Indium oxide composite material, preparation method and application thereof, and gas sensor

Abstract

The application provides an indium oxide composite material and a preparation method, application and gas sensor thereof. The indium oxide composite material comprises Au x Pt (1‑x) -In2O3, 0 x Pt (1‑x) -In2O3, In2O3 as a core, In2O3 as a three-dimensional micron flower structure, Au x Pt (1‑x) -In2O3, Au x Pt (1‑x) modified on the surface of In2O3. The three-dimensional micron flower structure In2O3 serves as a core, the three-dimensional micron flower structure increases the specific surface area of In2O3, the increase of the total adsorbed gas molecules, the sharp reduction of the number of most carriers in the surface layer of the indium oxide material, the formation of a wider space depletion layer in the surface layer of the indium oxide material, and the promotion of the gas sensing performance of the indium oxide material; the Au x Pt (1‑x) alloy modified indium oxide retains high catalytic activity and synergistic catalytic effect, and significantly improves the gas sensing performance of the indium oxide composite material.

Description

Technical Field

[0001] This application belongs to the technical field of gas-sensitive materials and their preparation processes, and more specifically, it relates to indium oxide composite materials, their preparation methods, applications, and gas sensors. Background Technology

[0002] To enable real-time monitoring of various toxic and harmful gases in the atmosphere and to provide a comfortable and safe environment for human production and life, gas sensor technology has emerged. A gas sensor is a device that converts information such as the type and concentration of a target gas into an electrical signal. It can detect changes in this signal by measuring current, resistance, capacitance, and potential. It is reported that there are currently over 6,000 types of sensors in my country, while internationally there are over 20,000. With the widespread application of gas sensors, the performance requirements are becoming increasingly stringent. Sensors are required not only to have good sensitivity and selectivity, but also high stability, cost-effectiveness, ease of integration, and low power consumption.

[0003] Among numerous gas sensors, semiconductor metal oxide gas sensors have been most widely used due to their advantages such as low cost, small size, and mature manufacturing process. Currently, for the detection of NO2 gas, various metal oxide gas-sensitive materials such as ZnO, SnO2, In2O3, and WO3 are available. WO3 material has a high response value but a long response time; SnO2 material has a shorter response time than WO3, but a lower response value; ZnO material has a very short response time, but its optimal operating temperature is high and its response value is low.

[0004] Compared with the aforementioned semiconductor oxide materials, In2O3 materials have advantages such as a wide band gap, low cost, richer nanostructure morphology, and ease of fabrication into materials with large specific surface area. At the same time, compared with other metal oxide gas-sensitive materials, gas sensors constructed from In2O3 materials have the characteristics of low detection limit, high response value, and stable device performance for NO2 gas. Therefore, In2O3 gas sensors have very good application prospects in the field of gas sensing.

[0005] In recent years, significant progress has been made in research on using In2O3 composite materials as gas-sensitive materials to construct gas sensors. However, current research on In2O3 composite materials has the following shortcomings:

[0006] (1) Early research on the gas-sensing properties of noble metal-In2O3 composite materials mainly focused on the composite of a single noble metal with In2O3 material, and the response value was low.

[0007] (2) In existing bimetallic-In2O3 composite materials, the bimetal is combined with the matrix material in the form of metal oxide, which reduces the gas-sensing effect;

[0008] (3) Existing bimetallic-In2O3 composite gas sensors have high operating temperatures and are not convenient to use. Summary of the Invention

[0009] Based on this, the purpose of this application is to provide indium oxide composite materials, their preparation methods, applications, and gas sensors, in order to solve the technical problem of low gas sensing performance of existing In2O3 composite materials.

[0010] To achieve the above-mentioned objectives, the technical solution of this application is as follows:

[0011] In a first aspect, an indium oxide composite material is provided, comprising Au x Pt (1-x) -In₂O₃, 0 < x < 1, Au x Pt (1-x) -In₂O₃ uses In₂O₃ as its core, and In₂O₃ has a three-dimensional micron flower structure, Au x Pt (1-x) -Au contained in In2O3 x Pt (1-x) Indium oxide composites modified on the surface of In2O3 are used for gas-sensitive testing of NO2 gas.

[0012] Optionally, x is 0.25-0.75; and / or,

[0013] Au x Pt (1-x) For alloy nanoparticles; and / or,

[0014] The three-dimensional micron flower structure of In₂O₃ is composed of layered structures, Au x Pt (1-x) It is applied to the surface of a lamellar structure.

[0015] Optionally, the thickness of the layered structure is 7nm-12nm; and / or,

[0016] The lamellar structures have a width of 1 μm-6 μm and a length of 12 μm-75 μm; and / or,

[0017] The diameter of the three-dimensional micron flower structure is 2μm-12μm; and / or,

[0018] Au x Pt (1-x) The particle size ranges from 10 nm to 20 nm; and / or,

[0019] Aux Pt (1-x) The content ratio of In₂O₃ is in the range of (0.5-1.5) mg: 100 mg; and / or,

[0020] The particle size range of indium oxide composite materials is 2μm-12μm.

[0021] Secondly, a method for preparing indium oxide composite material is provided, comprising the following steps:

[0022] Indium source and water are mixed and treated, and a growth reaction is carried out in an environment with a pH of 3.3-3.7 and under heating conditions to obtain a mixture containing precipitates;

[0023] The mixture was subjected to a first solid-liquid separation process to obtain the In2O3 precursor;

[0024] The In2O3 precursor was dried and sintered to obtain In2O3 powder with a three-dimensional micron flower structure.

[0025] In2O3 powder was dispersed in a dispersion solvent to obtain an In2O3 mixed solution;

[0026] Provides containing Au x Pt (1-x) The alloy powder suspension A was mixed with an In2O3 mixed solution to obtain suspension B;

[0027] The B suspension was subjected to a second solid-liquid separation and drying process to obtain the indium oxide composite material.

[0028] Optionally, the reactants for the growth reaction further include a surfactant, comprising the indium source, the surfactant, and water; and / or,

[0029] In the step of mixing indium source and water, and carrying out a growth reaction in an environment with a pH of 3.3-3.7 under heating conditions to obtain a mixture containing precipitate, at least one of the following conditions must be met:

[0030] The indium source includes at least one of indium chloride tetrahydrate and indium nitrate;

[0031] The mixing process includes stirring and ultrasonic treatment;

[0032] Adjust the pH using urea or sodium bicarbonate solution;

[0033] The heating conditions are 110℃-130℃, and the holding time is 10h-14h.

[0034] Optionally, the mass ratio of indium source, surfactant, and water is 4-6:5-7:60-80; and / or,

[0035] The surfactant includes at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide.

[0036] Optionally, before sintering the In2O3 precursor, the In2O3 precursor is further subjected to a drying treatment, which includes a drying treatment at a temperature of 50℃-70℃; and / or,

[0037] The sintering process includes at least one of the conditions in (1) to (3):

[0038] (1) The sintering temperature is 350℃-450℃;

[0039] (2) The sintering time is 1.5h-2.5h;

[0040] (3) The temperature is increased to the sintering temperature at a heating rate of 1℃ / min-4℃ / min.

[0041] Alternatively, in suspension A, 0 < Au x Pt (1-x) The concentration of nanoparticles is <4 mg / mL; and / or,

[0042] The concentration of the In₂O₃ mixed solution is 8 mg / mL-12 mg / mL; and / or,

[0043] In suspension B, Au x Pt (1-x) The alloy comprises 0.8 wt% to 1.2 wt% of In₂O₃ by mass; and / or,

[0044] In the step of performing a second solid-liquid separation treatment and drying treatment on suspension B, the drying treatment temperature is 50℃-70℃; and / or,

[0045] Au x Pt (1-x) The preparation method of the alloy includes the following steps:

[0046] A mixture of chloro gold compound, chloroplatinum compound, and stabilizer is subjected to a multi-temperature stage oil bath reflux reaction to obtain a dual-gold mixture, which includes Au. x Pt (1-x) alloy.

[0047] Thirdly, the application of the above-mentioned indium oxide composite material or the indium oxide composite material prepared by the above-mentioned method in the detection of NO2 is provided.

[0048] Fourthly, a gas sensor is provided, comprising a gas-sensitive ceramic tube and an indium oxide composite material or an indium oxide composite material prepared by the above-mentioned method for preparing the indium oxide composite material, wherein the indium oxide composite material is coated on the surface of the gas-sensitive ceramic tube.

[0049] The beneficial effects of this application are as follows:

[0050] The indium oxide composite material provided in this application uses In2O3 with a three-dimensional micron flower structure as the core. The three-dimensional micron flower structure increases the specific surface area of ​​In2O3. The increase in specific surface area increases the number of gas molecule adsorption sites on the surface of the indium oxide material, thereby increasing the total number of adsorbed gas molecules. The number of majority carriers in the surface layer of the indium oxide material decreases sharply, and a wider space depletion layer will be formed on the surface of the indium oxide material, thereby improving the gas-sensing performance of the indium oxide material; at the same time, Au... x Pt (1-x) Bimetallic alloys modify indium oxide, where the bimetal exists not in oxide form, thus preserving the Au content. x Pt (1-x) The high catalytic activity and synergistic catalytic effect of the alloy; the large specific surface area of ​​In2O3, the high catalytic activity of the noble metals gold and platinum, and the synergistic effect between the two metals significantly improve the gas sensitivity of the indium oxide composite material. When the indium oxide composite material is applied to gas-sensitive devices, it can significantly improve the response value and extend the minimum detection limit performance of the gas-sensitive device under room temperature conditions, and improve the ease of use of the gas-sensitive device.

[0051] The method for preparing indium oxide composite materials provided in this application involves synthesizing a three-dimensional micron-flower structure In2O3 with a large specific surface area via a hydrothermal method, and then using Au... x Pt (1-x) The alloy is modified on the surface of In2O3. The preparation method is linked to the structure and morphology of the material. By controlling the growth process parameters, the material with the preset properties can be obtained. The preparation method is safe, reliable, simple and reproducible, and has good prospects for industrial application. Attached Figure Description

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0053] Figure 1 This is a process flow diagram of the preparation method of the indium oxide composite material of Example 1 of this application;

[0054] Figure 2 This is a schematic flowchart of steps S6-S9 in the preparation method of indium oxide composite material in Example 1 of this application;

[0055] Figure 3(a) is a SEM image of the In2O3 micron flower material of Example 1 of this application, (b) is a SEM image of the indium oxide composite material, and (cd) is a SEM image of the In2O3 micron flower material at a magnification.

[0056] Figure 4 This is a TEM image of the indium oxide composite material of Example 1 of this application;

[0057] Figure 5 Au in Embodiments 1-3 of this application x Pt (1-x) EDS diagram of the In2O3 composite material;

[0058] Figure 6 The In2O3 micron flower material and Au used in the embodiments and comparative examples of this application x Pt (1-x) XRD pattern of In2O3 composite material;

[0059] Figure 7 The In2O3 micron flower material and Au used in the embodiments and comparative examples of this application x Pt (1-x) - Detection limit diagram of NO2 by In2O3 composite material at room temperature;

[0060] Figure 8 Au in Example 1 0.75 Pt 0.25 -When In2O3 composite material is used in gas sensors, the gas sensor's response curves under different humidity conditions at room temperature are shown.

[0061] Figure 9 Au in Example 1 0.75 Pt 0.25 -When In2O3 composite material is used in gas sensors, the gas sensor's response dot plots under different humidity conditions at room temperature are shown. Detailed Implementation

[0062] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0063] This application provides an indium oxide composite material, including Au. x Pt (1-x) -In₂O₃, 0 < x < 1, Au x Pt (1-x) -In₂O₃ uses In₂O₃ as its core, and In₂O₃ has a three-dimensional micron flower structure, Au x Pt(1-x) -Au contained in In2O3 x Pt (1-x) Indium oxide composites modified on the surface of In2O3 are used for gas-sensitive testing of NO2 gas.

[0064] The indium oxide composite material provided in this application uses In2O3 with a three-dimensional micron flower structure as the core. The three-dimensional micron flower structure increases the specific surface area of ​​In2O3. This increased specific surface area increases the number of gas molecule adsorption sites on the surface of the indium oxide material, thereby increasing the total number of adsorbed gas molecules. The number of majority carriers in the surface layer of the indium oxide material decreases sharply, resulting in a wider depletion layer on the surface of the indium oxide material, thus improving the gas-sensing performance of the indium oxide material. Simultaneously, Au... x Pt (1-x) Bimetallic alloys modify indium oxide, where the bimetal exists not in oxide form, thus preserving the Au content. x Pt (1-x) The alloy exhibits high catalytic activity and synergistic catalytic effect. The large specific surface area of ​​In2O3, the high catalytic activity of the noble metals gold and platinum, and the synergistic effect between the two metals significantly enhance the gas sensitivity of the indium oxide composite material. This results in a substantial increase in the response value and the extension of the lowest detection limit of the gas sensor when the indium oxide composite material is applied to gas sensors at room temperature, as well as improved ease of use.

[0065] In this embodiment of the application, Au x Pt (1-x) It consists of nanoscale alloy particles bonded to the surface of the three-dimensional micron flower structure of In2O3.

[0066] In some embodiments, x is 0.25-0.75, in which case Au x Pt (1-x) -In2O3 is Au (0.25-0.75) Pt (0.75-0.25) -In₂O₃, through experiments, it was found that when x = 0.25-0.75, Au x Pt (1-x) The alloy exhibits a significant bimetallic synergistic catalytic effect, while the indium oxide composite material demonstrates superior gas sensitivity.

[0067] In some embodiments, the three-dimensional micron flower structure of In2O3 is composed of a combination of layered structures, Au x Pt (1-x) It is applied to the surface of a lamellar structure.

[0068] In some embodiments, the thickness of the sheet-like structure is 7nm-12nm.

[0069] In some embodiments, the width of the lamellar structure is 1μm-6μm and the length is 12μm-75μm.

[0070] In some embodiments, the diameter of the three-dimensional micron flower structure is 2μm-12μm.

[0071] In some embodiments, Au x Pt (1-x) The particle size ranges from 10nm to 20nm, and the relatively small size of the nanoparticles is beneficial to the enhancement of bimetallic catalysis.

[0072] In some embodiments, Au x Pt (1-x) The content ratio of indium oxide to In2O3 is in the range of (0.5-1.5) mg:100 mg. Excessive surface bimetallic modification will lead to a decrease in gas-sensing performance. The gas-sensing performance of indium oxide composites in this ratio range is better.

[0073] In some embodiments, the particle size range of the indium oxide composite material is 2 μm-12 μm.

[0074] This application also provides a method for preparing the above-mentioned indium oxide composite material, including the following steps:

[0075] S1: The indium source and water are mixed and treated, and the growth reaction is carried out in an environment with a pH of 3.3-3.7 and under heating conditions to obtain a mixture containing precipitates.

[0076] Indium source and water are heated to form precipitated indium hydroxide, and a three-dimensional micron flower structure of indium hydroxide is initially obtained.

[0077] In some embodiments, the reactants for the growth reaction also include a surfactant. The indium source, surfactant, and water are mixed, and the pH of the solution environment for the growth reaction is 3.5-3.9. The main function of the surfactant is to accelerate or inhibit the growth rate of certain crystal faces of the growth crystal material, thereby improving the crystal growth effect of indium hydroxide.

[0078] In some embodiments, the mass ratio of indium source, surfactant and water is 4-6:5-7:60-80. By controlling the mass ratio of indium source, surfactant and water, a micron flower structure composed of nanosheets can be finally obtained, thereby greatly increasing the specific surface area of ​​the reaction product.

[0079] In some embodiments, the indium source includes at least one of indium chloride tetrahydrate and indium nitrate.

[0080] In some embodiments, the surfactant includes at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide.

[0081] Adjust the pH using urea or sodium bicarbonate solution.

[0082] When indium chloride is selected as the indium source, the reaction principle is as follows:

[0083]

[0084] In this process, In(OH)3 is used as a precursor material, and sodium bicarbonate solution is used to adjust the pH value of the reaction solution to a range of 3.5-3.9, which facilitates the precipitation and sedimentation of In(OH)3.

[0085] In some embodiments, the mixing process includes stirring and ultrasonic treatment. Stirring can be performed using magnetic stirring, followed by ultrasonic treatment, to fully disperse the components in the solution and facilitate a uniform reaction.

[0086] In some embodiments, after ultrasonic treatment, the cells are heated to carry out a growth reaction under heating conditions. The heating temperature is 110°C-130°C, and the holding time is 10-14 hours.

[0087] S2: The mixture is subjected to a first solid-liquid separation process to obtain the In2O3 precursor.

[0088] The In2O3 precursor is mainly indium hydroxide. Indium hydroxide is insoluble in the above-mentioned surfactant and water, forming a precipitate. Through solid-liquid separation, indium oxide and / or indium hydroxide are obtained.

[0089] In some embodiments, the first solid-liquid separation process may be centrifugal separation, and the obtained precipitate is washed alternately by centrifugation with ethanol and deionized water.

[0090] S3: The In2O3 precursor is sintered to obtain In2O3 powder with a three-dimensional micron flower structure.

[0091] The hydroxide contained in the In2O3 precursor is decomposed into oxide by sintering, which further strengthens the three-dimensional micron flower structure of indium oxide crystal.

[0092] In some embodiments, before sintering the In2O3 precursor, the In2O3 precursor is also dried at a temperature of 50°C-70°C to remove liquid from the In2O3 precursor.

[0093] In some embodiments, the sintering temperature is 350℃-450℃. Experiments have shown that when the heating rate is selected as 1℃ / min-4℃ / min, and the temperature is increased from room temperature to the sintering temperature, such as 350℃-450℃, the decomposition effect of indium hydroxide is better, resulting in a better three-dimensional micron flower structure of indium oxide crystals and reducing the formation of crystal defects.

[0094] After sintering, the product was naturally cooled to room temperature to obtain indium oxide with a three-dimensional micron flower structure.

[0095] If drying is performed before sintering, the sample is transferred to the sintering equipment after drying and heated from room temperature to 350℃-450℃.

[0096] S4: Disperse In2O3 powder in a dispersion solvent to obtain an In2O3 mixed solution.

[0097] The In₂O₃ mixed solution is a suspension mixture; the dispersing solvent provides a suitable solution environment, which is beneficial for the next step of Au processing. x Pt (1-x) The alloy is in full contact with the surface of indium oxide.

[0098] In some embodiments, the dispersion solvent includes ethanol, indium oxide, and Au. x Pt (1-x) The alloy powders are insoluble in ethanol, and ethanol does not participate in the reaction. After the reaction is complete, the powders are easily removed without causing pollution.

[0099] S5: Provides products containing Au x Pt (1-x) The alloy powder suspension A was mixed with an In2O3 mixed solution to obtain suspension B.

[0100] Au x Pt (1-x) The alloy comes into full contact with indium oxide, preparing it for the next process.

[0101] In some embodiments, 0 < Au in suspension A x Pt (1-x) The concentration of nanoparticles is <4 mg / mL; the concentration of the In2O3 mixed solution is 8 mg / mL-12 mg / mL.

[0102] In some embodiments, Au x Pt (1-x) The alloy powder accounts for 0.8wt%-1.2wt% of the In2O3 mass in the In2O3 mixed solution. Based on the structural design of indium oxide composites, this mass ratio range facilitates the formation of Au at x = 0.25-0.75. x Pt (1-x) -In2O3.

[0103] In some embodiments, Au in suspension A x Pt (1-x) The preparation method of alloy powder includes the following steps:

[0104] A mixture of chloro gold compound, chloroplatinum compound, and stabilizer is subjected to a multi-temperature stage oil bath reflux reaction to obtain a dual-gold mixture, which includes Au. x Pt (1-x) alloy.

[0105] The multi-temperature stage oil bath reflux reaction includes the following steps:

[0106] After mixing the chloro gold compound, chloroplatinum compound and stabilizer, the reaction solution is slowly heated to 210℃-230℃ and held for 8min-12min; then heated to 230℃-250℃ and held for 8min-12min, and then naturally cooled to room temperature.

[0107] When tetrachloroauric acid is used as the chloro-gold compound, it is unstable and can decompose into HCl and Au (similar to H₂PtCl₆) at high temperatures. The specific reaction principle is as follows:

[0108]

[0109] In some embodiments, the mass ratio of chlorogold compound to chloroplatinum compound is (0.01-59):(0.01-78).

[0110] In some embodiments, the chlorogold compound includes chloroauric acid or chloroaurate, and chloroaurate includes, for example, at least one of HAuCl4·3H2O and NaAuCl4·2H2O.

[0111] In some embodiments, the chloroplatinum compound includes at least one of H2PtCl6·6H2O, PtCl2, and (NH4)2PtCl6.

[0112] In some embodiments, the stabilizer includes at least one of oleylamine, sodium citrate, and ammonia.

[0113] S6: The B suspension is subjected to a second solid-liquid separation and drying process to obtain indium oxide composite material.

[0114] Au in suspension B x Pt (1-x) Alloy powder is mixed with indium oxide and kept in solid form. The liquid in the B suspension is removed through solid-liquid separation. The resulting precipitate is dried to obtain the target product Au. x Pt (1-x) Modified indium oxide composite material.

[0115] In the step of performing a second solid-liquid separation and drying treatment on suspension B, the drying temperature is 50℃-70℃.

[0116] In some embodiments, the second solid-liquid separation process includes centrifugation.

[0117] In some embodiments, the drying temperature is 50°C-70°C.

[0118] In some embodiments, the indium oxide composite material is further ground after obtaining it to obtain the desired particle size of the indium oxide composite material.

[0119] The method for preparing indium oxide composite materials provided in this application involves synthesizing a three-dimensional micron-flower structure In2O3 with a large specific surface area using a hydrothermal method, and then using Au... x Pt (1-x) The alloy is modified on the surface of In2O3. The preparation method is linked to the structure and morphology of the material. By controlling the growth process parameters, the material with the preset properties can be obtained. The preparation method is safe, reliable, simple and reproducible, and has good prospects for industrial application.

[0120] This application also provides the application of the above-mentioned indium oxide composite material in the detection of NO2. It has good gas sensitivity at room temperature, high response value, and the response to 1 ppm NO2 is increased from 242 to 2658. At the same time, the minimum detection limit is reduced from 50 ppb to less than 5 ppb.

[0121] This application provides a gas sensor, including a gas-sensitive ceramic tube and the aforementioned indium oxide composite material, wherein the indium oxide composite material is coated on the surface of the gas-sensitive ceramic tube.

[0122] The following examples illustrate this.

[0123] Example 1

[0124] The indium oxide composite material in this embodiment includes Au. 0.75 Pt 0.25 -In₂O₃, with In₂O₃ as the core, In₂O₃ having a three-dimensional micron flower structure, Au 0.75 Pt 0.25 The alloy is applied to the surface of In2O3.

[0125] like Figure 1 and Figure 2 As shown, the preparation method of the indium oxide composite material in this embodiment includes the following steps:

[0126] S1: Take 0.6g indium chloride tetrahydrate (InCl3·4H2O), 0.7g sodium dodecyl sulfonate and 0.45g urea and add them to 80mL of deionized water in sequence. After stirring magnetically, sonicate for 30min (ultrasonic frequency of 40KHz) to obtain a mixture.

[0127] S2: Transfer the mixture to a 100mL Teflon-lined stainless steel reactor and place the reactor in an oven. Slowly raise the internal temperature of the oven from room temperature to 120℃ and keep it at that temperature for 12 hours. Then allow it to cool naturally to room temperature to obtain the primary product.

[0128] S3: Remove the upper clear solution from the primary product, retain the precipitate at the bottom, and wash with alternating centrifugation using ethanol and deionized water to obtain a white powder In2O3 precursor.

[0129] S4: Place the In2O3 precursor in an oven and dry it at 70℃ for 10 hours to obtain the dried In2O3 precursor.

[0130] S5: The dried In2O3 precursor was loaded into a ceramic boat and placed in a tube furnace. The furnace was slowly heated to 400℃ at a heating rate of 2℃ / min and held at that temperature for 2 hours. After sintering, it was naturally cooled to room temperature to obtain a pale yellow In2O3 powder with a three-dimensional micron flower structure. The structure of the In2O3 powder is as follows: Figure 3 As shown in (a).

[0131] S6: Place the three-necked flask on an oil bath, add 10 mL of oleylamine under magnetic stirring, slowly heat to 110 °C and maintain for 10 min, then quickly add chloroauric acid trihydrate (HAuCl4·3H2O) and chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in a mass ratio of 44 mg:20 mg. After the reactants in the flask are completely dissolved, slowly heat the reaction solution to 220 °C and maintain for 10 min, then heat to 240 °C and maintain for 10 min, and then allow it to cool naturally to room temperature to obtain the bimetallic primary product.

[0132] S7: Wash and centrifuge the initial bimetallic product to obtain bimetallic Au. 0.75 Pt 0.25 Finally, Au 0.75 Pt 0.25 The nanoparticles were prepared into a solution at a concentration of 2 mg / mL and dispersed in n-hexane solvent to form a suspension.

[0133] S8: Take 100 mg of the above In2O3 micron flower powder and disperse it in 20 mL of ethanol solvent. Sonicate for 30 min (ultrasonic frequency of 40 kHz), then stir for 20 min to obtain indium oxide suspension.

[0134] S9: Add 1 mL of Au to the indium oxide suspension. 0.75 Pt 0.25 The suspension was stirred for 25 min, washed, centrifuged, and the precipitate was collected. The precipitate was placed in a drying oven and dried at 60 °C for 10 h to obtain Au. 0.75 Pt 0.25-In2O3 composite material, Au 0.75 Pt 0.25 The structure of the In2O3 composite material is as follows: Figure 3 (b)-(d) and Figure 4 As shown.

[0135] in, Figure 3 (a) is a SEM image of In2O3. In2O3 is a three-dimensional micron flower structure composed of extremely thin lamellar structures, with an average diameter of 6-7 μm.

[0136] Figure 3 (b) is Au 0.75 Pt 0.25 The SEM image of the In2O3 composite material shows that, after gold-platinum bimetallic modification, Au... 0.75 Pt 0.25 -In2O3 composite materials still maintain a good morphology of three-dimensional micron flower structure, and their average diameter remains basically unchanged.

[0137] Figure 3 Images (c) and (d) are SEM images of In₂O₃ at further magnification, obtained by... Figure 3 As can be seen from (c), the thickness of the In2O3 material sheets is approximately 10 nm, while Figure 3 As shown in (d), the accurate thickness of the In2O3 material layers cannot be directly observed because the In2O3 material layers are thin and assembled together.

[0138] Figure 4 Au 0.75 Pt 0.25 TEM image of the In2O3 composite material. Figure 4 In (a), the In2O3 microflora has a diameter of about 6 μm. These microflora are composed of very thin lamellar structures and have some tiny particles distributed on their surface.

[0139] From high resolution Figure 4 (b) In the figure, in addition to the In2O3(222) crystal plane stripes (with an interplanar spacing of 0.29 nm), Au(200) crystal plane stripes (with an interplanar spacing of 0.20 nm) and Pt(111) crystal plane stripes (with an interplanar spacing of 0.23 nm) can also be observed from a nanoparticle, indicating that the gold-platinum bimetallic alloy nanoparticles have been successfully modified onto the surface of the In2O3 micron-flower; at the same time, the Au can also be estimated. 0.75 Pt 0.25 The nanoparticles are approximately 15 nm in size.

[0140] Figure 4 The electron diffraction pattern in Figure (a) shows the synthesized Au 0.75 Pt 0.25-In2O3 composite materials are polycrystalline materials.

[0141] Example 2

[0142] The indium oxide composite material in this embodiment includes Au. 0.5 Pt 0.5 -In₂O₃, with In₂O₃ as the core, In₂O₃ having a three-dimensional micron flower structure, Au 0.5 Pt 0.5 The alloy is applied to the surface of the In2O3.

[0143] The preparation method of the indium oxide composite material in this embodiment includes the following steps:

[0144] S1: Take 0.5g indium chloride tetrahydrate (InCl3·4H2O), 0.7g sodium dodecyl sulfonate and 0.45g urea and add them to 60mL of deionized water in sequence. After stirring magnetically, sonicate for 20min (ultrasonic frequency of 40KHz) to obtain a mixture.

[0145] S2: Transfer the mixture to a 100mL Teflon-lined stainless steel reactor and place the reactor in an oven. Slowly raise the internal temperature of the oven from room temperature to 120℃ and keep it at that temperature for 12 hours. Then allow it to cool naturally to room temperature to obtain the primary product.

[0146] S3: Remove the upper clear solution from the primary product, retain the precipitate at the bottom, and wash with alternating centrifugation using ethanol and deionized water to obtain a white powder In2O3 precursor.

[0147] S4: The In2O3 precursor was placed in an oven and dried at 60°C for 12 hours to obtain the dried In2O3 precursor.

[0148] S5: The dried In2O3 precursor was loaded into a ceramic boat and placed in a tube furnace. It was slowly heated to 400℃ at a heating rate of 2℃ / min and held for 2 hours. After sintering, it was naturally cooled to room temperature to obtain a light yellow In2O3 powder with a three-dimensional micron flower structure.

[0149] S6: Place the three-necked flask on an oil bath, add 10 mL of oleylamine under magnetic stirring, slowly heat to 110 °C and maintain for 10 min, then quickly add chloroauric acid trihydrate (HAuCl4·3H2O) and chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in a mass ratio of 29.5 mg:39 mg. After the reactants in the flask are completely dissolved, slowly heat the reaction solution to 220 °C and maintain for 10 min, then heat to 240 °C and maintain for 10 min, and then allow it to cool naturally to room temperature to obtain the bimetallic primary product.

[0150] S7: Wash and centrifuge the initial bimetallic product to obtain bimetallic Au. 0.5 Pt 0.5 Then Au 0.5 Pt 0.5 The nanoparticles were prepared into a solution at a concentration of 2 mg / mL and dispersed in n-hexane solvent to form a suspension.

[0151] S8: Take 100mg of In2O3 micronized flower powder and disperse it in 20mL of ethanol solvent. Sonicate for 30min (ultrasonic frequency of 40KHZ), then stir for 20min to obtain an indium oxide suspension.

[0152] S9: Add 0.8 mL of Au to the indium oxide suspension. 0.5 Pt 0.5 The suspension was stirred for 25 min, washed, centrifuged, and the precipitate was collected. The precipitate was placed in a drying oven and dried at 60 °C for 12 h to obtain Au. 0.5 Pt 0.5 -In2O3 composite material.

[0153] Example 3

[0154] The indium oxide composite material in this embodiment includes Au. 0.25 Pt 0.75 -In₂O₃, with In₂O₃ as the core, In₂O₃ having a three-dimensional micron flower structure, Au 0.25 Pt 0.75 The alloy is applied to the surface of the In2O3.

[0155] The preparation method of the indium oxide composite material in this embodiment includes the following steps:

[0156] S1: Take 0.6g indium chloride tetrahydrate (InCl3·4H2O), 0.5g sodium dodecyl sulfonate and 0.55g urea and add them to 80mL of deionized water in sequence. After stirring magnetically, sonicate for 30min (ultrasonic frequency of 40KHz) to obtain a mixture.

[0157] S2: Transfer the mixture to a 100mL Teflon-lined stainless steel reactor and place the reactor in an oven. Slowly raise the internal temperature of the oven from room temperature to 120℃ and keep it at that temperature for 12 hours. Then allow it to cool naturally to room temperature to obtain the primary product.

[0158] S3: Remove the upper clear solution from the primary product, retain the precipitate at the bottom, and wash with alternating centrifugation using ethanol and deionized water to obtain a white powder In2O3 precursor.

[0159] S4: The In2O3 precursor was placed in an oven and dried at 60°C for 12 hours to obtain the dried In2O3 precursor.

[0160] S5: The dried In2O3 precursor was loaded into a ceramic boat and placed in a tube furnace. It was slowly heated to 400℃ at a heating rate of 2℃ / min and held for 2 hours. After sintering, it was naturally cooled to room temperature to obtain a light yellow In2O3 powder with a three-dimensional micron flower structure.

[0161] S6: Place the three-necked flask on an oil bath, add 8 mL of oleylamine under magnetic stirring, slowly heat to 110°C and maintain for 10 min, then quickly add chloroauric acid trihydrate (HAuCl4·3H2O) and chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in a mass ratio of 15 mg:59 mg. After the reactants in the flask are completely dissolved, slowly heat the reaction solution to 220°C and maintain for 10 min, then heat to 240°C and maintain for 10 min, and then allow it to cool naturally to room temperature to obtain the bimetallic primary product.

[0162] S7: Wash and centrifuge the initial bimetallic product to obtain bimetallic Au. 0.25 Pt 0.75 Finally, Au 0.25 Pt 0.75 The nanoparticles were prepared into a solution at a concentration of 0.5 mg / mL and dispersed in n-hexane solvent to form a suspension.

[0163] S8: Take 100 mg of the above In2O3 micron flower powder and disperse it in 20 mL of ethanol solvent. Sonicate for 30 min (ultrasonic frequency of 40 kHz), then stir for 20 min to obtain indium oxide suspension.

[0164] S9: Add 0.6 mL of Au to the indium oxide suspension. 0.25 Pt 0.75 The suspension was stirred for 20 min, washed, centrifuged, and the precipitate was collected. The precipitate was placed in a drying oven and dried at 60 °C for 12 h to obtain Au. 0.25 Pt 0.75 -In2O3 composite material.

[0165] Comparative Example 1

[0166] The gas-sensitive material in this comparative example is pure indium oxide, and the preparation method of pure indium oxide is as described in S1-S5 of Example 1.

[0167] Comparative Example 2

[0168] The indium oxide composite material in this comparative example includes Au. 1.0 -In₂O₃ composite material, using only elemental gold to modify indium oxide, with In₂O₃ as the core, In₂O₃ having a three-dimensional micron flower structure, Au 1.0 It is applied to the surface of In2O3.

[0169] The preparation method of the indium oxide composite material in this comparative example is the same as that in Example 1, except that chloroplatinic acid hexahydrate is not added in step S6, and the amount of chloroauric acid trihydrate added is 59 mg.

[0170] Comparative Example 3

[0171] The indium oxide composite material in this comparative example includes Pt 1.0 -In₂O₃ composite material, using only platinum-modified indium oxide, with In₂O₃ as the core, In₂O₃ having a three-dimensional micron flower structure, Pt 1.0 It is applied to the surface of In2O3.

[0172] The preparation method of the indium oxide composite material in this comparative example is the same as that in Example 1, except that chloroauric acid trihydrate is not added in step S6, and the amount of chloroplatinic acid hexahydrate added is 78 mg.

[0173] The products of Examples 1-3 and Comparative Examples 1-3 were subjected to elemental composition and distribution tests, gas-sensing performance characterization tests, etc., and the test results are as follows: Figures 5-9 As shown.

[0174] Figure 5 (af) represents the EDS test results of the indium oxide composite materials of Examples 1-3, further determining Au x Pt (1-x) The composition and distribution of elements in In2O3 composite materials, among which, Figure 5 Figures (a, b) and (c) show the surface scan distribution of elements O, In, Pt, and Au, respectively. Figure (f) shows the percentage of each of the four elements: In, O, Pt, and Au. As can be seen from the figures, In, O, Pt, and Au are evenly distributed in the Au region. x Pt (1-x) In the In₂O₃ composite material, the percentages of In and O are 66.44% and 32.46%, respectively. The oxygen content is relatively high, which originates from oxygen adsorbed on the surface of the material. This corresponds to Au. 0.75 Pt 0.25 -In₂O₃、Au 0.5 Pt 0.5 -In2O3 and Au 0.25 Pt 0.75 -In₂O₃ composite material, the atomic percentages of Au and Pt are Au and Pt, respectively. 0.8 Pt 0.3 Au 0.56 Pt 0.62 and Au 0.0.21 Pt 0.79 Au x Pt (1-x)The atomic percentages of Au and Pt in the In2O3 composite material are basically consistent with the initial design values.

[0175] Figure 6 In2O3 micro-flower materials and Au are presented. x Pt (1-x) XRD pattern of In2O3 composite material, the figure shows:

[0176] (1) The diffraction peaks of each sample at 2θ = 21.497°, 30.585°, 35.462°, 37.692°, 41.846°, 45.688°, 49.293°, 51.024°, 55.983°, 59.132°, 60.667°, 62.180° and 63.673° correspond to the (211), (222), (400), (411), (332), (431), (521), (440), (611), (541), (622), (631) and (444) crystal planes of In2O3, which is consistent with the cubic structure of In2O3 in the standard card (JCPDS 71-2194); Au x Pt (1-x) After modification with nanoparticles, Au x Pt (1-x) The characteristic peak positions of the In2O3 composite material did not change significantly.

[0177] (2) As shown in the red box in the figure, when the proportion of Pt reaches 0.75 or above, diffraction peaks appear in the spectrum at 2θ = 39.754°, 46.233° and 67.452°, which correspond to the (111), (200) and (220) crystal planes of Pt, respectively; and the intensity of the corresponding diffraction peaks increases with the increase of Pt content.

[0178] (3) No Au peak was clearly observed in the XRD pattern, which may be because the Au diffraction peak was obscured because it was close to the diffraction peak of other materials in the composite material.

[0179] Figure 7 In2O3 micro-flower materials and Au are presented. x Pt (1-x) - Detection limit diagram of In2O3 composite material for different NO2 concentrations at room temperature. The test conditions are as follows: sensor operating temperature is fixed at room temperature (27℃), ambient humidity is fixed at 30%, and the detected NO2 concentrations are 1ppm, 500ppb, 300ppb, 100ppb, 50ppb, 20ppb, and 5ppb. As shown in the figure:

[0180] (1) Examples 1-3 successfully obtained Au with high response to NO2 at room temperature.x Pt (1-x) -In2O3 composite material;

[0181] (2) At room temperature, Au 0.75 Pt 0.25 - The In2O3 composite material has a response value of 2658 to 1ppm NO2, which is 11 times that of the pure In2O3 micron-flower material (242). The gas-sensing response values ​​of different materials show the following general trend: Au x Pt (1-x) The gas sensor response value of bimetallic modified In2O3 > the gas sensor response value of monometallic modified In2O3 > the gas sensor response value of pure In2O3;

[0182] (3) When the NO2 gas concentration drops to 5 ppb, Au 0.75 Pt 0.25 The response value of the In2O3 composite material is still as high as 30, i.e., Au 0.75 Pt 0.25 -In2O3 composite materials have a detection limit as low as 5 ppb for NO2 gas, exhibiting extremely high sensitivity.

[0183] Au from Example 1 0.75 Pt 0.25 In₂O₃ composite materials are used in gas sensors. Figure 8 and Figure 9 The following is given: containing Au 0.75 Pt 0.25 The performance of an In₂O₃ composite gas sensor at room temperature for 1 ppm NO₂ under different humidity conditions is shown in the graph. The test conditions are as follows: the operating temperature of the gas sensor is fixed at room temperature (27°C), the ambient humidity ranges from 30% to 90%, and the detected NO₂ concentration is fixed at 1 ppm. Figure 8 The graphs show curves under different humidity levels. Figure 9 This is a line graph showing different humidity levels.

[0184] Depend on Figure 8 and Figure 9 It can be concluded that it contains Au. 0.75 Pt 0.25 The response value of the In₂O₃ gas sensor gradually decreases with increasing humidity, and the response values ​​at 30%, 50%, 70%, and 90% humidity are 2640, 2374, 2093, and 1701, respectively; Au-containing... 0.75 Pt 0.25 The In2O3 gas sensor showed a maximum response value decrease of 35% at 30% and 90% humidity. This is because the increased humidity caused water molecules to occupy more gas adsorption sites, thus reducing the response value.

[0185] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An indium oxide composite material, characterized in that: Including Au x Pt (1-x) -In₂O₃, where x is 0.25-0.75, and Au x Pt (1-x) -In₂O₃ uses In₂O₃ as its core, wherein the In₂O₃ has a three-dimensional micron flower structure, and the Au... x Pt (1-x) -In₂O₃ contains Au in non-oxide form x Pt (1-x) The indium oxide composite material, modified on the surface of In2O3, is used for gas-sensitive testing of NO2 gas.

2. The indium oxide composite material as described in claim 1, characterized in that: Au x Pt (1-x) For alloy nanoparticles; and / or, The three-dimensional micron flower structure of In2O3 is composed of layered structures, and the Au x Pt (1-x) It is applied to the surface of the lamellar structure.

3. The indium oxide composite material as described in claim 2, characterized in that: The thickness of the lamellar structure is 7nm-12nm; and / or, The lamellar structure has a width of 1μm-6μm and a length of 12μm-75μm; or, The diameter of the three-dimensional micron flower structure is 2μm-12μm; or, Au x Pt (1-x) The particle size ranges from 10 nm to 20 nm; or, Au x Pt (1-x) The content ratio of In₂O₃ is in the range of (0.5-1.5) mg: 100 mg; or, The particle size range of the indium oxide composite material is 2μm-12μm.

4. A method for preparing an indium oxide composite material as described in any one of claims 1 to 3, characterized in that: Includes the following steps: Indium source and water are mixed and treated, and a growth reaction is carried out in an environment with a pH of 3.3-3.7 and under heating conditions to obtain a mixture containing precipitates; The mixture was subjected to a first solid-liquid separation process to obtain the In2O3 precursor. The In2O3 precursor was sintered to obtain In2O3 powder with a three-dimensional micron flower structure. The In2O3 powder was dispersed in a dispersion solvent to obtain an In2O3 mixed solution; Provides Au in non-oxide form x Pt (1-x) The alloy A suspension is mixed with the In2O3 mixed solution to obtain suspension B; The B suspension was subjected to a second solid-liquid separation and drying process to obtain an indium oxide composite material.

5. The method for preparing the indium oxide composite material as described in claim 4, characterized in that: The reactants for the growth reaction also include a surfactant, and the indium source, surfactant, and water are mixed and treated; and / or, In the step of mixing indium source and water, and carrying out a growth reaction in an environment with a pH of 3.3-3.7 and under heating conditions to obtain a mixture containing precipitate, at least one of the following conditions must be met: The indium source includes at least one of indium chloride tetrahydrate and indium nitrate; The mixing process includes stirring and ultrasonic treatment; Adjust the pH using urea or sodium bicarbonate solution; The heating conditions are 110℃-130℃, and the holding time is 10h-14h.

6. The method for preparing the indium oxide composite material as described in claim 5, characterized in that: The mass ratio of the indium source, surfactant, and water is 4-6:5-7:60-80; and / or, The surfactant includes at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide.

7. The method for preparing the indium oxide composite material according to any one of claims 4 to 6, characterized in that: Before sintering the In2O3 precursor, the In2O3 precursor is also dried at a temperature of 50°C-70°C; and / or The sintering process includes at least one of the following conditions (1) to (3): (1) The temperature is 350℃-450℃; (2) The sintering time is 1.5h-2.5h; (3) The temperature is increased to the sintering temperature at a heating rate of 1℃ / min - 4℃ / min.

8. The method for preparing the indium oxide composite material according to any one of claims 4 to 6, characterized in that: In suspension A, 0 < Au x Pt (1-x) Nanoparticle concentration < 4 mg / mL; and / or The concentration of the In₂O₃ mixed solution is 8 mg / mL - 12 mg / mL; and / or In the B suspension, the Au x Pt (1-x) The alloy comprises 0.8 wt%-1.2 wt% of the In₂O₃ by mass; and / or In the step of performing a second solid-liquid separation treatment and drying treatment on the B suspension, the drying treatment temperature is 50℃-70℃; and / or, Au x Pt (1-x) The preparation method of the alloy includes the following steps: A chloro-gold compound, a chloro-platinum compound, and a stabilizer are mixed and subjected to a multi-temperature stage oil bath reflux reaction to obtain a dual-gold mixture, wherein the dual-gold mixture includes Au. x Pt (1-x) alloy.

9. The application of the indium oxide composite material prepared by the preparation method of the indium oxide composite material according to any one of claims 1 to 3 or according to any one of claims 4 to 8 in the detection of NO2.

10. A gas sensor, characterized in that: The indium oxide composite material includes a gas-sensitive ceramic tube and an indium oxide composite material as described in any one of claims 1 to 3 or an indium oxide composite material as described in any one of claims 4 to 8, wherein the indium oxide composite material is coated on the surface of the gas-sensitive ceramic tube.

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