Composite material based on Fe2O3 and Nb2C as well as preparation method and application of composite material

Abstract

The invention relates to the field of gas sensors, and discloses a composite material based on Fe2O3 and Nb2C as well as a preparation method and application thereof. The composite material based on the Fe2O3 and the Nb2C is prepared from the Nb2C and Fe2O3 nano particles loaded on the Nb2C. The composite material based on Fe2O3 and Nb2C has a relatively large specific surface area and excellent catalytic activity, can work under a room temperature condition when being applied to a sensor, is high in response speed to H2S, wide in detectable H2S volume concentration range and low in detection lower limit, and is simple to operate in a preparation process and easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of gas sensors, specifically to a composite material based on Fe2O3 and Nb2C, its preparation method, and its application. Background Technology

[0002] Hydrogen sulfide is a colorless and harmful gas released during the decomposition of sewage sludge, sulfur-containing organic matter, and crude oil refining. Although hydrogen sulfide emits a pungent "rotten egg" odor, due to the dullness of human sense of smell, it is impossible to detect dangerous concentrations of hydrogen sulfide in time. The lethal concentration of hydrogen sulfide is only 120 ppm. Therefore, hydrogen sulfide poisoning accidents are characterized by suddenness, group occurrence, and high mortality rate.

[0003] Among various semiconductor gas sensors, including ZnO, SnO2, Co3O4, CuO, and Fe2O3, Fe2O3-based sensors have broad application prospects due to their advantages such as high sensitivity and low cost. However, existing Fe2O3 sensors have high operating temperature requirements and poor selectivity, which are not conducive to practical applications.

[0004] MXene is a novel two-dimensional material with excellent electrical conductivity, low density, and a stable layered structure. MXene can be used in many industrial applications, such as supercapacitors, photodegradation, solid-state batteries, electromagnetic absorption, and organic molecule adsorption. Due to the large gaps between MXene layers, other nanomaterials can easily penetrate into the layers and form nanocomposite materials. Furthermore, the presence of surface functional groups (-O, -OH, -F) in MXene gives it hydrophilicity, making it easy to form stable colloidal solutions and allowing it to be processed into various structures. Because of these functional groups, it can effectively serve as a functional group for the adsorption of metal cations and gases, and Nb₂C is one of the high-performance and widely used MXene materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of high operating temperature and poor selectivity of existing Fe2O3 hydrogen sulfide sensors, and to provide a composite material based on Fe2O3 and Nb2C. This Fe2O3@Nb2C composite material has a large specific surface area and excellent catalytic activity. When used in sensors, it can operate at room temperature and has a fast response to hydrogen sulfide. It can detect a wide range of hydrogen sulfide volume concentrations with a low detection limit. The preparation process is simple and easy to industrialize.

[0006] To achieve the above objectives, the present invention provides a composite material based on Fe2O3 and Nb2C, wherein the composite material includes Nb2C and Fe2O3 nanoparticles supported on Nb2C.

[0007] Preferably, the content of Fe2O3 nanoparticles is 5-30 wt%, based on the total weight of the Fe2O3 and Nb2C-based composite material.

[0008] Preferably, the thickness of the Nb2C is 5–200 nm, and more preferably 10–100 nm.

[0009] Preferably, the Fe2O3 nanoparticles have a particle size of 5–80 nm, more preferably 5–40 nm.

[0010] A second aspect of the present invention provides a method for preparing a composite material based on Fe2O3 and Nb2C, the method comprising the following steps:

[0011] (1) Mix Fe2O3 nanoparticles, Nb2C and the first solvent;

[0012] (2) The material obtained in step (1) is subjected to solid-liquid separation, and then the obtained solid material is freeze-dried.

[0013] Preferably, in step (1), the weight ratio of Fe2O3 nanoparticles to Nb2C is 0.1 to 0.5:1, more preferably 0.1 to 0.3:1.

[0014] Preferably, in step (1), the weight ratio of Nb2C to the first solvent is 1:50 to 100.

[0015] Preferably, the first solvent is selected from one or more of water, ethanol, acetone and n-hexane.

[0016] Preferably, in step (1), the mixing conditions include: a temperature of 50 to 80°C and a time of 5 to 24 hours.

[0017] Preferably, in step (2), the freeze-drying conditions include: a temperature of -70 to -40°C and a time of 5 to 30 hours.

[0018] Preferably, in step (1), the method for preparing Nb2C includes: mixing Nb2AlC with a solution containing fluoride ions and hydrogen ions and then carrying out a first reaction.

[0019] Preferably, the conditions for the first reaction include: a temperature of 10–50°C and a time of 24–50 h.

[0020] Preferably, in step (1), the preparation method of the Fe2O3 nanoparticles includes: mixing iron salt, urea and water for hydrothermal reaction, followed by solid-liquid separation, and then heat-treating the solid phase material after solid-liquid separation.

[0021] Preferably, the concentration of the iron salt, calculated as iron element, is 0.1–0.8 mol / L.

[0022] Preferably, the concentration of urea is 0.2–1 mol / L.

[0023] Preferably, the molar ratio of iron salt to urea is 1:1 to 3, wherein the iron salt is calculated as iron element.

[0024] Preferably, the hydrothermal reaction conditions include: a temperature of 100–180°C and a time of 5–40 h.

[0025] Preferably, the heat treatment conditions include: a temperature of 450–550°C and a time of 3–5 hours.

[0026] A third aspect of the present invention provides a composite material based on Fe2O3 and Nb2C prepared by the above method.

[0027] The fourth aspect of this invention provides the application of the above-mentioned Fe2O3 and Nb2C-based composite material in hydrogen sulfide detection.

[0028] The fifth aspect of the present invention provides a hydrogen sulfide sensor comprising the aforementioned composite material based on Fe2O3 and Nb2C.

[0029] The sixth aspect of the present invention provides a method for preparing the above-mentioned hydrogen sulfide sensor, the method comprising the following steps: mixing and grinding the above-mentioned composite material based on Fe2O3 and Nb2C with an organic solvent, then coating it onto the surface of a ceramic tube with electrodes and drying it under vacuum so that the composite material based on Fe2O3 and Nb2C forms a sensing film.

[0030] Preferably, the weight ratio of the Fe2O3 and Nb2C-based composite material to the organic solvent is 1:1 to 10; more preferably, it is 1:1 to 5.

[0031] Preferably, the thickness of the sensing film is 100–2000 μm; more preferably, it is 200–1000 μm.

[0032] A seventh aspect of the present invention provides a method for detecting hydrogen sulfide, the method comprising contacting the aforementioned composite material based on Fe2O3 and Nb2C with a mixed gas containing hydrogen sulfide.

[0033] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0034] (1) When the composite material based on Fe2O3 and Nb2C described in this invention is used in a sensor, it can work at room temperature and has a fast response speed to hydrogen sulfide. It can detect a wide range of hydrogen sulfide concentrations and has a low detection limit. It can respond to 0.01ppmH2S within 10s, and the detection range is 0.01ppm~100ppm. This is mainly because Fe2O3 nanoparticles have a large specific surface area, which can quickly adsorb and dissociate hydrogen sulfide as active sites. Secondly, the composite material based on Fe2O3 and Nb2C has distinct layers, which provides an ideal diffusion channel for the rapid diffusion of hydrogen sulfide. Furthermore, Fe2O3 nanoparticles are embedded inside the Nb2C layers, which avoids the aggregation of Fe2O3 nanoparticles and inhibits the collapse of Nb2C, which is beneficial to the improvement of charge migration, transport and sensing performance.

[0035] (2) The method for preparing composite materials based on Fe2O3 and Nb2C described in this invention is simple to operate, easy to industrialize, and conducive to the large-scale production and application of sensors. Attached Figure Description

[0036] Figure 1 This is a scanning electron microscope image of Nb2C prepared in Comparative Example 1;

[0037] Figure 2 This is a scanning electron microscope image of the Fe2O3 nanoparticles prepared in Comparative Example 2;

[0038] Figure 3 This is a scanning electron microscope image of Fe2O3@Nb2C prepared in Example 1;

[0039] Figure 4 This is a graph showing the resistance variation of the hydrogen sulfide sensor prepared in Example 1 in different concentrations of hydrogen sulfide. Detailed Implementation

[0040] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0041] 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.

[0042] In one aspect, the present invention provides a composite material based on Fe2O3 and Nb2C, wherein the composite material includes Nb2C and Fe2O3 nanoparticles supported on Nb2C.

[0043] In a preferred embodiment, to improve the stability and sensitivity to hydrogen sulfide gas of the Fe2O3 and Nb2C-based composite material, the content of the Fe2O3 nanoparticles is 5-30 wt%, based on the total weight of the Fe2O3 and Nb2C-based composite material; specifically, the content of the Fe2O3 nanoparticles can be 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt%.

[0044] In a preferred embodiment, the thickness of the Nb2C is 5–200 nm, preferably 10–100 nm; specifically, the thickness of the Nb2C can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0045] In a preferred embodiment, the Fe2O3 nanoparticles have a particle size of 5–80 nm, preferably 5–40 nm; specifically, the Fe2O3 nanoparticles have a particle size of 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, or 40 nm.

[0046] The Fe2O3 and Nb2C-based composite material described in this invention exhibits good conductivity and stability, along with excellent sensitivity and response to hydrogen sulfide. This is primarily due to the fact that Fe2O3 nanoparticles, acting as active sites, can rapidly adsorb and dissociate hydrogen sulfide. By loading Fe2O3 nanoparticles onto the Nb2C substrate, the sensitivity to hydrogen sulfide can be further enhanced. Furthermore, the embedding of Fe2O3 nanoparticles within the Nb2C layer prevents surface aggregation of Fe2O3 nanoparticles and inhibits Nb2C collapse, which is beneficial for improving charge migration, transport, and sensing performance, while also increasing the utilization rate of the Fe2O3 nanoparticles.

[0047] A second aspect of the present invention provides a method for preparing a composite material based on Fe2O3 and Nb2C, the method comprising the following steps:

[0048] (1) Mix Fe2O3 nanoparticles, Nb2C and the first solvent;

[0049] (2) The material obtained in step (1) is subjected to solid-liquid separation, and then the obtained solid material is freeze-dried.

[0050] In a preferred embodiment, in order to improve the stability of the composite material based on Fe2O3 and Nb2C and its sensitivity to hydrogen sulfide gas, in step (1), the weight ratio of Fe2O3 nanoparticles to Nb2C is 0.1 to 0.5:1, preferably 0.1 to 0.3:1; specifically, the weight ratio of Fe2O3 nanoparticles to Nb2C can be 0.1:1, 0.2:1 or 0.3:1.

[0051] In a preferred embodiment, in order to better disperse Nb2C, in step (1), the weight ratio of Nb2C to the first solvent is 1:50 to 100; specifically, the weight ratio of Nb2C to the first solvent can be 1:50, 1:60, 1:70, 1:80, 1:90 or 1:100.

[0052] In this invention, there are no special requirements for the first solvent; any solvent conventionally used in the art is acceptable. In a preferred embodiment, the first solvent is selected from one or more of water, ethanol, acetone, and n-hexane; in a specific embodiment, the first solvent is water and ethanol, wherein the weight ratio of water to ethanol is 1:1 to 10, preferably 1:1 to 5.

[0053] In a specific embodiment, in order to further disperse Nb2C, in step (1), Nb2C and the first solvent are mixed and then ultrasonicated, and then mixed with Fe2O3 nanoparticles.

[0054] In a preferred embodiment, in step (1), the conditions for ultrasound include: power of 300-800W, temperature of 0-40℃, and time of 10-300min; more preferably, the conditions for ultrasound include: power of 300-600W, temperature of 0-20℃, and time of 60-100min.

[0055] In a preferred embodiment, in order to further improve the stability of the Fe2O3 and Nb2C-based composite material and its sensitivity to hydrogen sulfide gas, the mixing conditions in step (1) include: a temperature of 50-80°C and a time of 5-24h; specifically, the temperature can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, and the time can be 5h, 8h, 12h, 16h, 20h or 24h.

[0056] In a preferred embodiment, in step (2), solid-liquid separation is performed by centrifugation at a speed of 3000-15000 r / min; more preferably, the speed of centrifugation is 6000-10000 r / min.

[0057] In a preferred embodiment, in step (2), the freeze-drying conditions include: a temperature of -70 to -40°C and a time of 5 to 30 hours; specifically, the temperature can be -70°C, -65°C, -60°C, -55°C, -50°C, -45°C, or -40°C; and the time can be 5 hours, 10 hours, 12 hours, 16 hours, 20 hours, 25 hours, or 30 hours.

[0058] In a preferred embodiment, step (1) involves the preparation of Nb2C by mixing Nb2AlC with a solution containing fluoride ions and hydrogen ions and then carrying out a first reaction.

[0059] In a preferred embodiment, the conditions for the first reaction include: a temperature of 10–50°C and a time of 24–50 h; specifically, the temperature can be 10°C, 20°C, 30°C, 35°C, 40°C, or 50°C; and the time can be 24 h, 36 h, 48 h, or 50 h.

[0060] In a preferred embodiment, the method for preparing Nb2C further includes solid-liquid separation, washing, vacuum filtration, drying, ultrasonication, and solid-liquid separation treatment of the material after the first reaction. The solid-liquid separation, washing, drying, and ultrasonication are all conventional methods in the art.

[0061] In a specific implementation, a polytetrafluoroethylene membrane with a pore size of 0.22 μm is used to perform vacuum filtration on the washed material.

[0062] In a specific embodiment, the preparation method of Nb2C includes: mixing Nb2AlC with hydrofluoric acid and reacting it, then performing solid-liquid separation and washing until the pH value of the supernatant is 6, then using a polytetrafluoroethylene membrane with a pore size of 0.22 μm to vacuum filter the washed material, then drying it in a vacuum drying oven, dispersing the dried material in water for ultrasonic treatment, and finally performing solid-liquid separation.

[0063] In this invention, there are no special requirements for the solution containing fluoride ions and hydrogen ions, as long as the fluoride ions and hydrogen ions in the solution can remove the Al atoms in Nb2AlC. For example, it can be a mixture of hydrofluoric acid or inorganic acid and fluoride salt.

[0064] The Nb2C prepared by the above method has a sheet-like microstructure with a thickness of 5-200 nm. This structure is conducive to the embedding of Fe2O3 nanoparticles into the Nb2C layer, avoids the aggregation of Fe2O3 nanoparticles and inhibits the collapse of Nb2C, which is beneficial to the improvement of charge migration, transport and sensing performance, and can also provide an ideal diffusion channel for H2S.

[0065] In a preferred embodiment, in step (1), the method for preparing the Fe2O3 nanoparticles includes: mixing iron salt, urea and water for a hydrothermal reaction, followed by solid-liquid separation, and then heat-treating the solid phase material after solid-liquid separation.

[0066] In a preferred embodiment, the concentration of the iron salt, calculated as elemental iron, is 0.1–0.8 mol / L; specifically, the concentration of the iron salt can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, or 0.8 mol / L.

[0067] In a preferred embodiment, the concentration of urea is 0.2 to 1 mol / L; specifically, the concentration of urea can be 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, or 1 mol / L.

[0068] In a preferred embodiment, the molar ratio of iron salt to urea is 1:1 to 3, wherein the iron salt is calculated as iron element; specifically, the molar ratio of iron salt to urea can be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3.

[0069] In a preferred embodiment, the hydrothermal reaction conditions include: a temperature of 100–180°C and a time of 5–40 h; specifically, the temperature can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C; and the time can be 5 h, 8 h, 12 h, 16 h, 20 h, 24 h, 28 h, 32 h, 36 h, or 40 h.

[0070] In a preferred embodiment, the heat treatment conditions include: a temperature of 450–550°C and a time of 3–5 hours; specifically, the temperature can be 450°C, 500°C, or 550°C; and the time can be 3 hours, 4 hours, or 5 hours.

[0071] In a preferred embodiment, the method for preparing the Fe2O3 nanoparticles further includes washing and drying the solid material before heat treatment after solid-liquid separation, wherein the washing and drying are conventional methods in the art.

[0072] In a specific embodiment, the preparation method of the Fe2O3 nanoparticles includes: mixing iron salt, urea and water, then placing them in a hydrothermal reactor for hydrothermal reaction, separating the solid and liquid products after the hydrothermal reaction, washing them with ethanol and water and drying them in a vacuum drying oven, and finally placing them in a muffle furnace for heat treatment.

[0073] In the preparation method of Fe2O3 nanoparticles of the present invention, there are no special requirements for the iron salt. Any iron salt commonly used in the art can be used, for example, ferric chloride.

[0074] The Fe2O3 nanoparticles prepared by the above method have a large specific surface area and excellent catalytic activity, and can rapidly adsorb and catalyze the reaction of hydrogen sulfide.

[0075] A third aspect of the present invention provides a composite material based on Fe2O3 and Nb2C prepared by the above method.

[0076] The fourth aspect of this invention provides the application of the above-mentioned Fe2O3 and Nb2C-based composite material in hydrogen sulfide detection.

[0077] The fifth aspect of the present invention provides a hydrogen sulfide sensor comprising the aforementioned composite material based on Fe2O3 and Nb2C.

[0078] The sensor prepared by the composite material based on Fe2O3 and Nb2C described in this invention has high sensitivity to hydrogen sulfide and can directly address the problem of monitoring and detecting hydrogen sulfide leaks in the atmospheric environment. It can detect leaked hydrogen sulfide in the environment with high selectivity and speed at room temperature, reduce the hazards caused by hydrogen sulfide leaks, and thus ensure the safety of personnel, environment and equipment.

[0079] The sixth aspect of the present invention provides a method for preparing the above-mentioned hydrogen sulfide sensor, the method comprising the following steps: mixing and grinding the above-mentioned composite material based on Fe2O3 and Nb2C with an organic solvent, then coating it onto the surface of a ceramic tube with electrodes and drying it under vacuum so that the composite material based on Fe2O3 and Nb2C forms a sensing film.

[0080] In a preferred embodiment, the weight ratio of the Fe2O3 and Nb2C-based composite material to the organic solvent is 1:1 to 10; preferably 1:1 to 5. Specifically, the weight ratio of the Fe2O3 and Nb2C-based composite material to the organic solvent can be 1:1, 1:2, 1:3, 1:4, or 1:5. Based on this, the dispersion will not be too thin to coat due to excessive use of organic solvent, nor will the dispersion be too thick due to insufficient use of organic solvent, resulting in uneven coating and affecting the gas-sensing performance of the hydrogen sulfide sensor.

[0081] In this invention, there are no special requirements for the organic solvent; any commonly used solvent in the art is acceptable, such as ethanol, acetone, glycerol, or terpineol.

[0082] In this invention, there are no special requirements for the conditions of vacuum drying; any conditions conventionally applicable in the art are acceptable.

[0083] In a preferred embodiment, to further improve the sensitivity of the hydrogen sulfide sensor, the thickness of the sensing film is 100–2000 μm; preferably 200–1000 μm; specifically, the thickness of the sensing film can be 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm.

[0084] A seventh aspect of the present invention provides a method for detecting hydrogen sulfide, the method comprising contacting the aforementioned composite material based on Fe2O3 and Nb2C with a mixed gas containing hydrogen sulfide.

[0085] When the composite material based on Fe2O3 and Nb2C described in this invention is used to detect hydrogen sulfide, it can operate at room temperature and has a fast response speed to hydrogen sulfide. It can detect a wide range of hydrogen sulfide concentrations and has a low detection limit. It can respond to 0.01ppmH2S within 10s, and the detection range is 0.01ppm to 100ppm.

[0086] The following examples further illustrate the composite material based on Fe2O3 and Nb2C, its preparation method, and its application according to the present invention. The examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0087] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials and instruments used in the following embodiments are commercially available, including a Hitachi SU3800 scanning electron microscope and an energy dispersive spectroscopy (EDS) spectrometer.

[0088] Example 1

[0089] Preparation of Nb2C(S1):

[0090] A1: Add 1.5g Nb2AlC to 30ml of 35% hydrofluoric acid, stir at 30℃ for 24h, then centrifuge, wash with deionized water until the pH of the supernatant is 6, and collect the precipitate.

[0091] A2: The precipitate collected in step A1 was washed again with deionized water, then vacuum filtered using a polytetrafluoroethylene membrane with a pore size of 0.22 μm, and then dried in a vacuum drying oven at 70°C for 24 h.

[0092] A3: Disperse the intermediate material obtained in step A2 in deionized water, sonicate at 30°C for 30 min, and then separate by centrifugation to obtain Nb2C(S1);

[0093] Preparation of Fe2O3 nanoparticles (M1)

[0094] B1: Ferric chloride and urea were dissolved in deionized water, with the concentration of ferric chloride being 0.3 mol / L and the concentration of urea being 0.45 mol / L. The molar ratio of ferric chloride to urea was 1:1.5. The above mixed solution was placed in a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 160°C for 24 h. After the reaction was completed, solid-liquid separation was performed. The solid intermediate was then centrifuged and washed three times with ultrapure water and ethanol. It was placed in a vacuum drying oven at 70°C for 8 h and finally heat-treated in a muffle furnace at 500°C for 4 h to obtain Fe2O3 nanoparticles (M1).

[0095] Preparation of Fe2O3@Nb2C(K1)

[0096] (1) Mix 0.2g Nb2C(S1) and 20g of the first solvent (V(ethanol):V(water) = 4:1) and then perform ultrasonic treatment. The ultrasonic treatment power is 500W, the temperature is 20℃, and the time is 30min. Then add 0.04g of Fe2O3 nanoparticles (M1), stir for 2h under light-protected conditions, and then reflux for 5h at 50℃.

[0097] (2) The above intermediate product was separated into solid and liquid phases by centrifugation at a speed of 8000 r / min. It was then washed with deionized water and freeze-dried at -50℃ for 12 h to obtain Fe2O3@Nb2C(K1) (its microstructure is shown in Figure 1). Figure 3 (as shown);

[0098] Fabrication of sensor (N1)

[0099] Take 4 mg of terpineol in a mortar, add 1 mg of Fe2O3@Nb2C(K1) and grind for 5 min. Then coat it on the surface of the ceramic tube of the interdigitated gold electrode and dry it under vacuum so that Fe2O3@Nb2C(K1) forms a sensing film to obtain the sensor (N1).

[0100] Example 2

[0101] Preparation of Nb2C(S2):

[0102] A1: Add 2g Nb2AlC to 50mL of 9mol / L HCl aqueous solution containing 4g LiF, stir at 40℃ for 36h, then centrifuge, wash with deionized water until the pH of the supernatant is 6, and collect the precipitate.

[0103] A2: The precipitate collected in step A1 was washed again with deionized water, then vacuum filtered using a polytetrafluoroethylene membrane with a pore size of 0.22 μm, and then dried in a vacuum drying oven at 60°C for 10 h.

[0104] A3: Disperse the intermediate material obtained in step A2 in deionized water, sonicate at 25°C for 30 min, and then separate it using a centrifuge to obtain Nb2C(S2);

[0105] Preparation of Fe2O3 nanoparticles (M2)

[0106] B1: Ferric chloride and urea were dissolved in deionized water, with the concentration of ferric chloride being 0.3 mol / L and the concentration of urea being 0.6 mol / L. The molar ratio of ferric chloride to urea was 1:2. The above mixed solution was placed in a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 150°C for 8 hours. After the reaction was completed, solid-liquid separation was performed. The solid intermediate was then washed three times by centrifugation with ultrapure water and ethanol. It was placed in a vacuum drying oven at 70°C for 12 hours and finally heat-treated in a muffle furnace at 480°C for 4 hours to obtain Fe2O3 nanoparticles (M2).

[0107] Preparation of Fe2O3@Nb2C(K2)

[0108] (1) Mix 0.5g Nb2C(S2) and 40g of the first solvent (V(ethanol):V(water) = 6:1) and then sonicate. The sonication power is 800W, the temperature is 30℃ and the time is 20min. Then add 0.15g of Fe2O3 nanoparticles (M2), stir for 2h under light-protected conditions, and then reflux for 5h at 50℃.

[0109] (2) The above intermediate product was separated into solid and liquid by centrifugation at a speed of 7000 r / min. Then it was washed with deionized water and freeze-dried at -60℃ for 12 h to obtain Fe2O3@Nb2C(K2).

[0110] Fabrication of sensor (N2)

[0111] Take 4 mg of terpineol in a mortar, add 1 mg of Fe2O3@Nb2C(K2) and grind for 8 min. Then coat it on the surface of the ceramic tube of the interdigitated gold electrode and dry it under vacuum so that Fe2O3@Nb2C(K2) forms a sensing film to obtain the sensor (N2).

[0112] Example 3

[0113] Preparation of Nb2C(S3):

[0114] A1: Add 2g Nb2AlC to 40mL of 9mol / L HCl aqueous solution containing 3g LiF, stir at 30℃ for 48h, then centrifuge, wash with deionized water until the pH of the supernatant is 6, and collect the precipitate.

[0115] A2: The precipitate collected in step A1 was washed again with deionized water, then vacuum filtered using a polytetrafluoroethylene membrane with a pore size of 0.22 μm, and then dried in a vacuum drying oven at 70°C for 12 h.

[0116] A3: Disperse the intermediate material obtained in step A2 in deionized water, sonicate at 25°C for 30 min, and then separate by centrifugation to obtain Nb2C(S3);

[0117] Preparation of Fe2O3 nanoparticles (M3)

[0118] B1: Ferric chloride and urea were dissolved in deionized water, with the concentration of ferric chloride being 0.3 mol / L and the concentration of urea being 0.75 mol / L. The molar ratio of ferric chloride to urea was 1:2.5. The above mixed solution was placed in a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 150°C for 12 h. After the reaction was completed, solid-liquid separation was performed. The solid intermediate was then centrifuged and washed three times with ultrapure water and ethanol. It was placed in a vacuum drying oven at 70°C for 24 h and finally heat-treated in a muffle furnace at 500°C for 4 h to obtain Fe2O3 nanoparticles (M3).

[0119] Preparation of Fe2O3@Nb2C(K3)

[0120] (1) Mix 0.3g Nb2C(S3) and 25g of the first solvent (V(ethanol):V(water) = 5:1) and then sonicate. The sonication power is 800W, the temperature is 25℃ and the time is 60min. Then add 0.12g of Fe2O3 nanoparticles (M3), stir for 2h under light-protected conditions, and then reflux at 60℃ for 4h.

[0121] (2) The above intermediate product was separated into solid and liquid by centrifugation at a speed of 7000 r / min. Then it was washed with deionized water and freeze-dried at -70℃ for 14 h to obtain Fe2O3@Nb2C(K3).

[0122] Fabrication of sensor (N3)

[0123] Take 5 mg of terpineol in a mortar, add 1 mg of Fe2O3@Nb2C(K3) and grind for 3 min. Then coat it onto the ceramic tube surface of the interdigitated gold electrode to form a sensing film of Fe2O3@Nb2C(K3) after vacuum drying, and obtain the sensor (N3).

[0124] Example 4

[0125] Preparation of Nb2C(S4):

[0126] A1: Add 2g Nb2AlC to 50ml of 35% hydrofluoric acid, stir at 30℃ for 36h, then centrifuge, wash with deionized water until the pH of the supernatant is 6, and collect the precipitate.

[0127] A2: The precipitate collected in step A1 was washed again with deionized water, then vacuum filtered using a polytetrafluoroethylene membrane with a pore size of 0.22 μm, and then dried in a vacuum drying oven at 80°C for 8 hours.

[0128] A3: Disperse the intermediate material obtained in step A2 in deionized water, sonicate at 15°C for 30 min, and then separate it using a centrifuge to obtain Nb2C(S4);

[0129] Preparation of Fe2O3 nanoparticles (M4)

[0130] B1: Ferric chloride and urea were dissolved in deionized water, with the concentration of ferric chloride being 0.3 mol / L and the concentration of urea being 0.54 mol / L. The molar ratio of ferric chloride to urea was 1:1.8. The above mixed solution was placed in a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 160°C for 24 h. After the reaction was completed, solid-liquid separation was performed. The solid intermediate was then centrifuged and washed three times with ultrapure water and ethanol. It was placed in a vacuum drying oven at 60°C for 36 h and finally heat-treated in a muffle furnace at 500°C for 5 h to obtain Fe2O3 nanoparticles (M4).

[0131] Preparation of Fe2O3@Nb2C(K4)

[0132] (1) Mix 0.5g Nb2C(S4) and 45g of the first solvent (V(ethanol):V(water) = 4:1) and then sonicate. The sonication power is 700W, the temperature is 30℃ and the time is 100min. Then add 0.15g of Fe2O3 nanoparticles (M4), stir for 2h under light-protected conditions, and then reflux at 60℃ for 4h.

[0133] (2) The above intermediate product was separated into solid and liquid by centrifugation at a speed of 8000 r / min. Then it was washed with deionized water and freeze-dried at -70℃ for 10 h to obtain Fe2O3@Nb2C(K4).

[0134] Fabrication of sensor (N4)

[0135] Take 5 mg of terpineol in a mortar, add 1 mg of Fe2O3@Nb2C(K4) and grind for 1 min. Then coat it on the surface of the ceramic tube of the interdigitated gold electrode and vacuum dry it so that Fe2O3@Nb2C(K4) forms a sensing film to obtain the sensor (N4).

[0136] Example 5

[0137] The procedure was carried out in accordance with Example 1, except that the amount of Fe2O3 nanoparticles used was 0.01g.

[0138] Example 6

[0139] The procedure was carried out in accordance with Example 1, except that the amount of Fe2O3 nanoparticles used was 0.2g.

[0140] Example 7

[0141] The procedure was carried out in accordance with Example 1, except that the concentration of iron salt was 1 mol / L and the concentration of urea was 1 mol / L.

[0142] Example 8

[0143] The procedure was carried out in accordance with Example 1, except that the concentration of iron salt was 0.1 mol / L and the concentration of urea was 0.1 mol / L.

[0144] Example 9

[0145] The procedure was carried out in accordance with Example 1, except that the concentration of iron salt was 0.1 mol / L and the concentration of urea was 0.5 mol / L.

[0146] Example 10

[0147] The procedure was carried out in accordance with Example 1, except that the amount of the first solvent used was 25g.

[0148] Comparative Example 1

[0149] Preparation of Nb2C(S1):

[0150] A1: Add 1.5g Nb2AlC to 30ml of 35% hydrofluoric acid, stir at 30℃ for 24h, then centrifuge, wash with deionized water until the pH of the supernatant is 6, and collect the precipitate.

[0151] A2: The precipitate collected in step A1 was washed again with deionized water, then vacuum filtered using a polytetrafluoroethylene membrane with a pore size of 0.22 μm, and then dried in a vacuum drying oven at 70°C for 24 h.

[0152] A3: The intermediate material obtained in step A2 was dispersed in deionized water, sonicated at 30°C for 30 min, and then separated by centrifugation to obtain Nb2C(S1) (its microstructure is as follows). Figure 1 (as shown);

[0153] Fabrication of sensor (N11)

[0154] Take 4 mg of terpineol in a mortar, add 1 mg of Nb2C(S1) and grind for 5 min. Then coat it on the surface of the ceramic tube of the interdigitated gold electrode and vacuum dry it so that Nb2C(S1) forms a sensing film to obtain the sensor (N11).

[0155] Comparative Example 2

[0156] Preparation of Fe2O3 nanoparticles (M1)

[0157] B1: Ferric chloride and urea were dissolved in deionized water, with ferric chloride concentration of 0.3 mol / L and urea concentration of 0.45 mol / L, and the molar ratio of ferric chloride to urea was 1:1.5. The above mixed solution was placed in a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 160℃ for 24 h. After the reaction, solid-liquid separation was performed, and the solid intermediate was washed three times by centrifugation with ultrapure water and ethanol. It was then placed in a vacuum drying oven at 70℃ for 8 h, and finally heat-treated in a muffle furnace at 500℃ for 4 h to obtain Fe2O3 nanoparticles (M1) (the microstructure of which is shown in the figure). Figure 2 (as shown);

[0158] Fabrication of sensor (N12)

[0159] Take 4 mg of terpineol in a mortar, add 1 mg of Fe2O3 nanoparticles (M1) and grind for 5 min. Then coat it on the surface of the ceramic tube of the interdigitated gold electrode and vacuum dry it so that the Fe2O3 nanoparticles (M1) form a sensing film to obtain the sensor (N12).

[0160] Test case

[0161] (1) The morphology of the Fe2O3@Nb2C composite material prepared in Example 1, the Nb2C prepared in Comparative Example 1, and the Fe2O3 nanoparticles prepared in Comparative Example 2 were characterized by scanning electron microscopy. Figure 1 This is a scanning electron microscope image of Nb2C prepared in Comparative Example 1. Figure 2 This is a scanning electron microscope image of the Fe2O3 nanoparticles prepared in Comparative Example 2. Figure 3 Scanning electron microscope images of Fe2O3@Nb2C prepared in Example 1 are shown in Table 1. The test results of the thickness of Nb2C and the particle size of Fe2O3 nanoparticles are shown in Table 1.

[0162] Depend on Figure 1 It can be seen that Nb₂C is a layered nanosheet with a thickness of about 100 nm; from Figure 2 It can be seen that the Fe2O3 nanoparticles are spherical with a particle size of about 6 nm; from Figure 3 It can be seen that Fe2O3 nanoparticles are loaded onto Nb2C to form Fe2O3@Nb2C;

[0163] (2) The products prepared in Examples 1-10 and Comparative Examples 1-2 were subjected to semi-quantitative EDS analysis using an energy dispersive spectrometer to calculate the loading of Fe2O3 nanoparticles. The results are shown in Table 1.

[0164] (3) The thickness of the sensing film and the original resistance of the sensors prepared in the test examples and comparative examples were measured. The sensors were then placed in hydrogen sulfide with a concentration of 0.01 ppm, and the resistance change was measured. The results are shown in Table 2. Figure 4 This is a graph showing the change in resistance of the sensor prepared in Example 1 in different concentrations of hydrogen sulfide;

[0165] Depend on Figure 4 It can be seen that the sensor prepared in Example 1 has good sensitivity to hydrogen sulfide, and its resistance changes significantly with the increase of hydrogen sulfide concentration, indicating higher sensitivity.

[0166] (4) Test the response of the sensor prepared by Fe2O3@Nb2C in Example 1 to interfering gases, including carbon dioxide, methane, carbon monoxide and nitric oxide;

[0167] The sensor prepared in Example 1 was placed in carbon dioxide of different volume concentrations. The results showed that, at the same volume concentration, the response intensity of carbon dioxide was only 4% of that of hydrogen sulfide. The sensor prepared in Example 1 was placed in methane gas of different volume concentrations. The results showed that, at the same volume concentration, the response intensity of methane was only 1.8% of that of hydrogen sulfide. The sensor prepared in Example 1 was placed in carbon monoxide gas of different volume concentrations. The results showed that, at the same volume concentration, the response intensity of carbon monoxide was only 1.3% of that of hydrogen. The sensor prepared in Example 1 was placed in nitric oxide gas of different volume concentrations. The results showed that, at the same volume concentration, the response intensity of nitric oxide was only 1.9% of that of hydrogen sulfide.

[0168] The above results indicate that the sensor prepared by Fe2O3@Nb2C in this invention is selective for gases, exhibiting high sensitivity and fast response only when the detected gas is hydrogen sulfide.

[0169] Table 1

[0170]

[0171]

[0172] Table 2

[0173]

[0174] As can be seen from the results in Tables 1 and 2, the Fe2O3@Nb2C described in this invention has a large specific surface area. When the concentration of hydrogen sulfide is 0.01 ppm, the sensor prepared using Fe2O3@Nb2C has excellent sensitivity to hydrogen sulfide, and its resistance changes significantly.

[0175] 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 composite material based on Fe2O3 and Nb2C, characterized in that, The composite material based on Fe2O3 and Nb2C includes Nb2C and Fe2O3 nanoparticles supported on Nb2C.

2. The composite material based on Fe2O3 and Nb2C according to claim 1, characterized in that, Based on the total weight of the composite material based on Fe2O3 and Nb2C, the content of Fe2O3 nanoparticles is 5-30 wt%.

3. The composite material based on Fe2O3 and Nb2C according to claim 1 or 2, characterized in that, The thickness of the Nb2C is 5–200 nm, preferably 10–100 nm.

4. The composite material based on Fe2O3 and Nb2C according to any one of claims 1-3, characterized in that, The Fe2O3 nanoparticles have a particle size of 5–80 nm, preferably 5–40 nm.

5. A method for preparing composite materials based on Fe2O3 and Nb2C, characterized in that, The method includes the following steps: (1) Mix Fe2O3 nanoparticles, Nb2C and the first solvent; (2) The material obtained in step (1) is subjected to solid-liquid separation, and then the obtained solid material is freeze-dried.

6. The method according to claim 5, characterized in that, In step (1), the weight ratio of Fe2O3 nanoparticles to Nb2C is 0.1 to 0.5:1, preferably 0.1 to 0.3:

1.

7. The method according to claim 5 or 6, characterized in that, In step (1), the weight ratio of Nb2C to the first solvent is 1:50 to 100.

8. The method according to claim 7, characterized in that, The first solvent is selected from one or more of water, ethanol, acetone and n-hexane.

9. The method according to claim 7, characterized in that, In step (1), the mixing conditions include a temperature of 50–80°C and a time of 5–24 h.

10. The method according to claim 5, characterized in that, In step (2), the freeze-drying conditions include: a temperature of -70 to -40°C and a time of 5 to 30 hours.

11. The method according to claim 5, characterized in that, In step (1), the method for preparing Nb2C includes: mixing Nb2AlC with a solution containing fluoride ions and hydrogen ions and then carrying out a first reaction.

12. The method according to claim 11, characterized in that, The conditions for the first reaction include: a temperature of 10–50°C and a time of 24–50 h.

13. The method according to claim 5, characterized in that, In step (1), the preparation method of the Fe2O3 nanoparticles includes: mixing iron salt, urea and water for hydrothermal reaction, then separating the solid and liquid phases, and then heat-treating the solid phase material after solid-liquid separation.

14. The method according to claim 13, characterized in that, The concentration of iron salts, calculated as elemental iron, is 0.1–0.8 mol / L.

15. The method according to claim 13 or 14, characterized in that, The concentration of urea is 0.2–1 mol / L.

16. The method according to claim 13, characterized in that, The molar ratio of iron salt to urea is 1:1 to 3, where the iron salt is calculated as iron element.

17. The method according to any one of claims 13-16, characterized in that, The conditions for hydrothermal reaction include a temperature of 100–180℃ and a time of 5–40 h.

18. The method according to claim 17, characterized in that, The heat treatment conditions include a temperature of 450–550℃ and a time of 3–5 hours.

19. The Fe2O3 and Nb2C based composite material prepared by the method of any one of claims 5-18.

20. The application of the Fe2O3 and Nb2C based composite material according to any one of claims 1-4 and 19 in the detection of hydrogen sulfide.

21. A hydrogen sulfide sensor, characterized in that, The hydrogen sulfide sensor comprises the composite material based on Fe2O3 and Nb2C as described in any one of claims 1-4 and 19.

22. A method for preparing the hydrogen sulfide sensor of claim 21, characterized in that, The method includes the following steps: mixing and grinding the Fe2O3 and Nb2C-based composite material according to any one of claims 1-4 and 19 with an organic solvent, then coating it onto the surface of a ceramic tube with electrodes and drying it under vacuum to form a sensing film from the Fe2O3 and Nb2C-based composite material.

23. The method according to claim 22, characterized in that, The weight ratio of the Fe2O3 and Nb2C-based composite material to the organic solvent is 1:1 to 10; preferably 1:1 to 5.

24. The method according to claim 22 or 23, characterized in that, The thickness of the sensing film is 100–2000 μm; preferably 200–1000 μm.

25. A method for detecting hydrogen sulfide, characterized in that, The method involves contacting the Fe2O3 and Nb2C-based composite material as described in any one of claims 1-4 and 19 with a mixed gas containing hydrogen sulfide.

Images