Method and device for detecting self-humidifying capability of membrane electrode

Abstract

The application discloses a kind of membrane electrode self-humidification capacity detection method and device, it is related to fuel cell technical field, by respectively obtaining the first polarization curve of first relative humidity condition and the second polarization curve of second relative humidity condition of the cathode side of to-be-measured sample;To-be-measured sample is operated under the first relative humidity condition in the cathode side of to-be-measured sample, respectively selects characteristic current density point in front and behind intersection point and carries out electrochemical impedance spectroscopy test, solves relaxation time distribution function using regularization method, according to the characteristic peak of relaxation time distribution function identified according to center frequency range, judge the change condition of high frequency characteristic peak area;And according to the import and export water flux of anode and cathode of to-be-measured sample, determine the net water migration coefficient of to-be-measured sample;When detecting that net water migration coefficient is smaller and the amplitude of high frequency characteristic peak area reduction is greater, determine that the self-humidification capacity of membrane electrode is stronger. The self-humidification capacity of membrane electrode can be accurately detected.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a method and apparatus for detecting the self-humidification capability of a membrane electrode. Background Technology

[0002] Fuel cell self-humidification refers to the ability of the membrane electrode assembly (MEA) of a fuel cell (usually a proton exchange membrane fuel cell) to effectively wet the proton exchange membrane with water generated by the electrochemical reaction without relying on external humidification equipment, especially the humidified and dried inlet side (usually the anode).

[0003] Proton exchange membrane fuel cells (PEMFCs) require adequate humidification of the membrane electrode assembly (MEA) to ensure proton conduction efficiency. Traditional systems rely on external humidification equipment, but this increases system size and energy consumption. Self-humidification technology achieves internal water balance within the MEA through material and structural design, but current technologies lack systematic verification methods for its effectiveness. Current assessments of self-humidification capabilities largely rely on single polarization curve analysis, such as the crossover of voltage curves under different humidity conditions.

[0004] However, a single indicator is easily affected by operating conditions and cannot distinguish the impact of self-humidification from external water management. Summary of the Invention

[0005] This invention provides a method and apparatus for detecting the self-humidification capability of a membrane electrode, which can accurately detect the self-humidification capability of the membrane electrode.

[0006] In a first aspect, embodiments of the present invention provide a method for detecting the self-humidifying capability of a membrane electrode, comprising:

[0007] A first polarization curve of the sample under test is obtained under a first relative humidity condition on the cathode side, and a second polarization curve is obtained under a second relative humidity condition on the cathode side, and it is determined whether there is an intersection point between the first polarization curve and the second polarization curve; wherein, the sample under test includes at least one fuel cell containing a membrane electrode, and the first relative humidity is less than the second relative humidity;

[0008] When it is determined that there is an intersection point between the first polarization curve and the second polarization curve, it is determined that the membrane electrode has self-humidification capability, and the first current density at the intersection point is recorded.

[0009] When the cathode side of the sample to be tested is under the first relative humidity condition, the sample to be tested is run, and characteristic current density points are selected before and after the intersection point for electrochemical impedance spectroscopy testing. The relaxation time distribution function is solved using a regularization method, and the characteristic peaks of the relaxation time distribution function are identified according to the center frequency range to determine the change in the area of ​​the high-frequency characteristic peaks. The characteristic current density points include at least the intersection point, a second current density point with a current density less than the first current density, and a third current density point with a current density greater than the first current density.

[0010] The water migration coefficient of the test sample is determined based on the inlet and outlet water flux of the anode and cathode of the test sample when the test sample is operated under the first relative humidity condition on the cathode side of the test sample.

[0011] When the water migration coefficient is smaller and the area of ​​the high-frequency characteristic peak decreases more significantly, the self-humidifying ability of the membrane electrode is determined to be stronger.

[0012] Optionally, under the first relative humidity condition at the cathode side of the sample to be tested, the sample is run, and characteristic current density points are selected before and after the intersection point for electrochemical impedance spectroscopy testing. The relaxation time distribution function is solved using a regularization method, and the characteristic peaks of the relaxation time distribution function are identified based on the center frequency range. The change in the area of ​​the high-frequency characteristic peaks is determined, including:

[0013] When the cathode side of the sample under test is under the first relative humidity condition, the operating current density of the sample under test is sequentially set to the current density of the selected characteristic current density points; at each characteristic current density point, after the output of the sample under test stabilizes, a disturbance signal with constant amplitude is applied to the sample under test within a preset frequency range, and the response is measured synchronously to obtain impedance data in complex form.

[0014] The impedance data is analyzed using a regularization method to solve for the relaxation time distribution function;

[0015] In the spectrum of the relaxation time distribution function, high-frequency characteristic peaks belonging to the charge transfer process are identified based on the characteristic frequency range corresponding to the relaxation time.

[0016] The area of ​​the high-frequency characteristic peak is calculated by numerically integrating the log(τ) interval covered by the high-frequency characteristic peak; where τ is the relaxation time.

[0017] The change in the area of ​​the high-frequency characteristic peak is determined based on the trend of the change in the area of ​​the high-frequency characteristic peak as the current density increases.

[0018] Optionally, the water migration coefficient of the test sample is determined based on the inlet and outlet water fluxes of the anode and cathode of the test sample when the cathode side of the test sample is under the first relative humidity condition, including:

[0019] The dry gas flow rate and dew point temperature of the anode inlet, anode outlet, cathode inlet, and cathode outlet of the sample under the first relative humidity condition are obtained after the sample reaches a steady state.

[0020] Based on the ideal gas law, the water vapor saturated vapor pressure data table, the dew point temperature, and the dry gas flow rate, determine the anode inlet water flux, anode outlet water flux, cathode inlet water flux, and cathode outlet water flux.

[0021] The amount of purified water migrated from the anode to the cathode is determined based on the anode inlet water flux, the anode outlet water flux, the cathode inlet water flux, and the cathode outlet water flux.

[0022] The water migration coefficient is determined based on the water migration amount and the total water production during the operation of the sample to be tested.

[0023] Optionally, the membrane electrode satisfies at least one of the following: the proton exchange membrane contains a water-retaining substance; the anode catalyst layer is doped with a water-retaining substance; or a hydrophilic anode catalyst is prepared by modifying the catalyst support with a hydrophilic substance or by directly modifying the catalyst.

[0024] Optionally, acquiring the first polarization curve of the sample under a first relative humidity condition on the cathode side, and the second polarization curve under a second relative humidity condition on the cathode side, and determining whether the first polarization curve and the second polarization curve have an intersection point includes:

[0025] Under constant preset sample temperature, preset gas pressure, and preset excess coefficient of cathode-side gas, the first polarization curve and the second polarization curve of the sample to be tested are obtained.

[0026] Plot the graph to identify whether there are any intersection points between the first polarization curve and the second polarization curve;

[0027] The preset sample temperature is 50–90℃, the preset gas pressure is 150–300kPa, the preset cathode-side gas excess coefficient is 1.5–1.8, the first relative humidity is 0%–40%RH, and the second relative humidity is 60%–90%RH.

[0028] Optionally, the intersection point satisfies the following condition: the first voltage of the cathode side of the sample under the first relative humidity condition exceeds the second voltage of the cathode side of the sample under the second relative humidity condition in the preset current density region.

[0029] Optionally, when the area of ​​the high-frequency characteristic peak in the relaxation time distribution function decreases and the rate of change is greater than 5%, the membrane electrode is determined to have strong self-humidification capability.

[0030] Optionally, if the water migration coefficient is less than or equal to -0.1 and the rate of change is greater than 5%, the membrane electrode is determined to have strong self-humidification ability.

[0031] Optionally, after acquiring the first polarization curve of the sample under a first relative humidity condition on the cathode side and the second polarization curve under a second relative humidity condition on the cathode side, and determining whether the first polarization curve and the second polarization curve have an intersection point, the method further includes:

[0032] If it is determined that the first polarization curve and the second polarization curve do not intersect, it is determined that the membrane electrode does not have self-humidification capability.

[0033] Secondly, embodiments of the present invention also provide a device for detecting the self-humidification capability of a membrane electrode, comprising:

[0034] The crossover point determination module is used to acquire the first polarization curve of the sample under test under a first relative humidity condition on the cathode side and the second polarization curve under a second relative humidity condition on the cathode side, and to determine whether there is a crossover point between the first polarization curve and the second polarization curve; wherein, the sample under test includes at least one fuel cell containing a membrane electrode, and the first relative humidity is less than the second relative humidity;

[0035] A current density recording module is used to determine that the membrane electrode has self-humidification capability when the intersection point determination module determines that there is an intersection point between the first polarization curve and the second polarization curve, and to record the first current density at the intersection point.

[0036] The high-frequency characteristic peak area change judgment module is used to run the test sample under the first relative humidity condition on the cathode side of the test sample, select characteristic current density points before and after the intersection point for electrochemical impedance spectroscopy testing, solve the relaxation time distribution function using a regularization method, identify the characteristic peaks of the relaxation time distribution function according to the center frequency range, and judge the change of the high-frequency characteristic peak area; wherein, the characteristic current density points include at least the intersection point, a second current density point with a current density less than the first current density, and a third current density point with a current density greater than the first current density;

[0037] The water migration coefficient determination module is used to determine the water migration coefficient of the test sample based on the inlet and outlet water flux of the anode and cathode of the test sample when the test sample is operated under the first relative humidity condition on the cathode side of the test sample.

[0038] The self-humidification capability determination module determines that the membrane electrode has a stronger self-humidification capability when it detects that the smaller the water migration coefficient and the greater the reduction in the area of ​​the high-frequency characteristic peak.

[0039] This invention provides a method and apparatus for detecting the self-humidification capability of a membrane electrode. First, a rapid and intuitive qualitative screening is performed by determining whether there is an intersection point between the first and second polarization curves. After determining the existence of an intersection point, electrochemical impedance spectroscopy (EIS) is conducted near the intersection point, and the relaxation time distribution function is calculated to specifically track changes in the area of ​​high-frequency characteristic peaks characterizing the membrane hydration state. If self-humidification is effective, it will increase with increasing current (increased water production), and the high-frequency resistance should decrease significantly, specifically manifested as a greater reduction in the area of ​​the high-frequency characteristic peaks. This verifies from an electrochemical mechanism perspective that the "intersection point" phenomenon indeed originates from improved membrane hydration, rather than other factors. Finally, the net water migration coefficient is calculated by accurately measuring the water flux. A negative net water migration coefficient with a larger absolute value quantitatively demonstrates that the greater the amount of net water migrates from the cathode to the anode, the stronger the self-humidification capability. These three steps form a tight logical loop, integrating macroscopic performance, microscopic mechanisms, and quantitative material migration, resulting in a more stringent evaluation standard, more comprehensive information dimensions, and more reliable results for detecting the self-humidification capability of fuel cell membrane electrodes. This method can accurately detect the self-humidification capability of membrane electrodes.

[0040] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a flowchart of a method for detecting the self-humidification capability of a membrane electrode according to an embodiment of the present invention;

[0043] Figure 2 This is a partial flowchart of a method for detecting the self-humidification capability of a membrane electrode according to an embodiment of the present invention;

[0044] Figure 3 This is another part of the flowchart of a method for detecting the self-humidification capability of a membrane electrode provided in an embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram of the structure of a membrane electrode self-humidification capability detection device provided in an embodiment of the present invention. Detailed Implementation

[0046] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0048] Figure 1 This is a flowchart illustrating a method for detecting the self-humidification capability of a membrane electrode according to an embodiment of the present invention. This embodiment is applicable to detecting the self-humidification capability of a membrane electrode. The method can be executed by a device for detecting the self-humidification capability of a membrane electrode, which can be implemented in hardware and / or software. (Reference) Figure 1 The method includes the following steps:

[0049] S110. Obtain the first polarization curve of the sample under test under the first relative humidity condition on the cathode side and the second polarization curve under the second relative humidity condition on the cathode side, and determine whether there is an intersection point between the first polarization curve and the second polarization curve; wherein, the sample under test includes at least one fuel cell containing a membrane electrode, and the first relative humidity is less than the second relative humidity.

[0050] It should be noted that before obtaining the first and second polarization curves, the membrane electrode assembly (MEA) needs to be assembled into a test sample and its airtightness tested. Specifically, this can be done by alternately stacking the prepared self-humidifying MEA and bipolar plates between the two end plates using a positioning device, and then securing them with a set clamping force applied by screws or straps to assemble the test sample. The test sample can be a single fuel cell or a fuel cell stack.

[0051] Specifically, when performing polarization curve testing, under constant stack temperature, gas pressure, and excess coefficient of gas on the cathode side, the first polarization curve of the sample under test under the first relative humidity condition on the cathode side and the second polarization curve under the second relative humidity condition on the cathode side are tested respectively, and the intersection point of the two polarization curves is identified by plotting.

[0052] S120. When it is determined that there is an intersection point between the first polarization curve and the second polarization curve, it is determined that the membrane electrode has self-humidification capability, and the first current density at the intersection point is recorded.

[0053] S130. Under the condition of the first relative humidity on the cathode side of the sample to be tested, the sample to be tested is run, and characteristic current density points are selected before and after the intersection point for electrochemical impedance spectroscopy testing. The relaxation time distribution function is solved using the regularization method. The characteristic peaks of the relaxation time distribution function are identified according to the center frequency range, and the changes in the area of ​​the high-frequency characteristic peaks are judged. Among them, the characteristic current density points include at least the intersection point, the second current density point with a current density less than the first current density, and the third current density point with a current density greater than the first current density.

[0054] Specifically, EIS (electrochemical impedance spectroscopy) analysis of fuel cells is a core in-situ diagnostic technique. It analyzes the kinetic information of various internal physicochemical processes by applying a small sinusoidal perturbation to the fuel cell stack and measuring its response. The regularization method can be Tikhonov regularization.

[0055] For example, when the first current density at the intersection is Ic, the current density at the characteristic current density point can be 0.5Ic, Ic, or 1.5Ic.

[0056] S140. Determine the water migration coefficient of the test sample based on the inlet and outlet water flux of the anode and cathode of the test sample when the test sample is operated under the first relative humidity condition on the cathode side of the test sample.

[0057] Specifically, the net water migration coefficient is a key physical quantity for quantitatively evaluating the self-humidifying capability of a fuel cell membrane electrode assembly (MEA). Its standard definition is the ratio of the net water flux migrating from the anode to the cathode to the theoretical total water production flux of the fuel cell stack calculated according to Faraday's law. When the cathode side of the test sample is under first relative humidity conditions, the water flux at the anode and cathode inlet / outlet can be accurately measured using a mass flow meter and a dew point meter, and the total water production of the test sample can be calculated, thereby determining the net water migration coefficient.

[0058] S150. When the water migration coefficient is smaller and the area of ​​the high-frequency characteristic peak decreases more significantly, the self-humidification capability of the membrane electrode is determined to be stronger.

[0059] Specifically, after determining that the first polarization curve and the second polarization curve intersect, thus confirming that the membrane electrode has self-humidification capability, the magnitude of the decrease in the area of ​​the high-frequency characteristic peak of the relaxation time distribution function as the current density (reaching the first current density Ic and above) increases, along with the net water migration coefficient, together constitute the core criteria for quantifying the magnitude of the membrane electrode's self-humidification capability. The smaller the net water migration coefficient and the greater the decrease in the area of ​​the high-frequency characteristic peak, the stronger the membrane electrode's self-humidification capability.

[0060] This embodiment first performs a rapid and intuitive qualitative screening by determining whether there is an intersection point between the first and second polarization curves. After determining the existence of an intersection point, electrochemical impedance spectroscopy (EIS) is performed near the intersection point, and the relaxation time distribution function is solved to specifically track the change in the area of ​​the high-frequency characteristic peaks that characterize the membrane hydration state. If self-humidification is effective, it will increase with the increase of current (increased water production), and the high-frequency resistance should decrease significantly, specifically manifested as a greater reduction in the area of ​​the high-frequency characteristic peaks. This verifies from an electrochemical mechanism perspective that the "intersection point" phenomenon does indeed originate from the improvement of membrane hydration, rather than other factors. Finally, the net water migration coefficient is calculated by accurately measuring the water flux. A negative net water migration coefficient with a larger absolute value quantitatively proves that the amount of net water migrated from the cathode to the anode is greater, and the self-humidification capability is stronger. These three steps form a rigorous logical closed loop, integrating macroscopic performance, microscopic mechanisms, and quantitative material migration, forming a more stringent evaluation standard, more comprehensive information dimensions, and more reliable results for detecting the self-humidification capability of fuel cell membrane electrodes. It can accurately detect the self-humidification capability of membrane electrodes.

[0061] Figure 2 This is a partial flowchart of a method for detecting the self-humidifying ability of a membrane electrode according to an embodiment of the present invention. Optionally, based on the above embodiment, refer to... Figure 2 Step S130 includes:

[0062] S131. Under the condition of first relative humidity on the cathode side of the sample to be tested, the operating current density of the sample to be tested is sequentially set to the current density of selected characteristic current density points; the characteristic current density points include at least the intersection point, the second current density point with a current density less than the first current density, and the third current density point with a current density greater than the first current density.

[0063] Specifically, after confirming the crossover point, it is necessary to maintain the same sample temperature, gas pressure, and gas flow parameters as when performing polarization curve testing. Under the condition of the first relative humidity on the cathode side of the sample to be tested, the operating current density of the sample to be tested is sequentially set to the current density of the selected characteristic current density point.

[0064] S132. At each characteristic current density point, after the output of the sample under test stabilizes, a disturbance signal with constant amplitude is applied to the sample under test within a preset frequency range, and the response is measured synchronously to obtain impedance data in complex form.

[0065] Specifically, the disturbance signal can be a sinusoidal current or voltage disturbance signal, and the response can be a voltage or current response. Complex impedance data can be obtained through a frequency response analyzer or equivalent equipment.

[0066] S133. Use regularization to analyze the impedance data and solve for the relaxation time distribution function.

[0067] Specifically, the relaxation time distribution function γ(τ) can be solved by constructing and minimizing the objective function, which is: Φ=‖Z_exp-Z_fit(γ)‖²+λ‖Lγ‖², where Z_exp is the measured impedance vector, Z_fit is the fitted impedance vector calculated based on the relaxation time distribution model, L is the discretization operator of the second derivative of the relaxation time distribution function γ(τ), and λ is the regularization parameter, which is determined by the L-curve method or the generalized cross-validation method.

[0068] S134. In the spectrum of the relaxation time distribution function, identify the high-frequency characteristic peaks belonging to the charge transfer process based on the characteristic frequency range corresponding to the relaxation time.

[0069] Specifically, in the calculated relaxation time distribution function γ(τ)~log(τ) spectrum, high-frequency characteristic peaks belonging to the charge transfer process can be identified based on the characteristic frequency range corresponding to the relaxation time τ. It should be noted that in the dielectric spectrum, log(τ) by default refers to log... 10 (τ).

[0070] S135. Perform numerical integration on the log(τ) interval covered by the high-frequency characteristic peak to calculate the area of ​​the high-frequency characteristic peak; where τ is the relaxation time.

[0071] S136. Based on the trend of the high-frequency characteristic peak area changing with the increase of current density, determine the change of the high-frequency characteristic peak area.

[0072] Specifically, by comparing and analyzing the area of ​​high-frequency characteristic peaks at different characteristic current density points, we can observe the trend of their change with increasing current density (especially before and after the crossover point Ic), thereby helping to characterize the effect of self-humidification on electrochemical kinetics.

[0073] This embodiment calculates the area of ​​the high-frequency characteristic peak and judges the change of the high-frequency characteristic peak area based on the trend of the high-frequency characteristic peak area as the current density increases. Thus, the self-humidification capability of the membrane electrode can be accurately detected by the change of the high-frequency characteristic peak area.

[0074] Figure 3 This is another part of the flowchart of a method for detecting the self-humidification capability of a membrane electrode provided in an embodiment of the present invention. Optionally, based on the above embodiments, refer to... Figure 3 Step S140 includes:

[0075] S141. Obtain the dry gas flow rate and dew point temperature of the anode inlet, anode outlet, cathode inlet, and cathode outlet of the sample under the first relative humidity condition on the cathode side of the sample to be tested, after the sample has reached a steady state.

[0076] Specifically, when the cathode side of the sample under test is under the first relative humidity condition, the same stack temperature, gas pressure, and gas flow rate parameters as during polarization curve testing need to be maintained. A mass flow meter can be used to accurately measure the dry gas volumetric flow rate or mass flow rate at the anode inlet, anode outlet, and cathode inlet / outlet; a dew point meter can be used to accurately measure the dew point temperature of the gas flow at the anode inlet, anode outlet, cathode inlet, and cathode outlet.

[0077] S142. Based on the ideal gas law, the water vapor saturated vapor pressure data table, the dew point temperature, and the dry gas flow rate, determine the anode inlet water flux, anode outlet water flux, cathode inlet water flux, and cathode outlet water flux.

[0078] Specifically, the partial pressure of water vapor in the inlet and outlet airflow of each flow path can be calculated based on the ideal gas law, water vapor saturated vapor pressure data table, and dew point temperature. Then, combined with the measured dry gas flow rate, the anode inlet water flux F can be calculated respectively. H2O,a,in Anode outlet water flux F H2O,a,out Cathode inlet water flux F H2O,c,in and cathode outlet water flux F H2O,c,out The units are mol / s or g / s.

[0079] For example, the saturated vapor pressure of water vapor at the dew point temperature of the anode inlet, anode outlet, cathode inlet, and cathode outlet, obtained from the water vapor saturated vapor pressure data table, is the water vapor partial pressure P in the corresponding flow path. H2O Then, using the ideal gas law PV=nRT, the dry gas flow rate n is calculated and determined. dry =PQ dry / RT; where P is absolute pressure; Q dry R is the dry gas volumetric flow rate; R is the ideal gas constant (8.314 J / (mol·K)); and T is the actual temperature (in K). Then, according to the formula F... H2O =n dry ×P H2O / (PP) H2O ) Calculate the water flux; where, F H2O Replace with F as needed H2O,a,in F H2O,a,out F H2O,c,in F H2O,c,out Substitute the corresponding n values ​​for the anode and cathode inlet / outlet of each electrode. dry P H2O P can be calculated.

[0080] S143. Determine the amount of purified water that migrates from the anode to the cathode based on the anode inlet water flux, anode outlet water flux, cathode inlet water flux, and cathode outlet water flux.

[0081] Specifically, the amount of purified water migrated from the anode to the cathode, F H2O,net,atoc The calculation formula is: F H2O,net,atoc =(F H2O,a,in -F H2O,a,out )+(F H2O,c,out -F H2O,c,in )-F H2O,gen Total water production F during stack operation H2O,gen According to Faraday's law, the calculation formula is: F H2O,gen =I×n cell / 2F, where I is the pile current, n cell Let F be the number of cells per cell, and F be the Faraday constant.

[0082] S144. Determine the water migration coefficient based on the water migration amount and the total water production during the operation of the sample to be tested.

[0083] Specifically, the net water migration coefficient α is defined as the ratio of the net water migration from the anode to the cathode to the total water production of the fuel cell stack, and the calculation formula is: α = F H2O,net,atoc / F H2O,genThe water migration coefficient is used to quantitatively characterize the ability of the membrane electrode to reverse the flow of product water from the cathode to the anode to humidify the anode intake air under low cathode humidity conditions. The more negative the value, the stronger the self-humidification ability.

[0084] This embodiment determines the amount of purified water migrated from the anode to the cathode by measuring the anode inlet water flux, anode outlet water flux, cathode inlet water flux, and cathode outlet water flux. Based on the amount of purified water migrated and the total water production during the operation of the sample, the purified water migration coefficient is determined, which can accurately detect the self-humidification capability of the membrane electrode.

[0085] Optionally, based on the above embodiments, the membrane electrode satisfies at least one of the following: the proton exchange membrane contains a water-retaining substance, the anode catalyst layer is doped with a water-retaining substance, and a hydrophilic anode catalyst is prepared by modifying the catalyst support with a hydrophilic substance or by directly modifying the catalyst.

[0086] Specifically, the water-retaining substances added to the proton exchange membrane can be Pt nanoparticles, Al2O3, TiO2, ZrO2, SiO2, and graphene oxide, etc., and the water-retaining substances doped in the anode catalyst layer can be Pt nanoparticles, Al2O3, TiO2, ZrO2, SiO2, and graphene oxide, etc., while the hydrophilic substances can be SnO2, SiO2, and ZrO2, etc.

[0087] Optionally, based on the above embodiments, step S110 includes: obtaining the first polarization curve and the second polarization curve of the sample to be tested assembled from the membrane electrode and the bipolar plate under constant preset sample temperature, preset gas pressure and preset excess coefficient of cathode side gas; plotting to identify whether there is an intersection point between the first polarization curve and the second polarization curve; wherein, the preset sample temperature is 50–90℃, the preset gas pressure is 150–300kPa, the preset excess coefficient of cathode side gas is 1.5–1.8, the first relative humidity condition is 0%–40%RH, and the second relative humidity condition is 60%–90%RH.

[0088] This embodiment can further accurately detect the self-humidification capability of the membrane electrode by setting the preset sample temperature to 50–90℃, the preset gas pressure to 150–300kPa, the preset excess coefficient of the cathode-side gas to 1.5–1.8, the first relative humidity condition to 0%–40%RH, and the second relative humidity condition to 60%–90%RH.

[0089] Optionally, based on the above embodiments, the intersection point satisfies the following: the first voltage on the cathode side of the sample under the first relative humidity condition exceeds the second voltage on the cathode side of the sample under the second relative humidity condition in the preset current density region.

[0090] This embodiment, by limiting the intersection point to satisfy the condition that the first voltage under the first relative humidity condition exceeds the second voltage under the second relative humidity condition in the preset high current density region, can further accurately detect the self-humidification capability of the membrane electrode.

[0091] Optionally, based on the above embodiments, when the area of ​​the high-frequency characteristic peak in the relaxation time distribution function decreases and the rate of change is greater than 5%, the membrane electrode is determined to have strong self-humidification capability.

[0092] This embodiment determines that the membrane electrode has strong self-humidification ability by limiting the area of ​​the high-frequency characteristic peak to decrease and the rate of change to be greater than 5%, which can further accurately detect the self-humidification ability of the membrane electrode.

[0093] Optionally, based on the above embodiments, when the water migration coefficient is less than or equal to -0.1 and the rate of change is greater than 5%, the membrane electrode is determined to have strong self-humidification ability.

[0094] This embodiment determines that the membrane electrode has strong self-humidification ability by limiting the water migration coefficient to less than or equal to -0.1 and the rate of change to greater than 5%, which can further accurately detect the self-humidification ability of the membrane electrode.

[0095] Optionally, based on the above embodiments, after step S110, the method further includes: when it is determined that the first polarization curve and the second polarization curve do not have an intersection point, it is determined that the membrane electrode does not have self-humidification capability.

[0096] Figure 4 This is a schematic diagram of the structure of a membrane electrode self-humidification capability detection device provided in an embodiment of the present invention, with reference to... Figure 4 The device includes:

[0097] The crossover point determination module 410 is used to acquire the first polarization curve of the sample under test when the cathode side is under a first relative humidity condition, and the second polarization curve when the cathode side is under a second relative humidity condition, and to determine whether there is a crossover point between the first polarization curve and the second polarization curve; wherein, the sample under test includes at least one fuel cell containing a membrane electrode assembly, and the first relative humidity is less than the second relative humidity; the current density recording module 420 is used to determine that the membrane electrode assembly has self-humidification capability when the crossover point determination module determines that there is a crossover point between the first polarization curve and the second polarization curve, and to record the first current density at the crossover point; the high-frequency characteristic peak area change determination module 430 is used to run the sample under test when the cathode side of the sample is under the first relative humidity condition, and to select characteristic current densities before and after the crossover point respectively. Electrochemical impedance spectroscopy (EIS) tests are performed at specific points. The relaxation time distribution function is solved using a regularization method. The characteristic peaks of the relaxation time distribution function are identified based on the center frequency range, and the changes in the area of ​​the high-frequency characteristic peaks are judged. Among them, the characteristic current density points include at least the crossover point, the second current density point with a current density less than the first current density, and the third current density point with a current density greater than the first current density. The water migration coefficient determination module 440 is used to determine the water migration coefficient of the test sample based on the inlet and outlet water flux of the anode and cathode of the test sample when the test sample is operated under the first relative humidity condition on the cathode side of the test sample. The self-humidification ability judgment module 450 is used to determine that the smaller the water migration coefficient and the greater the reduction in the area of ​​the high-frequency characteristic peaks, the stronger the self-humidification ability of the membrane electrode.

[0098] The membrane electrode self-humidification capability detection device provided in this embodiment of the invention can execute the membrane electrode self-humidification capability detection method provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects of the method. For contents not described in detail in the embodiments of the invention, please refer to the membrane electrode self-humidification capability detection method provided in the above embodiments.

[0099] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0100] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for detecting the self-humidifying capability of a membrane electrode, characterized in that, include: A first polarization curve of the sample under test is obtained under a first relative humidity condition on the cathode side, and a second polarization curve is obtained under a second relative humidity condition on the cathode side, and it is determined whether there is an intersection point between the first polarization curve and the second polarization curve; wherein, the sample under test includes at least one fuel cell containing a membrane electrode, and the first relative humidity is less than the second relative humidity; When it is determined that there is an intersection point between the first polarization curve and the second polarization curve, it is determined that the membrane electrode has self-humidification capability, and the first current density at the intersection point is recorded. When the cathode side of the sample to be tested is under the first relative humidity condition, the sample to be tested is run, and characteristic current density points are selected before and after the intersection point for electrochemical impedance spectroscopy testing. The relaxation time distribution function is solved using a regularization method, and the characteristic peaks of the relaxation time distribution function are identified according to the center frequency range to determine the change in the area of ​​the high-frequency characteristic peaks. The characteristic current density points include at least the intersection point, a second current density point with a current density less than the first current density, and a third current density point with a current density greater than the first current density. The water migration coefficient of the test sample is determined based on the inlet and outlet water flux of the anode and cathode of the test sample when the test sample is operated under the first relative humidity condition on the cathode side of the test sample. When the water migration coefficient is smaller and the area of ​​the high-frequency characteristic peak decreases more significantly, the self-humidifying ability of the membrane electrode is determined to be stronger.

2. The method for detecting the self-humidifying ability of a membrane electrode according to claim 1, characterized in that, With the cathode side of the sample under the first relative humidity condition, the sample is run, and characteristic current density points are selected before and after the intersection point for electrochemical impedance spectroscopy testing. The relaxation time distribution function is solved using a regularization method, and the characteristic peaks of the relaxation time distribution function are identified based on the center frequency range. The changes in the area of ​​the high-frequency characteristic peaks are determined, including: When the cathode side of the sample under test is under the first relative humidity condition, the operating current density of the sample under test is sequentially set to the current density of the selected characteristic current density points; at each characteristic current density point, after the output of the sample under test stabilizes, a disturbance signal with constant amplitude is applied to the sample under test within a preset frequency range, and the response is measured synchronously to obtain impedance data in complex form. The impedance data is analyzed using a regularization method to solve for the relaxation time distribution function; In the spectrum of the relaxation time distribution function, high-frequency characteristic peaks belonging to the charge transfer process are identified based on the characteristic frequency range corresponding to the relaxation time. The area of ​​the high-frequency characteristic peak is calculated by numerically integrating the log(τ) interval covered by the high-frequency characteristic peak; where τ is the relaxation time. The change in the area of ​​the high-frequency characteristic peak is determined based on the trend of the change in the area of ​​the high-frequency characteristic peak as the current density increases.

3. The method for detecting the self-humidifying ability of a membrane electrode according to claim 1, characterized in that, The net water migration coefficient of the test sample is determined based on the inlet and outlet water fluxes of the anode and cathode of the test sample when the test sample is operated under the first relative humidity condition on the cathode side. The dry gas flow rate and dew point temperature of the anode inlet, anode outlet, cathode inlet, and cathode outlet of the sample under the first relative humidity condition are obtained after the sample reaches a steady state. Based on the ideal gas law, the water vapor saturated vapor pressure data table, the dew point temperature, and the dry gas flow rate, determine the anode inlet water flux, anode outlet water flux, cathode inlet water flux, and cathode outlet water flux. The amount of purified water migrated from the anode to the cathode is determined based on the anode inlet water flux, the anode outlet water flux, the cathode inlet water flux, and the cathode outlet water flux. The water migration coefficient is determined based on the water migration amount and the total water production during the operation of the sample to be tested.

4. The method for detecting the self-humidifying ability of a membrane electrode according to claim 1, characterized in that, The membrane electrode satisfies at least one of the following: the proton exchange membrane contains a water-retaining substance; the anode catalyst layer is doped with a water-retaining substance; and a hydrophilic anode catalyst is prepared by modifying the catalyst support with a hydrophilic substance or by directly modifying the catalyst.

5. The method for detecting the self-humidifying ability of a membrane electrode according to claim 1, characterized in that, Acquiring the first polarization curve of the sample under test under a first relative humidity condition on the cathode side, and the second polarization curve under a second relative humidity condition on the cathode side, and determining whether there is an intersection point between the first polarization curve and the second polarization curve includes: Under constant preset sample temperature, preset gas pressure, and preset excess coefficient of cathode-side gas, the first polarization curve and the second polarization curve of the sample to be tested are obtained. Plot the graph to identify whether there are any intersection points between the first polarization curve and the second polarization curve; The preset sample temperature is 50–90℃, the preset gas pressure is 150–300kPa, the preset cathode-side gas excess coefficient is 1.5–1.8, the first relative humidity is 0%–40%RH, and the second relative humidity is 60%–90%RH.

6. The method for detecting the self-humidifying ability of a membrane electrode according to claim 1, characterized in that, The intersection point satisfies the following condition: the first voltage of the cathode side of the sample under the first relative humidity condition exceeds the second voltage of the cathode side of the sample under the second relative humidity condition in the preset current density region.

7. The method for detecting the self-humidifying ability of a membrane electrode according to claim 2, characterized in that, When the area of ​​the high-frequency characteristic peak in the relaxation time distribution function decreases and the rate of change is greater than 5%, the membrane electrode is determined to have strong self-humidification capability.

8. The method for detecting the self-humidifying ability of a membrane electrode according to claim 3, characterized in that, When the water migration coefficient is less than or equal to -0.1 and the rate of change is greater than 5%, the membrane electrode is determined to have strong self-humidification ability.

9. The method for detecting the self-humidifying ability of a membrane electrode according to claim 1, characterized in that, After acquiring the first polarization curve of the sample under a first relative humidity condition on the cathode side and the second polarization curve under a second relative humidity condition on the cathode side, and determining whether the first polarization curve and the second polarization curve have an intersection point, the method further includes: If it is determined that the first polarization curve and the second polarization curve do not intersect, it is determined that the membrane electrode does not have self-humidification capability.

10. A device for detecting the self-humidifying capability of a membrane electrode, characterized in that, include: The crossover point determination module is used to acquire the first polarization curve of the sample under test under a first relative humidity condition on the cathode side and the second polarization curve under a second relative humidity condition on the cathode side, and to determine whether there is a crossover point between the first polarization curve and the second polarization curve; wherein, the sample under test includes at least one fuel cell containing a membrane electrode, and the first relative humidity is less than the second relative humidity; A current density recording module is used to determine that the membrane electrode has self-humidification capability when the intersection point determination module determines that there is an intersection point between the first polarization curve and the second polarization curve, and to record the first current density at the intersection point. The high-frequency characteristic peak area change judgment module is used to run the test sample under the first relative humidity condition on the cathode side of the test sample, select characteristic current density points before and after the intersection point for electrochemical impedance spectroscopy testing, solve the relaxation time distribution function using a regularization method, identify the characteristic peaks of the relaxation time distribution function according to the center frequency range, and judge the change of the high-frequency characteristic peak area; wherein, the characteristic current density points include at least the intersection point, a second current density point with a current density less than the first current density, and a third current density point with a current density greater than the first current density; The water migration coefficient determination module is used to determine the water migration coefficient of the test sample based on the inlet and outlet water flux of the anode and cathode of the test sample when the test sample is operated under the first relative humidity condition on the cathode side of the test sample. The self-humidification capability determination module determines that the membrane electrode has a stronger self-humidification capability when it detects that the smaller the water migration coefficient and the greater the reduction in the area of ​​the high-frequency characteristic peak.

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