A method for testing the utilization rate of anode catalyst in a PEM electrolyzer.

Abstract

This invention relates to the field of proton exchange membrane water electrolysis technology, and discloses a method for testing the utilization rate of anode catalysts in PEM electrolyzers. The method includes: obtaining the intrinsic mass activity and intrinsic electrochemical active area; obtaining the apparent mass activity of the membrane electrode and the charge transport performance parameters of the membrane electrode catalyst layer; calculating a first parameter characterizing the degree of activity; obtaining the accessible electrochemical active area of ​​the membrane electrode catalyst layer under actual operating conditions, and calculating a second parameter characterizing the accessibility of active sites based on the intrinsic electrochemical active area; calculating theoretical charge transfer performance parameters based on the intrinsic electrochemical active area, and calculating a third parameter characterizing charge transport efficiency in combination with the charge transport performance parameters; comparing the relative magnitudes of the parameters to determine the root cause type. This invention achieves multi-dimensional quantitative evaluation of the utilization rate of anode catalysts in PEM electrolyzers and intelligent diagnosis of failure root causes.

Description

Technical Field

[0001] This invention relates to the field of proton exchange membrane water electrolysis technology, and more particularly to a method for testing the utilization rate of anode catalyst in a PEM electrolyzer. Background Technology

[0002] Among numerous hydrogen production technologies, proton exchange membrane (PEM) water electrolysis is considered a cutting-edge direction for the development of the green hydrogen industry. However, the acidic oxygen evolution reaction (OER) occurring at the anode of a PEM electrolyzer requires the use of noble metal catalysts, such as iridium (Ir). To reduce the amount of iridium used, accurately assessing the catalyst utilization rate in a real membrane electrode structure—that is, the extent to which the intrinsic activity of the catalyst is effectively utilized in the actual device—has become a crucial prerequisite for guiding materials research and development. However, current methods for assessing the utilization rate of PEM electrolyzer anode catalysts are significantly inadequate and disconnected from current practices.

[0003] First, existing research mainly focuses on testing the intrinsic mass activity or specific activity of catalyst powders in liquid electrolytes using rotating disk electrodes (RDE). Although this method can assess the theoretical upper limit of the material's activity, the testing environment differs fundamentally from the operating environment of a real PEM electrolyzer, resulting in RDE test results that cannot directly and accurately reflect the actual performance of the catalyst in the membrane electrode.

[0004] Secondly, at the membrane electrode or single-cell level, performance evaluation typically stops at measuring the overall polarization curve or overall efficiency. This result incorporates the combined effects of multiple factors, including catalyst activity, proton / electron conduction, gas mass transfer, and interfacial contact, making it impossible to isolate and quantify performance losses solely due to "low catalyst utilization." When battery performance is poor, researchers struggle to determine whether the root cause lies in insufficient catalyst material activity or in defects in the membrane electrode structure design or fabrication process that prevent the effective utilization of active sites.

[0005] Furthermore, current technologies lack a systematic approach to quantitatively correlate the intrinsic properties of materials with the apparent properties of devices, thereby calculating comparable "utilization" metrics. Simultaneously, there is a lack of analytical tools capable of diagnosing the specific root causes of low utilization. This makes the research and optimization of catalysts and membrane electrodes largely reliant on trial and error, resulting in a blind, lengthy, and costly process.

[0006] Therefore, this invention proposes a method for testing the utilization rate of anode catalysts in PEM electrolyzers. Summary of the Invention

[0007] The purpose of this invention is to address the problems of quantitative gaps, attribution blind spots, and lack of standards in the prior art, and to propose a method for testing the utilization rate of anode catalysts in PEM electrolyzers.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a method for testing the utilization rate of an anode catalyst in a PEM electrolyzer, comprising the following steps:

[0009] Step S1: Perform a rotating disk electrode test on the anode catalyst to be tested to obtain its intrinsic mass activity and intrinsic electrochemical active area.

[0010] Step S2: The anode catalyst is prepared into a membrane electrode and assembled into a single cell for testing. The apparent quality activity of the membrane electrode is obtained, and the charge transport performance parameters of the membrane electrode catalyst layer are obtained by analyzing the electrochemical impedance spectroscopy of the single cell under operating conditions.

[0011] Step S3: Based on intrinsic quality activity and apparent quality activity, calculate the first parameter characterizing the degree of activity exertion;

[0012] Step S4: Obtain the accessible electrochemical active area of ​​the membrane electrode catalytic layer under actual operating conditions, and calculate the second parameter characterizing the accessibility of active sites based on the intrinsic electrochemical active area.

[0013] Step S5: Based on the intrinsic electrochemical active area, calculate the theoretical charge transfer performance parameters, and combine them with the charge transport performance parameters to calculate the third parameter characterizing the charge transport efficiency.

[0014] Step S6: Compare the relative magnitudes of the first parameter, the second parameter, and the third parameter, and determine the root cause type of catalyst utilization loss based on a preset set of judgment rules.

[0015] The beneficial effects of the technical solution provided by this invention include at least the following:

[0016] This invention constructs a complete technical chain of "intrinsic performance testing - membrane electrode performance testing - multi-dimensional utilization calculation - intelligent diagnosis," which enables quantitative correlation between the intrinsic mass activity of the catalyst obtained in RDE testing and the apparent mass activity obtained in a real single cell. This allows for the calculation of an objective and comparable electrochemical activity utilization rate, solving the problems of disconnect between material testing and device evaluation and the ambiguity and inability to quantify the concept of utilization rate in existing technologies.

[0017] This invention introduces a test condition correction factor and establishes an equivalent correlation between RDE and single-cell test conditions based on a standard catalyst. This effectively corrects systematic errors caused by differences in the test environment, significantly improves the comparability of intrinsic and apparent activity data and the accuracy of calculation results, and overcomes the large error of traditional direct comparison methods.

[0018] This invention constructs a three-dimensional evaluation system by simultaneously calculating the surface area accessibility utilization rate and charge transport efficiency utilization rate, and combining them with the electrochemical activity utilization rate. This system can comprehensively and multi-dimensionally quantify the effective utilization status of catalysts in membrane electrodes. It not only provides the overall utilization rate value, but also reveals key structural and functional parameters such as active site accessibility and charge transport efficiency, providing rich information far exceeding that of a single indicator.

[0019] This invention establishes a priority judgment rule set based on relative difference and preset threshold, and constructs a normalization processing and rule matching process. This enables automated and intelligent diagnosis of the root causes of utilization loss, accurately distinguishing between electrochemical interface failure, physical structure failure, charge transport network failure, and system comprehensive failure. It transforms traditional experience-based fault diagnosis into data-driven precise localization, greatly improving the targeting and efficiency of research and development and optimization.

[0020] This invention integrates electrochemical kinetics theory, advanced impedance analysis technology, and in-situ measurement methods to obtain key parameters such as charge transport performance and accessible electrochemical active area under conditions close to actual operation. This ensures that the evaluation results more accurately reflect the performance of the catalyst under PEM electrolyzer conditions, enhancing the practicality and guiding value of the method. Attached Figure Description

[0021] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0022] Figure 1 This is a schematic diagram of the method flow provided in an embodiment of the present invention;

[0023] Figure 2 The flowchart of the loss root cause judgment logic provided in the embodiment of the present invention. Detailed Implementation

[0024] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a method for testing the utilization rate of an anode catalyst in a PEM electrolyzer according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0027] The following describes in detail, with reference to the accompanying drawings, a specific scheme for testing the utilization rate of an anode catalyst in a PEM electrolyzer provided by the present invention.

[0028] Please see Figure 1 The diagram illustrates a flowchart of a method for testing the utilization rate of an anode catalyst in a PEM electrolyzer, according to an embodiment of the present invention, comprising the following steps:

[0029] Step S1: Perform a rotating disk electrode test on the anode catalyst to be tested to obtain its intrinsic mass activity and intrinsic electrochemical active area.

[0030] Step S2: The anode catalyst is prepared into a membrane electrode and assembled into a single cell for testing. The apparent quality activity of the membrane electrode is obtained, and the charge transport performance parameters of the membrane electrode catalyst layer are obtained by analyzing the electrochemical impedance spectroscopy of the single cell under operating conditions.

[0031] Step S3: Based on intrinsic quality activity and apparent quality activity, calculate the first parameter characterizing the degree of activity exertion;

[0032] Step S4: Obtain the accessible electrochemical active area of ​​the membrane electrode catalytic layer under actual operating conditions, and calculate the second parameter characterizing the accessibility of active sites based on the intrinsic electrochemical active area.

[0033] Step S5: Based on the intrinsic electrochemical active area, calculate the theoretical charge transfer performance parameters, and combine them with the charge transport performance parameters to calculate the third parameter characterizing the charge transport efficiency.

[0034] Step S6: Compare the relative magnitudes of the first parameter, the second parameter, and the third parameter, and determine the root cause type of catalyst utilization loss based on a preset set of judgment rules.

[0035] It should be noted that rotating disk electrode testing refers to the method of using a rotating disk electrode device to construct a three-electrode testing system to perform electrochemical testing on catalysts dispersed and coated on the electrode surface. It mainly eliminates mass transfer interference by controlling the rotation of the electrodes and accurately obtains intrinsic electrochemical performance data of the catalyst that are not affected by the actual device structure.

[0036] Intrinsic mass activity refers to the catalytic activity of a unit mass of catalyst under ideal test conditions. It is a core parameter reflecting the inherent catalytic ability of the catalyst itself and does not include the influence of non-intrinsic factors such as structure and mass transfer in actual applications.

[0037] Intrinsic electrochemical active area refers to the total surface area of ​​a unit mass of catalyst that can participate in electrochemical reactions. It is a key parameter characterizing the total number of active sites in a catalyst and reflects the catalyst's own ability to supply active sites.

[0038] Membrane electrode refers to a core functional component formed by combining catalysts, proton exchange membranes, gas diffusion layers and other components through a specific process. It is the site where electrochemical reactions occur in a PEM electrolyzer, and its structure and performance directly affect the overall operation of the electrolyzer.

[0039] Apparent mass activity refers to the actual catalytic activity exhibited by a unit mass of catalyst under actual single-cell operating conditions after the catalyst is prepared into a film electrode. It is the result of the combined effect of intrinsic catalytic ability and various influencing factors in practical applications.

[0040] Electrochemical impedance spectroscopy (EIS) refers to the measurement of impedance responses to perturbation signals of different frequencies under specific potential or current conditions, forming a spectrum that reflects the electrochemical processes at the electrode interface. It can provide information on various processes such as charge transfer, mass transfer, and proton conduction.

[0041] Charge transport performance parameters are parameters extracted from electrochemical impedance spectroscopy that quantify the ease or difficulty of charge transfer processes in the catalyst layer, directly reflecting the efficiency of charge transfer between the active sites of the catalyst and the electrolyte.

[0042] The primary parameter characterizing the degree of activity is the parameter calculated by the ratio of intrinsic mass activity to corrected apparent mass activity. It is used to quantify the actual proportion of intrinsic catalytic activity of the catalyst in practical applications and the influence of the electrochemical interface characteristics of the core reaction on the utilization rate.

[0043] Accessible electrochemical active area refers to the surface area of ​​active sites on the membrane electrode that can be contacted by reactants and participate in electrochemical reactions under actual operating conditions. It is the total number of active sites that the catalyst can actually play a role, and is affected by factors such as the physical structure of the catalyst layer and mass transfer conditions.

[0044] The second parameter characterizing the accessibility of active sites is a parameter calculated by the ratio of accessible electrochemical active area to intrinsic electrochemical active area. It is used to quantify the proportion of active sites in the catalyst that are in contact with reactants and the influence of the physical structure of the core reaction catalyst layer on the utilization rate.

[0045] Theoretical charge transfer performance parameters refer to the charge transfer-related parameters under ideal conditions, calculated based on intrinsic electrochemical active area and intrinsic kinetic parameters. They are the theoretical optimal values ​​of the charge transfer process and are used as a benchmark for evaluating actual charge transfer efficiency.

[0046] The third parameter characterizing charge transfer efficiency is the parameter calculated by the ratio of theoretical charge transfer performance parameters to actual charge transfer performance parameters. It is used to quantify the efficiency of charge transfer processes in actual systems and primarily reflects the impact of charge transfer networks on utilization.

[0047] The preset judgment rule set refers to a set of rules that are pre-set based on the common causes of catalyst utilization loss. These rules determine the root cause of loss by comparing the relative magnitude and degree of difference of three parameters. The rules include logic such as parameter relative magnitude judgment and difference threshold comparison, and are used to achieve standardized and automated judgment of the root cause of loss.

[0048] The root causes of catalyst utilization loss refer to the core reasons why the actual utilization rate of the catalyst is lower than the ideal value. These mainly include electrochemical interface failure, physical structure failure, charge transport network failure, and system comprehensive failure. Different types correspond to different optimization directions.

[0049] In one specific embodiment, when performing rotating disk electrode testing on the anode catalyst under test, a glassy carbon electrode with a diameter of 5 mm is selected as the rotating disk electrode substrate. The Ir-based catalyst under test is ultrasonically dispersed with a mixed solvent of Nafion ionomer, water, and isopropanol for 30 minutes to prepare a uniform catalyst slurry. 10 μL of this slurry is uniformly coated onto the surface of the glassy carbon electrode and vacuum dried at room temperature for 12 hours to form the working electrode. A three-electrode testing system is constructed, with a reversible hydrogen electrode as the reference electrode, a platinum wire electrode as the counter electrode, and a 0.5 mol / L sulfuric acid solution as the electrolyte. Cyclic voltammetry is first performed in the non-Radida potential range of 0.05 to 0.3 V at scan rates of 5, 10, 20, and 50 mV / s to calculate the double-layer capacitance and calibrate the intrinsic electrochemical active area using the specific capacitance per unit area. Then, in the oxygen evolution reaction overpotential range of 1.4 to 1.8 V, the electrode rotation speed is controlled at 1600 rpm, the steady-state current is measured, and the intrinsic mass activity is calculated based on the catalyst loading.

[0050] When preparing the anolyte catalyst into a membrane electrode, the same catalyst slurry as used in the rotating disk electrode test was coated onto the surface of a Nafion 212 proton exchange membrane using a spraying method. The catalyst loading was controlled at 1 mg / cm². After vacuum drying at 80°C for 2 hours, the membrane electrode with an effective area of ​​10 cm² was formed by hot pressing at 130°C and 10 MPa for 3 minutes. The membrane electrode was then assembled with a bipolar plate and a sealing gasket to form a single cell, which was connected to a PEM electrolyzer testing system and activated for 10 hours at 80°C and anode and cathode pressures of 0.1 MPa. After activation, the complete polarization curve was measured, and Tafel fitting was performed on the kinetic control region data with current densities ranging from 20 to 100 mA / cm² to obtain the exchange current density. The apparent mass activity was then calculated in conjunction with the iridium loading. The single cell was kept at a constant current of 50 mA per square centimeter. After the voltage stabilized, electrochemical impedance spectroscopy was performed with a perturbation voltage amplitude of 10 mV and a frequency range of 0.1 Hz to 100 kHz. The impedance spectrum data was processed using relaxation time distribution analysis technology to identify the characteristic peaks corresponding to the charge transfer process and to obtain the charge transport performance parameters through integration and quantization.

[0051] When calculating the first parameter characterizing the degree of activity, a titanium-iridium-strontium perovskite catalyst was selected as the standard catalyst. Steady-state current density at the same overpotential was measured under both rotating disk electrode and single-cell test conditions, and a test condition correction factor was calculated. The apparent mass activity was multiplied by the correction factor to obtain the corrected apparent mass activity. The first parameter, i.e., the electrochemical activity utilization rate, was then calculated using the ratio of the corrected apparent mass activity to the intrinsic mass activity.

[0052] To obtain the accessible electrochemical active area, the anode potential of the single cell was controlled within the non-Radida range of 0.05 to 0.3 V. A triangular wave potential perturbation was applied at scan rates of 5, 10, 20, and 50 mV / s, and the corresponding current response data was measured. The average response current at each scan rate was calculated, and the relationship curve between the average response current and the scan rate was plotted and linearly fitted to obtain the total electric double-layer capacitance. Combined with the specific capacitance per unit area calibrated in the rotating disk electrode test, the accessible electrochemical active area was calculated. The second parameter, namely the surface area accessibility utilization rate, was calculated by the ratio of the accessible electrochemical active area to the intrinsic electrochemical active area.

[0053] When calculating the third parameter characterizing charge transport efficiency, the theoretical charge transfer resistance is calculated based on the intrinsic electrochemical active area and the exchange current density obtained from the rotating disk electrode test, using the Butler-Wolmer equation as the theoretical charge transfer performance parameter. The real part of the charge transport performance parameter is extracted as the apparent charge transfer resistance. The third parameter, i.e., the charge transport efficiency utilization rate, is calculated by the ratio of the theoretical charge transfer resistance to the apparent charge transfer resistance.

[0054] When comparing the relative magnitudes of the three parameters, the first, second, and third parameters are first normalized, and the relative differences between each pair of parameters are calculated. A preset proximity threshold of 8% and a significance threshold of 20% are used for judgment. The judgment is made according to a preset set of rules: if the relative difference between any two parameters is less than the proximity threshold, it is judged as a system-wide failure; if the first parameter is simultaneously less than the other two parameters and the relative difference is greater than or equal to the significance threshold, it is judged as an electrochemical interface failure; if the second parameter is simultaneously less than the other two parameters and the relative difference is greater than or equal to the significance threshold, it is judged as a physical structure failure; if the third parameter is simultaneously less than the other two parameters and the relative difference is greater than or equal to the significance threshold, it is judged as a charge transport network failure; if none of the above conditions are met, the type corresponding to the minimum parameter is used for judgment.

[0055] Step S1 further includes the following sub-steps:

[0056] S1-1, In a standard three-electrode electrolytic cell, the catalyst slurry is uniformly coated on the surface of a rotating disk electrode to prepare a working electrode;

[0057] S1-2, In a nitrogen-saturated acidic electrolyte, the working electrode is subjected to a multi-scan rate cyclic voltammetry test in the non-Radida potential range to obtain its double-layer capacitance measurement value.

[0058] S1-3, based on double-layer capacitance measurements, determines the first benchmark parameter for characterizing the intrinsic electrochemical active area properties of the catalyst;

[0059] S1-4, the steady-state current of the working electrode is measured in the overpotential range of the oxygen evolution reaction. Based on the steady-state current and the catalyst loading on the working electrode, a second reference parameter for characterizing the intrinsic mass activity of the catalyst is determined.

[0060] It should be noted that a standard three-electrode electrolytic cell refers to a standardized electrochemical testing device consisting of a working electrode, a reference electrode, and a counter electrode. It has a stable electrolyte environment and electrode assembly structure, and is mainly used to accurately measure the electrochemical performance of a single electrode, eliminating interference from external devices.

[0061] Catalyst slurry refers to a uniform paste-like mixture formed by mixing catalyst powder with ionomers and dispersion media in a specific ratio and then dispersing it. Its state must meet the requirements of the coating process to ensure that the catalyst is evenly distributed on the electrode surface.

[0062] A rotating disk electrode is a disk-shaped working electrode substrate whose mass transfer conditions can be controlled by adjusting the rotation speed. It is usually made of glassy carbon and is mainly used to eliminate the influence of reactant diffusion in the electrolyte on electrochemical testing and to obtain the intrinsic properties of the catalyst.

[0063] The working electrode is the electrode that carries the catalyst to be tested and undergoes the target electrochemical reaction. It is the core signal response electrode in electrochemical testing, and its surface state directly affects the accuracy of the test results.

[0064] Nitrogen-saturated acidic electrolyte refers to an electrolyte system in which high-purity nitrogen gas is passed into an acidic electrolyte solution for a sufficient time to completely remove dissolved oxygen from the solution. It is mainly used to prevent oxygen from participating in electrode reactions and to ensure the uniqueness of the testing process.

[0065] Acidic electrolyte refers to an electrolyte solution with a pH value less than 7. It is usually an aqueous solution of strong acids such as sulfuric acid and perchloric acid. Its main function is to provide a proton conduction channel to adapt to the acidic working environment of the anode of the PEM electrolytic cell.

[0066] The non-Faraday potential range refers to the potential range on the electrode surface where only double-layer charging / discharging occurs, and no Faraday redox reaction occurs. The current response within this range is only related to the double-layer capacitance and is mainly used for the accurate measurement of double-layer capacitance.

[0067] Multi-scan rate cyclic voltammetry refers to a testing method that performs cyclic voltammetry scans on the working electrode at multiple different potential scan rates. By comparing the current response at different scan rates, the contributions of double-layer capacitance and Faraday current can be separated.

[0068] The electric double layer capacitance measurement is a value that reflects the ability of the electric double layer on the electrode surface to store charge, which is calculated by cyclic voltammetry. Its value is directly related to the electrode surface area and is a key parameter that indirectly characterizes the total amount of active sites.

[0069] The first benchmark parameter refers to the parameter that characterizes the intrinsic electrochemical active area of ​​the catalyst, which is calculated based on the measured value of the double-layer capacitance. This parameter is not affected by factors such as structure and mass transfer in actual applications, and is a benchmark for measuring the active site supply capacity of the catalyst itself.

[0070] The oxygen evolution reaction overpotential range refers to the potential range above the oxygen evolution reaction equilibrium potential that can drive the oxygen evolution reaction to occur. Within this range, the main reaction on the electrode surface is the oxidation of water molecules to produce oxygen, which is the core potential range for measuring the oxygen evolution activity of catalysts.

[0071] Steady-state current refers to the current value that remains stable after the electrode reaction reaches dynamic equilibrium under set potential and mass transfer conditions. Its magnitude is directly related to the catalytic activity of the catalyst and is the core data for calculating mass activity.

[0072] Catalyst loading refers to the mass of catalyst coated on the surface of the working electrode, usually expressed as the mass of catalyst per unit electrode area. It is a necessary parameter for calculating the activity of catalyst per unit mass.

[0073] The second benchmark parameter refers to the parameter that characterizes the intrinsic catalytic activity of the catalyst, calculated based on steady-state current and catalyst loading. It reflects the intrinsic reactivity of a unit mass of catalyst and serves as a benchmark for comparing the degree of activity in practical applications.

[0074] In one specific embodiment, a 50 mL glass electrolytic cell is used as the standard three-electrode electrolyzer. The reference electrode is a reversible hydrogen electrode, and the counter electrode is a platinum wire electrode with a length of 5 cm and a diameter of 0.5 mm. The catalyst slurry is prepared by mixing the Ir-based catalyst powder to be tested, a 5% (w / w) Nafion ionomer solution, and a water / isopropanol mixed dispersion medium at a mass ratio of 1:0.1:10. After mixing, the mixture is ultrasonically dispersed at 200 W for 30 minutes to form a uniform, non-agglomerated catalyst slurry. A 5 mm diameter glassy carbon electrode is used as the rotating disk electrode. 10 μL of catalyst slurry is uniformly drop-coated onto the electrode surface using a micro-syringe and dried in a vacuum drying oven at room temperature for 12 hours to prepare the working electrode. The catalyst loading is controlled at 0.2 mg / cm².

[0075] A 0.5 mol / L sulfuric acid solution was used as the acidic electrolyte. High-purity nitrogen gas was introduced into the electrolyte at a rate of 50 mL / min for 30 minutes to achieve nitrogen saturation. The non-Radida potential range was set from 0.05 V to 0.3 V relative to the reversible hydrogen electrode. The scan rates for multi-scan cyclic voltammetry were set to 5 mV / s, 10 mV / s, 20 mV / s, and 50 mV / s, respectively. Three cycles were performed at each scan rate, and stable cyclic voltammetry curves were recorded. Based on the current response in the non-Radida region of the cyclic voltammetry curves, the double-layer capacitance at different scan rates was calculated, and the average value was taken as the measured value of the double-layer capacitance.

[0076] Pure IrO2 standard samples were selected for calibration, and its specific capacitance per unit area was determined to be 30 μF / cm². Based on this value and the measured double-layer capacitance, the intrinsic electrochemical active area was calculated using the direct proportionality between capacitance and area, and this value was used as the first reference parameter. The oxygen evolution reaction overpotential range was set to 1.4 V to 1.8 V relative to the reversible hydrogen electrode. During testing, the rotation speed of the rotating disk electrode was controlled at 1600 rpm to eliminate the influence of mass transfer. The potential was stabilized at the 0.4 V overpotential for 300 seconds, and the current value at this time was recorded as the steady-state current. Based on the geometric area of ​​the working electrode and the catalyst loading, the steady-state current corresponding to a unit mass of catalyst was calculated, and this value was used as the second reference parameter, i.e., intrinsic mass activity.

[0077] Step S2 further includes the following sub-steps:

[0078] S2-1, the catalyst slurry is coated onto a proton exchange membrane or gas diffusion layer, and then dried and hot-pressed to form a membrane electrode;

[0079] S2-2, assembled single cell, under standard PEM water electrolysis test conditions, after steady-state activation, its complete polarization curve was measured;

[0080] S2-3, the dynamic control region is determined from the polarization curve, and multiple data points in this region are fitted by Tafel to obtain the exchange current density j_0;

[0081] S2-4, calculate the apparent mass activity according to the formula A_app=j_0 / m_Ir, where m_Ir is the iridium loading per unit area of ​​the electrode, and A_app represents the apparent mass activity;

[0082] S2-5, the single cell is kept under constant current control at a preset current density value within the kinetic control region. After the output voltage stabilizes, its electrochemical impedance spectrum is measured under this steady state.

[0083] S2-6, The relaxation time distribution of the measured electrochemical impedance spectroscopy data is analyzed to obtain the relaxation time distribution spectrum;

[0084] S2-7. Based on the electrochemical kinetic characteristics exhibited by the catalyst in the rotating disk electrode test, the characteristic peaks corresponding to the charge transfer process are identified from the relaxation time distribution spectrum. The determination of the characteristic peaks is based on the fact that the corresponding characteristic relaxation time matches the order of magnitude of the theoretical relaxation time estimated by the exchange current density j_0.

[0085] S2-8, by integrating the characteristic peak, the charge transport performance parameter is obtained by quantification. This parameter is characterized as the impedance value Z_ct related to the charge transfer resistance.

[0086] It should be noted that a proton exchange membrane is a polymer thin film with proton conduction function. As the core component of a membrane electrode, it can separate the positive and negative electrode reactants and provide a proton transport channel to ensure the orderly conduction of electrochemical reactions.

[0087] The gas diffusion layer is a porous conductive material layer located between the catalyst layer and the bipolar plate. It has functions of gas transport, electron conduction and drainage, and is mainly used to optimize the contact efficiency between the reactants and the catalyst layer.

[0088] Drying refers to the process of placing the proton exchange membrane or gas diffusion layer coated with catalyst slurry under a specific temperature and environment to remove the dispersion medium. It is necessary to ensure that the catalyst layer does not crack or agglomerate after drying.

[0089] Hot pressing refers to a process of pressing and bonding dried components under set temperature, pressure and time conditions. It is mainly used to enhance the bonding strength between the catalyst layer and the substrate and optimize the interfacial contact performance.

[0090] A single cell refers to the smallest electrolysis unit assembled from components such as membrane electrode, bipolar plate, and sealing gasket. It can independently realize the hydrogen production reaction by electrolyzing water and is used to test the actual operating performance of the membrane electrode.

[0091] Standard PEM electrolysis water test conditions refer to preset standardized operating parameters, including temperature, pressure, electrolyte supply method, etc., which are mainly used to ensure the comparability and repeatability of test results.

[0092] Steady-state activation refers to the process of allowing a single cell to run continuously for a period of time under set test conditions, so that the catalyst activity and interfacial contact state reach a stable state, providing a stable benchmark for subsequent performance testing.

[0093] The polarization curve is a curve that describes the relationship between the output voltage and current density of a single cell. It can reflect the operating characteristics of the electrolyzer under different loads and includes characteristic regions such as the kinetic control region, the ohmic control region, and the mass transfer control region.

[0094] The kinetic control region refers to the low current density area in the polarization curve. In this region, the voltage change is mainly determined by the electrochemical reaction kinetic rate, and the effects of mass transfer and ohmic loss are negligible. It is the key region for obtaining kinetic parameters.

[0095] Tafel fitting is a mathematical processing method that involves linearly fitting data points in the kinetic control region of a polarization curve to obtain relevant parameters of the Tafel equation. It is mainly used to quantify the kinetic rate of electrochemical reactions.

[0096] The exchange current density j_0 refers to the current density of the forward and reverse reactions when the electrochemical reaction reaches equilibrium. It is a core kinetic parameter characterizing the intrinsic catalytic activity of a catalyst, and the larger the value, the faster the reaction kinetics.

[0097] The iridium loading per unit area electrode refers to the mass of iridium element coated in the catalytic layer of a unit area membrane electrode. It is a fundamental parameter for calculating mass activity and directly affects catalyst cost and utilization efficiency.

[0098] The preset current density value refers to a constant current density parameter that is pre-set according to the range of the kinetic control region. It is necessary to ensure that this value is within the kinetic control region to avoid mass transfer or ohmic loss interfering with the charge transfer performance test.

[0099] Stable output voltage means that when a single cell is running at a constant current density, the fluctuation range of the output voltage is controlled within a preset range, indicating that the electrochemical reaction has reached dynamic equilibrium. At this time, electrochemical impedance spectroscopy can be performed.

[0100] Relaxation time distribution analysis is an analytical method that converts electrochemical impedance spectroscopy data into a relationship between resistivity and characteristic frequency. It can separate the impedance contributions of different kinetic processes and achieve accurate identification of specific processes.

[0101] The relaxation time distribution spectrum refers to the spectrum obtained through relaxation time distribution analysis. The characteristic frequency is plotted on the horizontal axis and the resistivity is plotted on the vertical axis. The characteristic peaks of different relaxation times correspond to different electrochemical processes.

[0102] Electrochemical kinetic characteristics refer to the inherent properties of a catalyst in an electrochemical reaction, such as rate behavior and reaction mechanism. These characteristics can be obtained through rotating disk electrode testing and are used as a basis for process identification.

[0103] Charge transfer refers to the electrochemical process by which reactants gain or lose electrons at the active sites of a catalyst. It is the core step of an electrochemical reaction, and the magnitude of its resistance directly affects the reaction rate.

[0104] Characteristic relaxation time refers to the time parameter corresponding to the characteristic frequency of each characteristic peak in the relaxation time distribution spectrum. Different electrochemical processes have specific relaxation time magnitudes, which are the key basis for distinguishing different processes.

[0105] The theoretical relaxation time refers to the estimated relaxation time of the corresponding charge transfer process calculated based on parameters such as exchange current density and double-layer capacitance. It is used as a reference standard for identifying characteristic peaks of charge transfer.

[0106] The impedance value Z_ct is a specific numerical value that characterizes the resistance to the charge transfer process. Its magnitude is negatively correlated with the charge transfer rate. The smaller the value, the higher the charge transfer efficiency.

[0107] In one specific embodiment, the catalyst slurry prepared in step S1 is coated onto the surface of a Nafion 212 proton exchange membrane by spraying, with the catalyst loading controlled at 1 mg / cm². After coating, the membrane is dried in a vacuum drying oven at 80°C for 2 hours, and then hot-pressed at 130°C and 10 MPa for 3 minutes to form a membrane electrode with an effective area of ​​10 cm².

[0108] A single cell was assembled by combining a membrane electrode assembly (MEA) with a graphite bipolar plate and a fluororubber sealing gasket. Standard PEM water electrolysis test conditions were set as follows: temperature 80℃, anode pressure 0.1 MPa, cathode pressure 0.1 MPa, with 0.5 mol / L sulfuric acid electrolyte introduced at the anode and high-purity hydrogen gas introduced at the cathode. The single cell was started for steady-state activation and run continuously for 10 hours, maintaining stable test conditions throughout. After activation, a complete polarization curve was measured using an electrochemical workstation within a current density range of 0 to 2 A / cm².

[0109] The current density range of 20 to 100 mA / cm² was selected from the polarization curve as the kinetic control region, within which voltage changes are mainly driven by the oxygen evolution reaction kinetics. Five uniformly distributed data points within this region were selected, and Tafel fitting was performed with overpotential as the ordinate and the logarithm of current density as the abscissa to obtain the Tafel slope and exchange current density j_0, where the measured value of j_0 is 0.015 mA / cm².

[0110] The actual iridium content in the catalytic layer of the membrane electrode was measured by inductively coupled plasma atomic emission spectrometry, and the iridium loading m_Ir per unit area electrode was found to be 1 mg per square centimeter. The apparent mass activity A_app was calculated to be 0.015 A per mg of iridium according to the formula A_app=j_0 / m_Ir.

[0111] The single cell was kept under constant current control at a preset current density of 50 mA per square centimeter within the kinetic control region. The output voltage was monitored in real time. When the voltage fluctuation was less than 5 mV per hour, the output voltage was considered stable. At this time, an electrochemical workstation was used to perform electrochemical impedance spectroscopy. The test parameters were set to a disturbance voltage amplitude of 10 mV and a frequency range of 0.1 Hz to 100 kHz. Ten data points were collected for each decimal frequency range.

[0112] The measured electrochemical impedance spectroscopy data were imported into the DRTTool analysis software for relaxation time distribution analysis. The software was set to the default analysis parameters to obtain the relaxation time distribution spectrum. Based on the catalyst electrochemical kinetic characteristics obtained from the rotating disk electrode test in step S1, and combined with the exchange current density j_0, the theoretical relaxation time was calculated, which is on the order of 10^-2 seconds.

[0113] The characteristic peak corresponding to the charge transfer process was identified from the relaxation time distribution spectrum. The characteristic relaxation time of this peak is 0.04 to 0.06 seconds, which matches the theoretical relaxation time order of magnitude. The characteristic peak was integrated using software integration to quantify the charge transport performance parameters, and the corresponding impedance value Z_ct is 80 ohms.

[0114] Step S3 further includes the following sub-steps:

[0115] S3-1, Based on the difference between the rotating disk electrode test conditions in step S1 and the single cell test conditions in step S2, determine the test condition correction factor α, wherein the difference includes temperature, pressure and electrolyte concentration;

[0116] S3-2, Read the apparent quality activity A_app obtained from step S2, and calculate the corrected apparent quality activity A_app_corr=A_app×α;

[0117] S3-3, Read the second reference parameter A_int obtained from step S1 to characterize the intrinsic mass activity of the catalyst;

[0118] S3-4, calculate the first parameter characterizing the degree of activity according to the following formula: U_A = (A_app_corr / A_int) × 100%, where U_A is the first parameter characterizing the degree of activity, and the first parameter is the electrochemical activity rate.

[0119] Further, in sub-step S3-1, the step of determining the test condition correction factor α includes:

[0120] A standard catalyst is selected, which is an iridium-based perovskite catalyst with a well-defined crystal structure, and the standard catalyst exhibits reproducible electrochemical performance in repeated tests.

[0121] Using a standard catalyst, under the same rotating disk electrode test conditions as in step S1, the steady-state current density was measured at a specific overpotential η_ref, denoted as I_RDE;

[0122] Using a standard catalyst, under the same membrane electrode preparation process and single-cell test conditions as in step S2, the steady-state current density was measured at the same overpotential η_ref corresponding to the cell voltage, and denoted as I_MEA.

[0123] The test condition correction factor is calculated as follows: α = I_MEA / I_RDE, where α is the test condition correction factor and η_ref is the preset reference overpotential value, which is located within the oxygen evolution reaction kinetic control region of the standard catalyst.

[0124] It should be noted that the test condition correction factor α is a coefficient used to eliminate the influence of environmental parameter differences between the rotating disk electrode test and the single cell test on the activity data. It is determined by the ratio of the activity of the standard catalyst under the two test conditions to ensure the comparability of activity data under different test systems.

[0125] Temperature difference refers to the temperature difference between the room temperature environment of the rotating disk electrode test and the high temperature operating environment of the single cell test. Temperature changes affect the reaction kinetic rate and ion transport efficiency.

[0126] Pressure difference refers to the difference between the ambient pressure conditions of the rotating disk electrode test and the specific working pressure of the single cell test. Pressure changes can affect the solubility of reactants and the mass transfer rate.

[0127] Electrolyte concentration difference refers to the difference in the concentration of acidic electrolyte in two test systems. The concentration change will affect the proton conduction rate and the contact efficiency of reactive sites.

[0128] The corrected apparent quality activity A_app_corr refers to the activity value obtained by correcting the apparent quality activity obtained from single-cell testing with a correction factor α to eliminate the influence of differences in test conditions. This value is closer to the activity performance of the catalyst under ideal intrinsic test conditions.

[0129] The second benchmark parameter A_int is a parameter obtained through rotating disk electrode testing that characterizes the intrinsic quality activity of the catalyst. It is not affected by the testing environment and device structure and serves as a benchmark for measuring the degree of activity.

[0130] Electrochemical activity utilization rate refers to the ratio of the catalyst's activity after testing correction to its intrinsic activity under actual single-cell operating conditions. It reflects the comprehensive influence of factors such as electrochemical interface characteristics and mass transfer conditions on the catalyst's activity utilization.

[0131] Standard catalysts are iridium-based perovskite catalysts with well-defined crystal structures, stable chemical compositions, and reproducible electrochemical performance. Their catalytic performance is stable and known, and they are mainly used to establish correlations between test conditions and to calibrate correction factors.

[0132] A well-defined crystal structure means that the crystallographic characteristics of the catalyst, such as the atomic arrangement and lattice parameters, have been determined through characterization methods. The structure is regular and free of obvious defects, ensuring the stability and repeatability of its electrochemical performance.

[0133] Reproducible electrochemical performance refers to the fact that when a standard catalyst is tested multiple times under the same test conditions, the fluctuation range of the activity data obtained is within a preset range, demonstrating good test stability and serving as a calibration benchmark.

[0134] The specific overpotential η_ref refers to the pre-set overpotential value located within the kinetic control region of the oxygen evolution reaction of the standard catalyst. At this overpotential, the reaction rate is mainly controlled by kinetics, and the mass transfer effect is negligible, ensuring the comparability of activity data.

[0135] Steady-state current density I_RDE refers to the current density measured after a standard catalyst reaches reaction equilibrium at a specific overpotential η_ref under rotating disk electrode testing conditions, reflecting the activity of the standard catalyst under ideal testing conditions.

[0136] The membrane electrode preparation process refers to the preparation process of catalyst slurry coating, drying, hot pressing, etc., which is completely consistent with step S2, to ensure that the membrane electrode prepared by the standard catalyst has the same structure as the membrane electrode of the catalyst to be tested.

[0137] Steady-state current density I_MEA refers to the current density measured after the membrane electrode prepared with the standard catalyst reaches stable operation under the same overpotential η_ref under single-cell test conditions, reflecting the activity of the standard catalyst under actual application conditions.

[0138] In one specific implementation, the rotating disk electrode test conditions in step S1 are room temperature 25°C, atmospheric pressure 0.1 MPa, and sulfuric acid electrolyte of 0.5 mol / L; the single cell test conditions in step S2 are temperature 80°C, pressure 0.1 MPa, and sulfuric acid electrolyte of 0.5 mol / L. The core difference between the two is the temperature.

[0139] Titanium-iridium-strontium perovskite catalyst was selected as the standard catalyst. This catalyst has a regular perovskite crystal structure, and after repeated testing, its electrochemical activity fluctuation range is less than 5%, demonstrating reproducible electrochemical performance.

[0140] Rotating disk electrode tests were conducted using a standard catalyst, with test conditions identical to those in step S1: When preparing the catalyst slurry, the ratio of standard catalyst, Nafion ionomer, and dispersion medium was 1:0.1:10, and the slurry was ultrasonically dispersed for 30 minutes; it was coated onto the surface of a 5 mm diameter glassy carbon electrode with a loading of 0.2 mg / cm²; and the steady-state current density was measured in 0.5 mol / L sulfuric acid electrolyte at a specific overpotential η_ref = 0.4 V, yielding I_RDE = 10 mA / cm².

[0141] The membrane electrode was prepared using a standard catalyst according to the membrane electrode preparation process in step S2: catalyst loading of 1 mg / cm², vacuum drying at 80°C for 2 hours, hot pressing at 130°C and 10 MPa for 3 minutes, resulting in an effective area of ​​10 cm². After assembling a single cell, it was run under the same test conditions as in step S2. The anode overpotential was adjusted to η_ref = 0.4 V by adjusting the cell voltage, and the steady-state current density was measured to obtain I_MEA = 8 mA / cm².

[0142] The test condition correction factor is calculated using the formula α = I_MEA / I_RDE. Substituting the values, we get α = 8 mA / cm² / 10 mA / cm² = 0.8.

[0143] The apparent mass activity of the catalyst to be tested, A_app, measured in step S2, is read as 0.015 A per milligram of iridium. The corrected apparent mass activity is calculated according to the formula A_app_corr = A_app × α, resulting in A_app_corr = 0.015 × 0.8 = 0.012 A per milligram of iridium.

[0144] The second reference parameter A_int = 1.62 amperes per milligram of iridium was read from step S1. The first parameter was calculated according to the formula U_A = (A_app_corr / A_int) × 100%, and U_A = (0.012 / 1.62) × 100% ≈ 0.74%. This value is the electrochemical activity utilization rate of the catalyst to be tested.

[0145] Step S4 further includes the following sub-steps:

[0146] S4-1 controls the operating voltage of a single cell to keep the anode potential in the non-Radida potential range where oxygen evolution reaction does not occur, in the single-cell operation state.

[0147] S4-2, applying a triangular wave potential perturbation to a single cell within a potential range at multiple different scan rates v, and simultaneously measuring the corresponding current response data, wherein the amplitude of the triangular wave potential perturbation is set to ensure that the electrochemical response of the membrane electrode catalytic layer is in the linear region.

[0148] S4-3, based on current response data, the average response current I_avg at each scan rate v is determined by calculating the average value of the absolute value of the current within each complete disturbance cycle;

[0149] S4-4, plot the relationship curve between the average response current I_avg and the scan rate v, and perform linear fitting on the curve within the linear response range of the scan rate v to obtain its slope as the total double layer capacitance C_dl_MEA of the membrane electrode catalytic layer.

[0150] S4-5, Based on the total double-layer capacitance C_dl_MEA and the specific capacitance per unit area C_s of the catalyst material, the accessible electrochemical active area S_app is calculated according to the formula S_app=C_dl_MEA / C_s, where C_s is obtained by the rotating disk electrode test calibration in step S1;

[0151] S4-6, calculate the second parameter characterizing the accessibility of active sites according to the following formula: U_S=(S_app / S_int)×100%, where U_S is the second parameter characterizing the accessibility of active sites, S_int is the first benchmark parameter obtained from step S1 for characterizing the intrinsic electrochemical active area characteristics of the catalyst, and the second parameter is the surface area accessibility utilization rate.

[0152] It should be noted that the single-cell operating state refers to the working state of a single cell under preset test conditions such as temperature and pressure, which can stably output voltage or current. At this time, the interface state of the membrane electrode catalytic layer and the distribution of reactants are in dynamic equilibrium.

[0153] Working voltage control refers to adjusting the output voltage of a single cell through electrochemical testing equipment to ensure that the anode potential falls precisely within the target range, thereby ensuring the uniformity of the electrode reaction during the test.

[0154] Anode potential refers to the potential value of the anode of a single cell relative to the reference electrode. Its magnitude directly determines the type of reaction that occurs on the anode surface and is the core parameter for controlling electrode reactions.

[0155] Triangular wave potential perturbation refers to a small-amplitude perturbation signal in which the potential changes in a triangular waveform over time. Its potential change is symmetrical and the rate is uniform. It is mainly used to excite the linear electrochemical response on the electrode surface and avoid nonlinear distortion.

[0156] The scan rate v refers to the rate of potential change in a triangular wave potential disturbance. Multiple different scan rate settings are used to verify the linearity of the response and to separate the double-layer capacitance from other current contributions.

[0157] Current response data refers to the recorded data of how the current generated by a single cell changes over time after a potential disturbance is applied. Its amplitude and waveform are directly related to processes such as the double-layer capacitance and Faraday reaction on the electrode surface.

[0158] The linear region refers to the range in which the electrochemical response is directly proportional to the potential perturbation. Within this range, the current response is contributed only by the double-layer capacitance and is not affected by nonlinear factors such as the Radius reaction, thus ensuring the accuracy of the double-layer capacitance measurement.

[0159] A complete disturbance cycle refers to the complete process of a triangular wave potential starting from the initial potential, rising, falling, and returning to the initial potential. The potential change pattern is consistent in each cycle, which is used to obtain a stable current response.

[0160] The average absolute value of the current refers to the arithmetic mean calculated by taking the absolute value of all current data within a complete disturbance cycle. It is used to eliminate the influence of the opposite current direction during the potential rise and fall phases and to highlight the contribution of the double-layer capacitance.

[0161] The average response current I_avg refers to the average current calculated based on a complete perturbation cycle at each scan rate. Its magnitude is directly related to the scan rate and the double-layer capacitance, and it is the core data for calculating capacitance.

[0162] The linear response range refers to the range of scan rates in which the average response current I_avg has a strictly linear relationship with the scan rate v. Within this range, the double-layer charging / discharging process is lag-free and the capacitance value is stable.

[0163] Linear fitting refers to performing linear regression analysis on I_avg-v data points within the linear response range, and determining the slope and intercept of the fitted line using the least squares method. The slope directly corresponds to the double-layer capacitance.

[0164] The total electric double layer capacitance C_dl_MEA refers to the total capacitance of the electric double layer formed on the surface of all accessible active sites in the catalytic layer of the membrane electrode. Its magnitude is proportional to the accessible electrochemical active area and is a key parameter that indirectly characterizes the total number of accessible active sites.

[0165] The specific capacitance per unit area, C_s, refers to the double-layer capacitance corresponding to a unit electrochemically active area. It is an inherent characteristic parameter of the catalyst material and needs to be calibrated through standard tests to convert the capacitance value into an area value.

[0166] The accessible electrochemical active area S_app refers to the surface area of ​​active sites on the membrane electrode that can be contacted by reactants and participate in electrochemical reactions under actual operating conditions, reflecting the actual number of active sites that the catalyst can play a role.

[0167] Surface area accessibility utilization rate refers to the ratio of accessible electrochemical active area to intrinsic electrochemical active area, expressed as a percentage. It is a core parameter characterizing the physical accessibility of active sites and reflects the influence of catalyst layer structure, mass transfer conditions, etc. on the contact efficiency of active sites.

[0168] In one specific implementation, the single cell is kept under the standard test conditions of step S2 (temperature 80°C, pressure 0.1 MPa), and the operating voltage of the single cell is controlled by an electrochemical workstation. The anode potential is adjusted to 0.05 V to 0.3 V relative to the reversible hydrogen electrode, which is the non-Radida potential range where the oxygen evolution reaction does not occur.

[0169] Four different scan rates v were set: 5 mV / s, 10 mV / s, 20 mV / s, and 50 mV / s. The amplitude of the triangular wave potential perturbation was set to 20 mV. This amplitude was verified in preliminary experiments to ensure that the electrochemical response of the membrane electrode catalytic layer is in the linear region without nonlinear distortion.

[0170] A triangular wave potential perturbation was applied using an electrochemical workstation, and current response data at each scan rate was collected synchronously. The data sampling frequency was set to 100 Hz to ensure complete capture of current changes in each perturbation cycle.

[0171] For the current response data at each scan rate, three complete disturbance cycles are extracted, the average value of the absolute current in each cycle is calculated, and the average value of the three cycles is taken to obtain the average response current I_avg corresponding to that scan rate.

[0172] Based on the I_avg data corresponding to the four scan rates, a relationship curve was plotted with the scan rate v as the abscissa and the average response current I_avg as the ordinate. The results were verified by linear regression analysis, showing that the data in the range of 5 mV / s to 50 mV / s exhibited a strict linear relationship, and this range is the linear response range.

[0173] Linear fitting was performed on the data within the linear response range, and the slope of the fitted line was 0.8 millifarads. This slope is the total double-layer capacitance of the membrane electrode catalytic layer, C_dl_MEA = 0.8 millifarads.

[0174] The specific capacitance per unit area C_s was calibrated by rotating disk electrode test in step S1. Pure IrO2 standard sample was selected, and its specific capacitance per unit area was measured to be 30 microfarads per square centimeter. According to the formula S_app=C_dl_MEA / C_s, the available electrochemical active area was calculated by substituting the values, and S_app=0.8×10³ microfarads / 30 microfarads per square centimeter≈26.67 square centimeters.

[0175] The first reference parameter S_int = 40 square centimeters obtained in step S1 is read. The second parameter is calculated according to the formula U_S = (S_app / S_int) × 100%, and U_S = (26.67 / 40) × 100% ≈ 66.67%. This value is the surface area accessibility of the catalyst to be tested.

[0176] Step S5 further includes the following sub-steps:

[0177] S5-1, based on the first reference parameter S_int and the exchange current density j_0 obtained by the rotating disk electrode test, the theoretical charge transfer resistance R_ct_ideal is calculated according to the electrochemical kinetic formula;

[0178] S5-2, extract the real part from the charge transport performance parameter Z_ct and use it as the apparent charge transfer resistance R_ct_app;

[0179] S5-3, the third parameter characterizing charge transfer efficiency is obtained by calculating the following formula: U_R = (R_ct_ideal / R_ct_app) × 100%, where U_R is the third parameter characterizing charge transfer efficiency, and the third parameter is the charge transfer efficiency utilization rate.

[0180] Further, in sub-step S5-1, the step of calculating the theoretical charge transfer resistance R_ct_ideal based on the electrochemical kinetic formula includes:

[0181] Based on the intrinsic dynamics of the charge transfer process described by the Butler-Wolmer equation or the Tafel equation, a theoretical correlation is established between the exchange current density j_0 and the charge transfer resistance R_ct.

[0182] Substituting the first reference parameter S_int and the exchange current density j_0 into the theoretical correlation, R_ct_ideal is calculated.

[0183] It should be noted that the electrochemical kinetic formula is a mathematical expression that describes the quantitative relationship between the electrochemical reaction rate and parameters such as potential and concentration. It reflects the intrinsic laws of the charge transfer process and is the basis for calculating the theoretical charge transfer resistance.

[0184] The theoretical charge transfer resistance R_ct_ideal refers to the resistance value of the charge transfer process under ideal conditions, calculated based on the intrinsic electrochemical parameters of the catalyst. This value is not affected by intrinsic factors such as the actual catalyst layer structure and interface state, and is a benchmark for measuring charge transport efficiency.

[0185] The charge transport performance parameter Z_ct refers to the impedance parameter related to the charge transfer process obtained from the relaxation time distribution analysis. It includes real and imaginary parts and comprehensively reflects the impedance characteristics of the charge transfer process.

[0186] The real part refers to the component of the impedance parameter that is in phase with the current. This part directly corresponds to the resistance loss in the charge transfer process and is the core indicator for quantifying the resistance to charge transfer.

[0187] The apparent charge transfer resistance R_ct_app refers to the real part extracted from the charge transport performance parameters obtained from actual tests. It reflects the total resistance of the charge transfer process in the membrane electrode catalytic layer under actual operating conditions, including intrinsic resistance and non-intrinsic resistance.

[0188] Charge transfer efficiency is the ratio of theoretical charge transfer resistance to apparent charge transfer resistance, expressed as a percentage. It is used to quantify the efficiency of charge transfer processes in a real system and reflects the degree of optimization of the charge transfer network.

[0189] The Butler-Wolmer equation is the core kinetic equation describing the relationship between electrochemical reaction rate and overpotential. It is applicable to all potential ranges and can comprehensively reflect the intrinsic laws of charge transfer processes.

[0190] The Tafel equation is a simplified form of the Butler-Wolmer equation in the high overpotential range. It presents a linear relationship between overpotential and the logarithm of current density, making it easy to quickly extract kinetic parameters from polarization curves.

[0191] The intrinsic kinetic relationship of the charge transfer process refers to the charge transfer rate law determined solely by the characteristics of the catalyst itself, without considering external factors such as mass transfer and ohmic loss. It is the core basis for establishing theoretical correlations.

[0192] Theoretical correlations refer to quantitative relationships between exchange current density and charge transfer resistance derived from electrochemical kinetic equations, which can directly correlate kinetic parameters with impedance parameters.

[0193] In one specific implementation, the first reference parameter S_int = 40 square centimeters obtained in step S1 is read, and the exchange current density j_0 = 0.15 amps per square meter is obtained by rotating the disk electrode test (calculated from the steady-state current and electrode area in step S1).

[0194] The theoretical charge transfer resistance R_ct_ideal is calculated based on the principles of electrochemical kinetics. According to the linear relationship of the Butler-Wolmer equation at low overpotentials, the charge transfer resistance R_ct and the exchange current density j_0 satisfy the formula R_ct = R × T / (n × F × j_0). Where R is the molar gas constant, taken as 8.314 joules per molar Kelvin; T is the absolute temperature at the time of testing, taken as 298 Kelvin; n is the number of electrons transferred in the oxygen evolution reaction, taken as 4; and F is the Faraday constant, taken as 96485 coulombs per mole.

[0195] First, calculate the theoretical charge transfer resistance per unit area, R_ct_A: R_ct_A = (8.314 × 298) / (4 × 96485 × 0.15) ≈ 0.0427 ohms per square meter.

[0196] Furthermore, the resistivity per unit area R_ct_A is converted to the theoretical charge transfer resistance R_ct_ideal for the entire catalyst sample. Since R_ct_A is in ohms per square meter, while j_0 is in amperes per square meter and S_int is in square centimeters per milligram of iridium, unit conversion and integration are necessary. R_ct_ideal characterizes the total charge transfer resistance per milligram of iridium catalyst under ideal conditions. Based on the equivalent physical meaning of the relationship R_ct_ideal = R_ct_A / (j_0 × S_int), and considering the units of the aforementioned parameters, numerical calculations yield R_ct_ideal to be approximately 711 ohms per milligram per ampere. This value represents the benchmark for ideal charge transfer performance calculated based on the intrinsic activity parameters of the catalyst.

[0197] The membrane electrode assembly (MEA) of the catalyst was prepared according to step S2, and a single-cell test was performed. Its electrochemical impedance spectroscopy was measured under stable operating conditions, and the impedance value Z_ct corresponding to the charge transfer process was identified and quantified by relaxation time distribution analysis. The real part of this complex impedance value Z_ct was extracted as the apparent charge transfer resistance R_ct_app of the MEA under actual operating conditions. It is assumed that R_ct_app is measured to be 1422 ohm-milligrams per ampere.

[0198] Finally, the third parameter U_R, characterizing the charge transport efficiency, is calculated according to the formula in step S5-3, i.e., the charge transport efficiency utilization rate: U_R = (R_ct_ideal / R_ct_app) × 100% = (711 / 1422) × 100% ≈ 50%. This result indicates that in this implementation case, the actual membrane electrode's charge transport resistance reaches twice the ideal theoretical value, and the charge transport efficiency utilization rate is 50%. This suggests that there is significant room for optimization in the electrode's microstructure regarding charge conduction, possibly stemming from factors such as catalyst agglomeration, uneven ionomer distribution, or contact resistance.

[0199] Step S6 further includes the following sub-steps:

[0200] S6-1, normalize the first parameter U_A, the second parameter U_S and the third parameter U_R of the input;

[0201] S6-2, Calculate the relative difference between pairs of parameters based on the normalized parameters;

[0202] S6-3, Match the calculated relative difference with the preset judgment rule set;

[0203] S6-4, output the matching root cause type judgment result, the root cause type includes electrochemical interface failure type, physical structure failure type, charge transport network failure type and system comprehensive failure type.

[0204] Please see Figure 2 The flowchart of the loss root cause judgment logic provided in the embodiment of the present invention.

[0205] Furthermore, in sub-step S6-3, the preset set of judgment rules is executed in the following priority order, and the judgment terminates once the condition is met:

[0206] (1) When the relative difference between any two of U_A, U_S, and U_R is less than the predetermined proximity threshold, it is judged as a system comprehensive failure type;

[0207] (2) When U_A is simultaneously less than both U_S and U_R, and the relative difference between U_A and both is greater than or equal to the predetermined significance threshold, it is judged as an electrochemical interface failure type.

[0208] (3) When U_S is less than both U_A and U_R, and the relative difference between U_S and both is greater than or equal to the predetermined significance threshold, it is judged as a physical structure failure type.

[0209] (4) When U_R is less than both U_A and U_S, and the relative difference between U_R and U_S is greater than or equal to the predetermined significance threshold, it is judged as a charge transport network failure type.

[0210] (5) According to the type corresponding to the minimum parameter, if U_A is the minimum value, it is judged as electrochemical interface failure type; if U_S is the minimum value, it is judged as physical structure failure type; if U_R is the minimum value, it is judged as charge transport network failure type.

[0211] Wherein, the predetermined salience threshold is greater than or equal to the predetermined proximity threshold.

[0212] It should be noted that normalization preprocessing refers to the process of scaling the three parameters to the same numerical range according to a uniform ratio, eliminating the influence of differences in the absolute values ​​of each parameter, and ensuring the fairness of the relative difference calculation.

[0213] The relative difference is the ratio of the absolute difference between two normalized parameters to the larger of the two, expressed as a percentage. It is used to quantify the degree of deviation between two parameters and to reflect the significance of the differences in the corresponding influencing factors.

[0214] Electrochemical interface failure refers to one of the root causes, which is caused by abnormal electrochemical interface characteristics, such as excessive coverage of ionomers or adsorption of impurities at active sites, and is characterized by a significantly low electrochemical activity rate.

[0215] Physical structure failure refers to one of the root causes, which is caused by defects in the physical structure of the catalyst layer, such as catalyst agglomeration and pore blockage, and is characterized by a significantly low surface area accessibility and utilization rate.

[0216] Charge transport network failure refers to one of the root causes caused by obstructed charge transport channels, such as blocked proton conduction or poor electron conduction contact, which manifests as a significantly low charge transport efficiency utilization rate.

[0217] Systemic comprehensive failure refers to one of the root cause types, which is caused by multiple factors such as electrochemical interface, physical structure, and charge transport network. It is characterized by relatively small differences in the three parameters and no single dominant factor.

[0218] Priority order refers to the order in which the judgment rules are executed. It is logically ordered as "comprehensive failure, single factor failure, minimum value judgment" to ensure that complex comprehensive problems are identified first, and then the single dominant problem is located.

[0219] The proximity threshold refers to a pre-set critical value where the difference between the judgment parameters is small. When the relative difference between any two parameters is less than this value, it is judged as a comprehensive failure caused by the combined effect of multiple factors.

[0220] The significance threshold is a preset critical value for judging whether the difference between parameters is significant. When a parameter is smaller than the other two parameters at the same time and the difference reaches the value, it is judged as a single failure dominated by the factor corresponding to that parameter.

[0221] In one specific implementation, the three parameters calculated in steps S3 to S5 are input: the first parameter U_A = 0.74%, the second parameter U_S = 66.67%, and the third parameter U_R = 22%.

[0222] The three parameters were preprocessed by normalization using a linear normalization method, which scaled the parameter values ​​to the range of 0-100. The results after normalization maintained the original proportional relationship: U_A=0.74, U_S=66.67, U_R=22.00.

[0223] The relative difference between each pair of parameters is calculated based on the normalized parameters. The formula is: Relative difference = |XY| / max(X,Y)×100%. The results are: the relative difference between U_A and U_S is approximately 98.9%, the relative difference between U_A and U_R is approximately 96.6%, and the relative difference between U_S and U_R is approximately 67.0%.

[0224] The preset proximity threshold is 8%, the significance threshold is 20%, and the significance threshold is greater than or equal to the proximity threshold, which meets the rule requirements.

[0225] The judgment rule set is executed in priority order: First, it is checked whether the system comprehensive failure condition is met. Since the relative difference between any two is greater than the proximity threshold of 8%, it is not met. Next, the electrochemical interface failure condition is checked. U_A is simultaneously less than U_S and U_R, and the relative difference between U_A and U_S is greater than the significance threshold of 20%. This condition is met, and the subsequent judgment is terminated.

[0226] The output root cause type judgment result is electrochemical interface failure type, indicating that the loss of catalyst utilization is mainly due to abnormal electrochemical interface characteristics, which needs to be improved by optimizing the catalyst layer interface contact and reducing excessive coverage of ionomers.

[0227] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for anode catalyst utilization test for a PEM electrolyzer, characterized by, Includes the following steps: Step S1: Perform a rotating disk electrode test on the anode catalyst to be tested to obtain its intrinsic mass activity and intrinsic electrochemical active area. Step S2: The anode catalyst is prepared into a membrane electrode and assembled into a single cell for testing. The apparent quality activity of the membrane electrode is obtained, and the charge transport performance parameters of the membrane electrode catalyst layer are obtained by analyzing the electrochemical impedance spectroscopy of the single cell under operating conditions. Step S3: Based on intrinsic quality activity and apparent quality activity, calculate the first parameter characterizing the degree of activity exertion; Step S4: Obtain the accessible electrochemical active area of ​​the membrane electrode catalytic layer under actual operating conditions, and calculate the second parameter characterizing the accessibility of active sites based on the intrinsic electrochemical active area. Step S5: Based on the intrinsic electrochemical active area, calculate the theoretical charge transfer performance parameters, and combine them with the charge transport performance parameters to calculate the third parameter characterizing the charge transport efficiency. Step S6: Compare the relative magnitudes of the first parameter, the second parameter, and the third parameter, and determine the type of root cause that leads to the loss of catalyst utilization based on a preset set of judgment rules. Step S3 further includes the following sub-steps: S3-1, Based on the difference between the rotating disk electrode test conditions in step S1 and the single cell test conditions in step S2, determine the test condition correction factor α, wherein the difference includes temperature, pressure and electrolyte concentration; S3-2, Read the apparent quality activity A_app obtained from step S2, and calculate the corrected apparent quality activity A_app_corr=A_app×α; S3-3, Read the second reference parameter A_int obtained from step S1 to characterize the intrinsic mass activity of the catalyst; S3-4, calculate the first parameter characterizing the degree of activity according to the following formula: U_A = (A_app_corr / A_int) × 100%, where U_A is the first parameter characterizing the degree of activity, and the first parameter is the electrochemical activity rate; Step S4 further includes the following sub-steps: S4-1, in single-cell operation, controls its operating voltage to keep the anode potential in the non-Radida potential range where oxygen evolution reaction does not occur; S4-2, applying a triangular wave potential perturbation to a single cell within a potential range at multiple different scan rates v, and simultaneously measuring the corresponding current response data, wherein the amplitude of the triangular wave potential perturbation is set to ensure that the electrochemical response of the membrane electrode catalytic layer is in the linear region. S4-3, based on current response data, the average response current I_avg at each scan rate v is determined by calculating the average value of the absolute value of the current within each complete disturbance cycle; S4-4, plot the relationship curve between the average response current I_avg and the scan rate v, and perform linear fitting on the curve within the linear response range of the scan rate v to obtain its slope as the total double layer capacitance C_dl_MEA of the membrane electrode catalytic layer. S4-5, Based on the total double-layer capacitance C_dl_MEA and the specific capacitance per unit area C_s of the catalyst material, the accessible electrochemical active area S_app is calculated according to the formula S_app=C_dl_MEA / C_s, where C_s is obtained by the rotating disk electrode test calibration in step S1; S4-6, calculate the second parameter characterizing the accessibility of active sites according to the following formula: U_S=(S_app / S_int)×100%, where U_S is the second parameter characterizing the accessibility of active sites, S_int is the first benchmark parameter obtained from step S1 for characterizing the intrinsic electrochemical active area characteristics of the catalyst, and the second parameter is the surface area accessibility utilization rate. Step S5 further includes the following sub-steps: S5-1, based on the first reference parameter S_int and the exchange current density j_0 obtained by the rotating disk electrode test, the theoretical charge transfer resistance R_ct_ideal is calculated according to the electrochemical kinetic formula; S5-2, extract the real part from the charge transport performance parameter Z_ct and use it as the apparent charge transfer resistance R_ct_app; S5-3, the third parameter characterizing charge transfer efficiency is calculated according to the following formula: U_R = (R_ct_ideal / R_ct_app) × 100%, where U_R is the third parameter characterizing charge transfer efficiency, and the third parameter is the charge transfer efficiency utilization rate.

2. The method for testing the utilization rate of anode catalyst in a PEM electrolyzer according to claim 1, characterized in that: Step S1 further includes the following sub-steps: S1-1, In a standard three-electrode electrolytic cell, the catalyst slurry is uniformly coated on the surface of a rotating disk electrode to prepare a working electrode; S1-2, In a nitrogen-saturated acidic electrolyte, the working electrode is subjected to a multi-scan rate cyclic voltammetry test in the non-Radida potential range to obtain its double-layer capacitance measurement value. S1-3, based on double-layer capacitance measurements, determines the first benchmark parameter for characterizing the intrinsic electrochemical active area properties of the catalyst; S1-4, the steady-state current of the working electrode is measured in the overpotential range of the oxygen evolution reaction. Based on the steady-state current and the catalyst loading on the working electrode, a second reference parameter for characterizing the intrinsic mass activity of the catalyst is determined.

3. The method for testing the utilization rate of anode catalyst in a PEM electrolyzer according to claim 1, characterized in that: Step S2 further includes the following sub-steps: S2-1, the catalyst slurry is coated onto a proton exchange membrane or gas diffusion layer, and then dried and hot-pressed to form a membrane electrode; S2-2, assembled single cell, under standard PEM water electrolysis test conditions, after steady-state activation, its complete polarization curve was measured; S2-3, the dynamic control region is determined from the polarization curve, and multiple data points in this region are fitted by Tafel to obtain the exchange current density j_0; S2-4, calculate the apparent mass activity according to the formula A_app=j_0 / m_Ir, where m_Ir is the iridium loading per unit area of ​​the electrode, and A_app represents the apparent mass activity; S2-5, the single cell is kept under constant current control at a preset current density value within the kinetic control region. After the output voltage stabilizes, its electrochemical impedance spectrum is measured under this steady state. S2-6, The relaxation time distribution of the measured electrochemical impedance spectroscopy data is analyzed to obtain the relaxation time distribution spectrum; S2-7. Based on the electrochemical kinetic characteristics exhibited by the catalyst in the rotating disk electrode test, the characteristic peaks corresponding to the charge transfer process are identified from the relaxation time distribution spectrum. The determination of the characteristic peaks is based on the fact that the corresponding characteristic relaxation time matches the order of magnitude of the theoretical relaxation time estimated by the exchange current density j_0. S2-8, by integrating the characteristic peak, the charge transport performance parameter is obtained by quantification. This parameter is characterized as the impedance value Z_ct related to the charge transfer resistance.

4. The anode catalyst utilization test method for a PEM electrolyzer according to claim 1, characterized by, In sub-step S3-1, the step of determining the test condition correction factor α includes: A standard catalyst is selected, which is an iridium-based perovskite catalyst with a well-defined crystal structure, and the standard catalyst exhibits reproducible electrochemical performance in repeated tests. Using a standard catalyst, under the same rotating disk electrode test conditions as in step S1, the steady-state current density was measured at a specific overpotential η_ref, denoted as I_RDE; Using a standard catalyst, under the same membrane electrode preparation process and single-cell test conditions as in step S2, the steady-state current density was measured at the same overpotential η_ref corresponding to the cell voltage, and denoted as I_MEA. The test condition correction factor is calculated as follows: α = I_MEA / I_RDE, where α is the test condition correction factor and η_ref is the preset reference overpotential value, which is located within the oxygen evolution reaction kinetic control region of the standard catalyst.

5. The anode catalyst utilization test method for a PEM electrolyzer of claim 1, wherein, In sub-step S5-1, the step of calculating the theoretical charge transfer resistance R_ct_ideal based on the electrochemical kinetic formula includes: Based on the intrinsic dynamics of the charge transfer process described by the Butler-Wolmer equation or the Tafel equation, a theoretical correlation is established between the exchange current density j_0 and the charge transfer resistance R_ct. Substituting the first reference parameter S_int and the exchange current density j_0 into the theoretical correlation, R_ct_ideal is calculated.

6. The method for testing the utilization rate of anode catalyst in a PEM electrolyzer according to claim 1, characterized in that: Step S6 further includes the following sub-steps: S6-1, normalize the first parameter U_A, the second parameter U_S and the third parameter U_R of the input; S6-2, Calculate the relative difference between pairs of parameters based on the normalized parameters; S6-3, Match the calculated relative difference with the preset judgment rule set; S6-4, output the matching root cause type judgment result, the root cause type includes electrochemical interface failure type, physical structure failure type, charge transport network failure type and system comprehensive failure type.

7. The method for testing the utilization rate of anode catalyst in a PEM electrolyzer according to claim 6, characterized in that, In sub-step S6-3, the preset set of judgment rules is executed in the following priority order, and the judgment terminates once the condition is met: (1) When the relative difference between any two of U_A, U_S, and U_R is less than the predetermined proximity threshold, it is judged as a system comprehensive failure type; (2) When U_A is simultaneously less than both U_S and U_R, and the relative difference between U_A and both is greater than or equal to the predetermined significance threshold, it is judged as an electrochemical interface failure type. (3) When U_S is less than both U_A and U_R, and the relative difference between U_S and both is greater than or equal to the predetermined significance threshold, it is judged as a physical structure failure type. (4) When U_R is less than both U_A and U_S, and the relative difference between U_R and U_S is greater than or equal to the predetermined significance threshold, it is judged as a charge transport network failure type. (5) According to the type corresponding to the minimum parameter, if U_A is the minimum value, it is judged as electrochemical interface failure type; if U_S is the minimum value, it is judged as physical structure failure type; if U_R is the minimum value, it is judged as charge transport network failure type. Wherein, the predetermined salience threshold is greater than or equal to the predetermined proximity threshold.

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