Preparation method of core-shell nanofiber gas-sensitive material based on platinum-doped cobalt oxide and tin oxide heterostructure

Abstract

The present invention discloses a novel gas-sensitive material, specifically a method for preparing a core-shell nanofiber gas-sensitive material based on a platinum-doped cobalt oxide / tin oxide heterostructure. The present invention utilizes a cobalt source, a tin source, a platinum source, and a polymer as raw materials, and produces a nanoscale platinum-doped cobalt oxide / tin oxide gas-sensitive material with high sensitivity and rapid response to hydrogen sulfide gas via coaxial electrospinning. This gas-sensitive material exhibits excellent gas-sensing properties for H2S gas at room temperature, with a short response time, enabling rapid detection of low-concentration H2S gas, a short recovery time, and excellent cyclic stability. Therefore, the gas-sensitive material of the present invention possesses excellent sensitivity and stability, and has broad application prospects, including applications in environmental monitoring, industrial safety, and gas sensors.

Description

Technical Field

[0001] The present invention relates to the field of gas sensor preparation, and in particular to a core-shell nanofiber gas-sensitive material based on a platinum-doped cobalt oxide-tin oxide heterostructure, a preparation method thereof, and an application thereof in low-concentration hydrogen sulfide detection at room temperature. Background Art

[0002] Hydrogen sulfide (H2S) gas is a toxic pollutant that degrades air quality and harms human health. Its presence in both indoor and outdoor environments is considered a hazard. H2S is commonly generated and released through various human activities, primarily in oil and gas wells, crude oil refining, sulfur springs, coal mines, coal gasification plants, the decomposition of sulfur-containing organic matter, and the food processing industry. H2S is also produced for a variety of applications, including organosulfur synthesis, metallurgical operations, analytical, and catalytic applications. H2S levels as low as 10 ppm are considered harmful to organisms. Concentrations exceeding 10 ppm can cause coma, critical poisoning, personal distress, olfactory dysfunction, organ damage, and interference with mitochondrial function. Furthermore, current H2S gas-sensitive materials generally suffer from high operating temperatures and low response values, limiting their practical applications. Therefore, the development of high-performance room-temperature H2S gas-sensitive materials is essential to ensure the safe use of H2S gas. Summary of the Invention

[0003] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art and to provide a method for preparing a core-shell nanofiber gas-sensitive material based on a platinum-doped cobalt oxide-tin oxide heterostructure, which can effectively detect the concentration of hydrogen sulfide gas in the air of a workplace at room temperature.

[0004] To solve the above technical problems, the present invention adopts the following technical solution: a method for preparing a core-shell nanofiber gas-sensitive material based on a platinum-doped cobalt oxide-tin oxide heterostructure, comprising the following steps:

[0005] S1: mixing chloroplatinic acid solution, cobalt nitrate solution, and dimethylimidazole solution, allowing them to react, and separating the precipitate from the solution to obtain Pt@ZIF-67 crystalline material;

[0006] S2: preparing a shell solution and a core solution; the shell solution is a mixture of a tin source, a polymer, and an organic solvent; the core solution is a mixture of a Pt@ZIF-67 crystal material, a polymer, and an organic solvent;

[0007] S3: adding the shell solution and core solution prepared in S2 to a coaxial electrospinning device for coaxial electrospinning to obtain precursor nanofibers with a Pt-Co@Sn core-shell structure;

[0008] S4: calcining the Pt-Co@Sn core-shell structured precursor nanofibers in S3 to obtain Pt-Co3O4@SnO2 core-shell structured nanofibers.

[0009] Preferably, the solvent of the chloroplatinic acid solution in S1 is anhydrous ethanol; the solvent of the cobalt nitrate solution and the dimethylimidazole solution is methanol; the mass concentrations of the chloroplatinic acid solution, cobalt nitrate solution, and dimethylimidazole solution are 9-11 g / L, 48-52 g / L, and 24-26 g / L, respectively.

[0010] Preferably, the mass ratio of the tin source, polymer, and organic solvent in S2 is 0.4-0.6:1.2-1.6:9-10; the mass ratio of the Pt@ZIF-67 crystal material, polymer, and organic solvent is 0.2-0.3:0.4-0.5:4-5.

[0011] Preferably, the tin source in S2 is one or more of tin acetate, tin nitrate, stannous oxalate, tetraphenyltin, tetrabutyltin, tin dichloride, and tin tetrachloride.

[0012] Preferably, the polymer in S2 is one or more of polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl nitrile, cellulose acetate, and polyacrylonitrile.

[0013] Further preferably, the organic solvent in S2 comprises N,N-dimethylformamide and tetrahydrofuran, and the volume ratio of N,N-dimethylformamide to tetrahydrofuran is 4:1.

[0014] Further preferably, in the coaxial electrospinning of S3, the shell and core layer solutions are prepared using 5 ml syringes, the shell solution syringe advancing speed is 0.004 mm / min, the core layer solution syringe advancing speed is 0.0025 mm / min, the applied voltage is 17-20 kV, and the ambient humidity is controlled at 45-55%.

[0015] More preferably, the calcination temperature in S4 is 500° C. and is kept at this temperature for 2 hours.

[0016] The present invention also provides a core-shell nanofiber gas-sensitive material based on a platinum-doped cobalt oxide and tin oxide heterostructure obtained by the above preparation method.

[0017] The present invention also provides the use of a core-shell nanofiber gas-sensitive material based on a platinum-doped cobalt oxide-tin oxide heterostructure in the detection of low-concentration hydrogen sulfide at room temperature.

[0018] In terms of the molecular structure design of gas-sensitive materials, the present invention adopts the method of constructing heterojunction, doping precious metals, metal-organic framework derivatization, and coaxial electrospinning to prepare Pt-Co3O4@SnO2 core-shell structured nanofibers, which have the following advantages: First, due to the different work functions of the two materials in the heterojunction, charge redistribution is required to achieve balance, which accelerates the movement of electrons, expands the thickness of the depletion layer, and improves the gas-sensitive performance; second, the introduction of precious metals promotes the dissociation of oxygen molecules due to the combined effects of electronic sensitization and chemical sensitization, producing more reactive chemically adsorbed oxygen ions, which then overflow on the surface of the metal oxide and react with more target gas molecules, causing the release of electrons, resulting in a rapid change in resistance, thereby significantly improving the gas sensing performance; third, the semiconductor metal oxide derived from the metal-organic framework using MOF as a self-sacrificing template has regular internal pores, a large specific surface area, and open metal sites, which significantly enhances the gas-sensitive performance and has unique advantages in gas sensing.

[0019] Regarding the synthesis of gas-sensing materials, ZIF-67 is a metal-organic framework (MOF) composed of cobalt ions and 2-methylimidazole ligands. ZIF-67 possesses a unique pore structure and can be efficiently converted into high-surface-area cobalt tetroxide during heat treatment. During calcination, the organic components in ZIF-67 decompose, and the metallic cobalt is oxidized to cobalt oxide (Co3O4), preserving the original porous structure of ZIF-67. This porous structure is crucial for the adsorption and diffusion of gas molecules. Co3O4 and tin oxide (SnO2) react through the interface to form a heterojunction structure, possibly involving Co-O-Sn bonding. This interfacial bonding enhances the charge transfer efficiency and the stability of the heterostructure, contributing to improved gas sensing sensitivity. The introduction of platinum significantly increases the surface catalytic activity of the Co3O4 / SnO2 material, promoting faster reactions of gas molecules on the surface. The presence of platinum can also modulate the electronic structure of the material, improving the sensitivity and response speed of gas detection.

[0020] Regarding the specific preparation methods for gas-sensing materials, the coaxial electrospinning method enables the construction of a core-shell structure at the nanoscale, uniformly distributing platinum-doped cobalt oxide within a tin oxide shell. By adjusting the spinning parameters, the fiber diameter, core-shell ratio, and platinum doping level can be precisely controlled, thereby optimizing the material's gas-sensing performance. The core-shell structure creates a heterojunction effect, enhancing gas molecule adsorption and charge transfer efficiency, thereby improving sensitivity and selectivity for specific gases. Furthermore, platinum doping further improves the material's surface activity, lowers the operating temperature, and enhances response speed and reproducibility. After coaxial electrospinning, the MOF organic template and polymer support remain within the nanofibers. High-temperature calcination completely removes these organic components, preserving the inorganic oxide framework and forming pure cobalt oxide and tin oxide. The calcination process causes the cobalt oxide and tin oxide to transform from an amorphous to a crystalline state, significantly improving the material's stability and conductivity. Furthermore, by manipulating the calcination temperature and time, the material's crystallinity and phase composition can be optimized for optimal gas-sensing performance. During the calcination process, the interface between the platinum-doped cobalt oxide and the tin oxide further solidifies, enhancing the stability of the heterostructure and ensuring the durability of the core-shell structure in practical applications. This step is crucial for ensuring the long-term performance and reproducible response of the material.

[0021] The present invention has the beneficial effects of using a cobalt source, a tin source, a platinum source, and a polymer as raw materials to produce a nanoscale platinum-doped cobalt oxide / tin oxide gas-sensitive material (Pt-Co3O4@SnO2) with high sensitivity and rapid response to hydrogen sulfide gas via coaxial electrospinning. This gas-sensitive material exhibits excellent gas-sensing performance for H2S gas at room temperature, achieving a response value of 15,800 at a H2S concentration of 200 ppb, a response time of 47 seconds, and a recovery time of 8 seconds. This demonstrates superior gas-sensing performance, a short response time, and the ability to rapidly detect low-concentration H2S gas. The recovery time is also short, demonstrating good cyclic stability. Therefore, the gas-sensitive material of the present invention possesses excellent sensitivity and stability and can be widely used for H2S gas detection in fields such as room-temperature environmental monitoring, industrial safety, and gas sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 These are the corresponding curves of Examples 1-4 and Comparative Examples 1-2 for H2S with a gas concentration of 2 ppm at room temperature.

[0023] Figure 2 These are the corresponding curves of Examples 1-4 and Comparative Examples 1-2 for H2S with a gas concentration of 200 ppb at room temperature. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] (1) Preparation of Pt@ZIF-67 crystals: 6.56 g of dimethylimidazole and 5.82 g of cobalt nitrate hexahydrate were dissolved in 250 ml of methanol. The two solutions were then mixed with 10 ml of a 10 g / L chloroplatinic acid solution and stirred for 2 h. The resulting solution was allowed to react at room temperature for 24 h to obtain Pt@ZIF-67 crystals, which were collected by centrifugation and dried for later use.

[0027] (2) Preparation of shell and core layer solutions: To prepare the shell layer solution, 0.6 g of tin tetrachloride pentahydrate and 1.5 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a shell layer solution. To prepare the core layer solution, 0.4 g of dried Pt@ZIF-67 crystals and 1.0 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a core layer solution.

[0028] (3) Coaxial electrospinning: The prepared shell solution and core solution were injected into a coaxial electrospinning device using a 5 ml syringe. The shell solution needle was pushed at a speed of 0.004 mm / min, and the core solution needle was pushed at a speed of 0.0025 mm / min. The voltage was controlled at 18 kV, the collection distance was 15 cm, the collection device speed was 300 rpm, and the ambient humidity was controlled at 45-55%. Under these conditions, Pt-Co@Sn core-shell structure precursor nanofibers were obtained.

[0029] (4) Calcination: The precursor nanofibers were heated to 500 °C in an air atmosphere and kept warm for 2 h to obtain Pt-Co3O4@SnO2 core-shell structure nanofibers, completing the preparation of the gas-sensitive material.

[0030] (5) Test sample preparation: The calcined powder sample was ground in a mortar and then dispersed in a small amount of ethanol. After ultrasonic centrifugation, it was deposited on a gold interdigital electrode and allowed to stand at room temperature until the ethanol evaporated completely. A gas sensor capable of detecting hydrogen sulfide was obtained.

[0031] Example 2

[0032] (1) Preparation of Pt@ZIF-67 crystals: 6.56 g of dimethylimidazole and 5.82 g of cobalt nitrate hexahydrate were dissolved in 250 ml of methanol. The two solutions were then mixed with 15 ml of a 10 g / L chloroplatinic acid solution and stirred for 2 h. The resulting solution was allowed to react at room temperature for 24 h to obtain Pt@ZIF-67 crystals, which were collected by centrifugation and dried for later use.

[0033] (2) Preparation of shell and core layer solutions: To prepare the shell layer solution, 0.6 g of tin tetrachloride pentahydrate and 1.5 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a shell layer solution. To prepare the core layer solution, 0.4 g of dried Pt@ZIF-67 crystals and 1.0 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a core layer solution.

[0034] (3) Coaxial electrospinning: The prepared shell solution and core solution were injected into a coaxial electrospinning device using a 5 ml syringe. The shell solution needle was pushed at a speed of 0.004 mm / min, and the core solution needle was pushed at a speed of 0.0025 mm / min. The voltage was controlled at 18 kV, the collection distance was 15 cm, the collection device speed was 300 rpm, and the ambient humidity was controlled at 45-55%. Under these conditions, Pt-Co@Sn core-shell structure precursor nanofibers were obtained.

[0035] (4) Calcination: The precursor nanofibers were heated to 500 °C in an air atmosphere and kept warm for 2 h to obtain Pt-Co3O4@SnO2 core-shell structure nanofibers, completing the preparation of the gas-sensitive material.

[0036] (5) Test sample preparation: The calcined powder sample was ground in a mortar and then dispersed in a small amount of ethanol. After ultrasonic centrifugation, it was deposited on a gold interdigital electrode and allowed to stand at room temperature until the ethanol evaporated completely. A gas sensor capable of detecting hydrogen sulfide was obtained.

[0037] Example 3

[0038] (1) Preparation of Pt@ZIF-67 crystals: 6.56 g of dimethylimidazole and 5.82 g of cobalt nitrate hexahydrate were dissolved in 250 ml of methanol. The two solutions were then mixed with 20 ml of a 10 g / L chloroplatinic acid solution and stirred for 2 h. The resulting solution was allowed to react at room temperature for 24 h to obtain Pt@ZIF-67 crystals, which were collected by centrifugation and dried for later use.

[0039] (2) Preparation of shell and core layer solutions: To prepare the shell layer solution, 0.6 g of tin tetrachloride pentahydrate and 1.5 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a shell layer solution. To prepare the core layer solution, 0.4 g of dried Pt@ZIF-67 crystals and 1.0 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a core layer solution.

[0040] (3) Coaxial electrospinning: The prepared shell solution and core solution were injected into a coaxial electrospinning device using a 5 ml syringe. The shell solution needle was pushed at a speed of 0.004 mm / min, and the core solution needle was pushed at a speed of 0.0025 mm / min. The voltage was controlled at 18 kV, the collection distance was 15 cm, the collection device speed was 300 rpm, and the ambient humidity was controlled at 45-55%. Under these conditions, Pt-Co@Sn core-shell structure precursor nanofibers were obtained.

[0041] (4) Calcination: The precursor nanofibers were heated to 500 °C in an air atmosphere and kept warm for 2 h to obtain Pt-Co3O4@SnO2 core-shell structure nanofibers, completing the preparation of the gas-sensitive material.

[0042] (5) Test sample preparation: The calcined powder sample was ground in a mortar and then dispersed in a small amount of ethanol. After ultrasonic centrifugation, it was deposited on a gold interdigital electrode and allowed to stand at room temperature until the ethanol evaporated completely. A gas sensor capable of detecting hydrogen sulfide was obtained.

[0043] Example 4

[0044] (1) Preparation of Pt@ZIF-67 crystals: 6.56 g of dimethylimidazole and 5.82 g of cobalt nitrate hexahydrate were dissolved in 250 ml of methanol. The two solutions were then mixed with 20 ml of a 10 g / L chloroplatinic acid solution and stirred for 2 h. The resulting solution was allowed to react at room temperature for 24 h to obtain Pt@ZIF-67 crystals, which were collected by centrifugation and dried for later use.

[0045] (2) Preparation of shell and core layer solutions: To prepare the shell layer solution, 0.6 g of tin tetrachloride pentahydrate and 1.5 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a shell layer solution. To prepare the core layer solution, 0.4 g of dried Pt@ZIF-67 crystals and 1.0 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a core layer solution.

[0046] (3) Coaxial electrospinning: The prepared shell solution and core solution were injected into a coaxial electrospinning device using a 5 ml syringe. The shell solution needle was pushed at a speed of 0.004 mm / min, and the core solution needle was pushed at a speed of 0.0025 mm / min. The voltage was controlled at 18 kV, the collection distance was 15 cm, the collection device speed was 300 rpm, and the ambient humidity was controlled at 45-55%. Under these conditions, Pt-Co@Sn core-shell structure precursor nanofibers were obtained.

[0047] (4) Calcination: The precursor nanofibers were heated to 500 °C in an air atmosphere and kept warm for 2 h to obtain Pt-Co3O4@SnO2 core-shell structure nanofibers, completing the preparation of the gas-sensitive material.

[0048] (5) Test sample preparation: The calcined powder sample was ground in a mortar and then dispersed in a small amount of ethanol. After ultrasonic centrifugation, it was deposited on a gold interdigital electrode and allowed to stand at room temperature until the ethanol evaporated completely. A gas sensor capable of detecting hydrogen sulfide was obtained.

[0049] Comparative Example 1

[0050] (1) Preparation of ZIF-67 crystals: 6.56 g of dimethylimidazole and 5.82 g of cobalt nitrate hexahydrate were dissolved in 250 ml of methanol. The two solutions were mixed and stirred for 2 h. The resulting solution was allowed to react at room temperature for 24 h to obtain ZIF-67 crystals, which were collected by centrifugation and dried for later use.

[0051] (2) Preparation of spinning solution: 0.4 g of dried ZIF-67 crystals and 1.0 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio of 4:1), and stirred evenly to form a spinning solution.

[0052] (3) Electrospinning: The prepared solution was electrospun using a 5 ml syringe at a needle speed of 0.004 mm / min, a control voltage of 18 kV, a collection distance of 15 cm, a collection device speed of 300 rpm, and an ambient humidity of 45-55%. Under these conditions, ZIF-67 / PAN precursor nanofibers were obtained.

[0053] (4) Calcination: The precursor nanofibers were heated to 500 °C in an air atmosphere and kept at this temperature for 2 h to obtain Co3O4 nanofibers, thus completing the preparation of MOF-derived Co3O4 gas-sensitive materials.

[0054] (5) Test sample preparation: The calcined powder sample was ground in a mortar and then dispersed in a small amount of ethanol. After ultrasonic centrifugation, it was deposited on a gold interdigital electrode and allowed to stand at room temperature until the ethanol evaporated completely. A gas sensor capable of detecting hydrogen sulfide was obtained.

[0055] Comparative Example 2

[0056] (1) Preparation of ZIF-67 crystals: 6.56 g of dimethylimidazole and 5.82 g of cobalt nitrate hexahydrate were dissolved in 250 ml of methanol. The two solutions were mixed and stirred for 2 h. The resulting solution was allowed to react at room temperature for 24 h to obtain ZIF-67 crystals, which were collected by centrifugation and dried for later use.

[0057] (2) Preparation of shell and core layer solutions: To prepare the shell layer solution, 0.6 g of tin tetrachloride pentahydrate and 1.5 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a shell layer solution. To prepare the core layer solution, 0.4 g of dried ZIF-67 crystals and 1.0 g of polyacrylonitrile were dissolved in 10 mL of a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio: 4:1), and stirred until uniform and transparent to form a core layer solution.

[0058] (3) Coaxial electrospinning: The prepared shell solution and core solution were injected into a coaxial electrospinning apparatus using 5 ml syringes. The shell solution needle was pushed at a speed of 0.004 mm / min, and the core solution needle was pushed at a speed of 0.0025 mm / min. The voltage was controlled at 18 kV, the collection distance was 15 cm, the collection device speed was 300 rpm, and the ambient humidity was controlled at 45-55%. Under these conditions, Co@Sn core-shell structure precursor nanofibers were obtained.

[0059] (4) Calcination: The precursor nanofibers were heated to 500 °C in an air atmosphere and kept warm for 2 h to obtain Co3O4@SnO2 core-shell structure nanofibers, completing the preparation of the gas-sensitive material.

[0060] (5) Test sample preparation: The calcined powder sample was ground in a mortar and then dispersed in a small amount of ethanol. After ultrasonic centrifugation, it was deposited on a gold interdigital electrode and allowed to stand at room temperature until the ethanol evaporated completely. A gas sensor capable of detecting hydrogen sulfide was obtained.

[0061] The gas sensing performance of the gas sensors prepared in Examples 1-4 and Comparative Examples 1-2 to H2S of different concentrations at room temperature was tested. The test results are shown in Table 1.

[0062] Table 1 Gas sensing performance of different nanomaterial sensors to different concentrations of H2S at room temperature

[0063]

[0064] The response time and recovery time are the time taken to reach 90% of the maximum response and recovery respectively.

[0065] It can be seen from Table 1 that: First, the response values ​​of Examples 1-4 are significantly higher than those of the comparative example, especially the response value of Example 2 at a H2S gas concentration of 200ppb reaches 15800, indicating that its gas-sensing performance is superior. This shows that the Pt-Co3O4@SnO2 structure has good performance in terms of sensitivity to H2S gas. The response time is generally short, with the shortest being 47s in Example 2, indicating that the material has advantages in rapid detection. The recovery time is also maintained in a relatively short range, usually 6-8s, showing good cyclic stability. The presence of Pt may further enhance the catalytic activity of the material, help accelerate the oxidation reaction of H2S, thereby increasing the response speed and response value, proving that the prepared Pt-Co3O4@SnO2 core-shell structure nanofibers can well detect low concentrations (200ppb) of H2S gas, and have significant use value.

[0066] Second, Comparative Example 2 has significant improvements in response value and reaction speed compared to Comparative Example 1, reflecting certain optimization in material design. Although neither has reached the gas-sensing performance level of the embodiment, Comparative Example 2 shows better potential. This is because the design of the core-shell structure can effectively increase the specific surface area of ​​the material, thereby increasing the contact area between the gas molecules and the material, promoting gas adsorption and reaction, and enhancing the sensitivity of the sensor. The improvement of Comparative Example 2 enables it to have certain gas-sensing capabilities in certain applications, while Comparative Example 1 has almost no practical application value. There is still room for improvement in the structural optimization of Comparative Example 2 to further enhance the gas-sensing performance.

[0067] Third, Example 2 exhibits the best gas-sensing performance, but as the amount of Pt added increases, the gas-sensing performance of Examples 3 and 4 shows a declining trend. This is because when the Pt content is too high, it can lead to saturation of catalytic sites, preventing effective adsorption of gas molecules and limiting the reaction rate. Excessive Pt content can cause particle agglomeration, reducing the effective specific surface area and lowering the overall gas-sensing performance of the material.

[0068] In summary, the Pt-Co3O4@SnO2 gas-sensing material prepared in this invention exhibits excellent gas-sensing performance for H2S gas at room temperature, with a short response time, enabling rapid detection of low-concentration H2S gas. It also exhibits a short recovery time and good cycling stability. Therefore, the gas-sensing material of this invention possesses excellent sensitivity and stability and is widely applicable to H2S gas detection in fields such as environmental monitoring, industrial safety, and gas sensors at room temperature.

[0069] The description and drawings of the present invention are considered to be illustrative rather than restrictive. On the basis of the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features according to the disclosed technical content without creative work, and all of them are within the scope of protection of the present invention.

Claims

1. A method for preparing a core-shell nanofiber gas-sensitive material based on a platinum-doped cobalt oxide and tin oxide heterostructure, characterized in that: The following steps are involved: S1: mixing chloroplatinic acid solution, cobalt nitrate solution, and dimethylimidazole solution, allowing them to react, and separating the precipitate from the solution to obtain Pt@ZIF-67 crystalline material; S2: preparing a shell solution and a core solution; the shell solution is a mixture of a tin source, a polymer, and an organic solvent; the core solution is a mixture of a Pt@ZIF-67 crystal material, a polymer, and an organic solvent; S3: adding the shell solution and core solution prepared in S2 to a coaxial electrospinning device for coaxial electrospinning to obtain precursor nanofibers with a Pt-Co@Sn core-shell structure; S4: calcining the Pt-Co@Sn core-shell structured precursor nanofibers in S3 to obtain Pt-Co3O4@SnO2 core-shell structured nanofibers.

2. The preparation method according to claim 1, characterized in that The solvent of the chloroplatinic acid solution in S1 is anhydrous ethanol; the solvent of the cobalt nitrate solution and the dimethylimidazole solution is methanol; the mass concentrations of the chloroplatinic acid solution, cobalt nitrate solution, and dimethylimidazole solution are 9-11 g / L, 48-52 g / L, and 24-26 g / L, respectively.

3. The preparation method according to claim 1, characterized in that The mass ratio of the tin source, polymer, and organic solvent in S2 is 0.4-0.6:1.2-1.6:9-10; the mass ratio of the Pt@ZIF-67 crystal material, polymer, and organic solvent is 0.2-0.3:0.4-0.5:4-5.

4. The preparation method according to claim 1, characterized in that The tin source in S2 is one or more of tin acetate, tin nitrate, stannous oxalate, tetraphenyltin, tetrabutyltin, tin dichloride, and tin tetrachloride.

5. The preparation method according to claim 1, characterized in that The polymer in S2 is one or more of polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl nitrile, cellulose acetate, and polyacrylonitrile.

6. The preparation method according to claim 1, characterized in that The organic solvent in S2 includes N,N-dimethylformamide and tetrahydrofuran, and the volume ratio of N,N-dimethylformamide to tetrahydrofuran is 4:

1.

7. The preparation method according to claim 1, characterized in that In the coaxial electrospinning of S3, the shell and core layer solutions are prepared using 5ml syringes, the shell solution syringe advancing speed is 0.004mm / min, the core layer solution syringe advancing speed is 0.0025mm / min, the applied voltage is 17-20kV, and the ambient humidity is controlled at 45-55%.

8. The preparation method according to claim 1, characterized in that The calcination temperature in S4 is 500° C. and is kept at this temperature for 2 hours.

9. A core-shell nanofiber gas-sensitive material based on a platinum-doped cobalt oxide and tin oxide heterostructure obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the platinum-doped cobalt oxide-tin oxide heterostructure core-shell nanofiber gas-sensitive material according to claim 9 in detecting low-concentration hydrogen sulfide at room temperature.

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