A heat pump gas diffusion layer based on cold start and over-temperature protection and its preparation method and application

Abstract

The present invention provides a heat pump type gas diffusion layer based on cold start and over-temperature protection, and its preparation method and application, which belong to the field of fuel cells. The present invention provides a heat pump type gas diffusion layer based on cold start and over-temperature protection, and a heat pump adsorbent metal organic framework (MOF) material, MIL-101 (Cr), is introduced into the microporous layer. MIL-101 (Cr) can adsorb water and release heat energy at low temperatures, reduce the water content on the outside of the membrane electrode and in the gas diffusion layer during the cold start process, delay the freezing process, and provide a certain auxiliary effect for its warming. When the temperature exceeds the normal operating temperature, MIL-101 (Cr) desorbs water and absorbs heat energy to assist the membrane electrode in water retention and cooling. Thereby, it achieves the function of assisting in regulating water and heat management for the cold start and over-temperature protection of the fuel cell.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a heat pump type gas diffusion layer based on cold start and over-temperature protection, and a preparation method and application thereof. Background Art

[0002] A fuel cell is a power generation device that converts the chemical energy of a fuel and an oxidant directly into electrical energy. However, barriers to the use of fuel cell electric vehicles in cold and high-altitude regions have significantly limited their widespread adoption. To broaden the application of fuel cells and make them more adaptable to these harsh environments, research on fuel cell cold start technology has become a key development trend to overcome this bottleneck. The core of cold start technology lies in balancing the water content within the fuel cell and the heating rate. During startup, if a large amount of water is generated at the cathode while the temperature within the stack remains below freezing, the membrane electrode (ME) can become covered with ice, leading to startup failure and even irreversible damage to the ME and GDL. Excessive drying of the anode during shutdown and purge can also lead to poor startup performance and even failure. Therefore, balancing the relationship between water content and temperature within the ME is crucial for fuel cell cold start. Furthermore, during hydrogen fuel cell operation, localized overheating can occasionally occur, resulting in dehydration and performance degradation of the membrane, potentially leading to irreversible damage to the ME. Therefore, it is crucial to provide auxiliary control of the ME where these localized overheating occur to prevent performance degradation or membrane damage.

[0003] As a key component of the membrane electrode (MEA) of a proton exchange membrane fuel cell, the gas diffusion layer (GDL) diffuses the reactant gases (hydrogen, air, and water vapor) and supports the catalyst layer. It also promptly discharges the water generated during the fuel cell reaction. Traditional GDLs rely on macropores and micropores to participate in water management of the MEA and provide no additional assistance for cold start technology. Designing a GDL that can assist in water and heat management of the MEA during cold starts and local overheating may be a new approach. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a heat pump gas diffusion layer based on cold start and over-temperature protection, as well as its preparation method and application. The heat pump gas diffusion layer provided by the present invention provides auxiliary functions of water and heat regulation for cold start of fuel cells.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a heat pump type gas diffusion layer based on cold start and over-temperature protection, comprising a stacked base layer and a microporous layer, wherein the microporous layer contains a heat pump adsorbent material, and the heat pump adsorbent material is a metal organic framework material.

[0007] Preferably, the metal organic framework material is MIL-101 (Cr).

[0008] Preferably, the grain size of the MIL-101(Cr) is 40-200 nm.

[0009] Preferably, the MIL-101(Cr) grows on the surface of the chopped carbon fibers.

[0010] Preferably, the material of the base layer includes carbon paper, carbon cloth, carbon felt or a conductive polymer-based film.

[0011] Preferably, the thickness of the microporous layer is 20-50 μm.

[0012] The present invention also provides a method for preparing a heat pump type gas diffusion layer based on cold start and over-temperature protection as described in the above technical solution, comprising the following steps:

[0013] mixing the metal organic framework material and a solvent to obtain a slurry;

[0014] The slurry is coated on the surface of the base layer and then subjected to a pressing heat treatment to obtain the heat pump type gas diffusion layer based on cold start and over-temperature protection.

[0015] Preferably, the slurry further contains conductive carbon black and PTFE emulsion.

[0016] Preferably, the pressing heat treatment comprises the following steps: keeping the temperature at 250° C. for 30 to 40 minutes, then heating the temperature to 330° C. and keeping the temperature for 30 to 40 minutes; the pressure of the pressing heat treatment is 0.2 to 0.25 MPa.

[0017] The present invention also provides the application of the heat pump gas diffusion layer based on cold start and over-temperature protection described in the above technical solution or the heat pump gas diffusion layer based on cold start and over-temperature protection prepared by the preparation method described in the above technical solution in a fuel cell.

[0018] The present invention provides a heat pump type gas diffusion layer based on cold start and over-temperature protection, comprising a stacked base layer and a microporous layer, wherein the microporous layer contains a heat pump adsorbent material, and the heat pump adsorbent material is a metal organic framework material.

[0019] The present invention introduces a heat pump adsorption adsorbent material metal organic framework (MOF). By utilizing the water absorption characteristics of this type of MOF material, it can adsorb water molecules that diffuse to the surface of the catalyst layer at the beginning of cold start operation, forming bound water in the MOF material, reducing the free water content between the catalyst layer and the gas diffusion layer, and at the same time releasing adsorption heat, helping to accelerate the temperature rise of the membrane electrode, delaying the freezing process of the membrane electrode, and performing certain water management and thermal regulation auxiliary functions on the outside of the membrane electrode and inside the gas diffusion layer. In addition, when hydrogen fuel cells operate at high electrical density, the temperature generally does not exceed 80°C. Once overheating occurs, the membrane electrode will first suffer from severe dehydration, and even irreversible failure may occur. The MOF material will gradually desorb at high temperature, absorb heat, release crystal water, provide a certain water retention effect and assist in cooling the membrane electrode. In particular, when the temperature approaches 85°C, it will reach its maximum desorption peak, absorbing heat energy with the highest efficiency, releasing water molecules, thereby assisting in cooling the membrane electrode and providing a certain amount of water, playing an auxiliary role in protecting the membrane electrode.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention uses the heat pump adsorbent MOF material MIL-101 (Cr) as the key material of the microporous layer of the gas diffusion layer. MIL-101 (Cr) can adsorb water and release heat energy at low temperatures, reducing the water content outside the membrane electrode and inside the gas diffusion layer during the cold start process, and providing a certain auxiliary effect for its heating.

[0022] 2. The MIL-101(Cr) described in the present invention desorbs water and absorbs heat energy when the temperature exceeds the normal operating temperature, thereby helping to accelerate the cooling of the membrane electrode and releasing water molecules to prevent the membrane electrode from drying out due to local overheating.

[0023] 3. The heat pump adsorbent material MIL-101(Cr) of the present invention has nanocrystalline particles with a size of 40 to 200 nm and uses chopped carbon fibers as a growth substrate so as to achieve the effect of being distributed in most pores of the microporous layer.

[0024] 4. The heat pump adsorbent material MIL-101(Cr) described in the present invention has an ultra-high specific surface area, high adsorption capacity and a stable framework structure. During the adsorption and desorption of water, no volume change occurs, which adds additional burden to the membrane electrode.

[0025] 5. The heat pump adsorbent material MIL-101(Cr) of the present invention has extremely high thermal stability, and its pyrolysis temperature is much higher than the operating temperature of the fuel cell, which can ensure that it will not be pyrolyzed during long-term use.

[0026] The present invention also provides a method for preparing the heat pump type gas diffusion layer based on cold start and over-temperature protection as described in the above technical solution. The preparation method of the present invention is simple to operate and suitable for industrial application. DETAILED DESCRIPTION

[0027] The present invention provides a heat pump type gas diffusion layer based on cold start and over-temperature protection, comprising a stacked base layer and a microporous layer, wherein the microporous layer contains a heat pump adsorbent material, and the heat pump adsorbent material is a metal organic framework material.

[0028] In the present invention, unless otherwise specified, the raw materials used are commercially available products in the art.

[0029] In the present invention, the metal organic framework material is preferably MIL-101 (Cr), which can adsorb water and release heat energy at low temperatures, desorb water and absorb heat energy at high temperatures, thereby starting the auxiliary regulation function during cold start and membrane electrode overtemperature.

[0030] In the present invention, the grain size of the MIL-101(Cr) is preferably 40 to 200 nm.

[0031] In the present invention, the MIL-101(Cr) is preferably grown on the surface of the chopped carbon fibers.

[0032] In the present invention, the mass of the MIL-101(Cr) is preferably 40 to 50% of the mass of the chopped carbon fibers.

[0033] In the present invention, the MIL-101(Cr) is preferably prepared under conventional hydrothermal conditions by adding chopped carbon fibers as a substrate in a solution system to attach and grow nano-scale MIL-101(Cr) crystals.

[0034] In the present invention, the material of the base layer preferably includes carbon paper, carbon cloth, carbon felt or a conductive polymer-based film.

[0035] In the present invention, the thickness of the microporous layer is preferably 20 to 50 μm.

[0036] The present invention also provides a method for preparing a heat pump type gas diffusion layer based on cold start and over-temperature protection as described in the above technical solution, comprising the following steps:

[0037] mixing the metal organic framework material and a solvent to obtain a slurry;

[0038] The slurry is coated on the surface of the base layer and then subjected to a pressing heat treatment to obtain the heat pump type gas diffusion layer based on cold start and over-temperature protection.

[0039] The invention mixes the metal organic framework material and the solvent to obtain slurry.

[0040] In the present invention, the solvent is preferably an anhydrous ethanol-isopropanol mixture, and the volume ratio of anhydrous ethanol to isopropanol in the mixture is preferably 1:1.

[0041] In the present invention, the slurry preferably further contains conductive carbon black and PTFE emulsion.

[0042] In the present invention, the mass concentration of PTFE in the PTFE emulsion is preferably 10-15%.

[0043] In the present invention, the added amount of the conductive carbon black is preferably 15-20% of the mass of the PTFE emulsion.

[0044] In the present invention, the mass of the MIL-101(Cr) is preferably 40-50% of the mass of the conductive carbon black.

[0045] In a specific embodiment of the present invention, the slurry is preferably prepared by a method comprising the following steps: first dispersing conductive carbon black into an anhydrous ethanol-isopropanol mixed solution, adding PTFE emulsion, stirring magnetically for 5 minutes, ultrasonically oscillating for 30 minutes as a cycle, repeating three times, and finally stirring magnetically for 10 to 20 minutes to obtain the slurry.

[0046] In the present invention, the frequency of the ultrasonic oscillation is preferably 40 kHz, and the temperature is preferably room temperature.

[0047] After obtaining the slurry, the present invention coats the slurry on the surface of the base layer and then performs a pressing heat treatment to obtain the heat pump type gas diffusion layer based on cold start and over-temperature protection.

[0048] In the present invention, the coating is preferably spraying, and the spraying is preferably performed on a hot plate. The temperature of the hot plate is preferably 50 to 60° C., and the thickness of the spraying is preferably 50 to 60 μm.

[0049] In the present invention, the pressing heat treatment preferably includes the following steps: keeping the temperature at 250°C for 30 to 40 minutes, then heating to 330°C and keeping the temperature for 30 to 40 minutes; the pressure of the pressing heat treatment is preferably 0.2 to 0.25 MPa.

[0050] The present invention also provides the application of the heat pump gas diffusion layer based on cold start and over-temperature protection described in the above technical solution or the heat pump gas diffusion layer based on cold start and over-temperature protection prepared by the preparation method described in the above technical solution in a fuel cell.

[0051] The present invention has no particular limitation on the specific manner of the application, and any manner familiar to those skilled in the art may be used.

[0052] To further illustrate the present invention, the heat pump gas diffusion layer based on cold start and over-temperature protection, its preparation method and application provided by the present invention are described in detail below with reference to examples, but they should not be understood as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] A heat pump type gas diffusion layer based on cold start and over-temperature protection, wherein the microporous layer contains a heat pump type adsorbent material metal organic framework (MOF) MIL-101 (Cr).

[0055] Under conventional hydrothermal conditions, short-cut carbon fibers are added to the solution system of the MOF material MIL-101(Cr) as a substrate to attach and grow nano-scale MIL-101(Cr) crystals with a grain size of 40 to 100 nm.

[0056] The microporous layer is prepared by mixing an anhydrous ethanol-isopropanol (volume ratio of 1:1) mixed solution, short carbon fibers with attached growth of MIL-101 (Cr), conductive carbon black and PTFE emulsion. The preparation of the microporous layer includes the following steps: first dispersing the conductive carbon black into the anhydrous ethanol-isopropanol mixed solution, and adding the PTFE emulsion, magnetic stirring for 5 minutes, ultrasonic oscillation for 30 minutes as a cycle, repeating three times, and finally magnetic stirring for 20 minutes to obtain a microporous layer slurry; the PTFE mass concentration in the PTFE emulsion is 10%, the amount of conductive carbon black added is 15% of the mass of the PTFE emulsion, the mass of the short carbon fibers with attached growth of MIL-101 (Cr) is 40% of the mass of the conductive carbon black, wherein the mass content of MIL-101 (Cr) is 40% of the mass of the short carbon fibers, the frequency of the ultrasonic oscillation is 40 kHz, and the temperature is room temperature; the obtained slurry is coated on the surface of the base layer, and the spraying process is carried out on a hot plate at a temperature of 60°C and a spraying thickness of 60 μm.

[0057] The base layer material is carbon paper with a thickness of 180 μm.

[0058] After coating, the pressing heat treatment is carried out at a temperature of 250° C. for 30 minutes, then the temperature is raised to 330° C. for 30 minutes; the pressing pressure is 0.2 MPa.

[0059] Example 2

[0060] A heat pump type gas diffusion layer based on cold start and over-temperature protection is characterized in that its microporous layer contains the heat pump adsorbent material metal organic framework (MOF) MIL-101 (Cr).

[0061] Under conventional hydrothermal conditions, the MOF material MIL-101(Cr) was added to the solution system with chopped carbon fibers as a substrate to grow nano-scale MIL-101(Cr) crystals with a grain size of 40 to 150 nm.

[0062] The microporous layer is prepared by mixing an anhydrous ethanol-isopropanol (volume ratio of 1:1) mixed solution, short carbon fibers with attached growth of MIL-101 (Cr), conductive carbon black and PTFE emulsion. The preparation includes the following steps: first dispersing the conductive carbon black into the anhydrous ethanol-isopropanol mixed solution, and adding the PTFE emulsion, magnetic stirring for 5 minutes, ultrasonic oscillation for 30 minutes as a cycle, repeating three times, and finally magnetic stirring for 20 minutes to obtain a microporous layer slurry; the PTFE mass concentration in the PTFE emulsion is 10%, the added amount of the conductive carbon black is 20% of the PTFE mass, the mass of the short carbon fibers with attached growth of MIL-101 (Cr) is 45% of the mass of the conductive carbon black, wherein the mass content of MIL-101 (Cr) is 50% of the mass of the short carbon fibers, the frequency of the ultrasonic oscillation is 40kHz, and the temperature is room temperature; the obtained slurry is coated on the surface of the base layer, and the spraying process is carried out on a hot plate at a temperature of 60°C and a spraying thickness of 60μm.

[0063] The base layer material is carbon paper with a thickness of 180 μm.

[0064] After coating, a pressing heat treatment is performed at a temperature of 250° C. for 30 minutes, then the temperature is raised to 330° C. for 30 minutes; the pressing pressure is 0.2 MPa.

[0065] Example 3

[0066] A heat pump type gas diffusion layer based on cold start and over-temperature protection is characterized in that its microporous layer contains the heat pump adsorbent material metal organic framework (MOF) MIL-101 (Cr).

[0067] Under conventional hydrothermal conditions, the MOF material MIL-101(Cr) was added to the solution system with chopped carbon fibers as a substrate to grow nano-scale MIL-101(Cr) crystals with a grain size of 40 to 200 nm.

[0068] The microporous layer is prepared by mixing an anhydrous ethanol-isopropanol (volume ratio of 1:1) mixed solution, short carbon fibers with attached growth of MIL-101 (Cr), conductive carbon black and PTFE emulsion. The preparation includes the following steps: first dispersing the conductive carbon black into an anhydrous ethanol-isopropanol (1:1) mixed solution, and adding the PTFE emulsion, performing magnetic stirring for 5 minutes and ultrasonic oscillation for 30 minutes as a cycle, repeating three times, and finally magnetic stirring for 20 minutes to obtain a microporous layer slurry; the PTFE mass concentration in the PTFE emulsion is 15%, the added amount of the conductive carbon black is 20% of the PTFE mass, the mass of the short carbon fibers with attached growth of MIL-101 (Cr) is 50% of the mass of the conductive carbon black, wherein the mass content of MIL-101 (Cr) is 40% of the mass of the short carbon fibers, the frequency of the ultrasonic oscillation is 40kHz, and the temperature is room temperature; the obtained slurry is coated on the surface of the base layer, and the spraying process is carried out on a hot plate at a temperature of 60°C and a spraying thickness of 60μm.

[0069] The base layer material is carbon paper with a thickness of 180 μm.

[0070] After coating, a pressing heat treatment is performed at a temperature of 250° C. for 30 minutes, then the temperature is raised to 330° C. for 30 minutes; the pressing pressure is 0.25 MPa.

[0071] Comparative Example 1

[0072] The chopped carbon fibers with attached growth of MIL-101(Cr) described in Example 3 were replaced with chopped carbon fibers without attached MIL-101(Cr) of the same mass, and the gas diffusion layers were prepared under the same other conditions for comparison.

[0073] Generally speaking, the energy required to raise the temperature of 1g of water by 1°C is 4.1J. 677.98J, 758.64J, and 848.02J of heat can respectively raise the temperature of 161.42g, 180.63g, and 201.91g of water by 1°C. Table 1 shows the performance parameters of the gas diffusion layers prepared in Examples 1 to 3 and Comparative Example 1. As can be seen from Table 1, the embodiments of the present invention can significantly regulate the temperature near the gas diffusion layer through the adsorption / desorption of water.

[0074] Table 1 Performance parameters of the gas diffusion layers obtained in Examples 1 to 3 and Comparative Example 1

[0075]

[0076]

[0077] In summary, 1. The present invention adopts the heat pump adsorbent MOF material MIL-101 (Cr) as the key material of the microporous layer of the gas diffusion layer. MIL-101 (Cr) can adsorb water and release heat energy at low temperatures, reduce the water content on the outside of the membrane electrode and in the gas diffusion layer during cold start, and provide a certain auxiliary effect for its heating.

[0078] 2. The MIL-101(Cr) described in the present invention desorbs water and absorbs heat energy when the temperature exceeds the normal operating temperature, thereby helping to accelerate the cooling of the membrane electrode and releasing water molecules to prevent the membrane electrode from drying out due to local overheating.

[0079] 3. The heat pump adsorbent material MIL-101(Cr) of the present invention has nanocrystalline particles with a size of 40 to 200 nm and uses chopped carbon fibers as a growth substrate so as to achieve the effect of being distributed in most pores of the microporous layer.

[0080] 4. The heat pump adsorbent material MIL-101(Cr) described in the present invention has an ultra-high specific surface area, high adsorption capacity and a stable framework structure. During the adsorption and desorption of water, no volume change occurs to add additional burden to the membrane electrode.

[0081] 5. The heat pump adsorbent material MIL-101(Cr) described in the present invention has extremely high thermal stability. Its pyrolysis temperature is above 340°C, which is much higher than the operating temperature of the fuel cell. This ensures that it will not be pyrolyzed during long-term use. The water molecules adsorbed in the rigid frame will not expand in volume when the water freezes.

[0082] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A heat pump type gas diffusion layer based on cold start and over-temperature protection, characterized in that: It comprises a base layer and a microporous layer which are stacked, wherein the microporous layer contains a heat pump adsorbent material, and the heat pump adsorbent material is a metal organic framework material; The metal organic framework material is MIL-101 (Cr); the grain size of the MIL-101 (Cr) is 40 to 200 nm; The MIL-101(Cr) grows on the surface of the chopped carbon fibers, and the mass of the MIL-101(Cr) is 40% of the mass of the chopped carbon fibers.

2. The heat pump type gas diffusion layer according to claim 1, characterized in that: The material of the base layer includes carbon paper, carbon cloth, carbon felt or conductive polymer-based film.

3. The heat pump type gas diffusion layer according to claim 1 or 2, characterized in that: The thickness of the microporous layer is 20 to 50 μm.

4. The method for preparing a heat pump type gas diffusion layer based on cold start and over-temperature protection according to any one of claims 1 to 3, characterized in that: The following steps are involved: mixing the metal organic framework material and a solvent to obtain a slurry; The slurry is coated on the surface of the base layer and then subjected to a pressing heat treatment to obtain the heat pump type gas diffusion layer based on cold start and over-temperature protection.

5. The preparation method according to claim 4, characterized in that The slurry also contains conductive carbon black and PTFE emulsion.

6. The preparation method according to claim 4, characterized in that The pressing heat treatment comprises the following steps: keeping the temperature at 250° C. for 30 to 40 minutes, then heating the temperature to 330° C. and keeping the temperature for 30 to 40 minutes; the pressure of the pressing heat treatment is 0.2 to 0.25 MPa.

7. Use of the heat pump gas diffusion layer with cold start and over-temperature protection according to any one of claims 1 to 3 or the heat pump gas diffusion layer with cold start and over-temperature protection prepared by the preparation method according to any one of claims 4 to 6 in a fuel cell.

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