A method for preparing NiSeZn(g-C3N4) / CNFs composite material and its application

Abstract

The application provides a preparation method and application of a composite material NiSeZn(g-C3N4) / CNFs. The preparation comprises the following steps: after alkali treatment of carbon nanofibers, the carbon nanofibers are grafted and modified by using a silane coupling agent, and are subjected to frozen denaturation treatment; NiSeZn(g-C3N4) is grown on the modified carbon nanofibers, and NiSeZn(g-C3N4) / CNFs are prepared by twice calcination. The preparation method of the composite material NiSeZn(g-C3N4) / CNFs provided by the application enhances the comprehensive performance of the composite material, such as the electrical conductivity, the thermal conductivity, the bending strength and the compressive strength, and is beneficial to the application in a hydrogen fuel cell composite bipolar plate. In the method, the raw materials used are safe, and the cleaning liquid can be recycled, so that the generation of waste liquid can be reduced, and the environmental hazard problem caused by the soaking mode is avoided.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite bipolar plate material technology, specifically relating to a method for preparing a composite material NiSeZn(g-C3N4) / CNFs and its application. Background Technology

[0002] Bipolar plates are an important component of hydrogen fuel cells, serving functions such as connecting individual modules, separating reactant gases, collecting current, dissipating heat, and draining water.

[0003] Bipolar plates can be classified into metal bipolar plates and composite material bipolar plates based on their materials. Metal bipolar plates (e.g., patent publication number CN109560305A) have good mechanical, electrical, and thermal conductivity properties, but poor corrosion resistance. Therefore, a coating is usually added to the surface (e.g., patent publication number CN210628419U), and the mechanical, electrical, and thermal conductivity properties of the coating also affect the performance of the bipolar plate. Composite material bipolar plates, on the other hand, can combine excellent mechanical, electrical, thermal, and corrosion resistance properties.

[0004] There is considerable research on composite bipolar plates, such as patent publication number CN117747169A, which includes a resin matrix, a curing agent, and a modified conductive filler. The modified conductive filler is a carbon-based material treated with a modifier. The modifier includes any one or a combination of at least two of styrene pyrene butyrate, polybutylene phenylacetate, polyacrylic acid, polybutyl acrylate, or polystyrene. The composite bipolar plate is obtained by mixing the resin matrix, curing agent, and modified conductive filler to form a coating slurry, which is then coated onto the surface of a carbon fiber prepreg and pressed. However, due to the poor dispersion and tendency of carbon-based materials to entangle and agglomerate, the modification effect of the mixed coating slurry is unstable. Furthermore, the surface coating method does not alter the internal morphology of the carbon fibers, resulting in poor reinforcement.

[0005] For example, patent publication number CN117352765A describes immersing expanded graphite preforms in a solution containing aniline, with a molar mass ratio of aniline to expanded graphite preforms of (0.3-0.8) mol:10g, for in-situ polymerization. After post-treatment, an EG-PANI composite material is obtained. This EG-PANI composite material is then combined with phenolic resin using a vacuum impregnation method to obtain a PANI-EG-PF composite material. The PANI-EG-PF composite material is then used in a hot-pressing process to fabricate a hydrogen fuel cell composite bipolar plate. However, this method uses a large amount of aniline, which is highly toxic, and the immersion method leaves behind a large amount of impregnation waste liquid, posing an immeasurable threat to the environment. Furthermore, the overall performance of the composite material needs further improvement. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a nanocomposite material NiSeZn(g-C3N4) / CNFs and its preparation method. To achieve the above objectives, this invention adopts the following technical solution:

[0007] A method for preparing a composite material NiSeZn(g-C3N4) / CNFs includes the following steps:

[0008] S1. After treating carbon nanofibers with alkali, add them to ethylene glycol, sonicate them, add silane coupling agent and melamine for grafting modification, wash the modified carbon nanofibers with water, and recover the washing liquid.

[0009] S2. After adding the cleaning solution to dopamine and CE resin and stirring to react, the product is dried, calcined, cooled, and then ground to nanoscale.

[0010] S3. Prepare an aqueous solution containing melamine and ZnSO4 as dispersion system A;

[0011] S4. Disperse the modified carbon nanofibers obtained in step S1 in ethanol, add nano-sized nickel selenide and the calcined product obtained in S2, and heat to obtain dispersion system B.

[0012] S5. Add dispersion system B to dispersion system A, sonicate and then centrifuge;

[0013] S6. The centrifuged sample is calcined to obtain the composite material NiSeZn(g-C3N4) / CNFs.

[0014] In the composite material described above, preferably, in step S1, the alkali treatment is soaking in an alkaline solution; the soaking time is 1-2 hours; the amount of ethylene glycol used is ethylene glycol to carbon nanofibers at a volume-to-mass ratio of 1:1-3, in units of L:kg; the ultrasonic treatment time is 20-30 minutes.

[0015] Furthermore, the alkaline solution is a sodium hydroxide solution with a concentration of 20-40 wt%; the soaking time is 1-2 hours.

[0016] In the composite material described above, preferably, in step S1, the mass ratio of carbon nanofibers, silane coupling agent, and melamine is 50–85:1.7–3.6:0.8–1.5. Further, the silane coupling agent is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent.

[0017] In the composite material described above, preferably, in step S1, the cleaned modified carbon nanofibers require freeze-drying treatment at a temperature of -10 to 0°C for 3 to 10 hours. Further, the freeze-drying temperature is -5 to 0°C for 5 to 8 hours.

[0018] In the composite material described above, preferably, in step S2, the mass ratio of cleaning liquid to dopamine is 100-125:6.8-9.3, and the mass ratio of dopamine to CE resin is 1-2:3-7;

[0019] The stirring reaction temperature is 50–65℃, and the reaction time is 24–40 h; the calcination temperature is 200–320℃, and the calcination time is 50–70 min; and the material is ground to 200–600 nm.

[0020] In the composite material described above, preferably, in step S3, the mass ratio of melamine to ZnSO4 is 15-21:7.35-9, wherein the mass concentration of melamine is 13%-20%.

[0021] In the composite material described above, preferably, in step S4, nickel selenide is added at a mass ratio of nickel selenide to carbon nanofibers of 0.1 to 0.3:1; the heating temperature is 80°C and the heating time is 15 to 20 minutes.

[0022] In the composite material described above, preferably, in step S5, the addition rate of dispersion system B to dispersion system A is less than 1 L / min, and the ultrasonic treatment time is 1.5 to 2.3 h.

[0023] Preferably, in step S6, the calcination of the composite material described above is divided into two calcination processes: the first calcination process is calcination at 600-750°C for 2.1-2.3 hours; the second high-temperature and high-pressure calcination process is calcination at 10-11 GPa and 1100-1200°C for 5-10 minutes.

[0024] The composite material NiSeZn(g-C3N4) / CNFs obtained by the preparation method described above is used in the preparation of composite bipolar plates for hydrogen fuel cells.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention provides a method for preparing the NiSeZn(g-C3N4) / CNFs nanocomposite material. First, carbon nanofibers are treated with an alkali, then grafted and modified with N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent (Z-6020), followed by freeze-drying. NiSeZn(g-C3N4) is then grown on the modified carbon nanofibers to prepare NiSeZn(g-C3N4) / CNFs. Finally, a second high-temperature, high-pressure calcination process enhances the composite material's electrical conductivity, thermal conductivity, flexural strength, and compressive strength. The preparation method provided by this invention uses safe raw materials, and the cleaning solution can be recycled, reducing wastewater generation and avoiding environmental hazards caused by immersion methods.

[0027] The nanocomposite material NiSeZn(g-C3N4) / CNFs of this invention has high electrical conductivity (195 S / cm), high thermal conductivity (6.3 × 10 W / mK), good flexural strength (51.7 MPa) and compressive strength (91.4 MPa), and excellent overall performance, which is beneficial for its application in composite bipolar plates of hydrogen fuel cells. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating a method for preparing the nanocomposite material NiSeZn(g-C3N4) / CNFs according to the present invention. Detailed Implementation

[0029] The present invention relates to a nanocomposite material NiSeZn(g-C3N4) / CNFs and its preparation method, comprising: 1. Preparing modified carbon nanofibers (CNFs); alkali treatment; graft modification; freeze-drying treatment; 2. Growing NiSeZn(g-C3N4) on the modified carbon nanofibers to prepare NiSeZn(g-C3N4) / CNFs. Specifically, the carbon nanofibers are first subjected to alkali treatment, then grafted and modified with N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent, followed by freeze-drying treatment; then NiSeZn(g-C3N4) is grown on the modified carbon nanofibers to prepare NiSeZn(g-C3N4) / CNFs, and finally subjected to a second high-temperature and high-pressure calcination process to enhance the electrical conductivity, thermal conductivity, flexural strength, and compressive strength of the composite material. Nickel selenide (NiSe) and zinc (Zn) both have high discharge specific capacity, and their combination can improve the discharge specific capacity of electrode materials; combining them with graphitic carbon nitride (g-C3N4) can further improve electronic conductivity; and modifying them onto carbon nanofibers can improve the strength of composite materials.

[0030] The following embodiments are used to further illustrate the present invention, but should not be construed as limiting the present invention. Any modifications or substitutions made to the present invention without departing from its spirit and essence are within the scope of the present invention.

[0031] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, all reagents used in this method are of analytical grade or higher.

[0032] Example 1

[0033] A method for preparing the composite material NiSeZn(g-C3N4) / CNFs, the process flow diagram is shown below. Figure 1 As shown, the specific steps include the following:

[0034] I. Preparation of modified carbon nanofibers (CNFs)

[0035] Alkali treatment: 50g of carbon nanofibers were treated with 32wt% sodium hydroxide solution for 1.5h.

[0036] Grafting modification: The alkali-treated carbon nanofibers were then placed in 50 mL of ethylene glycol and ultrasonically dispersed for 20 min. 3.6 g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent (Z-6020) and 0.8 g of melamine were added, and the mixture was heated to 80 °C and ultrasonically dispersed for another 1 h. Grafted carbon nanofibers were obtained, washed with water, centrifuged, and the washing liquid was recovered.

[0037] Freeze-drying treatment: The grafted modified carbon nanofibers were frozen at -5℃ for 8 hours, then freeze-dried in a vacuum drying oven, and ground and sieved through a 200-mesh sieve.

[0038] II. NiSeZn(g-C3N4) was grown on grafted modified carbon nanofibers to prepare NiSeZn(g-C3N4) / CNFs;

[0039] Cleaning solution drying and calcination: Add 9.3g of dopamine and 19.6g of CE resin to 100g of cleaning solution, stir and react at 50℃ for 40h, dry and then calcine at 200℃ for 70min, cool and grind to nanoscale (200nm).

[0040] In this invention, the cleaning fluid can be recycled, which reduces the amount of waste fluid.

[0041] Preparation of dispersion system A: Dissolve 15g of melamine in 80g of deionized water, add 13g of ZnSO4·7H2O, stir and heat in a water bath at 80℃ for 40min to obtain dispersion system A;

[0042] Preparation of dispersion system B: The CNFs obtained above were dispersed in an ethanol solution, 8.5g of nano-sized nickel selenide and the above-mentioned calcined product were added, and the mixture was stirred and heated in a water bath at 80℃ for 20min to obtain dispersion system B.

[0043] Blending loading: Add dispersion system B to dispersion system A at a rate of less than 1 L / min; ultrasonically disperse for 1.5 h, followed by centrifugation.

[0044] First calcination process: The sample is then calcined at 600℃ for 2.3h. The resulting sample is named NiSeZn(g-C3N4) / CNFs. After that, the sample is ground and sieved through a 500-mesh sieve.

[0045] Third, secondary high-temperature and high-pressure calcination process: The NiSeZn(g-C3N4) / CNFs sample is placed in the top press and calcined at 10 GPa and 1200℃ for 5 min.

[0046] Example 2

[0047] I. Preparation of modified carbon nanofibers (CNFs)

[0048] Alkali treatment: 85g of carbon nanofibers were treated with 25wt% sodium hydroxide solution for 1-2 hours.

[0049] Grafting modification: The alkali-treated carbon nanofibers were then placed in 50 mL of ethylene glycol and ultrasonically dispersed for 30 min. 1.7 g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent (Z-6020) and 1.5 g of melamine were added, and the mixture was heated to 55 °C and ultrasonically dispersed for another 3 h to obtain grafted modified carbon nanofibers. The grafted modified carbon nanofibers were then washed with water and centrifuged to recover the washing liquid.

[0050] Freeze-drying treatment: The grafted modified carbon nanofibers were frozen at 0°C for 5 hours, then freeze-dried in a vacuum drying oven, and ground and sieved through a 300-mesh sieve.

[0051] II. NiSeZn(g-C3N4) was grown on grafted modified carbon nanofibers to prepare NiSeZn(g-C3N4) / CNFs;

[0052] Cleaning solution drying and calcination: Add 6.8g of dopamine and 31.2g of CE resin to 125g of cleaning solution, stir and react at 65℃ for 24h, dry and then calcine at 320℃ for 50min, cool and grind to nanoscale (600nm).

[0053] Preparation of dispersion system A: Dissolve 21g of melamine in 75g of deionized water, add 15.8g of ZnSO4·7H2O, stir and heat in a water bath for 25min to obtain dispersion system A;

[0054] Preparation of dispersion system B: The CNFs obtained above are dispersed in an ethanol solution, 15g of nano-sized nickel selenide and the above-mentioned calcined product are added, and the mixture is stirred and heated in a water bath at 80℃ for 15min to obtain dispersion system B.

[0055] Blending loading: Add dispersion system B to dispersion system A at a rate of less than 1 L / min; ultrasonically disperse for 2.3 h, followed by centrifugation;

[0056] First calcination process: The sample is then calcined at 750℃ for 2.1h, and the resulting sample is named NiSeZn(g-C3N4) / CNFs. After that, the sample is ground and sieved through a 600-mesh sieve.

[0057] Third, secondary high-temperature and high-pressure calcination process: The NiSeZn(g-C3N4) / CNFs sample is placed in the top press and calcined at 11 GPa and 1100℃ for 10 min.

[0058] Example 3

[0059] I. Preparation of modified carbon nanofibers (CNFs)

[0060] Alkali treatment: 68g of carbon nanofibers were treated with 28wt% sodium hydroxide solution for 2h.

[0061] Grafting modification: The alkali-treated carbon nanofibers were then placed in 50 mL of ethylene glycol and ultrasonically dispersed for 25 min. 2.9 g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent (Z-6020) and 1.2 g of melamine were added, and the mixture was heated to 72 °C and ultrasonically dispersed for another 1.6 h. Grafted modified carbon nanofibers were obtained. These were then washed with water and centrifuged to recover the washing liquid.

[0062] Freeze-drying treatment: The grafted modified carbon nanofibers were frozen at -3℃ for 6 hours, then freeze-dried in a vacuum drying oven, and ground and sieved through a 260-mesh sieve.

[0063] II. NiSeZn(g-C3N4) was grown on modified carbon nanofibers to prepare NiSeZn(g-C3N4) / CNFs;

[0064] Cleaning solution drying and calcination: Add 8.3g of dopamine and 20.9g of CE resin to 105g of cleaning solution, stir and react at 55℃ for 30h, dry and then calcine at 240℃ for 60min, cool and grind to nanoscale (400nm).

[0065] Preparation of dispersion system A: Dissolve 18g of melamine in 77g of deionized water, add 14.2g of ZnSO4·7H2O, stir and heat in a water bath at 80℃ for 28min to obtain dispersion system A;

[0066] Preparation of dispersion system B: The CNFs obtained above were dispersed in an ethanol solution, 10.5g of nano-sized nickel selenide and the above-mentioned calcined product were added, and the mixture was stirred and heated in a water bath at 80℃ for 18min to obtain dispersion system B.

[0067] Blending loading: Add dispersion system B to dispersion system A at a rate of less than 1 L / min; ultrasonically disperse for 2 h, followed by centrifugation.

[0068] First calcination process: The sample is then calcined at 680℃ for 2.2h. The resulting sample is named NiSeZn(g-C3N4) / CNFs. After that, the sample is ground and sieved through a 550-mesh sieve.

[0069] Third, secondary high-temperature and high-pressure calcination process: The NiSeZn(g-C3N4) / CNFs sample is placed in a top press and calcined at 10.6 GPa and 1180℃ for 7 min.

[0070] Comparative Example 1

[0071] The difference from Example 1 is that the mass ratio of carbon nanofibers, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent (Z-6020), and melamine is 100:1:0.5.

[0072] Comparative Example 2

[0073] The difference from Example 1 is that the mass ratio of nanoscale nickel selenide to carbon nanofibers is 0.5:1.

[0074] Comparative Example 3

[0075] The difference from Example 1 is that the secondary high-temperature and high-pressure calcination process involves placing the sample in a top press and sintering it at 15 GPa and 1500 °C for 15 minutes.

[0076] Comparative Example 4

[0077] The difference from Example 1 is that the cleaning solution was dried and calcined, then cooled and ground to 200 mesh.

[0078] Test Experiment

[0079] The composite bipolar plates prepared from the nanocomposite materials of Examples 1, 2, 3 and Comparative Examples 1, 2, 3 and 4 were subjected to the following tests: electrical conductivity (S / cm), thermal conductivity (×10w / mk), flexural strength (MPa), and compressive strength (MPa). The test standards were in accordance with GB / T20042.6-2011 "Proton exchange membrane fuel cells Part 6: Test methods for bipolar plate characteristics". The results are shown in Table 1 below.

[0080] Table 1. Performance of materials in each embodiment and comparative example.

[0081] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 electrical conductivity 192 186 195 180 191 167 155 thermal conductivity 5.9 5.4 6.3 4.3 5.1 4.8 4.6 flexural strength 49.8 43.9 51.7 43.9 36.8 30.7 40.9 compressive strength 80.7 88.2 91.4 84.4 81.9 71.1 76.5

[0082] The NiSeZn(g-C3N4) / CNFs nanocomposite material of this invention, through graft modification, freeze-drying, and secondary high-temperature and high-pressure calcination, enhances the composite material's comprehensive properties, including electrical conductivity (195 S / cm), thermal conductivity (6.3 × 10 W / mK), flexural strength (51.7 MPa), and compressive strength (91.4 MPa), making it advantageous for application in hydrogen fuel cell composite bipolar plates. Furthermore, the preparation method provided by this invention uses safe raw materials and recycles the cleaning solution, reducing waste liquid generation and avoiding environmental pollution.

Claims

1. A method for preparing a composite material NiSeZn(g-C3N4) / CNFs, characterized in that, It includes the following steps: S1. After treating carbon nanofibers with alkali, add them to ethylene glycol, sonicate them, add silane coupling agent and melamine for grafting modification, wash the modified carbon nanofibers with water, and recover the washing liquid. S2. After adding the cleaning solution to dopamine and CE resin and stirring to react, the product is dried, calcined, cooled, and then ground to nanoscale. S3. Prepare an aqueous solution containing melamine and ZnSO4 as dispersion system A; S4. Disperse the modified carbon nanofibers obtained in step S1 in ethanol, add nano-sized nickel selenide and the calcined product obtained in S2, and heat to obtain dispersion system B. S5. Add dispersion system B to dispersion system A, sonicate and then centrifuge; S6. The centrifuged sample was calcined to obtain the composite material NiSeZn(g-C3N4) / CNFs; In step S6, the calcination is divided into two calcination processes. The first calcination process is calcination at 600-750℃ for 2.1-2.3 hours. The second high-temperature and high-pressure calcination process is calcination at 10-11 GPa and 1100-1200℃ for 5-10 minutes.

2. The preparation method according to claim 1, characterized in that, In step S1, the alkali treatment involves soaking in an alkaline solution for 1-2 hours. The amount of ethylene glycol used is ethylene glycol to carbon nanofibers at a volume-to-mass ratio of 1:1-3, with units of L:kg. The ultrasonic treatment time is 20-30 minutes.

3. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of carbon nanofibers, silane coupling agent, and melamine is 50–85: 1.7~3.6; 0.8~1.5; the silane coupling agent is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane coupling agent.

4. The preparation method according to claim 1, characterized in that, In step S1, the modified carbon nanofibers after cleaning need to undergo freeze-denaturation treatment. The freeze-denaturation temperature is -10 to 0°C, and the treatment time is 3 to 10 hours.

5. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of cleaning solution to dopamine is 100-125:6.8-9.3, and the mass ratio of dopamine to CE resin is 1-2:3-7; the stirring reaction temperature is 50-65℃, and the reaction time is 24-40h; the calcination temperature is 200-320℃, and the calcination time is 50-70min; and the material is ground to 200-600nm.

6. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of melamine to ZnSO4 is 15–21: 7.35~9, of which, The mass concentration of melamine is 13% to 20%.

7. The preparation method according to claim 1, characterized in that, in step S4, the amount of nickel selenide is added according to the mass ratio of nickel selenide to carbon nanofibers of 0.1 to 0.3:1; the heating temperature is 80°C and the heating time is 15 to 20 min.

8. The preparation method according to claim 1, characterized in that, In step S5, the addition rate of dispersion system B to dispersion system A is less than 1 L / min, and the ultrasonic treatment time is 1.5 to 2.3 h.

9. The application of the composite material NiSeZn(g-C3N4) / CNFs obtained by the preparation method according to any one of claims 1-8 in the preparation of composite bipolar plates for hydrogen fuel cells.

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