A composite material capable of improving gas-sensing performance of low-concentration acetone and preparation method thereof

Abstract

This invention designs an n-p type heterojunction gas-sensitive composite material and its preparation method to improve the gas-sensing performance of low-concentration acetone. The material of this invention is a mesoporous Fe2O3 / Cr2O3 gas-sensitive composite material with n-type nanoporous Fe2O3 as the main component and p-type nanoporous Cr2O3 as surface particles. First, Fe2O3 is grown in the interstices of SiO2 nanospheres, and then Cr2O3 is composited with Fe2O3 by impregnation to obtain the n-p type heterojunction mesoporous Fe2O3-Cr2O3 gas-sensitive composite material. This gas-sensitive material possesses a mesoporous structure and a large specific surface area to provide sufficient reaction sites. Furthermore, the p-type nanoporous Cr2O3 is used to adjust the band structure of the gas-sensitive material, thereby improving its sensitivity and selectivity for specific gases. The preparation method used in this invention uses inexpensive and widely available raw materials, and the chemical preparation steps are simple. The obtained n-p type heterojunction Fe2O3 / Cr2O3 gas-sensitive material can improve the sensitivity and stability of low-concentration acetone gas detection.

Description

Technical Field

[0001] This invention relates to the field of gas-sensitive materials, specifically to an np heterostructure mesoporous gas-sensitive composite material and its preparation method. Background Technology

[0002] Acetone detection has important applications in many fields. While acetone is mildly toxic, long-term exposure can cause serious harm to the human body. During the industrial production, transportation, storage, and use of acetone, leaks frequently cause environmental pollution, poisoning, fires, and explosions, posing a persistent threat to industrial safety. Furthermore, studies show that the concentration of acetone in the exhaled breath of normal individuals is 0.3–0.9 ppm, while the concentration exceeds 1.8 ppm in the exhaled breath of patients with type 1 diabetes. Acetone in exhaled breath can serve as an important biomarker for the early non-invasive diagnosis of diabetes. Therefore, real-time monitoring of toxic and biomarker-significant volatile organic compounds like acetone is essential.

[0003] Hematite (α-Fe₂O₃) is a non-toxic, environmentally friendly, and low-cost metal oxide that has found wide application in photocatalysis, magnetism, lithium-ion batteries, and gas sensing materials, showing great promise for future development. However, its further application is limited by issues such as excessively high optimal operating temperature, low sensitivity, and excessively high detection concentration limits in low-concentration acetone sensing.

[0004] To improve the gas-sensing performance of Fe2O3, previous reports suggest considering methods such as improving morphology, increasing specific surface area, and altering band structure. Mesoporous structures, due to their high specific surface area and low carrier recombination rate, can effectively enhance gas-sensing performance. Meanwhile, pn heterostructures can improve the band structure of the material and adjust the thickness of the electron depletion layer or hole accumulation layer at the interface between the two materials to achieve the same goal. Zhang et al. synthesized rGO / α-Fe2O3 composites with different rGO contents (0.1wt%-4.0wt%), and the addition of rGO lowered the optimal operating temperature (Sens. Actuators B Chem. 2017, 241, 904–914). Xu et al. successfully prepared sea urchin-shaped SnO2 / α-Fe2O3 heterostructure microspheres through a two-step hydrothermal treatment (Sens. Actuators B Chem. 2023, 379, 133288). This shows that assembling n-type and p-type oxides into heterostructured composite structures through certain techniques provides a possibility for developing gas-sensitive materials with high sensitivity and selectivity. Summary of the Invention

[0005] To address the shortcomings of the aforementioned technologies, this invention designs an np-type heterojunction gas-sensitive composite material and its preparation method to improve the gas-sensing performance of low-concentration acetone. This material is a mesoporous Fe2O3 / Cr2O3 gas-sensitive composite material with n-type nanoporous Fe2O3 as the main component and p-type nanoporous Cr2O3 as surface particles. This invention's gas-sensitive material possesses a mesoporous structure and a large specific surface area to provide sufficient reaction sites. Furthermore, the p-type nanoporous Cr2O3 is used to adjust the band structure of the gas-sensitive material, thereby improving its sensitivity and selectivity for specific gases. The preparation method used in this invention utilizes inexpensive and widely available raw materials, and the chemical preparation steps are simple. The obtained np-type heterojunction Fe2O3 / Cr2O3 gas-sensitive material, when used for low-concentration acetone gas detection, can improve the sensitivity and stability of the gas-sensitive material.

[0006] This invention discloses an np-type heterostructure gas-sensitive material that can improve the gas-sensing performance of low-concentration acetone. The material is characterized by first growing Fe2O3 in the interstices of SiO2 nanospheres, and then combining Cr2O3 with Fe2O3 via an impregnation method to obtain an np-type heterostructure mesoporous Fe2O3-Cr2O3 gas-sensitive composite material. The specific preparation steps are as follows:

[0007] 1) At room temperature, dissolve 8.8g of polyether P123 in 141.3525g of 1.6 mol / L HCl and deionized water, and stir at medium speed for 2 hours;

[0008] 2) Add 21.33 mL of tetraethyl orthosilicate to the mixture dropwise, and stir for 5 minutes after the addition is complete, then let it stand for 24 hours;

[0009] 3) After hydrothermal heating at 130℃ for 24 hours, crystallization was carried out; after natural cooling, the mixture was cooled and crystallized; it was washed with deionized water until neutral and dried; then calcined at 5℃ / min to 550℃ for 6 hours to obtain SiO2 nanosphere powder.

[0010] 4) Add 1g of SiO2 nanosphere powder and 3.3622g of Fe(NO3)3•9H2O to a polytetrafluoroethylene beaker at a ratio of Si:Fe=1:0.5, and simultaneously add 90ml of ethanol. Stir the above solution at 50℃ until the ethanol solution evaporates, then add 40ml of n-hexane to the polytetrafluoroethylene beaker and stir at 50℃ until dry.

[0011] 5) Dry the powder sample in an oven at 220℃ for 2 hours; after washing, dry it in a vacuum drying oven at 80℃ for 8 hours; calcine the powder in a muffle furnace at 650℃ for 6 hours at a heating rate of 1℃ / min.

[0012] 6) Remove the SiO2 nanospheres in two steps using 100 ml of 2 mol / L NaOH solution in an 80℃ water bath. Then wash the sample with deionized water and ethanol until neutral. Finally, dry it in an oven at 90℃ for 6 hours to obtain a pure mesoporous Fe2O3 sample.

[0013] 7) Chromium nitrate Cr(NO3)3•9H2O was mixed with 0.1g Fe2O3 sample in 100 mL of anhydrous ethanol at a certain ratio and stirred at room temperature for 20 hours.

[0014] 8) The suspension was centrifuged and washed to obtain the precursor; the precursor was dried overnight in an oven at 60°C, and then calcined at 500°C for 2 hours at a rate of 1°C / min to obtain mesoporous Fe2O3-Cr2O3 gas-sensitive composite materials with different Cr2O3 composite amounts.

[0015] The present invention discloses an NP heterogeneous gas-sensitive material that can improve the gas-sensing performance of low-concentration acetone. The material is characterized by its application in low-concentration acetone gas detection, specifically comprising the following steps:

[0016] The material was uniformly coated on a silver electrode sheet and placed on the worktable of the CGS-4TPs gas sensing measurement system. An atmosphere with a relative humidity of 30% was used as the interfering gas to conduct acetone gas sensing tests. The optimal operating temperature, sensitivity, and stability of the sample in response to 10 ppm acetone were obtained.

[0017] The beneficial effects of this invention are:

[0018] 1) The preparation method used in this invention uses inexpensive and widely available raw materials, and the chemical preparation steps are simple; 2) The obtained np-type heterojunction mesoporous Fe2O3-Cr2O3 gas-sensitive material can improve the sensitivity and stability of the gas-sensitive material when used for low-concentration acetone gas detection. Attached Figure Description

[0019] Figure 1 The XRD diffraction pattern of this invention proves that the composition of the obtained material is Fe2O3 / Cr2O3.

[0020] Figure 2Figure 2(am) shows a transmission electron microscope image of the Fe2O3 / Cr2O3 composite material of this invention. As shown in Figure 2(am), the Fe2O3 / Cr2O3 composite material is granular with a diameter of approximately 1494.1 nm, composed of nanoscale particles, and exhibits a mesoporous structure. Figure 2(cg) is a high-magnification transmission electron microscope image of the Fe2O3 / Cr2O3 composite material of this invention; Figure 2(hj) is a Fast Fourier Transform (FFT) image of the crystal surface, with spacings of 0.268 nm, 0.269 nm, and 0.266 nm corresponding to the (012) crystal plane of Fe2O3, the (104) crystal plane of Cr2O3, and the (104) crystal plane of iron oxide, respectively. Figure 2(km) is an elemental spectrum of the Fe2O3 / Cr2O3 composite material, confirming the presence of Cr, Fe, and O elements, and showing that chromium oxide is uniformly covered on the surface of iron oxide.

[0021] Figure 3 The working temperature and response curves of the material of the present invention demonstrate that the np-type heterojunction mesoporous Fe2O3-Cr2O3 gas-sensitive material obtained in this invention can reduce its optimal working temperature and increase its gas-sensitive response value when used for low-concentration acetone gas detection.

[0022] Figure 4 The image shows a seven-day gas-sensitive test result of 10 ppm in Example 4 of this invention, demonstrating that the np-type heterojunction mesoporous Fe2O3-Cr2O3 gas-sensitive material obtained by this invention has excellent stability when used for low-concentration acetone gas-sensitive detection.

[0023] Figure 5 The nitrogen adsorption and desorption diagrams for Examples 1-5 of the present invention illustrate that the np-type heterojunction Fe2O3-Cr2O3 gas-sensitive material obtained by the present invention has a mesoporous structure and a large specific surface area. Detailed Implementation

[0024] The following specific embodiments further illustrate the present invention. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] Example 1

[0026] 1) At room temperature, dissolve 8.8g of polyether P123 in 141.3525g of 1.6 mol / L HCl and deionized water, and stir at medium speed for 2 hours;

[0027] 2) Add 21.33 mL of tetraethyl orthosilicate to the mixture dropwise, and stir for 5 minutes after the addition is complete, then let it stand for 24 hours;

[0028] 3) After hydrothermal heating at 130℃ for 24 hours, crystallization was carried out; after natural cooling, the mixture was cooled and crystallized; it was washed with deionized water until neutral and dried; then calcined at 5℃ / min to 550℃ for 6 hours to obtain SiO2 nanosphere powder.

[0029] 4) Add 1g of SiO2 nanosphere powder and 3.3622g of Fe(NO3)3•9H2O to a polytetrafluoroethylene beaker at a ratio of Si:Fe=1:0.5, and simultaneously add 90ml of ethanol. Stir the above solution at 50℃ until the ethanol solution evaporates, then add 40ml of n-hexane to the polytetrafluoroethylene beaker and stir at 50℃ until dry.

[0030] 5) Dry the powder sample in an oven at 220℃ for 2 hours; after washing, dry it in a vacuum drying oven at 80℃ for 8 hours; calcine the powder in a muffle furnace at 650℃ for 6 hours at a heating rate of 1℃ / min.

[0031] 6) Remove the SiO2 nanospheres in two steps using 100 ml of 2 mol / L NaOH solution in an 80°C water bath. Then wash the sample with deionized water and ethanol until neutral, and finally dry it in an oven at 90°C for 6 hours to obtain a pure mesoporous Fe2O3 sample.

[0032] The specific surface area of ​​the pure Fe2O3 sample obtained in Example 1 was 86.91 m². 2 / g, optimal operating temperature is 300℃, and the response to 10ppm acetone is 7.

[0033] Example 2

[0034] 1) At room temperature, dissolve 8.8g of polyether P123 in 141.3525g of 1.6 mol / L HCl and deionized water, and stir at medium speed for 2 hours;

[0035] 2) Add 21.33 mL of tetraethyl orthosilicate to the mixture dropwise, and stir for 5 minutes after the addition is complete, then let it stand for 24 hours;

[0036] 3) After hydrothermal heating at 130℃ for 24 hours, crystallization was carried out; after natural cooling, the mixture was cooled and crystallized; it was washed with deionized water until neutral and dried; then calcined at 5℃ / min to 550℃ for 6 hours to obtain SiO2 nanosphere powder.

[0037] 4) Add 1g of SiO2 nanosphere powder and 3.3622g of Fe(NO3)3•9H2O to a polytetrafluoroethylene beaker at a ratio of Si:Fe=1:0.5, and simultaneously add 90ml of ethanol. Stir the above solution at 50℃ until the ethanol solution evaporates, then add 40ml of n-hexane to the polytetrafluoroethylene beaker and stir at 50℃ until dry.

[0038] 5) Dry the powder sample in an oven at 220℃ for 2 hours; after washing, dry it in a vacuum drying oven at 80℃ for 8 hours; calcine the powder in a muffle furnace at 650℃ for 6 hours at a heating rate of 1℃ / min.

[0039] 6) Remove the SiO2 nanospheres in two steps using 100 ml of 2 mol / L NaOH solution in an 80℃ water bath. Then wash the sample with deionized water and ethanol until neutral. Finally, dry it in an oven at 90℃ for 6 hours to obtain a pure mesoporous Fe2O3 sample.

[0040] 7) Mix 0.008 g of chromium nitrate Cr(NO3)3•9H2O and 0.1 g of Fe2O3 sample in 100 mL of anhydrous ethanol and stir at room temperature for 20 hours;

[0041] 8) The suspension was centrifuged and washed to obtain the precursor. The precursor was dried overnight in an oven at 60°C and then calcined at 500°C for 2 hours at a rate of 1°C / min to obtain the mesoporous Fe2O3 / Cr2O3 composite material.

[0042] The specific surface area of ​​the mesoporous Fe2O3 / Cr2O3 composite material obtained in Example 2 was 63.73 m². 2 / g, with an optimal operating temperature of 240℃ and a response of 11.5 to 10 ppm acetone.

[0043] Example 3

[0044] 1) At room temperature, dissolve 8.8g of polyether P123 in 141.3525g of 1.6 mol / L HCl and deionized water, and stir at medium speed for 2 hours;

[0045] 2) Add 21.33 mL of tetraethyl orthosilicate to the mixture dropwise, and stir for 5 minutes after the addition is complete, then let it stand for 24 hours;

[0046] 3) After hydrothermal heating at 130℃ for 24 hours, crystallization was carried out; after natural cooling, the mixture was cooled and crystallized; it was washed with deionized water until neutral and dried; then calcined at 5℃ / min to 550℃ for 6 hours to obtain SiO2 nanosphere powder.

[0047] 4) Add 1g of SiO2 nanosphere powder and 3.3622g of Fe(NO3)3•9H2O to a polytetrafluoroethylene beaker at a ratio of Si:Fe=1:0.5, and simultaneously add 90ml of ethanol. Stir the above solution at 50℃ until the ethanol solution evaporates, then add 40ml of n-hexane to the polytetrafluoroethylene beaker and stir at 50℃ until dry.

[0048] 5) Dry the powder sample in an oven at 220℃ for 2 hours; after washing, dry it in a vacuum drying oven at 80℃ for 8 hours; calcine the powder in a muffle furnace at 650℃ for 6 hours at a heating rate of 1℃ / min.

[0049] 6) Remove the SiO2 nanospheres in two steps using 100 ml of 2 mol / L NaOH solution in an 80℃ water bath. Then wash the sample with deionized water and ethanol until neutral. Finally, dry it in an oven at 90℃ for 6 hours to obtain a pure mesoporous Fe2O3 sample.

[0050] 7) Mix 0.01g of chromium nitrate Cr(NO3)3•9H2O and 0.1g of Fe2O3 sample in 100 mL of anhydrous ethanol and stir at room temperature for 20 hours;

[0051] 8) The suspension was centrifuged and washed to obtain the precursor. The precursor was dried overnight in an oven at 60°C and then calcined at 500°C for 2 hours at a rate of 1°C / min to obtain the mesoporous Fe2O3 / Cr2O3 composite material.

[0052] The specific surface area of ​​the mesoporous Fe2O3 / Cr2O3 composite material obtained in Example 3 was 60.20 m². 2 / g, with an optimal operating temperature of 230℃ and a response of 13 to 10 ppm acetone.

[0053] Example 4

[0054] 1) At room temperature, dissolve 8.8g of polyether P123 in 141.3525g of 1.6 mol / L HCl and deionized water, and stir at medium speed for 2 hours;

[0055] 2) Add 21.33 mL of tetraethyl orthosilicate to the mixture dropwise, and stir for 5 minutes after the addition is complete, then let it stand for 24 hours;

[0056] 3) After hydrothermal heating at 130℃ for 24 hours, crystallization was carried out; after natural cooling, the mixture was cooled and crystallized; it was washed with deionized water until neutral and dried; then calcined at 5℃ / min to 550℃ for 6 hours to obtain SiO2 nanosphere powder.

[0057] 4) Add 1g of SiO2 nanosphere powder and 3.3622g of Fe(NO3)3•9H2O to a polytetrafluoroethylene beaker at a ratio of Si:Fe=1:0.5, and simultaneously add 90ml of ethanol. Stir the above solution at 50℃ until the ethanol solution evaporates, then add 40ml of n-hexane to the polytetrafluoroethylene beaker and stir at 50℃ until dry.

[0058] 5) Dry the powder sample in an oven at 220℃ for 2 hours; after washing, dry it in a vacuum drying oven at 80℃ for 8 hours; calcine the powder in a muffle furnace at 650℃ for 6 hours at a heating rate of 1℃ / min.

[0059] 6) Remove the SiO2 nanospheres in two steps using 100 ml of 2 mol / L NaOH solution in an 80℃ water bath. Then wash the sample with deionized water and ethanol until neutral. Finally, dry it in an oven at 90℃ for 6 hours to obtain a pure mesoporous Fe2O3 sample.

[0060] 7) Mix 0.015 g of chromium nitrate Cr(NO3)3•9H2O and 0.1 g of Fe2O3 sample in 100 mL of anhydrous ethanol and stir at room temperature for 20 hours;

[0061] 8) The suspension was centrifuged and washed to obtain the precursor. The precursor was dried overnight in an oven at 60°C and then calcined at 500°C for 2 hours at a rate of 1°C / min to obtain the mesoporous Fe2O3 / Cr2O3 composite material.

[0062] The specific surface area of ​​the mesoporous Fe2O3 / Cr2O3 composite material obtained in Example 4 is 64.98 m². 2 / g, with an optimal operating temperature of 220℃ and a response of 20.97 to 10 ppm acetone.

[0063] Example 5

[0064] 1) At room temperature, dissolve 8.8g of polyether P123 in 141.3525g of 1.6 mol / L HCl and deionized water, and stir at medium speed for 2 hours;

[0065] 2) Add 21.33 mL of tetraethyl orthosilicate to the mixture dropwise, and stir for 5 minutes after the addition is complete, then let it stand for 24 hours;

[0066] 3) After hydrothermal heating at 130℃ for 24 hours, crystallization was carried out; after natural cooling, the mixture was cooled and crystallized; it was washed with deionized water until neutral and dried; then calcined at 5℃ / min to 550℃ for 6 hours to obtain SiO2 nanosphere powder.

[0067] 4) Add 1g of SiO2 nanosphere powder and 3.3622g of Fe(NO3)3•9H2O to a polytetrafluoroethylene beaker at a ratio of Si:Fe=1:0.5, and simultaneously add 90ml of ethanol. Stir the above solution at 50℃ until the ethanol solution evaporates, then add 40ml of n-hexane to the polytetrafluoroethylene beaker and stir at 50℃ until dry.

[0068] 5) Dry the powder sample in an oven at 220℃ for 2 hours; after washing, dry it in a vacuum drying oven at 80℃ for 8 hours; calcine the powder in a muffle furnace at 650℃ for 6 hours at a heating rate of 1℃ / min.

[0069] 6) Remove the SiO2 nanospheres in two steps using 100 ml of 2 mol / L NaOH solution in an 80℃ water bath. Then wash the sample with deionized water and ethanol until neutral. Finally, dry it in an oven at 90℃ for 6 hours to obtain a pure mesoporous Fe2O3 sample.

[0070] 7) Mix 0.02 g of chromium nitrate Cr(NO3)3•9H2O and 0.1 g of Fe2O3 sample in 100 mL of anhydrous ethanol and stir at room temperature for 20 hours;

[0071] 8) The suspension was centrifuged and washed to obtain the precursor. The precursor was dried overnight in an oven at 60°C, and then calcined at 500°C for 2 hours at a rate of 1°C / min to obtain the mesoporous Fe2O3 / Cr2O3 composite material.

[0072] The specific surface area of ​​the mesoporous Fe2O3 / Cr2O3 composite material obtained in Example 5 was 61.37 m². 2 / g, with an optimal operating temperature of 220℃ and a response of 17.4 to 10 ppm acetone.

Claims

1. A method for preparing an np heterogeneous gas-sensitive material that can improve the gas-sensing performance of low-concentration acetone, characterized in that, The gas-sensitive material is a mesoporous Fe2O3 / Cr2O3 composite gas-sensitive material. Its structure is an np heterojunction gas-sensitive material composed mainly of n-type nano-Fe2O3 and p-type nano-Cr2O3 as surface particles. The specific surface area of ​​the mesoporous Fe2O3 / Cr2O3 composite gas-sensitive material is 60.2–64.98 m². 2 / g, the preparation steps of this material are as follows: 1) At room temperature, dissolve 8.8g of polyether P123 in 141.3525g of 1.6 mol / L HCl and deionized water, and stir at medium speed for 2 hours; 2) Add 21.33 mL of tetraethyl orthosilicate to the mixture dropwise, and stir for 5 minutes after the addition is complete, then let it stand for 24 hours; 3) After hydrothermal heating at 130℃ for 24 hours, crystallization was carried out; after natural cooling, the mixture was cooled and crystallized; it was washed with deionized water until neutral and dried; then calcined at 5℃ / min to 550℃ for 6 hours to obtain SiO2 nanosphere powder. 4) Add 1g of SiO2 nanosphere powder and 3.3622g of Fe(NO3)3•9H2O to a polytetrafluoroethylene beaker at a ratio of Si:Fe=1:0.5, and simultaneously add 90ml of ethanol. Stir the above solution at 50℃ until the ethanol solution evaporates, then add 40ml of n-hexane to the polytetrafluoroethylene beaker and stir at 50℃ until dry. 5) Dry the powder sample in an oven at 220℃ for 2 hours; after washing, dry it in a vacuum drying oven at 80℃ for 8 hours; calcine the powder in a muffle furnace at 650℃ for 6 hours at a heating rate of 1℃ / min. 6) Remove the SiO2 nanospheres in two steps using 100 ml of 2 mol / L NaOH solution in an 80℃ water bath. Then wash the sample with deionized water and ethanol until neutral. Finally, dry it in an oven at 90℃ for 6 hours to obtain a pure mesoporous Fe2O3 sample. 7) Mix 0.008 g to 0.02 g of chromium nitrate Cr(NO3)3•9H2O with 0.1 g of Fe2O3 sample in 100 mL of anhydrous ethanol and stir at room temperature for 20 hours. 8) The suspension was centrifuged and washed to obtain the precursor; the precursor was dried overnight in an oven at 60°C, and then calcined at 500°C for 2 hours at a rate of 1°C / min to obtain mesoporous Fe2O3-Cr2O3 gas-sensitive composite materials with different Cr2O3 composite amounts.

2. A method for preparing an np heterogeneous gas-sensitive material that can improve the gas-sensing performance of low-concentration acetone according to claim 1, characterized in that, The material was applied to the detection of low concentration acetone gas, specifically including the following steps: the material was uniformly coated on a silver electrode sheet and placed on the worktable of the CGS-4TPs gas sensing measurement system. An atmosphere with a relative humidity of 30% was used as the interfering gas to conduct acetone gas sensing tests, and the optimal operating temperature, sensitivity and stability of the sample in response to 10 ppm acetone were obtained.

3. A method for preparing an np heterogeneous gas-sensitive material that can improve the gas-sensing performance of low-concentration acetone according to claim 2, characterized in that, The optimal operating temperature of the composite gas-sensitive material is 220–240°C, and its response to 10 ppm acetone is 11.5–20.97.

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