A method of determining pinhole size in low temperature proton exchange membrane fuel cell components

Abstract

This invention provides a method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component. A circuit board is attached tightly to the cathode side of the fuel cell bipolar plate. The current signal on the cathode side of the fuel cell is collected. The fuel cell is started, and it is placed in an open-circuit or running state. After reaching a preset current density, back pressure is applied to both the anode and cathode sides of the fuel cell, ensuring that the back pressure on the anode side is greater than that on the cathode side. The temperature of the fuel cell is controlled, and the difference between the back pressures on the anode and cathode sides is gradually increased until a local negative current density is detected. The difference between the back pressures on the anode and cathode sides at the point where the negative current density occurs is recorded. The pinhole size is then calculated using a formula. This invention solves the problem of the inability to detect the pinhole size of the membrane electrode in online technology.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more particularly to a method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component. Background Technology

[0002] Currently, the two major challenges facing the large-scale application of fuel cells are lifespan and cost. For membrane electrode assemblies (MEAs), a key component of commercial proton exchange membrane fuel cells, durability is of paramount importance.

[0003] Pinholes on the membrane electrode assembly (MEA) can affect its durability. During the MEA production process and fuel cell assembly, the MEA may be accidentally damaged, resulting in pinholes. Most literature suggests that pinholes on the MEA can lead to hydrogen leakage, posing safety issues and causing a rapid decline in fuel cell performance. Therefore, the detection of pinholes on the MEA is crucial for the large-scale application of fuel cells.

[0004] Existing methods for detecting pinholes in membrane electrodes can only detect the presence of pinhole defects online, or require disassembling the battery to determine the location and size of the pinholes. The size of the pinholes cannot be detected during battery operation. Summary of the Invention

[0005] To address the aforementioned technical problem of the inability to detect pinhole size in membrane electrode assemblies (MEAs) online, this invention provides a method for determining pinhole size in components of a cryogenic proton exchange membrane fuel cell. The invention primarily utilizes a circuit board mounted on the cathode side of the bipolar plate to detect the current density distribution on the cathode side of the MEA. By recording the back voltage difference when negative current densities occur, the pinhole size is calculated using a formula. This method allows for the simple and convenient determination of pinhole size on the MEA without disassembling the fuel cell, is applicable to various operating conditions, and is convenient for practical application.

[0006] The technical means employed in this invention are as follows:

[0007] A method for determining the pinhole size in a cryogenic proton exchange membrane fuel cell stack component includes the following steps:

[0008] S1. Place the circuit board tightly against the cathode side of the fuel cell bipolar plate and collect the current signal from the cathode side of the fuel cell.

[0009] S2. Start the fuel cell to put it in an open circuit or running state. After reaching the preset current density, apply back pressure to the anode side and cathode side of the fuel cell respectively to ensure that the back pressure on the anode side is greater than the back pressure on the cathode side, thereby controlling the temperature of the fuel cell.

[0010] S3. Gradually increase the difference between the back pressure on the anode side and the cathode side until a local negative current density is detected.

[0011] S4. Record the back pressure difference between the anode side and the cathode side as P when the negative current density occurs. C The size of the pinhole is calculated using the following formula:

[0012]

[0013] Among them, P C This represents the back voltage difference between the anode and cathode sides when a negative current density occurs.

[0014] σ is a function of temperature during fuel cell operation. Consult relevant technical literature to clarify the corresponding function values ​​of temperature and σ.

[0015] θ is the water contact angle. Different membrane electrodes correspond to different water contact angles, which are determined based on the actual membrane electrode used.

[0016] r is the radius of the pinhole.

[0017] Furthermore, in step S2, the overall current density of the fuel cell during operation is less than 500 mA / cm². 2 .

[0018] Furthermore, in step S2, the temperature of the fuel cell during open circuit or operation is 60–80°C.

[0019] Furthermore, the stoichiometric ratio of hydrogen intake on the anode side is 1.5 to 2.5, and the stoichiometric ratio of air intake on the cathode side is 2.5 to 3.5.

[0020] Further, in step S3, the difference between the anode-side back pressure and the cathode-side back pressure is 0.1 to 1.2 bar.

[0021] Furthermore, in step S2, the humidity on the anode side and the cathode side is 10% to 100%.

[0022] Furthermore, the circuit board is a PCB circuit board manufactured with Hall elements, and the circuit board fully covers the membrane electrode area.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The present invention provides a method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell stack component. By setting a circuit board on the cathode side of the bipolar plate, detecting the current density distribution on the cathode side of the membrane electrode, recording the back pressure difference when a negative current density occurs, and substituting it into the surface tension formula to calculate the pinhole size, the pinhole size on the membrane electrode can be obtained simply and conveniently, which is convenient for practical application.

[0025] 2. The present invention provides a method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell stack component. By setting a circuit board on the cathode side of the bipolar plate and detecting the current density distribution on the cathode side of the membrane electrode, the size of the membrane electrode pinhole can be obtained without disassembling the fuel cell. It can also detect the size of the pinhole caused by membrane electrode damage in situ online during the open circuit or operation of the fuel cell, and has a wide range of applications.

[0026] Based on the above reasons, this invention can be widely applied in fields such as fuel cells. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a current density distribution diagram of the fuel cell when the anode-side back pressure is 0.1 bar in Embodiment 1 of the present invention.

[0029] Figure 2 This is a current density distribution diagram of the fuel cell with an anode-side back pressure of 0.12 bar in Embodiment 1 of the present invention.

[0030] Figure 3 This is a graph showing the diameter test data of holes drilled on the membrane electrode using the femtosecond laser drilling method in Embodiment 1 of the present invention.

[0031] Figure 4 This is a graph showing the diameter test data of the membrane electrode after it was placed in water using the femtosecond laser drilling method in Embodiment 1 of the present invention. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] This invention provides a method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component, the specific steps of which are as follows:

[0036] S1. The circuit board (PCB) is attached tightly to the cathode side of the fuel cell bipolar plate to collect the current signal on the cathode side of the fuel cell and obtain the distribution of current density.

[0037] S2. Start the fuel cell to put it in an open circuit or running state. After reaching the preset current density, apply back pressure (back pressure refers to the pressure at the outlet) to the anode side and cathode side of the fuel cell respectively to ensure that the back pressure on the anode side is greater than the back pressure on the cathode side, thereby controlling the temperature of the fuel cell.

[0038] S3. Gradually increase the difference between the back pressure on the anode side and the cathode side until a local negative current density is detected.

[0039] S4. Record the back pressure difference between the anode side and the cathode side as P when the negative current density occurs. C The size of the pinhole is calculated using the following formula:

[0040]

[0041] Among them, P C This represents the back voltage difference between the anode and cathode sides when a negative current density occurs.

[0042] σ is a temperature function during fuel cell operation. The corresponding function value of temperature and σ can be found in relevant technical literature. For example, when the temperature is 80℃, the temperature function σ is 0.06268 N / m.

[0043] θ is the water contact angle. Different membrane electrodes correspond to different water contact angles, which can be determined based on the actual membrane electrode used.

[0044] r is the radius of the pinhole.

[0045] Furthermore, the circuit board is a PCB circuit board made of Hall element, and the circuit board effectively covers the reaction area of ​​the fuel cell, that is, the circuit board fully covers the membrane electrode area. If the circuit board does not cover the membrane electrode area, it will cause detection errors.

[0046] Furthermore, in step S2, the overall current density of the fuel cell during operation does not exceed 500 mA / cm². 2 Excessive current density will generate excessive water, causing the local negative current density to disappear, making it impossible to accurately detect the presence of the pinhole. Moreover, the current density exceeds 500 mA / cm². 2 Applying a much higher pressure to the anode side would be extremely dangerous.

[0047] Furthermore, in step S2, the temperature of the fuel cell during open circuit or operation is 60–80°C.

[0048] Furthermore, in step S3, the back pressure difference between the anode side and the cathode side is 0.1 to 1.2 bar. Within the tolerance range of the membrane electrode, the pressure difference between the anode side and the cathode side can be increased to 1.2 bar, which can detect pinholes with a diameter of 10 μm or more.

[0049] Furthermore, in step S2, the stoichiometric ratio of hydrogen intake on the anode side is 1.5 to 2.5, and the stoichiometric ratio of air intake on the cathode side is 2.5 to 3.5. Ensuring the stoichiometric ratio between the anode side and the cathode side is to ensure that the chemical reaction can proceed normally. Under normal circumstances, the hydrogen intake on the anode side needs to be higher than the theoretical value.

[0050] Furthermore, in step S2, the humidity of the anode side and the cathode side is 10% to 100% in order to fill the pinhole with water generated during the operation of the fuel cell.

[0051] Furthermore, in step S2, the humidity of the anode side and the cathode side is 100% to ensure that the pinhole is completely filled with water, making the measurement results more accurate.

[0052] During actual testing, it was found that water would clog the pinholes and generate capillary surface tension. Therefore, it is necessary to ensure that the back pressure on the anode side is greater than that on the cathode side. As the pressure increases, when the back pressure on the anode side is greater than the surface tension, water will be discharged from the pinholes, resulting in a negative current density, which facilitates detection.

[0053] The method described in this embodiment is used to detect pinhole size in the Gore membrane. A femtosecond laser is used to quantitatively drill holes in the Gore membrane, with a hole diameter of approximately 10 μm. The detection conditions are: the operating current density of the fuel cell is 100 mA / cm². 2;

[0054] The stoichiometric ratio of hydrogen intake on the anode side is 1.5, and the stoichiometric ratio of air intake on the cathode side is 3.0.

[0055] The humidity on both the anode side and the cathode side is 100%.

[0056] The operating temperature of the fuel cell is 80℃, and the corresponding temperature function σ is 0.06268N / m;

[0057] The water contact angle of the Gore membrane is θ = 0°.

[0058] Initially, the back pressure values ​​on the anode side and the cathode side are equal. During the detection process, the back pressures on the anode side and the cathode side are gradually increased. The current density distribution on the cathode side is collected through the circuit board (PCB). When the back pressure value on the anode side is 0.1 bar and the back pressure value on the cathode side is 0 bar, the current density distribution on the cathode side is as follows. Figure 1 As shown, no negative current density values ​​appeared in the current density data.

[0059] By increasing the back pressure difference between the anode side and the cathode side, the circuit board (PCB) continues to collect the current density distribution on the cathode side, such as... Figure 2 As shown, when the back pressure on the anode side is 1.2 bar and the back pressure on the cathode side is 0 bar, negative current density begins to appear in the current density, P. C With a pressure of 1.2 bar, substituting the value into the formula, the pinhole radius r = 1.253 μm was calculated, and the measured pinhole diameter was approximately 2.5 μm, indicating high measurement accuracy. However, during actual operation of the fuel cell, the membrane electrode assembly (MEA) will swell due to the influence of water, causing the actual pinhole diameter on the MEA to decrease. Therefore, there is a certain error between the calculated and actual values. Figure 3 As shown, when using the femtosecond laser drilling method, it is impossible to guarantee that the minimum aperture is 10 μm; only that the diameter of the pinhole on the surface of the membrane electrode is 10 μm. The aperture size of the membrane electrode after immersion in water is as follows: Figure 4 As shown, due to swelling in water, the pore size on the membrane electrode is smaller than that in the dry case.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component, characterized in that, Includes the following steps: S1. Place the circuit board tightly against the cathode side of the fuel cell bipolar plate and collect the current signal from the cathode side of the fuel cell. S2. Start the fuel cell to put it in an open circuit or running state. After reaching the preset current density, apply back pressure to the anode side and cathode side of the fuel cell respectively to ensure that the back pressure on the anode side is greater than the back pressure on the cathode side, thereby controlling the temperature of the fuel cell. S3. Gradually increase the difference between the back pressure on the anode side and the cathode side until a local negative current density is detected. S4. Record the back pressure difference between the anode side and the cathode side as P when the negative current density occurs. C The size of the pinhole is calculated using the following formula: Among them, P C This represents the back voltage difference between the anode and cathode sides when a negative current density occurs. This is a function of the temperature during fuel cell operation; The water contact angle varies depending on the membrane electrode used. r is the radius of the pinhole.

2. The method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component according to claim 1, characterized in that, In step S2, the overall current density of the fuel cell during operation does not exceed 500 mA / cm². 2 .

3. The method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component according to claim 2, characterized in that, In step S2, the temperature of the fuel cell during open circuit operation or operation is 60–80°C.

4. The method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component according to claim 3, characterized in that, The stoichiometric ratio of hydrogen intake on the anode side is 1.5 to 2.5, and the stoichiometric ratio of air intake on the cathode side is 2.5 to 3.

5.

5. The method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component according to claim 4, characterized in that, In step S3, the difference between the anode-side back pressure and the cathode-side back pressure is 0.1 to 1.2 bar.

6. The method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component according to claim 5, characterized in that, In step S2, the humidity on the anode side and the cathode side is 10% to 100%.

7. The method for determining the pinhole size in a low-temperature proton exchange membrane fuel cell component according to claim 6, characterized in that, The circuit board is a PCB circuit board made of Hall element, and the circuit board fully covers the membrane electrode area.

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