Biomass-based modified carbon microspheres, composite proton exchange membrane and preparation methods of biomass-based modified carbon microspheres and composite proton exchange membrane

Abstract

The preparation method comprises the following steps: carrying out a hydrothermal reaction on an agricultural and forestry waste biomass-organic wastewater mixture, carrying out suction filtration separation on a product, and recording a liquid product as a primary hydrothermal liquid product; carrying out hydrothermal reaction on the primary hydrothermal liquid product, carrying out suction filtration separation, recording a liquid product as a secondary hydrothermal liquid product, and washing a solid product; performing ultrasonic treatment and drying on the solid product to obtain TWQ; 1, 3-propanesulfonic acid and ammonia water are added into the DA solution, and SDA is obtained through centrifugation, solid collection, washing and drying; sDA and TWQ are placed in a triaminomethane hydrochloric acid solution, a product is subjected to centrifugation, solid collection, flushing and drying, and SDA-TWQ is obtained. The invention also provides a composite proton exchange membrane based on the carbon microspheres and a preparation method thereof. The carbon microspheres provided by the invention have the advantages of renewable raw materials, simple process, low cost and environmental protection; when the carbon microspheres are used for preparing the proton exchange membrane, the structural stability and the proton conduction efficiency can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of proton exchange membranes, and in particular to a biomass-based modified carbon microsphere, a composite proton exchange membrane and a preparation method thereof. Background Art

[0002] As a highly efficient clean energy technology, direct methanol fuel cells (DMFCs) require their core component, the proton exchange membrane (PEM), to achieve a precise balance between proton conduction efficiency and methanol barrier properties. While the current mainstream perfluorosulfonic acid membrane has excellent proton conduction performance, it faces challenges such as insufficient stability under high-temperature and low-humidity conditions, poor environmental compatibility, and high production costs. Therefore, non-fluorinated sulfonated aromatic polymers, such as sulfonated polyetheretherketone (SPEEK), have become important alternative materials due to their controllable sulfonation degree and cost advantages. However, the insufficient proton conduction efficiency caused by their low acidity and the degradation of mechanical properties caused by high sulfonation form an inherent contradiction.

[0003] In response to the above problems, a simple and convenient way to deal with it is to introduce fillers into the polymer matrix. For example, patent CN202010154583.9 discloses a microsphere / polyarylethersulfone-based composite proton exchange membrane, which is beneficial to reducing the swelling rate of a high-sulfonation matrix under high temperature and high humidity conditions. Patent CN 103715438 B discloses a graphene oxide / SPEEK composite proton exchange membrane that exhibits high mechanical properties, proton exchange membrane rate and peak power density. Although the above-mentioned filler modification strategy can partially improve the performance, it introduces new problems such as complex preparation process, unsustainable raw materials and solvent pollution.

[0004] Carbon microspheres are an ideal filler choice due to their high specific surface area, pore structure, mechanical strength, and water absorption properties. They can improve the structural stability and water retention of the polymer matrix while inhibiting methanol penetration. Among them, the cost of preparing carbon microspheres from traditional fossil-based raw materials is high and unsustainable. However, sugars (such as glucose, xylose), organic acids (formic acid, acetic acid), and furan compounds (HMF, furfural) in biomass hydrothermal liquid products can be used as alternative carbon sources to reduce costs and environmental impact. Based on this, carbon microspheres can be prepared using biomass hydrothermal liquid as a carbon source and used as an introduced filler in a non-fluorinated sulfonated aromatic polymer matrix. However, directly synthesized carbon microspheres still need further functional modification to achieve their maximum effect.

[0005] Dopamine, a versatile binder chemical, can self-polymerize into sulfonated dopamine (SDA) under mild conditions. Using this to modify carbon microspheres further allows the acidic groups in the sulfonated polymer matrix to interact with the sulfonic acid side chains in SDA, thereby enhancing water absorption and proton conductivity. This strategy offers new avenues for developing high-performance, low-cost, and environmentally friendly proton exchange membranes. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a biomass-based modified carbon microspheres, a composite proton exchange membrane and a preparation method. The composite proton exchange membrane is prepared based on the biomass-based modified carbon microspheres, which can avoid the long-standing technical contradiction in the existing proton exchange membrane field that the proton conduction efficiency and dimensional stability are difficult to coordinately optimize, as well as the high cost, complex preparation process and environmental pollution problems of traditional filler modification methods.

[0007] The present invention adopts the following technical solutions to solve the above technical problems:

[0008] A method for preparing biomass-based modified carbon microspheres comprises the following steps:

[0009] (1) crushing and sieving agricultural and forestry waste biomass, and filtering organic wastewater at the same time; mixing the sieved agricultural and forestry waste biomass with the filtered organic wastewater to obtain an agricultural and forestry waste biomass-organic wastewater mixture;

[0010] (2) A hydrothermal reaction is performed on a mixture of agricultural and forestry waste biomass and organic wastewater; after the reaction is completed, the hydrothermal product is filtered and separated, and the separated liquid product is recorded as the primary hydrothermal liquid product, and the solid product is recorded as hydrothermal charcoal;

[0011] (3) taking the primary hydrothermal liquid product obtained in step (2) and performing a hydrothermal reaction again; after the reaction is completed, the hydrothermal product is separated by suction filtration, and the separated liquid product is recorded as the secondary hydrothermal liquid product, and the solid product is rinsed with deionized water and collected;

[0012] (4) ultrasonically cleaning and drying the solid product collected in step (3) to obtain carbon microspheres TWQ;

[0013] (5) Place dopamine hydrochloride in anhydrous ethanol and stir evenly to obtain DA solution;

[0014] (6) adding 1,3-propanesulfonic acid and ammonia water to the DA solution obtained in step (5) and stirring; after stirring, centrifuging the mixed solution, collecting the solid, washing it with ethanol, and then drying it to obtain sulfonated dopamine SDA;

[0015] (7) The SDA obtained in step (6) and the TWQ obtained in step (4) are placed in a triaminomethane hydrochloric acid solution and stirred for reaction; after the reaction is completed, the mixed solution is centrifuged to collect the solid product and rinsed with ethanol; finally, the solid product is dried to obtain polydopamine carbon microspheres SDA-TWQ.

[0016] As one preferred embodiment of the present invention, in step (1), the agricultural and forestry waste biomass is one or more of rape straw, wheat straw, and corn straw; and the organic wastewater is one or more of agricultural and forestry waste pyrolysis liquid, biogas slurry, and pulp and papermaking wastewater. More preferably, the agricultural and forestry waste biomass is corn straw; and the organic wastewater is biogas slurry or agricultural and forestry waste pyrolysis liquid.

[0017] As one of the preferred embodiments of the present invention, in step (1), the agricultural and forestry waste biomass and organic wastewater are screened / filtered with a mesh size of 80 to 180; and the mixing ratio of the screened agricultural and forestry waste biomass to the filtered organic wastewater is 1:(10 to 15). More preferably, the agricultural and forestry waste biomass and organic wastewater are screened / filtered with a mesh size of 80; and the mixing ratio of the screened agricultural and forestry waste biomass to the filtered organic wastewater is 1:12.5.

[0018] As one of the preferred embodiments of the present invention, in step (2), the hydrothermal reaction conditions are: hydrothermal temperature of 180-250°C, hydrothermal time of 30-120 min, hydrothermal power of 30-60 kW / kg; using a suction filtration device (Buchner funnel, suction flask and vacuum filter) for suction filtration separation, the hydrothermal liquid product is collected and used for subsequent testing; the drying temperature of the hydrothermal charcoal is 80-105°C, and the drying time is 16-24 h. More preferably, the hydrothermal reaction conditions are: hydrothermal temperature of 220°C, hydrothermal time of 120 min, hydrothermal power of 60 kW / kg; using a vacuum filter for suction filtration separation; the drying temperature of the hydrothermal charcoal is 105°C, and the drying time is 18 h.

[0019] As one of the preferred embodiments of the present invention, in step (3), the hydrothermal reaction conditions are: hydrothermal temperature 160-220°C, hydrothermal time 60-120min, and hydrothermal power 30-60kW / kg. A suction filtration device (Buchner funnel, suction flask, and vacuum filter) is used for solid-liquid separation. The secondary hydrothermal liquid product can be used as a liquid organic nutrient fertilizer later. The solid product on the filter paper is repeatedly rinsed 1-3 times with deionized water and collected. More preferably, the hydrothermal reaction conditions are: hydrothermal temperature 180°C, hydrothermal time 60min, and hydrothermal power 60kW / kg; a vacuum filter is used for solid-liquid separation; the solid product on the filter paper is repeatedly rinsed 2 times with deionized water and collected.

[0020] As one of the preferred embodiments of the present invention, in step (4), the ultrasonic cleaning conditions are: ultrasonic power 10-50 kHz, ultrasonic time 10-20 minutes, repeated 2-3 times; and the drying conditions are: temperature 70-105°C, time 12-18 hours. More preferably, the ultrasonic cleaning conditions are: ultrasonic power 40 kHz, ultrasonic time 15 minutes, repeated 2 times; and the drying conditions are: temperature 80°C, time 18 hours.

[0021] As one of the preferred embodiments of the present invention, in step (5), 2-3 g of dopamine hydrochloride is placed in 200-300 ml of anhydrous ethanol and stirred at room temperature. More preferably, 2.27 g of dopamine hydrochloride is placed in 300 ml of anhydrous ethanol and stirred at room temperature.

[0022] As one preferred embodiment of the present invention, in step (6), the amount of 1,3-propanesulfonic acid and ammonia water added is 1.5-2.3 g and 0.8-1.1 ml, respectively; the stirring temperature is 50°C; the drying temperature is 50°C, and the drying time is 16-24 hours. More preferably, the amount of 1,3-propanesulfonic acid and ammonia water added is 1.6 g and 0.832 ml, respectively; the stirring temperature is 50°C; the drying temperature is 50°C, and the drying time is 18 hours.

[0023] As one preferred embodiment of the present invention, in step (7), the amount of SDA and TWQ added is 0.5-0.7 g, the amount of trisaminomethane hydrochloric acid solution (pH 8.5) used is 400-452 ml, stirring is performed at room temperature, and the drying temperature is 40-60°C, and the drying time is 12-16 hours. More preferably, the amount of SDA and TWQ added is 0.5 g, the amount of trisaminomethane hydrochloric acid solution (pH 8.5) used is 400 ml, stirring is performed at room temperature, and the drying temperature is 45°C, and the drying time is 14 hours.

[0024] A biomass-based modified carbon microsphere is prepared by adopting the above-mentioned preparation method of biomass-based modified carbon microsphere.

[0025] A method for preparing a biomass-based modified carbon microsphere composite proton exchange membrane:

[0026] (1) dissolving a sulfonated aromatic polymer in an organic solvent to obtain a sulfonated aromatic polymer solution;

[0027] (2) adding polydopamine carbon microspheres SDA-TWQ to the sulfonated aromatic polymer solution and stirring and mixing to obtain a sulfonated aromatic polymer SDA-TWQ mixed solution, and then ultrasonically dispersing the solution; the SDA-TWQ is prepared using the above-mentioned method for preparing biomass-based modified carbon microspheres;

[0028] (3) The sulfonated aromatic polymer SDA-TWQ mixed solution after ultrasonic dispersion is injected into a mold and then dried to obtain a composite proton exchange membrane.

[0029] As one preferred embodiment of the present invention, in step (1), the organic solvent is N,N-dimethylformamide; the sulfonated aromatic polymer is sulfonated polyetheretherketone (SPEEK) or sulfonated polyethersulfone (PES); and the mass of the sulfonated aromatic polymer in the resulting sulfonated aromatic polymer solution is 5 to 10 wt % of the total solution. More preferably, the sulfonated aromatic polymer is sulfonated polyetheretherketone (SPEEK); and the mass of the sulfonated aromatic polymer in the resulting sulfonated aromatic polymer solution is 6.35 wt %.

[0030] As one preferred embodiment of the present invention, in step (2), the amount of SDA-TWQ added is 0.1% to 2% of the mass of the sulfonated aromatic polymer; the ultrasonic power of the ultrasonic dispersion is 25 to 75 kHz, and the ultrasonic time is 10 to 40 minutes. More preferably, the amount of SDA-TWQ added is 0.5% of the mass of the sulfonated aromatic polymer; the ultrasonic power of the ultrasonic dispersion is 25 kHz, and the ultrasonic time is 40 minutes.

[0031] As one of the preferred embodiments of the present invention, in step (3), the amount of the sulfonated aromatic polymer SDA-TWQ mixed solution injected into the mold is 0.3-0.5 mL / cm 2 ; Drying temperature 50 ~ 80 ℃, drying time 12 ~ 24h. More preferably, the amount of sulfonated aromatic polymer SDA-TWQ mixed solution injected into the mold is 0.3mL / cm 2 ; Drying temperature 70℃, drying time 20h.

[0032] A biomass-based modified carbon microsphere composite proton exchange membrane is prepared by adopting the above-mentioned preparation method of the biomass-based modified carbon microsphere composite proton exchange membrane.

[0033] The advantages of the present invention over the prior art are:

[0034] (1) The hydrothermal charcoal obtained by fixing carbon elements in agricultural and forestry wastes through hydrothermal reaction can be used as a soil conditioner to improve the air permeability and water holding capacity of the soil, and can also play a role in adsorbing and slowly releasing nutrient ions in the soil;

[0035] (2) The highly active components such as water-soluble glucose, organic acid and furfural in the hydrothermal liquid product of the present invention can completely replace fossil carbon sources and self-assemble to form carbon microspheres through a benzene ring condensation mechanism, thereby achieving zero carbon source cost while effectively reducing the high COD and organic matter content in the hydrothermal liquid product. In addition, the secondary liquid product after extracting the carbon microspheres in the present invention can also be used as a liquid organic fertilizer to sterilize and promote plant growth.

[0036] (3) Compared with various fillers introduced into traditional proton exchange membrane substrates, the carbon microspheres prepared by the method of the present invention have significant advantages in terms of raw material renewability, process simplicity and cost controllability. Their uniform spherical structure and surface hydrophilicity give the matrix excellent interfacial compatibility;

[0037] (4) The carbon microspheres modified with sulfonated dopamine in the present invention have surface hydroxyl groups (-OH) and sulfonic acid groups (-SO3H) in the acidic polymer base forming a cross-linked network through hydrogen bonding, which not only maintains the high water absorption performance of the membrane material but also inhibits the swelling effect, significantly enhancing its structural stability; at the same time, the acidic groups in the sulfonated polymer matrix and the sulfonic acid side chains in SDA further interact with each other, thereby greatly improving the proton conduction efficiency of the proton exchange membrane (PEM); in addition, the dense and uniform microstructure of the carbon microspheres in the present invention not only effectively inhibits the methanol permeation phenomenon, but also improves the oxidative stability of the composite proton exchange membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a SEM image of the biogas slurry carbon microspheres ZYTWQ in Example 1;

[0039] Figure 2 is a SEM image of the pyrolysis liquid carbon microspheres RJYTWQ in Example 2;

[0040] Figure 3 is the SEM image of the carbon microspheres SDA-UPTWQ in Comparative Example 1;

[0041] Figure 4 is a SEM image of the 0.5% SDA-ZYTWQ composite proton exchange membrane in Example 3;

[0042] Figure 5 is a SEM image of the 0.5% SDA-RJYTWQ composite proton exchange membrane in Example 4;

[0043] Figure 6 This is the SEM image of the SPEEK proton exchange membrane in Comparative Example 2. DETAILED DESCRIPTION

[0044] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0045] At the same time, the biogas slurry mentioned in the following embodiments refers to the anaerobic fermentation liquid of organic waste in the livestock and poultry breeding process, and the agricultural and forestry waste pyrolysis liquid refers to the organic waste liquid by-product of wood pyrolysis; the reagent products and experimental methods used, unless otherwise specified, are conventional reagents or methods in the field and will not be repeated here.

[0046] Example 1

[0047] The biomass-based modified carbon microspheres (SDA-ZYTWQ) of this embodiment are prepared as follows:

[0048] (1) The corn straw raw material was crushed and passed through an 80-mesh sieve, and the biogas slurry (ZY) was filtered through a 100-mesh sieve. Then the two were mixed at a solid-liquid ratio of 1:12.5 to obtain a lignocellulose-biogas slurry mixture.

[0049] (2) The lignocellulose-biogas slurry mixture was hydrothermally reacted at 220°C for 120 min at a hydrothermal power of 60 kW / kg. After completion of the reaction, the mixture was separated by filtration using a vacuum filter. The separated liquid product was recorded as the primary hydrothermal liquid product and collected for subsequent experiments. The solid product was recorded as hydrothermal charcoal and dried at 105°C for 18 h for use as a soil conditioner.

[0050] (3) The primary hydrothermal liquid product obtained in step (2) was subjected to a second hydrothermal reaction at 180° C. for 60 min at a hydrothermal power of 60 kW / kg. After the reaction was completed, the hydrothermal product was filtered and separated using a vacuum filter. The separated liquid product was recorded as the secondary hydrothermal liquid product. The solid product on the filter paper was rinsed twice with deionized water and collected.

[0051] (4) The solid product collected in step (3) was ultrasonically cleaned at 50 kHz for 15 min, repeated twice, and then dried at 80 ° C for 18 h. The obtained product was biogas slurry carbon microspheres, denoted as ZYTWQ (SEM image see Figure 1 ).

[0052] (5) Weigh 2.27 g of dopamine hydrochloride and place it in 300 mL of anhydrous ethanol. Stir at room temperature, ultrasonically disperse for 30 min, and magnetically stir for 24 h to form a uniform solution, which is recorded as DA solution.

[0053] (6) 1.6 g of 1,3-propanesulfonic acid and 0.832 ml of ammonia water were added to the DA solution, and the mixture was stirred at 50 °C and 600 rpm for 18 h. After the reaction, the mixed solution was centrifuged at 7000 rpm for 15 min, the solid was collected, rinsed with ethanol, and then dried at 50 °C for 18 h. The obtained product was sulfonated dopamine, which was recorded as SDA.

[0054] (7) Weigh 0.5 g of SDA and 0.5 g of ZYTWQ in 400 ml of trisaminomethane hydrochloric acid solution (pH 8.5), and then stir at 600 rpm for 15 h at room temperature. After the reaction is complete, the mixed solution is centrifuged at 10,000 rpm for 10 min, the solid is collected, and rinsed with ethanol. It is then dried at 45 °C for 14 h. The resulting product is sulfonated polydopamine carbon microspheres, denoted as SDA-ZYTWQ.

[0055] Example 2

[0056] The biomass-based modified carbon microspheres (SDA-RJYTWQ) of this embodiment are prepared as follows:

[0057] (1) The corn straw raw material was crushed and passed through an 80-mesh sieve. The agricultural and forestry waste pyrolysis liquid (RJY) was filtered through a 100-mesh sieve. Then the two were mixed at a solid-liquid ratio of 1:12.5 to obtain a lignocellulose-pyrolysis liquid mixture.

[0058] (2) The lignocellulose-pyrolysis liquid mixture was hydrothermally reacted at 220°C for 120 min at a hydrothermal power of 60 kW / kg. After completion of the reaction, the mixture was separated by filtration using a vacuum filter. The separated liquid product was recorded as the primary hydrothermal liquid product and collected for subsequent experiments. The solid product was recorded as hydrothermal charcoal and dried at 105°C for 18 h for use as a soil conditioner.

[0059] (3) The primary hydrothermal liquid product obtained in step (2) was subjected to a second hydrothermal reaction at 180° C. for 60 min at a hydrothermal power of 60 kW / kg. After the reaction was completed, the hydrothermal product was filtered and separated using a vacuum filter. The separated liquid product was recorded as the secondary hydrothermal liquid product. The solid product on the filter paper was rinsed twice with deionized water and collected.

[0060] (4) The solid product collected in step (3) was ultrasonically cleaned at 50 kHz for 15 min, repeated twice, and then dried at 80 ° C for 18 h. The obtained product was pyrolysis liquid carbon microspheres, denoted as RJYTWQ (SEM image see Figure 2 ).

[0061] (5) Weigh 2.27 g of dopamine hydrochloride and place it in 300 mL of anhydrous ethanol. Stir at room temperature, ultrasonically disperse for 30 min, and magnetically stir for 24 h to form a uniform solution, which is recorded as DA solution.

[0062] (6) 1.6 g of 1,3-propanesulfonic acid and 0.832 ml of ammonia water were added to the DA solution, and the mixture was stirred at 50 °C and 600 rpm for 18 h. After the reaction, the mixed solution was centrifuged at 7000 rpm for 15 min, the solid was collected, rinsed with ethanol, and then dried at 50 °C for 18 h. The obtained product was sulfonated dopamine, which was recorded as SDA.

[0063] (7) Weigh 0.5 g of SDA and 0.5 g of RJYTWQ in 400 ml of trisaminomethane hydrochloric acid solution (pH 8.5), and then stir at 600 rpm for 15 h at room temperature. After the reaction is complete, the mixed solution is centrifuged at 10,000 rpm for 10 min, the solid is collected, and rinsed with ethanol. It is then dried at 45 °C for 14 h. The resulting product is sulfonated polydopamine carbon microspheres, denoted as SDA-RJYTWQ.

[0064] Comparative Example 1

[0065] The preparation method of the carbon microspheres (SDA-UPTWQ) in this comparative example is basically the same as that in Example 1, except that the biogas slurry is replaced with deionized water, and the final product is recorded as SDA-UPTWQ (SEM image is shown in FIG. Figure 3 ).

[0066] Example 3

[0067] The biomass-based modified carbon microsphere composite proton exchange membrane (SDA-ZYTWQ composite proton exchange membrane) of this embodiment is prepared as follows:

[0068] (1) 6.52 g of dry sulfonated polyetheretherketone (SPEEK) and 102.53 g of N,N-dimethylformamide (DMF) were placed in a beaker and stirred at 80°C and 600 rpm for 240 min to obtain a SPEEK solution.

[0069] (2) SDA-ZYTWQ (Example 1) with a mass of 0.5% of SPEEK was added to the SPEEK solution and stirred at 300 rpm for 15 min. Subsequently, ultrasonic dispersion was performed at 25 kHz for 40 min to form a SPEEK / SDA-ZYTWQ mixed solution.

[0070] (3) SPEEK / SDA-ZYTWQ mixed solution was added at 0.3 mL / cm 2 The mixed solution was injected into the mold and evenly distributed in the mold using the casting method. Before being placed in the oven for drying, the support in the oven was adjusted to a level using a level gauge, and then the mold was dried at 70°C for 20 h. The dried membrane was designated as a 0.5% SDA-ZYTWQ composite proton exchange membrane (SEM image see Figure 4 ).

[0071] Example 4

[0072] A biomass-based modified carbon microsphere composite proton exchange membrane (SDA-RJYTWQ composite proton exchange membrane) of this embodiment is prepared as follows:

[0073] (1) 6.52 g of dry sulfonated polyetheretherketone (SPEEK) and 102.53 g of N,N-dimethylformamide (DMF) were placed in a beaker and stirred at 80°C and 600 rpm for 240 min to obtain a SPEEK solution.

[0074] (2) SDA-RJYTWQ (Example 2) with a mass of 0.5% of SPEEK was added to the SPEEK solution and stirred at 300 rpm for 15 min. Subsequently, ultrasonic dispersion was performed at 25 kHz for 40 min to form a SPEEK / SDA-RJYTWQ mixed solution.

[0075] (3) SPEEK / SDA-RJYTWQ mixed solution was added at 0.3 mL / cm 2 The mixed solution was injected into the mold and evenly distributed in the mold using the casting method. Before being placed in the oven for drying, the support in the oven was adjusted to a horizontal level using a level gauge, and then the mold was dried at 70°C for 20 h. The dried membrane was designated as a 0.5% SDA-RJYTWQ composite proton exchange membrane (SEM image see Figure 5 ).

[0076] Comparative Example 2

[0077] The preparation method of a biomass-based modified carbon microsphere composite proton exchange membrane (SPEEK proton exchange membrane) in this comparative example is basically the same as that in Example 3, except that: no carbon microsphere filler is added to the SPEEK solution, and the SPEEK solution is directly placed in an oven for drying. The membrane after drying is recorded as SPEEK proton exchange membrane (SEM image is shown in FIG. Figure 6 ).

[0078] Experimental example

[0079] SEM images of the carbon microspheres or composite proton exchange membranes prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were analyzed. Performance tests were also conducted on the composite proton exchange membranes prepared in Example 3, Example 4, and Comparative Example 2, including water absorption, swelling ratio, proton exchange membrane ratio, oxidative stability, methanol permeability, and power density.

[0080] The size of the composite proton exchange membrane used for the test was 3 cm × 3 cm. The test results of water absorption, swelling rate, and proton exchange membrane rate were tested at 80°C. The water absorption (WU) and swelling rate (SR) of the composite membrane proton exchange membrane were calculated from their mass in the dry (Wd) and wet (Ww) states, and their area in the dry (Ad) and wet (Aw) states, respectively, using the following formulas:

[0081]

[0082] The oxidative stability of the composite membrane proton exchange membrane was evaluated using the Fenton test: a certain mass of the composite membrane was immersed in Fenton solution (3.0 wt% H2O2 and 4 mg / L FeSO4), and the remaining weight of each composite membrane was measured after being placed in a water bath at 60°C for 5 h to evaluate its oxidative stability.

[0083] The electrochemical impedance R (Ω) of the composite membrane was measured by an electrochemical workstation at a frequency of 0.1 Hz to 1.0 MHz and a humidity of 100%, in the temperature range of 20 to 80 ° C. The impedance R of the composite membrane, the distance L between the working electrode and the reference electrode (here 2.50 cm), and the cross-sectional area A (cm 2 ) into the following formula to calculate the proton exchange membrane efficiency σ (S·cm -1 ), the calculation formula is as follows:

[0084]

[0085] Methanol permeability was measured in a homemade diffusion cell divided into two separate glass compartments by a composite proton exchange membrane. Methanol (2 mol / L) was then added to chamber A and deionized water was added to chamber B, with stirring at 70°C. Changes in methanol concentration were measured using a gas chromatograph equipped with a flame ionization detector. The methanol permeability was calculated using the following formula:

[0086]

[0087] Fuel cell performance test The composite proton exchange membrane was sandwiched between the anode (catalyst is Pt-Ru, 4.0 mg cm -2 ) and cathode (catalyst is Pt, 2.0 mg·cm -2 ) to prepare the membrane electrode assembly. Then the test was carried out on the electrochemical workstation. During the test, O2 was 100mL·min -1 The flow rate of methanol (2M) was 1 mL min -1 The flow rate is provided to the anode.

[0088] The performance test results are shown in Table 1.

[0089] Table 1 Performance test results of various proton exchange membranes

[0090]

[0091] From the SEM images ( Figures 1 to 6 ) can be seen:

[0092] (2) The carbon microspheres in Comparative Example 1 are mainly discretely distributed carbon microspheres, with low particle aggregation in some areas; the surface of the carbon microspheres is relatively rough, but most areas still retain carbon blocks and fragment structures. Compared with Comparative Example 1, the field of view of the SEM image in Example 1 is completely covered with regular carbon microspheres, and the particle size is relatively uniform and densely distributed. The number of carbon microspheres in Example 2 is significantly increased compared to Comparative Example 1, showing dense carbon microsphere coverage and improved particle uniformity. However, it can still be seen from the high-magnification image that the carbon microspheres have some adhesion.

[0093] (2) The cross section of the composite proton exchange membrane of Comparative Example 2 exhibited a relatively dense and smooth microstructure, with no obvious phase separation characteristics. Compared with Comparative Example 2, Example 3 exhibited a relatively flat and dense structure, and no obvious agglomeration phenomenon was observed, indicating that SDA-ZYTWQ was evenly distributed in the SPEEK substrate. The SEM image of the cross section of the composite proton exchange membrane of Example 4 showed large pores and small particle structures in some areas, indicating that the dispersion of SDA-RJYTWQ in the matrix was poor, and agglomeration occurred, which would cause its performance to deteriorate relatively.

[0094] From the results in Table 1 we can see that:

[0095] (1) The pure SPEEK proton exchange membrane in Comparative Example 2 has poor water absorption and swelling performance at 80°C, with a water absorption rate of only 37.62% and a swelling rate of 45.63%. The oxidation stability is 84.47%, and the methanol permeability is 53.30 cm 2 ·s -1 ) is at a relatively high level, and the proton exchange membrane rate (0.076S·cm -1 ) and power density (66.65mW·cm -2 This is because the intensified movement of SPEEK molecular chains under high temperature conditions weakens the intermolecular forces and relaxes the membrane structure, which in turn increases the swelling rate and intensifies the penetration of methanol, resulting in a decrease in performance.

[0096] (2) Compared with Comparative Example 2 and Example 4, the various properties of the SDA-ZYTWQ composite proton exchange membrane of Example 3 were improved. By introducing 0.5 wt% of SDA-ZYTWQ, the water absorption rate was increased to 57.02% by utilizing its surface hydrophilic functional groups, and the hydrogen bond network formed with the polymer substrate suppressed the movement of the SPEEK molecular chain, reducing the swelling rate to 33.65%. The dense barrier formed by SDA-ZYTWQ in the SPEEK matrix effectively blocked the penetration of methanol (44.02 cm 2 ·s -1 ) and Fenton's reagent oxidation (oxidative stability 95.20%), the acidic groups in SPEEK further interacted with the sulfonic acid side chains in SDA-ZYTWQ, forming a continuous proton transport path. In addition, the -OH groups on SDA-ZYTWQ formed a hydrogen bond network with the sulfonic acid groups through hydrogen bonds, which together promoted the proton conductivity to jump to 0.159 S·cm -1 , the final power density reaches 106.01mW·cm -2 The results show that SDA-ZYTWQ effectively improves the performance of the composite membrane by synergistically regulating the microstructure, inhibiting swelling, and optimizing the proton exchange membrane path.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing biomass-based modified carbon microspheres, characterized in that: The steps include: (1) crushing and sieving agricultural and forestry waste biomass, and filtering organic wastewater at the same time; mixing the sieved agricultural and forestry waste biomass with the filtered organic wastewater to obtain an agricultural and forestry waste biomass-organic wastewater mixture; (2) A hydrothermal reaction is performed on a mixture of agricultural and forestry waste biomass and organic wastewater; after the reaction is completed, the hydrothermal product is filtered and separated, and the separated liquid product is recorded as the primary hydrothermal liquid product, and the solid product is recorded as hydrothermal charcoal; (3) taking the primary hydrothermal liquid product obtained in step (2) and performing a hydrothermal reaction again; after the reaction is completed, the hydrothermal product is separated by suction filtration, and the separated liquid product is recorded as the secondary hydrothermal liquid product, and the solid product is rinsed with deionized water and collected; (4) ultrasonically cleaning and drying the solid product collected in step (3) to obtain carbon microspheres TWQ; (5) Place dopamine hydrochloride in anhydrous ethanol and stir evenly to obtain DA solution; (6) adding 1,3-propanesulfonic acid and ammonia water to the DA solution obtained in step (5) and stirring; after stirring, centrifuging the mixed solution, collecting the solid, washing it with ethanol, and then drying it to obtain sulfonated dopamine SDA; (7) The SDA obtained in step (6) and the TWQ obtained in step (4) are placed in a triaminomethane hydrochloric acid solution and stirred for reaction; after the reaction is completed, the mixed solution is centrifuged to collect the solid product and rinsed with ethanol; finally, the solid product is dried to obtain polydopamine carbon microspheres SDA-TWQ.

2. The method for preparing biomass-based modified carbon microspheres according to claim 1, characterized in that: In the step (2), the hydrothermal reaction conditions are: hydrothermal temperature 180-250° C., hydrothermal time 30-120 min, and hydrothermal power 30-60 kW / kg; in the step (3), the hydrothermal reaction conditions are: hydrothermal temperature 160-220° C., hydrothermal time 60-120 min, and hydrothermal power 30-60 kW / kg.

3. The method for preparing biomass-based modified carbon microspheres according to claim 1, characterized in that: In the step (4), the ultrasonic cleaning conditions are: ultrasonic power 10-50kHz, ultrasonic time 10-20min, repeated 2-3 times; and drying conditions are: temperature 70-105°C, time 12-18h.

4. The method for preparing biomass-based modified carbon microspheres according to claim 1, wherein: In step (5), 2-3 g of dopamine hydrochloride is placed in 200-300 ml of anhydrous ethanol and stirred at room temperature; In the step (6), the addition amounts of 1,3-propanesulfonic acid and ammonia water are 1.5-2.3 g and 0.8-1.1 ml, respectively; the stirring temperature is 50° C.; the drying temperature is 50° C.; and the drying time is 16-24 h; In the step (7), the added amounts of SDA and TWQ are both 0.5-0.7 g, the amount of triaminomethane hydrochloric acid solution used is 400-452 ml; stirring is performed at room temperature; the drying temperature is 40-60° C., and the drying time is 12-16 h.

5. A biomass-based modified carbon microsphere, characterized in that: The method is prepared by any one of claims 1 to 4.

6. A method for preparing a biomass-based modified carbon microsphere composite proton exchange membrane, characterized in that: Here’s how: (1) dissolving a sulfonated aromatic polymer in an organic solvent to obtain a sulfonated aromatic polymer solution; (2) adding polydopamine carbon microspheres SDA-TWQ to the sulfonated aromatic polymer solution and stirring and mixing to obtain a sulfonated aromatic polymer SDA-TWQ mixed solution, and then ultrasonically dispersing the solution; the SDA-TWQ is prepared by the method according to any one of claims 1 to 4; (3) The sulfonated aromatic polymer SDA-TWQ mixed solution after ultrasonic dispersion is injected into a mold and then dried to obtain a composite proton exchange membrane.

7. The method for preparing a biomass-based modified carbon microsphere composite proton exchange membrane according to claim 6, characterized in that: In the step (1), the organic solvent is N,N-dimethylformamide; the sulfonated aromatic polymer is sulfonated polyetheretherketone SPEEK or sulfonated polyethersulfone PES; and in the obtained sulfonated aromatic polymer solution, the mass of the sulfonated aromatic polymer is 5-10 wt % of the entire solution.

8. The method for preparing a biomass-based modified carbon microsphere composite proton exchange membrane according to claim 6, characterized in that: In the step (2), the amount of SDA-TWQ added is 0.1% to 2% of the mass of the sulfonated aromatic polymer; the ultrasonic power of the ultrasonic dispersion is 25 to 75 kHz, and the ultrasonic time is 10 to 40 minutes.

9. The method for preparing a biomass-based modified carbon microsphere composite proton exchange membrane according to claim 6, characterized in that: In the step (3), the amount of the sulfonated aromatic polymer SDA-TWQ mixed solution injected into the mold is 0.3-0.5 mL / cm 2 ; Drying temperature 50~80℃, drying time 12~24h.

10. A biomass-based modified carbon microsphere composite proton exchange membrane, characterized in that: The method is prepared by any one of claims 6 to 9.

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