claims 1 to 9, wherein the proton-donating functional group in the spherical pore is a Bronsted acid type functional group.   The proton conductive composite type according to claim 10, wherein the Bronsted acid type functional group is at least one selected from the group consisting of a sulfonic acid group, a phosphoric acid group and a carboxylic acid group. Electrolyte membrane.   The proton-donating functional group is contained at a rate of 0.2 to 2.8 mmol / g per unit mass of the inorganic porous material. Proton conductive composite electrolyte membrane.   The proton-donating functional group is contained at a rate of 0.3 to 1.2 mmol / g per unit mass of the inorganic porous body, according to any one of claims 1 to 11. Proton conductive composite electrolyte membrane.   The Equivalent Weight (EW) value (dry inorganic porous material weight per equivalent of proton-donating functional group) of the inorganic porous material is 350 to 3600 g / eq. The proton conductive composite electrolyte membrane according to any one of the items.   The Equivalent Weight (EW) value (dry inorganic porous body weight per equivalent of proton donating functional group) of the inorganic porous body is 890 to 2700 g / eq. The proton conductive composite electrolyte membrane according to any one of the items.   The proton-conducting composite electrolyte according to any one of claims 1 to 15, wherein the hydrocarbon-based electrolyte is formed by adding a functional group that exhibits proton conductivity to a hydrocarbon-based resin. film.   The proton-conducting composite electrolyte membrane according to any one of claims 1 to 16, wherein the hydrocarbon-based electrolyte has an ion exchange capacity of at least 1 meq / g to 6 meq / g.   The proton conductive composite electrolyte membrane according to any one of claims 1 to 17, wherein the hydrocarbon electrolyte is made of a polyether polymer.   The proton-conducting composite electrolyte membrane according to any one of claims 1 to 18, wherein the hydrocarbon-based electrolyte is a polyether ether sulfone. In producing the proton conductive composite electrolyte membrane according to any one of claims 1 to 19,
1. Mixing an inorganic sol and a spherical organic resin using a solvent;
2. A step of stirring the mixed solution to form a suspension;
3. Filtering the suspension to form a membrane,
4). Removing excess water from the filtration molded membrane;
5. A step of drying the filtration molded membrane,
6). A step of heating and baking the filtration molded membrane to obtain an inorganic porous body,
7). Introducing a proton-donating functional group into the inner wall surface of the spherical pore of the inorganic porous body;
8). Fixing the proton-donating functional group;
9. Impregnating the spherical pores of the inorganic porous body with a hydrocarbon-based electrolyte;
10. Drying and forming a proton conductive composite electrolyte membrane,
A method for producing a proton-conductive composite electrolyte membrane, comprising: A fuel cell using the proton conductive composite electrolyte membrane according to any one of claims 1 to 19.

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