A fuel cell gas diffusion layer water overpressure test system and method

Abstract

This invention discloses a testing system for the water breakthrough pressure of a fuel cell gas diffusion layer and a method for measuring the water breakthrough pressure of the gas diffusion layer. This method evaluates the gas-liquid transport capacity of the gas diffusion layer by measuring its water breakthrough pressure. The water breakthrough pressure measurement system includes a water tank, a gas diffusion layer holder, a pressure loading device, a differential pressure detector, a detection unit, and a thermostat. This invention enables the measurement of the pressure difference across the gas diffusion layer without initiating a fuel cell reaction, allowing for analysis of the water breakthrough pressure and thus assessing the diffusion layer's performance. This detection method ensures sampling accuracy while shortening detection time, saving detection costs, and improving detection efficiency.

Description

Technical Field

[0001] This invention relates to a system and method for testing the water overpressure of a gas diffusion layer in a fuel cell. Background Technology

[0002] During fuel cell operation, water generated in the catalyst layer needs to reach a certain pressure to overcome capillary forces, be transported through the gas diffusion layer to the flow field, and be discharged from the cell by the gas flow. In previous studies, liquid water in the pores overcame capillary forces and external pressure to enter the microporous layer; the pressure overcome in this process is called the breakthrough pressure.

[0003] When fuel cells operate under high humidity and high current density, the moisture generated inside the cell can hinder gas transport, leading to a decline in cell performance. The gas diffusion layer plays a crucial role in the gas-liquid two-phase transport within the cell, and improving its gas-liquid transport capability is essential for enhancing cell performance.

[0004] By optimizing the microstructure of the gas diffusion layer, its gas-liquid transport capacity can be effectively improved. Currently, there are few methods for independently measuring the performance of the gas diffusion layer in fuel cells; often, the capillary pressure is indirectly calculated by measuring the water contact angle. This invention proposes a method to judge the mass transfer performance of the gas diffusion layer by directly measuring the water breakthrough pressure.

[0005] Wu Gangsheng proposed a self-designed and assembled measuring instrument that utilizes the gravity of liquid water as an equivalent breakthrough pressure. Measurements are taken by observing the surface of the gas diffusion layer through the addition of liquid water using a graduated cylinder. While this method is simple, it requires highly skilled personnel and is susceptible to significant errors due to human factors.

[0006] Based on the above research, this invention discloses a fuel cell gas diffusion layer water overpressure testing system and method. By using computer-controlled detection to reduce the influence of human factors, the system can efficiently and accurately measure the diffusion layer overpressure and rapidly detect the diffusion layer performance. Summary of the Invention

[0007] This invention provides a fuel cell gas diffusion layer water breakthrough pressure testing system and method. The purpose is to enable the gas diffusion layer to measure the pressure difference on both sides of the gas diffusion layer and analyze the water breakthrough pressure without the fuel cell reaction, thereby testing the performance of the diffusion layer.

[0008] The specific technical solution of this invention is as follows:

[0009] A fuel cell gas diffusion layer water overpressure testing system includes: a water tank filled with an appropriate volume of water to provide water pressure inside a gas diffusion layer holder; a gas diffusion layer holder connected to the water tank, consisting of a clamp and a rubber gasket, which are used to fix the gas diffusion layer; a pneumatic loading device connected to the air layer of the water tank, which controls the air pressure above the water surface by introducing high-pressure air to monitor and regulate the gas pressure in real time; a differential pressure detector including two pressure sensors and a data processor, wherein the pressure sensors are respectively set on both sides of the gas diffusion layer sample and kept at the same horizontal plane, one pressure sensor is connected to water and the other pressure sensor is connected to the atmosphere, used to detect the pressure difference on both sides of the gas diffusion layer sample, i.e., water overpressure, and record it; a detection unit connected to the gas diffusion layer holder, used to detect whether water has overpressured the gas diffusion layer sample; and a thermostat located outside the gas diffusion layer holder, used to adjust the test temperature of the diffusion layer sample and keep the test temperature constant.

[0010] The invention is further characterized by:

[0011] The water tank has good airtightness and is equipped with an air valve and a water inlet at the top. The water tank consists of an air layer and a liquid water layer. The air layer is connected to the air pressure loading device, and the liquid water layer is connected to the differential pressure detector and the gas diffusion layer holder, respectively.

[0012] The gas diffusion layer holder includes a clamp and a rubber gasket. The clamp and rubber gasket fix the gas diffusion layer sample, with liquid water on one side and air on the other.

[0013] The differential pressure detector includes two pressure sensors and a data processor. The pressure sensors are located on both sides of the gas diffusion layer sample and are kept at the same horizontal level.

[0014] The detection unit includes a digital camera and an image processor, which are connected to the air side of the gas diffusion layer holder to detect and record the surface condition of the gas diffusion layer sample in real time.

[0015] A method for testing the water overpressure in a fuel cell gas diffusion layer includes the following steps: S1) Before starting the experiment, check the airtightness of the apparatus. Place a sample of a common commercial gas diffusion layer into the gas diffusion layer holder and fix it in place. Add liquid water above the height of the differential pressure detector, close the gas valve, and gradually increase the pressure to 10 kPa on one side of the diffusion layer sample using the gas pressure loading device. Observe whether the reading of the differential pressure detector gradually increases. If the reading of the differential pressure detector does not change, there is a gas leak, and the apparatus should be checked again. If the reading gradually increases, the apparatus is airtight. S2) Start the experiment by placing a 2 cm x 2 cm gas diffusion layer sample into the gas diffusion layer holder and fixing it. Turn on the thermostat and control the measurement temperature to reach the preset experimental temperature of 60 ℃. Gradually increase the pressure on one side of the diffusion layer sample through the gas pressure loading device. Observe the surface condition of the other side of the diffusion layer through the detection unit. When water droplets just appear on the surface, record the pressure difference value of the differential pressure detector. S3) Perform multiple experiments. After each experiment, turn off the gas pressure loading device, open the gas valve, wait for the differential pressure detector value to remain at zero, replace the gas diffusion layer sample, and repeat the experimental steps in S2. Beneficial effects

[0016] This invention provides a fuel cell gas diffusion layer water breakthrough pressure testing system and method. This system allows for the measurement of the pressure difference across the gas diffusion layer without a fuel cell reaction, enabling analysis of the water breakthrough pressure and performance testing of the diffusion layer. This significantly reduces experimental costs and workload, and shortens the experimental cycle. Furthermore, the computer-controlled gas pressure loading device, differential pressure detector, detection unit, and thermostat greatly minimize the influence of human factors on the experimental results, making the results more accurate and scientific. 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. Example

[0018] To check the airtightness of the apparatus, a standard commercial gas diffusion layer sample was placed in the gas diffusion layer holder and fixed. Liquid water exceeding the height of the differential pressure detector was added, and the gas valve was closed. The pressure on one side of the diffusion layer sample was gradually increased to 10 kPa using the gas pressure loading device. The gradual increase in the differential pressure detector reading indicated good airtightness. To begin the experiment, a 2 cm x 2 cm hydrophobic gas diffusion layer sample was placed in the gas diffusion layer holder and fixed. The thermostat was turned on, and the measurement temperature was controlled to 60 °C. The pressure on one side of the diffusion layer sample was gradually increased using the gas pressure loading device. The surface condition of the other side of the diffusion layer was observed through the detection unit. The first water droplet was observed, and the differential pressure detector reading was 11.57 kPa, which was recorded. The gas pressure loading device was closed, the gas valve was opened, and after the differential pressure detector reading remained at zero, the above steps were repeated with a gas diffusion layer sample treated with ultrasonic spraying. The differential pressure detector reading was 5.24 kPa, which was recorded.

[0019] Single cells were assembled from samples with gas diffusion layers treated by ultrasonic spraying and those with gas diffusion layers treated only by hydrophobic spraying, and polarization and power density curves were tested. After hydrophilic ultrasonic spraying treatment, the peak power density of the assembled single cell increased from 220 mW / cm². 2Increased to 591 mW / cm 2 Performance increased by 169%. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 Digital photographs of water breakthrough pressure for gas diffusion layer sample a (treated with simple hydrophobic treatment) and gas diffusion layer sample b (treated with hydrophilic ultrasonic spray treatment);

[0022] Figure 3 Polarization and power density curves for a gas diffusion layer sample with a purely hydrophobic treatment;

[0023] Figure 4 Polarization and power density curves of the gas diffusion layer sample treated with hydrophilic ultrasonic spray.

Claims

1. A method for testing the water overpressure in the gas diffusion layer of a fuel cell, characterized in that, A complete testing system includes: A water tank, filled with an appropriate volume of water, provides water pressure inside the gas diffusion layer holder; A gas diffusion layer holder, connected to a water tank, consists of a clamp and a rubber washer, which are used to fix the gas diffusion layer. The pneumatic loading device is connected to the air at the top of the water tank and is used to control the air pressure on the water surface, and to monitor and regulate the gas pressure in real time. Differential pressure detectors are connected to both sides of the gas diffusion layer to detect and record the pressure difference across the gas diffusion layer sample. The detection unit, connected to the gas diffusion layer clamping device, is used to detect whether water has broken through the gas diffusion layer sample. The thermostat, located outside the gas diffusion layer holder, is used to adjust the test temperature of the diffusion layer sample and maintain a constant test temperature.

2. The method for testing the water overpressure in the gas diffusion layer of a fuel cell according to claim 1, characterized in that, The water tank is isolated from outside air, has good airtightness, and has an air valve at the top. The water tank includes an air layer and a liquid water layer. The air layer is connected to a pneumatic loading device, and the liquid water layer is connected to a differential pressure detector and a gas diffusion layer holder, respectively.

3. The method for testing the water overpressure in the gas diffusion layer of a fuel cell according to claim 2, characterized in that, The gas diffusion layer holder includes a clamp and a rubber gasket, which fix the gas diffusion layer.

4. The method for testing the water overpressure in the gas diffusion layer of a fuel cell according to claim 3, characterized in that, The differential pressure detector includes two pressure sensors and a data processor. The pressure sensors are respectively set on both sides of the gas diffusion layer sample and kept at the same horizontal plane. One pressure sensor is connected to water, and the other pressure sensor is connected to the atmosphere.

5. The method for testing the water overpressure in the gas diffusion layer of a fuel cell according to claim 4, characterized in that, The detection unit is connected to the gas diffusion layer holder and includes a digital camera and an image processor.

6. The method for testing the water overpressure in the gas diffusion layer of a fuel cell according to claim 5, characterized in that, Includes the following steps: S1) Before starting the experiment, check the airtightness of the apparatus. Place a sample of a common commercial gas diffusion layer into the gas diffusion layer holder and fix it in place. Add liquid water above the height of the differential pressure detector, close the gas valve, and gradually increase the pressure of the diffusion layer sample to the required experimental level using the gas pressure loading device. Observe whether the reading of the differential pressure detector gradually increases. If the reading of the differential pressure detector does not change, there is a gas leak, and the apparatus needs to be checked again. If the reading gradually increases, the airtightness is good. S2) To begin the experiment, place the required size gas diffusion layer sample into the gas diffusion layer holder and secure it. Turn on the thermostat and control the measurement temperature to reach the preset experimental temperature. Start the gas pressure loading device to gradually increase the pressure on the diffusion layer sample. Observe the surface condition on the other side of the gas diffusion layer through the detection unit. When water droplets just appear on the surface, the differential pressure detector records the differential pressure value. S3) Perform multiple experiments. After each experiment, turn off the gas pressure loading device, open the gas valve and wait for the differential pressure detector value to remain at zero. Then replace the gas diffusion layer sample and repeat the experimental steps in S2.

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