Silicon-based bipolar plate surface coating and preparation method and application thereof

Abstract

The invention discloses a silicon-based bipolar plate surface coating and a preparation method and application thereof. The silicon-based bipolar plate surface coating comprises a titanium transition layer and a compact diamond-like carbon functional layer which are sequentially stacked on the surface of the silicon-based bipolar plate. The preparation method comprises the following steps: depositing the titanium transition layer on the surface of the silicon-based bipolar plate by adopting a magnetron sputtering technology, and depositing the compact diamond-like carbon functional layer on the surface of the titanium transition layer by adopting a magnetic filtration vacuum arc ion plating technology. According to the silicon-based bipolar plate surface coating prepared by the invention, the oxidation resistance is remarkably improved by virtue of stronger C-C bonds and higher chemical inertness while low contact resistance (less than or equal to 6 m omega.cm < 2 >) is maintained. After being baked for 2 hours at the temperature of 200 DEG C, the contact resistance change rate is stably controlled within 3%, and excellent high-temperature stability is shown, so that the problems that a silicon-based bipolar plate coating is low in resistance but is easy to oxidize at high temperature and the resistance is increased when a traditional preparation method is used are solved.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a high-performance, high-density surface coating for silicon-based bipolar plates in fuel cells, its preparation method, and its application. Background Technology

[0002] Currently, countries worldwide are vigorously developing new energy vehicles powered by proton exchange membrane fuel cells (PEMFCs). PEMFCs produce only water and heat during energy conversion, releasing no greenhouse gases. They also boast advantages such as low noise, high conversion efficiency, durability, and rapid start-up at room temperature. Therefore, PEMFC applications are rapidly expanding in sectors such as transportation, aviation, and new energy vehicles. Although PEMFC development is rapid, large-scale commercialization is still some distance away. Currently, in addition to challenges such as inadequate infrastructure, low market acceptance, and high costs, other technical issues need to be addressed, including water management, thermal management, and insufficient durability. Overcoming key technological bottlenecks to achieve zero-carbon emission green hydrogen production, efficient and low-cost hydrogen storage and transportation, and steadily advancing the construction of hydrogen refueling stations are effective ways to solve this problem. Furthermore, accelerating the commercialization of PEMFCs requires improving the overall performance of its key components, price competitiveness, and the reliability and stability of battery operation. Specifically, the national government needs to introduce relevant policies and industry standards, formulate a development strategy for the fuel cell industry, encourage enterprises to invest heavily and deepen cooperation with universities, strive to overcome the technological bottlenecks of key core components, and promote the healthy and rapid development of PEMFC and related industries.

[0003] Bipolar plates are the core component of PEMFCs, typically accounting for over 80% of the total fuel cell mass, 50% of the total fuel cell stack volume, and 40% of the total fuel cell stack cost. A key function of bipolar plates is as gas-water channels, uniformly guiding reactant gases into the membrane electrode assembly (MEA) of the fuel cell through surface flow fields, while simultaneously facilitating the discharge of generated water. Therefore, materials with good electrical conductivity, corrosion resistance, hydrophobicity, and sufficient mechanical strength are usually selected as raw materials for bipolar plates.

[0004] PEMFC bipolar plates can be classified into graphite bipolar plates, metal bipolar plates, material bipolar plates, and silicon-based bipolar plates based on the material used. Traditional silicon-based bipolar plates often rely on a higher concentration of sp(s) in the surface coating to increase conductivity and reduce contact resistance. 2 Hybridized carbon atoms conduct electricity with π electrons, but sp electrons... 2 The boundaries of clusters and various dangling bonds are active sites for chemical reactions. These sites are prone to oxidation and react with oxygen, cutting off the path of electron transport within the coating and leading to an increase in the bulk resistance of the coating. Summary of the Invention

[0005] The main objective of this invention is to provide a silicon-based bipolar plate surface coating and its preparation method, thereby solving the problem that silicon-based bipolar plate coatings have low resistance but are prone to oxidation and increased resistance at high temperatures when using a single preparation method.

[0006] Another object of the present invention is to provide the application of the surface coating of the silicon-based bipolar plate.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: A first aspect of this invention provides a surface coating for a silicon-based bipolar plate, comprising: a titanium transition layer and a dense diamond-like carbon functional layer sequentially stacked on the surface of the silicon-based bipolar plate, wherein the dense diamond-like carbon functional layer contains hybrid carbon sp³ / sp 2 The ratio is in the range of 0.3 to 0.4.

[0008] A second aspect of this invention provides a method for preparing the surface coating of the silicon-based bipolar plate, comprising: A titanium transition layer was deposited on the surface of a silicon-based bipolar plate using magnetron sputtering technology. A dense diamond-like carbon functional layer was deposited on the surface of the titanium transition layer using magnetic filtering vacuum arc ion plating technology.

[0009] A third aspect of the present invention provides the application of the silicon-based bipolar plate surface coating in the field of fuel cells.

[0010] Compared with the prior art, the advantages of the present invention include: 1) This invention innovatively combines magnetron sputtering technology with magnetically filtered vacuum arc ion plating technology. First, the titanium (Ti) transition layer prepared by magnetron sputtering not only has good adhesion to the silicon substrate, but also effectively alleviates the problems of thermal expansion coefficient mismatch and stress concentration between the GLC coating and the silicon substrate; 2) The titanium transition layer structure of the present invention is dense and can act as the first barrier to block oxygen diffusion. Then, a dense diamond-like carbon (GLC) functional layer is prepared by magnetic filtering vacuum arc ion plating technology. This technology can effectively filter out large particles generated by arc ion plating. The obtained GLC coating is dense and non-porous with a smooth and flat surface, which can provide the largest contact area, thereby achieving low contact resistance, which can be as low as about 6 mΩ·cm². It also forms a second gas barrier layer to reduce the impact of oxygen penetrating the coating at high temperature and oxidizing the silicon substrate. 3) The surface coating of the silicon-based bipolar plate prepared by this invention contains more sp 3Structurally closer to diamond-like carbon (DLC) coatings, it ensures low resistance while having stronger C-C bonds and better chemical inertness, resulting in stronger oxidation resistance and a high oxidation initiation temperature of around 300-400℃. After a short baking period of 2 hours at 200℃, there is almost no risk of oxidation. Its contact resistance change rate can be stably controlled within 3%, which fully demonstrates its excellent stability and oxidation resistance in high-temperature environments. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0012] Figure 1 This is a thickness diagram of the GLC coating prepared using a silicon-based bipolar plate as the substrate in Embodiment 1 of the present invention. Figure 2 This is a surface morphology diagram of the GLC coating based on a silicon-based bipolar plate in Embodiment 1 of the present invention; Figure 3 This is a Raman spectral image of the GLC coating based on a silicon-based bipolar plate in Embodiment 1 of the present invention. Figure 4 This is a comparison chart of contact resistance data for bipolar plates with GLC coating, uncoated bipolar plates, and bipolar plates with GLC coating after baking in Embodiment 1 of the present invention. Figure 5 This is a comparison chart of contact resistance data between a GLC-coated bipolar plate and an uncoated bipolar plate, and the GLC coating after baking, in Embodiment 2 of the present invention. Figure 6 This is a comparison chart of contact resistance data between a bipolar plate with GLC coating and an uncoated bipolar plate, and after baking the GLC coating, in Embodiment 3 of the present invention. Detailed Implementation

[0013] In view of the problem that the existing silicon-based bipolar plate coating has low resistance but is prone to oxidation and increased resistance at high temperatures when using a single preparation method, the inventors of this invention have proposed the technical solution of the present invention through long-term research and extensive practice. The main innovation is to prepare a coating on the surface of a silicon-based bipolar plate with titanium (Ti) as the transition layer and high-purity dense GLC as the functional layer by synergistic combination of magnetron sputtering and magnetic filtering vacuum arc ion plating technology.

[0014] The following will further explain the technical solution, its implementation process, and its principles. However, it should be understood that within the scope of this invention, the above-mentioned technical features of this invention and the technical features specifically described below (in embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here.

[0015] As one aspect of the technical solution of the present invention, the surface coating of a silicon-based bipolar plate includes: a titanium (Ti) transition layer and a dense diamond-like carbon functional layer sequentially stacked on the surface of the silicon-based bipolar plate, wherein the dense diamond-like carbon functional layer has a sp³ / sp 2 The ratio is between 0.3 and 0.4. This invention obtains extremely strong chemical inertness and antioxidant properties through a large number of sp3 hybrid carbons.

[0016] In some embodiments, the thickness of the dense diamond-like carbon functional layer is 100 nm to 200 nm.

[0017] In some embodiments, the thickness of the titanium transition layer is 20 nm to 100 nm.

[0018] In some embodiments, the thickness of the coating on the silicon-based bipolar plate is 120~300 nm.

[0019] In some embodiments, the silicon-based bipolar plate surface coating of the present invention is rich in sp³ hybrid carbon, which is closer to diamond-like carbon (DLC). While maintaining low contact resistance (≤6 mΩ·cm²), it significantly improves antioxidant performance due to stronger C-C bonds and higher chemical inertness.

[0020] In some implementations, after baking at 200°C for 2 hours, the contact resistance change rate of the coating on the surface of the silicon-based bipolar plate is within 3%, exhibiting excellent high-temperature stability, thereby solving the problem that the silicon-based bipolar plate coating has low resistance but is easily oxidized and has increased resistance at high temperatures when using traditional preparation methods.

[0021] As another aspect of the technical solution of the present invention, it relates to a method for preparing the surface coating of the silicon-based bipolar plate, which includes: A titanium transition layer was deposited on the surface of a silicon-based bipolar plate using magnetron sputtering technology. A dense diamond-like carbon functional layer was deposited on the surface of the titanium transition layer using magnetic filtering vacuum arc ion plating technology.

[0022] In some preferred embodiments, the preparation method specifically includes: A protective gas is introduced into the vacuum chamber of the magnetron sputtering equipment to control the gas pressure in the vacuum chamber to ≤1Pa; A titanium target is activated for magnetron sputtering, and a pulsed bias voltage is applied to the silicon-based bipolar plate, thereby depositing a titanium transition layer on the surface of the silicon-based bipolar plate.

[0023] This invention utilizes a Ti transition layer prepared by magnetron sputtering, which not only exhibits strong adhesion to the silicon substrate but also effectively alleviates the problems of thermal expansion coefficient mismatch and stress concentration between the GLC coating and the silicon substrate. Furthermore, the dense structure of the Ti transition layer itself acts as a first barrier to prevent oxygen diffusion. Moreover, the depth of this Ti transition layer is well-suited to the significant difference in thermal expansion coefficients and the bonding challenges between silicon and carbon materials, playing a crucial role in stress buffering and interface strengthening.

[0024] In some preferred embodiments, the protective gas includes argon, but is not limited to this.

[0025] In some preferred embodiments, a protective gas is introduced to control the pressure in the vacuum chamber at 0.3 Pa to 0.8 Pa.

[0026] In some preferred embodiments, the process conditions of the magnetron sputtering technology include: a target current of 80A to 160A for the titanium target, a pulse bias voltage of -150V to -300V applied to the silicon-based bipolar plate, a deposition temperature of 120 to 150°C, and a deposition time of 10 min to 30 min, preferably 20 min to 30 min.

[0027] In some preferred embodiments, the preparation method specifically includes: Turn on the graphite target and stabilize the arc current at 100 A~200 A; A pulsed negative bias of 650 V to 750 V (high-energy ions, promoting sp³ formation) and a filtered current of 7 A to 14 A are applied to a silicon-based bipolar plate with a deposited titanium transition layer. The total deposition time is 30 min to 60 min (to ensure sufficient densification), forming a dense diamond-like carbon functional layer (also known as a GLC coating) on ​​the surface of the titanium transition layer.

[0028] This invention uses magnetic filtration vacuum arc ion plating technology to prepare GLC coatings. This technology can effectively filter out large particles generated by arc ion plating. The resulting GLC coating is dense and non-porous with a smooth and flat surface, providing the maximum contact area and thus achieving low contact resistance, which can be as low as about 6 mΩ·cm². It also forms a second gas barrier layer to reduce the impact of oxygen penetrating the coating at high temperatures and causing oxidation of the silicon substrate.

[0029] In some preferred embodiments, the preparation method further includes: after the titanium transition layer is deposited, when the temperature of the vacuum chamber drops to 80°C~100°C and the vacuum degree is ≤0.8Pa, the graphite target is opened.

[0030] In some preferred embodiments, the preparation method further includes: pretreating the surface of the silicon-based bipolar plate before depositing the titanium transition layer, the pretreating including: The silicon-based bipolar plate was ultrasonically cleaned, dried, and then placed in a magnetron sputtering apparatus. The chamber of the magnetron sputtering equipment was evacuated to a background vacuum level not exceeding 2 × 10⁻⁶. -4 Torr, the temperature is heated to 120~150℃; A pulse bias voltage of -500V to -800V is applied to the silicon-based bipolar plate, through A Ion bombardment of the substrate surface for 30 to 60 minutes of continuous ion cleaning.

[0031] In some more preferred embodiments, the method for preparing the surface coating of the silicon-based bipolar plate specifically includes: S1. Clean and dry the surface of the silicon-based bipolar plate; S2. The silicon-based bipolar plate is placed into a vacuum chamber, evacuated and heated to prepare a coating on the surface of the silicon-based bipolar plate (also known as a GLC film).

[0032] Furthermore, in step S2, the GLC film comprises an underlying Ti transition layer and a surface layer of dense diamond-like carbon functional layer (i.e., GLC layer).

[0033] Further, in step S2, the protective gas is Ar gas, and Ar gas is introduced to control the gas pressure in the vacuum chamber to ≤1Pa; the Ti target is turned on, a Ti transition layer is deposited, the deposition time is 20~30min, and the Ti target is turned off; when the temperature inside the chamber is adjusted to 80~100℃ and the vacuum degree is ≤0.8Pa, the graphite target is turned on, a dense diamond-like carbon functional layer is deposited, the multi-arc current is 100~200A, the bias voltage is -750~-650V, and the deposition time is 30~60min.

[0034] In some more specific embodiments, a method for preparing a surface coating on a silicon-based bipolar plate includes the following steps: (1) Pretreatment of silicon bipolar plate: The silicon bipolar plate substrate is ultrasonically cleaned in acetone and anhydrous ethanol in sequence to remove surface oil and impurities. After drying in a clean vacuum furnace, it is loaded into the coating equipment. (2) Heating and vacuuming: Evacuate the furnace cavity to a background vacuum level not exceeding 2×10 -4 Torr heats the furnace rack to 120~150℃; (3) Ion cleaning: Apply a pulse bias voltage of -500V to -800V to the silicon-based bipolar plate, and then clean it by A. Ion bombardment of the substrate surface for 30-60 minutes is used to activate the surface and remove surface impurities. (4) Magnetron sputtering deposition of Ti transition layer: a. Adjust the argon gas flow rate to stabilize the working pressure of the vacuum chamber at 0.3~0.8 Pa; b. Turn on the magnetron sputtering power supply for the titanium target and adjust the target current to 80~160A; c. Apply a pulsed bias voltage of -150V to -300V to a silicon-based bipolar plate and deposit for 10 to 30 minutes to form a dense titanium transition layer with a thickness of 20 to 100 nm on the surface of the silicon-based bipolar plate. (5) Magnetic filtration vacuum arc ion plating deposition of GLC conductive coating: a. Turn off the titanium target power supply and wait for the temperature to drop below 100℃. Turn on the graphite target (99.99% purity) power supply, and stabilize the arc current at 100~200 A after arc ignition; b. Apply a pulsed bias voltage of -650V to -750V and a filtered current of 7 to 14A to a silicon-based bipolar substrate with a Ti transition layer deposited on it. The total deposition time is 30 to 60 minutes, and a dense GLC conductive coating with a thickness of 100 nm to 200 nm is finally formed on the Ti transition layer.

[0035] The silicon-based bipolar plate surface coating prepared by this invention contains more sp 3 Structurally closer to diamond-like carbon (DLC) coatings, it maintains low resistance while exhibiting stronger C-C bonds and better chemical inertness, resulting in enhanced oxidation resistance and a high oxidation initiation temperature of approximately 300-400°C. Short-term baking at 200°C for 2 hours carries virtually no risk of oxidation. Its contact resistance change rate can be stably controlled within 3%, fully demonstrating its excellent stability and oxidation resistance under high-temperature conditions. This effect stems from the synergy between the Ti transition layer optimized for silicon substrates and the dense GLC coating with high sp³ content, forming a perfect barrier against oxygen diffusion.

[0036] In summary, this invention achieves high overall density and defect-free coating through a double-layer structure and specific high-energy process, while also achieving low resistance (≤6 mΩ·cm²) and high barrier properties.

[0037] As another aspect of the technical solution of the present invention, it relates to the application of the silicon-based bipolar plate surface coating in the field of fuel cells.

[0038] Furthermore, the fuel cell includes a proton exchange membrane fuel cell (PEMFC).

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. It should be noted that the following embodiments are intended to facilitate understanding of this invention and are not intended to limit it in any way. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the manufacturer.

[0040] Example 1

[0041] In this embodiment, the surface of a commercial silicon-based bipolar plate (size 210mm×210mm×0.3mm, bulk contact resistance of 8~9mΩ·cm²) is treated. The specific method for preparing the surface coating of the silicon-based bipolar plate is as follows: 1. Pretreatment of silicon-based bipolar plates The silicon-based bipolar plate substrate was sequentially placed in acetone and anhydrous ethanol for ultrasonic cleaning for 15 minutes each, and finally dried in a clean vacuum oven. 2. Heating and vacuuming GLC coating deposition is performed using coating equipment manufactured by Shanghai Nafeng, equipped with a double-bend electromagnetic filtration system. Parts are loaded into the vacuum chamber, the chamber door is closed, a vacuum is evacuated, and the chamber is heated to a vacuum level better than 2×10⁻⁶. -4 Torr, the temperature reaches 130℃; 3. Ion cleaning Argon gas is introduced into the vacuum chamber, and the vacuum level is ≤4×1 3 Torr applies a -650V pulse bias to the substrate and performs A for 45 minutes. Ion cleaning removes dust and other impurities adhering to the surface and activates the surface of the silicon-based bipolar plate; 4. Magnetron sputtering deposition of Ti transition layer After ion cleaning, Ar gas was introduced to control the pressure in the vacuum chamber at 0.5 Pa. The DC magnetron sputtering power supply for the titanium target (99.99% purity) was turned on, and the target current was set to 130 A. A pulsed bias of -250 V was applied to the substrate, and a Ti transition layer with a thickness of approximately 25 nm was deposited at 130 °C for 15 minutes. 5. Magnetic filtration vacuum arc ion plating deposition of GLC coating Turn off the titanium target power supply and allow the temperature to drop to 100°C. Turn on the graphite target (99.99% purity) power supply, and stabilize the arc current at 150 A after arc ignition. Apply a pulsed bias of -700V and a filtered current of 10A to the substrate, and deposit for 40 minutes to form a dense GLC coating with a thickness of approximately 180 nm.

[0042] The following performance tests were performed on the surface coating of the silicon-based bipolar plate obtained by the above treatment: The film thickness and surface morphology of the coated sample prepared on a silicon-based bipolar plate substrate were characterized using dual-beam scanning electron microscopy (FIB-SEM). The electron beam intensity was 4 kV, and the coating thickness was as follows: Figure 1 As shown, the surface morphology is as follows Figure 2 As shown. The surface carbon film was analyzed using Raman spectroscopy (LabRAM, Horiba Jpbin Yvon SAS) at a laser wavelength of 532 nm. The results are as follows. Figure 3 As shown, the Id / Ig ratio is 1.40. The interfacial contact resistance (ICR) between the gas diffusion layer (simulated using carbon paper) and the coated sample was measured using a Hepu resistance meter (CHT3545, range 10mΩ-1000mΩ). A continuous pressure of 0.1MPa to 1.9MPa was applied, and the contact resistance at 1.5MPa was observed and recorded. The method proposed by Davies was then used for calculation, resulting in an average ICR of 5.7mΩ·cm². After baking at 200℃ for 2h, the contact resistance was 5.8mΩ·cm², with a resistance change rate of approximately 1.7%. This is compared with the contact resistance data of an uncoated bipolar plate. Figure 4 As shown.

[0043] Example 2

[0044] In this embodiment, the surface of a commercial silicon-based bipolar plate (size 210mm×210mm×0.6mm, bulk contact resistance of 10~11 mΩ·cm²) is treated. The specific method for preparing the surface coating of the silicon-based bipolar plate is as follows: 1. Pretreatment of silicon-based bipolar plates The silicon-based bipolar plate substrate was sequentially placed in acetone and anhydrous ethanol for ultrasonic cleaning for 15 minutes each, and finally dried in a clean vacuum oven. 2. Heating and vacuuming GLC coating deposition is performed using coating equipment manufactured by Shanghai Nafeng, equipped with a double-bend electromagnetic filtration system. Parts are loaded into the vacuum chamber, the chamber door is closed, a vacuum is evacuated, and the chamber is heated to a vacuum level better than 2×10⁻⁶. -3 Torr, the temperature reaches 120℃; 3. Ion cleaning Argon gas is introduced into the vacuum chamber, and the vacuum level is ≤4×1 3 Torr applies a -500V pulse bias to the substrate and performs A for 30 minutes. Ion cleaning removes dust and other impurities adhering to the surface and activates the surface of the silicon-based bipolar plate; 4. Magnetron sputtering deposition of Ti transition layer After ion cleaning, Ar gas was introduced to control the pressure in the vacuum chamber at 0.3 Pa. The DC magnetron sputtering power supply for the titanium target (99.99% purity) was turned on, and the target current was set to 80 A. A pulsed bias of -150 V was applied to the substrate, and a Ti transition layer with a thickness of approximately 20 nm was deposited at 150 °C for 10 minutes. 5. Magnetic filtration vacuum arc ion plating deposition of GLC coating Turn off the titanium target power supply and allow the temperature to drop below 100°C. Turn on the graphite target (99.99% purity) power supply, and stabilize the arc current at 100 A after arc ignition. Apply a pulsed bias of -650V and a filtered current of 14A to the substrate, and deposit for 30 minutes to form a dense GLC coating with a thickness of approximately 100 nm.

[0045] The following performance tests were performed on the surface coating of the silicon-based bipolar plate obtained by the above treatment: The interfacial contact resistance (ICR) between the gas diffusion layer (simulated using carbon paper) and the coated sample was measured using a Hepu resistance meter (CHT3545, range 10mΩ-1000mΩ). A continuous pressure of 0.1 MPa to 1.9 MPa was applied, and the contact resistance at 1.5 MPa was observed and recorded. The method proposed by Davies was then used for calculation, ultimately yielding an average ICR of 6.1 mΩ·cm². After baking at 200℃ for 2 hours, the contact resistance was 6.2 mΩ·cm², with a resistance change rate of approximately 1.6%. This was compared with the contact resistance data of an uncoated bipolar plate. Figure 5 As shown.

[0046] Example 3

[0047] In this embodiment, the surface of a commercial silicon-based bipolar plate (size 210mm×210mm×0.6mm, bulk contact resistance of 10~11 mΩ·cm²) is treated. The specific method for preparing the surface coating of the silicon-based bipolar plate is as follows: 1. Pretreatment of silicon-based bipolar plates The silicon-based bipolar plate substrate was sequentially placed in acetone and anhydrous ethanol for ultrasonic cleaning for 15 minutes each, and finally dried in a clean vacuum oven. 2. Heating and vacuuming GLC coating deposition is performed using coating equipment manufactured by Shanghai Nafeng, equipped with a double-bend electromagnetic filtration system. Parts are loaded into the vacuum chamber, the chamber door is closed, a vacuum is evacuated, and the chamber is heated to a vacuum level better than 2×10⁻⁶. -3 Torr, with temperatures reaching 150°C; 3. Ion cleaning Argon gas is introduced into the vacuum chamber, and the vacuum level is ≤4×1 3Torr applies a -800V pulse bias to the substrate and performs A for 60 minutes. Ion cleaning removes dust and other impurities adhering to the surface and activates the surface of the silicon-based bipolar plate; 4. Magnetron sputtering deposition of Ti transition layer After ion cleaning, Ar gas was introduced to control the pressure in the vacuum chamber at 0.8 Pa. The DC magnetron sputtering power supply for the titanium target (99.99% purity) was turned on, and the target current was set to 160 A. A pulsed bias of 300 V was applied to the substrate, and deposition was carried out at 120 °C for 30 minutes to form a Ti transition layer with a thickness of approximately 100 nm. 5. Magnetic filtration vacuum arc ion plating deposition of GLC coating Turn off the titanium target power supply and allow the temperature to drop below 100°C. Turn on the graphite target (99.99% purity) power supply, and stabilize the arc current at 200 A after arc ignition. Apply a -750V pulse bias voltage and a 7A filtered current to the substrate, and deposit for 60 minutes to form a dense GLC coating with a thickness of approximately 200 nm.

[0048] The following performance tests were performed on the surface coating of the silicon-based bipolar plate obtained by the above treatment: The interfacial contact resistance (ICR) between the gas diffusion layer (simulated using carbon paper) and the coated sample was measured using a Hepu resistance meter (CHT3545, range 10mΩ-1000mΩ). A continuous pressure of 0.1 MPa to 1.9 MPa was applied, and the contact resistance at 1.5 MPa was observed and recorded. The method proposed by Davies was then used for calculation, ultimately yielding an average ICR of 5.9 mΩ·cm². After baking at 200℃ for 2 hours, the contact resistance was 6.1 mΩ·cm², with a resistance change rate of approximately 3%. This was compared with the contact resistance data of an uncoated bipolar plate. Figure 6 As shown.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 is that no titanium transition layer was deposited.

[0051] The contact resistance of the obtained coating was 6.6 mΩ·cm², which changed to 10.3 mΩ·cm² after baking at 200℃ for 2 hours, with a contact resistance change rate of 56%.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 1 is that the sp³ / sp ratio in the dense GLC coating is higher. 2 It is approximately 0.2.

[0054] The contact resistance of the obtained coating was 5.9 mΩ·cm², which changed to 7.3 mΩ·cm² after baking at 200℃ for 2 hours, with a change rate of 23%.

[0055] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A surface coating for a silicon-based bipolar plate, characterized in that, include: A titanium transition layer and a dense diamond-like carbon functional layer are sequentially stacked on the surface of a silicon-based bipolar plate, wherein the dense diamond-like carbon functional layer contains hybrid carbon sp³ / sp 2 The ratio is 0.3 to 0.

4.

2. The silicon-based bipolar plate surface coating according to claim 1, characterized in that: The thickness of the dense diamond-like carbon functional layer is 100 nm to 200 nm; and / or, the thickness of the titanium transition layer is 20 nm to 100 nm; And / or, the thickness of the coating on the surface of the silicon-based bipolar plate is 120~300 µm.

3. The silicon-based bipolar plate surface coating according to claim 1, characterized in that: The contact resistance of the surface coating of the silicon-based bipolar plate is below 6 mΩ·cm²; and / or, after baking at 200°C for 2 hours, the change rate of the contact resistance of the surface coating of the silicon-based bipolar plate is within 3%.

4. The method for preparing the surface coating of the silicon-based bipolar plate as described in any one of claims 1 to 3, characterized in that, include: A titanium transition layer was deposited on the surface of a silicon-based bipolar plate using magnetron sputtering technology. A dense diamond-like carbon functional layer was deposited on the surface of the titanium transition layer using magnetic filtering vacuum arc ion plating technology.

5. The preparation method according to claim 4, characterized in that, include: A protective gas is introduced into the vacuum chamber of the magnetron sputtering equipment to control the gas pressure in the vacuum chamber to ≤1Pa; A titanium target is activated for magnetron sputtering, and a pulsed bias voltage is applied to the silicon-based bipolar plate, thereby depositing a titanium transition layer on the surface of the silicon-based bipolar plate.

6. The preparation method according to claim 5, characterized in that: The protective gas includes argon; and / or, the protective gas is introduced to control the pressure in the vacuum chamber at 0.3 Pa to 0.8 Pa; And / or, the process conditions of the magnetron sputtering technology include: a target current of 80A~160A for the titanium target, a pulse bias voltage of -150V~-300V applied to the silicon-based bipolar plate, a deposition temperature of 120℃~150℃, and a deposition time of 10 min~30 min, preferably 20 min~30 min.

7. The preparation method according to claim 4, characterized in that, include: Turn on the graphite target and stabilize the arc current at 100 A~200 A; A pulsed negative bias voltage of 650 V to 750 V and a filtered current of 7 A to 14 A are applied to a silicon-based bipolar plate with a deposited titanium transition layer. The total deposition time is 30 min to 60 min, forming a dense diamond-like carbon functional layer on the surface of the titanium transition layer.

8. The preparation method according to claim 7, characterized in that, include: After the titanium transition layer is deposited, the graphite target is opened when the temperature of the vacuum chamber drops to 80℃~100℃ and the vacuum degree is ≤0.8Pa. And / or, the preparation method further includes: pretreating the surface of the silicon-based bipolar plate before depositing the titanium transition layer, the pretreatment including: The silicon-based bipolar plate was ultrasonically cleaned, dried, and then placed in a magnetron sputtering apparatus. The chamber of the magnetron sputtering equipment was evacuated to a background vacuum level not exceeding 2 × 10⁻⁶. -4 Torr, the temperature is heated to 120℃~150℃; A pulse bias voltage of -500V to -800V is applied to the silicon-based bipolar plate, through A Ion bombardment of the substrate surface for 30 to 60 minutes of continuous ion cleaning.

9. The application of the silicon-based bipolar plate surface coating according to any one of claims 1 to 3 in the field of fuel cells.

10. The application according to claim 9, characterized in that: The fuel cell includes a proton exchange membrane fuel cell.

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