Block polymer for cathode catalyst layer, cathode catalyst layer slurry, membrane electrode and preparation method

Abstract

The present invention provides a block polymer for a cathode catalyst layer, a cathode catalyst layer slurry, a membrane electrode, and a preparation method. The membrane electrode comprises a cathode GDE, a proton exchange membrane, and an anode GDE; the cathode / anode GDE comprises a cathode gas diffusion layer and a cathode / anode catalyst layer applied to one side of a microporous layer on the cathode gas diffusion layer; the cathode catalyst layer comprises a cathode catalyst and a non-fluorinated polyamide-sulfonated imine block polymer FOS. When FOS is used as the cathode catalyst layer ionomer, the present invention improves the proton conductivity of the cathode catalyst layer, optimizes the three-phase interface structure of the catalyst, ionomer, and oxygen, and facilitates the full utilization of Pt active sites. The flexible segments in the rigid-flexible block structure of FOS form a cavity structure, which allows for more storage of free phosphoric acid, enhances the acid retention capacity of the cathode catalyst layer, ensures uniform distribution of phosphoric acid in the cathode catalyst layer, and solves the problem of significantly reduced battery performance due to increased membrane electrode impedance caused by phosphoric acid loss.

Description

Technical Field

[0001] The present invention belongs to the field of high-temperature proton exchange membrane fuel cells, and particularly relates to a block polymer for a cathode catalyst layer, a cathode catalyst layer slurry, a membrane electrode and a preparation method. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) are considered the most promising fuel cell due to their high energy conversion efficiency, high power density, zero pollutant emissions, and low operating noise. Depending on the operating temperature, PEMFCs are categorized into low-temperature PEMFCs (LT-PEMFCs) based on Nafion membranes and high-temperature PEMFCs (HT-PEMFCs) based on phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes. Currently commercially successful low-temperature PEMFCs have limitations such as high fuel gas purity requirements and complex water and heat management systems, limiting their application scenarios. Therefore, HT-PEMFCs, operating at temperatures above 120°C, have attracted significant attention due to their rapid reaction kinetics, high tolerance to fuel / air impurities, simple plate design, and improved heat and water management. These advantages make them promising candidates for the next generation of PEMFCs, suitable for applications in hydrogen fuel vehicles and combined heat and power (CHP) systems. However, since PA is the primary proton transport carrier in HT-PEMFCs, it covers the active sites of Pt in the catalyst layer, poisoning the catalyst and significantly reducing its activity. Furthermore, the unevenly distributed PA can block the mass transfer channels in the catalyst layer, making oxygen diffusion more difficult and leading to acid flooding under high current density operating conditions. Furthermore, as the battery operates for longer, the PA in the membrane electrode is lost to the external environment along with the fuel gas and water vapor, causing acid deficiency in the catalyst layer and the membrane. This reduces the proton transport channels in the membrane electrode and reduces the effective three-phase reaction interface in the catalyst layer, ultimately leading to a sharp decline in battery performance.

[0003] The currently widely adopted solution is to introduce a certain amount of hydrophobic polymers such as polytetrafluoroethylene (PTFE) into the catalyst layer. PTFE molecules can improve the distribution of PA in the catalyst layer and bind the catalyst particles together, thereby improving battery performance. However, PTFE molecules are not conductive and cannot serve as proton transport channels in the catalyst layer, which reduces the number of active sites in the catalyst and is not conducive to improving battery performance. Furthermore, PTFE molecules are acid-phobic and lack the ability to retain phosphoric acid, making it difficult to control the loss of phosphoric acid during battery operation, affecting the performance and lifespan of high-temperature proton exchange membrane fuel cells. Summary of the Invention

[0004] In order to overcome the deficiencies in the prior art, the inventors have conducted intensive research and provided a block polymer for a cathode catalyst layer, a cathode catalyst layer slurry, a membrane electrode, and a preparation method. FOS is used as the cathode catalyst layer ionomer, and the sulfonimide groups in FOS are utilized as proton transport carriers to construct more effective three-phase reaction interfaces, further increasing the proton transport channels in the cathode catalyst layer. Furthermore, a cavity structure is formed by the rigid-flexible block structure in FOS, thereby increasing the acid retention capacity of the catalyst layer, effectively overcoming the problem of phosphoric acid loss, and improving the performance and service life of the battery.

[0005] The technical solutions provided by the present invention are as follows:

[0006] In a first aspect, a method for preparing a block polymer for a cathode catalyst layer comprises:

[0007] Step 1: Add p-toluenesulfonamide, sodium hydroxide, and deionized water to a reaction vessel equipped with a reflux condenser; after the reaction mixture is stirred and uniformly mixed at 95±5°C, slowly add benzenesulfonyl chloride dropwise to the solution and stir at 95±5°C until the reaction is complete; then adjust the pH of the solution to neutral, filter to remove the white precipitate, adjust the pH of the solution again to 1-2, filter to obtain the white precipitate, and recrystallize to obtain product 1;

[0008] Step 2: LiOH·H2O and product 1 were completely dissolved in deionized water, KMnO4 was slowly added to the reaction vessel, the reaction mixture was stirred at 95±5°C until the reaction was complete, filtered, the filtrate was acidified, the final product was collected, and vacuum dried to obtain product 2;

[0009] Step 3: Add the product II, a mixture of dimethyl 5-aminoisophthalate, LiCl, triphenyl phosphite TPP, pyridine, and an aprotic organic solvent to a reaction vessel, and stir at 100±5°C under an inert atmosphere until the reaction is complete. After the reaction is completed, the mixture is distilled under reduced pressure and then poured into a sufficient amount of cold isopropanol. The white precipitate is filtered, washed, and vacuum dried to obtain the product III.

[0010] Step 4: Add product 3 and deionized water to a reaction vessel and stir to dissolve; then dissolve NaOH in deionized water and add dropwise to the mixture, stir at room temperature overnight, adjust the pH of the solution to 1-2 with concentrated HCl to obtain a yellow powder, and vacuum dry to obtain SIDA;

[0011] Step 5: 4,4'-(9-fluorenylidene)diphenylamine FDA, 1,8-octanedioic acid, SIDA, LiCl, triphenyl phosphite, pyridine and an aprotic organic solvent are mixed and stirred in an inert atmosphere for reaction; after the reaction is completed, the mixture is cooled to 70±5°C and then poured into cold methanol. The light yellow precipitate is filtered to obtain the precipitate, which is washed continuously with methanol and deionized water and dried under reduced pressure to obtain a non-fluorinated polyamide-sulfonated imine polymer (FOS) for the cathode catalyst layer.

[0012] In combination with the first aspect, in step 1, the molar ratio of p-toluenesulfonamide, benzenesulfonyl chloride and sodium hydroxide is (1-1.05):1:(1-1.05).

[0013] In combination with the first aspect, in step 3, the molar ratio of the second product to dimethyl 5-aminoisophthalate is 1:1 to 1.05.

[0014] In combination with the first aspect, in step 5, the molar ratio of 4,4'-(9-fluorenylidene)diphenylamine FDA, 1,8-suberic acid and SIDA is 1:x%:(100-x)%, x%=10% to 90%.

[0015] In a second aspect, a block polymer for a cathode catalyst layer is prepared by the method for preparing a block polymer for a cathode catalyst layer described in the first aspect.

[0016] In the third aspect, a cathode catalyst layer slurry comprises a cathode catalyst and the non-fluorinated polyamide-sulfonated imine block polymer FOS described in the second aspect, wherein the mass ratio of the non-fluorinated polyamide-sulfonated imine block polymer FOS to the carbon support in the cathode catalyst is (5-15):100.

[0017] In a fourth aspect, a cathode gas diffusion electrode comprises a cathode gas diffusion layer and a cathode catalyst layer applied on one side of the microporous layer of the cathode gas diffusion layer; the cathode catalyst layer is prepared using the cathode catalyst layer slurry described in the third aspect.

[0018] In the fifth aspect, a membrane electrode comprises a cathode GDE, a proton exchange membrane and an anode GDE; the cathode GDE comprises a cathode gas diffusion layer and a cathode catalyst layer applied on one side of the microporous layer of the cathode gas diffusion layer; the anode GDE comprises an anode gas diffusion layer and an anode catalyst layer applied on one side of the microporous layer of the anode gas diffusion layer; the cathode catalyst layer is prepared using the cathode catalyst layer slurry described in the third aspect.

[0019] In a sixth aspect, a method for preparing a membrane electrode comprises:

[0020] S1, uniformly dispersing an anode catalyst and an anode hydrophobic binder in a water-alcohol solution to prepare an anode catalyst slurry;

[0021] S2, coating the anode catalyst slurry on the anode gas diffusion layer to obtain the anode GDE;

[0022] S3, uniformly dispersing the cathode catalyst and the dissolved non-fluorinated polyamide-sulfonated imine polymer (FOS) solution in an organic solvent to form a cathode catalyst slurry;

[0023] S4, coating the cathode catalyst slurry on the cathode gas diffusion layer to obtain a cathode GDE;

[0024] S5, laminating the anode GDE, the proton exchange membrane and the cathode GDE in sequence, and compounding them by hot pressing to obtain a membrane electrode.

[0025] In a seventh aspect, a high-temperature proton exchange membrane fuel cell adopts the cathode gas diffusion electrode described in the fourth aspect, or adopts the membrane electrode described in the fifth aspect.

[0026] The block polymer for cathode catalyst layer, cathode catalyst layer slurry, membrane electrode and preparation method provided by the present invention have the following beneficial effects:

[0027] The present invention adopts FOS as the cathode catalyst layer ionomer and utilizes the sulfonimide group in FOS as a proton transport carrier, thereby optimizing the three-phase interface structure of the catalyst, ionomer and oxygen or air, further increasing the proton transport channel of the cathode catalyst layer, improving the proton conductivity of the cathode catalyst layer, and facilitating the full utilization of the Pt active sites. The rigid-flexible block structure in FOS forms a cavity structure, thereby storing more free phosphoric acid, enhancing the acid retention capacity of the cathode catalyst layer, ensuring the effective distribution of phosphoric acid in the cathode catalyst layer, and solving the problem of significantly reduced battery performance due to increased membrane electrode impedance caused by phosphoric acid loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic structural diagram of a high-temperature proton exchange membrane fuel cell;

[0029] Figure 2 is the SEM image of FOS;

[0030] Figure 3 is the NMR result of FOS;

[0031] Figure 4 is the infrared spectrum of FOS;

[0032] Figure 5 The membrane electrode polarization characteristic curves of different cathode catalyst layers of Example 1-2 and Comparative Example 1-2;

[0033] Figure 6 The membrane electrode impedance diagrams of different cathode catalyst layers of Example 1-2 and Comparative Example 1-2 are shown. DETAILED DESCRIPTION

[0034] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0035] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0036] like Figure 1 As shown, the high-temperature proton exchange membrane fuel cell includes:

[0037] The membrane electrode comprises a cathode GDE 10, a proton exchange membrane 1, and an anode GDE 20. The cathode GDE 10 comprises a cathode gas diffusion layer 12 and a cathode catalyst layer 11 applied on one side of the cathode gas diffusion layer; the anode GDE 20 comprises an anode gas diffusion layer 22 and an anode catalyst layer 21 applied on one side of the anode gas diffusion layer;

[0038] A cathode monopolar plate 13 and a first end plate 14 provided on the cathode 10 side; and

[0039] An anode monopolar plate 23 and a second end plate 24 are provided on the anode 20 side.

[0040] The proton exchange membrane is a polybenzimidazole membrane (PBI), and the PBI is treated by doping with phosphoric acid.

[0041] The cathode gas diffusion layer 12 includes a support layer 121 and a microporous layer 122. The support layer 121 is located on the side of the microporous layer 122 away from the proton exchange membrane 1. The anode gas diffusion layer 22 includes a support layer 221 and a microporous layer 222. The support layer 221 is located on the side of the microporous layer 222 away from the proton exchange membrane 1.

[0042] High-temperature proton exchange membrane fuel cells operate at temperatures between 140°C and 220°C, using a phosphoric acid-doped PBI membrane. When operating, hydrogen is introduced to the anode, where it undergoes a hydrogen reduction reaction (HOR) to generate hydrogen. Air or oxygen is introduced to the cathode, where it undergoes an oxygen reduction reaction (ORR) to generate water.

[0043] In the membrane electrode, the cathode catalyst layer contains a cathode catalyst and a non-fluorinated polyamide-sulfonated imine block polymer (FOS). As a proton-transport functionalized polymer constructed at a nanoscale three-phase interface, the non-fluorinated polyamide-sulfonated imine block polymer (FOS), with a molecular formula shown in Formula I, is an ionic polymer with a block structure. The decomposition temperature of FOS is as high as 345°C, fully meeting the operating conditions of 140-220°C in HT-PEMFCs. Furthermore, the proton conductivity of FOS tends to increase with increasing temperature.

[0044]

[0045] A non-fluorinated polyamide-sulfonated imine polymer (FOS) with a block structure is introduced into the cathode catalyst layer of the membrane electrode. Due to the presence of groups in the FOS molecular structure, it can be precisely anchored to the active sites of supported catalysts (such as PtCo / C) through hydrogen bonding and other interactions, achieving the construction of a nanoscale three-phase interface on the catalyst surface. The introduction of this non-fluorinated polyamide-sulfonated imine block polymer with excellent proton conductivity reduces the catalyst layer's dependence on traditional non-conductive polymer ionomers (such as PTFE), and the introduction of sulfonimide ions improves proton conductivity.

[0046] The preparation method of non-fluorinated polyamide-sulfonated imine polymer (FOS) comprises the following steps:

[0047] Step 1: The synthesis of 4-methyldiphenylsulfonyl imide (hereinafter referred to as Product 1) is as follows: p-toluenesulfonamide, sodium hydroxide, and deionized water are added to a reaction vessel equipped with a reflux condenser. After the reaction mixture is stirred at 95±5°C and uniformly mixed, benzenesulfonyl chloride is slowly added dropwise over 1-2 hours and stirred at 95±5°C overnight. The pH of the solution is then adjusted to 7 with dilute HCl, and the white precipitate is removed by filtration. The pH of the solution is then adjusted again with dilute HCl to 1-2, and the white precipitate is filtered and recrystallized to obtain Product 1.

[0048] In this step, the molar ratio of p-toluenesulfonamide, benzenesulfonyl chloride and sodium hydroxide is (1-1.05):1:(1-1.05).

[0049] In this step, after the reaction is completed, the pH value of the solution is adjusted to 7 with dilute HCl, and the white precipitate p-toluenesulfonamide is removed by filtration, which helps to increase the product concentration of product 1.

[0050] Step 2: The synthesis process of product 2 is as follows: LiOH·H2O and product 1 are completely dissolved in deionized water at 95±5°C, KMnO4 is slowly added to the reaction vessel within 1 to 2 hours, the reaction mixture is stirred at 95±5°C overnight, MnO2 and unreacted KMnO4 are removed by filtration, the filtrate is acidified with concentrated HCl, the final product is collected, and vacuum dried at 100±5°C for at least 24 hours to obtain product 2.

[0051] In this step, the molar ratio of LiOH·H2O, product 1 and KMnO4 is (1-1.1):1:(2-2.1).

[0052] Step 3: The synthesis process of dimethyl 5-(4-(N-phenylsulfonyl)sulfonamido)benzamido)isophthalate (hereinafter referred to as Product III) is as follows: Product II, a mixture of dimethyl 5-aminoisophthalate, LiCl, triphenyl phosphite (TPP), N-methylpyrrolidone (NMP), and pyridine are added to a reaction vessel and stirred overnight at 100±5°C under an argon atmosphere. After the reaction is completed, the mixture is distilled under reduced pressure and then poured into a sufficient amount of cold isopropanol. The white precipitate is filtered to obtain a white precipitate, which is then washed with isopropanol and deionized water. The final product is dried under vacuum at 100±5°C overnight to obtain Product III.

[0053] In this step, the molar ratio of the second product to dimethyl 5-aminoisophthalate is 1:1 to 1.05.

[0054] Step 4: Hydrolysis of Product 3 in an alkaline aqueous solution to obtain sulfonyl imide diacid monomer (hereinafter referred to as SIDA): Add Product 3 and deionized water to a reaction vessel and stir to dissolve. Then, dissolve NaOH in deionized water and add it dropwise to the mixture over 1-2 hours. Stir overnight at room temperature. Adjust the pH of the solution to 1-2 with concentrated HCl to obtain yellow powder SIDA. Dry under vacuum at 100±5°C for at least 24 hours.

[0055] In this step, the molar ratio of product three to NaOH is 1:4-8.

[0056] Step 5: Final synthesis of FOS: 4,4'-(9-fluorenylidene)diphenylamine (FDA), 1,8-octanedioic acid, SIDA, LiCl, and triphenyl phosphite were mixed with NMP and pyridine and stirred under an argon atmosphere for 2-3 hours. After the reaction was complete, the mixture was cooled to 70±5°C and poured into cold methanol. The pale yellow precipitate was filtered and washed sequentially with methanol and deionized water. The precipitate was then dried under reduced pressure at 100±5°C for at least 12 hours to obtain the polymer FOS.

[0057] In this step, the molar ratio of 4,4'-(9-fluorenylene)diphenylamine FDA, 1,8-suberic acid and SIDA is 1:x%:(100-x)%, x%=10% to 90%, preferably x%=30% to 70%.

[0058] In this step, the stirring reaction time in an argon atmosphere should not exceed 3 h to ensure the yield of the reactants.

[0059] The non-fluorinated polyamide-sulfonated imine polymer (FOS) with a block structure introduced into the cathode catalyst layer not only has a high proton conductivity, but also because of the introduction of more sulfonimide groups in its side chain, it can enhance the movement of protons between the catalyst layers and also play a role in building a three-phase interface. In addition, the rigidity of FOS —Flexibility The block structure can achieve effective enrichment of phosphoric acid (PA), which greatly ensures the effective distribution of phosphoric acid in the cathode catalyst layer, ensures the long-term retention ability of PA, greatly increases the three-phase interface within the electrode, and improves the catalyst utilization as well as the performance and service life of the battery.

[0060] The cathode catalyst is at least one of Pt / C, PtFe / C or PtCo / C; wherein the mass fraction of the precious metal is 5% to 70%. The loading of the precious metal in the cathode catalyst layer is 0.5-1.0 mg / cm 2 The “noble metal” described herein refers to Pt (platinum).

[0061] In the cathode catalyst layer, the mass ratio of the non-fluorinated polyamide-sulfonated imine block polymer FOS to the carbon support in the cathode catalyst is (5-15):100.

[0062] In the membrane electrode, the cathode gas diffusion layer (GDL) comprises a support layer and a microporous layer. The support layer is located on the side of the microporous layer away from the proton exchange membrane. The support layer is carbon paper and / or carbon cloth, while the microporous layer comprises carbon powder and PTFE, with the PTFE content in the microporous layer ranging from 5% to 25%. The carbon powder is at least one of activated carbon, graphitized carbon, carbon nanotubes, carbon nanoribbons, and carbon nanospheres. A cathode catalyst layer is coated on the cathode GDL to form the cathode GDE.

[0063] In the membrane electrode, the anode catalyst layer comprises an anode catalyst and an anode hydrophobic binder. The anode catalyst comprises at least one of Pt / C, PtFe / C, or PtCo / C, wherein the mass fraction of the precious metal is 5% to 70%. The precious metal loading in the anode catalyst layer is 0.3-0.5 mg / cm 2The anode hydrophobic binder is at least one of PTFE, polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-chlorotrifluoroethylene copolymer (ECTFE), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and polydimethylsiloxane (PDMS).

[0064] In a membrane electrode (MEA), an anode catalyst layer is coated on an anode gas diffusion layer (GDL), forming the anode GDE. The anode GDL has the same structure and material selection as the cathode GDL. However, different raw material components and contents are selected based on specific requirements.

[0065] The present invention also provides a method for preparing the membrane electrode, the method comprising:

[0066] S1, uniformly dispersing an anode catalyst and an anode hydrophobic binder in a water-alcohol solution to form an anode catalyst slurry; the water-alcohol solution may be water-isopropyl alcohol.

[0067] S2, coating the anode catalyst slurry on the anode gas diffusion layer to obtain the anode GDE;

[0068] S3, uniformly dispersing the cathode catalyst and the dissolved non-fluorinated polyamide-sulfonated imine polymer (FOS) solution in an organic solvent to form a cathode catalyst slurry; the organic solvent may be N,N-dimethylacetamide (DMAC) and N-methylpyrrolidone (NMP).

[0069] S4, coating the cathode catalyst slurry on the cathode gas diffusion layer to obtain a cathode GDE;

[0070] S5, laminating the anode GDE, the proton exchange membrane and the cathode GDE in sequence, and compounding them by hot pressing to obtain a membrane electrode.

[0071] The solid content of the anode catalyst slurry and the cathode catalyst slurry is maintained at 0.2-0.25.

[0072] Example

[0073] The preparation method of the non-fluorinated polyamide-sulfonated imine polymer (FOS) in Example 1 and Comparative Examples 1-2 comprises the following steps:

[0074] Step 1: The synthesis of 4-methyldiphenylsulfonyl imide (hereinafter referred to as Product 1) is as follows: p-Toluenesulfonamide (17.12 g, 100 mmol), sodium hydroxide (4.22 g, 105 mmol), and 150 mL of deionized water were added to a 250 mL two-necked round-bottom flask equipped with a reflux condenser. After the reaction mixture was stirred at 95°C for uniform mixing, benzenesulfonyl chloride (17.66 g, 100 mmol) was slowly added dropwise over 2 hours and stirred at 95°C overnight. The pH of the solution was then adjusted to 7 with dilute HCl, and the white precipitate was removed by filtration. The pH of the solution was again adjusted to 1 with dilute HCl, and the white precipitate was filtered and recrystallized to obtain Product 1, weighing 20.22 g, with a yield of approximately 65%.

[0075] Step 2: LiOH·H2O (2.045 g, 50 mmol) and product 1 (15.57 g, 50 mmol) were completely dissolved in deionized water (300 mL) at 95°C. KMnO4 (16.583 g, 105 mmol) was slowly added to a 500 mL round-bottom flask over 2 h. The reaction mixture was stirred at 95°C overnight. After filtering to remove MnO2 and unreacted KMnO4, the filtrate was acidified with concentrated HCl. The final product was collected after acidification three times and dried in vacuo at 100°C for 24 h to obtain product 2. The mass of product 2 was 14.47 g, and the yield was 84.9%.

[0076] Step 3: 5-(4-(N-phenylsulfonyl)sulfonamido)benzamido)isophthalic acid dimethyl ester (hereinafter referred to as product III): A mixture of product II (13.654 g, 40 mmol), 5-aminoisophthalic acid dimethyl ester (8.368 g, 40 mmol), LiCl (3.2 g, 4%), triphenyl phosphite TPP (10 mL), NMP (40 mL) and pyridine (PY, 30 mL) was added to a 100 mL two-necked round-bottom flask and stirred at 100° C. under an argon atmosphere overnight. After the reaction was completed, the mixture was distilled under reduced pressure and then poured into 500 mL of cold isopropanol. The white precipitate was filtered to obtain a white precipitate, which was then washed with isopropanol and deionized water. The final product was dried under vacuum at 100° C. overnight to obtain product III. The mass of product III was 17.57 g, and the yield was 82.3%.

[0077] Step 4: Hydrolysis of product 3 in an alkaline aqueous solution to obtain sulfonyl imide diacid monomer (hereinafter referred to as SIDA): Product 3 (15.35 g, 20 mmol) and 40 mL of deionized water were added to a 150 mL round-bottom flask and stirred to dissolve. NaOH (4.8 g, 120 mmol) was then dissolved in 40 mL of deionized water and added dropwise to the mixture over 2 hours. The mixture was stirred at room temperature overnight. The pH of the solution was adjusted to 1 with concentrated HCl to obtain a yellow powder of SIDA (8.84 g, 87.6%), which was then dried under vacuum at 100°C for 24 hours.

[0078] Step 5: 4,4'-(9-fluorenylidene)diphenylamine FDA (0.6969 g, 2 mmol), 1,8-octanedioic acid [2 (100-x)% mmol], SIDA (2x% mmol), LiCl (0.32 g, 4%), and triphenyl phosphite (TPP, 1 mL) were mixed with NMP (4 mL) and pyridine (3 mL) and stirred under an argon atmosphere for 3 h. After the reaction was complete, the mixture was cooled to 70°C and poured into cold methanol (100 mL). The precipitate was filtered to obtain a light yellow precipitate, which was washed successively with methanol and deionized water and dried under reduced pressure at 100°C for 12 h. The yield of the resulting polymer FOS was above 92%.

[0079] Table 1

[0080]

[0081]

[0082] When preparing the non-fluorinated polyamide-sulfonated imine polymer (FOS) in Example 1 and Comparative Examples 1-2, x%=50%, and the molar ratio of SIDA, suberic acid and FDA is 1:1:2. Figure 2 , NMR results are shown in Figure 3 The infrared spectra of FOS at different x values ​​are shown in Figure 4 .

[0083] Example 1

[0084] A method for preparing a high-temperature proton exchange membrane fuel cell membrane electrode assembly is as follows:

[0085] Preparation of the gas diffusion layer: First, Vulcan XC-72 carbon powder and PTFE emulsion were mixed, an appropriate amount of ethanol was added, and ultrasonic stirring was performed to prepare a slurry. This slurry was then applied to commercial Toray carbon paper. The carbon powder loading and PTFE content were then determined gravimetrically. Finally, the slurry was heat-treated in a muffle furnace at 340°C for 25 minutes and cooled to room temperature to obtain the gas diffusion layer.

[0086] Preparation of anode GDE (anode catalyst layer + anode gas diffusion layer): weigh the required Pt / C catalyst, add a small amount of deionized water to stir and wet it, then add a certain amount of PTFE aqueous alcohol solution, and ultrasonically disperse it evenly to obtain a catalyst slurry; the above slurry is evenly coated on the microporous layer surface of the anode gas diffusion layer by pneumatic spraying.

[0087] Preparation of the cathode GDE (cathode catalyst layer + cathode gas diffusion layer): Weigh a certain amount of non-fluorinated polyamide-sulfonated imine block polymer molecules, add a certain amount of DMAC solution, and stir at room temperature for at least 4 hours to ensure full dissolution, thereby obtaining a non-fluorinated polyamide-sulfonated imine solution. Weigh the required PtCo / C catalyst, add the required DMAC solution, and ultrasonically disperse it uniformly. Then, dropwise add an appropriate amount of the dissolved and dispersed non-fluorinated polyamide-sulfonated imine solution. The mixed slurry is ultrasonically dispersed and stirred again to ensure that the non-fluorinated polyamide-sulfonated imine molecules are evenly dispersed in the catalyst slurry, thereby obtaining a cathode catalyst layer catalyst slurry. This slurry is evenly coated on the microporous surface of the cathode gas diffusion layer using a pneumatic spray method, thereby obtaining a cathode catalyst layer containing non-fluorinated polyamide-sulfonated imine molecules.

[0088] PBI / H3PO4 composite membranes were prepared using an immersion method: S1: Cut the PBI membrane to the desired size; S2: Soak the cut membrane in 85 wt.% phosphoric acid at 120°C for the desired time; S3: Blot the membrane with filter paper to remove excess phosphoric acid, then quickly weigh the membrane to determine the phosphate adsorption capacity. The mass ratio of phosphoric acid to resin was used to determine the phosphate adsorption capacity (MPA / PBI) (mass of adsorbed phosphoric acid / initial mass of the polybenzimidazole membrane). Repeat the cycle S2 → S3 until the phosphate adsorption capacity reached 400 wt.%.

[0089] The prepared electrodes (anode GDE, cathode GDE) and PBI / H3PO4 composite membrane are stacked in a mold in a certain order. Then, the membrane electrode is placed in a hot press to heat-press and shape the membrane electrode to obtain a fuel cell membrane electrode. The membrane electrode is then placed in a sealed bag and stored for future use.

[0090] The active area of ​​the membrane electrode is 4 cm 2 The cathode and anode gas diffusion layers have the same composition and structure, consisting of a support layer and a microporous layer. The support layer is mainly Torray carbon paper with a thickness of 140 microns. The microporous layer is mainly composed of carbon powder and PTFE; the type of carbon powder is Vulcan XC-72; the carbon powder loading in the microporous layer is 4mg / cm 2 PTFE content 25%; microporous layer thickness 40 microns. The anode catalyst layer uses 30wt% Pt / C catalyst (Pt mass fraction is 30wt%) and PTFE, with a platinum loading of 0.3mg / cm 2The PTFE content in the anode catalyst layer is 20%. The cathode catalyst layer is composed of 46.9wt% PtCo / C (Pt mass fraction is 46.9wt%) and FOS, with a Pt loading of 0.6mgPt / cm 2 , the FOS content is FOS / C=0.15.

[0091] Example 2

[0092] The difference between this embodiment and embodiment 1 is that in the high-temperature proton exchange membrane fuel cell membrane electrode assembly in embodiment 2, the FOS content of the cathode catalyst layer is FOS / C=0.10.

[0093] Comparative Example

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 1 is that in the high-temperature proton exchange membrane fuel cell membrane electrode assembly in Comparative Example 1, the FOS content of the cathode catalyst layer is FOS / C=0.20.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that in the high-temperature proton exchange membrane fuel cell membrane electrode assembly in Comparative Example 2, the cathode catalyst layer is composed of only 46.9wt% PtCo / C, and the Pt loading is 0.6mgPt / cm 2 .

[0098] Performance testing

[0099] With reference to GB / T 20042.5-2009, polarization curve tests were conducted on the membrane electrode of the obtained high-temperature proton exchange membrane fuel cell. The specific operating conditions were: single cell operating temperature of 160°C, pure hydrogen feed for the anode, atmospheric pressure air feed for the cathode, and cathode / anode feed stoichiometric ratio of 3 / 1.5, respectively.

[0100] According to GB / T 20042.5-2009, the membrane electrode impedance of high-temperature proton exchange membrane fuel cells was tested. The specific operating conditions were: single cell operating temperature of 160°C, pure hydrogen feed to the anode, atmospheric pressure air feed to the cathode, and cathode / anode feed stoichiometric ratio of 3 / 1.5 times @ 0.5A cm -2 , the discharge current density is 0.5A cm -2 .

[0101] Test results are shown in Figures 4-5Among them, "no PTFE and no FOS" means that the solid component in the preparation of the catalyst layer slurry is only 46.9wt% PtCo / C, representing Comparative Example 2; FOS / C = 0.10, 0.15, 0.20 means that the mass ratio of the non-fluorinated polyamide-sulfonated imide (FOS) to carbon in the preparation of the catalyst layer slurry is 0.10, 0.15, 0.20, representing Example 2, Example 1 and Comparative Example 1, respectively.

[0102] See also Figure 5 The membrane electrode polarization characteristic curves of the cathode composition of Example 1-2 of the present invention and the cathode composition of Comparative Example 1-2 were measured. Figure 5 It can be seen that at 0.1A / cm 2 Under the conditions of 0.5A / cm2, the voltages of the membrane electrodes corresponding to the cathode compositions of Examples 1 and 2 of the present invention and the cathode compositions of Comparative Examples 1 and 2 were 0.618V, 0.637V, 0.581V and 0.619V respectively. 2 Under the conditions of 0.5 ℃ and 1.5 ℃, the voltages of the membrane electrodes corresponding to the cathode compositions of Examples 1 and 2 of the present invention and those of Comparative Examples 1 and 2 were measured to be 0.450 V, 0.438 V, 0.307 V and 0.396 V, respectively. The maximum power densities of the membrane electrodes corresponding to the cathode compositions of Examples 1 and 2 of the present invention and those of Comparative Examples 1 and 2 were measured to be 0.264 W / cm 2 , 0.239W / cm 2 , 0.156W / cm 2 and 0.209W / cm 2 Compared with the membrane electrode with cathode composition in comparative example 2, the maximum power density of the membrane electrode with non-fluorinated polyamide-sulfonated imine cathode catalyst layer in embodiment 1 of the present invention is 55mW / cm higher than that of the corresponding membrane electrode with cathode composition in comparative example 2. 2 In the high current density region, at the same current density, the cell voltage of Example 1 of the present invention is higher than the membrane electrode voltage corresponding to the cathode composition of Comparative Example 2, resulting in higher overall cell performance.

[0103] See also Figure 6Impedance spectrum, it can be seen that compared with Comparative Example 2, Example 1-2 is significantly reduced in the high, medium and low frequency areas of the impedance spectrum. Although the two use the same anode composition, there is a gap in the anode impedance part, which shows that FOS has an effect on the redistribution of phosphoric acid. The non-fluorinated polyamide-sulfonated imine polymer (FOS) in the cathode part retains more phosphoric acid in the cathode part, thereby increasing the anode impedance. However, the most significant impedance gap is the charge transfer resistance of the cathode. Example 1-2 is significantly lower than Comparative Example 2. This is mainly due to the introduction of non-fluorinated polyamide-sulfonated imine polymer (FOS) into the cathode part of Example 1-2. Due to its good proton conductivity, it enhances the proton conductivity of the cathode catalyst layer, thereby reducing the charge transfer barrier at the three-phase interface of the catalyst layer. At the same time, its retention effect on PA enables it to still operate stably in the low-frequency mass transfer zone.

[0104] In summary, when the present invention adopts a non-fluorinated polyamide-sulfonated imine polymer (FOS) as the cathode catalyst layer ionomer, the non-fluorinated polyamide-sulfonated imine polymer acts as a carrier for proton transfer by introducing a sulfonyl imide group. In addition, the block structure of the rigid and flexible chains of FOS enables it to effectively retain PA in the catalyst layer, which greatly ensures the effective distribution of phosphoric acid in the catalyst layer, greatly increases the three-phase interface within the electrode, and at the same time reduces the problem of phosphoric acid loss caused by long-term operation of the battery by PA, thereby improving the catalyst utilization rate and the performance and life of the battery. The introduction of this non-fluorinated polyamide-sulfonated imine polymer reduces the catalyst layer's dependence on traditional polymer ionomers, while improving the proton transfer efficiency of the three-phase interface, it can optimize the multiphase material transport of the catalyst layer, solving the problems of phosphoric acid distribution and loss in traditional catalyst layers.

[0105] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

[0106] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for preparing a block polymer for a cathode catalyst layer, characterized in that: include: Step 1: Add p-toluenesulfonamide, sodium hydroxide, and deionized water to a reaction vessel equipped with a reflux condenser; after the reaction mixture is stirred and uniformly mixed at 95±5°C, slowly add benzenesulfonyl chloride dropwise to the solution and stir at 95±5°C until the reaction is complete; then adjust the pH of the solution to neutral, filter to remove the white precipitate, adjust the pH of the solution again to 1-2, filter to obtain the white precipitate, and recrystallize to obtain product 1; Step 2: LiOH·H2O and product 1 were completely dissolved in deionized water, KMnO4 was slowly added to the reaction vessel, the reaction mixture was stirred at 95±5°C until the reaction was complete, filtered, the filtrate was acidified, the final product was collected, and vacuum dried to obtain product 2; Step 3: Add the product II, a mixture of dimethyl 5-aminoisophthalate, LiCl, triphenyl phosphite TPP, pyridine, and an aprotic organic solvent to a reaction vessel, and stir at 100±5°C under an inert atmosphere until the reaction is complete. After the reaction is completed, the mixture is distilled under reduced pressure and then poured into a sufficient amount of cold isopropanol. The white precipitate is filtered, washed, and vacuum dried to obtain the product III. Step 4: Add product 3 and deionized water to a reaction vessel and stir to dissolve; then dissolve NaOH in deionized water and add dropwise to the mixture, stir at room temperature overnight, adjust the pH of the solution to 1-2 with concentrated HCl to obtain a yellow powder, and vacuum dry to obtain SIDA; Step 5: 4,4'-(9-fluorenylidene)diphenylamine FDA, 1,8-octanedioic acid, SIDA, LiCl, triphenyl phosphite, pyridine and an aprotic organic solvent are mixed and stirred in an inert atmosphere for reaction; after the reaction is completed, the mixture is cooled to 70±5°C, then poured into cold methanol, filtered to obtain a light yellow precipitate, washed continuously with methanol and deionized water, and dried under reduced pressure to obtain a non-fluorinated polyamide-sulfonated imine polymer FOS for the cathode catalyst layer; the molar ratio of 4,4'-(9-fluorenylidene)diphenylamine FDA, 1,8-octanedioic acid and SIDA is 1:x%:(100-x)%, x%=10%~90%.

2. The method for preparing a block polymer for a cathode catalyst layer according to claim 1, characterized in that: In step 1, the molar ratio of p-toluenesulfonamide, benzenesulfonyl chloride and sodium hydroxide is (1-1.05):1:(1-1.05); and / or In step 3, the molar ratio of product 2 to dimethyl 5-aminoisophthalate is 1:1 to 1.

05.

3. A block polymer for a cathode catalyst layer, characterized in that: The block polymer is prepared by the method for preparing the block polymer for cathode catalyst layer according to claim 1 or 2.

4. A cathode catalyst layer slurry, characterized in that: The method comprises a cathode catalyst and the non-fluorinated polyamide-sulfonated imine block polymer FOS according to claim 3, wherein the mass ratio of the non-fluorinated polyamide-sulfonated imine block polymer FOS to the carbon support in the cathode catalyst is (5-15):

100.

5. A cathode gas diffusion electrode, characterized in that: It comprises a cathode gas diffusion layer and a cathode catalyst layer applied on one side of the microporous layer of the cathode gas diffusion layer; the cathode catalyst layer is prepared by using the cathode catalyst layer slurry according to claim 4.

6. A membrane electrode, characterized in that It comprises a cathode GDE, a proton exchange membrane and an anode GDE; the cathode GDE comprises a cathode gas diffusion layer and a cathode catalyst layer applied on one side of the microporous layer of the cathode gas diffusion layer; the anode GDE comprises an anode gas diffusion layer and an anode catalyst layer applied on one side of the microporous layer of the anode gas diffusion layer; the cathode catalyst layer is prepared using the cathode catalyst layer slurry according to claim 4.

7. The membrane electrode according to claim 6, characterized in that The anode catalyst layer comprises an anode catalyst and an anode hydrophobic binder, wherein the anode catalyst includes at least one of Pt / C, PtFe / C or PtCo / C; the anode hydrophobic binder is at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-chlorotrifluoroethylene copolymer (ECTFE), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and polydimethylsiloxane (PDMS).

8. The membrane electrode according to claim 6, characterized in that The cathode catalyst is at least one of Pt / C, PtFe / C or PtCo / C; The proton exchange membrane is a polybenzimidazole membrane PBI, and the PBI is doped with phosphoric acid.

9. A method for preparing a membrane electrode according to any one of claims 6 to 8, characterized in that: include: S1, uniformly dispersing an anode catalyst and an anode hydrophobic binder in a water-alcohol solution to prepare an anode catalyst slurry; S2, coating the anode catalyst slurry on the anode gas diffusion layer to obtain the anode GDE; S3, uniformly dispersing the cathode catalyst and the dissolved non-fluorinated polyamide-sulfonated imine polymer FOS solution in an organic solvent to form a cathode catalyst slurry; S4, coating the cathode catalyst slurry on the cathode gas diffusion layer to obtain a cathode GDE; S5, laminating the anode GDE, the proton exchange membrane and the cathode GDE in sequence, and compounding them by hot pressing to obtain a membrane electrode.

10. A high-temperature proton exchange membrane fuel cell, characterized in that: The cathode gas diffusion electrode according to claim 5 or the membrane electrode according to claim 6 is used.

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