Microporous layer with efficient water management and method of making and use thereof

Abstract

The application belongs to the technical field of proton exchange membrane fuel cell cathode microporous layer preparation, and particularly relates to a microporous layer with high efficient water management and a preparation method and application thereof, and comprises the following steps: a mixed solution containing Co, Fe and Zn is prepared; the mixed solution is subjected to centrifugal treatment, and then freeze-drying is performed to obtain a precursor powder; the precursor powder is placed into a tube furnace to perform carbonization treatment, and a ZIF derived porous conductive material is prepared; the ZIF derived porous conductive material is mixed with a Nafion solution, water and an organic solvent in proportion to prepare a suspension, and then ultrasonic treatment is performed to obtain a microporous layer slurry; a base layer is placed on a heating table, a functional structure is prepared through a specific method, and the microporous layer is obtained after solvent evaporation. The ZIF material with high porosity and good conductivity is introduced into the microporous layer formula, and good gas transmission and water management capability can be realized, and oxygen transmission resistance is reduced.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane fuel cell cathode microporous layer preparation technology, specifically relating to a microporous layer with efficient water management, its preparation method and application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) use hydrogen and oxygen as reactants. Due to their low operating temperature and zero emissions, PEMFCs are widely used as stationary and portable electronic devices, thus gaining widespread attention as a future energy source. The widespread adoption of this renewable energy system has promoted the development of the hydrogen economy and is considered a potential solution to the global energy crisis. As is well known, a PEMFC consists of multiple components, including a proton exchange membrane (PEM), a catalyst layer (CL), a gas diffusion layer (GDL), and bipolar plates (BPs). The GDL mainly consists of a substrate layer and a microporous layer (MPL). The MPL improves the contact interface between the substrate layer and the CL. In a PEMFC, hydrogen and oxygen pass through the MPL to the catalyst layers at the anode and cathode, respectively. Water generated in the cathode catalyst layer tends to move into the membrane or return to the MPL.

[0003] Various water management problems can occur in fuel cells, referring to the phenomenon of "water shortage" or "flooding" inside the fuel cell. Of course, the proton exchange membrane with ionic groups is ionized by water. To maintain effective proton conductivity, the correct water content is required. However, excessive water can cause electrode flooding, thus hindering the electrochemical reaction. Therefore, MPL's material design can achieve more efficient water management and better electrochemical performance. Summary of the Invention

[0004] The purpose of this invention is to provide a microporous layer with efficient water management, its preparation method, and its application. This method introduces ZIF material with high porosity into the microporous layer, which can optimize the management of liquid water generated in the system during the operation of a proton exchange membrane fuel cell, resulting in a proton exchange membrane fuel cell with high electrochemical performance, thereby solving the technical problem of optimizing fuel cell water management in the actual use of proton exchange membrane fuel cells.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention provides a method for preparing a microporous layer with efficient water management, comprising the following steps:

[0007] (1) A mixed solution containing Co, Fe and Zn doped porous precursors was prepared by using an alcohol-based synthesis method;

[0008] (2) The mixed solution prepared in step (1) is centrifuged and then freeze-dried to obtain precursor powder. The precursor powder is placed in a tube furnace for carbonization treatment to prepare ZIF-derived porous conductive material doped with Co and Fe elements.

[0009] (3) The ZIF-derived porous conductive material obtained in step (2) is mixed with Nafion ionomer, water and organic solvent in proportion to form a suspension, and then subjected to ultrasonic treatment to obtain a microporous layer slurry.

[0010] (4) The substrate is placed on a heating stage, and the microporous layer slurry prepared in step (3) is sprayed onto carbon paper using a specific method to form a specific functional structure. After the solvent evaporates, the microporous layer is obtained.

[0011] Furthermore, in step (1), the specific preparation steps of the mixed solution are as follows:

[0012] 1) Dissolve compounds containing Co, Fe, and Zn elements in methanol, then add polyvinylpyrrolidone, sonicate for 10 min, and then magnetically stir for 20 min to obtain a homogeneous and transparent mixture.

[0013] 2) Add Ketjen black to the mixture prepared above to absorb metal atoms, then perform ultrasonic treatment for 5 minutes and magnetic stirring for 40 minutes in sequence, and then perform ice water bath treatment to obtain the mixture in ice water bath;

[0014] 3) A methanol solution containing 2-methylimidazole was rapidly added to the mixture in the ice-water bath under magnetic stirring at 400 rpm, and stirring was continued for 40 min to obtain a mixed solution of Co, Fe and Zn doped porous precursors.

[0015] Among them, the compound containing Fe is one of anhydrous ferrous sulfate or ferrous sulfide, the compound containing Co is one of cobalt nitrate hexahydrate, cobalt acetate, or cobalt acetate, and the compound containing Zn is zinc acetate.

[0016] Furthermore, in step (2), the specific steps of the carbonization treatment are as follows: the precursor powder is heated in 50-500 mL / min. -1 Under Ar protection, pyrolyze at 900-1500℃ for 2-5 hours, and after carbonization, naturally cool to room temperature under continuous Ar flow.

[0017] Furthermore, in step (3), the mass ratio of the ZIF-derived porous conductive material to Nafion ionomer, water, and organic solvent is (25-50):(1-10):(13-25):(32-64); the concentration of the suspension is 1-10 g / L; and the ultrasonic treatment time is 60 min.

[0018] Furthermore, in step (4), the temperature of the heating stage is 60-80°C, the base layer includes any one of carbon paper, carbon cloth, and foam metal, and the specific method includes obtaining the specific functional structure by means of template, screen printing or inkjet printing.

[0019] The present invention also provides a microporous layer with efficient water management prepared by the preparation method described above.

[0020] The present invention also provides an application of the microporous layer with efficient water management described above in improving the water management and electrochemical performance of fuel cells.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention provides a low-temperature (80°C) method for preparing microporous layers with efficient water management. It is applicable to a wide range of raw materials, has a simple preparation process, and uses mild processing conditions.

[0023] Compared to conventional microporous layer preparation methods, this invention introduces ZIF material, which has high porosity and good conductivity, into the microporous layer formulation. This enables better gas transport and water management capabilities, reduces oxygen transport resistance, and yields a proton exchange membrane fuel cell with high electrochemical performance. Furthermore, the fabricated functional structure utilizes a patterned construction, which effectively maintains the dynamic balance of water within the membrane electrode assembly, achieving better water management and ultimately improving fuel cell performance.

[0024] Water produced by the hydrogen-oxygen reaction and water molecules introduced by external reactant gases can cause water management imbalances within the fuel cell, leading to "flooding" and "water shortage" problems. This affects gas transport efficiency, reduces reaction rates, and impacts the ionomers in the catalyst layer and the proton conductivity of the proton exchange membrane. Existing research indicates that water management imbalances during fuel cell operation result in a significant decrease in the fuel cell's electrochemical performance, providing strong evidence for this hypothesis. Therefore, introducing highly conductive porous ZIF materials into the microporous layer material, compared to materials such as carbon black, acetylene black, and carbon nanotubes, can improve reaction efficiency due to the higher porosity of ZIF materials, resulting in a significant improvement in the electrochemical performance of proton exchange membrane fuel cells during actual operation. Attached Figure Description

[0025] Figure 1 This is a transmission electron microscope image of the ZIF material prepared in Example 1;

[0026] Figure 2 Contact angle test of the microporous layer prepared in Example 1;

[0027] Figure 3The polarization curve of the proton exchange membrane fuel cell prepared in Example 1 under test conditions of 100 kPa RH 100% is shown.

[0028] Figure 4 The polarization curve of the microporous layer prepared in Example 1 under test conditions of 100 kPa RH 70% for a proton exchange membrane fuel cell.

[0029] Figure 5 The polarization curve of the proton exchange membrane fuel cell prepared in Example 1 under test conditions of 100 kPa RH 30% is shown.

[0030] Figure 6 The images show specific functional structures of the prepared microporous layers. The left image shows a strip-shaped structure obtained by spraying a template; the middle image shows a dot-shaped structure obtained by inkjet printing; and the right image shows a star-shaped structure obtained by screen printing. Detailed Implementation

[0031] A method for preparing a microporous layer with efficient water management at low temperature, the method comprising the following steps:

[0032] (1) Using an alcohol-based synthesis method, compounds containing Co, Fe, and Zn elements were dissolved in methanol (40-120 ml), followed by the addition of polyvinylpyrrolidone. The mixture was ultrasonically treated for 10 min and then magnetically stirred for 20 min to obtain a homogeneous and transparent mixture. Then, Ketjen black (0.1-0.3 g) was added to the above solution to absorb metal atoms, followed by ultrasonic treatment for 5 min and magnetic stirring for 40 min, and then an ice-water bath treatment to obtain a mixture in the ice-water bath. A methanol solution (40-120 ml) containing 2-methylimidazole (3-6.2 g) was rapidly added to the mixture in the ice-water bath under magnetic stirring at 400 rpm, and stirring was continued for 40 min to obtain a mixed solution of Co, Fe, and Zn doped porous precursors.

[0033] (2) The above mixed solution was stirred at room temperature for 72 hours; then recovered using a centrifuge and freeze-dried to obtain precursor powder; the precursor powder was transferred to a tube furnace for carbonization treatment to obtain ZIF material obtained from Co and Fe doped ZIF-CB hybrid precursor.

[0034] (3) The ZIF material and Nafion ionomer prepared by mixing water and organic solvent are prepared into a suspension with a total concentration of 1-10 g / L in a certain proportion, and then ultrasonically treated for 2 hours to obtain a microporous slurry.

[0035] (4) The base layer is placed on the heating stage, and the above-mentioned microporous layer slurry is sprayed onto the carbon paper using a specific method to form a specific functional structure, thus preparing a microporous layer.

[0036] In step (1), the compound containing Fe is one of anhydrous ferrous sulfate (0.005-0.22g) or ferrous sulfide; the compound containing Co is one of cobalt nitrate hexahydrate (0.08-0.0326g) or cobalt acetate or cobalt acetate; the compound containing Zn is one of zinc acetate (0.312-1.248g); and Ketjen black (0.1-0.3g) is used as the base. The alcohol-based synthesis method used specifically involves slowing down the growth rate of Zif in a methanol solution, which can result in a smaller particle size of the synthesized material.

[0037] In step (2), the centrifuge is used for recycling 3-5 times, with each rotation speed of 10,000-30,000 r / min. The carbonization process is specifically carried out at 50-500 mL / min. -1 Under Ar protection, at 900-1500℃ (heating rate of 15℃ min) -1 After pyrolysis for 2-5 hours and carbonization, the material is naturally cooled to room temperature under continuous Ar flow. The resulting ZIF, or zeolite-like imidazole ester framework material, is a zeolite-like MOF material synthesized by reacting Zn(I) or Co(II) with imidazole ligands. Common zeolite-like imidazole ester framework materials include ZIF-1, ZIF-2, ZIF-4, ZIF-5, ZIF-7, ZIF-8, ZIF-9, ZIF-10, ZIF-11, ZIF-12, ZIF-14, and ZIF-15. -20, ZIF-23, ZIF-60, ZIF-61, ZIF-62, ZIF-64, ZIF-65, ZIF-67, ZIF-68, ZIF-69, ZIF-70, ZIF-71, ZIF-72, Z IF-73, ZIF-74, ZIF-75, ZIF-77, ZIF-78, ZIF-90, ZIF-95, ZIF-100, ZIF-224, ZIF-268, Zn / Co-ZIF, nZIF-8, etc.;

[0038] In step (3), the mass ratio of ZIF material, Nafion ionomer, water and organic solvent is (25-50):(1-10):(13-25):(32-64), and the organic solvent is one of ethylene glycol, tetrahydrofuran, anhydrous ethanol, isopropanol or methanol.

[0039] In step (4), the temperature of the heating stage is 60-80℃. The substrate layer includes any one of carbon paper, carbon cloth, and foamed metal. Specific methods include spraying (stenciling), inkjet printing, screen printing, etc. The specific functional structure of the final microporous layer is as follows: Figure 6As shown, the microporous layer is fabricated into strip-shaped structures (1 mm wide, 20 mm long) with a spacing of 1 mm; dot-shaped structures (1 mm in diameter) with a spacing of 1 mm; and star-shaped structures (1 mm in diameter) with a spacing of 1 mm. These structures form pressure drops at the fuel cell's inlet and outlet. By designing the functional structure of the microporous layer, the accumulated liquid water inside the fuel cell can be drained through the pressure drop, solving the flooding problem. (Except for...) Figure 6 Other similar non-completely covered specific functional structures are also included in this invention.

[0040] The following examples are used to further illustrate the present invention, but are not limited to the present invention.

[0041] Example 1

[0042] (1) Dissolve 1.248 g zinc acetate, 0.326 g cobalt nitrate hexahydrate, and 0.022 g anhydrous ferrous sulfate in 80 mL of methanol and 1.2 g polyvinylpyrrolidone. After sonication for 10 minutes, stir magnetically for 20 minutes to obtain a homogeneous and transparent mixture. Then, add 0.2 g Ketjen black to the above solution to absorb metal atoms, followed by sonication for 5 minutes and magnetic stirring for 30 minutes. Quickly add 80 mL of methanol containing 4.92 g 2-methylimidazole to the mixture in an ice-water bath under magnetic stirring (400 rpm) and continue stirring for 40 minutes.

[0043] (2) The mixture was stirred continuously at room temperature for 72 h. It was then recovered using a centrifuge and freeze-dried. The precursor powder was transferred to a tube furnace and heated at 200 ml / min. -1 Pyrolysis at 950℃ for 2 hours under Ar was performed, followed by carbonization and then natural cooling to room temperature under continuous Ar flow. No further post-treatment was performed after the precursor pyrolysis. ZIF material was obtained from the Co,Fe-doped ZIF-CB hybrid precursor. Transmission electron microscopy images of the ZIF material are shown below. Figure 1 As shown

[0044] (3) The synthesized ZIF material was prepared into a slurry according to a certain ratio. The ZIF material (Co / Fe-NC) and Nafion ionomer were mixed with deionized water and isopropanol to form a suspension (1:4:3:7). Then, the suspension was ultrasonically treated for 60 min to obtain a microporous layer slurry.

[0045] (4) A 2cm × 2cm piece of carbon paper (Toray 060) was cut as a substrate and placed on an 80℃ heating table. The above slurry was sprayed onto the carbon paper to prepare a microporous layer. It was named MPL-Z. GDL-3260 was used as a control sample and named MPL-C.

[0046] To verify the above effects, fuel cell performance tests were conducted on the self-made microporous layer. The specific steps are as follows:

[0047] Fuel cell testing

[0048] (1) The MPL-Z is attached to one side of the cathode catalyst layer, and the proton exchange membrane fuel cell is assembled on a pair of 5cm... 2 Between the single serpentine graphite bipolar flow field and the PTFE gasket, the compression rate is 21% and the torque is 4.5 Nm;

[0049] (2) Provide 1000 mL / min to the cathode -1 Air, anode supply constant flow rate of 200 mL / min -1 H2. The single cell operates at a temperature of 80℃ and a back pressure of 100kPa, with relative humidity of 100%RH, 70%RH and 30%RH under different test conditions;

[0050] (3) Using the linear voltammetric scanning method, the voltage is scanned from the open circuit voltage to 0.2V at a scanning speed of 0.35V / min;

[0051] The contact angle test of the microporous layer is as follows: Figure 2 As shown, the polarization curve of the proton exchange membrane fuel cell under the test conditions of 100 kPa RH 100% is as follows. Figure 3 As shown, the polarization curve of the proton exchange membrane fuel cell under the test conditions of 100 kPa RH 70% is as follows. Figure 4 As shown, the polarization curve of the proton exchange membrane fuel cell under the test conditions of 100 kPa RH 30% is as follows. Figure 5 As shown.

[0052] In summary, at high relative humidity, MPL-Z exhibits excellent hydrophobicity due to its large contact angle. Its high gas transport efficiency effectively solves the "flooding" problem. MPL-Z also possesses good porosity and conductivity, increasing the hydrogen-oxygen reaction rate. The generated water effectively addresses the "water shortage" problem, resulting in excellent water management balance in proton exchange membrane fuel cells. This improves the electrochemical performance of the battery.

[0053] Example 2

[0054] (1) Dissolve 1.248 g zinc acetate, 0.326 g cobalt nitrate hexahydrate, and 0.022 g anhydrous ferrous sulfate in 80 mL methanol and 1.2 g polyvinylpyrrolidone. After sonication for 10 minutes, stir magnetically for 20 minutes to obtain a homogeneous and transparent mixture. Then, add 0.4 g Ketjen black to the above solution to absorb metal atoms, followed by sonication for 5 minutes and magnetic stirring for 30 minutes. Quickly add 80 mL methanol containing 4.92 g 2-methylimidazole to the mixture in an ice-water bath under magnetic stirring (400 rpm) and continue stirring for 40 minutes.

[0055] (2) The mixture was stirred continuously at room temperature for 72 h. It was then recovered using a centrifuge and freeze-dried. The precursor powder was transferred to a tube furnace and heated at 200 ml / min. -1 Pyrolysis at 1100℃ for 2 hours under Ar, followed by carbonization, and then natural cooling to room temperature under continuous Ar flow. No further post-treatment is performed after the precursor pyrolysis; ZIF material is obtained from the Co,Fe-doped ZIF-CB hybrid precursor.

[0056] (3) The synthesized ZIF material was prepared into a slurry according to a certain ratio. The ZIF material (Co / Fe-NC) and Nafion ionomer were mixed with deionized water and isopropanol to form a suspension (2:5:3:7). Then, the suspension was ultrasonically treated for 60 min to obtain a microporous layer slurry.

[0057] (4) A 2cm × 2cm piece of carbon paper (Toray 060) was cut as a substrate and placed on an 80℃ heating table. The above slurry was sprayed onto the carbon paper to prepare a microporous layer. It was named MPL-Z. GDL-3260 was used as a control sample and named MPL-C.

[0058] To verify the above effects, fuel cell performance tests were conducted on the self-made microporous layer.

[0059] Same as Example 1.

[0060] Example 3

[0061] (1) Dissolve 1.248 g zinc acetate, 0.326 g cobalt nitrate hexahydrate, and 0.022 g anhydrous ferrous sulfate in 80 mL of methanol and 1.2 g polyvinylpyrrolidone. After sonication for 10 minutes, magnetic stirring for 20 minutes yields a homogeneous and transparent mixture. Then, add 0.6 g Ketjen black to the above solution to absorb metal atoms, followed by sonication for 5 minutes and magnetic stirring for 30 minutes. Quickly add 80 mL of methanol containing 4.92 g 2-methylimidazole to the mixture in an ice-water bath under magnetic stirring (400 rpm) and continue stirring for 40 minutes.

[0062] (2) The mixture was stirred continuously at room temperature for 72 h. It was then recovered using a centrifuge and freeze-dried. The precursor powder was transferred to a tube furnace and heated at 200 ml / min. -1 Pyrolysis was performed at 1250℃ for 2 hours under Ar, followed by carbonization, and then natural cooling to room temperature under continuous Ar flow. No further post-treatment was performed after the precursor pyrolysis, and ZIF material was obtained from the Co,Fe-doped ZIF-CB hybrid precursor.

[0063] (3) The synthesized ZIF material was prepared into a slurry according to a certain ratio. The ZIF material (Co / Fe-NC) and Nafion ionomer were mixed with deionized water and isopropanol to form a suspension (1:4:3:7). Then, the suspension was ultrasonically treated for 60 min to obtain a microporous layer slurry.

[0064] (4) A 2cm × 2cm piece of carbon paper (Toray 060) was cut as a substrate and placed on an 80℃ heating table. The above slurry was sprayed onto the carbon paper to prepare a microporous layer. It was named MPL-Z. GDL-3260 was used as a control sample and named MPL-C.

[0065] To verify the above effects, fuel cell performance tests were conducted on the self-made microporous layer.

[0066] Same as Example 1.

[0067] Example 4

[0068] (1) Dissolve 1.248 g zinc acetate, 0.326 g cobalt nitrate hexahydrate, and 0.022 g anhydrous ferrous sulfate in 80 mL methanol and 1.2 g polyvinylpyrrolidone. After sonication for 10 minutes, stir magnetically for 20 minutes to obtain a homogeneous and transparent mixture. Then, add 0.4 g Ketjen black to the above solution to absorb metal atoms, followed by sonication for 5 minutes and magnetic stirring for 30 minutes. Quickly add 80 mL methanol containing 4.92 g 2-methylimidazole to the mixture in an ice-water bath under magnetic stirring (400 rpm) and continue stirring for 40 minutes.

[0069] (2) The mixture was stirred continuously at room temperature for 72 h. It was then recovered using a centrifuge and freeze-dried. The precursor powder was transferred to a tube furnace and heated at 200 ml / min. -1 Pyrolysis under Ar for 2 hours, followed by carbonization, and then natural cooling to room temperature under continuous Ar flow. No further post-treatment is performed after the precursor pyrolysis; ZIF material is obtained from the Co,Fe-doped ZIF-CB hybrid precursor.

[0070] (3) The synthesized ZIF material was prepared into a slurry according to a certain ratio. The ZIF material (Co / Fe-NC) and Nafion ionomer were mixed with deionized water and isopropanol to form a suspension. Then, the suspension was ultrasonically treated for 60 min to obtain a microporous layer slurry.

[0071] (4) A 2cm × 2cm piece of carbon paper (Toray 060) was cut as a substrate and placed on a 70℃ heating stage. The above slurry was sprayed onto the carbon paper to prepare a microporous layer. It was named MPL-Z. GDL-3260 was used as a control sample and named MPL-C.

[0072] To verify the above effects, fuel cell performance tests were conducted on the self-made microporous layer.

[0073] Same as Example 1.

[0074] Example 5

[0075] (1) Dissolve 1.248 g zinc acetate, 0.326 g cobalt nitrate hexahydrate, and 0.022 g anhydrous ferrous sulfate in 80 mL methanol and 1.2 g polyvinylpyrrolidone. After sonication for 10 minutes, stir magnetically for 20 minutes to obtain a homogeneous and transparent mixture. Then, add 0.4 g Ketjen black to the above solution to absorb metal atoms, followed by sonication for 5 minutes and magnetic stirring for 30 minutes. Quickly add 80 mL methanol containing 4.92 g 2-methylimidazole to the mixture in an ice-water bath under magnetic stirring (400 rpm) and continue stirring for 40 minutes.

[0076] (2) The mixture was stirred continuously at room temperature for 72 h. It was then recovered using a centrifuge and freeze-dried. The precursor powder was transferred to a tube furnace and heated at 200 ml / min. -1 Pyrolysis under Ar for 2 hours, followed by carbonization, and then natural cooling to room temperature under continuous Ar flow. No further post-treatment is performed after the precursor pyrolysis; ZIF material is obtained from the Co,Fe-doped ZIF-CB hybrid precursor.

[0077] (3) The synthesized ZIF material was prepared into a slurry according to a certain ratio. The ZIF material (Co / Fe-NC) and Nafion ionomer were mixed with deionized water and isopropanol to form a suspension. Then, the suspension was ultrasonically treated for 60 min to obtain a microporous layer slurry.

[0078] (4) A 2cm x 2cm gas diffusion layer (GDL3260) is cut as a substrate and placed on an 80°C heating table. The above-mentioned slurry is sprayed onto carbon paper using a special mold. Different types of MPLs are then produced using specially designed molds. For example... Figure 6 As shown, the ZIF conductive material slurry is designed as a strip structure (each unit is 1 mm wide and 20 mm long). The spacing between the strips is 1 mm. This is used to prepare a microporous layer.

[0079] To verify the above effects, fuel cell performance tests were conducted on the self-made microporous layer.

[0080] Same as Example 1.

[0081] Example 6

[0082] (1) Dissolve 1.248 g zinc acetate, 0.326 g cobalt nitrate hexahydrate, and 0.022 g anhydrous ferrous sulfate in 80 mL methanol and 1.2 g polyvinylpyrrolidone. After sonication for 10 minutes, stir magnetically for 20 minutes to obtain a homogeneous and transparent mixture. Then, add 0.4 g Ketjen black to the above solution to absorb metal atoms, followed by sonication for 5 minutes and magnetic stirring for 30 minutes. Quickly add 80 mL methanol containing 4.92 g 2-methylimidazole to the mixture in an ice-water bath under magnetic stirring (400 rpm) and continue stirring for 40 minutes.

[0083] (2) The mixture was stirred continuously at room temperature for 72 h. It was then recovered using a centrifuge and freeze-dried. The precursor powder was transferred to a tube furnace and heated at 200 ml / min. -1 Pyrolysis under Ar for 2 hours, followed by carbonization, and then natural cooling to room temperature under continuous Ar flow. No further post-treatment is performed after the precursor pyrolysis; ZIF material is obtained from the Co,Fe-doped ZIF-CB hybrid precursor.

[0084] (3) The synthesized ZIF material was prepared into a slurry according to a certain ratio. The ZIF material (Co / Fe-NC) and Nafion ionomer were mixed with deionized water and isopropanol to form a suspension. Then, the suspension was ultrasonically treated for 60 min to obtain a microporous layer slurry.

[0085] (4) A 2cm x 2cm gas diffusion layer (GDL3260) is cut as a substrate and placed on an 80°C heating table. The above-mentioned slurry is sprayed onto carbon paper using a special mold. Different types of MPLs are then produced using specially designed molds. For example... Figure 6 As shown, the ZIF conductive material slurry is designed as a dotted structure (each unit is 1 mm wide and 1 mm long). The spacing between the dots is 1 mm. This is used to prepare a microporous layer.

[0086] To verify the above effects, fuel cell performance tests were conducted on the self-made microporous layer.

[0087] Same as Example 1.

[0088] The cathode microporous layer (MPL) was made of (Co / Fe-NC)ZIF conductive material. High-conductivity porous particles were obtained by conveniently introducing Co and Fe elements into the ZIF-8 framework precursor and pyrolyzing it at 950℃. The nanoscale porous particles were controllably sprayed onto carbon fiber paper to form the microporous layer. Its effect on proton exchange membrane fuel cells (PEMFCs) was investigated. The platinum loading was 0.3 mg / cm³. 2At these conditions, PEMFCs equipped with Z-MPL achieved excellent limiting power density peaks at 100% and 30% relative humidity. This invention demonstrates the importance of ZIF-derived conductive and porous materials for improving the performance of PEMFCs under extreme conditions.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a microporous layer with efficient water management, characterized in that, Includes the following steps: (1) A mixed solution containing Co, Fe and Zn doped porous precursors was prepared by using an alcohol-based synthesis method; (2) The mixed solution prepared in step (1) is centrifuged and then freeze-dried to obtain precursor powder. The precursor powder is placed in a tube furnace for carbonization treatment to prepare ZIF-derived porous conductive material doped with Co and Fe elements. (3) The ZIF-derived porous conductive material obtained in step (2) is mixed with Nafion ionomer, water and organic solvent in proportion to form a suspension, and then subjected to ultrasonic treatment to obtain a microporous layer slurry. (4) Base layer: Placed on a heating stage, the microporous layer slurry prepared in step (3) is sprayed onto carbon paper using a specific method to form a patterned specific functional structure. After the solvent evaporates, the microporous layer is obtained. In step (1), the specific preparation steps of the mixed solution are as follows: 1) Dissolve compounds containing Co, Fe, and Zn elements in methanol, then add polyvinylpyrrolidone, sonicate for 10 min, and then magnetically stir for 20 min to obtain a homogeneous and transparent mixture. 2) Add Ketjen black to the mixture prepared above to absorb metal atoms, then perform ultrasonic treatment for 5 minutes and magnetic stirring for 40 minutes in sequence, and then perform ice water bath treatment to obtain the mixture in ice water bath; 3) A methanol solution containing 2-methylimidazole was rapidly added to the mixture in the ice-water bath under magnetic stirring at 400 rpm, and stirring was continued for 40 min to obtain a mixed solution of Co, Fe and Zn doped porous precursors. Among them, the compound containing Fe is one of anhydrous ferrous sulfate or ferrous sulfide, the compound containing Co is one of cobalt nitrate hexahydrate or cobalt acetate, and the compound containing Zn is zinc acetate. In step (2), the specific steps of the carbonization treatment are as follows: the precursor powder is heated in 50-500 mL / min. -1 Under Ar protection, pyrolyze at 900-1500℃ for 2-5 hours, and after carbonization, naturally cool to room temperature under continuous Ar flow. In step (3), the mass ratio of the ZIF-derived porous conductive material to Nafion ionomer, water, and organic solvent is (25-50):(1-10):(13-25):(32-64); the concentration of the suspension is 1-10 g / L; and the ultrasonic treatment time is 2 h. In step (4), the temperature of the heating stage is 60-80°C, the base layer includes any one of carbon paper, carbon cloth, and foam metal, and the specific method includes obtaining the patterned specific functional structure by means of template, screen printing or inkjet printing.

2. A microporous layer with efficient water management prepared by the preparation method according to claim 1.

3. An application of the microporous layer with efficient water management as described in claim 2 in improving the water management and electrochemical performance of fuel cells.

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