KR102539053B1 - Blending membrane for fuel cell by imide acid based polymer and sulfonic acid based polymer and synthetic process thereof - Google Patents

Abstract

The present invention relates to a blended polymer electrolyte membrane for a fuel cell and a method for manufacturing the same, and a mixed polymer electrolyte in which PDDPCSFS and SPmax-1200 polymer are mixed in different ratios forms an excellent ion conduction channel and has improved performance compared to individual polymers. It can be usefully used in the field of fuel cells.

Description

Blending membrane for fuel cell using imide acid polymer and sulfonic acid polymer and its synthesis method {Blending membrane for fuel cell by imide acid based polymer and sulfonic acid based polymer and synthetic process thereof}

The present invention relates to a blended polymer electrolyte membrane for a fuel cell, a manufacturing method thereof, and the like.

Polymer electrolyte fuel cells (PEFCs) have attracted worldwide attention and are considered as a potential alternative to fossil fuels due to several special properties such as high current and power density, environmental friendliness and excellent efficiency. In general, the proton exchange membrane, which is a key component of PEFC, plays an important role by converting H ₂ and an oxidant into electrical energy, and serves as a proton conduction medium. Therefore, the invention of new PEMs is a key research field for high-performance PEFCs. So far, Nafions, a polyfluorosulfonic acid-based membrane, has been utilized as a standard commercial material such as PEM due to its unique micromorphological structure, high σ, and thermal and mechanical stability. However, the use of these membranes has problems such as difficulty in synthesis, environmental friendliness, difficulty in structural modification and high cost. Therefore, research is required to develop a new PEM other than Nafion for fuel cell applications.

Sulphonated aromatic polymers have been considered promising PEM materials because of their high σ, low methanol permeability, and high thermal and chemical stability. Poly(ether sulfone), polybenzimidazole, sulfonated poly(etheretherketone), sulfonated poly(imide) and sulfonated poly(phenylenesulfone) have been studied as alternatives to PFSA-based membranes. However, most of these SAPs exhibited lower oxidation and mechanical stability due to the presence of ether linkages in the polymer backbone. In addition, σ of the sulfonated polymer film is highly dependent on the degree of sulfonation (DS). In addition, a high DS causes high membrane expansion, which greatly degrades the performance of the membrane. Therefore, the challenge of developing PEM-based highly sulfonated polymer membranes lies between the goals of improving mechanical properties and increasing σ. σ is the most important membrane property, and mechanical stability is an important property in practical use of PEMs. Considering the above-mentioned problems, various strategies have been introduced to improve the durability of membranes, such as adding metal ion scavengers, adding crosslinking agents, and mixing hydrophobic polymers.

In particular, blending is one of the most promising and simple approaches to improve the mechanical properties of highly sulfonated polymer membranes. Blend polymer membranes showed improved performance, higher mechanical and thermal stability, and improved durability, but most blend polymers exhibited lower σ.

On the other hand, many polymeric membranes based on poly(phenylene) (without ether linkages) have been widely utilized as alternatives to Nafion. This is because these membranes and their derivatives, such as poly(2,5-benzophenone), exhibit excellent thermal, chemical and mechanical stability due to their fully aromatic structure. More importantly, not only is the σ of this membrane comparable to that of Nafion, but this membrane is cheaper and has lower hydrogen crossover. From the above discussion, it is clear that the design and formulation of new mixed polymer electrolytes based on poly(phenylene)s/fluorosulfonylimide polymers are important for high-performance fuel cells, but there are still insufficient studies on this.

Korean Registered Patent Publication No. 10-1911070

The inventors of the present invention completed the present invention by finding that a mixed polymer electrolyte in which PDDPCSFS and SPmax-1200 polymer are mixed at different ratios forms an excellent ion conduction channel and exhibits improved performance compared to individual polymers.

Accordingly, the present invention is a polymer, including SPmax-1200 (sulfonated Pmax-1200) and PDDPCSFS (poly (2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carbonyl) sulfamoyl fluoride-co-styrene) A composition for preparing an electrolyte membrane is provided.

In addition, the present invention provides a polymer electrolyte membrane comprising the above composition.

In addition, the present invention provides a fuel cell including the polymer electrolyte membrane.

In addition, the present invention provides a method for manufacturing the polymer electrolyte membrane.

In order to achieve the object of the present invention, the present invention SPmax-1200 (sulfonated Pmax-1200) and PDDPCSFS (poly (2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carbonyl) sulfamoyl fluoride-co- A composition for preparing a polymer electrolyte membrane comprising styrene) is provided.

In one embodiment of the present invention, the weight ratio of the SPmax-1200 and PDDPCSFS may be 9: 1 to 8: 2.

In addition, the present invention provides a polymer electrolyte membrane comprising the above composition.

In addition, the present invention provides a fuel cell including the polymer electrolyte membrane.

In addition, the present invention provides a) preparing a mixture comprising SPmax-1200 and PDDPCSFS and

b) providing a method for manufacturing a polymer electrolyte membrane comprising the step of irradiating the mixture with infrared rays.

In one embodiment of the present invention, in the manufacturing method, the weight ratio of SPmax-1200 and PDDPCSFS may be 9: 1 to 8: 2.

In one embodiment of the present invention, SPmax-1200 and PDDPCSFS in the mixture may be contained in 2 to 4% (w / v) based on the total weight of the mixture.

In one embodiment of the present invention, step a) may be performed at 90 to 110 °C.

The present invention relates to a blended polymer electrolyte membrane for a fuel cell and a method for manufacturing the same, and a mixed polymer electrolyte in which PDDPCSFS and SPmax-1200 polymer are mixed in different ratios forms an excellent ion conduction channel and has improved performance compared to individual polymers. It can be usefully used in the field of fuel cells.

1 relates to ¹ H NMR spectra ((a) DDPCSF monomer, (b) PDDPCSFS polymer, (c) Pmax-1200 polymer, (d) SPmax-1200 polymer).
Figure 2 shows the IEC and WU (a) of the membrane prepared at 80 °C and the thermal decomposition curve (b) of the membrane.
Figure 3 shows the proton conductivity of the membrane at different temperatures under constant RH (80%) (a), the proton conductivity of the membrane at different RH at 80 °C (b), and the Fenton's reagent test on the membrane at 80 °C (c). , and the tensile stress and elongation (d) of the membrane at 25 °C at 50% RH.
Figure 4 shows the cell performance of the polymer membrane under fully humidified inlet conditions (RHa / RHc = 100% / 100%) at 70 °C.
5a and b show tapping mode atomic force microscope (AFM) images of the polymer electrolyte membrane ((a) 9: 1 mixture, (b) 8: 2 mixture), and c and d in FIG. 5 show the FE of the polymer electrolyte membrane. -SEM images are shown ((c) 9: 1 mixture, (d) 8: 2 mixture).
6 shows a photograph of the polymer membrane of the present invention.
7 shows the ¹⁹ F NMR spectra of the FSO ₂ NCO monomer.
8 shows the ¹⁹ F NMR spectra of the DDPCSF monomer.
9 shows the ¹⁹ F NMR spectra of the PDDPCSFS polymer.
10 shows FTIR spectra of DDPCSF and PDDPCSF.
11 shows FTIR spectra of Pmax-1200 and SPmax-1200.

The inventors of the present invention completed the present invention by finding that a mixed polymer electrolyte in which PDDPCSFS and SPmax-1200 polymer are mixed at different ratios forms an excellent ion conduction channel and exhibits improved performance compared to individual polymers.

Accordingly, the present invention is a polymer, including SPmax-1200 (sulfonated Pmax-1200) and PDDPCSFS (poly (2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carbonyl) sulfamoyl fluoride-co-styrene) A composition for preparing an electrolyte membrane is provided.

In the present invention, the SPmax-1200 is sulfonated Pmax-1200, and may be a polymer represented by Formula 1 below.

[Formula 1]

(In the above formula, n is an integer from 1 to 800)

In the present invention, PDDPCSFS is an abbreviation of poly(2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carbonyl)sulfamoyl fluoride-co-styrene and may be a polymer represented by Formula 1 below.

[Formula 2]

(In the above formula, m is an integer from 1 to 600)

In the present invention, the weight ratio of the SPmax-1200 and the PDDPCSFS may be 9: 1 to 8: 2, preferably 8: 2.

When the polymer compound is mixed, an excellent ion conduction channel is formed and excellent IEC, WU, σ, dimensional and mechanical properties are exhibited. PDDPCSFS may be included in a weight ratio of up to 20%, and when it is included more than that, there is a problem in that the mechanical properties of the film are greatly reduced. In one embodiment of the present invention, it was confirmed that the blend 8:2 polymer electrolyte exhibited excellent IEC values (2.19 meq./g) and σ values (117.50 mS/cm) at 80° C. under a constant RH (80%). In addition, in one embodiment of the present invention, the blend 8:2 polymer electrolyte has excellent hydrophobic-hydrophilic phase separation, which was confirmed through AFM and FE-SEM images of the polymer electrolyte. Therefore, the blended polymer electrolyte of the present invention is effective in manufacturing a high-performance fuel cell with improved σ and mechanical stability.

As another aspect, the present invention provides a polymer electrolyte membrane comprising the above composition.

As another aspect, the present invention provides a fuel cell including the polymer electrolyte membrane.

Since the polymer electrolyte membrane and the fuel cell contain the polymer electrolyte composition, they have improved σ and mechanical stability. The fuel cell may have a conventional configuration used in the art, which is easily applicable to those skilled in the art.

In another aspect, the present invention provides a) preparing a mixture comprising SPmax-1200 and PDDPCSFS, and

b) providing a method for manufacturing a polymer electrolyte membrane comprising the step of irradiating the mixture with infrared rays.

The mixture can be prepared by dissolving SPmax-1200 and PDDPCSFS in a solvent by heating.

The infrared irradiation may use a conventional infrared lamp, and may be irradiated while spreading the mixture on a substrate.

The wavelength of the infrared light may be 400 to 4000λ.

In the manufacturing method, the weight ratio of SPmax-1200 and PDDPCSFS may be 9: 1 to 8: 2, preferably 8: 2.

In the mixture, SPmax-1200 and PDDPCSFS may be contained in an amount of 2 to 4% (w/v), preferably 3% (w/v), based on the total weight of the mixture.

Step a) may be performed at 90 to 110 °C, preferably at 100 °C.

Hereinafter, a preferred embodiment is presented to aid understanding of the present invention. However, the following examples are provided to more easily understand the present invention, and the content of the present invention is not limited by the following examples.

<Example>

<Example 1: Materials and Methods>

Example 1-1. ingredient

Methylene chloride (MC), benzene, 1,4-dioxane, dimethyl sulfoxide (DMSO), methanol (MeOH), tetrahydrofuran (THF), benzoyl peroxide (BPO), styrene, 1H-pyrrole-2,5-dione (99% ), fuming sulfuric acid (SO ₃ 65%) and triethylamine (TEA) (99.5%) were purchased from Sigma-Aldrich (St. Louis, MO).

Pmax-1200 polymer (Mw 296,000 g/mol), antimony trifluoride (SbF ₃ ), and sulfurisocyanatidic chloride were procured from Alfa Aesar (Ward Hill, MA). All chemicals and reagents were of analytical grade and used without further purification.

Meanwhile, the full names of the abbreviations used in the present invention are as follows.

PDDPCSFS: poly(2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carbonyl)sulfamoyl fluoride-co-styrene

SPmax-1200: sulfonated Pmax-1200

σ: proton conductivity

WU: water uptake

IEC: ion exchange capacity

RH: relative humidity

PEFCs: Polymer electrolyte fuel cells

PEMs: proton exchange membranes

PFSA: polyfluorosulfonic acid

SAPs: Sulfonated aromatic polymers

DS: degree of sulfonation

PVB: poly(vinyl butyral)

PVA: poly(vinyl alcohol)

PVDF-co-HFP: polyvinylideneuoride-co-hexafluoropropylene

MC: Methylene chloride

DMSO: dimethyl sulfoxide

MeOH: methanol

THF: tetrahydrofuran

BPO: benzoyl peroxide

TEA: triethylamine

SbF ₃ : antimony trifluoride

DDPCSF: 2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carbonyl)sulfamoyl fluoride

GPC: gel permeation chromatography

Mw: average molecular weight

EIS: electrochemical impedance spectroscopy

AC: alternative current

EB: elongation at break

TS: tensile stress

ESI: electronic supplementary information section

λ: hydration number

Δt: through-plane change

Δl: in-plane change

Example 1-2. Synthesis of PDDPCSFS

[Scheme 1a]

Reaction Scheme 1a shows the synthesis route of PDDPCSFS (poly(2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carbonyl)sulfamoyl fluoride-co-styrene) polymer.

To synthesize the PDDPCSFS polymer, 29.05 g of antimony trifluoride (0.163 mol) was first put into a two-necked round bottom flask and 60 g of sulfur-isocyanatidic chloride (0.424 mol) was slowly added at 0 °C under N ₂ atmosphere. After that, the reaction temperature was gradually raised to 70 °C and stirred for 48 hours. Then, the reaction mixture was distilled at 85 °C using the dean-stack method to obtain pure colorless acidic liquid of sulfurisocyanatidic fluoride in 85% yield.

Second, to prepare (2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carbonyl)sulfamoyl fluoride (DDPCSF) monomer, recrystallized 1H-pyrrole-2,5-dione (0.1 mol) 10 g (recrystallized from water) was taken in a 1-neck 250 mL flask and 30 and 1 mL MC and catalyst TEA respectively were added. Then, 15.5 g of sulfurisocyanatidic fluoride (0.12 mol) prepared in 30 mL of benzene was slowly added, the reaction temperature was adjusted to 50 °C, and the mixture was stirred for 24 hours. After completion of the addition reaction, white DDPCSF precipitated. Then, the mixture was immediately filtered and washed with cold MC to remove unreacted sulfurisocyanatidic fluoride and 1H-pyrrole-2,5-dione. The resulting DDPCSF was collected in high purity and high yield (75%) and stored in a vacuum oven at 60 °C.

Finally, before synthesizing the PDDPCSFS polymer, 3.0 g of the prepared DDPCSF monomer (0.014 mol) was taken in a 100 mL 1-neck round bottom flask and 8 mL of 1,4-dioxane was added to dissolve the DDPCSF monomer under N ₂ atmosphere. . 1.55 mL of styrene (0.014 mol) was added to another three-necked round bottom flask and mechanically stirred. Then, the prepared DDPCSF solution and 0.16 g of BPO (0.007 mol) were each added to the flask at 25° C. under an inert atmosphere. After completion of the addition, the reaction temperature was adjusted to 80 °C and stirred for 36 hours. After 36 hours, the brown mixture was poured into MeOH to extract the polymer and washed with water containing 30% hydrochloric acid to remove impurities. The product was washed several times with distilled water for further purification. Finally, the resulting PDDPCSFS polymer was collected and stored in a vacuum oven at 90 °C.

Example 1-3. Synthesis of SPmax-1200

[Scheme 1b]

Scheme 1b above shows the synthesis route of SPmax-1200 polymer.

3 g of Pmax-1200 contained in 30 mL of anhydrous chloroform in a two-necked round bottom flask was slowly added with 10 mL of fuming H ₂ SO ₄ (65% SO ₃ ) (0.077 mol) under N ₂ atmosphere at 40 °C. Stir for an hour. The resulting SPmax-1200 was extracted using MeOH and distilled water, respectively. It was then filtered and dried overnight at 80 °C to collect high purity SPmax-1200 polymer.

Example 1-4. Preparation of blend polymer membranes

[Scheme 2]

Scheme 2 above illustrates a method for preparing a blended polymer membrane.

A mixture of SPmax-1200 and PDDPCSFS was added at 3% (w/v) in DMSO solvent, dissolved at 100 °C, and then exposed on a glass plate under an IR lamp overnight to cast a blended polymer film (thickness of 40-50 um). Blend polymer films were cast using 90:10 (wt %) and 80:20 (wt %) ratios of SP-max and PDDPCSFS polymers and were labeled as Blend (9 : 1) and Blend (8 : 2), respectively. . 20% by weight of PDDPCSFS is the largest percentage in the blended polymer film, and above this ratio the mechanical properties of the film are greatly reduced.

Example 1-5. instrumentation and measurement

The structural characteristics of the synthesized monomer and polymer were confirmed using Nicolet iS5 FTIR Spectrometry (Serial no. ASB1100426) and JEOL (400 YH) and FTIR spectra for ¹ H and ¹⁹ F NMR, respectively. DMSO- d ₆ was used as a solvent and tetramethylsilane (TMS) was used as an internal standard for NMR analysis. In general, the intrinsic viscosities of PDDPCSFS, SPmax-1200, Blend (9:1), and Blend (8:2) were about 1.25, 1.45, 1.43, and 1.40 g/dL, respectively, in DMSO solvent, RheoSense, hts-VROC at 30 °C. ™ Viscometer. The average molecular weight (Mw) of the polymer was measured using a gel permeation chromatography (GPC) system (PerkinElmer, Series 200) using a polystyrene standard gel column and THF as an eluent at a flow rate of 1.0 mL min ^-1 . fitted. The thermal properties of the prepared polymer membranes were investigated using a TGA-N 1000 analyzer (Scinco, Chicago, IL, USA) at about 30-800 °C in an inert N ₂ atmosphere at a scan rate of 10 °C/min. σ of the membrane is Newton 4th Ltd. (N4L) Impedance Analysis Interface (PSM 1735) was performed using an MTS 740 Flat Film Test System (Scribner Associates Inc., Southern Pines, NC, USA). To measure electrochemical impedance spectroscopy (EIS), a 1 cm x 3 cm polymer membrane prepared was immersed in distilled water for 25-30 minutes to stabilize it. After that, it was placed in a water vapor environment for 12 hours for equilibration. σ at 30–80 °C under 80% RH condition and 80 °C under 30–80% RH condition was calculated by measuring the alternative current (AC) potential difference. EIS measurements were performed under open-circuit conditions in the frequency range of 1Hz-0.1MHz with an AC amplitude of 10mV. A force of 3.5 MPa was applied to the electrodes when the sample was placed between the electrodes for measurement. In general, the σ of the membrane was evaluated according to the following equation.

[Equation 1]

σ = [L/R _mem x A]

where L, A and R _mem represent the film thickness, electrode area and corresponding resistance, respectively. In addition, the chemical stability of the membrane was evaluated by heating the membrane with Fenton's reagent (3 ppm Fe2 ⁺ , 3% _H2O2 ) at 80 °C, and _the chemical degradation was recorded by weighing the membrane at 1 h intervals up to 9 h. did Membrane mechanical properties, including elongation at break (EB) and tensile stress (TS), were measured using the ASTM D882 standard test method in an IUMT system (Model 5544) at 25 °C, RH 50%, and 10 N load. It became.

Example 1-6. Surface Analysis and Cell Test Measurement Methods

The cell voltage and power density of the synthesized membranes were measured by a single cell test method under fully humidified inlet conditions (anode RH / cathode RH = 100% / 100%). Membrane electrode assemblies (MEAs) with an active area of 8 cm ² were prepared using a decal method based on a catalyst coated membrane (CCM). A 190 mm thick Toray carbon paper (TGPH-060, Toray Inc.) was used as the gas diffusion layer (GDL) on both the anode and cathode sides.

Carbon-supported Pt (Hispec 13100, Johnson Matthey Inc.) was used as both anode and cathode catalysts, and the catalyst layer loading in this work was 0.2 mg Pt/cm ² . Immediately after, the catalyst layer was transferred to the membrane by the decal method at 130 °C and 10 MPa for 5 minutes to make CCM for MEA. During operation, fully humidified H ₂ and air at 70 °C were supplied to the anode and cathode, respectively. The stoichiometry of hydrogen and air was maintained at 1.5/2.0 and the inlet humidity was RH _a /RH _c = 100%/100%. Polarization curves were measured galvanostatically at 70 °C and ambient pressure using a commercial test station (Scitech, Korea Inc) at a scan rate of 36 mA/s for each step.

The hydrophilic and hydrophobic phase separation of the membrane was evaluated by field emission scanning electron microscopy (FE-SEM, JEOL 7401F) and trapping mode atomic force microscopy (AFM) using a Nanoscope (R) IIIA, microfabricated microfabricated microscopy with an amplitude set point of 0.7785 V. Evaluated using a cantilever.

Example 1-7. WU, IEC and dimensional change measurements

To measure the WU of the prepared polymer membrane, the membrane was soaked in distilled water at 80 °C for 24 hours. Then, the WU of the membrane was calculated using the equation

WU (%) = {(W _wet - W _dry )/W _dry } × 100

Here, W _dry and W _wet mean the weight of the membrane in dry and wet conditions, respectively.

However, the membrane was soaked in 1N NaCl solution at 80 °C for 24 h to exchange H ⁺ ions with Na ⁺ . Then, the exchanged H ⁺ solution was titrated with 0.01 N NaOH solution to measure IEC as follows.

IEC (meq./g) = (V _NaOH × M _NaOH ) / W _dry

where NaOH, NaOH, and Dry correspond to the volume, molar concentration, and weight of the membrane of NaOH, respectively. As a result, the dimensional change and hydration number (λ) of the PEM were investigated by immersing the membrane in water at 80 °C for 24 hours and evaluated as follows.

λ= (10 × WU)/(IEC × 18)

Δl (%) = {(l _wet - l _dry )/l _dry } × 100

Δt (%) = {(t _wet - t _dry )/t _dry } × 100

where λ, l and t denote the number of hydrations, length and thickness of the membrane, respectively.

<Example 2: Confirmation of characteristics of the monomer and polymer of the present invention>

A PDDPCSFS polymer, imide-based polymer electrolyte was prepared with an Mw of 189,000 g/mol, followed by a stepwise reaction of sulfurisocyanatidic chloride, 1H-pyrrole-2,5-dione, and styrene, respectively. In addition, a high Mw SPmax-1200 polymer electrolyte (296,000 g/mol) was synthesized from the reaction between Pmax-1200 and fuming H ₂ SO ₄ (65% SO ₃ ). Finally, a blended polymer membrane with excellent mechanical properties was prepared using PDDPCSFS and SPmax-1200 polymer, respectively.

An image of the polymer membrane is shown in FIG. 6 . The chemical structure of the synthesized monomer, sulfisocyanatidic fluoride, was confirmed by ¹⁹ F NMR as shown in FIG. 7 . One singlet peak was observed at about 62.12 ppm, indicating the presence of one F atom in the structure of the sulfurisocyanatidic fluoride monomer. In addition, the structural morphologies of DDPCSF monomer, PDDPCSFS and SPmax-1200 polymer were analyzed through ¹ H NMR, ¹⁹ F NMR and FTIR spectroscopic analysis, respectively. Figure 1a shows the ¹ H NMR spectrum of the DDPCSF monomer. Two singlet peaks were observed at around 7 and 12.4 ppm for CH-CH and NeH protons, indicating the successful addition of sulfisocyanatidic fluoride to the 1H-pyrrole-2,5-dione structure. These peaks were shifted and at the same time some additional peaks appeared in the ¹ H NMR spectrum (Fig. 1b) due to polymer formation. Peaks at about 11.0–11.4, 6.1–7.5, 3.5–3.6, 2.9–3.1 and 1.6–2.1 ppm are NeH, phenyl ring, aliphatic CH, aliphatic CH (1H-pyrrole-2,5-dione ring) protons and aliphatic CH ₂ , suggesting the structure of the PDDPCSFS polymer, respectively. The presence of F-atoms in DDPCSF and PDDPCSFS was confirmed by ¹⁹ F NMR analysis (Fig. 8 and Fig. 9, respectively). One single peak appeared at about 52.38 ppm in both spectra, indicating that there is one F atom in the DDPCSF and PDDPCSFS structures.

10 shows FTIR spectra of DDPCSF and PDDPCSFS, respectively.

Broad stretching and bending vibrational bands were observed at around 3302 and 1596 cm ⁻¹ , corresponding to the NeH vibrational frequencies of the PDDPCSFS polymer, whereas they appeared at around 3154 and 1593 cm ⁻¹ in the spectrum of the DDPCSF monomer. Asymmetric and symmetric stretching vibration bands of SO for sulfonate groups appeared at about 1459 and 1321 cm ^-1 and 1445 and 1324 cm ^-1 in the spectra of DDPCSF monomer and PDDPCSFS polymer, respectively. In addition, SeF stretching bands at about (685 and 691) cm ⁻¹ appeared in the spectrum of the DDPCSF monomer and PDDPCSFS polymer, respectively, suggesting the presence of fluorosulfonyl imide groups in the monomer and polymer structures.

1 c and d show ¹ H NMR spectra of Pmax-1200 and SPmax-1200, respectively.

A proton peak at about 6.9–8.1 ppm was observed for phenyl protons at Pmax-1200 (Fig. 1c). After sulfonation, a phenyl ring proton peak appeared at about 7.0-8.1 ppm together with a new single peak at about 4.6-5.0 ppm for the -SO ₃ H group (Fig. 1d), indicating that the sulfonated polymer SPmax- 1200 indicates successful synthesis.

The structure of SPmax-1200 was further confirmed by FTIR analysis as shown in FIG. 11 . A broad characteristic peak in the range of 2700–3600 cm ⁻¹ was observed because SO ₃ H vibrational stretching overlapped with CH vibrational stretching, but this peak was not present in the spectrum of Pmax-1200. In addition, asymmetric and symmetric stretching bands of SO appeared at 1590 and 1453 cm ^-1 and CO stretching bands were observed at 1724 cm ^-1 , confirming the successful synthesis of SPmax-1200.

<Example 3: Confirmation of WU, IEC, number of hydration, dimensions and thermal characteristics of membrane>

Figure 2a shows the IEC and WU for the membrane.

The fabricated membranes showed a gradual increase in WU (approximately 30.05–63.29%) with increasing IEC (approximately 1.35–2.19 meq./g), whereas Nafion 117 exhibited 32.17% WU with an IEC value of 0.91 meq./g. In particular, the IEC values of blend (9:1) and blend (8:2) were about 2.09 and 2.19 meq./g, respectively, which were high or comparable to other reported polymer electrolyte membranes. This may be due to the synergistic effect of SO ₃ H and imide groups in the polymer network of the blend polymer.

In addition, the mechanical stability was evaluated by measuring the dimensional change and the number of hydration (l) of the prepared membrane. The membrane exhibited similar or lower dimensional change (through-plane (Δt) and in-plane (Δl) change) than Nafion 117 (Table S1 in ESI). The values of Δl and Δt were about 6.50, 11.25, 11.45 and 12.50% and about 20.50, 25.50, 32.50 and 33.50% for PDDPCSFS, SPmax-1200, Blend (9:1) and Blend (8:2), respectively. For Nafion 117, it was about 14.10 and 32.31%. The Δl value of the membrane was significantly lower than the Δt value due to the aromatic rigid polymer backbone. In addition, l was about 19.95 and 19.75 for Blend (9: 1) and Blend (8: 2), respectively, and about 16.05, 17.50, and 19.60 for PDDPCSFS, SPmax, and Nafion 117, respectively (Table 1). The lower the λ value of the blended polymer, the better the water resistance and mechanical stability.

Figure 2b shows the thermal decomposition curve of the membrane.

PDDPCSFS and Nafion 117 exhibited two-step pyrolysis. PDDPCSFS showed rapid decomposition with a weight loss of 83% at about 330–402 °C, which could be attributed to the decomposition of imide-based side rings and main chain, respectively. PDDPCSFS exhibited a second weight loss around 403–588 °C due to aromatic ring decomposition of the PDDPCSFS polymer. On the other hand, the first and second weight losses of Nafion 117 were 288–381 °C and 388–511 °C, showing 12 and 96% weight loss, respectively, which correspond to the decomposition of sulfonyl groups and main chain of Nafion 117 polymer. can do.

Additionally, SPmax-1200 and blend polymers exhibited a three-step degradation curve. The first and second stage decompositions were observed for the decomposition of -SO ₃ H and -CONHSO ₂ F groups, while the third decomposition was due to decomposition of the main polymer backbone.

A major advantage of blend polymers is that the -CONHSO ₂ F and -SO ₃ H groups decompose prior to decomposition of the main polymer backbone. More importantly, the blended polymer has lower thermal stability compared to PDDPCSFS. The thermal stability was slightly higher compared to SPmax-1200, suggesting that a morphological change occurred in the blend polymer, and this result is consistent with the results of IEC and WU.

<Example 4: Proton Conductivity, Chemical and Mechanical Stability of Membrane>

σ is one of the main phenomena of PEM and is achieved to improve high current and power density. Figures 3a and 3b show the σ of membranes prepared at different temperatures (about 30-80 °C) under constant RH (80%) and different RH ranges (about 30-80%) under 80 °C, respectively. The σ of the film increased with increasing temperature at constant RH, and increased with increasing RH at constant temperature. This may be due to more polymer chain segmentation motion and favorable dissociation of sulfonic acid and fluorosulfonyl protons in the polymer backbone chain.

Blend (9:1) and Blend (8:2) membranes exhibit significantly higher σ (ca. 93.14 and 117.50 mS/cm) than Nafion 117 (ca. 80.46 mS/cm) at 80 °C under constant RH (80%). shown (Fig. 3a). In particular, the Blend (9:1) and Blend (8:2) membranes showed σ similar to that of Nafion 117 at a constant temperature (80 °C) and 80% RH (Fig. 3b). However, the results of the mixed electrolyte prepared in the present invention are higher than or similar to those of other reported polymer electrolytes.

Note that σ of the blend polymer increased with increasing PDDPCSFS content in the blend polymer matrix. This phenomenon is due to the interaction between -SO ₃ H groups of SPmax-1200 and -CONHSO ₂ F groups of PDDPCSFS polymer. The supergaseous acidity and location of the fluorosulfonylimide groups in the side rings interact to form higher σ by forming well-distinct ion channels throughout the polymer network of the mixed polymer membrane. And this result agrees well with the IEC and WU results of the synthesized polymer.

Figure 3c shows the chemical degradation of the membrane prepared by Fenton's reagent in terms of weight loss over time at 80 °C for 9 h. All membranes showed relatively higher chemical stability compared to other reported ether-linked containing polymer membranes. The C-C polymer backbone and the presence of fluorosulfonylimide groups contribute significantly to the higher chemical stability of the membrane due to its less susceptibility to free radical attack.

Fig. 3d shows the TS and EB (%) of the membrane at 25 °C with RH of 50%.

The synthesized membranes exhibited TS ranging from about 20.1 to 48.45 MPa, whereas Nafion 117 showed a TS of 17.40 MPa. The high TS of the membrane may be due to its high molecular weight and strong intermolecular bonds. The EB (%) of the membrane was significantly lower than that of Nafion 117, reflecting the short strain rate in the fabrication process of the membrane electrolyte assembly.

<Example 5: Cell performance and surface morphology of membrane>

Figure 4 shows the polarization curve for single cell performance of the membrane.

Polarization curves were measured galvanostatically at 70° C. and ambient pressure with a scan rate of 36 mA/s for each step. The fuel cells with PDDPCSFS and SPmax-1200 electrolyte membrane showed maximum power densities of 0.45 and 0.48 W/cm ² . Also, the maximum power densities of the fuel cells using Blend (9:1) and Blend (8:2) membrane electrolytes were about 0.55 and 0.59 W/cm ² , respectively. On the other hand, the fuel cell using the Nafion 117 electrolyte showed a maximum power density of 0.60 W/cm ² . However, these maximum power densities of blended polymer electrolytes are greater than or comparable to previously reported polymer electrolytes. This improved cell performance of the blend polymers can be attributed to the presence of -SO ₃ H and -CONHSO ₂ F groups, and the results are also consistent with the conductivity results.

In addition, it can be seen that the prepared blend membrane exhibits excellent open-circuit voltage, so that the membrane can withstand long durability during operation. This improved stability also indicates that the prepared blend membrane is free of free radical reaction effects. Free radicals were formed at the electrode/electrolyte interface during the incomplete reduction process at the cathode site.

The effective interaction of -SO ₃ H of SPmax-1200 and -CONHSO ₂ F of PDDPCSFS can create a shielding effect of functional groups. This function preserves functional groups from degradation and metal oxides generally act as free radical scavengers. These results further promote the oxygen reduction reaction at the electrode site and make the barrier for the transport of protons smaller at the electrode/electrolyte interface. This result indicates that the mixed membrane can be used as a potential candidate for fuel cell applications.

Figure 5a and b show trapping mode surface views of Blend (9:1) and Blend (8:2) polymer membranes analyzed by AFM. Brown segments represent hydrophobic aromatic domains, while dark black channel-shaped segments represent hydrophilic groups with water in the membrane. In general, the content of the polymer backbone and acid moiety has a significant effect on the morphology of the polymer film. Blend (8 : 2) showed excellent hydrophilic-hydrophobic phase separation, probably due to the synergistic effect of -HSO ₃ and -CONHSO ₂ F groups. As a proof of this image, Blend (8:2) shows a higher σ compared to Blend (9:1), indicating good phase separation in the polymer network to facilitate cationization.

In addition, the surface morphology of the blended polymer electrolyte membrane was further confirmed by FE-SEM analysis as shown in Fig. 5c and d. The blend membrane showed dark and light regions, which could be attributed to hydrophilic and hydrophobic phase separation. Phase separation was obtained due to the presence of fluorosulfonylimide and sulfonic acid groups in the blend polymer membrane. In particular, these groups accelerated the movement of protons across the polymer matrix and as a result the blended polymer membranes showed enhanced conductivities. As mentioned above, the analysis results indicate that fluorosulfonylimide and sulfonic acid-containing poly(phenylene) blended polymer membranes are promising candidates as electrolytes for fuel cell applications.

Claims (8)

SPmax-1200 (sulfonated Pmax-1200) and PDDPCSFS (poly (2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carbonyl) sulfamoyl fluoride-co-styrene) represented by Formula 1 below , Composition for producing a polymer electrolyte membrane:
[Formula 1]

(In the above formula, n is an integer from 1 to 800).
According to claim 1, The weight ratio of the SPmax-1200 and PDDPCSFS is 9: 1 to 8: 2, the composition for preparing a polymer electrolyte membrane.
A polymer electrolyte membrane comprising the composition of claim 1.
A fuel cell comprising the polymer electrolyte membrane of claim 3.
a) preparing a mixture comprising SPmax-1200 and PDDPCSFS represented by Formula 1 below, and
b) a method for producing a polymer electrolyte membrane comprising the step of irradiating the mixture with infrared rays:
[Formula 1]

(In the above formula, n is an integer from 1 to 800).
The method of claim 5, wherein the weight ratio of the SPmax-1200 and the PDDPCSFS is 9: 1 to 8: 2.
The method of claim 5, wherein SPmax-1200 and PDDPCSFS in the mixture are contained in an amount of 2 to 4% (w/v) based on the total weight of the mixture.
The method of claim 5, wherein step a) is performed at 90 to 110 °C.

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