KR20090113175A - Preparation method of composite membranes crosslinked with anhydrous aliphatic monomer containing sulfonic acid-acrylamide and polymer electrolyte fuel cells using the same - Google Patents

Abstract

PURPOSE: A method for preparing composite membranes crosslinked with anhydrous aliphatic monomer containing sulfonic acid-acrylamide is provided to ensure excellent ion conductivity and high durability and to reduce manufacturing cost. CONSTITUTION: A method for preparing composite membranes crosslinked with anhydrous aliphatic monomer containing sulfonic acid-acrylamide comprises a step of forming a membrane by synthesizing polyelectrolyte on a porous polymer support. The polyelectrolyte is cross-linked with sulfonic acid-aliphatic liquid monomer and an acrylamide-based cross-linking agent.

Description

Preparation method of composite membranes crosslinked with anhydrous aliphatic monomer containing sulfonic acid-acrylamide and polymer electrolyte fuel cells using the same}

The present invention relates to a method for producing a sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous crosslinked polymer electrolyte composite membrane and a polymer fuel cell using the same.

In detail, the present invention is made by simplifying a manufacturing process while having excellent hydrogen ion conductivity by impregnating a photopolymeric crosslinked film by impregnating a microporous polymer support membrane in a mixed solution containing an aliphatic monomer containing sulfonic acid, an acrylamide crosslinking agent and a photoinitiator. The present invention relates to a method for preparing a sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous crosslinked polymer electrolyte composite membrane capable of reducing manufacturing costs, and a polymer fuel cell using the same.

In general, fuel cells are generally alkaline fuel cells (AFC), phosphate (Phosphoric Acid Fuel Cell (PAFC)), molten carbonate (Molten Carbonate Fuel Cell (MCFC)), solids depending on the type of electrolyte used. Solid Oxide Fuel Cell (SOFC), Direct Methanol Fuel Cell (DMFC), and Polymer Electrolyte Membrane Fuel Cell (PEMFC) are classified.

Among the fuel cell types, the polymer fuel cell and the direct methanol fuel cell use polymers as electrolytes, and thus there is no risk of corrosion or evaporation due to electrolytes, and high current density per unit area can be obtained. Compared with the US and Japan, the output characteristics are much higher and the operating temperature is lower than that of the US, Japan, to use them as portable power sources such as automobiles, distributed power sources (on-site) and electronic devices for homes and public buildings. In Europe and other countries, development of this is being actively promoted. In addition, the ion conductive polymer electrolyte membrane is one of the most important key components in determining performance and price in a polymer electrolyte fuel cell or a direct methanol fuel cell.

Currently used polymer electrolyte membranes are mainly Nafion (trade name manufactured by DuPont), Premion (trade name manufactured by Flemion, Asahi Glass), Asiplex (trade name manufactured by Asahi Chemical), and Dow XUS (Dow XUS). , Dow Chemical Co., Ltd. namely, perfluorosulfonate ionomer membranes such as electrolyte membranes are widely used, but due to their high price, they are a considerable burden to commercialize the polymer fuel cell as a power source for power generation. It is acting as a.

On the other hand, in order to solve such a burden, hydrocarbon-based polymers such as polyether ether ketone, polysulfone, polyimide, etc., which are relatively inexpensive and have various commercial applications. The research on is active. The above polymer is manufactured as an ion conductive polymer by sulfonation reaction and then applied as a fuel cell electrolyte membrane by casting into an electrolyte membrane.

In addition, Teflon is a method for improving redox resistance and thermal / mechanical stability, which are the major disadvantages of the above hydrocarbon-based polymers, and for improving low bonding properties with electrodes due to excessive swelling during membrane electrode assembly (MEA) manufacturing. A method of fabricating a composite membrane by impregnating a perfluorinated or hydrocarbon-based polymer in its pores in a porous support having excellent mechanical, thermal and oxidation resistance has been proposed. Commercialized examples include W.L. Gore & Associates' Gore-select has a thin thickness of 20 to 40㎛ and excellent mechanical and electrochemical properties.

In order to produce a membrane that can exhibit better performance of a fuel cell utilizing the excellent properties of the composite membrane as described above, styrene, a hydrocarbon monomer instead of Nafion, is combined with a divinylbenzene crosslinking agent with Teflon, polyethylene (PE), and polyvinylidenedi A method of impregnating and crosslinking by impregnating a variety of porous supports such as fluoride (PVDF) and sulfonation, and a method of preparing an electrolyte membrane by crosslinking by impregnating an acrylic sulfonic acid monomer and a water-soluble crosslinking agent into a porous support as described above are proposed.

When the styrene-divinylbenzene crosslinked electrolyte membrane as described above is dried, it is brittle due to an increase in brittleness, and has a drawback that mechanical stability is inferior in mass production and processing into electrodes in the form of thin films or composite membranes. In addition, acrylic sulfonic acid cross-linked electrolyte pore-filling membrane is known to have a disadvantage in that a wide range of commercialization is not possible due to the drawback of such a hydrocarbon-based polymer membrane because of poor durability.

Accordingly, an object of the present invention is to impregnate a porous polymer support in the anhydrous state with a durable acrylamide-based crosslinking agent in a sulfonic acid-containing aliphatic liquid monomer having high hydrogen ion conductivity and then optically crosslinking to improve physical properties and durability of the composite membrane, thereby improving conventional polymer electrolytes. It is to provide a method for producing a polymer electrolyte composite membrane for a fuel cell having an improved hydrogen ion conductivity than a composite membrane and a fuel cell using the same.

In order to achieve the above object, the present invention has the following features.

A polymer electrolyte crosslinked with a sulfonic acid-containing aliphatic liquid monomer and an acrylamide-based crosslinking agent is synthesized on a porous polymer support to form a membrane. Here, the porous polymer support uses a porous hydrocarbon membrane having a pore volume of 30-60%, a pore size of 0.05-0.1 micrometers, and a thickness of 20-55 micrometers.

In particular, the sulfonic acid-containing aliphatic liquid monomer-acrylamide crosslinked polymer electrolyte is synthesized in a mixed solution of an anhydride state in which a high concentration of sulfonic acid-containing aliphatic liquid monomer, acrylamide-based crosslinking agent, and an initiator is not less than 95% pure without water. When the solution of the sulfonic acid monomer and the crosslinking agent was mixed at 100 parts by weight, 60 to 90 parts by weight of the sulfonic acid-containing aliphatic liquid monomer, 10 to 40 parts by weight of the acrylamide-based crosslinking agent and 100 parts by weight of the mixed solution were added to 100 parts by weight of the mixed solution. It is formed by adding 0.1 to 0.5 parts by weight of an initiator. The initiator is preferably formed by adding 0.2 parts by weight.

At this time, the high-concentration sulfonic acid-containing aliphatic liquid monomer containing no water improves ion exchange capacity and thus has high ion conductivity. In addition, when the content of the sulfonic acid-containing aliphatic liquid monomer is less than 60 parts by weight, the ion exchange capacity may be insufficient to improve the ionic conductivity, and the preparation of the electrolyte mixture solution is difficult. This is equivalent to the role of reducing the durability of the membrane due to the lack of crosslinking degree when the content of the crosslinking agent is less than 10 parts by weight, and difficult to prepare the electrolyte mixture solution when the content of the crosslinking agent is greater than 40 parts by weight, and the crosslinking degree is too high.

The sulfonic acid-containing aliphatic liquid monomer is one selected from a high concentration of liquid monomer having a purity of 95% or more, such as vinyl sulfonic acid, allyl sulfonic acid, 2-methyl-2-propene-1-sulfonic acid, and 3-sulfopropyl acrylic acid, which do not contain water. Apply above.

In addition, the acrylamide crosslinking agent is applied to at least one selected from acrylamide containing two or more carbon double bonds such as N, N'-bisacryloylpiperazine.

On the other hand, the initiator is selected from the Doracure or Irgacure series of Ciba Geigy of Switzerland as a photoinitiator.

The crosslinking agent for the polymerization influences the degree of crosslinking of the composite membrane and plays a role of determining the swelling degree and mechanical properties of the membrane according to the amount thereof. Although an acrylamide-based crosslinking agent is provided as a kind of such a crosslinking agent, the type of crosslinking agent is not limited, and an initiator for polymerization may be used without particular limitation.

As described above, the present invention comprises the steps of: (a) impregnating a porous polymer support with a mixed solution composed of a sulfonic acid-containing aliphatic liquid monomer, an acrylamide-based crosslinking agent and an initiator; (b) after stacking the porous support impregnated in step (a) between the PET film, it is prepared by performing a photocrosslinking step.

At this time, in the step of photo-crosslinking, the porous support impregnated with the mixed solution containing the photoinitiator is laminated between the PET film up and down to irradiate 30 mJ / cm 2-150 mJ / cm 2 of ultraviolet light to photocrosslink.

In addition, the porous polymer support is used a hydrocarbon-based material excellent in chemical resistance, oxidation resistance and mechanical stability, for example polyethylene, polypropylene, polyimide, polyamideimide, polypropylene oxide, polyether sulfone, polyurethane And the like can be used.

In this manner, a polymer electrolyte composite membrane having a thickness of 20 to 55 μm containing a sulfonic acid-containing aliphatic liquid monomer-acrylamide crosslinked polymer electrolyte may be prepared.

According to the above production method, a fuel cell having a polymer composite membrane having a hydrogen ion conductivity of 0.07-0.12 S / cm at room temperature and a methanol permeability of 0.1 kg / m < 2 >

As described above, in the present invention, in order to improve the mechanical properties of the polymer electrolyte composite membrane, a conventional styrene-divinylbenzene crosslinked electrolyte is used by using a PE as a porous support and using a sulfonic acid-containing aliphatic liquid monomer and an acrylamide crosslinking agent together. Compared with the composite membrane prepared by the acrylic sulfonic acid crosslinked electrolyte, an effect having excellent ionic conductivity and high durability is obtained.

In addition, the present invention can reduce the manufacturing cost due to the simple manufacturing process and thinning and there is an effect that can be expected to develop a continuous manufacturing process.

Prior to the description of the examples, various tests and performance evaluation methods of the polymer composite membranes prepared by various examples to be described below are presented.

1. Tensile strength

The tensile force (kpsi) of the electrolyte membrane was measured according to the method described in ASTM 882.

2.hydrogen ion conductivity

After immersing the membrane prepared in Example in distilled water at 25 ° C. for 1 hour, the glass substrate was fixed between two glass substrates on which a rectangular platinum electrode was fixed without removing water on the membrane surface, and then fixed at 100 Hz. A 4 MHz alternating current impedance measurement was performed to measure the hydrogen ion conductivity of the membrane.

3. Methanol transmittance

An electrolyte membrane sample was mounted in the methanol permeability measuring apparatus shown in FIG. As time passes, methanol passes through the membrane sample and moves toward the distilled water. Thus, the methanol permeability (kg / m2? H) of the membrane is measured by gas chromatography by collecting a portion of the distilled water side solution after 2 hours at room temperature. Calculated.

4. Fuel Cell Performance

-For direct methanol fuel cell (DMFC) performance measurement using the polymer electrolyte membrane for a fuel cell prepared according to the embodiment, a polymer electrolyte was prepared using a fuel electrode containing 3 mg / cm 2 of PtRu / C and an air electrode containing 1 mg / cm 2 of Pt / C. Membrane Electrode Assembly of 5 cm2 effective area was fabricated by attaching to the membrane, and then mounted on a unit cell performance evaluation apparatus, and then, 1 mol / min methanol solution was flowed into the anode at a rate of 1 ml / min under 60 ° C. The performance of the fuel cell was measured by flowing it to the cathode at a rate of 50 ml / min.

At this time, in order to measure the performance of the hydrogen ion exchange membrane fuel cell (PEMFC), a membrane electrode assembly having a size of 5 cm2 effective area was bonded by bonding an anode and an oxygen electrode containing 0.4 mg / cm2 of Pt / C with a polymer electrolyte membrane. ), And mounted in a unit cell performance evaluation apparatus, and then flowing hydrogen in a 100% humidified state at a rate of 100 ml / min to a fuel electrode under a 70 ° C condition, and 100 ml / min oxygen in a 100% humidified state in the air electrode. The performance of the fuel cell was measured by flowing the oxygen electrode at a speed.

Hereinafter, various embodiments to which the present invention is applied will be described in detail with reference to the accompanying drawings.

<Example 1>

In Example 1, 95% or more of high concentration vinylsulphonic acid: N, N'-bisacryloylpiperazine containing no water was mixed and stirred at 80:20 parts by weight, and 10 parts by weight of methanol was added to 100 parts by weight of the mixed solution. Doracure1173 diluted to parts by weight was mixed to 1 part by weight.

Thereafter, the solution is impregnated with a porous support based on polyethylene having a film thickness of 30 μm, pore size of 0.07 μm, and pore distribution of 40% so that the monomer solution is sufficiently infiltrated into the support, and then the support is polyethylene terephthalate (PET) film. Ultraviolet energy was irradiated to put in between 150 mJ / cm <2>.

After performing the crosslinking process, the PET film was removed, the by-products of the surface of the composite membrane were removed to make the surface uniform, and then washed several times with ultrapure water to obtain a polymer composite membrane.

Tensile strength, hydrogen ion conductivity, and methanol permeability were measured by the method described above for the composite membrane prepared as described above, and the results as shown in Table 1 were obtained.

<Example 2>

In Example 2, a composite membrane was prepared under the same conditions as in Example 1 using N, N'-methylenebismethacrylamide instead of N, N'-bisacryloylpiperazine as a crosslinking agent.

Tensile strength, hydrogen ion conductivity, and methanol permeability were measured by the method described above for the composite membrane prepared as described above, and the results as shown in Table 1 were obtained.

Tensile strength, hydrogen ion conductivity, and methanol permeability were measured by the method described above for the composite membrane prepared as described above, and the results as shown in Table 1 were obtained.

Comparative Example

In the comparative example, the tensile strength, proton conductivity, and methanol permeability of a commercially available ion exchange membrane, Nafion 117 or 112 membrane (Dupont, USA) were measured by the method described above to obtain the results as shown in Table 1.

<Measurement Result According to Each Example> Example 1 Example 2 Comparative Example Nafion 117, 112 Tensile strength (kpsi) 23.0 (MD) 20.0 (TD) 23.0 (MD) 20.0 (TD) 6.3 (MD) 4.7 (TD) Hydrogen ion conductivity (S / cm) 0.12 0.07 0.08 Methanol Permeability (Kg / m2? H) 0.1 0.08 0.28 MD: machine direction TD: transverse direction

Referring to Table 1, the polymer electrolyte composite membrane prepared according to the present invention was found to have a similar or higher hydrogen ion conductivity than the membrane of the comparative example.

In addition, the polymer electrolyte composite membrane prepared according to the present invention had excellent tensile strength, and methanol permeability was stable at 1/3-1/4 level compared to the membrane of the comparative example, so that if the mass production system was established by a continuous manufacturing process, As an environmentally friendly hydrocarbon fuel cell membrane, the commercial membrane of the comparative example may be replaced.

In particular, the polymer electrolyte composite membrane prepared according to the present invention forms a transparent membrane after preparation and is insoluble in most organic solvents when complete crosslinking is performed by each crosslinking agent as shown in FIGS. 2B to 2D in the state of FIG. 2A. Confirmed.

Figure 2a shows a polymer electrolyte composite membrane before the crosslinking process is performed. 2B shows a polymer electrolyte composite membrane in which N, N′-bisacryloylpiperazine is applied as a crosslinking agent. 2C shows a polymer electrolyte composite membrane in which N, N'-methylenebismethacrylamide is applied as a crosslinking agent.

3 is a result graph showing the performance of the direct methanol fuel cell (DMFC) using the polymer electrolyte composite membrane prepared according to the present invention.

Referring to the drawings, the fuel cell using the polymer electrolyte composite membrane prepared by the process of Example 1 of the present invention, compared with the fuel cell prepared by the aforementioned Nafion 117 membrane, the characteristics of the potential, current density, power density It can be seen that this excellent fuel cell can be produced with improved performance.

4 is a graph showing the results of hydrogen ion exchange membrane fuel cell (PEMFC) performance using the polymer electrolyte membrane prepared by the present invention.

Referring to the drawings, the fuel cell using the polymer electrolyte composite membrane prepared by the process of Example 1 of the present invention, compared with the fuel cell prepared by the Nafion 112 membrane described above, the characteristics of the potential, current density, power density It can be seen that this excellent fuel cell can be produced with improved performance.

1 is a schematic diagram of an apparatus for measuring the methanol permeability of a polymer electrolyte membrane prepared by the present invention.

Figures 2a to 2c is an illustration of a state in which the polymer electrolyte composite membrane prepared by the present invention is changed through a crosslinking process.

Figure 3 is a result graph showing the performance of the direct methanol fuel cell (DMFC) using the polymer electrolyte composite membrane prepared by the present invention.

Figure 4 is a graph showing the results of hydrogen ion exchange membrane fuel cell (PEMFC) using the polymer electrolyte membrane prepared by the present invention.

Claims (8)

A method for producing a sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous cross-linked polymer electrolyte composite membrane, comprising: synthesizing a polymer electrolyte cross-linked with a sulfonic acid-containing aliphatic liquid monomer and an acrylamide-based crosslinking agent on a porous polymer support. The method of claim 1, The porous polymer support is a sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous crosslinking comprising a porous hydrocarbon membrane having a pore volume of 30 to 60%, a pore size of 0.05 to 0.1 micrometers, and a thickness of 20 to 55 micrometers. Method for producing a polymer electrolyte composite membrane. The method of claim 1, The sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous crosslinked polymer electrolyte is synthesized into a mixed solution containing not less than 95% of a high concentration of sulfonic acid-containing aliphatic liquid monomer, acrylamide-based crosslinking agent, and initiator, and the sulfonic acid monomer and crosslinking agent When 100 parts by weight of the mixed solution was contained, 60 to 90 parts by weight of the sulfonic acid-containing aliphatic liquid monomer, 10 to 40 parts by weight of the acrylamide-based crosslinking agent and 100 parts by weight of the initiator were 0.1 to 0.5 based on 100 parts by weight of the mixed solution. A method for producing a sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous crosslinked polymer electrolyte composite membrane, comprising adding parts by weight. The method of claim 1, The acrylamide crosslinking agent is a sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous crosslinking agent, characterized in that at least one member selected from acrylamide crosslinking agents including two or more carbon double bonds such as N, N'-bisacryloylpiperazine. Method for producing a polymer electrolyte composite membrane. The method of claim 3, wherein The initiator is any one of the Doracure or Irgacure series manufactured by Ciba Geigy as a photoinitiator, the method for producing a sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous crosslinked polymer electrolyte composite membrane. (a) impregnating the porous polymer support with a mixed solution consisting of a sulfonic acid-containing aliphatic liquid monomer, an acrylamide-based crosslinking agent and an initiator; (b) a method of manufacturing a sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous crosslinked polymer electrolyte composite membrane, comprising laminating the porous support impregnated in step (a) between PET films and then photocrosslinking. The method of claim 6, In the step of photocrosslinking, sulfonic acid characterized in that the porous support impregnated with the mixed solution containing the photoinitiator is laminated between the PET film up and down to irradiate UV energy of 30 mJ / cm2-150 mJ / cm2 to photocrosslink A method for producing a containing aliphatic liquid monomer-acrylamide anhydrous crosslinked polymer electrolyte composite membrane. Prepared by the method according to any one of claims 1 to 7, Produced using a method for preparing a sulfonic acid-containing aliphatic liquid monomer-acrylamide anhydrous crosslinked polymer electrolyte composite membrane characterized by a polymer composite membrane having a hydrogen ion conductivity of 0.07-0.12 S / cm at room temperature and a methanol permeability of 0.1 kg / m2? H or less. Fuel cell.

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