Metal bipolar plate and preparation method and application thereof

Abstract

The invention discloses a metal bipolar plate and a preparation method and application thereof, and belongs to the technical field of metal bipolar plates. The metal bipolar plate comprises a metal bipolar plate body, wherein the surface of the metal bipolar plate body is sequentially provided with a bottom layer, a transition layer and a functional surface layer from inside to outside; the base layer is a metal film layer, and the metal contained in the base layer comprises at least one of Ti and Zr; the transition layer is composed of metal and carbon, the functional surface layer is composed of metal and carbon, the metal in the functional surface layer comprises at least one of Ti and Zr, and the carbon in the metal-doped amorphous carbon layer is mainly of an amorphous carbon structure and further comprises a graphite phase and a diamond phase. Metal elements in the doped metal amorphous carbon layer are in solid solution and / or embedded in the amorphous carbon structure in a carbide nanocrystalline form. The metal bipolar plate has good conductivity and corrosion resistance, has an effective protection effect on the metal bipolar plate in an acidic and humid and hot environment of a cathode of a proton exchange membrane fuel cell, and keeps good performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal bipolar plates, in particular to a metal bipolar plate and a preparation method and application thereof. BACKGROUND

[0002] The bipolar plate is one of the core components in a proton exchange membrane fuel cell (PEMFC), and accounts for a large part of the weight and cost of the entire cell. The performance of the bipolar plate directly affects the performance of the fuel cell. Compared with the traditional graphite bipolar plate, the metal bipolar plate gradually becomes the mainstream of the bipolar plate due to its high mechanical performance, high specific gravity, good electrical conductivity and other characteristics.

[0003] The metal bipolar plate is prone to corrosion in the strong acid and humid PEMFC environment, and the dissolved metal ions can poison the proton membrane and the catalyst layer. Moreover, the formation of the passivation film on the surface of the metal bipolar plate will increase the interfacial contact resistance between the gas diffusion layer (GDL) and the bipolar plate, and seriously reduce the output performance of the PEMFC stack. Therefore, coordinating and controlling the corrosion and electrical conductivity of the metal bipolar plate has become a major problem to be solved for the development of hydrogen fuel cells.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a metal bipolar plate and a preparation method and application thereof to solve or improve the above technical problems.

[0006] In a first aspect, the present application provides a metal bipolar plate, which comprises a metal bipolar plate body, and the surface of the metal bipolar plate body is sequentially provided from inside to outside with a primer layer, a transition layer and a functional surface layer. The primer layer is a metal film layer, and the metal in the metal film layer comprises at least one of Ti and Zr. The transition layer is composed of metal and carbon, the metal in the transition layer is the same as that in the metal film layer, and the carbon in the transition layer is the same as that in the functional surface layer. The functional surface layer is a doped metal amorphous carbon layer composed of metal and carbon, the metal in the functional surface layer comprises at least one of Ti and Zr; the content of the metal in the doped metal amorphous carbon layer is 1% to 8% in terms of atomic percentage; the carbon in the doped metal amorphous carbon layer mainly presents an amorphous carbon structure, and the carbon in the doped metal amorphous carbon layer further comprises a graphite phase and a diamond phase; the metal elements in the doped metal amorphous carbon layer are solid-solved in the amorphous carbon structure, and / or embedded in the amorphous carbon structure in the form of carbide nanocrystals.

[0007] In an optional embodiment, the material of the metal bipolar plate body comprises stainless steel or titanium alloy.

[0008] In an optional embodiment, the thickness of the primer layer is 20 nm to 200 nm. And / or, the thickness of the transition layer is 10nm~100nm; And / or, the thickness of the functional surface layer is 200nm~600nm.

[0009] In an optional implementation, the stable current density of the metal bipolar plate does not exceed 1 μA / cm². 2 ; And / or, the interfacial contact resistance of the metal bipolar plates under a pressure of 1.4 MPa does not exceed 10 mΩ·cm. 2 .

[0010] In a second aspect, the present invention provides a method for preparing a metal bipolar plate as described in any of the foregoing embodiments, comprising the following steps: sequentially preparing an underlayer, a transition layer and a functional surface layer on the surface of the metal bipolar plate body.

[0011] In optional embodiments, the underlayer is prepared by magnetron sputtering, arc ion plating, or plasma-assisted chemical vapor deposition.

[0012] In an optional implementation, the underlayer is prepared by magnetron sputtering. The magnetron sputtering conditions include: a metal target power of 2kW to 5kW, an argon flow rate of 100mL / min to 200mL / min, and a deposition time of 4min to 40min.

[0013] In optional embodiments, the transition layer is prepared by magnetron sputtering, arc ion plating, or plasma-assisted chemical vapor deposition.

[0014] In an optional embodiment, the transition layer is prepared by magnetron sputtering. The magnetron sputtering conditions include: the metal target power is gradually reduced from 2kW~5kW to 0.1kW~0.5kW, the graphite target power is gradually increased from 0.1kW~0.5kW to 2kW~5kW, the argon flow rate is 100mL / min~200mL / min, and the deposition time is 3min~30min.

[0015] In optional embodiments, the functional surface layer is prepared by magnetron sputtering, arc ion plating, or plasma-assisted chemical vapor deposition.

[0016] In an optional embodiment, the functional surface layer is prepared by magnetron sputtering. The magnetron sputtering conditions include: Ar gas flow rate of 100 mL / min to 200 mL / min, graphite target power of 2 kW to 5 kW, Ti target power of 0.05 kW to 0.20 kW, and deposition time of 60 min to 180 min.

[0017] In an optional implementation, the metal bipolar plate body is first cleaned and plasma etched before the underlayer is prepared.

[0018] In an optional embodiment, the plasma etching conditions include: a bias voltage of -150V to -300V, an ion source current of 60A to 100A, an argon flow rate of 50mL / min to 100mL / min, and an etching time of 20min to 40min.

[0019] Thirdly, the present invention provides a fuel cell having a metal bipolar plate according to any of the foregoing embodiments.

[0020] The beneficial effects of this invention include: The metal bipolar plate provided by this invention includes a metal bipolar plate body, the surface of which, from the inside out, is provided with an underlayer, a transition layer, and a functional surface layer. The underlayer serves to prevent corrosive liquids from eroding the substrate through gaps and to enhance the bonding strength between the protective layer and the substrate. The transition layer is composed of metal and carbon. The metal in the transition layer is the same as the metal in the metal film layer, and the carbon in the transition layer is the same as the carbon in the doped metal amorphous carbon layer, thus achieving a transition between the underlayer and the functional surface layer. This results in a complete overall film structure without obvious film interfaces, which helps reduce interface resistance and interface defects. The functional surface layer is a doped metal amorphous carbon layer composed of metal and carbon. The metal in the functional surface layer includes at least one of Ti and Zr. By specifically doping the amorphous carbon layer of the functional surface layer with the aforementioned metal, the amorphous carbon layer structure can be made denser, and a carbide phase with low resistivity and low corrosion tendency can be formed, effectively improving the overall conductivity and corrosion resistance of the material. The carbon in this doped amorphous carbon layer is mainly in an amorphous carbon structure, and the carbon in this doped amorphous carbon layer also includes a graphite phase (sp). 2 ) and diamond phase (sp 3 The graphite phase can promote the conductivity of the thin film, while the diamond phase can prevent corrosion ion erosion. Metal elements exist in the amorphous carbon structure through solid solution or embedding, and can form carbide phases with amorphous carbon to promote the densification of the thin film. The low-resistance and corrosion-resistant carbide phases can further improve the conductivity and corrosion resistance of the thin film.

[0021] Therefore, the metal bipolar plate provided by the present invention has good conductivity and corrosion resistance, and effectively protects the metal bipolar plate and maintains good performance in the acidic and humid environment of the proton exchange membrane fuel cell cathode. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of the metal bipolar plate prepared in Example 1 of the present invention; Figure 2 The graph shows the interface contact resistance test results of the metal bipolar plates doped with amorphous carbon layers in Embodiment 1 and Comparative Example 4 of this invention. Figure 3 The graph shows the potentiostatic polarization test results of the metal bipolar plates doped with amorphous carbon layers in Examples 1 and 4 of this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0025] The following is a detailed description of the metal bipolar plate, its preparation method, and its application provided by the present invention.

[0026] The present invention provides a metal bipolar plate, which includes a metal bipolar plate body, and the surface of the metal bipolar plate body is provided with an underlayer, a transition layer and a functional surface layer from the inside to the outside.

[0027] In some alternative implementations, the material of the metal bipolar plate body may include stainless steel or titanium alloy, which can ensure that the metal bipolar plate body has a certain degree of corrosion resistance.

[0028] In this invention, the underlayer is a metal film layer, and the metal in the metal film layer includes at least one of Ti and Zr. The underlayer serves to prevent corrosive liquid from eroding the substrate through gaps and to improve the bonding strength between the protective layer and the substrate.

[0029] In some alternative implementations, the metal in the underlayer may be only Ti; in other alternative implementations, the metal in the underlayer may be only Zr; in still other alternative implementations, the metal in the underlayer may contain both Ti and Zr.

[0030] Ti and Zr metals themselves possess good electrical conductivity and stability, exhibiting low corrosion susceptibility in PEMFCs environments. Replacing them with metals that are unstable under PEMFC conditions would cause the corrosive liquid to continue eroding the metal bipolar plate substrate, significantly shortening the bipolar plate's lifespan.

[0031] In some alternative implementations, the thickness of the substrate can be 20nm to 200nm, such as 20nm, 50nm, 100nm, 120nm, 150nm, 180nm, or 200nm, or other values ​​within the range of 20nm to 200nm. In some preferred implementations, the thickness of the substrate can be 20nm to 150nm.

[0032] If the thickness of the underlayer is too thin, it will easily lead to a weak ability of the underlayer to prevent corrosion by the corrosive liquid; if the thickness of the underlayer is too thick, the columnar structure of the metal underlayer will be obvious, which will affect the integrity of the film and increase the interfacial contact resistance and pore resistance of the film, thereby reducing the ICR value and corrosion resistance of the film.

[0033] In this invention, the transition layer is composed of metal and carbon. The metal in the transition layer is the same as the metal in the metal film layer, and the carbon in the transition layer is the same as the carbon in the functional surface layer (doped metal amorphous carbon layer). This achieves a transition between the bottom layer and the functional surface layer, making the overall film structure complete and without obvious film interfaces, which is beneficial to reducing interface resistance and interface defects.

[0034] In some alternative implementations, the thickness of the transition layer can be 10nm to 100nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, or other values ​​within the range of 10nm to 100nm.

[0035] If the transition layer is too thin, it can easily lead to a significant delamination structure in the film, increasing the pore resistance of the film and reducing the overall density of the film; if the transition layer is too thick, it can easily lead to a high interfacial contact resistance.

[0036] In this invention, the functional surface layer is a doped metal amorphous carbon layer composed of metal and carbon.

[0037] The metal in the functional surface layer includes at least one of Ti and Zr. In some optional embodiments, the metal in the functional surface layer may be only Ti; in other optional embodiments, the metal in the functional surface layer may be only Zr; in still other optional embodiments, the metal in the functional surface layer may contain both Ti and Zr. In some more typical embodiments, the metal in the functional surface layer is Ti.

[0038] It should be emphasized that the metals in the functional surface layer of this invention must strictly adopt the above-mentioned elements in order to enable the material to have both good conductivity and corrosion resistance. If elements such as Mo are used, although the conductivity of the material can be improved to a certain extent, it is impossible to make the material have good corrosion resistance at the same time as high conductivity. Therefore, it is difficult to avoid and improve the problem of corrosion of metal bipolar plates in the strongly acidic and humid PEMFC environment.

[0039] The metal content in the doped amorphous carbon layer, measured as an atomic percentage, is 1% to 8%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%, or other values ​​within the range of 1% to 8%. In some preferred embodiments, the metal content in the doped amorphous carbon layer is 1% to 5%. In some even preferred embodiments, the metal content in the doped amorphous carbon layer is 3%.

[0040] If the metal content in the doped metal amorphous carbon layer is less than 1%, it is not conducive to improving the density of the film; if the metal content in the doped metal amorphous carbon layer is higher than 8%, the corrosion resistance of the film will decrease.

[0041] In this invention, the carbon in the doped metal amorphous carbon layer mainly exhibits an amorphous carbon structure, and the carbon in the doped metal amorphous carbon layer also includes a graphite phase (sp). 2 ) and diamond phase (sp 3 The metal elements in the doped metal amorphous carbon layer are dissolved in the amorphous carbon structure and / or embedded in the amorphous carbon structure in the form of carbide nanocrystals.

[0042] The aforementioned graphite phase can promote the conductivity of the thin film, while the diamond phase can prevent corrosion ion attack. In addition, metallic elements exist in the amorphous carbon structure through solid solution or embedding, and can form carbide phases with amorphous carbon to promote film densification. Furthermore, the low-resistance and corrosion-resistant carbide phases can further enhance the conductivity and corrosion resistance of the thin film.

[0043] In some alternative embodiments, the thickness of the functional surface layer can be 200nm to 600nm, such as 200nm, 300nm, 400nm, 500nm, or 600nm, or other values ​​within the range of 200nm to 600nm. In some preferred embodiments, the thickness of the functional surface layer can be 300nm to 600nm.

[0044] If the functional surface layer is too thin, the film's durability will be insufficient; if the functional surface layer is too thick, the stress on the amorphous carbon layer will be too great, leading to gaps and defects in the amorphous carbon film and exacerbating corrosion.

[0045] Continuing from the above, by doping an appropriate amount of metal (Ti and / or Zr, preferably Ti) into the amorphous carbon layer of the functional surface, the amorphous carbon layer structure can be made more compact. On the other hand, by doping the above metals in a specific amount, a carbide phase with low resistivity and low corrosion tendency (such as titanium carbide) can be formed, which can effectively improve the overall conductivity and corrosion resistance of the material.

[0046] In some alternative implementations, the stable current density of the metal bipolar plate does not exceed 1 μA / cm². 2Preferably, the value should not exceed 0.3 μA / cm. 2 For example, it can be 0.082 μA / cm 2 ~0.3μA / cm 2 .

[0047] In some alternative implementations, the interfacial contact resistance of the metal bipolar plates under a pressure of 1.4 MPa does not exceed 10 mΩ·cm. 2 Preferably, the Ω·cm value should not exceed 3.35 mΩ·cm. 2 For example, it can be 2.86 mΩ·cm 2 ~3.34mΩ·cm 2 .

[0048] Accordingly, the present invention also provides a method for preparing the above-mentioned metal bipolar plate, comprising the following steps: sequentially preparing an underlayer, a transition layer and a functional surface layer on the surface of the metal bipolar plate body.

[0049] In some alternative implementations, the metal bipolar plate body is first cleaned and plasma etched before the underlayer is prepared.

[0050] The cleaning process can involve using an alkaline cleaning agent and deionized water in sequence for ultrasonic cleaning until the surface is free of stains.

[0051] Plasma etching can be performed using high-bias glow discharge plasma etching, ion source etching, or arc ion etching. Taking ion source etching as an example, the conditions for plasma etching may include: a bias voltage of -150V to -300V (e.g., -150V, -200V, -250V, or -300V), an ion source current of 60A to 100A (e.g., 60A, 70A, 80A, 90A, or 100A), an argon flow rate of 50mL / min to 100mL / min (e.g., 50mL / min, 80mL / min, or 100mL / min), and an etching time of 20min to 40min (e.g., 20min, 30min, or 40min). In some preferred embodiments, the bias voltage is -200V to -300V, the ion source current is 60A to 90A, the argon flow rate is 50mL / min to 80mL / min, and the etching time is 20min to 35min.

[0052] In some alternative implementations, magnetron sputtering, arc ion plating, or plasma-assisted chemical vapor deposition can be used to prepare the underlayer. Taking magnetron sputtering as an example, the magnetron sputtering conditions include: a metal target power of 2kW to 5kW (e.g., 2kW, 3kW, 4kW, or 5kW), an argon flow rate of 100mL / min to 200mL / min (e.g., 100mL / min, 150mL / min, or 200mL / min), and a deposition time of 4min to 40min (e.g., 4min, 10min, 20min, 30min, or 40min).

[0053] In some alternative embodiments, the transition layer can be prepared by magnetron sputtering, arc ion plating, or plasma-assisted chemical vapor deposition. Taking the preparation of the transition layer by magnetron sputtering as an example, the magnetron sputtering conditions include: the metal target power is gradually reduced from 2kW~5kW to 0.5kW, the graphite target power is gradually increased from 0.5kW to 2kW~5kW, the argon flow rate is 100mL / min~200mL / min (e.g., 100mL / min, 150mL / min, or 200mL / min), and the deposition time is 3min~30min (e.g., 3min, 5min, 10min, 15min, 20min, 25min, or 30min).

[0054] In some alternative implementations, the functional surface layer can be prepared using magnetron sputtering, arc ion plating, or plasma-assisted chemical vapor deposition. Taking the preparation of the functional surface layer using magnetron sputtering as an example, the magnetron sputtering conditions include: Ar gas flow rate of 100 mL / min to 200 mL / min (e.g., 100 mL / min, 150 mL / min, or 200 mL / min), graphite target power of 2 kW to 5 kW (e.g., 2 kW, 3 kW, 4 kW, or 5 kW), Ti target power of 0.05 kW to 0.20 kW (e.g., 0.05 kW, 0.1 kW, 0.15 kW, or 0.2 kW), and deposition time of 60 min to 180 min (e.g., 60 min, 90 min, 120 min, 150 min, or 180 min).

[0055] Among them, Ti target power affects Ti deposition efficiency; if Ti target power is too low, it will lead to low Ti bottom layer deposition efficiency or low amorphous carbon layer doping; if Ti target power is too high, it will lead to high Ti bottom layer deposition efficiency, affecting film quality or high amorphous carbon layer doping.

[0056] In conclusion, the method for preparing the metal bipolar plate provided by this invention is simple and easy to operate, and can obtain a film layer with high uniformity in a short time, thereby reducing production costs.

[0057] In addition, the present invention also provides a fuel cell having the aforementioned metal bipolar plates.

[0058] This fuel cell has excellent electrical conductivity and corrosion resistance, is applicable to a wide range of scenarios, and has a long service life.

[0059] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0060] Example 1 This embodiment provides a metal bipolar plate, which includes a metal bipolar plate body. The surface of the metal bipolar plate body is provided with a base layer with a thickness of 150 nm, a transition layer with a thickness of 60 nm, and a functional surface layer with a thickness of 400 nm from the inside to the outside.

[0061] Its preparation methods include: (1) Using 316L stainless steel as the body of the metal bipolar plate, ultrasonic cleaning was performed on it in turn using alkaline cleaning agent and deionized water for 20 minutes.

[0062] (2) The cleaned metal bipolar plate body was etched by ion source using a multi-functional vacuum coating equipment. The ion source etching parameters included: bias voltage of -300V, ion source current of 60A, argon flow rate of 50mL / min, and etching time of 25min.

[0063] (3) A multifunctional vacuum coating equipment was used to perform magnetron sputtering on the metal bipolar plate body after plasma etching to deposit the bottom layer. The magnetron sputtering conditions included: the target material was a Ti target, the Ti target power was 5kW, the argon flow rate was 170mL / min, and the deposition time was 30min.

[0064] (4) A multifunctional vacuum coating equipment was used for magnetron sputtering to deposit a transition layer on the surface of the substrate. The magnetron sputtering conditions included: the target material was a Ti target and a graphite target, wherein the power of the Ti target was gradually reduced from 5kW to 0.5kW, the power of the graphite target was gradually increased from 0.5kW to 4.5kW, the argon flow rate was 170mL / min, and the deposition time was 20min.

[0065] (5) A multifunctional vacuum coating equipment is used for magnetron sputtering to deposit a functional surface layer on the surface of the transition layer. The magnetron sputtering conditions include: the target material is a graphite target and a Ti target, wherein the power of the graphite target is 4.5kW, the power of the Ti target is 0.15kW, the argon flow rate is 170mL / min, and the deposition time is 120min.

[0066] Example 2 This embodiment provides a metal bipolar plate, which includes a metal bipolar plate body. The surface of the metal bipolar plate body is provided with a base layer with a thickness of 200 nm, a transition layer with a thickness of 45 nm, and a functional surface layer with a thickness of 200 nm from the inside to the outside.

[0067] Its preparation methods include: (1) Using 316L stainless steel as the body of the metal bipolar plate, ultrasonic cleaning was performed on it in turn using alkaline cleaning agent and deionized water for 20 minutes.

[0068] (2) The cleaned metal bipolar plate body was etched by ion source using a multi-functional vacuum coating equipment. The ion source etching parameters included: bias voltage of -150V, ion source current of 100A, argon flow rate of 100mL / min, and etching time of 40min.

[0069] (3) A multifunctional vacuum coating equipment was used to perform magnetron sputtering on the metal bipolar plate body after plasma etching to deposit the bottom layer. The magnetron sputtering conditions included: the target material was a Zr target, the Zr target power was 4kW, the argon flow rate was 150mL / min, and the deposition time was 40min.

[0070] (4) A multifunctional vacuum coating equipment was used for magnetron sputtering to deposit a transition layer on the surface of the substrate. The magnetron sputtering conditions included: the target material was a Zr target and a graphite target, wherein the Zr target power was gradually reduced from 4kW to 0.5kW, the graphite target power was gradually increased from 0.5kW to 4kW, the argon flow rate was 150mL / min, and the deposition time was 20min.

[0071] (5) A multifunctional vacuum coating equipment is used for magnetron sputtering to deposit a functional surface layer on the surface of the transition layer. The magnetron sputtering conditions include: the target material is a graphite target and a Ti target, wherein the power of the graphite target is 4kW, the power of the Ti target is 0.2kW, the argon flow rate is 150mL / min, and the deposition time is 60min.

[0072] Example 3 This embodiment provides a metal bipolar plate, which includes a metal bipolar plate body. The surface of the metal bipolar plate body is provided with a base layer with a thickness of 20 nm, a transition layer with a thickness of 100 nm, and a functional surface layer with a thickness of 600 nm from the inside to the outside.

[0073] Its preparation methods include: (1) Using 316L stainless steel as the body of the metal bipolar plate, ultrasonic cleaning was performed on it in turn using alkaline cleaning agent and deionized water for 20 minutes.

[0074] (2) The cleaned metal bipolar plate body was etched by ion source using a multi-functional vacuum coating equipment. The ion source etching parameters included: bias voltage of -200V, ion source current of 90A, argon flow rate of 80mL / min, and etching time of 35min.

[0075] (3) A multifunctional vacuum coating equipment was used to perform magnetron sputtering on the metal bipolar plate body after plasma etching to deposit the bottom layer. The magnetron sputtering conditions included: the target material was a Ti target, the Ti target power was 5kW, the argon flow rate was 200mL / min, and the deposition time was 30min.

[0076] (4) A multifunctional vacuum coating equipment is used for magnetron sputtering to deposit a transition layer on the surface of the substrate. The magnetron sputtering conditions include: the target material is a Ti target and a graphite target, wherein the power of the Ti target is gradually reduced from 5kW to 0.5kW, the power of the graphite target is gradually increased from 0.5kW to 5kW, the argon flow rate is 200mL / min, and the deposition time is 30min.

[0077] (5) A multifunctional vacuum coating equipment is used for magnetron sputtering to deposit a functional surface layer on the surface of the transition layer. The magnetron sputtering conditions include: the target material is a graphite target and a Ti target, wherein the power of the graphite target is 5kW, the power of the Ti target is 0.05kW, the argon flow rate is 200mL / min, and the deposition time is 180min.

[0078] Example 4 This embodiment provides a metal bipolar plate, which includes a metal bipolar plate body. The surface of the metal bipolar plate body is provided with a base layer with a thickness of 120 nm, a transition layer with a thickness of 10 nm, and a functional surface layer with a thickness of 400 nm from the inside to the outside.

[0079] Its preparation methods include: (1) Using 316L stainless steel as the body of the metal bipolar plate, ultrasonic cleaning was performed on it in turn using alkaline cleaning agent and deionized water for 20 minutes.

[0080] (2) The cleaned metal bipolar plate body was etched by ion source using a multi-functional vacuum coating equipment. The ion source etching parameters included: bias voltage of -250V, ion source current of 80A, argon flow rate of 70mL / min, and etching time of 30min.

[0081] (3) A multifunctional vacuum coating equipment was used to perform magnetron sputtering on the metal bipolar plate body after plasma etching to deposit the bottom layer. The magnetron sputtering conditions included: the target material was a Ti target, the Ti target power was 3kW, the argon flow rate was 120mL / min, and the deposition time was 35min.

[0082] (4) A multifunctional vacuum coating equipment is used for magnetron sputtering to deposit a transition layer on the surface of the substrate. The magnetron sputtering conditions include: the target material is a Ti target and a graphite target, wherein the power of the Ti target is gradually reduced from 3kW to 0.1kW, the power of the graphite target is gradually increased from 0.1kW to 3kW, the argon flow rate is 120mL / min, and the deposition time is 3min.

[0083] (5) A multifunctional vacuum coating equipment is used for magnetron sputtering to deposit a functional surface layer on the surface of the transition layer. The magnetron sputtering conditions include: the target material is a graphite target and a Ti target, wherein the power of the graphite target is 3kW, the power of the Ti target is 0.05kW, the argon flow rate is 120mL / min, and the deposition time is 180min.

[0084] Example 5 This embodiment provides a metal bipolar plate, which includes a metal bipolar plate body. The surface of the metal bipolar plate body is provided with an 80nm thick base layer, a 30nm thick transition layer, and a 300nm thick functional surface layer from the inside to the outside.

[0085] Its preparation methods include: (1) Using 316L stainless steel as the body of the metal bipolar plate, ultrasonic cleaning was performed on it in turn using alkaline cleaning agent and deionized water for 20 minutes.

[0086] (2) The cleaned metal bipolar plate body was etched by ion source using a multi-functional vacuum coating equipment. The ion source etching parameters included: bias voltage of -300V, ion source current of 60A, argon flow rate of 60mL / min, and etching time of 20min.

[0087] (3) A multifunctional vacuum coating equipment was used to perform magnetron sputtering on the metal bipolar plate body after plasma etching to deposit the bottom layer. The magnetron sputtering conditions included: the target material was a Ti target, the Ti target power was 2kW, the argon flow rate was 100mL / min, and the deposition time was 40min.

[0088] (4) A multifunctional vacuum coating equipment is used for magnetron sputtering to deposit a transition layer on the surface of the substrate. The magnetron sputtering conditions include: the target material is a Ti target and a graphite target, wherein the power of the Ti target is gradually reduced from 2kW to 0.3kW, the power of the graphite target is gradually increased from 0.3kW to 2kW, the argon flow rate is 100mL / min, and the deposition time is 20min.

[0089] (5) A multifunctional vacuum coating equipment is used for magnetron sputtering to deposit a functional surface layer on the surface of the transition layer. The magnetron sputtering conditions include: the target material is a graphite target and a Ti target, wherein the power of the graphite target is 2kW, the power of the Ti target is 0.1kW, the argon flow rate is 100mL / min, and the deposition time is 180min.

[0090] Comparative Example 1 The difference between this comparative example and Example 1 is that the Ti target power corresponding to the functional surface layer is 0.3kW.

[0091] Comparative Example 2 The difference between this comparative example and Example 1 is that the Ti target power corresponding to the functional surface layer is 0.5kW.

[0092] Comparative Example 3 The difference between this comparative example and Example 1 is that the Ti target power corresponding to the functional surface layer is 0.7kW.

[0093] Comparative Example 4 The difference between this comparative example and Example 1 is that the Ti target power corresponding to the functional surface layer is 0kW.

[0094] Comparative Example 5 The difference between this comparative example and Example 1 is that there is no underlayer or transition layer; the functional surface layer is deposited directly on the surface of the metal bipolar plate body.

[0095] Comparative Example 6 The difference between this comparative example and Example 1 is that the metal in the doped metal amorphous carbon layer is Mo.

[0096] Comparative Example 7 The difference between this comparative example and Example 1 is that the functional surface layer deposition time is 30 min, and the final thickness of the deposited functional surface layer is approximately 100 nm.

[0097] Comparative Example 8 The difference between this comparative example and Example 1 is that the functional surface layer deposition time is 240 min, and the final thickness of the deposited functional surface layer is approximately 800 nm.

[0098] Test case (1) Taking the metal bipolar plate prepared in the example as an example, its microstructure was tested, and the results are as follows: Figure 1 As shown.

[0099] Depend on Figure 1 It can be seen that the surface of the metal bipolar plate body is formed from the inside out with an underlayer, a transition layer and a functional surface layer.

[0100] Furthermore, taking Example 1 and Comparative Example 4 as examples, the interfacial contact resistance and constant potential polarization (0.84V vs. SHE) of the functional surface layer in the metal bipolar plates obtained from both were tested, and the results are as follows: Figure 2 and Figure 3 As shown.

[0101] (2) The performance of the metal bipolar plates prepared in Examples 1-5 and Comparative Examples 1-8 was compared, and the results are shown in Table 1.

[0102] The atomic percentage of Ti was determined by X-ray photoelectron spectroscopy (XPS).

[0103] The stable current density was measured as follows: The stable current density of the fuel cell metal bipolar plate was measured by constant potential polarization test (0.64V, vs. Ag / AgCl, 12h) in a simulated PEMFC cell cathode environment (H2SO4 at pH=3 and HF at 5ppm, 80℃). The interface contact resistance is measured as follows: Test the interface contact resistance of the fuel cell metal bipolar plate under a pressure of 1.4 MPa according to GB / T 20042.6-2024.

[0104] Table 1 Test Results

[0105] As shown in Table 1, the metal bipolar plates prepared in Examples 1-5 of this application all exhibit good corrosion resistance and conductivity, meeting the US DOE standard. Compared to Comparative Example 4, which was undoped, the conductivity and corrosion resistance of the titanium-doped amorphous carbon films prepared in Examples 1-5 are improved. However, the corrosion current density of the metal bipolar plates prepared in Comparative Examples 1-3 is significantly increased, failing to meet the US DOE standard, indicating that doping the amorphous carbon film with a certain amount of titanium is beneficial to improving its conductivity and corrosion resistance. The metal bipolar plate prepared in Comparative Example 5 lacks an underlayer, failing to effectively block corrosion ions and leading to premature failure, demonstrating the necessary role of an underlayer in extending the service life of bipolar plates. The functional surface layer of the metal bipolar plate prepared in Comparative Example 6 is doped with Mo. Since Mo cannot form a stable metal passivation film in the PEMFCs environment, the corrosion current density is high, indicating that doping the functional surface layer with stable titanium has a significant advantage in improving bipolar plate performance. The functional surface layer of the metal bipolar plate prepared in Comparative Example 7 was too thin, resulting in a shorter bipolar plate lifespan. The functional surface layer of the metal bipolar plate prepared in Comparative Example 8 was too thick, which easily led to more gap defects in the amorphous carbon layer, accelerating corrosion. Comparative Examples 7 and 8 demonstrate that an appropriate functional surface layer thickness can ensure that the bipolar plate possesses both excellent performance and a long service life.

[0106] In summary, the metal bipolar plate provided by this invention has good conductivity and corrosion resistance, and effectively protects the metal bipolar plate and maintains good performance in the acidic and humid environment of the proton exchange membrane fuel cell cathode.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A metal bipolar plate, characterized in that, The metal bipolar plate includes a metal bipolar plate body, and the surface of the metal bipolar plate body is provided with an underlayer, a transition layer and a functional surface layer from the inside to the outside. The underlayer is a metal film layer, and the metal in the metal film layer includes at least one of Ti and Zr; The transition layer is composed of metal and carbon, wherein the metal in the transition layer is the same as the metal in the metal film layer, and the carbon in the transition layer is the same as the carbon in the functional surface layer; The functional surface layer is a doped metal amorphous carbon layer composed of metal and carbon. The metal in the functional surface layer includes at least one of Ti and Zr. The metal content in the doped metal amorphous carbon layer is 1% to 8% by atomic percentage. The carbon in the doped metal amorphous carbon layer is mainly in the form of amorphous carbon structure, and the carbon in the doped metal amorphous carbon layer also includes graphite phase and diamond phase. The metal elements in the doped metal amorphous carbon layer are dissolved in the amorphous carbon structure and / or embedded in the amorphous carbon structure in the form of carbide nanocrystals.

2. The metal bipolar plate according to claim 1, characterized in that, The material of the metal bipolar plate body includes stainless steel or titanium alloy.

3. The metal bipolar plate according to claim 1, characterized in that, The thickness of the substrate layer is 20nm~200nm; And / or, the thickness of the transition layer is 10nm~100nm; And / or, the thickness of the functional surface layer is 200nm~600nm.

4. The metal bipolar plate according to any one of claims 1 to 3, characterized in that, The stable current density of the metal bipolar plate does not exceed 1 μA / cm. 2 ; And / or, the interfacial contact resistance of the metal bipolar plate under a pressure of 1.4 MPa does not exceed 10 mΩ·cm. 2 .

5. A method for preparing a metal bipolar plate as described in any one of claims 1 to 4, characterized in that, Includes the following steps: An underlayer, a transition layer, and a functional surface layer are sequentially prepared on the surface of the metal bipolar plate body.

6. The preparation method according to claim 5, characterized in that, The functional surface layer is prepared by magnetron sputtering, arc ion plating, or plasma-assisted chemical vapor deposition. Preferably, the substrate is prepared by magnetron sputtering, and the magnetron sputtering conditions include: a metal target power of 2kW to 5kW, an argon flow rate of 100mL / min to 200mL / min, and a deposition time of 4min to 40min.

7. The preparation method according to claim 5, characterized in that, The transition layer is prepared by magnetron sputtering, arc ion plating, or plasma-assisted chemical vapor deposition. Preferably, the transition layer is prepared by magnetron sputtering. The magnetron sputtering conditions include: the metal target power is gradually reduced from 2kW~5kW to 0.1kW~0.5kW, the graphite target power is gradually increased from 0.1kW~0.5kW to 2kW~5kW, the argon flow rate is 100mL / min~200mL / min, and the deposition time is 3min~30min.

8. The preparation method according to claim 5, characterized in that, The functional surface layer is prepared by magnetron sputtering, arc ion plating, or plasma-assisted chemical vapor deposition. Preferably, the functional surface layer is prepared by magnetron sputtering, and the magnetron sputtering conditions include: Ar gas flow rate of 100 mL / min to 200 mL / min, graphite target power of 2 kW to 5 kW, Ti target power of 0.05 kW to 0.20 kW, and deposition time of 60 min to 180 min.

9. The preparation method according to claim 5, characterized in that, Before preparing the underlayer, the metal bipolar plate body is first cleaned and plasma etched. Preferably, the plasma etching conditions include: a bias voltage of -150V to -300V, an ion source current of 60A to 100A, an argon flow rate of 50mL / min to 100mL / min, and an etching time of 20min to 40min.

10. A fuel cell, characterized in that, The fuel cell has a metal bipolar plate as described in any one of claims 1 to 4.

Images