High-entropy nitride coating fuel cell metal pole plate and preparation method thereof

Abstract

The invention discloses a high-entropy nitride coating fuel cell metal pole plate and a preparation method thereof. The preparation method comprises the following steps: pretreating a metal pole plate; sequentially depositing a transition layer and a high-entropy nitride layer on the pretreated metal polar plate by adopting a radio frequency magnetron sputtering method; the high-entropy nitride layer is composed of (AlTiVNbCr) AgN, the transition layer is composed of metal nitride, and metal elements in the metal nitride are composed of at least one and at most four of Al, Ti, V, Nb and Cr; according to the method, the transition layer and the high-entropy nitride layer are sequentially deposited on the metal pole plate under the corresponding deposition process conditions, the obtained transition layer and the obtained high-entropy nitride layer can form a compact equiaxed crystal structure, and therefore the migration path of Ag surface segregation is effectively prolonged, and Ag surface segregation is restrained.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cell metal plates, and in particular relates to a high entropy nitride coated fuel cell metal plate and a preparation method thereof. Background Art

[0002] Traditional PEMFC bipolar plates are mostly single-plate graphite plates with a thickness of 2mm, which is difficult to meet the technical update requirements of small volume and high energy density of automotive battery packs. Replacing the traditional 2mm thick graphite plates with metal plates with a thickness of less than 0.5mm is an effective way to achieve the reduction of size and weight of automotive fuel cells. However, since metal plates are easily passivated and corroded, corrosive ions can easily contaminate the membrane electrode and cause catalyst poisoning, which seriously affects the service life of proton exchange membrane fuel cells.

[0003] Nitride coatings such as TiN and CrN have attracted extensive attention from researchers due to their good electrical conductivity and excellent corrosion resistance. However, the contact resistance between the nitride coating prepared by physical vapor deposition techniques such as magnetron sputtering and the gas diffusion layer is high. Therefore, many studies are devoted to reducing the contact resistance between the coating and the gas diffusion layer. Among them, the addition of precious metal Ag to the coating can give full play to its advantages of stable chemical properties and not reacting with other substances in the coating to form new compounds. It is mainly dispersed in the coating in the form of nanocrystals, which significantly reduces the contact resistance between the coating and the gas diffusion layer. However, in the microstructure of the nitride coating with columnar crystals as the basic feature, Ag will undergo surface segregation, and the Ag particles that spontaneously migrate to the surface of the coating will react with the fluoride ions and sulfate ions in the acidic solution of the fuel cell and dissolve, resulting in a decrease in the corrosion resistance and contact resistance stability of the coating, which in turn seriously restricts the engineering application of Ag-doped nitride coatings.

[0004] The Chinese patent with publication number CN 114540752 A discloses that a pure titanium layer, a titanium nitride layer and a silver-doped titanium nitride layer with an equiaxed crystal structure are periodically deposited on a metal substrate in sequence by a magnetron sputtering method, so that there is no columnar interface that runs through the entire thickness of the coating in the conductive corrosion-resistant coating, thereby reducing the contact resistance of the coating. However, the method is complex and requires frequent control of the start and stop of the magnetron sputtering equipment, resulting in low deposition efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a high entropy nitride coated fuel cell metal plate and a preparation method thereof, wherein high entropy alloy is used to replace Ti, and continuous deposition can be performed to improve deposition efficiency.

[0006] The present invention adopts the following technical solution: a method for preparing a high entropy nitride coated fuel cell metal plate, comprising:

[0007] Pre-treating the metal plate;

[0008] A transition layer and a high entropy nitride layer are sequentially deposited on the pretreated metal plate by radio frequency magnetron sputtering; the high entropy nitride layer is composed of (AlTiVNbCr)AgN, the transition layer is composed of metal nitride, and the metal elements in the metal nitride are composed of at least one and at most four of Al, Ti, V, Nb, and Cr;

[0009] The process conditions for depositing the high entropy nitride layer are:

[0010] The gas pressure in the vacuum chamber is less than or equal to 1.0 Pa, high entropy alloy target and silver target are used as sputtering sources, argon and nitrogen are used as working gases, the high entropy alloy target power is 175-200 W, the maximum power of the Ag target is 2-15 W, the substrate bias is -250--100 V, and the substrate temperature is 300-450 ° C.

[0011] Preferably, the power of the Ag target is gradually increased during the deposition of the high entropy nitride layer.

[0012] Preferably, the process conditions for depositing the transition layer are:

[0013] The gas pressure in the vacuum chamber is less than or equal to 1.2 Pa, the metal target power is 150 to 200 W, the substrate bias voltage is -250 to -50 V, and the substrate temperature is 250 to 450°C.

[0014] Preferably, the flow rate of nitrogen is gradually increased during the deposition of the transition layer.

[0015] Preferably, the process conditions for depositing the high entropy nitride layer are:

[0016] The gas pressure in the vacuum chamber is 0.8 Pa, the power of the high entropy alloy target is 175 W, the maximum power of the Ag target is 2 W, the substrate bias is -250 V, and the temperature of the substrate is 300 °C.

[0017] Preferably, the process conditions for depositing the high entropy nitride layer are:

[0018] The gas pressure in the vacuum chamber is 0.9 Pa, the power of the high entropy alloy target is 180 W, the maximum power of the Ag target is 5 W, the substrate bias is -200 V, and the temperature of the substrate is 350 °C.

[0019] Another technical solution of the present invention: a high entropy nitride coated fuel cell metal plate, prepared based on the above preparation method;

[0020] Both the transition layer and the high entropy nitride layer have dense equiaxed crystal structures.

[0021] Preferably, the thickness of the metal electrode plate is less than or equal to 0.5 mm, and the sum of the thickness of the transition layer and the high entropy nitride layer is 1 to 3 μm.

[0022] Preferably, the nitrogen content in the transition layer gradually increases along a first direction, and the first direction is from the metal plate to the high entropy nitride layer;

[0023] The content of silver element in the high entropy nitride layer gradually increases along the first direction.

[0024] Preferably, the atomic percentages of each element in (AlTiVNbCr)AgN are as follows: Al 10at.%~15at.%, Ti 10at.%~12at.%, V 5at.%~8at.%, Nb 5at.%~8at.%, Cr 8at.%~12at.%, Ag 2at.%~15at.%, N 45at.%~60at.%.

[0025] The beneficial effect of the present invention is that the present invention deposits a transition layer and a high entropy nitride layer on a metal electrode in sequence under corresponding deposition process conditions, so that the obtained transition layer and high entropy nitride layer can form a dense equiaxed crystal structure, thereby effectively extending the migration path of Ag surface segregation and inhibiting Ag surface segregation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of the metal plate prepared in Example 1 of the present invention;

[0027] Figure 2 This is a scanning electron microscope image of a metal plate prepared in the comparative example of Example 1 of the present invention;

[0028] Figure 3 Schematic diagram of the potentiodynamic polarization curve of the metal electrode prepared in Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Since metal plates are an effective way to reduce the weight of fuel cells, it is necessary to solve the problem that metal plates are easily passivated and corroded. The present invention provides a conductive corrosion-resistant coating, which can prevent the passivation and corrosion of metal plates, thereby providing a new technical path for reducing the weight of automotive fuel cells.

[0031] High entropy nitride coatings have attracted extensive attention from researchers due to their excellent corrosion resistance, but their contact resistance is relatively high due to their high mixing entropy effect. The addition of metallic silver can effectively reduce the contact resistance of nitride coatings, but the spontaneous escape behavior of silver limits the application of this method of reducing the contact resistance of coatings by silver doping.

[0032] Therefore, studying the method of inhibiting the spontaneous escape of silver in silver-doped high-entropy nitride coatings has important scientific significance and engineering value for the metallization of fuel cell plates, and provides a theoretical basis and experimental support for the subsequent development of fuel cell metal plates.

[0033] The invention discloses a method for preparing a metal plate of a high entropy nitride coating fuel cell, comprising: pre-treating the metal plate; sequentially depositing a transition layer and a high entropy nitride layer on the pre-treated metal plate by radio frequency magnetron sputtering; the high entropy nitride layer is composed of (AlTiVNbCr)AgN, the transition layer is composed of metal nitride, and the metal elements in the metal nitride are composed of at least one and at most four of Al, Ti, V, Nb, and Cr; the process conditions for depositing the high entropy nitride layer are: the pressure in the vacuum chamber is less than or equal to 1.0 Pa, a high entropy alloy target and a silver target are used as sputtering sources, argon and nitrogen are used as working gases, the power of the high entropy alloy target is 175 to 200 W, the maximum power of the Ag target is 2 to 15 W, the substrate bias is -250 to -100 V, and the temperature of the substrate is 300 to 450° C. Preferably, the power of the Ag target gradually increases during the deposition of the high entropy nitride layer.

[0034] The present invention deposits a transition layer and a high entropy nitride layer on a metal electrode in sequence under corresponding deposition process conditions, so that the obtained transition layer and high entropy nitride layer can form a dense equiaxed crystal structure, thereby effectively extending the migration path of Ag surface segregation and inhibiting Ag surface segregation.

[0035] Target power, substrate bias, substrate temperature and working gas pressure are key process parameters that affect the microstructure of the coating. By adjusting the target power, the thickness and density of the film can be controlled, defects can be reduced, and the uniformity and surface quality of the film can be improved. The substrate bias affects the bombardment of the substrate surface by positive ions, which helps to improve the crystallinity of the film and reduce interface defects. The increase in substrate temperature helps the migration and diffusion of sputtered atoms on the substrate surface, which is conducive to the formation of a continuous and dense film; the substrate temperature can also affect the grain size, phase composition and microstructure of the film. The working gas pressure affects the glow discharge in the vacuum chamber and the motion trajectory of the sputtered atoms. By adjusting the gas pressure, the sputtering process can be optimized, and the sputtering efficiency and film quality can be improved.

[0036] Therefore, the present invention mainly regulates the microstructure of the high entropy nitride coating by regulating the four process parameters of target power, substrate bias, substrate temperature and working gas pressure. Among them, the change of Ag target power is mainly for regulating the contact resistance of the coating.

[0037] In the present invention, pretreatment refers to the degreasing and decontamination of the metal plate. Specifically, the metal plate is first degreased by placing the metal plate in a solution containing a degreasing agent and ultrasonically degreasing the plate for 5 to 10 minutes; the degreased metal plate is ultrasonically cleaned in deionized water for 2 to 3 times, each cleaning time is 3 to 5 minutes; the ultrasonically cleaned metal plate is ultrasonically cleaned in anhydrous ethanol for 2 to 3 times, each cleaning time is 3 to 5 minutes.

[0038] Plasma cleaning of the metal substrate under vacuum conditions includes: the air pressure in the vacuum chamber is 0.5 Pa, the bias voltage of the metal substrate (ie, the pretreated metal plate) is -400 V, the temperature of the metal substrate is 100° C., and the cleaning time is 10 to 20 minutes.

[0039] Metal plate pretreatment can remove impurities such as oil, rust, and scale on the substrate surface, so that the substrate surface reaches a certain degree of cleanliness and roughness, providing a good foundation for subsequent coating processing. This helps the coating to better adhere to the substrate surface and improves the uniformity and density of the coating.

[0040] In one embodiment, the process conditions for depositing the transition layer are: the pressure in the vacuum chamber is less than or equal to 1.2 Pa, the power of the metal target is 150 to 200 W, the substrate bias is -250 to -50 V, and the temperature of the substrate (i.e., the metal plate after plasma cleaning) is 250 to 450° C. The metal target can be a single metal target or an alloy metal target, which can be selected according to actual experimental conditions. The deposition time is preferably 5 to 20 minutes to ensure that the thickness of the transition layer meets the technical requirements. Moreover, the flow rate of nitrogen gradually increases during the deposition of the transition layer.

[0041] The transition layer can reduce the sudden change of physical properties between the coating and the substrate, ease stress concentration, and reduce the internal stress caused by lattice mismatch and thermal expansion coefficient difference. This helps to maintain a stable bond between the coating and the substrate and prevent the coating from falling off or cracking during use.

[0042] The presence of the transition layer can also significantly improve the stability and durability of the coating. It not only prevents the coating from being eroded and damaged by the external environment during use, but also allows it to withstand certain mechanical and thermal stresses without being damaged or falling off. This enables the coating to maintain its excellent performance and service life under more severe working conditions.

[0043] The nitrogen flow rate gradually increases during the deposition of the transition layer mainly to achieve a gradient transition between the nitride components. Through the gradient transition of the components, a continuously changing transition layer can be formed between different materials, making the combination of the two materials closer, thereby improving the bonding strength of the overall structure. This gradual transition layer can reduce the stress concentration caused by sudden changes in material properties and avoid cracks or peeling at the bonding interface.

[0044] In the embodiment of the present invention, the distance between the metal substrate and the target material is 60-65 mm.

[0045] Embodiment 1:

[0046] This embodiment uses a 0.5 mm thick stainless steel plate as the metal substrate (ie, the metal plate), and the specific preparation method is as follows:

[0047] (1) Pretreatment of metal substrate: Place the stainless steel electrode plate in a solution containing a degreasing agent and perform ultrasonic degreasing for 5 minutes; then ultrasonically clean the degreased stainless steel electrode plate twice in deionized water for 3 minutes each time, and then ultrasonically clean it twice in anhydrous ethanol for 3 minutes each time, and blow dry it for later use. The cleaned stainless steel electrode plate is placed in a vacuum chamber with a target-substrate distance of 60 mm. Vacuum to 3×10 -3 After 30 sccm of argon gas was introduced to maintain the pressure in the vacuum chamber at about 0.5 Pa, and plasma cleaning was carried out for 10 min under the conditions of -400 V bias voltage of the stainless steel electrode and 100°C.

[0048] (2) Preparation of transition layer: AlTi target power is 150 W, stainless steel plate bias is -250 V, temperature is 250 °C, deposition time is 5 min, argon and nitrogen are continuously passed during deposition, and the flow rate of nitrogen is continuously increased to ensure that the air pressure in the vacuum chamber is 1.0 Pa. The workpiece holder speed during the preparation process is 5 r / min.

[0049] (3) Preparation of high entropy nitride layer: The AlTiVNbCr target power was maintained at 175 W, the Ag target power was gradually increased from 0 W to 2 W within 2 minutes (maintained at 2 W after 2 minutes), the stainless steel electrode (referring to the metal electrode after the transition layer is deposited) was biased at -250 V, the temperature was 300 °C, the air pressure in the vacuum chamber was 0.8 Pa, the workpiece holder rotation speed was 5 r / min, and the deposition time was 120 min.

[0050] In this embodiment, the thickness of the conductive corrosion-resistant coating (a general term for the transition layer and the high entropy nitride layer) is measured to be 1.2 μm, and the surface contact resistance of the fuel cell metal plate is 3.5 mΩ·cm 2 , the corrosion current density is 0.28μA·cm -2 .

[0051] Embodiment 2:

[0052] In this embodiment, the metal substrate is a 0.5 mm thick stainless steel plate. The specific preparation method is as follows:

[0053] (1) Sample pretreatment: Place the stainless steel plate in a solution containing a degreasing agent and perform ultrasonic degreasing for 10 minutes; then ultrasonically clean the degreased stainless steel plate twice in deionized water, each time for 5 minutes, and then ultrasonically clean it twice in anhydrous ethanol, each time for 5 minutes, and blow dry for later use. The cleaned stainless steel plate is placed in a vacuum chamber with a target-substrate distance of 62 mm. Vacuum to 3×10 -3 After 30 0.05 Pa, 20 sccm of argon gas was introduced to maintain the pressure in the vacuum chamber at about 0.5 Pa, and then plasma cleaning was carried out for 15 min under the conditions of -400 V bias voltage of the stainless steel electrode and 100 °C temperature.

[0054] (2) Preparation of transition layer: TiAlCr target power is 175 W, stainless steel plate bias is -200 V, temperature is 300 °C, deposition time is 15 min, argon and nitrogen are continuously passed during the deposition process, and the flow rate of nitrogen is gradually increased to ensure that the air pressure in the vacuum chamber is 0.9 Pa. The workpiece holder speed during the preparation process is 5 r / min.

[0055] (3) Preparation of high entropy nitride layer: The AlTiVNbCr target power was maintained at 180 W, the Ag target power was increased from 0 W to 5 W within 5 min (maintained at 5 W after 5 min), the stainless steel plate bias was -200 V, the temperature was 350 °C, the vacuum chamber pressure was 0.9 Pa, the workpiece holder rotation speed was 5 r / min, and the deposition time was 160 min.

[0056] The thickness of the conductive corrosion-resistant coating in this embodiment is measured to be 2 μm, and the surface contact resistance of the fuel cell metal plate is 3.4 mΩ·cm. 2 , the corrosion current density is 0.66μA·cm -2 .

[0057] Embodiment 3:

[0058] In this embodiment, the metal substrate is a 0.5 mm stainless steel plate. The specific preparation method is as follows:

[0059] (1) Sample pretreatment: Place the stainless steel plate in a solution containing a degreasing agent and perform ultrasonic degreasing for 10 minutes; then ultrasonically clean the degreased stainless steel plate in deionized water for 3 times, each time for 5 minutes, and then ultrasonically clean it in anhydrous ethanol for 3 times, each time for 5 minutes, and blow dry for later use. The cleaned stainless steel plate is placed in a vacuum chamber with a target-substrate distance of 65 mm. Vacuum to 3×10 -3 After 30 0.05 Pa, 20 sccm of argon gas was introduced to maintain the pressure in the vacuum chamber at about 0.5 Pa, and then plasma cleaning was carried out for 20 min under the conditions of -400 V bias voltage of the stainless steel electrode and 100 °C.

[0060] (2) Preparation of transition layer: Cr target power is 200 W, stainless steel plate bias is -50 V, temperature is 450 °C, deposition time is 20 min, argon and nitrogen are continuously passed during the deposition process, and the flow rate of nitrogen is continuously increased to ensure that the air pressure in the vacuum chamber is 1.2 Pa. The workpiece holder speed during the preparation process is 5 r / min.

[0061] (3) Preparation of high entropy nitride layer: The AlTiVNbCr target power was maintained at 200 W, the Ag target power was gradually increased from 0 W to 15 W within 15 minutes (maintained at 15 W after 15 minutes), the stainless steel plate bias was -100 V, the temperature was 450 °C, the air pressure in the vacuum chamber was 1.0 Pa, and the deposition time was 180 minutes.

[0062] The thickness of the conductive corrosion-resistant coating in this embodiment is measured to be 3 μm, and the surface contact resistance of the fuel cell metal plate is 2.8 mΩ·cm. 2 , the corrosion current density is 4.9μA·cm -2 .

[0063] Embodiment 4:

[0064] In this embodiment, the metal substrate is a 0.5 mm thick stainless steel plate. The specific preparation method is as follows:

[0065] (1) Sample pretreatment: Place the stainless steel plate in a solution containing a degreasing agent and perform ultrasonic degreasing for 8 minutes; then ultrasonically clean the degreased stainless steel plate in deionized water for 3 times, each time for 4 minutes, and then ultrasonically clean it in anhydrous ethanol for 3 times, each time for 4 minutes, and blow dry for later use. Place the cleaned metal plate in a vacuum chamber with a target-substrate distance of 60 mm. Vacuum to 3×10 -3 After 30 0.05 Pa, 20 sccm of argon gas was introduced to maintain the pressure in the vacuum chamber at about 0.5 Pa, and then plasma cleaning was carried out for 15 min under the conditions of -400 V bias voltage of the stainless steel electrode and 100 °C temperature.

[0066] (2) Preparation of transition layer: AlTiNbCr target power is 200 W, stainless steel plate bias is -200 V, temperature is 300 °C, deposition time is 15 min, argon and nitrogen are continuously passed during the deposition process, and the flow rate of nitrogen is gradually increased to ensure that the pressure in the vacuum chamber is 1.2 Pa. The workpiece holder speed during the preparation process is 5 r / min.

[0067] (3) Preparation of high entropy nitride layer: The target power of AlTiVNbCr was maintained at 200 W, the target power of Ag was increased from 0 W to 10 W within 10 min (maintained at 10 W after 10 min), the bias voltage of the stainless steel electrode was -200 V, the temperature was 450 °C, the pressure in the vacuum chamber was 1.0 Pa, the workpiece holder speed was 5 r / min, and the deposition time was 180 min.

[0068] The thickness of the conductive corrosion-resistant coating in this embodiment is measured to be 1.7 μm, and the surface contact resistance of the fuel cell metal plate is 2.6 mΩ·cm. 2 , the corrosion current density is 6.77μA·cm -2 .

[0069] Example 1 Comparative Example:

[0070] This embodiment uses a 0.5 mm thick stainless steel plate as the metal substrate, and the specific preparation method is as follows:

[0071] (1) Pretreatment of metal substrate: Place the stainless steel electrode plate in a solution containing a degreasing agent and perform ultrasonic degreasing for 5 minutes; then ultrasonically clean the degreased stainless steel electrode plate twice in deionized water for 3 minutes each time, and then ultrasonically clean it twice in anhydrous ethanol for 3 minutes each time, and blow dry it for later use. The cleaned stainless steel electrode plate is placed in a vacuum chamber with a target-substrate distance of 60 mm. Vacuum to 3×10 -3 After 30 sccm of argon gas was introduced to maintain the pressure in the vacuum chamber at about 0.5 Pa, and plasma cleaning was carried out for 10 min under the conditions of -400 V bias voltage of the stainless steel electrode and 100°C.

[0072] (2) Preparation of transition layer: AlTi target power is 150 W, stainless steel plate bias is -250 V, temperature is 250 °C, deposition time is 5 min, argon and nitrogen are continuously passed during deposition, and the flow rate of nitrogen is continuously increased to ensure that the air pressure in the vacuum chamber is 1.0 Pa. The workpiece holder speed during the preparation process is 5 r / min.

[0073] (3) Preparation of high entropy nitride layer: The AlTiNbCr target power was maintained at 175 W, the Ag target power was gradually increased from 0 W to 2 W within 2 min (maintained at 2 W after 2 min), the stainless steel plate bias was -250 V, the temperature was 300 °C, the vacuum chamber pressure was 0.8 Pa, the workpiece holder rotation speed was 5 r / min, and the deposition time was 120 min.

[0074] In this embodiment, the thickness of the conductive corrosion-resistant coating is measured to be 1.5 μm, and the surface contact resistance of the fuel cell metal plate is 10.4 mΩ·cm. 2 , the corrosion current density is 6.7μA·cm -2 .

[0075] The present invention adopts a radio frequency sputtering method to prepare an equiaxed crystal structure conductive corrosion-resistant coating, avoids the formation of a columnar crystal interface throughout the entire coating thickness, effectively blocks the corrosive medium in the fuel cell environment from reaching the metal plate surface, and the corrosion current density can be reduced to 1μA·cm -2 In addition, due to the high amount of Ag doped in Examples 3 and 4, the corrosion resistance of the coating is slightly reduced, that is, the corrosion current density is slightly increased. At the same time, the present invention can inhibit the spontaneous escape of silver in the silver-doped high-entropy nitride coating, and the contact resistance is less than 10mΩ·cm at a contact pressure of 1.5MPa. -2 .

[0076] The coating has both electrical conductivity and corrosion resistance, can extend the service life of the metal plate of the fuel cell, has a simple preparation method, and has good electrical conductivity and corrosion resistance effects.

[0077] like Figure 1 As shown, it is an electron microscope image of the fuel cell metal plate prepared in Example 1. It can be seen that the fuel cell metal transition layer and the silver-doped high entropy nitride layer prepared in this example are both equiaxed crystal structures, there is no columnar interface running through the entire coating thickness, and the silver in the silver-doped high entropy nitride coating is evenly distributed at the cluster interface of the coating, which effectively prolongs the path of the spontaneous escape of silver in the silver-doped high entropy nitride coating, thereby effectively inhibiting the spontaneous escape of silver in the silver-doped high entropy nitride coating.

[0078] During the deposition of the transition layer, the coating grows in the form of layer islands. In the early stage of growth, the coating grains are small. As the deposition time increases, the coating nucleates in the form of islands and grows into coarse columnar crystals. In this embodiment, due to the short deposition time, coarse columnar crystals have not yet grown, so the transition layer grown is also an equiaxed crystal structure.

[0079] It can be seen from this that after adding the V element to the selected high entropy alloy target, the high entropy nitride layer can be adjusted in combination with the process to form a dense equiaxed crystal structure, thereby achieving the purpose of the invention.

[0080] Figure 2 This is the metal plate prepared in the comparative example of Example 1. It can be seen from the electron microscope image that the silver-doped high-entropy nitride layer on the surface of the fuel cell metal plate prepared in this example is a columnar crystal structure, and there is a columnar interface running through the entire thickness of the coating. The silver in the silver-doped high-entropy nitride coating is mainly distributed in the columnar interface of the coating, which provides a path for the spontaneous escape of silver in the silver-doped high-entropy nitride coating, allowing silver to easily escape spontaneously to the surface of the coating.

[0081] Figure 3The polarization curves of the prepared fuel cell metal plates include Examples 1-4. It can be seen from the polarization curves that the corrosion current density of Example 1 (the light red curve in the figure, the target power of silver is 2W) and Example 2 (the light yellow curve in the figure, the target power of silver is 5W) is less than 1μA·cm -2 , the corrosion resistance is good. With the increase of silver doping, the corrosion current density gradually increases. This is due to excessive silver doping. Excessive silver doping causes the silver in the high entropy nitride layer to connect into nano silver wires, which become corrosion channels.

[0082] The present invention also discloses a high entropy nitride coated fuel cell metal plate, which is prepared based on the above preparation method; the transition layer and the high entropy nitride layer are both dense equiaxed crystal structures.

[0083] Preferably, the thickness of the metal plate is less than or equal to 0.5 mm, and the sum of the thickness of the transition layer and the high entropy nitride layer is 1 to 3 μm. The nitrogen content in the transition layer gradually increases along a first direction, and the first direction is from the metal plate to the high entropy nitride layer; the silver content in the high entropy nitride layer gradually increases along the first direction.

[0084] It can be seen from this that the components of the conductive corrosion-resistant coating change continuously from the transition layer to the surface of the high-entropy nitride layer, and the fuel cell metal plate with the conductive corrosion-resistant coating has both conductivity and corrosion resistance, and has the characteristics of low contact resistance, corrosion resistance, and good process stability.

[0085] In one embodiment, the atomic percentage of each element in (AlTiVNbCr)AgN is as follows: Al 10at.%~15at.%, Ti 10at.%~12at.%, V 5at.%~8at.%, Nb 5at.%~8at.%, Cr 8at.%~12at.%, Ag 2at.%~15at.%, N 45at.%~60at.%.

[0086] Al, Cr, Ti, and Nb elements have good corrosion resistance and oxidation resistance, and Nb element is a refractory metal element with excellent high temperature performance, which can prevent the metal plate from corrosion and oxidation in the service environment. The V element has the effect of refining the grains, and can be combined with process adjustment to form a dense equiaxed crystal structure in the high entropy nitride layer, thereby achieving the purpose of the invention. The Ag element is an element with the best conductivity and the lowest contact resistance. Adding precious metal Ag to the coating can give play to its advantages of stable chemical properties and not reacting with other substances in the coating to form new compounds. It is mainly dispersed in the coating in the form of nanocrystals, which significantly reduces the contact resistance between the coating and the gas diffusion layer. The introduction of the N element can form metal nitrides. Compared with single metal elements, nitride elements have more excellent corrosion resistance.

[0087] The combination of different metal elements and the difference in the number of components will affect the thermal expansion coefficient and thermal conductivity of the metal nitride layer. Therefore, the bonding force between the metal plate and the high entropy nitride coating is improved by regulating the combination of different metal elements and the number of components.

Claims

1. A method for preparing a high entropy nitride coated fuel cell metal plate, It is characterized in that include: Pre-treating the metal plate; A transition layer and a high entropy nitride layer are sequentially deposited on the pretreated metal plate by using a radio frequency magnetron sputtering method; The high entropy nitride layer is composed of (AlTiVNbCr)AgN, the transition layer is composed of metal nitride, and the metal elements in the metal nitride are composed of at least one and at most four of Al, Ti, V, Nb, and Cr; The process conditions for depositing the high entropy nitride layer are: The gas pressure in the vacuum chamber is less than or equal to 1.0 Pa, high entropy alloy target and silver target are used as sputtering sources, argon and nitrogen are used as working gases, the high entropy alloy target power is 175-200 W, the maximum power of the Ag target is 2-15 W, the substrate bias is -250--100 V, and the substrate temperature is 300-450 ° C.

2. A method for preparing a high entropy nitride coated fuel cell metal plate as claimed in claim 1, It is characterized in that The power of the Ag target gradually increases during the deposition of the high entropy nitride layer.

3. A method for preparing a high entropy nitride coated fuel cell metal plate as claimed in claim 2, It is characterized in that The process conditions for depositing the transition layer are: The gas pressure in the vacuum chamber is less than or equal to 1.2 Pa, the metal target power is 150 to 200 W, the substrate bias voltage is -250 to -50 V, and the substrate temperature is 250 to 450°C.

4. A method for preparing a high entropy nitride coated fuel cell metal plate as claimed in claim 3, It is characterized in that The flow rate of nitrogen is gradually increased during the deposition of the transition layer.

5. A method for preparing a high entropy nitride coated fuel cell metal plate as claimed in claim 2, It is characterized in that The process conditions for depositing the high entropy nitride layer are: The gas pressure in the vacuum chamber is 0.8 Pa, the power of the high entropy alloy target is 175 W, the maximum power of the Ag target is 2 W, the substrate bias is -250 V, and the temperature of the substrate is 300 °C.

6. A method for preparing a high entropy nitride coated fuel cell metal plate as claimed in claim 2, It is characterized in that The process conditions for depositing the high entropy nitride layer are: The gas pressure in the vacuum chamber is 0.9 Pa, the power of the high entropy alloy target is 180 W, the maximum power of the Ag target is 5 W, the substrate bias is -200 V, and the temperature of the substrate is 350 °C.

7. A high entropy nitride coated fuel cell metal plate, It is characterized in that Prepared based on the preparation method according to any one of claims 1 to 6; The transition layer and the high entropy nitride layer both have a dense equiaxed crystal structure.

8. A high entropy nitride coated fuel cell metal plate as claimed in claim 7, It is characterized in that The thickness of the metal plate is less than or equal to 0.5 mm, and the sum of the thickness of the transition layer and the high entropy nitride layer is 1 to 3 μm.

9. A high entropy nitride coated fuel cell metal plate as claimed in claim 7, It is characterized in that The nitrogen content in the transition layer gradually increases along a first direction, and the first direction is from the metal plate to the high entropy nitride layer; The silver content in the high entropy nitride layer gradually increases along the first direction.

10. A high entropy nitride coated fuel cell metal plate as claimed in claim 7, It is characterized in that The atomic percentages of each element in the (AlTiVNbCr)AgN are as follows: Al 10at.%~15at.%, Ti 10at.%~12at.%, V 5at.%~8at.%, Nb 5at.%~8at.%, Cr 8at.%~12at.%, Ag 2at.%~15at.%, and N45at.%~60at.%.

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