Preparation method of titanium nitride-based coating for surface of anode titanium-based bipolar plate of PEM electrolytic cell

Abstract

The invention discloses a preparation method of a titanium nitride-based coating for the surface of a PEM electrolytic cell anode titanium-based bipolar plate. The titanium nitride-based coating has the effects that the corrosion resistance and the conductivity of the bipolar plate can be improved, a catalyst can be carried to improve the electrolytic efficiency, the dosage of the catalyst is reduced, and the service life of the catalyst is prolonged. An existing material preparation method is high in cost, low in efficiency and high in equipment requirement. On the other hand, the precious metal iridium serving as the catalyst is limited in annual yield and high in price. According to the invention, a nano-scale titanium nitride-based material is prepared through a self-propagating combustion synthesis reaction, the nano-scale titanium nitride-based material is used as a skeleton to carry an iridium-containing oxide catalyst, the contact resistance of the coating can reach 2.10 m omega.cm < 2 > under the pressure of 1.7 V and 143.6 N / cm < 2 >, and the coating is suitable for a high-potential PEM electrolyzed water system.

Description

Technical Field

[0001] The invention relates to the field of hydrogen production by electrolysis of water, and in particular to a method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate of an anode of a PEM electrolyzer. Background Art

[0002] PEM water electrolysis has high current density, small electrolyzer volume, and rapid load change, which is well matched with wind power, photovoltaic power and other power generation with large volatility and randomness. However, it has not been widely used so far, firstly because its cost is higher than that of alkaline water electrolysis, and secondly because the domestic reserves of precious metal iridium as a catalyst are small and cannot meet the large-scale demand.

[0003] The bipolar plates of PEM electrolyzers usually use stainless steel as the base material. Under irregular voltage changes, harsh environments and long-term immersion in corrosive electrolytes, metal bipolar plates will be severely corroded, and a layer of anti-passivation coating needs to be added to the surface to improve its corrosion resistance and conductivity. At the same time, due to the slow kinetics of the anode oxygen evolution reaction, the coating also serves as a carrier for the catalyst to improve the electrolysis efficiency, reduce the amount of catalyst used, and extend the service life of the catalyst. Therefore, the coating needs to have good conductivity, a large specific surface area, a reasonable surface pore size distribution and good corrosion resistance.

[0004] TiN has metallic properties and extremely low room temperature resistivity. It is also acid and alkali resistant, has strong bonding strength with metals, and has high catalytic activity. Therefore, it is particularly suitable for use as an anode corrosion-resistant coating material. However, the preparation process of nano-TiN is long and energy-intensive, so the preparation cost is high. On the other hand, the precious metal iridium and its oxides are currently the most effective anode catalysts, but the mining rate of Ir ore is only 4~9t / a. Therefore, to achieve the installation of terawatt-level PEM electrolyzers, the total Ir loading must be reduced by 2 orders of magnitude. Multi-metal oxides are an effective way to dope non-precious metals in precious metals. Summary of the invention

[0005] In order to solve the above problems, the present invention aims to provide a method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolytic cell anode. The technical solution of the present invention is as follows: A method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode, the method comprising the following steps: S1 uses Fe-Al-Ti-BN system to prepare nano-scale TiN powder with controllable stoichiometric ratio, particle size and morphology through combustion synthesis process; S2 uses a precursor method to load iridium oxide (IrO2) on the surface of TiN powder to obtain IrO2@TiN powder carrying IrO2 catalyst; S3 uses electrophoretic deposition to prepare a dense, uniform, and continuous IrO2@TiN coating loaded with catalyst particles on the surface of a Ti-based bipolar plate.

[0006] Preferably, in step S1, the raw materials for the test include the following raw materials in terms of mass ratio: The mass ratio of aluminum powder, iron powder, titanium powder and boron nitride powder is Al:Fe:Ti:BN=(0-30):(0-30):(50-60):(15-20), preferably, Al:Fe:Ti:BN=10:20:53.4:16.6. Further preferably, in step S1, Iron powder (Fe, purity>99wt%, size 45μm), aluminum powder (Al, purity>99wt%, size 45μm), titanium powder (Ti, purity>99.5wt%, size 25μm), boron nitride powder (BN, purity>99.5wt%, size 0.5μm). More preferably, the purity of iron powder>99wt%, size 43-47μm; the purity of aluminum powder>99wt%, size 43-47μm; the purity of titanium powder>99.5wt%, size 20-30μm; the purity of boron nitride powder>99.5wt%, size 0.3-0.7μm.

[0007] Preferably, in step S1, the molar ratio of BN / Ti remains unchanged and is always 0.57-0.62, more preferably 0.6, while the content of iron powder and aluminum powder is adjustable.

[0008] Preferably, the specific operation of step S1 is that the raw material powders are premixed and then evenly mixed in a ball mill, and pressed into a green body with a density of 60% to 80% of the theoretical density (theoretical density is the density when each powder in the powder has no holes at all), and a combustion synthesis reaction is performed to obtain nano-scale TiN powder.

[0009] Preferably, the combustion atmosphere in step S1 is 1-3 MPa nitrogen.

[0010] Preferably, the specific operation steps of the precursor method in step S2 are as follows: S2.1 Add TiN nanopowder into pure water at a liquid-solid ratio of (13-18): (18-25) (mL / mg), disperse evenly, add H2IrCl6·6H2O solution into pure water at a volume ratio of (13-18):1, the concentration of H2IrCl6·6H2O solution is 18-22mgIr / mL, stir evenly and disperse, then add NaNO3 at a mass ratio of Ir:NaNO3=1:(280-320), disperse by ultrasonic, stir for 3-5 h, and then dry; S2.2 After drying, grind in a mortar until a uniform fine powder is formed, transfer to a muffle furnace and calcine at 420-470 °C for 35-45 min at a heating rate of 2.5-3.5 °C / min; S2.3 After calcination is completed, take out the molten salt and dissolve it with a large amount of deionized water, wash it by centrifugation several times, take the precipitate and disperse it evenly with ethanol, dry it in a vacuum drying oven, and after cooling, grind it again and collect it to prepare the required IrO2@TiN powder carrying IrO2 catalyst.

[0011] Further preferably, the specific operation steps of the precursor method in step S2 are as follows: S2.1 Add TiN nanopowder to pure water at a liquid-solid ratio of 15:20 (mL / mg), disperse evenly, add H2IrCl6·6H2O solution at a volume ratio of 15:1 in pure water, the concentration of H2IrCl6·6H2O solution is 20 mgIr / mL, stir and disperse evenly, add NaNO3 at a mass ratio of Ir:NaNO3=1:300, disperse by ultrasonic, stir for 3-5 h, and then dry in a forced air drying oven at 55-65 °C; S2.2 After drying, grind in a mortar until a uniform fine powder is formed, transfer to a muffle furnace and calcine at 420-470 °C for 35-45 min at a heating rate of 2.5-3.5 °C / min; S2.3 After calcination is completed, take out the molten salt and dissolve it with a large amount of deionized water, wash it by centrifugation several times, take the precipitate and disperse it evenly with ethanol, dry it in a vacuum drying oven at 55-65 ℃ for 2.5-3.5 h, and after cooling, grind and collect it again to prepare the required IrO2@TiN powder carrying IrO2 catalyst.

[0012] Preferably, the specific operation steps of the electrophoretic deposition method in step S3 are as follows: S3.1 Place the titanium sheet in acetone, ethanol, and deionized water for ultrasonic cleaning in turn, then etch it in a solution of hydrofluoric acid, nitric acid, and water in a volume ratio of 1: (6-9): (8-12) for 8-12 s to remove the surface oxide layer, and then use deionized water for ultrasonic cleaning after acid etching; S3.2 Prepare a 6-14 g / L suspension of IrO2@TiN powder obtained in step S2 with anhydrous ethanol as solvent, add PEI and stir with a magnetic stirrer at a speed of 100-200 rpm for 0.8-1.2 h, then ultrasonically oscillate at an ultrasonic power of 550-650 W for 8-12 min to break up the agglomerates, and the mass ratio of IrO2@TiN powder:PEI is = 1: (0.11-0.15) (wt%); S3.3 Use a constant voltage power supply at 5V for electrophoretic deposition for 90-300s, graphite as the anode, the sample as the cathode, the electrode spacing is 13-17 mm, and the deposit is vacuum dried at 55-65℃ for 10-14 h to obtain the IrO2@TiN coating.

[0013] Further preferably, the specific operation steps of the electrophoretic deposition method in step S3 are as follows: S3.1 Place the titanium sheet in acetone, ethanol, and deionized water for ultrasonic cleaning in sequence, then etch it in a solution of hydrofluoric acid, nitric acid, and water in a volume ratio of 1:8:10 for 10 s to remove the surface oxide layer, and then use deionized water for ultrasonic cleaning after acid etching; S3.2 Prepare a 10 g / L suspension of IrO2@TiN powder obtained in step S2 (the particle size of IrO2@TiN powder is 20 nm) with anhydrous ethanol as solvent, add PEI (cationic polymer polyethyleneimine (PEI, molecular weight 600)) and stir with a magnetic stirrer for 1 hour, then ultrasonically oscillate for 10 minutes to break up the agglomerates, the mass ratio of IrO2@TiN powder: PEI is = 1:0.14 (wt%); S3.3 Use a constant voltage power supply at 5V for electrophoretic deposition for 90~300s, graphite as the anode, the sample as the cathode, the electrode spacing is 15 mm, and the deposit is vacuum dried at 60℃ for 12 h to obtain the IrO2@TiN coating.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention can quickly prepare nano-scale titanium nitride powder with controllable stoichiometric ratio, morphology and particle size at low cost; and can quickly prepare titanium nitride-based iridium-containing coatings for bipolar plates of PEM electrolyzers at low cost. The obtained coating can improve the corrosion resistance and conductivity of the plate, and can carry catalysts to improve electrolysis efficiency, reduce the amount of catalyst used, and extend the service life of the catalyst.

[0015] 2. The present invention prepares nano-scale titanium nitride-based materials through self-propagating combustion synthesis reaction, and uses it as a framework to carry iridium oxide catalyst. The coating can 2 Contact resistance under pressure reaches 2.10mΩ·cm 2 , suitable for high potential PEM water electrolysis system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 XRD spectra of combustion synthesis products; Figure 2 SEM images of combustion synthesis products; Figure 3 TEM image and element distribution of IrO2@TiN powder; Figure 4 XRD spectrum of the sample after electrophoretic deposition; Figure 5 Potentiodynamic polarization curves of Ti substrate and substrate with deposited coating; Figure 6 Variation of interfacial contact resistance with pressure. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention. Rather than all the embodiments, all other embodiments obtained by ordinary technicians in this field without innovative work based on the embodiments of the present invention are within the scope of protection of the present invention.

[0018] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0019] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. In the event of a conflict with any incorporated document, the contents of this specification shall prevail.

[0020] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0021] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0022] The invention combines the combustion synthesis process and the electrophoretic deposition method to quickly prepare a dense, uniform and continuous TiN coating of iridium oxide catalyst particles at low cost.

[0023] First, Fe-Al-Ti-BN system was used to prepare nano-scale TiN powder with controllable stoichiometric ratio, particle size and morphology through combustion synthesis process. The raw materials used in the experiment include iron powder (Fe, purity>99wt%, size 45μm), aluminum powder (Al, purity>99wt%, size 45μm), titanium powder (Ti, purity>99.5wt%, size 25μm), boron nitride powder (BN, purity>99.5wt%, size 0.5μm), and the material ratio is shown in the table below. The key is that the molar ratio of BN / Ti remains unchanged, always at 0.6, while the content of iron powder and aluminum powder can be adjusted. The original powder is simply pre-mixed and evenly mixed in a ball mill, and pressed into a green body with a density of 75% of the theoretical density. The combustion synthesis reaction is carried out in a 2MPa nitrogen atmosphere to obtain nano-scale TiN powder.

[0024] Table 1 Components of mixed powder

[0025] Next, the precursor method is used to load iridium oxide (IrO2) on the TiN surface. The specific operation steps of the precursor method are as follows: add 20 mg TiN nanopowder to 15 mL pure water, disperse it evenly, and then add 1 mL of 20 mg Ir / mL of H2IrCl6·6H2O solution, after uniform stirring and dispersion, NaNO3 was added at a mass ratio of Ir:NaNO3=1:300, ultrasonic dispersion was performed, stirring at room temperature for 4 h, and then dried overnight at 60 °C in a blast drying oven. After taking out, it was ground in a mortar until it formed a uniform fine powder, transferred to a muffle furnace and calcined at 450 °C for 40 min at a heating rate of 3 °C / min. After calcination, the molten salt was taken out and dissolved with a large amount of deionized water, centrifuged and washed several times, and the precipitate was dispersed evenly with ethanol, dried at 60 °C in a vacuum drying oven for 3 h, and after cooling, ground and collected again to prepare the desired TiN powder carrying IrO2 catalyst (IrO2@TiN powder).

[0026] Then, a dense, uniform, and continuous IrO2@TiN coating loaded with catalyst particles was prepared on the surface of the Ti-based bipolar plate by electrophoretic deposition. The particle size of titanium nitride is about 20 nm. The titanium sheet was ultrasonically cleaned in acetone, ethanol, and deionized water in turn, and then etched for 10 s in a solution of hydrofluoric acid, nitric acid, and water in a volume ratio of 1:8:10 to remove the surface oxide layer. After etching, ultrasonic cleaning was performed with deionized water. A 10 g / L titanium nitride suspension was prepared with anhydrous ethanol as the solvent. After adding PEI, it was stirred with a magnetic stirrer for 1 h, and then ultrasonically oscillated for 10 min to break up the agglomerates. Electrophoretic deposition was performed at 5 V for 90 to 300 s using a constant voltage power supply, with graphite as the anode, the sample as the cathode, and the electrode spacing of 15 mm. The deposit was vacuum dried at 60 ° C for 12 h to obtain the IrO2@TiN coating (see Figure 4 ).

[0027] The powder distribution generated by the combustion synthesis reaction was characterized by XRD and SEM ( Figure 2 ), it can be seen that the main product of all the formulas in Table 1 is TiN, with a size of 20nm~90nm. TEM characterization of IrO2@TiN powder shows that IrO2 is uniformly attached to the TiN surface ( Figure 3 ).

[0028] XRD characterization of the Ti plate after electrophoretic deposition ( Figure 4 ), we can see three strong peaks with diffraction angles of 40.151°, 53.101°, and 70.660°, which correspond to the (101), (102), and (103) crystal planes of the Ti matrix, respectively, while the diffraction angles of 36.662°, 42.596°, and 61.811° correspond to the (111), (200), and (220) crystal planes of TiN, respectively. It can be seen that a layer of TiN film was successfully deposited on the Ti substrate by electrophoretic deposition.

[0029] The substrate with IrO2@TiN coating was placed in 0.5 mol / L H2SO4+ 2 mg / LF − Electrochemical tests were carried out in the solution to evaluate its performance in the PEM water electrolysis anode environment. Figure 5 The potentiodynamic polarization comparison curves of Ti substrate with and without coating show that the sample after deposition treatment shows a higher corrosion potential (628.575 mV), the corrosion potential of Ti substrate is 507.718 mV, and the corrosion current density of Ti / IrO2@TiN is 0.727 μA / cm 2 , compared with 4.250μA / cm of Ti substrate 2 It has been reduced by an order of magnitude; Figure 6The curve of interface contact resistance after coating deposition with pressure, Ti / IrO2@TiN at a pressure of 143.6 N / cm 2 The contact resistance can reach 2.10 mΩ·cm 2 , which is 28% lower than that of the untreated Ti matrix.

[0030] Example 1: Changing the ratio of Al and Fe Example 1-1 First, aluminum powder (Al, purity> 99wt%, size 45μm), titanium powder (Ti, purity> 99.5wt%, size 25μm), boron nitride powder (BN, purity> 99.5wt%, size 0.5μm), the material ratio is Al:Ti:BN=30:53.4:16.6. The original powders are simply pre-mixed and evenly mixed in a ball mill, and pressed into a green body with a density of 75% of the theoretical density. The combustion synthesis reaction is carried out in a 2MPa nitrogen atmosphere, and the product is TiN powder with a particle size of 20~30nm.

[0031] Next, the precursor method is used to load iridium oxide (IrO2) on the TiN surface. The specific operation steps of the precursor method are as follows: add 20 mg TiN nanopowder to 15 mL pure water, disperse it evenly, and then add 1 mL of 20 mg Ir / mL of H2IrCl6·6H2O solution, after uniform stirring and dispersion, NaNO3 was added at a mass ratio of Ir:NaNO3=1:300, ultrasonic dispersion was performed, stirring at room temperature for 4 h, and then dried overnight at 60 °C in a blast drying oven. After taking out, it was ground in a mortar until it formed a uniform fine powder, transferred to a muffle furnace and calcined at 450 °C for 40 min at a heating rate of 3 °C / min. After calcination, the molten salt was taken out and dissolved with a large amount of deionized water, centrifuged and washed several times, and the precipitate was dispersed evenly with ethanol, dried at 60 °C in a vacuum drying oven for 3 h, and after cooling, ground and collected again to prepare the desired TiN powder carrying IrO2 catalyst (IrO2@TiN powder).

[0032] After iridium oxide (IrO2) was loaded on the TiN surface by the precursor method, it was deposited on the surface of the Ti-based bipolar plate for 100s by electrophoretic deposition to prepare a dense, uniform and continuous IrO2@TiN coating loaded with catalyst particles.

[0033] Example 1-2 The material ratio is Al:Fe:Ti:BN=20:10:53.4:16.6. The combustion product is TiN powder with a particle size of 70-90 nm. Others are the same as in Example 1-1.

[0034] Examples 1-3 The material ratio is Al:Fe:Ti:BN=10:20:53.4:16.6. The combustion product is TiN powder with a particle size of 50-70 nm. Others are the same as in Example 1-1 Examples 1-4 The material ratio is Fe:Ti:BN=30:53.4:16.6. The combustion product is TiN powder with a particle size of 30-40 nm. Others are the same as in Example 1-1.

[0035] Examples 1-5 The material ratio is Al:Ti:BN=40:45.8:14.2. The combustion product contains obvious molten Al balls, which cannot be used to load IrO2. Others are the same as in Example 1-1.

[0036] Examples 1-6 The material ratio is Fe:Ti:BN=40:45.8:14.2. The combustion product contains obvious molten Fe balls, which cannot be used to load IrO2. Others are the same as in Example 1-1.

[0037] Examples 1-7 The material ratio is Al:Fe:Ti:BN=10:10:61:19. The combustion product contains obvious unreacted Ti and BN, which cannot be used to load IrO2. Others are the same as in Example 1-1. It can be seen from Example 1 that TiN can be prepared by a combustion synthesis process using an Al-Fe-Ti-BN system, wherein Al and Fe are used as additives, and their mass and proportion account for 30% of the total mass of the raw materials. When the mass and proportion of the additives are less than 30%, Ti and BN cannot react fully, and unreacted Ti and BN will obviously exist in the product, and it cannot be used as a raw material for the TiN coating; when the mass and proportion of the additives are greater than 30%, the additives melt and aggregate at high temperatures, and there are a large number of obvious additive particles in the product, which cannot be used as a raw material for the TiN coating. Under the premise that the mass and proportion of the additives account for 30% of the total mass, the masses of Al and Fe can fluctuate within 0~30% respectively, and the products meet the requirements for preparing the coating. Example 2 Example 1-1 is based on the best example, and the electrophoretic deposition time is changed.

[0038] Example 1-1 The electrophoretic deposition time was 100 s to prepare a dense, uniform, and continuous IrO2@TiN coating loaded with catalyst particles at a pressure of 143.6 N / cm 2 The interface contact resistance is 2.53 mΩ·cm 2 Example 2-1 150s, a dense, uniform, and continuous IrO2@TiN coating with catalyst particles was prepared at a pressure of 143.6 N / cm 2 The interface contact resistance is 2.25 mΩ·cm 2 .

[0039] Example 2-2 200s, a dense, uniform, and continuous IrO2@TiN coating with catalyst particles was prepared at a pressure of 143.6 N / cm 2 The interface contact resistance is 2.18 mΩ·cm 2 .

[0040] Example 2-3 250s, a dense, uniform, and continuous IrO2@TiN coating with catalyst particles was prepared at a pressure of 143.6 N / cm 2 The interface contact resistance is 2.31 mΩ·cm 2 .

[0041] Example 2-4 300s, a dense, uniform, and continuous IrO2@TiN coating with catalyst particles was prepared at a pressure of 143.6 N / cm 2 The interface contact resistance is 2.56 mΩ·cm 2 .

[0042] Example 2-5 After 400s, fine cracks appeared on the surface of the prepared coating, and the dense requirement could not be met. 2 The interface contact resistance is 3.43 mΩ·cm 2 .

[0043] Example 2-6 90s, TiN particles on the substrate surface did not form a coating and could not completely cover the Ti substrate. 2 The interface contact resistance is 3.32 mΩ·cm 2 . It can be seen from Example 2 that, from the appearance of the coating, a dense, uniform, and continuous IrO2@TiN coating loaded with catalyst particles can be prepared when the electrophoretic deposition time is in the range of 100 to 300 seconds. When the time is less than 100 seconds, the amount of TiN particles deposited is small and cannot completely cover the Ti substrate; when the time is longer than 300 seconds, the deposited coating is too thick, and cracks are generated under the action of tensile stress in the coating, and even shedding may occur. From the perspective of contact resistance, the coating prepared with an electrophoretic deposition time in the range of 100 to 300 seconds has a contact resistance of 143.6 N / cm 2 The contact resistance is lower than that of Ti substrate (2.92 mΩ·cm). 2When the time is less than 100s, the surface of the Ti substrate is not completely covered with TiN, and the contact resistance increases significantly, reaching 3.32mΩ·cm 2 When the time is longer than 300s, the coating is incomplete and the contact resistance also increases significantly, reaching 3.43mΩ·cm 2 . Example 3 Based on Example 1-1, the molar ratio of BN / Ti was changed, Example 1-1 0.6.

[0044] Example 3-1: Al:Ti:BN=30:60:10. The product contains TiN with a particle size of 180~230nm.

[0045] Example 3-2: Al:Ti:BN=30:57:13, the product contains TiN with a particle size of 90~130nm.

[0046] Example 3-3: Al:Ti:BN=30:54:16 (0.57), the product contains TiN with a particle size of 60~90nm.

[0047] Example 3-4: Al:Ti:BN=30:53:17 (0.62), the product contains TiN with a particle size of 30~50nm.

[0048] Example 3-5: Al:Ti:BN=30:52:18 (0.67), the product contains TiN and unreacted BN. It can be seen from Example 3 that when the molar ratio of BN / Ti is 0.57-0.62, only TiN powder with a particle size of 20-90nm is included in the product, and when the molar ratio is 0.6, the particle size is the smallest and the product is optimal.

[0049] When the molar ratio of BN / Ti is 0.57-0.62, only TiN is present in the product, which can reduce the subsequent impurity removal steps. When the amount of Ti is excessive, the amount of TiN generated is determined by the amount of BN, which will cause a waste of raw materials and increase costs; at the same time, the reaction of titanium powder and nitrogen releases a large amount of heat, which will cause the titanium powder in the direction of the combustion wave to melt, increase the particle size of the product TiN, and cannot be used for coating preparation.

[0050] Example 4 Based on Example 1-1, the combustion synthesis atmosphere was changed. Example 1-1: A combustion synthesis reaction was carried out in a 2MPa nitrogen atmosphere, and the product contained only TiN.

[0051] Example 4-1: Combustion synthesis reaction was carried out in a 1MPa nitrogen atmosphere, and the product contained a small amount of TiB2 impurity phase in addition to TiN Example 4-2: A combustion synthesis reaction was carried out in a 0 MPa nitrogen atmosphere, and in addition to TiN, a TiB2 impurity phase was present in the product.

[0052] Example 4-3: Combustion synthesis reaction was carried out in a 2MPa helium atmosphere, but the reaction could not proceed.

[0053] Example 4-4: Combustion synthesis reaction was carried out in a 2MPa argon atmosphere, but the reaction could not proceed.

[0054] It can be seen from Example 4 that in the process of preparing TiN by combustion synthesis reaction of Ti and BN, other gases such as helium and argon cannot be used, and only nitrogen can be used. This is because compared with other simple protective gases, nitrogen will also react with titanium to generate a large amount of heat, providing the required high temperature environment for Ti and BN to start the reaction. At the same time, the reaction of Ti and BN requires high pressure, and the reaction cannot be fully carried out when the nitrogen pressure is too low. The pressure of 2MPa is obtained by experiment, not by calculation of chemical equations.

[0055] The technical solution of the present invention is explained through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above specific embodiments to be implemented. Any improvements made by technicians in the relevant field based on the present invention, or equivalent replacement of the materials selected by the present invention, etc., fall within the scope of protection of the patent.

Claims

1. A method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode, characterized in that: The method comprises the following steps: S1 uses Fe-Al-Ti-BN system to prepare nano-sized TiN powder through combustion synthesis process; S2 uses the precursor method to load iridium oxide on the surface of TiN powder to obtain IrO2@TiN powder carrying IrO2 catalyst; S3 uses electrophoretic deposition to load IrO2@TiN powder carrying IrO2 catalyst on the surface of Ti-based bipolar plates to prepare IrO2@TiN coating.

2. The method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode according to claim 1, characterized in that: In step S1, the raw materials used for the test include the following raw materials in terms of mass ratio: The mass ratio of aluminum powder, iron powder, titanium powder and boron nitride powder is (0-30): (0-30): (50-60): (15-20), preferably, Al:Fe:Ti:BN=10:20:53.4:16.

6.

3. The method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode according to claim 1, characterized in that: In the step S1, The purity of iron powder is >99wt%, and the size is 43-47μm; the purity of aluminum powder is >99wt%, and the size is 43-47μm; the purity of titanium powder is >99.5wt%, and the size is 20-30μm; the purity of boron nitride powder is >99.5wt%, and the size is 0.3-0.7μm.

4. The method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode according to claim 1, characterized in that: In the step S1, the molar ratio of BN / Ti remains unchanged and is always 0.57-0.62, preferably 0.6, while the content of iron powder and aluminum powder is adjustable.

5. The method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode according to claim 1, characterized in that: The specific operation of step S1 is that the raw material powders are premixed and then evenly mixed in a ball mill, pressed into a green body with a density of 60% to 80% of the theoretical density, and subjected to a combustion synthesis reaction to obtain nano-scale TiN powder.

6. The method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode according to claim 5, characterized in that: The combustion atmosphere in step S1 is 1-3 MPa nitrogen.

7. The method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode according to claim 1, characterized in that: The specific operation steps of the precursor method in step S2 are as follows: S2.1 Add TiN nanopowder into pure water at a liquid-solid ratio of (13-18): (18-25) (mL / mg), disperse evenly, add H2IrCl6·6H2O solution into pure water at a volume ratio of (13-18):1, the concentration of H2IrCl6·6H2O solution is 18-22 mgIr / mL, stir evenly and disperse, add NaNO3 at a mass ratio of Ir:NaNO3=1:(280-320), disperse by ultrasonic, stir for 3-5 h, and then dry; S2.2 After drying, grind in a mortar until a uniform fine powder is formed, transfer to a muffle furnace and calcine at 420-470 °C for 35-45 min at a heating rate of 2.5-3.5 °C / min; S2.3 After calcination is completed, take out the molten salt and dissolve it with a large amount of deionized water, wash it by centrifugation several times, take the precipitate and disperse it evenly with ethanol, dry it in a vacuum drying oven, and after cooling, grind it again and collect it to prepare the required IrO2@TiN powder carrying IrO2 catalyst.

8. The method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode according to claim 7, characterized in that: The specific operation steps of the precursor method in step S2 are as follows: S2.1 Add TiN nanopowder to pure water at a liquid-solid ratio of 15:20 (mL / mg), disperse evenly, add H2IrCl6·6H2O solution at a volume ratio of 15:1 in pure water, the concentration of H2IrCl6·6H2O solution is 20 mgIr / mL, stir and disperse evenly, add NaNO3 at a mass ratio of Ir:NaNO3=1:300, disperse by ultrasonic, stir for 3-5 h, and then dry in a forced air drying oven at 55-65°C; S2.2 After drying, grind in a mortar until a uniform fine powder is formed, transfer to a muffle furnace and calcine at 420-470 °C for 35-45 min at a heating rate of 2.5-3.5 °C / min; S2.3 After calcination is completed, take out the molten salt and dissolve it with a large amount of deionized water, wash it by centrifugation several times, take the precipitate and disperse it evenly with ethanol, dry it in a vacuum drying oven at 55-65 ℃ for 2.5-3.5 h, and after cooling, grind and collect it again to prepare the required IrO2@TiN powder carrying IrO2 catalyst.

9. The method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode according to claim 1, characterized in that: The specific operation steps of the electrophoretic deposition method in step S3 are as follows: S3.1 Place the titanium sheet in acetone, ethanol, and deionized water for ultrasonic cleaning in turn, then etch it in a solution of hydrofluoric acid, nitric acid, and water in a volume ratio of 1: (6-9): (8-12) for 8-12 s to remove the surface oxide layer, and then use deionized water for ultrasonic cleaning after acid etching; S3.2 Prepare a 6-14 g / L IrO2@TiN powder suspension obtained in step S2 with anhydrous ethanol as solvent, add PEI and stir with a magnetic stirrer at a speed of 100-200 rpm for 0.8-1.2 h, then ultrasonically oscillate at an ultrasonic power of 550-650 W for 8-12 min to break up the agglomerates, and the mass ratio of IrO2@TiN powder:PEI is = 1: (0.11-0.15) (wt%); S3.3 Use a constant voltage power supply to perform electrophoretic deposition for 90-300s, with graphite as the anode and the sample as the cathode. The electrode spacing is 13-17mm. The deposit is vacuum dried at 55-65℃ for 10-14h to obtain the IrO2@TiN coating.

10. The method for preparing a titanium nitride-based coating on the surface of a titanium-based bipolar plate for a PEM electrolyzer anode according to claim 9, characterized in that: The specific operation steps of the electrophoretic deposition method in step S3 are as follows: S3.1 Place the titanium sheet in acetone, ethanol, and deionized water for ultrasonic cleaning in sequence, then etch it in a solution of hydrofluoric acid, nitric acid, and water in a volume ratio of 1:8:10 for 10 s to remove the surface oxide layer, and then use deionized water for ultrasonic cleaning after acid etching; S3.2 Prepare a 10 g / L suspension of IrO2@TiN powder obtained in step S2 with anhydrous ethanol as solvent, add PEI and stir with a magnetic stirrer for 1 hour, then ultrasonically oscillate for 10 minutes to break up the agglomerates, the mass ratio of IrO2@TiN powder:PEI is =1:0.14 (wt%); S3.3 Use a constant voltage power supply at 5V for electrophoretic deposition for 90~300s, graphite as the anode, the sample as the cathode, the electrode spacing is 15 mm, and the deposit is vacuum dried at 60℃ for 12 h to obtain the IrO2@TiN coating.

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