A pinhole inspection method for low-temperature proton exchange membrane fuel cells

Abstract

The present invention provides a method for detecting pinholes in a low-temperature proton exchange membrane fuel cell, comprising the following steps: placing a circuit board on the cathode side of the fuel cell, collecting the current signal on the cathode side of the fuel cell, placing the fuel cell in an open circuit or operating state, and after reaching a preset current density and temperature, applying back pressure on the anode and cathode sides of the fuel cell, respectively, ensuring that the anode back pressure is greater than the cathode back pressure, gradually increasing the difference between the anode and cathode back pressures, detecting the presence of a local negative current density, indicating the presence of a pinhole on the membrane electrode, and continuing to increase the anode back pressure. The negative current density increases with the increase in the anode back pressure, resulting in several locations with local negative current density. The location with the largest absolute value of the negative current density is the location of the membrane electrode pinhole. The technical solution of the present invention solves the problem in the prior art of being unable to detect the location of membrane electrode pinholes online.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a method for inspecting pinholes in low-temperature proton exchange membrane fuel cells. Background Art

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

[0003] Pinholes on the membrane electrode will affect the durability of the membrane electrode. During the production process of the membrane electrode and the assembly process of the fuel cell, the membrane electrode will be accidentally damaged and pinholes will appear. In addition, most literatures believe that pinholes on the membrane electrode will cause hydrogen leakage, safety problems, and is also one of the reasons for the rapid decline in fuel cell performance. Therefore, the detection of pinholes on the membrane electrode is very important for the large-scale application of fuel cells.

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

[0005] In response to the aforementioned technical problem of being unable to detect the location of membrane electrode pinholes online, a method for detecting pinholes in low-temperature proton exchange membrane fuel cells is provided. The present invention primarily utilizes a circuit board installed on the cathode side of the fuel cell to detect the distribution of current density on the cathode side of the membrane electrode, allowing the location of pinholes on the membrane electrode to be determined while the fuel cell is open-circuited or online. This method eliminates the need to disassemble the cell, resulting in a wide range of applications and simple, convenient operation, making it easy to implement in practice.

[0006] The technical means adopted in the present invention are as follows:

[0007] A method for inspecting pinholes in a low-temperature proton exchange membrane fuel cell comprises the following steps:

[0008] S1. placing a circuit board (PCB) on the cathode side of a fuel cell and collecting a current signal on the cathode side of the fuel cell;

[0009] S2. Start the fuel cell and place the fuel cell in an open circuit (OCV) or operating state. After reaching a preset current density and temperature, apply back pressure to the anode and cathode sides of the fuel cell, respectively, to ensure that the anode back pressure is greater than the cathode back pressure.

[0010] S3, gradually increasing the difference between the back pressure on the anode side and the back pressure on the cathode side, and detecting the presence of a local negative current density, indicating the presence of a pinhole on the membrane electrode;

[0011] S4. Continue to increase the anode side back pressure. The negative current density will increase with the increase of the anode side back pressure value. There will be two or more locations of local negative current density. The location with the largest absolute value of the negative current density is the location of the membrane electrode pinhole.

[0012] Furthermore, in step S2, the back pressure difference between the anode side and the cathode side is greater than 0.1 bar.

[0013] Furthermore, in step S3, the back pressure difference between the anode side and the cathode side is 0.1-1.2 bar.

[0014] Furthermore, in step S2, the overall current density of the fuel cell during operation does not exceed 500 mA / cm 2 .

[0015] Furthermore, in step S2, the humidity of the anode side and the cathode side is 10% to 60%.

[0016] Furthermore, in step S2, the stoichiometric ratio of the hydrogen intake amount on the anode side is 1.5-2.5, and the stoichiometric ratio of the air intake amount on the cathode side is 2.5-3.5.

[0017] Furthermore, the circuit board is a PCB circuit board manufactured by the Hall element, and the circuit board fully covers the membrane electrode area.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The present invention provides a method for inspecting pinholes in low-temperature proton exchange membrane fuel cells. By setting a circuit board on the cathode side of the fuel cell, the distribution of current density on the cathode side of the membrane electrode can be detected when the fuel cell is open-circuited or online, and the location of the pinholes on the membrane electrode can be determined without disassembling the battery. The method has a wide range of applications, is simple and convenient to operate, and is easy to use in practice.

[0020] 2. The present invention provides a low-temperature proton exchange membrane fuel cell pinhole inspection method. By making the back pressure on the anode side greater than the back pressure on the cathode side by more than 0.1 bar, it eliminates the situation where water blocks the pinhole and causes the pinhole to be undetectable. The humidity on the anode and cathode sides is required to be maintained below 60% to prevent excessive water content, which may result in the absence of local negative current density and affect the detection results.

[0021] Based on the above reasons, the present invention can be widely promoted in the fields of fuel cells and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 This is a current density distribution diagram of the fuel cell in Example 1 of the present invention in an open circuit state.

[0024] Figure 2 This is a current density distribution diagram when the fuel cell in Example 2 of the present invention is in an operating state and the anode side back pressure is 0.2 bar.

[0025] Figure 3 This is a current density distribution diagram when the fuel cell in Example 2 of the present invention is in an operating state and the anode side back pressure is 0.6 bar.

[0026] Figure 4 The fuel cell in Example 3 of the present invention is at 200mA / cm 2 Current density distribution diagram under working conditions. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​described in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The techniques, methods and equipment known to ordinary technicians in the relevant fields may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0031] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0032] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0033] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] The present invention provides a method for inspecting pinholes in a low-temperature proton exchange membrane fuel cell, the specific steps of which are as follows:

[0036] S1. placing a printed circuit board (PCB) close to the cathode side of a fuel cell and collecting a current signal from the cathode side of the fuel cell;

[0037] S2. Start the fuel cell and place the fuel cell in an open circuit (OCV) or operating state. After reaching a preset current density and temperature, apply back pressure to the anode and cathode sides of the fuel cell, respectively, to ensure that the anode back pressure is greater than the cathode back pressure.

[0038] S3, gradually increasing the difference between the back pressure on the anode side and the back pressure on the cathode side, and detecting the presence of a local negative current density, indicating the presence of a pinhole on the membrane electrode;

[0039] S4. Continue to increase the anode side back pressure. The negative current density will increase with the increase of the anode side back pressure value. Several locations of local negative current density will appear. The location with the largest absolute value of the negative current density is the location of the membrane electrode pinhole.

[0040] Furthermore, in step S2, the back pressure difference between the anode side and the cathode side is greater than 0.1 bar. In order to exclude water blocking the pinhole, which may cause an erroneous detection result, if water blocks the pinhole during the detection process, the existence of the pinhole cannot be detected.

[0041] Furthermore, in step S3, the back pressure difference between the anode side and the cathode side is 0.1-1.2 bar.

[0042] Furthermore, in step S2, the overall current density of the fuel cell during operation does not exceed 500 mA / cm 2 Too high a current density will produce excessive water, causing the local negative current density to disappear and making it impossible to accurately detect the presence of pinholes. Moreover, the current density exceeds 500 mA / cm 2 It is necessary to apply a greater anode pressure, which is very likely to cause danger.

[0043] Furthermore, in step S2, the humidity of the anode side and the cathode side is 10% to 60% to prevent the water content from being too high, causing the negative current density not to appear locally, making it impossible to detect the presence of the pinhole and affecting the detection accuracy.

[0044] Furthermore, in step S2, the stoichiometric ratio of the hydrogen intake on the anode side is 1.5 to 2.5, and the stoichiometric ratio of the air intake on the cathode side is 2.5 to 3.5. The stoichiometric ratio between the anode side and the cathode side is ensured to ensure that the chemical reaction can proceed normally. Generally, the hydrogen intake on the anode side needs to be higher than the theoretical value.

[0045] Furthermore, the circuit board is a PCB circuit board manufactured with Hall elements, which has the characteristics of high integration, multiple collection test points and high resolution. If there are fewer collection test points, it will affect the collection and detection of key signals, resulting in inaccurate detection results.

[0046] Furthermore, 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 membrane electrode area is not covered, detection errors may occur.

[0047] Furthermore, the inspection method is applicable to pinholes with a diameter of more than 10 μm.

[0048] Theoretically, the appearance of a negative current density indicates the presence of a pinhole. However, in actual testing, it was found that in the open circuit state, factors such as equipment and measurement have a certain impact on the test results, and the appearance of a negative current density does not necessarily mean the presence of a pinhole. Therefore, during the test, the method of increasing the back pressure difference between the anode side and the cathode side is adopted to eliminate the interference of water on the test results and further accurately judge the situation of the pinhole. Because the gas diffuses after passing through the pinhole, multiple negative current density areas will appear, and the point with the largest absolute value is the pinhole position. Therefore, within the tolerance range of the membrane electrode, the back pressure difference between the anode side and the cathode side is increased to 1.2 bar, and the minimum diameter of the pinhole that can be detected is 10um.

[0049] When the fuel cell is in an open circuit state, the stoichiometric ratio of the hydrogen intake on the anode side is 1.5, the stoichiometric ratio of the air intake on the cathode side is 3.5, the humidity on the anode side is 60%, the humidity on the cathode side is 60%, the back pressure on the anode side is 0.2 bar greater than the back pressure on the cathode side, and the distribution of the current density on the cathode side is collected through the circuit board. The distribution of the current density is as follows: Figure 1 As shown in the figure, the minimum negative current density is -27mA / cm 2 , then the location of the minimum amplitude current density is the pinhole position of the membrane electrode.

[0050] Example 2

[0051] The difference between Example 2 and Example 1 is that the fuel cell is at a current density of 100 mA / cm 2In the working operation state, the stoichiometric ratio of the hydrogen intake on the anode side is 2, the stoichiometric ratio of the air intake on the cathode side is 3.5, the anode side back pressure value is set to 0.2 bar, the cathode side back pressure value is set to 0.1 bar, and then the anode side back pressure is gradually increased to 0.6 bar, and the cathode side back pressure value is kept unchanged, and the cathode side current density distribution is collected through the circuit board.

[0052] When the anode side back pressure is greater than the cathode side back pressure by 0.1 bar, the current density distribution is as follows: Figure 2 As shown, there is no negative current density region, and the existence of pinholes cannot be detected.

[0053] Gradually increase the anode side back pressure value and keep the cathode side back pressure value unchanged, so that the anode side back pressure is greater than the cathode side back pressure by 0.5 bar. The current density distribution at this time is as follows Figure 3 As shown in Figure 2, there are multiple negative current density areas, among which the minimum negative current density is -425 mA / cm 2 , which is the pinhole position on the membrane electrode.

[0054] Example 3

[0055] The difference between Example 3 and Example 1 is that the fuel cell is at a current density of 200 mA / cm 2 In the working state, the anode side back pressure value is greater than the cathode side back pressure value by 0.3 bar, and the cathode side current density distribution is collected by the circuit board. Figure 4 As shown, the minimum negative current density is -350mA / cm 2 , which is the pinhole position on the membrane electrode.

[0056] The low-temperature proton exchange membrane fuel cell pinhole inspection method described in the present invention can detect the presence and specific location of pinholes in situ online when the fuel cell is open or in operation. It has a wide range of applications, can eliminate many objective factors, and has accurate detection results with high precision and simple operation, making it easy to apply in actual production.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 inspecting pinholes in a low-temperature proton exchange membrane fuel cell, characterized in that: The following steps are involved: S1. placing the circuit board close to the cathode side of the fuel cell and collecting the current signal of the cathode side of the fuel cell; S2. Start the fuel cell and place the fuel cell in an open circuit or operating state. After reaching a preset current density and temperature, apply back pressure to the anode and cathode sides of the fuel cell, respectively, to ensure that the anode back pressure is greater than the cathode back pressure. S3, gradually increasing the difference between the back pressure on the anode side and the back pressure on the cathode side, and detecting a local negative current density, indicating the presence of a pinhole on the membrane electrode; S4. Continue to increase the anode side back pressure. The negative current density will increase with the increase of the anode side back pressure value. Several locations of local negative current density will appear. The location with the largest absolute value of the negative current density is the location of the membrane electrode pinhole.

2. The low-temperature proton exchange membrane fuel cell pinhole inspection method according to claim 1, characterized in that: In step S2, the back pressure difference between the anode side and the cathode side is greater than 0.1 bar.

3. The low-temperature proton exchange membrane fuel cell pinhole inspection method according to claim 2, characterized in that: In step S3, the back pressure difference between the anode side and the cathode side is 0.1-1.2 bar.

4. The low-temperature proton exchange membrane fuel cell pinhole inspection method according to claim 3, characterized in that: In step S2, the overall current density of the fuel cell during operation does not exceed 500 mA / cm 2 .

5. The low-temperature proton exchange membrane fuel cell pinhole inspection method according to claim 4, characterized in that: In step S2 , the humidity of the anode side and the cathode side is 10% to 60%.

6. The low-temperature proton exchange membrane fuel cell pinhole inspection method according to claim 5, characterized in that: In step S2, the stoichiometric ratio of the hydrogen intake amount on the anode side is 1.5-2.5, and the stoichiometric ratio of the air intake amount on the cathode side is 2.5-3.

5.

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

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