A novel method for measuring the cold start process of a proton exchange membrane fuel cell

Abstract

This invention discloses a novel measurement method for the cold start process of a proton exchange membrane fuel cell. The measurement method includes the following steps: (1) fixture and MEA heat capacity testing; (2) fixture assembly and MEA parameter acquisition; (3) investigation of the influence of convective heat transfer; (4) activation process; (5) testing of changes in reactive surface area, hydrogen permeation, and impedance before and after cold start; (6) purging process; (7) low-temperature settling; (8) cold start experiment; (9) shutdown, battery removal, and temperature recovery. The measurement method standardizes the measurement issues in the cold start process of a proton exchange membrane fuel cell, integrates experimental data, facilitates the discovery of influencing factors and patterns in the cold start process of a proton exchange membrane fuel cell, and saves manpower and resources.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane fuel cell technology, specifically relating to a novel method for measuring the cold start process of a proton exchange membrane fuel cell. Background Technology

[0002] The startup process of a proton exchange membrane fuel cell at low temperatures (below 0°C) can be called a low-temperature start-up or cold start. The key to a successful cold start is ensuring that the cell temperature transitions from below zero to above zero before the generated ice covers the three-phase reaction interface. If the cell temperature fails to rise during the cold start process, and the generated ice has already blocked the reactant gas transport channels, the cell will stop working, and the cold start will fail.

[0003] A qualified proton exchange membrane fuel cell (PEMFC) needs to achieve a low-temperature (below 0°C) start-up process while maintaining normal operation at room temperature. The U.S. Department of Energy (DOE) has set a 2020 cold start requirement of achieving self-start at -30°C within 30 seconds and auxiliary heating start-up at -40°C, which presents a significant challenge for the commercialization of fuel cells. Therefore, it is necessary to conduct in-depth research on the cold start performance of PEMFCs.

[0004] Current research on cold start can be categorized into two types based on whether external heating is required: self-starting and assisted starting. Self-starting refers to the membrane electrode assembly (MEA) achieving cold start through the heat generated by its own electrochemical reaction, while assisted starting requires an external power source. Theoretically, a combined strategy of self-starting and assisted starting can create a more complete cold start method, which is more conducive to achieving cold start of proton exchange membrane fuel cells. In actual research and development, cold start research at the membrane electrode assembly level mainly focuses on self-starting, which involves studying purge time, MEA geometry, catalyst materials, etc.; while assisted starting is more suitable for stack-level cold start research.

[0005] Simulating the cold start process of a proton exchange membrane fuel cell in the laboratory and measuring various experimental parameters during the cold start process, as well as analyzing the impact of these experimental parameters on the cold start process, is of great significance for designing proton exchange membrane fuel cells with better cold start performance.

[0006] The measurement method for the cold start process of proton exchange membrane fuel cells disclosed in related technologies mainly includes the following experimental parameters that need to be observed during the cold start process: start-up temperature, start-up duration, cell voltage change trend (Vt), internal resistance change during cold start (HFR-t), reactive surface area change (CV), icing location (SEM), icing amount, ice morphology (SEM), and degree of cell performance degradation (hydrogen permeation LSV, IV curve changes, number of cold starts), etc. [1-4]However, these measurement methods for the cold start process of proton exchange membrane fuel cells still have some problems. On the one hand, the experimental parameters they focus on are relatively one-sided, making it difficult to create a standardized database. On the other hand, the experimental methods used in these measurement methods are not perfect enough, which may cause some qualified proton exchange membrane fuel cells to fail to achieve a cold start under the conditions of these test methods.

[0007] Therefore, the measurement method for the cold start process of proton exchange membrane fuel cells in related technologies still needs further optimization.

[0008] [1] Linjun Li, Shixue Wang, Like Yue, Guozhuo Wang. Cold-start method for proton-exchange membrane fuel cells based on locally heating the cathode.

[0009] [2] Linjun Li, Shixue Wang, Like Yue, Guozhuo Wang. Cold-start icing characteristics of proton-exchange membrane fuel cells.

[0010] [3] Han Liu, Dechun Si, Han Ding, Shangshang Wang, Jianbo Zhang, YongLiu. Cold start capability and durability of electrospun catalyst layer for proton exchange membrane fuel cell.

[0011] [4] Lin Rui, Yike Zhu, Meng Ni, Zhenghua Jiang, Diming Lou, Lihang Han, DiZhong. Consistency analysis of polymer electrolyte membrane fuel cell stack during cold start. Summary of the Invention

[0012] This invention is based on the inventor's discovery and understanding of the following facts and problems: Current methods for measuring the cold start process of proton exchange membrane fuel cells (PEMFCs) produce inconsistent experimental data, making it difficult to create a standardized database. Furthermore, the experimental techniques employed are not yet perfect, and some qualified PEMFCs fail to achieve a smooth cold start under these testing conditions. Therefore, further research is needed to standardize the measurement of PEMFC cold start processes, integrate experimental data, and facilitate the discovery of influencing factors and patterns during the cold start process, thereby saving human and material resources.

[0013] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a novel measurement method for the cold start process of proton exchange membrane fuel cells, standardizing measurement issues during the cold start process, integrating experimental data, facilitating the discovery of influencing factors and patterns during the cold start process, and saving manpower and resources.

[0014] A novel method for measuring the cold start process of a proton exchange membrane fuel cell includes the following steps:

[0015] (1) Fixture and MEA thermal capacity test;

[0016] (2) Fixture assembly and MEA parameter acquisition;

[0017] (3) Investigation into the effects of convective heat transfer;

[0018] (4) Activation process;

[0019] (5) Tests on changes in reactive surface area, hydrogen permeation, and impedance before and after cold start;

[0020] (6) Purging process;

[0021] (7) Let it stand at low temperature;

[0022] (8) Cold start experiment;

[0023] (9) Stop the machine and remove the battery to allow it to return to its original temperature.

[0024] The advantages and technical effects of the novel proton exchange membrane fuel cell cold start process measurement method of this invention are as follows:

[0025] (1) The measurement method of the present invention standardizes the measurement problem in the cold start process of proton exchange membrane fuel cell, realizes the integration of experimental data, facilitates the discovery of the influencing factors in the cold start process of proton exchange membrane fuel cell, and saves manpower and material resources.

[0026] (2) In the measurement method of this embodiment, the combination order of the measurement steps determines the error that the experiment can be performed. The order is derived after a lot of reference and verification, and is not a simple combination. If the experiment with less destructive effects is performed first, the following experiments can still be performed for the proton exchange membrane fuel cell. If the experiment with greater destructive effects is performed first, the battery will be damaged and the battery needs to be replaced to continue. However, the consistency of the battery cannot be guaranteed, which has a greater impact on the accuracy of the measurement results.

[0027] (3) No research has been found on the influence of insulation materials and external environment on the cold start process in the related technologies. However, the test method of the present invention defines it intuitively through formula, which makes it easy to find the influence of insulation materials and external environment on the cold start process.

[0028] (4) Most of the measurement methods in related technologies focus on the Vt curve of cold start, while the measurement method of this invention is an intuitive and comprehensive consideration, and the measurement results are more stable and easier to evaluate.

[0029] In some embodiments, step (1) specifically includes the following steps: wrapping the clamp with thermal insulation material, inserting DC heating rods of known power into the two heating holes of the clamp, recording the temperature of the clamp at room temperature, recording the time it takes for the clamp to rise from room temperature to 80°C, and calculating the heat capacity of the clamp according to formula (1).

[0030]

[0031] Where T represents temperature, ρC p S represents heat capacity, τ is the time step, and S is the time value. T The source term representing temperature;

[0032] The heat capacity of the MEA is calculated using product parameters and the measured MEA thickness.

[0033] In some embodiments, step (1) further includes a subsequent processing step: if the heat capacity of the MEA is less than three orders of magnitude greater than the heat capacity of the fixture, then the process is carried out by adding an insulating pad between the manifold and the fixture, wherein the insulating pad is made of silica aerogel material and the thickness of the insulating pad is 10 mm; if the heat capacity of the MEA is at least three orders of magnitude greater than the heat capacity of the fixture, then the influence of the fixture can be eliminated.

[0034] In some embodiments, step (2) specifically includes the following steps: completing the assembly of a 5cm×5cm small proton exchange membrane fuel cell and measuring the parameters of the MEA; or, using a 5cm×5cm small proton exchange membrane fuel cell product and finding the parameters of the MEA according to the product instructions; the parameters of the MEA include the thickness of the MEA and the GDL thickness.

[0035] In some embodiments, step (3) specifically includes the following steps: purging the proton exchange membrane fuel cell at 30°C; placing it in an environmental chamber at -30°C for 3 hours, purging without starting, inserting two heating rods of the same power, the heating rods not wrapped with insulating strips, and observing the time t1 required for the proton exchange membrane fuel cell to start up to 0°C;

[0036] The proton exchange membrane fuel cell was shut down and purged at 30°C. It was then placed in an environmental chamber at -30°C for 3 hours without starting, and only purged. Two heating rods of the same power were inserted, and the heating rods were wrapped with insulating strips. The time t2 required for the proton exchange membrane fuel cell to start up to 0°C was observed.

[0037] The convective heat transfer coefficient h is calculated according to formula (2).

[0038]

[0039] Where Q is the heat consumed by convection diffusion, S is the heat of heating, A is the surface area of ​​the battery in contact with the outside world participating in convection heat transfer, t1 is the time required for the battery to start up to 0℃ without the insulating strip, and t2 is the time required for the battery to start up to 0℃ with the insulating strip.

[0040] In some embodiments, step (4) specifically includes the following steps: using H2 and O2 for purging, with a stoichiometric ratio of H2 to O2 of 2:3, a battery temperature of 70°C, a back pressure of 0.6 bar, a relative humidity of 65%, running at 0.6V for 2 hours under constant pressure, running at 0.4V for 2 hours under constant pressure, and measuring the IV curve, from low current density to high current density, and then from high current density to low current density, measuring a voltage value every 3 minutes, and averaging the two measurements.

[0041] In some embodiments, step (5) specifically includes the following steps: First, a GEIS test is performed, with the amounts of H2 and O2 set to 600 sccm and 2000 sccm respectively, the temperature at 70°C, the relative humidity at 100%, and the current density at 1 A cm⁻¹. -2 The frequency ranges from 10kHz to 0.1Hz;

[0042] 0.5Acm -2The system was run at constant current for 15 minutes at the current density, followed by CV testing. The temperature was lowered to 30℃, the relative humidity was 100%, O2 was turned off, and N2 was introduced. The amounts of H2 and N2 were set to 200 sccm and 50 sccm, respectively. The initial voltage was set to 0.05V, the cycle limit was 0.05-1.25V, the final voltage was 0.05V, the scan rate was 10mV / s, the step size was 2mV, the number of cycles was 6-10 until it stabilized, and the maximum current was 1000mA.

[0043] Finally, an LSV test was performed. With the ventilation conditions unchanged, the LSV module was turned on, and the scan voltage was set to 0-0.8V, with a scan range of 1-100mV s. -1 .

[0044] In some embodiments, step (6) specifically includes the following steps: using N2 at a flow rate of 1000 sccm, 70°C, and a relative humidity of 35% for 1-2 hours, with the same cathode and anode, until a stable state is reached. The standard for determining stability is that the HFR reaches a stable value, ensuring that the modal water content is 3-5%.

[0045] In some embodiments, step (7) specifically includes the following steps: the proton exchange membrane fuel cell is placed in a constant temperature chamber, the temperature of which is set to -10°C to -30°C, and left to stand for 3 hours.

[0046] In some embodiments, step (8) specifically includes the following steps: starting the proton membrane fuel cell using a constant current start method, with the current density set to 50-100 mA cm⁻¹. -2 The stoichiometric ratio of H2 to O2 was 1.5:2.0, the relative humidity was 0%, and the Vt curve, HFR-t curve, and Tt curve were measured. The threshold for cold start failure was when the voltage dropped to 0-0.1V.

[0047] In some embodiments, step (9) specifically includes the following steps: stop the machine, set the temperature of the constant temperature chamber to 30°C, allow the battery to fully thaw, when the battery temperature reaches the ambient temperature, blow for 30 minutes to blow out the melted liquid water inside, heat up again, repeat steps (2)-(9) at least 5 times, and finally take out the MEA and perform SEM testing to observe whether there is a difference in the degree of damage between the two membrane electrodes. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the proton exchange membrane fuel cell test system used in the measurement method of this embodiment of the invention;

[0049] Figure labeling: 1-Constant temperature chamber; 2-Proton exchange membrane fuel cell; 3-Insulation pad; 4-Hydrogen pipeline; 5-Oxygen pipeline; 6-Electrochemical workstation; 7-SEM. Detailed Implementation

[0050] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. The present invention is described in detail below with reference to the embodiments and the accompanying drawings.

[0051] Example 1

[0052] Experimental equipment and materials

[0053] (1) 5cm×5cm small MEA and carbon paper, fixture (direct flow or serpentine flow).

[0054] (2) Fuel Cell Testing Platform

[0055] (3) Electrochemical workstation

[0056] (4) Load (used to control current density)

[0057] (5) Type K thermocouple (used for temperature measurement)

[0058] (6) DC heating element (heating rod)

[0059] Experimental steps

[0060] A novel method for measuring the cold start process of a proton exchange membrane fuel cell includes the following steps:

[0061] (1) Fixture and MEA thermal capacity test

[0062] Objective: To measure the heat capacity of the fixture, compare the heat capacity of the MEA with that of the fixture, and analyze whether the insufficient temperature rise of the single cell is due to the excessive heat capacity of the fixture.

[0063] Method: Wrap the fixture with insulation material, insert DC heating rods (power must be known) into the two heating holes of the fixture, record the temperature of the fixture at room temperature, record the time it takes for the fixture to rise from room temperature to 80°C, and calculate the heat capacity of the fixture using formula (1):

[0064]

[0065] Where T represents temperature, ρC p S represents heat capacity, τ is the time step, and S is the time value. T The source term representing temperature (which can be calculated from the power of the heating rod).

[0066] The heat capacity of the MEA can also be calculated using product parameters and the measured MEA thickness. The product parameters here refer to those listed in the instruction manual of the purchased or self-made MEA. The heat capacity of the MEA can be calculated by multiplying the heat capacity parameter in the manual by the thickness. Product yields will inevitably have some error; therefore, experimentally measuring the heat capacity of the MEA will ensure greater accuracy.

[0067] Subsequent handling: If the heat capacity of the MEA is less than three orders of magnitude greater than that of the fixture, it can be addressed by adding an insulating gasket between the manifold and the fixture. The gasket material is silica aerogel with a thickness of 10 mm. Conversely, if the heat capacity of the MEA is at least three orders of magnitude greater than that of the fixture, the influence of the fixture can be ruled out.

[0068] (2) Fixture assembly and MEA parameter acquisition

[0069] Objectives: (1) Obtaining MEA parameters helps to clearly understand the cold start capability of proton exchange membrane fuel cells, which facilitates the prediction of subsequent experiments; (2) If model development and calibration are carried out later, the MEA parameters are valuable; (3) If loss experiments are carried out later, the initial state of the proton exchange membrane fuel cell must be clear for comparison.

[0070] Method: Assemble a 5cm×5cm small proton exchange membrane fuel cell and measure MEA parameters (including MEA thickness, GDL thickness, etc.). Alternatively, purchase a 5cm×5cm small proton exchange membrane fuel cell product and find the MEA parameters (including MEA thickness, GDL thickness, etc.) according to the product instructions.

[0071] (3) Investigation of the impact of convective heat transfer

[0072] Objective: To investigate the effect of convective heat transfer on cold start results.

[0073] Methods: The proton exchange membrane fuel cell was shut down and purged at 30°C under the following conditions: dry N2 purging flow rate of 1000 sccm, identical anode and cathode, and purging time of 30 min. The fuel cell was then placed in an environmental chamber at -30°C for 3 h, purged without startup under the same conditions as described above, with two heating rods of equal power inserted (the heating rods were not wrapped with insulating strips). The time t1 required for the proton exchange membrane fuel cell to start up to 0°C was observed.

[0074] The proton exchange membrane fuel cell was shut down and purged at 30℃ under the following conditions: dry N2 purging flow rate of 1000 sccm, same anode and cathode, and time of 30 min. After being placed in an environmental chamber at -30℃ for 3 h, the fuel cell was purged without startup under the same conditions as described above, with two heating rods of the same power inserted and wrapped with insulating strips. The time t2 required for the proton exchange membrane fuel cell to start up to 0℃ was observed.

[0075] The convective heat transfer coefficient h is calculated according to formula (2).

[0076]

[0077] Where Q is the heat consumed by convection diffusion, S is the heat of heating, A is the surface area of ​​the battery in contact with the outside world participating in convection heat transfer, t1 is the time required for the battery to start up to 0℃ without the insulating strip, and t2 is the time required for the battery to start up to 0℃ with the insulating strip.

[0078] The larger the convective heat transfer coefficient h, the greater the impact of convective heat transfer on cold start and the more heat is lost. Conversely, the smaller the convective heat transfer coefficient h, the smaller the impact of convective heat transfer on cold start and the less heat is lost.

[0079] (4) Activation process

[0080] Objective: The performance of proton exchange membrane fuel cells that have just been supplied with hydrogen and air is generally poor. The purpose of the activation process is to activate the proton exchange membrane fuel cell and keep the cell in an optimal operating state.

[0081] Methods: The stoichiometric ratio of H2 to O2 was 2:3. The battery temperature was 70℃, the back pressure was 0.6 bar, and the relative humidity was 65%. The battery was operated at 0.6V for 2 hours and then at 0.4V for 2 hours under constant voltage conditions. The IV curve was measured, with voltage values ​​measured every 3 minutes from low to high voltage density and then from high to low voltage density. The average of two measurements was taken.

[0082] (5) Tests on changes in reactive surface area, hydrogen permeation, and impedance before and after cold start.

[0083] Objective: After a cold start, there is generally a decrease in reactive surface area, an increase in hydrogen permeation, and an increase in cathode active resistance. Based on this, we aim to study whether the percentage changes of the above parameters are different for fuel cells of different sizes after a cold start.

[0084] Method: First, GEIS was measured under the following conditions: 600 sccm H2 and 2000 sccm O2, temperature 70℃, relative humidity 100%, and current density set to 1 A cm⁻¹. -2 The frequency ranges from 10kHz to 0.1Hz.

[0085] 0.5Acm -2 The system was run under constant current for 15 minutes at a constant current density, followed by CV testing. The temperature was lowered to 30℃, the relative humidity was 100%, O2 was turned off, and N2 was introduced. The amounts of H2 and N2 were set to 200 sccm and 50 sccm, respectively. The initial voltage was set to 0.05V, the cycle limit was 0.05-1.25V, the final voltage was 0.05V, the scan rate was 10mV / s, the step size was 2mV, the number of cycles was 6-10 until it stabilized, and the maximum current was 1000mA.

[0086] Finally, an LSV test was performed. With the ventilation conditions unchanged, the LSV module was turned on, and the scan voltage was set to 0-0.8V, with a scan range of 1-100mV s. -1 .

[0087] (6) Purging process

[0088] Objective: To ensure that the modal water content is between 3 and 5, too high a content will accelerate the freezing inside the fuel cell, while too low a content will result in poor battery performance and difficulty in starting.

[0089] Method: Purge with N2 at 70℃ and 35% relative humidity for 1-2 hours at a flow rate of 1000 sccm, with the same cathode and anode, until a stable state is reached. The criterion for stability is that the HFR reaches a stable value, ensuring that the modal water content is 3-5%.

[0090] (7) Let it stand at low temperature:

[0091] Objective: To achieve uniform internal temperature in proton exchange membrane fuel cells, ensuring all cells reach ambient temperature.

[0092] Method: The proton exchange membrane fuel cell was placed in a constant temperature chamber, the chamber was started, and the temperature inside the chamber was set to -10℃ / -20℃ / -30℃, and left to stand for 3 hours.

[0093] (8) Cold start experiment

[0094] Objective: The Vt curve shows the duration of cold start, the HFR-t curve shows the change in internal resistance and infers the time of ice formation, and the Tt curve allows for real-time monitoring of battery temperature changes.

[0095] Method: The proton exchange membrane fuel cell was started using a constant current start-up method: the current density was set to 50 mA / cm². -2 / 100mA cm -2 The stoichiometric ratio of H2 to O2 was 1.5:2.0, the relative humidity was 0%, and the Vt curve, HFR-t curve, and Tt curve were measured. The threshold for cold start failure was when the voltage dropped to 0-0.1V.

[0096] (9) Stop the machine and remove the battery to allow it to return to its original temperature.

[0097] Purpose: To warm up the battery in preparation for the next cold start.

[0098] Method: Shut down the machine and set the temperature of the constant temperature chamber to 30℃ to allow the battery to fully thaw. When the battery temperature reaches the ambient temperature, purge with dry N2 for 30 minutes at a flow rate of 1000 sccm. The anode and cathode are the same. Blow out the melted liquid water inside. Heat up again. In order for the battery to recover its own capacity before the next cycle, the power needs to be restored to at least 50% of the previous level. Then return to step (2) and perform 5 rounds of thawing and cold start experiments. Finally, take out the MEA. If possible, perform SEM to observe the degree of damage to the two membrane electrodes and whether there are differences. The main purpose is to observe the location of the freezing point. In addition, it is to see the degree of damage to the MEA and predict how many cold start damage experiments can be performed, which determines the battery life.

[0099] The measurement method of this invention is performed using both a fuel cell testing platform and an electrochemical workstation. Figure 1 This is a schematic diagram of the proton exchange membrane fuel cell testing system used in the measurement method of this embodiment of the invention. Figure 1 As shown, the proton exchange membrane fuel cell 2 is placed in a constant temperature chamber 1. Hydrogen line 4 and oxygen line 5 are connected to the anode and cathode of the proton exchange membrane fuel cell 2, respectively. An insulating pad 3 is placed between the current collector and the clamp. During the experiment, a nitrogen line 6 and an electrochemical workstation 7 can be connected to the proton exchange membrane fuel cell 2 for GEIS, CV, and other measurements. After the experiment, the membrane electrode inside the cell is sliced, and the freezing point is observed using SEM 8.

[0100] Example 2

[0101] In step (1), silica aerogel material is applied to the end plate by spraying, and the other steps are the same as in Example 1.

[0102] Comparative Example 1

[0103] Step (1) The insulation pad uses a rigid silicone sheet, and the other steps are the same as in Example 1. It was found that the thermal insulation performance of silica aerogel is about 10% better than that of silicone sheet. In Comparative Example 1, the insulation pad used in step (1) is a rigid silicone sheet, which dissipates heat faster and makes it more difficult for the battery to start cold.

[0104] Comparative Example 2

[0105] In step (8), the chemical ratio of hydrogen to oxygen is 1.5:4, and the other steps are the same as in Example 1. This results in a waste of gas and no improvement in battery cold-start performance.

[0106] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0107] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for measuring the cold start process of a proton exchange membrane fuel cell, characterized in that, Includes the following steps: (1) Fixture and MEA thermal capacity test; (2) Fixture assembly and MEA parameter acquisition; (3) Investigation into the impact of convective heat transfer; (4) Activation process; (5) Tests on changes in reactive surface area, hydrogen permeation, and impedance before and after cold start; (6) The purging process; (7) Let stand at low temperature; (8) Cold start experiment; (9) Stop the machine and remove the battery to allow it to return to its original temperature.

2. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 1, characterized in that, Step (1) specifically includes the following steps: wrapping the clamp with insulation material, inserting DC heating rods of known power into the two heating holes of the clamp, recording the temperature of the clamp at room temperature, recording the time it takes for the clamp to rise from room temperature to 80°C, and calculating the heat capacity of the clamp according to formula (1). （1）； Where T represents temperature, Indicates heat capacity, It is the time step, S T The source term representing temperature; The heat capacity of the MEA is calculated using product parameters and the measured MEA thickness.

3. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 2, characterized in that, Step (1) also includes subsequent processing: if the heat capacity of the MEA is less than three orders of magnitude greater than the heat capacity of the fixture, then the process is carried out by adding an insulating pad between the manifold and the fixture. The insulating pad is made of silica aerogel material and the thickness of the insulating pad is 10 mm. If the heat capacity of the MEA is at least three orders of magnitude greater than the heat capacity of the fixture, then the influence of the fixture can be eliminated.

4. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 1, characterized in that, Step (2) specifically includes the following steps: completing the assembly of the 5cm×5cm small proton exchange membrane fuel cell and measuring the parameters of the MEA; or, using the 5cm×5cm small proton exchange membrane fuel cell product and finding the parameters of the MEA according to the product instructions; the parameters of the MEA include the thickness of the MEA and the GDL thickness.

5. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 1, characterized in that, Step (3) specifically includes the following steps: the proton exchange membrane fuel cell is shut down and purged at 30°C; it is placed in an environmental chamber at -30°C for 3 hours, purged without starting, and two heating rods of the same power are inserted. The heating rods are not wrapped with insulating strips. The time t1 required for the proton exchange membrane fuel cell to start up to 0°C is observed. The proton exchange membrane fuel cell was shut down and purged at 30°C. It was then placed in an environmental chamber at -30°C for 3 hours without starting, and only purged. Two heating rods of the same power were inserted, and the heating rods were wrapped with insulating strips. The time t2 required for the proton exchange membrane fuel cell to start up to 0°C was observed. The convective heat transfer coefficient h is calculated according to formula (2). （2）； Where Q is the heat consumed by convection diffusion, S is the heat of heating, A is the surface area of ​​the battery in contact with the outside world participating in convection heat transfer, t1 is the time required for the battery to start up to 0℃ without the insulating strip, and t2 is the time required for the battery to start up to 0℃ with the insulating strip.

6. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 1, characterized in that, Step (4) specifically includes the following steps: using H2 and O2 for purging, with a stoichiometric ratio of H2 to O2 of 2:3, a battery temperature of 70°C, a back pressure of 0.6 bar, a relative humidity of 65%, and running at 0.6V for 2 hours under constant pressure and 0.4V for 2 hours under constant pressure, and measuring the IV curve, from low current density to high current density and then from high current density to low current density, measuring a voltage value every 3 minutes, and averaging the two measurements.

7. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 1, characterized in that, Step (5) specifically includes the following steps: First, perform GEIS testing, with H2 and O2 amounts set to 600 sccm and 2000 sccm respectively, temperature at 70℃, relative humidity at 100%, and current density at 1 A cm⁻¹. -2 The frequency ranges from 10kHz to 0.1Hz; 0.5Acm -2 The system was run at constant current for 15 minutes at the current density, followed by CV testing. The temperature was lowered to 30℃, the relative humidity was 100%, O2 was turned off, and N2 was introduced. The amounts of H2 and N2 were set to 200 sccm and 50 sccm, respectively. The initial voltage was set to 0.05V, the cycle limit was 0.05-1.25V, the final voltage was 0.05V, the scan rate was 10mV / s, the step size was 2mV, the number of cycles was 6-10 until it stabilized, and the maximum current was 1000mA. Finally, an LSV test was performed. With the ventilation conditions unchanged, the LSV module was turned on, and the scan voltage was set to 0-0.8V, with a scan range of 1-100mV s. -1 .

8. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 1, characterized in that, Step (6) specifically includes the following steps: purge with N2 at a flow rate of 1000 sccm, 70°C, and relative humidity of 35% for 1-2 hours, with the same cathode and anode, until a stable state is reached. The standard for determining stability is that the HFR reaches a stable value, ensuring that the modal water content is 3-5%.

9. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 1, characterized in that, Step (7) specifically includes the following steps: the proton exchange membrane fuel cell is placed in a constant temperature chamber, the temperature of which is set to -10℃ to -30℃, and left to stand for 3 hours.

10. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 1, characterized in that, Step (8) specifically includes the following steps: starting the proton membrane fuel cell using a constant current start method, with the current density set to 50-100 mA cm⁻¹. -2 The stoichiometric ratio of H2 to O2 was 1.5:2.0, the relative humidity was 0%, and the Vt curve, HFR-t curve, and Tt curve were measured. The threshold for cold start failure was when the voltage dropped to 0-0.1V.

11. The method for measuring the cold start process of a proton exchange membrane fuel cell according to claim 9, characterized in that, Step (9) specifically includes the following steps: stop the machine, set the temperature of the constant temperature chamber to 30°C, allow the battery to fully thaw, when the battery temperature reaches the ambient temperature, blow for 30 minutes to blow out the melted liquid water inside, heat up again, repeat steps (2)-(9) at least 5 times, and finally take out the MEA and perform SEM testing to observe whether there is a difference in the degree of damage between the two membrane electrodes.

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