Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating and preparation method thereof

Abstract

The invention discloses a Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating and a preparation method thereof, and belongs to the technical field of coating deposition. The coating is attached to a substrate and sequentially comprises a titanium transition layer and a titanium-zirconium double-doped amorphous carbon coating from inside to outside, the titanium transition layer is made of pure Ti, and the percentage content of Ti atoms in the titanium-zirconium double-doped amorphous carbon coating is 5.8%, the percentage content of Zr atoms in the titanium-zirconium double-doped amorphous carbon coating is 14%, and the percentage content of C atoms in the titanium-zirconium double-doped amorphous carbon coating is 80.2%; the thickness of the titanium transition layer is 100 + / -10 nm, and the thickness of the titanium-zirconium double-doped amorphous carbon coating is 300 + / -50 nm. The invention provides a composite coating prepared by adopting an advanced PVD (Physical Vapor Deposition) technology, such as a deep oscillation magnetron sputtering technology, so that the conductivity, the corrosion resistance and the long-term stability of the bipolar plate are improved. According to the invention, Ti / Zr bimetals are synergistically doped in a single coating to realize gradient optimization of sp / spcarbon proportion, and high conductivity and high corrosion resistance are both considered.

Description

Technical Field

[0001] This invention relates to the field of coating deposition technology, specifically to a Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating and its preparation method. Background Technology

[0002] Metal bipolar plates (such as 316L stainless steel) in proton exchange membrane fuel cells (PEMFCs) are susceptible to corrosion in the acidic environment of PEMFCs (80–90℃, pH 2–3), leading to ion dissolution, battery performance degradation, and structural failure. Pure α-C coatings suffer from high internal stress, weak adhesion, and pinhole defects, making it difficult to meet DOE 2025 standards (contact resistance <10 mΩ·cm², corrosion current <1 μA·cm²). -2 Single metal doping (such as Ti or Zr) makes it difficult to balance conductivity and corrosion resistance: Ti doping reduces resistance but lacks corrosion resistance, while Zr doping improves corrosion resistance but limits conductivity.

[0003] Existing technologies employ a multi-layer structure (binder layer + transition layer + surface layer), which improves adhesion and high-temperature resistance, but the process is complex, the coating thickness is large (micrometer-level), and it does not optimize for the conductivity and post-corrosion contact resistance stability of fuel cell bipolar plates. Existing technologies generate nitride particles through nitriding to reduce stress, but this introduces an additional heat treatment step, which may lead to substrate deformation or coating phase transformation. Furthermore, their multi-layer design (such as diffusion layers and seed layers) increases process complexity and cost. None of the aforementioned existing technologies solve the problem of a sharp increase in contact resistance under corrosive environments, and they lack research on the mechanism of precise control of Ti / Zr atomic-level gradient doping and the sp² / sp³ ratio.

[0004] Therefore, how to develop a simplified process to achieve a coating with high adhesion, low stress, and high density within a nanometer-thickness, and significantly improve the contact resistance stability after corrosion, as well as the preparation method of a Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating, the coating is attached to the substrate and consists of a titanium transition layer and a titanium-zirconium dual-doped amorphous carbon coating from the inside to the outside.

[0008] The titanium transition layer is made of pure Ti, and the titanium-zirconium dual-doped amorphous carbon coating contains 5.8% Ti atoms, 14% Zr atoms, and 80.2% C atoms.

[0009] The thickness of the titanium transition layer is 100±10 nm, and the thickness of the titanium-zirconium dual-doped amorphous carbon coating is 300±50 nm.

[0010] This invention provides a method for preparing a Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating, comprising the following steps:

[0011] (1) Matrix pretreatment: The matrix was ultrasonically cleaned in acetone and ethanol in sequence, and then dried with nitrogen gas for later use;

[0012] (2) Ion cleaning: Place the substrate on the sample stage in the vacuum chamber of the deep oscillation magnetron sputtering equipment, and evacuate the vacuum chamber to ≤1×10 -4 Pa, argon gas is introduced at a flow rate of 150 sccm, deep oscillation magnetron sputtering power supply: Ti target, bias voltage -500 V, ion cleaning time 30 min;

[0013] (3) Preparation of titanium transition layer: Ti target connected to deep oscillation magnetron sputtering power supply, sample stage rotated, Ar flow rate of 80 sccm, Ti target power of 1-2 kW, pulse frequency of 100 kHz, bias voltage of -100 V, deposition temperature of 200℃, deposition time of 5-10 min;

[0014] (4) Install Ti, Zr, and C targets on three different target positions of the deep oscillation magnetron sputtering equipment, start the sample stage rotation, keep the deep oscillation magnetron sputtering power supply connected to Ti, Zr, and C targets on, introduce Ar into the vacuum chamber, with an Ar flow rate of 80 sccm, a power of 0.5-1.5 kW for Ti targets, a power of 0.5-1.5 kW for Zr targets, a power of 1-3 kW for C targets, a pulse frequency of 100 kHz, a bias voltage of -100 V, a deposition temperature of 200℃, and a deposition time of 30-50 min to obtain a titanium-zirconium double-doped amorphous carbon coating.

[0015] Furthermore, in step (1), the substrate is 316L stainless steel.

[0016] Furthermore, in step (1), the ultrasonic power for ultrasonic cleaning of the substrate in acetone is 500-1000 W and the ultrasonic time is 10-20 min, and the ultrasonic power for ultrasonic cleaning of the substrate in ethanol is 500-1000 W and the ultrasonic time is 10-20 min.

[0017] Furthermore, in step (4), the sample stage rotation speed is 3-6 rpm.

[0018] Furthermore, in step (4), the power of the Ti target is 1.0 kW and the power of the Zr target is 1.0 kW.

[0019] Coating design principles

[0020] 1. Structural differences from existing technologies:

[0021] This invention employs a Ti / Zr gradient co-doped structure within a single α-C layer, which differs from the existing multilayer system of "binder layer-transition layer-surface layer" and the complex stacked structure of "seed layer-diffusion layer-gradient layer-nitride layer". This invention achieves atomic-level compositional gradients through DOMS technology, avoiding stress concentration and bonding issues caused by multilayer interfaces. The coating thickness is only 300±50 nm, far thinner than existing technologies (typically >1 μm).

[0022] 2. Bimetallic synergistic mechanism:

[0023] Ti doping: forms a low-resistivity TiC phase (contact resistance decreases), but excessive Ti leads to an excessively high sp² carbon ratio, resulting in decreased corrosion resistance.

[0024] Zr doping: forms a dense ZrO2 passivation film (corrosion current decreases) and a strongly bonded Zr-C network (bonding force increases), but excessive Zr increases resistance.

[0025] Synergistic effect: Through Ti / Zr dual doping and DOMS gradient power modulation, the following are achieved: TiC phase ensures electron transport capability and offsets Zr's electrical resistance disadvantage; ZrO2 film extends the penetration path of corrosive media and makes up for Ti's insufficient corrosion resistance; the sp² / sp³ ratio gradient distribution is optimized (confirmed by Raman spectroscopy), with high sp³ at the interface to improve corrosion resistance and high sp² on the surface to ensure conductivity.

[0026] The beneficial effects of this invention are:

[0027] 1. Ingredient and structural innovation:

[0028] This invention employs a Ti / Zr bimetallic gradient co-doped single α-C layer, abandoning the complex multi-layer structure of existing technologies. By atomically gradient-controlled sp² / sp³ ratio, it achieves a synergistic improvement in conductivity and corrosion resistance.

[0029] 2. Technological Innovation:

[0030] This invention employs deep oscillating magnetron sputtering (DOMS) to achieve low-temperature, nanoscale, gradient doping. Compared with FCVA and multi-arc ion plating + nitriding, it has the advantages of simplified process, low stress, and strong adhesion.

[0031] 3. Performance Breakthrough:

[0032] The post-corrosion contact resistance stability is industry-leading (increase <9%), significantly outperforming existing technologies at the same thickness, and simultaneously meets the DOE 2025 standard (contact resistance <10 mΩ·cm). 2 Corrosion current <1 μA·cm -2 ).

[0033] This invention provides a Ti / Zr dual-doped amorphous carbon (α-C) composite coating prepared using advanced PVD technology, such as deep oscillating magnetron sputtering (DOMS) technology, which significantly improves the conductivity, corrosion resistance and long-term stability of bipolar plates.

[0034] This invention aims to achieve gradient optimization of the sp² / sp³ carbon ratio in a single coating through Ti / Zr bimetallic synergistic doping, thus balancing high conductivity (high sp²) and high corrosion resistance (high sp³).

[0035] The Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating of this invention is a hydrogen-free carbon-based coating. It is prepared by sputtering high-purity graphite (99.99%) target material and argon gas as sputtering gas, without the need to introduce H-containing gas, and is a carbon-containing mixed coating material. Attached Figure Description

[0036] Figure 1 This is a schematic diagram illustrating the coating deposition principle of the present invention.

[0037] Figure 2 This is a schematic diagram of the coating structure.

[0038] Figure 3 Raman spectra of coatings with different doping ratios. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating, which is attached to the substrate and consists of a titanium transition layer and a titanium-zirconium dual-doped amorphous carbon coating from the inside to the outside.

[0042] The titanium transition layer is made of pure Ti. The titanium-zirconium dual-doped amorphous carbon coating contains 5.8% Ti atoms, 14% Zr atoms, and 80.2% C atoms.

[0043] The thickness of the titanium transition layer is 100±10 nm, and the thickness of the titanium-zirconium dual-doped amorphous carbon coating is 300±50 nm.

[0044] A method for preparing a Ti / Zr composite-doped hydrogen-free carbon-based metal bipolar plate coating includes the following steps:

[0045] (1) Pretreatment of the substrate: The 10*20 cm316L stainless steel substrate was ultrasonically cleaned in acetone and ethanol in sequence. The ultrasonic power of the substrate was 1000 W and the ultrasonic time was 10 min when ultrasonically cleaning the substrate in acetone. The ultrasonic power of the substrate was 1000 W and the ultrasonic time was 10 min when ultrasonically cleaning the substrate in ethanol. Then it was dried with nitrogen and set aside for later use.

[0046] (2) Ion cleaning: Place the substrate on the sample stage in the vacuum chamber of the deep oscillation magnetron sputtering equipment, and evacuate the vacuum chamber to ≤1×10 -4 Pa, argon gas is introduced at a flow rate of 150 sccm, deep oscillation magnetron sputtering power supply: bias voltage -500V, ion cleaning time 30 min;

[0047] (3) Preparation of titanium transition layer: Ti target connected to deep oscillation magnetron sputtering power supply, sample stage rotated, Ar flow rate was 80 sccm, Ti target power was 2 kW, pulse frequency was 100 kHz, bias voltage was -100 V, deposition temperature was 200℃, and deposition time was 5 min.

[0048] (4) Install Ti, Zr, and C targets on three different target positions of the oscillating magnetron sputtering equipment, start the sample stage rotation at 6 rpm, keep the deep oscillating magnetron sputtering power supply connected to Ti, Zr, and C targets on, introduce Ar into the vacuum chamber at a flow rate of 80 sccm, set the power of Ti target to 1.0 kW, the power of Zr target to 1.0 kW, the power of C target to 2 kW, the pulse frequency to 100 kHz, the bias voltage to -100 V, the deposition temperature to 200℃, and the deposition time to 40 min to obtain a titanium-zirconium double-doped amorphous carbon coating. The obtained Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating is designated as sample 3.

[0049] Comparative Example 1

[0050] Except for the Ti target power being 2.0 kW and the Zr target power being 0 kW, the other steps and parameters were the same as in Example 1, and the resulting Ti-doped hydrogen-free carbon-based metal bipolar plate coating was designated as Sample 1.

[0051] Comparative Example 2

[0052] Except for the power of the Ti target being 1.5 kW and the power of the Zr target being 0.5 kW, the other steps and parameters were the same as in Example 1. The resulting Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating was designated as Sample 2.

[0053] Comparative Example 3

[0054] Except for the power of the Ti target being 0.5 kW and the power of the Zr target being 1.5 kW, the other steps and parameters were the same as in Example 1. The resulting Ti / Zr composite doped hydrogen-free carbon-based metal bipolar plate coating was designated as Sample 4.

[0055] Comparative Example 4

[0056] Except for the Ti target power being 0 kW and the Zr target power being 2.0 kW, the other steps and parameters were the same as in Example 1, and the resulting Zr-doped hydrogen-free carbon-based metal bipolar plate coating was designated as Sample 5.

[0057] Performance data and advantages analysis

[0058] 1. Electrochemical and electrical performance (24-hour constant potential polarization pH=3 H2SO4+0.1ppm HF), performance data are shown in Table 1.

[0059] Table 1

[0060]

[0061] in conclusion:

[0062] Overall best (sample 3): When Ti / Zr=1:1, a TiC-ZrC-ZrO2 composite protective mesh is formed. The initial contact resistance (4.5 mΩ·cm²) and corrosion current (0.12 μA·cm⁻²) are both better than the DOE standard. Moreover, the resistance increase after corrosion is only 8.9%, which is much lower than the comparative sample (maximum 46.2%) and existing technology (usually >15%).

[0063] Mechanism verification: through Raman spectroscopy ( Figure 2 This study confirms that as the Zr content increases, the D / G peak intensity ratio decreases, the sp³ carbon ratio increases, and the corrosion resistance is enhanced; at the same time, Ti ensures the conductive base network, achieving synergistic optimization.

[0064] Technical effect: The present invention achieves better resistance stability after corrosion with a thinner coating (300 nm), which solves the pain points of "high corrosion resistance but low conductivity" or "complex multi-layer structure" in the prior art.

[0065] Figure 1 This is a schematic diagram illustrating the coating deposition principle of the present invention.

[0066] Figure 2 This is a schematic diagram of the coating structure.

[0067] Figure 3 Raman spectra of coatings with different doping ratios.

[0068] Gaussian fitting revealed that the intensity ratio of the D peak to the G peak decreased with increasing Zr content, indicating a decrease in the degree of graphitization of the coating. 3 The proportion of -C bonds increases due to sp 3 -C has excellent chemical inertness, which is beneficial for improving the corrosion resistance of coatings.

[0069] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A Ti / Zr co-doped hydrogen-free carbon-based metal bipolar plate coating, characterized in that, The coating is attached to a substrate and comprises, from inside to outside, a titanium transition layer and a titanium-zirconium double-doped amorphous carbon coating layer. The titanium transition layer is made of pure Ti, the titanium-zirconium double-doped amorphous carbon coating layer contains 5.8% of Ti atoms, 14% of Zr atoms and 80.2% of C atoms. The thickness of the titanium transition layer is 100±10 nm, and the thickness of the titanium-zirconium double-doped amorphous carbon coating layer is 300±50 nm.

2. A method of making the Ti / Zr co-doped hydrogen-free carbon-based metal bipolar plate coating of claim 1, characterized by, The method comprises the following steps: (1) substrate pretreatment: sequentially ultrasonic cleaning the substrate in acetone and ethanol, and then blowing dry with nitrogen; (2) Ion cleaning: the substrate was placed on the sample table in the vacuum chamber of the deep oscillation magnetron sputtering equipment, the vacuum chamber was vacuumized to ≤1×10 -4 Pa, argon was introduced, the argon flow was 150 sccm, the deep oscillation magnetron sputtering power supply was a Ti target, the bias voltage was -500 V, and the ion cleaning time was 30 min. (3) preparing the titanium transition layer: connecting the Ti target to the deep oscillation magnetron sputtering power supply, rotating the sample table, Ar flow rate is 80 sccm, Ti target power is 1-2 kW, pulse frequency is 100 kHz, bias voltage is -100 V, deposition temperature is 200℃, and deposition time is 5-10 min; (4) installing the Ti target, Zr target and C target on three different target positions of the deep oscillation magnetron sputtering device, starting the sample table rotation, keeping the deep oscillation magnetron sputtering power supply connected to the Ti target, Zr target and C target turned on, introducing Ar into the vacuum chamber, Ar flow rate is 80 sccm, Ti target power is 0.5-1.5 kW, Zr target power is 0.5-1.5 kW, C target power is 1-3 kW, pulse frequency is 100 kHz, bias voltage is -100 V, deposition temperature is 200℃, and deposition time is 30-50 min, thereby obtaining the titanium-zirconium double-doped amorphous carbon coating layer.

3. The method of claim 2, wherein the Ti / Zr co-doped hydrogen-free carbon- based metal bipolar plate coating is prepared by a method comprising: In step (1), the substrate is 316L stainless steel.

4. The method of claim 2, wherein the Ti / Zr co-doped hydrogen-free carbon- based metal bipolar plate coating is prepared by a method comprising: In step (1), the ultrasonic power for ultrasonic cleaning the substrate in acetone is 500-1000 W, and the ultrasonic time is 5-10 min; the ultrasonic power for ultrasonic cleaning the substrate in ethanol is 500-1000 W, and the ultrasonic time is 5-10 min.

5. The method of claim 2, wherein the Ti / Zr co-doped hydrogen-free carbon- based metal bipolar plate coating is prepared by a method comprising: In step (4), the rotation speed of the sample table is 3-6 rpm.

6. The method of claim 2, wherein the Ti / Zr co-doped hydrogen-free carbon- based metal bipolar plate coating is prepared by a method comprising: In step (4), the power of the Ti target is 1.0 kW, and the power of the Zr target is 1.0 kW.

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