A phosphoric acid low-adsorption electrode for high-temperature polymer electrolyte membrane fuel cells and its preparation method

Abstract

This invention discloses a phosphoric acid low-adsorption electrode plate for high-temperature polymer electrolyte membrane fuel cells and its preparation method. The method includes the following steps: (1) preparing a composite plate using a high-temperature, high-pressure melt pressing method or a solution mixing, volatilization, and shaping method; (2) etching a flow field structure onto the composite plate obtained in step (1), the flow field structure including grooves and ridges; (3) adding polymer material I to solvent A while stirring, and after the polymer material I is completely dissolved, adding graphene while stirring; (4) spraying the groove modification solution and ridge modification solution obtained in step (3) onto the grooves and ridges of the electrode plate with the etched flow field obtained in step (2), respectively, followed by drying, and then cooling to room temperature. The modified electrode plate provided by this invention is suitable for phosphoric acid fuel cells and high-temperature polymer electrolyte membrane fuel cells, effectively reducing phosphoric acid adsorption, slowing phosphoric acid loss from the membrane electrode, and extending the membrane electrode life.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature fuel cell technology, specifically relating to a phosphoric acid low-adsorption electrode plate for high-temperature polymer electrolyte membrane fuel cells and its preparation method. Background Technology

[0002] High-temperature polymer fuel cells have become a research hotspot due to their strong CO tolerance (coal content in the fuel can reach 5%). However, excessive phosphoric acid loss poses a significant challenge to the performance and lifespan of the fuel cell membrane electrode assembly (MEA). Currently, the electrodes of high-temperature fuel cells are mainly composites of graphite and polymer. The presence of porous structures within the electrodes and the regeneration pores formed by polymer degradation during lifespan testing cause phosphoric acid to gradually permeate into the electrodes through capillary action. This makes excessive phosphoric acid adsorption by the electrodes one of the main factors contributing to phosphoric acid loss.

[0003] Currently, researchers are trying to alleviate the problem of phosphoric acid loss caused by phosphoric acid adsorption by the plates by replacing graphite bipolar plates with metal bipolar plates (FUEL CELLS 16, 2016, No.1, 39–45). However, in high-temperature phosphoric acid environments, metal bipolar plates suffer from severe corrosion, which ultimately affects battery performance and lifespan. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a phosphoric acid low-adsorption electrode plate for high-temperature polymer electrolyte membrane fuel cells and its preparation method. Using graphite-based materials as the main component, the adsorption of phosphoric acid by the electrode plate is mitigated and corrosion is avoided through material composition and structure optimization and process development during the preparation process.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] This invention provides a method for preparing a phosphoric acid low-adsorption electrode plate for a high-temperature polymer electrolyte membrane fuel cell, the method comprising the following steps:

[0007] (1) Composite board preparation: Composite boards are prepared by high temperature and high pressure melt pressing or solution mixing volatilization shaping method;

[0008] (2) Sculpting of the flow field: The composite plate obtained in step (1) is sculpted to form a flow field structure, which includes grooves and ridges;

[0009] (3) Preparation of the solution for modifying the electrode surface: Add polymer material I to solvent A while stirring. After polymer material I is completely dissolved, add graphene while stirring. Stir for 0.5-2 h, and then sonicate or cell disrupt for 0.1-1 h. The total mass ratio of polymer material I and graphene to the volume ratio of solvent A is 1:20-1:5 g / mL, and the mass ratio of polymer material I to graphene is 1:13-1:4, to obtain the groove modification solution. The total mass ratio of polymer material I and graphene to the volume ratio of solvent A is 1:50-1:10 g / mL, and the mass ratio of polymer material to graphene is 1:30-1:10, to obtain the ridge modification solution.

[0010] (4) Surface modification of the electrode plate: The groove modification solution and ridge modification solution obtained in step (3) are sprayed onto the groove and ridge of the electrode plate with the engraved flow field obtained in step (2), respectively, and then dried and cooled to room temperature.

[0011] In the above technical solution, further, in step (1), the high-temperature and high-pressure melt pressing method includes the following steps:

[0012] A. First, thoroughly mix the carbon material with polymer material II;

[0013] B. Spread the mixture obtained in step A into the composite board mold. The thickness of the spread mixture is 1-3 mm higher than the depth of the mold. Place a metal plate on the mixture.

[0014] C. Place the mold into a hot press and press it together, then cool it down, and finally remove the composite plate.

[0015] In the above technical solution, further, in step A, the carbon material includes one or more of artificial graphite, flexible graphite, carbon fiber, carbon nanotubes, and graphene; the polymer material II includes one or more of polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene ether (PPO), polyvinylidene fluoride (PVDF), polysulfone (PSU), polyarylsulfone (PASF), polyarylate (PAR), polypyrrole (PPy), poly(styrene-ethylene-butene) block copolymer (SEBS), perfluoroethylene propylene (FEP), and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA); the mass ratio of the polymer material II to the carbon material is 1:20-1:8.

[0016] The carbon material and polymer material II are mixed using one or more of the following: an ultra-low mesh pulverizer, a planetary ball mill, a vertical spiral mixer, a planetary auger mixer, a V-type mixer, a double cone mixer, and a cylindrical mixer. The mixing operation adopts an intermittent phase method. The operation procedure of the pulverizer is that the initial mixing time does not exceed 20 seconds, and then the mixing time is gradually extended by 10 seconds each time. When the single running time reaches 1 minute, the time is no longer extended and continues to be mixed for 1 minute, with an interval of 5-20 minutes in between. The planetary ball mill uses a step-by-step acceleration and time extension method for mixing. The initial run is 10 rpm in both directions for 2 minutes, and then the speed is gradually increased in increments of 20 rpm. When the speed is increased to 300 rpm, it is no longer increased and continues to run at 300 rpm for 2 times. When using vertical spiral mixers, planetary auger mixers, V-type mixers, double cone mixers, and cylindrical mixers for solid mixing, an intermittent operation mode is used. The first three mixing times are 5 minutes with an interval of 1 minute in between, and the next four mixing times are 3 minutes with an interval of 3 minutes.

[0017] In the above technical solution, further, in step B, the metal plate is a copper plate, aluminum plate, zinc plate, iron plate, or alloy plate, and the thickness of the metal plate is 0.5-2mm. The metal plate has a hole for inserting a feedback temperature sensor, wherein the diameter of the hole is 0.1mm larger than the diameter of the sensor, and the depth is 1 / 2 the length or width of the metal plate.

[0018] In step B, the limiting height of the composite plate mold and the area of ​​the template can be adjusted according to the design dimensions of the electrode plate and the flow field structure.

[0019] In the above technical solution, further, in step C, the hot-pressing temperature is 350-500℃, and the hot-pressing process is divided into two steps: the first step has a pressure of 0-100 psi and a hot-pressing time of 10-20 min; the second step has a hot-pressing pressure of 10-150 psi / cm². 2 The hot pressing time is 2-6 minutes;

[0020] In step C, the cooling device is a steel plate with an internal circulating liquid, which is water at a temperature of 3-20℃.

[0021] In the above technical solution, further, in step (1), the solution mixing, evaporation, and shaping method includes the following steps:

[0022] A. Dissolve or disperse polymer material II in solvent B;

[0023] B. Add the carbon material to the polymer solution or dispersion obtained in step A, mix well, and then pour it into the composite plate mold;

[0024] C. Place the mold in an oven at 50-120℃ and heat for 0.5-6 hours to evaporate the solvent, then place it in an oven at 200-500℃ for 0.1-1 hours to bake, then place it in a cooling device to cool, and finally remove the composite board.

[0025] In the above technical solution, further, in step A, the polymer material II includes polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene ether (PPO), polyvinylidene fluoride (PVDF), polysulfone (PSU), polyarylsulfone (PASF), polyarylate (PAR), polypyrrole (PPy), poly(styrene-ethylene-butene) block copolymer (SEBS), perfluoroethylene propylene (FEP), tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA), and fluororubber. The polymer material II comprises one or more of the following: N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, chloroform, carbon tetrachloride, 1,1,2,2-tetrachloroethane, 1,1,1,2-tetrachloroethane, tetrahydrofuran, cyclobutanone, cyclohexanone, acetone, methyl isobutyl ketone, ethyl acetate, butyl acetate, isopropanol, ethanol, and water; the polymer material II is dissolved or dispersed in solvent B at a temperature of room temperature - 120°C. The polymer material II is added to solvent B by first adding a certain amount of solvent B to a container, and then adding polymer material II to solvent B while mechanically stirring at a speed of 80-300 rpm.

[0026] In the above technical solution, further, in step B, the carbon material includes one or more of artificial graphite, flexible graphite, carbon fiber, carbon nanotubes, and graphene; the mass ratio of polymer material II to carbon material is 1:25-1:10; the ratio of the total mass of polymer material II and carbon material to the volume of solvent B is 0.6-3 g / mL. The carbon material is added to the polymer solution obtained in step A in batches, with the first addition not exceeding 1 / 10 of the total amount added, the second addition not exceeding 1 / 8 of the total amount added, and the interval between each addition being ≥15 minutes. During addition, the solution must be mechanically stirred and sonicated simultaneously.

[0027] In the above technical solution, further, in step C, the cooling device is a steel plate with circulating liquid inside, and the circulating liquid is water with a temperature of 3-20℃.

[0028] In the above technical solution, further, in step (2), in the flow field structure, the width of the groove is 1-2 mm, the width of the ridge is 1-2 mm, and the depth of the groove is 0.6-0.7 mm;

[0029] In the above technical solution, further, in step (3), the polymer material I is one or more of polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysulfone (PSU), polyarylsulfone (PASF), polyarylate (PAR), polypyrrole (PPy), and perfluororubber; the solvent A is one or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, cyclobutanone, cyclohexanone, acetone, methyl isobutyl ketone, ethyl acetate, and butyl acetate.

[0030] In step (3), the method of spraying the modification solution onto the electrode plate engraved with the flow field is ultrasonic spraying or air pressure spraying; during the spraying process, one or two of the following methods, namely high-power ultrasound and cell disruption, are used to interfere with the modification solution to avoid the sedimentation of graphite solid particles.

[0031] In the above technical solution, further, in step (4), the drying method is as follows: the first drying temperature is 80-120℃ and the drying time is 1-4h; the second drying temperature is 350-500℃ and the drying time is 0.5-2h; after drying, the thickness of the modification material in the groove of the electrode flow field is 0.1-0.2mm, and the thickness of the modification material in the ridge of the electrode flow field is 0.02-0.2mm.

[0032] In another aspect, the present invention provides a phosphoric acid low-adsorption electrode plate prepared by the above preparation method.

[0033] The beneficial effects of this invention are as follows:

[0034] This invention uses graphite-based materials as the main component. By optimizing the material composition and structure of the electrode during the preparation process and combining it with process development, the adsorption of phosphoric acid by the electrode is alleviated while avoiding corrosion of the electrode. The modified electrode provided by this invention is suitable for phosphoric acid fuel cells and high-temperature polymer electrolyte membrane fuel cells. It can effectively reduce the adsorption of phosphoric acid, slow down the loss of phosphoric acid from the membrane electrode, and extend the life of the membrane electrode. Attached Figure Description

[0035] Figure 1 This is a graph showing the phosphoric acid content in the electrode plates after the battery start-stop test in Example 1. Detailed Implementation

[0036] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0037] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0038] Example 1

[0039] 1. Composite board preparation

[0040] This embodiment uses a high-temperature, high-pressure melt pressing method to prepare the composite board:

[0041] Mix 25g of polysulfone and 250g of graphene in a vertical spiral mixer for 5 minutes, with a 1-minute interval, repeating this process three times. Then mix for 3 minutes with a 3-minute interval four times. Spread the mixed solid evenly in the limiting area of ​​a self-made mold. The limiting area has equal length and width of 10cm and a depth of 12mm. The thickness of the solid spread in the mold is 1mm higher than the depth of the limiting area. Place a 1.5mm thick copper plate on top of the solid and then place them together on a 400℃ hydraulic press. First, pre-press with a force of 20 pounds for 15 minutes, then increase the pressure to 8000 pounds for hot pressing for 6 minutes. After hot pressing, quickly place the mixture in a cooling device at 15℃ for 20 minutes to cool.

[0042] 2. Flow field sculpting

[0043] The pressed electrode plate is placed on a vertical machining center for flow field engraving. The flow field is a serpentine flow field with a length and width of 7cm, a groove and ridge width of 1.2mm, and a groove depth of 0.7mm.

[0044] 3. Preparation of solutions for electrode surface modification

[0045] (a) Preparation of the modification solution in the flow field trench: 5g of perfluororubber was added to 700mL of a solution of cyclohexanone and butyl acetate mixed in a volume ratio of 1:1 while stirring. The perfluororubber was stirred at room temperature for 12h until it was completely dissolved. Then, 40g of graphene was added while stirring. After stirring for 1h, the solution was placed in a high-power ultrasonic machine for 0.5h to complete the preparation of the modification solution in the trench.

[0046] (b) Preparation of the ridge-mounted modification solution: The preparation of the ridge-mounted solution is the same as the preparation method and process of the solution in the trench, except that the ratio of polymer to solvent and the ratio of polymer to graphene in the solution are different. The specific implementation process is as follows: 5g of perfluororubber is added to 2000mL of a solution of cyclohexanone and butyl acetate in a volume ratio of 1:1 while stirring. After stirring at room temperature for 12h, the perfluororubber is completely dissolved. Then, 80g of graphene is added while stirring. After stirring for 1h, the solution is placed in a high-power ultrasonic machine for 0.5h to complete the preparation of the ridge-mounted modification solution.

[0047] 4. Surface finishing of electrode plates

[0048] The modification solution prepared in step 3 for the flow field grooves and ridges was sprayed onto the flow field grooves and ridges respectively using ultrasonic spraying. During the spraying process, the coating surface was dried using a hot air blower or drying oven before spraying a new solution. Spraying was stopped when the thickness of the modified surface in the grooves was 0.2 mm and the thickness of the modified surface on the ridges was about 0.05 mm. The sprayed electrode was then placed in an oven and dried at 100°C for 4 hours, and then the temperature was increased to 400°C for 1 hour. After drying, the electrode was quickly removed from the oven and cooled to room temperature to complete the modification of the electrode.

[0049] 5. Test of modified electrode plates

[0050] The membrane electrode was assembled into a single cell with a compression ratio of 0.85. Tests were conducted using the modified bipolar plate prepared above and a commercially available phenolic resin-graphite composite plate. The test conditions were 160℃ and 200 mA / cm². 2 A constant current start-stop test was conducted, with the start-stop mode being 10 hours of operation followed by 14 hours of intermittent operation. After 200 hours of testing, the battery was disassembled for analysis of the phosphoric acid content in the plates (the specific method for testing phosphoric acid content is referenced in the patent "A Method for Determining the Phosphoric Acid Content in a PBI / H3PO4 Doped Film" (Publication No. CN112834540A)).

[0051] Figure 1 To test the phosphoric acid content at different locations within the cathode-side electrode of the battery using different electrode plates, from... Figure 1 It can be seen that the electrode plate designed in this invention can significantly reduce the adsorption of phosphoric acid (by about 3-4 times), especially at the cathode gas outlet, where the adsorption of phosphoric acid by the electrode plate is significantly reduced.

[0052] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing a phosphoric acid low-adsorption electrode plate for a high-temperature polymer electrolyte membrane fuel cell, characterized in that, The method includes the following steps: (1) Composite plate preparation: Carbon material and polymer material II are used as raw materials to prepare composite plates by high temperature and high pressure melt pressing or solution mixing volatilization shaping method; (2) Sculpting of the flow field: The composite plate obtained in step (1) is sculpted to form a flow field structure, which includes grooves and ridges; (3) Preparation of the solution for modifying the electrode surface: Polymer material I is added to solvent A while stirring. After polymer material I is completely dissolved, graphene is added while stirring. Stir for 0.5-2 h, and then sonicate or cell disrupt for 0.1-1 h. The total mass ratio of polymer material I and graphene to the volume ratio of solvent A is 1:20-1:5 g / mL, and the mass ratio of polymer material I to graphene is 1:13-1:4, thus obtaining the modification solution in the electrode flow field groove. The total mass ratio of polymer material I and graphene to the volume ratio of solvent B is 1:50-1:

10. The mass ratio of polymer material I to graphene material is 1:30-1:10, and a ridge-modified solution for the electrode flow field is obtained. The ratio of polymer material I to solvent and the ratio of polymer material I to graphene material in the ridge-modified solution and the groove-modified solution are different. The polymer material I is one or more of polyphenylene sulfide (PPS), polyphenylene ether (PPO), polysulfone (PSU), polyarylsulfone (PASF), polyarylate (PAR), polypyrrole (PPy), and perfluororubber. (4) Surface modification of the electrode plate: The groove modification solution and ridge modification solution obtained in step (3) are sprayed onto the groove and ridge of the electrode plate with the flow field obtained in step (2), respectively, and then dried and cooled to room temperature.

2. The preparation method according to claim 1, characterized in that, In step (1), the high-temperature and high-pressure melt pressing method includes the following steps: A. First, thoroughly mix the carbon material with polymer material II; B. Spread the mixture obtained in step A into the composite board mold. The thickness of the spread mixture is 1-3 mm higher than the depth of the mold. Place a metal plate on the mixture. C. Place the mold into a hot press and press it together, then cool it down, and finally remove the composite plate.

3. The preparation method according to claim 2, characterized in that, In step A, the carbon material includes one or more of artificial graphite, flexible graphite, carbon fiber, carbon nanotubes, and graphene; the polymer material II includes one or more of polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene ether (PPO), polyvinylidene fluoride (PVDF), polysulfone (PSU), polyarylsulfone (PASF), polyarylate (PAR), polypyrrole (PPy), poly(styrene-ethylene-butene) block copolymer (SEBS), perfluoroethylene propylene (FEP), and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA); the mass ratio of polymer material II to carbon material is 1:20 to 1:

8. In step B, the metal plate is a copper plate, aluminum plate, zinc plate, iron plate or alloy plate, and the thickness of the metal plate is 0.5-2mm; In step C, the hot-pressing temperature is 350-500℃, and the hot-pressing process is divided into two steps. The first step has a pressure of 0-100 psi and a hot-pressing time of 10-20 min. The second step has a hot-pressing pressure of 10-150 psi / cm². 2 The hot pressing time is 2-6 minutes.

4. The preparation method according to claim 1, characterized in that, In step (1), the solution mixing, evaporation, and shaping method includes the following steps: A. Dissolve or disperse polymer material II in solvent B; B. Add the carbon material to the polymer solution or dispersion obtained in step A, mix well, and then pour it into the composite plate mold; C. Place the mold in an oven at 50-120℃ and heat for 0.5-6 hours to evaporate the solvent, then place it in an oven at 200-500℃ for 0.1-1 hours to bake, then place it in a cooling device to cool, and finally remove the composite board.

5. The preparation method according to claim 4, characterized in that, In step A, the polymer material II comprises one or more of the following: polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene ether (PPO), polyvinylidene fluoride (PVDF), polysulfone (PSU), polyarylsulfone (PASF), polyarylate (PAR), polypyrrole (PPy), poly(styrene-ethylene-butene) block copolymer (SEBS), perfluoroethylene propylene (FEP), and tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA); the solvent B is one or more of the following: N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, chloroform, carbon tetrachloride, 1,1,2,2-tetrachloroethane, 1,1,1,2-tetrachloroethane, tetrahydrofuran, cyclobutanone, cyclohexanone, acetone, methyl isobutyl ketone, ethyl acetate, butyl acetate, isopropanol, ethanol, and water; the polymer material II is dissolved or dispersed in solvent B at a temperature of room temperature - 120°C. In step B, the carbon material includes one or more of artificial graphite, flexible graphite, carbon fiber, carbon nanotubes, and graphene; the mass ratio of polymer material II to carbon material is 1:25 to 1:10; and the ratio of the total mass of polymer material II and carbon material to the volume of solvent B is 0.6-3 g / mL.

6. The preparation method according to claim 1, characterized in that, In step (2), the width of the groove in the flow field structure is 1-2 mm, the width of the ridge is 1-2 mm, and the depth of the groove is 0.6-0.7 mm.

7. The preparation method according to claim 1, characterized in that, In step (3), solvent A is one or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, cyclobutanone, cyclohexanone, acetone, methyl isobutyl ketone, ethyl acetate, and butyl acetate.

8. The preparation method according to claim 1, characterized in that, In step (4), the drying method is as follows: the first drying temperature is 80-120℃ and the drying time is 1-4 h; the second drying temperature is 350-500℃ and the drying time is 0.5-2 h; after drying, the thickness of the modification material in the groove of the electrode flow field is 0.1-0.2 mm, and the thickness of the modification material in the ridge of the electrode flow field is 0.02-0.2 mm.

9. A phosphoric acid low-adsorption electrode plate prepared by the preparation method according to any one of claims 1-8.

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