A method for preparing and applying a gas diffusion layer that enhances gas-liquid mass transfer

Abstract

This invention discloses a method for preparing and applying a gas diffusion layer that enhances gas-liquid mass transfer. The invention involves using a mold with a specific pore size to apply a hydrophilic reagent and then punching holes to construct a hydrophilic porous structure on the gas diffusion layer, thereby increasing its hydrophilicity. This invention facilitates the removal of liquid water from the fuel cell, effectively alleviating problems such as low drainage efficiency and "flooding" caused by the generation of liquid water during water vapor transport, thus improving the performance of the fuel cell. This invention is simple to operate, low in cost, and easily industrialized.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a gas diffusion layer that enhances gas-liquid mass transfer. Background Technology

[0002] A fuel cell is an energy conversion device that converts hydrogen and oxygen energy into electrical energy. It has advantages such as high efficiency and environmental friendliness, and can be widely used in new energy vehicles, power plants, aerospace, mobile power supplies and other fields.

[0003] The gas diffusion layer (GDL) is one of the key components of a fuel cell. During fuel cell operation, liquid water is generated. If this water is not drained in a timely and effective manner, it can accumulate, hindering further gas reactions and significantly degrading fuel cell performance. The gas diffusion layer plays a crucial role in supporting the catalyst layer and transporting gas and liquid water within the fuel cell. Therefore, preparing a gas diffusion layer with excellent mass transfer properties is essential for improving fuel cell performance.

[0004] Weber et al. (Journal of Power Sources. Volume 195, Issue 16. 2010. pp. 5292-5304) proposed a macroscopic modeling method considering the chemical and structural properties of the gas diffusion medium in fuel cells. The model results show that adding hydrophilic materials to the hydrophobic gas diffusion layer (GDL) can enhance water transport between the catalyst layer and the GDL, achieving more efficient liquid transport capabilities. This strongly demonstrates the scientific validity of constructing hydrophilic porous structures on the gas diffusion layer.

[0005] Kitahara et al. (Journal of Power Sources. Volume 199, Issue. 2011. pp. 29-36) proposed a bilayer microporous layer consisting of a hydrophobic layer coated with a hydrophilic layer (using polyvinyl alcohol, PVA, and TiO2). In low-humidity environments, they argued that the hydrophilic microporous layer maintains the wettability of the proton exchange membrane, ensuring efficient hydrogen proton transport, while the hydrophobic microporous layer prevents water from being carried away by dry air or oxygen. However, as the thickness of the hydrophilic layer increases, the oxygen transported to the electrode decreases, leading to an increase in concentration overpotential and reduced performance. Under high humidity conditions, the PVA-coated hydrophilic layer exacerbates water flooding of the cathode catalyst layer, resulting in an increased concentration overpotential and thus reducing fuel cell performance.

[0006] CN118738429A discloses a method for preparing a hydrophilic microporous layer for a proton exchange membrane fuel cell membrane electrode. The method involves coating a hydrophilic microporous layer slurry onto the cathode catalyst layer or onto the hydrophobic microporous layer of the cathode gas diffusion layer, followed by drying the coated slurry to obtain the hydrophilic microporous layer for the proton exchange membrane fuel cell membrane electrode. This method effectively reduces the contact resistance between the microporous layer and the catalyst layer, and reduces the mass transport resistance within the electrode, thus mitigating the "flooding" problem. However, the carbon materials involved in the hydrophilic reagent are expensive, resulting in high production costs.

[0007] CN116377759B discloses a method for obtaining a double-layer adhesive film through spraying and drying, followed by pulse electrolysis to obtain carbon paper with one side hydrophobic and the other side hydrophilic. This method is beneficial for drainage and also enhances the bonding force between polytetrafluoroethylene and the substrate carbon paper. However, this method is complex to operate and has high electrolysis costs. Summary of the Invention

[0008] Based on the above research, the purpose of this invention is to provide a method for preparing and applying an enhanced gas-liquid mass transfer gas diffusion layer. This method is simple to operate, has low cost, and is conducive to industrialization.

[0009] To achieve this objective, the present invention employs the following technical solution: A method for preparing an enhanced gas-liquid mass transfer gas diffusion layer and its application, the method comprising the following steps: 1. Standard preparation of microporous layer. Carbon black (Vulcan XC-72R) and polytetrafluoroethylene (PTFE) solution are weighed and mixed according to a specified ratio to prepare an ink-like coating. Carbon paper is cut to a specific size. It is then subjected to ultrasonic treatment for several hours, dried, and immersed in a PTFE solution until the PTFE content reaches 30% of the carbon paper. The impregnated carbon paper is then heat-treated in a muffle furnace.

[0010] 2. Prepare hydrophilic reagents of different concentrations. Add the film-forming agent (polyacrylic acid), hydrophilic agent (OT-75), and deionized water sequentially in a mass ratio of 3:(1~12):24, meaning the amount of hydrophilic agent used ranges from 0.01 to 0.30 mg / cm³. 2 It was then subjected to ultrasonic treatment for 1 hour.

[0011] 3. Prepare a gas diffusion layer with a hydrophilic porous structure. Select a pore size mold, check its integrity, and clean its surface. Place the pore-punching mold, dipped in a small amount of hydrophilic reagent, onto the air compressor. Set the air compressor to appropriate pressure parameters and start the equipment to press the carbon paper. Gently remove the mold to ensure that the pore structure and gap distribution of the gas diffusion layer are uniform and undamaged, and that the pore size meets expectations, establishing hydrophilic channels that facilitate the passage of liquid water.

[0012] 4. Drying. Place the above gas diffusion layer in a constant temperature oven at 110 ℃ for 30 min to dry until the hydrophilic reagent on the surface of the gas diffusion layer is completely dry.

[0013] 5. Repeat the above steps of dipping, punching, and drying to prepare different amounts of hydrophilic agent ranging from 0.01 to 0.3 mg / cm³. 2 The gas diffusion layer.

[0014] 6. Single-cell performance testing. Assemble the battery using the gas diffusion layer described above and conduct single-cell performance testing.

[0015] Beneficial effects: This invention provides a method for preparing and applying an enhanced gas-liquid mass transfer gas diffusion layer. A hydrophilic pore structure is prepared by dipping a specially sized mold into a hydrophilic reagent. To a certain extent, the hydrophilic pore structure alters the chaotic movement of liquid water in traditional gas diffusion layers, enabling ordered transport of liquid water, reducing transport resistance, and improving fuel cell performance. Comparison with standard gas diffusion layers with uniform pore size distribution shows that the GDL with hydrophilic pore structure has higher liquid water transport efficiency. The limiting current density and power density of the fuel cell are significantly improved.

[0016] If modifications or substitutions to this invention are required, please refer to the examples in the accompanying drawings, which illustrate various experimental details. All mentioned details will also be explained and described separately. Our purpose is not to limit the invention to the specific experimental examples, but to include all modifications, equivalents, and substitutions within the scope of protection defined by the appended claims. Detailed Implementation

[0017] The following non-limiting embodiments can help those skilled in the art to more fully understand the present invention, but do not impose any limitations on the invention.

[0018] Step 1: Preparation of the hydrophobic diffusion layer: A microporous layer is sprayed onto ordinary carbon paper. Carbon black (Vulcan XC-72R) and polytetrafluoroethylene (PTFE) solution are weighed according to a specific ratio and mixed to prepare an ink-like coating. The mixture is ultrasonically sprayed for 60 minutes, then ultrasonically atomized and sprayed onto the surface of the carbon paper. Hydrophobic treatment is then performed. The prepared diffusion layer is repeatedly immersed in the PTFE solution until the PTFE content on the carbon paper reaches 30 wt%. Finally, the impregnated carbon paper is heat-treated in a muffle furnace.

[0019] Step 2: Prepare hydrophilic reagents of different concentrations: Add film-forming agent (polyacrylic acid), hydrophilic agent (OT-75) and deionized water in sequence at a mass ratio of 3:(1~12):24, and sonicate for 1 h.

[0020] Example 1 Cut the hydrophobic diffusion layer prepared in step 1 into 4 mm * 4 mm pieces, place them flat on a rubber plate, and mark the mold position. Select a mold with a steel needle aperture of 92 μm, and dip it into a hydrophilic agent with a concentration of 0.11 mg / cm³. 2 The hydrophilic reagent was precisely applied to the corresponding marked positions. The pressure parameters of the press were set to 30 kg, and the hole-making process was started. The diffusion layer was placed in a 110 ℃ constant temperature oven to dry for 30 min, and then the gas diffusion layer was removed, weighed, and recorded.

[0021] Example 2 The concentration of the hydrophilic reagent was 0.14 mg / cm², and all other operations and conditions were the same as in Example 1.

[0022] Example 3 The concentration of the hydrophilic reagent was 0.07 mg / cm², and all other operations and conditions were the same as in Example 1.

[0023] Example 4 The concentration of the hydrophilic reagent was 0.09 mg / cm², and all other operations and conditions were the same as in Example 1.

[0024] Effect Example Polarization curve and power density curve testing of fuel cells

[0025] Table 1. Effects of the Examples and Comparative Examples project Peak power density (W / cm²) Example 1 1.17 Example 2 1.16 Example 3 1.11 Example 4 1.15 Comparative Example 0.99 The gas diffusion layers prepared in each embodiment and comparative example were assembled into fuel cells, and CCM membrane electrode assemblies were used as catalyst coating membranes. Battery performance testing conditions: cathode: 419 mL / min air, anode: 110 mL / min hydrogen. Polarization curves and power density curves were measured, and the highest point of the power density curve was the peak power density value of the fuel cell. Attached Figure Description

[0026] Figure 1 This is a polarization curve of a fuel cell in Embodiment 1 of the present invention.

[0027] Figure 2 This is the polarization curve of the fuel cell in Embodiment 2 of the present invention.

[0028] Figure 3 This is the polarization curve of the fuel cell in Embodiment 3 of the present invention.

[0029] Figure 4 This is the polarization curve of the fuel cell in Embodiment 4 of the present invention.

[0030] Figure 5 This is a comparative polarization curve of the fuel cell of this invention.

Claims

1. A method for preparing and applying a gas diffusion layer that enhances gas-liquid mass transfer, characterized in that, Includes the following steps: S1) Microporous layer preparation: Weigh carbon black (Vulcan XC-72R) and polytetrafluoroethylene (PTFE) solution according to the proportion to prepare ink-like coating, perform ultrasonic treatment for several hours, dry and then soak in PTFE solution to make the PTFE content on the carbon paper reach a certain mass fraction, and put the impregnated carbon paper into a muffle furnace for heat treatment. S2) Prepare hydrophilic reagents of different concentrations. S3) Prepare a gas diffusion layer with a hydrophilic porous structure. Select a mold with a suitable pore size, apply a small amount of hydrophilic reagent, set the appropriate pressure parameters for the air compressor, and start the equipment to press the carbon paper. Gently remove the mold to ensure that the pore structure and gap distribution of the gas diffusion layer are uniform and undamaged, and that the pore size meets expectations. S4) Drying: Place the above gas diffusion layer in a constant temperature oven to dry until the hydrophilic reagent on the surface of the gas diffusion layer is completely dry. S5) Single-cell performance test. Assemble the battery with the above gas diffusion layer and conduct single-cell performance tests.

2. The method for preparing and applying an enhanced gas-liquid mass transfer gas diffusion layer according to claim 1, characterized in that, The hydrophilic agent includes a film-forming agent (polyacrylic acid), a hydrophilic agent (OT-75), and deionized water, with a mass ratio of 3:(1-12):24, meaning the amount of hydrophilic agent used ranges from 0.01 to 0.30 mg / cm³. 2 It was then subjected to ultrasonic treatment for 1 hour.

3. The diffusion layer perforation process according to claim 1, S5, is characterized in that... First, fix the mold on the press, then place the carbon paper flat on the silicone rubber plate, and perforate the diffusion layer under a certain pressure.

4. As described in claim 3, characterized in that, The dies used for piercing are made of stainless steel. The diameter d of the steel needles used in the piercing dies ranges from 60μm to 150μm.

5. As described in claim 4, characterized in that, The dies used for perforation consist of regularly arranged steel needles with a spacing D of 1500μm to 4000μm.

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