A modified titanium bipolar plate for a proton exchange membrane water electrolysis cell and its preparation method

Abstract

This invention discloses a method for preparing a modified proton exchange membrane water electrolyzer, belonging to the technical field of proton exchange membrane water electrolyzers. The method specifically includes the following steps: S1) Degreasing a titanium substrate with acetone, then ultrasonically cleaning it in ethanol and deionized water to remove residual impurities, followed by acid treatment, cleaning with deionized water, and finally drying; S2) Treating the titanium substrate treated in S1) with a thermal spraying method to obtain a titanium bipolar plate with a tantalum coating; S3) Nitriding the titanium bipolar plate obtained in S2) using a powder immersion reaction-assisted coating method to obtain a titanium bipolar plate with a tantalum / titanium nitride composite coating. This invention improves the corrosion resistance and conductivity of titanium sheets by forming a dense and uniform conductive coating on the surface of the titanium sheet through powder embedding reaction-assisted coating and nitriding in metal nitride powder.

Description

Technical Field

[0001] This invention belongs to the technical field of proton exchange membrane water electrolyzers, specifically relating to a modified titanium bipolar plate for a proton exchange membrane water electrolyzer and its preparation method. Background Technology

[0002] Bipolar plates, also known as flow field plates, are one of the key materials in PEM water electrolysis cells, accounting for approximately 40% of the total cost. Reducing bipolar plate costs is crucial for controlling overall cell costs. Compared to bipolar plates made of other materials, metal bipolar plates offer advantages such as stable mechanical properties, good gas barrier properties, ease of processing, and lower cost, making them widely used in high-power fuel cell stacks. However, during stack operation, harsh working environments can lead to surface corrosion and passivation of metal bipolar plates. The corroded metal ions have a toxic effect on the membrane electrode assembly, causing a decline in stack performance. In early water electrolysis cells, materials that easily form passivation films were often used directly to fabricate bipolar plates to protect the metal from further corrosion. However, the conductivity of the bipolar plate decreases due to the presence of the passivation film. Therefore, relying solely on the inherent properties of metal materials to simultaneously meet the requirements of high corrosion resistance and low contact resistance is difficult to achieve. One method involves magnetron sputtering a noble metal coating (Au, IrO2, Pt), but this is costly. Another method is electrochemical nitriding to improve the conductivity and corrosion resistance of the substrate material, but this method is complex and expensive. Therefore, there is an urgent need to find a simple, efficient, low-cost, and stable nitriding method to replace the traditional electrochemical nitriding process. Summary of the Invention

[0003] The main objective of this invention is to provide a modified titanium bipolar plate for a proton exchange membrane (PEM) water electrolyzer and its preparation method, overcoming the shortcomings of existing technologies. Specifically, addressing the problem of increased internal resistance and reduced power efficiency of the PEM water electrolyzer bipolar plate due to oxidation at high anodic potential, this invention employs a combination of thermal spraying and PIRAC nitriding to prepare a highly conductive and corrosion-resistant composite coating. Simultaneously, by embedding nitriding into chromium nitride powder to form a dense and uniform conductive coating on the titanium sheet surface, the corrosion resistance and conductivity of the titanium sheet are improved. Results of the highly conductive tantalum / titanium nitride coating prepared by this invention show significantly improved corrosion resistance; in a 0.5 mol / L H₂SO₄ + 2 ppm F⁻ solution, its corrosion current density is 0.124 μA / cm², and its conductivity is also significantly improved compared to the substrate, with a contact resistance of 0.6 mΩcm² at 143.6 N cm⁻².

[0004] According to a first aspect of the present invention, a method for preparing a modified proton exchange membrane water electrolysis cell titanium bipolar plate is provided, characterized in that the method specifically includes the following steps:

[0005] S1) The titanium substrate is degreased with acetone, then removed and ultrasonically cleaned in ethanol and deionized water to remove residual impurities on the surface. It is then acid-treated, cleaned with deionized water, and finally dried.

[0006] S2) The titanium substrate after S1) is treated by thermal spraying to obtain a titanium bipolar plate with a tantalum coating on the surface;

[0007] S3) The titanium bipolar plate obtained in S2) is subjected to nitriding treatment using the powder immersion reaction-assisted coating (PIRAC) method to obtain a titanium bipolar plate with a tantalum / titanium nitride composite coating on the surface.

[0008] Furthermore, the titanium substrate in S1) is industrial pure titanium sheet TA1;

[0009] The acid treatment time is 10–15 seconds; the acid treatment solution is a mixed solution of HF, HNO3, and H2O, with a volume ratio of 1:8–12:20–30. This acid etching time is beneficial for optimizing the surface morphology of the titanium sheet and facilitating the bonding of the thermal spraying slurry to the titanium substrate; this solution ratio is beneficial for controlling the reaction rate and preventing NO... x The generation of gas poses a hazard to workers.

[0010] Furthermore, the specific steps of S2) are as follows:

[0011] S2.1) Prepare the spraying slurry and set aside;

[0012] S2.2) Place the spray slurry prepared in S2.1) into a mixer, stir for a period of time, and then take it out to obtain a suspension with uniform texture and certain viscosity.

[0013] S2.3) The heating stage temperature is controlled at 180–210°C, and the spraying direction is tilted at a 40–55° angle to the plane of the titanium sheet. The suspension described in S2.2) is uniformly sprayed onto the titanium substrate to obtain a titanium bipolar plate with a tantalum coating. Under normal conditions, the boiling point of DMAc (NN dimethylacetamide) liquid is 164°C. The temperature of the heating stage should be set high enough to allow DMAc to evaporate quickly and for the effective components in the suspension to combine with the titanium substrate as quickly as possible. A suitable spraying angle can ensure uniform spraying onto the substrate surface.

[0014] Furthermore, the spraying slurry in step S2.1) consists of tantalum metal powder, resin, and N,N-dimethylacetamide (DMAc).

[0015] The tantalum metal powder has a mass fraction of 50%-80%, and the ratio of slurry to solvent in the spraying slurry is 1:3, 1:3.5, 1:4, or 1:4.5. This ratio allows more tantalum particles to adhere to the surface of the titanium substrate while saving material usage.

[0016] Furthermore, the resin is a polyimide resin.

[0017] Furthermore, in step S2.2), the stirrer speed is 1000-1400 r / min, and the stirring time is 1-4 h. The stirring speed needs to be high enough, and the stirring time needs to be long enough to ensure that the components in the spray liquid can be fully mixed to form a suspension with a uniform texture and a certain viscosity.

[0018] Furthermore, in step S2.3), the titanium substrate should be preheated on a heating table for 2-5 minutes before spraying, using spray guns of different diameters, ranging from 0.2-0.5 mm. The spraying pressure should be controlled at 0.3-0.5 MPa, and the slurry dosage should be 0.03-0.08 ml / cm³. 2 Preheating the titanium substrate in advance ensures rapid evaporation of DMAc; a suitable nozzle diameter prevents the liquid content in the gas-liquid mixture sprayed from the spray gun from being too high, making it difficult to evaporate quickly and affecting the coating effect; the pressure ensures uniform coating effect, while excessively high pressure and high airflow speed may blow away the titanium substrate; the amount of slurry can control the spraying speed and prevent the coating from being too thin or too thick.

[0019] Furthermore, the specific steps of S3) are as follows:

[0020] S3.1) Place the nitrogen source and the titanium bipolar plate treated in S2) into a crucible, and then seal it;

[0021] S3.2) The sealed crucible obtained in S3.1) is placed in a vacuum tube furnace, heated and held for a period of time to prepare a titanium bipolar plate with a tantalum / titanium nitride composite coating.

[0022] Furthermore, in step S3.1), the nitrogen source is chromium nitride, and the crucible is an alumina crucible.

[0023] Furthermore, in step S3.2), the heating rate of the vacuum tube furnace is set to 5–7 °C / min, the holding temperature range is 700 °C–1000 °C, and the holding time is 1–4 h. Different settings of the tube furnace temperature and time parameters can decisively affect the nitriding effect. The temperature significantly affects the bonding ability between titanium and active nitrogen atoms, while the holding time can influence the thickness of the resulting nitride coating.

[0024] According to a second aspect of the present invention, a modified titanium bipolar plate for a proton exchange membrane water electrolyzer is provided, characterized in that the modified titanium bipolar plate for the proton exchange membrane water electrolyzer is prepared by the method described in any one of the above aspects.

[0025] According to a third aspect of the technical solution of the present invention, a proton exchange membrane water electrolyzer is provided, characterized in that the proton exchange membrane water electrolyzer employs a modified titanium bipolar plate as described above.

[0026] The beneficial effects of this invention are:

[0027] 1. Through thermal spraying technology, tantalum powder is atomized into extremely fine particles using a high-speed airflow and sprayed onto the surface of a titanium substrate at a high velocity. Based on tantalum's exceptionally stable chemical properties—it is virtually unaffected by inorganic acids and alkalis at room temperature (except for hydrofluoric acid), and only dissolves in concentrated sulfuric acid, concentrated phosphoric acid, and strong alkaline solutions at high temperatures—this process achieves an initial improvement in the corrosion resistance of the titanium substrate surface. This spraying process is simple, efficient, flexible, and convenient, requiring no special equipment, and is low in cost and widely applicable.

[0028] 2. Tantalum powder was sprayed onto a titanium substrate using a thermal spraying method, resulting in a titanium substrate with a tantalum coating. Based on this, the tantalum-coated sample was embedded in a nitrogen source in a crucible using PIRAC technology. At high temperature, the active single-atom nitrogen generated by the decomposition of the unstable nitrogen source (Cr2N, Cu3N, Mo2N, etc.) diffused into the substrate and bonded to it, forming a composite nitride coating containing TiN and TaN. The TiN coating exhibits high strength, good wear resistance, good oxidation resistance, good corrosion resistance, and good electrical conductivity. TaN is a material with good electrical conductivity; at room temperature, the conductivity of TaN is less than 0.28 mΩ·cm. 2 The composite coating formed by the two nitrides has excellent corrosion resistance and conductivity. Compared with the sample that was not sprayed and was simply embedded and nitrided, the composite nitride coating has better conductivity than the simple TiN coating. Even after long-term constant potential polarization in the high potential environment of simulated PEM water electrolysis anode, it still has low corrosion current and stable contact resistance.

[0029] 3. There is a wide range of room for improvement. This invention can also improve the metal bipolar plate to different degrees and in different directions by introducing different types of conductive materials and matrix materials and adjusting the different proportions of each component. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the preparation method of modified titanium bipolar plates for a proton exchange membrane water electrolysis cell according to the present invention.

[0031] Figure 2 SEM image of a titanium sheet subjected to tantalum spraying and nitriding in Example 1 of the present invention.

[0032] Figure 3 The graph shows the potentiodynamic polarization curves at different nitriding insulation temperatures in Example 1 of the present invention, using the method of the present invention.

[0033] Figure 4 Example 2 shows the surface metallographic morphology of thermally sprayed samples with different tantalum powders as a percentage of the spray slurry mass, using the method of the present invention.

[0034] Figure 5 The graph shows the contact resistance data at different nitriding insulation temperatures under Example 1 of the method of the present invention.

[0035] Figure 6 This is an AC impedance curve of Example 1 using the method of the present invention. Detailed Implementation

[0036] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0037] The terms "first," "second," etc., used in this disclosure are for distinguishing similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented, for example, in orders other than those illustrated or described herein.

[0038] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0039] Multiple, including two or more.

[0040] And / or, it should be understood that, for the purposes of this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone.

[0041] This invention provides a modified titanium bipolar plate for a proton exchange membrane (PEM) water electrolysis cell and its preparation method, applicable to PEM water electrolysis cells. The method specifically involves: degreasing a titanium substrate with acetone and anhydrous ethanol, followed by cleaning with deionized water; acid washing the treated titanium substrate; thermal spraying the treated titanium substrate to prepare a tantalum coating on its surface; and finally, nitriding the treated titanium substrate with PIRAC powder to obtain the modified titanium bipolar plate. Specifically, as shown... Figure 1 As shown, the present invention is achieved through the following technical solution:

[0042] S1) Pretreatment of titanium sheets;

[0043] Using titanium sheets as a substrate, in order to remove grease and passivation film from the surface of the titanium sheets, the titanium sheets are degreased with organic solvents, then removed and ultrasonically cleaned in ethanol and deionized water to remove residual impurities on the surface, and then acid treated.

[0044] The titanium sheet is treated in an acid pickling solution for 10–15 seconds, then rinsed with deionized water and dried in a vacuum oven.

[0045] S2) A tantalum coating is prepared on the surface of a titanium sheet by thermal spraying.

[0046] The spray coating slurry is composed of tantalum metal powder, N,N-dimethylacetamide (DMA), and resin. The percentage of tantalum powder, the ratio of slurry to solvent, and the curing time after spraying are controlled.

[0047] Use a spray gun with a nozzle diameter of 0.3mm, control the spraying pressure at 0.3-0.5MPa, and use slurry at a rate of 0.03-0.08ml / cm³. 2 ;

[0048] The acid-etched titanium sheet was placed on a heating stage and preheated for 2-5 minutes at 200°C. The spraying direction was kept at a 45° angle to the titanium bipolar plate. The prepared tantalum-containing slurry was evenly sprayed onto the titanium substrate using a spray gun, with equal amounts sprayed on both sides of the plate. After spraying, the coated titanium bipolar plate was placed in a vacuum drying oven to dry for a certain period of time. After the bipolar plate cooled, it was rinsed with deionized water and then placed in a 50°C oven to dry, thus obtaining a titanium sheet sample with tantalum on its surface.

[0049] S3) The process of preparing tantalum / titanium nitride composite coating on titanium sheet surface by PIRAC nitriding method;

[0050] The nitriding experiment used high-purity Cr2N powder (99.99%) with an average particle size of 30 μm as the nitrogen source. The pretreated pure titanium substrate and Cr2N powder were buried together in an alumina crucible, which was then sealed with a high-temperature resistant binder and dried in a vacuum oven for 2 hours. The crucible was then placed in a tube furnace filled with high-purity N2 and heated to 700℃-1000℃, then held at that temperature for 2 hours. The heating rate was 5℃ / min. After cooling to room temperature with the furnace, the samples were removed. The entire cooling process was carried out under high-purity N2 protection. The pure titanium substrate and the samples nitrided at various temperatures were labeled TA1, TA1-700, TA1-800, TA1-900, and TA1-1000, respectively.

[0051] The nitriding process consists of three steps: the first step is to embed the treated titanium sheet substrate and Cr2N powder together into an alumina crucible, then seal the alumina crucible with a high-temperature resistant adhesive, and dry it in a vacuum drying oven.

[0052] The second part involves placing the crucible in a tube furnace filled with high-purity N2 and heating it to a certain temperature, then maintaining the temperature for a certain time. After cooling to room temperature with the furnace, the sample is removed. The entire cooling process is carried out under the protection of high-purity N2. The third part involves rinsing the nitrided titanium sheet with deionized water and drying it for later use.

[0053] Furthermore, the acid treatment volume ratio is HF:HNO3:H2O = 1:8~12:20~30.

[0054] Furthermore, the composition of the spraying slurry is as follows: tantalum accounts for 50%-80% of the slurry, and the ratio of slurry to solvent is 1:3, 1:3.5, 1:4, or 1:4.5.

[0055] Furthermore, the curing time after spraying is 1h to 4h, and the curing temperature is 120℃.

[0056] Furthermore, the heat preservation temperature during nitriding treatment is 700℃~1000℃, and the heat preservation time is 2 hours.

[0057] The present invention also provides a modified titanium bipolar plate for a proton exchange membrane water electrolyzer, and a proton exchange membrane water electrolyzer using the modified titanium bipolar plate.

[0058] Example 1:

[0059] The titanium sheet was ultrasonically treated in acetone, ethanol and deionized water to remove organic matter from its surface. Then, it was acid-treated in a volume ratio (HF:HNO3:H2O = 1:8:10) to remove the oxide film on the surface. After rinsing with deionized water, it was dried and stored.

[0060] The thermal spraying slurry for tantalum on titanium sheets consists of tantalum metal powder, N,N-dimethylacetamide (DMAc), and resin. Tantalum accounts for 50% of the slurry by mass, and the slurry:solvent ratio is 1:3.5. The acid-etched titanium substrate is placed on a heating stage and preheated for 2 minutes at 200℃. A 0.3mm nozzle spray gun is used, with a spraying pressure of 0.45MPa and a slurry volume of 0.05ml / cm³. 2 The spraying direction is maintained at a 45° angle to the titanium bipolar plate. The prepared tantalum-containing slurry is evenly sprayed onto the titanium substrate using a spray gun, ensuring equal amounts are sprayed onto both sides of the plate. After spraying, the titanium bipolar plate is placed in a 120°C vacuum drying oven for 2 hours. After cooling, the bipolar plate is rinsed with deionized water and then placed in a 50°C oven for further drying.

[0061] The nitriding experiment used high-purity Cr2N powder (99.99%) with an average particle size of 30 μm as the nitrogen source. The treated titanium substrate and Cr2N powder were buried together in an alumina crucible, which was then sealed with a high-temperature resistant adhesive and dried in a vacuum drying oven for 2 hours. The crucible was then placed in a tube furnace filled with high-purity N2 and heated to 700℃, 800℃, 900℃, and 1000℃, respectively, and held at that temperature for 2 hours. The heating rate was 5℃ / min. After cooling to room temperature with the furnace, the sample was removed. The entire cooling process was carried out under the protection of high-purity N2.

[0062] After treatment, the titanium sheet samples were washed with deionized water and dried for morphological characterization. SEM images of the samples after 2 hours of nitriding at different temperatures are shown below. Figure 1 As shown, when the temperature is suitable, the surface of the titanium substrate is completely covered by relatively uniform nitride particles. However, when the temperature is too high, due to thermal expansion, the nitride particles become uneven in size, resulting in an uneven surface and noticeable gaps between the particles. These unevenly sized nitride particles affect the effective contact area between the bipolar plate and the diffusion layer, impacting the interfacial contact resistance. The gaps also make the coating more susceptible to corrosion, affecting the bipolar plate's corrosion resistance in acidic solutions.

[0063] After processing, the titanium sheet samples were washed with deionized water, dried, and then subjected to electrochemical tests. Figure 3 and Figure 5-6As shown, the corrosion potential of the treated sample was significantly increased compared to the titanium substrate. Tafel fitting of the strongly polarized region in the curve revealed a significant decrease in the self-corrosion current; with a suitable temperature, the self-corrosion current could even be reduced by two orders of magnitude. The contact resistance of samples treated at different nitriding temperatures was significantly lower than that of the titanium substrate. This is because a uniform and dense nitride coating was formed on the sample surface after treatment, replacing the oxide film on the titanium substrate, thus greatly improving conductivity. It is generally believed that the semi-circular radius of the impedance spectrum corresponds to the magnitude of the impedance value; generally, the larger the impedance radius, the stronger the corrosion resistance of the coating. From... Figure 6 As can be seen, the semi-circular radius of the samples treated with tantalum spraying at 900℃ and 1000℃ is significantly larger than that of the untreated titanium substrate, and the surface has better corrosion resistance at this time. This is related to the formation of a more stable passivation film after nitriding treatment.

[0064] Example 2:

[0065] The titanium sheet was ultrasonically treated in acetone, ethanol and deionized water to remove organic matter from its surface. Then, it was acid-treated in a volume ratio (HF:HNO3:H2O = 1:8:20) to remove the oxide film on the surface. After rinsing with deionized water, it was dried and stored.

[0066] The thermal spraying slurry for tantalum on titanium sheets consists of tantalum metal powder, N,N-dimethylacetamide (DMAc), and resin. The tantalum content in the slurry is 50%, 60%, 70%, and 80% by mass, with a slurry-to-solvent ratio of 1:4. The acid-etched titanium substrate is placed on a heating stage and preheated for 5 minutes at 200°C. A 0.3mm nozzle spray gun is used, with a spraying pressure of 0.3MPa and a slurry volume of 0.03ml / cm³. 2 The spraying direction is maintained at a 45° angle to the titanium bipolar plate. The prepared tantalum-containing slurry is evenly sprayed onto the titanium substrate using a spray gun, ensuring equal amounts are sprayed onto both sides of the plate. After spraying, the titanium bipolar plate is placed in a 120°C vacuum drying oven for 3 hours. After cooling, the bipolar plate is rinsed with deionized water and then placed in a 50°C oven for further drying.

[0067] The nitriding experiment used high-purity Cr2N powder (99.99%) with an average particle size of 30 μm as the nitrogen source. The treated titanium substrate and Cr2N powder were buried together in an alumina crucible, which was then sealed with a high-temperature resistant adhesive and dried in a vacuum drying oven for 2 hours. The crucible was then placed in a tube furnace filled with high-purity N2 and heated to 800℃, then held at that temperature for 2 hours. The heating rate was 5℃ / min. After cooling to room temperature with the furnace, the sample was removed. The entire cooling process was carried out under the protection of high-purity N2.

[0068] After processing, the titanium sheet samples were washed with deionized water, dried, and then their morphology was characterized. Metallurgical microscopy was used to examine the samples. Figure 4 As shown, tantalum particles are present on the surface of the coated sample, and these particles are clearly visible at different magnifications. Furthermore, the tantalum on the coating surface does not completely cover the titanium substrate; instead, it adheres to the substrate surface in the form of bumps. This utilizes the properties of tantalum to improve coating performance while reducing the amount used and lowering costs.

[0069] Example 3:

[0070] The titanium sheet was ultrasonically treated in acetone, ethanol and deionized water to remove organic matter from its surface. Then, it was acid-treated in a volume ratio (HF:HNO3:H2O = 1:12:30) to remove the oxide film on the surface. After rinsing with deionized water, it was dried and stored.

[0071] The thermal spraying slurry for tantalum on titanium sheets consists of tantalum metal powder, N,N-dimethylacetamide (DMAc), and resin. Tantalum accounts for 70% of the slurry by mass, and the slurry:solvent ratios are 1:3, 1:3.5, 1:4, and 1:4.5. The acid-etched titanium substrate is placed on a heating platform and preheated for 3 minutes at 200℃. A 0.3mm nozzle spray gun is used, the spraying pressure is controlled at 0.5MPa, and the slurry volume is 0.08ml / cm². 2 The spraying direction is maintained at a 45° angle to the titanium bipolar plate. The prepared tantalum-containing slurry is evenly sprayed onto the titanium substrate using a spray gun, ensuring equal amounts are sprayed onto both sides of the plate. After spraying, the titanium bipolar plate is placed in a 120°C vacuum drying oven for 2 hours. After cooling, the bipolar plate is rinsed with deionized water and then placed in a 50°C oven for further drying.

[0072] The nitriding experiment used high-purity Cr2N powder (99.99%) with an average particle size of 30 μm as the nitrogen source. The treated titanium substrate and Cr2N powder were buried together in an alumina crucible, which was then sealed with a high-temperature resistant adhesive and dried in a vacuum drying oven for 2 hours. The crucible was then placed in a tube furnace filled with high-purity N2 and heated to 900℃, then held at that temperature for 2 hours. The heating rate was 5℃ / min. After cooling to room temperature with the furnace, the sample was removed. The entire cooling process was carried out under the protection of high-purity N2.

[0073] The processed titanium sheet samples were washed with deionized water and dried. Then, broadband and narrow-spectrum scanning analyses were performed on the prepared samples using X-ray photoelectron spectroscopy (XPS, Kratos, AXIS ULTRADLD) to characterize their elemental composition and valence state changes. The scanning range was 0–1200 eV, with a scanning interval of 1 eV.

[0074] Example 4:

[0075] The titanium sheet was ultrasonically treated in acetone, ethanol and deionized water to remove organic matter from its surface. Then, it was acid-treated in a volume ratio (HF:HNO3:H2O = 1:8:30) to remove the oxide film on the surface. After rinsing with deionized water, it was dried and stored.

[0076] The thermal spraying slurry for tantalum on titanium sheets consists of tantalum metal powder, N,N-dimethylacetamide (DMAc), and resin. Tantalum accounts for 80% of the slurry by mass, and the slurry:solvent ratio is 1:3.5. The acid-etched titanium substrate is placed on a heating stage and preheated for 4 minutes at 200℃. A 0.3mm nozzle spray gun is used, the spraying pressure is controlled at 0.35MPa, and the slurry volume is 0.06ml / cm². 2 The spraying direction is maintained at a 45° angle to the titanium bipolar plate. The prepared tantalum-containing slurry is evenly sprayed onto the titanium substrate using a spray gun, ensuring equal amounts are sprayed onto both sides of the plate. After spraying, the titanium bipolar plate is placed in a 120°C vacuum drying oven for 1 hour, 2 hours, 3 hours, and 4 hours. After cooling, the bipolar plate is rinsed with deionized water and then placed in a 50°C oven for further drying.

[0077] The nitriding experiment used high-purity Cr2N powder (99.99%) with an average particle size of 30 μm as the nitrogen source. The treated titanium substrate and Cr2N powder were buried together in an alumina crucible, which was then sealed with a high-temperature resistant adhesive and dried in a vacuum drying oven for 2 hours. The crucible was then placed in a tube furnace filled with high-purity N2 and heated to 1000℃, then held at that temperature for 2 hours. The heating rate was 5℃ / min. After cooling to room temperature with the furnace, the sample was removed. The entire cooling process was carried out under the protection of high-purity N2.

[0078] After processing, the titanium sheet samples were washed with deionized water and dried for morphological characterization. The microstructure of the sample surface was observed using a scanning electron microscope (SEM), and the elemental composition of the sample surface was characterized using the built-in EDS function.

[0079] In summary, the method of this invention improves the corrosion resistance and conductivity of titanium sheets by embedding a reactive coating nitriding process into metal nitride powder, thereby forming a dense and uniform conductive coating on the surface of the titanium sheet. This method has broad application prospects for improving the durability of bipolar plates in future proton exchange membrane water electrolyzers.

[0080] The above provides a detailed description of a method for preparing a modified proton exchange membrane water electrolyzer titanium bipolar plate, as provided in the embodiments of this application.

[0081] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A method for preparing a modified proton exchange membrane water electrolysis cell titanium bipolar plate, characterized in that, The method specifically includes the following steps: S1) The titanium substrate is degreased with acetone, then removed and ultrasonically cleaned in ethanol and deionized water to remove residual impurities on the surface. It is then acid-treated, cleaned with deionized water, and finally dried. S2) The titanium substrate after S1) is treated by thermal spraying to obtain a titanium bipolar plate with a tantalum coating on the surface; The specific steps of S2 are as follows: S2.1) Prepare the spraying slurry and set aside; S2.2) The spray slurry prepared in S2.1) is placed in a mixer and stirred for a period of time before being taken out to obtain a suspension with uniform texture and certain viscosity. S2.3) The temperature of the heating table is controlled at 180~210℃, and the spraying direction is tilted at an angle of 40~55° to the plane of the titanium sheet. The suspension described in S2.2) is uniformly sprayed onto the titanium substrate to obtain a titanium bipolar plate with a tantalum coating on the surface. S3) The titanium bipolar plate obtained in S2) is subjected to nitriding treatment by powder immersion reaction-assisted coating method to form a composite nitride coating containing TiN and TaN, thereby obtaining a titanium bipolar plate with a tantalum / titanium nitride composite coating on the surface. The specific steps of S3 are as follows: S3.1) Place the nitrogen source and the titanium bipolar plate treated in S2) into a crucible and then seal it, wherein the nitrogen source is chromium nitride and the crucible is an alumina crucible; S3.2) The sealed crucible obtained in S3.1) is placed in a vacuum tube furnace, heated and held for a period of time to form a composite nitride coating containing TiN and TaN, thereby obtaining a titanium bipolar plate with a tantalum / titanium nitride composite coating.

2. The method according to claim 1, characterized in that, The titanium substrate in S1) is industrial pure titanium sheet TA1; The acid treatment time is 10 to 15 seconds; the acid treatment solution is a mixed solution of HF, HNO3 and H2O, with a volume ratio of 1:8 to 12:20 to 30.

3. The method according to claim 1, characterized in that, The spray slurry in S2.1) consists of tantalum metal powder, resin, and N,N-dimethylacetamide (DMAc). The tantalum metal powder has a mass fraction of 50%-80%, and the ratio of slurry to solvent in the spraying slurry is 1:3, 1:3.5, 1:4, or 1:4.

5. The resin is a polyimide resin.

4. The method according to claim 1, characterized in that, In S2.2), the stirrer speed is 1000-1400 r / min, and the stirring time is 1-4h.

5. The method according to claim 1, characterized in that, In step S2.3), the titanium substrate is preheated on a heating table for 2-5 minutes before spraying. Different nozzle diameters (0.2-0.5 mm) are used; the spraying pressure is controlled at 0.3-0.5 MPa; and the slurry volume is 0.03-0.08 ml / cm³. 2 .

6. The method according to claim 1, characterized in that, In S3.2), the heating rate of the vacuum tube furnace is set to 5~7℃ / min, the holding temperature range is 700℃~1000℃, and the holding time is 1~4h.

7. A modified titanium bipolar plate for a proton exchange membrane water electrolysis cell, characterized in that, The modified proton exchange membrane water electrolyzer titanium bipolar plate is prepared using the method described in any one of claims 1 to 6.

8. A proton exchange membrane water electrolysis cell, characterized in that, The proton exchange membrane water electrolyzer uses the modified titanium bipolar plate according to claim 7.

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