CN115395039A - Metal bipolar plate and manufacturing method thereof - Google Patents
Metal bipolar plate and manufacturing method thereof Download PDFInfo
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- CN115395039A CN115395039A CN202210909995.8A CN202210909995A CN115395039A CN 115395039 A CN115395039 A CN 115395039A CN 202210909995 A CN202210909995 A CN 202210909995A CN 115395039 A CN115395039 A CN 115395039A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0223—Composites
- H01M8/0228—Composites in the form of layered or coated products
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0206—Metals or alloys
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0206—Metals or alloys
- H01M8/0208—Alloys
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0213—Gas-impermeable carbon-containing materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0215—Glass; Ceramic materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M2008/1095—Fuel cells with polymeric electrolytes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Abstract
The invention provides a metal bipolar plate, which comprises a metal substrate, and a passivation layer and an inert material layer which are sequentially formed on the metal substrate, wherein the corrosion current density of the inert material layer meets the following requirements: inert material layer 0.5mM H at 80 deg.C 2 SO 4 The self-etching current density in +0.1ppm HF solution is 5X 10 ‑7 A/cm 2 The following; and/or, the inert material layer is 0.5mM H at 80 DEG C 2 SO 4 (ii) a corrosion current density at +0.84V (vs SHE) in +0.1ppm HF solution of 1X 10 ‑8 A/cm 2 The following. According to the technical scheme, the composite film layer is formed on the metal substrate and comprises a passivation layer and an inert material layer. The inert material layer can maintain stable performance in the working environment of the PEMFC, the passivation layer can form compact oxide at the defect when the inert material layer has defects, so that the defects are blocked, the metal bipolar plate is prevented from being failed because an acid solution in the PEMFC directly contacts the metal substrate, and meanwhile, the inert material layer on the outer side can be kept relatively complete, so that the metal bipolar plate can maintain good use performance. The invention also provides a preparation method of the metal bipolar plate.
Description
Technical Field
The invention relates to the technical field of fuel cells, in particular to a corrosion-resistant coating of a metal bipolar plate and a preparation method thereof.
Background
Proton Exchange Membrane Fuel Cells (PEMFCs) generate electric current through redox reactions using hydrogen and oxygen respectively introduced into the interior of the PEMFC as energy sources. The power generation process does not involve Carnot cycle, so that the energy utilization rate is high, no pollution is caused, the working temperature is low, the starting speed is high, and the energy generation system is considered to be a novel energy source which is most suitable for being applied to vehicles in recent years.
The bipolar plate is one of the core components on the PEMFC. In the operating process of the PEMFC, the bipolar plate plays multiple roles, including supporting a Membrane Electrode (MEA), conducting current, conducting gas, removing reaction heat, etc., and the mass and volume of the bipolar plate respectively account for more than 70% and 80% of the total fuel cell. Therefore, the bipolar plate needs to have good mechanical properties, electrical conductivity and thermal conductivity, and also needs to have corrosion resistance in an acidic and high-temperature environment because the internal working environment of the fuel cell contains sulfuric acid (pH =2 to 3) and hydrofluoric acid (0.1 ppm) and the working temperature can reach 80 ℃.
Common PEMFC bipolar plates include graphite bipolar plates, metal bipolar plates, and composite bipolar plates. The graphite bipolar plate has excellent electrical conductivity, thermal conductivity and corrosion resistance, has stable performance in a working environment, but is brittle and has poor mechanical performance, and the graphite bipolar plate is manufactured by adopting a die-casting forming mode or an expanded graphite forming mode and the like, so that the manufacturing process is complex and the thickness is large. The composite bipolar plate is usually formed by compounding graphite and metal or other carbon materials, and is usually produced by die-casting and the like, so that the manufacturing process is complex.
The metal bipolar plate also has good electrical conductivity and thermal conductivity, has strong mechanical processing performance and fewer manufacturing procedures compared with a graphite bipolar plate and a composite material bipolar plate, can be used for manufacturing ultrathin bipolar plates and is applied to fuel cells with small volume and high power density. Common stainless steel bipolar plates are often severely corroded in acid and high-temperature battery environments, the surfaces of the stainless steel bipolar plates are passivated, and the conductivity of the bipolar plates is affected. Compared with stainless steel plates, the aluminum bipolar plate and the magnesium bipolar plate have obvious advantages in the aspects of processing performance and improvement of the weight specific power of the PEMFC, but once the aluminum and the magnesium are exposed to an acid environment, the aluminum and the magnesium are quickly corroded, and the working stability of the PEMFC is seriously influenced. In the prior art, the modification of the aluminum plate usually adopts a surface magnetron sputtering method to deposit corrosion-resistant materials such as carbon on the surface of the aluminum plate so as to protect the aluminum plate. Because magnetron sputtering often is difficult to avoid the cladding material to appear defects such as perforation and crackle, and single rete often can not provide abundant protection to aluminum plate and magnesium board, the coating inefficacy still exists that leads to aluminum plate or magnesium board to dissolve during the use risk.
Disclosure of Invention
The invention aims to solve the problem that the membrane layer in the prior art is easy to lose efficacy in use, so that the metal bipolar plate is corroded. The invention provides a metal bipolar plate, which comprises a metal substrate, and a passivation layer and an inert material layer which are sequentially formed on the metal substrate, wherein the corrosion current density of the inert material layer meets the following requirements:
inert material layer 0.5mM H at 80 deg.C 2 SO 4 The self-etching current density in +0.1ppm HF solution is 5X 10 -7 A/cm 2 The following; and/or the presence of a gas in the gas,
inert material layer 0.5mM H at 80 deg.C 2 SO 4 (iii) corrosion current density at +0.84V (vs. SHE) in +0.1ppm HF solution at 1X 10 -8 A/cm 2 The following.
The inert material layer is used as the outermost film layer which is directly contacted with the corrosion medium, and the self-corrosion current density and the corrosion current density under the anode potential directly determine the corrosion speed of the whole metal polar plate and the service life of the metal polar plate, so that the lower the inert material layer is, the better the corrosion speed is. The inert material layer with the corrosion current density meeting the above conditions has good corrosion resistance in normal working environment.
According to the technical scheme, the composite film layer is formed on the metal substrate and comprises a passivation layer and an inert material layer. The inert material layer protects the metal substrate from corrosion in an acidic environment, so that the metal bipolar plate can stably work in the PEMFC. Since the inert material layer is generally thin, it is difficult to avoid the defects of through-holes or cracks during its formation. In the technical scheme of the invention, once the inert material layer has a defect, the acid solution contacts the passivation layer material through the defect to form compact oxide at the defect to block the defect, so that the metal bipolar plate is prevented from losing effectiveness due to the fact that the acid solution directly contacts the metal substrate, and meanwhile, the inert material layer on the outer side can be kept relatively complete, so that the metal bipolar plate can maintain good conductivity.
Preferably, in the metallic bipolar plate of the present invention:
the metal substrate contains at least one of aluminum, magnesium, titanium, iron, and copper; and/or the presence of a gas in the atmosphere,
the passivation layer comprises nickel and/or chromium; and/or the presence of a gas in the gas,
the inert material layer comprises at least one of conductive ceramic, silicon nitride, amorphous carbon and graphite
Magnesium and aluminum plates are generally avoided in PEMFCs because they are highly susceptible to corrosion in the acidic environment of PEMFCs, resulting in rapid failure of the bipolar plate. By adopting the technical scheme of the invention, two films are formed on the metal substrate, even if the inert material layer on the surface layer of the metal bipolar plate is damaged in the using process of the metal bipolar plate, the inert material layer can be quickly filled up by the oxidation film formed by the passivating material in an acid environment, and the using stability of the metal bipolar plate containing magnesium or aluminum in the metal substrate can be effectively ensured. Of course, the composite film layer of the present invention can effectively protect metal substrates such as magnesium and aluminum which are easily dissolved by acid, and other metal substrates made of materials which are stable in an acidic environment, such as titanium alloy substrates, stainless steel plates, copper alloy plates, etc., can have more stable performance when the composite film layer of the present invention is used.
Preferably, the metal substrate in the present invention is composed of at least one of a pure aluminum plate, a pure magnesium plate, an aluminum alloy plate, a magnesium aluminum alloy plate, a titanium alloy plate, and a stainless steel plate. More preferably, the metal substrate is a pure aluminum plate, a pure magnesium plate, an aluminum alloy plate, a magnesium alloy plate or a magnesium aluminum alloy plate.
Preferably, the passivation layer in the present invention is a pure nickel layer, a pure chromium layer or a nichrome layer.
The nickel and the chromium can form a compact oxide film in the acid environment of the PEMFC, so that the corrosion of a corrosive medium on the metal bipolar plate is greatly slowed down, and the service life of the metal bipolar plate is remarkably prolonged.
The inert material used to form the inert material layer in the present invention means a material that can exist stably and has good electrical conductivity in the operating environment of a Proton Exchange Membrane Fuel Cell (PEMFC), i.e., in acidity (pH =2 to 3) and high temperature (70 to 90 ℃). The material for forming the passivation layer is a material which has good conductivity and can form a dense oxide film layer in an acidic environment.
Preferably, the inert material layer of the present invention has an over-plane resistance of 15m Ω -cm 2 The following.
The inert material of the present invention generally has good electrical conductivity to maintain high electrical conductivity of the metal bipolar plate. In addition, the conductivity of the inert material layer has an effect on the output power of the fuel cell, so that the lower its through-plane resistance, the better.
The inert material layer is used as the outermost film layer which is directly contacted with the corrosion medium, and the self-corrosion current density and the corrosion current density under the anode potential directly determine the corrosion speed of the whole metal polar plate and the service life of the metal polar plate, so that the lower the inert material layer is, the better the corrosion speed is. The inert material layer with the corrosion current density meeting the above conditions has good corrosion resistance in normal working environment.
Preferably, the inert material layer is a conductive ceramic, silicon nitride, amorphous carbon, graphite, and metal dopants of the above materials, such as Ti (C-doped)/C or Cr (C-doped)/C. These materials have stable performance, good conductivity and economy, and are suitable for industrial production.
Preferably, the thickness of the metal substrate is 100 to 300 μm.
Preferably, the thickness of the passivation layer is 10 μm to 50 μm.
The passivation layer is used as a key barrier for covering the metal polar plate to avoid the environment of the fuel cell, and simultaneously determines whether the outer inert material layer can be continuously attached to the bipolar plate after micropores appear, if the thickness of the middle layer is less than 10 mu m, a corrosive medium is caused to contact the metal substrate through the holes, galvanic corrosion can be caused, the corrosion rate of the bipolar plate is greatly accelerated, and therefore, the thickness of the middle layer is more than 10 mu m, and the through holes can be effectively avoided. Preferably, the thickness of the passivation layer is 10 to 30 μm; more preferably, the thickness of the passivation layer is 15 to 30 μm.
Preferably, the layer of inert material has a thickness of from 1 μm to 5 μm, more preferably from 1 μm to 2 μm. In the invention, the inert material layer plays a main protection role in the use process of the metal bipolar plate, and the thickness of the inert material layer is more than 1 mu m
The small thickness of the passivation layer and the inert material layer is beneficial to realizing the light weight of the metal bipolar plate.
In the present invention, the passivation layer and the inert material layer may be a single layer or multiple layers, preferably multiple layers, so as to avoid through holes. So long as the total thickness of the passivation layer and the inert material layer is controlled to be 10 μm to 50 μm and 1 μm to 5 μm, respectively.
In another aspect, the present invention provides a method for manufacturing a metal bipolar plate, the metal bipolar plate including a metal substrate, and a passivation layer and an inert material layer sequentially formed on the metal substrate, the inert material layer having a corrosion current density satisfying:
inert material layer 0.5mM H at 80 deg.C 2 SO 4 The self-etching current density in +0.1ppm HF solution is 5X 10 -7 A/cm 2 The following; and/or the presence of a gas in the gas,
inert material layer 0.5mM H at 80 deg.C 2 SO 4 (ii) a corrosion current density at +0.84V (vs SHE) in +0.1ppm HF solution of 1X 10 -8 A/cm 2 The following;
the manufacturing method comprises the following steps:
pretreatment: mechanically polishing and cleaning the metal substrate;
forming a passivation layer: carrying out chemical plating or electroplating on the metal substrate to form a passivation layer on the surface of the metal substrate;
forming an inert material layer: and carrying out physical vapor deposition or chemical vapor deposition on the metal substrate with the passivation layer to form an inert material layer on the surface of the passivation layer.
Preferably, in the step of forming the passivation layer, the metal substrate is dried after being chemically plated or electroplated, the drying temperature is 50 to 80 ℃, and the drying time is 10 to 30min.
Specifically, the metal substrate is polished by sand paper during pretreatment, for example, 2000-mesh sand paper is selected; the passivation layer on the surface of the metal substrate is also polished before the inert material layer is formed, for example, 7000 mesh sandpaper is used, and the mesh number of the sandpaper can be adjusted according to the type of metal to be polished. The metal substrate or the passivation layer has certain roughness by polishing, so that the adhesion of a subsequent plating layer can be improved.
Preferably, the passivation layer is formed on the metal substrate by electroless plating, and the electroless plating solution contains nickel sulfate and/or chromic anhydride.
Preferably, the concentration of the nickel sulfate in the chemical plating solution is 0.05-0.09 mol/L, and the concentration of the chromic anhydride is 0.3-0.6 mol/L
The invention adopts an intermediate passivation layer formed by metals which are easy to passivate in the PEMFC use environment and materials which can maintain stable performance in the PEMFC use environment as outer inert material layers, utilizes the passivation layer to cover the surface of a metal bipolar plate to avoid corrosion of corrosive media to the metal bipolar plate, can also avoid galvanic corrosion generated by corroding a contact matrix to enable the film layer to rapidly lose efficacy, and simultaneously ensures the conductivity of the film-substrate interface combination; the outer inert material layer can fill the holes of the middle layer, and then the corrosion current density of the bipolar plate can be obviously reduced under the coordination of the middle layer, so that long-term protection is provided for the metal polar plate; in practical application, the type of the middle layer can be adjusted according to the type of the metal bipolar plate, the applicability of the film layers is wide, the inner film layer and the outer film layer are respectively prepared, and the quality of the film layers is easier to ensure.
Compared with the prior art, the multi-process preparation of the film layer can effectively avoid the problem of through-hole, prevent the film layer from losing effectiveness due to galvanic corrosion generated by leaking out of the metal substrate, and particularly prevent the film layer from losing effectiveness for metals with poor corrosion resistance such as aluminum, magnesium and the like; meanwhile, when the material of the metal polar plate needs to be changed, the components of the middle layer film layer and the inert material layer can be quickly adjusted to be matched with each other, so that wider film layer adaptability is provided; the preparation process of the film layer is a common industrial surface modification method, the cost is low, and the raw materials are easy to obtain; the inner and outer films are respectively prepared by different processes, the overall quality control of the films is not required to be considered in a centralized manner, and the quality control of each film can be carried out in sequence, so that the high-quality films can be obtained conveniently.
Drawings
Figure 1 shows a schematic view of a cross section of a metallic bipolar plate of the invention in the thickness direction;
FIG. 2 shows that the metallic bipolar plate of example 1 of the present invention has 0.5mM H at 80 deg.C 2 SO 4 A 0.84V (vs SHE) constant potential polarization current density curve in +0.1ppm HF solution;
fig. 3 shows the results of the contact resistance test of the metallic bipolar plate of example 1 of the present invention;
FIG. 4 shows that the metallic bipolar plate of example 2 of the present invention has 0.5mM H at 80 deg.C 2 SO 4 Constant potential polarization current density curve of 0.84V (vs SHE) in +0.1ppm HF solution.
FIG. 5 shows an electron micrograph of a metallic bipolar plate of example 1 of the present invention when it is not in use;
fig. 6 shows an electron micrograph of the metallic bipolar plate of example 1 of the present invention after 24h potentiostatic test.
Reference numerals:
1-a metal substrate; 2-a passivation layer; 3-inert material layer.
Detailed Description
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The self-etching current density was measured as follows: the metal bipolar plate was placed at 80 ℃ in 0.5mM H 2 SO 4 In +0.1ppm HF, the current density through the layer of inert material was measured.
The corrosion current density was measured as follows: the metal bipolar plate was placed at 80 ℃ in 0.5mM H 2 SO 4 The current density through the layer of inert material was measured in a solution of +0.1ppm HF, using a standard hydrogen electrode as a reference electrode.
The through-plane resistance is measured as follows: the test was carried out according to ASTM C611-98 (2016).
The technical solution of the present invention will be described in further detail with reference to examples. It should be clear that the following examples are only intended to describe the specific embodiments of the present invention and do not set any limit to the scope of protection of the present invention.
Examples
The metallic bipolar plates of examples 1-4 were prepared by sequentially performing the following steps:
(1) Pretreatment: and mechanically polishing and cleaning the metal substrate.
Specifically, the metal substrate is mechanically polished, and the pure magnesium bipolar plate is cleaned by ultrasonic vibration sequentially through acetone and absolute ethyl alcohol.
(2) Forming a passivation layer: and carrying out chemical plating on the metal substrate to form a passivation layer on the surface of the metal substrate.
Specifically, the metal substrate is firstly subjected to acid cleaning activation treatment by adopting a phosphoric acid solution and a hydrofluoric acid solution, and then is soaked in a chemical plating solution sold in the market for 1-2 hours, so that a passivation layer with the thickness of 10-50 microns is formed on the surface of the metal substrate. For example, in one embodiment of the present invention, in order to form a pure nickel layer on the surface of a metal substrate, the metal substrate is immersed in NiSO 4 In solution, wherein NiSO 4 The concentration of (A) is 0.05-0.09 mol/L; in another embodiment of the present invention, in order to form a pure Cr layer on a surface of a metal substrate, the metal substrate is immersed in a chromic anhydride solution, wherein the concentration of chromic anhydride is 0.3 to 0.6mol/L. Of course, in other possible embodiments of the present invention, the electroless plating solution may contain both nickel sulfate and chromic anhydride to form nichrome on the surface of the metal substrate.
In other embodiments of the present invention, the passivation layer formed on the surface of the metal substrate may be formed by electroplating, and the passivation layer formed by electroplating with the application of the anode and the current may be faster than that formed by electroless plating. However, the current density and the substrate shape during electroplating affect the electroplating effect, and the electroless plating utilizes the autocatalytic reaction generated on the metal surface, is not limited by the substrate shape, and can form a uniform passivation layer on any substrate surface. The vapor deposition has high requirements on the surface quality of a sample and is easy to have defects. Therefore, in the technical scheme of the invention, chemical plating is preferably used when the passivation layer is formed on the surface of the metal substrate, so that the operation is simpler.
When the passivation layer is formed on the surface of the metal substrate by using the electroless plating, the thickness of the passivation layer is related to the concentration of the plating solution and the time for which the metal substrate is soaked in the plating solution, and a larger concentration of the plating solution and a longer soaking time of the plating solution can be used as required in order to obtain a larger thickness of the passivation layer.
(3) Drying the passivation layer: the drying temperature is 50-80 ℃, and the drying time is 10-30 min.
(4) Forming an inert material layer: and carrying out physical vapor deposition or chemical vapor deposition on the metal substrate with the passivation layer so as to form an inert material layer on the surface of the passivation layer.
Specifically, the metal substrate coated with the passivation layer is placed in a vacuum cavity of a magnetron sputtering device at 3 × 10 -3 And carrying out surface etching on the substrate by adopting argon ions under the vacuum degree of Pa, wherein the etching time is 5min. Then, a high-purity graphite target (not less than 99.5%) is used for sputtering the amorphous carbon film layer to the surface of the passivation layer 2, the sputtering is carried out for 30 minutes, and the thickness of the coating is about 10-50 mu m. Accordingly, ti or Cr may be doped in the amorphous carbon layer during the magnetron sputtering process using both Ti and Cr targets to form, for example, a TiC, ti (C doped)/C or Cr (C doped)/C film layer.
The metallic bipolar plate of comparative example 1 was manufactured using a process similar to the above-described method, except that the thickness of the passivation layer formed on the surface of pure magnesium in comparative example 1 was not within the range defined by the present invention.
Table 1 shows the compositions and the respective plating thicknesses of the metal bipolar plates in examples 1 to 4 of the present invention and comparative example 1, in which Al alloy was 6061 aluminum alloy and the purity of magnesium was > 99.9%.
TABLE 1
Table 2 shows specific parameters of the metal bipolar plate manufacturing process in examples 1 to 4 of the present invention and comparative example 1.
TABLE 2
Layers of inert material according to examples 1-4 of the invention were 0.5mM H at 80 deg.C 2 SO 4 The self-corrosion current density in +0.1ppm HF solution is 5 × 10- 7 A/cm 2 The following; also, the inert material layers of examples 1-4 were 0.5mM H at 80 deg.C 2 SO 4 The corrosion current density at +0.84V (vs. SHE) in +0.1ppm HF solution is 1X 10- 8 A/cm 2 The following.
After 24h constant potential test is carried out on the metal bipolar plates of the embodiments 1-4 in the invention, the corrosion current densities are all lower than 1 x 10- 7 A/cm 2 Namely, the metal bipolar plate has very slow corrosion speed under the use environment of the PEMFC, and the composite film layer consisting of the passivation layer and the inert material layer can effectively protect metals such as magnesium, aluminum and the like which are easy to corrode in a solution. Fig. 1 is a schematic view of a thickness-wise cross section of a metallic bipolar plate consisting of a metallic substrate 1, a passivation layer 2 and a layer 3 of inert material according to an embodiment of the present invention.
FIG. 2 is H at pH =3, 80 ℃ of the metallic bipolar plate of example 1 2 SO 4 Constant potential polarization current density curve of 0.84V (vs SHE) in solution (containing 0.1ppm HF). It can be seen from the figure that the stabilized corrosion current density is lower than 5X 10 -8 A/cm 2 The corrosion performance requirement index of the United states energy department for the fuel cell bipolar plate in 2020 is met.
Fig. 4 is a constant potential polarization current density curve of the metal bipolar plate of example 2 under the same electrochemical environment as the metal bipolar plate of example 1, and the corrosion current density does not change significantly, so that the excellent adjustability and protection of the corrosion-resistant coating to different metal substrates can be seen.
The metal bipolar plates of examples 1-4 of the present invention all had contact resistances of < 10m Ω cm under a clamping force of 1.4MPa 2 And meets the requirement index of the United states energy department for the contact resistance of the fuel cell bipolar plate in 2020.
The results of the contact resistance test of the metallic bipolar plate of example 1 are shown in fig. 3, from which it can be seen that the contact resistance is significantly reduced with an increase in pressure, and is 7.23m Ω cm under a clamping force of 1.4MPa 2 。
Fig. 5 and fig. 6 show electron micrographs of the metal bipolar plate of example 1 before and after 24h potentiostatic test, and it can be seen that the surface topography of the metal bipolar plate before and after the test has not changed significantly, which indicates that the composite film layer of the present invention can effectively protect a pure Mg substrate.
The passivation layer thickness of the pure Mg surface in comparative example 1 was only 6 μm, which did not satisfy the requirements for the service performance of the metallic bipolar plate in the present invention.
While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing is a more detailed description of the invention, taken in conjunction with the specific embodiments thereof, and that no limitation of the invention is intended thereby. Various changes in form and detail, including simple deductions or substitutions, may be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (10)
1. A metal bipolar plate, comprising a metal substrate, and a passivation layer and an inert material layer sequentially formed on the metal substrate, wherein the inert material layer has a corrosion current density satisfying:
the inert material layer is 0.5mM H at 80 DEG C 2 SO 4 The self-etching current density in +0.1ppm HF solution is 5X 10 -7 A/cm 2 The following; and/or the presence of a gas in the gas,
the inert material layer is at 80 DEG C0.5mM H 2 SO 4 (iii) corrosion current density at +0.84V (vs. SHE) in +0.1ppm HF solution at 1X 10 -8 A/cm 2 The following.
2. The metallic bipolar plate of claim 1,
the metal substrate comprises at least one of aluminum, magnesium, titanium, iron and copper; and/or the presence of a gas in the atmosphere,
the passivation layer comprises nickel and/or chromium; and/or the presence of a gas in the gas,
the inert material layer includes at least one of a conductive ceramic, silicon nitride, amorphous carbon, and graphite.
3. The metallic bipolar plate of claim 1 or 2, wherein a contact resistance of said metallic bipolar plate is 10m Ω -cm at a clamping force of 1.4MPa 2 Hereinafter, it is preferably 8 m.OMEGA.cm 2 The following.
4. Metallic bipolar plate according to claim 1 or 2, wherein the inert material has an over-plane resistance of 15m Ω -cm 2 The following.
5. The metallic bipolar plate of claim 1 or 2, wherein said passivation layer has a thickness of 10 μm to 50 μm.
6. Metallic bipolar plate according to claim 1 or 2, wherein the layer of inert material has a thickness of 1 μm to 5 μm.
7. A method for manufacturing a metal bipolar plate is characterized in that,
the metal bipolar plate comprises a metal substrate, and a passivation layer and an inert material layer which are sequentially formed on the metal substrate, wherein the corrosion current density of the inert material layer satisfies the following conditions:
the inert material layer is 0.5mM H at 80 DEG C 2 SO 4 The self-etching current density in +0.1ppm HF solution is 5X 10 -7 A/cm 2 The following; and/or the presence of a gas in the gas,
the inert material layer is 0.5mM H at 80 DEG C 2 SO 4 (iii) corrosion Current Density at 1X 10 at +0.84V (vs SHE) in +0.1ppm HF solution -8 A/cm 2 The following;
the manufacturing method comprises the following steps:
pretreatment: mechanically polishing and cleaning the metal substrate;
forming a passivation layer: performing chemical plating or electroplating on the metal substrate to form the passivation layer on the surface of the metal substrate;
forming an inert material layer: and carrying out physical vapor deposition or chemical vapor deposition on the metal substrate with the passivation layer so as to form the inert material layer on the surface of the passivation layer.
8. The manufacturing method according to claim 7,
the metal substrate comprises at least one of aluminum, magnesium, titanium, iron and copper; and/or the presence of a gas in the gas,
the passivation layer comprises nickel and/or chromium; and/or the presence of a gas in the gas,
the inert material layer includes at least one of a conductive ceramic, silicon nitride, amorphous carbon, and graphite.
9. The method of manufacturing according to claim 8, wherein the passivation layer is formed on the metal substrate using electroless plating, and the electroless plating solution contains nickel sulfate and/or chromic anhydride.
10. The method according to claim 9, wherein the concentration of nickel sulfate in the electroless plating solution is 0.05 to 0.09mol/L, and the concentration of chromic anhydride is 0.3 to 0.6mol/L.
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