KR101630212B1 - A composite membrane comprising nonwoven PAI-PTM and sulfonated poly(arylene ether sulfone) as hydrocarbon-based electrolyte therein and the use thereof - Google Patents

Abstract

The present invention relates to poly (amide-co-imide) (PAI) resins and poly (trimellitic anhydride chloride-co-4,4'-methylenedianiline) PTM non-woven fabric prepared by electrospinning a solution containing a mixture of trimellitic anhydride chloride-co-4,4'-methylenedianiline (PTM) resin mixture and a hydrocarbon-based polymer electrolyte impregnated therewith, A membrane-electrode assembly (MEA) having the composite membrane, and a fuel cell having the membrane-electrode assembly.

Description

A composite membrane prepared by impregnating a PAI-PTM nonwoven fabric with a hydrocarbon-based polymer electrolyte and a use thereof.

The present invention relates to poly (amide-co-imide) (PAI) resins and poly (trimellitic anhydride chloride-co-4,4'-methylenedianiline) PTM non-woven fabric prepared by electrospinning a solution containing a mixture of trimellitic anhydride chloride-co-4,4'-methylenedianiline (PTM) resin mixture and a composite membrane comprising a hydrocarbon- A membrane-electrode assembly (MEA) having the composite membrane, and a fuel cell having the membrane-electrode assembly.

Proton exchange membrane (PEM) is a proton exchange membrane fuel cell (PEMFC) capable of directly converting chemical energy into electrical energy for portable electronic devices, automobiles and large buildings. The proton exchange membrane (PEMFC) Is widely studied as one of. Nafion is a commercial membrane for PEMFCs with high proton conductivity, low dimensional changes in water, and excellent cell performance in a variety of environments. However, Nafion membranes are expensive and lose proton conductivity and durability at high temperatures (> 80 ° C). Accordingly, many researchers are trying to develop an inexpensive membrane using various aromatic polymers. As a result of this effort, it has been found that a high thermal resistance, such as a sulfonated poly (arylene ether sulfone) (SPAES), an excellent mechanical strength and a low gas permeability ) Have been studied as PEM materials for replacing Nafion membranes over the past several decades due to their excellent properties. Above all, it has the advantage of lowering the total cost of PEMFC application through low cost production process for commercialization. However, in the hydrocarbon-based copolymer, the dimensional stability and the proton conductivity . In order to achieve a proton conductivity similar to that of Nafion, hydrocarbon-based copolymers must contain a large number of sulfonic acid groups within the polymer chain, leading to high water absorption and low dimensional stability. This phenomenon leads to a decrease in the durability of the PEM due to film damage. In order to overcome these fatal disadvantages, a composite material containing a porous polymer material such as poly (tetrafluoroethylene) (PTFE), liquid crystal polymer (LCP) and polyimide (PI) It is developing membrane. These porous materials can improve the dimensional stability of composite membranes and durability in fuel cell testing. For example, composite membranes for PEMFC applications were prepared using porous PTFE and sulfonated poly (arylene ether ketone) (SPAEK). In order to improve the interfacial compatibility between the PTFE base and the SPAEK copolymer, a polystyrene sulfonate is grafted on the PTFE base material to increase the hydrophilicity and a partially fluorinated structure To synthesize SPAEK copolymer. These membranes showed mechanical stability and excellent performance. During the durability test of a single cell, these membrane electrode assemblies (MEAs) did not decrease in performance and the open circuit voltage (OCV) did not decrease for 40 hours. PI (polyimide) nanofibers have been reported and are added to SPAES copolymers for application to high temperature PEMFCs. Composite membranes containing novel PI nanofibers reduce dimensional changes and give better flexibility. High temperature and low relative humidity , The phosphosilicate was coated on the PI nanofibers to improve water retention properties and proton conductivity in the composite membranes. The proton conductivity of the improved composite membranes gave better performance than the pure polymer membranes at high temperatures and low relative humidity. For a direct methanol fuel cell (DMFC), a porous liquid prepared by melt-blown Composite membranes using liquid crystal polymers (LCP) were also devised. Such composite membranes, made by two SPAES copolymers, exhibited reduced dimensional changes and improved mechanical strength. The composite membrane showed comparable performance to that of Nafion.

However, materials such as PI, PTFE and LCP used for the production of the composite membrane can achieve the purpose of increasing the mechanical strength. However, since it is an expensive material, the cost of the fuel cell having the composite membrane using the support , These materials are unsuitable for mass production of a composite membrane and a fuel cell having the composite membrane. Therefore, a novel support capable of maintaining an excellent ionic conductivity while providing an improved mechanical strength to replace these materials, and a composite membrane using the novel support are required.

Accordingly, the present inventors have made intensive studies in order to find a novel support capable of maintaining excellent ionic conductivity of a hydrocarbon-based polymer electrolyte impregnated therewith while improving mechanical strength. As a result, it has been found that a poly (Trimellitic anhydride) (poly (amide-co-imide); PAI) as a lubricant with a low molecular weight poly (trimellitic anhydride chloride-co-4,4'- methylenedianiline chloride-co-4,4'-methylenedianiline) PTM oligomer in an appropriate ratio, and the composite membrane prepared by impregnating a high porosity non-woven fabric with a hydrocarbon-based polymer electrolyte has an improved mechanical strength and dimensions Stability and excellent ionic conductivity, it is confirmed that the fuel cell having the fuel cell exhibits excellent cell performance, Castle was.

It is an object of the present invention to provide a poly (amide-co-imide) (PAI) resin and a poly (trimellitic anhydride chloride-co-4,4'-methylenedianiline) a composite membrane comprising a PAI-PTM nonwoven fabric prepared by electrospinning a solution containing a poly (trimellitic anhydride chloride-co-4,4'-methylenedianiline) resin mixture and a hydrocarbon-based polymer electrolyte impregnated therewith ); A method of producing the composite membrane; A membrane-electrode assembly (MEA) having the composite membrane; And a fuel cell having the membrane-electrode assembly (MEA).

A first aspect of the present invention is a polyimide resin composition comprising a poly (amide-co-imide) (PAI) resin and a poly (trimellitic anhydride chloride-co-4,4'-methylenedianiline a composite membrane comprising a PAI-PTM nonwoven fabric prepared by electrospinning a solution containing a poly (trimellitic anhydride chloride-co-4,4'-methylenedianiline) resin mixture and a hydrocarbon-based polymer electrolyte impregnated therewith composite membrane.

In a second aspect of the present invention, there is provided a method of producing a composite membrane according to the first aspect of the present invention, comprising the steps of: preparing a mixed resin solution containing PAI resin and PTM resin in a weight ratio of 4: 6 to 7: 3; Preparing a nonwoven fabric by electrospinning the solution; And impregnating both surfaces of the nonwoven fabric with a hydrocarbon-based polymer electrolyte, thereby producing a composite membrane.

A third aspect of the present invention provides a membrane-electrode assembly having a composite membrane according to the first aspect of the present invention.

A fourth aspect of the present invention provides a fuel cell having the membrane-electrode assembly according to the third aspect of the present invention.

Hereinafter, the present invention will be described in detail.

The present invention aims to compensate for weak mechanical properties which are disadvantages of hydrocarbon-based electrolyte membranes in the production of an electrolyte membrane containing a hydrocarbon-based polymer that exhibits excellent ionic conductivity and can replace expensive fluorine-based electrolytes such as Nafion. Since the nonwoven fabric prepared by mixing PAI, which is excellent in strength and thermal stability, with PTM oligomer and electrospun, can be made to have a small thickness and at the same time has a high porosity, a hydrocarbon-based polymer electrolyte such as a sulfonated poly Sulfonated poly (arylene ether sulfone); SPAES) copolymer exhibits excellent ionic conductivity as well as exhibits improved strength and thermal stability. Therefore, it is useful as an ion exchange membrane for a fuel cell driven at a high temperature It is characterized by the discovery that it can be used All.

The "PAI (amide-co-imide)" is a thermosetting or thermoplastic amorphous polymer having mechanical, thermal and chemical resistance. It is a material that can simultaneously show the advantages of polyamide and polyimide such as high strength, melt processibility, high heat capacity and wide chemical resistance. It is produced by Solvay Advanced Polymers and sold under the trade name Torlon and can be easily prepared from isocyanate and TMA (trimellic acid-anhydride) using NMP as a solvent. Preferably, commercialized products may be purchased and used or synthesized by methods known in the art.

The "PTM (trimellitic anhydride chloride-co-4,4'-methylenedianiline)" is a soluble polymer having a low molecular weight and high reactivity. By using the PTM in combination with PAI, the roughness of the PAI can be reduced and the PAI-PTM mixture can act as a lubricant to facilitate molding.

Preferably, the concentration of the solution comprising the PAI resin and the PTM resin mixture may be from 10 to 30% by weight. And more preferably 20% by weight. When the concentration of the solution containing the PAI resin and the PTM resin mixture is less than 10% by weight, the viscosity of the solution is too low to form a nonwoven fabric by electrospinning, or it is difficult to radiate in the form of a too thin fiber to provide sufficient strength as desired . On the other hand, when the concentration of the solution exceeds 30% by weight, the viscosity of the solution is high, so that the electrospun solution can not be formed into a fiber having a predetermined thickness, bubbles or the like are formed and the finally formed nonwoven fabric has uniformity for impregnating the electrolyte solution It may be irregularly formed without having one pore or difficult to achieve a desired porosity.

Also preferably, the PAI resin and the PTM resin mixture may contain PAI and PTM in a weight ratio of 4: 6 to 7: 3. More preferably in a weight ratio of 5: 5. When the PTM content exceeds 60% by weight, that is, when the PTM content of the low molecular weight is high, even if the mixed solution is electrospun, it can not be formed into a long fiber having a uniform thickness and is formed into an irregular thickness and short- Or it may be difficult to form a nonwoven fabric by spinning in a form containing a large number of bubbles. When the content of PTM is less than 30%, the nonwoven fabric is formed into a fiber having a micrometer- May be difficult to provide a pore size and porosity suitable for impregnating the electrolyte solution.

Preferably, the PAI-PTM nonwoven fabric has 60 to 90% porosity. The PAI-PTM nonwoven fabric is characterized by having pores having a diameter of 15 to 20 μm. Due to the presence of pores in the nonwoven fabric and the high porosity, a large amount of electrolyte can be contained in the pores, which can offset the decrease in ionic conductivity due to the low proton conductivity of PAI-PTM.

Preferably, the composite membrane has a thickness of 10 to 30 占 퐉. The PAI-PTM nonwoven fabric containing the electrolyte solution in the composite membrane can provide improved mechanical strength and dimensional stability as compared with a membrane made of a polymer itself, which is required as an electrolyte membrane of a fuel cell, while the conductivity of the non- The resistance is low. Therefore, in order to minimize this, the composite membrane can maintain the mechanical strength, but the thickness is minimized to lower the resistance, and the conductivity is improved by impregnating the conductive electrolyte solution.

Meanwhile, as a non-limiting example of the polymer electrolyte that can be impregnated into the support according to the present invention, there is a hydrocarbon-based polymer electrolyte. Non-limiting examples of hydrocarbon-based polymer electrolytes include sulfonated polyimides, sulfonated poly (arylene ether sulfone) (SPAES), sulfonated poly (ether ether ketone) ether ketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (SPSU), sulfonated polystyrene (SPS), sulfonated polyphosphazene sulfonated polyphosphazene (SPP), sulfonated poly (ether sulfone) (SPES), sulfonated poly (ether ketone) (SPEK), sulfonated polyarylene ether benzimide Sulfonated poly (arylene ether benzimidazole); SPAEBI). A preferable example of the hydrocarbon-based polymer electrolyte is a sulfonated poly (arylene ether sulfone) copolymer or a polymer of the following formula (1).

[Chemical Formula 1]

In the above formula, l, m and n are each independently an integer of 1 or more.

The hydrocarbon-based electrolyte containing a sulfonate group can interact with the hydrophilic functional groups of PAI and PTM through sulfonic acid groups, so that it can provide excellent compatibility when impregnated into the support prepared therefrom.

The SPAES impregnated in the PAI-PTM nonwoven fabric as an electrolyte is preferably 40 to 60 mol% sulfonated. If the degree of sulfonation is more than 60%, the hydrophilic property of the membrane becomes high, and it may dissolve in water and be dissolved in the support without being impregnated in the support. On the other hand, when the degree of sulfonation is less than 40%, the ion conductivity of the membrane may be significantly deteriorated.

In one embodiment of the present invention, a SPAES copolymer having a degree of sulfonation of 50 mol% and exhibiting high conductivity and not being soluble in a solvent was synthesized. It was confirmed that the composite membrane (Example 3) prepared by impregnating the SPAES copolymer with the porous support according to the present invention improved not only proton conductivity but also mechanical properties, dimensional stability and durability. Particularly, as a result of measurement of the dimensional change in the wet and dry state, it was confirmed that the dimensional change in the direction of the area which can cause the breakage of the electrolyte membrane was remarkably reduced (FIG. 6). Further, the effect of the porous support according to the present invention was confirmed by comparing the properties of the composite membrane produced according to Example 3 with that of the pure SPAES copolymer polymer membrane through a fuel cell drive test. However, the proton conductivity measured at various temperatures and humidity is decreased in the composite membrane, which is due to the blocking of the proton pathway by the porous support. However, since the porous support according to the present invention exhibits enhanced strength, Can be canceled.

The composite membrane according to the present invention comprises a mixed resin solution containing a PAI resin and a PTM resin in a weight ratio of 4: 6 to 7: 3; Preparing a nonwoven fabric by electrospinning the solution; And impregnating the SPAES solution onto both sides of the nonwoven fabric.

At this time, preferably, the nonwoven fabric produced by electrospinning may further be treated at 250 to 400 ° C for 10 minutes to 3 hours. By treating the PAI-PTM nonwoven fabric used as a support in this manner at a high temperature, the solvent resistance of the support can be improved. Since the support prepared according to the above method has a high porosity and a constant pore size, it is suitable for use as an electrolyte membrane by impregnating the pores with an electrolyte solution. Also, since the nonwoven fabric can be made to have a thin thickness, the reduced proton conductivity of the composite membrane due to proton pathway blocking by the support itself with low proton conductivity can be offset by shortening the path.

The present invention also provides a membrane-electrode assembly with a composite membrane according to the present invention.

The present invention can produce a membrane-electrode assembly (MEA) through a composite membrane according to the present invention between the reducing electrode and the oxidizing electrode by, for example, high-temperature pressurization. At this time, the pressure is preferably 0.5 to 2 tons (ton) and the temperature is preferably 40 to 250 ° C.

The catalyst that can be used for the membrane-electrode assembly may be Pt, Pt-Ru, Pt-Sn or Pt-Pd alloy catalysts or Pt / C or Pt-Ru / C plated with fine carbon particles, Metal materials such as Ru, Bi and Sn Mo may be deposited on Pt, but any material suitable for the oxidation of hydrogen and the reduction reaction of oxygen may be used without limitation. Also commercially available from Johnson Matthey, E-Tek, etc. may be used. Since the electrode catalysts bonded to both surfaces of the electrolyte membrane act as cathodes and anodes, they may be used in different amounts depending on the reaction rate at both electrodes, and other types of catalysts may be used.

The membrane-electrode assembly may be manufactured using a method known to those skilled in the art. For example, various methods such as a decal method, a spray method, and a catalyst coated gas diffusion media (CCG) method may be used . In a specific embodiment of the present invention, a membrane-electrode assembly was produced using the CCG method, but the method of manufacturing the membrane-electrode assembly is not limited thereto.

Specifically, a non-limiting method for preparing the membrane-electrode assembly includes: applying a catalyst slurry in which a catalyst, a proton conductive polymer, and a dispersion medium are mixed on a gas diffusion layer (GDL), followed by drying to form a catalyst layer; Aligning the catalyst layer formed on the GDL so that the catalyst layer faces the electrolyte membrane on both sides of the composite membrane obtained by impregnating the PAI-PTM nonwoven fabric according to the present invention with an electrolyte solution of SPAES copolymer; And stacking the laminate so that the catalyst layers are in contact with each other, followed by hot pressing to form a membrane-electrode assembly.

Furthermore, the present invention provides a fuel cell having the membrane-electrode assembly according to the present invention.

Fuel cells are devices that convert chemical energy from fuel into electrical energy through chemical reaction with oxygen or other oxidants. The fuel cell includes a fuel electrode (anode) that produces hydrogen ions and electrons by oxidation of a fuel material, an anode (cathode) where reduction of oxygen or other oxidizing agent by hydrogen ion and reaction with electrons occurs, And an electrolyte layer capable of efficiently transferring hydrogen ions to the air electrode. In the fuel cell, hydrogen ions and electrons move from the fuel electrode to the air electrode through an external circuit electrically connected to the electrolyte layer, respectively. The fuel cell may use hydrogen, hydrocarbon, alcohol (methanol, ethanol, etc.) as the fuel, and oxygen, air, chlorine, chlorine dioxide, or the like may be used as the oxidizing agent.

Fuel cells include polymer electrolyte membrane fuel cell (PEMFC), direct methanol fuel cell (DMFC) using alcohol as fuel, direct ethanol fuel cell (DEFC), alkaline fuel cell (AFC), Phosphoric Acid Fuel Cell (PAFC), Molten Carbonate Fuel Cell (MCFC), and Solid Oxide Fuel Cell (SOFC). . Both the polymer electrolyte fuel cell, the direct methanol fuel cell and the direct ethanol fuel cell can operate at relatively low temperatures compared to other fuel cells and can be produced at capacities of 1 to 10 kW. Further, since it can be downsized, it can be stacked to improve the output, and can be usefully used for a notebook computer or an auxiliary power source device because it is easy to carry. Accordingly, in order to reduce the volume of the unit cell, an electrolyte membrane prepared by using an ion conductive polymer between the fuel electrode and the air electrode is placed in the form of a sandwich and compressed to form a membrane-electrode assembly in which a fuel electrode- electrolyte membrane- So that the battery can be constructed. The electrolyte membrane that can be used for the membrane-electrode assembly should have a high hydrogen ion transfer capacity, but not only the permeability of the fuel material should be low, but also exhibit high thermal stability and exhibit stable ion conductivity even under battery operating conditions of about 100 ° C. And chemical durability. Therefore, it should not be decomposed even under long-term use or acidic conditions.

Preferably, the fuel cell having the membrane-electrode assembly according to the present invention may be a polymer electrolyte fuel cell, a direct methanol fuel cell, or a direct ethanol fuel cell.

The novel composite membrane obtained by impregnating a non-woven fabric prepared by mixing PAI and PTM according to the present invention with a certain ratio and electrospun is impregnated with a SPAES50 copolymer as a hydrocarbon-based polymer electrolyte. The new composite membrane is uniformly present in the nonwoven fabric having a high porosity Since the polymer electrolyte includes the hydrocarbon-based polymer electrolyte through the pores, the polymer electrolyte has excellent ionic conductivity, but by improving the mechanical strength by the non- Since the disadvantages of the existing hydrocarbon-based polymer electrolyte membrane have been overcome, Can be usefully used as an electrolyte membrane having excellent mechanical properties, dimensional stability and durability required for fuel cells and the like.

FIG. 1 schematically shows an electrospinning process using a PAI / PTM blend.
2 is a schematic view illustrating a process of synthesizing an SPAES copolymer.
3 shows (a) low magnification and (b) high magnification SEM images of fabricated PAI / PTM nonwoven fabric (PAI / PTM nonwoven).
4 is a graph showing the pore size distribution of the PAI / PTM nonwoven fabric.
5 shows an image of a composite membrane composed of a SPAES 50 and a PAI / PTM nonwoven fabric. (a) shows the real, (b) shows the surface, and (c) shows the cross-sectional image.
6 is a diagram showing dimensional changes of Nafion 212, SPAES 50 and PAI-PTM / SP50. Area, thickness and volume were measured and shown together.
7 is a graph showing the proton conductivity of Nafion 212, SPAES50 and PAI-PTM / SP50 according to temperature at 100% relative humidity conditions.
8 is a graph showing the single cell performance of Nafion 212, SPAES 50 and PAI-PTM / SP50. (a) shows the performance at 80 ° C and 100% relative humidity, (b) shows the performance change of the composite membrane according to OCV (open circuit voltage) holding test time as a function of cell voltage Respectively.
FIG. 9 is a diagram showing the durability test result of the synthetic membrane using the OCV sustain method. FIG. (a) and (b) show OCV changes and hydrogen crossover according to test time, respectively.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited by these examples.

Example  1: substance

4,4'-Difluorodiphenyl sulfone (DFDPS) and poly (amide-co-imide) resin, Torlon® 4000T-HV) were purchased from Solvay Advanced Polymers And 3,3'-disulfonated-4,4'-difluorodiphenyl sulfone (SDFDPS) was synthesized by a known method. 4,4'-Bisphenol (BP, TCI) and DFDPS were recrystallized with ethanol before use. N-methyl-2-pyrrolidone (NMP, Junsei), anhydrous toluene (Aldrich), 95-97% sulfuric acid (Merck), dimethylformamide (DMF, Aldrich) The resin (poly (trimellitic anhydride chloride-co-4,4'-methylenedianiline) resin, Aldrich) was used without further processing. Anhydrous potassium carbonate (K ₂ CO ₃ , Aldrich) was dried in a vacuum at 200 ° C. for 48 hours before use. A stainless steel needle (MN-21G-13, Iwashita Engineering, Japan) having an inner diameter of 0.60 mm, an outer diameter of 0.90 mm and a length of 13 mm was used for the electrospinning process.

Example  2: PAI / PTM  Non-woven( nonwoven )

Since the hydrolysis of the resin may be caused by moisture, the PAI resin was dried before being used for electrospinning. DMF to prepare a mixed solution (equal weight ratio) of PAI and PTM resin. As shown in Figure 1, the PAI-PTM solution was released from the syringe by a tensile force resulting from the applied electric field. Electrospun fibers were collected on a cylindrical drum collector. The electrical voltage was 10 kV and a syringe pump (KD Scientific-100, USA) was used to deliver the solution at a constant throughput. The distance from the nozzle tip to the collector was fixed at 10 cm. The formed PAI-PTM nonwoven fabric was cured at 290 ° C for 1 hour to improve the maximum physical properties by imidization or cyclization.

Example  3: Preparation of membrane

SPAES50 was synthesized by a known method using SDFDPS, DFDPS and BP in a four-necked flask equipped with a mechanical stirrer. FIG. 2 schematically shows a method of synthesizing a polymer used as an ionomer for preparing a composite membrane. The mixture was cast on a glass plate using NMP solvent (N-methyl-2-pyrrolidone; 7 wt%) and dried in a nitrogen atmosphere at 60 ° C for 12 hours and at 80 ° C for 12 hours to prepare a pristine membrane Respectively. To provide a composite membrane, the PAI-PTM nonwoven fabric was placed in a steel frame and secured with a clip. SPAES 50 solution (10 wt%) was then evenly filled into the pores of the brushed nonwoven with a brush on a PAI-PTM substrate and dried at 80 ° C for 20 minutes using an infrared lamp. The impregnating process was repeated on the top and bottom of the PAI-PTM nonwoven fabric until the composite membrane had a thickness of about 30 μm. To completely remove the remaining solvent, the prepared membrane was dried in vacuo overnight at < RTI ID = 0.0 > 80 C. < / RTI > Finally, the membrane was acidified with 1.5 M sulfuric acid for 24 hours and washed with deionized water for 24 hours at room temperature.

Example  4: Characterization of membranes

The pore size distribution of the PAI-PTM nonwoven fabric was measured using a high-order capillary flow porometer (ACFP-1500AE, wet / dry up method using Galwick solution). The dimensional changes (area, thickness, and volume) were determined by the difference in volume and mass between the wet film measured in water and the dry film measured after vacuum drying at 120 ° C overnight. Mechanical properties of PAI-PTM fiber and nonwoven fabric were confirmed using a material testing machine (LLOYD instrument LR5K) at a crosshead speed of 10 mm / min at room temperature. Surface and cross-sectional images of PAI-PTM nonwoven fabric and composite membrane were observed using a scanning electron microscope (SEM, XL-30S FEG, Philips). Prior to SEM image processing, the specimens were coated with platinum for 2 minutes under vacuum using a sputter coating machine (Sputter Coater, Q150T ES, Quorumtech, USA).

In a fully hydrated state, the temperature was changed in an in-plane direction (from 25 ° C to 80 ° C) over a frequency range of 0.1 Hz to 20 kHz using a four-probe conductivity cell while using an AC impedance analyzer 1280, Impedance / gain phase analyzer) to measure the proton conductivity of the membrane. The equilibration time was 1 hour in the temperature chamber (ESPEC, SH-241) before each measurement. The proton conductivity was calculated using the following equation (1): < EMI ID =

Proton Conductivity (S / cm) = l / R x S (1)

1 is a distance between electrodes, R is an electrochemical impedance spectroscopy (EIS) curve (x axis = real part (Z '), y axis = imaginary part (Z' The resistance of the calculated film, and S is the cross-sectional surface area.

In order to evaluate the performance of a single cell, Pt / C, and Nafion binder (50 wt% Pt / C, 0.4 mg Pt / cm 2, FuelCellPower Inc.) with a gas diffusion layer (gas-diffusion layers) coated with a membrane electrode assembly (membrane electrode assemblies; MEA) were prepared. The electrode was applied to the cathode and the anode, and the active surface area of the electrode was 5 cm ² . The prepared membrane electrode assembly was activated with hydrogen (240 sccm) at the cathode and air (600 sccm) at the anode at 80 ° C for 24 hours. After activation, the membrane electrode assembly was subjected to a backpressure at 0, 80 ° C and 100% relative humidity using a test station (FCT-TS300, Fuel Cell Technologies, Inc.) with a step change of 50 mV / To < RTI ID = 0.0 > 0.5 < / RTI > The hydrogen crossover of the DC power supply (Agilent N5744A) was measured after nitrogen purging for 10 minutes with an anode. A working electrode and a reference electrode were respectively fabricated on the anode and the cathode. Thereafter, a potential of 0.15 to 0.5 V was applied to the single cell while changing stepwise by 1 mV per 100 ms. The current generated as the hydrogen passing through the membrane from the cathode was oxidized at the anode was recorded.

Experimental Example  One: PAI - PTM  Characterization of nonwoven fabric

First, it was measured by SEM for morphological analysis of PAI-PTM nonwoven fabric. 3A and 3B show the low magnification and high magnification images of the PAI-PTM nonwoven fabric, respectively. From this it was confirmed that the fibers were successfully produced (non-woven fabric thickness = 20 ± 2 μm). The average diameter of the fibers in the PAI-PTM nonwoven fabric was determined to be 1500 to 1800 nm, and it was confirmed that each fiber had a constant diameter. Further, the average pore size of the PAI-PTM nonwoven fabric was measured to be about 17.5 μm. As shown in FIG. 4, the pore size was mostly in the range of 10 μm to 30 μm. The porosity of the PAI-PTM nonwoven fabric, calculated in terms of mass and volume, was 85%. From these results, pore structure was developed in PAI-PTM nonwoven fabric for use as a substrate of composite membrane. In order to confirm the mechanical properties of such a porous substrate, tensile tests of PAI-PTM fibers and nonwoven fabric were performed at room temperature and the results are shown in Table 1.

sample Young's modulus
(Young's modulus / MPa) The tensile strength
(tensile strenth / MPa) Elongation
(elongation at break /%) PAI / PTM fiber 4219.8 176.1 13.2 PAI / PTM nonwoven fabric 259.1 13.1 28.9

Since the fibers inhibit the swelling of the ionomer by water, the Young's modulus and tensile strength of the fibers in the nonwoven fabric are important factors in the dimensional stability of the membrane. PAI-PTM fibers exhibited significantly higher Young's modulus and tensile strength (4219.8 MPa and 176.1 MPa) compared to SPAES50. However, such mechanical properties were significantly reduced in the PAI-PTM nonwoven fabric due to the PAI-PTM fibers not aligned regularly, perpendicular to the pore structure. Nevertheless, it has been confirmed that the Young's modulus and tensile strength of the PAI-PTM nonwoven fabric have values suitable for use as substrates in composite membranes (259.1 MPa and 13.1 MPa).

Experimental Example  2: Composite membrane  Shape and dimensional stability

According to Example 3, the shape and dimensional stability of the composite membrane (hereinafter referred to as PAI-PTM / SP50) prepared using PAI-PTM nonwoven fabric and SPAES50 were confirmed. First, images of the surface and cross-section of the composite membrane prepared by SEM were obtained and shown in FIG. The composite membrane was dark yellow due to the PAI-PTM nonwoven (Fig. 5A). As shown in Figures 5b and 5c, it was confirmed from the surface and cross-sectional shapes of the composite membrane that the SPAES50 copolymer was successfully filled into the pores of the PAI-PTM nonwoven fabric. The thickness of the composite membrane was adjusted to 35 μm. A series of composite membranes were prepared and the dimensional changes were measured and are shown in FIG. FIG. 6 shows dimensional changes in the area, thickness and volume of Nafion 212, SPAES 50 and PAI-PTM / SP50. SPAES50 exhibited a higher dimensional change compared to Nafion 212, but in PAI-PTM / SP50 the value decreased from 107 vol.% To 80 vol.% Due to the multi-fibrous substrate. In particular, a significant change occurred in area-based variation where a 45% reduction occurred. This reduction in area based variation can improve durability by preventing mechanical failure of the membrane during operation under various humidity conditions. On the other hand, the thickness-based variation was somewhat increased in PAI-PTM / SP50 due to the increase in the swelling force in the thickness direction by the PAI-PTM nonwoven fabric inhibiting swelling in the area direction.

Experimental Example  3: Composite membrane  Electrochemical characterization

The proton conductivity of the membrane was confirmed using electrochemical impedance spectroscopy (EIS) under varying temperature under fully hydrated conditions and the results are shown in FIG. All membranes used in the experiment increased the proton conductivity as the temperature increased from 25 ℃ to 80 ℃. The proton conductivities of SPAES50 (0.080 S / cm and 0.170 S / cm respectively at 25 ° C and 80 ° C / 100% RH) were similar to those of Nafion 212 (0.082 S / cm and 0.164 S / cm) / SP50 (0.061 S / cm and 0.110 S / cm) showed lower proton conductivity compared to SPAES50 at all measured temperatures. Thus, the lower proton conductivity of PAI-PTM / SP50 can be deduced to be due to the presence of PAI-PTM nonwoven which can not transport protons. Therefore, as the ratio of PAI-PTM nonwoven fabric in the composite membrane increased, the proton transport capability decreased. This means that the level of reduction of the proton conductivity of the composite membrane can be determined by the porosity of the nonwoven fabric.

The membrane-electrode assembly was fabricated by CCG method using Nafion 212, SPAES50 and PAI-PTM / SP50, and its single cell performance was verified to compare the original membrane and the composite membrane. The results are shown in FIG. 8A. At 80 ℃, relative humidity 100% PAI-PTM / current density of SP50 is from 0.6 V SPAES50 (1.12 A / cm 2) and Nafion 212 (1.02 A / cm ²⁾ and was similar to the level of 1.07 A / cm ^2. The superior performance of this PAI-PTM / SP50 is due to the thinner thickness of the SPAES50 and Nafion 212 (about 50 μm), resulting in a narrower proton path and reduced membrane resistance. FIG. 8B shows the performance change of the PAI-PTM / SP50 according to the OCV (open circuit voltage) holding test time in the hydration state. OCV persistence tests were carried out to measure the chemical durability of membranes, which can generate harmful peroxides by diffusion of hydrogen and oxygen. The resulting peroxide decomposes the film and therefore gas crossover occurs due to the pinhole of the film. When the OCV continuous test time exceeded 410 hours, the PAI-PTM / SP50 maintained its performance. However, after 746 hours, the performance of the PAI-PTM / SP50 decreased to half of the initial value, and the OCV level also decreased to 0.8V (Fig. 9A). In the present invention, not only OCV changes were monitored, but also hydrogen cross-mixing was observed during the durability test. Hydrogen cross - mixing is the diffusion of hydrogen gas through the membrane from the cathode to the anode, and the occurrence of this hydrogen cross - mixing implies that the membrane is damaged. The hydrogen cross-mixing of PAI-PTM / SP50 with OCV duration test time is shown in Figure 9b. The initial hydrogen crossover mixing level of PAI-PTM / SP50 showed almost unrecognized current density. This means that each electrode was successfully separated by the membrane. After 410 hours, but maintaining the hydrogen cross-mixing is similar to the initial state, PAI-PTM / SP50 has been damaged after 746 hours, wherein the maximum cross-mixing of hydrogen was 0.17 A / cm ^2. The results of this hydrogen cross-hybridization showed the same tendency as the performance and OCV values. PAI-PTM / SP50 can be used as a composite membrane for proton exchange membrane fuel cells (PEMFC) using a nonwoven fabric, compared to the membrane of the present invention having durability using the OCV sustaining method at 80 ° C for about 400 hours. .

Claims (14)

Poly (amide-co-imide) (PAI) resin and poly (trimellitic anhydride chloride-co-4,4'-methylenedianiline) -CO-4,4'-methylenedianiline; PTM) resin mixture, and a hydrocarbon-based polymer electrolyte containing a sulfonic acid group impregnated with the PAI-PTM nonwoven fabric.
The method according to claim 1,
Wherein the concentration of the solution containing the PAI resin and the PTM resin mixture is 10 to 30 wt%.
The method according to claim 1,
Wherein the PAI resin and PTM resin mixture comprises PAI and PTM in a weight ratio of 4: 6 to 7: 3.
The method according to claim 1,
Wherein the PAI-PTM nonwoven fabric has a porosity of 60 to 90%.
The method according to claim 1,
Wherein the PAI-PTM nonwoven fabric has pores having a diameter of 15 to 20 占 퐉.
The method according to claim 1,
Wherein the proton exchange membrane for a fuel cell has a thickness of 10 to 30 占 퐉.
The method according to claim 1,
Wherein the hydrocarbon-based polymer is a sulfonated poly (arylene ether sulfone) (SPAES) copolymer or a polymer of the following formula (1):
[Chemical Formula 1]

In the above formula, l, m and n are each independently an integer of 1 or more.
8. The method of claim 7,
Wherein the hydrocarbon-based polymer has a sulfonation degree of 40 to 60%.
9. A method of producing a proton exchange membrane for a fuel cell according to any one of claims 1 to 8,
Preparing a mixed resin solution containing a PAI resin and a PTM resin in a weight ratio of 4: 6 to 7: 3;
Preparing a nonwoven fabric by electrospinning the solution; And
And impregnating both surfaces of the nonwoven fabric with a hydrocarbon-based polymer electrolyte containing a sulfonated group, thereby producing a proton exchange membrane for a fuel cell.
10. The method of claim 9,
Treating the nonwoven fabric produced by electrospinning at 250 to 400 ° C for 10 minutes to 3 hours.
10. The method of claim 9,
Wherein the hydrocarbon-based polymer is a sulfonated poly (arylene ether sulfone) (SPAES) copolymer or a polymer of the following formula (1): < EMI ID =
[Chemical Formula 1]

In the above formula, l, m and n are each independently an integer of 1 or more.
12. The method of claim 11,
Wherein the hydrocarbon-based polymer has a degree of sulfonation of 40 to 60%.
A membrane-electrode assembly (MEA) having a proton exchange membrane for a fuel cell according to any one of claims 1 to 8.
A fuel cell comprising the membrane-electrode assembly according to claim 13.

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