A ternary heterogeneous composite gas-sensitive material, its preparation method, and its application in detecting H2S, a decomposition product of SF6.

Abstract

This invention relates to the field of gas-sensitive materials technology, and particularly to a ternary heterogeneous composite gas-sensitive material, its preparation method, and its application in detecting H2S, a product of SF6 decomposition. Preparation method: S1, a homogeneous precursor solution is prepared by adding a tungsten source, a molybdenum source, and thioacetamide to deionized water, and the pH value is adjusted before a hydrothermal reaction is carried out. After the reaction, the solution is naturally cooled, centrifuged, washed, and dried to obtain a two-dimensional layered WS2 / MoS2 powder; S2, the powder is dispersed in an organic solvent to obtain suspension A, and a precursor salt solution B is obtained by dissolving a soluble iron salt and sodium acetate in water; solution B is slowly added dropwise to suspension A to obtain a mixed suspension, followed by a hydrothermal reaction; S3, the hydrothermal product is naturally cooled to room temperature, centrifuged, dried, and then calcined under a protective atmosphere to obtain the gas-sensitive material. The gas-sensitive material prepared by this invention has high sensitivity to H2S.

Description

Technical Field

[0001] This invention relates to the field of gas-sensitive materials technology, and in particular to a ternary heterogeneous composite gas-sensitive material, its preparation method, and its application in detecting SF6 decomposition product H2S. Background Technology

[0002] SF6 is a widely used insulating arc-extinguishing medium in high-voltage GIS, circuit breakers, oil-immersed transformers, and other power switchgear. When partial discharge, insulation degradation, or contact erosion faults occur inside power equipment, the SF6 inside the tank will decompose under the bombardment of electric arcs, high temperatures, and high-energy particles. This decomposition will react with trace amounts of moisture and solid insulation impurities in the equipment to generate characteristic decomposition impurity gases such as H2S. H2S is a key characteristic marker of SF6 insulation failure and internal partial discharge defects. The continuous accumulation of trace amounts of H2S will accelerate the corrosion of metal cavities and the aging of insulating materials, inducing major power safety accidents such as equipment grounding, short circuits, and insulation breakdown. Therefore, accurate and rapid online detection of trace amounts of H2S in the SF6 atmosphere is a core technical means for condition-based maintenance and early warning of latent faults in high-voltage electrical equipment.

[0003] Currently, the mainstream detection methods for H2S, the decomposition product of SF6 in the power industry, include gas chromatography, infrared spectroscopy, and electrochemical sensors. However, chromatographic and infrared equipment is bulky and expensive, making it impossible to achieve on-site, real-time online monitoring. Commercial electrochemical sensors have short lifespans, are susceptible to interference from SF6 gas, HF, SO2, and other coexisting decomposition byproducts, and exhibit poor selectivity. Semiconductor resistive gas sensors, with their advantages of small size, integration into online monitoring devices, low cost, and rapid response, have become the preferred solution for online detection of trace amounts of H2S from partial discharge of SF6.

[0004] Two-dimensional transition metal chalcogenides (TMDs) MoS2 and WS2 are popular substrates for trace gas detection due to their large specific surface area, abundant edge adsorption sites, and ease of modification in thin layers. WS2 / MoS2 binary composites can further optimize gas diffusion channels by constructing layered heterostructures. However, pure WS2 / MoS2 composites suffer from drawbacks such as weak electrical conductivity, low interfacial charge transfer efficiency, insufficient anti-interference ability in SF6 multi-impurity mixed atmospheres, and significant degradation of gas-sensing stability over long-term use, making it difficult to meet the requirements for accurate quantitative detection of ppm-level H2S in SF6 atmospheres in power plant applications. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a ternary heterogeneous composite gas-sensitive material, its preparation method, and its application in detecting SF6 decomposition product H2S.

[0006] The first objective of this invention is to provide a method for preparing a ternary heterogeneous composite gas-sensitive material, comprising the following steps: S1. Add tungsten source, molybdenum source and thioacetamide to deionized water to prepare a uniform precursor solution, and adjust its pH value to 2.5-3.5 before carrying out a hydrothermal reaction. After the reaction is completed, allow it to cool naturally, centrifuge, wash and dry to obtain two-dimensional layered WS2 / MoS2 powder. S2. Disperse the two-dimensional layered WS2 / MoS2 powder in an organic solvent to obtain suspension A. Dissolve soluble iron salt and sodium acetate in water to obtain precursor salt solution B. Slowly add solution B dropwise into suspension A to obtain mixed suspension. Perform hydrothermal reaction on the mixed suspension. S3. The hydrothermal product was naturally cooled to room temperature, centrifuged, dried, and then calcined under a protective atmosphere to obtain the α-Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material. In the Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material, the loading of Fe2O3 is 8wt% to 12wt%.

[0007] More preferably, the Fe2O3 loading is 10%. When the Fe2O3 loading is 10%, the Fe2O3 nanoparticles are more uniformly dispersed on the surface of the WS2 / MoS2 sheets, which can provide sufficient catalytic active sites while retaining the open diffusion channels of the two-dimensional layered material, avoiding local agglomeration and active site shielding caused by excessive Fe2O3. An unreasonable Fe2O3 loading can easily lead to nanoparticle agglomeration, blockage of gas diffusion channels between two-dimensional layers, and shielding of active sites, which will degrade the sensitivity and stability of H2S detection under SF6 mixed atmosphere.

[0008] Further, in step S1, the mass ratio of tungsten source to molybdenum source is (1.2-1.5):1; the mass ratio of the sum of the tungsten source and molybdenum source to thioacetamide is 1:(2.8-3.5).

[0009] Furthermore, in step S1, the hydrothermal reaction conditions are: 180–200 °C, reaction time 12–24 h.

[0010] Furthermore, in suspension A, the mass-to-volume ratio of the two-dimensional layered WS2 / MoS2 powder to the organic solvent is 0.4–0.6 g: 25–35 mL; in precursor salt solution B, the mass ratio of the soluble iron salt to sodium acetate is (0.95–1.05): 1.

[0011] Furthermore, the soluble iron salt is one or more of ferric nitrate, ferric chloride, and ferric sulfate.

[0012] Furthermore, in step S3, the water is kept at 120–180 °C for 12–18 h.

[0013] Furthermore, calcination is carried out at 280–320 °C for 1.5–2.5 h.

[0014] The second objective of this invention is to provide a ternary heterogeneous composite gas-sensitive material prepared using the above-described preparation method.

[0015] A third objective of this invention is to provide an application of the ternary heterogeneous composite gas-sensitive material as described above in the detection of H2S, a product of SF6 decomposition.

[0016] Furthermore, a gas-sensitive sensor is employed, the gas-sensitive sensor comprising interdigitated electrodes and a gas-sensitive sensing layer coated on the interdigitated electrodes, the gas-sensitive sensing layer comprising the aforementioned ternary heterogeneous composite gas-sensitive material.

[0017] The beneficial effects of this invention are: Improving detection sensitivity: This invention involves in-situ loading of Fe2O3 nanoparticles (preferably α-Fe2O3, which is an environmentally friendly n-type metal oxide with excellent catalytic activity and strong physicochemical stability) onto the surface and edge regions of a two-dimensional layered WS2 / MoS2 material. This creates a tight contact interface between the metal oxide phase and the two-dimensional chalcogenide phase, forming a metal oxide / TMDs composite heterostructure. This allows for the regulation of carrier transport and surface band structure, thus combining the gas diffusion advantages of two-dimensional layered materials, the catalytic activation effect of Fe2O3, and the electronic regulation effect of the heterostructure interface. Simultaneously, the catalytic specificity of Fe2O3 enhances the targeted adsorption capacity for H2S, effectively amplifying the resistance changes caused by H2S adsorption and reaction, thereby improving the sensor's response sensitivity to H2S.

[0018] Improved selectivity and stability: The chemical stability of the Fe2O3 / WS2 / MoS2 composite material helps to improve the selectivity for the target gas while reducing interference with other gases, thus improving the stability of the sensor.

[0019] Improved selectivity and targeted adsorption capacity: The α-Fe2O3 loaded on the surface of the ternary heteromaterial of this invention has specific catalytic adsorption activity for H2S. In a mixed atmosphere of various SF6 decomposition impurities such as SO2, HF, CO, and CF4, it only produces a significant resistance response to H2S, and the interfering gases hardly produce a detection signal. The targeted adsorption capacity is outstanding, which greatly improves the sensor's on-site anti-interference ability and long-term detection stability.

[0020] Lower operating temperature: Compared with traditional gas-sensitive materials, this material exhibits excellent gas-sensitive performance at lower operating temperatures, which helps to reduce the energy consumption and cost of the sensor.

[0021] Achieving flexibility and portability: Fe2O3 / WS2 / MoS2 material sensors based on flexible substrates are flexible and portable, making them easy to monitor and detect in real time in various environments. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the preparation of the Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material of the present invention; Figure 2 This is a SEM image of the Fe2O3 / WS2 / MoS2 ternary heterocomposite gas-sensitive material prepared in Example 1; Figure 3 This is the XRD pattern of the Fe2O3 / WS2 / MoS2 ternary heterocomposite gas-sensitive material prepared in Example 1; Figure 4 This is the response of the sensor A12 prepared in Example 1 to different concentrations of H2S at 40°C; Figure 5 This is a long-term stability test of the sensor A12 prepared in Example 1 against 30 ppm H2S at 40°C. Detailed Implementation

[0023] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings to further illustrate the technical solutions of the present invention. However, the present invention is not limited to these embodiments.

[0024] The Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material and gas-sensitive sensor of the present invention are prepared as follows: 1. Preparation of two-dimensional layered WS2 / MoS2 powder Weigh out sodium tungstate dihydrate and sodium molybdate dihydrate according to the mass ratio of tungsten source to molybdenum source = (1.2~1.5):1, and then add thioacetamide according to the mass ratio of total tungsten and molybdenum metal salts to thioacetamide = 1:(2.8~3.5). Add all solid raw materials to 80–150 mL of deionized water and stir at room temperature for 40–90 min until the solids are completely dissolved to prepare a homogeneous precursor solution.

[0025] The pH of the precursor solution was adjusted to 2.5–3.5 by slow titration with 0.5–2 mol / L dilute hydrochloric acid. The liquid was transferred into a polytetrafluoroethylene-lined hydrothermal reactor, sealed, and then kept at a constant temperature of 180–200 °C in an oven for 12–24 h. After the reaction is complete, the vessel is allowed to cool naturally to room temperature of 20–30 °C, and the solid product is collected by high-speed centrifugation at 8000–12000 r / min. Wash with deionized water and anhydrous ethanol alternately for 3 to 5 cycles, with each wash using 40 to 80 mL of solvent. The washed precipitate was transferred to a vacuum oven and dried at a constant temperature of 55-65 ℃ for 10-14 h, preferably at 60 ℃ for 12 h, to obtain two-dimensional layered WS2 / MoS2 powder.

[0026] 2. Preparation of Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive materials Take 0.4–0.6 g of the two-dimensional layered WS2 / MoS2 powder obtained above, disperse it in 25–35 mL of isopropanol solvent, stir at room temperature for 20–40 min for pre-dispersion, and then sonicate at room temperature for 1.5–2.5 h, preferably 2 h, to obtain suspension A.

[0027] Weigh out ferric nitrate nonahydrate and sodium acetate according to the mass ratio of metal nitrate to sodium acetate = (0.95~1.05):1. Dissolve the two raw materials separately in 25~35 mL of deionized water, stir each for 20~50 min, then mix them together and continue stirring for 30~50 min to obtain precursor salt solution B. Based on the target metal oxide loading of 8wt% to 12wt%, the feeding ratio of liquids A and B is precisely matched, and the optimal ratio corresponds to a loading of 10wt%.

[0028] Under uniform stirring conditions, solution B is slowly added dropwise to suspension A at a rate of 1–3 mL / min. After mixing, the mixture is transferred to a hydrothermal reactor and kept at 120–180 °C for 12–18 h. Once the hydrothermal process is complete, the mixture is allowed to cool naturally to room temperature.

[0029] The solid product was washed three times by centrifugation with anhydrous ethanol. Centrifugation parameters: speed 10000-12000 r / min, single centrifugation time 10-20 min, and the supernatant was discarded and the solid precipitate was retained after each centrifugation. After washing, the solid is dried at 60–80 °C for 12–24 h, preferably at 70 °C for 18 h; The dried powder can be calcined at 280–320 °C for 1.5–2.5 h in a nitrogen atmosphere, preferably at 300 °C for 2 h, to finally obtain the Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material.

[0030] 3. Fabrication of a dedicated gas sensor for SF6 partial discharge H2S detection Weigh 45–55 mg of Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material, add 5–10 wt% PEG powder with a molecular weight of 4000 as a film-forming aid, and grind thoroughly for 15–35 min until the solid phase is uniformly mixed; Add 0.4–0.6 mL of anhydrous ethanol and sonicate at room temperature for 8–15 min, preferably 10 min, to prepare a stable gas-sensitive coating slurry.

[0031] Commercial alumina interdigitated electrodes are ultrasonically cleaned by immersion in anhydrous ethanol for 3–8 minutes and then air-dried at room temperature before use. A pipette was used to quantitatively aspirate 1.5–2.5 μL of slurry and evenly drop it onto the sensitive area of ​​the interdigitated electrode. After coating, the electrode was placed in a ceramic boat and dried in a forced-air oven at 190–210 °C for 20–26 h until the solvent was completely evaporated and solidified into a sensitive film, thus obtaining a resistive gas sensor adapted for detecting H2S from the partial discharge decomposition of SF6 in electric power.

[0032] A schematic diagram of the preparation of the Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material of the present invention is shown below. Figure 1 As shown.

[0033] The room temperature in the following examples refers to 25°C.

[0034] Example 1 (1) Preparation of two-dimensional layered WS2 / MoS2 powder Accurately weigh 646.7 mg of sodium tungstate dihydrate and 474.4 mg of sodium molybdate dihydrate, and add them at a tungsten source / molybdenum source mass ratio of 1.36:1. Then weigh 3.14 g of thioacetamide (TAA), controlling the total mass ratio of tungsten and molybdenum metal salts to thioacetamide to be 1:2.8. Add all solid materials at once to 110 mL of deionized water, and mechanically stir at 25°C for 60 min until the solids are completely dissolved to obtain a clear and homogeneous precursor solution. Adjust the pH of the precursor solution to 3.0 by uniform titration with 1.0 mol / L dilute hydrochloric acid.

[0035] The pH-adjusted precursor solution was transferred into a polytetrafluoroethylene-lined stainless steel hydrothermal reactor and sealed. The reactor was heated to 190℃ in an oven and kept at a constant temperature for 18 hours. After the reaction was completed, the temperature was allowed to drop naturally to 25℃. The solid product was separated by high-speed centrifugation at 10,000 r / min. The product was washed four times with alternating cycles of deionized water and anhydrous ethanol, with a solvent volume of 60 mL per wash. The precipitate was then placed in a vacuum drying oven and dried at a constant temperature of 60℃ for 12 hours. The product was then ground through a 200-mesh sieve to obtain a two-dimensional layered WS2 / MoS2 powder with a complete layered structure.

[0036] (2) Preparation of Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material Accurately weigh 0.4 g of the above two-dimensional layered WS2 / MoS2 powder, disperse it in 30 mL of anhydrous isopropanol solvent, pre-dispersettle it by magnetic stirring at room temperature for 30 min, and then continuously sonicate it at room temperature for 2 h with an ultrasonic power of 300 W to obtain a uniformly dispersed suspension A without agglomeration.

[0037] According to the ratio of iron nitrate nonahydrate to anhydrous sodium acetate approximately 1:1, 202.39 mg of iron nitrate nonahydrate and 202.39 mg of anhydrous sodium acetate were weighed and dissolved separately in 30 mL of deionized water. After stirring each solution for 35 min, they were mixed and stirred for another 40 min to obtain precursor salt solution B. Based on the theoretical loading of 10 wt% α-Fe2O3, the ratio of solutions A and B was precisely matched. Under stirring at room temperature, solution B was slowly added dropwise to suspension A at a dropping rate of 2 mL / min. The mixed suspension was transferred to a hydrothermal reactor, sealed, and kept at 150℃ for 15 h to achieve in-situ uniform growth of the iron-based precursor on the surface of WS2 / MoS2 sheets.

[0038] The hydrothermal product was naturally cooled to room temperature, centrifuged at 11,000 r / min, and washed three times with anhydrous ethanol (each centrifugation lasting 15 min). The precipitate was dried at 70℃ for 18 h. The dried powder was placed in a tube furnace under a high-purity N2 protective atmosphere (nitrogen flow rate 50 mL / min), and calcined at 300℃ for 2 h. The powder was then naturally cooled with the furnace and sieved to obtain a 10wt% Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material.

[0039] (3) Fabrication of gas-sensitive sensor Take 50 mg of ternary composite powder, add 7.5 wt% of PEG4000 (preferably 5-10 wt% intermediate addition), and grind in an agate mortar in the dark for 25 min to achieve uniform solid-phase mixing; add 0.5 mL of anhydrous ethanol dropwise, and sonicate at room temperature for 10 min to obtain a gas-sensitive slurry with moderate viscosity, no stratification, and stable film formation.

[0040] The alumina-based interdigitated electrode was ultrasonically cleaned in anhydrous ethanol for 5 min and then air-dried in a dust-free environment at room temperature. Using a precision pipette with a volume range of 0~5 μL, 2 μL of slurry was quantitatively pipetted and uniformly applied to the sensitive active area of ​​the interdigitated electrode. The coated electrode was placed in a ceramic boat and dried in a forced-air drying oven at 200℃ for 24 h until the organic solvent was completely evaporated and solidified into a dense sensitive film. The finished product was designated as sensor A1.

[0041] Example 2 The overall preparation process, raw material ratio, hydrothermal / drying / calcination, slurry preparation, and coating process parameters are completely consistent with those of Example 1. The only difference is in step (2) iron salt feeding: accurately weigh 161.91 mg of ferric nitrate nonahydrate and 163.61 mg of anhydrous sodium acetate, and control the theoretical α-Fe2O3 loading at 8wt%; the remaining process parameters, post-processing, and sensor preparation process remain unchanged, and 8wt% Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material and corresponding sensor A2 are obtained.

[0042] Example 3 The basic process of the whole process is based on Example 1, with differentiated limiting steps (2) Iron source feeding: 242.87 mg of ferric nitrate nonahydrate and 245.42 mg of anhydrous sodium acetate, with a theoretical α-Fe2O3 loading of 12wt%; the parameters for synthesis, post-calcination, slurry preparation, and electrode coating and curing are uniformly based on the standard of Example 1, and finally 12wt% Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material and sensor A3 are prepared.

[0043] Comparative Example 1 Two-dimensional layered WS2 / MoS2 powder was prepared according to steps (1) to (2) of Example 1, omitting the entire process of Fe source doping, in-situ hydrothermal loading, and tubular furnace calcination; the obtained two-dimensional layered WS2 / MoS2 powder was directly used to prepare a single WS2 / MoS2 matrix control sensor D1.

[0044] Comparative Example 2 The two-dimensional layered WS2 / MoS2 powder was omitted. Instead, ferric nitrate nonahydrate and anhydrous sodium acetate were dissolved in isopropanol-deionized water mixed solvent according to the feeding ratio in Example 1. Single-phase α-Fe2O3 nanoparticles were prepared by hydrothermal treatment, washing, drying, and calcination at 300°C in a N2 atmosphere for 2 hours, as described in Example 1. Subsequent slurry preparation, interdigitated electrode drop coating, and high-temperature curing processes were the same as in Example 1, resulting in a pure iron oxide control sensor D2.

[0045] Comparative Example 3 Using only sodium tungstate dihydrate as the tungsten source and eliminating the molybdenum source, the remaining raw material ratios, S1 hydrothermal synthesis, washing and drying processes were completely consistent with step (1) of Example 1 to prepare pure two-dimensional WS2 sheet powder; the subsequent slurry preparation, interdigital electrode coating, and curing sensor preparation processes were the same as in Example 1 to obtain pure WS2 control sensor D3.

[0046] Comparative Example 4 Using only sodium molybdate dihydrate as the molybdenum source and eliminating the tungsten source, the remaining raw material ratios, S1 hydrothermal synthesis, washing and drying processes were completely consistent with step (1) of Example 1 to prepare pure two-dimensional MoS2 sheet powder; the subsequent slurry preparation, interdigital electrode coating, and curing sensor preparation processes were the same as in Example 1 to obtain pure MoS2 control sensor D4.

[0047] Comparative Example 5 Using only sodium tungstate dihydrate as the tungsten source and without adding molybdenum source, the proportions of other raw materials, hydrothermal synthesis of S1, washing and drying process parameters are completely consistent with step (1) of Example 1 to prepare pure two-dimensional WS2 sheet powder; the subsequent WS2 powder dispersion, ferric nitrate nonahydrate and sodium acetate solution preparation, hydrothermal composite, centrifugal washing, drying, nitrogen atmosphere calcination, slurry preparation, interdigital electrode drop coating and curing process are all consistent with Example 1, and finally 10wt% Fe2O3 / WS2 binary composite powder and corresponding control sensor D5 are obtained.

[0048] Comparative Example 6 Sodium molybdate dihydrate was used as the molybdenum source, without adding a tungsten source. The process conditions for hydrothermal preparation of pure WS2 two-dimensional nanosheets in the remaining S1 stage, the preparation of iron salt precursor solution, the in-situ hydrothermal loading of Fe2O3, high-temperature calcination, gas-sensitive slurry preparation, and electrode coating curing process were all performed according to the standard of Example 1, resulting in a 10wt% Fe2O3 / MoS2 binary composite material and a matching sensor D6.

[0049] Test Example 1 The material obtained in Example 1 was observed by scanning electron microscopy (SEM), and the SEM images are as follows: Figure 2 As shown, from Figure 2 As can be seen, the prepared material has a two-dimensional sheet-like structure. This two-dimensional structure provides more adsorption and reaction surfaces for gas molecules, potentially enhancing the gas-sensing performance of the material. Simultaneously, Fe2O3 nanoparticles loaded onto the surface of the two-dimensional nanosheets are clearly visible. These particles are uniformly distributed on the nanosheets, forming a composite material. This composite structure combines the advantages of WS2 / MoS2 and Fe2O3, further improving the gas-sensing performance of the material.

[0050] Test Example 2 The material obtained in Example 1 was subjected to XRD analysis, and the XRD pattern is shown below. Figure 3 As shown, from Figure 3 It can be seen that, compared with WS2 / MoS2 materials, the prepared material exhibits new diffraction peaks. This is because the loading of Fe2O3 nanoparticles results in new diffraction peaks in the crystal structure of the prepared material, which represents new crystal structure characteristics, optimizes the material's performance, and particularly improves its gas-sensing properties.

[0051] Test Example 3 As target gas molecules adsorb onto the surface of the Fe2O3 / WS2 / MoS2 sensor, electrons are transferred from the sensor material to the target molecules, causing a change in the resistance of the Fe2O3 / WS2 / MoS2 sensor. This change can be converted into an electrical signal for output, thereby enabling the detection of the target gas. This test example evaluates the gas-sensing performance of the Fe2O3 / WS2 / MoS2 sensor for gas H2S.

[0052] Test Example 4 To simulate the mixed decomposition gas environment of an internal fault in an SF6 power plant, common coexisting interfering gases in the field were selected: SO2, HF, CO, and CF4. Mixed atmospheres of 30 ppm of a single interfering gas and 30 ppm H2S + 30 ppm of a single interfering gas were prepared respectively. The response values ​​of sensor A1 (10wt% Fe2O3 / WS2 / MoS2) to each gas were tested under the same operating conditions at 240 ℃. The targeted adsorption and anti-interference capabilities of the material for H2S were quantitatively characterized. The test results are shown in Table 2.

[0053] The response curve of sensor A1 to 50 ppm H2S was measured: Sensor A1 obtained in Example 1 was placed in a gas-sensitive testing system, and its dynamic response to different concentrations of H2S was tested at an operating temperature of 240 °C. During the test, air was used as the reference atmosphere, and different concentrations of H2S were introduced into the test chamber. The response curve of the sensor resistance as a function of the atmosphere was recorded. The response value S was calculated according to S=Ra / Rg, where Ra is the resistance value of the sensor in air, and Rg is the resistance value of the sensor in the H2S atmosphere.

[0054] from Figure 4 and Figure 5 As can be seen, sensor A1 exhibits a significant response to H2S concentrations ranging from 1 to 80 ppm, and the response value increases with increasing H2S concentration. The linear fit is S = 0.46784C + 2.10333, with a correlation coefficient R² = 0.99377, indicating that the sensor has good quantitative detection capability within the tested concentration range. Figure 5 The long-term stability test of the prepared Fe2O3 / WS2 / MoS2 sensor A1 against 30 ppm H2S at 240℃ showed that the response value of the prepared Fe2O3 / WS2 / MoS2 sensor A1 fluctuated very little during the long-term test, indicating that sensor A1 has good long-term stability.

[0055] Under the same test conditions, the responses of the sensors in Examples 1-3 and Comparative Examples 1-2 to H2S were tested respectively. Among them, the 10% Fe2O3 / WS2 / MoS2 sensor showed superior response performance, mainly attributed to the uniform dispersion of Fe2O3 particles and sufficient active sites at this loading level, while without significant blockage of the lamellar diffusion channels. Testing revealed that the response curves of Fe2O3 / WS2 / MoS2 sensors A2-A3 and D1-D2 to 30 ppm H2S exhibited similar trends to those of Fe2O3 / WS2 / MoS2 sensor A1, all showing a trend of first increasing and then decreasing with temperature. The response value reached its maximum at an operating temperature of 240℃, as detailed in Table 1.

[0056] Table 1. Maximum response values ​​of different sensors to 30ppm H2S (240℃)

[0057] According to the test data in Table 1, the sensors (A1, A2, A3) prepared by Fe2O3 modified WS2 / MoS2 ternary composite material have significantly better maximum response values ​​to 30 ppm H2S at an operating temperature of 240 ℃ than sensors (D1-D6) made of other single or binary materials.

[0058] Specifically, among the modified samples with different Fe2O3 doping ratios, the A1 sensor with 10% Fe2O3 doping showed the best gas-sensing performance, with a response value of 12.3; the A2 sensor with 8% doping had a response value of 8.1, and the A3 sensor with 12% doping had a response value of 7.9. As a control, the pure WS2 / MoS2 sensor D1 without Fe2O3 loading had a response value of only 2.8, the pure Fe2O3-based sensor D2 had a response value of 4.7, and the pure WS2 and MoS2 sensors had response values ​​of 1.6 and 1.9, respectively. This indicates that the response level of single-phase materials is much lower than that of the Fe2O3-modified composite samples.

[0059] The above test results demonstrate that composite Fe2O3 on the WS2 / MoS2 substrate can significantly improve the material's gas-sensing response to H2S, and there is a significant synergistic effect among the three components. When the Fe2O3 doping amount is adjusted to an appropriate ratio (10wt%), more heterojunction interfaces and gas-active adsorption sites can be constructed on the material surface, optimizing carrier transport efficiency, accelerating the redox reaction of H2S on the sensitive layer surface, and ultimately significantly improving the device response value. This result fully verifies that the Fe2O3 / WS2 / MoS2 ternary composite sensing material has outstanding gas-sensing advantages and material modification value in the field of high-temperature H2S gas detection.

[0060] Table 2. Response values ​​of sensor A1 to 30 ppm of various gases / gas mixtures (240℃)

[0061] As shown in Table 2, the sensor's response to the four coexisting interfering gases SO2, HF, CO, and CF4 is close to 1, with almost no obvious signal response, indicating that the ternary material has extremely weak adsorption and activation ability for the above-mentioned impurity gases. Under all mixed atmospheres containing H2S, the sensor response value only slightly decreases, remaining in the range of 11.43~12.01, with a very small difference from pure H2S (12.3). This proves that Fe2O3 nanoparticles endow the material with specific catalytic adsorption sites for H2S, and the ternary heterogeneous interface can selectively capture H2S molecules. It has almost no adsorption response to other SF6 decomposition byproducts, and has extremely strong targeted recognition ability, making it suitable for the accurate detection of trace amounts of H2S in mixed SF6 atmospheres with multiple impurities in power field applications.

[0062] For any points not covered above, existing technologies shall apply.

[0063] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a ternary heterogeneous composite gas-sensitive material, characterized in that, Includes the following steps: S1. Add tungsten source, molybdenum source and thioacetamide to deionized water to prepare a uniform precursor solution, and adjust its pH value to 2.5-3.5 before carrying out a hydrothermal reaction. After the reaction is completed, allow it to cool naturally, centrifuge, wash and dry to obtain two-dimensional layered WS2 / MoS2 powder. S2. Disperse the two-dimensional layered WS2 / MoS2 powder in an organic solvent to obtain suspension A. Dissolve soluble iron salt and sodium acetate in water to obtain precursor salt solution B. Slowly add solution B dropwise into suspension A to obtain mixed suspension. Perform hydrothermal reaction on the mixed suspension. S3. The hydrothermal product was naturally cooled to room temperature, centrifuged, dried, and then calcined under a protective atmosphere to obtain the Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material. In the Fe2O3 / WS2 / MoS2 ternary heterogeneous composite gas-sensitive material, the loading of Fe2O3 is 8wt% to 12wt%.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of tungsten source to molybdenum source is (1.2-1.5):1; the mass ratio of the sum of the tungsten source and molybdenum source to thioacetamide is 1:(2.8-3.5).

3. The preparation method according to claim 1, characterized in that, In step S1, the hydrothermal reaction conditions are: 180–200℃, reaction time 12–24 h.

4. The preparation method according to claim 1, characterized in that, In suspension A, the mass-to-volume ratio of the two-dimensional layered WS2 / MoS2 powder to the organic solvent is 0.4–0.6 g: 25–35 mL; in precursor salt solution B, the mass ratio of the soluble iron salt to sodium acetate is (0.95–1.05):

1.

5. The preparation method according to claim 1, characterized in that, Soluble iron salts are one or more of ferric nitrate, ferric chloride, and ferric sulfate.

6. The preparation method according to claim 1, characterized in that, In step S3, the water is kept at 120–180 °C for 12–18 h using hydrothermal heat.

7. The preparation method according to claim 1, characterized in that, Calcination at 280–320 °C for 1.5–2.5 h.

8. A ternary heterogeneous composite gas-sensitive material prepared by the preparation method according to any one of claims 1-7.

9. The application of the ternary heterogeneous composite gas-sensitive material as described in claim 8 in the detection of H2S, a product of SF6 decomposition.

10. The application as described in claim 9, characterized in that, A gas-sensitive sensor is used, which includes interdigitated electrodes and a gas-sensitive sensing layer coated on the interdigitated electrodes. The gas-sensitive sensing layer includes the ternary heterogeneous composite gas-sensitive material.

Images