Au-doped bimetallic oxide CeO2-SnO2 composite gas sensitive material and preparation method and application thereof, gas sensitive sensor and preparation method and application thereof

Abstract

The invention relates to the technical field of gas sensors, and discloses an Au-doped bimetallic oxide CeO2 (at) SnO2 composite gas sensitive material and a preparation method and application thereof, a gas sensitive sensor and a preparation method and application thereof, and the Au-doped bimetallic oxide CeO2 (at) SnO2 composite gas sensitive material comprises a CeO2 (at) SnO2 composite material and Au nanoparticles loaded on the surface of the CeO2 (at) SnO2 composite material. The Au-doped bimetallic oxide CeO2 (at) SnO2 composite gas-sensitive material is successfully prepared through an improved hydrothermal synthesis method and an impregnation doping method and is prepared into a sensor, and the sensor shows excellent gas-sensitive performance, including high sensitivity and low-concentration response to transformer oil dissolved gases H2 and C2H2.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, specifically to Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive materials, their preparation methods and applications, and gas-sensitive sensors, their preparation methods and applications. Background Technology

[0002] During long-term operation, the internal oil-paper insulation system of power transformers undergoes thermal decomposition due to heat and electrical stress, releasing characteristic gases such as hydrogen (H2) and acetylene (C2H2). These gases are soluble in transformer oil, and changes in their concentration can reflect early signs of equipment failure. Traditional detection methods, such as gas chromatography, while highly accurate, require offline sampling and laboratory analysis, resulting in long detection cycles, bulky equipment, and the inability to monitor in real time, making it difficult to meet the needs of intelligent operation and maintenance of the power grid.

[0003] Metal oxide semiconductor (MOS) gas sensors have become a research hotspot for alternative solutions due to their simple structure, fast response, and low cost. However, single SnO2-based sensors have drawbacks such as insufficient sensitivity to low-concentration gases and high energy consumption due to high operating temperatures, which limit their engineering applications. Summary of the Invention

[0004] The purpose of this invention is to overcome the limitations of existing technologies for detecting dissolved gases in transformer oil, such as long detection cycles, inability to monitor in real time, insufficient sensitivity of single metal oxide semiconductor resistive sensors, and energy consumption due to high operating temperatures. This invention provides Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive materials, their preparation methods and applications, and gas-sensitive sensors, their preparation methods and applications. This method successfully prepares Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive materials and fabricates them into sensors through a modified hydrothermal synthesis and impregnation doping method, exhibiting excellent gas-sensing performance, including high sensitivity and low concentration response to dissolved gases H2 and C2H2 in transformer oil.

[0005] To achieve the above objectives, the present invention provides an Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material, wherein the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material comprises a CeO2@SnO2 composite material and Au nanoparticles loaded on the surface of the CeO2@SnO2 composite material.

[0006] The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material has a specific surface area of ​​100~300 m². 2 / g.

[0007] Furthermore, the molar ratio of Ce to Sn in the CeO2@SnO2 composite material is 1:1 to 10. This range ensures the formation of a stable heterojunction structure in the composite material, enhances electron transfer, and thus improves gas-sensing performance. The molar ratio of Ce to Sn can be controlled by precisely measuring the amount of cerium salt and tin salt added to the reaction.

[0008] Preferably, the ratio of the amount of Au nanoparticles to the amount of Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is 0.1 to 1:100. This ratio represents the loading amount of Au nanoparticles in the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material. This range is to ensure that the Au nanoparticles are uniformly loaded on the surface of the composite material, forming an effective synergistic effect of electronic and chemical sensitization, thereby improving the gas-sensitive response sensitivity. The loading amount of Au nanoparticles can be precisely controlled by adjusting the concentration and amount of chloroauric acid solution.

[0009] A second aspect of the present invention provides a method for preparing the above-mentioned Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material, comprising: The tin salt solution is mixed with the alkaline solution to obtain solution A; Solution B is obtained by mixing a cerium salt solution with a surfactant solution. Solution A and solution B are mixed, followed by ultrasonication and heating, and then a hydrothermal reaction is carried out. After the hydrothermal reaction is completed, the mixture is cooled, and the material obtained after cooling is subjected to solid-liquid separation to obtain a solid product. The solid product is then washed, dried, and calcined in sequence to obtain a CeO2@SnO2 composite material. The stabilizer solution, CeO2@SnO2 composite material, chloroauric acid solution and reducing agent solution are mixed and stirred to obtain a mixture. The mixture is then subjected to solid-liquid separation to obtain a solid material. The solid material is washed and dried to obtain an Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material.

[0010] In a specific embodiment of the present invention, the solvents for the tin salt solution, alkaline solution, cerium salt solution, surfactant solution, stabilizer solution, chloroauric acid solution, and reducing agent solution are all water.

[0011] In this invention, the tin salt in the tin salt solution is a soluble tin salt. Preferably, the tin salt in the tin salt solution of this invention is selected from one or more of tin tetrachloride pentahydrate, tin tetrachloride (SnCl4), and tin sulfate (SnSO4). In a specific embodiment, the tin salt in the tin salt solution is selected from tin tetrachloride pentahydrate.

[0012] Specifically, the method for preparing the tin salt solution includes: mixing tin salt with water and stirring at 60~80℃ (the preparation at this temperature is to accelerate the dissolution efficiency and ensure complete dissolution) to dissolve the tin salt in the water and obtain a tin salt solution.

[0013] In a preferred embodiment, the concentration of the tin salt solution is 0.1~1 mol / L; this concentration range ensures that the tin source is fully dissolved and stably dispersed, avoiding insufficient SnO2 nucleation in the subsequent hydrothermal reaction due to too low a concentration, or particle agglomeration due to too high a concentration, thereby ensuring the uniformity and high sensitivity of the composite gas-sensitive material.

[0014] In this invention, the alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, barium hydroxide solution and ammonia solution; wherein the concentration of the alkaline solution is 0.5~2 mol / L.

[0015] In this invention, the alkaline solution reacts with tin salt to generate a precursor and adjusts the pH value, providing a suitable chemical environment for subsequent reactions. Controlling the concentration of the alkaline solution within the above-mentioned range ensures that the pH value is suitable in the hydrothermal reaction, which can promote the full hydrolysis of tin salt to generate a uniform SnO2 precursor, while avoiding excessively high concentrations that could lead to excessively fast reaction rates and abnormal particle agglomeration, thereby ensuring the structural regularity and gas-sensitive performance stability of the composite material.

[0016] Preferably, the molar ratio of tin in the tin salt solution to alkali in the alkaline solution is 1:1 to 1.5; within this ratio range, it can be ensured that the alkaline solution provides sufficient OH-. - It completely hydrolyzes with tin salt to generate Sn(OH)4, the precursor of SnO2, while avoiding excessive alkali that could lead to excessive particle growth or agglomeration, thus ensuring the uniformity of the CeO2@SnO2 core-shell structure and high gas-sensitive response activity.

[0017] Furthermore, the cerium salt in the cerium salt solution of the present invention is a soluble cerium salt. Preferably, the cerium salt in the cerium salt solution of the present invention is selected from one or more of cerium nitrate hexahydrate, cerium ammonium nitrate, cerium sulfate, and cerium chloride. In a specific embodiment, the cerium salt in the cerium salt solution is selected from cerium nitrate hexahydrate.

[0018] The concentration of the cerium salt solution is 0.05~0.5 mol / L; within this concentration range, the concentration of cerium ions (Ce) can be ensured. 3+ / Ce 4+ Uniform nucleation occurs during the hydrothermal reaction, avoiding excessively high concentrations that lead to CeO2 particle agglomeration or excessively low concentrations that result in incomplete core-shell structure coverage.

[0019] Furthermore, the concentration of the surfactant solution is 0.005~0.05 mol / L; within this concentration range, a stable micelle template can be formed, effectively controlling the size and dispersion of CeO2 nanoparticles, while avoiding excessively high concentrations that could cause template residues to affect the active sites on the material surface, and excessively low concentrations that would lose their structure-guiding effect.

[0020] The surfactant of the present invention can be a cationic, anionic, or nonionic surfactant. Preferably, the surfactant is selected from one or more of hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyvinylpyrrolidone (PVP).

[0021] In a preferred embodiment, the molar ratio of cerium in the cerium salt solution to surfactant in the surfactant solution is 1:0.5~2. Within this ratio range, it can be ensured that the surfactant micelles fully encapsulate the cerium ion precursor, promote the uniform coating of CeO2 on the SnO2 surface to form a core-shell structure, and at the same time prevent excessive surfactant from inhibiting grain growth or insufficient surfactant from causing coating layer defects.

[0022] In a preferred embodiment, the molar ratio of cerium in solution B to tin in solution A is 1:1 to 10. Controlling the molar ratio of tin to cerium during the preparation process, and thus controlling the molar ratio of Ce to Sn in the finished CeO2@SnO2 composite material, can ensure uniform composite of the bimetallic oxides and avoid structural defects or performance degradation due to imbalance in the ratio.

[0023] To ensure uniform mixing of all materials, ultrasonication is required before heating. Preferably, the ultrasonication time is 10-30 minutes. The heating described in this invention is carried out under stirring conditions. In a preferred embodiment, the heating conditions include a temperature of 60-80°C and a time of 2-4 hours.

[0024] Furthermore, the conditions for the hydrothermal reaction include: a temperature of 100~160°C and a time of 8~16 hours.

[0025] The above-mentioned heating and hydrothermal reaction conditions can provide sufficient thermodynamic driving force to promote the uniform hydrolysis of tin salt and cerium salt and form a stable CeO2@SnO2 core-shell structure, while avoiding excessive temperature leading to abnormal particle coarsening or excessive time leading to agglomeration, thereby ensuring the high specific surface area and excellent gas-sensitive response characteristics of the composite material.

[0026] In a specific implementation, after the hydrothermal reaction is completed, the material is naturally cooled to room temperature. The material obtained after cooling is then subjected to solid-liquid separation (usually by centrifugation) to obtain a solid product. The solid product is then washed by alternating centrifugation with anhydrous ethanol and deionized water a total of 6 times (3 times each with anhydrous ethanol and deionized water) to obtain a centrifuged and washed solid product. The centrifuged and washed solid product is then dried and calcined to obtain the CeO2@SnO2 (SCO) composite material.

[0027] In this invention, room temperature refers to 20-30℃.

[0028] The drying conditions include a temperature of 60-80°C and a time of 12-24 hours.

[0029] Furthermore, the calcination conditions include a temperature of 400~600°C and a time of 2~5 hours; controlling the calcination conditions within this range can thoroughly remove residual organic matter on the material surface and promote the appropriate crystallization of CeO2@SnO2 grains.

[0030] In a preferred embodiment of the present invention, the concentration of the stabilizer solution is 0.001~0.05 mol / L, which can effectively stabilize the dispersibility of CeO2@SnO2 nanoparticles and control their size.

[0031] The stabilizer is selected from polyvinylpyrrolidone (PVP) and / or polyvinyl alcohol.

[0032] Preferably, the concentration of the chloroauric acid solution is 0.001~0.01 mol / L to ensure Au 3+ It is uniformly adsorbed onto the surface of the material.

[0033] In this invention, the concentration of the reducing agent solution is 0.01~0.1 mol / L, which is sufficient to fully reduce Au. 3+ For gold nanoparticles (Au) 0 This avoids excessively high concentrations that could lead to violent reactions and Au particle agglomeration, thus synergistically optimizing the gas-sensitive catalytic activity of the composite material. The reducing agent is selected from one or more of NaBH4 (sodium borohydride), ascorbic acid (vitamin C), sodium citrate, and potassium borohydride (KBH4), and is used to reduce the noble metal salt to the corresponding nano-metal particles.

[0034] In the preparation method of this invention, the loading of Au nanoparticles in the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is controlled by controlling the ratio of Au element in chloroauric acid solution to the amount of CeO2@SnO2 composite material, so as to meet the corresponding requirements.

[0035] Furthermore, the ratio of the amount of reducing agent in the reducing agent solution to the amount of Au in the chloroauric acid solution is 1~2:1, that is, n 还原剂 =(1~2)n Au This stoichiometric ratio ensures that the reducing agent completely reduces Au in chloroauric acid. 3+ Au nanoparticles are incorporated to ensure uniform dispersion of Au particles on the surface of the CeO2@SnO2 composite material, thereby achieving highly efficient gas-sensitive catalytic activity; where n 还原剂 This indicates the amount of reducing agent in the reducing agent solution.

[0036] Preferably, the weight ratio of Au element in the chloroauric acid solution to the weight ratio of stabilizer in the stabilizer solution is 1~3:1, i.e., m Au =(1~3) m 稳定剂 Within this range, it can be ensured that the stabilizer molecular chains fully encapsulate the Au particles, preventing aggregation during reduction through steric hindrance; where m Au The weight of Au in a chloroauric acid solution is expressed in m. 稳定剂 This indicates the weight of the stabilizer in the stabilizer solution.

[0037] Further, the process of mixing the stabilizer solution, CeO2@SnO2 composite material, chloroauric acid solution, and reducing agent solution, and then stirring to obtain the mixture includes: mixing the stabilizer solution with the CeO2@SnO2 composite material, stirring at a speed of 300~500 rpm for 10~30 seconds to ensure uniform adsorption of the stabilizer on the surface of the SCO composite material, then mixing with the chloroauric acid solution, stirring for 2~5 minutes to ensure sufficient contact between the chloroauric acid and the SCO composite material, and then quickly (the purpose of rapid addition is to shorten the Au...) 3+ During the free diffusion time in the solution, to avoid local overconcentration leading to agglomeration of reduced gold nanoparticles (AuNPs), the solution is mixed with the reducing agent solution and stirred for 1-3 hours to reduce gold ions to gold nanoparticles and load them onto the surface of the SCO composite material, thus obtaining a mixture.

[0038] Specifically, the mixture is subjected to solid-liquid separation (preferably centrifugation) to obtain a solid material. The solid material is then washed 6 times by alternating centrifugation with deionized water and anhydrous ethanol (3 times each with anhydrous ethanol and deionized water), followed by drying to obtain an Au-doped bimetallic oxide CeO2@SnO2 (Au-SCO) composite gas-sensitive material.

[0039] The drying conditions include a temperature of 60-80°C and a time of 12-24 hours.

[0040] This invention provides a novel Au-SCO composite gas-sensitive material, in which CeO2, an important rare earth oxide, possesses abundant oxygen vacancies and excellent oxygen storage / release capabilities, effectively promoting the adsorption and reaction of gas molecules on the material surface. When SnO2 and CeO2 are combined, the heterojunction structure formed between them facilitates electron transfer, accelerating the charge transfer process and improving the sensor's sensitivity and selectivity. Furthermore, the introduction of CeO2 can effectively modulate the surface properties of SnO2, increasing active sites and further enhancing sensor performance. On the other hand, doping noble metal nanoparticles (such as Au) into metal oxide semiconductor materials is also an important strategy for improving gas-sensing performance. Au nanoparticles not only possess excellent catalytic properties, reducing the adsorption and reaction activation energy of gas molecules on the sensor surface, but also form heterojunction structures through interaction with metal oxides, further promoting electron transfer. The Au-SCO composite gas-sensitive material can utilize the catalytic sensitization effect and heterojunction effect of gold nanoparticles, and its application in sensors can significantly improve the sensor's sensitivity and stability to target gases.

[0041] Based on this, a third aspect of the present invention provides an application of the above-mentioned Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material in a gas sensor.

[0042] The fourth aspect of the present invention provides a gas sensor, wherein the surface of the electrode of the ceramic substrate of the gas sensor is coated with the above-mentioned Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material.

[0043] The ceramic substrate with electrodes in this invention is a special functional element based on conventional materials in the field of sensors, used to support gas-sensitive materials and transmit electrical signals.

[0044] Preferably, the thickness of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material coated on the surface of each gold electrode of the ceramic substrate of the gas sensor is 0.1~5 μm to ensure the sensitivity of the gas-sensitive response.

[0045] The fifth aspect of this invention provides a method for preparing the above-mentioned gas sensor, comprising the following steps: A suspension was obtained by mixing Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material with an organic solvent and then subjecting it to ultrasonic treatment. The suspension is coated onto the surface of the electrodes on the ceramic substrate and then dried to obtain the dried ceramic substrate. The dried ceramic substrate is then soldered onto a six-pin socket to obtain a gas sensor.

[0046] Preferably, the organic solvent is selected from one or more of volatile organic solvents such as anhydrous ethanol, anhydrous methanol, and N,N-dimethylformamide.

[0047] The solid-liquid ratio of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material to the organic solvent is 1g:5~20mL to ensure that the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is fully dispersed in the organic solvent to form a uniform suspension system, thus avoiding particle agglomeration or uneven dispersion caused by excessive solid content.

[0048] In a specific embodiment, the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is mixed with an organic solvent and then subjected to ultrasonic treatment for 30 minutes to obtain a suspension.

[0049] In a specific embodiment, the ceramic substrate used in this invention is 3×3 mm. 2 An alumina ceramic substrate, wherein gold electrodes are integrated on both sides of the alumina ceramic substrate (each integrated gold electrode is strip-shaped, 0.5 mm wide, and the gap between two adjacent gold electrodes is 1 mm).

[0050] Specifically, the drying conditions include a temperature of 60-80°C and a time of 12-24 hours.

[0051] The sixth aspect of the present invention provides an application of the above-mentioned gas sensor in the detection of H2 and C2H2.

[0052] This invention provides an Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material prepared by hydrothermal synthesis and its application in gas sensors. This composite material combines the excellent electron transport properties of SnO2 with the superior redox characteristics of CeO2. By achieving uniform dispersion and interfacial synergy of the two at the nanoscale, the specific surface area of ​​the material is significantly improved. This invention overcomes the technical bottlenecks in gas-sensitive material design, such as single material composition, insufficient reactivity, and unstable response performance, providing a new technical approach for constructing highly sensitive and stable gas sensors.

[0053] Au nanoparticles were impregnated into CeO2@SnO2 composite materials to construct an Au-SCO multi-component composite structure, which was then fabricated into a sensor to enhance the performance of gas sensors. The introduction of Au forms highly dispersed metal nanoparticles on the material surface, endowing the material with excellent surface plasmon resonance and catalytic activity, further improving its responsiveness to gas molecules. It also promotes rapid electron transfer between the two components. The introduction of Au nanoparticles further enriches the surface properties of the material and provides more active sites.

[0054] The Au-doped CeO2@SnO2 composite gas-sensitive material of this invention is obtained through a modified hydrothermal synthesis method combined with impregnation reduction doping technology. The introduction of CeO2 helps to regulate the surface structure and electronic properties of SnO2, enhancing its surface activity. The doping of Au nanoparticles further promotes the electron transfer effect at the heterojunction interface, thereby enhancing the response performance to dissolved gases H2 and C2H2 in transformer oil. Furthermore, the obtained gas-sensitive material is mixed with a solvent and coated onto a ceramic substrate, ultimately yielding a high-performance gas sensor based on the Au-doped CeO2@SnO2 composite gas-sensitive material for detecting dissolved gases H2 and C2H2 in transformer oil. This sensor possesses advantages such as fast response speed and high detection sensitivity, making it suitable for status sensing and fault early warning of power grid transformer equipment.

[0055] Compared with the prior art, the present invention has the following technical effects: Enhanced redox activity: CeO2 has unique redox reversibility and high concentration of oxygen vacancies. When combined with SnO2, it can effectively improve the adsorption and reaction activity of materials for oxygen and reducing gases H2 and C2H2, enhance the interfacial reaction efficiency between gas molecules H2 and C2H2 and active oxygen, and improve the sensitivity of gas sensors when made into gas sensors.

[0056] Constructing heterojunction interfaces: SnO2 and CeO2 form a stable n–n type heterojunction structure during recombination, which enhances electron migration channels, effectively reduces interface resistance, and increases carrier migration rate. When used in sensors, this can improve the response sensitivity of gas-sensitive devices.

[0057] Noble metal doping promotes catalytic reactions: Au nanoparticles are uniformly loaded onto the surface of SnO2-CeO2 by impregnation. The surface catalytic activity of Au significantly promotes the dissociation, adsorption and oxidation reaction of gas molecules, thereby further improving the gas response sensitivity of the material. Attached Figure Description

[0058] Figure 1 This is a schematic diagram illustrating the preparation of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of the present invention; Figure 2 This is a SEM image of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material from Example 6; Figure 3 These are the XRD patterns of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 6, the SnO2 material of Comparative Example 1, and the CeO2 material of Comparative Example 3. Figure 4The N2 adsorption-desorption curves are those of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 6, the SnO2 material of Comparative Example 1, the CeO2 material of Comparative Example 3, and the CeO2@SnO2 composite material of Comparative Example 5. Figure 5 The gas sensors of Example 12, Comparative Examples 2, 4, and 6 are the response curves of the gas sensors to 20 ppm H2 at different operating temperatures. Figure 6 The gas sensors of Example 12, Comparative Examples 2, 4, and 6 are the response curves of the gas sensors to 20 ppm C2H2 at different operating temperatures. Detailed Implementation

[0059] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0060] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0061] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0062] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions provided in the various embodiments of this invention can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0063] The present invention will be described in detail below through embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0064] A schematic diagram of the preparation of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of the present invention is shown below. Figure 1 As shown.

[0065] The room temperature in the following examples refers to 25°C.

[0066] Example 1 (1) Add 3.5 g of tin tetrachloride pentahydrate (SnCl4·5H2O) to 20 mL of deionized water and heat to 60 °C in a water bath with stirring to dissolve the tin salt in the water to obtain a tin salt solution with a concentration of 0.5 mol / L. Then, add 10 mL of 1 mol / L alkaline solution (sodium hydroxide (NaOH) solution) dropwise to the tin salt solution. The molar ratio of tin element in the tin salt solution to alkali in the alkaline solution is 1:1. Mix and stir evenly to obtain solution A. (2) In another beaker, 1.1 g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was dissolved in 20 mL of deionized water to obtain a cerium salt solution with a concentration of 0.13 mol / L. 25.3 mL of a surfactant (hexadecyltrimethylammonium bromide, CTAB) solution with a concentration of 0.05 mol / L was added to the cerium salt solution and the stirring was continued until the mixture was homogeneous. The molar ratio of cerium element in the cerium salt solution to surfactant in the surfactant solution was 1:0.5, and solution B was obtained. (3) Mix a certain amount of solution A and solution B, control the molar ratio of cerium in solution B to tin in solution A to be 1:3, then sonicate for 20 minutes, and then transfer to a 250 mL three-necked flask. Stir and heat in a 60 °C constant temperature water bath for 2 hours to obtain a mixture. Place the mixture in a high pressure vessel with a polytetrafluoroethylene liner and hydrothermally react at 120 °C for 12 hours. After the hydrothermal reaction is completed, cool naturally to room temperature. Centrifuge the material obtained after cooling to collect the precipitate and obtain a solid product. Wash the solid product with anhydrous ethanol and deionized water alternately 6 times (3 times each with anhydrous ethanol and deionized water) to obtain a centrifuged and washed solid product. Dry the centrifuged and washed solid product in a vacuum oven at 60 °C for 12 hours, and then calcine it in an air atmosphere at 400 °C for 2 hours to obtain CeO2@SnO2 (SCO) composite material. (4) Prepare a 0.005 mol / L chloroauric acid (HAuCl4) solution. Weigh 0.5 g of the SCO composite material obtained in step (3). Slowly add a 0.01 mol / L stabilizer (polyvinylpyrrolidone, PVP) solution to the beaker containing the SCO composite material and mix. Stir at 300 rpm for 10 seconds to allow PVP to be uniformly adsorbed onto the surface of the SCO composite material. Then, accurately add a certain volume of chloroauric acid solution using a pipette and mix. Continue stirring for 2 minutes to ensure that the chloroauric acid and SCO composite material are fully in contact. Then, quickly add a certain amount of 0.05 mol / L reducing agent (NaBH4) solution and mix. Continue stirring for 1 hour to promote the Au 3+ The Au nanoparticles were reduced and loaded onto the surface of the SCO composite material to obtain a mixture. The amount of Au in the added chloroauric acid solution was controlled so that the final ratio of Au nanoparticles to the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material was 0.5:100. Au = m 稳定剂 n 还原剂 = 1.8 n Au The ratio of the amount of reducing agent in the added reducing agent solution to the amount of Au in the chloroauric acid solution was 1.8:1, and the ratio of the weight of Au in the chloroauric acid solution to the weight of the stabilizer in the stabilizer solution was 1:1. The mixture was centrifuged to collect the precipitate, and a solid material was obtained. The solid material was washed 6 times by alternating centrifugation with anhydrous ethanol and deionized water (3 times each with anhydrous ethanol and deionized water), and then dried in a vacuum oven at 60 °C for 24 hours to obtain the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material.

[0067] Example 2 The method of Example 1 is implemented, except that in step (3), the molar ratio of cerium in solution B to tin in solution A is controlled to be 1:5; in step (4), the amount of Au in the added chloroauric acid solution is controlled so that the final ratio of the amount of Au nanoparticles to the amount of Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is 0.3:100.

[0068] Example 3 The method is implemented according to Example 1, except that in step (3), the molar ratio of cerium in solution B to tin in solution A is controlled to be 1:7.

[0069] Example 4 The method of Example 1 was implemented, except that in step (3), the molar ratio of cerium in solution B to tin in solution A was controlled to be 1:8; in step (4), a 0.05 mol / L stabilizer solution was slowly added to a beaker containing SCO composite material and mixed; the amount of Au in the added chloroauric acid solution was controlled so that the final ratio of the amount of Au nanoparticles to the amount of Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material was 0.7:100.

[0070] Example 5 The method of Example 1 was implemented, except that in step (3), the molar ratio of cerium in solution B to tin in solution A was controlled to be 1:9; in step (4), the concentration of the reducing agent solution was 0.01 mol / L; and the amount of Au in the added chloroauric acid solution was controlled so that the final ratio of the amount of Au nanoparticles to the amount of Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material was 0.9:100.

[0071] Example 6 An Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is disclosed. This material comprises a CeO2@SnO2 composite material and Au nanoparticles loaded on the surface of the CeO2@SnO2 composite material. The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is prepared using the method described in Example 1. The molar ratio of Ce to Sn in the CeO2@SnO2 composite material is 1:3. The molar ratio of Au nanoparticles to the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is 0.5:100. This Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is designated as Au-SCO5 composite gas-sensitive material.

[0072] Example 7 An Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is disclosed, comprising a CeO2@SnO2 composite material and Au nanoparticles loaded on the surface of the CeO2@SnO2 composite material. The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is prepared using the method described in Example 2. The molar ratio of Ce to Sn in the CeO2@SnO2 composite material is 1:5, and the molar ratio of Au nanoparticles to the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is 0.3:100.

[0073] Example 8 An Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is disclosed, comprising a CeO2@SnO2 composite material and Au nanoparticles loaded on the surface of the CeO2@SnO2 composite material. The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is prepared using the method described in Example 3. The molar ratio of Ce to Sn in the CeO2@SnO2 composite material is 1:7, and the molar ratio of Au nanoparticles to the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is 0.5:100.

[0074] Example 9 An Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is disclosed, comprising a CeO2@SnO2 composite material and Au nanoparticles loaded on the surface of the CeO2@SnO2 composite material. The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is prepared using the method described in Example 4. The molar ratio of Ce to Sn in the CeO2@SnO2 composite material is 1:8, and the molar ratio of Au nanoparticles to the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is 0.7:100.

[0075] Example 10 An Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is disclosed, comprising a CeO2@SnO2 composite material and Au nanoparticles loaded on the surface of the CeO2@SnO2 composite material. The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is prepared using the method described in Example 5. The molar ratio of Ce to Sn in the CeO2@SnO2 composite material is 1:9, and the molar ratio of Au nanoparticles to the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is 0.9:100.

[0076] Example 11 The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive materials in Examples 6-10 combine the excellent electron transport properties of SnO2 with the excellent redox properties of CeO2. By achieving uniform dispersion and interfacial synergy of the two at the nanoscale, the specific surface area of ​​the material is significantly improved. The introduction of Au nanoparticles further enriches the surface properties of the material and provides more active sites. This composite gas-sensitive material exhibits extremely high sensitivity to transformer oil dissolved gases such as H2 and C2H2, and can be applied to gas sensors, further improving the sensitivity of gas sensors.

[0077] The ceramic substrates used in the following examples and comparative examples are all 3×3 mm. 2 An alumina ceramic substrate, wherein gold electrodes are integrated on both sides of the alumina ceramic substrate (each integrated gold electrode is strip-shaped, 0.5 mm wide, and the gap between two adjacent gold electrodes is 1 mm).

[0078] Example 12 A gas sensor (Au-SCO5 gas sensor) is provided, wherein the surface of the electrode of the ceramic substrate of the gas sensor is coated with the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 6.

[0079] Example 13 A gas sensor, wherein the surface of the electrode of the ceramic substrate of the gas sensor is coated with the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 7.

[0080] Example 14 A gas sensor, wherein the surface of the electrode of the ceramic substrate of the gas sensor is coated with the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 8.

[0081] Example 15 A gas sensor, wherein the surface of the electrode of the ceramic substrate of the gas sensor is coated with the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 9.

[0082] Example 16 A gas sensor, wherein the surface of the electrode of the ceramic substrate of the gas sensor is coated with the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 10.

[0083] Example 17 The method for preparing the gas sensor in Example 12 specifically includes the following steps: S1. The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 6 was mixed with an organic solvent (anhydrous ethanol) at a solid-liquid ratio of 1g:10mL and then subjected to ultrasonic treatment for 30 minutes to obtain a uniform suspension. S2. Using a dropper, the suspension is uniformly coated onto the surface of each gold electrode on the ceramic substrate, ensuring a consistent coating thickness. Then, it is dried in a vacuum oven at 60°C for 24 hours to form a uniform sensitive layer film, resulting in a dried ceramic substrate. The dried ceramic substrate is then soldered onto a six-pin socket to complete the assembly, thus obtaining a gas sensor. The thickness of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material coated on the surface of each gold electrode on the ceramic substrate of the gas sensor is 5 μm.

[0084] Example 18 The gas sensor preparation method of Example 13 is carried out according to the method of Example 17, except that the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 7 is used in step S1 to prepare the gas sensor.

[0085] Example 19 The gas sensor preparation method of Example 14 is carried out according to the method of Example 17, except that the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 8 is used in step S1 to prepare the gas sensor.

[0086] Example 20 The gas sensor preparation method of Example 15 is carried out according to the method of Example 17, except that the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 9 is used in step S1 to prepare the gas sensor.

[0087] Example 21 The gas sensor preparation method of Example 16 is carried out according to the method of Example 17, except that the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 10 is used in step S1 to prepare the gas sensor.

[0088] Example 22 The gas sensors in Examples 12-16 all have good sensitivity and can be used to detect H2 and C2H2.

[0089] Comparative Example 1 The method was implemented according to Example 1, except that the solution A obtained in step (1) was directly transferred to a 250 mL three-necked flask and heated in a constant temperature water bath at 60 °C for 2 hours. Then it was placed in a high pressure vessel with a polytetrafluoroethylene liner and hydrothermally reacted at 120 °C for 12 hours. After the hydrothermal reaction was completed, it was naturally cooled to room temperature. The material obtained after cooling was centrifuged to collect the precipitate and obtain a solid product. The solid product was washed 6 times by alternating centrifugation with anhydrous ethanol and deionized water (3 times each by centrifugation with anhydrous ethanol and deionized water) to obtain a centrifuged and washed solid product. The centrifuged and washed solid product was dried in a vacuum oven at 60 °C for 12 hours and then calcined in an air atmosphere at 400 °C for 2 hours to obtain SnO2 material.

[0090] Comparative Example 2 The method of Example 17 was implemented, except that in step S1, the SnO2 material in Comparative Example 1 was used instead of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material in Example 6 to obtain a gas-sensitive sensor (SnO2 gas-sensitive sensor).

[0091] Comparative Example 3 The method was implemented according to Example 1, except that solution A was not prepared. Solution B was directly transferred to a 250 mL three-necked flask and heated with stirring in a 60 °C constant temperature water bath for 2 hours. Then, it was placed in a polytetrafluoroethylene-lined autoclave and hydrothermally reacted at 120 °C for 12 hours. After the hydrothermal reaction, it was naturally cooled to room temperature. The material obtained after cooling was collected by centrifugation to obtain a solid product. The solid product was washed 6 times by alternating centrifugation with anhydrous ethanol and deionized water (3 times each with anhydrous ethanol and deionized water) to obtain a centrifuged and washed solid product. The centrifuged and washed solid product was dried in a vacuum oven at 60 °C for 12 hours and then calcined in an air atmosphere at 400 °C for 2 hours to obtain CeO2 material.

[0092] Comparative Example 4 The method of Example 17 was implemented, except that in step S1, the CeO2 material in Comparative Example 3 was used instead of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material in Example 6 to obtain a gas-sensitive sensor (CeO2 gas-sensitive sensor).

[0093] Comparative Example 5 CeO2@SnO2 (SCO) composite material was prepared by the method in steps (1) to (3) of Example 1.

[0094] Comparative Example 6 The method of Example 17 was implemented, except that in step S1, the CeO2@SnO2 (SCO) composite material of Comparative Example 5 was used instead of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 6 to obtain a gas-sensitive sensor (SCO gas-sensitive sensor).

[0095] Comparative Example 7 The method of Example 1 was implemented, except that in step (4), no stabilizer solution was used to obtain the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material.

[0096] Comparative Example 8 The method of Example 17 was implemented, except that in step S1, the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 6 was replaced with the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Comparative Example 7 to obtain a gas-sensitive sensor.

[0097] Test Example 1 The Au-doped CeO2@SnO2 composite gas-sensitive material of Example 6 was examined using scanning electron microscopy (SEM). The SEM images are shown below. Figure 2 As shown, from Figure 2 As can be seen, the Au-doped CeO2@SnO2 composite gas-sensitive material particles prepared in this invention still maintain a certain degree of surface roughness, which is beneficial to gas detection performance. This roughness provides sufficient surface area and active sites for the adsorption and reaction of gas molecules, while also ensuring rapid diffusion and transport of gas molecules within the material. Therefore, the gas sensor prepared using this material can respond more quickly to changes in gas concentration and shorten the response time. Further SEM analysis of the Au-doped CeO2@SnO2 composite gas-sensitive materials in Examples 7-10 showed results consistent with... Figure 2 Similarly, the surface of these Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive materials all maintain a certain degree of roughness.

[0098] Test Example 2 XRD analysis was performed on the Au-doped bimetallic oxide CeO2@SnO2 (Au-SCO) composite gas-sensitive material of Example 6, the SnO2 material of Comparative Example 1, and the CeO2 material of Comparative Example 3. The XRD patterns are shown below. Figure 3 As shown, from Figure 3It can be clearly observed that the Au-SCO composite gas-sensitive material contains characteristic peaks belonging to both SnO2 and CeO2, confirming that the Au-SCO composite gas-sensitive material contains both SnO2 and CeO2 components, and that they coexist in crystalline form. At the same time, the doping of Au does not affect the crystal form of SCO, indicating that Au is doped in the form of metal particles. This suggests that the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material includes CeO2@SnO2 composite material and Au nanoparticles loaded on the surface of CeO2@SnO2 composite material. Further XRD analysis was performed on the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive materials in Examples 7-10. The results were consistent with... Figure 3 Similarly, the Au-SCO composite gas-sensitive materials in Examples 7-10 simultaneously exhibit characteristic peaks belonging to SnO2 and CeO2, and coexist in crystalline form. Furthermore, the doping of Au does not affect the crystal structure of SCO, indicating that Au is doped in the form of metal particles. Moreover, these Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive materials all include CeO2@SnO2 composite materials and Au nanoparticles loaded on the surface of CeO2@SnO2 composite materials.

[0099] Test Example 3 The N2 adsorption-desorption curves of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material of Example 6, the SnO2 material of Comparative Example 1, the CeO2 material of Comparative Example 3, and the CeO2@SnO2 (SCO) composite material of Comparative Example 5 were measured. The specific procedures were as follows: First, each material was placed in a surface area and porosity analyzer. Then, the materials were degassed at 120°C to remove adsorbed impurity gases from the material surface. Next, nitrogen was introduced into the testing system as the adsorbate. By precisely controlling the partial pressure of nitrogen, the nitrogen concentration was gradually increased, and the amount of nitrogen adsorbed by each material at different nitrogen concentrations was recorded. After measuring the adsorption process, the nitrogen concentration was gradually decreased, and the desorption process was measured, recording the amount of nitrogen released during desorption. The N2 adsorption-desorption curves of each material were obtained by plotting the relationship between the adsorption amount and the partial pressure of nitrogen.

[0100] The N2 adsorption-desorption curve is as follows: Figure 4 As shown, from Figure 4 It can be seen that the specific surface area of ​​the Au-SCO composite gas-sensitive material in Example 6 is 227 m². 2 The surface area ( / g) was significantly higher than that of the SCO composite material (176 m²). 2 / g), SnO2 specific surface area (116 m²) 2 / g) and CeO2 specific surface area (85 m²) 2 / g). This is mainly attributed to the heterojunction effect generated when CeO2 and SnO2 are combined. The lattice mismatch at the interface induces the formation of defects (such as oxygen vacancies) and promotes the generation of mesopores / micropores. Simultaneously, the loading of Au nanoparticles may further alter the morphology of the support through surface modification, thereby increasing the specific surface area. The high specific surface area of ​​the Au-SCO composite gas-sensitive material provides more adsorption sites for gas molecules, thus enhancing the material's adsorption capacity for target gases; The N2 adsorption-desorption curves of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive materials in Examples 7-10 were detected using the same method. The results showed that the N2 adsorption-desorption curves of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive materials in Examples 7-10 were 168 μm. 2 / g、171 m 2 / g、166 m 2 / g、165 m 2 / g, and all of them have mesoporous / microporous structures.

[0101] Test Example 4 As target gas molecules adsorb onto the surface of the gas sensor, electrons are transferred from the sensor material to the target molecules, causing a change in the resistance of the gas 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 gas sensor for H2 and C2H2 dissolved gases in transformer oil.

[0102] The response curves of the gas sensor in Example 12, and the gas sensors in Comparative Examples 2, 4, and 6 to 20 ppm H2 were measured. First, each gas sensor was placed in a test chamber with a controlled atmosphere. Then, a mixed gas containing 20 ppm H2 (typically nitrogen or air as the balance gas) was injected into the test chamber using a precise gas flow controller. Simultaneously, a high-precision temperature and humidity control system was used to maintain the stability and consistency of the test environment. The response values ​​of each gas sensor to 20 ppm H2 at different temperatures were measured, and the response curves were obtained, as shown below. Figure 5 As shown.

[0103] The response curves of the gas sensor in Example 12, and the gas sensors in Comparative Examples 2, 4, and 6 to 20 ppm C2H2 were determined as follows: First, each gas sensor was placed in a test chamber with a controlled atmosphere. Then, a mixed gas containing 20 ppm C2H2 (typically nitrogen or air as the balance gas) was injected into the test chamber using a precise gas flow controller. Simultaneously, a high-precision temperature and humidity control system was used to maintain the stability and consistency of the test environment. The response values ​​of each gas sensor to 20 ppm C2H2 at different temperatures were measured, and the response curves were obtained, as shown below. Figure 6 As shown.

[0104] from Figure 5 As can be seen, the gas sensor of Example 12 exhibits excellent response characteristics at various test temperatures. At 150°C, the response value to 20 ppm H2 is as high as 50.7, which is significantly better than the gas sensors of Comparative Example 2 (response value 18.1), Comparative Example 4 (response value 22.7) and Comparative Example 6 (response value 35.9) at the same temperature. The response enhancement factors are 2.8, 2.2 and 1.4 times, respectively, which further verifies the synergistic enhancement effect produced by noble metal doping and bimetallic oxide composite. from Figure 6 As can be seen, at the optimal temperature (150°C), the response values ​​of each sensor to 20 ppm C2H2 are as follows: SnO2 gas sensor is 5.7, CeO2 gas sensor is 12.4, and SCO gas sensor is 49.5. The gas sensor in Example 12 has the highest response value, reaching 57.3, which is about 10 times that of the pure SnO2 gas sensor. This fully demonstrates the significant advantage of the synergistic effect of the composite structure and noble metal in enhancing the C2H2 response. The response value is calculated using the formula for an n-type semiconductor gas sensor: S=R g / R a S is the response value, R g R is the resistance value of the gas sensor in air. a This represents the resistance value of the gas sensor in the gas being measured. The response time, recovery time, and stability of the gas sensor of Example 12, and the gas sensors of Comparative Examples 2, 4, and 6 were further tested at an operating temperature of 150°C. The results are shown in Table 1. The response time is measured by placing the gas sensor in a clean air environment and stabilizing the baseline. Then, 20 ppm of target gas (usually nitrogen or air as the balance gas) is rapidly introduced. The time required for the sensor resistance value to change from the initial value to 90% of the total change is recorded as the response time. The recovery time is measured as follows: after the sensor reaches a stable response to the target gas, it is quickly switched back to a clean air environment, and the time required for its resistance value to recover from the stable response value to 90% of the initial baseline value is recorded. The stability testing method is as follows: The gas sensor is continuously operated for 30 days in a target gas of 20 ppm H2 (usually nitrogen or air as the equilibrium gas), and its response value to the target gas is measured at regular intervals every day. When calculating the stability change rate, the response value of the first detection on day 1 is compared with the response value of the last detection on day 30, and the rate of change of the response value over 30 days is statistically analyzed. The calculation formula is: Rate of change (%) = (First response value - Last response value) / First response value × 100% The response curves of the gas sensors of Examples 13-16 and Comparative Example 8 to 20 ppm H2, the response curves to 20 ppm C2H2, the response time, the recovery time, and the stability were tested using the same method. The gas sensors of Examples 13-16 and Comparative Example 8 all showed the maximum response values ​​to 20 ppm H2 and 20 ppm C2H2 at an operating temperature of 150℃. The specific maximum response value, response time, recovery time, and stability are shown in Table 1.

[0105] Table 1 As shown in Table 1, the Au-SCO5 gas sensor in Example 12 exhibited the highest response values ​​(50.7 and 57.3) to 20 ppm H2 and C2H2 at an operating temperature of 150°C, significantly outperforming the response values ​​of comparative examples 2 (SnO2), 4 (CeO2), and 6 (SCO). The response values ​​of the other examples were also superior to the comparative examples, fully demonstrating the enhancement effect brought about by the synergistic combination of gold nanoparticle doping and bimetallic oxides. Furthermore, it was superior to the response values ​​(36.7 and 42.7) of comparative example 8 (without stabilizer), indicating that the addition of the stabilizer further optimized the dispersibility of the Au nanoparticles, reduced agglomeration, and thus enhanced the gas-sensing response. Furthermore, the response time and recovery time of the Au-SCO5 gas sensor in Example 12 were 16.5 seconds and 18.3 seconds, respectively, which were significantly faster than the other comparative examples, including Comparative Example 8 without stabilizer (19.8 seconds and 21.7 seconds). The response and recovery times of the other examples were also faster than the comparative examples, indicating that the stabilizer, by regulating the surface structure of the material, promoted the adsorption and desorption kinetics of gas molecules, resulting in excellent rapid detection capabilities. In the stability test, the gas sensor of the examples showed minimal fluctuation in response value during 30 consecutive days of testing, demonstrating excellent response consistency and long-term stability. In contrast, the single metal oxide sensors of Comparative Examples 2 and 4 were significantly inferior in terms of response intensity, response time, and stability. Although Comparative Example 6 outperformed the single oxide in performance, it still did not match the overall performance of the gas sensor in the examples. While the composite material without stabilizer (Comparative Example 8) outperformed the single oxide, it still did not match the overall performance of the examples, highlighting the triple enhancement effect of Au doping, bimetallic oxide synergy, and stabilizer regulation.

[0106] It should be understood that any parts not described in detail in this specification belong to the prior art.

[0107] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material, characterized in that, The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material includes a CeO2@SnO2 composite material and Au nanoparticles loaded on the surface of the CeO2@SnO2 composite material.

2. The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material according to claim 1, characterized in that, The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material has a specific surface area of ​​100~300 m². 2 / g; and / or The molar ratio of Ce to Sn in the CeO2@SnO2 composite material is 1:1~10; and / or The ratio of the amount of Au nanoparticles to the amount of Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material is 0.1~1:

100.

3. The preparation method of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material according to claim 1 or 2, characterized in that, include: The tin salt solution is mixed with the alkaline solution to obtain solution A; Solution B is obtained by mixing a cerium salt solution with a surfactant solution. Solution A and solution B are mixed, followed by ultrasonication and heating, and then a hydrothermal reaction is carried out. After the hydrothermal reaction is completed, the mixture is cooled, and the material obtained after cooling is subjected to solid-liquid separation to obtain a solid product. The solid product is then washed, dried, and calcined in sequence to obtain a CeO2@SnO2 composite material. The stabilizer solution, CeO2@SnO2 composite material, chloroauric acid solution and reducing agent solution are mixed and stirred to obtain a mixture. The mixture is then subjected to solid-liquid separation to obtain a solid material. The solid material is washed and dried to obtain an Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material.

4. The preparation method according to claim 3, characterized in that, The tin salt in the tin salt solution is selected from one or more of tin tetrachloride pentahydrate, tin tetrachloride, and tin sulfate; and / or The concentration of the tin salt solution is 0.1~1 mol / L; and / or The alkaline solution is selected from one or more of sodium hydroxide solution, potassium hydroxide solution, barium hydroxide solution, and ammonia solution; and / or The concentration of the alkaline solution is 0.5~2 mol / L; and / or The molar ratio of tin in the tin salt solution to alkali in the alkaline solution is 1:1 to 1.

5.

5. The preparation method according to claim 3 or 4, characterized in that, The cerium salt in the cerium salt solution is selected from one or more of cerium nitrate hexahydrate, cerium ammonium nitrate, cerium sulfate, and cerium chloride; and / or The concentration of the cerium salt solution is 0.05~0.5 mol / L; and / or The concentration of the surfactant solution is 0.005~0.05 mol / L; and / or The surfactant is selected from one or more of cetyltrimethylammonium bromide, sodium dodecyl sulfate, and polyvinylpyrrolidone; and / or The molar ratio of cerium in the cerium salt solution to surfactant in the surfactant solution is 1:0.5~2.

6. The preparation method according to claim 3, characterized in that, The molar ratio of cerium in solution B to tin in solution A is 1:1~10.

7. The preparation method according to claim 3 or 6, characterized in that, The heating is carried out under stirring conditions; and / or The heating conditions include: a temperature of 60-80°C and a time of 2-4 hours; and / or The conditions for the hydrothermal reaction include: a temperature of 100–160°C and a time of 8–16 hours; and / or The calcination conditions include a temperature of 400-600°C and a time of 2-5 hours.

8. The preparation method according to claim 3, characterized in that, The concentration of the stabilizer solution is 0.001~0.05 mol / L; and / or The stabilizer is selected from polyvinylpyrrolidone and / or polyvinyl alcohol; and / or The concentration of the chloroauric acid solution is 0.001~0.01 mol / L; and / or The concentration of the reducing agent solution is 0.01~0.1 mol / L; and / or The reducing agent is selected from one or more of NaBH4, ascorbic acid, sodium citrate, and potassium borohydride; and / or The ratio of the amount of reducing agent in the reducing agent solution to the amount of Au in the chloroauric acid solution is 1~2:1; and / or The weight ratio of Au in the chloroauric acid solution to the weight of the stabilizer in the stabilizer solution is 1~3:

1.

9. The preparation method according to claim 3, characterized in that, The process of mixing and stirring the stabilizer solution, CeO2@SnO2 composite material, chloroauric acid solution and reducing agent solution to obtain a mixture includes: mixing the stabilizer solution with the CeO2@SnO2 composite material, stirring at a speed of 300~500 rpm for 10~30 seconds, then mixing with the chloroauric acid solution, stirring for 2~5 minutes, then mixing with the reducing agent solution, and stirring for 1~3 hours to obtain the mixture.

10. The preparation method according to claim 3 or 9, characterized in that, The drying conditions include a temperature of 60-80°C and a time of 12-24 hours.

11. The application of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material as described in claim 1 or 2 in gas-sensitive sensors.

12. A gas-sensitive sensor, characterized in that, The surface of the electrodes on the ceramic substrate of the gas sensor is coated with the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material as described in claim 1 or 2.

13. The gas sensor according to claim 12, characterized in that, The Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material coated on the surface of the electrodes of the ceramic substrate of the gas sensor has a thickness of 0.1~5 μm.

14. A method for preparing a gas sensor according to claim 12 or 13, characterized in that, include: A suspension was obtained by mixing Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material with an organic solvent and then subjecting it to ultrasonic treatment. The suspension is coated onto the surface of the electrodes on the ceramic substrate and then dried to obtain the dried ceramic substrate. The dried ceramic substrate is then soldered onto a six-pin socket to obtain a gas sensor.

15. The preparation method according to claim 14, characterized in that, The organic solvent is selected from one or more of anhydrous ethanol, anhydrous methanol, and N,N-dimethylformamide; and / or The solid-liquid ratio of the Au-doped bimetallic oxide CeO2@SnO2 composite gas-sensitive material to the organic solvent is 1 g: 5~20 mL; and / or The drying conditions include a temperature of 60-80℃ and a time of 12-24 hours.

16. The application of the gas sensor according to claim 12 or 13 in the detection of H2 and C2H2.

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