Preparation method and application of Fe2O3 nanosheet array material

Abstract

The invention discloses a method for in-situ construction of a Fe2O3 nanosheet array material on the surface of a ceramic tube, which comprises the following steps: by taking K3 [Fe (CN) 6] as a reaction raw material, 1-hexadecyl-3-methylimidazolium hexafluorophosphate as a surfactant and water as a reaction solvent, putting a mixed solution composed of the substances into a stainless steel reaction kettle, immersing the ceramic tube in the stainless steel reaction kettle, and carrying out in-situ construction of the Fe2O3 nanosheet array material on the surface of the ceramic tube; the preparation method comprises the following steps: putting a ceramic tube into a reaction kettle, reacting at 150-180 DEG C for 6-10 hours, after the reaction is finished, naturally cooling the ceramic tube to room temperature, respectively washing the ceramic tube with absolute ethyl alcohol and ultrapure water for multiple times, and then putting the ceramic tube into a vacuum drying oven for vacuum drying at 60-80 DEG C for 6-10 hours. The dried ceramic tube is subjected to roasting treatment in the air atmosphere at the temperature of 300-600 DEG C, the gas sensitive element covered with the Fe2O3 nanosheet array film sensitive layer is obtained, and the gas sensitive element has the good response characteristic to H2S gas at the operation temperature of 130 DEG C. The method has the effective benefit of solving the problem that almost all Fe2O3 materials constructed on the surface of a ceramic tube in situ by the existing method have one-dimensional nanorods and nanotube arrays, and the method is the first application of the Fe2O3 nanosheet array material in a gas sensor.

Description

Technical Field

[0001] The invention relates to a preparation method of a Fe2O3 nanosheet array material and application of the Fe2O3 nanosheet array material as a gas sensitive material. Background Art

[0002] Fe2O3 is an environmentally friendly n-type semiconductor metal oxide. It is widely used in the field of gas sensors because of its advantages such as low price, high sensitivity and strong chemical stability. Although it has many advantages mentioned above, studies have found that gas sensors constructed based on Fe2O3 generally have problems such as high operating temperature, high energy consumption and complicated manufacturing process. These problems have seriously restricted the further development and application of this type of sensor. In order to solve the above problems, researchers have developed a variety of synthetic strategies to further improve the performance of Fe2O3-based sensitive materials. Among them, regulating and improving the micromorphology of the material is one of the most effective methods. Although various Fe2O3-based sensitive materials with novel micromorphologies have been reported in the literature, nanosheet array materials with two-dimensional nanosheets as the basic building unit are rarely reported. It is well known that two-dimensional materials have a larger specific surface area than materials with other morphologies, which is very beneficial for gas adsorption and conduction. At the same time, the nanosheet array structure interlaced with two-dimensional nanosheets as the basic building unit will further enhance the material's mass conduction ability because it further increases the connectivity of the layer structure. Based on the great advantages of nanosheet array materials in gas molecule adsorption and conduction, the development of this type of Fe2O3-based sensitive materials will have broad application prospects. In addition, no matter what the morphology of the material is, in the process of constructing the sensor sensitive element, the material needs to be prepared into a slurry and coated on the test substrate (ceramic tube or interdigitated electrode). In this process, it is easy to cause problems such as uneven coating and poor connectivity with the substrate. At present, the Fe2O3-based sensitive materials that can be in-situ constructed on the surface of the test substrate are almost all nanorods, nanotubes or nanowires with a one-dimensional structure. Therefore, the development of a new synthesis method to construct the Fe2O3 nanosheet array material with a two-dimensional structure in-situ on the test substrate will have broad application prospects. Summary of the invention

[0003] The purpose of the present invention is to provide a method for in-situ construction of Fe2O3 nanosheet arrays on the surface of a ceramic tube. The method solves the problem that when Fe2O3 is in-situ constructed on the surface of a test substrate in the existing method, the morphology of Fe2O3 is almost entirely nanorods, nanotubes and nanowires with a one-dimensional structure.

[0004] The Fe2O3 nanosheet array material of the present invention is synthesized by the following method: 1. Add K3[Fe(CN)6] to water and stir magnetically until completely dissolved, then add 1-hexadecyl-3-methylimidazolium hexafluorophosphate and continue stirring to obtain a reddish brown clear solution; 2. Transfer the above solution into a hydrothermal kettle of appropriate volume, immerse the ceramic tube into the above solution, and conduct hydrothermal reaction. After the reaction is completed, cool the kettle naturally to room temperature and take out the ceramic tube. Wash the ceramic tube with anhydrous ethanol and ultrapure water several times, and obtain a ceramic tube covered with nanosheet array morphology precursor after vacuum drying; 3. Heat-treating the ceramic tube covered with the precursor, so that the precursor on the surface of the ceramic tube is converted into a Fe2O3 nanosheet array thin film sensitive layer.

[0005] The method for making the gas sensor of the present invention is as follows: A heating resistance wire was inserted into the cavity of the ceramic tube covered with the Fe2O3 nanosheet array thin film sensitive layer, and the ceramic tube was welded as a whole on a small hexagonal base to prepare a gas sensor, which was then aged at 120°C for three days.

[0006] The obvious benefits of the present invention are: The present invention discloses a method for in-situ construction of Fe2O3 nanosheet array materials on the surface of a ceramic tube and preparing them into gas sensors. The method solves the problem that when the existing synthesis method constructs Fe2O3 in-situ on a test substrate, the material morphology is almost entirely nanorods, nanotubes or nanowires with a one-dimensional structure. The product structure of the present invention is stable, the morphology is uniform, the synthesis method is simple, and the cost is low. The Fe2O3 nanosheet array material in-situ constructed on the surface of the ceramic tube is in close contact with the ceramic tube and covers evenly. The Fe2O3 nanosheet array material synthesized by the method exhibits excellent gas-sensitive performance to H2S. At the optimal operating temperature of 130°C, the sensitivity to H2S with a concentration of 50 ppm is 76. This method is the first application of Fe2O3 nanosheet array materials in the field of gas sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0008] Figure 1 This is a scanning electron microscope image of a precursor with a nanosheet array morphology; Figure 2 This is a scanning electron microscope image of the Fe2O3 nanosheet array material prepared after heat treatment of the precursor; Figure 3 This is the XRD spectrum of Fe2O3 nanosheet array material; Figure 4 The response-recovery curve of Fe2O3 nanosheet array material to different concentrations of H2S; Figure 5 This is the linear response relationship of Fe2O3 nanosheet array material to 1-50 ppm H2S. DETAILED DESCRIPTION

[0009] Dissolve 0.3600-0.6000 g K3[Fe(CN)6] in 25-35 mL water and stir magnetically until completely dissolved; 0.0479-0.0879 g of 1-hexadecyl-3-methylimidazolium hexafluorophosphate was dissolved in the above solution and stirred magnetically until it was completely dissolved to obtain a reddish brown clear solution.

[0010] Transfer the above solution into a hydrothermal kettle, immerse the ceramic tube in the solution, react at 150-180 °C for 6-10 h, cool naturally to room temperature, take out the ceramic tube and wash it with anhydrous ethanol and ultrapure water respectively, and then vacuum dry it at 60-80 °C for 6-10 h.

[0011] The dried ceramic tube was heat treated at 300-600 °C. The SEM image of the precursor without heat treatment is shown in Figure 1 As shown in the figure, the prepared precursor presents a nanosheet array morphology composed of a large number of two-dimensional nanosheets interlaced. The scanning electron microscopy image of the Fe2O3 nanosheet array obtained by heat treatment at 600 °C is shown in Figure 2 As shown in the figure, the product after heat treatment at 600℃ still has the same nanosheet array morphology as the precursor.

[0012] XRD spectrum of the product heat treated at 600℃ ( Figure 3 ) It can be seen that all diffraction peaks in the XRD spectrum of the product are consistent with the spectrum of the standard XRD card JCPDS: 39-0238, indicating that the product is pure phase β-Fe2O3.

[0013] In order to obtain the gas-sensing performance of the prepared Fe2O3 nanosheet array material, a heating resistor wire was inserted into the middle of a ceramic tube covered with a Fe2O3 nanosheet array thin film sensitive layer, and the heating resistor wire and the ceramic tube were welded as a whole to a small hexagonal base to construct a gas-sensitive element.

[0014] The gas sensing performance test is as follows: First, a glass bottle with a volume of 10 L and a vent at the top and bottom was evacuated, and then different volumes of H2S gas were injected into the glass container and air was put in from the bottom of the bottle. While the air pressure inside and outside the bottle was adjusted with air, different concentrations of H2S gas were obtained. After the gas sensor obtained a stable resistance value in the air, the gas sensor was inserted into the glass bottle containing H2S gas for 60 seconds, and then the element was taken out.

[0015] During the test, the response value R of the gas sensor is given by the formula R = Ra / R g Among them, R a Indicates the stable resistance value of the gas sensor in the air, R g It indicates the resistance value of the gas sensor after being exposed to H2S gas of a certain concentration for 60 seconds.

[0016] Depend on Figure 4 It can be seen that the Fe2O3 nanosheet array sensor obtained by heat treatment at 600 ℃ has good response characteristics to H2S gas with a concentration of 1~50 ppm at an operating temperature of 130 ℃. Its response value to 50 ppm H2S is 76, and the gas sensor has a good linear response relationship to H2S gas with different concentrations. Its linear response fitting coefficient R 2 = 0.9711 (see Figure 5 ).

Claims

1. A method for preparing a Fe2O3 nanosheet array material is as follows: (1) Dissolve 0.3600-0.6000 g K3[Fe(CN)6] in 25-35 mL water and stir magnetically until completely dissolved. Dissolve 0.0479-0.0879 g 1-hexadecyl-3-methylimidazolium hexafluorophosphate in the above solution and stir magnetically until fully dissolved to obtain a reddish brown clear solution. (2) The red-brown solution was transferred into a hydrothermal reactor, and the ceramic tube was immersed in the solution. The reaction was carried out at 150-180 °C for 6-10 h. After the hydrothermal reactor was naturally cooled to room temperature, the ceramic tube was taken out and washed with anhydrous ethanol and ultrapure water respectively, and then vacuum dried at 60-80 °C for 6-10 h. (3) The dried ceramic tube is calcined at 300-600°C in an air atmosphere.

2. The method for preparing the Fe2O3 nanosheet array according to claim 1, characterized in that In step (1), 0.3600-0.6000 g K3[Fe(CN)6] was dissolved in 25-35 mL water.

3. The method for preparing the Fe2O3 nanosheet array according to claim 1, characterized in that In step (1), 0.0479-0.0879 g of 1-hexadecyl-3-methylimidazolium hexafluorophosphate is dissolved in 25-35 mL of water.

4. The method for preparing the Fe2O3 nanosheet array according to claim 1, characterized in that In step (2), the ceramic tube is reacted at 150-180°C for 6-10 hours.

5. The method for preparing the Fe2O3 nanosheet array according to claim 1, characterized in that In step (2), the ceramic tube is placed in a vacuum dryer at 60 to 80 °C for 6 to 10 hours.

6. The method for preparing the Fe2O3 nanosheet array according to claim 1, characterized in that In step (3), the ceramic tube is placed in an air atmosphere and sintered at 300-600°C.

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