A method for detecting the coating of bipolar plates in a proton exchange membrane electrolyzer.

Abstract

This invention discloses a method for detecting the bipolar plate coating of a proton exchange membrane electrolyzer, relating to the field of proton exchange membrane electrolyzer technology. The detection method includes the following steps: assembling titanium sheets with a bipolar plate coating in an electrolyzer to obtain an electrolyzer containing titanium sheets; first, cyclically activating the electrolyzer containing titanium sheets at different current densities, and then operating it at a constant current density to test the stability of the bipolar plate coating. This invention introduces titanium sheets coated with a bipolar plate into the electrolyzer and performs operating condition tests to realistically reproduce the corrosive environment of the electrolyzer; the use of thin titanium sheets for testing is very convenient, and further allows for the evaluation of the contact resistance between the coating and the gas diffusion layer of the electrolyzer, as well as morphological characterization such as scanning electron microscopy (SEM), thereby more accurately and intuitively evaluating the lifetime and surface conductivity of the bipolar plate coating, and assessing the degree of corrosion on the coating surface.

Description

Technical Field

[0001] This invention relates to the field of proton exchange membrane electrolyzer technology, and more specifically, to a method for detecting the coating of bipolar plates in a proton exchange membrane electrolyzer. Background Technology

[0002] Proton exchange membrane (PEM) water electrolysis for hydrogen production is considered an effective solution to the challenges of renewable energy conversion and storage; however, its commercial application is limited by the high cost of the electrolyzer. The key issue is that the high oxidation potential during electrolyzer operation necessitates the use of high-purity titanium as the anode bipolar plate material. However, the high oxidation potential experienced by the bipolar plate during operation still leads to passivation and the formation of a poorly conductive TiO2 layer. This phenomenon increases the contact resistance at the interface between the bipolar plate and the diffusion layer, reducing the efficiency of the electrolyzer.

[0003] To prevent passivation and corrosion of bipolar plates, a highly conductive and electrochemically resistant coating is typically applied to their surface. However, most current evaluation systems for bipolar plate coatings are detached from actual operating conditions, leading to discrepancies between the evaluations and real-world performance. This hinders the development of bipolar plate coatings, making it difficult to identify corrosion-resistant coatings that perform well under real-world conditions, and may even cause some excellent coatings capable of withstanding PEM water electrolysis to be overlooked.

[0004] In existing technologies, a non-in-situ three-electrode method is used, with glassy carbon as the counter electrode (CE), saturated calomel as the reference electrode (RE), and the sample as the working electrode (WE). This study tested the corrosion current density of the coating by simulating the corrosion environment inside a PEM electrolyzer, and maintained it at a constant potential of 2V for 100 hours, followed by testing the surface conductivity of the coating. However, the actual PEM electrolyzer has a large influent flow rate, and the ultrapure water has extremely low conductivity (18.25 MΩ·cm), making the pH at the bipolar plate interface close to neutral.

[0005] Another method using the in-situ three-electrode approach revealed that the electrochemical oxidation potential of the bipolar plates (approximately 1 V @ 2 A / cm) 2 This is much lower than the voltage of the entire electrolytic cell (approximately 1.8V@2A / cm). 2 However, the actual electrochemical oxidation potential of bipolar plates is related to the conductivity of the water sample and operating conditions (such as current density). The complexity of operating conditions and the difficulty in accurately detecting the corrosive environment at the bipolar plate make the non-in-situ three-electrode coating testing method far removed from actual operating conditions, making it difficult to accurately assess the lifetime and surface conductivity of the bipolar plate coating.

[0006] Furthermore, existing technologies have reported on directly sputtering TiN coatings onto the bipolar plates of actual electrolytic cells for operational testing. However, since the area of ​​the bipolar plate differs from the actual electrochemical reaction area, and the oxidation levels at the channel ridges of the bipolar plate are not uniform, it is difficult to directly assess the conductivity of the coating by measuring the contact resistance of the bipolar plate coating using contact resistance testing equipment. Simultaneously, due to the large size of the bipolar plate, it is difficult to characterize the morphology of the post-reaction coating and assess the degree of corrosion on the coating surface using equipment such as scanning electron microscopy.

[0007] Therefore, there is an urgent need to develop an evaluation method for bipolar plate coatings and optimize the selection of bipolar plate coating materials in order to more accurately evaluate the lifespan and surface conductivity of bipolar plate coatings, as well as the degree of corrosion on the coating surface.

[0008] In view of this, the present invention is hereby proposed. Summary of the Invention

[0009] The purpose of this invention is to provide a method for detecting bipolar plate coatings in proton exchange membrane electrolyzers. This detection method is suitable for screening anti-corrosion coatings that meet the requirements of actual working conditions. It satisfies the testing requirements under actual working conditions and facilitates post-characterization of the coating after long-term testing. It can accurately screen bipolar plate coating materials suitable for PEM water electrolysis conditions, and more accurately assess the lifespan and surface conductivity of the bipolar plate coating, as well as the degree of corrosion on the coating surface.

[0010] In a first aspect, the present invention provides a method for detecting the coating of a bipolar plate in a proton exchange membrane electrolyzer, the method comprising the following steps:

[0011] Titanium sheets with bipolar plate coatings are assembled in an electrolytic cell to obtain an electrolytic cell containing titanium sheets.

[0012] The electrolytic cell containing titanium sheets was first activated by cycling at different current densities, and then operated at a constant current density to test the stability of the bipolar plate coating.

[0013] Furthermore, the electrolytic cell comprises, in sequence, a cathode bipolar plate, a cathode diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, an anode gas diffusion layer, a titanium sheet with a bipolar plate coating, and an anode bipolar plate.

[0014] Furthermore, one side of the titanium sheet has a bipolar plate coating, and the bipolar plate coating is in contact with the anode gas diffusion layer.

[0015] Furthermore, the torque for assembling the electrolytic cell is 3 N·m or more, preferably 4 N·m.

[0016] Furthermore, the thickness-direction compressibility of the anode gas diffusion layer is <20%.

[0017] Furthermore, the thickness of the titanium sheet is 50–150 μm, preferably 100 μm.

[0018] Furthermore, the thickness of the bipolar plate coating is 0.01–1 μm.

[0019] Furthermore, the bipolar plate coating includes a metal coating and / or a metal nitride coating.

[0020] Furthermore, the metal in the metal coating includes any one or a combination of at least two of Ti, Zr, Cr, or Pt.

[0021] Furthermore, the metal nitride in the metal nitride coating includes any one or a combination of at least two of TiN, CrN, or ZrN.

[0022] Furthermore, the cyclic activation and operation of the electrolyzer containing titanium sheets are carried out on a multi-channel proton exchange membrane electrolyzer test platform.

[0023] Furthermore, before the cyclic activation, circulating water needs to be introduced and the temperature increased.

[0024] Preferably, the flow rate of the circulating water is 100-300 mL / min, and more preferably 200 mL / min.

[0025] Preferably, the temperature is raised to 75-85°C, more preferably 80°C.

[0026] Furthermore, the cyclic activation at different current densities specifically involves:

[0027] 1–5 A / cm 2 Select at least three current densities within the current density range, and run each at the selected current density for at least 20 minutes.

[0028] Furthermore, the operation under the constant current density specifically refers to:

[0029] 1–5 A / cm 2 Select a constant current density within the current density range and operate at the constant current density for at least 100 hours.

[0030] Furthermore, the detection method further includes the following steps:

[0031] The morphology of the bipolar plate coating on the surface of a titanium sheet after operation at a constant current density was characterized using field emission scanning electron microscopy.

[0032] Furthermore, the detection method further includes the following steps:

[0033] The anode gas diffusion layer of the electrolytic cell is placed between two electrodes, and pressure is applied to both sides of the electrodes. The resistance value R1 under different pressure conditions is recorded.

[0034] The anode gas diffusion layer of the electrolytic cell and the titanium sheet with bipolar plate coating are combined and placed between two electrodes. Pressure is applied to both sides of the electrodes, and the resistance value R2 under different pressure conditions is recorded; wherein the bipolar plate coating is in contact with the anode gas diffusion layer.

[0035] The contact resistance R between the anode gas diffusion layer and the bipolar plate coating of the electrolytic cell is calculated using the following formula I. contact ;

[0036]

[0037] Furthermore, the electrode is a gold-plated copper electrode.

[0038] Furthermore, the pressure range of the applied pressure is 0.1 to 2 MPa.

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

[0040] (1) The detection method of the present invention introduces a titanium sheet coated with a bipolar plate into the electrolytic cell and performs working condition tests to truly restore the corrosive environment of the electrolytic cell.

[0041] (2) The detection method described in this invention is very convenient to use a titanium sheet coated with a bipolar plate for testing. At the same time, it can evaluate the contact resistance between the coating and the gas diffusion layer of the electrolytic cell, and perform morphological characterization such as scanning electron microscopy (SEM). Attached Figure Description

[0042] 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.

[0043] Figure 1 This is a schematic diagram of the assembly of the electrolytic cell described in this invention.

[0044] Among them, 1 is the cathode bipolar plate, 2 is the cathode diffusion layer, 3 is the cathode catalyst layer, 4 is the proton exchange membrane, 5 is the anode catalyst layer, 6 is the anode gas diffusion layer, 7 is the titanium sheet with bipolar plate coating, and 8 is the anode bipolar plate.

[0045] Figure 2A This is a schematic diagram of the contact resistance test of the anode gas diffusion layer described in this invention.

[0046] Figure 2B This is a schematic diagram of the contact resistance test of the combination of the anode gas diffusion layer and the titanium sheet with bipolar plate coating in the electrolytic cell of the present invention.

[0047] Among them, 101 is the power supply, 102 is the current collector, 103 is the gold-plated copper electrode, 6 is the anode gas diffusion layer, 7 is the titanium sheet with bipolar plate coating, and 71 is the bipolar plate coating.

[0048] Figure 3 Polarization curves of Pt and TiN coatings provided in Examples 1 and 2 applied to an electrolytic cell.

[0049] Figure 4 The polarization curve decoupling diagrams of the Pt and TiN coatings provided in Examples 1 and 2 applied to the electrolytic cell.

[0050] Figure 5 The decay rate diagram of the Pt and TiN coatings provided in Examples 1 and 2 applied to the electrolytic cell.

[0051] Figure 6 Contact resistance test results after stability testing of Pt and TiN coatings provided in Example 1 and Example 2 in an electrolytic cell.

[0052] Figure 7A The image shows a scanning electron microscope (SEM) image of the TiN coating surface before the reaction provided in Example 2.

[0053] Figure 7B The image is a scanning electron microscope (SEM) image of the TiN coating surface after a 400-hour working condition test provided in Example 2.

[0054] Figure 8A This is a surface view of the TiN coating that has not been tested.

[0055] Figure 8B The image shows the surface of the TiN coating after a 400-hour working condition test, as provided in Embodiment 2 of the present invention.

[0056] Figure 8C The image shows the surface of the TiN coating after testing using the three-electrode method provided in Comparative Example 1 of this invention.

[0057] Figure 9 This is a comparison diagram of the contact resistance after testing using the method provided in Embodiment 2 of the present invention and the three-electrode method provided in Comparative Example 1.

[0058] Figure 10A The diagram shows the working conditions of the bipolar plate coating before and after the reaction, provided for Comparative Example 2.

[0059] Figure 10B The diagram provided for Comparative Example 2 shows the working condition of directly testing contact resistance using bipolar plates. Detailed Implementation

[0060] 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.

[0061] 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.

[0062] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0063] In a first aspect, the present invention provides a method for detecting the coating of a bipolar plate in a proton exchange membrane electrolyzer, the method comprising the following steps:

[0064] Titanium sheets with bipolar plate coatings are assembled in an electrolytic cell to obtain an electrolytic cell containing titanium sheets.

[0065] The electrolytic cell containing titanium sheets was first activated by cycling at different current densities, and then operated at a constant current density to test the stability of the bipolar plate coating.

[0066] In the detection method described in this invention, titanium sheets coated with bipolar plate coatings are introduced into the electrolytic cell and subjected to operating condition tests to realistically reproduce the corrosive environment of the electrolytic cell. Introducing titanium sheets coated with bipolar plate coatings for testing is very convenient and is a suitable method for screening anti-corrosion coatings that meets the actual operating conditions. It satisfies the testing requirements under actual operating conditions and facilitates the post-characterization of the coating after long-term testing. It can accurately screen bipolar plate coating materials suitable for PEM water electrolysis conditions and more accurately evaluate the lifespan and surface conductivity of the bipolar plate coating, as well as assess the degree of corrosion on the coating surface.

[0067] As an optional embodiment of the present invention, such as Figure 1 As shown, the electrolytic cell includes, in sequence, a cathode bipolar plate 1, a cathode diffusion layer 2, a cathode catalyst layer 3, a proton exchange membrane 4, an anode catalyst layer 5, an anode gas diffusion layer 6, a titanium sheet 7 with a bipolar plate coating, and an anode bipolar plate 8.

[0068] In this invention, before conducting stability testing of the bipolar plate coating, the cathode bipolar plate 1, cathode diffusion layer 2, cathode catalyst layer 3, proton exchange membrane 4, anode catalyst layer 5, anode gas diffusion layer 6, titanium sheet 7 with bipolar plate coating, and anode bipolar plate 8 are assembled in sequence according to the positioning hole position (that is, the titanium sheet 7 with bipolar plate coating is assembled between the anode gas diffusion layer 6 and the anode bipolar plate 8). During this assembly process, fastening bolts, nuts, and torque wrenches can be used to clamp the battery.

[0069] As an optional embodiment of the present invention, one side of the titanium sheet 7 with the bipolar plate coating has the bipolar plate coating, and the bipolar plate coating is in contact with the anode gas diffusion layer 6.

[0070] As an optional embodiment of the present invention, the torque for assembling the electrolytic cell is 3 N.m or more, for example, it can be 3 N.m, 3.2 N.m, 3.4 N.m, 3.6 N.m, 3.8 N.m, 4 N.m, 4.2 N.m, 4.4 N.m, 4.5 N.m, etc.

[0071] In a preferred embodiment of the present invention, the torque for assembling the electrolytic cell is 4 N·m.

[0072] It should be noted that the present invention uses fastening bolts, nuts and torque wrenches to clamp the battery. The battery assembly force should meet the following requirements: the torque should be above 3 N.m, preferably 4 N.m, to ensure that the contact resistance between the gas diffusion layer and the bipolar plate is minimized.

[0073] As an optional embodiment of the present invention, the thickness direction compressibility of the anode gas diffusion layer is <20%, for example, it can be 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, etc.

[0074] As an optional embodiment of the present invention, the thickness of the titanium sheet is 50-150 μm, for example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, etc.

[0075] In a preferred embodiment of the present invention, the thickness of the titanium sheet is 100 μm.

[0076] As an optional embodiment of the present invention, the thickness of the bipolar plate coating is 0.01 to 1 μm, for example, it can be 0.001 μm, 0.005 μm, 0.1 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, etc.

[0077] As an optional embodiment of the present invention, the bipolar plate coating includes a metal coating and / or a metal nitride coating.

[0078] As an optional embodiment of the present invention, the metal in the metal coating includes any one or a combination of at least two of Ti, Zr, Cr or Pt.

[0079] As an optional embodiment of the present invention, the metal nitride in the metal nitride coating includes any one or a combination of at least two of TiN, CrN, or ZrN.

[0080] As an optional embodiment of the present invention, the cyclic activation and operation of the electrolyzer containing titanium sheets is carried out on a multi-channel proton exchange membrane electrolyzer test platform.

[0081] As an optional embodiment of the present invention, circulating water needs to be introduced and the temperature increased before the cyclic activation.

[0082] More specifically, the steps for testing the stability of the bipolar plate coating are as follows: the electrolytic cell containing titanium sheets is installed on a multi-channel proton exchange membrane electrolytic cell test platform, circulating water is introduced and the temperature is increased, and then the cell is first activated by cycling at different current densities, and then run at a constant current density to test the stability of the bipolar plate coating.

[0083] As an optional embodiment of the present invention, the flow rate of the circulating water is 100-300 mL / min, for example, it can be 100 mL / min, 120 mL / min, 140 mL / min, 160 mL / min, 180 mL / min, 220 mL / min, 240 mL / min, 260 mL / min, 280 mL / min, 300 mL / min, etc.

[0084] In a preferred embodiment of the present invention, the flow rate of the circulating water is 200 mL / min.

[0085] As an optional embodiment of the present invention, the temperature is raised to 75-85, for example, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, etc.

[0086] In a preferred embodiment of the present invention, the temperature is raised to 80°C.

[0087] As an optional embodiment of the present invention, the cyclic activation under different current densities specifically includes the following steps:

[0088] 1–5 A / cm 2 Select at least three current densities within the current density range, and run each at the selected current density for at least 20 minutes.

[0089] As an optional embodiment of the present invention, the current density range is 1–5 A / cm². 2 For example, it could be 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 At least three current densities should be selected within the range.

[0090] As an optional embodiment of the present invention, each of the selected current densities is operated for at least 20 minutes, for example, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes, 32 minutes, 34 minutes, 35 minutes, 40 minutes, etc.

[0091] As a preferred embodiment of the present invention, the cyclic activation under different current densities specifically includes the following steps:

[0092] At a current of 2A / cm 2 3A / cm 2 4A / cm 2 Each of the following steps runs for 30 minutes, and the cycle is repeated three times.

[0093] As an optional embodiment of the present invention, the operation under constant current density specifically includes the following steps:

[0094] 1–5 A / cm 2 Select a constant current density within the current density range and operate at the constant current density for at least 100 hours.

[0095] As an optional embodiment of the present invention, the current density range is 1–5 A / cm². 2 For example, it could be 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 Choose a constant current density within the range.

[0096] As an optional embodiment of the present invention, the running time is at least 100 hours, for example, it can be 100 hours, 150 hours, 200 hours, 250 hours, 300 hours, 350 hours, 400 hours, 450 hours, 500 hours, 550 hours, 600 hours, etc.

[0097] As a preferred embodiment of the present invention, the operation under constant current density specifically includes the following steps:

[0098] After the cycle activation is completed, the electrolytic cell containing titanium sheets is then heated to 2A / cm. 2 It operates for 400 hours within the current density range.

[0099] In this invention, the stability testing of the bipolar plate coating includes, but is not limited to: plotting polarization curves, decoupling polarization curves, and calculating voltage decay rate.

[0100] The plotting of the polarization curve refers to the curve representing the relationship between electrode potential and polarization current or polarization current density. That is, the corresponding voltage is recorded at different current densities, and the polarization curve is plotted with current density as the abscissa and voltage as the ordinate.

[0101] Wherein, the decoupling of the polarization curve refers to: ηOER refers to the OER overpotential of the electrolyzer performance; ηohm refers to the ohmic overpotential of the electrolyzer performance; and ηmt refers to the mass transfer overpotential of the electrolyzer performance. Through the electrolyzer at 0.025 A / cm 2 -0.1A / cm 2 The polarization curve within the current density range can be used to calculate the Tafel curve of the electrolytic cell device, thereby calculating the OER overpotential under the entire current density; the ohmic overpotential (ηohm=I×R) of the electrolytic cell device can be calculated by testing the high-frequency resistance of the electrolytic cell; the mass transfer overpotential ηmt can be obtained by subtracting the OER overpotential and the ohmic overpotential from the total overpotential of the electrolytic cell.

[0102] The calculation of the voltage decay rate refers to: running the device for a long time under a constant current density range, statistically analyzing the voltage values ​​at different times, plotting a curve, and calculating the decay rate of the device.

[0103] As an optional embodiment of the present invention, the detection method further includes the following steps:

[0104] The morphology of the bipolar plate coating on the surface of a titanium sheet after operation at a constant current density was characterized using field emission scanning electron microscopy.

[0105] In this invention, field emission scanning electron microscopy (SEM) is further used to characterize the surface morphology of the coating after the operating condition test (i.e., the bipolar plate coating on the titanium sheet surface after long-term operation under constant current density). After long-term operation, the presence of corrosion on the surface of the bipolar plate coating is observed to more intuitively and accurately detect whether the bipolar plate coating can withstand the corrosive environment at the bipolar plate.

[0106] As an optional embodiment of the present invention, the detection method further includes the following steps (such as...). Figure 2A and Figure 2B As shown):

[0107] The anode gas diffusion layer of the electrolytic cell is placed between two electrodes, and pressure is applied to both sides of the electrodes. The resistance value R1 under different pressure conditions is recorded.

[0108] The anode gas diffusion layer of the electrolytic cell and the titanium sheet with bipolar plate coating are combined and placed between two electrodes. Pressure is applied to both sides of the electrodes, and the resistance value R2 under different pressure conditions is recorded; wherein, the bipolar plate coating 71 is in contact with the anode gas diffusion layer 6.

[0109] The contact resistance R between the anode gas diffusion layer and the bipolar plate coating of the electrolytic cell is calculated using the following formula I. contact ;

[0110]

[0111] In this invention, the above steps are further used to perform contact resistance testing on the coating after the working condition test (i.e., the bipolar plate coating on the surface of the titanium sheet after long-term operation under constant current density), so as to more intuitively and accurately detect whether the bipolar plate coating still maintains good conductivity after long-term operation.

[0112] As an optional embodiment of the present invention, the electrode is a gold-plated copper electrode 103.

[0113] As an optional embodiment of the present invention, the pressure range of the applied pressure is 0.1 to 2 MPa, for example, it can be 0.1 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1 MPa, 1.2 MPa, 1.4 MPa, 1.6 MPa, 1.8 MPa, 2 MPa, etc.

[0114] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0115] Example 1

[0116] This embodiment provides a method for detecting the coating of a bipolar plate in a proton exchange membrane electrolyzer, the method comprising the following steps:

[0117] S1. Test method for bipolar plate coating under operating conditions:

[0118] According to the positioning hole positions, the cathode bipolar plate, cathode diffusion layer, cathode catalyst layer, proton exchange membrane, anode catalyst layer, anode gas diffusion layer, titanium sheet with bipolar plate coating (titanium sheet thickness is 100μm, the bipolar plate coating is Pt coating, thickness is 0.3μm), and anode bipolar plate are assembled in sequence (the titanium sheet of the anode bipolar plate is cut into 20mm*20mm pieces, and the double corners are cut off to allow the anode circulating water to flow in). The battery is clamped using fastening bolts, nuts, and torque wrenches. The battery assembly force should meet the following requirements: torque of 4N.m, ensuring minimum contact resistance between the gas diffusion layer and the bipolar plate, and thickness direction compression ratio of the cathode diffusion layer <20%.

[0119] S2. Stability test of bipolar plate coating in electrolytic cell:

[0120] The electrolyzer was installed on the multi-channel proton exchange membrane electrolyzer test platform, and circulating water was introduced (flow rate 200 ml / min). After the temperature rose to 80°C, the current was increased to 2 A / cm². 2 3A / cm 2 4A / cm 2 Maintain the temperature for 30 minutes, repeating the cycle three times; after the activation process, maintain the electrolytic cell at 2 A / cm. 2 The system was operated for 400 hours at a given current density; polarization curves, polarization decoupling diagrams, and decay rate diagrams in the electrolytic cell were plotted.

[0121] S3. Contact resistance test between bipolar plate coating and gas diffusion layer:

[0122] The anode gas diffusion layer of the electrolytic cell was placed between two electrodes, and pressure (0.1-2.0 MPa) was applied to both sides of the electrodes. The resistance value R1 under different pressure conditions was recorded.

[0123] The anode gas diffusion layer of the electrolytic cell and the titanium sheet with bipolar plate coating are combined and placed between two electrodes. Pressure (0.1-2.0 MPa) is applied to both sides of the electrodes, and the resistance value R2 under different pressure conditions is recorded. The bipolar plate coating is in contact with the anode gas diffusion layer. The bipolar plate coating is the bipolar plate coating on the surface of the titanium sheet after running at a constant current density for 400 hours.

[0124] The contact resistance R between the anode gas diffusion layer and the bipolar plate coating of the electrolytic cell is calculated using the following formula I. contact ;

[0125]

[0126] S4. Observation using an emission scanning electron microscope:

[0127] The morphology of the bipolar plate coating on the surface of a titanium sheet after 400 hours of operation at a constant current density was characterized using field emission scanning electron microscopy.

[0128] Example 2

[0129] This embodiment provides a method for detecting the coating of a bipolar plate in a proton exchange membrane electrolyzer, the method comprising the following steps:

[0130] S1. Test method for bipolar plate coating under operating conditions:

[0131] According to the positioning hole positions, the cathode bipolar plate, cathode diffusion layer, cathode catalyst layer, proton exchange membrane, anode catalyst layer, anode gas diffusion layer, titanium sheet with bipolar plate coating (titanium sheet thickness is 100μm, the bipolar plate coating is TiN coating, thickness is 0.3μm), and anode bipolar plate are assembled in sequence (the titanium sheet of the anode bipolar plate is cut into 20mm*20mm pieces, and the corners are cut off to allow the anode circulating water to flow in). The battery is clamped using fastening bolts, nuts, and torque wrenches. The battery assembly force should meet the following requirements: torque of 4N.m, ensuring minimum contact resistance between the gas diffusion layer and the bipolar plate, and thickness direction compression ratio of the cathode diffusion layer <20%.

[0132] S2. Stability test of bipolar plate coating in electrolytic cell:

[0133] The electrolyzer was installed on the multi-channel proton exchange membrane electrolyzer test platform, and circulating water was introduced (flow rate 200 mL / min). After the temperature rose to 80°C, the current was increased to 2 A / cm². 2 3A / cm 2 4A / cm 2 Maintain the temperature for 30 minutes, repeating the cycle three times; after the activation process, maintain the electrolytic cell at 2 A / cm. 2 The system was operated for 400 hours at a given current density; polarization curves, polarization decoupling diagrams, and decay rate diagrams in the electrolytic cell were plotted.

[0134] S3. Contact resistance test between bipolar plate coating and gas diffusion layer:

[0135] The anode gas diffusion layer of the electrolytic cell was placed between two electrodes, and pressure (0.1-2.0 MPa) was applied to both sides of the electrodes. The resistance value R1 under different pressure conditions was recorded.

[0136] The anode gas diffusion layer of the electrolytic cell and the titanium sheet with bipolar plate coating are combined and placed between two electrodes. Pressure (0.1-2.0 MPa) is applied to both sides of the electrodes, and the resistance value R2 under different pressure conditions is recorded. The bipolar plate coating is in contact with the anode gas diffusion layer. The bipolar plate coating is the bipolar plate coating on the surface of the titanium sheet after running at a constant current density for 400 hours.

[0137] The contact resistance R between the anode gas diffusion layer and the bipolar plate coating of the electrolytic cell is calculated using the following formula I. contact ;

[0138]

[0139] S4. Observation using an emission scanning electron microscope:

[0140] The morphology of the bipolar plate coating on the surface of a titanium sheet after 400 hours of operation at a constant current density was characterized using field emission scanning electron microscopy.

[0141] The test results for the steps in Examples 1 and 2 above are shown below:

[0142] Figure 3 Polarization curves of the Pt and TiN coatings provided in Examples 1 and 2 applied in an electrolytic cell. Figure 3 As shown, sputtering Pt and TiN coatings on the surface of titanium sheets improves the overall performance of the electrolytic cell.

[0143] Figure 4 The Pt and TiN coatings provided in Examples 1 and 2 are shown in the polarization decoupling diagrams when applied to an electrolytic cell. Figure 4 As shown, overpotential decomposition of the polarization curves reveals that the improved electrolytic cell performance is mainly reflected in the reduction of ohmic overpotential. This indicates that the application of Pt and TiN coatings reduces the contact resistance at the interface between the titanium bipolar plate and the diffusion layer, thereby improving the electrolytic cell's performance and electrolysis efficiency. Using highly conductive Pt and TiN coatings as coatings for the titanium bipolar plate further enhances the overall stability of the device.

[0144] Figure 5 The decay rate diagrams of the Pt and TiN coatings provided in Examples 1 and 2 applied in an electrolytic cell are shown. Figure 5 As shown, the decay rate of the uncoated bipolar plate is 65.2 μV / h, while the decay rates of the devices after coating with corrosion-resistant and highly conductive TiN and Pt are 32.6 μV / h and 37.8 μV / h, respectively, and the stability is improved compared with the uncoated titanium bipolar plate.

[0145] Figure 6Contact resistance test results after stability testing of the Pt and TiN coatings provided in Examples 1 and 2 in an electrolytic cell. Figure 6 As shown, contact resistance tests were performed on the Pt and TiN coatings after 400 hours of operating condition testing. Both the TiN and Pt coatings maintained good conductivity after 400 hours of operating condition stability testing.

[0146] Figure 7A The image shows a scanning electron microscope (SEM) image of the TiN coating surface before the reaction provided in Example 2. Figure 7B This is a scanning electron microscope (SEM) image of the TiN coating surface after a 400-hour operating condition test, as provided in Example 2. Figure 7A and Figure 7B The comparison shows that after 400 hours of operation, there was no obvious corrosion on the TiN coating surface, indicating that the TiN coating can withstand the corrosive environment at the bipolar plate.

[0147] In summary, to prevent the bipolar plates of the electrolytic cell from oxidizing and corroding during long-term operation, a corrosion-resistant and highly conductive coating is needed to improve the performance and electrolysis efficiency of the electrolytic cell. Pt and TiN are key materials that can be applied to the bipolar plate coating of PEM electrolytic cells in the future.

[0148] Comparative Example 1

[0149] This comparative example provides a three-electrode testing method, which specifically includes the following steps:

[0150] The test coating was used as the working electrode, mercurous sulfate or a reversible hydrogen electrode as the reference electrode, and a carbon rod as the counter electrode in an H-type electrolytic cell. Air or oxygen was introduced at a flow rate of 20 mL / min into an H₂SO₄ electrolyte solution at 80°C, with an F⁻ content of 0.1 mg / L and pH = 3 to simulate the anodic environment of the electrolytic cell. A potential of 2 V (vs. RHE) was applied to the sample in the simulated anodic environment and maintained for at least 100 h.

[0151] The comparison results between Example 2 and Comparative Example 1 are shown below:

[0152] Figure 8A This is a surface view of the TiN coating that was not tested. Figure 8A As shown, the initial TiN coating surface appears golden yellow.

[0153] Figure 8B This is a surface image of the TiN coating after a 400-hour operating condition test, as provided in Embodiment 2 of the present invention. Figure 8B As shown, after testing for 400 hours using the working condition detection method of the present invention, the TiN coating on the surface of the titanium sheet darkened slightly, with only partial oxidation.

[0154] Figure 8C This is a surface image of the TiN coating after testing using the three-electrode method provided in Comparative Example 1 of this invention. Figure 8C As shown, after only 24 hours of testing using the traditional three-electrode method, the TiN coating completely peeled off, and a pale yellow TiO2 layer was formed on the surface of the titanium sheet.

[0155] Figure 9 This is a comparison graph showing the contact resistance after testing using the method provided in Embodiment 2 of the present invention and the three-electrode method provided in Comparative Example 1. Figure 9 As shown, after 24 hours of testing using the traditional three-electrode method, the contact resistance on the surface of the titanium sheet is much greater than that after testing using the operating condition detection method.

[0156] In summary, the traditional three-electrode testing method provided in Comparative Example 1 differs significantly from actual working conditions, seriously overestimating the corrosive environment of the bipolar plates in the PEM electrolytic cell, making it difficult to accurately screen bipolar plate coatings.

[0157] Comparative Example 2

[0158] This comparative example provides a traditional bipolar plate operating condition testing method, which specifically includes the following steps:

[0159] The coating to be tested is deposited on the surface of the bipolar plate of the electrolytic cell using methods such as electroplating or magnetron sputtering. The electrolytic cell is installed on a multi-channel proton exchange membrane electrolytic cell test platform, and circulating water is introduced under a constant current density (e.g., 2 A / cm²). 2 Stability tests were conducted on the current density.

[0160] The comparison results between Example 2 and Comparative Example 2 are shown below:

[0161] Figure 10A The diagram shows the bipolar plate coating before and after the reaction, as provided for Comparative Example 2. Figure 10A As shown, the coating is directly sputtered onto the bipolar plate for operational testing. However, due to the tight encapsulation of the PEM water electrolysis device requiring bolt positioning holes, the area of ​​the bipolar plate is larger than the actual reactive area. Therefore, this method is difficult to accurately quantify key properties such as the conductivity of the surface coating after the actual reaction.

[0162] Figure 10B The diagram provided for Comparative Example 2 shows the operating conditions for directly testing contact resistance using bipolar plates. Figure 10B As shown, the bipolar plate is thick and has a large area, requiring large equipment to analyze the surface coating, which makes it very inconvenient to characterize the surface morphology of the coating after working condition testing.

[0163] In summary, the bipolar plate operating condition testing method proposed in this invention not only realistically reproduces the actual operating condition testing environment of bipolar plates in a PEM electrolytic cell, but also improves the convenience of characterizing key coating properties. This method has high accuracy, effectively solves the problem of bipolar plate coating testing, optimizes the selection of coating materials, and thus reduces the overall cost of the electrolytic cell.

[0164] 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 detecting the coating of a bipolar plate in a proton exchange membrane electrolyzer, characterized in that, The detection method includes the following steps: Titanium sheets with bipolar plate coatings are assembled in an electrolytic cell to obtain an electrolytic cell containing titanium sheets. The electrolytic cell containing titanium sheets was first activated by cycling at different current densities, and then operated at a constant current density to test the stability of the bipolar plate coating.

2. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 1, characterized in that, The electrolytic cell comprises, in sequence, a cathode bipolar plate, a cathode diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, an anode gas diffusion layer, a titanium sheet with a bipolar plate coating, and an anode bipolar plate.

3. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 1 or 2, characterized in that, One side of the titanium sheet has a bipolar plate coating, and the bipolar plate coating is in contact with the anode gas diffusion layer. And / or, the torque for assembling the electrolytic cell is 3 Nm or more; And / or, the thickness-direction compressibility of the anode gas diffusion layer is <20%.

4. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 3, characterized in that, The torque required to assemble the electrolytic cell is 4 Nm.

5. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 1 or 2, characterized in that, The thickness of the titanium sheet is 50~150 μm; And / or, the thickness of the bipolar plate coating is 0.01~1 μm; And / or, the bipolar plate coating includes a metal coating and / or a metal nitride coating; The metal in the metal coating includes any one or a combination of at least two of Ti, Zr, Cr or Pt. The metal nitride coating includes any one or a combination of at least two of TiN, CrN, or ZrN.

6. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 5, characterized in that, The thickness of the titanium sheet is 100 μm.

7. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 1, characterized in that, The cyclic activation and operation of the electrolyzer containing titanium sheets were carried out on a multi-channel proton exchange membrane electrolyzer test platform.

8. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 1, characterized in that, Before the cyclic activation, circulating water needs to be introduced and the temperature increased.

9. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 8, characterized in that, The flow rate of the circulating water is 100~300 mL / min.

10. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 9, characterized in that, The flow rate of the circulating water is 200 mL / min.

11. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 8, characterized in that, The temperature is raised to 75~85℃.

12. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 11, characterized in that, The temperature is raised to 80°C.

13. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 1, characterized in that, The cyclic activation at different current densities specifically refers to: 1~5 A / cm 2 Select at least three current densities within the current density range, and run each at each selected current density for at least 20 minutes. And / or, the operation under the constant current density specifically refers to: 1~5 A / cm 2 Select a constant current density within the range of current densities, and operate at the constant current density for at least 100 h.

14. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 1, characterized in that, The detection method further includes the following steps: The morphology of the bipolar plate coating on the surface of a titanium sheet after operation at a constant current density was characterized using field emission scanning electron microscopy.

15. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 1 or 2, characterized in that, The detection method further includes the following steps: The anode gas diffusion layer of the electrolytic cell is placed between two electrodes, and pressure is applied to both sides of the electrodes. The resistance value R1 under different pressure conditions is recorded. The anode gas diffusion layer of the electrolytic cell and the titanium sheet with bipolar plate coating are combined and placed between two electrodes. Pressure is applied to both sides of the electrodes, and the resistance value R2 under different pressure conditions is recorded; wherein the bipolar plate coating is in contact with the anode gas diffusion layer. The contact resistance R between the anode gas diffusion layer and the bipolar plate coating of the electrolytic cell is calculated using the following formula I. contact ; Formula I.

16. The method for detecting the coating of the bipolar plate in a proton exchange membrane electrolyzer according to claim 15, characterized in that, The electrode is a gold-plated copper electrode; And / or, the pressure range of the applied pressure is 0.1~2 MPa.

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