Aluminum-based metal plate and preparation method and application thereof

Abstract

The invention relates to the technical field of fuel cells, and provides an aluminum-based metal plate and a preparation method and application thereof.The aluminum-based metal plate comprises an aluminum base material, a metal layer, a transition layer and a carbon coating, and the metal layer, the transition layer and the carbon coating are sequentially deposited on the surface of the aluminum base material through a magnetron sputtering ion plating method; the transition layer is obtained by intermittently starting a metal target for deposition while starting a carbon target for magnetron sputtering ion plating; the power of the metal target is gradually reduced along with the increase of the thickness of the transition layer; the corresponding system temperature of the metal layer, the transition layer and the carbon coating during magnetron sputtering ion plating is 200-350 DEG C. The compact protective coating is obtained by controlling the temperature of magnetron sputtering ion plating and the component gradient change of the transition layer, and the protective coating can cope with the harsh corrosion environment in the fuel cell, has important significance in improving the quality of the bipolar plate and controlling the cost of the bipolar plate, and is suitable for large-scale popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and particularly to an aluminum-based metal plate, a preparation method thereof, and an application thereof. Background Art

[0002] A fuel cell directly converts the chemical energy stored in fuels (such as hydrogen, natural gas, etc.) and oxidants (such as air, oxygen) into electrical energy through an electrochemical reaction, and is an efficient and environmentally friendly power generation device. A proton exchange membrane fuel cell (PEMFC) has the advantages of fast startup, low operating temperature, noiselessness, and no pollution, and has broad application prospects in automobiles, residential houses, small and medium-sized power stations, and portable devices.

[0003] The structure of a proton exchange membrane fuel cell mainly includes a membrane electrode assembly (MEA), a bipolar plate (BP), a current collector, an end plate, etc. During the operation of a proton exchange membrane fuel cell, the function of the bipolar plate is to support the membrane electrode assembly, collect current, conduct heat, distribute gas, and isolate fuels and oxidants. Since most of the currently used proton exchange membranes are perfluorosulfonic acid membranes, the chain ends of their molecular branches are sulfonic acid groups with strong oxidizing properties; at the same time, since the perfluorosulfonic acid membrane degrades during the use of the fuel cell and releases fluoride ions, in the fuel cell working environment, the bipolar plate must be able to withstand sulfonic acid with pH = 2 - 3, hydrofluoric acid with a concentration of about 2 ppm, and an environmental condition of about 70°C, which poses extremely high requirements for the corrosion resistance of the bipolar plate.

[0004] Traditional graphite bipolar plates exhibit very excellent corrosion resistance and electrical conductivity, but due to their disadvantages such as poor mechanical strength, large volume, many defects, high processing cost, and low processing efficiency, it is becoming increasingly difficult for them to meet the requirements of vehicle fuel cells for smaller volume, higher power density, lower manufacturing cost, higher reliability, and convenience for large-scale promotion. In contrast, bipolar plates made of metal have the advantages of thin volume, high mechanical strength, high gas resistance rate, good processing performance, and high resource recovery rate. However, ordinary metal bipolar plates usually have the defect of poor corrosion resistance, and the strategy of surface treatment or surface covering with a special coating on the metal bipolar plate has become the mainstream research direction for improving the corrosion resistance of fuel cell metal bipolar plates.

[0005] Currently, the research on metal bipolar plates mainly focuses on coating a protective coating on the surface of stainless steel or titanium plates. Although many breakthroughs have been made in the research on preparing protective coatings on the surfaces of the above two metals, most of the technical targets specified in DOE 2025 have been achieved, but there are still some key targets that are difficult to achieve. For example, titanium alloys are expensive, and using titanium alloys as substrates is difficult to meet the cost requirements for bipolar plates in DOE 2025 (2 $·kW -1). However, stainless steel has a relatively high weight and it is difficult to meet the requirements of DOE 2025 for mass power density (0.18 kg·kW -1 ). Although the mass can be controlled by reducing the thickness of the bipolar plate, blindly reducing the thickness will surely damage its mechanical properties.

[0006] In view of this, the present invention is proposed. SUMMARY OF THE INVENTION

[0007] Aluminum and its alloys have the advantages of light weight, excellent electrical and thermal conductivity, good mechanical properties and machining properties, and are very suitable as candidate substrates for metal bipolar plates. However, experiments have found that due to the special surface composition of aluminum and its alloys, conventional surface coatings are difficult to effectively protect this material to obtain a low corrosion current density and a material that can be used for components such as fuel cell bipolar plates. Through research on the surface structure of aluminum and its alloys, the present invention discovers that when a metal layer, a transition layer, and a carbon coating are sequentially deposited on the surface of the aluminum substrate by magnetron sputtering ion plating; in particular, the transition layer is obtained by intermittently enabling the metal target to deposit while enabling the carbon target for magnetron sputtering ion plating; controlling the power of the metal target to gradually decrease as the thickness of the transition layer increases, and the system temperatures corresponding to the metal layer, the transition layer, and the carbon coating during magnetron sputtering ion plating are all 200~350°C, the corrosion current density can be effectively reduced, and the obtained aluminum-based metal plate has multiple technical advantages when used for components such as fuel cell bipolar plates.

[0008] In a first aspect, the present invention provides an aluminum-based metal plate, comprising: an aluminum substrate, and a metal layer, a transition layer, and a carbon coating sequentially deposited on the surface of the aluminum substrate by magnetron sputtering ion plating; The transition layer is obtained by intermittently enabling the metal target to deposit while enabling the carbon target for magnetron sputtering ion plating; the power of the metal target gradually decreases as the thickness of the transition layer increases; The system temperatures corresponding to the metal layer, the transition layer, and the carbon coating during magnetron sputtering ion plating are all 200~350°C, preferably 300°C; The aluminum substrate can be selected from commercially pure aluminum or aluminum alloy; The composition of the metal layer is selected from one or more of titanium, chromium, tantalum, niobium, nickel, and aluminum; The material of the carbon coating is selected from one or more of diamond-like amorphous carbon, graphite-like amorphous carbon, and metal atom-doped amorphous carbon; The composition of the metal target is selected from one or more of titanium, chromium, tantalum, niobium, nickel, and aluminum.

[0009] According to the aluminum-based metal plate provided by the present invention, the aluminum alloy is commercially pure aluminum, 3xxx series aluminum alloy, 5xxx series aluminum alloy, or 6xxx series aluminum alloy.

[0010] According to the aluminum-based metal plate provided by the present invention, the doped metal atoms in the metal atom-doped amorphous carbon are selected from one or more of titanium, chromium, tantalum, niobium, nickel, ruthenium, iridium, platinum, gold, and silver.

[0011] In the magnetron sputtering ion plating method of the present invention, physical or chemical vapor deposition is adopted, and at the same time, physical or chemical methods are used to bombard and etch the coating to obtain a dense, defect-free and uniform coating.

[0012] According to the aluminum-based metal plate provided by the present invention, depositing the metal layer includes: after the aluminum substrate is subjected to glow cleaning, it is placed in the coating chamber, and the first metal target is used for the first magnetron sputtering ion plating to obtain the metal layer with a thickness of 5-200 nm; the thickness of the metal layer is preferably 10-50 nm.

[0013] According to the aluminum-based metal plate provided by the present invention, during the first magnetron sputtering ion plating process, an inert atmosphere is adopted, and the vacuum degree is 1.0×10 -1 ~3.0×10 -1 Pa, the power of the first metal target is 50-150 W, the voltage of the bias power supply is 50-300 V, the duty cycle is 30%-80%, and the deposition time is 5-30 min.

[0014] The inert atmosphere is preferably argon.

[0015] According to the aluminum-based metal plate provided by the present invention, after depositing the metal layer, the first carbon target is enabled to continue the second magnetron sputtering ion plating. While enabling the first carbon target, the second metal target is intermittently enabled to obtain the transition layer with a thickness of 20-150 nm; the thickness of the transition layer is preferably 50-100 nm; the composition of the second metal target is selected from one or more of titanium, chromium, tantalum, niobium, nickel, and aluminum.

[0016] According to the aluminum-based metal plate provided by the present invention, during the second magnetron sputtering ion plating process, an inert atmosphere is adopted, and the vacuum degree is 1.0×10 -1 ~3.0×10 -1 Pa, the voltage of the bias power supply is 50-150 V, the duty cycle is 30%-80%, the power of the first carbon target is 50-100 W, the initial power of the second metal target is 80-150 W, the power of the second metal target at the last time of enabling is 30-50 W, and the total deposition time is 5-180 min.

[0017] According to the aluminum-based metal plate provided by the present invention, during the second magnetron sputtering ion plating process, the time for each enabling of the second metal target is 1-3 min, the time difference between two adjacent enablements of the second metal target is 1-3 min, and the power difference between two adjacent enablements of the second metal target is 5-25 W.

[0018] For the aluminum-based metal plate provided by the present invention, the second metal target is used 5 to 8 times.

[0019] Through the above process, a multi-layer nano-coating can be obtained, and along the thickness direction, the composition of the nano-coating gradually changes from mainly metal to mainly carbon.

[0020] Preferably, the thickness of the nano-coating is 2 to 20 nm.

[0021] For the aluminum-based metal plate provided by the present invention, the first metal target and the second metal target have the same composition.

[0022] For the aluminum-based metal plate provided by the present invention, after depositing the transition layer, the second carbon target is enabled to continue the third magnetron sputtering ion coating to obtain the carbon coating with a thickness of 5 to 100 nm; the thickness of the carbon coating is preferably 10 to 50 nm.

[0023] For the aluminum-based metal plate provided by the present invention, during the third magnetron sputtering ion coating process, an inert atmosphere is adopted, the vacuum degree is 1.0×10 -1 ~3.0×10 -1 Pa, the power of the second carbon target is 50 to 250 W, the bias power supply voltage is 50 to 150 V, the duty cycle is 30% to 80%, and the deposition time is 5 to 360 min.

[0024] For the aluminum-based metal plate provided by the present invention, during the glow cleaning process, an inert atmosphere is adopted, the vacuum degree is 0.8 to 6 Pa, the temperature is 100 to 400 °C, the bias power supply voltage is 800 to 1200 V, the duty cycle is 30% to 80%, and the glow cleaning time is 10 to 60 min.

[0025] In a second aspect, the present invention also provides a preparation method of the aluminum-based metal plate as described above.

[0026] The preparation method of the aluminum-based metal plate provided by the present invention includes: The aluminum substrate is ground, polished, degreased, and cleaned to obtain a pretreated substrate; wherein, the grinding and polishing include successively grinding with #400, #600, #1000, #1500, and #2000 sandpapers, and then polishing with polishing pastes of 2.5 μm and 0.5 μm particle sizes; the degreasing and cleaning include ultrasonically cleaning the aluminum substrate in acetone, ethanol, and deionized water and drying it.

[0027] The pretreated substrate is subjected to glow cleaning and then placed in a coating chamber, and the first metal target is enabled to perform the first magnetron sputtering ion coating to obtain the metal layer; After depositing the metal layer, the first carbon target is enabled to continue the second magnetron sputtering ion coating. While enabling the first carbon target, the second metal target is intermittently enabled to obtain the transition layer; After depositing the transition layer, the second carbon target is enabled to continue the third magnetron sputtering ion coating to obtain the carbon coating.

[0028] Thirdly, the present invention also provides the application of the aluminum-based metal plate as described above and the aluminum-based metal plate prepared by the preparation method as described above in electrolytic water hydrogen production; the aluminum-based metal plate is a bipolar plate, an end plate, an electrodialysis plate or a bipolar membrane plate in a hydrogen fuel cell.

[0029] An aluminum-based metal plate, a preparation method thereof and an application provided by the present invention. The aluminum-based metal plate includes an aluminum substrate, and a metal layer, a transition layer and a carbon coating sequentially deposited on the surface of the aluminum substrate by a magnetron sputtering ion coating method; the transition layer is deposited by intermittently enabling a metal target while enabling a carbon target for magnetron sputtering ion coating; the power of the metal target gradually decreases as the thickness of the transition layer increases; the system temperatures corresponding to the metal layer, the transition layer and the carbon coating during magnetron sputtering ion coating are all 200-350°C. By controlling the temperature of magnetron sputtering ion coating and the compositional gradient change of the transition layer, the present invention obtains a denser protective coating, which can cope with the harsh corrosion environment inside the fuel cell. At the same time, this method selects an aluminum substrate as the substrate, which has significant advantages in cost, weight, thermal conductivity and electrical conductivity compared with titanium and stainless steel substrates. The present invention is of great significance for improving the quality of bipolar plates and controlling the cost of bipolar plates, and is suitable for large-scale popularization and application. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is an open circuit potential curve graph of Examples 1-4 and Comparative Examples 1-2 provided by the present invention.

[0032] Figure 2 It is a potentiodynamic polarization curve graph of Examples 1-4 and Comparative Examples 1-2 provided by the present invention.

[0033] Figure 3 It is a surface macroscopic photograph graph of Examples 1-4 and Comparative Examples 1-2 provided by the present invention.

[0034] Figure 4It is the transmission electron microscope image of Example 1 provided by the present invention.

[0035] Figure 5 It is the line scan image of element distribution of Example 1 provided by the present invention. Detailed implementation manners

[0036] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] The following Figures 1 to 5 describes an aluminum-based metal plate and its preparation method and application of the present invention.

[0038] For those technical or conditions not specified in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For the reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through regular channels.

[0039] Example 1 A preparation method of an aluminum-based metal bipolar plate, the steps are as follows: (1) Grind and polish a 5083 aluminum alloy plate to obtain a substrate with a thickness of 2 mm; (2) Wash the substrate obtained in step (1), and the process is as follows: First, put the substrate into a hydrocarbon cleaning agent (acetone) for degreasing cleaning for 20 min. After degreasing, ultrasonically wash the substrate with water; Then put the substrate into another hydrocarbon cleaning agent (ethanol) for ultrasonic cleaning for 20 min. After cleaning, put the substrate into pure water for ultrasonic cleaning and drying.

[0040] (3) Load the substrate washed in step (3) into a magnetron sputtering ion coating furnace, evacuate to below 3.0×10 -3 Pa, introduce argon, set the vacuum degree to 5.0 Pa, set the furnace temperature to 300 °C, set the bias voltage to 1000 V, and the duty cycle to 80%. Carry out glow cleaning on the substrate for 30 min. After the cleaning is completed, keep the temperature at 300 °C throughout the process and sequentially carry out metal layer deposition, transition layer deposition and corrosion-resistant carbon coating deposition to obtain the aluminum-based metal bipolar plate; specifically: Metal layer deposition: After loading the processed substrate into the coating chamber, introduce argon, and set the vacuum degree to 5×10 - 1Pa, turn on the titanium target, set the target power to 100 W, set the bias power supply voltage to 80 V, duty cycle 50%, set the deposition time to 5 min, and obtain a metal layer with a thickness of 15 nm; Interlayer deposition: Introduce argon gas and set the vacuum degree to 5×10 -1 Pa, turn on the titanium target, set the target power to 100 W, at the same time turn on the carbon target, set the target power to 100 W, set the bias power supply voltage to 80 V, duty cycle 50%, set the deposition time to 2 min, then turn off the titanium target, maintain the carbon target power at 100 W, and set the deposition time to 2 min. Repeat the above process, and reduce the titanium target power by 10 W each time until the last time when the titanium target power is 40 W, and obtain an interlayer with a total thickness of 74 nm.

[0041] Corrosion-resistant carbon coating deposition: Introduce argon gas and set the vacuum degree to 5×10 -1 Pa, turn on the carbon target, set the target power to 120 W, set the bias power supply voltage to 80 V, duty cycle 50%, set the deposition time to 10 min, and obtain a corrosion-resistant carbon coating with a thickness of 24 nm.

[0042] Example 2 The same as step (3) of Example 1, the difference is only that: the furnace temperature is set to 350 °C under all processes in step (3).

[0043] Example 3 The same as step (3) of Example 1, the difference is only that: the furnace temperature is set to 250 °C under all processes in step (3).

[0044] Example 4 The same as step (3) of Example 1, the difference is only that: the furnace temperature is set to 200 °C under all processes in step (3).

[0045] Comparative Example 1 The same as step (3) of Example 1, the difference is only that: the furnace temperature is set to room temperature under all processes in step (3).

[0046] Comparative Example 2 The same as step (3) of Example 1, the difference is only that: during the interlayer deposition process, the titanium target power remains unchanged at 100 W in each repeated process.

[0047] Test Example The surface macroscopic photos of the aluminum-based metal bipolar plates prepared in the above examples and comparative examples are as Figure 3 shown. Each aluminum-based metal bipolar plate is respectively placed in a 0.5 M H2SO4 acidic corrosion solution containing 2 ppm hydrofluoric acid at 70 °C, and its open circuit potential curve and potentiodynamic polarization curve are measured, asFigures 1 to 2 As shown. The corrosion current density and corrosion potential of the obtained aluminum-based metal bipolar plates are shown in Table 1 below.

[0048] At the same time, the aluminum-based metal bipolar plate prepared in Example 1 was also subjected to transmission electron microscopy testing and elemental distribution line scanning testing, and the results are as Figure 4 as 5 shown. From Figure 4 as 5 it can be seen that the coating is composed of the bottommost metal layer, the transition layer, and the top amorphous carbon layer. Among them, the transition layer is an alternating layer structure of a carbon layer and a carbon-metal composite coating layer. From the direction of the metal layer to the transition layer, the thickness of the carbon-metal composite coating layer gradually decreases, and from the direction of the metal layer to the transition layer, the proportion of the metal component in the carbon-metal composite coating layer gradually decreases.

[0049] Table 1

[0050] It can be seen from the above data that the gradient coating of the transition layer and the magnetron sputtering temperature play a key role in the corrosion resistance of the coating. The two work together synergistically. Among them, with the increase of temperature, the corrosion current density of the sample first decreases and then increases, and the corrosion potential first shifts positively and then negatively. At 300 °C, the sample has the lowest corrosion current density and the most positive corrosion potential, indicating that the sample has the best corrosion resistance.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An aluminum-based metal plate, characterized in that, Comprising: an aluminum substrate, and a metal layer, a transition layer, and a carbon coating sequentially deposited on the surface of the aluminum substrate by magnetron sputtering ion plating; the transition layer is obtained by intermittently enabling a metal target to deposit while enabling a carbon target for magnetron sputtering ion plating; the power of the metal target gradually decreases as the thickness of the transition layer increases; the system temperatures corresponding to the metal layer, the transition layer, and the carbon coating during magnetron sputtering ion plating are all 200 - 350 °C; the aluminum substrate can be selected from commercially pure aluminum or aluminum alloy; the composition of the metal layer is selected from one or more of titanium, chromium, tantalum, niobium, nickel, and aluminum; the material of the carbon coating is selected from one or more of diamond-like amorphous carbon, graphite-like amorphous carbon, and metal atom-doped amorphous carbon; the composition of the metal target is selected from one or more of titanium, chromium, tantalum, niobium, nickel, and aluminum.

2. The aluminum-based metal plate according to claim 1, characterized in that, Depositing the metal layer includes: after the aluminum substrate is subjected to glow cleaning, it is placed in a coating chamber, and a first metal target is enabled for first magnetron sputtering ion plating to obtain the metal layer with a thickness of 5 - 200 nm; Preferably, during the first magnetron sputtering ion coating process, an inert atmosphere is adopted, the vacuum degree is 1.0×10 -1 ~3.0×10 -1 Pa, the power of the first metal target is 50~150W, the voltage of the bias power supply is 50~300V, the duty cycle is 30%~80%, and the deposition time is 5~30min.

3. The aluminum-based metal plate according to claim 1 or 2, characterized in that, after depositing the metal layer, a first carbon target is enabled to continue second magnetron sputtering ion plating. While enabling the first carbon target, a second metal target is intermittently enabled to obtain the transition layer with a thickness of 20 - 150 nm; the composition of the second metal target is selected from one or more of titanium, chromium, tantalum, niobium, nickel, and aluminum; Preferably, during the second magnetron sputtering ion coating process, an inert atmosphere is adopted, the vacuum degree is 1.0×10 -1 ~3.0×10 -1 Pa, the bias power supply voltage is 50~150V, the duty cycle is 30%~80%, the power of the first carbon target is 50~100W, the initial power of the second metal target is 80~150W, the power of the second metal target when it is enabled for the last time is 30~50W, and the total deposition time is 5~180min.

4. The aluminum-based metal plate according to claim 3, wherein during the second magnetron sputtering ion plating process, the time for each enabling of the second metal target is 1 - 3 min, the time difference between adjacent enablements of the second metal target is 1 - 3 min, and the power difference between adjacent enablements of the second metal target is 5 - 25 W; Preferably, the number of times of enabling the second metal target is 5 - 8 times.

5. The aluminum-based metal plate according to claim 3 or 4, characterized in that, The first metal target and the second metal target have the same composition.

6. The aluminum-based metal plate according to any one of claims 1 to 5, characterized in that, After depositing the transition layer, a second carbon target is enabled to continue third magnetron sputtering ion plating to obtain the carbon coating with a thickness of 5 - 100 nm; Preferably, during the third magnetron sputtering ion coating process, an inert atmosphere is adopted, and the vacuum degree is 1.0×10 -1 ~3.0×10 -1 Pa, the power of the second carbon target is 50~250W, the voltage of the bias power supply is 50~150V, the duty cycle is 30%~80%, and the deposition time is 5~360min.

7. The aluminum-based metal plate according to claim 2, characterized in that, During the glow cleaning process, an inert atmosphere is used, the vacuum degree is 0.8 - 6 Pa, the temperature is 100 - 400 °C, the bias power supply voltage is 800 - 1200 V, the duty cycle is 30% - 80%, and the time for glow cleaning is 10 - 60 min.

8. The preparation method of the aluminum-based metal plate according to any one of claims 1 - 7.

9. The preparation method of the aluminum-based metal plate according to claim 8, wherein, Comprising: grinding, polishing, degreasing, and cleaning the aluminum substrate to obtain a pretreated substrate; after the pretreated substrate is subjected to glow cleaning, it is placed in a coating chamber, and a first metal target is enabled for first magnetron sputtering ion plating to obtain the metal layer; after depositing the metal layer, a first carbon target is enabled to continue second magnetron sputtering ion plating. While enabling the first carbon target, a second metal target is intermittently enabled to obtain the transition layer; after depositing the transition layer, a second carbon target is enabled to continue third magnetron sputtering ion plating to obtain the carbon coating.

10. The application of the aluminum-based metal plate according to any one of claims 1 - 7, or the aluminum-based metal plate prepared by the preparation method according to claim 8 or 9, in hydrogen production by electrolysis of water; the aluminum-based metal plate is a bipolar plate, an end plate, an electrodialysis plate, or a bipolar membrane plate in a hydrogen fuel cell.

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