A transition metal compound composite coating and a method for preparing and using the same

Abstract

The application belongs to the technical field of surface engineering protection, and discloses a transition metal compound composite coating, a preparation method and application thereof; wherein the transition metal compound composite coating is a composite multilayer structure, and comprises n same periodic structures deposited in sequence, and n is greater than or equal to 2; wherein each periodic structure comprises a titanium nitride coating and a niobium nitride coating. The application specifically discloses a high-conductivity strong-corrosion-resistance transition metal compound composite coating, and can solve the technical problems of high cost, high corrosion current density, low corrosion overpotential and poor conductivity in the prior art.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of surface engineering protection, and particularly relates to a transition metal compound composite coating and a preparation method and application thereof. BACKGROUND

[0002] The development of hydrogen energy is expected to solve the two serious problems of global energy depletion and environmental pollution, and can help achieve the low-carbon target, and has broad prospects in the fields of transportation, construction, energy storage, industry, etc.

[0003] Proton exchange membrane water electrolyzer (PEMWE) is a high-quality batch hydrogen production potential equipment favored by today's society, which has the advantages of high current density, safe and reliable operation under high pressure, fast start-up speed, low operating temperature and environmental friendliness, etc.

[0004] As a key component of PEMWE, bipolar plates not only play a role in collecting current, separating oxidizing agent and reducing agent, mechanical support, and uniform delivery of reaction medium, but also occupy most of the volume and cost (example explanatory, about 70% of the total mass and 30% of the price). The working environment of PEMWE is often acidic and high-temperature humid environment, so the plate must have high mechanical strength, high corrosion resistance, low interfacial contact resistance, lightweight, effective manufacturability and other properties. At present, according to the different preparation materials, the bipolar plate is mainly divided into three types of metal bipolar plate, graphite bipolar plate and composite bipolar plate; among them, dense graphite can meet most of the requirements of bipolar plates, but there are challenges in toughness, high potential corrosion and manufacturability; composite bipolar plates have advantages in effective manufacturability, but still have the problem of poor electronic conductivity; the mechanical and physical properties of metal bipolar plates are relatively superior, and the cost is more competitive compared with non-porous graphite and composite materials, so it has become the first choice for commercial bipolar plates.

[0005] In the working environment of PEMWE, under the corrosion action of strong acid medium, on the one hand, the surface of the metal bipolar plate will be passivated, increasing the interfacial contact resistance between the bipolar plate and the gas diffusion layer, and reducing the conductivity; on the other hand, when the passivation film is broken and the metal bipolar plate is corroded, metal ions that may poison the catalyst and the proton exchange membrane will be released, both of which will reduce the output power and service life of PEMME. At present, scholars at home and abroad have done a lot of research work in this field, and surface coating is the most commonly used modification method; among them, in order to have high conductivity and high corrosion resistance, the noble metal loading range of domestic and foreign coatings is still 1-3 mgcm -2 , which is relatively high in cost. SUMMARY

[0006] The present application aims to provide a transition metal compound composite coating, a preparation method and application thereof, so as to solve one or more technical problems existing in the prior art. The present application specifically discloses a high-conductivity and high-corrosion-resistance transition metal compound composite coating, which can solve the technical problems of high cost, high corrosion current density, low corrosion overpotential and poor conductivity in the prior art.

[0007] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0008] The present application provides a transition metal compound composite coating, which is a composite multilayer structure and comprises n same periodic structures deposited in sequence, n≥2.

[0009] Each periodic structure comprises a titanium nitride coating and a niobium nitride coating.

[0010] The present application is further improved in that,

[0011] The value of n ranges from 2 to 8.

[0012] The present application is further improved in that,

[0013] The transition metal compound composite coating is deposited on the surface of a metal bipolar plate.

[0014] In each periodic structure, the titanium nitride coating is relatively close to the metal bipolar plate, and the niobium nitride coating is relatively far away from the metal bipolar plate.

[0015] The present application is further improved in that,

[0016] The titanium nitride in the titanium nitride coating is in a face-centered cubic phase, and the niobium nitride in the niobium nitride coating is in a hexagonal close-packed phase.

[0017] The present application is further improved in that,

[0018] In each periodic structure, the preferred crystal face orientation of the single-layer titanium nitride coating is (200), and the thickness is 25nm-35nm.

[0019] In each periodic structure, the preferred crystal face orientation of the single-layer niobium nitride coating is (101) and (102), and the thickness is 10nm-20nm.

[0020] The present application is further improved in that,

[0021] Under a working voltage of 2.0V, the corrosion current density of the transition metal compound composite coating is less than 1×10 - 7 A cm -2 ;

[0022] The interface contact resistance of the transition metal compound composite coating is less than 8 mΩcm 2 .

[0023] The application provides a preparation method of a transition metal compound composite coating.

[0024] Based on the metal bipolar plate after polishing and cleaning pretreatment, a transition metal compound composite coating is prepared by a pulse laser deposition process.

[0025] The pulse laser deposition process is adopted, a TiN target with a purity of 99.9 % is used as target material, and a titanium nitride coating is formed on the surface of the metal bipolar plate.

[0026] Based on the transition metal compound composite coating with one period structure, the pulse laser deposition process is further adopted, a TiN target and a NbN target with a purity of 99.9 % are used as target material, and a titanium nitride coating and a niobium nitride coating are alternately formed, so that a transition metal compound composite coating with n period structures is prepared.

[0027] The application is further improved, and the step of adopting the pulse laser deposition process, using a TiN target with a purity of 99.9 % as target material, and forming a titanium nitride coating on the surface of the metal bipolar plate comprises the following steps.

[0028] The metal bipolar plate is placed in a reaction cavity, the vacuum degree of the reaction cavity is less than 2*10 -4 Pa, a TiN target with a purity of 99.9 % is used as target material, and a titanium nitride coating is formed on the surface of the metal bipolar plate by using nitrogen as working gas.

[0029] The pulse laser deposition process adopts a pulse frequency of 6 Hz-10 Hz, an energy of 350 mJ-450 mJ, the gas pressure of the reaction cavity is 2 Pa-4 Pa, the deposition temperature is 400 DEG C-600 DEG C, and the deposition time is 300 s-650 s.

[0030] The application is further improved, and the step of adopting the pulse laser deposition process, using a NbN target with a purity of 99.9 % as target material, and forming a niobium nitride coating on the surface of the titanium nitride coating comprises the following steps.

[0031] The metal bipolar plate with the titanium nitride coating is placed in a reaction cavity, the vacuum degree of the reaction cavity is less than 2*10 -4 Pa, a NbN target with a purity of 99.9 % is used as target material, and a niobium nitride coating is formed on the surface of the titanium nitride coating by using nitrogen as working gas.

[0032] The pulse laser deposition process adopts a pulse frequency of 6Hz-10Hz, an energy of 350mJ-450mJ, a reaction cavity gas pressure of 2Pa-4Pa, a deposition temperature of 400 DEG C-600 DEG C, and a deposition time of 300s-650s.

[0033] The metal bipolar plate is used for a proton exchange membrane fuel cell or a proton exchange membrane water electrolyzer.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] The transition metal compound composite coating can be deposited on the surface of the metal bipolar plate, and is composed of a titanium nitride coating and a niobium nitride coating deposited in sequence to form a composite multilayer structure, thereby improving the compactness of the coating.

[0036] In the preparation method, the transition metal compound composite coating with high conductivity and high corrosion resistance is prepared by the pulse laser deposition process, and the uniformity of the phases of each layer is ensured by the pulse laser deposition process and the multilayer design of the periodic composite structure, and the porosity defects in each layer are effectively dislocated, thereby improving the compactness of the coating. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows; obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0038] Figure 1 is a schematic diagram of the transition metal compound composite coating in the embodiment of the present application, taking n=2 as an example;

[0039] Figure 2 is a schematic diagram of the SEM surface test result in embodiment 1 of the present application;

[0040] Figure 3 is a schematic diagram of the SEM cross-section test result in embodiment 1 of the present application;

[0041] Figure 4 is a schematic diagram of the XRD test result in embodiment 1 of the present application;

[0042] Figure 5 is a schematic diagram of the XPS test result in embodiment 1 of the present application;

[0043] Figure 6 is a comparative schematic diagram of the potentiodynamic scanning test results of embodiment 1, embodiment 2, comparative example 1 and comparative example 2 of the present application;

[0044] Figure 7 is a comparative schematic diagram of the contact resistance test results of embodiment 1, embodiment 2 and comparative example 1 of the present application. DETAILED DESCRIPTION

[0045] In order to make the objects, technical solutions and advantages of the present application more clear, the technical solutions in the present application will be described clearly and completely in the following with reference to the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. In addition, the terms "include" and "have" and any variations thereof are intended to cover the non-exclusive inclusion, for example, the process, method, system, product or equipment including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or equipment.

[0046] Please refer to Figure 1The transition metal compound composite coating provided by the embodiment of the present application has high conductivity and high corrosion resistance, and is a composite multilayer structure composed of n same periodic structures deposited in sequence, n≥2.

[0047] The transition metal compound composite coating provided by the embodiment of the present application is used for being deposited on the surface of a bipolar plate (explained as a metal substrate), and is composed of a titanium nitride coating and a niobium nitride coating deposited in sequence to form a composite multilayer structure, thereby improving the compactness of the coating. In the coating provided by the embodiment of the present application, the titanium nitride and the niobium nitride are selected to form a multilayer structure and are coated on the bipolar plate, so that the corrosion medium in the electrolyte can effectively penetrate the coating through the pore defects and the like, and then corrode the substrate, thereby reducing the probability of coating failure. In this way, the bipolar plate can have excellent conductivity and corrosion resistance, thereby reducing the manufacturing cost of the bipolar plate and significantly prolonging the service life of the bipolar plate. The improvement measures of the present application are of great significance to improving the performance, stability and economy of the overall equipment.

[0048] In the further preferred technical solution of the embodiment of the present application, the value range of n is 2-8, so as to ensure the compactness of the coating and control the cost.

[0049] In the further preferred technical solution of the embodiment of the present application, in each periodic structure, the titanium nitride coating is the coating relatively close to the bipolar plate, and the niobium nitride coating is the coating relatively far away from the bipolar plate. Specifically, the transition metal compound composite coating is used for being formed on the surface of the bipolar plate, and the material of the bipolar plate is titanium alloy or stainless steel. Illustratively, when the material is titanium alloy, the titanium nitride coating in the transition metal compound composite coating is the first layer of coating deposited on the surface of the metal substrate, and the niobium nitride coating is deposited after the titanium nitride coating. The titanium nitride coating contains titanium elements like the titanium alloy substrate, and the compatibility of the titanium nitride coating with the titanium substrate is better than that of the niobium nitride coating.

[0050] In the preferred technical solution of the embodiment of the present application, the titanium nitride in the titanium nitride coating is face-centered cubic phase, and the niobium nitride in the niobium nitride coating is hexagonal close-packed phase. In addition, the preferred crystal face orientation of the single-layer titanium nitride coating is (200), and the thickness is 25-35 nm; the preferred crystal face orientation of the single-layer niobium nitride coating is (101) and (102), and the thickness is 10-20 nm.

[0051] In the embodiment of the present application, a preparation method of a transition metal compound composite coating with high conductivity and high corrosion resistance is provided, which comprises the following steps:

[0052] Step (1), first, the surface of the metal bipolar plate is pretreated to provide the metal bipolar plate as a substrate; specifically, the metal bipolar plate can be polished with SiC paper having a particle size of 240#, 600#, 1000#, 2000# and 3000#; then, the surface of the substrate is polished to a mirror state with diamond polishing paste having a particle size of 0.5 μm, and the polished substrate is ultrasonically cleaned with acetone, alcohol and deionized water for 15 min, respectively, and finally, the substrate is naturally air-dried; in addition, the metal bipolar plate is a stainless steel bipolar plate or a titanium alloy bipolar plate;

[0053] Step (2), a pulse laser deposition technique is used to deposit a titanium nitride coating on the surface of the metal bipolar plate by using a TiN target with a purity of 99.9% as a target material; specifically, the air-dried substrate is fixed on a sample table and transferred into a deposition chamber, the substrate is heated to 400-600 ℃, and the vacuum degree in the chamber is less than 2×10 -4 After the vacuum degree is less than 2×10

[0054] Step (3), a pulse laser deposition technique is used to deposit a niobium nitride coating on the surface of the titanium nitride coating by using a NbN target with a purity of 99.9% as a target material, so as to obtain a high-conductivity and high-corrosion-resistance transition metal compound composite coating; specifically, the laser switch is turned off, the deposition target material is set to a niobium nitride target with a purity of 99.9%, the substrate temperature, nitrogen partial pressure, laser frequency and laser energy remain unchanged, and the deposition time is 300-650 s.

[0055] Step (4), steps (2) and (3) are taken as one process cycle, and n cycles are repeated to obtain a transition metal compound composite coating with high conductivity and high corrosion resistance; after natural cooling to room temperature, the sample is taken out of the chamber.

[0056] In the preparation method provided by the embodiment, the pulse laser deposition process is used to prepare a transition metal compound composite coating with high conductivity and high corrosion resistance, which is prepared by using the pulse laser deposition process and the multi-layer design of the periodic composite structure, so as to effectively dislocate the porosity defects in each layer and improve the compactness of the coating while ensuring the uniformity of each layer.

[0057] Specifically, in the preparation method, the pulse laser deposition technique is used to place the metal bipolar plate in a reaction chamber, the vacuum degree is less than 2×10 -4The pulse laser deposition technology uses a pulse frequency of 6-10 Hz, an energy of 350-450 mJ, a reaction cavity gas pressure of 2-4 Pa, a deposition temperature of 400-600 DEG C, and a deposition time of 300-650 s.

[0058] In the preparation method, the pulse laser deposition technology is used, the reaction cavity vacuum degree is less than 2*10 -4 The pulse laser deposition technology uses a pulse frequency of 6-10 Hz, an energy of 350-450 mJ, a reaction cavity gas pressure of 2-4 Pa, a deposition temperature of 400-600 DEG C, and a deposition time of 300-650 s.

[0059] Further specifically, in the laser pulse deposition, the plating layer process is changed, the nitrogen gas partial pressure, the substrate temperature, the deposition time and other parameters are optimized, a single layer coating with uniform composition and phase is obtained, the generation of multiple phases in the single layer is avoided, the influence of impurity phases is reduced, and the corrosion resistance of each layer of coating is ensured to play; in addition, the deposition of the titanium nitride coating and the niobium nitride coating is taken as one cycle, a multi-layer structure of the transition metal compound composite coating with multiple cycles is prepared, through the multi-layer design, the defects such as pores in each layer are effectively staggered, the compactness of the coating is improved, the corrosion medium in the electrolyte is effectively reduced to pass through the defects such as pores to corrode the substrate, and the failure probability of the coating is reduced; finally, the self-corrosion current density of the prepared transition metal compound composite coating is less than 2*10 -9 A cm -2 , and the corrosion current density is less than 1*10 -7 A cm -2 , which is comparable to or even better than the noble metal plating layer on the market; the interface contact resistance is less than 8 mΩcm 2 , while maintaining high corrosion resistance, also has good electrical conductivity, and the noble metal load is 0 mg cm -1 , and the cost is low.

[0060] In view of the defects of the prior art, the new technical scheme is creatively proposed through long-term research and a large number of practices, and is mainly aimed at the problems of low cost, high conductivity and high corrosion resistance that cannot be considered together and insufficient comprehensive performance of the surface coating modification of the metal bipolar plate of the proton exchange membrane water electrolysis cell. The high-conductivity and high-corrosion-resistance transition metal compound composite coating disclosed by the application can be used in the coating of the metal bipolar plate of the proton exchange membrane fuel cell or the proton exchange membrane water electrolysis cell.

[0061] Comparative Example 1

[0062] In the present comparative example, a single-layer titanium nitride coating prepared by a magnetron reactive sputtering with optimized process parameters is prepared by the following method:

[0063] S1. A TA1 commercial titanium plate is selected as the substrate, the substrate is polished with SiC paper having particle sizes of 240#, 600#, 1000#, 2000# and 3000#, and then the surface of the substrate is polished to a mirror state with diamond polishing paste having a particle size of 0.5 μm; the polished substrate is ultrasonically cleaned with acetone, alcohol and deionized water, and the cleaning time is 15 min, respectively; and finally the substrate is naturally air-dried;

[0064] S2. The air-dried substrate is fixed on a sample table and conveyed into a deposition chamber, and the substrate is heated to 300℃, and after the vacuum degree in the chamber is less than 5x10 -4 Pa, high-purity argon is introduced, the argon flow rate is adjusted, and the argon flow rate is maintained at about 20 sccm; high-purity nitrogen is introduced, the nitrogen flow rate is adjusted, and the nitrogen flow rate is maintained at about 6 sccm;

[0065] S3. A 99.99% pure titanium target is used as the target material, a target material baffle is used to block the target material, the sputtering power is set to 100 W, and pre-sputtering is performed for 15 min to remove impurities such as oxides on the surface of the target material;

[0066] S4. After the pre-sputtering is completed, the target material baffle is removed, and formal sputtering deposition is started, the sample table is kept rotating at a constant speed during the deposition to make the deposition more uniform, the deposition time is 150 min, and the thickness of the deposited titanium nitride coating is 372.88 mm;

[0067] S5. The sample is naturally cooled to room temperature and taken out of the chamber.

[0068] It is tested that the self-corrosion current density of the coating sample is about 5.9x10 -7 A cm -2 , the corrosion current density thereof is about 1x10 -5 A cm -2 at a working voltage of 2.0 V, the corrosion resistance is good, and the interface contact resistance is about 261.56 mΩcm 2, the noble metal loading is 0 mg cm -2 .

[0069] Comparative Example 2

[0070] In the present comparative example, a TA1 commercial titanium plate without any treatment is used.

[0071] The coating sample is tested to have a self-corrosion current density of about 2.4 x 10 -4 A cm -2 , and a corrosion current density of about 1 x 10 -4 A cm -2 at a working voltage of 2.0 V, and poor corrosion resistance.

[0072] Example 1

[0073] In the present example, the preparation method of the transition metal compound composite coating with high conductivity and high corrosion resistance is as follows:

[0074] S1. The substrate is a TA1 commercial titanium plate, and the substrate is polished with SiC paper with particle sizes of 240#, 600#, 1000#, 2000# and 3000#, and then polished to a mirror surface state with diamond polishing paste with a particle size of 0.5 μm. The polished substrate is ultrasonically cleaned with acetone, alcohol and deionized water, and the cleaning time is 15 min, respectively. Finally, the substrate is naturally air-dried;

[0075] S2. The air-dried substrate is fixed on a sample table and conveyed into a deposition chamber. The substrate is heated to 400℃, and after the vacuum degree in the chamber is less than 2 x 10 -4 Pa, high-purity nitrogen gas is introduced, the nitrogen gas flow rate is adjusted so that the nitrogen partial pressure is maintained at about 2 Pa; the deposition target material is set to a 99.9% purity titanium nitride target material, the laser frequency is set to 8 Hz, the laser energy is set to 400 mJ, the deposition time is set to 600 s, and the laser switch is turned on to start depositing the titanium nitride coating;

[0076] S3. The laser switch is turned off, the deposition target material is set to a 99.9% purity niobium nitride target material, the substrate temperature, the nitrogen partial pressure, the laser frequency and the laser energy remain unchanged, the deposition time is set to 400 s, and the laser is turned on.

[0077] S4. The laser switch is turned off, the deposition target material is set to a 99.9% purity titanium nitride target material, the substrate temperature, the nitrogen partial pressure, the laser frequency and the laser energy remain unchanged, the deposition time is set to 600 s, and the laser is turned on.

[0078] S5. The laser switch is turned off, the deposition target material is set to a 99.9% purity niobium nitride target material, the substrate temperature, the nitrogen partial pressure, the laser frequency and the laser energy remain unchanged, the deposition time is set to 400 s, and the laser is turned on.

[0079] S6. Turn off the laser switch, set the deposition target to 99.9% purity titanium nitride target, the substrate temperature, nitrogen partial pressure, laser frequency and laser energy remain unchanged, the deposition time is 600s, turn on the laser;

[0080] S7. Turn off the laser switch, set the deposition target to 99.9% purity niobium nitride target, the substrate temperature, nitrogen partial pressure, laser frequency and laser energy remain unchanged, the deposition time is 400s, turn on the laser;

[0081] S8. Turn off the laser switch, set the deposition target to 99.9% purity titanium nitride target, the substrate temperature, nitrogen partial pressure, laser frequency and laser energy remain unchanged, the deposition time is 600s, turn on the laser;

[0082] S9. Turn off the laser switch, set the deposition target to 99.9% purity niobium nitride target, the substrate temperature, nitrogen partial pressure, laser frequency and laser energy remain unchanged, the deposition time is 400s, turn on the laser;

[0083] S10. Turn off the laser switch, set the deposition target to 99.9% purity titanium nitride target, the substrate temperature, nitrogen partial pressure, laser frequency and laser energy remain unchanged, the deposition time is 600s, turn on the laser;

[0084] S11. Turn off the laser switch, set the deposition target to 99.9% purity niobium nitride target, the substrate temperature, nitrogen partial pressure, laser frequency and laser energy remain unchanged, the deposition time is 400s, turn on the laser;

[0085] S12. Turn off the laser switch, set the deposition target to 99.9% purity titanium nitride target, the substrate temperature, nitrogen partial pressure, laser frequency and laser energy remain unchanged, the deposition time is 600s, turn on the laser;

[0086] S13. Turn off the laser switch, set the deposition target to 99.9% purity niobium nitride target, the substrate temperature, nitrogen partial pressure, laser frequency and laser energy remain unchanged, the deposition time is 400s, turn on the laser;

[0087] S14. Turn off the laser switch, naturally cool to room temperature, take out the sample from the chamber.

[0088] Please refer to Figures 2 to 5 , Figure 2 The SEM surface test results are shown, and it can be seen that the prepared coating surface is complete and uniform; Figure 3 The SEM cross-section test results are shown, and it can be seen that the prepared coating presents obvious 6 periodic structures; Figure 4The XRD test results are shown, and it can be seen that the main components of the prepared coating are face-centered cubic phase titanium nitride and close-packed hexagonal phase niobium nitride, and the preferred orientation of the titanium nitride is the (200) crystal face, and the preferred orientation of the niobium nitride is the (101) and (102) crystal faces; Figure 5 The XPS test results are shown, and it can be seen that the existing form of Nb on the surface of the coating is mainly niobium nitride; based on the above test results, the self-corrosion current density of the composite coating sample is about 1.8 x 10 -9 A cm -2 , and the corrosion current density thereof is less than 1 x 10 -7 A cm -2 , which is comparable to or even better than the noble metal plating on the market; the interface contact resistance is about 7.42 mΩcm 2 , which greatly improves the conductivity of the substrate while maintaining high corrosion resistance, and the noble metal load is 0 mg cm -2 .

[0089] Embodiment 2

[0090] In the embodiment of the application, the preparation method of the transition metal compound composite coating which takes into account high conductivity and high corrosion resistance is as follows:

[0091] S1. The substrate is a TA1 commercial titanium plate, the substrate is polished using SiC paper with particle sizes of 240#, 600#, 1000#, 2000# and 3000#, and then the surface of the substrate is polished to a mirror state using diamond polishing paste with a particle size of 0.5 μm; the polished substrate is ultrasonically cleaned with acetone, alcohol and deionized water, and the cleaning time is 15 min respectively, and finally the substrate is naturally air-dried;

[0092] S2. The air-dried substrate is fixed on a sample table and conveyed into a deposition chamber, the substrate is heated to 400℃, after the vacuum degree in the chamber is less than 2 x 10 -4 Pa, high-purity nitrogen gas is introduced, the nitrogen gas flow rate is adjusted so that the nitrogen gas partial pressure is maintained at about 2 Pa; the deposition target material is set to a 99.9% purity titanium nitride target material, the laser frequency is set to 8 Hz, the laser energy is 400 mJ, the deposition time is 600 s, and the laser switch is turned on to start depositing the titanium nitride coating;

[0093] S3. The laser switch is turned off, the deposition target material is set to a 99.9% purity niobium nitride target material, the substrate temperature, the nitrogen gas partial pressure, the laser frequency and the laser energy remain unchanged, the deposition time is 400 s, and the laser is turned on;

[0094] S4. The laser switch is turned off, the deposition target material is set to a 99.9% purity titanium nitride target material, the substrate temperature, the nitrogen gas partial pressure, the laser frequency and the laser energy remain unchanged, the deposition time is 600 s, and the laser is turned on;

[0095] S5. Turn off the laser switch, set the deposition target to 99.9% purity niobium nitride target, keep the substrate temperature, nitrogen partial pressure, laser frequency and laser energy unchanged, the deposition time is 400s, and turn on the laser;

[0096] S6. Turn off the laser switch, set the deposition target to 99.9% purity titanium nitride target, keep the substrate temperature, nitrogen partial pressure, laser frequency and laser energy unchanged, the deposition time is 600s, and turn on the laser;

[0097] S7. Turn off the laser switch, set the deposition target to 99.9% purity niobium nitride target, keep the substrate temperature, nitrogen partial pressure, laser frequency and laser energy unchanged, the deposition time is 400s, and turn on the laser;

[0098] S8. Turn off the laser switch, set the deposition target to 99.9% purity titanium nitride target, keep the substrate temperature, nitrogen partial pressure, laser frequency and laser energy unchanged, the deposition time is 600s, and turn on the laser;

[0099] S9. Turn off the laser switch, set the deposition target to 99.9% purity niobium nitride target, keep the substrate temperature, nitrogen partial pressure, laser frequency and laser energy unchanged, the deposition time is 400s, and turn on the laser;

[0100] S10. Turn off the laser switch, and naturally cool to room temperature, and take out the sample from the chamber.

[0101] The test shows that the self-corrosion current density of the composite coating sample is about 3.7 x 10 -9 A cm -2 , and the corrosion current density is less than 5 x 10 -7 A cm -2 , which is comparable to or even better than the noble metal plating on the market; the interface contact resistance is about 15.89 mΩcm 2 , which greatly improves the conductivity of the substrate while maintaining high corrosion resistance, and the noble metal load is 0 mg cm -2 .

[0102] Please refer to Figure 6 and Figure 7 , based on the performance test analysis and comparison of Comparative Examples 1, 2 and Examples 1, 2 as follows:

[0103] The electrochemical performance test of the corrosion resistance of the sample was carried out by using a three-electrode system on an Autolab electrochemical workstation. The sample to be tested was the working electrode, and the exposed area was 1 cm 2Pt, and the reference electrode is saturated calomel electrode. The bipolar plate of simulated PEMWE is high temperature and strong acid working environment, and the test electrolyte is 0.5M H2SO4+5ppm F － Solution. The stable open circuit voltage is measured in the open circuit condition for 1h, the linear voltammetry scanning of the potential range of-1~2V (vs. SCE) is carried out on the sample, the scanning speed is 1mV / s, the dynamic response of the test sample to the working potential and the influence of the potential on the corrosion resistance are tested, and the results are shown in Figure 6 The Tafel fitting is carried out on the results to obtain the data such as the corrosion potential and the corrosion current. The self-corrosion current density of the example 1 is 1.8×10 -9 A cm -2 The self-corrosion current density of the example 2 is 3.7×10 -9 A cm -2 The self-corrosion current density of the comparative example 1 is 5.9×10 -7 A cm -2 The self-corrosion current density of the comparative example 2 is 2.4×10 -4 A cm -2 The surface of the composite coating prepared in the example of the present application has better corrosion resistance than the substrate and the single-layer coating.

[0104] The assembly pre-tightening force of 1.5MPa is applied to the sample surface, and the contact resistance test is carried out, and the results are shown in Figure 7 The contact resistance of the example 1 is 7.42mΩcm 2 The contact resistance of the example 2 is 15.89mΩcm 2 The contact resistance of the comparative example 1 is 261.56mΩcm 2 .

[0105] Based on the above comparative analysis, it is proved that the product prepared in the example of the present application maintains good conductivity while maintaining high corrosion resistance.

[0106] Example 3

[0107] The preparation method of the transition metal compound composite coating provided by the example of the present application comprises the following steps:

[0108] The transition metal compound composite coating is prepared by the pulse laser deposition process based on the polished and cleaned pretreated metal bipolar plate; wherein,

[0109] The pulse laser deposition process is adopted, a TiN target with a purity of 99.9% is used as a target material, and a titanium nitride coating is formed on the surface of the metal bipolar plate; the pulse laser deposition process is adopted, a NbN target with a purity of 99.9% is used as a target material, and a niobium nitride coating is formed on the surface of the titanium nitride coating, thereby forming a transition metal compound composite coating with one period structure;

[0110] Based on the transition metal compound composite coating with one period structure, the pulse laser deposition process is further adopted, a TiN target with a purity of 99.9% and a NbN target with a purity of 99.9% are used as target materials, and a titanium nitride coating and a niobium nitride coating are alternately formed, thereby obtaining a transition metal compound composite coating with two period structures;

[0111] In the step of forming the titanium nitride coating on the surface of the metal bipolar plate by using the TiN target with a purity of 99.9% as the target material, the metal bipolar plate is placed in a reaction cavity, the vacuum degree of the reaction cavity is less than 2*10 -4 Pa, a TiN target with a purity of 99.9% is used as the target material, nitrogen is used as the working gas, and the titanium nitride coating is formed on the surface of the metal bipolar plate; in the pulse laser deposition process, the pulse frequency is 6 Hz, the energy is 350 mJ, the gas pressure of the reaction cavity is 2 Pa, the deposition temperature is 400 DEG C, and the deposition time is 300 s;

[0112] In the step of forming the niobium nitride coating on the surface of the titanium nitride coating by using the NbN target with a purity of 99.9% as the target material, the metal bipolar plate on which the titanium nitride coating is deposited is placed in a reaction cavity, the vacuum degree of the reaction cavity is less than 2*10 - 4 Pa, a NbN target with a purity of 99.9% is used as the target material, nitrogen is used as the working gas, and the niobium nitride coating is formed on the surface of the titanium nitride coating; in the pulse laser deposition process, the pulse frequency is 6 Hz, the energy is 350 mJ, the gas pressure of the reaction cavity is 2 Pa, the deposition temperature is 400 DEG C, and the deposition time is 300 s.

[0113] Embodiment 4

[0114] The difference between the preparation method of the embodiment of the application and the embodiment 3 is that,

[0115] Based on the transition metal compound composite coating with one period structure, the pulse laser deposition process is further adopted, a TiN target with a purity of 99.9% and a NbN target with a purity of 99.9% are used as target materials, and a titanium nitride coating and a niobium nitride coating are alternately formed, thereby obtaining a transition metal compound composite coating with five period structures;

[0116] The step of depositing the titanium nitride coating on the surface of the metal bipolar plate includes: placing the metal bipolar plate in a reaction cavity, the vacuum degree of the reaction cavity being less than 2*10 -4 The step of depositing the titanium nitride coating on the surface of the metal bipolar plate includes: placing the metal bipolar plate in a reaction cavity, the vacuum degree of the reaction cavity being less than 2*10

[0117] The step of depositing the titanium nitride coating on the surface of the metal bipolar plate includes: placing the metal bipolar plate in a reaction cavity, the vacuum degree of the reaction cavity being less than 2*10 - 4 The step of depositing the titanium nitride coating on the surface of the metal bipolar plate includes: placing the metal bipolar plate in a reaction cavity, the vacuum degree of the reaction cavity being less than 2*10

[0118] Embodiment 5

[0119] The preparation method of the embodiment of the application is different from that of the embodiment 3 only in that,

[0120] Based on the transition metal compound composite coating with one period structure, the titanium nitride coating and the niobium nitride coating are alternately deposited by using the 99.9% pure TiN target and the 99.9% pure NbN target as the target material respectively by the pulse laser deposition process, so that the transition metal compound composite coating with eight period structures is prepared.

[0121] The step of depositing the titanium nitride coating on the surface of the metal bipolar plate includes: placing the metal bipolar plate in a reaction cavity, the vacuum degree of the reaction cavity being less than 2*10 -4 The step of depositing the titanium nitride coating on the surface of the metal bipolar plate includes: placing the metal bipolar plate in a reaction cavity, the vacuum degree of the reaction cavity being less than 2*10

[0122] The step of depositing the titanium nitride coating on the surface of the metal bipolar plate includes: placing the metal bipolar plate in a reaction cavity, the vacuum degree of the reaction cavity being less than 2*10 - 4Pa; the NbN target with 99.9% purity is used as the target material, nitrogen is used as the working gas, and the niobium nitride coating is formed on the surface of the titanium nitride coating; wherein the pulse frequency of the pulse laser deposition process is 10 Hz, the energy is 450 mJ, the gas pressure of the reaction cavity is 4 Pa, the deposition temperature is 600 DEG C, and the deposition time is 650 s.

[0123] Finally, it should be noted that: the above examples are used to illustrate the technical solutions of the present application, but not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: the specific embodiments of the present application can be modified or replaced by the same, without departing from the spirit and scope of the present application, any modification or equivalent replacement, which should be covered within the protection scope of the claims of the present application.

Claims

1. A transition metal compound composite coating, characterized in that, The transition metal compound composite coating is a composite multilayer structure, comprising n identical periodic structures deposited sequentially, where n≥2; wherein each periodic structure includes a titanium nitride coating and a niobium nitride coating. In each periodic structure, the preferred crystal orientation of the monolayer titanium nitride coating is (200), and the thickness is 25 nm ~ 35 nm; in each periodic structure, the preferred crystal orientation of the monolayer niobium nitride coating is (101) and (102), and the thickness is 10 nm ~ 20 nm. At an operating voltage of 2.0V, the corrosion current density of the transition metal compound composite coating is less than 1×10⁻⁶. -7 Acm -2 The interfacial contact resistance of the transition metal compound composite coating is less than 8 mΩ cm. 2 ; The transition metal compound composite coating was prepared using a pulsed laser deposition process.

2. The transition metal compound composite coating according to claim 1, characterized in that, The value of n ranges from 2 to 8.

3. The transition metal compound composite coating according to claim 1, characterized in that, The transition metal compound composite coating is deposited on the surface of the metal bipolar plate; In each periodic structure, the titanium nitride coating is relatively close to the metal bipolar plate, while the niobium nitride coating is relatively far from the metal bipolar plate.

4. The transition metal compound composite coating according to claim 1, characterized in that, The titanium nitride in the titanium nitride coating is a face-centered cubic phase; the niobium nitride in the niobium nitride coating is a close-packed hexagonal phase.

5. A method for preparing the transition metal compound composite coating according to claim 1, characterized in that, Includes the following steps: A transition metal compound composite coating was prepared using a pulsed laser deposition process based on a pre-treated metal bipolar plate that had undergone grinding and cleaning. A titanium nitride coating is deposited on the surface of a metal bipolar plate using pulsed laser deposition with a TiN target of 99.9% purity. A niobium nitride coating is then deposited on the surface of the titanium nitride coating using a NbN target of 99.9% purity, forming a transition metal compound composite coating with a periodic structure. Based on a transition metal compound composite coating with a periodic structure, a pulsed laser deposition process was used to alternately deposit titanium nitride coating and niobium nitride coating using TiN and NbN targets with 99.9% purity, respectively, to prepare a transition metal compound composite coating with n periodic structures. The step of depositing a titanium nitride coating on the surface of a metal bipolar plate using pulsed laser deposition with a 99.9% pure TiN target includes: placing the metal bipolar plate in a reaction chamber, wherein the vacuum level of the reaction chamber is less than 2 × 10⁻⁶. -4 Pa; using a 99.9% pure TiN target as the target material and nitrogen as the working gas, a titanium nitride coating is formed on the surface of a metal bipolar plate; wherein, the pulsed laser deposition process uses a pulse frequency of 6 Hz~10Hz, an energy of 350 mJ~450mJ, a gas pressure of 2 Pa~4Pa in the reaction chamber, a deposition temperature of 400℃~600℃, and a deposition time of 300 s~650s; The step of depositing a niobium nitride coating on the surface of a titanium nitride coating using a pulsed laser deposition process with a 99.9% pure NbN target as the target material includes: placing a metal bipolar plate with a deposited titanium nitride coating in a reaction chamber, wherein the vacuum degree of the reaction chamber is less than 2 × 10⁻⁶. -4 Pa; using a 99.9% pure NbN target as the target material and nitrogen as the working gas, a niobium nitride coating is formed on the surface of the titanium nitride coating; wherein, the pulsed laser deposition process uses a pulse frequency of 6Hz~10Hz, an energy of 350 mJ~450mJ, a gas pressure of 2 Pa~4Pa in the reaction chamber, a deposition temperature of 400℃~600℃, and a deposition time of 300s~650s.

6. A metal bipolar plate, said metal bipolar plate being used in a proton exchange membrane fuel cell or a proton exchange membrane water electrolyzer, characterized in that, The surface of the metal bipolar plate is deposited with a transition metal compound composite coating as described in any one of claims 1 to 4.

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