A method for quickly detecting whether membrane electrode mass transfer and drainage are normal

Abstract

The present invention relates to a method for detecting the performance of a membrane electrode, and in particular to a method for quickly detecting whether the mass transfer and drainage of a membrane electrode are normal within the entire effective area, comprising the following steps: (1) connecting the positive and negative electrodes of a single cell to a constant voltage output, and measuring the current intensity I0; (2) taking out the membrane electrode of the single cell, covering the insulating film at the corresponding positions on the two side surfaces, and then reassembling it into a single cell, reconnecting it to the constant voltage output, and measuring the current intensity I1; (3) the total effective area of ​​the single side surface of the membrane electrode is recorded as S0, and the area of ​​the insulating film covering the side surface is recorded as S1; (4) when I0 / S0=A0, I1 / (S0-S1)=A1, when the ratio difference between A0 and A1 is ≤10%, it indicates that the mass transfer and drainage of the fuel cell membrane electrode are normal as a whole, otherwise, it is abnormal, thereby resulting in uneven distribution of the membrane electrode current density. Compared with the prior art, the detection method of the present invention can quickly and easily determine whether the mass transfer and drainage of a fuel cell membrane electrode (MEA) in a single cell are normal.

Description

Technical Field

[0001] The invention relates to a method for detecting membrane electrode performance, and in particular to a method for quickly detecting whether mass transfer and drainage of a membrane electrode are normal. Background Art

[0002] Membrane Electrode Assembly (MEA) is the place where electrochemical reactions occur in proton exchange membrane fuel cells and is the core link of fuel cell technology. The membrane electrode is the "chip" of proton exchange membrane fuel cells, and its cost accounts for more than 60% of the total cost of the fuel cell stack.

[0003] The performance test and evaluation of the membrane electrode (MEA) or CCM prepared in production is usually carried out in a single cell or a short stack of fuel cells, mainly involving the influence of current, voltage, polarization curve, air flow stoichiometry on membrane electrode performance, the influence of current-voltage discharge curve and performance curve, the influence of hydrogen flow stoichiometry on the discharge curve of the membrane electrode, the influence of current-voltage performance curve, whether the drainage is normal, etc. Among them, whether the drainage on the bipolar plate is normal will affect the mass transfer and diffusion of air and hydrogen in the membrane electrode of a single cell, and then affect the working performance and efficiency of the fuel cell. Mass transfer includes the timely diffusion of oxygen in the air and the penetration into the membrane electrode to produce electrochemical reactions, and also includes the timely diffusion of hydrogen and the penetration into the membrane electrode to produce electrochemical reactions. This penetration and diffusion process is affected by many factors such as the thickness of the carbon diffusion layer material and whether the drainage is normal.

[0004] The fuel cell membrane electrode test can measure the output performance of the membrane electrode, and at the same time, the working state of the membrane electrode can be characterized by means of some electrochemical testing methods. Common membrane electrode test methods mainly include polarization curve test, linear potential scanning test, AC impedance test, etc., which can examine the power generation performance of the membrane electrode, the active area of ​​the catalyst, the hydrogen permeation of the membrane electrode, the contact impedance of the membrane electrode, etc. When a large amount of water is generated and accumulated in the membrane electrode, the permeation, diffusion and mass transfer of air and hydrogen will be affected, and then the various performances of the fuel cell and the single cell will be affected. This effect can be reflected from the current-voltage polarization curve of the membrane electrode. At present, there is a technology in the prior art to test the current density distribution of the membrane electrode. This technology is essentially to divide the effective area of ​​the membrane electrode into many equal parts, and make many equal parts of the membrane electrode into independent small batteries under the same test conditions, connect the positive and negative electrodes separately, and test the discharge results separately, but this technology requires the design and production of special test equipment, and the measurement and other aspects are very complicated, and the cost is too high after being too fine. Summary of the invention

[0005] The purpose of the present invention is to provide a method for quickly detecting whether the mass transfer and drainage of the membrane electrode are normal by detecting whether the current density distribution on the membrane electrode as a whole is uniform, so as to solve the problem in the prior art that it is difficult to judge whether the mass transfer and drainage of the membrane electrode performance are normal, and realize the rapid and easy detection of the mass transfer and drainage of the membrane electrode.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for quickly detecting whether membrane electrode mass transfer and drainage are normal comprises the following steps:

[0008] (1) Connect the positive and negative electrodes of a single battery to the two ends of a constant voltage discharge, and measure the current intensity I0 of the single battery discharged under constant voltage;

[0009] (2) Take out the membrane electrode of the above single cell, cover the corresponding positions on both sides of the membrane electrode with an insulating film, and then assemble it into a single cell. Reconnect the two ends of the above constant voltage discharge and measure the current intensity I1 of the single cell.

[0010] (3) The total effective area of ​​the single-side surface of the membrane electrode is recorded as S0, and the area of ​​the insulating film covering the side surface is recorded as S1;

[0011] (4) I0 / S0 = A0, I1 / (S0-S1) = A1. When the ratio difference between A0 and A1 is ≤10%, it indicates that the mass transfer and drainage of the fuel cell membrane electrode are normal as a whole. Otherwise, it is abnormal. The method of judging whether the mass transfer and drainage of the membrane electrode are normal is to detect whether the current density distribution on the membrane electrode as a whole is uniform.

[0012] When the ratio difference between A0 and A1 is more than 10%, it indicates that the membrane electrode as a whole has regional mass transfer and drainage abnormalities, resulting in uneven distribution of membrane electrode current density, and the membrane electrode needs to be replaced.

[0013] Where I0 / S0 refers to the ratio of the current intensity I0 of the normal uncovered membrane electrode at a specified constant voltage discharge to the total effective area S0 (square centimeters) of the membrane electrode, denoted as A0;

[0014] I1 / (S0-S1) refers to the I1 / (S0-S1) ratio of the discharge under the same operating conditions (specified constant voltage discharge, the same hydrogen and air stoichiometric ratio, temperature, etc.) after the corresponding positions on the two sides of the membrane electrode are covered with insulating films.

[0015] Preferably, the area of ​​the insulating film is 1 / 5 to 2 / 3 of the effective area of ​​the membrane electrode.

[0016] Preferably, the area of ​​the insulating film is 1 / 3 to 2 / 3 of the effective area of ​​the membrane electrode.

[0017] Preferably, the insulating film is made of a material that is insulating, water-impermeable, and air-impermeable.

[0018] Preferably, the insulating film is made of polyester, polyimide, or polytetrafluoroethylene.

[0019] Preferably, the thickness of the insulating film is 1 - 10 μm.

[0020] Preferably, the thickness of the insulating film is 2 - 6 μm.

[0021] Preferably, adjust the position of the insulating film covering the membrane electrode, measure the current intensity of the membrane electrode at different positions, and determine whether the mass transfer and water drainage of each part of the membrane electrode are normal.

[0022] Preferably, repeat steps (2) - (4) 3 - 5 times. If it is determined that the mass transfer and water drainage are normal each time, it is considered normal.

[0023] Preferably, when it is determined that the mass transfer and water drainage are normal, use insulating films of different areas to cover different parts of the membrane electrode, and determine whether the mass transfer and water drainage of the entire membrane electrode are normal.

[0024] The working principle of the present invention is as follows:

[0025] The method for determining whether the mass transfer and water drainage of a fuel cell membrane electrode are normal by detecting whether the current density distribution on the entire membrane electrode is uniform. First, measure the current intensity of the membrane electrode without covering the insulating film under certain operating conditions, and record it as the initial value I0. Cover the upper and lower surfaces of the membrane electrode with an insulating film of a known area at corresponding positions, and measure the current intensity of the membrane electrode in this state under the same operating conditions as the previous measurement, and record it as the experimental value I1. When the ratio of the normal non-covered membrane electrode I0 / S0 (the ratio of the current intensity I0 at a specified constant voltage discharge to the total effective area S0 (square centimeters) of the membrane electrode is denoted as A0), and the ratio of A0 / S0 to I1 / (S0 - S1) during discharge under the same operating conditions (specified constant voltage discharge, the same hydrogen and air stoichiometry, temperature, etc.) after covering the corresponding positions on both sides of the membrane electrode with the insulating film is the same, it indicates that the mass transfer and water drainage of the fuel cell membrane electrode are normal. If I0 / S0 < I1 / (S0 - S1), and the ratio difference is more than 10%, it indicates that the mass transfer and water drainage of the membrane electrode are abnormal.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. Through the detection method of the present invention, it is possible to quickly and simply determine whether the mass transfer and water drainage of a fuel cell membrane electrode (MEA) in a single cell are normal.

[0028] 2. The detection method of the present invention only needs to measure the current intensity under a constant voltage, and the result can be obtained through simple calculation. It has strong applicability and can be connected to a computer program and a control device to realize automatic detection. It can also be manually calculated when there is a lack of automatic equipment or when necessary. By detecting whether the current density distribution on the membrane electrode as a whole is uniform, it can be judged whether the mass transfer and drainage of the membrane electrode are normal. DETAILED DESCRIPTION

[0029] The present invention is described in detail below through specific embodiments.

[0030] A method for quickly detecting whether membrane electrode mass transfer and drainage are normal comprises the following steps:

[0031] (1) Connect the positive and negative electrodes of a single battery to the two ends of a constant voltage discharge, and measure the current intensity I0 of the single battery discharged under constant voltage;

[0032] (2) Take out the membrane electrode of the above single cell, cover the corresponding positions on both sides of the membrane electrode with an insulating film, and then assemble it into a single cell. Reconnect the two ends of the above constant voltage discharge and measure the current intensity I1 of the single cell.

[0033] (3) The total effective area of ​​the single-side surface of the membrane electrode is recorded as S0, and the area of ​​the insulating film covering the side surface is recorded as S1;

[0034] (4) I0 / S0 = A0, I1 / (S0-S1) = A1. When the ratio difference between A0 and A1 is ≤10%, it indicates that the fuel cell membrane electrode mass transfer and drainage are normal. Otherwise, it is abnormal. When the ratio difference between A0 and A1 is >10%, it indicates that the membrane electrode mass transfer and drainage are abnormal and the membrane electrode needs to be replaced.

[0035] The area of ​​the insulating film is 1 / 5 to 2 / 3 of the membrane electrode area, more specifically, 1 / 3 to 2 / 3. The material used for the insulating film is an inert, insulating, water-tight, air-tight, harmless, and stable material, more specifically, polyester (PET) or polyimide (PI) or polytetrafluoroethylene (PTFE). The thickness of the insulating film is 1 to 10 μm, more specifically, 2 to 6 μm. The insulating film is attached to the front and back sides of the membrane electrode with a small amount of double-sided tape with a thickness of 1 μm, and the covered area, shape, and position must remain the same.

[0036] This detection method also requires adjusting the position of the insulating film covering the membrane electrode to measure the current intensity of the membrane electrode at different positions to determine whether the mass transfer and drainage of each part of the membrane electrode are normal; or using insulating films of different areas to cover different parts of the membrane electrode to determine whether the mass transfer and drainage of the entire membrane electrode are normal. The entire detection process needs to repeat steps (2) to (4) 3 to 5 times. When it is determined that the mass transfer and drainage of each position are normal, it is considered that the mass transfer and drainage of the entire membrane are normal.

[0037] Example 1

[0038] For effective area S0 of 300cm 2 The automotive membrane electrode was measured. First, the current intensity of the membrane electrode was measured when it was not covered with an insulating film: the membrane electrode was assembled into a single cell and connected to a 0.6V voltage at both ends. The hydrogen stoichiometric ratio was set to 1.2, the air stoichiometric ratio was set to 2.5, the operating temperature was 65°C, and the relative humidity of hydrogen and air was 60%. The current density was measured to be 1A / cm 2 , the current intensity I0 is 300A.

[0039] The thickness is 2 μm and the covering area S1 is 150 cm 2 The polyester insulating film is sequentially covered on the upper and lower effective areas of the membrane electrode. Under the same operating conditions, the current intensity I1 is 151A.

[0040] A0=I0 / S0=1A / cm 2 , A1=I1 / (S0-S1)=1.01A / cm 2 It can be seen that A0 / S0 is basically equal to A1 / (S0-S1), which indicates that the mass transfer and drainage of the upper and lower membrane electrodes are normal, and it is effective power generation.

[0041] Example 2

[0042] The same automotive membrane electrode as in Example 1 (effective area S0 is 300 cm 2 ), under the same operating conditions as in Example 1, the current intensity I0 when the insulating film is not covered is 300A, A0=I0 / S0=1A / cm 2 .

[0043] The thickness is 6 μm and the covering area S1 is 150 cm 2 The polyimide insulating film is sequentially covered on the upper and lower effective areas of the membrane electrode. After measurement, the current intensity I1 is 130A, A1 = I1 / (S0-S1) = 0.87A / cm 2 ; Take out the membrane electrode and move the insulating film to the upper and lower effective areas of the membrane electrode. The covering area S2 is still 150cm 2 After measurement, the current intensity I2 is 170A, A2 = I2 / (S0-S2) = 1.13A / cm 2 The ratios of A1 and A2 to A0 are both over 10%, which indicates that the mass transfer and drainage of the upper and lower membrane electrodes in the left half of the membrane electrode are abnormal.

[0044] This indicates that the mass transfer and drainage of the membrane electrode in some areas are abnormal.

[0045] Example 3

[0046] The same automotive membrane electrode as in Example 1 (effective area S0 is 300 cm 2 ), under the same operating conditions as in Example 1, the current intensity I0 when the insulating film is not covered is 300A, A0=I0 / S0=1A / cm 2 .

[0047] The thickness is 3 μm and the covering area S1 is 100 cm 2 The polytetrafluoroethylene insulating film is sequentially covered on the upper and lower effective areas of the membrane electrode. After measurement, the current intensity I1 is 204A, A1 = I1 / (S0-S1) = 1.02A / cm 2 ; The difference between the ratio of A0 and A1 is ≤10%, which indicates that the mass transfer and drainage of this part of the membrane electrode are normal, and it is effective power generation. Take out the membrane electrode, remove the insulating film at that position and change the position of the insulating film, and measure three more times at the effective area of ​​the membrane electrode that has not been measured until the entire membrane electrode has been measured. The measured current intensity I x The results are 204A (x=1), 201A (x=2), 213A (x=3) and 210A (x=4), and the current density is 1.02A / cm 2 , 1.01A / cm 2 , 1.07A / cm 2 , 1.05A / cm 2 It can be seen that the ratios to A0 are all less than 10%, which indicates that the mass transfer and drainage of the entire membrane electrode are normal, and that power generation is effective.

[0048] Example 4

[0049] The same automotive membrane electrode as in Example 1 (effective area S0 is 300 cm 2 ), under the same operating conditions as in Example 1, the current intensity I0 when the insulating film is not covered is 300A, A0=I0 / S0=1A / cm 2 .

[0050] The thickness is 7 μm and the covering area S1 is 60 cm 2 The polyester insulating film is sequentially covered on the upper and lower effective areas of the membrane electrode. After measurement, the current intensity I1 is 250A, A1 = I1 / (S0-S1) = 1.04A / cm 2; The ratio of A0 is <0.1, which indicates that the mass transfer and drainage of this part of the membrane electrode are normal, and it is effective power generation. Take out the membrane electrode, remove the insulating film at that position and change the area and position of the insulating film. Measure the membrane electrode where the effective area is not measured 4 more times until the entire membrane electrode is measured. Measure the covering area S of the insulating film used. x 60cm respectively 2 (x=1)、100cm 2 (x=2)、150cm 2 (x=3)、180cm 2 (x=4) and 200cm 2 (x=5), the measured current intensity I x The results are 250A (x=1), 208A (x=2), 151A (x=3), 129A (x=4) and 105A (x=5), and the current density is 1.04A / cm 2 , 1.04A / cm 2 , 1.01A / cm 2 , 1.08A / cm 2 , 1.05A / cm 2 It can be seen that the ratios to A0 are all less than 10%, which indicates that the mass transfer and drainage of the entire membrane electrode are normal, and that power generation is effective.

[0051] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for quickly detecting whether the mass transfer and drainage of membrane electrodes are normal. It is characterized in that The following steps are involved: (1) Connect the positive and negative electrodes of a single battery to the two ends of a constant voltage discharge device and measure the current intensity I of the single battery discharged at a constant voltage. 0 ; (2) Take out the membrane electrode of the above single cell, cover the corresponding positions on both sides of the membrane electrode with an insulating film, and then assemble it into a single cell. Reconnect the two ends of the above constant voltage discharge and measure the current intensity I of the single cell. 1 ; (3) The total effective area of ​​the membrane electrode on one side is denoted as S 0 The area of ​​the insulating film covering the side surface is recorded as S 1 ; (4) I 0 / S 0 =A 0 , I 1 / (S 0 -S 1 ) = A 1 , when A 0 With A 1 When the ratio difference is ≤10%, it indicates that the fuel cell membrane electrode has normal mass transfer and drainage as a whole. Otherwise, it is abnormal. The method of judging whether the membrane electrode mass transfer and drainage are normal is to detect whether the current density distribution on the membrane electrode as a whole is uniform. Adjust the position of the insulating film covering the membrane electrode, measure the current intensity of the membrane electrode at different positions, and judge whether the mass transfer and drainage of each part of the membrane electrode are normal; When it is determined that the mass transfer and drainage are normal, use insulating films of different areas to cover different parts of the membrane electrode to determine whether the mass transfer and drainage of the entire membrane electrode are normal; The area of ​​the insulating film is 1 / 5 to 2 / 3 of the effective area of ​​the membrane electrode; The insulating film is made of an insulating, water-tight and air-tight material; The thickness of the insulating film is 1-10 μm.

2. A method for rapidly detecting whether membrane electrode mass transfer and drainage are normal according to claim 1, It is characterized in that When A 0 With A 1 When the ratio difference is >10%, it indicates that there are regional mass transfer and drainage abnormalities in the membrane electrode as a whole, resulting in uneven distribution of membrane electrode current density.

3. A method for rapidly detecting whether the mass transfer and drainage of membrane electrode are normal according to claim 1, It is characterized in that The material of the insulating film is polyester, polyimide or polytetrafluoroethylene.

4. A method for rapidly detecting whether membrane electrode mass transfer and drainage are normal according to claim 1, It is characterized in that The thickness of the insulating film is 2-6 μm.

5. A method for rapidly detecting whether membrane electrode mass transfer and drainage are normal according to claim 1, It is characterized in that Repeat steps (2) to (4) 3 to 5 times. If the mass transfer and drainage are normal, then it is normal.