阅读说明：本技术 一种用于氢燃料电池金属双极板复合膜层及制备方法 (Metal bipolar plate composite film layer for hydrogen fuel cell and preparation method thereof ) 是由 陈桂敏 程立明 于 2019-11-25 设计创作，主要内容包括：本发明公开了一种用于氢燃料电池金属双极板复合膜层及制备方法,包括金属双极板基体和沉积在金属双极板基体表面的复合膜层,所述的复合膜层从下至上包括依次沉积的CrNiPd层、CrSiC层和C层。通过将清洗洁净的金属双极板基体放入磁控溅射设备的真空腔室中,依次经抽真空、加热、通入氩气、离子源清洗处理后,首先采用磁控溅射法依次沉积CrNiPd层、CrSiC层,之后采用等离子体喷涂法在CrSiC层表面喷涂石墨C层。所制作的保护膜大大提高了电池双极板的耐腐蚀性能,延长了其使用寿命,而且减小了金属双极板与扩散层之间的接触电阻,有效提高了燃料电池性能。(The invention discloses a composite film layer of a metal bipolar plate for a hydrogen fuel cell and a preparation method thereof. The method comprises the steps of putting a cleaned metal bipolar plate substrate into a vacuum chamber of magnetron sputtering equipment, sequentially performing vacuumizing, heating, argon gas introduction and ion source cleaning treatment, firstly sequentially depositing a CrNiPd layer and a CrSiC layer by a magnetron sputtering method, and then spraying a graphite C layer on the surface of the CrSiC layer by a plasma spraying method. The manufactured protective film greatly improves the corrosion resistance of the battery bipolar plate, prolongs the service life of the battery bipolar plate, reduces the contact resistance between the metal bipolar plate and the diffusion layer and effectively improves the performance of the fuel battery.)

1. A composite membrane layer of metal bipolar plate for hydrogen fuel cell is characterized in that: the metal bipolar plate comprises a metal bipolar plate substrate and a composite film layer deposited on the surface of the metal bipolar plate substrate, wherein the composite film layer sequentially comprises a CrNiPd layer, a CrSiC layer and a C layer from bottom to top.

2. The composite membrane layer of metal bipolar plate for hydrogen fuel cell as claimed in claim 1, wherein: the general chemical structure formula of the crystal structure in the CrNiPd layer is Cr_x1Ni_y1Pd_z1Said Cr being_x1Ni_y1Pd_z1Wherein x1 is 0.5-0.7, y1 is 0.1-0.3, and z1 is 0.1-0.3; the general chemical structure formula of the CrSiC layer is Cr_x2Si_y2C_z2Said Cr being_x2Si_y2C_z2Medium x 2: y2+ z2 is 1: 1.

3. The composite membrane layer of metal bipolar plate for hydrogen fuel cell as claimed in claim 1, wherein: the thickness of the CrNiPd layer is 0.2-0.5 μm, the thickness of the CrSiC layer is 0.4-0.8 μm, and the thickness of the C layer is 0.1-0.3 μm.

4. The composite membrane layer of metal bipolar plate for hydrogen fuel cell as claimed in claim 3, wherein: the C layer is a graphite C layer.

5. The method for preparing the metal bipolar plate composite membrane layer for the hydrogen fuel cell according to any one of claims 1 to 4, is characterized by comprising the following steps:

putting a cleaned metal bipolar plate substrate into a vacuum chamber of magnetron sputtering equipment, sequentially performing vacuumizing, heating, argon gas introduction and ion source cleaning treatment, and firstly sequentially depositing a CrNiPd layer, a CrSiC layer and a C layer by adopting a magnetron sputtering method, wherein the steps are as follows:

(1) simultaneously starting a Cr target, a Ni target and a Pd target, and depositing a CrNiPd layer on the surface of the bipolar plate substrate;

(2) closing the Cr target, the Ni target and the Pd target, and introducing C under the condition of keeping the total air pressure₂H₂To C₂H₂Keeping the partial pressure between the Cr target and the argon gas stable, then simultaneously starting the Cr target and the Si target, and depositing a CrSiC layer;

and then depositing a graphite C layer on the surface of the CrSiC layer by adopting a plasma spraying method.

6. The method of claim 5, wherein: the magnetron sputtering condition comprises total gas pressure, and the total gas pressure is kept stable and controlled at 3.0 x 10 in the sputtering process^-1Pa-5.0×10^-1Pa。

7. The method of claim 6, wherein: in the step (2), the partial pressure of argon and C₂H₂The partial pressure ratio is 1:0.9-1.0: 0.7.

8. The method of claim 6, wherein: the magnetron sputtering conditions further comprise workpiece bias, target current, auxiliary deposition current and sputtering time;

the workpiece bias voltage and the auxiliary deposition current are kept stable in the magnetron sputtering process, the workpiece bias voltage is set to-100-200V, and the auxiliary deposition current is 0-1A;

in the step (1), the Cr target current is 20-30A, the Ni target current is 10-15A, and the Pd target current is 10-15A; in the step (2), the Cr target current is 20-30A, and the Si target current is 15-20A;

the sputtering time in the step (1) is 30-60 min, and the sputtering time in the step (2) is 30-90 min.

9. The method of claim 5, wherein: the ion source cleaning is to bombard the surface of the bipolar plate substrate for 10min to 30min by adopting argon gas with working pressure under workpiece bias voltage of-800V to-900V and ion source current of 3A to 5A.

10. The method of claim 5, wherein: during sputtering, the temperature in the vacuum chamber is controlled at 150-250 ℃.

Technical Field

The invention belongs to the field of battery bipolar plate manufacturing, and particularly relates to a metal bipolar plate composite film layer for a hydrogen fuel battery and a preparation method thereof.

Background

The Proton Exchange Membrane Fuel Cell (PEMFC) is a power generation device which can directly convert chemical energy in hydrogen and oxygen into electric energy through electrochemical reaction, and has the advantages of wide hydrogen source, higher efficiency than that of a traditional internal combustion engine, environmental friendliness and only water as a product due to the working temperature of the PEMFC in a normal temperature range, and is considered as the most efficient clean power generation technology in the 21 st century. The bipolar plate is one of the most critical components of the PEMFC, occupies 60 to 70 percent of the cost of the cell, occupies 70 to 80 percent of the total weight of the fuel cell, and is also a critical factor for limiting the service life of the cell. The bipolar plate materials of PEMFCs are mainly three types: graphite materials, composite materials and metallic materials. At present, the material used by the fuel cell bipolar plate is mainly graphite, which has good thermal conductivity and electric conductivity, stable chemical property and good corrosion resistance, but the graphite material has large brittleness and poor mechanical property, so that the fuel cell bipolar plate is not easy to produce in large batch. The metal material bipolar plate has high strength and good electric and heat conducting properties, is suitable for mass production, can effectively reduce the volume and the cost of the fuel cell, and is the first choice for the currently accepted fuel cell industrialization, and the raw materials are cheap. However, in the working environment of the fuel cell, the bipolar plate can endure sulfonic acid with the pH value of 2-3, hydrofluoric acid with the concentration of about 0.1ppm and the environmental condition of about 80 ℃, the metal bipolar plate is very easy to corrode in the strong acid and high temperature working environment of the fuel cell, the catalyst is polluted, the service life of the fuel cell is seriously reduced, and the metal bipolar plate can form a passivation film on the surface in the acid environment, so that the contact resistance of the bipolar plate and the gas diffusion layer is increased. Therefore, the main development direction of the metal bipolar plate is to improve the corrosion resistance of the metal bipolar plate and reduce the contact resistance of the bipolar plate. At present, the corrosion-resistant film with good conductivity is formed on the surface of the stainless steel by modifying the surface of the stainless steel, so as to solve the new technical problem.

There are many processes for performing surface deposition film processing, including thermal spraying, screen printing, sol-gel, electroplating, electroless plating, sputtering, and Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD). However, the method has some problems in general, including two main aspects, namely that the film has defects of micropores, looseness and the like, and the film has poor adhesive force and is easy to fall off; secondly, the film material is mostly made of noble metals or rare metals, so that the production cost is high, for example, Au, Ag, Pt and other metals are adopted.

Disclosure of Invention

Aiming at the problems, the invention provides a metal bipolar plate composite film layer for a hydrogen fuel cell and a preparation method thereof.

The technical purpose is achieved, the technical effect is achieved, and the invention is realized through the following technical scheme:

the composite film layer comprises a metal bipolar plate substrate and a composite film layer deposited on the surface of the metal bipolar plate substrate, and the composite film layer sequentially comprises a CrNiPd layer, a CrSiC layer and a C layer from bottom to top.

As a further improvement of the invention, the general chemical structure formula of the crystal structure in the CrNiPd layer is Crx1Niy1Pdz1, x1 in the Crx1Niy1Pdz1 is 0.5-0.7, y1 is 0.1-0.3, and z1 is 0.1-0.3; the chemical structure general formula of the CrSiC layer is Crx2Siy2Cz2, and x2 in the Crx2Siy2Cz 2: y2+ z2 is 1: 1.

As a further improvement of the invention, the thickness of the CrNiPd layer is 0.2-0.5 μm, the thickness of the CrSiC layer is 0.4-0.8 μm, and the thickness of the C layer is 0.1-0.3 μm.

As a further improvement of the invention, the C layer is a graphite C layer.

The method for preparing the composite membrane layer of the metal bipolar plate for the hydrogen fuel cell comprises the following steps:

putting a cleaned metal bipolar plate substrate into a vacuum chamber of magnetron sputtering equipment, sequentially performing vacuumizing, heating, argon gas introduction and ion source cleaning treatment, and firstly sequentially depositing a CrNiPd layer, a CrSiC layer and a C layer by adopting a magnetron sputtering method, wherein the steps are as follows:

(1) simultaneously starting a Cr target, a Ni target and a Pd target, and depositing a CrNiPd layer on the surface of the bipolar plate substrate;

(2) closing the Cr target, the Ni target and the Pd target, keeping the partial pressure between C2H2 and C2H2 and argon stable under the condition of keeping the total air pressure, and then simultaneously opening the Cr target and the Si target to deposit a CrSiC layer;

and then depositing a graphite C layer on the surface of the CrSiC layer by adopting a plasma spraying method.

Further, the magnetron sputtering condition comprises the total gas pressure, and the total gas pressure is kept stable in the sputtering process and is controlled to be 3.0 multiplied by 10 < -1 > Pa to 5.0 multiplied by 10 < -1 > Pa.

Further, in the step (2), the partial pressure of argon and C₂H₂The partial pressure ratio is 1:0.9-1.0: 0.7.

Further, the magnetron sputtering conditions further include workpiece bias, target current, auxiliary deposition current, and sputtering time; the workpiece bias voltage and the auxiliary deposition current are kept stable in the magnetron sputtering process, the workpiece bias voltage is set to-100-200V, and the auxiliary deposition current is 0-1A; in the step (1), the Cr target current is 20-30A, the Ni target current is 10-15A, and the Pd target current is 10-15A; in the step (2), the Cr target current is 20-30A, and the Si target current is 15-20A; the sputtering time in the step (1) is 30-60 min, and the sputtering time in the step (2) is 30-90 min.

Further, the ion source cleaning adopts argon gas with working pressure, and bombards the surface of the bipolar plate substrate for 10min-30min under workpiece bias voltage of-800V-900V and ion source current of 3-5A.

Further, during sputtering, the temperature in the vacuum chamber is controlled to be 150-250 ℃.

The invention has the beneficial effects that:

(1) the film layer manufactured on the surface of the bipolar plate has strong binding force with the base material and is compact, the defects of poor binding force between the film layer and the base body and poor corrosion resistance in the prior art can be effectively overcome, and each layer has good conductivity, so that the metal bipolar plate and the diffusion layer have small contact resistance, the performance of the fuel cell is effectively improved, and the service life of the cell is prolonged.

(2) The invention ensures that all film layers of the plated composite film are tightly combined, the transition is uniform, the thickness is controllable, and the method is simple to operate.

Drawings

FIG. 1 is a schematic structural diagram of a composite protective film made according to the present invention;

FIG. 2 is a Tafel plot obtained using a linear potential scan;

FIG. 3 is SEM scans of processed bipolar plates of two embodiments of the present invention (a) case 1, (b) case 2;

wherein: 1-CrNiPd layer, 2-CrSiC layer and 3-C layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The following detailed description of the principles of the invention is provided in connection with the accompanying drawings.

First, the implementation step

The invention adopts a 316L or 304 stainless steel base material with 0.1-0.15mm as a battery bipolar plate, and the specific process for manufacturing the CrNiPd + CrSiC + C composite protective film layer on the surface of the battery bipolar plate is as follows:

1. pretreatment of a workpiece: putting the workpiece into ultrasonic cleaning equipment to sequentially carry out ultrasonic oil removal cleaning, pure water ultrasonic cleaning, pure water rinsing, water removal and vacuum heating drying, wherein the vacuum degree is-100 Pa to-200 Pa in the vacuum heating drying process, the heating temperature is 80 ℃, the heating drying process lasts for 60 minutes, and the cleaned workpiece is sampled and selected to meet the cleaning requirement by Dain pen test, wherein the cleaning requirement is more than or equal to 70 dyn/cm;

2. ion source cleaning: loading the cleaned workpiece into a vacuum chamber by magnetron sputtering, and pumping the vacuum system from atmospheric state to 6.0 × 10^-3Pa-8.0×10^-3Pa, starting a heating device to heat the temperature in the furnace to 150-250 ℃, and then filling argon with the partial pressure of 3.0 multiplied by 10^-1Pa-5.0×10^-1Pa, setting the bias voltage of the workpiece to-800-900V, starting the ion source current to 3-5A, and carrying out the ion bombardment process on the workpiece for 10-30 min. The battery pole plate is cleaned by an effective ion source, an oxide film on the surface of the battery pole plate can be effectively removed, and the binding force between the Cr layer and the base material is increased, so that the adhesion force of the protective pole plate is effectively increased.

3. Bottom CrNiPd layer deposition: after the ion source cleaning is finished, the partial pressure of argon is kept to be 3.0 multiplied by 10^-1Pa-5.0×10^{- 1}Pa, resetting the workpiece bias to-100V-200V, and opening the auxiliary sinkAccumulating current 0-1A, starting Cr target current to maintain at 20-30A (direct current), starting Ni target current to maintain at 10-15A; and starting the Pd target, maintaining the current at 10-15A for 30-60 min, and finishing the deposition of the CrNiPd layer 1. The metal CrNiPd layer of the deposited conductive bottom layer is Cr in a ternary solid solution structure_x1Ni_y1Pd_z1The solid solution has a structure in which x1 is 0.5 to 0.7, y1 is 0.1 to 0.3, and z1 is 0.1 to 0.3, and is a dense film layer, and the structure of the solid solution can be adjusted by controlling the magnitude of each sputtering target current. The solid solution has the advantages of stable property, compact structure, strong binding force with a base material and strong corrosion resistance.

4. Deposition of a corrosion-resistant CrSiC layer: after the deposition of the CrNiPd layer 1 is finished, the workpiece bias voltage and the auxiliary deposition current are kept, the Cr target is closed, and C is introduced₂H₂Gas, keeping the vacuum degree of the furnace body at 3.0 x 10^-1Pa-5.0×10^-1Pa, and adjusting partial pressure of argon and C₂H₂After the partial pressure ratio is 1:0.9-1.0:0.7 and the Cr target is stabilized, the Cr target is turned on again, the current is maintained at 20-30A, the Si target is turned on, the current is maintained at 15-20A, the duration is 30-90min, and the deposition of the CrSiC layer 2 is completed. The general chemical structure formula of the CrSiC layer is Cr_x2Si_y2C_z2A stable and compact film is obtained by adjusting the technological parameters of the magnetron sputtering equipment, and the corrosion resistance of the coating is greatly improved. And by controlling the atomic number of Cr, Si and C, when x 2: the ratio of y2+ z2 was 1:1, the obtained CrSiC layer exhibited good conductivity, and the optimal ratio of y2 to z2 in the CrSiC layer was 1: 1.

5. And (3) depositing a graphite C layer: putting the bipolar plate workpiece plated with the CrSiC layer into plasma spraying equipment, setting the distance between the workpiece and a spray gun to be 10-12cm, setting the spraying angle to be 90 degrees, and setting the scanning speed of the spray gun to be 50 m/s; opening the main gas Ar inlet valve, the gas inlet rate is 40L/min, and the auxiliary gas H₂The air inlet speed is 2-4L/min; starting a power supply of the equipment, wherein the power is 20-25 Kw; and opening a powder feeding gun, wherein the powder feeding speed is 10-15g/min, and obtaining the graphite C layer. The C layer sprayed on the surface of the CrSiC layer by adopting a plasma spraying technology has a compact structure, can block the permeation of corrosive media, is a non-metal layer and greatly enhances the corrosion resistance of the bipolar plate(ii) a On the other hand, the crystal structure of the metal bipolar plate is a uniform graphite structure layer, so that the metal bipolar plate has better conductivity, and the conductivity of the metal bipolar plate is ensured.

The structure of the protective film layer manufactured by adopting the steps is shown in figure 1, wherein the thickness of the CrNiPd layer 1 is 0.2-0.5 μm, the thickness of the CrSiC layer 2 is 0.4-0.8 μm, and the thickness of the C layer 3 is 0.1-0.3 μm.

Second, performance test

(1) And (3) conductivity test: the contact resistance of the bipolar plate and the carbon paper was tested under a pressure of 1.5 Mpa.

(2) And (3) corrosion resistance testing: simulating the working environment of fuel cell, 80 deg.C, containing 5X 10^-6F^-H with pH of 1₂SO₄Solution, linear potential scan was performed on the samples.

(3) And (3) SEM appearance observation: the film thickness is obtained by testing the microscopic morphology of the coating, and the compactness of the film of the workpiece prepared under the process condition can be observed.

Third, result analysis

Bipolar plates were prepared using the process parameter conditions as shown in tables 1 and 2

Table 1: magnetron sputtering process parameters

Table 2: plasma spraying process parameters

Case(s)	Power supply (Kw)	Main gas Ar flow (L/min)	Spraying distance (cm)	Powder delivery Rate (g/min)
					Case 1	25	40	10	12
Case 2	20	40	10	10

Performance testing

(1) And (3) conductivity test:

table 3: contact resistance performance test

As can be seen from the data in Table 3, the contact resistance is 7.5 m.OMEGA.cm compared to stainless steel²Compared with the non-plated stainless steel base material, the contact resistance of the plated bipolar plate treated by the method is reduced to a certain extent, and the conductivity is improved.

(2) And (3) corrosion resistance testing:

table 4: linear potential scan test

As can be seen from FIG. 2 and Table 4, the scanning rate of the plated bipolar plate is 1mV/s, the potential scanning range is-0.2V-1V (vs. SCE), the corrosion current density of the plated bipolar plate is obviously reduced compared with that of the substrate, the corrosion potential is obviously increased and moves to the positive potential, i.e. the corrosion resistance is greatly enhanced.

(3) SEM topography observation, as can be seen in fig. 3, the obtained protective film had a three-layer structure, and the relevant data values are recorded in table 5.

Table 5: thickness data of protective film

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.