Preparation method of PANI-ZIF-8 / PA composite coating on surface of metal bipolar plate

Abstract

The application discloses a preparation method of a PANI-ZIF-8 / PA composite coating on a metal bipolar plate surface, and comprises the following steps: firstly, placing a pretreated metal bipolar plate in a mixed solution, obtaining a conductive polymer PANI bottom layer through a constant current deposition method, then dispersing ZIF-8 and PA in deionized water to obtain ZIF-8 / PA paint, and then spin-coating the ZIF-8 / PA paint on the PANI coating to form a PANI-ZIF-8 / PA composite coating. The application improves the adhesion of the PANI bottom layer on the metal bipolar plate through the electro-deposition technology, and improves the corrosion resistance of the PANI-ZIF-8 / PA composite coating through the surface ZIF-8 / PA coating, so that the application has a good application prospect in the fields of proton exchange membrane fuel cells and hydrogen production by water electrolysis.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal corrosion protection, and particularly relates to a preparation method of a PANI-ZIF-8 / PA composite coating on a metal bipolar plate surface. BACKGROUND

[0002] Proton exchange membrane fuel cell (PEMFC) involves fuel (H2 and O2) and product (H2O), which are all super-clean substances, more friendly to the natural environment, pollution-free, and high in power generation efficiency, so PEMFC is known as one of the most promising power generation devices. PEMFC will degrade SO4 2- , Cl - and F - corrosive ions during operation, so that the solution is weakly acidic, and therefore the bipolar plate material needs to have strong corrosion resistance, and the selection of the bipolar plate material is particularly important. Metals are hot materials for manufacturing stainless steel plates due to their good electrical conductivity, thermal conductivity and mechanical properties, and common metal materials include some noble metals such as gold and platinum, but the prices of the noble metals are high, and the noble metals are not suitable for wide application; stainless steel (SS) is the first choice material due to its good corrosion resistance, easy processing, low cost and high commercial value. However, in the acidic working environment of the bipolar plate, stainless steel faces serious corrosion problems, and therefore certain measures need to be taken to prevent corrosion of the stainless steel.

[0003] The conductive polymer coating has good physical shielding performance and anode protection effect, and has broad research prospects in the field of metal corrosion protection. However, a single conductive polymer coating has problems such as pore defects, poor adhesion, insufficient conductivity and the like, which limit its application in the field of bipolar plates.

[0004] In the acidic working environment of PEMFC, polyaniline has better development prospects in the corrosion protection of metal stainless steel plates due to its high conductivity and environmental stability, and is widely used in the surface corrosion protection of materials. DeBerry W found that the stainless steel bipolar plate coated with the conductive polyaniline coating can produce good protection effect on the anode; Karpakam V prepared polyaniline / molybdate composite material with oxalic acid, and the polyaniline / molybdate composite material has good corrosion resistance, but the pore structure of the polyaniline affects its long-term immersion performance. Therefore, the single conductive polymer coating or the composite coating doped with a simple slow-release agent has poor adhesion on the stainless steel bipolar plate, and the long-term service performance of the coating is insufficient, and therefore the existing technology needs to be improved to improve the corrosion resistance. SUMMARY

[0005] This application addresses the shortcomings of existing technologies, such as poor adhesion and poor long-term immersion performance on stainless steel bipolar plates, by providing a method for preparing a PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate. The method involves spin-coating ZIF-8 material, which has excellent physical shielding properties, onto a polyaniline coating to obtain a composite coating with high conductivity, high corrosion resistance, and high adhesion, thus meeting the requirements of proton exchange membrane fuel cells and proton exchange membrane water electrolysis for metal bipolar plates.

[0006] Technical solution:

[0007] To achieve the above objectives, this application provides the following technical solution:

[0008] A method for preparing a PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate, the method comprising the following steps:

[0009] Step 1: Sand the metal bipolar plate substrate with sandpaper, sonicate with ethanol for 10 minutes, and then clean with deionized water;

[0010] Step 2: Dissolve 3-5g of 98% sulfuric acid in 100mL of deionized water by mass-volume ratio, and stir continuously at a speed of [missing information].

[0011] Add 2-4g of aniline dropwise at 500-1000rpm to obtain an aniline prepolymer solution, i.e., a polyaniline solution.

[0012] Step 3: Using the metal bipolar plate substrate cleaned with deionized water in Step 1 as the working electrode, the platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, a polyaniline coating is prepared by constant current deposition in the aniline prepolymer solution obtained in Step 2.

[0013] Step 4: Dissolve 5-8g of zinc nitrate hexahydrate and 5.5-7.5g of 2-methylimidazole in 100-200ml of methanol according to the mass-volume ratio, stir vigorously at 1500-2000rpm for 5min, centrifuge at 8000rpm for 10min, repeat the centrifugation process 3-5 times, and dry at 80℃ overnight to obtain ZIF-8 material;

[0014] Step 5: Dissolve 50-100 mg of water-based acrylate PA in 3-5 ml of deionized water by mass-volume ratio, sonicate for 10 min, continuously stir the acrylic resin solution at a stirring speed of 800-1000 rpm, add 100-200 mg of ZIF-8 material obtained in step 4 to the acrylic resin solution to form a ZIF-8 / PA mixture.

[0015] Step 6: Spin-coat the ZIF-8 / PA mixture obtained in Step 5 onto the surface of the polyaniline coating obtained in Step 3 using a spin coater. Each spin coat covers the entire sample surface. Repeat the spin coating process 3-5 times and allow it to air dry for 24 hours to obtain the PANI-ZIF-8 / PA composite coating on the surface of the metal bipolar plate.

[0016] Furthermore, in step 1, the metal bipolar plate substrate is a 304 stainless steel substrate.

[0017] Furthermore, in step 2, the molar ratio of aniline to sulfuric acid is 1:3-3:1.

[0018] Furthermore, the stirring reaction time in step 2 is 1-6 hours.

[0019] Furthermore, in step 3, the polarization current during constant current deposition is 0.1-10 mA / cm. 2 The deposition time is 10-40 min.

[0020] Furthermore, in step 4, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:4-2:1.

[0021] Furthermore, the continuous stirring reaction time in step 5 is 24-36 hours.

[0022] Furthermore, in step 6, the spin coating speed of the spin coater is 1000-4000 rpm, and the spin coating time is 30-120 s.

[0023] Beneficial effects:

[0024] This application provides a method for preparing a PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate, which has the following advantages compared with the prior art:

[0025] 1. This application effectively solves the problem of pore defects in single conductive polymer coatings by spin-coating ZIF-8 material with excellent physical shielding properties onto the original conductive polyaniline coating substrate, and significantly improves the corrosion resistance of conductive polymer coatings;

[0026] 2. The spin-coated ZIF-8 / PA coating of this application improves the interface structure between the coating and the metal substrate, prolongs the path for corrosive ions to penetrate into the coating and contact the metal surface, and improves the adhesion and long-term anti-corrosion performance of the PANI coating on the metal surface.

[0027] 3. The products generated after the partial collapse of the ZIF-8 material introduced in this application under acidic conditions exhibit excellent corrosion inhibition properties. 2-Methylimidazole is both a ligand for the synthesis of ZIF-8 and an active corrosion inhibitor. The corrosion resistance of the composite coating is enhanced through the combined effects of slow release and shielding. Attached Figure Description

[0028] Figure 1 The images show the surface coating changes of pure polyaniline coating and composite coating (PANI-ZIF-8 / 100PA) during the immersion test, where (a) is the pure polyaniline coating before immersion, (b) is the PANI-ZIF-8 / 100PA before immersion, (c) is the pure polyaniline coating after immersion, and (d) is the PANI-ZIF-8 / 100PA after immersion. Detailed Implementation

[0029] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Example 1:

[0031] A method for preparing a PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate includes the following steps:

[0032] Step 1: Sand the 304 stainless steel substrate with sandpaper, sonicate with ethanol for 10 minutes, and then clean with deionized water;

[0033] Step 2: Dissolve 4g of sulfuric acid in 100mL of deionized water and stir continuously at a speed of 500-1000rpm. At the same time, add 2.79g of aniline dropwise to obtain an aniline prepolymer solution, i.e., a polyaniline solution.

[0034] Step 3: Using the 304 stainless steel substrate cleaned with deionized water in Step 1 as the working electrode, the platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, a polyaniline coating is prepared by constant current deposition at 5 mA for 20 min in the polyaniline solution obtained in Step 2.

[0035] Step 4: Dissolve 5.95g of zinc nitrate hexahydrate and 6.568g of 2-methylimidazole in 100-200ml of methanol, stir vigorously at 1500-2000rpm for 5min, centrifuge at 8000rpm for 10min, repeat the centrifugation process 3-5 times, and dry at 80℃ overnight to obtain ZIF-8 material;

[0036] Step 5: Dissolve 100 mg of aqueous acrylic resin in 5 mL of deionized water, sonicate for 10 min, and stir continuously for 24 h at a stirring speed of 800-1000 rpm. Slowly add 200 mg of ZIF-8 material prepared in step 4 to the acrylic resin solution to form a ZIF-8 / PA mixture.

[0037] Step 6: Spin-coat the ZIF-8 / PA mixture prepared in Step 5 onto the polyaniline coating surface prepared in Step 3 at 2000 rpm for 10 min using a spin coater. Spin coat the entire sample surface each time, and repeat 3-5 times. Allow to air dry naturally for 24 h to obtain the PANI-ZIF-8 / PA composite coating on the surface of the metal bipolar plate. This coating is used as a conductive and anti-corrosion coating on the surface of the metal bipolar plate in proton exchange membrane fuel cells and proton exchange membrane water electrolysis for hydrogen production.

[0038] Example 2:

[0039] A method for preparing a PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate includes the following steps:

[0040] Step 1: Sand the 304 stainless steel substrate with sandpaper, sonicate with ethanol for 10 minutes, and then clean with deionized water;

[0041] Step 2: Dissolve 4g of sulfuric acid in 100mL of deionized water, stir continuously at 500-1000rpm, and add 2.79g of aniline dropwise to obtain aniline prepolymer solution, i.e., polyaniline solution.

[0042] Step 3: Using the 304 stainless steel substrate cleaned with deionized water in Step 1 as the working electrode, the platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, the polyaniline solution obtained in Step 2 is deposited with a constant current of 5mA for 20min to prepare a polyaniline coating.

[0043] Step 4: Dissolve 5.95g of zinc nitrate hexahydrate and 6.568g of 2-methylimidazole in 100-200ml of methanol, stir vigorously at 1500-2000rpm for 5min, centrifuge at 8000rpm for 10min, repeat the centrifugation process 3-5 times, and dry at 80℃ overnight to obtain ZIF-8 material;

[0044] Step 5: Dissolve 50 mg of aqueous acrylate in 5 mL of deionized water, sonicate for 10 min, and stir continuously for 24 h at a stirring speed of 800-1000 rpm. Slowly add 200 mg of the ZIF-8 material prepared in step 4 to the acrylic resin solution to form a ZIF-8 / PA mixture.

[0045] Step 6: Spin-coat the ZIF-8 / PA mixture prepared in Step 5 onto the polyaniline coating surface prepared in Step 3 using a spin coater at 2000 rpm. Spin coat the entire sample surface each time, and spin coat 3-5 times. Allow it to air dry naturally for 24 hours to obtain the PANI-ZIF-8 / PA composite coating on the surface of the metal bipolar plate.

[0046] Example 3:

[0047] A method for preparing a PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate includes the following steps:

[0048] Step 1: Sand the 304 stainless steel substrate with sandpaper, sonicate with ethanol for 10 minutes, and then clean with deionized water;

[0049] Step 2: Dissolve 4g of 98% sulfuric acid in 100mL of deionized water and stir continuously at a speed of 500-1000rpm. At the same time, add 2.79g of aniline dropwise to obtain an aniline prepolymer solution, i.e., a polyaniline solution.

[0050] Step 3: Using the 304 stainless steel substrate cleaned with deionized water in Step 1 as the working electrode, the platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, the polyaniline solution obtained in Step 2 is deposited with a constant current of 5mA for 20min to prepare a polyaniline coating.

[0051] Step 4: Dissolve 5.95g of zinc nitrate hexahydrate and 6.568g of 2-methylimidazole in 100-200ml of methanol, stir vigorously at 1500-2000rpm for 5min, centrifuge at 8000rpm for 10min, repeat the centrifugation process 3-5 times, and dry at 80℃ overnight to obtain ZIF-8 material;

[0052] Step 5: Dissolve 100 mg of aqueous acrylate in 5 mL of deionized water, sonicate for 10 min, and stir continuously for 24 h at a stirring speed of 800-1000 rpm. Slowly add 100 mg of the ZIF-8 material prepared in step 4 to the acrylic resin solution to form a ZIF-8 / PA mixture.

[0053] Step 6: Spin-coat the ZIF-8 / PA mixture prepared in Step 5 onto the polyaniline coating surface prepared in Step 3 using a spin coater at 2000 rpm. Each spin coat covers the entire sample surface. Repeat the spin coat process 3-5 times and allow to air dry for 24 hours to obtain the PANI-ZIF-8 / PA composite coating on the surface of the metal bipolar plate.

[0054] Example 4:

[0055] A method for preparing a PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate includes the following steps:

[0056] Step 1: Sand the 304 stainless steel substrate with sandpaper, sonicate with ethanol for 10 minutes, and then clean with deionized water;

[0057] Step 2: Dissolve 4g of 98% sulfuric acid in 100mL of deionized water and stir continuously at a speed of 800-1000rpm. At the same time, add 2.79g of aniline dropwise to obtain an aniline prepolymer solution, i.e., a polyaniline solution.

[0058] Step 3: Using the 304 stainless steel substrate cleaned with deionized water in Step 1 as the working electrode, the platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, the polyaniline solution obtained in Step 2 is deposited with a constant current of 5mA for 20min to prepare a polyaniline coating.

[0059] Step 4: Dissolve 5.95g of zinc nitrate hexahydrate and 6.568g of 2-methylimidazole in 100-200ml of methanol, stir vigorously at 1500-2000rpm for 5min, centrifuge at 8000rpm for 10min, repeat the centrifugation process 3-5 times, and dry at 80℃ overnight to obtain ZIF-8 material;

[0060] Step 5: Dissolve 50 mg of aqueous acrylate in 5 mL of deionized water, sonicate for 10 min, and continuously stir the acrylic resin solution for 24 h at a stirring speed of 800-1000 rpm. Slowly add 100 mg of ZIF-8 material prepared in step 4 to the acrylic resin solution to form a ZIF-8 / PA mixture.

[0061] Step 6: Spin-coat the ZIF-8 / PA mixture prepared in Step 5 onto the polyaniline coating surface prepared in Step 3 using a spin coater at 2000 rpm. Each spin coat covers the entire sample surface. Repeat the spin coat process 3-5 times and allow to air dry for 24 hours to obtain the PANI-ZIF-8 / PA composite coating on the surface of the metal bipolar plate.

[0062] Table 1 Corrosion voltage and corrosion current obtained from four types of PANI-ZIF-8 / PA composite coatings (PANI-200ZIF-8 / 100PA, PANI-200ZIF-8 / 50PA, PANI-100ZIF-8 / 100PA, PANI-100ZIF-8 / 50PA), pure polyaniline coating, and 304SS.

[0063]

[0064] From Table 1 and Figure 1 It is evident that, protected by the polyaniline and PANI-ZIF-8 / PA composite coating, the stainless steel bipolar plate exhibits superior performance. corr The significant reduction indicates that the coating can significantly reduce the corrosion rate of the bipolar plate by corrosive media. Immersion tests revealed that the pure polyaniline coating has poor adhesion to stainless steel and is prone to peeling off, while the PANI-ZIF-8 / PA composite coating maintained its integrity after immersion tests, indicating good long-term service performance.

Claims

1. A method for preparing a PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate, characterized in that, The method includes the following steps: Step 1: Sand the metal bipolar plate substrate with sandpaper, sonicate with ethanol for 10 minutes, and then clean with deionized water; Step 2: Dissolve 3-5g of 98% sulfuric acid in 100mL of deionized water by mass-volume ratio, and stir continuously at a stirring speed of 500-1000rpm. At the same time, add 2-4g of aniline dropwise to obtain aniline prepolymer solution, i.e., polyaniline solution. Step 3: Using the metal bipolar plate substrate cleaned with deionized water in Step 1 as the working electrode, the platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, a polyaniline coating is prepared by constant current deposition in the aniline prepolymer solution obtained in Step 2. Step 4: Dissolve 5-8g of zinc nitrate hexahydrate and 5.5-7.5g of 2-methylimidazole in 100-200ml of methanol according to the mass-volume ratio, stir vigorously at 1500-2000rpm for 5min, centrifuge at 8000rpm for 10min, repeat the centrifugation process 3-5 times, and dry at 80℃ overnight to obtain ZIF-8 material; Step 5: Dissolve 50-100 mg of water-based acrylate PA in 3-5 ml of deionized water by mass-volume ratio, sonicate for 10 min, continuously stir the acrylic resin solution at a stirring speed of 800-1000 rpm, add 100-200 mg of ZIF-8 material obtained in step 4 to the acrylic resin solution to form a ZIF-8 / PA mixture. Step 6: Spin-coat the ZIF-8 / PA mixture obtained in Step 5 onto the surface of the polyaniline coating obtained in Step 3 using a spin coater. Each spin coat covers the entire sample surface. Repeat the spin coating process 3-5 times and allow it to air dry for 24 hours to obtain the PANI-ZIF-8 / PA composite coating on the surface of the metal bipolar plate.

2. The method for preparing the PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate according to claim 1, characterized in that: In step 2, the molar ratio of aniline to sulfuric acid is 1:3-3:

1.

3. The method for preparing the PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate according to claim 1, characterized in that: The stirring reaction time in step 2 is 1-6 hours.

4. The method for preparing the PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate according to claim 1, characterized in that: In step 3, the polarization current during constant current deposition is 0.1-10 mA / cm. 2 The deposition time is 10-40 min.

5. The method for preparing the PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate according to claim 1, characterized in that: In step 4, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:4-2:

1. The mixture is stirred vigorously for 5 minutes and then centrifuged at 8000 rpm.

6. The method for preparing the PANI-ZIF-8 / PA composite coating on the surface of the metal bipolar plate according to claim 1, characterized in that, The continuous stirring reaction time in step 5 is 24-36 hours.

7. The method for preparing the PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate according to claim 1, characterized in that: In step 6, the spin coating speed of the spin coater is 1000-4000 rpm, and the spin coating time is 30-120 s.

8. The method for preparing the PANI-ZIF-8 / PA composite coating on the surface of a metal bipolar plate according to claim 1, characterized in that: In step 1, the metal bipolar plate substrate is a 304 stainless steel substrate.

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