Gas Sensing Material for Monitoring Characteristic Substance CO of Environmental Protection Gas, Preparation Method and Application

Abstract

The present invention discloses a gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas, a preparation method and an application, which relate to the technical field of gas-sensitive materials. The preparation method includes: dissolving tin tetrachloride pentahydrate, sodium hydroxide and polyvinylpyrrolidone, adding ammonium fluoride, reacting at 155 °C to 165 °C, and calcining the product at 295 °C to 305 °C after drying to obtain SnO2 nanoparticles; ultrasonically mixing the deionized water dispersion of SnO2 and the ethylene glycol dispersion of MoS2 nanosheets, and then drying to obtain a MoS2 / SnO2 composite material with a mesoporous hollow nanotube structure, wherein the volume ratio of ethylene glycol to deionized water is 0.9 to 1.1:1. The MoS2 / SnO2 gas-sensitive material of the present invention has the advantages of low density, high pore volume, large specific surface area, strong structural stability, etc. When applied to a CO resistive sensor, it has good selectivity for CO, high sensitivity, and good long-term stability.

Description

Technical Field

[0001] The present invention relates to the technical field of gas-sensitive materials, and in particular to a gas-sensitive material for monitoring an environmentally friendly gas characteristic substance CO, a preparation method and an application thereof. Background Art

[0002] SF6 is the most widely used insulating gas in the power industry, but due to its strong greenhouse effect, people have been looking for alternative gases in recent years, including C4F7N, C5F 10 O has attracted wide attention due to its good insulation performance and environmentally friendly nature. However, in actual application scenarios, some C4F7N, C5F 10 O gas will decompose to form a series of fluorocarbons. Due to the presence of trace amounts of water and oxygen in the equipment, these fluorocarbons will further react to form by-products, which will lead to a decrease in the insulation performance of the gas, causing electrical equipment failures and even threatening the stable operation of the power grid.

[0003] CO is environmentally friendly C4F7N, C5F 10 O mixed gas is one of the stable byproducts generated under fault conditions. Therefore, monitoring the generation of CO can diagnose the fault decomposition of insulating gas and provide timely warning to prevent further expansion of accidents. The traditional method of using GCMS to detect CO cannot meet the miniaturization and real-time nature of on-site detection due to its large footprint and cumbersome operation method. The low cost, low power consumption and small size of resistive sensors bring hope for the online monitoring of CO and are expected to meet the needs of daily real-time monitoring.

[0004] Gas-sensitive materials are the core of resistive gas sensors and are also the bottleneck for the practical application of such sensors at this stage. Existing resistive sensors for monitoring CO have the defects of high device weight, low sensitivity, and stability and selectivity that need to be improved. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0006] To this end, the first aspect of the present invention provides a method for preparing a gas-sensitive material for monitoring environmental gas characteristic CO, comprising:

[0007] Dissolve tin tetrachloride pentahydrate, sodium hydroxide and polyvinyl pyrrolidone to obtain a clear mixed solution, add ammonium fluoride to the mixed solution, react at 155°C to 165°C for 23h to 25h, and then naturally cool to room temperature, wash the reaction product, dry it, and then calcine it at 295°C to 305°C to obtain SnO2 nanoparticles;

[0008] Disperse the SnO2 nanoparticles in deionized water to obtain a SnO2 dispersion, disperse the MoS2 nanosheets in ethylene glycol to obtain a MoS2 nanosheet dispersion, ultrasonically mix the SnO2 dispersion and the MoS2 nanosheet dispersion, and then dry to obtain a MoS2 / SnO2 composite material; wherein, the volume ratio of the ethylene glycol to the deionized water is (0.9~1.1):1, and the microstructure of the MoS2 / SnO2 composite material is a hollow nanotube structure with mesopores.

[0009] Further, in the MoS2 / SnO2 composite material, the mass fraction of MoS2 is 1%~5%, and the mass fraction of SnO2 is 95%~99%.

[0010] Further, for the ultrasonic mixing, the ultrasonic temperature is 80°C~120°C, and the ultrasonic time is 1h~2h.

[0011] Further, it also includes: dissolving the tin tetrachloride pentahydrate, the sodium hydroxide and the polyvinylpyrrolidone in an ethanol aqueous solution, and stirring to obtain a clear mixed solution; wherein, the mass ratio of the tin tetrachloride pentahydrate, the sodium hydroxide and the polyvinylpyrrolidone is (3.5~3.7):(2.3~2.5):1, and the volume concentration of ethanol in the ethanol aqueous solution is 45%~55%.

[0012] Further, the addition amount of ammonium fluoride is 0.09wt%~0.11wt% of the mixed solution.

[0013] In the second aspect of the present invention, a gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas is provided, which is the MoS2 / SnO2 composite material prepared by the above preparation method.

[0014] In the third aspect of the present invention, an application of a gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas is provided, and the above gas-sensitive material is used to prepare a resistive sensor for CO.

[0015] Further, the resistive sensor for CO is used to monitor the environmental protection insulating gas C4F7N and / or the decomposition component CO of the environmental protection insulating gas C5F 10 O.

[0016] Further, the preparation method of the resistive sensor for CO includes:

[0017] Add the MoS2 / SnO2 composite material into deionized water, ultrasonically disperse to obtain a MoS2 / SnO2 suspension, and uniformly coat the MoS2 / SnO2 suspension on the electrode surface of the resistive sensor for CO, and dry it; wherein, the concentration of the MoS2 / SnO2 suspension is 14mg / mL~16mg / mL.

[0018] Further, the coating thickness of the MoS2 / SnO2 composite material is 40 μm to 60 μm.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The preparation method of the gas-sensitive material for monitoring the characteristic substance CO of the environmental protection gas provided by the present invention, on the one hand, regulates the morphology of SnO2 nanoparticles through ammonium fluoride, and obtains single SnO2 nanoparticles with a particle size less than 40 nm that stably exist; on the other hand, by controlling the volume ratio of deionized water in the SnO2 dispersion liquid to ethylene glycol in the MoS2 dispersion liquid, the optimal fusion effect of SnO2 nanoparticles and MoS2 nanosheets is obtained, and a MoS2 / SnO2 composite material with a mesoporous hollow nanotube structure is obtained. This composite material has the advantages of low density, high pore volume, large specific surface area, and strong structural stability. It is used to monitor the decomposition component CO of the environmental protection insulating gas C4F7N and / or the environmental protection insulating gas C5F 10 O, and is applied to a CO resistive sensor, which is beneficial to reducing the weight of the device, has good selectivity for CO, high sensitivity, and good long-term stability. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0022] Figure 1a It is the SEM micrograph of SnO2 prepared in Example 1 (ammonium fluoride ratio 0.1 wt%) of the present invention.

[0023] Figure 1b It is the SEM micrograph of SnO2 prepared by adding 0.1 wt% sodium citrate for regulation in the embodiment provided by the present invention.

[0024] Figure 1c It is the SEM micrograph of SnO2 prepared by adding 0.1 wt% sodium dodecyl sulfate for regulation in the embodiment provided by the present invention.

[0025] Figure 2a It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared in Example 1 of the present invention.

[0026] Figure 2b It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared with NMP as the dispersion solvent of MoS2 nanosheets in the embodiment provided by the present invention.

[0027] Figure 2c It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared with DMF as the dispersion solvent of MoS2 nanosheets provided by the embodiment of the present invention.

[0028] Figure 3a It is the SEM micrograph of SnO2 prepared in Comparative Example 1 of the present invention.

[0029] Figure 3b It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared in Comparative Example 1 of the present invention.

[0030] Figure 4a It is the SEM micrograph of SnO2 prepared in Comparative Example 2 of the present invention.

[0031] Figure 4b It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared in Comparative Example 2 of the present invention.

[0032] Figure 5 It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared in Comparative Example 3 of the present invention.

[0033] Figure 6 It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared in Comparative Example 4 of the present invention.

[0034] Figure 7 It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared in Comparative Example 5 of the present invention.

[0035] Figure 8 It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared in Comparative Example 6 of the present invention.

[0036] Figure 9 It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared in Comparative Example 7 of the present invention.

[0037] Figure 10 It is the SEM micrograph of the MoS2 / SnO2 gas-sensitive material prepared in Comparative Example 8 of the present invention.

[0038] Figure 11 It is the response curve of the CO sensor prepared with the MoS2 / SnO2 composite material of Example 1 of the present invention to different concentrations of CO, the characteristic decomposition component of C5F 10 O gas.

[0039] Figure 12 It is the CO sensor prepared with the MoS2 / SnO2 composite material of Comparative Example 1 of the present invention for C5F 10Response curve of the decomposition component CO (50 ppm) of O gas.

[0040] Figure 13 The CO sensor prepared with the MoS2 / SnO2 composite material of Comparative Example 2 of the present invention for C5F 10 Response curve of the decomposition component CO (50 ppm) of O gas.

[0041] Figure 14 The CO sensor prepared with the MoS2 / SnO2 composite material of Comparative Example 3 of the present invention for C5F 10 Response curve of the decomposition component CO (50 ppm) of O gas.

[0042] Figure 15 The CO sensor prepared with the MoS2 / SnO2 composite material of Comparative Example 4 of the present invention for C5F 10 Response curve of the decomposition component CO (50 ppm) of O gas.

[0043] Figure 16 The CO sensor prepared with the MoS2 / SnO2 composite material of Comparative Example 5 of the present invention for C5F 10 Response curve of the decomposition component CO (50 ppm) of O gas.

[0044] Figure 17 The CO sensor prepared with the MoS2 / SnO2 composite material of Comparative Example 6 of the present invention for C5F 10 Response curve of the decomposition component CO (50 ppm) of O gas.

[0045] Figure 18 The CO sensor prepared with the MoS2 / SnO2 composite material of Comparative Example 7 of the present invention for C5F 10 Response curve of the decomposition component CO (50 ppm) of O gas.

[0046] Figure 19 The CO sensor prepared with the MoS2 / SnO2 composite material of Comparative Example 8 of the present invention for C5F 10 Response curve of the decomposition component CO (50 ppm) of O gas.

[0047] Figure 20 The selectivity schematic diagram of the decomposition component of O gas by the CO sensor prepared with the MoS2 / SnO2 composite material of Example 1 of the present invention for C5F 10 Selectivity schematic diagram of the decomposition component of O gas.

[0048] Figure 21The long-term stability data graph of CO, a characteristic decomposition component of C5F 10 O gas, detected by the CO sensor prepared with the MoS2 / SnO2 composite material of Example 1 and Comparative Examples 1-8 of the present invention. Specific Embodiments

[0049] To better understand the above technical solutions, the technical solutions of the embodiments of the present application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific features in the embodiments of the present application and the embodiments are detailed descriptions of the technical solutions of the embodiments of the present application, rather than limitations on the technical solutions of the present application. Without conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0050] In the first aspect of the embodiments of the present invention, a method for preparing a gas-sensitive material for monitoring a characteristic substance CO of an environmental protection gas is provided, including:

[0051] Dissolve stannous chloride pentahydrate, sodium hydroxide, and polyvinylpyrrolidone to obtain a clear mixed solution. Add ammonium fluoride to the mixed solution, react at 155°C to 165°C for 23h to 25h, then naturally cool to room temperature, wash the reaction product, dry it, and calcine it at 295°C to 305°C to obtain SnO2 nanoparticles;

[0052] Disperse the SnO2 nanoparticles in deionized water to obtain a SnO2 dispersion, disperse MoS2 nanosheets in ethylene glycol to obtain a MoS2 nanosheet dispersion, ultrasonically mix the SnO2 dispersion and the MoS2 nanosheet dispersion, and then dry it to obtain a MoS2 / SnO2 composite material; wherein, the volume ratio of the ethylene glycol to the deionized water is (0.9 to 1.1):1, and the microscopic morphology of the MoS2 / SnO2 composite material is a hollow nanotube structure with mesopores.

[0053] The method for preparing a gas-sensitive material for monitoring a characteristic substance CO of an environmental protection gas provided by the embodiments of the present invention, on the one hand, regulates the morphology of SnO2 nanoparticles through ammonium fluoride to obtain single SnO2 nanoparticles with a particle size less than 40nm that stably exist; on the other hand, by controlling the volume ratio of deionized water in the SnO2 dispersion to ethylene glycol in the MoS2 dispersion, the optimal fusion effect of SnO2 nanoparticles and MoS2 nanosheets is obtained, and a MoS2 / SnO2 composite material with a hollow nanotube structure with mesopores (on the wall of the hollow nanotube aggregated by nanoparticles, and there are mesopores on the wall) is obtained. This composite material has the advantages of low density, high pore volume, large specific surface area, and strong structural stability.

[0054] In a feasible implementation, in the MoS2 / SnO2 composite material, the mass fraction of MoS2 is 1% - 5%, and the mass fraction of SnO2 is 95% - 99%.

[0055] In a feasible implementation, for the ultrasonic mixing, the ultrasonic temperature is 80°C - 120°C, and the ultrasonic time is 1h - 2h.

[0056] Specifically, we optimized the ultrasonic temperature and time for the fusion of MoS2 and SnO2 and found that the ultrasonic temperature is 80°C - 120°C. When the temperature is lower than 80°C or higher than 120°C, effective fusion cannot occur, and when the temperature is higher than 120°C, there is a risk of boiling. The preferred ultrasonic temperature is 90°C - 110°C. The ultrasonic time is 1h - 2h. When the time is less than 1h, the fusion of MoS2 and SnO2 is not completed. When the time is too long, it is uneconomical and has no obvious effect on increasing the yield. The preferred ultrasonic time is 60min - 70min.

[0057] In a feasible implementation, it further includes: dissolving the tin tetrachloride pentahydrate, the sodium hydroxide, and the polyvinylpyrrolidone in an ethanol aqueous solution, and stirring to obtain the clear mixed solution; wherein, the mass ratio of the tin tetrachloride pentahydrate, the sodium hydroxide, and the polyvinylpyrrolidone is (3.5 - 3.7):(2.3 - 2.5):1, and the volume concentration of ethanol in the ethanol aqueous solution is 45% - 55%.

[0058] In a feasible implementation, the addition amount of ammonium fluoride is 0.09wt% - 0.11wt% of the mixed solution.

[0059] Specifically, we found in the experiment that by controlling the addition amount of ammonium fluoride in the mixed solution, the morphology of SnO2 can be regulated. When the addition amount of ammonium fluoride is 0.09wt% - 0.11wt% of the mixed solution, the prepared SnO2 can form stable single particles with a particle size less than 40nm and a high yield.

[0060] In the second aspect of the embodiments of the present invention, a gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas is provided, which is the MoS2 / SnO2 composite material prepared by the above preparation method.

[0061] In the third aspect of the embodiments of the present invention, an application of a gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas is provided, and the above gas-sensitive material is used to prepare a resistive sensor for CO.

[0062] In a feasible implementation, the resistive sensor for CO is used to monitor the environmental protection insulating gas C4F7N and / or the decomposition component CO of the environmental protection insulating gas C5F 10 O.

[0063] The detection principle of the MoS2 / SnO2 composite material for CO lies in:

[0064] When the MoS2 / SnO2 composite material is exposed to air, the surface of the gas-sensitive material will absorb O2 molecules in the air and transport electrons to form oxygen anions:

[0065]

[0066]

[0067] This will lead to the formation of a depletion layer and a high-resistance state on the surface of the gas-sensitive material. When the reducing gas CO is introduced, the CO molecules on the surface of the sensing material will react with O2:

[0068]

[0069] During this reaction process, CO will release electrons to the gas-sensitive material, resulting in a decrease in resistance.

[0070] In a feasible implementation manner, the preparation method of the resistive sensor for CO includes:

[0071] Adding the MoS2 / SnO2 composite material into deionized water, ultrasonically dispersing it to obtain a MoS2 / SnO2 suspension, and uniformly coating the MoS2 / SnO2 suspension on the electrode surface of the resistive sensor for CO, and then drying it; wherein, the concentration of the MoS2 / SnO2 suspension is 14 mg / mL to 16 mg / mL.

[0072] Specifically, through experiments, we obtained that a concentration of 14 mg / mL to 16 mg / mL of the MoS2 / SnO2 suspension is suitable for coating and drying. If the concentration is too low, it will cause too much suspension required for coating, which is not conducive to subsequent drying; if the concentration is too high, it will cause the suspension to be dense, which is not conducive to uniform coating.

[0073] In a feasible implementation manner, the coating thickness of the MoS2 / SnO2 composite material is 40 μm to 60 μm.

[0074] Specifically, a coating thickness lower than 40 μm will result in poor material strength and easy fracture, and a coating thickness higher than 60 μm will result in tight bonding between the bottom layer material and the electrode, but the surface layer material is easy to fall off.

[0075] The following will elaborate on the present invention in combination with specific experimental processes and examples, but they should not be construed as limiting the protection scope of the present invention.

[0076] (I) Investigation of the morphology regulator in the preparation of SnO2 nanoparticles

[0077] We separately selected ammonium fluoride, sodium citrate, and sodium dodecyl sulfate as morphology regulators for the preparation of SnO2 nanoparticles for experiments, as follows.

[0078] (1) Ammonium fluoride

[0079] The preparation of SnO2 nanoparticles includes the following steps: Dissolve 0.9 g of tin tetrachloride pentahydrate, 0.6 g of sodium hydroxide, and 0.25 g of polyvinylpyrrolidone in 20 ml of an ethanol aqueous solution (the volume ratio of ethanol to deionized water is 1:1), stir for 1 h to obtain a clear mixture, then add ammonium fluoride in a proportion of 0.1 wt%, react at 160 °C for 24 h, naturally cool to room temperature, wash the reaction product with deionized water and ethanol, dry at 80 °C for 12 h, and then calcine at 300 °C for 1 h to obtain SnO2 nanoparticles. As Figure 1a shown, by adding ammonium fluoride, the synthesis of SnO2 nanoparticles was successful, stable single particles could be formed, and the yield was higher.

[0080] (2) Sodium citrate

[0081] The preparation of SnO2 nanoparticles includes the following steps: Dissolve 0.9 g of tin tetrachloride pentahydrate, 0.6 g of sodium hydroxide, and 0.25 g of polyvinylpyrrolidone in 20 ml of an ethanol aqueous solution (the volume ratio of ethanol to deionized water is 1:1), stir for 1 h to obtain a clear mixture, then add sodium citrate in a proportion of 0.1 wt%, react at 160 °C for 24 h, naturally cool to room temperature, wash the reaction product with deionized water and ethanol, dry at 80 °C for 12 h, and then calcine at 300 °C for 1 h to obtain SnO2 nanoparticles. As Figure 1b shown, by adding sodium citrate, the synthesis of SnO2 nanoparticles failed, presenting a cheese-like morphology.

[0082] (3) Sodium dodecyl sulfate

[0083] The preparation of SnO2 nanoparticles includes the following steps: Dissolve 0.9 g of tin tetrachloride pentahydrate, 0.6 g of sodium hydroxide, and 0.25 g of polyvinylpyrrolidone in 20 ml of an ethanol aqueous solution (the volume ratio of ethanol to deionized water is 1:1), stir for 1 h to obtain a clear mixture, then add sodium dodecyl sulfate in a proportion of 0.1 wt%, react at 160 °C for 24 h, naturally cool to room temperature, wash the reaction product with deionized water and ethanol, dry at 80 °C for 12 h, and then calcine at 300 °C for 1 h to obtain SnO2 nanoparticles. As Figure 1c shown, by adding sodium dodecyl sulfate, the synthesis of SnO2 nanoparticles failed, presenting large irregular plate-like products like a turtle's back.

[0084] Therefore, this application selects ammonium fluoride as the morphology regulator for the preparation of SnO2 nanoparticles.

[0085] (2) Investigation of the Dispersing Solvent for MoS2 Nanosheets

[0086] We separately selected ethylene glycol, N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF) as the dispersing solvents for MoS2 nanosheets and mixed them with the aqueous dispersion of SnO2. The preparation method of SnO2 nanoparticles was as follows: Dissolve 0.9 g of stannic chloride pentahydrate, 0.6 g of sodium hydroxide, and 0.25 g of polyvinylpyrrolidone in 20 ml of an ethanol aqueous solution (the volume ratio of ethanol to deionized water was 1:1), stir for 1 h to obtain a clear mixture, then add ammonium fluoride at a ratio of 0.1 wt%, react at 160 °C for 24 h, naturally cool to room temperature, wash the reaction product with deionized water and ethanol, dry at 80 °C for 12 h, and then calcine at 300 °C for 1 h to obtain SnO2 nanoparticles, as Figure 1a shown.

[0087] (1) Ethylene glycol

[0088] Disperse 99 mg of the obtained SnO2 nanoparticles in 5 mL of deionized water, and disperse 1 mg of MoS2 nanosheets in 5 mL of ethylene glycol. The volume ratio of ethylene glycol to deionized water was 1:1. Add the MoS2 nanosheet mixture to the SnO2 mixture, ultrasonicate at 100 °C for 1 h, then collect the mixture and dry it in an 80 °C oven for 12 h to obtain the MoS2 / SnO2 composite material, as Figure 2a shown. When the volume ratio of ethylene glycol to deionized water was 1:1, it was found that SnO2 and MoS2 were just fused together to form hollow nanotubes with mesopores.

[0089] (2) NMP

[0090] Disperse 99 mg of the obtained SnO2 nanoparticles in 5 mL of deionized water, and disperse 1 mg of MoS2 nanosheets in 5 mL of NMP. The volume ratio of ethylene glycol to deionized water was 1:1. Add the MoS2 nanosheet mixture to the SnO2 mixture, ultrasonicate at 100 °C for 1 h, then collect the mixture and dry it in an 80 °C oven for 12 h to obtain the MoS2 / SnO2 composite material, as Figure 2b shown. SnO2 and MoS2 could not be effectively fused.

[0091] (3) DMF

[0092] Disperse 99 mg of the obtained SnO2 nanoparticles in 5 mL of deionized water, and disperse 1 mg of MoS2 nanosheets in 5 mL of DMF. The volume ratio of ethylene glycol to deionized water was 1:1. Add the MoS2 nanosheet mixture to the SnO2 mixture, ultrasonicate at 100 °C for 1 h, then collect the mixture and dry it in an 80 °C oven for 12 h to obtain the MoS2 / SnO2 composite material, as Figure 2cAs shown, SnO2 and MoS2 were severely dissolved and lost their original morphology.

[0093] Therefore, ethylene glycol was selected as the dispersion solvent for MoS2 nanosheets in this application.

[0094] Next, the dosages of ammonium fluoride and ethylene glycol were further investigated. In Example 1 and Comparative Examples 1-8, we investigated the addition ratio of ammonium fluoride in step S1 and the volume ratio of ethylene glycol to deionized water in step S2, as shown in Table 1 in detail.

[0095] Table 1

[0096]

[0097] Example 1 A method for preparing a gas-sensitive material for monitoring the characteristic substance CO of environmental protection gases, comprising the following steps:

[0098] S1. Dissolve 0.9 g of stannous chloride pentahydrate, 0.6 g of sodium hydroxide, and 0.25 g of polyvinylpyrrolidone in 20 ml of an ethanol aqueous solution (the volume ratio of ethanol to deionized water is 1:1), stir for 1 h to obtain a clear mixture, then add ammonium fluoride in a proportion of 0.1 wt%, react at 160 °C for 24 h, naturally cool to room temperature, wash the reaction product with deionized water and ethanol, dry at 80 °C for 12 h, and then calcine at 300 °C for 1 h to obtain SnO2 nanoparticles.

[0099] S2. Disperse 99 mg of the obtained SnO2 nanoparticles in 5 mL of deionized water, disperse 1 mg of MoS2 nanosheets in 5 mL of ethylene glycol, the volume ratio of ethylene glycol to deionized water is 1:1, add the MoS2 nanosheet mixture to the SnO2 mixture, ultrasonically treat at 100 °C for 1 h, then collect the mixture and dry it in an oven at 80 °C for 12 hours to obtain a MoS2 / SnO2 composite material (the mass proportion of MoS2 is 1%).

[0100] As Figure 1a shown, the SnO2 material prepared in Example 1 can form stable single particles and has a high yield. The characterization results of the MoS2 / SnO2 composite material prepared in Example 1 are as Figure 2a shown. It can be seen that the MoS2 / SnO2 composite material prepared in Example 1 just fuses into a hollow nanotube with mesopores. This is because 0.1 wt% of ammonium fluoride was added in step S1 of Example 1, and the volume ratio of ethylene glycol to deionized water added in step S2 is 1:1, and the two cooperate to change the microscopic morphology of the material.

[0101] Comparative Example 1

[0102] The difference between Comparative Example 1 and Example 1 is that in step S1, ammonium fluoride in a proportion of 0.05 wt% was further added thereto. Step S2 is the same as that in Example 1.

[0103] The SnO2 nanoparticles prepared in Comparative Example 1 are as Figure 3a shown. When adding half the amount of ammonium fluoride in Example 1, the SnO2 material cannot form stable single particles and has a lower yield than that in Example 1. The MoS2 / SnO2 composite material prepared in Comparative Example 1 is as Figure 3b shown. When using half the amount of ammonium fluoride, a shaped SnO2 cannot be synthesized, and the change in the MoS2 / SnO2 composite material is not obvious, but filaments start to appear in the amorphous substance.

[0104] Comparative Example 2

[0105] The difference between Comparative Example 2 and Example 1 is that in step S1, an additional 0.2 wt% of ammonium fluoride is added thereto. Step S2 is the same as that in Example 1.

[0106] The SnO2 nanoparticles prepared in Comparative Example 2 are as Figure 4a shown. When adding twice the amount of ammonium fluoride in Example 1, the edges of the SnO2 particles are etched and the yield is the same as that in Example 1. The MoS2 / SnO2 composite material prepared in Comparative Example 2 is as Figure 4b shown. Due to the etching of the edges of the SnO2 particles (small balls), spherical protrusions grow from the spherical shells formed by the fragmentation of the obtained MoS2 / SnO2 composite material particles (small balls).

[0107] Comparative Example 3

[0108] The difference between Comparative Example 3 and Comparative Example 1 is that in step S2, 99 mg of the obtained SnO2 nanoparticles are dispersed in 10 mL of deionized water, and 1 mg of MoS2 nanosheets are dispersed in 5 mL of ethylene glycol, and the volume ratio of ethylene glycol to deionized water is 1:2.

[0109] The MoS2 / SnO2 composite material prepared in Comparative Example 3 is as Figure 5 shown, and it is still an amorphous substance.

[0110] Comparative Example 4

[0111] The difference between Comparative Example 4 and Comparative Example 1 is that in step S2, 99 mg of the obtained SnO2 nanoparticles are dispersed in 2.5 mL of deionized water, and 1 mg of MoS2 nanosheets are dispersed in 5 mL of ethylene glycol, and the volume ratio of ethylene glycol to deionized water is 2:1.

[0112] The MoS2 / SnO2 composite material prepared in Comparative Example 4 is as Figure 6 shown. When the amount of ethylene glycol increases, the morphology of the MoS2 / SnO2 composite material changes slightly, and more filaments appear in the amorphous substance.

[0113] Comparative Example 5

[0114] The step S1 of Comparative Example 5 is the same as that of Example 1. The difference between Comparative Example 5 and Example 1 lies in that, in step S2, 99 mg of the obtained SnO2 nanoparticles are dispersed in 10 mL of deionized water, and 1 mg of MoS2 nanosheets are dispersed in 5 mL of ethylene glycol, and the volume ratio of ethylene glycol to deionized water is 1:2.

[0115] The MoS2 / SnO2 composite material prepared in Comparative Example 5 is as Figure 7 shown, and it can be found that the fusion is incomplete.

[0116] Comparative Example 6

[0117] The step S1 of Comparative Example 6 is the same as that of Example 1. The difference between Comparative Example 6 and Example 1 lies in that, in step S2, 99 mg of the obtained SnO2 nanoparticles are dispersed in 2.5 mL of deionized water, and 1 mg of MoS2 nanosheets are dispersed in 5 mL of ethylene glycol, and the volume ratio of ethylene glycol to deionized water is 2:1.

[0118] The MoS2 / SnO2 composite material prepared in Comparative Example 6 is as Figure 8 shown, and it can be found that there is excessive fusion, losing the mesoporous morphology on the nanotubes and the nanotubes stacking too densely to become fine solid tubes, and this morphology is not conducive to increasing the specific surface area.

[0119] Comparative Example 7

[0120] The difference between Comparative Example 7 and Comparative Example 5 is that, in step S1, 0.2 wt% of ammonium fluoride is further added thereto.

[0121] The MoS2 / SnO2 composite material prepared in Comparative Example 7 is as Figure 9 shown, and 0.2 wt% of ammonium fluoride results in excessive etching of the spheres. Subsequently, the volume ratio of ethylene glycol to deionized water is 1:2, resulting in the spheres breaking into spherical shells.

[0122] Comparative Example 8

[0123] The difference between Comparative Example 8 and Comparative Example 6 is that, in step S1, 0.2 wt% of ammonium fluoride is further added thereto.

[0124] The MoS2 / SnO2 composite material prepared in Comparative Example 8 is as Figure 10 shown, and 0.2 wt% of ammonium fluoride results in excessive etching of the spheres. Subsequently, the volume ratio of ethylene glycol to deionized water is 2:1, resulting in an exacerbation of the spheres breaking into spherical shells and the fragmented substances aggregating into clusters.

[0125] Performance test

[0126] Perform performance tests on the CO sensors prepared in Example 1 and Comparative Examples 1-8.

[0127] 1. Sensitivity

[0128] The response of the sensor is defined by the ratio of Ra and Rg:

[0129] (12)

[0130] where Ra is the resistance of the sensor in air and Rg is the resistance of the sensor in the target gas. The response time is defined as the time required to obtain 90% of the total resistance change of the gas sensor during the adsorption process. In the case of desorption, it is defined as the recovery time.

[0131] Figure 11 Response curve of the CO sensor prepared for Example 1 to different concentrations of the characteristic decomposition component CO of C5F 10 O gas. It can be seen from this that the prepared CO sensor has a response height of 1.18 for 50 ppm CO, and the response time and recovery time are 34 s and 28 s respectively.

[0132] Figure 12 Response curve of the CO sensor prepared for Comparative Example 1 to the characteristic decomposition component CO (50 ppm) of C5F 10 O gas. It can be seen from this that the CO sensor prepared for Comparative Example 1 has a response height of 1 for 50 ppm CO (i.e., no response, and the sensor resistance value only fluctuates near the baseline), so there is also no response time and recovery time.

[0133] Figure 13 Response curve of the CO sensor prepared for Comparative Example 2 to the characteristic decomposition component CO (50 ppm) of C5F 10 O gas. It can be seen from this that the CO sensor prepared for Comparative Example 2 has a response height of 1.05 for 50 ppm CO, and the response time and recovery time are 54 s and 352 s respectively.

[0134] Figure 14 Response curve of the CO sensor prepared for Comparative Example 3 to the characteristic decomposition component CO (50 ppm) of C5F 10 O gas. It can be seen from this that the CO sensor prepared for Comparative Example 3 has a response height of 1 for 50 ppm CO (i.e., no response, and the sensor resistance value only fluctuates near the baseline), so there is also no response time and recovery time.

[0135] Figure 15 Response curve of the CO sensor prepared for Comparative Example 4 to the characteristic decomposition component CO (50 ppm) of C5F 10 O gas. It can be seen from this that the CO sensor prepared for Comparative Example 4 has a response height of 1 for 50 ppm CO (i.e., no response, and the sensor resistance value only fluctuates near the baseline), so there is also no response time and recovery time.

[0136] Figure 16 Response curve of the CO sensor prepared in Comparative Example 5 to the characteristic decomposition component CO (50 ppm) of C5F 10 O gas. As can be seen, the response height of the CO sensor prepared in Comparative Example 5 to 50 ppm CO is 1.1, and the response time and recovery time are 44 s and 40 s respectively.

[0137] Figure 17 Response curve of the CO sensor prepared in Comparative Example 6 to the characteristic decomposition component CO (50 ppm) of C5F 10 O gas. As can be seen, the response height of the CO sensor prepared in Comparative Example 6 to 50 ppm CO is 1.08, and the response time and recovery time are 26 s and 22 s respectively.

[0138] Figure 18 Response curve of the CO sensor prepared in Comparative Example 7 to the characteristic decomposition component CO (50 ppm) of C5F 10 O gas. As can be seen, the response height of the CO sensor prepared in Comparative Example 7 to 50 ppm CO is 1.05, and the response time and recovery time are 47 s and 431 s respectively.

[0139] Figure 19 Response curve of the CO sensor prepared in Comparative Example 8 to the characteristic decomposition component CO (50 ppm) of C5F 10 O gas. As can be seen, the response height of the CO sensor prepared in Comparative Example 8 to 50 ppm CO is 1.03, and the response time and recovery time are 68 s and 297 s respectively.

[0140] By comparison, the CO sensor prepared in Example 1 of the present invention has better sensitivity, short response and recovery times, indicating that the CO sensor prepared by the method of the present invention can effectively improve the sensitivity of the sensor, reduce the response and recovery times, prove the effect of ammonium fluoride and ethylene glycol on the regulation of the material microstructure, and the hollow tubular structure enhances the sensing performance.

[0141] 2. Selectivity

[0142] The selectivity of a sensor refers to the anti-interference ability of a gas sensor to a target gas under the same test conditions.

[0143] Figure 20 Selectivity schematic diagram of the CO sensor prepared in Example 1 of the present invention to the characteristic decomposition components of C5F 10 O gas. As can be seen from Figure 20 It can be seen that the test results of the characteristic decomposition components of C5F 10 O gas show that the sensor prepared in Example 1 of the present invention has the highest response height to CO and has good selectivity.

[0144] 3. Stability

[0145] The stability of the gas-sensitive material reflects the stability of the detection ability of the sensor during long-term use, and can also be called the lifespan of the sensor. For example Figure 21 is the long-term stability data graph of the CO sensor prepared in Example 1 and Comparative Examples 1-8 of the present invention for the characteristic decomposition component CO of C5F 10 O gas. It can be seen from Figure 21 that the response height of the CO sensor prepared in Example 1 of the present invention to CO remains basically unchanged within one month, indicating that the CO sensor prepared by the method of the present invention has good long-term stability; while the response height of the CO sensors prepared in Comparative Examples 1-8 to CO begins to decline after half a month, and the long-term stability is not good.

[0146] It is easy for those skilled in the art to understand that, on the premise of no conflict, the above advantageous methods can be freely combined and superimposed. The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application. The above is only the preferred implementation manner of the present application. It should be noted that for those of ordinary skill in the art in the technical field of the present application, several improvements and variations can be made without departing from the technical principle of the present application, and these improvements and variations should also be regarded as the protection scope of the present application.

Claims

1. A preparation method of a gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas, characterized in that, Comprising: Dissolve stannic chloride pentahydrate, sodium hydroxide and polyvinylpyrrolidone to obtain a clear mixed solution. Add ammonium fluoride to the mixed solution, react at 155°C - 165°C for 23h - 25h, then naturally cool to room temperature, wash the reaction product, dry it, and calcine it at 295°C - 305°C to obtain SnO2 nanoparticles; wherein, the addition amount of ammonium fluoride is 0.09wt% - 0.11wt% of the mixed solution Disperse the SnO2 nanoparticles in deionized water to obtain a SnO2 dispersion, disperse MoS2 nanosheets in ethylene glycol to obtain a MoS2 nanosheet dispersion, ultrasonically mix the SnO2 dispersion and the MoS2 nanosheet dispersion, and then dry it to obtain a MoS2 / SnO2 composite material; wherein, the volume ratio of ethylene glycol to deionized water is (0.9 - 1.1):1, and the microstructure of the MoS2 / SnO2 composite material is a mesoporous hollow nanotube structure 2. The preparation method of the gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas according to claim 1, characterized in that, In the MoS2 / SnO2 composite material, the mass fraction of MoS2 is 1% - 5%, and the mass fraction of SnO2 is 95% - 99% 3. The preparation method of the gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas according to claim 2, characterized in that, For the ultrasonic mixing, the ultrasonic temperature is 80°C - 120°C, and the ultrasonic time is 1h - 2h 4. The preparation method of the gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas according to claim 1 or 3, characterized in that, Also comprising: Dissolve the stannic chloride pentahydrate, the sodium hydroxide and the polyvinylpyrrolidone in an ethanol aqueous solution, and stir to obtain the clear mixed solution; wherein, the mass ratio of the stannic chloride pentahydrate, the sodium hydroxide and the polyvinylpyrrolidone is (3.5 - 3.7):(2.3 - 2.5):1, and the volume concentration of ethanol in the ethanol aqueous solution is 45% - 55% 5. A gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas, characterized in that, It is the MoS2 / SnO2 composite material prepared by the preparation method according to any one of claims 1 - 4 6. Application of a gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas, characterized in that, The gas - sensitive material according to claim 5 is used for preparing a resistive sensor for CO 7. The application of the gas-sensitive material for monitoring the environmental protection gas characteristic CO as claimed in claim 6, characterized in that, The resistive sensor for CO is used to monitor the environmentally friendly insulating gas C4F7N and / or the decomposition component CO of the environmentally friendly insulating gas C5F 10 O.

8. The application of the gas-sensitive material for monitoring the environmental protection gas characteristic CO as claimed in claim 6, wherein, The preparation method of the resistive sensor for CO includes: Add the MoS2 / SnO2 composite material into deionized water, ultrasonically disperse it to obtain a MoS2 / SnO2 suspension, uniformly coat the MoS2 / SnO2 suspension on the electrode surface of the resistive sensor for CO, and dry it; wherein, the concentration of the MoS2 / SnO2 suspension is 14mg / mL - 16mg / mL 9. The application of the gas-sensitive material for monitoring the characteristic substance CO of environmental protection gas according to claim 8, characterized in that, The coating thickness of the MoS2 / SnO2 composite material is 40μm - 60μm

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