KR100896339B1 - Proton-conducting polymer, polymer membrane comprising the polymer, method for maufacturing the same, and fuel cell using the same - Google Patents

Abstract

An organic-inorganic composite proton conductive polymer membrane is provided.

The polymer according to the present invention is characterized by having a repeating unit of the following Formula 1.

(1)

(One)

 Since the organic-inorganic composite proton conductive polymer membrane according to the present invention has a higher moisture content than a conventional fluorine-based membrane, there is less overmoisture phenomenon at high current densities, thereby improving the efficiency of the battery, and the fuel cell is stable even at a high temperature of 100 ° C. or higher. It is possible to prevent the poisoning of the catalyst by extending the life of the fuel cell.

Poly (fluorinated aromatic ether), fuel cell

Description

Proton-conducting polymer, polymer membrane comprising the polymer, method for maufacturing the same, and fuel cell using the same}

1 shows the structure of a typical hydrogen ion exchange membrane fuel cell.

2 is a view showing the results of the Fenton test for the proton conductive polymer film prepared by Example 1 and Comparative Example 2.

3 is a graph measuring the temperature at which the structure of the proton conductive polymer prepared in Comparative Example 2 is decomposed using TGA.

Figure 4 is a graph measuring the temperature at which the structure of the organic-inorganic composite proton conductive polymer prepared in Example 1 decomposes using TGA.

Figure 5 (a) is a SEM image of the surface of the organic-inorganic composite proton conductive polymer film prepared in Example 1.

FIG. 5 (b) shows the EDAX Zr mapping result for the surface of the organic-inorganic composite proton conductive polymer membrane according to Example 1. FIG.

FIG. 5C is a result of EDAX P mapping on the surface of the organic-inorganic composite proton conductive polymer membrane according to Example 1. FIG.

Figure 5 (d) is a cross-sectional SEM photograph of the organic-inorganic composite proton conductive polymer membrane according to Example 1.

Figure 5 (e) is the EDAX Zr mapping results for the cross section of the organic-inorganic composite proton conductive polymer membrane according to Example 1.

5 (f) shows the EDAX P mapping result of the surface of the organic-inorganic composite proton conductive polymer membrane according to Example 1. FIG.

6 is a TEM photograph of the proton conductive polymer membrane prepared in Example 1. FIG.

FIG. 7 is a diagram showing the results of X-ray diffraction experiments on the proton conductive polymer membranes prepared in Example 1 and Comparative Example 2. FIG.

8 is a view showing the XPS (PHI1500 ESCA system) experimental results for the proton conductive polymer membrane prepared in Example 1 and Comparative Example 2.

FIG. 9 is a result of linear sweep voltametry (LSV) measurement of the organic-inorganic composite proton conductive polymer membrane prepared in Example 1. FIG.

10 (a) shows a current density-voltage curve for the fuel cell manufactured by Comparative Example 5, and FIG. 10 (b) shows a current density-power density curve under the same conditions.

FIG. 11A shows a current density-voltage curve for the fuel cell manufactured in Example 4, and FIG. 11B shows a current density-power density curve under the same conditions.

FIG. 12 shows current density-voltage curves for the fuel cell manufactured by Example 4 and Comparative Example 4. FIG.

FIG. 13 is a performance test result for the fuel cell manufactured in Example 4. FIG.

<Explanation of symbols for the main parts of the drawings>

11 hydrogen ion exchange membrane 12 anode catalyst layer

13 ... cathode catalyst layer 14 ... anode support layer

15 ... cathode support layer 16 ... carbon plate

The present invention relates to an organic-inorganic composite proton conductive polymer membrane, and more particularly, to a proton conductive polymer membrane having no water flooding phenomenon, excellent high temperature characteristics, and low manufacturing cost, a method of manufacturing the same, and a fuel cell employing the same. It is about.

In recent years, along with environmental problems, exhaustion of energy sources, and the practical use of fuel cell vehicles, development of high-performance fuel cells with high energy efficiency and operation at room temperature and reliability are urgently required. Accordingly, there is also a demand for the development of polymer membranes that can increase the efficiency of fuel cells.

The fuel cell is a new power generation system that converts the energy generated by the electrochemical reaction between fuel gas and oxidant gas directly into electrical energy. It is a molten carbonate electrolyte fuel cell operating at high temperature (500 to 700 ℃), and it operates near 200 ℃. Phosphate electrolyte fuel cells, alkaline electrolyte fuel cells operating at room temperature to about 100 ° C. or less, and polymer electrolyte fuel cells.

On the other hand, the polymer electrolyte fuel cell is a direct methanol fuel cell using a hydrogen ion exchange membrane fuel cell (Proton Exchange Membrane Fuel Cell (PEMFC)) and liquid methanol directly supplied to the anode as a fuel ( Direct Methanol Fuel Cell (DMFC). The polymer electrolyte fuel cell is a future clean energy source that can replace fossil energy, and has high power density and energy conversion efficiency. In addition, since it can operate at room temperature and can be miniaturized and sealed, it can be widely used in fields such as pollution-free automobiles, household power generation systems, mobile communication equipment, medical equipment, military equipment, and space business equipment.

PEMFC is a power generation system for producing direct current electricity from the electrochemical reaction of hydrogen and oxygen, the basic structure of such a cell is shown in FIG.

Referring to FIG. 1, a fuel cell has a structure in which a hydrogen ion exchange membrane 11 is interposed between an anode and a cathode.

The hydrogen ion exchange membrane 11 has a thickness of 50 to 200 μm and is made of a solid polymer electrolyte, and the anode and the cathode are respectively supported by the support layers 14 and 15 for supplying the reactor, and the oxidation / reduction reaction of the reactor. It consists of a gas diffusion electrode (hereinafter referred to collectively referred to as a gas diffusion electrode ") of the catalyst layers 12, 13, which occur. Reference numeral 16 in Fig. 1 has a groove for gas injection. A carbon sheet, which also functions as a current collector.

In the PEMFC having the structure as described above, an oxidation reaction occurs at the anode while hydrogen, which is a reactive gas, is converted into hydrogen ions and electrons. At this time, the hydrogen ions are transferred to the cathode via the hydrogen ion exchange membrane (11). On the other hand, in the cathode, a reduction reaction occurs and oxygen molecules receive electrons and are converted into oxygen ions, and oxygen ions react with hydrogen ions from the anode to be converted into water molecules. As shown in FIG. 1, catalyst layers 12 and 13 are formed on support layers 14 and 15, respectively, in the gas diffusion electrode of PEMFC. At this time, the support layers (14) and (15) are made of carbon cloth or carbon paper, and are surface-treated to facilitate the passage of water and the water generated as a result of the reaction between the reactant and the hydrogen ion exchange membrane (11). In the PEMFC, hydrogen, which is a reactive gas, may be obtained by reforming natural gas or methanol. In this reforming reaction, carbon monoxide is generated, and poisoning of the platinum catalyst of the anode causes a problem of significantly deteriorating cell performance. Therefore, in order to increase the poisoning resistance to the carbon monoxide, it is necessary to allow the cell reaction to occur at a high temperature of 100 ° C or higher.

       On the other hand, PEMFC uses a proton conductive polymer membrane as a hydrogen ion exchange membrane interposed between the anode and the cathode. The polymer used as the polymer membrane has high ionic conductivity, electrochemical safety, mechanical properties as a conductive membrane, and operating temperature. The requirements must be met, such as thermal stability, manufacturability as a thin film to reduce resistance, and low expansion effect when containing liquid. Currently, a perfluorosulfonic acid polymer membrane having a fluorinated alkylene in the main chain and a sulfonic acid group at the terminal of the fluorinated vinyl ether side chain is used (for example, manufactured by Nafion, Dupont). However, the fluorine-based membrane has a high manufacturing cost due to the complicated fluorine substitution process, and thus is difficult to apply to a fuel cell for automobiles. Since moisture content is not good, a high temperature of 100 ° C. or more is required to prevent poisoning of the catalyst. In operation, moisture evaporates, the ion conductivity drops sharply, the operation of the battery is stopped, and even when operated at temperatures below 100 ° C, water flooding occurs at the cathode at high current densities. Therefore, there is a problem that the effective area of the electrode is drastically reduced and the efficiency of the battery is lowered.

On the other hand, the Republic of Korea Patent Publication No. 2004-94612 discloses a proton conductive polymer of the polyarylene ether series, but because the moisture content is too large, the mechanical properties are poor, the expansion of the polymer when the operation of the battery is excessive The interfacial contact efficiency with the electrode is reduced, and there is a fear that the life of the battery is shortened.

Accordingly, the first technical problem to be achieved by the present invention is an organic-inorganic composite proton conductive polymer membrane which can reduce catalyst poisoning due to excellent moisture properties and excellent ionic conductivity at high temperature. To provide.

The second technical problem to be achieved by the present invention is to provide a method for producing the organic-inorganic composite proton conductive polymer membrane.

The third technical problem to be achieved by the present invention is to provide a fuel cell comprising the organic-inorganic composite proton conductive polymer membrane.

In order to achieve the first technical problem the present invention

It provides a proton conductive polymer having a repeating unit of the formula (1).

Wherein n is an integer of 100 to 100,000, m, m ', l, l' is an integer of 0 or 1, m and m 'and l and l' are not 0 at the same time, and l or l 'is 0 Is a hydrogen atom instead of ZrP, and ZrP is zirconium phosphate hydrate)

According to one embodiment of the present invention, the number average molecular weight of the polymer may be 5,000 to 1,000,000.

In addition, the equivalent weight of the polymer is preferably 250 to 2,500.

According to a preferred embodiment of the present invention, the content of zirconium phosphate in the proton conductive polymer may be 10 to 25% by weight.

       The present invention to achieve the second technical problem

(a) dissolving decafluorobiphenyl and 4,4 '-(hexafluoroisopropylidene) diphenol in an organic solvent, adding potassium carbonate (K ₂ CO ₃ ), followed by stirring and heating;

(b) cooling the solution and pouring it into an aqueous acetic acid solution to precipitate the polymer;

(c) dissolving the polymer obtained above in an aprotic organic solvent and then sulfonating with addition of a strong acid-giving agent;

(d) dissolving the polymer in acetone to form a film; And

(e) immersing the polymer membrane in a zirconium chloride solution, and then again immersing in a phosphate solution provides a method for producing an organic-inorganic complex proton conductive polymer membrane.

According to a preferred embodiment of the present invention, the aprotic organic solvent may be chloroform or 1,1,2,2-tetrachloroethane.

In addition, the strong acid-giving agent may be chlorosulfonic acid (chlorosulfonic acid), acetyl sulfonate (acetyl sulfonate) or fuming sulfuric acid (fuming H ₂ SO ₄ ).

According to another embodiment of the present invention, the sulfonation step may adjust the degree of sulfonation (Degree of sulfonation) by controlling the reaction time and the amount of the strong acid-giving agent.

The reaction time of the sulfonation step is preferably 1 hour to 2 hours.

In addition, the molar ratio of the proton conductive polymer and the strong acid-giving agent in the sulfonation step is preferably 1:10 to 1:30.

The present invention provides a fuel cell, characterized in that produced by employing the proton conductive polymer membrane in order to achieve the third technical problem.

Hereinafter, the present invention will be described in more detail.

The base polymer used in the proton conductive polymer membrane according to the present invention has a sulfonic acid group in a poly (fluorinated aromatic ether) polymer chain prepared by nucleophilic substitution reaction of an aryl halide and a diphenol derivative. It is attached and a chemical bond is formed between the oxygen atom of sulfonic acid and the Zr atom of zirconium phosphate. In the base polymer, the polymer backbone is thermally and chemically stable, and maintains mechanical strength when appropriately moisturized. However, due to the influence of sulfonic acid groups, there is a concern that the mechanical strength deteriorates when the water is excessively moistened. Accordingly, although the proton conductive polymer membrane according to the present invention can reduce the moisture content by forming a chemical bond between the oxygen atom of the sulfonic acid group and the zirconium atom of zirconium phosphate, it is ion conductive due to the role of the zirconium phosphate as a hydrophilic inorganic substance. Rather, it can be improved. The zirconium phosphate not only serves as an inorganic filler, but also serves as a crosslinking agent as described below, and serves to improve mechanical properties by crosslinking the base polymer.

In particular, the organic-inorganic composite proton conductive polymer membrane according to the present invention forms crosslinks by reacting zirconium atoms present in zirconium phosphate with sulfonic acid groups present in the main chain of the polymer, and thus excellent in water absorption and high temperature mechanical properties. Has the advantage.

In addition, the organic-inorganic composite proton conductive polymer membrane according to the present invention has a reduced moisture content, thereby reducing volume expansion than the pure base polymer without using zirconium phosphate, and mechanical strength since the zirconium phosphate plays a role as an inorganic filler. It will also increase.

On the other hand, sulfonic acid groups and zirconium phosphate serves to allow the proton to move. That is, protons are conducted by sulfonic acid groups, and their conductivity is further increased by water, and this proton conduction is largely caused by the Grotusus mechanism. The mechanism causes protons to jump to non-covalent electron pairs of neighboring water molecules in the form of H ₃ O ⁺ ions. .

The zirconium phosphate is a hydrophilic inorganic material, present in the presence of zirconium phosphate hydrate in the presence of water, has a layered structure of about 0.76nm interval layer, excellent compatibility with organic polymers, high conductivity of hydrogen ions as well as water molecules Since the hydrogen bond with is strong, the moisture content can be maintained even at a high temperature of 100 ° C or higher.

The content of the zirconium phosphate is preferably 10 to 25% by weight of the total proton conductive polymer, but when the content is less than 10% by weight, the addition effect thereof is insufficient, and when the content exceeds 25% by weight, the brittleness of the polymer membrane becomes poor. Because it is not desirable.

The n value of the base polymer repeating unit is preferably 100 to 10,000, and the number average molecular weight is preferably 5,000 to 1,000,000. When the number average molecular weight is less than 5,000, the physical properties of the base polymer are poor. Since it is difficult to dissolve, casting of a polymer film is difficult and undesirable.

In the present specification, the equivalent weight is a numerical value representing the degree of sulfonation in the polymer, and means the average molecular weight of the polymer in which one equivalent of the sulfone group is substituted. Therefore, the smaller this value, the more sulfonated. The equivalent weight can be calculated by dividing the dry weight of the polymer by the concentration of sulfone groups (g / eq), and the concentration of the sulfone groups is obtained by immersing the polymer in 0.1 N sodium hydroxide solution for 12 hours. After using phenolphthalein as indicator, it can be obtained by titration with 0.1 N hydrochloric acid. The equivalent weight is preferably 250 to 2,500, and more preferably 400 to 1,200. If the equivalent weight is less than 250, it is difficult to form a polymer membrane, and if the equivalent weight is more than 2,500, it is difficult to secure ion conductivity. I can't. On the other hand, since the equivalent weight and the ion exchange capacity (Ion Exchange Capacity) has a relationship of IEC = 1 / EW x 1000, the IEC of the proton conductive polymer membrane used in the present invention is 0.4 to 4, preferably 0.8 to 2.5 to be.

Proton conductive polymer membrane prepared by casting the proton conductive polymer according to the present invention is very easy to sulfonate the base polymer, the production cost is low and mass production is possible, by further containing zirconium phosphate moisture content and ions By controlling the conductivity, there is an advantage that the mechanical properties and the ion conductivity can be optimally set. In the case of incorporating zirconium phosphate into a conventional proton conductive polymer, the moisture content is increased due to the role of the zirconium phosphate, but in the proton conductive polymer according to the present invention, the moisture content is rather reduced as the zirconium phosphate is incorporated. Lays. The reason for this is that chemical bonds are formed between the oxygen atom of the sulfonic acid group and the zirconium atom of zirconium phosphate in the base polymer, thereby reducing the area for interaction between the unshared electron pair of the oxygen atom and the H ₃ O ⁺ ion. to be. Therefore, the area in which water molecules exist near the main chain of the proton conductive polymer according to the present invention is reduced, thereby improving the mechanical properties of the polymer. In summary, the organic-inorganic composite proton conductive polymer membrane according to the present invention forms a crosslink by forming a chemical bond between the zirconium phosphate and the oxygen atom of the sulfonic acid group, while reducing the moisture content and improving the hydrophilic property. Due to the role of the zirconium phosphate as an inorganic material, the ion conductivity may also be improved.

Due to the characteristics of the base polymer constituting the polymer film, it is advantageous to blend the other polymers or to add other organic and inorganic additives to easily control the physical properties, so that the application range is wide. Examples of the polymer that can be blended with the polymer according to the present invention include polyurethane, polyetherimide, polyetherketone, polyether-ketone, polyurea, polypropylene, polystyrene, polysulfone, polyethersulfone, polyether Ethersulfone, polyphenylenesulfone, polyaramid, polybenzimidazole, poly (bisbenzoxazole-1,4-phenylene), poly (bisbenzo (bis-thiazole) -1,4-phenylene) , Polyphenylene oxide, polyphenylene sulfide, polyparaphenylene, polytrifluorostyrene sulfonic acid, polyvinylphosphonic acid or polystyrene sulfonic acid.

Method for producing a proton conductive polymer according to an embodiment of the present invention is as follows.

First, decafluorobiphenyl and 4,4 '-(hexafluoroisopropylidene) diphenol are polymerized by an addition-elimination reaction as in Scheme 1 below to obtain a poly (fluorinated aromatic ether).

 The potassium carbonate is used in excess and acts as a base. First, the benzene ring may be activated due to the fluorine atom bonded to the decafluoro biphenyl, and the addition reaction may occur. In the next step, the removal reaction of the fluorine atom occurs.

Next, the sulfonated polymer may be obtained by adding a strong acid-giving agent to the matrix polymer as in Scheme 2 below.

Since the poly (fluorinated aromatic ether) is hydrophobic, an aprotic solvent, chloroform or 1,1,2,2-tetrachloroethane, is used as a solvent to dissolve it. The strong acid group imparting agent binds to the aromatic compound of the polymer main chain and imparts an acid group, and consequently, imparts ionic conductivity to the final polymer membrane. As the strong acid-giving agent, chlorosulfonic acid, acetyl sulfonate, fuming H ₂ SO ₄ , etc. may be used, and the sulfonation reaction may be performed using SO ₃ in the active site of the aromatic compound. H is substituted by a nucleophilic substitution reaction. The site of the nucleophilic substitution reaction is affected by the kind of substituents attached to the phenyl ring. If the substituents are phenyl ethers and isopropyl groups, they are electron donating groups, which activates the ortho and para positions of the phenyl ring, while in the case of isopropyl groups substituted with hexafluoro groups, electron withdrawing group), thus activating the meta position of the phenyl ring. Therefore, the former tends to have more sulfonation under the same sulfonation conditions, so that the moisture content in the vicinity of the polymer backbone is excessive, while in the latter, sulfonation time and reaction are less easy. There is an advantage that the degree of sulfonation can be properly adjusted according to the conditions. Also, unlike the case of poly (fluorinated aromatic ether) prepared using 4,4'-isopropylidene diphenol, poly (manufactured using 4,4 '-(hexafluoroisopropylidene) diphenol) In the case of fluorinated aromatic ethers), since there are many fluoro groups, the compatibility between the electrode and Nafion, which is usually used at the interface between the electrode and the proton conductive polymer, is good in the preparation of the membrane electrode assembly, and thus, the interface property is excellent. have.

Further, in the proton conductive polymer membrane according to the present invention, since the hexafluoro isopropylene group is present in the main chain of the polymer, by maintaining the hydrophobicity of the main chain portion appropriately, the moisture content is not excessive and the decomposition of the main chain can be suppressed.

On the other hand, in the case of Nafion, the sulfonation process is very complicated and the manufacturing cost is high, whereas the proton conductive polymer membrane according to the present invention has the advantage that the manufacturing cost is reduced and mass production is easy because the sulfonation step is very simple.

In the sulfonation step, the degree of sulfonation may be changed by reaction time, concentration of a strong acid imparting agent, concentration of a reaction polymer, reaction temperature or solvent, and the like in the present invention. The sulfonation degree was adjusted by changing the concentration. As the degree of sulfonation increases, the ion-exchange capacity (IEC) increases because the moisture content of the polymer increases, but it is not preferable because the polymer chain is excessively moistened due to the risk of collapse of the polymer chain. The ion exchange capacity is proportional to the inverse of the aforementioned equivalent weight.

It is preferable that the reaction time of the sulfonation step is 1 hour to 2 hours. If the sulfonation is less than 1 hour, the ionization is insufficient because the sulfonation is insufficient, and the process efficiency is lowered when the reaction time exceeds 2 hours. On the other hand, the molar ratio of the polymer and fuming sulfuric acid is preferably from 1:10 to 1:30. When the molecular weight is less than 1:10, since the sulfonation degree is not sufficient, the ionic conductivity is not high. It is not preferable because there is a risk of becoming poor.

The step of reacting zirconium phosphate on the proton conductive polymer membrane (base polymer membrane) prepared above is performed by immersing the polymer membrane in 0.5-2 M zirconium chloride solution and then immersing in 0.5-2 M phosphate solution. . The reaction amount in the step of reacting the zirconium phosphate can be controlled by the concentration of the zirconium chloride solution and phosphate solution, the reaction time and the reaction temperature.

The concentration of the zirconium chloride solution and the phosphoric acid solution is not particularly limited, the higher the concentration, the easier the reaction proceeds.

On the other hand, the time for immersing the polymer membrane in the zirconium chloride solution and the phosphate solution is preferably 4 to 10 hours, respectively, when the reaction time is less than 4 hours, the amount of zirconium phosphate to combine with sulfonic acid groups is too small, more than 10 hours In this case, the process efficiency is not preferable. The content of zirconium phosphate contained in the organic-inorganic composite proton conductive polymer membrane according to the present invention tends to be proportional to the reaction time.

In addition, the reaction temperature is also a variable that affects the content of the zirconium phosphate, the reaction temperature of the step of dipping in a zirconium chloride solution is preferably 20 to 50 ℃, the reaction temperature of the step of dipping in a phosphoric acid solution is 20 to 80 It is preferable that it is ° C. When the reaction temperature is less than 20 ℃, the reaction does not proceed properly, when immersed in the zirconium chloride solution, when the reaction temperature exceeds 50 ℃ there is a possibility that the mechanical properties of the polymer membrane is poor. On the other hand, when immersed in a phosphoric acid solution, the reaction temperature may be up to 80 ° C., because the mechanical properties of zirconium act as an inorganic filler in the polymer.

In the proton conductive polymer membrane according to the present invention, the zirconium phosphate is not simply uniformly mixed, but the oxygen of the sulfonic acid group present in the main chain of the polymer membrane is sequentially immersed in the zirconium chloride solution and the phosphate solution. By allowing chemical bonds to be formed between atoms and zirconium atoms, they serve as a crosslinking agent in the polymer membrane and are present permanently. Therefore, there is no fear that the zirconium phosphate will elute from the polymer membrane even during operation of the battery.

The fuel cell according to the present invention can be manufactured by a conventional manufacturing method of forming a single cell by placing the proton conductive polymer membrane prepared above between the cathode and the anode.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments, but the present invention is not limited thereto.

Example 1

1- (1) Of poly (fluorinated aromatic ethers)  Produce

17.05 g of decafloobiphenyl (made by Aldrich), 17.16 g of 4,4- (hexafluoroisopropylidene) diphenol (manufactured by Aldrich) and anhydrous N, N-dimethyl in a three-necked round bottom flask containing nitrogen 350 mL of acetamide (manufactured by Aldrich) was added and stirred to obtain a clear solution. Next, potassium carbonate (manufactured by Junsei Chemical Co., Ltd.) was added in excess, and then the temperature of the mixed solution was raised to 120 ° C. and reacted for 2 hours. After the reaction, the solution was put in a 1% acetic acid aqueous solution to obtain a white precipitate. The precipitate obtained above was washed several times with distilled water and dried in a vacuum oven for 24 hours to obtain a white polymer powder (Base Polymer: BP).

1- (2) Sulfonic acid groups  Having Of poly (fluorinated aromatic ethers)  Produce

2.0 g of the polymer powder obtained above was placed in a flask containing 198 mL of chloroform, and then the solution was stirred to obtain a clear solution. 98% fuming sulfuric acid was slowly added dropwise to the solution at a ratio of 1:20 (polymer: fuel sulfuric acid) by molar ratio, followed by stirring for 2 hours. The solution was slowly added to excess distilled water to give a white precipitate, which was then evaporated chloroform and washed several times with distilled water until the pH reached 7, followed by drying in a vacuum oven for 24 hours to give a sulfonated poly (fluorinated aromatic ether). (Sulfonated Base Polymer, hereinafter referred to as SBP-F). The following NMR data is for poly (fluorinated aromatic ether) before sulfonation, but only the data before sulfonation are attached since the peak becomes very complex and the peak assignment becomes difficult after sulfonation. However, when sulfonation is performed, it shifts toward the downfield from the peak before sulfonation.

Weight average molecular weight: 4.33 x 10 ⁵ , Number average molecular weight: 1.83 x 10 ⁴

¹ H-NMR (CD ₃ COCD ₃ ): δ 7.337 to 7.367 (d, 4H, Ar- H ), 7.483 to 7.510 (d, 4H, Ar- H )

¹⁹ F-NMR (CD ₃ COCD ₃ ): δ-150.618 to -150.569, -135.157 to -135.080, -60.30

1- (3) In the immersion stage  Determination of reaction temperature

1.0 g of the sulfonated base polymer prepared in 1- (2) was dissolved in acetone to prepare a proton conductive polymer membrane having a thickness of 175 μm. Next, in order to determine the optimum temperature of the step of immersing the proton conductive polymer membrane in 1M zirconium chloride solution and 1M phosphoric acid solution, the reaction temperature of each solution was changed from 20 ° C. to 60 ° C., and the polymer membranes were changed for 4 hours. After immersion, the resistance, ion conductivity and moisture content were checked and the results are shown in Table 1 below. Zr20 / P20 means that the temperature of the step of dipping in a zirconium chloride solution is 20 ℃, the temperature of the step of dipping in a phosphoric acid solution is 20 ℃.

Resistance (ohm / cm ² ) Ion Conductivity (Scm ^-1 ) Moisture Content (%) SBP-F 5.74 2.12 x 10 ^-3 120 Zr20 / P20 4.14 4.10 x 10 ^-3 101 Zr40 / P40 2.80 8.93 x 10 ^-3 91 Zr60 / P60 3.21 4.65 x 10 ^-3 86

Referring to Table 1, it can be seen that the reaction temperature of the zirconium chloride solution and the phosphate solution is optimal at 40 ° C, respectively.

Preparation of 1- (4) Organic-Inorganic Composite Proton Conductive Polymer Membrane

A transparent solution obtained by dissolving 1.0 g of the white powder obtained in Example 1- (2) in acetone was film cast and dried in a vacuum oven at 70 ° C. to prepare a 125 μm thick proton conductive polymer membrane. Next, the polymer membrane was immersed in purified water and then immersed in zirconium chloride (manufactured by Junsei) 1M solution at 40 ° C. for 4 hours. The membrane was washed with purified water to remove excess solution, and then immersed in 1M phosphate solution at 40 ° C. for 4 hours, and then washed several times with distilled water to remove excess acid, thereby reducing the amount of zirconium phosphate by 10% by weight of the total proton conductive polymer membrane. A phosphorus-inorganic composite proton conductive polymer membrane was prepared. The content of the zirconium phosphate was measured by comparing the mass before and after the immersion reaction of the SBP-F membrane.

Example 2

An organic-inorganic hybrid proton conductive polymer membrane having a zirconium phosphate content of 20% by weight of the total proton conductive polymer membrane was prepared in the same manner as in Example 1, except that the time for immersion in the zirconium chloride solution was 8 hours. .

Example 3

An organic-inorganic hybrid proton conductive polymer membrane having a zirconium phosphate content of 25% by weight of the total proton conductive polymer membrane was prepared in the same manner as in Example 1, except that the time for immersion in the zirconium chloride solution was 10 hours. .

Comparative Example 1

Nafion 115 (manufactured by DuPont) was added to a 30 vol.% H ₂ O ₂ solution and heated to remove organic substances from the surface, and then placed in 0.5 M sulfuric acid and heated for 1 hour to replace Na ⁺ with H ⁺ and washed with water. A proton conductive polymer membrane was prepared.

Comparative Example 2

A proton conductive polymer membrane was prepared in the same manner as in Example 1, except that the addition of zirconium phosphate was not performed.

Comparative Example 3

A proton conductive polymer membrane was prepared in the same manner as in Comparative Example 2, except that 2.0 g of 4,4'-isopropylidene diphenol was used instead of 4,4 '-(hexafluoroisopropylidene) diphenol.

Example 4 and Comparative Examples 4-5

Manufacture of Fuel Cells

Between the electrode doped with carbon catalyst 20% of platinum (manufactured by Bon Enterprises Inc.), a proton conductive polymer membrane prepared in Example 1 and Comparative Examples 1 and 2 was placed, and a hot pressing method was performed at 100 ° C and 15 atm. Membrane electrode assembly (MEA) was prepared by bonding together.

Test Example 1

Moisture content , Ion conductivity and length expansion

The proton conductive polymers prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were immersed in water, and then the hygroscopicity was measured by checking the weight change, and the ion conductivity was measured by an impedance analyzer: manufactured by Zahner elektrik. After obtaining the bulk resistance by Nyquist plot according to IM6), it was measured using Equation 1 below, and the length expansion rate was measured by the length change rate before and after the damping and the results are shown in Table 1 below.

                (a: thickness of film d: radius of electrode

σ: ion conductivity, R _b : bulk resistance)

Moisture Content (%) Ion Conductivity (Scm ^-1 ) Length expansion rate (%) Example 1 90.6 8.5 x 10 ^-3 20.1 Example 2 84.4 1.63 x 10 ^-2 18.4 Example 3 79.8 1.72 x 10 ^-2 17.6 Comparative Example 1 26.4 1.73 x 10 ^-2 14.0 Comparative Example 2 130.0 2.54 x 10 ^-3 22.7 Comparative Example 3 434.68 1.33 x 10 ^-2 52.3

As can be seen in Table 2, the organic-inorganic composite proton conductive polymer membrane according to the present invention has a moisture content of about three times as compared to the conventional fluorine-based proton conductive polymer membrane, so that the excessive moisture content can be reduced even at high current density. The efficiency and power density of the battery can be improved, and the Tg of Nafion is 120-130 ° C, whereas in the case of the proton conductive polymer according to the present invention, the Tg is 276 ° C and the moisture content decreases, so that The mechanical strength at high temperatures is excellent because the area through which water passes is reduced. Therefore, it is possible to operate at high temperatures and to prolong the life of the battery by preventing the poisoning of the catalyst. On the other hand, the organic-inorganic composite proton conductive polymer according to the present invention has an advantage that the moisture content is less than 60% and excellent in ionic conductivity as compared with the conventional sulfonated poly (fluorinated aromatic ether). Especially in the case of Comparative Example 3 prepared using 4,4, -isopropylidene diphenol, the moisture content is too excessive, the excess moisture near the main chain of the polymer, the mechanical properties are very poor, length expansion rate Since the polymer is too large, the expansion of the polymer during humidification results in poor interfacial contact between the proton-conducting polymer membrane and the catalyst layer during MEA production, an increase in resistance, and a short battery life. However, since the organic-inorganic composite proton conductive polymer membrane according to the present invention was prepared using 4,4 '-(hexafluoroisopropylidene) diphenol, hydrophobicity can be imparted to the polymer backbone, and zirconium phosphate may be added. The moisture content of the former sulfonated poly (fluorinated aromatic ether) itself is about 2/3 of that of the conductive polymer according to Comparative Example 3, and the addition of zirconium phosphate further improves the moisture content while further improving the ionic conductivity. By reducing the mechanical properties of the conductive polymer itself can be improved. The moisture content increases when zirconium phosphate is added to Nafion, but in the present invention, the moisture content tends to decrease with the addition of zirconium phosphate, which indicates that the Zr ^{4 +} ion of the zirconium phosphate is the oxygen of the sulfonyl group. This is evidence of chemical bonding with atoms. That is, as shown in the formula (1), by forming a chemical bond, it is determined that the amount of water present around the sulfonyl group can be reduced. If the zirconium phosphate is not chemically bonded to the oxygen atom of the sulfonyl group, the moisture content will increase rather than using the zirconium phosphate.

Test Example 2

Tensile strength  Measure

Tensile strength was measured using a tensile strength measuring device (INSTRON-4465, manufactured by Instron, Inc.) according to ASTM-1708. Specifically, the proton conductive polymer membranes prepared in Example 1 and Comparative Examples 1 to 3 were formed into rectangular strips. After cutting, the plate was fixed to two holders and the maximum tensile force immediately before fracture was measured while pulling at a speed of 2 mm / min, and the results are shown in Table 3 below. The tensile strength was measured by dividing the drying and the moisture.

Strength at drying (MPa) Strength at the time of humidity (MPa) Modulus Example 1 36.25 20.0 1494 Comparative Example 1 26.9 19.4 1427 Comparative Example 2 32.58 15.3 1024 Comparative Example 3 30.03 9.8 629

As can be seen in Table 2, it can be seen that the organic-inorganic composite proton conductive polymer according to the present invention has excellent mechanical strength even when wet. In particular, in the case of Comparative Example 3, since the moisture content is excessive, it can be seen that the mechanical strength is significantly reduced.

Test Example 3

Chemical stability test

Chemical stability was performed by Fenton test. Specifically, the proton conductive polymer membranes prepared by Examples 1 and ₂ are immersed in 65 ° C., 3% H ₂ O ₂ and FeSO ₄ solution, and the conductive polymer membrane is oxidized by hydroxy radicals. It was measured how long the polymer membrane can be chemically stable and the results are shown in FIG. Referring to FIG. 2, in the case of Comparative Example 2, the mass loss reached almost 100% before 7 hours had elapsed, but in Example 1, since the mass loss ratio was less than 10% even up to 20 hours or more, chemically You can see that it is very stable. This chemical stability is because, as already mentioned, it is possible to maintain an appropriate moisture content around the polymer backbone.

Test Example 4

Thermal stability  Test

The temperature at which the structures of the proton-conducting polymer membranes prepared in Examples 1 and 2 were decomposed while the temperature was raised using a Dupont thermogravimetric analyzer (TGA) 2050 was confirmed by a decrease in mass. The results are shown in FIGS. 3 and 4. It was. 3 is a result of the proton conductive polymer membrane prepared by Comparative Example 2, the -SO ₃ H group is decomposed at about 320 ℃ and the polymer backbone is rapidly decomposed at about 530 ℃, while the oil prepared according to Example 1 Referring to FIG. 4, which is a result of the inorganic composite proton conductive polymer membrane, the temperature at which the SO ₃ H group is decomposed is about 330 ° C., and the temperature at which the polymer main chain is decomposed is slowly decomposed until it reaches about 650 ° C. It can be seen that further increased. This is because zirconium phosphate, an inorganic material having excellent thermal stability, is chemically bonded to the polymer.

Test Example 5

SEM  And EDAX  observe

The organic-inorganic composite proton conductive polymer membrane prepared in Example 1 was subjected to FE-SEM experiments, and elemental mapping was performed using energy-dispersive spectroscopy (EX-200, manufactured by Horiba, Inc.) combined with SEM. EDAX was used to confirm the distribution of zirconium and phosphorus, and the results are shown in FIG. 5. Figure 5 (a) is a SEM image of the surface of the organic-inorganic composite proton conductive polymer membrane according to Example 1, Figure 5 (b) is the EDAX Zr mapping results for the surface, Figure 5 (C) EDAX for the surface P mapping result. On the other hand, Figure 5 (d) is a cross-sectional SEM photograph of the organic-inorganic composite proton conductive polymer membrane according to Example 1, Figure 5 (e) is the EDAX Zr mapping results for the cross section, Figure 5 (f) is a surface The result of EDAX P mapping for. Referring to FIG. 5, it can be seen that the organic-inorganic composite proton conductive polymer membrane according to the present invention has a uniform distribution of zirconium phosphate. You can check it.

Test Example 6

TEM  observe

The proton conductive polymer membrane prepared in Example 1 was immersed in acetone and stirred for 50 hours, the acetone solution was collected and ultra sonicated for 1 hour, followed by TEM analysis using JEOL 1200EX. 6 is shown. In the case of the organic-inorganic composite proton conductive polymer prepared according to the present invention, since it is crosslinked by zirconium phosphate, it was confirmed that it is almost insoluble in acetone. However, FIG. 6 is a fine polymer fragment present in a trace amount present in the solution collected above was observed by TEM. Referring to Figure 6 (a) it can be observed that the polymer is not dissolved, Figure 6 (b) is an enlarged picture of this. Referring to Figure 6 (b) it can be seen that the average crystal size of zirconium phosphate is about 20nm, which is consistent with the results predicted by XRD. In addition, it can be seen that zirconium phosphate is still present in the middle of the polymer chain, which is not simply uniformly dispersed inside the polymer membrane, but rather crosslinks between the polymer chain and the chain through chemical bonds. It is a proof of accomplishment. If the zirconium phosphate was simply dispersed, the base polymer would have been completely dissolved in acetone, and the zirconium phosphate would have been pulled out by ultra sonication. Accordingly, it can be seen that a chemical bond exists between the zirconium atom of the zirconium phosphate and the oxygen atom of the sulfonic acid group of the polymer, whereby the organic-inorganic composite protic polymer membrane according to the present invention is crosslinked.

Test Example 7

XRD Measure

X-ray diffraction experiments (DMAX-III, manufactured by Rigaku, Cu Kα radiation (30 kV, 20 mA)) were performed on the proton conductive polymer films prepared in Example 1 and Comparative Example 2, and the results are shown in FIG. 7. Referring to FIG. 7, 2θ values of 16-22 ° and 40-45 ° broad peaks appear, the first peak corresponding to scattering derived from amorphous or crystalline polyfluorocarbons, and the second peak is pseudo-teflon. It is a peak derived from the Teflon-like domain, and is a peak appearing because CF-groups exist in the basic skeleton. Referring to FIG. 7 (a) according to Example 1, it can be seen that four peaks derived from zirconium phosphate are present. Therefore, zirconium phosphate is present in the organic-inorganic composite proton conductive polymer membrane according to Example 1. You can see that.

Test Example 8

XPS  Measure

XPS (PHI1500 ESCA system) experiments were performed on the proton conductive polymer membranes prepared by Example 1 and Comparative Example 2, and the results for Zr3d are shown in FIG. 8. Referring to Figure 8, 3d _3/2 peak appears at 185.5eV, 3d _5/2 peak appears in the 183.5eV 3d _5/2 peak of the oxygen group of the zirconium phosphate in the acid proton-conducting polymer membrane according to the invention atom There is evidence of chemical bonding with. That is, in the case of ZrP there appear in originally 3d _5/2 peak of 182.5eV, in the case of ZrP present in the proton-conducting polymer membrane according to the present invention has been shifted towards a higher to 183.5eV, which zirconium and oxygen atom of the sulfonic acid group There may be evidence that a chemical bond exists between atoms.

Test Example 9

LSV  Measure

The organic sweep-produced polymer membrane prepared in Example 1 was subjected to LSV (Linear Sweep Voltametry) measurement to check hydrogen crossover rate and short circuit. That is, 200 m ³ / min of hydrogen is injected into the anode, 200 cm ³ / min of nitrogen is injected into the cathode, and ⁴ mV / s using a potentiostat / galvanostat (manufactured by Zahner) The LSV was measured in the range of 0 to 800 mV at a scan rate of and the results are shown in FIG. On the other hand, the LSV measurement was performed by changing the operating temperature of the cell to 25 ℃, 80 ℃, 100 ℃, 120 ℃ and 130 ℃. 9, the limiting current (limiting current) is very small in all the temperature range, because the hydrogen permeability is low as less than 1.0mA / cm ^{2 The} organic-inorganic composite proton conductive polymer membrane according to the present invention has a very high permeability of hydrogen It is low and it can be seen that no perforation is present in the composite membrane even when zirconium phosphate is added.

Test Example 10

Fuel cell test

The fuel cells prepared in Example 4 and Comparative Examples 4 to 5 were subjected to a cell test, hydrogen gas was injected to the anode side, oxygen gas was injected to the cathode side, and the injection speed was 300 cc / min. At this time, the respective gases are passed through the humidifier so that the fuel is not dried and the temperature of the cathode, anode, and cell can be individually controlled using a thyristor power regulator (TPR). As a method for obtaining data about current and voltage, an opposite current is applied to obtain a constant resistance in OCV (Open Circuit Voltage), and the current density vs. voltage, current density vs. power density are measured for each time. 10 to 12 are shown.

10 (a) shows the fuel cell prepared in Comparative Example 5 at 80 ° C./1 atm, 80 ° C./3 atm, 90 ° C./3 atm, 100 ° C./3 atm, 110 ° C./3 atm and 120 ° C. / The current density-voltage curve when operating at 3 atmospheres is shown, and FIG. 10 (b) shows the current density-power density curve under the same conditions.

On the other hand, Figure 11 (a) shows the fuel cell produced in Example 4 80 ℃ / 1 atm, 80 ℃ / 3 atm, 110 ℃ / 3 atm, 120 ℃ / 3 atm, 130 ℃ / 3 atm and 140 The current density-voltage curve when operating at 占 폚 / 3 atmospheres is shown, and Fig. 11 (b) shows the current density-power density curve under the same conditions. Comparing FIGS. 10 and 11, the performance of both batteries is similar at less than 100 ° C., but at a high temperature exceeding 100 ° C., the case of Example 4 shows a small voltage drop and high power density in a high current density region. It can be seen that it is excellent. On the other hand, in the case of Comparative Example 5, the voltage drops sharply when operating at 120 ° C, and data on voltage and power density is not shown at a current density of 300 mA / cm ² or more, which is very low at 0.4 V or less. It is because the measurement was difficult because of the large measurement error. Therefore, in the case of the comparative example 5, it turns out that the performance of a battery is very bad at the temperature of 120 degreeC or more.

On the other hand, Figure 12 shows the current density-voltage curve when operating the fuel cell cells prepared in Example 4 and Comparative Example 4 at 80 ~ 130 ℃, current density at 0.6V, 120 ℃ and 130 ℃ , The current density at which the maximum power density appears, and the maximum power density at that time are shown in Table 4 below.

Operating temperature; 120 ℃ Voltage: 0.6V Operating temperature; 130 ℃ voltage: 0.6V Example 4 Current density 760 mA / cm ² Current density 470 mA / cm ² Power density 481mW / cm ² Power density 300 mW / cm ² Comparative Example 4 Current density 620 mA / cm ² Current density 270mA / cm ² Power density 373mW / cm ² Power density 160 mW / cm ²

12 and Table 4, it can be seen that the fuel cell according to Example 4 shows a higher voltage in the higher current density region than the fuel cell according to Comparative Example 4, and the power density is also high. This is because zirconium phosphate can retain a large amount of water even at high temperatures. Particularly, the reason why the fuel cell according to the fourth embodiment has high voltage and high performance at high current density is that the organic-inorganic composite proton conductive polymer membrane according to the present invention has good hygroscopicity, so that no excessive moisture occurs even at high current density. It can be said that. The organic-inorganic composite proton conductive polymer membrane according to the present invention at 130 ° C. shows a current density of 174% of Comparative Example 4 (Nafion) and a maximum power density of 188%.

FIG. 13 shows a performance test result of a battery over time at voltages of 0.6 and 0.65V for the fuel cell manufactured in Example 4. FIG. Referring to FIG. 13, in the case of the fuel cell of Example 4, it can be seen that the performance of the battery is maintained almost the same for more than 40 hours.

In conclusion, it can be seen that the fuel cell according to the present invention has excellent high temperature performance and can suppress poisoning of the catalyst, thereby extending the life of the battery.

Since the organic-inorganic composite proton conductive polymer membrane according to the present invention has a higher moisture content than a conventional fluorine-based membrane, there is less overmoisture phenomenon at high current densities, thereby improving the efficiency of the battery. It is possible to prevent the poisoning of the catalyst by extending the life of the fuel cell. In addition, it is easier to manufacture than the conventional fluorine-based film, and even though the manufacturing cost is low, because it shows excellent battery characteristics can replace the fluorine-based film.

Claims (9)

An organic-inorganic composite proton conductive polymer membrane having a repeating unit of Formula 1 below.

(One) Wherein n is an integer of 100 to 100,000, m, m ', l, l' is an integer of 0 or 1, m and m 'and l and l' are not 0 at the same time, and l or l 'is 0 Is a hydrogen atom instead of ZrP, and ZrP is zirconium phosphate hydrate) The organic-inorganic composite proton conductive polymer membrane according to claim 1, wherein the polymer has a number average molecular weight of 5,000 to 1,000,000. The organic-inorganic composite proton conductive polymer membrane according to claim 1, wherein the equivalent weight of the polymer is 250 to 2,500. The organic-inorganic composite proton conductive polymer membrane of claim 1, wherein the content of zirconium phosphate is 10 to 25% by weight of the organic-inorganic composite proton conductive polymer membrane. (a) dissolving decafluorobiphenyl and 4,4 '-(hexafluoroisopropylidene) diphenol in an organic solvent, adding potassium carbonate (K ₂ CO ₃ ), followed by stirring and heating; (b) cooling the solution and pouring it into an aqueous acetic acid solution to precipitate the polymer; (c) dissolving the polymer obtained above in an aprotic organic solvent and then sulfonating with addition of a strong acid-giving agent; (d) dissolving the polymer in acetone to form a film; And (e) immersing the polymer membrane in a zirconium chloride solution, and then immersing it again in a phosphate solution. The method of claim 5, wherein the aprotic organic solvent is chloroform or 1,1,2,2-tetrachloroethane. The method of claim 5, wherein the strong acid-providing agent is chlorosulfonic acid (chlorosulfonic acid), acetyl sulfonate (acetyl sulfonate) or fuming sulfuric acid (fuming H ₂ SO ₄ ) Preparation of organic-inorganic complex proton conductive polymer membrane Way. The method of claim 5, wherein the content of zirconium phosphate in step (e) is controlled by reaction time or reaction temperature.       A fuel cell produced by employing the proton conductive polymer membrane according to any one of claims 1 to 4.

Images