Quantitative detection method for average pressure of hydrogen in PEM electrolyzed water cathode catalyst layer

Abstract

The invention provides a quantitative detection method for the average pressure of hydrogen in a PEM electrolyzed water cathode catalyst layer, and relates to the technical field of hydrogen production by electrolyzed water. The quantitative detection method comprises the following steps: carrying out a hydrolysis reaction in a PEM electrolytic cell, and calculating a hydrogen permeation flux N1 and a corresponding back pressure P1 under an electrolysis working condition; in another PEM electrolytic cell with the same structure, hydrogen is introduced into the cathode side, back pressure is applied to a cathode opening, meanwhile, inert gas is introduced into the anode side, an anode product channel is continuously purged, and the hydrogen permeation flux N2 under the hydrogen introduction working condition is calculated; gradually adjusting the back pressure under the hydrogen feeding working condition, repeating the step of testing the permeation flux under the hydrogen feeding working condition to obtain the hydrogen permeation flux under different back pressures, and drawing an N2-P2 curve; and determining a corresponding hydrogen back pressure value P2 when N1 is equal to N2, and calculating according to a formula deltaP = P2-P1 to obtain the average hydrogen pressure deltaP.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production technology through water electrolysis, and in particular to a quantitative method for detecting the average hydrogen pressure in the cathode catalyst layer of PEM water electrolysis. Background Technology

[0002] Proton exchange membrane (PEM) water electrolysis is a highly efficient and green hydrogen production technology. Due to its advantages such as rapid start-up, fast response, no pollution, and high current density, it is widely used in renewable energy hydrogen production and fuel cell systems. In a PEM electrolyzer, water decomposes at the anode to produce oxygen and protons. The protons migrate through the proton exchange membrane to the cathode, where they combine with electrons to generate hydrogen.

[0003] As a key component of the PEM electrolyzer, the cathode catalyst layer's microstructure and operating conditions significantly impact hydrogen production efficiency and electrolyzer performance. Particularly under high current density operating conditions, a non-uniform hydrogen distribution can form within the cathode catalyst layer. The accumulation of average hydrogen pressure can lead to restricted gas diffusion, increased average overpotential, and even performance degradation. Therefore, accurately assessing the average hydrogen pressure within the cathode catalyst layer is crucial for understanding the mass transfer processes within the PEM water electrolysis system and optimizing the catalyst layer structure.

[0004] However, current research on the average hydrogen pressure in the cathode catalyst layer mainly relies on simulation calculations or indirect inferences from macroscopic operating parameters, lacking a simple and reliable experimental method that can be used for practical system testing. Conventional micro-sensor embedding methods suffer from significant disturbances to the electrode structure, making it difficult to accurately reflect the actual operating conditions; while hydrogen concentration measurements at the gas exhaust end fail to reflect the average information within the catalyst layer. Therefore, there is an urgent need for a method that can accurately quantify the average hydrogen pressure in the catalyst layer without damaging the electrolyzer structure.

[0005] In PEM water electrolysis systems, the hydrogen partial pressure in the cathode catalyst layer is a critical parameter, directly affecting electrolysis efficiency and the quality of hydrogen generated. Current research on the average hydrogen pressure in the cathode catalyst layer primarily employs the following technical approaches:

[0006] 1. Numerical simulation methods:

[0007] Common methods include CFD (Computational Fluid Dynamics) simulations based on porous electrode theory and multiphase flow models. These methods can spatially resolve the gas distribution and average pressure within the cathode catalyst layer. For example, Briguglio N et al. established a gas transport model in the *International Journal of Hydrogen Energy* (2013) that incorporates gas concentration, pressure, and temperature to predict hydrogen accumulation within the catalyst layer (Briguglio, N., et al., *International Journal of Hydrogen Energy*, 2013, 38(26): 11519-11529). However, this method is highly dependent on model assumptions, difficult to perfectly match real electrolyzer conditions, and cannot be tested online.

[0008] 2. Embedded miniature pressure sensor

[0009] Some patents (such as US8999135B2) attempt to integrate miniature sensors into electrodes to obtain average pressure data, which theoretically can reflect real-world operating conditions. However, this type of method suffers from problems such as large interference from the electrode structure and poor sensor stability, limiting its application in high-current-density PEM electrolysis systems.

[0010] 3. Electrochemical impedance spectroscopy

[0011] Researchers have also attempted to infer the gas state of the catalyst layer by monitoring changes in the gas mass transfer process using EIS technology (Zhang et al., Journal of mechanical engineering, 2021, 57(14):40-51.), but this method requires complex fitting, the interpretation is subjective, and the results are not unique.

[0012] Currently, in the field of PEM water electrolysis technology, a precise and reliable quantitative measurement method has not yet been developed for the key parameter of hydrogen partial pressure in the cathode catalyst layer during operation. Existing techniques mainly rely on complex mathematical models and computer simulations for estimation. While these simulation methods can reflect the changing trend of hydrogen partial pressure to some extent, they are limited by various factors, such as model accuracy, the rationality of boundary condition settings, and the complexity of the actual operating environment, resulting in calculation results that often contain certain errors and uncertainties. Therefore, developing a method that can directly quantify the average hydrogen pressure in the cathode catalyst layer experimentally under operating conditions has significant research and engineering value.

[0013] In view of this, the present invention is hereby proposed. Summary of the Invention

[0014] One objective of this invention is to provide a quantitative method for detecting the average hydrogen pressure in the catalyst layer of a PEM (Polymer Electrolysis) water electrolysis cathode. This addresses the problems of existing methods for testing the local hydrogen pressure in the catalyst layer of a PEM water electrolysis cathode, such as significant structural interference, inability to accurately test under operating conditions, reliance on simulation and indirect calculation, and inability to quantify the internal gas state of the catalyst layer. This invention provides a quantitative method for detecting the average hydrogen pressure without damaging the electrolyzer structure, applicable to actual operating conditions, and capable of calculating the average hydrogen pressure in the catalyst layer based on experimental data.

[0015] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0016] In a first aspect, the present invention provides a method for quantitatively detecting the average hydrogen pressure in the catalyst layer of a PEM water electrolysis cathode, the method comprising:

[0017] Hydrolysis was carried out in a PEM electrolyzer. The hydrogen permeation flux N1 under the electrolysis conditions was calculated, and the corresponding back pressure was P1. The back pressure under the electrolysis conditions was gradually adjusted, and the permeation flux test under the electrolysis conditions was repeated to obtain the hydrogen permeation flux under different back pressures. The N1-P1 curve was plotted.

[0018] In another PEM electrolyzer with the same structure, hydrogen gas was introduced into the cathode side and a back pressure was applied at the cathode port. At the same time, inert gas was introduced into the anode side and the anode product channel was continuously purged. The hydrogen permeation flux N2 under the hydrogen supply condition was calculated. The back pressure under the hydrogen supply condition was gradually adjusted and the permeation flux test under the hydrogen supply condition was repeated to obtain the hydrogen permeation flux under different back pressures. The N2-P2 curve was plotted.

[0019] Determine the hydrogen back pressure value P2 corresponding to N1 = N2, and calculate the average hydrogen pressure ΔP using the formula ΔP = P2 - P1.

[0020] Furthermore, the hydrogen permeation flux N1 is calculated using the following steps:

[0021] After hydrolysis in a PEM electrolyzer, the gaseous products on the anode side are collected, and the volume fraction of hydrogen (V1) in the anode gas is measured by gas chromatography. The hydrogen permeation flux (N1) is then calculated based on the applied current density (I) and the Faraday constant (F). The calculation formula is shown below:

[0022]

[0023] Furthermore, in the electrolysis process, the applied current is 0.5–5 A / cm. 2 .

[0024] Furthermore, in the electrolysis operation, the applied back pressure ranges from 0.1 to 2 MPa.

[0025] Furthermore, the PEM electrolytic cell comprises, from cathode to anode, a titanium mesh, carbon paper, a membrane electrode, a titanium felt, and another titanium mesh arranged sequentially.

[0026] Furthermore, the membrane electrode includes a cathode catalytic layer and an anode catalytic layer;

[0027] The anode catalyst layer includes iridium, and the iridium loading is 0.1–1 mg / cm³. 2 ;

[0028] The cathode catalyst layer includes platinum, and the platinum loading is 0.1–1 mg / cm³. 2 .

[0029] Furthermore, the hydrogen permeation flux N2 is calculated using the following steps:

[0030] In another PEM electrolyzer with the same structure, hydrogen gas is introduced into the cathode side and a back pressure is applied at the cathode port. Simultaneously, inert gas is introduced into the anode side, and the anode product channel is continuously purged. A mixed gas sample discharged from the anode side is collected, and the volume fraction V2 of hydrogen gas in the mixed gas sample is determined by gas chromatography. The hydrogen gas flow rate Q2, membrane area S, and gas molar volume V are then analyzed. m The hydrogen permeation flux N2 is obtained by conversion; the calculation formula is shown below:

[0031]

[0032] Furthermore, in the hydrogen supply condition, the applied back pressure ranges from 0.1 to 2 MPa.

[0033] Furthermore, in the hydrogen-passing operation, the hydrogen gas is humid hydrogen gas with a water content of 90-95%.

[0034] Furthermore, the inert gas includes any one or a combination of at least two of nitrogen, helium, or argon.

[0035] Furthermore, the inert gas flow rate is 13–20 mL / min.

[0036] Furthermore, in the hydrogen-flowing operation, the PEM electrolyzer comprises, from cathode to anode, a titanium mesh, carbon paper, a membrane electrode, a titanium felt, and another titanium mesh arranged sequentially.

[0037] Furthermore, in the hydrogen-flow condition, the membrane electrode includes a cathode catalytic layer and an anode catalytic layer;

[0038] The anode catalyst layer includes iridium, and the iridium loading is 0.1–1 mg / cm³. 2 .

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) Achieve quantitative calculation of local hydrogen pressure in cathode catalyst layer: By comparing the hydrogen permeation flux under two working conditions and combining the experimentally measured data, this invention can accurately calculate the average local pressure of hydrogen in PEM electrolysis cathode catalyst layer, solving the problem of relying on simulation or indirect estimation in the prior art and making it difficult to obtain the real pressure value.

[0041] (2) Simple operation, mature testing methods and strong applicability: This invention is based on gas chromatography detection and conventional gas flux measurement. The instruments and testing methods used are mature and reliable, which are easy to deploy in laboratories or industrial sites, reducing the testing threshold and application cost.

[0042] (3) It has good promotion value and engineering application prospects: Given its clear principle, reliable results and strong adaptability, this method is not only suitable for in-depth research on mass transfer mechanism in scientific research scenarios, but can also be widely used in the fields of industrial electrolysis system operation optimization, electrode design evaluation and fault diagnosis. Attached Figure Description

[0043] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 This is a flowchart of the quantitative detection method for the average hydrogen pressure in the PEM electrolysis cathode catalyst layer of the present invention.

[0045] Figure 2 This is a schematic diagram of the operation for chromatographic testing of hydrogen in oxygen and a hydrogen permeation path diagram.

[0046] Figure 3 This is a schematic diagram of the operation for chromatographic testing of hydrogen in nitrogen and a hydrogen permeation path diagram.

[0047] Figure 4 The N1-P1 curve is shown for the electrolysis conditions provided in Example 1.

[0048] Figure 5 The N2-P2 curve under hydrogen flow conditions provided in Example 1.

[0049] Figure 6 A schematic diagram of the quantitative calculation method for the average hydrogen pressure provided in Example 1.

[0050] Figure 7The graphs show the variation of hydrogen permeation flux of the N115 membrane with cathode back pressure under different current densities provided in Examples 1-3.

[0051] Figure 8 The graphs show the variation of hydrogen permeation flux of the N115 membrane with I / C under different back pressures provided in Examples 4-6.

[0052] Figure 9 The graphs show the variation of hydrogen partial pressure in the catalyst layer with I / C under different back pressures provided in Examples 4-6.

[0053] Figure 10 The graphs show the variation of hydrogen permeation flux of the N115 membrane with cathode loading under different back pressures provided in Examples 7-9.

[0054] Figure 11 The graphs show the variation of hydrogen partial pressure in the catalyst layer with cathode loading under different back pressures provided in Examples 7-9. Detailed Implementation

[0055] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0056] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] In a first aspect, the present invention provides a method for quantitatively detecting the average hydrogen pressure in the catalyst layer of a PEM water electrolysis cathode, such as... Figure 1 As shown, the quantitative detection method includes:

[0058] Hydrolysis was carried out in a PEM electrolyzer. The hydrogen permeation flux N1 under the electrolysis conditions was calculated, and the corresponding back pressure was P1. The back pressure under the electrolysis conditions was gradually adjusted, and the permeation flux test under the electrolysis conditions was repeated to obtain the hydrogen permeation flux under different back pressures. The N1-P1 curve was plotted.

[0059] In another PEM electrolyzer with the same structure, hydrogen gas was introduced into the cathode side and a back pressure was applied at the cathode port. At the same time, inert gas was introduced into the anode side and the anode product channel was continuously purged. The hydrogen permeation flux N2 under the hydrogen supply condition was calculated. The back pressure under the hydrogen supply condition was gradually adjusted and the permeation flux test under the hydrogen supply condition was repeated to obtain the hydrogen permeation flux under different back pressures. The N2-P2 curve was plotted.

[0060] Determine the hydrogen back pressure value P2 corresponding to N1 = N2, and calculate the average hydrogen pressure ΔP using the formula ΔP = P2 - P1.

[0061] In this invention, since the hydrogen permeation principle is the same in both electrolysis and hydrogen operation conditions (diffusion permeation), the hydrogen permeation flux is directly proportional to the partial pressure of hydrogen in the cathode catalyst layer when other conditions remain unchanged. Therefore, the increase in permeation flux can be entirely attributed to the change in the partial pressure of hydrogen in the catalyst layer, thus directly mapping the permeation difference to a partial pressure difference, thereby obtaining the partial pressure of hydrogen in the catalyst layer under arbitrary back pressure and different current densities. It is worth noting that under electrolysis conditions, hydrogen is generated from the catalyst layer-membrane interface and diffuses towards the cathode outlet. Therefore, even with applied back pressure, the internal pressure of the catalyst layer is always higher than the cathode chamber pressure. The partial pressure obtained by this method is an accurate measure of this local overpressure, thus providing a reliable basis for subsequent catalyst layer structure optimization and safety assessment.

[0062] In this invention, a dual-cell comparison strategy of "permeation flux under electrolysis conditions - back pressure calibration under non-electrolysis conditions" is adopted for the first time to uniquely map the measured hydrogen permeation flux to the average hydrogen partial pressure of the cathode catalyst layer without embedding sensors. Specifically, by utilizing the proportional relationship between permeation flux and partial pressure under the same diffusion mechanism and using the calibration curve obtained by adjustable back pressure, the permeation flux generated during the electrolysis process is directly inverted, thereby quantitatively giving the hydrogen partial pressure of the catalyst layer corresponding to different current densities and back pressures under operating conditions, and realizing online and non-destructive evaluation of the mass transfer state inside the catalyst layer.

[0063] It should be noted that the principle of hydrogen permeation is analyzed as follows:

[0064] Hydrogen permeation is primarily based on diffusion permeation, driven by a concentration gradient, which causes hydrogen to diffuse to the anode side in the form of dissolved hydrogen. The common formula for calculating the pure diffusion hydrogen permeation flux (Formula I) can be derived from Fick's diffusion law and Henry's law. From this expression, factors influencing hydrogen permeation can be identified, including temperature, water content within the membrane, and the tortuosity of the water channels within the membrane. Among these, the hydrogen partial pressure at the cathode is a directly affecting factor.

[0065]

[0066] in, It is the hydrogen permeation flux; It is the effective diffusion coefficient of hydrogen gas inside the membrane; S H2 δ represents the solubility of hydrogen. m For film thickness; The partial pressure of hydrogen in the cathode catalyst layer is used. Since the partial pressure of gas in the catalyst layer is difficult to quantify, the average pressure of hydrogen in the cathode cavity is used as a substitute for the partial pressure of hydrogen.

[0067] Furthermore, the effective diffusion coefficient of hydrogen gas within the membrane... It is calculated using formula (Formula II).

[0068]

[0069] in, The water content within the membrane; τ refers to the tortuosity of the water channels within the membrane, D H2 is the diffusion coefficient of hydrogen.

[0070] It should be noted that the quantitative conversion of local hydrogen pressure can be fitted in several ways: linear fitting of permeation flux and hydrogen partial pressure difference; nonlinear fitting based on Fick's law or diffusion-dissolution model.

[0071] As an optional implementation method, such as Figure 2 As shown, the hydrogen permeation flux N1 is calculated using the following steps:

[0072] After hydrolysis in a PEM electrolyzer, the gaseous products on the anode side are collected, and the volume fraction of hydrogen (V1) in the anode gas is measured by gas chromatography. The hydrogen permeation flux (N1) is then calculated based on the applied current density (I) and the Faraday constant (F). The calculation formula is shown below:

[0073]

[0074] As an optional implementation, the applied current during the electrolysis process is 0.5–5 A / cm. 2 For example, it could be 0.5A / cm 2 1A / cm 2 1.5A / cm 2 2A / cm 2 2.5A / cm 2 3A / cm 2 3.5A / cm 2 4A / cm 2 4.5A / cm 2 5A / cm 2 wait.

[0075] As an optional implementation, the applied back pressure range in the electrolysis operation is 0.1 to 2 MPa, for example, it can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.8 MPa, 1 MPa, 1.2 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.8 MPa, 2 MPa, etc.

[0076] As an optional implementation, the PEM electrolytic cell includes, from cathode to anode, a titanium mesh, carbon paper, a membrane electrode, a titanium felt, and another titanium mesh arranged sequentially.

[0077] As an optional implementation, in the electrolysis process, during the assembly of the PEM electrolytic cell, the titanium mesh, carbon paper, membrane electrode, titanium felt, and titanium mesh are sequentially installed into the electrolytic cell from cathode to anode. Polytetrafluoroethylene gaskets are used during assembly to compress the cathode carbon paper by 15%. The assembled electrolytic cell is then installed on a multi-channel testing platform, and a preload of 3 N·m is applied to the cathode side.

[0078] As an optional implementation, in the electrolysis process, the membrane electrode includes a cathode catalyst layer and an anode catalyst layer.

[0079] As an optional implementation, in the electrolysis operation, the anode catalyst layer includes iridium, and the iridium loading is 0.1–1 mg / cm³. 2 For example, it could be 0.1 mg / cm³ 2 0.2 mg / cm 2 0.3 mg / cm 2 0.4 mg / cm 2 0.5 mg / cm 2 0.6 mg / cm 2 0.7 mg / cm 2 0.8 mg / cm 2 0.9 mg / cm 2 1mg / cm 2 wait.

[0080] As an optional implementation, in the electrolysis operation, the cathode catalyst layer includes platinum, and the platinum loading is 0.1–1 mg / cm³. 2 For example, it could be 0.1 mg / cm³ 2 0.2 mg / cm 2 0.3 mg / cm 2 0.4 mg / cm 2 0.5 mg / cm 2 0.6 mg / cm 2 0.7 mg / cm 2 0.8 mg / cm 20.9 mg / cm 2 1mg / cm 2 wait.

[0081] As an optional implementation method, such as Figure 3 As shown, the hydrogen permeation flux N2 is calculated using the following steps:

[0082] In another PEM electrolyzer with the same structure, hydrogen gas is introduced into the cathode side and a back pressure is applied at the cathode port. Simultaneously, inert gas is introduced into the anode side, and the anode product channel is continuously purged. A mixed gas sample discharged from the anode side is collected, and the volume fraction V2 of hydrogen gas in the mixed gas sample is determined by gas chromatography. The hydrogen gas flow rate Q2, membrane area S, and gas molar volume V are then analyzed. m The hydrogen permeation flux N2 is obtained by conversion; the calculation formula is shown below:

[0083]

[0084] It should be noted that hydrogen can be introduced at the cathode port of the electrolyzer, or a precision gas cavity or distribution plate can be set at the cathode back plate or the gas diffusion layer inlet to more uniformly simulate the hydrogen diffusion path in the catalyst layer; the hydrogen introduction method can be a constant pressure and constant flow system or a mass flow controller linkage feedback system, as long as a stable pressure difference can be controlled.

[0085] As an optional implementation, the applied back pressure range in the hydrogen supply condition is 0.1–2 MPa, for example, it can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.8 MPa, 1 MPa, 1.2 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.8 MPa, 2 MPa, etc.

[0086] As an optional implementation, in the hydrogen supply condition, the hydrogen is humid hydrogen with a water content of 90-95%, for example, it can be 90%, 91%, 92%, 93%, 94%, 95%, etc.

[0087] As an optional implementation, the inert gas includes any one or a combination of at least two of nitrogen, helium, or argon.

[0088] It should be noted that the present invention selects an inert gas that will not participate in the reaction, provided that it will not react with the membrane material and is easy to separate and analyze from hydrogen.

[0089] As an optional implementation, the inert gas flow rate is 13-20 mL / min, for example, it can be 13 mL / min, 13 mL / min, 14 mL / min, 15 mL / min, 16 mL / min, 17 mL / min, 18 mL / min, 19 mL / min, 20 mL / min, etc.

[0090] As an optional implementation, in the hydrogen-flowing condition, the PEM electrolyzer includes, from cathode to anode, a titanium mesh, carbon paper, a membrane electrode, a titanium felt, and another titanium mesh arranged sequentially.

[0091] As an optional implementation, in the hydrogen-passing condition, during the assembly process, the PEM electrolyzer is assembled from the cathode to the anode in the following order: titanium mesh, carbon paper, membrane electrode, titanium felt, and titanium mesh. During assembly, a polytetrafluoroethylene gasket is used to compress the cathode carbon paper by 15%. The assembled electrolyzer is then placed on a multi-channel testing platform, and a preload of 3 N·m is applied to the cathode side.

[0092] As an optional implementation, in the hydrogen supply condition, the membrane electrode includes a cathode catalyst layer and an anode catalyst layer.

[0093] As an optional implementation, in the hydrogen-flow condition, the anode catalyst layer includes iridium, and the iridium loading is 0.1–1 mg / cm³. 2 For example, it could be 0.1 mg / cm³ 2 0.2 mg / cm 2 0.3 mg / cm 2 0.4 mg / cm 2 0.5 mg / cm 2 0.6 mg / cm 2 0.7 mg / cm 2 0.8 mg / cm 2 0.9 mg / cm 2 1mg / cm 2 wait.

[0094] As an optional implementation, the method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer specifically includes the following steps:

[0095] I. Hydrogen content test on the oxygen side of the anode (electrolysis condition):

[0096] (I-1) In a PEM electrolytic cell, after hydrolysis reaction at a certain current density, the gaseous products on the anode side are collected under a series of different back pressures P1. The gaseous products on the anode side are dried and then passed into a gas chromatograph to measure the volume fraction V1% of hydrogen in the anode gas under a series of different back pressures P1.

[0097] (I-2) Based on the anode hydrogen concentration C1, the anode gas volume flow rate Q1 and the membrane area S, a series of different back pressure P1 hydrogen permeation flux N1 can be obtained by converting the volume fraction V1% of hydrogen contained in the anode gas.

[0098] (I-3) Plot the N1-P1 curve with back pressure P1 as the abscissa and the corresponding hydrogen permeation flux N1 as the ordinate.

[0099] II. Control permeation flux test (hydrogen and nitrogen purging condition):

[0100] (II-1) In another PEM electrolyzer with the same structure, hydrogen gas was introduced into the cathode side and a series of different back pressures P2 were applied to the cathode port. At the same time, inert gas was introduced into the anode side at a certain flow rate and the anode product channel was continuously purged. The mixed gas sample discharged from the anode side was collected. The mixed gas sample discharged from the anode side was dried and then introduced into a gas chromatograph to measure the volume fraction of hydrogen gas V2% in the mixed gas sample under a series of different back pressures P2.

[0101] (II-2) Based on the inert gas flow rate Q2 and the membrane area S, a series of hydrogen permeation fluxes N2 under different back pressures P2 are calculated from the hydrogen volume fraction V2% in the mixed gas sample.

[0102] (II-3) Plot the N2-P2 curve with back pressure P2 as the abscissa and the corresponding hydrogen permeation flux N2 as the ordinate.

[0103] III. Permeability Flux Difference Analysis and Pressure Inversion:

[0104] By using a fitting method, the hydrogen back pressure value P2 corresponding to N1 = N2 is determined. The average hydrogen pressure ΔP is then calculated using the formula ΔP = P2 - P1. Here, ΔP is the equivalent average local hydrogen pressure in the cathode catalyst layer region during the normal electrolysis reaction.

[0105] As an optional implementation, the quantitative detection method for the average hydrogen pressure in the PEM water electrolysis cathode catalyst layer further includes step IV, calculation and correction:

[0106] When necessary, the pressure value can be corrected based on parameters such as membrane thickness, diffusion coefficient, and operating temperature to further improve calculation accuracy. This method does not rely on embedded sensors or damage the membrane electrode structure, and can be flexibly applied in laboratories and engineering systems.

[0107] It should be noted that this invention uses gas chromatography to quantitatively analyze the hydrogen content in the anode product or the mixed gas purged with nitrogen. Other instruments and equipment with trace hydrogen detection capabilities, such as mass spectrometry (MS), micro thermal conductivity detector (μTCD), hydrogen selective sensor array, etc., can also be used as alternatives to chromatographic methods, as long as they can accurately detect trace hydrogen concentration changes.

[0108] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0109] Example 1

[0110] This embodiment provides a method for quantitatively detecting the average hydrogen pressure in the catalyst layer of a PEM water electrolysis cathode. The quantitative detection method includes the following steps:

[0111] I. Hydrogen content test on the oxygen side of the anode (electrolysis condition):

[0112] (I-0) The titanium mesh, carbon paper, membrane electrode, titanium felt, and titanium mesh are sequentially assembled into the electrolytic cell from cathode to anode. During assembly, a PTFE gasket is used to compress the cathode carbon paper by 15%. The assembled electrolytic cell is then placed on a multi-channel testing platform, with a preload of 3 N·m applied to the cathode side. The membrane electrode comprises 0.5 mg... Ir / cm 2 The anode catalyst layer, 0.3 mg Pt / cm 2 The cathode catalyst layer;

[0113] (I-1) In the above PEM electrolytic cell, at 0.5 A / cm 2 After hydrolysis at a current density, the anode-side gaseous products were collected sequentially under a series of different back pressures P1. The anode-side gaseous products were dried and then passed into a gas chromatograph to measure the volume fraction V1% of hydrogen in the anode gas under a series of different back pressures P1. Before the chromatographic test, 0.1%, 1.0%, 2.0%, and 5.0% hydrogen standard gases in argon were used to establish a standard curve.

[0114] (I-2) The volume fraction V1 of hydrogen in the anolyte gas was measured by gas chromatography; and the hydrogen permeation flux N1 under different back pressures P1 was calculated based on the applied current density I and the Faraday constant F. The calculation formulas are as follows:

[0115]

[0116] The details are shown in Table 1 below:

[0117] Table 1

[0118]

[0119] (I-3) Plot the N1-P1 curve with back pressure P1 as the x-axis and the corresponding hydrogen permeation flux N1 as the y-axis (e.g., ...). Figure 4 (As shown).

[0120] II. Control permeation flux test (hydrogen and nitrogen purging condition):

[0121] (II-1) In another PEM electrolyzer with the same structure, moist hydrogen gas was introduced into the cathode side, and a series of different back pressures P2 were applied to the cathode port. The circulating water wetted the membrane electrode on the anode side, and at the same time, inert gas was introduced into the anode side at a flow rate of 15 mL / min, and the anode product channel was continuously purged. The mixed gas sample discharged from the anode side was collected. The mixed gas sample discharged from the anode side was dried and then introduced into a gas chromatograph to determine the volume fraction of hydrogen V2% in the mixed gas sample under a series of different back pressures P2. The sample needs to be stabilized for 1 hour before each test.

[0122] (II-2) The volume fraction V2 of hydrogen in the mixed gas sample was determined by gas chromatography; and based on the inert gas flow rate Q2, membrane area S, and gas molar volume V... m The hydrogen permeation flux N2 under different back pressures P2 was calculated and is shown in Table 2 below:

[0123] Table 2

[0124]

[0125] (II-3) Plot the N2-P2 curve with back pressure P2 on the x-axis and the corresponding hydrogen permeation flux N2 on the y-axis (e.g., Figure 5 (As shown).

[0126] III. Permeability Flux Difference Analysis and Pressure Inversion:

[0127] By using a fitting method, the hydrogen back pressure value P2 corresponding to N1 = N2 is determined. The average hydrogen pressure ΔP is then calculated using the formula ΔP = P2 - P1. Figure 6 (as shown); where ΔP is the equivalent average local hydrogen pressure in the cathode catalyst layer region during normal electrolysis reaction;

[0128] The details are shown in Table 3 below:

[0129] Table 3

[0130]

[0131] Example 2

[0132] This embodiment provides a quantitative detection method for the average hydrogen pressure in the catalyst layer of a PEM electrolysis cathode. The only difference from Embodiment 1 is that the average hydrogen pressure is measured at 3 A / cm². 2 The current density was tested, and the results are shown in Table 4 below:

[0133] Table 4

[0134]

[0135] Example 3

[0136] This embodiment provides a quantitative detection method for the average hydrogen pressure in the catalyst layer of a PEM electrolysis cathode. The only difference from Embodiment 1 is that the average hydrogen pressure is measured at 5 A / cm². 2 The current density was tested, and the results are shown in Table 5 below:

[0137] Table 5

[0138]

[0139] Figure 7 The graphs show the variation of hydrogen permeation flux through the N115 membrane with cathode back pressure at different current densities, as provided in Examples 1-3. Figure 7 As shown, Examples 1 to 3 above have a strength of 0.5 A / cm. 2 3A / cm 2 5A / cm 2 Chromatographic testing of hydrogen in oxygen at current density showed that the hydrogen permeability of the N115 membrane itself could be obtained by testing hydrogen in nitrogen. Compared with the hydrogen in oxygen test, the partial pressure of hydrogen in the cathode catalyst layer under different current densities and back pressures could be obtained.

[0140] Examples 4-6

[0141] Examples 4-6 provide quantitative detection methods for the average hydrogen pressure in the catalytic layer of the PEM water electrolysis cathode. The difference from Example 1 is that the parameters are shown in Table 6 below:

[0142] Table 6

[0143] Current density Cathode back pressure Example 4 <![CDATA[3A / cm 2 ]]> Atmospheric pressure Example 5 <![CDATA[3A / cm 2 ]]> 1MPa Example 6 <![CDATA[3A / cm 2 ]]> 2MPa

[0144] Furthermore, (I-3) plots the N1-I / C curve with I / C as the abscissa and the corresponding hydrogen permeation flux N1 as the ordinate; and plots the ΔP-I / C curve with I / C as the abscissa and the corresponding calculated average hydrogen pressure ΔP as the ordinate.

[0145] Figure 8 The graphs show the variation of hydrogen permeation flux of the N115 membrane with I / C under different back pressures provided in Examples 4-6. Figure 9The graphs show the variation of hydrogen partial pressure in the catalyst layer with I / C under different back pressures provided in Examples 4-6.

[0146] like Figures 8-9 As shown in the results of hydrogen permeation tests under different I / C ratios, the change in I / C ratio has a significant impact on hydrogen transport and catalyst layer pressure. When the I / C ratio increases, the thickness of the ionomer film gradually increases, leading to a decrease in the porosity of the catalyst layer. Due to the reduced porosity, gas expulsion is hindered, resulting in increased hydrogen accumulation within the catalyst layer and consequently, increased hydrogen permeation. This is because the hydrogen transport path within the catalyst layer becomes longer, and the gas expulsion channel narrows, making it easier for hydrogen to permeate through the membrane to the anode side. Conversely, when the I / C ratio is too small, the ionomer film becomes thinner, and the gas production pressure per unit volume increases. In this case, the excessively high supersaturated gas concentration within the ionomer phase also leads to increased hydrogen permeation. This is because an excessively high gas concentration creates a high pressure gradient within the ionomer phase, making it easier for hydrogen to permeate through the membrane to the anode side.

[0147] Of particular note is that when the I / C ratio is 1.5, even when the cathode cavity is under normal pressure, at 3 A / cm 2 At high current densities, the average pressure in the catalyst layer reached 27 MPa. This result indicates that at high I / C ratios, hydrogen pressure accumulation within the catalyst layer is significant, which may adversely affect the performance and safety of the electrolyzer.

[0148] Examples 7-9

[0149] Examples 7-9 provide a quantitative detection method for the average hydrogen pressure in the PEM electrolysis cathode catalyst layer. The difference from Example 1 is that the parameters are as shown in Table 7 below:

[0150] Table 7

[0151] Current density Cathode back pressure Example 4 <![CDATA[3A / cm 2 ]]> Atmospheric pressure Example 5 <![CDATA[3A / cm 2 ]]> 1MPa Example 6 <![CDATA[3A / cm 2 ]]> 2MPa

[0152] Furthermore, (I-3) plots the N1-cathode loading curve with the cathode loading as the abscissa and the corresponding hydrogen permeation flux N1 as the ordinate; and plots the ΔP-cathode loading curve with the cathode loading as the abscissa and the corresponding calculated average hydrogen pressure ΔP as the ordinate.

[0153] Figure 10 The graphs show the variation of hydrogen permeation flux of the N115 membrane with cathode loading under different back pressures provided in Examples 7-9. Figure 11 The graphs show the variation of hydrogen partial pressure in the catalyst layer with cathode loading under different back pressures provided in Examples 7-9.

[0154] like Figures 10-11As shown, after hydrogen is generated, it diffuses from the interface between the catalyst layer and the membrane electrode assembly (MEA) towards the cathode port. The thickness of the catalyst layer has a significant impact on the hydrogen diffusion path and removal efficiency. With increasing cathode loading, the catalyst layer thickness gradually increases, which increases the hydrogen diffusion path. A longer diffusion path can lead to impeded hydrogen removal, especially under high loading conditions, where hydrogen permeation becomes more severe. This is because a thicker catalyst layer increases the transport resistance of hydrogen from the generation point to the cathode port, making it easier for hydrogen to permeate through the membrane to the anode side, thus increasing the amount of hydrogen permeate.

[0155] However, an excessively thin catalyst layer is also detrimental to mitigating hydrogen permeation. For example, when the cathode loading is 0.1 mg... Pt / cm 2 At this point, the catalyst layer thickness is only 1.9 μm. In this situation, the catalyst layer is too thin, and the unit production pressure increases significantly. This is because the thin catalyst layer cannot effectively contain and disperse the generated hydrogen, leading to a rapid increase in local pressure and thus exacerbating hydrogen permeation. In this case, although the catalyst layer is thin, the excessive unit production pressure allows hydrogen to more easily permeate through the membrane to the anode side, resulting in increased hydrogen permeation.

[0156] In summary, the detection method of this invention compares the difference in hydrogen content in oxygen and nitrogen in chromatographic tests. Given the known gas diffusion laws and catalyst layer channel characteristics, and considering that the hydrogen permeation principle is the same in both methods, with only the hydrogen transport path differing on the cathode side, the difference in test results can be correlated with the difference in hydrogen partial pressure on the cathode catalyst layer surface. This allows for the rapid calculation of the hydrogen partial pressure on the cathode catalyst layer surface. This method possesses advantages such as a clear principle, strong experimental feasibility, no need for embedded sensors, applicability to practical systems, and high conversion accuracy.

[0157] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for quantitatively detecting the average hydrogen pressure in the catalytic layer of a PEM electrolysis cathode, characterized in that, The quantitative detection method includes: Hydrolysis is carried out in a PEM electrolyzer. Calculate the hydrogen permeation flux N1 under electrolysis conditions, with the corresponding back pressure P1. In another PEM electrolyzer with the same structure, hydrogen gas was introduced into the cathode side and a back pressure was applied at the cathode port. At the same time, inert gas was introduced into the anode side and the anode product channel was continuously purged. The hydrogen permeation flux N2 under the hydrogen supply condition was calculated. The back pressure under the hydrogen supply condition was gradually adjusted and the permeation flux test under the hydrogen supply condition was repeated to obtain the hydrogen permeation flux under different back pressures. The N2-P2 curve was plotted. Determine the hydrogen back pressure value P2 corresponding to N1 = N2, and calculate the average hydrogen pressure ΔP using the formula ΔP = P2 - P1.

2. The method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer according to claim 1, characterized in that, The hydrogen permeation flux N1 is calculated using the following steps: After hydrolysis in a PEM electrolyzer, the gaseous products on the anode side are collected, and the volume fraction of hydrogen (V1) in the anode gas is measured by gas chromatography. The hydrogen permeation flux (N1) is then calculated based on the applied current density (I) and the Faraday constant (F). The calculation formula is shown below:

3. The method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer according to claim 2, characterized in that, During the electrolysis process, the applied current is 0.5–5 A / cm. 2 ; And / or, in the electrolysis conditions, the applied back pressure ranges from 0.1 to 2 MPa.

4. The method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer according to claim 1, characterized in that, In the electrolysis process, the PEM electrolytic cell includes, from cathode to anode, a titanium mesh, carbon paper, a membrane electrode, a titanium felt, and another titanium mesh arranged sequentially.

5. The method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer according to claim 4, characterized in that, The membrane electrode includes a cathode catalytic layer and an anode catalytic layer; The anode catalyst layer includes iridium, and the iridium loading is 0.1–1 mg / cm³. 2 ; The cathode catalyst layer includes platinum, and the platinum loading is 0.1–1 mg / cm³. 2 .

6. The method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer according to claim 1, characterized in that, The hydrogen permeation flux N2 is calculated using the following steps: In another PEM electrolyzer with the same structure, hydrogen gas is introduced into the cathode side and a back pressure is applied at the cathode port. Simultaneously, inert gas is introduced into the anode side, and the anode product channel is continuously purged. A mixed gas sample discharged from the anode side is collected, and the volume fraction V2 of hydrogen gas in the mixed gas sample is determined by gas chromatography. The hydrogen gas flow rate Q2, membrane area S, and gas molar volume V are then analyzed. m The hydrogen permeation flux N2 is obtained by conversion; the calculation formula is shown below:

7. The method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer according to claim 1 or 6, characterized in that, During the hydrogen supply operation, the applied back pressure ranges from 0.1 to 2 MPa.

8. The method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer according to claim 1 or 6, characterized in that, In the hydrogen supply condition, the hydrogen gas is moist hydrogen gas with a water content of 90-95%. Preferably, the inert gas includes any one or a combination of at least two of nitrogen, helium, or argon; Preferably, the inert gas flow rate is 13-20 mL / min.

9. The method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer according to claim 1, characterized in that, In the hydrogen-passing operation, the PEM electrolyzer consists of a titanium mesh, carbon paper, membrane electrode, titanium felt, and titanium mesh arranged sequentially from cathode to anode.

10. The method for quantitatively detecting the average hydrogen pressure in the PEM electrolysis cathode catalyst layer according to claim 9, characterized in that, In the hydrogen supply condition, the membrane electrode includes a cathode catalytic layer and an anode catalytic layer; The anode catalyst layer includes iridium, and the iridium loading is 0.1–1 mg / cm³. 2 .

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