PEMWE accelerated life test method based on start-stop working conditions

Abstract

The invention discloses a proton exchange membrane water electrolysis (PEMWE) accelerated life test method based on start-stop working conditions, and belongs to the technical field of proton exchange membrane water electrolysis life evaluation and durability test. The method comprises the following steps: installing a membrane electrode assembly to be tested in a testing device, introducing deionized water through an anode side, collecting hydrogen production gas through a cathode side, and setting a start-stop cycle of alternating power-on and power-off, so that the membrane electrode assembly bears electrochemical and thermomechanical combined stress. And monitoring the operation state in real time in the test process, characterizing the properties of a polarization curve, an electrochemical impedance spectroscopy and the like at a predetermined time point, and carrying out scanning electron microscope morphology analysis after the test is finished. According to the method, the performance attenuation effect can be remarkably amplified in a short test period, the failure mode of the membrane electrode assembly under the starting and stopping working conditions is revealed, and a reliable basis is provided for durability evaluation of different membrane materials, catalysts and structural systems.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of proton exchange membrane water electrolysis life evaluation and durability test, and particularly relates to a PEMWE accelerated life test method based on start-stop working conditions. BACKGROUND

[0002] Green hydrogen production gradually becomes an important pillar of future energy structure transformation. Proton exchange membrane water electrolysis (PEMWE) technology has become one of the key paths for renewable energy hydrogen production due to its high current density, high hydrogen purity, and fast response. However, due to the intermittent and fluctuating nature of renewable energy sources such as wind and solar power, PEMWE is often in a start-stop state in actual application, especially in unstable sunlight or frequent grid scheduling scenarios, the system may experience dozens of start-stop processes every day. Frequent start-stop not only poses challenges to the operation control of equipment, but also causes irreversible damage to membrane electrode assemblies (MEAs) and catalytic layer materials, which is one of the key bottlenecks limiting the life of PEMWE and commercial deployment.

[0003] Currently, the industry often uses accelerated aging methods under constant current or constant voltage conditions to track indicators such as voltage rise, internal resistance increase, and performance degradation when testing the life of PEMWE. However, this method mainly simulates continuous working conditions and ignores the coupling stress caused by transient electrochemical environmental changes during start-stop processes, such as membrane expansion and contraction, local detachment of the catalytic layer, and gas-liquid conversion mutation. Related studies have shown that a single start-stop may not immediately cause performance degradation, but after long-term repeated action, it is easy to cause mechanical fatigue of the anode catalytic layer, decrease of interface bonding force, and even breakage, thereby inducing structural degradation.

[0004] Therefore, there is an urgent need to develop an accelerated life test method that can simulate "start-stop stress sources" and is more close to real working conditions, improving the engineering applicability and forward-looking nature of test results. SUMMARY

[0005] The present application provides a PEMWE accelerated life test method based on start-stop working conditions to simulate and amplify the multi-field coupling stress caused by frequent start-stop of PEMWE in renewable energy grid-connected operation, accelerate the exposure of failure characteristics of membrane electrode assemblies in catalytic layer, interface structure, and mass transfer performance, and provide a scientific, repeatable, and actual working condition close test method for material optimization, structure improvement, and durability evaluation.

[0006] To achieve the above purpose, the technical solution adopted by the present application is as follows: A PEMWE accelerated life test method based on start-stop working conditions, comprising the following steps: (1) Install the membrane electrode assembly to be tested in a proton exchange membrane water electrolysis test device, and introduce deionized water through the anode side, and collect hydrogen gas produced on the cathode side; (2) Set the start-stop cycle mode, realize periodic start-stop by controlling the alternation of power-on and power-off, maintain open circuit potential during power-off, and make the membrane electrode assembly bear electrochemical and thermal mechanical combined stress under start-stop working conditions; (3) Real-time monitoring and recording of operating parameters during the test, and periodic electrochemical performance characterization within the test period to evaluate the performance degradation of the membrane electrode assembly.

[0007] Further, the conductivity of the deionized water is less than 1 μS / cm.

[0008] Further, the test temperature is controlled within the range of 75-85 ℃.

[0009] Further, the water flow rate of the anode is 15-25 mL / min.

[0010] Further, the working voltage of the power-on stage in step (2) is set to 1.8-2.2 V.

[0011] Further, the cycle of the start-stop cycle in step (2) is 5 s-10 min; preferably, the cycle of the start-stop cycle is 2 s-60 min; more preferably, the cycle of the start-stop cycle is 2 s-5 min.

[0012] Further, a deep power-off stage is inserted every 800-1200 times of start-stop cycle, the deep power-off lasts for 12-36 h, and the open circuit potential state is maintained during the deep power-off.

[0013] Further, the cumulative test duration of step (2) is not less than 1000 h.

[0014] Further, the periodic electrochemical performance characterization includes polarization curve test, electrochemical impedance spectroscopy test and / or Tafel curve test.

[0015] Further, after the test, the membrane electrode assembly is subjected to scanning electron microscope morphology analysis to observe the structural changes of the catalyst layer, diffusion layer and membrane-electrode interface.

[0016] Compared with the prior art, the present application has the following beneficial effects: 1. By comparison with the constant load working condition, the method of the present application significantly shortens the time period of significant performance degradation: the voltage rise in constant current aging within 200 hours is much smaller than that in start-stop working condition, and the mass transfer impedance increases significantly, indicating that the microstructure changes induced by start-stop have become the dominant factor of degradation.

[0017] 2. In the start-stop acceleration mode, the morphological characteristics such as wrinkles, micro-cracks and local peeling of the catalytic layer are clearly observed, while the above phenomena are not significant in the constant load mode, verifying the magnification and identification ability of the method of the application to the structural failure mode.

[0018] 3. The method of the application directly reveals the direct influence of start-stop behavior on the service life of the membrane electrode assembly, and builds an evaluation platform for material development and structure optimization; accordingly, an anode catalyst system more suitable for frequent start-stop scenarios can be screened, or the existing structure can be optimized through stress regulation (such as buffer layer design) to delay failure.

[0019] 4. The test working condition of the application is close to the actual application scenario, and can reflect the typical stress characteristics under grid-connected operation, and the results have clear engineering guiding significance.

[0020] 5. The method of the application has universality, and is suitable for acceleration evaluation of different electrode structures, different catalyst systems and different membrane materials, and is convenient for horizontal comparison and scheme screening.

[0021] 6. The method of the application provides experimental basis for building PEMWE design and evaluation standard with high reliability, has practicality and forward-looking, and can be used in scientific research evaluation, product verification and engineering life prediction occasions, and has clear application popularization value. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Polarization curve of Example 1.

[0023] Figure 2 Electrochemical impedance spectrum of Example 1.

[0024] Figure 3 Polarization curve of Comparative Example 1.

[0025] Figure 4 Electrochemical impedance spectrum of Comparative Example 1. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application. In addition, it is worth mentioning that the raw materials involved in the application are ordinary commercially available products unless otherwise specified.

[0027] Example 1 The present embodiment provides a PEMWE accelerated life test method based on start-stop working condition, comprising the following steps: (1) Assemble the membrane electrode assembly (MEA) to be tested in a single cell water electrolysis test device, and complete the sealing and no-load conduction check; continuously supply high-purity deionized water to the anode side, the conductivity is <1 μS / cm, and the water flow is 20 mL / min; the test temperature is controlled at 80°C and the constant temperature is stable for ≥30 min; collect hydrogen on the cathode side. Record the initial open circuit potential (OCV) and obtain the initial polarization curve, denoted as BoT (Begin of Test).

[0028] (2) Set the start-stop cycle mode, realize periodic start-stop by controlling the alternation of power-on and power-off, and use constant voltage 2.0 V in the power-on stage and maintain OCV state in the power-off stage; the power-on and power-off time ratio is 1:1; the cumulative test time is 8200 h; insert a 24 h OCV deep power-off every 1000 start-stop cycles. Set the following three start-stop frequencies for accelerated life test: (a) High frequency: power on for 6 s / power off for 6 s; (b) Medium frequency: power on for 30 s / power off for 30 s; (c) Low frequency: power on for 1 min / power off for 1 min.

[0029] (3) Monitor and record performance parameters such as operating voltage, temperature, and impedance in real time during the test, and obtain the polarization curve and electrochemical impedance spectrum at 0 h (BoT) and 150 h, respectively. The polarization curve obtained by the low frequency (power on for 1 min / power off for 1 min) in this example is shown in Figure 1 , and the electrochemical impedance spectrum is shown in Figure 2 .

[0030] Comparative Example 1 This comparative example provides a PEMWE accelerated life test method under constant load conditions, which is different from Example 1 in that step (2) does not use start-stop cycles, but uses constant current continuous power-on for aging evaluation, and the rest of the conditions are the same as Example 1. The polarization curve obtained in this comparative example is shown in Figure 3 , and the electrochemical impedance spectrum is shown in Figure 4 .

[0031] As can be seen from Figures 3-4 , after running for 150 h under constant current conditions, the polarization curve of the PEMWE moves up as a whole, indicating that the required voltage increases under the same current density, and the performance has declined to some extent; the high-frequency region intercept moves slightly to the right, and the semicircle diameter increases, indicating that the ohmic resistance and charge transfer resistance have both increased slightly, mainly due to the decrease in catalyst activity and the slight degradation of the interface structure.

[0032] As can be seen from Figures 1-2It can be seen that the performance degradation after 150 h of start-stop operation is more significant, the polarization curve shows higher voltage in the whole current density range, especially in the high current density range, the increase of the high frequency intercept and the semi-circle diameter in the impedance spectrum are significantly higher than that in the constant current operation, which reflects the simultaneous deterioration of the membrane resistance, contact resistance and interface reaction kinetics. This shows that the thermal mechanical stress and gas-liquid scouring introduced by start-stop cycle accelerate the structural damage and interface degradation of the membrane electrode, which increases the activation polarization and ohmic polarization, resulting in a much higher degradation rate than that in the constant current operation.

[0033] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A PEMWE accelerated life test method based on start-stop working condition, comprising the following steps: (1) installing the membrane electrode assembly to be tested in a proton exchange membrane water electrolysis test device, and introducing deionized water through the anode side and collecting hydrogen gas through the cathode side; (2) setting a start-stop cycle mode, realizing periodic start-stop by controlling the alternation of power-on and power-off, maintaining open circuit potential during power-off, and making the membrane electrode assembly bear electrochemical and thermal mechanical combined stress under the start-stop working condition; (3) monitoring and recording the operating parameters in real time during the test, and performing stage-by-stage electrochemical performance characterization within the test period to evaluate the performance degradation of the membrane electrode assembly.

2. The test method of claim 1, wherein, The conductivity of the deionized water is less than 1 μS / cm.

3. The test method of claim 1, wherein, The test temperature is controlled within the range of 75-85 ℃.

4. The test method of claim 1, wherein, The water flow rate of the anode is 15-25 mL / min.

5. The test method of claim 1, wherein, The working voltage of the power-on stage of step (2) is set to 1.8-2.2 V.

6. The test method of claim 1, wherein, The cycle of the start-stop cycle of step (2) is 2 s-60 min.

7. The test method of claim 1, wherein, A deep power-off stage is inserted every 800-1200 start-stop cycles, and the deep power-off lasts for 12-36 h, and the open circuit potential state is maintained during the deep power-off.

8. The test method of claim 1, wherein, The cumulative test duration of step (2) is not less than 1000 h.

9. The test method of claim 1, wherein, The stage-by-stage electrochemical performance characterization includes polarization curve test, electrochemical impedance spectroscopy test and / or Tafel curve test.

10. The test method of claim 1, wherein, After the test, the membrane electrode assembly is subjected to scanning electron microscope morphology analysis to observe the structural changes of the catalyst layer, diffusion layer and membrane-electrode interface.

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