CN115928017A - High-conductivity corrosion-resistant protective composite coating and preparation method and application thereof - Google Patents
High-conductivity corrosion-resistant protective composite coating and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a high-conductivity corrosion-resistant protective composite coating and a preparation method and application thereof. The high-conductivity corrosion-resistant protective composite coating comprises a chromium transition layer and a graphite-like amorphous carbon layer which are sequentially formed on the surface of a metal bipolar plate serving as a matrix(ii) a 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 more than 0.8. The graphite-like amorphous carbon coating in the high-conductivity corrosion-resistant protective composite coating has high conductivity and corrosion resistance, the chromium transition layer with the preferentially grown dense-arranged surface (110) is prepared by utilizing the high-power pulse magnetron sputtering technology under low negative bias, the compactness of the coating is effectively improved, and therefore long-acting protection on a metal bipolar plate is realized, and meanwhile, the preferentially oriented chromium transition layer (110) has an obvious catalytic effect on the graphite-like amorphous carbon layer and is beneficial to improving sp (sp) 2 And thus effectively reduces the contact resistance of the metal bipolar plate.
Description
Technical Field
The invention belongs to the technical field, and particularly relates to a high-conductivity corrosion-resistant protective composite coating as well as a preparation method and application thereof.
Background
Proton Exchange Membrane Fuel Cells (PEMFCs) are a new type of energy source that can convert hydrogen energy directly into electrical energy. The novel energy-saving power supply has the advantages of quick start, relatively low working temperature, quick response to various environments, no pollution, high energy efficiency and the like, and has good application prospects in the aspects of new energy automobiles, fixed and portable power supplies. One cell unit of a proton exchange membrane fuel cell is generally composed of Bipolar Plates (BPs), a Membrane Electrode (MEA), a gasket, and an end plate. In many assemblies, the bipolar plates account for 80% of the total mass, almost the entire volume, and about 18-28% of the manufacturing cost of the fuel cell. Bipolar plates are key functional components in a pem fuel cell stack and have the primary functions of conducting electrons, distributing chemical fuel, separating individual cells, supporting the membrane electrode, and facilitating water management within the cell. Therefore, it must satisfy the requirements of easy processing and molding, electrochemical corrosion resistance, low interface resistance, low cost, etc. At present, the traditional fuel cell widely uses graphite bipolar plates, but the volume is large, the strength is low, and the large-scale use is restricted. The metal plate with excellent performances such as high electrical conductivity, high thermal conductivity, high mechanical strength, low stamping cost, low gas permeability and the like is expected to replace graphite to become a main material of the bipolar plate.
The operating environment of a proton exchange membrane fuel cell is usually an acidic (pH = 2-3), warm and humid (65-90 ℃) environment. Under the acidic corrosive medium and high temperature environment, a passivation layer is generated on the surface of the metal bipolar plate, and the Interface Contact Resistance (ICR) between the metal bipolar plate and Gas Diffusion Layers (GDLs) is increased; meanwhile, the metal bipolar plate is easy to generate serious corrosion, which affects the output power of the battery and causes the rapid reduction of the battery performance. The deposition of the protective coating on the surface of the metal bipolar plate is an effective means for improving the surface conductivity and corrosion resistance of the metal bipolar plate. Commonly used protective coatings are noble metal coatings, metal nitride or carbide coatings, conductive polymer coatings, and the like. The amorphous carbon coating is a coating composed of diamond phases sp 3 And a graphite phase sp 2 Due to the excellent chemical inertness of carbon elements and the special structure of amorphous carbon, the hybrid structure coating formed by hybridization has many excellent performances, and has attracted wide attention in recent years for the application of amorphous carbon coatings in the surface protective coatings of metal bipolar plates. However, over time, corrosive media can still enter the coating/substrate interface through coating defects, causing metal corrosion and increased ICR, resulting in degraded plate performance.
Disclosure of Invention
The invention mainly aims to provide a high-conductivity corrosion-resistant protective composite coating, and a preparation method and application thereof, so as to overcome the defects of the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a high-conductivity corrosion-resistant protective composite coating, which comprises a chromium transition layer and a graphite-like amorphous carbon layer which are sequentially formed on the surface of a metal bipolar plate serving as a matrix; 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 more than 0.8; the thickness of the graphite-like amorphous carbon layer is 100-400 nm; and the corrosion current density of the high-conductivity corrosion-resistant protective composite coating is less than 2 multiplied by 10 under the standard working voltage of 0.6V -8 A/cm 2 Deep and deepThe product contact resistance is less than 3m omega cm 2 And the contact resistance is less than 8m omega cm after 24h of corrosion 2 And the contact resistance is increased within 5% after 48h of corrosion.
The embodiment of the invention also provides a preparation method of the high-conductivity corrosion-resistant protective composite coating, which comprises the following steps:
providing a metal bipolar plate as a substrate;
depositing a chromium transition layer on the surface of the metal bipolar plate by adopting a high-power pulse magnetron sputtering technology and taking a high-purity chromium target as a target material, wherein the orientation of a crystal face in the chromium transition layer is (110), and the bias voltage of a substrate is-160V-250V;
and depositing a graphite-like amorphous carbon layer on the surface of the chromium transition layer by adopting a direct-current magnetron sputtering technology and taking a high-purity graphite target as a target material, thereby obtaining the high-conductivity corrosion-resistant protective composite coating.
The embodiment of the invention also provides application of the high-conductivity corrosion-resistant protective composite coating in a proton exchange membrane fuel cell.
The embodiment of the invention also provides a bipolar plate for the proton exchange membrane fuel cell, which comprises a metal bipolar plate and a high-conductivity corrosion-resistant protective composite coating which is covered on the surface of the metal bipolar plate; the high-conductivity corrosion-resistant protective composite coating is the high-conductivity corrosion-resistant protective composite coating.
Compared with the prior art, the invention has the beneficial effects that:
(1) The high-conductivity corrosion-resistant protective composite coating provided by the invention comprises a (110) preferred orientation chromium transition layer (the preferred orientation crystal face texture coefficient is not less than 0.8), so that the prepared protective composite coating has excellent conductivity corrosion resistance, and meanwhile, the protective composite coating has stable performance in an acid high-temperature environment and keeps lower contact resistance for a long time;
(2) The high-conductivity corrosion-resistant protective composite coating provided by the invention comprises a chromium transition layer with preferred orientation (110), the transition layer preferentially grows on a close-packed surface (110), the crystal surface energy is low, the integral compactness of the coating can be improved, the long-time corrosion resistance of the coating is improved, meanwhile, the oxidation resistance of the transition layer is strong, the contact resistance is further prevented from greatly rising, and the long-acting protection on the metal bipolar plate is realized;
(3) The invention adopts high-power pulse magnetron sputtering technology as a preparation method of the chromium transition layer of the metal bipolar plate, two core parameters of substrate bias voltage and the thickness of the graphite-like amorphous carbon layer are optimized on the basis, the chromium transition layer with a smooth surface and a compact internal structure can be obtained, the bonding strength of the film and the substrate can be effectively improved, and the graphite-like amorphous carbon layer grown on the surface of the chromium transition layer has a smooth surface, a compact structure and high conductivity; meanwhile, the (110) preferred orientation chromium transition layer has obvious catalytic action on the graphite-like amorphous carbon layer with a certain thickness (100-400 nm) of the top layer, and is beneficial to improving sp 2 The content is more than 50 percent, thereby effectively reducing the contact resistance of the metal bipolar plate.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a graph showing XRD test results of coatings prepared in an exemplary embodiment of the present invention and comparative examples 1 to 2;
FIG. 2 is a graph showing the results of corrosion performance tests of the coatings prepared in example 1 of the present invention and comparative examples 1 to 3;
FIG. 3 is a graph showing the results of contact resistance performance tests of the coatings prepared in example 1 of the present invention and comparative examples 1 to 3;
FIGS. 4 a-4 c are surface topography maps of coatings prepared in example 1 of the present invention and comparative examples 1-2, respectively;
fig. 5 is a graph showing XPS test results of the coatings prepared in example 1 of the present invention and comparative example 3.
Detailed Description
In view of the defects of the prior art, the inventor of the present invention has made extensive research and practice to provide a technical solution of the present invention, which mainly aims at the problem that the application of the existing protective coating on the surface of a metal bipolar plate has insufficient comprehensive performance, and provides a controllable preparation method of a metal transition layer with preferred crystal plane orientation on the surface of the metal bipolar plate.
The technical solutions of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Specifically, as one aspect of the technical scheme of the invention, the high-conductivity corrosion-resistant protection composite coating comprises a chromium transition layer and a graphite-like amorphous carbon layer which are sequentially formed on the surface of a metal bipolar plate serving as a matrix; 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 more than 0.8; the thickness of the graphite-like amorphous carbon layer is 100-400 nm; and the corrosion current density of the high-conductivity corrosion-resistant protection composite coating is less than 2 multiplied by 10 under the standard working voltage of 0.6V -8 A/cm 2 The contact resistance in the deposition state is less than 3m omega cm 2 Contact resistance is less than 8m omega cm after 24h of corrosion 2 And the contact resistance is increased within 5% after 48h of corrosion.
The high-conductivity corrosion-resistant protective composite coating comprises a chromium transition layer with a preferred crystal face orientation (110), as shown in figure 1, the transition layer preferentially grows on a close-packed face (110), the crystal face energy is low, the integral compactness of the coating can be improved, the long-time corrosion resistance of the coating is improved, meanwhile, the oxidation resistance of the transition layer is high, the contact resistance is further prevented from being greatly increased, and the long-acting protection on the metal bipolar plate is realized; wherein, the (110) crystal face orientation not only can improve the compactness of the coating, but also is easier to form a graphite-like structure by interface catalysis due to lower crystal face energy
In some preferred embodiments, the thickness of the chromium transition layer is from 100 to 200nm.
Another aspect of the embodiment of the present invention further provides a preparation method of the foregoing high conductive corrosion-resistant protective composite coating, which includes:
providing a metal bipolar plate as a substrate;
depositing a chromium transition layer on the surface of the metal bipolar plate by adopting a high-power pulse magnetron sputtering technology and taking a high-purity chromium target as a target material, wherein the orientation of a crystal face in the chromium transition layer is (110), the texture coefficient of the preferred orientation crystal face is not less than 0.8, and the bias voltage of a substrate is-160V-250V;
and depositing a graphite-like amorphous carbon layer on the surface of the chromium transition layer by adopting a direct-current magnetron sputtering technology and taking a high-purity graphite target as a target material, thereby obtaining the high-conductivity corrosion-resistant protective composite coating.
In some preferred embodiments, the method of preparation comprises: the metal bipolar plate is placed in a reaction cavity by adopting a high-power pulse magnetron sputtering technology, a high-purity chromium target is used as a target material, an inert gas is used as a working gas, and a chromium transition layer is deposited and formed on the surface of the metal bipolar plate, wherein the high-power pulse magnetron sputtering technology adopts the pulse frequency of 200-400 Hz, the pulse width of 50-100 mus, the pulse voltage of 1000-1200V, the power of 3.0-4.5 kW, the air pressure of the reaction cavity is 1.4-2.1 mTorr, the introduction amount of the inert gas is 30-70 sccm, the deposition temperature is 80-100 ℃, and the deposition time is 15-25 min.
Further, the inert gas includes argon, and is not limited thereto.
In some preferred embodiments, the method of making comprises: depositing a graphite-like amorphous carbon layer on the surface of the chromium transition layer by adopting a direct-current magnetron sputtering technology and taking a high-purity graphite target as a target material and inert gas as working gas; wherein the power of the power supply of the sputtering source is 0.9-1.2 kW, the air pressure of the reaction cavity is 1.4-2.1 mTorr, the bias voltage of the matrix is-50V-250V, the introduction amount of inert gas is 30-70 sccm, the deposition temperature is 40-80 ℃, and the deposition time is 30-90 min.
In some preferred embodiments, the preparation method further comprises: and before the chromium transition layer is formed, etching the surface of the metal bipolar plate.
In some preferred embodiments, the etching process comprises: etching the metal bipolar plate for 30-60 min at room temperature by adopting an Ar ion etching method; the etching treatment adopts the following process conditions: the gas pressure of the reaction cavity is 2.0 x 10 -5 The argon flow is 40-100 sccm and the bias voltage is-150 to-450V below Torr, and the Ar ion etching method comprises glow etching and/or ion beam etching.
In some preferred embodiments, the metallic bipolar plate comprises a stainless steel bipolar plate or a titanium alloy bipolar plate.
The invention adopts high-power pulse magnetron sputtering technology, and has the technical characteristics of improving the ionization rate, refining crystal grains and ensuring that the surface of the prepared protective coating is smooth and the internal structure is compact.
Another aspect of the embodiments of the present invention also provides a use of the foregoing high conductive corrosion-resistant protective composite coating in a proton exchange membrane fuel cell.
The embodiment of the invention also provides a bipolar plate for the proton exchange membrane fuel cell, which comprises a metal bipolar plate and a high-conductivity corrosion-resistant protective composite coating covered on the surface of the metal bipolar plate; the high-conductivity corrosion-resistant protective composite coating is the high-conductivity corrosion-resistant protective composite coating.
In another aspect of the embodiments of the present invention, a proton exchange membrane fuel cell is further provided, which includes the bipolar plate for a proton exchange membrane fuel cell.
In another aspect of the embodiment of the present invention, a material is further provided, which includes a substrate, and the foregoing high conductive corrosion-resistant protective composite coating is further disposed on the substrate.
The technical solutions of the present invention are further described in detail below with reference to several preferred embodiments and the accompanying drawings, which are implemented on the premise of the technical solutions of the present invention, and a detailed implementation manner and a specific operation process are provided, but the scope of the present invention is not limited to the following embodiments.
The experimental materials used in the examples used below were all available from conventional biochemical reagents companies, unless otherwise specified.
Example 1
In this embodiment, the preparation method of the high-conductivity corrosion-resistant protective composite coating for the metal bipolar plate comprises the following steps:
s1, selecting 316L stainless steel as a substrate, ultrasonically cleaning a stainless steel bipolar plate, drying, placing the stainless steel bipolar plate into a vacuum chamber, fixing the stainless steel bipolar plate on a workpiece bracket, and vacuumizing to 2.0 multiplied by 10 -5 Turning on an ion source under the conditions that the argon flow is 100sccm and the bias voltage is-450V, adjusting the output voltage to 1200V, and etching the surface of the stainless steel bipolar plate for 60min by using argon plasma;
s2, introducing Ar gas into the cavity (the introduction amount of the Ar gas is 30 sccm), maintaining the air pressure of the cavity to be 1.4mTorr by adopting a high-power pulse magnetron sputtering technology, turning on a high-power pulse power supply connected with the chromium sputtering target, setting the power frequency to be 200Hz, the pulse width to be 50 mus, the pulse voltage to be 1200V, the power to be 3.0kW, the bias voltage of a substrate to be-160V, the deposition temperature to be 90 ℃, and depositing a chromium transition layer with the thickness of 150nm;
s3, continuously introducing Ar gas into the cavity (the introduction amount of the Ar gas is 70 sccm), adopting a direct-current magnetron sputtering technology, maintaining the air pressure of the cavity to be 2.1mTorr, turning on a direct-current power supply connected with the graphite sputtering target, setting the power to be 0.9kW, the bias voltage to be-100V, the deposition temperature to be 50 ℃, and depositing a graphite-like amorphous carbon layer with the thickness of 400nm so as to obtain the high-conductivity corrosion-resistant protective composite coating.
The corrosion current density is 1.8 multiplied by 10 under the standard working voltage of 0.6V through testing -8 A/cm 2 The as-deposited contact resistance was 2.4 m.OMEGA.cm 2 And the contact resistance after 24h of corrosion is 6.3m omega cm 2 And the contact resistance is 7.2m omega cm after 48h of corrosion 2 。
Example 2
In this embodiment, the preparation method of the metal bipolar plate high-conductivity corrosion-resistant protective composite coating is as follows:
s1, selecting 316L stainless steel as a substrate, ultrasonically cleaning a stainless steel bipolar plate, drying, placing the stainless steel bipolar plate into a vacuum chamber, fixing the stainless steel bipolar plate on a workpiece bracket, and vacuumizing to 2.010 -5 Turning on an ion source under the conditions that the flow of argon is 40sccm and the bias voltage is-150V, adjusting the output voltage to 1200V, and etching the surface of the stainless steel bipolar plate for 30min by utilizing argon plasma;
s2, introducing Ar gas (the introduction amount of the Ar gas is 60 sccm) into the cavity, maintaining the air pressure of the cavity to be 2.0mTorr by adopting a high-power pulse magnetron sputtering technology, turning on a high-power pulse power supply connected with the chromium sputtering target, setting the power frequency to be 400Hz, the pulse width to be 100 mu s, the pulse voltage to be 1000V, the power to be 4.5kW, the matrix bias voltage to be-180V, the deposition temperature to be 80 ℃, and depositing a chromium transition layer with the thickness of 200nm;
s3, continuously introducing Ar gas into the cavity (the introduction amount of the Ar gas is 30 sccm), adopting a direct-current magnetron sputtering technology, maintaining the air pressure of the cavity to be 1.4mTorr, turning on a direct-current power supply connected with the graphite sputtering target, setting the power to be 1.2kW, the bias voltage to be-250V, the deposition temperature to be 40 ℃, and depositing a graphite-like amorphous carbon layer with the thickness of 300nm so as to obtain the high-conductivity corrosion-resistant protective composite coating.
The corrosion current density is 1.3 multiplied by 10 under the standard working voltage of 0.6V through testing -8 A/cm 2 The as-deposited contact resistance was 2.9 m.OMEGA.cm 2 And the contact resistance after 24h of corrosion is 6.2m omega cm 2 And the contact resistance after 48h of corrosion is 7.1m omega cm 2 。
Example 3
In this embodiment, the preparation method of the metal bipolar plate high-conductivity corrosion-resistant protective composite coating is as follows:
s1, selecting titanium alloy as a substrate, ultrasonically cleaning a titanium alloy bipolar plate, drying, placing the titanium alloy bipolar plate into a vacuum chamber, fixing the titanium alloy bipolar plate on a workpiece bracket, and vacuumizing to 2.0 multiplied by 10 -5 Turning on an ion source under the conditions that the argon flow is 65sccm and the bias voltage is-250V, adjusting the output voltage to 1200V, and etching the surface of the stainless steel bipolar plate for 60min by using argon plasma;
s2, introducing Ar gas into the cavity (the introduction amount of the Ar gas is 70 sccm), maintaining the air pressure of the cavity to be 2.1mTorr by adopting a high-power pulse magnetron sputtering technology, turning on a high-power pulse power supply connected with the chromium sputtering target, setting the power frequency to be 300Hz, the pulse width to be 100 mus, the pulse voltage to be 1200V, the power to be 3.0kW, the bias voltage of a substrate to be-200V, the deposition temperature to be 100 ℃, and depositing a chromium transition layer with the thickness of 100nm;
s3, continuously introducing Ar gas into the cavity (the introduction amount of the Ar gas is 40 sccm), adopting a direct-current magnetron sputtering technology, maintaining the air pressure of the cavity to be 1.7mTorr, turning on a direct-current power supply connected with the graphite sputtering target, setting the power to be 0.9kW, the bias voltage to be-50V, the deposition temperature to be 80 ℃, and depositing a graphite-like amorphous carbon layer with the thickness of 200nm so as to obtain the high-conductivity corrosion-resistant protective composite coating.
The corrosion current density is 1.1 multiplied by 10 under the standard working voltage of 0.6V -8 A/cm 2 The as-deposited contact resistance was 2.7 m.OMEGA.cm 2 Contact resistance after 24 hours of etching was 6.9 m.OMEGA.. Cm 2 Contact resistance after 48h of etching was 7.8 m.OMEGA.. Cm 2 。
Example 4
In this embodiment, the preparation method of the metal bipolar plate high-conductivity corrosion-resistant protective composite coating is as follows:
s1, selecting titanium alloy as a substrate, ultrasonically cleaning a titanium alloy bipolar plate, drying, placing the titanium alloy bipolar plate into a vacuum chamber, fixing the titanium alloy bipolar plate on a workpiece bracket, and vacuumizing to 2.0 multiplied by 10 -5 Turning on an ion source under the conditions that the flow of argon is 70sccm and the bias voltage is-300V, adjusting the output voltage to 1200V, and etching the surface of the stainless steel bipolar plate for 45min by utilizing argon plasma;
s2, introducing Ar gas into the cavity (the introduction amount of the Ar gas is 50 sccm), maintaining the air pressure of the cavity to be 1.7mTorr by adopting a high-power pulse magnetron sputtering technology, turning on a high-power pulse power supply connected with the chromium sputtering target, setting the power frequency to be 300Hz, the pulse width to be 100 mus, the pulse voltage to be 1100V, the power to be 3.0kW, the bias voltage of a substrate to be-160V, the deposition temperature to be 90 ℃, and depositing a chromium transition layer with the thickness of 150nm;
s3, continuously introducing Ar gas into the cavity (the introduction amount of the Ar gas is 50 sccm), adopting a direct-current magnetron sputtering technology, maintaining the air pressure of the cavity to be 1.7mTorr, turning on a direct-current power supply connected with the graphite sputtering target, setting the power to be 1.0kW, the bias voltage to be-150V, the deposition temperature to be 60 ℃, and depositing a graphite-like amorphous carbon layer with the thickness of 200nm so as to obtain the high-conductivity corrosion-resistant protective composite coating.
The corrosion current density is 1.2 multiplied by 10 under the standard working voltage of 0.6V -8 A/cm 2 The as-deposited contact resistance was 2.7 m.OMEGA.cm 2 And the contact resistance is 7.3m omega cm after 24h of corrosion 2 Contact resistance after 48h of etching was 8.6 m.OMEGA.. Cm 2 。
Example 5
In this embodiment, the preparation method of the metal bipolar plate high-conductivity corrosion-resistant protective composite coating is as follows:
s1, selecting titanium alloy as a substrate, ultrasonically cleaning a titanium alloy bipolar plate, drying, placing the titanium alloy bipolar plate into a vacuum chamber, fixing the titanium alloy bipolar plate on a workpiece bracket, and vacuumizing to 2.0 multiplied by 10 -5 Turning on an ion source under the conditions that the flow of argon is 55sccm and the bias voltage is-200V, adjusting the output voltage to 1200V, and etching the surface of the stainless steel bipolar plate for 45min by utilizing argon plasma;
s2, introducing Ar gas into the cavity (the introduction amount of the Ar gas is 70 sccm), maintaining the air pressure of the cavity to be 2.1mTorr by adopting a high-power pulse magnetron sputtering technology, turning on a high-power pulse power supply connected with the chromium sputtering target, setting the power frequency to be 300Hz, the pulse width to be 100 mus, the pulse voltage to be 1100V, the power to be 3.0kW, the bias voltage of a substrate to be-250V, the deposition temperature to be 100 ℃, and depositing a chromium transition layer with the thickness of 150nm;
s3, continuously introducing Ar gas into the cavity (the introduction amount of the Ar gas is 35 sccm), adopting a direct-current magnetron sputtering technology, maintaining the air pressure of the cavity to be 1.5mTorr, turning on a direct-current power supply connected with the graphite sputtering target, setting the power to be 1.0kW, the bias voltage to be-150V, the deposition temperature to be 70 ℃, and depositing a graphite-like amorphous carbon layer with the thickness of 100nm so as to obtain the high-conductivity corrosion-resistant protective composite coating.
The corrosion current density is 1.1 multiplied by 10 under the standard working voltage of 0.6V 8 A/cm 2 The as-deposited contact resistance was 2.6 m.OMEGA.cm 2 Contact resistance after 24 hours of etching was 7.6 m.OMEGA.. Cm 2 Contact resistance after 48h of etching was 8.7 m.OMEGA.. Cm 2 。
Comparative example 1
This example was a comparative example to example 1, steps S1 and S3 were exactly the same as example 1, and the substrate bias was-400V in step S2, with the other parameters being the same as example 1.
Comparative example 2
In this example, which is a comparative example of example 1, steps S1 and S3 are exactly the same as example 1, and in step S2, the sputtering source is changed to dc magnetron sputtering, and other parameters are the same as example 1.
Comparative example 3
This example was a comparative example of example 1, steps S1 and S2 were exactly the same as example 1, and step S3 was performed with a graphite-like amorphous carbon layer having a thickness of 800nm, with the other parameters being the same as example 1.
Comparative example 4
This example is a comparative example of example 1, steps S1 and S3 are exactly the same as example 1, step S2 is a substrate bias of-100V, other parameters are the same as example 1, and the corrosion resistance and conductivity of the prepared coating are much lower than those of example 1.
And (3) performance test comparison:
the corrosion resistance of the sample is measured by adopting a three-electrode electrochemical test system, and the solution is 0.5 MH 2 SO 4 +5ppm HF solution at a solution temperature of 80 ℃ and the results are shown in FIG. 2. As can be seen from fig. 2: example 1 the sample has a corrosion current density of 1.8X 10 at a standard working voltage of 0.6V -8 A/cm 2 Compared with the United states department of energy standard (DOE 2020) 1 × 10 -6 A/cm 2 Reduced by about 2 orders of magnitude, and the corrosion current density of the sample of the comparative example 1 is 3.6 multiplied by 10 under the standard working voltage of 0.6V - 6 A/cm 2 Comparative example 2 sample having a corrosion current density of 1.3X 10 at a standard working voltage of 0.6V -6 A/cm 2 Comparative example 3 sample having a corrosion current density of 4.5X 10 at a standard operating voltage of 0.6V -8 A/cm 2 The corrosion current density of the examples is significantly reduced compared to the two comparative examples, indicating that the coatings prepared by the examples of the invention have better corrosion resistance.
The surface of the sample was subjected to a contact resistance test with an assembly pre-load of 1.5MPa, and the results are shown in FIG. 3, example 1The contact resistance of the deposition state (namely the high-conductivity corrosion-resistant protection composite coating) is 2.4m omega cm 2 After 24 hours of etching, the contact resistance increased slightly to 7.3 m.OMEGA.. Cm 2 After 48 hours of etching, the contact resistance increased slightly to 8.2 m.OMEGA.. Cm 2 Less than 10m omega cm meeting the standard requirement of the United states department of energy 2 The contact resistance in the as-deposited state (i.e., coating) in comparative example 1 was 7.7 m.OMEGA.. Cm 2 After 24 hours of etching, the contact resistance increased to 11.3 m.OMEGA.cm 2 After 48 hours of etching, the contact resistance increased to 26.4 m.OMEGA.cm 2 In comparative example 2, the contact resistance in the as-deposited state (i.e., coating layer) was 7.9 m.OMEGA.. Cm 2 After 24 hours of etching, the contact resistance increased to 11.8 m.OMEGA.cm 2 After 48 hours of etching, the contact resistance increased to 26.7 m.OMEGA.cm 2 In comparative example 3, the contact resistance in the as-deposited state (i.e., coating layer) was 22.3 m.OMEGA.. Cm 2 After 24 hours of etching, the contact resistance increased to 25.7 m.OMEGA.cm 2 After 48h of etching, the contact resistance increased to 29.5 m.OMEGA.. 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, and only the contact resistance of the example rises to the minimum extent along with the increase of the corrosion time, and only the example can meet the standard of the DOE2025, so that the initial conductivity of the example is proved to be better, and the performance of the example is influenced to a smaller extent by long-time corrosion.
FIGS. 4 a-4 c are surface topographies of example 1, comparative example 1, and comparative example 2, respectively, as determined by scanning electron microscopy analysis: the protective composite coating prepared in example 1 has a smooth and compact surface structure, and the coatings prepared in comparative examples 1 and 2 have rough and cracked surfaces, and the results show that the coating prepared in example 1 of the present invention by high power pulse magnetron sputtering contains a (110) preferred crystal plane oriented chromium transition layer, and the coating has a smoother and more compact surface, which further shows that the coating in example 1 has better protective performance.
In addition, the inventors of the present invention have also made experiments with other materials, process operations, and process conditions described in the present specification with reference to the above examples, and have obtained preferable results.
It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific embodiments, and all technical modifications made according to the technical solution of the present invention fall within the protection scope of the present invention without departing from the spirit of the present invention and the protection scope of the claims.
Claims (10)
1. A high-conductivity corrosion-resistant protective composite coating is characterized by comprising a chromium transition layer and a graphite-like amorphous carbon layer which are sequentially formed on the surface of a metal bipolar plate serving as a matrix; the preferred crystal plane orientation of the chromium transition layer is (110), the texture coefficient of the preferred crystal plane (110) in the chromium transition layer is more than 0.8, and the thickness of the graphite-like amorphous carbon layer is 100-400 nm; and the corrosion current density of the high-conductivity corrosion-resistant protection composite coating is less than 2 multiplied by 10 under the standard working voltage of 0.6V -8 A/cm 2 The contact resistance in the deposition state is less than 3m omega cm 2 Contact resistance is less than 8m omega cm after 24h of corrosion 2 And the contact resistance is increased within 5% after 48h of corrosion.
2. The highly conductive corrosion-resistant protective composite coating according to claim 1, wherein: the thickness of the chromium transition layer is 100-200 nm.
3. The method for preparing the high-conductivity corrosion-resistant protective composite coating according to claim 1 or 2, characterized by comprising:
providing a metal bipolar plate as a substrate;
depositing a chromium transition layer on the surface of the metal bipolar plate by adopting a high-power pulse magnetron sputtering technology and taking a high-purity chromium target as a target material, wherein the orientation of a crystal face in the chromium transition layer is (110), and the bias voltage of a substrate is-160V-250V;
and depositing a graphite-like amorphous carbon layer on the surface of the chromium transition layer by adopting a direct-current magnetron sputtering technology and taking a high-purity graphite target as a target material, thereby obtaining the high-conductivity corrosion-resistant protective composite coating.
4. The method according to claim 3, characterized by comprising: the metal bipolar plate is placed in a reaction cavity by adopting a high-power pulse magnetron sputtering technology, a high-purity chromium target is used as a target material, an inert gas is used as a working gas, and a chromium transition layer is deposited and formed on the surface of the metal bipolar plate, wherein the high-power pulse magnetron sputtering technology adopts the pulse frequency of 200-400 Hz, the pulse width of 50-100 mus, the pulse voltage of 1000-1200V, the power of 3.0-4.5 kW, the air pressure of the reaction cavity is 1.4-2.1 mTorr, the introduction amount of the inert gas is 30-70 sccm, the deposition temperature is 80-100 ℃, and the deposition time is 15-25 min.
5. The production method according to claim 3, characterized by comprising: depositing a graphite-like amorphous carbon layer on the surface of the chromium transition layer by adopting a direct-current magnetron sputtering technology and taking a high-purity graphite target as a target material and inert gas as working gas; wherein, the power of the power supply of the sputtering source is 0.9-1.2 kW, the air pressure of the reaction cavity is 1.4-2.1 mTorr, the bias voltage of the matrix is-50V-250V, the input amount of inert gas is 30-70 sccm, the deposition temperature is 40-80 ℃, and the deposition time is 30-90 min.
6. The method for preparing according to claim 3, characterized by further comprising: and before the chromium transition layer is formed, etching the surface of the metal bipolar plate.
7. The production method according to claim 6, wherein the etching treatment includes: etching the metal bipolar plate for 30-60 min at room temperature by adopting an Ar ion etching method; the etching treatment adopts the following process conditions: the gas pressure of the reaction cavity is 2.0 x 10 -5 The argon flow is 40-100 sccm and the bias voltage is-150 to-450V below Torr, and the Ar ion etching method comprises glow etching and/or ion beam etching.
8. The production method according to claim 3, characterized in that: the metal bipolar plate comprises a stainless steel bipolar plate or a titanium alloy bipolar plate.
9. Use of the highly conductive corrosion resistant protective composite coating of claim 1 or 2 in a proton exchange membrane fuel cell.
10. A bipolar plate for a proton exchange membrane fuel cell, comprising: the metal bipolar plate comprises a metal bipolar plate and a high-conductivity corrosion-resistant protection composite coating which is covered on the surface of the metal bipolar plate; wherein the high-conductivity corrosion-resistant protective composite coating is the high-conductivity corrosion-resistant protective composite coating in claim 1 or 2.
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