A dual-channel gas diffusion layer and its preparation method

Abstract

The present invention relates to the field of proton exchange membrane fuel cells, and particularly to a dual-channel gas diffusion layer and a preparation method thereof; the dual-channel gas diffusion layer includes: a carbon paper-based bottom layer, a single-walled carbon nanotube functional layer, and a hydrophobic microporous layer that are sequentially stacked; a plurality of grooves are formed on the single-walled carbon nanotube functional layer, and the bottom end of the hydrophobic microporous layer is embedded in the grooves; in the present invention, by arranging the single-walled carbon nanotube functional layer on the carbon paper-based bottom layer and arranging grooves on the single-walled carbon nanotube functional layer, not only can the carbon paper-based bottom layer be ensured to have sufficient supporting force, but also the single-walled carbon nanotube functional layer forms a structure with a hydrophilic-hydrophobic periodic distribution; the single-walled carbon nanotube functional layer of the present invention has reasonable wettability and microporous structure, which is helpful for the storage of liquid water. After the hydrophobic slurry is filled in the grooves regularly distributed on the surface of the single-walled carbon nanotube functional layer, the grooves are used as gas flow channels to realize the orderly transmission of water / gas.

Description

Technical Field

[0001] The present invention relates to the field of proton exchange membrane fuel cells, and particularly to a dual-channel gas diffusion layer and a preparation method thereof. Background Art

[0002] A proton exchange membrane fuel cell (PEMFC) is a hydrogen energy power generation device, which has outstanding advantages such as high efficiency, zero emission, and continuous power generation, and is a very promising new energy technology. During the actual operation of the fuel cell, protons are conducted from the anode to the cathode in the form of hydrated protons (H3O + ), which is a key factor determining the performance of the fuel cell. Its proton conductivity is linearly related to the water content in the membrane. Therefore, it is necessary to maintain good hydration of the proton exchange membrane to ensure its proton conductivity in a dry environment. However, excessive liquid water will cover the reaction active sites of the cathode catalyst layer and block the gas transport channels, causing the "flooding" phenomenon, increasing the oxygen diffusion resistance, and thus reducing the mass transfer performance of the fuel cell. Therefore, efficient water / gas management is crucial for realizing a high-performance PEMFC system.

[0003] The gas diffusion layer generally consists of a base layer and a microporous layer, and undertakes multiple functions such as supporting the catalyst layer, collecting current, transporting gas, and water management. It is one of the key materials affecting the performance of the membrane electrode. The traditional microporous layer is usually composed of a mixture of carbon black powder and a hydrophobic agent, with strong hydrophobicity, which helps to remove water smoothly, provides advantages under high humidity conditions, but will accelerate membrane dehydration and hinder proton conductivity under low humidity conditions. The gas diffusion layer modified with hydrophilic materials or hydrophilic coatings can effectively prevent "membrane drying" and improve the power generation performance of the battery in a dry environment. Lim et al. (Lim, I.S.; Kang, B.; Park, J. Y.; Kim, M. S. Performance improvement of polymerelectrolyte membrane fuel cell by gas diffusion layer with atomic-layer-deposited HfO2 on microporous layer. Energy Convers. Manage. 2021, 236,114070. https: / / doi.org / 10.1016 / j.enconman.2021.114070.) prepared HfO2-GDL by atomic layer deposition. The addition of the hydrophilic layer significantly improved the water retention capacity of the gas diffusion layer and reduced the membrane resistance. However, traditional hydrophilic substances have poor conductivity, which greatly increases the internal resistance of the fuel cell, and the adsorbed liquid water is extremely easy to block the pores, hindering the diffusion of reaction gases and reducing the mass transfer performance. In past reports, hydrophilic microporous layers were mostly prepared by mixing hydrophilic multi-walled carbon nanotubes with different carbon powders or in-situ growing carbon nanotubes. It was found that the dispersion of multi-walled carbon nanotubes in the microporous layer slurry was poor and the hydrophilic regions were randomly distributed, making it difficult to achieve effective water-vapor transport.

[0004] At present, the work on improving water / gas management of the gas diffusion layer still cannot effectively solve the contradiction between "membrane drying" and "water flooding" (i.e., water retention and mass transfer). The improvement of the self-humidifying performance under dry conditions often comes at the cost of sacrificing the mass transfer performance under high humidity conditions, and the water-vapor transport is disordered. Summary of the Invention

[0005] The object of the present invention is to provide a dual-channel gas diffusion layer and its preparation method for the deficiencies in the prior art.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention is to provide a preparation method of a dual-channel gas diffusion layer, and the steps include:

[0008] S1. Deposit the single-walled carbon nanotube dispersion on a hydrophobic-treated carbon paper substrate, and successively perform washing treatment, drying treatment, calcination treatment, and etching treatment to obtain the single-walled carbon nanotube functional layer;

[0009] S2. Coat the hydrophobic slurry on the surface of the single-walled carbon nanotube functional layer and perform sintering treatment to obtain the dual-channel gas diffusion layer.

[0010] Preferably, in step S1, the preparation method of the single-walled carbon nanotube dispersion includes: oxidizing the single-walled carbon nanotubes by an acid oxidation method and then performing ultrasonic treatment to obtain the single-walled carbon nanotube dispersion.

[0011] More preferably, the outer diameter of the single-walled carbon nanotubes is 1 - 4 nm, the length is 5 - 30 μm, and the oxygen-to-carbon ratio of the single-walled carbon nanotubes after oxidation treatment is 0.1 - 0.3; the concentration of the single-walled carbon nanotube dispersion is 0.001 - 0.1 mg / mL -1 .

[0012] Preferably, in step S1, the deposition includes at least one of suction filtration, dip coating, spraying, or spin coating.

[0013] Preferably, in step S1, the washing treatment includes: washing 1 - 10 times with deionized water; the temperature of the drying treatment is 60 - 80 °C; the temperature of the calcination treatment is 300 - 380 °C, and the time of the calcination treatment is 10 - 60 min.

[0014] Preferably, in step S1, the etching treatment is laser etching, the power of the laser etching is 5 - 30 W, the speed is 50 - 5000 mm / s, and the frequency is 10 - 80 kHz.

[0015] Preferably, in step S2, the preparation method of the hydrophobic slurry includes: ball-milling and mixing carbon powder, a hydrophobic agent, a solvent, and Triton X-100 in a mass ratio of 1:(0.1 - 1.0):(1 - 15):(0.1 - 0.5) to obtain the hydrophobic slurry.

[0016] More preferably, the carbon powder is at least one of Ketjen black, whisker carbon nanotubes, or acetylene black; the hydrophobic agent is at least one of polytetrafluoroethylene, polyvinylidene fluoride, or ethylene tetrafluoroethylene copolymer; the solvent is at least one of deionized water, ethanol, or isopropanol.

[0017] Preferably, in step S2, the coating method of the hydrophobic slurry is one of spraying method, wire bar coating, or doctor blade coating.

[0018] Preferably, in step S2, the sintering treatment includes: heating from room temperature to 230-280°C at a rate of 2-15°C / min, holding for 20-60 min, then heating to 350-380°C at a rate of 2-15°C / min, holding for 20-60 min, and finally cooling down.

[0019] The second aspect of the present invention is to provide a dual-channel gas diffusion layer prepared by the above preparation method, including: a carbon paper-based bottom layer, a single-walled carbon nanotube functional layer, and a hydrophobic microporous layer that are sequentially stacked;

[0020] A plurality of grooves are formed on the single-walled carbon nanotube functional layer, and the bottom end of the hydrophobic microporous layer is embedded in the grooves.

[0021] Preferably, the shape of the grooves includes at least one of a rectangle, a square, a circle, or a triangle.

[0022] Preferably, the depth of the grooves is 0.01-1 μm, the area of the grooves is 0.01-400 mm 2 , and the interval between adjacent grooves is 0.1-20 mm.

[0023] Preferably, the water contact angle range of the carbon paper-based bottom layer is 120°-150°.

[0024] Preferably, the thickness of the single-walled carbon nanotube functional layer is 0.01-1.0 μm.

[0025] Preferably, the water contact angle range of the single-walled carbon nanotube functional layer is 60°-120°.

[0026] Preferably, the thickness of the hydrophobic microporous layer is 20-100 μm.

[0027] The present invention adopts the above technical solutions, and compared with the prior art, has the following technical effects:

[0028] The present invention provides a single-walled carbon nanotube functional layer on the carbon paper-based bottom layer and forms grooves on the single-walled carbon nanotube functional layer, which not only ensures that the carbon paper-based bottom layer has sufficient supporting force, but also enables the single-walled carbon nanotube functional layer to form a structure with a periodic distribution of hydrophilic and hydrophobic properties;

[0029] The single-walled carbon nanotube functional layer of the present invention has reasonable wettability and a microporous structure, which helps to store liquid water. Multiple regularly distributed grooves on the surface of the single-walled carbon nanotube functional layer are filled with a hydrophobic slurry to serve as gas flow channels, realizing the orderly transmission of water / gas; the water generated by the cathode reaction preferentially concentrates and stores in the hydrophilic region, and the remaining hydrophobic regions provide a fast channel for oxygen to reach the catalytic layer; the present invention improves the performance of the gas diffusion layer by adjusting the balance between hydrophilicity and hydrophobicity, ensuring the wetting of the proton membrane in the fuel cell and at the same time enhancing the mass transfer performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the basic structure of the dual-channel gas diffusion layer in Embodiment 1 of the present invention;

[0031] Figure 2 It is the performance test result under the condition of 20%RH in the detection embodiment of the present invention; among them, the solid marks are polarization curves; the semi-hollow marks are power density curves;

[0032] Figure 3 It is the performance test result under the condition of 100%RH in the detection embodiment of the present invention; among them, the solid marks are polarization curves; the semi-hollow marks are power density curves. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0034] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0035] The present invention will be further described below in conjunction with the drawings and specific embodiments, but it is not limited to the present invention.

[0036] Embodiment 1

[0037] This embodiment provides a preparation method for a dual-channel gas diffusion layer, and the steps include:

[0038] S1. The single-walled carbon nanotubes with an outer diameter of 1 nm and a length of 5 μm are oxidized by an acid oxidation method, and the oxygen-carbon ratio of the oxidized single-walled carbon nanotubes is 0.1; a single-walled carbon nanotube dispersion with a concentration of 0.001 mg·mL -1 is prepared under the assistance of high-power ultrasonic waves;

[0039] The single-walled carbon nanotube dispersion is deposited on a hydrophobic-treated carbon paper substrate by spraying to form a single-walled carbon nanotube layer with a thickness of 0.01 μm. After washing once with deionized water, drying at 60 °C, and calcining at 300 °C for 10 min, the single-walled carbon nanotube functional layer is obtained. Set the power of laser etching to 5 W, the speed to 5000 mm / s, and the frequency to 10 kHz, and etch multiple rectangular grooves with an area of 0.01 mm 2 on the surface of the single-walled carbon nanotube functional layer, with a spacing of 0.1 mm;

[0040] S2. Mix Ketjenblack (KBs), fluorinated ethylene propylene copolymer (FEP), deionized water, and Triton X-100 by ball milling in a mass ratio of 1:0.1:1:0.1 to obtain a hydrophobic slurry. Then, coat the surface of the single-walled carbon nanotube functional layer with grooves by spraying method, and then sinter it. Heat from room temperature to 230 °C at a rate of 2 °C / min, hold for 20 min, continue to heat to 350 °C at a rate of 2 °C / min, hold for 20 min, and then cool down to obtain a dual-channel gas diffusion layer.

[0041] As Figure 1 shown, the dual-channel gas diffusion layer includes: a carbon paper base layer, a single-walled carbon nanotube functional layer, and a hydrophobic microporous layer stacked in sequence;

[0042] Several grooves are formed on the single-walled carbon nanotube functional layer, and the bottom end of the hydrophobic microporous layer is embedded in the grooves.

[0043] Example 2

[0044] This example provides another preparation method of the dual-channel gas diffusion layer. The steps include:

[0045] S1. Oxidize single-walled carbon nanotubes with an outer diameter of 2 nm and a length of 10 μm by the acid oxidation method, and the oxygen-carbon ratio of the oxidized single-walled carbon nanotubes is 0.15. Prepare a single-walled carbon nanotube dispersion with a concentration of 0.005 mg / mL under high-power ultrasonic assistance; -1 the single-walled carbon nanotube dispersion;

[0046] Deposit the single-walled carbon nanotube dispersion on a hydrophobic-treated carbon paper substrate by dip coating to form a single-walled carbon nanotube layer with a thickness of 0.1 μm. After washing three times with deionized water, drying at 60 °C, and calcining at 330 °C for 20 min, the single-walled carbon nanotube functional layer is obtained. Set the power of laser etching to 10 W, the speed to 3000 mm / s, and the frequency to 20 kHz, and etch multiple square grooves with an area of 1.44 mm 2 on the surface of the single-walled carbon nanotube functional layer, with a spacing of 5 mm;

[0047] S2. Mix carbon powder (whisker carbon nanotubes WCNTs: acetylene black ACET = 6:4), polyvinylidene fluoride (PVDF), deionized water, and Triton X-100 in a mass ratio of 1:0.3:2:0.2 by ball milling to obtain a hydrophobic slurry. Then, coat it on the surface of the single-walled carbon nanotube functional layer with grooves using a wire bar coating method, and then sinter it. Heat it from room temperature to 250 °C at a rate of 5 °C / min, hold for 30 min, continue to heat it to 360 °C at a rate of 5 °C / min, hold for 30 min, and then cool down to obtain a dual-channel gas diffusion layer.

[0048] Example 3

[0049] This example provides another method for preparing a dual-channel gas diffusion layer, and the steps include:

[0050] S1. Oxidize single-walled carbon nanotubes with an outer diameter of 3 nm and a length of 15 μm using an acid oxidation method, and the oxygen-carbon ratio of the oxidized single-walled carbon nanotubes is 0.3. Prepare a single-walled carbon nanotube dispersion with a concentration of 0.01 mg / mL under high-power ultrasonic assistance; -1

[0051] Deposit the single-walled carbon nanotube dispersion on a hydrophobic-treated carbon paper substrate by suction filtration to form a single-walled carbon nanotube layer with a thickness of 0.6 μm. Wash it 5 times with deionized water, dry it at 60 °C, and then calcine it at 350 °C for 30 min to obtain a single-walled carbon nanotube functional layer. Set the power of laser etching to 20 W, the speed to 1000 mm / s, and the frequency to 60 kHz, and etch multiple circular grooves with an area of 113.04 mm 2 and a spacing of 10 mm on the surface of the single-walled carbon nanotube functional layer;

[0052] S2. Mix carbon powder (whisker carbon nanotubes WCNTs: KBs = 8:2), polytetrafluoroethylene (PTFE), a solvent (isopropyl alcohol: deionized water = 2:1), and Triton X-100 in a mass ratio of 1:0.6:5:0.3 by ball milling to obtain a hydrophobic slurry. Then, coat it on the surface of the single-walled carbon nanotube functional layer with grooves using a doctor blade coating method, and then sinter it. Heat it from room temperature to 260 °C at a rate of 10 °C / min, hold for 30 min, continue to heat it to 360 °C at a rate of 10 °C / min, hold for 30 min, and then cool down to obtain a dual-channel gas diffusion layer.

[0053] Example 4

[0054] This example provides another method for preparing a dual-channel gas diffusion layer, and the steps include:

[0055] S1. Oxidize single-walled carbon nanotubes with an outer diameter of 4 nm and a length of 30 μm using the acid oxidation method. The oxygen-to-carbon ratio of the oxidized single-walled carbon nanotubes is 0.3. Prepare a single-walled carbon nanotube dispersion with a concentration of 0.1 mg / mL under high-power ultrasonic assistance; -1 Deposit the single-walled carbon nanotube dispersion on a hydrophobic-treated carbon paper substrate by suction filtration to form a single-walled carbon nanotube layer with a thickness of 1 μm. Wash it 10 times with deionized water, dry it at 80 °C, and then calcine it at 380 °C for 60 min to obtain the single-walled carbon nanotube functional layer. Set the power of laser etching to 25 W, the speed to 500 mm / s, and the frequency to 70 kHz, and etch multiple triangular grooves with an area of 205 mm

[0056] on the surface of the single-walled carbon nanotube functional layer, with a spacing of 15 mm; 2 ;

[0057] S2. Ball-mill and mix carbon powder (WCNTs:ACET = 5:3), PTFE, deionized water, and Triton X-100 in a mass ratio of 1:0.8:10:0.5 to obtain a hydrophobic slurry. Coat it on the surface of the single-walled carbon nanotube functional layer with grooves using the doctor blade coating method, and then sinter it. Heat it from room temperature to 280 °C at a rate of 15 °C / min, hold for 60 min, continue to heat it to 380 °C at a rate of 15 °C / min, hold for 60 min, and then cool down to obtain the dual-channel gas diffusion layer.

[0058] Comparative Example 1

[0059] This comparative example provides a method for preparing a gas diffusion layer, and the steps include:

[0060] First, ball-mill and mix carbon powder (WCNTs:KBs = 8:2), PTFE, a solvent (isopropyl alcohol:deionized water = 2:1), and Triton X-100 in a mass ratio of 1:0.6:10:0.3 to obtain a hydrophobic slurry. Coat it on the surface of a hydrophobic-treated carbon paper substrate using the doctor blade coating method, and then sinter it. Heat it from room temperature to 260 °C at a rate of 10 °C / min, hold for 30 min, continue to heat it to 360 °C at a rate of 10 °C / min, hold for 30 min, and then cool down to obtain the gas diffusion layer.

[0061] Comparative Example 2

[0062] This comparative example provides another method for preparing a gas diffusion layer, and the steps include:

[0063] Step 1. Oxidize single-walled carbon nanotubes with an outer diameter of 3 nm and a length of 15 μm using the acid oxidation method, and the oxygen-to-carbon ratio is 0.3. Prepare a single-walled carbon nanotube dispersion with a concentration of 0.01 mg / mL under high-power ultrasonic assistance;-1 Single-walled carbon nanotube dispersion;

[0064] Step 2: Deposit the carbon nanotube dispersion on a hydrophobically treated carbon paper substrate by suction filtration to form a single-walled carbon nanotube thin film layer with a thickness of 0.6 μm. Wash it 5 times with deionized water, dry it at 60 °C, and then calcine it at 350 °C for 30 min;

[0065] Step 3: Ball-mill and mix carbon powder (WCNTs: KBs = 8:2), PTFE, solvent (isopropyl alcohol: deionized water = 2:1), and Triton X-100 in a mass ratio of 1:0.6:10:0.3 to obtain a hydrophobic slurry. Coat the surface of the single-walled carbon nanotube thin film layer described in Step 2 using the doctor blade coating method, and then sinter it. Heat it from room temperature to 260 °C at a rate of 10 °C / min, hold for 30 min, continue to heat it to 360 °C at a rate of 10 °C / min, hold for 30 min, and then cool it to obtain the gas diffusion layer.

[0066] Comparative Example 3

[0067] This comparative example provides another method for preparing a gas diffusion layer. The steps include:

[0068] S1: Oxidize single-walled carbon nanotubes with an outer diameter of 2 nm and a length of 30 μm using the acid oxidation method. The oxygen-carbon ratio of the oxidized single-walled carbon nanotubes is 0.2. Prepare a single-walled carbon nanotube dispersion with a concentration of 0.1 mg / mL under high-power ultrasonic assistance; -1 Single-walled carbon nanotube dispersion;

[0069] Deposit the single-walled carbon nanotube dispersion on a hydrophobically treated carbon paper substrate by suction filtration to form a single-walled carbon nanotube layer with a thickness of 0.8 μm. Wash it 3 times with deionized water, dry it at 80 °C, and then calcine it at 360 °C for 30 min to obtain a single-walled carbon nanotube functional layer. Set the laser etching power to 35 W, the speed to 30 mm / s, and the frequency to 85 kHz, and etch multiple square grooves with an area of 400 mm 2 and a spacing of 20 mm on the single-walled carbon nanotube functional layer and the carbon paper substrate;

[0070] S2: Ball-mill and mix carbon powder (WCNTs: multi-walled carbon nanotubes MWCNTs: ACET = 5:3:2), PTFE, isopropyl alcohol, and Triton X-100 in a mass ratio of 1:1:15:0.5 to obtain a hydrophobic slurry. Coat the surface of the single-walled carbon nanotube functional layer with grooves using the doctor blade coating method, and then sinter it. Heat it from room temperature to 280 °C at a rate of 15 °C / min, hold for 60 min, continue to heat it to 380 °C at a rate of 15 °C / min, hold for 60 min, and then cool it to obtain the gas diffusion layer.

[0071] Comparative Example 4

[0072] This comparative example provides another method for preparing a dual-channel gas diffusion layer, and the steps include:

[0073] S1. Oxidize single-walled carbon nanotubes with an outer diameter of 5 nm and a length of 1 μm by the acid oxidation method, and the oxygen-carbon ratio of the oxidized single-walled carbon nanotubes is 0.3; prepare a single-walled carbon nanotube dispersion with a concentration of 0.1 mg / mL under high-power ultrasonic assistance; -1 of the single-walled carbon nanotube dispersion;

[0074] Deposit the single-walled carbon nanotube dispersion on a carbon paper substrate treated with hydrophobic treatment by suction filtration to form a single-walled carbon nanotube layer with a thickness of 1 μm, wash it 10 times with deionized water, dry it at 80 °C, and then calcine it at 380 °C for 60 min to obtain a single-walled carbon nanotube functional layer; set the power of laser etching to 25 W, the speed to 500 mm / s, and the frequency to 70 kHz, and etch a plurality of triangular grooves with an area of 205 mm 2 and a spacing of 15 mm on the surface of the single-walled carbon nanotube functional layer;

[0075] S2. Ball-mill and mix carbon powder (WCNTs:ACET = 5:3), PTFE, deionized water, and Triton X-100 in a mass ratio of 1:0.8:10:0.5 to obtain a hydrophobic slurry, and coat it on the surface of the single-walled carbon nanotube functional layer with grooves by the doctor blade coating method, and then sinter it. Heat it from room temperature to 280 °C at a rate of 15 °C / min, hold for 60 min, continue to heat it to 380 °C at a rate of 15 °C / min, hold for 60 min, and then cool it to obtain a dual-channel gas diffusion layer.

[0076] Comparative Example 5

[0077] This comparative example provides another method for preparing a dual-channel gas diffusion layer, and the steps include:

[0078] S1. Oxidize single-walled carbon nanotubes with an outer diameter of 4 nm and a length of 30 μm by the acid oxidation method, and the oxygen-carbon ratio of the oxidized single-walled carbon nanotubes is 0.01; prepare a single-walled carbon nanotube dispersion with a concentration of 0.1 mg / mL under high-power ultrasonic assistance; -1 of the single-walled carbon nanotube dispersion;

[0079] The single-walled carbon nanotube dispersion was deposited on a hydrophobic-treated carbon paper substrate by suction filtration to form a single-walled carbon nanotube layer with a thickness of 1 μm. After washing 10 times with deionized water and drying at 80 °C, it was calcined at 380 °C for 60 min to obtain the single-walled carbon nanotube functional layer. The power of laser etching was set to 25 W, the speed was 500 mm / s, and the frequency was 70 kHz. Multiple triangular grooves with an area of 205 mm 2 and a spacing of 15 mm were etched on the surface of the single-walled carbon nanotube functional layer;

[0080] S2. Carbon powder (WCNTs:ACET = 5:3), PTFE, deionized water, and Triton X-100 were ball-milled and mixed in a mass ratio of 1:0.8:10:0.5 to obtain a hydrophobic slurry. The slurry was coated on the surface of the single-walled carbon nanotube functional layer with grooves by a doctor blade coating method, and then sintered. It was heated from room temperature to 280 °C at a rate of 15 °C / min, held for 60 min, continued to be heated to 380 °C at a rate of 15 °C / min, held for 60 min, and then cooled to obtain a dual-channel gas diffusion layer.

[0081] Detection examples

[0082] The dual-channel gas diffusion layers prepared in Examples 1-4 and the gas diffusion layers prepared in Comparative Examples 1-5 were respectively cut into pieces of 2 cm × 2 cm and assembled into single cells for performance testing.

[0083] The specific test conditions were as follows:

[0084] The battery temperature was 80 °C, the relative humidity (RH) of the cathode and anode was 100%, 60%, and 20%, the oxygen / hydrogen gas stoichiometric ratio was 14.4 / 7.2 (the current density was 1 A / cm -2 ), and the cathode / anode back pressure was 60 kPa.

[0085] The test results are shown in Table 1 and Figures 2 - 3 as follows;

[0086] Table 1

[0087]

[0088] As can be seen from Table 1 and Figures 2 - 3 it can be known that under the condition of 20% RH and an output voltage of 0.6 V (the battery needs to have a certain water storage capacity at this voltage), the current density of Comparative Example 1 was significantly lower than that of Comparative Examples 2-3 and Examples 1-4. Under the condition of 100% RH and an output voltage of 0.6 V, its current density increased significantly. It can be seen that due to the lack of a single-walled carbon nanotube functional layer in Comparative Example 1, the water storage effect could not be achieved, and the battery performance was completely affected by the environment. The performance was poor when the environmental humidity was low, and the performance could be improved only when the environmental humidity was high;

[0089] Comparative Example 2 has a single-walled carbon nanotube functional layer, but no grooves are formed thereon. Although it can store water, it cannot balance hydrophobicity and water storage. When the output voltage is 0.6V, the reason why the performance of the battery prepared in Comparative Example 2 is not much different from that of Examples 1-4 is that at this voltage, the battery needs to store water, and Comparative Example 2 has a single-walled carbon nanotube functional layer, which has a certain water storage capacity. However, when the output voltage is 0.2V, the battery needs to drain water. At this time, the current density of Comparative Example 2 is significantly lower than that of Examples 1-4. It can be seen that Comparative Example 2 does not have excellent drainage performance.

[0090] Under the condition that the output voltage of Comparative Example 3 is 0.2V, the battery performance is significantly lower than that of Examples 1-4. This is because the laser etching energy is too high, passing through the single-walled carbon nanotube functional layer and breaking through the carbon paper base layer. And a high-performance gas diffusion layer requires the base layer to have high rigidity to stably support the catalyst layer and the electrolyte membrane. Therefore, the formation of large holes on the carbon paper base layer makes the mechanical properties of the gas diffusion layer poor, and it is easy to accumulate a large amount of water and difficult to drain, resulting in a performance decline.

[0091] Compared with Example 4, the performance of Comparative Example 4 is significantly worse within all test condition ranges. This is because the aspect ratio of the single-walled carbon nanotubes used is relatively small. On the one hand, the constructed porous functional layer is relatively loose, resulting in a decrease in conductivity. On the other hand, part of the single-walled carbon nanotube functional layer will fall off after laser treatment, thus affecting the final performance of the membrane electrode in Comparative Example 4. For Comparative Example 5, under low humidity conditions, the performance of Comparative Example 5 is significantly lower than that of Example 4. This is because after the single-walled carbon nanotubes in it are oxidized, the surface oxygen content is very low, and the oxygen-carbon ratio is only 0.01, which is much smaller than the oxygen-carbon ratio of Example 4. This makes the wettability of the assembled single-walled carbon nanotube functional layer decrease, resulting in poor water retention, thus reducing the battery performance.

[0092] The current density of Examples 1-4 increases by different amplitudes under the said environmental conditions, which means that the battery performance has been improved to a large extent, indicating that the presence of the hydrophilic-hydrophobic dual channels in their structures can both achieve water retention and improve mass transfer.

[0093] In summary, the dual-channel gas diffusion layer obtained by the present invention can optimize the battery performance in different humidity environments and broaden the application range of fuel cells.

[0094] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention accordingly. For those skilled in the art, it should be able to realize that all the equivalent replacements and obvious changes made by using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a dual-channel gas diffusion layer, characterized in that the steps Including: S1. Deposit a single-walled carbon nanotube dispersion liquid on a hydrophobically treated carbon paper substrate, and successively perform washing treatment, drying treatment, calcination treatment, and etching treatment to obtain a single-walled carbon nanotube functional layer. The preparation method of the single-walled carbon nanotube dispersion liquid includes: after oxidizing the single-walled carbon nanotubes by an acid oxidation method, performing ultrasonic treatment to obtain the single-walled carbon nanotube dispersion liquid; the outer diameter of the single-walled carbon nanotubes is 1-4 nm, the length is 5-30 μm, and the oxygen-carbon ratio of the single-walled carbon nanotubes after oxidation treatment is 0.1-0.3; the concentration of the single-walled carbon nanotube dispersion liquid is 0.001-0.1 mg / mL -1 ; the etching treatment is laser etching, the power of the laser etching is 5-30 W, the speed is 50-5000 mm / s, and the frequency is 10-80 kHz; S2. Coat a hydrophobic slurry on the surface of the single-walled carbon nanotube functional layer and perform sintering treatment to obtain the dual-channel gas diffusion layer. The dual-channel gas diffusion layer includes: a carbon paper base layer, a single-walled carbon nanotube functional layer, and a hydrophobic microporous layer that are sequentially stacked; a plurality of grooves are formed in the single-walled carbon nanotube functional layer, and the depth of the grooves is 0.01 - 1 μm. The groove is: multiple rectangular grooves with an area of 0.01 mm 2 , and a spacing of 0.1 mm; or, Multiple square grooves with an area of 1.44 mm 2 , with a spacing of 5 mm; or, Multiple circular grooves with an area of 113.04 mm 2 , a pitch of 10 mm; or, Multiple triangular grooves with an area of 205 mm 2 , with a spacing of 15 mm; The bottom end of the hydrophobic microporous layer is embedded in the grooves.

2. The preparation method according to claim 1, characterized in that, In step S2, the preparation method of the hydrophobic slurry includes: ball-milling and mixing carbon powder, a hydrophobic agent, a solvent, and Triton X-100 in a mass ratio of 1:(0.1 - 1.0):(1 - 15):(0.1 - 0.5) to obtain the hydrophobic slurry.

3. The preparation method according to claim 2, characterized in that, The carbon powder is at least one of Ketjen black, whisker carbon nanotubes, or acetylene black; the hydrophobic agent is at least one of polytetrafluoroethylene, polyvinylidene fluoride, or ethylene-propylene fluoride copolymer; the solvent is at least one of deionized water, ethanol, or isopropanol.

4. The preparation method according to claim 1, characterized in that, In step S2, the sintering treatment includes: heating from room temperature to 230 - 280 °C at a rate of 2 - 15 °C / min, holding for 20 - 60 min, then heating to 350 - 380 °C at a rate of 2 - 15 °C / min, holding for 20 - 60 min, and finally cooling.

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