Preparation method of samarium ferrite oxide modified by double noble metals Au and Pt and application of samarium ferrite oxide in detection of nitrogen dioxide

Abstract

The invention discloses a preparation method of double noble metal Au and Pt modified samarium ferrite oxide and application of the samarium ferrite oxide to detection of nitrogen dioxide, and relates to the technical field of nitrogen dioxide gas detection. The chemical formula of the double noble metal modified samarium ferrite oxide is X wt% of Au-Y wt% of Pt-SmFeO3, wherein 0 lt; x < = 5, 0lt; y < = 5. On the basis of SmFeO3, through Au and Pt double noble metal surface modification, the catalytic activity of the material is remarkably improved, the working temperature of NO2 detection is reduced, and the sensitivity and selectivity are improved. Specifically, at the working temperature of 120 DEG C, the response value of the double noble metal modified samarium ferrite oxide prepared by the invention to 500 ppb NO2 gas is 11.81.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen dioxide gas detection, and in particular to a preparation method of samarium ferrite oxide modified with dual noble metals Au and Pt and its application in detecting nitrogen dioxide. Background Art

[0002] Nitrogen dioxide (NO2) is a highly toxic gas with a pungent odor. It mainly comes from mining blasting, industrial combustion waste gas, urban automobile exhaust, and the industrial production and use of nitric acid and nitrogen fertilizer. It is a major factor causing environmental problems such as acid rain, photochemical smog, and corrosion. It is also extremely harmful to the human body and has a strong irritating effect on the respiratory tract. In severe cases, it can cause lung function problems. Therefore, the development of highly sensitive, low-temperature, and highly selective NO2 gas detection technology has important environmental and public health value.

[0003] Currently, semiconductor gas sensors, with their simple manufacturing process, low cost, high sensitivity, fast response recovery, and good stability, have gradually become an important tool for monitoring NO2 gas in industrial production and daily life. The gas-sensitive materials used in semiconductor gas sensors include n-type semiconductors and p-type semiconductors. Perovskite-type composite oxides (such as SmFeO3) as p-type semiconductors have become a research focus for gas-sensitive materials due to their stable crystal structure, excellent redox performance, and tunable surface chemical properties.

[0004] In the prior art, the paper “Study on NO2 Gas Sensing Performance of Perovskite Structure Metal Oxide Nanomaterials” (Huang Haotian, Huazhong University of Science and Technology, 2018) discloses the application of SmFeO3 with hollow microsphere structure and nanofiber structure as gas-sensitive materials in detecting NO2 gas. Specifically, the response of SmFeO3 with nanofiber structure to 10ppm of NO2 gas at 200°C is 92, the response of SmFeO3 with hollow microsphere structure to 1ppm of NO2 gas at 200°C is 19.92, and the response of SmFeO3 thick film to 2ppm of NO2 gas at an operating temperature of 200°C is 9. It can be seen that although the response value of SmFeO3 material to NO2 gas can be improved by adjusting its morphology and structure, it still has the defect of high operating temperature (≥200°C). CN118914301A discloses a material with a chemical formula of Xwt% Pt-Sm y Pr 1-yApplication of FeO3 gas-sensitive material in detecting nitrogen oxide gas. The response of this gas-sensitive material to 1 ppm NO2 gas at a working temperature of 130 °C is 8.93. In the above patent, by doping the SmFeO3 material with Pt and Pr bimetals, although the working temperature of the gas-sensitive material can be reduced, its sensitivity to NO2 gas is limited, which to a certain extent restricts its practical application. At the same time, in the "Ambient Air Quality Standard" GB3095-2012, the safety threshold for human contact with NO2 is stipulated to be 100 ppb. In the NO2 limit standard formulated by the US Environmental Protection Agency, the maximum allowable exposure concentration within a single hour is 100 ppb. It is mentioned in the journal "Research on Low-Power Blue Diode Photoacoustic Technology for ppb-Level NO2 Detection" (Jin Huawei et al., Acta Physica Sinica, vol. 68, No. 7 (2019)) that the concentration of NO2 in the atmosphere is generally 5-30 ppb. Thus, it is of great significance to effectively detect NO2 at the ppb level, but the perovskite gas-sensitive materials disclosed in the above existing technologies are only applicable to detecting NO2 gas at the ppm level.

[0005] Therefore, how to dope and modify the SmFeO3 material to prepare a gas-sensitive material for detecting NO2 gas, which can not only ensure that the gas-sensitive material can be used to detect NO2 gas at the ppb level, but also reduce its working temperature when used for NO2 gas detection, has important scientific significance and application prospects. Summary of the Invention

[0006] In view of the above existing technologies, the purpose of the present invention is to provide a preparation method of a double-precious-metal Au and Pt modified samarium ferrite oxide and its application in detecting nitrogen dioxide. The chemical formula of the double-precious-metal modified samarium ferrite oxide is X wt% Au - Y wt% Pt - SmFeO3, where 0 < X ≤ 5 and 0 < Y ≤ 5. Based on SmFeO3, the present invention significantly improves the catalytic activity of the material, reduces the working temperature of NO2 detection, and enhances the sensitivity and selectivity through the surface modification of Au and Pt bimetals. Specifically, at a working temperature of 120 °C, the response value of the double-precious-metal modified samarium ferrite oxide prepared by the present invention to 500 ppb NO2 gas is 11.81.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect of the present invention, a double-precious-metal Au and Pt modified samarium ferrite oxide is provided, and its chemical formula is X wt% Au - Y wt% Pt - SmFeO3; in the formula, X wt% is the doping amount of Au in the double-precious-metal Au and Pt modified samarium ferrite oxide, and Y wt% is the doping amount of Pt in the double-precious-metal Au and Pt modified samarium ferrite oxide; 0 < X ≤ 5 and 0 < Y ≤ 5.

[0009] Dual noble metals offer enhanced catalytic activity and electronic synergy, while A-site doping improves the controllability of lattice distortion and creates a more uniform energy band modulation region. By doping both Pt and Au into the A-site of the SmFeO3 material, the present invention not only guides the formation of a stable electron-hole structure on the surface of the gas-sensitive material but also creates multiple highly active catalytic centers in the local lattice, thereby achieving a higher response to low-concentration NO2 gas at a lower operating temperature.

[0010] The second aspect of the present invention provides a method for preparing the above-mentioned double noble metal Au and Pt modified samarium ferrite oxide, comprising the following steps:

[0011] (1) Sm(NO3)3·6H2O and Fe(NO3)3·9H2O were mixed and added to water, and citric acid was added and stirred to obtain a mixed solution; the pH of the mixed solution was adjusted to 9-11, stirred, filtered, and the filtered precipitate was collected, washed, and dried to obtain a SmFeO3 precursor;

[0012] (2) dispersing the SmFeO3 precursor in water, adding chloroauric acid and platinum dibromide to react, and after the reaction is completed, filtering and collecting the solid, washing, drying and calcining the solid to obtain samarium ferrite oxide modified with dual noble metals Au and Pt;

[0013] The added amount ratio of Sm(NO3)3·6H2O, Fe(NO3)3·9H2O, chloroauric acid, platinum dibromide, citric acid and water is (0.01-0.05)mol:(0.01-0.05)mol:(0.01-0.5)g:(0.01-0.5)g:(5-20)g:(50-150)mL.

[0014] Preferably, in step (1), the material-liquid ratio of Sm(NO3)3·6H2O and water is (0.01-0.05) mol:(40-100) mL.

[0015] Preferably, in step (1), 1-2 mol / L NaOH solution is used to adjust the pH of the mixed solution.

[0016] Preferably, in step (1), the stirring time is 1-2 h.

[0017] Preferably, in step (1), deionized water and ethanol are used for washing 3-5 times.

[0018] Preferably, in step (1), the drying method is vacuum drying, the drying temperature is 70-90° C., and the drying time is 6-12 h.

[0019] Preferably, in step (2), the material-liquid ratio of SmFeO3 precursor and water is (0.8-1.2) g:50 mL.

[0020] Preferably, in step (2), the reaction temperature is 60-80° C. and the reaction time is 2-4 h.

[0021] Preferably, in step (2), the drying method is vacuum drying, the drying temperature is 70-90° C., and the drying time is 6-12 h.

[0022] Preferably, in step (2), the calcination temperature is 400-600° C., and the calcination time is 2.5-3.5 h.

[0023] The third aspect of the present invention provides the use of the above-mentioned double noble metal Au and Pt modified samarium ferrite oxide in detecting NO2 gas.

[0024] Preferably, the NO2 gas concentration is 400-600 ppb.

[0025] The third aspect of the present invention provides the use of the above-mentioned double noble metal Au and Pt modified samarium ferrite oxide in the preparation of NO2 gas sensors.

[0026] Preferably, the NO2 gas sensor is prepared by the following method: mixing samarium ferrite oxide modified with dual precious metals Au and Pt, deionized water and terpineol in the ratio of (1-3) g: (5-10) mL: (1-3) mL to prepare a slurry; spin-coating the slurry on an alumina ceramic substrate to form a gas-sensitive film with a thickness of 50-200 μm, and aging the gas-sensitive film at 180-200° C. for 12-24 hours to obtain a NO2 gas sensor.

[0027] Preferably, the operating temperature of the NO2 gas sensor is 110-130°C.

[0028] Beneficial effects of the present invention:

[0029] 1. The present invention uses a co-precipitation method to prepare a SmFeO3 precursor, and then uses Au and Pt to modify the surface of the dual noble metals to prepare a samarium ferrite oxide modified with dual noble metals as a NO2 gas-sensitive material. The synergistic catalytic effect of Au and Pt significantly reduces the energy barrier of the NO2 adsorption reaction, promotes surface electron transfer and reaction activity, thereby reducing the operating temperature and improving the response value. At the same time, the modification of Au and Pt enhances the material's selective adsorption capacity for NO2 molecules, suppresses the response to other interfering gases, and exhibits excellent selectivity. Specifically, the samarium ferrite oxide modified with dual noble metals Au and Pt prepared by the present invention has a response value of 11.81 to 500 ppb NO2 gas at an operating temperature of 120°C.

[0030] 2. The SmFeO3 prepared by the co-precipitation method in the present invention has a nanoparticle structure with a particle size of 50-150nm and a large specific surface area, which can provide more adsorption and reaction sites for NO2 molecules, further improving the sensitivity and response speed.

[0031] 3. The preparation process of the present invention is simple and controllable. The resulting material remains stable under humidity fluctuations (relative humidity <50%) and exhibits excellent stability in long-term use (response value variation <5% within one month), making it suitable for environmental monitoring and industrial emission detection. Furthermore, the NO2 gas sensor prepared by the present invention has a low operating temperature, low energy consumption, and is easily integrated into portable devices, showing broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 : XRD pattern of the double noble metal Au and Pt modified samarium ferrite oxide prepared in Example 1;

[0033] Figure 2 : SEM image of the double noble metal Au and Pt modified samarium ferrite oxide prepared in Example 1;

[0034] Figure 3 : EDSMapping diagram of Au, Pt and Sm elements in the samarium ferrite oxide modified with dual noble metals Au and Pt prepared in Example 1;

[0035] Figure 4 : A graph showing the relationship between the gas-sensing performance of the materials prepared in Example 1 and Comparative Examples 1-3 to 500 ppb NO2 gas and temperature;

[0036] Figure 5 : A graph showing the relationship between the gas sensing performance of the double noble metal Au and Pt modified samarium ferrite oxide prepared in Example 1 to 500 ppb NO2 gas and humidity;

[0037] Figure 6 : Schematic diagram of the long-term gas-sensing stability of the double noble metal Au and Pt modified samarium ferrite oxide prepared in Example 1 to 500 ppb NO2 gas. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0039] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0040] The experimental materials used in the examples of the present invention are all conventional experimental materials in the art and can be purchased through commercial channels.

[0041] Example 1: Preparation of a double noble metal Au and Pt modified samarium ferrite oxide 2wt% Au-2wt% Pt-SmFeO3

[0042] (1) 4.445 g of Sm(NO3)3·6H2O and 4.040 g of Fe(NO3)3·9H2O were mixed and added to 100 mL of water, and then 10 g of citric acid was added and stirred evenly to obtain a mixed solution; 1 mol / L NaOH solution was added to the mixed solution under stirring to adjust the pH to 10.0, and the mixture was stirred for 1.5 h to allow the metal ions to undergo co-precipitation reaction. The filtered precipitate was collected and washed with deionized water and ethanol three times, and then dried in vacuum at 80°C for 8 h to obtain a SmFeO3 precursor;

[0043] (2) The SmFeO3 precursor was dispersed in 50 mL of deionized water, 0.082 g of chloroauric acid and 0.054 g of platinum dibromide were added, and the mixture was stirred at 70 ° C for 3 h. After the reaction was completed, the filtered solid was collected, washed, and placed in a vacuum dryer at 80 ° C for 8 h, and then calcined at 500 ° C for 3 h to obtain 2 wt% Au-2 wt% Pt-SmFeO3 of samarium ferrite oxide modified with dual precious metals Au and Pt.

[0044] The structure of the double noble metal Au and Pt modified samarium ferrite oxide 2wt% Au-2wt% Pt-SmFeO3 prepared in this example was characterized. Figure 1-Figure 3 shown.

[0045] Figure 1 The XRD pattern of double noble metal Au and Pt modified samarium ferrite oxide is shown in Figure 2. Figure 1 It can be seen that the crystallization peaks correspond to the (202), (121) and (002) crystal phases of SmFeO3 (No.39-1490), indicating that the material has a pure phase perovskite structure. Figure 2 It can be seen that the prepared double noble metal Au and Pt modified samarium ferrite oxide presents a typical nanoparticle structure with a particle size of about 50-150nm, a large specific surface area and porosity, providing abundant reaction sites and transmission channels for gas molecules. Figure 3 is the EDS Mapping diagram of Au, Pt, and Sm elements, Figure 3 It can be seen that the elements are evenly distributed, proving that Au and Pt are successfully loaded on the SmFeO3 surface.

[0046] Example 2: Preparation of a double noble metal Au and Pt modified samarium ferrite oxide 1wt% Au-3wt% Pt-SmFeO3

[0047] (1) 4.445 g of Sm(NO3)3·6H2O and 4.040 g of Fe(NO3)3·9H2O were mixed and added to 60 mL of water, and 15 g of citric acid was added and stirred evenly to obtain a mixed solution; 1 mol / L NaOH solution was added to the mixed solution under stirring to adjust the pH to 9.0, and the mixture was stirred for 2 h to allow the metal ions to undergo co-precipitation reaction. The filtered precipitate was collected and washed with deionized water and ethanol for 4 times, and then dried in vacuum at 70 ° C for 10 h to obtain a SmFeO3 precursor;

[0048] (2) The SmFeO3 precursor was dispersed in 60 mL of deionized water, 0.041 g of chloroauric acid and 0.081 g of platinum dibromide were added, and the mixture was stirred at 80 ° C for 2 h. After the reaction was completed, the filtered solid was collected, washed, and placed in a vacuum dryer at 70 ° C for 10 h, and then calcined at 600 ° C for 2 h to obtain 1 wt% Au-3 wt% Pt-SmFeO3 of samarium ferrite oxide modified with dual precious metals Au and Pt.

[0049] Example 3: Preparation of a double noble metal Au and Pt modified samarium ferrite oxide 3wt% Au-1wt% Pt-SmFeO3

[0050] (1) 4.445 g of Sm(NO3)3·6H2O and 4.040 g of Fe(NO3)3·9H2O were mixed and added to 40 mL of water, and then 8 g of citric acid was added and stirred evenly to obtain a mixed solution; 2 mol / L NaOH solution was added to the mixed solution under stirring to adjust the pH to 11.0, and the mixture was stirred for 1 h to allow the metal ions to undergo a co-precipitation reaction. The filtered precipitate was collected and washed with deionized water and ethanol for 5 times, and then dried in vacuum at 90°C for 6 h to obtain a SmFeO3 precursor;

[0051] (2) The SmFeO3 precursor was dispersed in 40 mL of deionized water, 0.123 g of chloroauric acid and 0.027 g of platinum dibromide were added, and the mixture was stirred at 60 ° C for 4 h. After the reaction was completed, the filtered solid was collected, washed, and placed in a vacuum dryer at 90 ° C for 6 h, and then calcined at 400 ° C for 4 h to obtain 3 wt% Au-1 wt% Pt-SmFeO3 of samarium ferrite oxide modified with dual precious metals Au and Pt.

[0052] Example 4: Preparation of NO2 gas sensor

[0053] The double noble metal-modified samarium ferrite oxide 2wt% Au-2wt% Pt-SmFeO3 prepared in Example 1, deionized water and pineol were mixed in a ratio of 1 g:5 mL:1 mL to obtain a slurry; the slurry was spin-coated on the surface of an alumina ceramic substrate at a speed of 800 rpm to form a gas-sensitive film with a thickness of 100 μm. The gas-sensitive film was placed in air and aged at 180°C for 18 hours to obtain a NO2 gas sensor.

[0054] Comparative Example 1: Preparation of SmFeO3 gas-sensitive material

[0055] The difference between this comparative example and Example 1 is that Pt and Au are not used to dope SmFeO3. The specific preparation method is:

[0056] 4.445 g of Sm(NO3)3·6H2O and 4.040 g of Fe(NO3)3·9H2O were mixed and added to 100 mL of water, and then 10 g of citric acid was added and stirred evenly to obtain a mixed solution; 1 mol / L NaOH solution was added to the mixed solution under stirring conditions to adjust the pH to 10.0, and the stirring was continued for 1.5 h to allow the metal ions to undergo a co-precipitation reaction. The filtered precipitate was filtered and collected, and the precipitate was washed with deionized water and ethanol three times, and then placed at 80°C for vacuum drying for 8 h to obtain SmFeO3 material.

[0057] Comparative Example 2: Preparation of 2wt% Au-SmFeO3 gas-sensitive material

[0058] The difference between this comparative example and Example 1 is that only Au is used to dope the SmFeO3 material. The specific preparation method is:

[0059] (1) 4.445 g of Sm(NO3)3·6H2O and 4.040 g of Fe(NO3)3·9H2O were mixed and added to 100 mL of water, and then 10 g of citric acid was added and stirred evenly to obtain a mixed solution; 1 mol / L NaOH solution was added to the mixed solution under stirring to adjust the pH to 10.0, and the mixture was stirred for 1.5 h to allow the metal ions to undergo co-precipitation reaction. The filtered precipitate was collected and washed with deionized water and ethanol three times, and then dried in vacuum at 80°C for 8 h to obtain a SmFeO3 precursor;

[0060] (2) The SmFeO3 precursor was dispersed in 50 mL of deionized water, 0.082 g of chloroauric acid was added, and the mixture was stirred at 70 ° C for 3 h. After the reaction was completed, the filtered solid was collected, washed, and placed in a vacuum dryer at 80 ° C for 8 h, and then calcined at 500 ° C for 3 h to obtain 2 wt% Au-SmFeO3 of samarium ferrite oxide modified with dual precious metals Au and Pt.

[0061] Comparative Example 3: Preparation of 2wt% Pt-SmFeO3 gas-sensitive material

[0062] The difference between this comparative example and Example 1 is that only Pt is used to dope SmFeO3. The specific preparation method is:

[0063] (1) 4.445 g of Sm(NO3)3·6H2O and 4.040 g of Fe(NO3)3·9H2O were mixed and added to 100 mL of water, and then 10 g of citric acid was added and stirred evenly to obtain a mixed solution; 1 mol / L NaOH solution was added to the mixed solution under stirring to adjust the pH to 10.0, and the mixture was stirred for 1.5 h to allow the metal ions to undergo co-precipitation reaction. The filtered precipitate was collected and washed with deionized water and ethanol three times, and then dried in vacuum at 80°C for 8 h to obtain a SmFeO3 precursor;

[0064] (2) The SmFeO3 precursor was dispersed in 50 mL of deionized water, 0.054 g of platinum dibromide was added, and the mixture was stirred at 70 ° C for 3 h. After the reaction was completed, the filtered solid was collected, washed, and placed in a vacuum dryer at 80 ° C for 8 h, and then calcined at 500 ° C for 3 h to obtain 2 wt% Pt-SmFeO3 of samarium ferrite oxide modified with dual precious metals Au and Pt.

[0065] Test Example 1:

[0066] The double noble metal Au and Pt modified samarium ferrite oxide prepared in Example 1 and the gas sensitive materials prepared in Comparative Examples 1-3 were coated on the gas sensitive film, and their gas sensitive responses (Rg / Ra) to NO2 gas were tested. The results are as follows: Figure 4-Figure 6 As shown in Figure 2, Ra is the resistance of the sensor in air, and Rg is the resistance in the measured gas. The experimental environment is: relative humidity (RH) 20%, ambient temperature 20°C.

[0067] Depend on Figure 4 It can be seen that the optimal operating temperature of the dual-noble metal Au and Pt-modified samarium ferrite oxide prepared in the present invention is 140°C. At 140°C, the response value of the 2wt% Au-2wt% Pt-SmFeO3 prepared in Example 1 to 500 ppb NO2 gas was 11.81; the response value of the SmFeO3 prepared in Comparative Example 1 was 2.18; the response value of the 2wt% Au-SmFeO3 prepared in Comparative Example 2 was 6.37; and the response value of the 2wt% Pt-SmFeO3 prepared in Comparative Example 3 was 6.89. These results demonstrate that dual-noble metal modification with Au and Pt has a significant synergistic effect in improving NO2 response values.

[0068] Figure 5The gas sensing performance of 2wt%Au-2wt%Pt-SmFeO3 of the double noble metal Au and Pt modified samarium ferrite oxide prepared in Example 1 to 500ppb NO2 gas at different humidity. Figure 5 It can be seen that the gas-sensing performance decreases slightly with the increase of relative humidity, but when the relative humidity is <40%, the response value change rate is <5%, indicating that the material has good humidity resistance.

[0069] Figure 6 The long-term stability of the double noble metal Au and Pt modified samarium ferrite oxide 2wt% Au-2wt% Pt-SmFeO3 prepared in Example 1 to 500ppb NO2 gas is shown. Figure 6 It can be seen that within one month, the response value change rate is <6%, indicating that the material has extremely high gas-sensing stability.

[0070] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A samarium ferrite oxide modified with dual noble metals Au and Pt, characterized in that: The chemical formula of the double noble metal Au and Pt modified samarium ferrite oxide is Xwt%Au-Ywt%Pt-SmFeO3; wherein, <X≤5,0<Y≤5。 2. The method for preparing the double noble metal Au and Pt modified samarium ferrite oxide according to claim 1, characterized in that: The following steps are involved: (1) Sm(NO3)3·6H2O and Fe(NO3)3·9H2O were mixed and added to water, and citric acid was added and stirred to obtain a mixed solution; the pH of the mixed solution was adjusted to 9-11, stirred, filtered, and the filtered precipitate was collected, washed, and dried to obtain a SmFeO3 precursor; (2) dispersing the SmFeO3 precursor in water, adding chloroauric acid and platinum dibromide to react, and after the reaction is completed, filtering and collecting the solid, washing, drying and calcining the solid to obtain samarium ferrite oxide modified with dual noble metals Au and Pt; The added amount ratio of Sm(NO3)3·6H2O, Fe(NO3)3·9H2O, chloroauric acid, platinum dibromide, citric acid and water is (0.01-0.05)mol:(0.01-0.05)mol:(0.01-0.5)g:(0.01-0.5)g:(5-20)g:(50-150)mL.

3. The method for preparing the double noble metal Au and Pt modified samarium ferrite oxide according to claim 2, characterized in that: In step (1), the material-liquid ratio of Sm(NO3)3·6H2O and water is (0.01-0.05) mol:(40-100) mL; and a 1-2 mol / L NaOH solution is used to adjust the pH of the mixed solution.

4. The method for preparing the double noble metal Au and Pt modified samarium ferrite oxide according to claim 2, wherein: In step (1), the stirring time is 1-2 hours, the drying method is vacuum drying, the drying temperature is 70-90° C., and the drying time is 6-12 hours.

5. The method for preparing the double noble metal Au and Pt modified samarium ferrite oxide according to claim 2, wherein: In step (2), the material-liquid ratio of SmFeO3 precursor and water is 1g:50mL.

6. The method for preparing the double noble metal Au and Pt modified samarium ferrite oxide according to claim 2, characterized in that: In step (2), the reaction temperature is 60-80°C and the reaction time is 2-4h.

7. The method for preparing the double noble metal Au and Pt modified samarium ferrite oxide according to claim 2, characterized in that: In step (2), the calcination temperature is 400-600° C., and the calcination time is 2.5-3.5 hours.

8. The use of the double noble metal Au and Pt modified samarium ferrite oxide according to claim 1 in detecting NO2 gas, characterized in that: The NO2 gas concentration is 400-600ppb.

9. Use of the double noble metal Au and Pt modified samarium ferrite oxide according to claim 1 in the preparation of a NO2 gas sensor.

10. The use according to claim 9, characterized in that The operating temperature of NO2 gas sensor is 110-130℃.

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