Protective coating for metal bipolar plate of fuel cell as well as preparation method and application of protective coating

Abstract

The invention belongs to the technical field of fuel cells, and particularly relates to a metal bipolar plate protective coating as well as a preparation method and application thereof. The zirconium or zirconium alloy bonding layer provided by the invention and the metal bipolar plate can form a strong bonding interface, and the interface is subjected to chemical reaction in the working environment of the fuel cell to form zirconium oxide, so that the self-corrosion potential of the coating is improved, and the coating is endowed with excellent corrosion resistance. Besides, zirconium or zirconium alloy is used as the bonding layer, so that the surface roughness of the protective coating can be reduced, the actual contact area of the protective coating is larger, and the electric contact performance is better. The protective coating interface of the metal bipolar plate provided by the invention has high binding force and excellent chemical inertness, the coating contains a CrN and Cr2N two-phase structure, the corrosion resistance of CrN is exerted, the conductivity is enhanced through the Cr2N phase, and high-reliability and long-life protection is provided for the metal bipolar plate of the fuel cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a metal bipolar plate protective coating and a preparation method and application thereof. Background Art

[0002] As a key component in the battery, the bipolar plate mainly plays the role of separating reactants, collecting current, assuming heat dissipation and drainage, supporting electrodes, and connecting battery cells in series, etc., and accounts for a large proportion of the entire battery volume, weight and cost. Among them, metal bipolar plates have the advantages of high conductivity, good thermal conductivity, excellent barrier properties, good formability and easy processing and manufacturing, and are considered to be the main development direction of future technology. However, the surface of metal bipolar plates is easily oxidized and corroded in an acidic working environment, which increases the interface contact resistance between the metal bipolar plate and the gas diffusion layer. At the same time, the metal cations precipitated by corrosion will reduce the activity of the catalyst, seriously affecting the performance and life of the battery.

[0003] Depositing conductive and corrosion-resistant coatings on the surface of metal bipolar plates through physical or chemical vapor deposition technology, such as amorphous carbon, nitrides, carbides, precious metals and their composite coatings, is considered to be one of the important ways to solve the above problems. However, the coatings prepared by physical vapor deposition have defects such as microcracks and holes. The corrosive medium will pass through these defects and cause serious damage to the interface between the coating and the metal bipolar plate. Due to the low interfacial bonding between the coating and the metal bipolar plate, when the battery is frequently started and stopped and under high load conditions, when the corrosion potential exceeds its pitting potential, it will accelerate the loss of underlying elements and cause the protective coating to peel off and fail.

[0004] Chinese patent CN 116368258 A discloses a fuel cell metal bipolar plate coating and preparation method, using metal Ti or Cr as a bonding layer to improve the bonding between the coating and the substrate, and then using cathode arc technology to deposit metal-doped hydrogen-free diamond-like carbon on the bonding layer as a protective coating. However, the barrier and passivation capabilities of the metal Ti or Cr bonding layer are limited, especially in the acidic working environment of hydrogen fuel cells, and its corrosion resistance cannot fully meet the application requirements of high reliability and long life. Summary of the invention

[0005] The object of the present invention is to provide a metal bipolar plate protective coating and a preparation method and application thereof. The metal bipolar plate protective coating provided by the present invention can meet the conductive and corrosion-resistant protection requirements of the metal bipolar plate surface.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a bonding layer of a metal bipolar plate protective coating, wherein the bonding layer is one of zirconium and a zirconium alloy; the zirconium alloy includes one of a zirconium-titanium alloy, a zirconium-chromium alloy, a zirconium-tantalum alloy, a zirconium-hafnium alloy and a zirconium-molybdenum alloy.

[0008] The present invention also provides a metal bipolar plate protective coating, comprising a bonding layer and a protective layer above the bonding layer; the bonding layer is the bonding layer described in the above scheme; the protective layer is a two-phase composite layer of CrN and Cr2N; the atomic ratio of chromium atoms to nitrogen atoms in the protective layer is 1:1 to 2:1.

[0009] Preferably, the thickness of the bonding layer is 30 to 300 nm; the thickness of the protective layer is 350 to 1000 nm.

[0010] The present invention also provides a method for preparing the metal bipolar plate protective coating described in the above scheme, and the preparation method of the bonding layer and the protective layer is physical vapor deposition.

[0011] Preferably, the physical vapor deposition includes one of multi-arc ion plating, high-power pulsed magnetron sputtering, direct current magnetron sputtering, medium frequency magnetron sputtering and radio frequency magnetron sputtering.

[0012] Preferably, when the bonding layer is plated by multi-arc ion plating, the preparation parameters are: temperature 200-500° C., argon gas flow rate 50-300 sccm, substrate bias -30-300 V, target current 50-150 A, and plating time 2-8 min.

[0013] Preferably, when the coating method of the bonding layer is high-power pulsed magnetron sputtering, the preparation parameters are: temperature 100-300°C, power 3-8kW, frequency 500-1500Hz, pulse width 20-100μs, working gas pressure 0.3-0.7Pa, substrate bias -50--150V, and coating time 10-30min.

[0014] Preferably, when the protective layer is deposited by multi-arc ion plating, the preparation parameters are: temperature 200-550°C, deposition time 8-25min, protective atmosphere flow rate 50-300sccm, substrate bias -30--300V, target current 50-150A.

[0015] Preferably, when the method of depositing the protective layer is high-power pulsed magnetron sputtering, the preparation parameters are: deposition temperature 100-300°C, power 3-8kW, frequency 500-1500Hz, pulse width 20-100μs, working gas pressure 0.3-0.7Pa, substrate bias -50--150V, and sputtering time 30-120min.

[0016] The present invention also provides the use of the metal bipolar plate protective coating described in the above scheme or the metal bipolar plate protective coating obtained by the preparation method described in the above scheme in a fuel cell.

[0017] The beneficial effects achieved by the present invention are as follows:

[0018] The present invention provides a bonding layer for a metal bipolar plate protective coating, wherein the bonding layer is one of zirconium and a zirconium alloy; the zirconium alloy includes one of a zirconium-titanium alloy, a zirconium-chromium alloy, a zirconium-tantalum alloy, a zirconium-hafnium alloy and a zirconium-molybdenum alloy. The present invention uses zirconium or a zirconium alloy as a bonding layer, which can reduce the surface roughness of the protective coating, so that it has a larger actual contact area, thereby having better electrical contact performance. The bonding layer provided by the present invention can form a strong bonding interface, and the interface undergoes a chemical reaction in the working environment of a fuel cell to form zirconium oxide, thereby increasing the self-corrosion potential of the coating and giving the coating excellent corrosion resistance. In summary, the present invention proposes to use zirconium and its alloy as a bonding layer for a metal bipolar plate coating, so that the interface between the coating and the metal bipolar plate not only has a high bonding force, but also can form a passivation product, thereby solving the problem of coating shedding due to corrosion of the bonding layer under harsh working conditions.

[0019] The present invention also provides a metal bipolar plate protective coating, including a bonding layer and a protective layer on the bonding layer; the bonding layer is the bonding layer described in the above scheme; the protective layer is a two-phase composite layer of CrN and Cr2N; the atomic ratio of chromium atoms and nitrogen atoms in the protective layer is 1:1 to 2:1. The metal bipolar plate provided by the present invention can form a strong bonding interface, and the interface undergoes a chemical reaction in the working environment of the fuel cell to form zirconium oxide, thereby increasing the self-corrosion potential of the coating and giving the coating excellent corrosion resistance. The interface of the metal bipolar plate protective coating provided by the present invention has high bonding force and excellent chemical inertness. The coating contains a two-phase structure of CrN and Cr2N. While exerting the corrosion resistance of CrN, the conductivity is enhanced by the Cr2N phase, providing high reliability and long-life protection for the metal bipolar plates of fuel cells.

[0020] The present invention also provides a method for preparing the metal bipolar plate protective coating of the above scheme. The preparation method provided by the present invention has simple steps, convenient operation and high feasibility.

[0021] The present invention also provides the use of the metal bipolar plate protective coating described in the above scheme or the metal bipolar plate protective coating obtained by the preparation method described in the above scheme in a fuel cell. The protective coating proposed by the present invention has a two-phase structure of CrN and Cr2N. By adjusting the composition of the coating, the coating has both excellent corrosion resistance and electrical conductivity, meeting the application requirements of the metal bipolar plate of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A schematic diagram of the structure of the metal bipolar plate protective coating prepared by the present invention;

[0024] Figure 2 The surface morphology of the metal bipolar plate protective coating prepared in Example 1 (a) and Example 2 (b) of the present invention;

[0025] Figure 3 The potentiodynamic polarization curves of the metal bipolar plate protective coatings prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention in a simulated hydrogen fuel cell cathode and anode environment;

[0026] Figure 4 The surface contact resistance of the metal bipolar plate protective coating prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0027] Figure 5 The potentiodynamic polarization curves of the metal bipolar plate protective coatings prepared in Examples 1 and 2 of the present invention in a simulated hydrogen fuel cell cathode and anode environment;

[0028] Figure 6 Surface contact resistance of the metal bipolar plate protective coating prepared in Example 1 and Example 2 of the present invention. DETAILED DESCRIPTION

[0029] The present invention provides a bonding layer of a metal bipolar plate protective coating, wherein the bonding layer is one of zirconium and a zirconium alloy; the zirconium alloy includes one of a zirconium-titanium alloy, a zirconium-chromium alloy, a zirconium-tantalum alloy, a zirconium-hafnium alloy and a zirconium-molybdenum alloy.

[0030] In the present invention, the thickness of the bonding layer is preferably 30 to 300 nm, and specifically may be 30 nm, 60 nm, 100 nm, 140 nm, 180 nm, 200 nm, 240 nm or 280 nm.

[0031] The present invention also provides a metal bipolar plate protective coating, comprising a bonding layer and a protective layer above the bonding layer, wherein the bonding layer is the bonding layer described in the above scheme; the protective layer is a two-phase composite layer of CrN and Cr2N; the atomic ratio of chromium atoms to nitrogen atoms in the protective layer is 1:1 to 2:1.

[0032] The metal bipolar plate protective coating provided by the present invention includes a bonding layer; the thickness of the bonding layer is preferably 30 to 300 nm, specifically 30 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 240 nm or 270 nm.

[0033] The metal bipolar plate protective coating provided by the present invention comprises a protective layer; the thickness of the protective layer is preferably 350 to 1000 nm, specifically 400 nm, 500 nm, 600 nm, 700 nm, 800 nm or 900 nm.

[0034] In the present invention, the atomic ratio of chromium atoms to nitrogen atoms in the protective layer is preferably 1.2:1 to 1.8:1, and specifically can be 1.4:1, 1.5:1, 1.6:1, 1.7:1 or 1.8:1.

[0035] In the present invention, the bonding layer and the protective layer are preferably in direct contact or not in direct contact (other layers are provided between the bonding layer and the protective layer).

[0036] The structure of the metal bipolar plate protective coating provided by the present invention is as follows Figure 1 As shown, the metal bipolar plate protective coating comprises a bonding layer and a protective layer on the bonding layer.

[0037] The present invention also provides a method for preparing the metal bipolar plate protective coating described in the above scheme, and the preparation method of the bonding layer and the protective layer is physical vapor deposition.

[0038] In the present invention, the physical vapor deposition preferably includes one of multi-arc ion plating, high-power pulsed magnetron sputtering, DC magnetron sputtering, medium-frequency magnetron sputtering and radio frequency magnetron sputtering, and more preferably multi-arc ion plating or high-power pulsed magnetron sputtering.

[0039] In the present invention, the method for preparing the metal bipolar plate protective coating preferably comprises the following steps:

[0040] A bonding layer is prepared on the surface of a metal bipolar plate, and then a protective layer is prepared on the bonding layer to obtain the metal bipolar plate protective coating on the surface of the metal bipolar plate; the bonding layer and the protective layer are prepared by physical vapor deposition.

[0041] The present invention prepares a bonding layer on the surface of a metal bipolar plate. In the present invention, the metal bipolar plate is preferably ultrasonically cleaned in a mixed solution of ethanol and acetone before use and then taken out for activation; the activation is preferably: the metal bipolar plate after ultrasonic cleaning is placed in a coating chamber for plasma etching; the plasma etching is preferably carried out in a protective atmosphere; the protective atmosphere is preferably argon; the flow rate of the protective atmosphere is preferably 50 to 300 sccm, specifically 50 sccm, 100 sccm, 150 sccm, 200 sccm, 250 sccm or 300 sccm; the substrate bias during the plasma etching is preferably -300 to -600 V, specifically -300 V, -400 V, -450 V, -500 V or -600 V, and the ion source power is preferably 2 to 8 kW, specifically 2 kW, 4 kW, 6 kW or 8 kW. The present invention cleans and activates the bipolar plate by metal, removes dirt, oxides or other impurities on the surface of the metal bipolar plate, and enhances the activity of the surface.

[0042] In the present invention, the physical vapor deposition preferably includes one of multi-arc ion plating, high-power pulsed magnetron sputtering, DC magnetron sputtering, medium-frequency magnetron sputtering and radio frequency magnetron sputtering, and more preferably multi-arc ion plating or high-power pulsed magnetron sputtering.

[0043] In the present invention, when the method for preparing the bonding layer is multi-arc ion plating, the bonding layer is preferably prepared by: applying a substrate bias and a target current to the pretreated metal bipolar plate under vacuum and heating conditions, and plating the bonding layer in a protective atmosphere; the target material is one of zirconium and a zirconium alloy; the zirconium alloy includes one of a zirconium-titanium alloy, a zirconium-chromium alloy, a zirconium-tantalum alloy, a zirconium-hafnium alloy and a zirconium-molybdenum alloy.

[0044] In the present invention, the multi-arc ion plating is preferably carried out in a vacuum chamber; the vacuum degree of the multi-arc ion plating is preferably 1×10 -3 ~5×10 -3 Pa, specifically 1×10 -3 Pa, 3×10 -3 Pa or 5×10 -3 Pa.

[0045] In the present invention, the rotating speed of the multi-arc ion plating turret is preferably 1-5 rpm, specifically 1 rpm, 3 rpm or 5 rpm.

[0046] In the present invention, the substrate bias voltage of the multi-arc ion plating is preferably -30 to -300 V, specifically -30 V, -90 V, -120 V, -150 V, -200 V, -250 V or -300 V; the target current of the multi-arc ion plating is preferably 50 to 150 A, specifically 50 A, 70 A, 90 A, 110 A, 120 A or 150 A.

[0047] In the present invention, the protective atmosphere of the multi-arc ion plating is preferably argon; the flow rate of the protective atmosphere is preferably 50 to 300 sccm, specifically 50 sccm, 100 sccm, 150 sccm, 200 sccm, 250 sccm or 300 sccm.

[0048] In the present invention, the temperature of the plated bonding layer is preferably 200-500°C, specifically 200°C, 300°C, 400°C or 500°C, and the plating time is preferably 2-8 min, specifically 2 min, 4 min, 6 min or 8 min.

[0049] In the present invention, when the method for preparing the bonding layer is high-power pulsed magnetron sputtering, the preparation of the bonding layer is preferably: applying a substrate bias to the pretreated metal bipolar plate under vacuum and heating conditions, and coating the bonding layer in a protective atmosphere; the target material is one of zirconium or zirconium alloys; the zirconium alloy includes one of zirconium-titanium alloy, zirconium-chromium alloy, zirconium-tantalum alloy, zirconium-hafnium alloy and zirconium-molybdenum alloy.

[0050] In the present invention, the high-power pulsed magnetron sputtering is preferably carried out in a vacuum chamber; the vacuum degree of the high-power pulsed magnetron sputtering is preferably 1×10 -3 ~5×10 -3 Pa, specifically 1×10 -3 Pa, 3×10 -3 Pa or 5×10 -3 Pa.

[0051] In the present invention, the temperature of the high-power pulsed magnetron sputtering is preferably 100-300°C, specifically 100°C, 150°C, 200°C, 250°C or 300°C.

[0052] In the present invention, the rotation speed of the turret for high-power pulsed magnetron sputtering is preferably 1-5 rpm, specifically 1 rpm, 3 rpm or 5 rpm.

[0053] In the present invention, the protective atmosphere of the high-power pulsed magnetron sputtering is preferably argon; the flow rate of the protective atmosphere is preferably 50 to 300 sccm, specifically 50 sccm, 100 sccm, 150 sccm, 200 sccm, 250 sccm or 300 sccm.

[0054] In the present invention, the average power of the high-power pulsed magnetron sputtering is preferably 3-8 kW, specifically 3 kW, 4 kW, 5 kW, 6 kW, 7 kW or 8 kW.

[0055] In the present invention, the frequency of the high-power pulsed magnetron sputtering is preferably 500-1500 Hz, specifically 500 Hz, 700 Hz, 900 Hz, 1000 Hz, 1200 Hz or 1500 Hz.

[0056] In the present invention, the pulse width of the high-power pulsed magnetron sputtering is preferably 20 to 100 μs, specifically 20 μs, 30 μs, 40 μs, 60 μs, 80 μs or 100 μs.

[0057] In the present invention, the working gas pressure of the high-power pulsed magnetron sputtering is preferably 0.3-0.7 Pa, specifically 0.3 Pa, 0.4 Pa, 0.5 Pa, 0.6 Pa or 0.7 Pa.

[0058] In the present invention, the substrate bias voltage of the high-power pulsed magnetron sputtering is preferably -50 to -150V, specifically -50V, -70V, -90V, -100V, -110V, -130V or -150V.

[0059] In the present invention, the plating time of the high-power pulsed magnetron sputtering is preferably 10 to 30 minutes, specifically 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes.

[0060] In the present invention, a bonding layer is firstly plated on the surface of the metal bipolar plate to improve the bonding force between the protective coating and the metal bipolar plate. Furthermore, the bonding layer prepared by the high-power pulsed magnetron sputtering method of the present invention has the advantages of smooth surface and dense structure, avoiding the disadvantages of columnar crystals and large particles in the bonding layer prepared by DC sputtering and multi-arc ion methods.

[0061] After preparing the bonding layer, the present invention prepares a protective layer on the bonding layer to obtain the metal bipolar plate protective coating on the surface of the metal bipolar plate. In the present invention, the physical vapor deposition preferably includes one of multi-arc ion plating, high-power pulsed magnetron sputtering, DC magnetron sputtering, medium-frequency magnetron sputtering and radio frequency magnetron sputtering, and more preferably multi-arc ion plating or high-power pulsed magnetron sputtering.

[0062] In the present invention, when the method for preparing the protective layer is multi-arc ion plating, the method for preparing the protective layer is preferably: applying a substrate bias and a target current to the metal bipolar plate coated with the bonding layer, and depositing the protective layer in nitrogen.

[0063] In the present invention, the multi-arc ion plating process parameters for preparing the protective layer are preferably consistent with those for preparing the bonding layer, except that: the target material is preferably a Cr target, the deposition temperature is preferably 200-550°C, specifically 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C or 550°C, the deposition time is preferably 8-25min, specifically 8min, 12min, 15min, 17min, 20min or 25min, and the nitrogen flow rate is preferably 50-90 0sccm, specifically 50sccm, 100sccm, 150sccm, 200sccm, 400sccm, 600sccm, 800sccm or 900sccm, the substrate bias is preferably -30 to -300V, specifically -30V, -70V, -100V, -150V, -200V, -250V or -300V, the target current is preferably 50 to 150A, specifically 50A, 80A, 100A, 120A or 150A.

[0064] In the present invention, when the method for preparing the protective layer is high-power pulsed magnetron sputtering, the method for preparing the protective layer is preferably: applying a substrate bias to the metal bipolar plate coated with the bonding layer, and depositing the protective layer in nitrogen.

[0065] In the present invention, the process parameters of the high-power pulsed magnetron sputtering for preparing the protective layer are preferably consistent with those for preparing the bonding layer, except that: the target material is preferably a Cr target, the deposition temperature is preferably 100-300°C, specifically 100°C, 130°C, 150°C, 180°C, 200°C, 240°C, 270°C or 300°C, the average power is preferably 3-8kW, specifically 3kW, 4kW, 5kW, 6kW, 7kW or 8kW, the frequency is preferably 500-1500Hz, specifically 500Hz, 800Hz, 1000Hz, 1200Hz or 1500Hz. 1500Hz, the pulse width is preferably 20-100μs, specifically 20μs, 40μs, 60μs, 80μs or 100μs, the working gas pressure is preferably 0.3-0.7Pa, specifically 0.3Pa, 0.4Pa, 0.5Pa, 0.6Pa or 0.7Pa, the substrate bias is preferably -50--150V, specifically -50V, -80V, -100V, -120V or -150V, the sputtering time is preferably 30-120min, specifically 30min, 50min, 70min, 90min or 120min.

[0066] The metal bipolar plate protective coating provided by the present invention not only has excellent membrane-base bonding strength, but also has excellent corrosion resistance and electrical conductivity, and is suitable for fuel cells, especially for proton exchange membrane fuel cells.

[0067] The present invention also provides the use of the metal bipolar plate protective coating described in the above scheme or the metal bipolar plate protective coating obtained by the preparation method described in the above scheme in a fuel cell.

[0068] The protective coating proposed by the present invention has a two-phase structure of CrN and Cr2N. By adjusting the composition of the coating, the coating has both excellent corrosion resistance and electrical conductivity, meeting the application requirements of fuel cell metal bipolar plates.

[0069] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0070] Example 1

[0071] The metal bipolar plate and 316L stainless steel sample after ultrasonic cleaning were clamped into the vacuum chamber. The mechanical pump was used to roughly evacuate the air to 5 Pa, and the molecular pump was used to highly evacuate the air to a pressure of 5×10 -3 Pa, the chamber temperature was raised to 300 °C, and the rotating speed was 1 rpm.

[0072] (1) Apply a 600 V bias, turn on the ion source, and etch the substrate at a power of 6 kW to remove the substrate oxide layer and contaminant layer;

[0073] (2) The Zr bonding layer was deposited by multi-arc ion plating technology at a deposition temperature of 300°C, with 120 sccm of argon gas, 100 V substrate bias and 90 A target current applied for 6 min.

[0074] (3) The CrN+Cr2N protective layer was deposited by multi-arc ion plating technology. A nitrogen gas with a flow rate of 650 sccm was introduced, a target current of 80 A and a substrate bias of -50 V were applied, and the deposition time was 15 min. After the furnace was cooled down, the protective coating of the metal bipolar plate was obtained. The surface morphology was as follows: Figure 2 (a) shown.

[0075] The metal bipolar plate protective coating prepared in this embodiment was tested for corrosion resistance, contact resistance (using Davies' contact resistance standard test method) and membrane-base bonding strength (press-in test). The corrosion resistance test was performed in an air-purged 80°C atmosphere with a concentration of 0.5 mol / L H2SO4 + 5 ppm F - Solution (simulating the cathode environment of hydrogen fuel cells) and hydrogen purge at 80°C with a concentration of 0.5 mol / L H2SO4 + 5 ppm F - solution (simulating the anode environment of a hydrogen fuel cell).

[0076] The test results show that the anode corrosion current density of the metal bipolar plate protective coating prepared in this embodiment is 4.884×10 -7 A.cm -2 The anode self-corrosion potential is 0.081 V, and the cathode corrosion current density is 7.956×10 -7 A.cm -2 , the cathode self-corrosion potential is 0.005V; the interface contact resistance is 5.12mΩ·cm 2 , the membrane-base bonding strength reaches HF 1 level.

[0077] Example 2

[0078] The metal bipolar plate and 316L stainless steel sample after ultrasonic cleaning were clamped into the vacuum chamber. The mechanical pump was used to roughly evacuate the air to 5 Pa, and the molecular pump was used to highly evacuate the air to a pressure of 5×10 -3 Pa, the chamber temperature was raised to 200 °C, and the rotating speed was 1 rpm.

[0079] (1) Apply a 600 V bias, turn on the ion source, and etch the substrate at a power of 6 kW to remove the substrate oxide layer and contaminant layer;

[0080] (2) The Zr bonding layer was deposited by high-power pulsed magnetron sputtering technology, with an average power of 5 kW, a fixed frequency of 1000 Hz, a pulse width of 30 μs, and a substrate holder rotating at 1 rpm at 200 °C. The bonding layer deposition time was fixed at 20 min, the argon gas flow rate was 100 sccm, the working gas pressure was maintained at 0.5 Pa, and the substrate bias was -100 V;

[0081] (3) A CrN+Cr2N protective layer was deposited by high-power pulsed magnetron sputtering technology. The average power was maintained at 5 kW, the substrate holder was rotated at 1 rpm at a fixed frequency of 1000 Hz, a pulse width of 30 μs, and 200°C. The protective layer deposition time was fixed at 60 min, the N2 / Ar gas flow rate was 80 / 100 sccm, the working gas pressure was maintained at 0.5 Pa, and the substrate bias voltage was -100 V. The metal bipolar plate protective coating was obtained, and the surface morphology was as follows: Figure 2 (b) as shown.

[0082] The corrosion resistance and contact resistance of the metal bipolar plate protective coating prepared in this embodiment were tested (using the contact resistance standard test method of Davies). The corrosion resistance test was performed in an air-purged 80°C atmosphere with a concentration of 0.5 mol / L H2SO4 + 5 ppm F - Solution (simulating the cathode environment of hydrogen fuel cells) and hydrogen purged at 80°C with a concentration of 0.5 mol / L H2SO4 + 5 ppm F - solution (simulating the anode environment of a hydrogen fuel cell).

[0083] The test results show that the anode corrosion current density of the metal bipolar plate protective coating prepared in this embodiment is 5.229×10 -7 A.cm -2 The anode self-corrosion potential is 0.414 V, and the cathode corrosion current density is 5.816×10 -7 A.cm -2 , the cathode self-corrosion potential is -0.107V; the interface contact resistance is 3.04mΩ·cm 2 .

[0084] Comparative Example 1

[0085] The metal bipolar plate and 316L stainless steel sample after ultrasonic cleaning were clamped into the vacuum chamber. The mechanical pump was used to roughly evacuate the air to 5 Pa, and the molecular pump was used to highly evacuate the air to a pressure of 5×10 -3 Pa, the chamber temperature was raised to 300 °C, and the rotating speed was 1 rpm.

[0086] (1) Apply a 600 V bias, turn on the ion source, and etch the substrate at a power of 6 kW to remove the substrate oxide layer and contaminant layer;

[0087] (2) The Cr bonding layer was deposited by multi-arc ion plating technology at a deposition temperature of 300°C, with 120 sccm of argon gas, 100 V substrate bias and 80 A target current applied for 6 min.

[0088] (3) The CrN+Cr2N protective layer was plated by multi-arc ion plating technology, with a nitrogen flow rate of 650 sccm, an 80 A target current and a 50 V substrate bias applied for a deposition time of 15 min. After the furnace was cooled down, the protective coating for the metal bipolar plate was obtained.

[0089] The test method of this comparative example is the same as that of Example 1. The test results show that the anode corrosion current density of the metal bipolar plate protective coating prepared in this comparative example is 1.428×10 -6 A.cm -2 , the anode self-corrosion potential is 0.014V, and the cathode corrosion current density is 7.329×10 -7 A.cm -2 , cathode self-corrosion potential 0.063V; interface contact resistance 17.68mΩ·cm 2 , the membrane-base bonding strength reaches HF 1 level.

[0090] Comparative Example 2

[0091] The metal bipolar plate and 316L stainless steel sample after ultrasonic cleaning were clamped into the vacuum chamber. The mechanical pump was used to roughly evacuate the air to 5 Pa, and the molecular pump was used to highly evacuate the air to a pressure of 5×10 -3 Pa, the chamber temperature was raised to 300 °C, and the rotating speed was 1 rpm.

[0092] (1) Apply a 600 V bias, turn on the ion source, and etch the substrate at a power of 6 kW to remove the substrate oxide layer and contaminant layer;

[0093] (2) The Ti bonding layer was plated using multi-arc ion plating technology at a deposition temperature of 300°C, with 120 sccm of argon gas, a 100 V substrate bias and a 70 A target current applied for 6 min.

[0094] (3) The CrN+Cr2N protective layer was plated by multi-arc ion plating technology, with a nitrogen flow rate of 650 sccm, an 80 A target current and a 50 V substrate bias applied for a deposition time of 15 min. After the furnace was cooled down, the protective coating for the metal bipolar plate was obtained.

[0095] The test method of this comparative example is the same as that of Example 1. The test results show that the anode corrosion current density of the metal bipolar plate protective coating prepared in this comparative example is 1.368×10 -6 A.cm -2 , the anode self-corrosion potential is 0.011V, and the cathode corrosion current density is 9.926×10 -7 A.cm-2 , cathode self-corrosion potential 0.015V; contact resistance 10.31mΩ·cm 2 , the membrane-base bonding strength reaches HF 1 level.

[0096] The test results of the metal bipolar plate protective coating (substrate is 316L stainless steel) prepared in Examples 1 to 2 of the present invention and Comparative Examples 1 to 2 are shown in Tables 1 and Figure 3 to Figure 6 As shown:

[0097] in, Figure 3 Potentiodynamic polarization curves of the metal bipolar plate protective coatings prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention in a simulated hydrogen fuel cell cathode and anode environment; Figure 4 The contact resistance diagram of the metal bipolar plate protective coating prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention; Figure 5 The potentiodynamic polarization curves of the metal bipolar plate protective coatings prepared in Examples 1 and 2 of the present invention in a simulated hydrogen fuel cell cathode and anode environment; Figure 6 The contact resistance of the metal bipolar plate protective coating prepared in Example 1 and Example 2 of the present invention.

[0098] Table 1 Characterization test results of corrosion resistance and electrical conductivity of the embodiments of the present invention and the comparative examples

[0099]

[0100] According to Table 1 and Figure 3 to Figure 6 It can be seen that the metal bipolar plate protective coating provided by the present invention has both excellent electrical conductivity and corrosion resistance.

[0101] It can be seen from the above embodiments that the metal bipolar plate protective coating provided by the present invention has excellent electrical conductivity, corrosion resistance and high interface adhesion, which improves the performance of the fuel cell as a whole.

[0102] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A bonding layer of a metal bipolar plate protective coating, characterized in that: The bonding layer is one of zirconium and a zirconium alloy; The zirconium alloy includes one of a zirconium-titanium alloy, a zirconium-chromium alloy, a zirconium-tantalum alloy, a zirconium-hafnium alloy and a zirconium-molybdenum alloy.

2. A metal bipolar plate protective coating, characterized in that: comprising a bonding layer and a protective layer on the bonding layer; The bonding layer is the bonding layer according to claim 1; The protective layer is a two-phase composite layer of CrN and Cr2N; The atomic ratio of chromium atoms to nitrogen atoms in the protective layer is 1:1 to 2:

1.

3. The metal bipolar plate protective coating according to claim 2, characterized in that: The thickness of the bonding layer is 30 to 300 nm; The thickness of the protective layer is 350-1000 nm.

4. The method for preparing the metal bipolar plate protective coating according to any one of claims 2 to 3, characterized in that: The preparation method of the bonding layer and the protective layer is physical vapor deposition.

5. The preparation method according to claim 4, characterized in that: The physical vapor deposition includes one of multi-arc ion plating, high-power pulse magnetron sputtering, direct current magnetron sputtering, medium frequency magnetron sputtering and radio frequency magnetron sputtering.

6. The preparation method according to claim 5, characterized in that: When the bonding layer is plated by multi-arc ion plating, the preparation parameters are: temperature 200-500° C., argon gas flow rate 50-300 sccm, substrate bias -30--300 V, target current 50-150 A, and plating time 2-8 min.

7. The preparation method according to claim 5, characterized in that: When the bonding layer is coated by high-power pulsed magnetron sputtering, the preparation parameters are: temperature 100-300°C, power 3-8kW, frequency 500-1500Hz, pulse width 20-100μs, working gas pressure 0.3-0.7Pa, substrate bias -50--150V, and coating time 10-30min.

8. The preparation method according to claim 5, characterized in that: When the protective layer is deposited by multi-arc ion plating, the preparation parameters are: temperature 200-550° C., deposition time 8-25 min, protective atmosphere flow rate 50-300 sccm, substrate bias -30--300 V, target current 50-150 A.

9. The preparation method according to claim 5, characterized in that: When the method of depositing the protective layer is high-power pulsed magnetron sputtering, the preparation parameters are: deposition temperature 100-300°C, power 3-8kW, frequency 500-1500Hz, pulse width 20-100μs, working gas pressure 0.3-0.7Pa, substrate bias -50--150V, and sputtering time 30-120min.

10. Use of the metal bipolar plate protective coating according to any one of claims 2 to 3 or the metal bipolar plate protective coating obtained by the preparation method according to any one of claims 4 to 9 in a fuel cell.

Images