A niobium-vanadium carbide-palladium composite material foil

Abstract

The application relates to the hydrogen energy technical field and discloses a niobium-vanadium carbide-palladium composite material foil, which comprises a niobium foil base, vanadium carbide ceramic self-healing layers covering two sides of the niobium foil base, and a palladium-based catalytic layer deposited on the surfaces of the vanadium carbide ceramic self-healing layers; V-C-B nano self-healing phases are dispersed in the vanadium carbide ceramic self-healing layers, the V-C-B nano self-healing phases are melted at 600-700 DEG C and generate vanadium carbide boron repair phases, and then fill microcracks; CeO2 nano clusters are loaded on the surface of the palladium-based catalytic layer.

Description

Technical Field

[0001] This invention relates to the field of hydrogen energy technology, and in particular to a niobium-vanadium carbide-palladium composite foil. Background Technology

[0002] With the rapid development of global science and technology and economy, the energy supply pattern is facing severe challenges. Traditional non-renewable energy sources, represented by coal and oil, have not only caused environmental problems such as global warming and air pollution in the long term, but also face the risk of gradual depletion due to limited resource reserves. Promoting clean energy substitution has become the core direction of global energy transformation.

[0003] Hydrogen energy, as a clean energy source with zero emissions and high energy conversion efficiency, shows broad application prospects in fields such as hydrogen fuel cells and chemical raw material preparation. Its energy storage density is as high as 33.33 kWh / kg, more than four times that of traditional fossil fuels, and its combustion product is only water, which can fundamentally reduce greenhouse gas emissions. This aligns with the energy development needs under the current goals and is considered an important component of the future energy system.

[0004] However, the development of my country's hydrogen energy industry still faces multiple bottlenecks, which restrict the large-scale application of hydrogen fuel cell technology. On the one hand, the high cost of green hydrogen production, the expensive cost of hydrogen storage equipment, and the low efficiency of long-distance hydrogen transportation lead to insufficient hydrogen supply stability and high end-user prices. On the other hand, in order to overcome the bottleneck of hydrogen storage and transportation, researchers have proposed a model of on-site hydrogen production and local hydrogen supply through methanol and water reforming. However, the core material for hydrogen purification in this model, palladium alloy separation membrane, has high production costs, forming a new technical and economic bottleneck that makes it difficult to meet the needs of large-scale industrialization.

[0005] To reduce the cost of hydrogen purification materials, existing technologies propose using body-centered cubic (BCC) non-precious metals such as vanadium, tantalum, and niobium to partially replace palladium alloys, and depositing a palladium layer on the surface of the non-precious metal substrate to achieve hydrogen catalytic separation. However, this type of non-precious metal-palladium composite system has significant performance defects: First, during long-term service, atomic interdiffusion easily occurs between the palladium layer and the BCC metal substrate, and the BCC metal itself exhibits hydrogen embrittlement, resulting in a significantly lower hydrogen permeability than pure palladium alloys. Second, under the frequent start-stop conditions of hydrogen fuel cells, the material is prone to microcracks due to alternating thermal stress, hydrogen atom penetration and erosion, or impacts from impurities such as sulfides (e.g., H2S) in the feed gas, leading to a continuous decline in hydrogen permeability. Furthermore, existing materials lack in-situ self-healing capabilities and cannot autonomously repair microcracks, resulting in a shortened material lifespan and further increasing the operation and maintenance costs and safety risks of hydrogen fuel cell systems. Summary of the Invention

[0006] The purpose of this invention is to provide a self-healing niobium-vanadium carbide ceramic-palladium composite foil, its preparation method, and its application in hydrogen purification. This composite foil possesses excellent microcrack self-healing ability, high hydrogen permeability, and outstanding sulfur poisoning resistance. It also exhibits good structural stability and environmental adaptability. It can be used as a low-cost, long-service-life separation material for hydrogen purification in hydrogen fuel cells and for hydrogen purification devices in methanol reforming. This invention effectively solves the problems of high cost of existing palladium alloy separation materials, low hydrogen permeability and susceptibility to hydrogen embrittlement in non-precious metal-palladium composite systems, lack of in-situ self-healing ability for microcracks, and weak sulfur poisoning resistance.

[0007] To achieve the above objectives, the present invention provides the following solution: A niobium-vanadium carbide-palladium composite foil includes a niobium foil substrate, a vanadium carbide ceramic self-healing layer covering both sides of the niobium foil substrate, and a palladium-based catalyst layer deposited on the surface of the vanadium carbide ceramic self-healing layer. The vanadium carbide ceramic self-healing layer contains VCB nano-self-healing phase, which melts at 600~700℃ to generate vanadium carbide boron repair phase, thereby filling microcracks. The palladium-based catalyst layer is supported on CeO2 nanoclusters.

[0008] Furthermore, the niobium foil substrate has a thickness of 50~300μm and a purity of ≥99.95%.

[0009] Furthermore, the vanadium carbide ceramic self-healing layer has a porous structure with a pore size of 3-15 nm and a thickness of 10-50 nm; the VCB nano self-healing phase has a particle size of 10-30 nm and a volume percentage of 5-15 vol in the vanadium carbide ceramic self-healing layer.

[0010] Furthermore, the thickness of the palladium-based catalyst layer is 50-100 nm; the particle size of the CeO2 nanoclusters is 5-10 nm.

[0011] The present invention also provides a method for preparing the above-mentioned niobium-vanadium carbide-palladium composite foil, comprising the following steps: S1. A vanadium layer and a VCB composite layer are co-deposited on the surface of a niobium foil substrate by dual-target magnetron sputtering, with a V:C:B molar ratio of 8:1:1, to form a composite layer containing a VCB nano-self-healing phase precursor. S2. Heat treatment at 80~120℃ for 20~40min in an oxygen atmosphere to form vanadium oxide-boron oxide composite precursor; S3. In a methane atmosphere, the temperature is increased to 800-1000℃ at a heating rate of 3-7℃ / min, and held for 1.5-2.5h for carbonization reduction to generate a vanadium carbide ceramic self-healing layer containing VCB nano self-healing phase. S4. A palladium layer and CeO2 nanoclusters are sequentially formed on the surface of the vanadium carbide ceramic self-healing layer by atomic layer deposition, wherein the thickness of the palladium layer is 50~100nm.

[0012] Furthermore, the thickness ratio of the vanadium layer to the VCB composite layer in step S1 is 3:1.

[0013] Furthermore, the CeO2 nanoclusters described in step S4 are deposited 50 times, with a thickness of approximately 5-20 nm.

[0014] Furthermore, before step S4, a pretreatment step of plasma cleaning for 5-15 minutes is included for the vanadium carbide ceramic self-healing layer.

[0015] The present invention also provides the application of the niobium-vanadium carbide-palladium composite foil described in any of the preceding claims in hydrogen purification or methanol reforming for hydrogen production in hydrogen fuel cells.

[0016] The present invention also provides the use of the niobium-vanadium carbide-palladium composite foil described above in the preparation of separation membranes for hydrogen purifiers.

[0017] One embodiment of this specification can achieve at least the following beneficial effects: 1. This invention introduces VCB nanoparticles into a vanadium carbide ceramic layer and utilizes their low-temperature melting characteristics to achieve autonomous repair of microcracks in the material without external intervention. That is, when microcracks appear in the material during service due to thermal stress and hydrogen atom penetration erosion caused by frequent start-stop of hydrogen fuel cells, the VCB nanoparticles can melt at a specific temperature to generate a vanadium carbide boron repair phase, which directly fills the crack gaps, restores the structural integrity and hydrogen permeability of the material, and avoids the problem of decreased hydrogen permeability and shortened service life caused by the continuous propagation of microcracks in traditional non-precious metal-palladium composite systems.

[0018] 2. This invention loads CeO2 nanoclusters on the surface of a palladium-based catalyst layer. The chemisorption of CeO2 nanoclusters can effectively fix sulfur ions in the feed gas and promote the regeneration of palladium catalytic active sites. This can effectively solve the problem that traditional palladium layers are easily occupied by sulfur ions, leading to a sharp decline in catalytic and hydrogen permeability performance. It breaks through the sulfur resistance limit of traditional palladium layers and ensures that the material can still be stably used in sulfur-containing gas source environments.

[0019] 3. This invention uses niobium foil as a substrate, significantly reducing the amount of precious metal palladium used compared to pure palladium alloy separation materials, thus significantly lowering material preparation costs. Simultaneously, the preparation process employs dual-target magnetron sputtering and atomic layer deposition (ALD) processes, both mature industrial-scale technologies with strong operational controllability and high product uniformity. This enables large-scale production of composite foil materials, avoiding the problems of low production efficiency and high costs caused by complex processes, and meeting the material production capacity and cost requirements for large-scale applications in the hydrogen energy industry. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a scanning electron microscope image of the niobium-vanadium carbide ceramic composite material, an intermediate product prepared after the vanadium carbide ceramic self-healing layer preparation process in Example 1. Figure 2 This is a scanning electron microscope image of the niobium-vanadium carbide ceramic-palladium composite material, the final product after the palladium-CeO2 catalytic antisulfur layer preparation process in Example 1. Figure 3 This is the curve showing the relationship between the hydrogen permeability coefficient and pressure difference of the niobium-vanadium carbide-palladium composite foil prepared in Example 1; Figure 4 This is a curve showing the retention rate of hydrogen permeability coefficient of the niobium-vanadium carbide ceramic-palladium composite foil provided in Example 1 of the present invention after operating in an 80ppm H2S atmosphere for 100 hours.

[0022] Figure 5 This is a scanning electron microscope image of the niobium-vanadium carbide ceramic composite material, an intermediate product prepared after the vanadium carbide ceramic self-healing layer preparation process in Example 2. Figure 6 This is a scanning electron microscope image of the niobium-vanadium carbide ceramic-palladium composite material, the final product after the palladium-CeO2 catalytic antisulfur layer preparation process in Example 2. Figure 7 This is the curve showing the relationship between the hydrogen permeability coefficient and pressure difference of the niobium-vanadium carbide-palladium composite foil prepared in Example 2; Figure 8 This is a curve showing the retention rate of hydrogen permeability coefficient of the niobium-vanadium carbide-palladium composite foil provided in Example 2 of the present invention after operating in an 80ppm H2S atmosphere for 100 hours; Figure 9This is a scanning electron microscope image of the niobium-vanadium carbide ceramic composite material, an intermediate product prepared after the vanadium carbide ceramic self-healing layer preparation process in Example 3. Figure 10 This is a scanning electron microscope image of the niobium-vanadium carbide ceramic-palladium composite material, the final product after the palladium-CeO2 catalytic antisulfur layer preparation process in Example 3. Figure 11 This is the curve showing the relationship between the hydrogen permeability coefficient and pressure difference of the niobium-vanadium carbide-palladium composite foil prepared in Example 3; Figure 12 This is a curve showing the retention rate of hydrogen permeability coefficient of the niobium-vanadium carbide-palladium composite foil provided in Example 3 of the present invention after operating in an 80ppm H2S atmosphere for 100 hours; Figure 13 This is a flowchart of the preparation method of the niobium-vanadium carbide-palladium composite foil provided by the present invention. Detailed Implementation

[0023] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products. In the following embodiments, unless otherwise explicitly stated, "%" refers to weight percentage.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] The purpose of this invention is to provide a niobium-vanadium carbide-palladium composite foil for the hydrogen energy field that combines microcrack self-healing ability, high hydrogen permeability, and sulfur poisoning resistance. This solves the problems of high cost of existing palladium alloy separation materials, low hydrogen permeability and easy hydrogen embrittlement of non-precious metal-palladium composite systems, lack of in-situ self-healing ability of microcracks, and weak sulfur poisoning resistance.

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] The niobium-vanadium carbide-palladium composite foil provided by this invention has a three-layer composite structure of "support-repair-catalysis" consisting of a substrate, a self-healing layer, and a catalytic layer. The substrate is a high-purity niobium foil, which provides structural support for the entire material and provides hydrogen diffusion channels. The self-healing layer is a porous vanadium carbide ceramic layer containing VCB nano-self-healing phase, which tightly covers both sides of the niobium foil substrate. It can both block the inter-diffusion of atoms between different layers and achieve self-repair of microcracks. The catalytic layer is a palladium base layer loaded with CeO2 nanoclusters, which is uniformly deposited on the surface of the vanadium carbide ceramic self-healing layer. It is mainly responsible for the catalytic dissociation of hydrogen and improves the material's resistance to sulfur poisoning.

[0028] Among them, the special structure of the porous vanadium carbide ceramic layer ensures selective hydrogen transport, the low-temperature melting characteristics of the VCB nano self-healing phase allow microcrack repair without external intervention, and the CeO2 nanoclusters maintain long-term catalytic activity in synergy with the palladium substrate through the chemical adsorption of sulfur ions. Together, the three constitute a stable hydrogen separation system.

[0029] In the substrate, the thickness of the niobium foil is controlled between 50 and 300 μm, with a purity of not less than 99.95%. Its body-centered cubic structure gives the material both good structural stability and hydrogen permeability. On the one hand, the niobium foil provides a reliable adhesion base for the self-healing layer and the catalyst layer, preventing deformation of the material during assembly or service. On the other hand, it guides hydrogen to diffuse smoothly from the inside to the self-healing layer, and compared to other non-precious metals such as vanadium and tantalum, niobium foil has lower hydrogen embrittlement sensitivity, reducing structural damage caused by hydrogen atom permeation during long-term use.

[0030] In the self-healing layer, the vanadium carbide ceramic layer exhibits a uniform porous structure with pore sizes ranging from 3 to 15 nm and a layer thickness of 10 to 50 nm. VCB nano-self-healing phases are uniformly dispersed within the layer. These nano-self-healing phases have particle sizes of 10 to 30 nm and account for 5 to 15 vol% of the volume in the vanadium carbide ceramic layer. The porous structure is crucial for the selective passage of hydrogen and effectively blocks atomic interpenetration between the niobium foil substrate and the palladium catalyst layer, preventing the formation of a degraded alloy phase after palladium and niobium diffusion, which would otherwise reduce hydrogen permeability. When microcracks develop in the material due to thermal stress or hydrogen atom erosion, the VCB nano-self-healing phase can melt at 600 to 700 °C, forming a vanadium carbide boron repair phase that fills the cracks. After repair, the hydrogen permeability coefficient of the material recovers to at least 90%, ensuring service life.

[0031] In the catalyst layer, the palladium substrate has a thickness of 50-100 nm. The dense palladium layer structure ensures that hydrogen gas is fully dissociated into hydrogen atoms on its surface, while preventing the passage of impurity gases such as nitrogen and carbon dioxide. CeO2 nanoclusters are loaded onto the palladium substrate surface in a specific manner, with a deposition cycle of up to 50 times, ultimately forming nanoclusters with a thickness of approximately 5-20 nm and a particle size of 5-10 nm. The surface of the CeO2 nanoclusters contains a large number of oxygen vacancies, which can react with sulfur ions (such as sulfur in H2S) in the feed gas. 2- Chemical adsorption occurs, preventing sulfur ions from occupying the catalytic active sites of palladium. Simultaneously, it promotes the regeneration of sulfur-contaminated palladium active sites, allowing the material to overcome the sulfur resistance limit of traditional palladium layers. Furthermore, before the catalytic layer forms, the vanadium carbide ceramic self-healing layer can be plasma-cleaned for 5-15 minutes to thoroughly remove residual carbide impurities from the surface, further enhancing the bonding strength between the self-healing layer and the catalytic layer and reducing the risk of interlayer delamination.

[0032] On a macroscopic scale, the niobium-vanadium carbide ceramic-palladium composite material of this invention presents a foil-like form, which can be directly assembled into a hydrogen purifier as a separation membrane without additional molding processing. This form not only adapts to the internal structure of hydrogen purification modules in hydrogen fuel cells and methanol reforming hydrogen production equipment, but also reduces material waste during assembly and lowers the overall size of the equipment.

[0033] The niobium-vanadium carbide-palladium composite foil exhibits excellent performance under typical service conditions: at 500℃ and a transmembrane pressure difference of 0.2 MPa, the hydrogen permeability coefficient can reach 7.2~8.5×10⁻⁶. -8 mol·m -1 ·s -1 ·Pa -0.5 It meets the requirements for efficient hydrogen separation. Even in a hydrogen atmosphere containing 80ppm H2S, after continuous operation at 500℃ for 100 hours, the hydrogen permeability coefficient remains at no less than 95%, which can fully cope with the purification scenarios of sulfur-containing gas sources in the field of hydrogen energy, and provide stable material support for applications such as hydrogen fuel cells and chemical hydrogen extraction.

[0034] like Figure 13 As shown, the present invention also provides a method for preparing the above-mentioned niobium-vanadium carbide-palladium composite foil, comprising the following steps: (1) A vanadium layer and a VCB composite layer were co-deposited on the surface of a niobium foil substrate by dual-target magnetron sputtering, with a V:C:B molar ratio of 8:1:1, forming a composite layer containing a VCB nano-self-healing phase precursor. The thickness ratio of the vanadium layer to the VCB composite layer was 3:1.

[0035] In practice, this step involves pre-treating the niobium foil substrate first. This is done by ultrasonically cleaning it with acetone and ethanol, followed by vacuum drying. The dried niobium foil substrate is then fixed onto the sample stage of a magnetron sputtering device. A 99.99% pure vanadium target and a VCB alloy target with a V:C:B molar ratio of 8:1:1 are used as sputtering sources. Under an argon atmosphere, a vanadium layer and a VCB composite layer are co-deposited on the surface of the niobium foil substrate using a dual-target magnetron sputtering process. During this process, the thickness ratio of the vanadium layer to the VCB composite layer must be controlled at 3:1, ultimately forming a composite layer containing a VCB nano-self-healing phase precursor.

[0036] (2) Heat treatment at 80~120℃ for 20~40min in an oxygen atmosphere to form vanadium oxide-boron oxide composite precursor.

[0037] (3) In a methane atmosphere, the temperature is increased to 800-1000℃ at a heating rate of 3-7℃ / min and held for 1.5-2.5h for carbonization reduction to generate a vanadium carbide ceramic self-healing layer containing VCB nano self-healing phase.

[0038] (4) A palladium layer and CeO2 nanoclusters are sequentially formed on the surface of the vanadium carbide ceramic self-healing layer by atomic layer deposition. The thickness of the palladium layer is 50-100 nm. The CeO2 nanoclusters are deposited 50 times and have a thickness of approximately 5-20 nm. Before starting this step, the vanadium carbide ceramic self-healing layer can also be pretreated by plasma cleaning for 5-15 minutes.

[0039] Example 1 Example 1 of the present invention prepares niobium-vanadium carbide-palladium composite foil according to the following steps: (1) Preparation of vanadium carbide ceramic self-healing layer Firstly, a niobium foil substrate with a purity ≥99.95% and a thickness of 200 μm was selected. It was then ultrasonically cleaned with acetone and ethanol for 20 min each, followed by vacuum drying at 60 °C for 12 h. The dried niobium foil was then fixed onto the sample stage of a magnetron sputtering system. A 99.99% pure vanadium metal target and a VCB alloy target (V:C:B molar ratio 8:1:1) were used as the sputtering source. The system was operated under an argon atmosphere (flow rate 25 sccm, background vacuum 3 × 10⁻⁶). -3 At a pressure of 10 nm, a vanadium layer and a VCB composite layer were co-deposited on the surface of a niobium foil substrate. The thickness of the vanadium layer was controlled to be 30 nm, and the thickness of the VCB composite layer was controlled to be 10 nm, with a thickness ratio of 3:1.

[0040] Subsequently, the deposited sample was transferred to a tube furnace, oxygen was introduced at a flow rate of 12 sccm, and the sample was heat-treated at 100°C for 30 min, followed by natural cooling to form a vanadium oxide-boron oxide composite precursor.

[0041] Subsequently, the aforementioned precursor was placed in a chemical vapor deposition furnace, and methane gas at a flow rate of 20 sccm was introduced, with argon gas at a flow rate of 20 sccm as the carrier gas. The temperature was increased to 900°C at a heating rate of 5°C / min, and held at this temperature for 2 hours to carry out a carbonization reduction reaction (reaction formula: VO). X + B2O3+ CH4→ VCB2+ CO + H2O). After the reaction is complete, the furnace is cooled to obtain a vanadium carbide ceramic self-healing layer containing the VCB nano self-healing phase.

[0042] The resulting vanadium carbide ceramic self-healing layer is shown in the scanning electron microscope image. Figure 1 As shown, Figure 1 This is a scanning electron microscope image of the niobium-vanadium carbide ceramic composite material prepared in Example 1. Figure 1 It can be seen that the ceramic layer has a porous structure with a pore size of about 8~12nm and a thickness of about 30nm. The VCB nano self-healing phase is uniformly dispersed with a particle size of about 20nm and a volume percentage of 10vol.

[0043] (2) Preparation of palladium-CeO2 catalytic antisulfur layer The niobium foil with the vanadium carbide ceramic self-healing layer prepared above was placed in a plasma cleaner and cleaned for 10 minutes at a power of 60 W with argon gas at a flow rate of 10 sccm to thoroughly remove residual carbides and other impurities on the surface.

[0044] The cleaned sample was transferred to an atomic layer deposition (ALD) apparatus. Dimethylpalladium (Pd(CH3)2) was used as the palladium precursor and hydrogen (H2) was used as the reducing gas. A palladium layer was deposited at a reaction temperature of 220°C, and the thickness of the palladium layer was controlled to be 80 nm.

[0045] Keeping the reaction temperature constant, the precursor was changed to tris(dimethylamino)cerium(III) (Ce(N(CH3)2)3), and oxygen (O2) was used as the oxidizing gas. After 50 deposition cycles, CeO2 nanoclusters with a thickness of about 12 nm were finally formed on the surface of the palladium layer.

[0046] The final niobium-vanadium carbide ceramic-palladium composite material was characterized by SEM, and the results are as follows: Figure 2 As shown. From Figure 2 As can be seen, the deposited palladium layer is dense and free of pinholes, and CeO2 nanoclusters are uniformly loaded on the surface of the palladium layer with a particle size of about 8 nm.

[0047] (3) Performance testing of composite foil The composite foil prepared in Example 1 was assembled in a hydrogen purification test device to test its hydrogen permeability and sulfur resistance.

[0048] First, the hydrogen permeability coefficient was tested: under conditions of 500℃ and a transmembrane pressure difference of 0.2 MPa, the hydrogen permeability coefficient was measured to be 7.5 × 10⁻⁶. -8 mol·m -1 ·s -1 ·Pa -0.5 When the pressure difference increases to 0.6 MPa, the hydrogen permeability coefficient increases to 9.3 × 10⁻⁶. -8 mol·m -1 ·s -1 ·Pa -0.5 The relationship between hydrogen permeability coefficient and pressure difference is shown in the curve. Figure 3 As shown.

[0049] Subsequent sulfur resistance tests were conducted: after 100 hours of continuous operation at 500°C in a hydrogen atmosphere containing 80 ppm H2S, the hydrogen permeability coefficient retention rate was measured to be 95.1%. The curve showing the hydrogen permeability coefficient retention rate over time is shown below. Figure 4 As shown.

[0050] Additional self-healing performance test: After artificially pre-fabricating microcracks in the material, it was repaired by holding it at 650℃ for 30 minutes. The hydrogen permeability coefficient of the material recovered to 92% after repair.

[0051] Example 2 In Example 2 of this invention, a niobium-vanadium carbide-palladium composite foil was prepared following similar steps to those in Example 1, with the main process parameters adjusted as follows: (1) Preparation of vanadium carbide ceramic self-healing layer: A niobium foil substrate with a thickness of 50 μm was selected. The co-deposited vanadium layer had a thickness of 15 nm, and the VCB composite layer had a thickness of 5 nm. The oxygen heat treatment conditions were adjusted to 80℃ for 20 minutes. The carbothermic reduction reaction conditions were adjusted to: heating rate 3℃ / min, reaction temperature 800℃, and holding time 1.5 hours. The resulting ceramic self-healing layer had a pore size of approximately 3-5 nm and a thickness of approximately 10 nm; the VCB nanophase had a particle size of approximately 10 nm and a volume percentage of approximately 5 vol%.

[0052] The resulting vanadium carbide ceramic self-healing layer is shown in the scanning electron microscope image. Figure 5 As shown, Figure 5 This is a scanning electron microscope image of the niobium-vanadium carbide ceramic composite material prepared in Example 2. Figure 5 It can be seen that the ceramic layer has a porous structure with a pore size of about 3~5nm and a thickness of about 10nm; the VCB nano self-healing phase is uniformly dispersed with a particle size of about 10nm and a volume percentage of 5vol.

[0053] (2) Preparation of palladium-CeO2 catalytic anti-sulfur layer: The plasma cleaning time was adjusted to 5 minutes. The thickness of the palladium layer after atomic layer deposition was 50 nm; the thickness of the CeO2 nanoclusters after 50 cycles was about 5 nm, and the particle size was about 5 nm.

[0054] The final niobium-vanadium carbide ceramic-palladium composite material was characterized by SEM, and the results are as follows: Figure 6 As shown. Figure 6 This is a scanning electron microscope image of the niobium-vanadium carbide ceramic-palladium composite material prepared in Example 2. Figure 6 As can be seen, the deposited palladium layer is dense and free of pinholes, and CeO2 nanoclusters are uniformly loaded on the surface of the palladium layer with a particle size of about 5 nm.

[0055] (3) Performance testing of composite foil The composite foil prepared in Example 2 was assembled in a hydrogen purification test device to test its hydrogen permeability, sulfur resistance and self-healing properties.

[0056] First, the hydrogen permeability coefficient was tested: under conditions of 500℃ and a transmembrane pressure difference of 0.2 MPa, the hydrogen permeability coefficient was measured to be 7.2 × 10⁻⁶. -8 mol·m -1 ·s -1 ·Pa -0.5 The relationship between hydrogen permeability coefficient and pressure difference is shown in the curve. Figure 7 As shown.

[0057] Subsequent sulfur resistance tests were conducted: after 100 hours of continuous operation at 500°C in a hydrogen atmosphere containing 80 ppm H2S, the hydrogen permeability coefficient retention rate was measured to be 95.0%. The curve showing the hydrogen permeability coefficient retention rate over time is shown below. Figure 8 As shown.

[0058] Additional self-healing performance test: After artificially pre-fabricating microcracks in the material, it was repaired by holding it at 600℃ for 30 minutes. The hydrogen permeability coefficient of the material recovered to 90% after repair.

[0059] Example 3 In Example 3 of this invention, a niobium-vanadium carbide-palladium composite foil was prepared following steps similar to those in Example 1, with the main process parameters adjusted as follows: (1) Preparation of vanadium carbide ceramic self-healing layer: A niobium foil substrate with a purity of 99.98% and a thickness of 300 μm was selected. The co-deposited vanadium layer had a thickness of 45 nm, and the VCB composite layer had a thickness of 15 nm. The oxygen heat treatment conditions were adjusted to 120℃ for 40 minutes. The carbothermic reduction reaction conditions were adjusted to: heating rate 7℃ / min, reaction temperature 1000℃, and holding time 2.5 hours. The resulting ceramic self-healing layer had a pore size of approximately 13-15 nm and a thickness of approximately 50 nm; the VCB nanophase had a particle size of approximately 30 nm and a volume percentage of approximately 15 vol%.

[0060] The resulting vanadium carbide ceramic self-healing layer is shown in the scanning electron microscope image. Figure 9 As shown. From Figure 9 As can be seen, the ceramic layer exhibits a uniform porous structure with a pore size distribution of approximately 13–15 nm and a layer thickness of approximately 50 nm. The VCB nano-self-healing phase is uniformly dispersed within the ceramic layer, with a particle size of approximately 30 nm and a volume percentage of approximately 15 vol%.

[0061] (2) Preparation of palladium-CeO2 catalytic anti-sulfur layer: The plasma cleaning time was adjusted to 15 minutes. The thickness of the palladium layer after atomic layer deposition was 100 nm; the thickness of the CeO2 nanoclusters after 50 cycles was about 20 nm, and the particle size was about 10 nm.

[0062] The final niobium-vanadium carbide ceramic-palladium composite material was characterized by SEM, and the results are as follows: Figure 10 As shown. From Figure 10 As can be seen, the deposited palladium layer is dense and free of pinholes, and CeO2 nanoclusters are uniformly loaded on the surface of the palladium layer with a particle size of about 10 nm.

[0063] (3) Performance testing of composite foil The composite foil prepared in Example 3 was assembled in a hydrogen purification test device to test its hydrogen permeability, sulfur resistance and self-healing properties.

[0064] First, the hydrogen permeability coefficient was tested: under conditions of 500℃ and a transmembrane pressure difference of 0.2 MPa, the hydrogen permeability coefficient was measured to be 8.5 × 10⁻⁶. -8 mol·m -1 ·s -1 ·Pa -0.5 The relationship between hydrogen permeability coefficient and pressure difference is shown in the curve. Figure 11 As shown.

[0065] Subsequent sulfur resistance tests were conducted: after 100 hours of continuous operation at 500°C in a hydrogen atmosphere containing 80 ppm H2S, the hydrogen permeability coefficient retention rate was measured to be 96.0%. The curve showing the hydrogen permeability coefficient retention rate over time is shown below. Figure 12 As shown.

[0066] Additional self-healing performance test: After artificially pre-fabricating microcracks in the material, it was repaired by holding it at 700℃ for 30 minutes. The hydrogen permeability coefficient of the material recovered to 93% after repair.

[0067] Examples 1-3 all achieve the following characteristics of niobium-vanadium carbide-palladium composite foil: Structural stability: The intermediate vanadium carbide ceramic layer effectively blocks the mutual diffusion between the palladium layer and the niobium foil substrate, enhancing the interlayer bonding force.

[0068] Self-healing ability: The VCB nanophase dispersed in the ceramic layer can melt and flow at 600~700℃, thereby effectively filling and repairing microcracks generated during the use of the material, and the hydrogen permeability coefficient recovery rate is ≥90%.

[0069] High hydrogen permeability and excellent sulfur resistance: The material exhibits a high hydrogen permeability coefficient (7.2~8.5×10⁻⁶) at 500℃ and a pressure difference of 0.2 MPa. -8 mol·m -1 ·s -1 ·Pa -0.5 Furthermore, after operating continuously for 100 hours in a harsh environment with 80 ppm H2S, the hydrogen permeability coefficient retention rate is ≥95%, fully meeting the stringent requirements for material performance in applications such as hydrogen purification for hydrogen fuel cells.

[0070] The present invention also provides the application of the niobium-vanadium carbide-palladium composite foil described in any of the preceding claims in hydrogen purification or methanol reforming for hydrogen production in hydrogen fuel cells.

[0071] The present invention also provides the use of the niobium-vanadium carbide-palladium composite foil described above in the preparation of separation membranes for hydrogen purifiers.

[0072] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A niobium-vanadium carbide-palladium composite foil, characterized in that, It includes a niobium foil substrate, a vanadium carbide ceramic self-healing layer covering both sides of the niobium foil substrate, and a palladium-based catalyst layer deposited on the surface of the vanadium carbide ceramic self-healing layer; The vanadium carbide ceramic self-healing layer contains VCB nano-self-healing phase, which melts at 600~700℃ to generate vanadium carbide boron repair phase, thereby filling microcracks. The palladium-based catalyst layer is supported on CeO2 nanoclusters.

2. The niobium-vanadium carbide-palladium composite foil according to claim 1, characterized in that, The niobium foil substrate has a thickness of 50~300μm and a purity of ≥99.95%.

3. The niobium-vanadium carbide-palladium composite foil according to claim 2, characterized in that, The vanadium carbide ceramic self-healing layer has a porous structure with a pore size of 3-15 nm and a thickness of 10-50 nm; the VCB nano self-healing phase has a particle size of 10-30 nm and a volume percentage of 5-15 vol in the vanadium carbide ceramic self-healing layer.

4. The niobium-vanadium carbide-palladium composite foil according to claim 1, characterized in that, The thickness of the palladium-based catalyst layer is 50-100 nm; the particle size of the CeO2 nanoclusters is 5-10 nm.

5. A method for preparing a niobium-vanadium carbide-palladium composite foil as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. A vanadium layer and a VCB composite layer are co-deposited on the surface of a niobium foil substrate by dual-target magnetron sputtering, with a V:C:B molar ratio of 8:1:1, to form a composite layer containing a VCB nano-self-healing phase precursor. S2. Heat treatment at 80~120℃ for 20~40min in an oxygen atmosphere to form vanadium oxide-boron oxide composite precursor; S3. In a methane atmosphere, the temperature is increased to 800-1000℃ at a heating rate of 3-7℃ / min, and held for 1.5-2.5h for carbonization reduction to generate a vanadium carbide ceramic self-healing layer containing VCB nano self-healing phase. S4. A palladium layer and CeO2 nanoclusters are sequentially formed on the surface of the vanadium carbide ceramic self-healing layer by atomic layer deposition, wherein the thickness of the palladium layer is 50~100nm.

6. The method for preparing the niobium-vanadium carbide-palladium composite foil according to claim 5, characterized in that, The thickness ratio of the vanadium layer to the VCB composite layer in step S1 is 3:

1.

7. The method for preparing the niobium-vanadium carbide-palladium composite foil according to claim 5, characterized in that, The deposition cycle of the CeO2 nanoclusters in step S4 is 50 times, and the thickness is about 5~20nm.

8. The method for preparing the niobium-vanadium carbide-palladium composite foil according to claim 5, characterized in that, Before step S4, a pretreatment step is also included, in which the vanadium carbide ceramic self-healing layer is plasma-cleaned for 5-15 minutes.

9. The application of the niobium-vanadium carbide-palladium composite foil as described in any one of claims 1-4 in hydrogen purification or methanol reforming for hydrogen production in hydrogen fuel cells.

10. Use of the niobium-vanadium carbide-palladium composite foil as described in any one of claims 1-4 in the preparation of a separation membrane for a hydrogen purifier.

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