Composite coating for bipolar plate, preparation method of composite coating, bipolar plate and fuel cell

Abstract

The invention provides a composite coating for a bipolar plate, a preparation method of the composite coating, the bipolar plate and a fuel cell, and belongs to the field of fuel cells. Comprising a transition metal layer; the amorphous carbon layer and the transition metal layer are arranged in a stacked mode, and the amorphous carbon layer is in regionalization distribution of high-sp3 hybridization and high-sp2 hybridization so as to correspondingly form a high-corrosion-resistance area and a high-conductivity area which are distributed in a regionalization mode. The transition metal layer serves as a bottom layer of the composite coating and provides a good adhesion substrate for the subsequent amorphous carbon layer. Meanwhile, regionalization setting of high sp3 hybridization and high sp2 hybridization of the amorphous carbon layer is carried out according to different functional requirements of different regions on the surface of the bipolar plate, so that a high corrosion-resistant region and a high conductive region which are distributed in a regionalization manner are correspondingly formed. Therefore, the corrosion resistance and the conductivity of the bipolar plate are improved at the same time.

Description

Technical Field

[0001] The present application relates to the field of fuel cell technology, and in particular to a composite coating for a bipolar plate and a preparation method thereof, a bipolar plate, and a fuel cell. Background Art

[0002] The proton exchange membrane fuel cell stack is mainly composed of bipolar plates, membrane electrodes and other components. The bipolar plates are divided into metal bipolar plates, graphite bipolar plates and composite bipolar plates. The surface of the metal bipolar plate is covered with a conductive corrosion-resistant coating, such as a precious metal coating, a carbon coating, a transition metal nitride or carbide, etc., which mainly plays a role in enhancing conductivity and corrosion resistance.

[0003] At present, most stainless steel-based metal bipolar plates use a composite coating that combines a transition metal base layer with an amorphous carbon conductive layer. The fuel cell metal bipolar plate coating is a component that fully covers the plate surface, which makes it difficult to balance the bipolar plate's requirements for corrosion resistance and conductivity. Therefore, it is urgent to develop a bipolar plate composite coating that can simultaneously improve the corrosion resistance and conductivity of the bipolar plate. Summary of the invention

[0004] The present application provides a composite coating for a bipolar plate and a preparation method, a bipolar plate, and a fuel cell to solve the following technical problem: how to simultaneously improve the corrosion resistance and conductivity of the bipolar plate.

[0005] In a first aspect, the present application provides a composite coating for a metal bipolar plate, the composite coating comprising:

[0006] a transition metal layer; and

[0007] an amorphous carbon layer, wherein the amorphous carbon layer and the transition metal layer are stacked, and the amorphous carbon layer has a high sp 3 Hybridization and high sp 2 The hybridized regional distribution corresponds to the formation of regionalized high corrosion resistance areas and high conductivity areas.

[0008] Optionally, the high sp 3 The hybrid amorphous carbon layer is distributed in the gas surface active area and the corresponding area of ​​the water surface of the metal bipolar plate. 3 sp hybrid amorphous carbon layer 3 The hybridization ratio is 70% to 100%.

[0009] Optionally, the high sp 2 The hybrid amorphous carbon layer is distributed in the corresponding area of ​​the inactive area of ​​the gas path of the metal bipolar plate. 2 sp hybrid amorphous carbon layer 2 The hybridization ratio is 30% to 100%.

[0010] Optionally, the thickness of the transition metal layer is 10 nm to 500 nm, and the thickness of the amorphous carbon layer is 10 nm to 500 nm.

[0011] Optionally, the composite coating meets the following performance: contact resistance is 3.5 mΩcm 2 ~4.5mΩcm 2 , corrosion current is 0.3μA / cm 2 ~0.5μA / cm 2 .

[0012] In a second aspect, the present application provides a method for preparing the composite coating according to any one embodiment of the first aspect, the method comprising:

[0013] The transition metal layer and the high sp 2 a hybrid amorphous carbon layer; and

[0014] The transition metal layer and the high sp 3 Hybrid amorphous carbon layer.

[0015] Optionally, the transition metal layer is deposited by first magnetron sputtering, the bias voltage of the first magnetron sputtering is -200V to -400V, and the power of the first magnetron sputtering is 2kW to 15kW.

[0016] Optionally, the amorphous carbon layer is deposited by second magnetron sputtering or cathode arc ion plating, the bias voltage of the second magnetron sputtering is 0 to -300V, the power of the second magnetron sputtering is 2kW to 15kW, and the current of the cathode arc ion plating is 40A to 120A.

[0017] In a third aspect, the present application provides a metal bipolar plate, the metal bipolar plate comprising:

[0018] Metal bipolar plate substrate; and

[0019] The composite coating described in any one of the embodiments of the first aspect covers at least a portion of the surface of the metal bipolar plate substrate; the transition metal layer of the composite coating is arranged adjacent to the metal bipolar plate substrate.

[0020] In a fourth aspect, the present application provides a fuel cell, comprising the metal bipolar plate described in the embodiment of the third aspect.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] The present application provides a composite coating for a metal bipolar plate, comprising: a transition metal layer; and an amorphous carbon layer, wherein the amorphous carbon layer and the transition metal layer are stacked, and the amorphous carbon layer has a high sp 3 Hybridization and high sp 2 The hybridized regional distribution corresponds to the formation of regionally distributed high corrosion resistance areas and high conductivity areas. The transition metal layer, as the bottom layer of the composite coating, provides a good adhesion base for the subsequent amorphous carbon layer. At the same time, the amorphous carbon layer is highly sp 3 Hybridization and high sp 2 The hybridized regional setting forms a high corrosion resistance area and a high conductivity area with regional distribution, thereby improving the corrosion resistance and conductivity of the bipolar plate at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 A schematic diagram of the structure of a composite coating for a metal bipolar plate provided in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of the structure of the gas path of the metal bipolar plate provided in an embodiment of the present application;

[0027] Figure 3 A schematic diagram of the structure of the water path surface of the metal bipolar plate provided in an embodiment of the present application;

[0028] Figure 4 A schematic diagram of a process for preparing a composite coating provided in an embodiment of the present application;

[0029] Reference numerals:

[0030] 1-composite coating, 11-transition metal layer, 12-amorphous carbon layer, 2-gas road surface, 21-gas road surface active area, 22-gas road surface inactive area, 3-water road surface. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0032] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0033] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0034] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0035] Currently, the coating of fuel cell metal bipolar plates fully covers the surface of the plate with the same component, which makes it difficult to balance the bipolar plate's requirements for corrosion resistance and conductivity.

[0036] The technical solution provided by the embodiments of the present application is to solve the above technical problems, and the overall idea is as follows:

[0037] Figure 1 A schematic diagram of the structure of a composite coating for a metal bipolar plate provided in an embodiment of the present application.

[0038] See also Figure 1 The present application provides a composite coating 1 for a metal bipolar plate, the composite coating 1 comprising:

[0039] a transition metal layer 11; and

[0040] The amorphous carbon layer 12 is stacked with the transition metal layer 11, and the amorphous carbon layer 12 has a high sp 3 Hybridization and high sp 2 The hybridized regional distribution corresponds to the formation of regionalized high corrosion resistance areas and high conductivity areas.

[0041] The metal bipolar plate composite coating 1 proposed in this application is designed to improve the performance of metal bipolar plates in fuel cells or other related applications through an innovative multi-layer structure. Specifically, the composite coating 1 consists of two layers: a transition metal layer 11 and an amorphous carbon layer 12, which work together. The transition metal layer 11, as the bottom layer of the composite coating 1, mainly provides a good adhesion base for the subsequent amorphous carbon layer 12, and can have a positive impact on the performance of the overall coating through its own chemical properties. The amorphous carbon layer 12 directly covers the transition metal layer 11 and is the core part of the composite coating 1. The key feature of this layer is its internal high sp 3 Hybridization and high sp 2 The hybridized carbon atoms are distributed in a regionalized manner. This special structural design brings two major advantages: high sp 3 Hybridized carbon structures generally have higher hardness and chemical stability, which makes the corresponding areas more resistant to corrosion by corrosive substances. 3 In the hybrid region, the coating exhibits excellent corrosion resistance, which helps to extend the service life of the metal bipolar plate. 2 The hybridized carbon structure tends to form a graphite-like layered structure, which has good electronic conductivity. 2 In the hybrid area, the coating can provide efficient electron transfer channels, ensuring the high conductivity of the metal bipolar plate in the fuel cell system, thereby optimizing the efficiency of the overall system.

[0042] By skillfully combining the transition metal layer 11 with the amorphous carbon layer 12 and utilizing the regional distribution characteristics inside the amorphous carbon layer 12, the composite coating 1 proposed in the present application exhibits significant advantages in the following aspects: Enhanced corrosion resistance: High sp 3 The hybrid area effectively resists the corrosive environment and prolongs the service life of the bipolar plate. Excellent conductivity: high sp 2 The hybridized region ensures fast electron transmission and improves the efficiency of the fuel cell system. Good adhesion: The close bonding between the transition metal layer 11 and the amorphous carbon layer 12 ensures the stability and reliability of the coating.

[0043] In summary, the composite coating 1 design provides an efficient and durable surface modification solution for metal bipolar plates, which is expected to significantly improve the overall performance and stability in applications such as fuel cells.

[0044] In some embodiments, the material of the transition metal layer 11 includes metal elements such as Ti, Nb, Cr, and their carbides and nitrides.

[0045] Figure 2 A schematic diagram of the structure of the gas path of the metal bipolar plate provided in an embodiment of the present application; Figure 3 A schematic diagram of the structure of the water path surface of the metal bipolar plate provided in an embodiment of the present application.

[0046] See also Figure 2 and Figure 3 In some embodiments, the high sp 3 The hybrid amorphous carbon layer 12 is distributed in the active area of ​​the gas surface 2 and the corresponding area of ​​the water surface 3 of the metal bipolar plate. 3 The sp3 hybridization ratio of the hybrid amorphous carbon layer 12 is 70% to 100%.

[0047] In some embodiments, the high sp 2 The hybrid amorphous carbon layer 12 is distributed in the corresponding area of ​​the inactive area of ​​the gas path 2 of the metal bipolar plate. 2 The sp 2 The hybridization ratio is 30% to 100%.

[0048] It is easy to understand that the gas road surface 2 is the gas (hydrogen and air or oxygen) flow plane in the fuel cell bipolar plate. The water road surface 3 is the coolant flow plane in the fuel cell bipolar plate. The active area of ​​the gas road surface 2 includes the flow channel area and the gas distribution area, which accounts for 30% to 70% of the total area of ​​the plate.

[0049] The active area of ​​the gas road surface 2 and the water road surface 3 are directly exposed to the corrosive environment during the operation of the battery stack, such as acidic or alkaline electrolytes, oxygen, hydrogen, etc. These factors can cause rapid corrosion of the material. Therefore, the main demand for this area is to improve the corrosion resistance. 3 The sp 3 The hybridization ratio is 70% to 100%, and the amorphous carbon layer 12 is a tetrahedral amorphous carbon coating (ta-C). This coating has a high proportion of sp 3 The ta-C coating is known for its high hardness and chemical stability. It can effectively resist the erosion of corrosive media, thereby significantly improving the durability of the bipolar plate in the active area.

[0050] Compared with the active area of ​​gas path 2, the inactive area of ​​gas path 2 is in a relatively mild environment during the operation of the stack and has a lower risk of corrosion. However, this area has higher requirements for conductivity to ensure smooth transmission of electrons between the bipolar plates. 2 Hybrid-dominated amorphous carbon coatings (aC), which are rich in sp 2 Hybrid bond, its structure is closer to graphite, so it has excellent conductivity. Although its corrosion resistance may not be as good as ta-C, this shortcoming can be accepted in the mild environment of the inactive area.

[0051] In summary, the present application sets up coating zones according to the different functional requirements of different areas on the surface of the bipolar plate. By using different types of amorphous carbon coatings in different working areas, this design achieves a dual improvement in the conductivity and durability of the bipolar plate. The a-C coating in the inactive area of ​​the gas pavement 2 provides an efficient electron transmission channel, reduces the internal resistance of the battery stack, and thus improves the overall efficiency of the system. At the same time, the ta-C coating in the active area of ​​the gas pavement 2 and the water pavement 3 effectively resists the erosion of corrosive media, extends the service life of the bipolar plate, and reduces the frequency of maintenance and replacement.

[0052] In some embodiments, the thickness of the transition metal layer 11 is 10 nm to 500 nm, and the thickness of the amorphous carbon layer 12 is 10 nm to 500 nm.

[0053] In the design of the composite coating 1 of the metal bipolar plate, the thickness selection of the transition metal layer 11 and the amorphous carbon layer 12 is a crucial parameter, which directly affects the performance of the coating and the final application effect. The thickness of the transition metal layer 11 is limited to 10nm to 500nm, and the thickness of the amorphous carbon layer 12 is limited to 10nm to 500nm, which can ensure good adhesion with the amorphous carbon layer 12 while maintaining good compatibility with the metal substrate. At the same time, it helps to improve the conductivity, corrosion resistance and mechanical properties of the metal bipolar plate. Exemplarily, the thickness of the transition metal layer 11 can be 10nm, 20nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, etc., and the thickness of the amorphous carbon layer 12 is 10nm, 20nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, etc.

[0054] In some embodiments, the composite coating 1 meets the following properties: contact resistance is 3.5mΩcm2~4.5mΩcm 2 , corrosion current is 0.3μA / cm2~0.5μA / cm 2 .

[0055] Contact resistance is an important parameter to measure the conductivity of the contact interface between the coating and the substrate or between coatings. Lower contact resistance means that electrons encounter less resistance when passing through the coating, thereby improving the overall conductivity efficiency. The contact resistance of composite coating 1 is controlled at 3.5mΩcm 2 ~4.5mΩcm 2 This indicates that the coating has good electrical conductivity while ensuring corrosion resistance. Corrosion current is an important indicator for evaluating the corrosion resistance of a material in a specific environment. A lower corrosion current means that the material dissolves more slowly in a corrosive environment, thereby improving the durability and service life of the material. The corrosion current of composite coating 1 was controlled at 0.3μA / cm 2 Up to 0.5μA / cm 2 This indicates that the coating has excellent corrosion resistance and can effectively resist the erosion of corrosive media. Therefore, the composite coating 1 provided by the present application successfully achieves a balance between conductivity and corrosion resistance through the carefully designed transition metal layer 11 and amorphous carbon layer 12 structure. The transition metal layer 11 provides a good adhesion substrate for the amorphous carbon layer 12 and can have a positive effect on the corrosion resistance of the coating through its own chemical properties. The amorphous carbon layer 12 has a high sp 3 Hybridization and high sp 2 The regional distribution characteristics of the hybrid form a high corrosion resistance area in the active area and a high conductivity area in the inactive area, thereby simultaneously meeting the performance requirements of the bipolar plate in different working areas.

[0056] Figure 4 A schematic flow chart of a method for preparing a composite coating 1 provided in an embodiment of the present application.

[0057] See also Figure 4 The present application provides a method for preparing the composite coating 1 described in any one of the above embodiments, the method comprising:

[0058] S1, sequentially depositing the transition metal layer 11 and the high sp 2 a hybrid amorphous carbon layer 12; and

[0059] S2, sequentially depositing the transition metal layer 11 and the high sp 3 Hybrid amorphous carbon layer 12 .

[0060] In some embodiments, the transition metal layer 11 is deposited by first magnetron sputtering, the bias voltage of the first magnetron sputtering is -200V to -400V, and the power of the first magnetron sputtering is 2kW to 15kW.

[0061] In some embodiments, the amorphous carbon layer 12 is deposited by second magnetron sputtering or cathode arc ion plating, the bias voltage of the second magnetron sputtering is 0 to -300 V, the power of the second magnetron sputtering is 2 kW to 15 kW, and the current of the cathode arc ion plating is 40 A to 120 A.

[0062] Limiting the parameter range of the first magnetron sputtering, the second magnetron sputtering and the cathode arc ion plating helps to deposit a uniform thickness of the film layer, a complete surface and good conductivity. Exemplarily, the bias voltage of the first magnetron sputtering is -200V, -250V, -300V, -350V, -400V, etc., and the power of the first magnetron sputtering is 2kW, 3kW, 5kW, 7kW, 9kW, 11kW, 13kW, 15kW, etc. The bias voltage of the second magnetron sputtering is 0, -50V, -100V, -150V, -200V, -300V, etc., the power of the second magnetron sputtering is 2kW, 3kW, 5kW, 7kW, 9kW, 11kW, 13kW, 15kW, etc., and the current of the cathode arc ion plating is 40A, 60A, 80A, 100A, 120A, etc.

[0063] The product prepared by the method for preparing the composite coating is the above-mentioned composite coating. The chemical composition and microstructure of the composite coating prepared by the method for preparing the composite coating can refer to the above-mentioned embodiment. Since the method for preparing the composite coating adopts part or all of the technical solutions of the composite coating embodiment, it at least has all the beneficial effects brought by the technical solutions of the composite coating embodiment, which will not be described one by one here.

[0064] Based on a general inventive concept, the present application provides a metal bipolar plate, the metal bipolar plate comprising:

[0065] Metal bipolar plate substrate; and

[0066] The composite coating described in any one of the above embodiments covers at least a portion of the surface of the metal bipolar plate substrate; the transition metal layer of the composite coating is arranged adjacent to the metal bipolar plate substrate.

[0067] Based on a general inventive concept, the present application provides a fuel cell, which includes the metal bipolar plate described in the above embodiment.

[0068] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0069] Example 1

[0070] The present embodiment provides a method for preparing a metal bipolar plate with a composite coating, which may include the following steps:

[0071] Step 1: Clean and dry the pressed fuel cell metal bipolar plate substrate for later use;

[0072] Step 2: Cover the active area of ​​the metal bipolar plate gas path (including the flow channel area and the gas distribution area) with a mask film, deposit a transition metal layer on the inactive area by magnetron sputtering (magnetron sputtering bias voltage is -300V, power is 6kW, thickness is 100nm, and the material of the transition metal layer is Ti), and then deposit an amorphous carbon film on the transition metal layer by cathode arc ion plating (current is 80A, thickness is 100nm, sp 2 The hybridization ratio is 70%), and the mixture is taken out for use;

[0073] Step 3: Remove the masking film from the active area of ​​the gas road surface, and cover the masking film on the inactive area of ​​the gas road surface;

[0074] Step 4: Deposit a transition metal layer on the active area of ​​the water and gas paths of the metal bipolar plate by magnetron sputtering (magnetron sputtering bias voltage is -400 V, power is 10 kW, thickness is 150 nm), and then deposit a tetrahedral amorphous carbon film (ta-C, sp) on the transition metal layer by cathodic arc ion plating (current 120 A). 3 The hybridization ratio is 90%), and it is taken out after completion;

[0075] Step 5: Remove the masking film, clean the surface of the plate, and the fuel cell metal bipolar plate with the composite coating is completed.

[0076] Example 2

[0077] The present embodiment provides a method for preparing a metal bipolar plate with a composite coating, which may include the following steps:

[0078] Step 1: Clean and dry the pressed fuel cell metal bipolar plate substrate for later use;

[0079] Step 2: Cover the active area of ​​the metal bipolar plate gas path (including the flow channel area and the gas distribution area) with a mask film, deposit a transition metal layer on the inactive area by magnetron sputtering (magnetron sputtering bias voltage is -250V, power is 5kW, thickness is 100nm, and the material of the transition metal layer is Ti), and then deposit an amorphous carbon film on the transition metal layer by cathode arc ion plating (current is 60A, thickness is 100nm, sp 2 The hybridization ratio is 90%), and the mixture is taken out for use;

[0080] Step 3: Remove the masking film from the active area of ​​the gas road surface, and cover the masking film on the inactive area of ​​the gas road surface;

[0081] Step 4: Deposit a transition metal layer on the active area of ​​the water and gas paths of the metal bipolar plate by magnetron sputtering (magnetron sputtering bias voltage is -400 V, power is 15 kW, thickness is 200 nm), and then deposit a tetrahedral amorphous carbon film (ta-C, sp) on the transition metal layer by cathodic arc ion plating (current 100 A). 3 The hybridization ratio is 75%), and it is taken out after completion;

[0082] Step 5: Remove the masking film, clean the surface of the plate, and the fuel cell metal bipolar plate with the composite coating is completed.

[0083] Comparative Example 1

[0084] The method for preparing a metal bipolar plate with a composite coating provided in this comparative example may include the following steps:

[0085] Step 1: Clean and dry the pressed fuel cell metal bipolar plate substrate for later use;

[0086] Step 2: Deposit a transition metal layer on the bipolar plate by magnetron sputtering (magnetron sputtering bias voltage is -300 V, power is 6 kW, thickness is 100 nm, and the material of the transition metal layer is Ti), and then deposit an amorphous carbon film on the transition metal layer by cathode arc ion plating (current is 80 A, thickness is 100 nm, sp 2 The hybridization ratio is 90%), and the mixture is taken out for use;

[0087] Step 3: Clean the surface of the plate, and the fuel cell metal bipolar plate with the composite coating is prepared.

[0088] Comparative Example 2

[0089] The method for preparing a metal bipolar plate with a composite coating provided in this comparative example may include the following steps:

[0090] Step 1: Clean and dry the pressed fuel cell metal bipolar plate substrate for later use;

[0091] Step 2: Deposit a transition metal layer on the bipolar plate by magnetron sputtering (magnetron sputtering bias voltage is -400 V, power is 10 kW, thickness is 150 nm, and the material of the transition metal layer is Ti), and then deposit a tetrahedral amorphous carbon film on the transition metal layer by cathode arc ion plating (current is 120 A, thickness is 100 nm, sp 3 The hybridization ratio is 90%), and the mixture is taken out for use;

[0092] Step 3: Clean the surface of the plate, and the fuel cell metal bipolar plate with the composite coating is prepared.

[0093] The composite coatings of the fuel cell metal bipolar plates obtained in Examples 1 to 2 and Comparative Examples 1 to 2 were subjected to contact resistance and corrosion current tests (the test methods refer to the bipolar plate material resistance test and corrosion current density test methods in the national standard GB / T 20042.6-2024), and the results are shown in Table 1.

[0094] Table 1 Contact resistance and corrosion current of the composite coating obtained in Examples 1 to 2 and Comparative Examples 1 to 2

[0095] Test items Example 1 Example 2 Comparative Example 1 Comparative Example 2 <![CDATA[Contact resistance (mΩcm 2 )]]> 4.5 3.7 3.1 8.2 <![CDATA[Corrosion current (μA / cm 2 )]]> 0.3 0.5 0.89 0.20

[0096] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0097] In the embodiment of the present invention, the active area of ​​the gas road surface of the bipolar plate and the water road surface are in a corrosive environment when the stack is running, so the corrosion resistance is improved by depositing a tetrahedral amorphous carbon coating (ta-C); the inactive area of ​​the gas road surface of the bipolar plate is in a relatively mild environment when the stack is running, so its corrosion resistance is sacrificed to a certain extent, and the sp 2 The hybrid-dominated amorphous carbon coating (aC) enhances its conductivity, thereby simultaneously improving the conductivity and durability of the bipolar plate.

[0098] In the embodiment of the present invention, the contact resistance of the composite coating is 3.5 mΩcm 2 ~4.5mΩcm 2 , corrosion current is 0.3μA / cm 2~0.5μA / cm 2 .

[0099] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A composite coating for a metal bipolar plate, characterized in that: The composite coating comprises: a transition metal layer; and an amorphous carbon layer, wherein the amorphous carbon layer and the transition metal layer are stacked, and the amorphous carbon layer has a high sp 3 Hybridization and high sp 2 The hybridized regional distribution corresponds to the formation of regionalized high corrosion resistance areas and high conductivity areas.

2. The composite coating according to claim 1, characterized in that: The high sp 3 The hybrid amorphous carbon layer is distributed in the gas surface active area and the corresponding area of ​​the water surface of the metal bipolar plate. 3 sp hybrid amorphous carbon layer 3 The hybridization ratio is 70% to 100%.

3. The composite coating according to claim 1, characterized in that: The high sp 2 The hybrid amorphous carbon layer is distributed in the corresponding area of ​​the inactive area of ​​the gas path of the metal bipolar plate. 2 sp hybrid amorphous carbon layer 2 The hybridization ratio is 30% to 100%.

4. The composite coating according to claim 1, characterized in that: The thickness of the transition metal layer is 10 nm to 500 nm, and the thickness of the amorphous carbon layer is 10 nm to 500 nm.

5. The composite coating according to claim 1, characterized in that: The composite coating meets the following properties: contact resistance is 3.5 mΩcm 2 ~4.5mΩcm 2 , corrosion current is 0.3μA / cm 2 ~0.5μA / cm 2 .

6. A method for preparing a composite coating according to any one of claims 1 to 5, characterized in that: The method comprises: The transition metal layer and the high sp 2 a hybrid amorphous carbon layer; and The transition metal layer and the high sp 3 Hybrid amorphous carbon layer.

7. The method according to claim 6, characterized in that The transition metal layer is deposited by first magnetron sputtering, the bias voltage of the first magnetron sputtering is -200V to -400V, and the power of the first magnetron sputtering is 2kW to 15kW.

8. The method according to claim 6, characterized in that The amorphous carbon layer is deposited by second magnetron sputtering or cathode arc ion plating, the bias voltage of the second magnetron sputtering is 0 to -300V, the power of the second magnetron sputtering is 2kW to 15kW, and the current of the cathode arc ion plating is 40A to 120A.

9. A metal bipolar plate, characterized in that: The metal bipolar plate comprises: Metal bipolar plate substrate; and The composite coating according to any one of claims 1 to 5, wherein the composite coating covers at least a portion of the surface of the metal bipolar plate substrate; the transition metal layer of the composite coating is arranged adjacent to the metal bipolar plate substrate.

10. A fuel cell, characterized in that: The fuel cell comprises the metal bipolar plate according to claim 9.

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