A metal-ceramic material (Nb) for bipolar plates in proton exchange membrane fuel cells 1-x Ta x )2AlC and its preparation method

Abstract

This invention belongs to the field of fuel cell technology, specifically relating to a metal-ceramic material for bipolar plates in proton exchange membrane fuel cells and its preparation method. The metal-ceramic material is a Ta-doped modified niobium-aluminum-carbon material, and the chemical formula of the modified niobium-aluminum-carbon is (Nb... 1‑ x Ta x 2AlC. The modified niobium aluminum carbon material prepared by this invention possesses the excellent properties of both metals and ceramics. This ceramic material exhibits excellent electrical and thermal conductivity at room temperature, a high elastic modulus, and a certain degree of ductility at room temperature, allowing it to be machined like metals and graphite. Simultaneously, it possesses the characteristics of ceramic materials, exhibiting high yield strength, high melting point, high thermal stability, and excellent corrosion resistance. Furthermore, the solid solution doping of Ta at the Nb position of the niobium aluminum carbon material significantly improves the corrosion resistance of the niobium aluminum carbon bulk, enabling it to operate stably in the PFMFC working environment.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a metal-ceramic material for bipolar plates of proton exchange membrane fuel cells and its preparation method. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are characterized by zero emissions and zero pollution, making them an ideal clean and environmentally friendly power generation technology and the ultimate energy solution. As a key component of fuel cells, the bipolar plate separates the fuel, oxidant, and coolant. It distributes the fuel and oxidant evenly to the electrodes through flow channels for electrochemical reactions, distributes the coolant to each cooling chamber to remove the heat generated by the reaction, and collects the current generated by the electrochemical reactions in each cell. Simultaneously, the bipolar plate supports the individual fuel cell cells, connecting them sequentially to form a stack. Therefore, bipolar plates must meet requirements such as high electrical and thermal conductivity, high mechanical strength, effective barrier against reaction fluids, good corrosion resistance, low material cost, and the ability to be mass-produced automatically.

[0003] Currently, there are three main types of bipolar plates: graphite bipolar plates, metallic bipolar plates, and composite bipolar plates. Graphite, with its high strength, high density, and excellent electrical and thermal conductivity, is the most traditional bipolar plate material. Its excellent durability and corrosion resistance also meet the acidic operating environment of PEMFC battery stacks, making it the most widely used bipolar plate material. However, graphite itself has a porous structure, requiring specific processes to seal the pores during processing. Even then, it's difficult to guarantee the final gas barrier properties of the graphite bipolar plate. Furthermore, graphite is brittle and fragile, making it impossible to produce thin plates. The cutting and processing cycle is long, and the graphitization temperature is high, resulting in high processing difficulty, high cost, and large volume. This hinders further improvements in the volumetric power density of the fuel cell stack, thus limiting its commercial development and application in passenger vehicles. Metallic bipolar plates have high strength and are easy to process. Ultra-thin bipolar plates are easily mass-produced, which can improve the specific power of fuel cells. However, the working environment of bipolar plates contains various corrosive ions, such as SO42-. 2- F -Metal bipolar plate materials are susceptible to corrosion, forming a passivation layer that increases the contact resistance between the bipolar plate and the diffusion layer, significantly impacting the output power and durability of the fuel cell stack. Metal / carbon composite bipolar plates, combining metal and graphite with a thin metal sheet as the substrate and graphite as the flow field, avoid direct metal contact with the electrodes, preventing corrosion. This approach retains the corrosion resistance of graphite bipolar plates while possessing the excellent conductivity and gas impermeability of metal bipolar plates, reducing the overall volume and mass of the fuel cell stack and achieving higher volumetric and mass power ratios. Although composite bipolar plates exhibit superior performance, extensive research is still needed to ensure their conductivity, mechanical properties, and long-term stability. Furthermore, their processing costs are still far from meeting the requirements for mass production. Therefore, developing a novel PEMFC bipolar plate material is of significant practical importance. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems of graphite bipolar plates, metal bipolar plates, and composite bipolar plates used in existing PEMFC technologies. This invention proposes a metal-ceramic material for proton exchange membrane fuel cell bipolar plates and its preparation method. This metal-ceramic material is a Ta-doped niobium-aluminum-carbon material. It is not a simple mixture or sintering of individual powders, but rather a single-phase material formed through in-situ hot-pressing reaction in a hot-pressing furnace. This modified niobium-aluminum-carbon metal-ceramic material shows promising practical application prospects in PEMFCs and can make a significant contribution to the development of bipolar plate materials.

[0005] The technical solution of this invention is:

[0006] A metal-ceramic material for bipolar plates in proton exchange membrane fuel cells, wherein the metal-ceramic material is a Ta-doped niobium aluminum carbon material, and the chemical formula of the modified niobium aluminum carbon is (Nb... 1-x Ta x )2AlC, where x is 0.01 to 0.20.

[0007] Furthermore, the density of the modified niobium aluminum carbon is (6.37–6.89) g / cm³. 3 It has a lower density than stainless steel, which can reduce the mass of the fuel cell stack.

[0008] Furthermore, the modified niobium-aluminum-carbon has a density higher than 95%, preferably higher than 97.5%, which can avoid the problem of gas leakage during service.

[0009] A method for preparing a metal-ceramic material for a proton exchange membrane fuel cell bipolar plate includes the following steps:

[0010] Raw materials Nb powder, Ta powder, Al powder, and graphite powder were prepared according to an atomic percentage ratio of Nb:Ta:Al:C = 2(1-x):2x:1. The prepared raw material powders were mixed with alcohol and then ball-milled for 15–36 hours, and then dried for later use. Next, they were cold-pressed under a pressure of 5–15 MPa, and then sintered in a hot-pressing sintering furnace at a temperature of 1680–1850℃ using argon as a protective gas for 40–95 minutes. Afterward, they were dried for later use.

[0011] Furthermore, x is 0.01 to 0.20.

[0012] Furthermore, the pressure in the hot-press sintering furnace is 50–75 MPa.

[0013] The raw materials used in this invention are synthesized into single-phase materials through a preparation process, and the use of this Ta-doped niobium-aluminum-carbon material as a bipolar plate for a proton exchange fuel cell is a first in the field. This modified niobium-aluminum-carbon material possesses the excellent properties of both metals and ceramics. Like metals, it exhibits excellent electrical and thermal conductivity at room temperature, a high elastic modulus, and ductility at room temperature, allowing it to be machined like metals and graphite. Simultaneously, it possesses the characteristics of ceramic materials, exhibiting high yield strength, high melting point, high thermal stability, and excellent corrosion resistance. Furthermore, the solid solution doping of Ta at the Nb sites significantly improves the corrosion resistance of the niobium-aluminum-carbon bulk material, enabling it to operate stably in the PFMFC working environment.

[0014] Application of a metal-ceramic material for proton exchange membrane fuel cell bipolar plates in the fabrication of proton exchange membrane fuel cell bipolar plates.

[0015] Furthermore, the modified niobium-aluminum-carbon material has an electrical conductivity of (3.0–3.4) × 10⁻⁶ at room temperature. 6 Ω -1 ·m -1 This ensures that it has good conductivity as a bipolar plate.

[0016] Furthermore, the modified niobium-aluminum-carbon material has a thermal conductivity of (41-45) W / m·K at room temperature, which ensures that the bipolar plate has high thermal conductivity.

[0017] Furthermore, potentiodynamic testing was conducted in a fuel cell simulation environment (H2SO4 concentration of 0.5 mol / L + 2 ppm HF, temperature 80℃), and the corrosion current density of the ceramic bipolar plate of the proton exchange membrane fuel cell was 0.02–0.26 μA / cm². 2 [Self-corrosion potential is 0.13–0.28 V (vs. SCE)].

[0018] Furthermore, at an assembly force of 150 N / cm2 Under the specified conditions, the contact resistance of the modified niobium-aluminum-carbon material is 0.8–7.5 mΩ·cm. 2 .

[0019] The beneficial effects of this invention are:

[0020] The Ta-doped modified niobium aluminum carbon cermet material prepared by this invention has excellent properties, including:

[0021] (1) High conductivity; which ensures that it has good conductivity as a bipolar plate;

[0022] (2) High thermal conductivity; the high thermal conductivity of this metal-ceramic material ensures that the bipolar plate has high thermal conductivity.

[0023] (3) Good thermal stability; This metal ceramic material is a single-phase material with a thermal decomposition temperature greater than 1680℃, high bond strength, and stable structure, which can ensure that the material will not change during its service life and avoid structural failure.

[0024] (4) High creep resistance; high creep resistance can reduce creep failure and reduce mechanical damage during the service of bipolar plates;

[0025] (5) Easy to process; good processing performance can reduce the processing cost of bipolar plate materials;

[0026] (6) Corrosion resistance; This metal ceramic material has good corrosion resistance and can prevent surface corrosion during service. At the same time, the solid solution doping of Ta element at the Nb position can greatly improve the corrosion resistance of the niobium aluminum carbon block, thereby avoiding damage to the electrode and the increase of surface resistance. Attached Figure Description

[0027] Figure 1 The 5 at.% Ta-doped modified niobium aluminum carbon material (Nb) prepared in Example 1 0.95 Ta 0.05 2. Surface morphology diagram of AlC block;

[0028] Figure 2 Polarization curves obtained by potentiodynamic testing of 5 at.% Ta-doped niobium aluminum carbon material in a fuel cell simulation environment (H2SO4 concentration of 0.5 mol / L + 2 ppm HF, temperature of 80℃);

[0029] Figure 3 The 10 at.% Ta-doped modified niobium aluminum carbon material (Ti) prepared in Example 2 0.9 Ta 0.1 SEM image of 3SiC2 bulk material. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0031] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments.

[0032] Example 1

[0033] A method for preparing a metal-ceramic material for a proton exchange membrane fuel cell bipolar plate, wherein this embodiment uses 5 at.% Ta-doped niobium-aluminum-carbon material, includes the following steps:

[0034] Nb, Ta, Al, and C elemental powders were used as the original synthetic materials. The raw material powders were prepared according to the ratio of Nb:Ta:Al:C = 1.9:0.1:1:1. The prepared raw material powders were mixed with alcohol and placed in a spherical mill for ball milling for 20 hours. The powders were then removed, sieved, and dried for later use. The powders were cold-pressed at a pressure of 8 MPa and then sintered in a hot-pressing sintering furnace under an argon atmosphere at a maximum pressure of 45 MPa for 70 minutes.

[0035] The prepared cermet material is a Ta-doped modified niobium aluminum carbon material with the chemical formula (Nb). 0.95 Ta 0.05 )2AlC, such as Figure 1 The image shows the dense (Nb) 0.95 Ta 0.05 )2 Surface morphology diagram of AlC block.

[0036] The density of the bulk material was determined to be 98% using the Archimedes method (ISO 18754). Φ30×5mm and 4×4×40mm diameter pieces were cut from the sintered, dense bulk material using wire cutting. 3 and 10×10×2mm 3 The bulk sample was then polished with 400#, 600#, 800#, 1000# and finally 2000# SiC sandpaper, then polished with polishing paste with a grit size W=1, and finally ultrasonically cleaned with alcohol in preparation for further experiments.

[0037] The sample density is 6.47 g / cm³. 3 The four-point method was used for testing (Nb). 0.95 Ta 0.05 The room temperature conductivity of the AlC bulk material is 3.4 × 10⁻⁶. 6 Ω -1 ·m-1 The unsteady-state method (Nb) is adopted. 0.95 Ta 0.05 The thermal conductivity of the 2AlC bulk material is 42 W / m·K. Potentiodynamic testing was conducted in a fuel cell simulation environment (0.5 mol / L H₂SO₄ and 2 ppm HF solution) at 80 °C, with assembly forces ranging from 50 to 200 N / cm. 2 Under these conditions, test (Nb) 0.95 Ta 0.05 )2AlC bulk material contact resistance.

[0038] like Figure 2 The figure shows the polarization curves obtained by performing potentiodynamic tests on 5 at.% Ta-doped modified niobium-aluminum-carbon material in a fuel cell simulation environment (H2SO4 concentration of 0.5 mol / L + 2 ppm HF, temperature of 80℃).

[0039] The tests showed that the corrosion current density of the V-doped modified niobium-aluminum-carbon material was 0.18 μA / cm² in a fuel cell simulation environment (0.5 mol / L H₂SO₄ and 2 ppm HF solution, temperature 80 °C). 2 [Corrosion potential 0.11V (vs. SCE)], under a pressure of 1.4MPa, its surface resistivity (ASR) is 2.7mΩ·cm. -2 It meets the DOE performance specifications, indicating (Nb 0.95 Ta 0.05 )2AlC bulk materials can be used as bipolar plate materials for proton exchange membrane fuel cells.

[0040] Example 2

[0041] A method for preparing a metal-ceramic material for a proton exchange membrane fuel cell bipolar plate, wherein this embodiment uses 10 at.% Ta-doped niobium-aluminum-carbon material, includes the following steps:

[0042] Nb, Ta, Al, and C elemental powders were used as the original synthetic materials. The raw material powders were prepared according to the ratio of Nb:Ta:Al:C = 1.8:0.2:1:1. The prepared raw material powders were mixed with alcohol and placed in a spherical mill for ball milling for 30 hours. The powders were then removed, sieved, and dried for later use. The powders were cold-pressed at a pressure of 7 MPa and then sintered in a hot-pressing sintering furnace under an argon atmosphere at a pressure of up to 60 MPa for 1750℃ for 65 minutes.

[0043] The prepared cermet material is a Ta-doped modified niobium aluminum carbon material with the chemical formula (Nb). 0.9 Ta 0.1 )2AlC, such as Figure 3 The image shows the dense (Nb) 0.9 Ta 0.1)2 Surface morphology diagram of AlC block.

[0044] The density of the bulk material was determined to be 97.3% using the Archimedes method (ISO 18754). Φ30×5mm and 4×4×40mm diameter pieces were cut from the sintered, dense bulk material using wire cutting. 3 and 10×10×2mm 3 The bulk sample was then polished with 400#, 600#, 800#, 1000# and finally 2000# SiC sandpaper, then polished with polishing paste with a grit size W=1, and finally ultrasonically cleaned with alcohol in preparation for further experiments.

[0045] The sample density is 6.64 g / cm³. 3 The four-point method was used for testing (Nb). 0.9 Ta 0.1 The room temperature conductivity of the 2AlC bulk material is 3.2 × 10⁻⁶. 6 Ω -1 ·m -1 The unsteady-state method was used to measure (Nb) 0.9 Ta 0.1 The thermal conductivity of the Al2C bulk material is 41 W / m·K. Potentiodynamic testing was conducted in a fuel cell simulation environment (0.5 mol / L H2SO4 and 2 ppm HF solution) at 80 °C, with assembly forces ranging from 50 to 200 N / cm. 2 Under these conditions, test (Nb) 0.9 Ta 0.1 )2AlC bulk material contact resistance.

[0046] Tests showed that the corrosion current density of the Ta-doped modified niobium-aluminum-carbon material was 0.09 μA / cm² in a fuel cell simulation environment (0.5 mol / L H₂SO₄ and 2 ppm HF solution, temperature 80℃). 2 [Corrosion potential 0.21V (vs. SCE)], under a pressure of 1.4MPa, its surface resistivity (ASR) is 3.5mΩ·cm. -2 It meets the DOE performance specifications, indicating (Nb 0.9 Ta 0.1 )2AlC bulk materials can be used as bipolar plate materials for proton exchange membrane fuel cells.

[0047] Example 3

[0048] A method for preparing a metal-ceramic material for a proton exchange membrane fuel cell bipolar plate, wherein this embodiment uses 18 at.% Ta-doped niobium-aluminum-carbon material, includes the following steps:

[0049] Nb, Ta, Al, and C elemental powders were used as the original synthetic materials. The raw material powders were prepared according to the ratio of Nb:Ta:Al:C = 1.64:0.36:1:1. The prepared raw material powders were mixed with alcohol and placed in a spherical mill for ball milling for 36 hours. The powders were then removed, sieved, and dried for later use. The powders were cold-pressed at a pressure of 13 MPa and then sintered in a hot-pressing sintering furnace under an argon atmosphere at a pressure of up to 72 MPa for 90 minutes at 1850℃.

[0050] The prepared cermet material is a Ta-doped modified niobium aluminum carbon material with the chemical formula (Nb). 0.82 Ta 0.18 )2AlC.

[0051] The density of the bulk material was determined to be 96.8% using the Archimedes method (ISO 18754). Φ30×5mm and 4×4×40mm diameter pieces were cut from the sintered, dense bulk material using wire cutting. 3 and 10×10×2mm 3 The bulk sample was then polished with 400#, 600#, 800#, 1000# and finally 2000# SiC sandpaper, then polished with polishing paste with a grit size W=1, and finally ultrasonically cleaned with alcohol in preparation for further experiments.

[0052] The sample density is 6.80 g / cm³. 3 The four-point method was used for testing (Nb). 0.82 Ta 0.18 The room temperature conductivity of the AlC bulk material is 3.1 × 10⁻⁶. 6 Ω -1 ·m -1 The unsteady-state method was used to measure (Nb) 0.82 Ta 0.18 The thermal conductivity of the Al2C bulk material is 41 W / m·K. Potentiodynamic testing was conducted in a fuel cell simulation environment (0.5 mol / L H2SO4 and 2 ppm HF solution) at 80 °C, with assembly forces ranging from 50 to 200 N / cm. 2 Under these conditions, test (Nb) 0.82 Ta 0.18 )2AlC bulk material contact resistance.

[0053] The tests showed that the corrosion current density of the Ta-doped modified niobium-aluminum-carbon material was 0.25 μA / cm² in a fuel cell simulation environment (0.5 mol / L H₂SO₄ and 2 ppm HF solution, temperature 80℃). 2 [Corrosion potential 0.27V (vs. SCE)], under a pressure of 1.4MPa, its surface resistivity (ASR) is 7.2mΩ·cm. -2 It meets the DOE performance specifications, indicating (Nb0.82 Ta 0.18 )2AlC bulk materials can be used as bipolar plate materials for proton exchange membrane fuel cells.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, alterations, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A metal-ceramic material for bipolar plates in proton exchange membrane fuel cells, characterized in that, The cermet material is a Ta-doped niobium aluminum carbon material, or simply modified niobium aluminum carbon material. The chemical formula of the modified niobium aluminum carbon material is (Nb... 1- x Ta x )2AlC, where x is 0.01~0.

20.

2. The metal-ceramic material for proton exchange membrane fuel cell bipolar plates according to claim 1, characterized in that, The density of the modified niobium-aluminum-carbon material is (6.37~6.89) g / cm³. 3 .

3. The metal-ceramic material for proton exchange membrane fuel cell bipolar plates according to claim 1, characterized in that, The density of the modified niobium-aluminum-carbon material is higher than 95%.

4. A method for preparing a metal-ceramic material for a proton exchange membrane fuel cell bipolar plate according to any one of claims 1-3, characterized in that, Includes the following steps: The raw materials Nb powder, Ta powder, Al powder and graphite powder were prepared according to the atomic percentage ratio Nb:Ta:Al:C=2(1-x):2x:1:

1. The prepared raw material powders were mixed with alcohol and then ball-milled for 15~36 h. After drying, they were cold-pressed under a pressure of 5~15 MPa and then sintered in a hot-pressing sintering furnace at a temperature of 1680~1850℃ using argon as a protective gas. The hot-pressing pressure was 50~75 MPa and the holding time was 40~95 min.

5. The application of the metal-ceramic material for proton exchange membrane fuel cell bipolar plates according to any one of claims 1-3 in the preparation of proton exchange membrane fuel cell bipolar plates.

6. The application according to claim 5, characterized in that, The modified niobium-aluminum-carbon material has an electrical conductivity of (3.0~3.4)×10⁻⁶ at room temperature. 6 S / m.

7. The application according to claim 5, characterized in that, The modified niobium-aluminum-carbon material has a thermal conductivity of (41~45) W / m·K at room temperature.

8. The application according to claim 5, characterized in that, Potentiodynamic testing was conducted in a fuel cell simulation environment with H₂SO₄ concentration of 0.5 mol / L + 2 ppm HF and temperature of 80℃. The corrosion current density of the modified niobium-aluminum-carbon material was 0.02~0.26 μA / cm². 2 The self-corrosion potential is 0.13~0.28 V (vs. SCE).

9. The application according to claim 5, characterized in that, At an assembly force of 150 N / cm 2 Under the specified conditions, the contact resistance of the modified niobium-aluminum-carbon material is 0.8~7.5 mΩ·cm. 2 .

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