Carbon-based coating bipolar plate as well as preparation method and application thereof

Abstract

The invention provides a carbon-based coating bipolar plate as well as a preparation method and application thereof. The carbon-based coating bipolar plate comprises a metal base material, a metal carbide coating and a carbon-based composite coating which are sequentially stacked, the carbon-based composite coating comprises multiple layers of SP2 hybrid carbon coatings and SP3 hybrid carbon coatings which are alternately stacked, the weight percentage of SP2 hybrid carbon atoms in the SP2 hybrid carbon coatings is 60-75%, and the weight percentage of SP3 hybrid carbon atoms in the SP3 hybrid carbon coatings is 70-85%. Metal carbide is arranged as the middle layer, amorphous carbon of different hybridization types is arranged as the surface layer, the cost of the bipolar plate can be reduced, the binding force between the metal substrate and the carbon-based composite coating is enhanced, SP2 hybridization carbon has good conductivity, SP3 hybridization carbon has excellent corrosion resistance, the reasonable SP2 hybridization carbon and SP3 hybridization carbon content is set, and the service life of the bipolar plate is prolonged. The bipolar plate has good conductivity and corrosion resistance, and the service life of the bipolar plate is remarkably prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cells, in particular to a carbon-based coating bipolar plate, a preparation method and application thereof. BACKGROUND

[0002] Proton exchange membrane fuel cell is a kind of fuel cell with acidic environment as internal environment medium, one of the main components is metal bipolar plate, which has the functions of distributing fuel, conducting current and supporting membrane electrode assembly. The metal bipolar plate works in a corrosive environment for a long time, the working temperature range is 80-90 DEG C, the working pH is about 3, and it is also under high potential and certain pressure conditions. In actual operation, the start-stop, idling and dynamic loading under vehicle working conditions also accelerate the corrosion failure of the metal bipolar plate. The dissolved metal ions also cause catalyst poisoning. In addition, the metal bipolar plate substrate is exposed to a corrosive environment, such as iron and other elements in stainless steel, which is prone to passivation, forming metal oxides, which greatly reduces the conductivity, directly leading to a sharp increase in the contact resistance between the metal bipolar plate and the gas diffusion layer, affecting the overall output power of the fuel cell and reducing the service life of the fuel cell.

[0003] However, according to the functional requirements and actual operating environment of the bipolar plate, the surface of the metal bipolar plate must be prepared with a coating with conductivity and corrosion resistance to meet the requirements of the fuel cell. The coating material used for surface treatment of the metal bipolar plate should have the following two characteristics: the coating material is a good conductor of electricity, and the coating needs to have strong adhesion with the metal plate substrate. In order to meet the above requirements, the current market coating can be divided into two categories: carbon-based coating and metal-based coating, among which carbon-based coating includes graphite, conductive polymers and diamond-like films, and metal-based coating includes noble metals, metal carbides and metal nitrides.

[0004] In order to pursue stable corrosion resistance and long service life, the current metal bipolar plate coating material is often gold and other noble metals, which has high cost and is difficult to meet the requirements of large-scale commercialization, seriously hindering the industrialization development of fuel cells. In order to reduce the cost of the metal bipolar plate assembly, carbon-based coating has gradually replaced noble metal-based coating and become the focus of research. The current preparation process of carbon-based coating includes arc ion plating, plasma chemical vapor deposition and magnetron sputtering process. However, the current market carbon-based coating mostly has problems such as not resistant to high potential, short service life and unstable carbon atom structure type, which leads to the fact that carbon-based coating cannot be widely applied.

[0005] In order to enable the carbon-based coating to achieve the same performance and service life as the noble metal coating, it is usually necessary to modify a plurality of elements or use other types of coatings simultaneously, but it may not achieve the purpose of reducing costs while reducing production efficiency. For example, the prior art discloses a metal carbide crystal composite coating and a preparation method thereof, which can greatly improve the corrosion resistance of the bipolar plate under acidic working conditions through multi-layer compounding and element modification, and has high electrical conductivity; but the preparation process is complex, the doping elements are more, the composition is difficult to control, and large-scale use cannot be realized. The prior art discloses a conductive and corrosion-resistant pre-coating for forming a metal bipolar plate and a preparation method thereof, which improves the bonding performance between the coating and the substrate through ion implantation and auxiliary diffusion, improves uniformity, electrical conductivity and corrosion resistance, and avoids coating cracking and peeling; but this process causes great challenges to the forming process and mold design of the bipolar plate and the surface treatment of the mold, and cannot effectively solve the coating quality problem caused by plastic deformation during the forming process.

[0006] Most of the current coating preparation processes can protect the metal bipolar plate to a certain extent, so that it can obtain a certain service life under fuel cell working conditions, but these coatings all have problems of interface resistance rising and matrix element loss after the stack is operated. The coating preparation process that can effectively protect the bipolar plate is very complicated and cannot be stably produced, the pre-coating process can cause the coating to crack and peel during the subsequent forming of the bipolar plate, which puts higher requirements on the forming mold, and the electrical conductivity, corrosion resistance and bonding strength of the coating are poor, which affects the performance of the metal bipolar plate.

[0007] At the same time, there is a problem of poor consistency of carbon-based coating bipolar plates in the industry, which is due to the difficulty in controlling the combination mode of carbon atoms in the carbon coating, many factors affecting its structure, leading to differences in electrical conductivity and corrosion resistance between different batches, directly affecting the output performance and service life of the whole stack. SUMMARY

[0008] The main purpose of the present application is to provide a carbon-based coating bipolar plate, a preparation method and application thereof, so as to solve the problems of high cost, poor electrical conductivity and corrosion resistance of the bipolar plate in the prior art, especially the problem that the carbon-based coating cannot balance high electrical conductivity and long service life.

[0009] In order to achieve the above purpose, according to one aspect of the present application, a carbon-based coating bipolar plate is provided, which comprises a metal substrate, a metal carbide coating and a carbon-based composite coating which are sequentially stacked in the direction close to the membrane electrode, the carbon-based composite coating comprises a plurality of SP 2 Hybrid carbon coating and multi-layer SP 3 Hybrid carbon coating, SP 2 Hybrid carbon coating and SP 3The hybrid carbon coating is alternately stacked, and SP 2 The hybrid carbon coating is close to the metal carbide coating, and SP 3 The hybrid carbon coating is close to the membrane electrode; wherein, SP 2 The hybrid carbon coating is SP 2 The weight percentage of the hybrid carbon atoms is 60-75%, and SP 3 The hybrid carbon coating is SP 3 The weight percentage of the hybrid carbon atoms is 70-85%.

[0010] Further, SP 2 The hybrid carbon coating is SP 2 The weight percentage of the hybrid carbon atoms is 65-72%, and SP 3 The hybrid carbon coating is SP 3 The weight percentage of the hybrid carbon atoms is 75-82%.

[0011] Further, the metal substrate comprises one or more of stainless steel, titanium and aluminum alloy; and / or in the metal carbide coating, the metal carbide comprises one or more of titanium carbide, vanadium carbide, chromium carbide and tungsten carbide, preferably titanium carbide.

[0012] Further, the thickness of the metal carbide coating is 20-60 nm; and / or SP 2 The number of the hybrid carbon coating is 3-6 layers, and the thickness of each layer is 15-30 nm; and / or SP 3 The number of the hybrid carbon coating is 3-6 layers, and the thickness of each layer is 15-30 nm.

[0013] According to another aspect of the present application, a preparation method of the carbon-based coating bipolar plate is provided, comprising the following steps: step S1, placing a metal substrate in a reaction chamber; evaporating a metal compound to obtain a metal-containing pre-reaction gas; introducing the metal-containing pre-reaction gas, a carbon-containing gas, an inert gas and ammonia into the reaction chamber to obtain a first mixed gas; exciting the first mixed gas into a plasma state and depositing on the surface of the metal substrate to obtain a metal carbide coating; step S2, introducing acetylene, an inert gas and hydrogen into the reaction chamber to obtain a second mixed gas; exciting the second mixed gas into a plasma state and depositing on the surface of the metal carbide coating to obtain SP 2 The hybrid carbon coating; step S3, introducing methane, an inert gas and ammonia into the reaction chamber to obtain a third mixed gas; exciting the third mixed gas into a plasma state and depositing on the surface of the SP 2 The hybrid carbon coating; step S3, introducing methane, an inert gas and ammonia into the reaction chamber to obtain a third mixed gas; exciting the third mixed gas into a plasma state and depositing on the surface of the SP 3 The hybrid carbon coating; step S4, repeating steps S2 and S3 in turn for 2-6 times to obtain the carbon-based coating bipolar plate.

[0014] Further, the reaction temperature, the working pressure and the plasma excitation voltage of the reaction chamber during the deposition of step S1, step S2 and step S3 are the same; preferably, the reaction temperature of the reaction chamber is 180-220℃, the working pressure is 50-300Pa, and the plasma excitation voltage is 400-600V; preferably, the inert gas comprises one or more of argon, helium and nitrogen.

[0015] Further, in step S1, the metal compound comprises one or more of TiCl4, TiO x , V2O5, Cr2O3 and WO3, x is 1-2; and / or the carbon-containing gas comprises one or more of methane, ethylene and acetylene; and / or the flow ratio of the metal-containing pre-reaction gas to the carbon-containing gas is (0.8-1.2):1; and / or the flow ratio of the carbon-containing gas, the inert gas and the ammonia is 1:(3-5):(3-5); and / or the deposition time of the titanium carbide coating is 3-6min; preferably, step S1 further comprises ultrasonic cleaning and / or plasma bombardment of the metal substrate before placing it in the reaction chamber.

[0016] Further, in step S2, the flow ratio of acetylene, the inert gas and hydrogen is 2:(3-5):(3-5); and / or the deposition time of the SP 2 hybrid carbon coating is 10-50s.

[0017] Further, in step S3, the flow ratio of methane, the inert gas and ammonia is 2:(3-5):(3-5); and / or the deposition time of the SP 3 hybrid carbon coating is 10-50s.

[0018] According to another aspect of the present application, a fuel cell is provided, comprising the carbon-based coating bipolar plate as described above.

[0019] By using the technical solution of the present application, a metal carbide is arranged as an intermediate layer on the surface of the metal substrate, and different hybrid types of amorphous carbon are arranged as surface layers, so that the use of noble metal can be avoided, and the cost of the bipolar plate is reduced. The metal carbide layer can enhance the bonding force between the metal substrate and the carbon-based composite coating, so that the surface carbon layer is not easy to fall off, and the service life of the bipolar plate is increased. The amorphous carbon layer is hybridized from SP 2 hybrid carbon and SP 3 hybrid carbon, wherein the SP 2 hybrid carbon has good electrical conductivity, the SP 3 hybrid carbon has excellent corrosion resistance due to the compact structure of the SP 2 hybrid carbon, and the content of the SP 3 hybrid carbon can combine the advantages of the two types of hybrid carbon, so as to improve the compactness of the coating, so that the bipolar plate has good electrical conductivity and corrosion resistance, and the service life is significantly increased. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application, and are incorporated herein by reference. The embodiments disclosed in the drawings are illustrative of the application and are not meant to limit the application as described in this patent. In the drawings:

[0021] Figure 1 A schematic view of a carbon-based coating bipolar plate structure according to an embodiment of the present application is shown.

[0022] In the above drawings, the following reference signs are used:

[0023] 10, metal substrate; 20, metal carbide coating; 30, carbon-based composite coating; 31, SP 2 hybrid carbon coating; 32, SP 3 hybrid carbon coating. DETAILED DESCRIPTION

[0024] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0025] As described in the background of the present application, the prior art has the problems of high cost, poor conductivity and poor corrosion resistance of the bipolar plate, especially the carbon-based coating cannot simultaneously achieve high conductivity and long service life. In order to solve the above problems, in a typical embodiment of the present application, a carbon-based coating bipolar plate is provided, which comprises, in the direction close to the membrane electrode, a metal substrate, a metal carbide coating, and a carbon-based composite coating stacked in sequence, the carbon-based composite coating comprises a plurality of layers of SP 2 hybrid carbon coating and a plurality of layers of SP 3 hybrid carbon coating, SP 2 hybrid carbon coating and SP 3 hybrid carbon coating alternately stacked, and SP 2 hybrid carbon coating close to the metal carbide coating, SP 3 hybrid carbon coating close to the membrane electrode; wherein SP 2 SP in the hybrid carbon coating 2 The weight percentage content of the hybrid carbon atoms is 60-75%, SP 3 SP in the hybrid carbon coating 3 The weight percentage content of the hybrid carbon atoms is 70-85%.

[0026] The application sets metal carbide as an intermediate layer on the surface of a metal substrate, and different hybrid types of amorphous carbon as surface layers, which can avoid using noble metals and reduce the cost of bipolar plates. The surface energy and ductility of the metal substrate and the carbon material are different, and the metal carbide with performance between the two can serve as a transition layer to improve the bonding strength of the coating and increase the service life of the bipolar plate.

[0027] The amorphous carbon is hybridized by graphite-like carbon (SP 2 ) and diamond-like carbon (SP 3 ), wherein the SP 2 hybridized carbon has a layered structure and is bonded to each other through van der Waals force, so it has high conductivity, but its structure is loose and thus has poor corrosion resistance; the SP 3 hybridized carbon is bonded to each other through strong covalent bonds, so it has a compact structure and thus has excellent corrosion resistance. The application sets a reasonable content of SP 2 hybridized carbon / SP 3 hybridized carbon, which can appropriately combine the advantages of the two types of hybridized carbon to improve the compactness of the coating, so that the bipolar plate has good conductivity and corrosion resistance and significantly increases the service life.

[0028] In addition, it can be understood that the SP 2 hybridized carbon coating and the SP 3 hybridized carbon coating are alternately stacked, which means that, in the direction close to the membrane electrode, the carbon-based coating bipolar plate comprises a metal substrate, a metal carbide coating, a SP 2 hybridized carbon coating, a SP 3 hybridized carbon coating, a SP 2 hybridized carbon coating and a SP 3 hybridized carbon coating, which are sequentially stacked. A plurality of groups of SP 2 hybridized carbon coatings can be arranged on the surface of the metal carbide coating in a specific order, the SP 3 hybridized carbon coating closest to the metal carbide coating is the farthest from the metal substrate and closest to the membrane electrode.

[0029] In a preferred embodiment, the weight percentage of SP 2 hybridized carbon atoms in the SP 2 hybridized carbon coating is 65-72%, so that the proportion of SP 2 hybridized carbon atoms is increased as much as possible to improve the conductivity; the weight percentage of SP 3 hybridized carbon atoms in the SP 3 hybridized carbon coating is 75-82%, so that the proportion of SP 3 hybridized carbon atoms is increased as much as possible to further improve the corrosion resistance. Under the above conditions, the best balance between the conductivity and corrosion resistance of the bipolar plate can be achieved.

[0030] In order to further reduce the cost of the bipolar plate, in a preferred embodiment, the metal substrate comprises one or more of stainless steel, titanium and aluminum alloy; and / or in the metal carbide coating, the metal carbide comprises one or more of titanium carbide, vanadium carbide, chromium carbide and tungsten carbide, preferably titanium carbide, which has better electrical conductivity and corrosion resistance, can further improve the performance of the bipolar plate and increase the service life of the bipolar plate.

[0031] In order to make the metal carbide coating more fully play the role of increasing the bonding force between the metal substrate and the surface carbon layer, in a preferred embodiment, the thickness of the metal carbide coating is 20-60 nm; and / or the SP 2 The number of the hybrid carbon coating is 3-6 layers, and the thickness of each layer is 15-30 nm; and / or the SP 3 The number of the hybrid carbon coating is 3-6 layers, and the thickness of each layer is 15-30 nm. By arranging the SP 2 The hybrid carbon coating and the SP 3 The hybrid carbon coating, the content of the hybrid carbon atoms can be more accurately controlled, thereby further improving the consistency between different batches of bipolar plates in industrial production.

[0032] In another typical embodiment of the present application, a preparation method of the above-mentioned carbon-based coating bipolar plate is also provided, which comprises the following steps: step S1, placing a metal substrate in a reaction chamber; evaporating a metal compound to obtain a metal-containing pre-reaction gas; introducing the metal-containing pre-reaction gas, a carbon-containing gas, an inert gas and ammonia into the reaction chamber to obtain a first mixed gas; exciting the first mixed gas into a plasma state and depositing it on the surface of the metal substrate to obtain a metal carbide coating; step S2, introducing acetylene, an inert gas and hydrogen into the reaction chamber to obtain a second mixed gas; exciting the second mixed gas into a plasma state and depositing it on the surface of the metal carbide coating to obtain a SP 2 Hybrid carbon coating; step S3, introducing methane, an inert gas and ammonia into the reaction chamber to obtain a third mixed gas; exciting the third mixed gas into a plasma state and depositing it on the surface of the SP 2 Hybrid carbon coating to obtain a SP 3 Hybrid carbon coating; step S4, repeating steps S2 and S3 in sequence for 2-6 times to obtain a carbon-based coating bipolar plate.

[0033] Specifically, the metal substrate is first placed in the reaction chamber as a deposition substrate, and then a metal compound is evaporated to obtain a metal-containing pre-reaction gas, which is introduced into the reaction chamber together with a carbon-containing gas, an inert gas and ammonia to obtain a first mixed gas; the first mixed gas is excited into a plasma state, in which process the carbon-containing gas provides a carbon source, and the inert gas and ammonia promote the formation of the excited state to obtain a metal carbide coating.

[0034] Afterwards, the preparation of the carbon-based composite coating is carried out: acetylene, inert gas and hydrogen are introduced into the reaction chamber to obtain a second mixed gas; the second mixed gas is excited into a plasma state, in which process acetylene is used as a carbon source and hydrogen is used as an activating agent; hydrogen can promote the formation of carbon-carbon double bonds, thereby promoting the SP 2 Hybrid carbon atoms are formed, which have excellent electrical conductivity and are deposited on the surface of the metal carbide coating to obtain a SP 2 Hybrid carbon coating.

[0035] Then methane, inert gas and ammonia are introduced into the reaction chamber to obtain a third mixed gas; the third mixed gas is excited into a plasma state, in which process methane is used as a carbon source and ammonia is used as an activating agent; the simultaneous action of methane and ammonia promotes the formation of carbon-carbon single bonds, thereby increasing the content of SP 3 Hybrid carbon atoms, which greatly improve the corrosion resistance of the coating, and are deposited on the surface of the SP 2 Hybrid carbon coating, to obtain a SP 3 Hybrid carbon coating.

[0036] Finally, steps S2 and S3 are repeated 2-6 times in sequence to obtain a metal carbide coating surface with SP 2 Hybrid carbon coating and SP 3 Hybrid carbon coating carbon-based coating bipolar plate.

[0037] The above preparation method can completely avoid the use of noble metals, and the preparation cost of the bipolar plate can be reduced by more than 50% compared with a gold coating. The present application prepares a carbon-based composite gradient coating on the surface of a metal bipolar plate, which reduces the preparation cost of the bipolar plate, and through control of the carbon source and the active gas, especially through control of different types of carbon-containing gas and activating gas introduced into the chamber, the combination form of carbon atoms is adjusted, so that the carbon atoms in the carbon-based composite coating have different hybrid types, and the SP 2 Hybrid type accounts for a high proportion, which plays a role in improving electrical conductivity, and the SP 3 Hybrid type accounts for a high proportion, which plays a role in improving corrosion resistance, and by orderly gradient distribution of the two hybrid carbon layers in the carbon-based composite coating, a bipolar plate with high electrical conductivity and excellent corrosion resistance is obtained. In addition, steps S2 and S3 are repeated 0-6 times in sequence, preferably 3-6 times, to improve the overall electrical conductivity, maximize the service life of the metal bipolar plate, and effectively improve the industrial production consistency of the carbon-based coating (and the bipolar plate comprising the same).

[0038] In order to better control the consistency and stability of the coating as a whole, in a preferred embodiment, the reaction temperature, working gas pressure and plasma excitation voltage of the reaction chamber during the deposition processes of step S1, step S2 and step S3 are the same; preferably, the reaction temperature of the reaction chamber is 180-220℃, the working gas pressure is 50-300Pa, and the plasma excitation voltage is 400-600V; preferably, the inert gas includes one or more of argon, helium and nitrogen. Since the present application adopts plasma-assisted chemical vapor deposition, a lower process temperature can be used, a higher deposition rate can be achieved at a lower temperature, the influence of temperature on the deposited material is further reduced, the coating thickness is easier to control, and the coating of a composite structure is more suitable for preparation. In addition, by controlling different gases and adjusting the deposition parameters in time, continuous operation of the deposition coating can be realized, further improving the production efficiency.

[0039] In order to make the coating type and thickness better meet the requirements of the bipolar plate, in a preferred embodiment, in step S1, the metal compound includes one or more of TiCl4, TiO x , V2O5, Cr2O3 and WO3, x is 1-2; and / or the flow ratio of the carbon-containing gas to the metal-containing pre-reaction gas is (0.8-1.2):1; and / or the flow ratio of the carbon-containing gas, inert gas and ammonia is 1:(3-5):(3-5); and / or the deposition time of the titanium carbide coating is 3-6min; preferably, step S1 further includes ultrasonic cleaning and / or plasma bombardment of the metal substrate before being placed in the reaction chamber, which can remove impurities and oxide films on the surface of the substrate, further increasing the adhesion of the subsequent coating to the surface of the substrate.

[0040] In order to make the proportion of different hybrid types of carbon atoms better meet the requirements of the bipolar plate, and better balance high conductivity and long service life, in a preferred embodiment, in step S2, the flow ratio of acetylene, inert gas and hydrogen is 2:(3-5):(3-5); and / or the deposition time of the SP 2 hybrid carbon coating is 10-50s, so that a carbon-based coating with thickness and specific hybrid atom distribution meeting the requirements can be further obtained, and the conductivity and service life of the bipolar plate coating are further improved.

[0041] Based on similar reasons, in a preferred embodiment, in step S3, the flow ratio of methane, inert gas and ammonia is 2:(3-5):(3-5); and / or the deposition time of the SP 3 hybrid carbon coating is 10-50s.

[0042] In yet another typical embodiment of the present invention, a fuel cell is also provided, comprising the carbon-based coated bipolar plate described above, which has a significantly increased service life.

[0043] Typical but not limiting, SP 2 SP in hybrid carbon coating 2 The weight percentage of hybrid carbon atoms is 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, or any two of these values.

[0044] Typical but not limiting, SP 3 SP in hybrid carbon coating 3 The weight percentage of hybrid carbon atoms is 70%, 71%, 72%, 73%, 74%, 75%, 76%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or any two of these values.

[0045] Typical, but not limiting, metal carbide coating thicknesses are 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, or any two of these values; SP 2 The thickness of a single layer of hybrid carbon coating is 15 nm, 20 nm, 25 nm, 30 nm, or any two of these values; SP 3 The thickness of a single layer of hybrid carbon coating is 15 nm, 20 nm, 25 nm, 30 nm or any two of these values.

[0046] Typically, but not limitingly, during the deposition process in steps S1, S2, and S3, the reaction temperature in the reaction chamber is within the range of 180°C, 190°C, 200°C, 210°C, 220°C, or any two of these values; the working gas pressure is within the range of 50Pa, 100Pa, 150Pa, 200Pa, 250Pa, 300Pa, or any two of these values; and the plasma excitation voltage is within the range of 400V, 450V, 500V, 550V, 600V, or any two of these values.

[0047] Typically, but not limitingly, in step S2, with the acetylene flow rate being 2, the inert gas flow rate is a range of 3, 3.5, 4, 4.5, 5, or any two of these values; the hydrogen flow rate is a range of 3, 3.5, 4, 4.5, 5, or any two of these values. 2 The deposition time of the hybrid carbon coating is 10s, 20s, 30s, 40s, 50s or any two of these values.

[0048] Typically but not limitedly, in step S3, the flow rate of the inert gas is 3, 3.5, 4, 4.5, 5 or any range value composed of any two of the above values, and the flow rate of the ammonia gas is 3, 3.5, 4, 4.5, 5 or any range value composed of any two of the above values, based on the flow rate of the methane being 2. 3 The deposition time of the hybrid carbon coating is 10 s, 20 s, 30 s, 40 s, 50 s or any range value composed of any two of the above values.

[0049] The application will be further described in detail below in conjunction with specific examples, which cannot be understood as limiting the scope of the application claimed.

[0050] Example 1

[0051] In step S1, the metal substrate (stainless steel) was ultrasonically cleaned and then placed in a reaction chamber; a metal compound (TiCl4) was evaporated to obtain a metal-containing pre-reaction gas; the metal-containing pre-reaction gas, carbon-containing gas (methane), inert gas (argon) and ammonia gas were introduced into the reaction chamber according to a flow rate ratio of 4:1:4:4 to obtain a first mixed gas; the first mixed gas was excited to a plasma state (an external voltage of 500 V) and deposited on the surface of the metal substrate (a reaction temperature of 200°C and a working gas pressure of 150 Pa) to obtain a metal carbide coating (titanium carbide, a deposition time of 5 min and a thickness of 40 nm);

[0052] In step S2, acetylene, inert gas (argon) and hydrogen were introduced into the reaction chamber according to a flow rate ratio of 2:4:4 to obtain a second mixed gas; the second mixed gas was excited to a plasma state (an external voltage of 500 V) and deposited on the surface of the metal carbide coating (a reaction temperature of 200°C and a working gas pressure of 150 Pa) to obtain SP 2 Hybrid carbon coating (deposition time of 30 s and single-layer thickness of 20 nm);

[0053] In step S3, methane, inert gas (argon) and ammonia were introduced into the reaction chamber according to a flow rate ratio of 2:4:4 to obtain a third mixed gas; the third mixed gas was excited to a plasma state (an external voltage of 500 V) and deposited on the surface of the SP 2 Hybrid carbon coating (deposition time of 30 s and single-layer thickness of 20 nm); 3 Hybrid carbon coating (deposition time of 30 s and single-layer thickness of 20 nm);

[0054] In step S4, steps S2 and S3 were repeated 3 times in sequence to obtain a carbon-based coating bipolar plate, and a structural schematic diagram is shown in Figure 1It can be seen that, in the direction close to the membrane electrode, the carbon-based coating bipolar plate comprises, in sequence, a metal substrate 10, a metal carbide coating 20, a carbon-based composite coating 30, and the carbon-based composite coating 30 comprises four layers of SP 2 hybrid carbon coating 31 and four layers of SP 3 hybrid carbon coating 32.

[0055] Examples 2 to 3

[0056] The difference from Example 1 is that the SP 2 hybrid carbon and SP 3 weight ratio of hybrid carbon, SP 2 SP in the hybrid carbon coating 2 weight percentage of hybrid carbon atoms, SP 3 SP in the hybrid carbon coating 3 weight percentage of hybrid carbon atoms, SP

[0057] Example 4

[0058] Step S1, the metal substrate (stainless steel) is ultrasonically cleaned and then placed in a reaction chamber; the metal compound (TiCl4) is evaporated to obtain a metal-containing pre-reaction gas; the metal-containing pre-reaction gas, carbon-containing gas (methane), inert gas (argon) and ammonia are introduced into the reaction chamber according to the flow ratio of 4:1:4:4 to obtain a first mixed gas; the first mixed gas is excited to a plasma state (an external voltage of 400V) and deposited on the surface of the metal substrate (the reaction temperature is 180℃ and the working gas pressure is 300Pa) to obtain a metal carbide coating (titanium carbide, the deposition time is 5min and the thickness is 40nm);

[0059] Step S2, acetylene, inert gas (argon) and hydrogen are introduced into the reaction chamber according to the flow ratio of 2:4:4 to obtain a second mixed gas; the second mixed gas is excited to a plasma state (an external voltage of 400V) and deposited on the surface of the metal carbide coating (the reaction temperature is 180℃ and the working gas pressure is 300Pa) to obtain SP 2 hybrid carbon coating (the deposition time is 30s and the single-layer thickness is 20nm);

[0060] Step S3, methane, inert gas (argon) and ammonia are introduced into the reaction chamber according to the flow ratio of 2:4:4 to obtain a third mixed gas; the third mixed gas is excited to a plasma state (an external voltage of 400V) and deposited on the surface of the SP 2 hybrid carbon coating (the deposition time is 30s and the single-layer thickness is 20nm); 3 hybrid carbon coating (the deposition time is 30s and the single-layer thickness is 20nm);

[0061] Step S4, steps S2 and S3 are repeated 3 times in turn, to obtain a carbon-based coated bipolar plate.

[0062] Example 5

[0063] Step S1, the metal substrate (stainless steel) is ultrasonically cleaned, and then placed in a reaction chamber; the metal compound (TiCl4) is evaporated to obtain a metal-containing pre-reaction gas; the metal-containing pre-reaction gas, carbon-containing gas (methane), inert gas (argon) and ammonia are introduced into the reaction chamber according to the flow ratio of 4:1:4:4 to obtain a first mixed gas; the first mixed gas is excited to a plasma state (an external voltage of 600V), and is deposited on the surface of the metal substrate (the reaction temperature is 220℃, and the working gas pressure is 50Pa) to obtain a metal carbide coating (titanium carbide, the deposition time is 5min, and the thickness is 40nm);

[0064] Step S2, acetylene, inert gas (argon) and hydrogen are introduced into the reaction chamber according to the flow ratio of 2:4:4 to obtain a second mixed gas; the second mixed gas is excited to a plasma state (an external voltage of 600V), and is deposited on the surface of the metal carbide coating (the reaction temperature is 220℃, and the working gas pressure is 50Pa) to obtain an SP 2 hybrid carbon coating (the deposition time is 30s, and the single-layer thickness is 20nm);

[0065] Step S3, methane, inert gas (argon) and ammonia are introduced into the reaction chamber according to the flow ratio of 2:4:4 to obtain a third mixed gas; the third mixed gas is excited to a plasma state (an external voltage of 600V), and is deposited on the surface of the SP 2 hybrid carbon coating (the reaction temperature is 220℃, and the working gas pressure is 50Pa) to obtain an SP 3 hybrid carbon coating (the deposition time is 30s, and the single-layer thickness is 20nm);

[0066] Step S4, steps S2 and S3 are repeated 3 times in turn, to obtain a carbon-based coated bipolar plate.

[0067] Example 6

[0068] Step S1: The metal substrate (stainless steel) is ultrasonically cleaned and then placed in the reaction chamber; the metal compound (TiCl4) is evaporated to obtain a metal-containing pre-reaction gas; the metal-containing pre-reaction gas, carbon-containing gas (ethylene), inert gas (argon), and ammonia are introduced into the reaction chamber at a flow rate ratio of 0.8:1:3:3 to obtain a first mixed gas; the first mixed gas is excited into a plasma state (applied voltage 500V) and deposited on the surface of the metal substrate (reaction temperature 200℃, working pressure 150Pa) to obtain a metal carbide coating (titanium carbide, deposition time 3min, thickness 20nm);

[0069] In step S2, acetylene, inert gas (argon), and hydrogen are introduced into the reaction chamber at a flow rate ratio of 2:3:3 to obtain a second mixed gas. This second mixed gas is then excited into a plasma state (applied voltage 500V) and deposited onto the surface of a metal carbide coating (reaction temperature 200℃, working pressure 150Pa) to obtain SP. 2 Hybrid carbon coating (deposition time 10s, single layer thickness 15nm);

[0070] In step S3, methane, inert gas (argon), and ammonia are introduced into the reaction chamber at a flow rate ratio of 2:3:3 to obtain a third mixed gas; the third mixed gas is excited into a plasma state (applied voltage 500V) and deposited on SP. 2 The surface of the hybrid carbon coating (reaction temperature 200℃, working pressure 150Pa) yielded SP. 3 Hybrid carbon coating (deposition time 10s, single layer thickness 15nm);

[0071] Step S4: Repeat steps S2 and S3 6 times in sequence to obtain a carbon-based coated bipolar plate.

[0072] Example 7

[0073] Step S1: The metal substrate (stainless steel) is ultrasonically cleaned and then placed in the reaction chamber; the metal compound (TiO2) is evaporated to obtain a metal-containing pre-reaction gas; the metal-containing pre-reaction gas, carbon-containing gas (acetylene), inert gas (argon), and ammonia are introduced into the reaction chamber at a flow ratio of 1.2:1:5:5 to obtain a first mixed gas; the first mixed gas is excited into a plasma state (applied voltage 500V) and deposited on the surface of the metal substrate (reaction temperature 200℃, working pressure 150Pa) to obtain a metal carbide coating (titanium carbide, deposition time 6min, thickness 60nm);

[0074] In step S2, acetylene, inert gas (argon), and hydrogen are introduced into the reaction chamber at a flow rate ratio of 2:5:5 to obtain a second mixed gas. This second mixed gas is then excited into a plasma state (applied voltage 500V) and deposited onto the surface of a metal carbide coating (reaction temperature 200℃, working pressure 150Pa) to obtain SP. 2 Hybrid carbon coating (deposition time 50s, single layer thickness 30nm);

[0075] In step S3, methane, inert gas (argon), and ammonia are introduced into the reaction chamber at a flow rate ratio of 2:5:5 to obtain a third mixed gas; the third mixed gas is excited into a plasma state (applied voltage 500V) and deposited on SP. 2 The surface of the hybrid carbon coating (reaction temperature 200℃, working pressure 150Pa) yielded SP. 3 Hybrid carbon coating (deposition time 50s, single layer thickness 30nm);

[0076] Step S4: Repeat steps S2 and S3 three times in sequence to obtain a carbon-based coated bipolar plate.

[0077] Comparative Example 1

[0078] The difference from Example 1 is that no titanium carbide coating is provided.

[0079] Comparative Example 2

[0080] The difference from Example 1 is that SP was not set. 2 and SP 3 The hybrid carbon is distributed in an ordered gradient, and the entire carbon-based coating is SP. 2 Carbon atoms with a hybrid carbon percentage of 70%.

[0081] Comparative Example 3

[0082] The difference from Example 1 is that SP was not set. 2 and SP 3 The hybrid carbon is distributed in an ordered gradient, and the entire carbon-based coating is SP. 3 Carbon atoms with a hybrid carbon percentage of 75%.

[0083] Comparative Example 4

[0084] The difference from Example 1 is that the applied voltage during plasma excitation is 300V, the reaction temperature in the reaction chamber is 150℃, and the working pressure is 400Pa.

[0085] Comparative Example 5

[0086] The difference from Example 1 is that the applied voltage during plasma excitation is 700V, the reaction temperature in the reaction chamber is 250℃, and the working pressure is 30Pa.

[0087] The bipolar plates of the above embodiments and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0088] Test method:

[0089] Types and contents of hybrid carbon atoms: The percentage of different hybrid carbon atoms in the coating is generally confirmed by XPS (X-ray photoelectron spectroscopy). Surface analysis is performed based on the photoelectric effect, and the percentage of different hybrid carbon atoms is calculated by peak values.

[0090] Conductivity and corrosion resistance: GB_T 20042.6-2024. The equipment used is a contact resistance tester with single-sided probe measurement and a pressure of 0.6 MPa. The contact resistance values ​​are measured before and after the constant potential polarization test. The lower the contact resistance before the constant potential polarization test, the better the conductivity. The smaller the change in contact resistance value before and after the constant potential polarization test, the better the corrosion resistance. The corrosion current density of the coating material is calculated based on the average corrosion current in the last 5 minutes of the test. The higher the corrosion current density, the better the corrosion resistance.

[0091] Service life: Based on the contact resistance measurements before and after corrosion and the corrosion current density test results, combined with empirical values, the service life of different types of coatings is predicted.

[0092] Table 1

[0093]

[0094]

[0095] As can be seen from the above, compared with the comparative examples, the embodiments of the present invention, by setting a metal carbide as an intermediate layer on the surface of the metal substrate and amorphous carbon of different hybrid types as a surface layer, can avoid the use of precious metals and reduce the cost of bipolar plates. The metal carbide layer can enhance the adhesion between the metal substrate and the carbon-based composite coating, making the surface carbon layer less prone to peeling off and increasing the service life of the bipolar plate. The amorphous carbon layer is made of SP 2 Hybrid carbon and SP 3 It is formed by the hybridization of carbon, of which SP 2 Hybrid carbon has good electrical conductivity, SP 3 The dense structure of hybrid carbon gives it excellent corrosion resistance. This application sets a reasonable SP... 2 Hybridized carbon and SP 3 The hybrid carbon content can combine the advantages of two types of hybrid carbon, thereby improving the density of the coating, giving the bipolar plate good conductivity and corrosion resistance, and significantly increasing its service life.

[0096] Furthermore, it can be seen that the overall effect is better when all process parameters are within the preferred range of the present invention.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon-based coated bipolar plate characterized by, The carbon-based coated bipolar plate comprises, in the direction close to the membrane electrode, a metal substrate, a metal carbide coating, a carbon-based composite coating comprising a plurality of SP 2 hybrid carbon coating and a plurality of SP 3 hybrid carbon coating, the SP 2 hybrid carbon coating and the SP 3 hybrid carbon coating one by one alternately stacked, and the SP 2 hybrid carbon coating close to the metal carbide coating, the SP 3 hybrid carbon coating close to the membrane electrode; wherein the SP 2 SP in the hybrid carbon coating 2 The weight percentage of the hybrid carbon atoms is 60-75%, and the SP 3 SP in the hybrid carbon coating 3 The weight percentage of the hybrid carbon atoms is 70-85%.

2. The carbon-based coated bipolar plate of claim 1, wherein, SP 2 SP in the hybrid carbon coating 2 SP in the hybrid carbon coating 3 SP in the hybrid carbon coating 3 SP in the hybrid carbon coating 3. Carbon-based coated bipolar plate according to claim 1 or 2, characterized in that The metal substrate comprises one or more of stainless steel, titanium and aluminum alloy; and / or in the metal carbide coating, the metal carbide comprises one or more of titanium carbide, vanadium carbide, chromium carbide and tungsten carbide, preferably titanium carbide.

4. The carbon-based coated bipolar plate according to any one of claims 1 to 3, characterized in that, the metal carbide coating has a thickness of 20-60 nm; and / or the SP 2 the number of hybrid carbon coatings is 3-6 layers, and the thickness of a single layer is 15-30 nm; and / or the SP 3 The number of the hybrid carbon coating layer is 3-6, and the thickness of the single layer is 15-30 nm.

5. The method of producing a carbon-based coated bipolar plate according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: S1, placing a metal substrate in a reaction chamber; evaporating a metal compound to obtain a metal-containing pre-reaction gas; introducing the metal-containing pre-reaction gas, a carbon-containing gas, an inert gas and ammonia into the reaction chamber to obtain a first mixed gas; exciting the first mixed gas into a plasma state and depositing on the surface of the metal substrate to obtain a metal carbide coating; Step S2, introducing acetylene, the inert gas and hydrogen into the reaction chamber to obtain a second mixed gas; exciting the second mixed gas into a plasma state and depositing on the surface of the metal carbide coating to obtain SP 2 Hybrid carbon coating; Step S3, introducing methane, the inert gas and the ammonia gas into the reaction chamber to obtain a third mixed gas; exciting the third mixed gas into a plasma state and depositing on the SP 2 surface of the hybrid carbon coating to obtain an SP 3 hybrid carbon coating; S4, sequentially repeating the step S2 and the step S3 for 2-6 times to obtain the carbon-based coating bipolar plate.

6. The production method according to claim 5, characterized by, In the deposition process of the step S1, the step S2 and the step S3, the reaction temperature, working gas pressure and plasma excitation voltage of the reaction chamber are the same; Preferably, the reaction temperature of the reaction chamber is 180-220℃, the working gas pressure is 50-300Pa, and the plasma excitation voltage is 400-600V. Preferably, the inert gas comprises one or more of argon, helium and nitrogen.

7. The production method according to claim 5 or 6, characterized by, In the step S1, The metal compound comprises one or more of TiCl4, TiO x , V2O5, Cr2O3, WO3, x is 1 to 2; and / or the carbon-containing gas comprises one or more of methane, ethylene, and acetylene; and / or The flow ratio of the metal-containing pre-reaction gas to the carbon-containing gas is (0.8-1.2):1; and / or the flow ratio of the carbon-containing gas, the inert gas and the ammonia is 1:(3-5):(3-5); and / or the deposition time of the titanium carbide coating is 3-6min; Preferably, the step S1 further comprises ultrasonic cleaning and / or plasma bombardment of the metal substrate before placing it in the reaction chamber.

8. The production method according to any one of claims 5 to 7, characterized by, In the step S2, The flow ratio of the acetylene, the inert gas and the hydrogen is 2:(3-5):(3-5); and / or The SP 2 The deposition time of the hybrid carbon coating is 10-50 s.

9. The production method according to any one of claims 5 to 8, characterized by, In the step S3, The flow ratio of the methane, the inert gas and the ammonia is 2:(3-5):(3-5); and / or The SP 3 The deposition time of the hybrid carbon coating is 10-50 s.

10. A fuel cell characterized by comprising: The carbon-based coating bipolar plate of any one of claims 1-4.

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