A highly conductive, corrosion-resistant composite coating and its preparation method and application

Abstract

The present invention discloses a highly conductive corrosion-resistant composite coating and its preparation method and application. The highly conductive corrosion-resistant composite coating comprises a chromium transition layer and a graphite-like amorphous carbon layer sequentially formed on the surface of a metal bipolar plate as a substrate; wherein the preferred crystal plane orientation of the chromium transition layer is (110), and the texture coefficient of the preferred oriented crystal plane (110) in the chromium transition layer is above 0.8. The graphite-like amorphous carbon coating in the highly conductive corrosion-resistant composite coating provided by the present invention has high conductivity and corrosion resistance. The chromium transition layer with preferential growth of a densely packed plane (110) is prepared by high-power pulsed magnetron sputtering technology under low negative bias, which effectively improves the density of the coating, thereby achieving long-term protection of the metal bipolar plate. At the same time, the (110) preferentially oriented chromium transition layer has a significant catalytic effect on the graphite-like amorphous carbon layer, which helps to improve sp 2 content, thereby effectively reducing the contact resistance of the metal bipolar plate.

Description

Technical Field

[0001] The present invention belongs to the technical field, and in particular relates to a highly conductive, corrosion-resistant, protective composite coating and a preparation method and application thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) are a new energy source that can directly convert hydrogen into electricity. Due to their advantages such as fast startup, relatively low operating temperature, rapid response to various environments, zero pollution, and high energy efficiency, they hold great promise for application in new energy vehicles, stationary, and portable power sources. A PEMFC cell typically consists of bipolar plates (BPs), a membrane electrode assembly (MEA), gaskets, and end plates. Among these components, the BPA accounts for 80% of the fuel cell's total mass, nearly all of its volume, and approximately 18%-28% of its manufacturing cost. The BPA is a key functional component in a PEMFC stack, with its primary functions including conducting electrons, distributing chemical fuels, separating individual cells, supporting the MEA, and facilitating water management within the cell. Therefore, it must meet requirements such as easy processing, resistance to electrochemical corrosion, low interfacial resistance, and low cost. Currently, graphite BPAs are widely used in conventional fuel cells, but their bulk and low strength hinder their large-scale adoption. Metal plates with excellent properties such as high electrical conductivity, high thermal conductivity, high mechanical strength, low stamping cost and low gas permeability are expected to replace graphite as the main material for bipolar plates.

[0003] The operating environment of proton exchange membrane fuel cells is usually acidic (pH = 2-3), warm and humid (65-90 ° C) environment. In acidic corrosive media and high temperature environments, a passivation layer is generated on the surface of the metal bipolar plate, increasing the interfacial contact resistance (ICR) between the metal bipolar plate and the gas diffusion layer (GDLs); at the same time, the metal bipolar plate is also prone to severe corrosion, affecting the battery output power and causing the battery performance to decline rapidly. Depositing a protective coating on the surface of the metal bipolar plate is an effective means to improve its surface conductivity and corrosion resistance. Commonly used protective coatings include precious metal coatings, metal nitride or carbide coatings, conductive polymer coatings, etc. Amorphous carbon coating is a kind of diamond phase sp 3 and graphite phase sp 2 Hybrid coatings, formed by hybridization, possess numerous excellent properties due to the excellent chemical inertness of carbon and the unique structure of amorphous carbon. In recent years, their application as protective coatings on the surfaces of metal bipolar plates has attracted widespread attention. However, over extended operation, corrosive media can still enter the coating / substrate interface through coating defects, causing metal corrosion and increased ICR, leading to degradation of plate performance. Summary of the Invention

[0004] The main purpose of the present invention is to provide a highly conductive corrosion-resistant protective composite coating and its preparation method and application, so as to overcome the shortcomings of the prior art.

[0005] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0006] An embodiment of the present invention provides a highly conductive, corrosion-resistant composite coating, comprising a chromium transition layer and a graphite-like amorphous carbon layer sequentially formed on the surface of a metal bipolar plate serving as a substrate; wherein the preferred crystal plane orientation of the chromium transition layer is (110), and the texture coefficient of the preferred crystal plane (110) in the chromium transition layer is greater than 0.8; the thickness of the graphite-like amorphous carbon layer is 100 to 400 nm; and the corrosion current density of the highly conductive, corrosion-resistant composite coating at a standard operating voltage of 0.6 V is less than 2×10 -8 A / cm 2 , the deposited contact resistance is less than 3mΩ·cm 2 , after 24 hours of corrosion, the contact resistance is less than 8mΩ·cm 2 After 48 hours of corrosion, the increase in contact resistance is within 5%.

[0007] The present invention also provides a method for preparing the aforementioned highly conductive, corrosion-resistant composite coating, which comprises:

[0008] providing a metal bipolar plate as a substrate;

[0009] A chromium transition layer is formed on the surface of the metal bipolar plate by using a high-power pulsed magnetron sputtering technology and a high-purity chromium target as a target material, wherein the orientation of the crystal plane in the chromium transition layer is (110) and the substrate bias voltage is -160V to -250V;

[0010] Furthermore, a DC magnetron sputtering technique is adopted with a high-purity graphite target as the target material to deposit a graphite-like amorphous carbon layer on the surface of the chromium transition layer, thereby obtaining a highly conductive and corrosion-resistant protective composite coating.

[0011] The embodiment of the present invention also provides the use of the aforementioned highly conductive, corrosion-resistant protective composite coating in a proton exchange membrane fuel cell.

[0012] An embodiment of the present invention also provides a bipolar plate for a proton exchange membrane fuel cell, which includes a metal bipolar plate and a high-conductivity, corrosion-resistant protective composite coating covered on the surface of the metal bipolar plate; wherein the high-conductivity, corrosion-resistant protective composite coating is the aforementioned high-conductivity, corrosion-resistant protective composite coating.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The highly conductive and corrosion-resistant protective composite coating provided by the present invention comprises a chromium transition layer with a (110) preferred orientation (the preferred orientation crystal plane texture coefficient is not less than 0.8), so that the prepared protective composite coating has excellent conductive and corrosion-resistant properties, and at the same time, the protective composite coating has stable performance in an acidic and high-temperature environment and maintains a low contact resistance for a long time;

[0015] (2) The highly conductive, corrosion-resistant composite coating provided by the present invention contains a chromium transition layer with a (110) preferred orientation. The transition layer is a close-packed plane (110) preferentially grown layer with a low crystal face energy, which can improve the overall density of the coating, thereby improving the long-term corrosion resistance of the coating. At the same time, the transition layer has a strong antioxidant capacity, further avoiding a significant increase in contact resistance, thereby achieving long-term protection of the metal bipolar plate;

[0016] (3) The present invention adopts high-power pulsed magnetron sputtering technology as a preparation method for the chromium transition layer of the metal bipolar plate. On this basis, the two core parameters of the substrate bias and the thickness of the graphite-like amorphous carbon layer are optimized to obtain a chromium transition layer with a smooth surface and a dense internal structure, which can effectively improve the membrane-base bonding strength and make the graphite-like amorphous carbon layer grown on its surface smooth, dense, and highly conductive; at the same time, the (110) preferentially oriented chromium transition layer has a significant catalytic effect on the graphite-like amorphous carbon layer within a certain thickness (100 to 400 nm) of the top layer, which helps to improve the sp 2 content (>50%), thereby effectively reducing the contact resistance of the metal bipolar plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 1 is an XRD test result diagram of the coating prepared in the typical embodiment of the present invention and Comparative Examples 1 and 2;

[0019] Figure 2 1 is a graph showing the corrosion performance test results of the coatings prepared in Example 1 and Comparative Examples 1 to 3 of the present invention;

[0020] Figure 3 1 is a graph showing the contact resistance performance test results of the coatings prepared in Example 1 and Comparative Examples 1 to 3 of the present invention;

[0021] Figure 4a-4cThey are surface morphologies of the coatings prepared in Example 1 of the present invention and Comparative Examples 1-2;

[0022] Figure 5 3 is an XPS test result diagram of the coatings prepared in Example 1 and Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0023] In view of the defects of the existing technology, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice. It mainly addresses the above-mentioned insufficient comprehensive performance of the current protective coating when applied on the surface of metal bipolar plates, and provides a controllable preparation method for a metal transition layer with preferential crystal plane orientation on the surface of a metal bipolar plate.

[0024] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] Specifically, as one aspect of the technical solution of the present invention, a highly conductive, corrosion-resistant composite coating is provided, comprising a chromium transition layer and a graphite-like amorphous carbon layer sequentially formed on the surface of a metal bipolar plate as a substrate; wherein the preferred crystal plane orientation of the chromium transition layer is (110), and the texture coefficient of the preferred crystal plane (110) in the chromium transition layer is greater than 0.8; the thickness of the graphite-like amorphous carbon layer is 100 to 400 nm; and the corrosion current density of the highly conductive, corrosion-resistant composite coating is less than 2×10 -8 A / cm 2 , the deposited contact resistance is less than 3mΩ·cm 2 , after 24 hours of corrosion, the contact resistance is less than 8mΩ·cm 2 After 48 hours of corrosion, the increase in contact resistance is within 5%.

[0026] The high-conductivity corrosion-resistant composite coating of the present invention comprises a chromium transition layer with a (110) preferred crystal plane orientation such as Figure 1 As shown in FIG, the transition layer preferentially grows on a close-packed plane (110), and has a low crystal plane energy, which can improve the overall density of the coating, thereby improving the long-term corrosion resistance of the coating. At the same time, the transition layer has a strong antioxidant capacity, further avoiding a significant increase in contact resistance, thereby achieving long-term protection for the metal bipolar plate; wherein, the (110) crystal plane orientation has a low crystal plane energy, which not only improves the density of the coating, but also makes it easier for the interface catalysis to form a graphite-like structure

[0027] In some preferred embodiments, the thickness of the chromium transition layer is 100-200 nm.

[0028] Another aspect of the embodiments of the present invention further provides a method for preparing the aforementioned highly conductive, corrosion-resistant protective composite coating, which comprises:

[0029] providing a metal bipolar plate as a substrate;

[0030] A chromium transition layer is formed on the surface of the metal bipolar plate by using a high-power pulsed magnetron sputtering technique and a high-purity chromium target as a target material, wherein the orientation of the crystal plane in the chromium transition layer is (110), and the texture coefficient of the preferred orientation crystal plane is not less than 0.8, and the substrate bias voltage is -160V to -250V;

[0031] Furthermore, a DC magnetron sputtering technique is adopted with a high-purity graphite target as the target material to deposit a graphite-like amorphous carbon layer on the surface of the chromium transition layer, thereby obtaining a highly conductive and corrosion-resistant protective composite coating.

[0032] In some preferred embodiments, the preparation method includes: using high-power pulsed magnetron sputtering technology to place the metal bipolar plate in a reaction chamber, using a high-purity chromium target as the target material and an inert gas as the working gas, and depositing a chromium transition layer on the surface of the metal bipolar plate, wherein the high-power pulsed magnetron sputtering technology uses a pulse frequency of 200-400 Hz, a pulse width of 50-100 μs, a pulse voltage of 1000-1200 V, a power of 3.0-4.5 kW, a gas pressure of 1.4-2.1 mTorr, an inert gas introduction amount of 30-70 sccm, a deposition temperature of 80-100° C., and a deposition time of 15-25 min.

[0033] Furthermore, the inert gas includes argon, but is not limited thereto.

[0034] In some preferred embodiments, the preparation method includes: using DC magnetron sputtering technology, using a high-purity graphite target as the target material, and using an inert gas as the working gas to deposit a graphite-like amorphous carbon layer on the surface of the chromium transition layer; wherein the sputtering source power is 0.9 to 1.2 kW, the reaction chamber pressure is 1.4 to 2.1 mTorr, the substrate bias is -50 V to -250 V, the inert gas injection amount is 30 to 70 sccm, the deposition temperature is 40 to 80°C, and the deposition time is 30 to 90 min.

[0035] In some preferred embodiments, the preparation method further comprises: etching the surface of the metal bipolar plate before forming the chromium transition layer.

[0036] In some preferred embodiments, the etching process includes: using Ar ion etching to etch the metal bipolar plate for 30 to 60 minutes at room temperature; the process conditions used in the etching process include: the reaction chamber pressure is 2.0×10-5 The argon gas flow rate is 40 to 100 sccm, the bias voltage is -150 to -450 V, and the Ar ion etching method includes glow etching and / or ion beam etching.

[0037] In some preferred embodiments, the metal bipolar plate includes a stainless steel bipolar plate or a titanium alloy bipolar plate.

[0038] The present invention adopts high-power pulse magnetron sputtering technology, and its technical characteristics are to improve the ionization rate, refine the grains, and make the prepared protective coating surface smooth and the internal structure dense.

[0039] Another aspect of the embodiments of the present invention further provides the use of the aforementioned highly conductive, corrosion-resistant protective composite coating in a proton exchange membrane fuel cell.

[0040] Another aspect of an embodiment of the present invention also provides a bipolar plate for a proton exchange membrane fuel cell, which includes a metal bipolar plate and a high-conductivity, corrosion-resistant protective composite coating covered on the surface of the metal bipolar plate; wherein the high-conductivity, corrosion-resistant protective composite coating is the aforementioned high-conductivity, corrosion-resistant protective composite coating.

[0041] Another aspect of the embodiments of the present invention further provides a proton exchange membrane fuel cell, which includes the bipolar plate for the proton exchange membrane fuel cell.

[0042] Another aspect of the embodiments of the present invention further provides a material including a substrate, on which the aforementioned highly conductive, corrosion-resistant, protective composite coating is also provided.

[0043] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0044] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0045] Example 1

[0046] In this embodiment, the preparation method of the highly conductive and corrosion-resistant composite coating for metal bipolar plates is as follows:

[0047] S1. The substrate is made of 316L stainless steel. The stainless steel bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece holder, and evacuated to 2.0×10 -5Torr or less, then, under the conditions of argon flow rate of 100 sccm and bias voltage of -450 V, turn on the ion source, adjust the output voltage to 1200 V, and use argon plasma to etch the surface of the stainless steel bipolar plate for 60 minutes;

[0048] S2. Ar gas was introduced into the chamber (the amount of Ar gas was 30 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 1.4 mTorr. The high-power pulse power supply connected to the chromium sputtering target was turned on and the power supply frequency was set to 200 Hz, the pulse width was 50 μs, the pulse voltage was 1200 V, the power was 3.0 kW, the substrate bias was -160 V, and the deposition temperature was 90°C. A chromium transition layer with a thickness of 150 nm was deposited.

[0049] S3. Continue to introduce Ar gas into the cavity (the amount of Ar gas introduced is 70 sccm), use DC magnetron sputtering technology, maintain the cavity pressure at 2.1 mTorr, turn on the DC power supply connected to the graphite sputtering target, set the power to 0.9 kW, the bias voltage to -100 V, the deposition temperature to 50°C, and deposit a graphite-like amorphous carbon layer with a thickness of 400 nm, thereby obtaining a highly conductive and corrosion-resistant protective composite coating.

[0050] According to the test, the corrosion current density is 1.8×10 -8 A / cm 2 The contact resistance of the deposited state is 2.4mΩ·cm 2 , the contact resistance after 24 hours of corrosion is 6.3mΩ·cm 2 , the contact resistance after 48h corrosion is 7.2mΩ·cm 2 .

[0051] Example 2

[0052] In this embodiment, the preparation method of the highly conductive and corrosion-resistant composite coating for metal bipolar plates is as follows:

[0053] S1. The substrate is made of 316L stainless steel. The stainless steel bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece holder, and evacuated to 2.0×10 -5 Torr or less, then, under the conditions of argon flow rate of 40 sccm and bias voltage of -150 V, turn on the ion source, adjust the output voltage to 1200 V, and use argon plasma to etch the surface of the stainless steel bipolar plate for 30 minutes;

[0054] S2. Ar gas was introduced into the chamber (the Ar gas flow rate was 60 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 2.0 mTorr. The high-power pulse power supply connected to the chromium sputtering target was turned on and the power supply frequency was set to 400 Hz, the pulse width was 100 μs, the pulse voltage was 1000 V, the power was 4.5 kW, the substrate bias was -180 V, and the deposition temperature was 80°C. A chromium transition layer with a thickness of 200 nm was deposited.

[0055] S3. Continue to introduce Ar gas into the cavity (the amount of Ar gas introduced is 30 sccm), use DC magnetron sputtering technology, maintain the cavity pressure at 1.4 mTorr, turn on the DC power supply connected to the graphite sputtering target, set the power to 1.2 kW, the bias voltage to -250 V, the deposition temperature to 40°C, and deposit a graphite-like amorphous carbon layer with a thickness of 300 nm, thereby obtaining a highly conductive and corrosion-resistant protective composite coating.

[0056] According to the test, the corrosion current density is 1.3×10 -8 A / cm 2 The contact resistance of the deposited state is 2.9mΩ·cm 2 , the contact resistance after 24h corrosion is 6.2mΩ·cm 2 , the contact resistance after 48h corrosion is 7.1mΩ·cm 2 .

[0057] Example 3

[0058] In this embodiment, the preparation method of the highly conductive and corrosion-resistant composite coating for metal bipolar plates is as follows:

[0059] S1. Titanium alloy is used as the substrate. The titanium alloy bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece holder, and evacuated to 2.0×10 -5 Torr or less, then, under the conditions of argon flow rate of 65 sccm and bias voltage of -250 V, the ion source was turned on, the output voltage was adjusted to 1200 V, and the surface of the stainless steel bipolar plate was etched with argon plasma for 60 min;

[0060] S2. Ar gas was introduced into the chamber (the Ar gas flow rate was 70 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 2.1 mTorr. The high-power pulse power supply connected to the chromium sputtering target was turned on and the power supply frequency was set to 300 Hz, the pulse width was 100 μs, the pulse voltage was 1200 V, the power was 3.0 kW, the substrate bias was -200 V, and the deposition temperature was 100°C. A chromium transition layer with a thickness of 100 nm was deposited.

[0061] S3. Continue to introduce Ar gas into the cavity (the amount of Ar gas introduced is 40 sccm), use DC magnetron sputtering technology, maintain the cavity pressure at 1.7 mTorr, turn on the DC power supply connected to the graphite sputtering target, set the power to 0.9 kW, the bias voltage to -50 V, the deposition temperature to 80 ° C, and deposit a graphite-like amorphous carbon layer with a thickness of 200 nm, thereby obtaining a highly conductive and corrosion-resistant protective composite coating.

[0062] According to the test, the corrosion current density is 1.1×10 -8 A / cm 2 The contact resistance of the deposited state is 2.7mΩ·cm 2 , the contact resistance after 24 hours of corrosion is 6.9mΩ·cm 2 , the contact resistance after 48h corrosion is 7.8mΩ·cm 2 .

[0063] Example 4

[0064] In this embodiment, the preparation method of the highly conductive and corrosion-resistant composite coating for metal bipolar plates is as follows:

[0065] S1. Titanium alloy is used as the substrate. The titanium alloy bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece holder, and evacuated to 2.0×10 -5 Torr or less, then, under the conditions of argon flow rate of 70 sccm and bias voltage of -300 V, the ion source was turned on, the output voltage was adjusted to 1200 V, and the surface of the stainless steel bipolar plate was etched by argon plasma for 45 minutes;

[0066] S2. Ar gas was introduced into the chamber (the amount of Ar gas was 50 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 1.7 mTorr. The high-power pulse power supply connected to the chromium sputtering target was turned on and the power supply frequency was set to 300 Hz, the pulse width was 100 μs, the pulse voltage was 1100 V, the power was 3.0 kW, the substrate bias was -160 V, and the deposition temperature was 90°C. A chromium transition layer with a thickness of 150 nm was deposited.

[0067] S3. Continue to introduce Ar gas into the cavity (the amount of Ar gas introduced is 50 sccm), use DC magnetron sputtering technology, maintain the cavity pressure at 1.7 mTorr, turn on the DC power supply connected to the graphite sputtering target, set the power to 1.0 kW, the bias voltage to -150 V, the deposition temperature to 60 ° C, and deposit a graphite-like amorphous carbon layer with a thickness of 200 nm, thereby obtaining a highly conductive and corrosion-resistant protective composite coating.

[0068] According to the test, the corrosion current density is 1.2×10 -8 A / cm2 The contact resistance of the deposited state is 2.7mΩ·cm 2 , after 24 hours of corrosion, the contact resistance is 7.3mΩ.cm 2 , the contact resistance after 48h corrosion is 8.6mΩ·cm 2 .

[0069] Example 5

[0070] In this embodiment, the preparation method of the highly conductive and corrosion-resistant composite coating for metal bipolar plates is as follows:

[0071] S1. Titanium alloy is used as the substrate. The titanium alloy bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece holder, and evacuated to 2.0×10 -5 Torr or less, then, under the conditions of argon flow rate of 55 sccm and bias voltage of -200 V, turn on the ion source, adjust the output voltage to 1200 V, and use argon plasma to etch the surface of the stainless steel bipolar plate for 45 minutes;

[0072] S2. Ar gas was introduced into the chamber (the Ar gas flow rate was 70 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 2.1 mTorr. The high-power pulse power supply connected to the chromium sputtering target was turned on and the power supply frequency was set to 300 Hz, the pulse width was 100 μs, the pulse voltage was 1100 V, the power was 3.0 kW, the substrate bias was -250 V, and the deposition temperature was 100°C. A chromium transition layer with a thickness of 150 nm was deposited.

[0073] S3. Continue to introduce Ar gas into the cavity (the amount of Ar gas introduced is 35 sccm), use DC magnetron sputtering technology, maintain the cavity pressure at 1.5 mTorr, turn on the DC power supply connected to the graphite sputtering target, set the power to 1.0 kW, the bias voltage to -150 V, the deposition temperature to 70 ° C, and deposit a graphite-like amorphous carbon layer with a thickness of 100 nm, thereby obtaining a highly conductive and corrosion-resistant protective composite coating.

[0074] According to the test, the corrosion current density is 1.1×10 8 A / cm 2 The contact resistance of the deposited state is 2.6mΩ·cm 2 , the contact resistance after 24 hours of corrosion is 7.6mΩ·cm 2 , the contact resistance after 48h corrosion is 8.7mΩ·cm 2 .

[0075] Comparative Example 1

[0076] This embodiment is a comparative example of embodiment 1. Steps S1 and S3 are exactly the same as those in embodiment 1. In step S2, the substrate bias voltage is -400 V. Other parameters are the same as those in embodiment 1.

[0077] Comparative Example 2

[0078] This embodiment serves as a comparative example of embodiment 1. Steps S1 and S3 are exactly the same as those in embodiment 1. In step S2, the sputtering source is changed to DC magnetron sputtering. Other parameters are the same as those in embodiment 1.

[0079] Comparative Example 3

[0080] This embodiment serves as a comparative example of embodiment 1. Steps S1 and S2 are exactly the same as those in embodiment 1. In step S3, the thickness of the graphite-like amorphous carbon layer is 800 nm. Other parameters are the same as those in embodiment 1.

[0081] Comparative Example 4

[0082] This example serves as a comparative example of Example 1. Steps S1 and S3 are identical to those of Example 1. In step S2, the substrate bias voltage is -100 V. Other parameters are the same as those of Example 1. The corrosion resistance and conductivity of the prepared coating are much lower than those of Example 1.

[0083] Performance test comparison:

[0084] The corrosion resistance of the samples was measured using a three-electrode electrochemical test system. The solution was 0.5M H2SO4+5ppm HF solution at a temperature of 80°C. The test results are shown in the figure below. Figure 2 As shown. Figure 2 It can be seen that the corrosion current density of the sample in Example 1 is 1.8×10 -8 A / cm 2 , compared to the U.S. Department of Energy standard (DOE2020) of 1×10 -6 A / cm 2 The corrosion current density of the sample in comparative example 1 at a standard working voltage of 0.6 V was 3.6×10 - 6 A / cm 2 The corrosion current density of the sample in comparative example 2 at a standard working voltage of 0.6 V is 1.3×10 -6 A / cm 2 The corrosion current density of the sample in comparative example 3 at a standard working voltage of 0.6 V is 4.5×10 -8 A / cm 2 The corrosion current density of the embodiment is significantly lower than that of the two comparative examples, indicating that the coating prepared in the embodiment of the present invention has better corrosion resistance.

[0085] Apply 1.5MPa assembly preload on the sample surface and test its contact resistance. The results are as follows: Figure 3 As shown, the contact resistance of the deposited state (i.e., the highly conductive corrosion-resistant composite coating) in Example 1 is 2.4 mΩ·cm 2 After 24 hours of corrosion, the contact resistance increased slightly to 7.3 mΩ·cm 2 After 48 hours of corrosion, the contact resistance increased slightly to 8.2 mΩ·cm 2 , meeting the U.S. Department of Energy standard of less than 10mΩ·cm 2 The contact resistance of the deposited state (ie, coating) in Comparative Example 1 is 7.7 mΩ·cm 2 After 24 hours of corrosion, the contact resistance increased to 11.3 mΩ·cm 2 After 48 hours of corrosion, the contact resistance increased to 26.4 mΩ·cm 2 The contact resistance of the deposited state (ie, coating) in Comparative Example 2 is 7.9 mΩ·cm 2 After 24 hours of corrosion, the contact resistance increased to 11.8 mΩ·cm 2 After 48 hours of corrosion, the contact resistance increased to 26.7 mΩ·cm 2 The contact resistance of the deposited state (ie, coating) in Comparative Example 3 is 22.3 mΩ·cm 2 After 24 hours of corrosion, the contact resistance increased to 25.7 mΩ·cm 2 After 48 hours of corrosion, the contact resistance increased to 29.5 mΩ·cm 2 The contact resistance of the high-conductivity corrosion-resistant protective composite coating in Example 1 and the contact resistance after 24 hours of corrosion are lower than those of the two comparative examples. At the same time, as the corrosion time increases, only the contact resistance of Example 1 increases the least, and only Example 1 can meet the DOE2025 standard, which proves that the initial conductivity of Example 1 is better and long-term corrosion has less impact on its performance.

[0086] Figure 4a-4c The surface morphologies of Example 1, Comparative Example 1 and Comparative Example 2 are respectively. Scanning electron microscopy analysis shows that the protective composite coating prepared in Example 1 has a smooth surface and a dense structure, while the coatings prepared in Comparative Examples 1 and 2 have rough surfaces and cracks. This result shows that the coating surface of Example 1 of the present invention, which is prepared by high-power pulsed magnetron sputtering and includes a chromium transition layer with a (110) preferred crystal plane orientation, is smoother and denser, further indicating that the coating in Example 1 has better protective performance.

[0087] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0088] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical variations made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the scope of protection of the present invention.

Claims

1. A highly conductive, corrosion-resistant composite coating, characterized in that The invention comprises a chromium transition layer and a graphite-like amorphous carbon layer sequentially formed on the surface of a metal bipolar plate as a substrate; wherein the preferred crystal plane orientation of the chromium transition layer is (110), and the texture coefficient of the preferred orientation crystal plane (110) in the chromium transition layer is greater than 0.8; and the corrosion current density of the highly conductive corrosion-resistant composite coating at a standard operating voltage of 0.6 V is 1.8×10 -8 A / cm 2 The contact resistance of the deposited state is 2.4mΩ•cm 2 , the contact resistance after 24 hours of corrosion is 6.3mΩ•cm 2 , the contact resistance after 48h corrosion is 7.2mΩ•cm 2 ; The preparation method of the highly conductive corrosion-resistant protective composite coating comprises: S1. The substrate is made of 316L stainless steel. The stainless steel bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece holder, and evacuated to 2.0×10 -5 Torr or less, then, under the conditions of argon flow rate of 100 sccm and bias voltage of -450 V, turn on the ion source, adjust the output voltage to 1200 V, and use argon plasma to etch the surface of the stainless steel bipolar plate for 60 minutes; S2. Ar gas was introduced into the chamber at a rate of 30 sccm. High-power pulsed magnetron sputtering was used, maintaining the chamber pressure at 1.4 mTorr. The high-power pulsed power supply connected to the chromium sputtering target was turned on with a frequency of 200 Hz, a pulse width of 50 µs, a pulse voltage of 1200 V, a power of 3.0 kW, a substrate bias of -160 V, and a deposition temperature of 90°C. A chromium transition layer with a thickness of 150 nm was deposited. S3. Continue to introduce Ar gas into the chamber at a rate of 70 sccm. Using DC magnetron sputtering technology, maintain the chamber pressure at 2.1 mTorr. Turn on the DC power supply connected to the graphite sputtering target and set the power to 0.9 kW, the bias voltage to -100 V, and the deposition temperature to 50°C. Deposit a graphite-like amorphous carbon layer with a thickness of 400 nm, thereby obtaining a highly conductive, corrosion-resistant, protective composite coating.

2. Use of the highly conductive, corrosion-resistant protective composite coating according to claim 1 in proton exchange membrane fuel cells.

3. A bipolar plate for a proton exchange membrane fuel cell, characterized in that: It comprises a metal bipolar plate and a highly conductive corrosion-resistant protective composite coating provided on the surface of the metal bipolar plate; wherein the highly conductive corrosion-resistant protective composite coating is the highly conductive corrosion-resistant protective composite coating according to any one of claims 1.

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