Vanadium carbide composite material, method of making same, and hydrogen detection applications

Abstract

The present application relates to the field of gas detection, in particular to a vanadium carbide composite material, a preparation method thereof and a hydrogen detection application. The vanadium carbide composite material comprises a V2CT x substrate and Pd nanoparticles loaded on the V2CT x substrate. The V2CT x substrate is a multilayer structure, and at least part of the Pd nanoparticles are loaded between layers of the V2CT x substrate multilayer structure. A hydrogen sensor using the vanadium carbide composite material of the present application can detect hydrogen with high sensitivity and selectivity in a room temperature environment.

Description

Technical Field

[0001] This invention relates to the field of gas detection, specifically to a vanadium carbide composite material, its preparation method, and its application in hydrogen detection. Background Technology

[0002] Hydrogen possesses unique characteristics such as high heat of combustion, environmental friendliness, and abundant reserves, making it an important next-generation clean energy source. However, the flammability and explosive range of hydrogen significantly hinder its application in modern energy systems, necessitating high-performance sensors to mitigate the hazards of hydrogen leaks. Currently, most hydrogen sensors are based on metal-oxide-semiconductor (MOS). MOS-based hydrogen sensors offer advantages such as high sensitivity, short response time, and low detection limits, but their application is limited by high operating temperatures and high power consumption. Pure palladium (Pd) or its alloy nanostructures exhibit low power consumption in hydrogen detection, but suffer from high cost and poor mechanical properties. These limitations restrict their widespread adoption and application. Against this backdrop, designing a room-temperature usable and adaptable hydrogen sensing material is of great significance. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems of high operating temperature, high power consumption (metal oxide semiconductor substrate hydrogen sensors), poor stability, low selectivity, and low sensitivity in existing hydrogen detection technologies. This invention provides a vanadium carbide composite material, a hydrogen sensor, its preparation method, and its application. The hydrogen sensor using the vanadium carbide composite material of this invention can detect hydrogen with high sensitivity and high selectivity at room temperature.

[0004] To achieve the above objectives, the present invention provides a vanadium carbide composite material, wherein the vanadium carbide composite material comprises V2CT. x Substrate and load in the V2CT x Pd nanoparticles on the substrate, the V2CT x The substrate has a multilayer structure, and at least some of the Pd nanoparticles are loaded on the V2CT. x Interlayer space of a multi-layered substrate structure.

[0005] Preferably, the multilayer structure has 20-60 layers.

[0006] Preferably, the V2CT x The substrate thickness is 5-150 nm, preferably 10-100 nm.

[0007] Preferably, the Pd nanoparticles have a particle size of 5-80 nm, more preferably 5-40 nm.

[0008] Preferably, the loading of Pd nanoparticles is 10-60% by weight relative to the total weight of the vanadium carbide composite material.

[0009] Preferably, the Pd nanoparticles are loaded on the V2CT x Substrate surface and the V2CT x Interlayer space of a multi-layered substrate structure.

[0010] According to a second aspect of the present invention, a method for preparing a vanadium carbide composite material is provided, characterized in that the method comprises: under light-shielding conditions, reacting a vanadium carbide composite material containing V2CT... x After the dispersion of nanosheets comes into contact with Pd nanoparticles, the resulting product undergoes a solid-liquid separation process.

[0011] Preferably, the one containing V2CT x The dispersion of nanosheets via V2CT x Nanosheets are obtained by dispersing them in a dispersion medium.

[0012] Preferably, by using V2CT x Nanosheets are obtained by dispersing them in a dispersion medium and then subjecting them to ultrasonication.

[0013] Preferably, the conditions for ultrasound include: power of 100-800W, temperature of 0-40℃, and time of 30-300min.

[0014] Preferably, V2CT x The weight ratio of nanosheets to dispersion medium is 1:50-200.

[0015] Preferably, the dispersion medium is one or more of water, ethanol, methanol and acetone.

[0016] Preferably, the dispersion medium is water and ethanol; more preferably, the volume ratio of ethanol to water is 1-5:1, and more preferably 1-3:1.

[0017] Preferably, the Pd nanoparticles and V2CT x The weight ratio of nanosheets is 0.1-0.6:1, preferably 0.1-0.3:1.

[0018] Preferably, the contact conditions include a temperature of 60-80°C and a time of 6-12 hours.

[0019] Preferably, the solid-liquid separation is centrifugation, and the centrifugation speed is 3000-15000 rpm, preferably 6000-10000 rpm.

[0020] Preferably, the method further includes a step of freeze-drying the solid phase obtained from solid-liquid separation.

[0021] Preferably, the method further includes a step of washing the solid phase obtained from solid-liquid separation with water before freeze-drying it.

[0022] Preferably, the freeze-drying conditions include: a temperature of -70 to -40°C and a time of 6 to 14 hours.

[0023] Preferably, the V2CT x Nanosheets are obtained by etching the precursor V2AlC using hydrofluoric acid or fluoride salts.

[0024] Preferably, the Pd nanoparticles are reduced to H2PdC by a reducing agent. l4 It is obtained from Pd ions in the solution.

[0025] Preferably, the reducing agent is one or more of hydrazine hydrate, sodium citrate, and sodium borohydride, and more preferably sodium citrate or sodium borohydride.

[0026] According to a third aspect of the present invention, a hydrogen sensor is provided, wherein the hydrogen sensor comprises: a sensing film formed on the surface of an electrode, the sensing film containing the vanadium carbide composite material described in the first aspect of the present invention or the vanadium carbide composite material prepared by the method described in the second aspect of the present invention.

[0027] According to a fourth aspect of the present invention, a method for preparing a hydrogen sensor is provided, wherein the method includes the step of coating a vanadium carbide composite material as described in the first aspect of the present invention or a vanadium carbide composite material prepared by the method described in the second aspect of the present invention onto an electrode surface to form a sensing film.

[0028] Preferably, the vanadium carbide composite material is dispersed in an organic solvent and then ground, and the abrasive is coated on the electrode surface to form a sensing film.

[0029] Preferably, the mass ratio of the organic solvent to the vanadium carbide composite material is 1-5:1, and more preferably 1-3:1.

[0030] Preferably, the thickness of the sensing film is 50-2000 μm, and more preferably 100-1000 μm.

[0031] According to a fifth aspect of the present invention, the application of the vanadium carbide composite material described in the first aspect of the present invention or the vanadium carbide composite material prepared by the method described in the second aspect of the present invention in the preparation of a hydrogen sensor is provided.

[0032] Through the above technical solution, the preparation method of vanadium carbide composite material of the present invention is simple to operate, highly stable, and easy to prepare on a large scale. Furthermore, the prepared hydrogen sensor has excellent performance characteristics such as being able to operate at room temperature, low power consumption, high stability, high selectivity, and high sensitivity. Attached Figure Description

[0033] Figure 1 The V2CT obtained in Example 1 x Scanning electron microscope image of nanosheets.

[0034] Figure 2 This is a scanning electron microscope image of the Pd nanoparticles obtained in Example 1.

[0035] Figure 3 This is a scanning electron microscope image of the vanadium carbide composite material obtained in Example 1.

[0036] Figure 4 The curves show the results of the hydrogen sensor made of vanadium carbide composite material obtained in Example 1 changing with different concentrations of hydrogen.

[0037] Figure 5 These are curves showing the resistance changes of hydrogen sensors made of different materials when placed in hydrogen gas of different concentrations.

[0038] Figure 6 These are photographs of the hydrogen sensors made from vanadium carbide composite materials in Examples 2-4. Detailed Implementation

[0039] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0040] A first aspect of the present invention provides a vanadium carbide composite material, wherein the vanadium carbide composite material comprises V2CT. x Substrate and load in the V2CT x Pd nanoparticles on the substrate, the V2CT x The substrate has a multilayer structure, and at least some of the Pd nanoparticles are loaded on the V2CT. x Interlayer space of a multi-layered substrate structure.

[0041] According to the present invention, the V2CT x The substrate has a multi-layer structure. Preferably, the number of layers in the multi-layer structure can be 20-60; more preferably, the number of layers in the multi-layer structure can be 30-50.

[0042] In this invention, the multilayer structure provides an ideal diffusion channel for the rapid diffusion of H2, which is beneficial to the improvement of charge migration, transport and sensing performance.

[0043] According to the present invention, as the V2CT x The substrate thickness is at the nanometer level; preferably, the V2CT... x The substrate thickness is 5-150 nm; more preferably, the V2CT x The substrate thickness is 10-100nm.

[0044] According to the present invention, the Pd nanoparticles are loaded on the V2CT x The surface and interlayer of the substrate, as the particle size of the Pd nanoparticles, are preferably 5-80 nm. In order to allow more Pd nanoparticles to be located in the layers of the multilayer structure, the particle size of the Pd nanoparticles is preferably 5-40 nm.

[0045] In this invention, the Pd nanoparticles provide the active sites required for rapid adsorption and dissociation of H2, which can synergistically accelerate the speed of H2 response.

[0046] According to the present invention, relative to the total weight of the vanadium carbide composite material, preferably, the loading of the Pd nanoparticles is 10-60% by weight, more preferably, the loading of the Pd nanoparticles is 10-30% by weight.

[0047] In this invention, by keeping the content of Pd nanoparticles within the above-mentioned range, sufficient interaction forces can be formed between the Pd nanoparticles and H2 molecules to further improve the high sensitivity to H2.

[0048] According to the present invention, preferably, the Pd nanoparticles are loaded on the V2CT x Substrate surface and the V2CT x Interlayer space within a multilayer substrate structure. This is achieved through V2CT. x The surface of the substrate is loaded with Pd nanoparticles, which allows H2 molecules in the air to rapidly aggregate around the vanadium carbide composite material. This is achieved through V2CT. x Interlayer loading of Pd nanoparticles in a multilayer substrate structure can further enhance sensitivity to H2 molecules. Furthermore, simultaneously in V2CT... x Loading Pd nanoparticles on the substrate surface and between layers of the multilayer structure prevents Pd nanoparticle aggregation on the surface and improves the utilization rate of Pd nanoparticles. Furthermore, the Pd nanoparticles loaded between layers also inhibit V2CT. x The collapse of multi-layered structures enhances their stability.

[0049] Based on the above advantages, the vanadium carbide composite material has the characteristics of high stability and high sensitivity, and has excellent performance in practical applications. It can achieve an ultra-fast response to 1% volume hydrogen gas within 10 seconds at room temperature, with a detection range of 1-40% volume.

[0050] A second aspect of the present invention provides a method for preparing a vanadium carbide composite material, wherein the method includes: under light-shielding conditions, reacting a vanadium carbide composite material containing V2CT... x After the dispersion of nanosheets comes into contact with Pd nanoparticles, the resulting product undergoes a solid-liquid separation process.

[0051] According to the present invention, preferably, the V2CT-containing x The dispersion of nanosheets via V2CT x Nanosheets are obtained by dispersing them in a dispersion medium; more preferably, by using V2CT. x Nanosheets are obtained by dispersing them in a dispersion medium and then subjecting them to ultrasonication.

[0052] By using V2CT x The nanosheets containing V2CT are obtained by ultrasonication after being dispersed in a dispersion medium. x When preparing a dispersion of nanosheets, preferably, the ultrasonic conditions include: power of 100-800W, temperature of 0-40℃, and time of 30-300min; more preferably, the ultrasonic conditions include: power of 300-500W, temperature of 0-20℃, and time of 60-240min.

[0053] According to the present invention, preferably, V2CT x The weight ratio of nanosheets to dispersion medium is 1:50-200; more preferably, V2CT x The weight ratio of nanosheets to dispersion medium is 1:50-100.

[0054] According to the present invention, preferably, the dispersion medium is one or more of water, ethanol, methanol and acetone; more preferably, the dispersion medium is water and ethanol; even more preferably, the volume ratio of ethanol to water is 1-5:1; particularly preferably, the volume ratio of ethanol to water is 1-3:1.

[0055] According to the present invention, the Pd nanoparticles and the V2CT x The weight ratio of the nanosheets is 0.1-0.6:1; preferably, the Pd nanoparticles and the V2CT... x The weight ratio of nanosheets is 0.1-0.3:1.

[0056] According to the present invention, preferably, the contact conditions include a temperature of 60-80°C and a time of 6-12 hours.

[0057] According to the present invention, preferably, the solid-liquid separation is centrifugation, and the centrifugation speed is 3000-15000 rpm, preferably, the centrifugation speed is 6000-10000 rpm.

[0058] According to the present invention, preferably, the method further includes a step of freeze-drying the solid phase obtained from solid-liquid separation. More preferably, the method further includes a step of washing the solid phase obtained from solid-liquid separation with water before freeze-drying;

[0059] According to the present invention, preferably, the freeze-drying conditions include: a temperature of -70 to -40°C and a time of 6 to 14 hours.

[0060] According to the present invention, the V2CT x Nanosheets can be obtained by etching the precursor V2AlC using hydrofluoric acid or fluoride salts.

[0061] Preferably, the mass concentration of the above-mentioned hydrofluoric acid is 10-40% by weight, more preferably 10-30% by weight.

[0062] Preferably, the molar ratio of the fluoride salt to V2AlC is 1-3:1, more preferably 1-2:1.

[0063] Preferably, the etching conditions include: etching time of 10-48 hours and etching temperature of 10-70°C.

[0064] According to the present invention, the Pd nanoparticles can be reduced to H2PdC by a reducing agent. l4 It is obtained from Pd ions in the solution.

[0065] According to the present invention, preferably, the reducing agent is one or more of hydrazine hydrate, sodium citrate and sodium borohydride; more preferably, the reducing agent is sodium citrate or sodium borohydride.

[0066] Because the chemical reduction process is relatively rapid, a protective agent such as polyvinylpyrrolidone is preferably added to prevent palladium particles from agglomerating. The amount of the protective agent added can be 40-80% of the molar amount of V2AlC.

[0067] Preferably, the H2PdC l4 The solvent used in the solution is one or more of triethylene glycol, ethylene glycol, and water.

[0068] Preferably, the reducing agent reacts with the H2PdC l4 H2PdC in solution l4 The molar ratio can be 1-15:1, more preferably 1-10:1.

[0069] A third aspect of the present invention provides a hydrogen sensor, wherein the hydrogen sensor includes: a sensing film formed on the surface of an electrode, the sensing film containing the vanadium carbide composite material described in the first aspect of the present invention or the vanadium carbide composite material prepared by the method described in the second aspect of the present invention.

[0070] The fourth aspect of the present invention provides a method for preparing a hydrogen sensor, wherein the method includes the step of coating a vanadium carbide composite material as described in the first aspect of the present invention or a vanadium carbide composite material prepared by the method described in the second aspect of the present invention onto an electrode surface to form a sensing film.

[0071] According to the present invention, before coating using the coating method, it is preferable to disperse the vanadium carbide composite material in an organic solvent (e.g., ethanol, acetone, glycerol, terpineol, etc.) and then grind it (e.g., in an agate mortar) to ensure uniform dispersion of the vanadium carbide composite material in the organic solvent. The mass ratio of the organic solvent to the vanadium carbide composite material can be 1-5:1, preferably 1-3:1. Too much organic solvent will make the vanadium carbide composite material dispersion too thin, making it impossible to coat onto the electrode. Too little organic solvent will make the vanadium carbide composite material too thick, resulting in uneven distribution of the material coated on the electrode and affecting the gas-sensing performance.

[0072] In this invention, the thickness of the sensing film is preferably 50-2000 μm, more preferably 100-1000 μm.

[0073] The fifth aspect of this invention provides the application of the vanadium carbide composite material described in the first aspect of this invention or the vanadium carbide composite material prepared by the method described in the second aspect of this invention in the preparation of hydrogen sensors.

[0074] The present invention will be described in detail below through embodiments, but the present invention is not limited to the following embodiments.

[0075] Example 1

[0076] 1) Synthesis of V2CT x Nanosheets

[0077] (1) Place 2g of V2AlC powder into 50ml of hydrofluoric acid (40 mol%) aqueous solution, stir at room temperature for 36h, and then centrifuge. After centrifugation, wash with deionized water several times until the pH of the supernatant is 6.

[0078] (2) The product was rinsed again with deionized water, vacuum filtered with a polytetrafluoroethylene membrane with a pore size of 0.22 μm, and then dried in a vacuum drying oven at 70°C for 8 hours.

[0079] (3) The dried powder was placed in deionized water and sonicated at 4°C, and then separated by centrifugation to obtain V2CT. x Nanosheets.

[0080] 2) Pd nanoparticles were prepared by sodium citrate reduction method.

[0081] (1) Add 1.0 ml / 0.03 mol / L H2PdC l4 A 50 ml round-bottom flask is prepared by adding 1.0 ml of a tetraethylene glycol trioxide solution, 1.0 ml of a 0.15 mol / L polyvinylpyrrolidone-tetraethylene glycol solution, 1.0 ml of a 0.045 mol / L sodium citrate-tetraethylene glycol solution, and 7.0 ml of tetraethylene glycol. The flask is then connected to a microwave reactor and rapidly heated for 60 seconds with a mechanical stirrer to obtain a polyvinylpyrrolidone-stabilized palladium nanoparticle colloidal solution.

[0082] (2) The palladium nanoparticle colloidal solution changed from brownish-yellow to dark brownish-black. Adding more than five times the volume of acetone to the colloidal solution and allowing it to stand for a period of time resulted in a viscous black precipitate (its morphology is as follows). Figure 2 (See diagram), wash and dry.

[0083] 3) Preparation of vanadium carbide composite materials

[0084] (1) V2CT x 0.5 g of nanosheets were dispersed in a dispersion medium with a V (ethanol) / V (water) ratio of 3:1 and subjected to ultrasonic treatment. The ultrasonic conditions included: power of 500 W, temperature of 10 °C, and time of 60 min.

[0085] (2) Add 0.1g of Pd nanoparticles, stir in the dark for 2h, and then heat at 60℃ for 4h under reflux;

[0086] (3) Perform solid-liquid separation to remove free Pd nanoparticles. The centrifugation speed is 7000 rpm.

[0087] (4) After washing with deionized water, the vanadium carbide composite material A1 was obtained by freeze drying at -50℃ for 8 hours.

[0088] The vanadium carbide composite material prepared in Example 1 was characterized using a scanning electron microscope (brand: Hitachi, model: SU3800). The V2CT prepared in Example 1... x SEM images of nanosheets are shown below. Figure 1 As shown, the SEM image of the Pd nanoparticles prepared in Example 1 is as follows. Figure 2 As shown, the SEM image of the vanadium carbide composite material prepared in Example 1 is as follows. Figure 3 As shown.

[0089] Depend on Figure 1 It can be seen that V2CT x It consists of layered nanosheets with a thickness of approximately 100 nm, forming a multilayered structure (about 30 layers); Figure 2 It can be seen that the size of the Pd nanoparticles is about 5nm, which is... Figure 3 It can be seen that Pd nanoparticles are loaded onto V2CT xThe nanosheets form a composite material on their surface and between layers.

[0090] Furthermore, semi-quantitative EDS analysis using an energy dispersive spectroscopy (EDS) instrument (brand: Hitachi, model: SU3800) revealed that the loading of the Pd nanoparticles was 15% by weight relative to the total weight of the vanadium carbide composite material.

[0091] Example 2

[0092] 1) Synthesis of V2CT x Nanosheets

[0093] (1) Put 2g of V2AlC powder into a mixed solution of 40ml hydrochloric acid and 3g lithium fluoride, stir at 35℃ for 48h, and then centrifuge. After centrifugation, wash with deionized water several times until the pH of the supernatant is 6.

[0094] (2) The product was rinsed again with deionized water, vacuum filtered with a polytetrafluoroethylene membrane with a pore size of 0.22 μm, and then dried in a vacuum drying oven at 70°C for 8 hours.

[0095] (3) The dried powder was placed in deionized water and sonicated at 4°C, and then separated by centrifugation to obtain V2CT. x Nanosheets.

[0096] 2) Pd nanoparticles were prepared by sodium borohydride reduction method.

[0097] (1) Add 1.0 ml / 0.03 mol / L H2PdC l4 A 100 ml round-bottom flask was prepared by adding 1.0 ml of a 0.15 mol / L polyvinylpyrrolidone-tetraethylene glycol solution and 5.0 ml of a 0.02 mol / L sodium borohydride-tetraethylene glycol solution. The flask was then connected to a microwave reactor and stirred rapidly with a mechanical stirrer for 6 hours to obtain a polyvinylpyrrolidone-stabilized palladium nanoparticle colloidal solution.

[0098] (2) The palladium nanoparticle colloidal solution changed from brownish-yellow to dark brownish-black. Adding more than five times the volume of acetone to the colloidal solution and allowing it to stand for a period of time resulted in a viscous black precipitate (its morphology is as follows). Figure 2 (See diagram), wash and dry.

[0099] 3) Preparation of vanadium carbide composite materials

[0100] (1) V2CT x 0.5 g of nanosheets were dispersed in a dispersion medium with a V(ethanol) / V(water) ratio of 3:1 and subjected to ultrasonic treatment. The ultrasonic conditions included: power of 800 W, temperature of 0 °C, and time of 60 min.

[0101] (2) Add 0.1g of Pd nanoparticles, stir in the dark for 2h, and then heat at 60℃ for 6h under reflux;

[0102] (3) Perform solid-liquid separation to remove free Pd nanoparticles. The centrifugation speed is 10,000 rpm.

[0103] (4) After washing with deionized water, the vanadium carbide composite material A2 was obtained by freeze drying at -50℃ for 8 hours.

[0104] The vanadium carbide composite material prepared in Example 2 was characterized using a scanning electron microscope (Hitachi, model SU3800). The V2CT obtained in Example 2 was analyzed. x SEM images of nanosheets show V2CT x The structure consists of layered nanosheets with a thickness of approximately 80 nm, forming a multilayered structure (about 40 layers). SEM images of the Pd nanoparticles show that their size is approximately 10 nm. SEM images of the vanadium carbide composite material show that Pd nanoparticles are loaded onto V2CT. x The nanosheets form a composite material on their surface and between layers.

[0105] Furthermore, semi-quantitative EDS analysis revealed that the loading of Pd nanoparticles was 18% by weight relative to the total weight of the vanadium carbide composite material.

[0106] Example 3

[0107] 1) Synthesis of V2CT x Nanosheets

[0108] (1) Put 2g of V2AlC powder into a mixed solution of 40ml hydrochloric acid and 3g lithium fluoride, stir at 35℃ for 48h, and then centrifuge. After centrifugation, wash with deionized water several times until the pH of the supernatant is 6.

[0109] (2) The product was rinsed again with deionized water, vacuum filtered with a polytetrafluoroethylene membrane with a pore size of 0.22 μm, and then dried in a vacuum drying oven at 70°C for 8 hours.

[0110] (3) The dried powder was placed in deionized water and sonicated at 0°C, and then separated by centrifugation to obtain V2CT. x Nanosheets.

[0111] 2) Pd nanoparticles were prepared by sodium borohydride reduction method.

[0112] (1) Add 1.0 ml / 0.03 mol / L H2PdC l4A 100 ml round-bottom flask was prepared by adding 1.0 ml of a 0.15 mol / L polyvinylpyrrolidone-tetraethylene glycol solution and 5.0 ml of a 0.02 mol / L sodium borohydride-tetraethylene glycol solution. The flask was then connected to a microwave reactor and stirred rapidly with a mechanical stirrer for 6 hours to obtain a polyvinylpyrrolidone-stabilized palladium nanoparticle colloidal solution.

[0113] (2) The palladium nanoparticle colloidal solution changed from brownish-yellow to dark brownish-black. Adding more than five times the volume of acetone to the colloidal solution and allowing it to stand for a period of time resulted in a viscous black precipitate, which was then washed and dried.

[0114] 3) Preparation of vanadium carbide composite materials

[0115] (1) V2CT x 0.4 g of nanosheets were dispersed in a dispersion medium with a V(ethanol) / V(water) ratio of 4:1 and subjected to ultrasonic treatment. The ultrasonic conditions included: power of 800 W, temperature of 30 °C, and time of 120 min.

[0116] (2) Add 0.1g of Pd nanoparticles, stir in the dark for 2h, and then heat at 60℃ for 6h under reflux;

[0117] (3) Perform solid-liquid separation to remove free Pd nanoparticles. The centrifugation speed is 8000 rpm.

[0118] (4) After washing with deionized water, the vanadium carbide composite material A3 was obtained by freeze drying at -70℃ for 8 hours.

[0119] The vanadium carbide composite material prepared in Example 1 was characterized using a scanning electron microscope (Hitachi, model SU3800). The V2CT obtained in Example 3 was also analyzed. x SEM images of nanosheets show V2CT x The structure consists of layered nanosheets with a thickness of approximately 70 nm, forming a multilayered structure (about 40 layers). SEM images of the Pd nanoparticles show that their size is approximately 13 nm. SEM images of the vanadium carbide composite material show that Pd nanoparticles are loaded onto V2CT. x The nanosheets form a composite material on their surface and between layers.

[0120] Furthermore, semi-quantitative EDS analysis revealed that the loading of the Pd nanoparticles was 22% by weight relative to the total weight of the vanadium carbide composite material.

[0121] Example 4

[0122] 1) Synthesis of V2CT x Nanosheets

[0123] (1) Place 2g of V2AlC powder into 50ml of hydrofluoric acid (40%) aqueous solution, stir at room temperature for 36h, then centrifuge. After centrifugation, wash with deionized water several times until the pH of the supernatant is 6.

[0124] (2) The product was rinsed again with deionized water, vacuum filtered with a polytetrafluoroethylene membrane with a pore size of 0.22 μm, and then dried in a vacuum drying oven at 70°C for 8 hours.

[0125] (3) The dried powder was placed in deionized water and sonicated at 4°C, and then separated by centrifugation to obtain V2CT. x Nanosheets.

[0126] 2) Pd nanoparticles were prepared by sodium citrate reduction method.

[0127] (1) Add 1.0 ml / 0.03 mol / L H2PdC l4 Add 1.0 ml of 0.15 mol / L polyvinylpyrrolidone-ethylene glycol solution, 1.0 ml of 0.045 mol / L sodium citrate-ethylene glycol solution, and 7.0 ml of ethylene glycol solution to a 50 ml round-bottom flask. Connect the flask to a microwave reactor and heat rapidly for 60 s with a mechanical stirrer to obtain a polyvinylpyrrolidone-stabilized palladium nanoparticle colloidal solution.

[0128] (2) The palladium nanoparticle colloidal solution changed from brownish-yellow to dark brownish-black. Five times more acetone was added to the colloidal solution, and after standing for a period of time, a viscous black precipitate was obtained. The precipitate was washed and dried.

[0129] 3) Preparation of vanadium carbide composite materials

[0130] (1) V2CT x 0.4 g of nanosheets were dispersed in a dispersion medium with a V (ethanol) / V (water) ratio of 5:1 and subjected to ultrasonic treatment. The ultrasonic conditions included: power of 500 W, temperature of 20 °C, and time of 60 min.

[0131] (2) Add 0.1g of Pd nanoparticles, stir in the dark for 2h, and then heat at 60℃ for 4h under reflux;

[0132] (3) Perform solid-liquid separation to remove free Pd nanoparticles. The centrifugation speed is 8000 rpm.

[0133] (4) After washing with deionized water, the vanadium carbide composite material A4 was obtained by freeze drying at -60℃ for 10h.

[0134] The vanadium carbide composite material prepared in Example 1 was characterized using a scanning electron microscope (brand: Hitachi, model: SU3800), wherein the V2CT prepared in Example 4... x The SEM images of the nanosheets show that V2CT x It consists of layered nanosheets with a thickness of approximately 90 nm, forming a multilayer structure (about 30 layers). The Pd nanoparticles are approximately 5 nm in size and are loaded onto V2CT. x The nanosheets form a composite material on their surface and between layers.

[0135] Furthermore, semi-quantitative EDS analysis revealed that the loading of the Pd nanoparticles was 22% by weight relative to the total weight of the vanadium carbide composite material.

[0136] Application Example 1

[0137] Take 2 mg of terpineol in a mortar, add 1 mg of vanadium carbide composite material A1 prepared in Example 1, grind thoroughly for 3 minutes, then use a brush to apply a small amount of material to the ceramic tube of the interdigitated gold electrode, and then vacuum dry to form a sensing film to obtain hydrogen sensor B1. The thickness of the formed sensing film is about 500 μm.

[0138] Application Example 2

[0139] Take 2 mg of terpineol in a mortar, add 1 mg of vanadium carbide composite material A2 prepared in Example 2, grind thoroughly for 3 minutes, then use a brush to apply a small amount of material to the ceramic tube of the interdigitated gold electrode, and then vacuum dry to form a sensing film to obtain hydrogen sensor B2. The thickness of the formed sensing film is about 400 μm.

[0140] Application Example 3

[0141] Take 2 mg of terpineol in a mortar, add 1 mg of vanadium carbide composite material A3 prepared in Example 3, grind thoroughly for 3 minutes, then use a brush to apply a small amount of material to the ceramic tube of the interdigitated gold electrode, and then vacuum dry to form a sensing film to obtain hydrogen sensor B3. The thickness of the formed sensing film is about 600 μm.

[0142] Application Example 4

[0143] Take 2 mg of terpineol in a mortar, add 1 mg of vanadium carbide composite material A4 prepared in Example 4, grind thoroughly for 3 minutes, then use a brush to apply a small amount of material to the ceramic tube of the interdigitated gold electrode, and then vacuum dry to form a sensing film to obtain hydrogen sensor B4. The thickness of the formed sensing film is about 500 μm.

[0144] Comparative Example 1

[0145] Take 2 mg of terpineol in a mortar and add 1 mg of V2CT prepared in Example 1.x After grinding the nanosheet material for 3 minutes, a small amount of the material was applied to the ceramic tube of the interdigitated gold electrode using a brush. Then, it was vacuum dried to form a sensing film, resulting in the hydrogen sensor D1. The thickness of the formed sensing film was approximately 300 μm.

[0146] Comparative Example 2

[0147] Take 2 mg of terpineol in a mortar, add 1 mg of Pd nanoparticles prepared in Example 1, grind thoroughly for 3 minutes, then use a brush to apply a small amount of material to the ceramic tube of the interdigitated gold electrode, and then vacuum dry to form a sensing film to obtain hydrogen sensor D2. The thickness of the formed sensing film is about 100 μm.

[0148] Test Example 1

[0149] The hydrogen sensors B1-B4, prepared using the vanadium carbide composite materials described in Examples 1-4, are as follows: Figure 6 The minimum detection limits for hydrogen shown in sensors B1-B4 are similar, all around 1%. The hydrogen sensor B1, made from vanadium carbide composite material in Example 1, uses the V2CT sensor from Comparative Example 1. x Hydrogen sensor D1, made of nanosheet material, and hydrogen sensor D2, made of Pd nanoparticles as described in Comparative Example 2, were placed in hydrogen gas of different concentrations. The changes in their resistance values ​​with varying hydrogen concentrations are shown below. Figure 5 As shown in the curve, B1's performance is significantly better than D1 and D2.

[0150] Depend on Figure 5 It can be seen that the hydrogen sensor B1-B4 made of vanadium carbide composite material can detect hydrogen rapidly (within 20 seconds) with high sensitivity at room temperature, and the response has good reversibility.

[0151] Depend on Figure 5 The comparison of the curves shows that the hydrogen sensing performance of the vanadium carbide composite material is superior to that of the single-component V2CT. x Nanosheets, Pd nanoparticles.

[0152] The hydrogen sensor B1, made of vanadium carbide composite material as described in Example 1, was placed in hydrogen gas of different concentrations. The changes in its resistance over time are shown below. Figure 4 As shown.

[0153] Test Example 2

[0154] Test application example 1: The hydrogen sensor prepared from vanadium carbide composite material responds to interfering gases.

[0155] Interfering gases include: hydrogen sulfide, methane, carbon monoxide, and nitric oxide.

[0156] The hydrogen sensor was placed in hydrogen sulfide gas of different concentrations. The results showed that, at the same concentration, the response intensity of hydrogen sulfide was only 1% of that of hydrogen.

[0157] The hydrogen sensor was placed in methane gas of different concentrations. The results showed that, at the same concentration, the response intensity of methane was only 0.8% of that of hydrogen.

[0158] The hydrogen sensor was placed in carbon monoxide gas of different concentrations. The results showed that, at the same concentration, the response intensity of carbon monoxide was only 0.8% of that of hydrogen.

[0159] The hydrogen sensor was placed in nitric oxide gas of different concentrations. The results showed that, at the same concentration, the response intensity of nitric oxide was only 0.8% of that of hydrogen.

[0160] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A vanadium carbide composite material, characterized in that, The vanadium carbide composite material includes V2CT. x Substrate and load in the V2CT x Pd nanoparticles on the substrate, the V2CT x The substrate has a multilayer structure, and at least some of the Pd nanoparticles are loaded on the V2CT. x Interlayer structure of a multi-layered substrate; The loading of Pd nanoparticles is 10-22% by weight relative to the total weight of the vanadium carbide composite material. The Pd nanoparticles loaded in the V2CT x Substrate surface and the V2CT x Interlayer structure of a multi-layered substrate; The multi-layer structure has 20-60 layers; The preparation method of the vanadium carbide composite material includes: under light-protected conditions, reacting V2CT-containing materials... x After the dispersion of nanosheets comes into contact with Pd nanoparticles, the product after contact is subjected to a solid-liquid separation step. The contact conditions include a temperature of 60-80℃ and a time of 6-12 hours.

2. The vanadium carbide composite material according to claim 1, wherein, The V2CT x The substrate thickness is 5-150nm.

3. The vanadium carbide composite material according to claim 2, wherein, The V2CT x The substrate thickness is 10-100nm.

4. The vanadium carbide composite material according to claim 1, wherein, The particle size of the Pd nanoparticles is 5-80 nm.

5. The vanadium carbide composite material according to claim 4, wherein, The Pd nanoparticles have a particle size of 5-40 nm.

6. A method for preparing the vanadium carbide composite material according to any one of claims 1-5, characterized in that, The method includes: under light-protected conditions, exposing V2CT-containing... x After the dispersion of nanosheets comes into contact with Pd nanoparticles, the product after contact is subjected to a solid-liquid separation step. The contact conditions include a temperature of 60-80℃ and a time of 6-12 hours.

7. The method according to claim 6, wherein, The one containing V2CT x The dispersion of nanosheets via V2CT x Nanosheets are obtained by dispersing them in a dispersion medium.

8. The method according to claim 7, wherein, By using V2CT x Nanosheets are obtained by dispersing them in a dispersion medium and then subjecting them to ultrasonication.

9. The method according to claim 8, wherein, The conditions for the ultrasound include: power of 100-800W, temperature of 0-40℃, and time of 30-300min.

10. The method according to claim 7, wherein, V2CT x The weight ratio of nanosheets to dispersion medium is 1:50-200.

11. The method according to claim 7, wherein, The dispersion medium is one or more of water, ethanol, methanol and acetone.

12. The method according to claim 11, wherein, The dispersion medium is a dispersion medium of water and ethanol.

13. The method according to claim 12, wherein, The volume ratio of ethanol to water is 1-5:

1.

14. The method according to claim 13, wherein, The volume ratio of ethanol to water is 1-3:

1.

15. The method according to claim 6, wherein, The Pd nanoparticles and V2CT x The weight ratio of nanosheets is 0.1-0.6:

1.

16. The method according to claim 15, wherein, The Pd nanoparticles and V2CT x The weight ratio of nanosheets is 0.1-0.3:

1.

17. The method according to claim 6, wherein, The solid-liquid separation is performed by centrifugation, and the centrifugation speed is 3000-15000 rpm.

18. The method according to claim 17, wherein, The centrifugation speed is 6000-10000 rpm.

19. The method according to claim 6, wherein, The method also includes a step of freeze-drying the solid phase obtained from solid-liquid separation.

20. The method according to claim 6, wherein, The method also includes a step of washing the solid phase obtained from solid-liquid separation with water before freeze-drying it.

21. The method according to claim 19, wherein, The freeze-drying conditions include: a temperature of -70 to -40°C and a time of 6 to 14 hours.

22. The method according to claim 6, wherein, The V2CT x Nanosheets are obtained by etching the precursor V2AlC using hydrofluoric acid or fluoride salts.

23. The method according to claim 6, wherein, The Pd nanoparticles are reduced to H2PdC by a reducing agent. l4 It is obtained from Pd ions in the solution.

24. The method according to claim 23, wherein, The reducing agent is one or more of hydrazine hydrate, sodium citrate, and sodium borohydride.

25. The method according to claim 24, wherein, The reducing agent is sodium citrate or sodium borohydride.

26. A hydrogen sensor, characterized in that, The hydrogen sensor includes a sensing membrane formed on the surface of an electrode, the sensing membrane comprising a vanadium carbide composite material as described in any one of claims 1-5.

27. A method for preparing a hydrogen sensor, characterized in that, The method includes the step of coating the vanadium carbide composite material according to any one of claims 1-5 onto the electrode surface to form a sensing film.

28. The method according to claim 27, wherein, The vanadium carbide composite material is dispersed in an organic solvent, then ground, and the abrasive is coated onto the electrode surface to form a sensing film.

29. The method according to claim 28, wherein, The mass ratio of the organic solvent to the vanadium carbide composite material is 1-5:

1.

30. The method according to claim 29, wherein, The mass ratio of the organic solvent to the vanadium carbide composite material is 1-3:

1.

31. The hydrogen sensor according to claim 26, wherein, The thickness of the sensing film is 100-2000 μm.

32. The hydrogen sensor according to claim 31, wherein, The thickness of the sensing film is 50-1000 μm.

33. The application of the vanadium carbide composite material according to any one of claims 1-5 in the preparation of a hydrogen sensor.

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