A gas-sensitive material, a gas-sensitive sensor, and a preparation method and application thereof

Abstract

The present invention provides a gas-sensitive material, a gas-sensitive sensor, and a preparation method and application thereof, which relate to the field of gas sensors. The preparation method of the gas-sensitive material comprises: soaking orange peel in a nickel nitrate solution to obtain a composite material having a metal nickel complex nanoarray on the surface; heat-treating the composite material to oxidize it to obtain a gas-sensitive material having a nickel oxide nanoarray on the surface. The present invention uses orange peel as a raw material, and the grown nickel oxide nanowires have a smaller size than the microspheres formed by agglomeration after general calcination, realizes the combination of nanomaterials and micron materials, has rich micro-nano structures and reactive sites, and is conducive to improving the gas-sensitive performance of the material; the raw materials for preparation have the advantages of being non-toxic and green, abundant and easy to obtain, and low in cost; the preparation process is simple and easy to operate; the gas-sensitive sensor prepared using the gas-sensitive material has excellent selectivity and high sensing response to ethylene glycol gas, which can meet the needs of ethylene glycol gas detection.

Description

Technical Field

[0001] The present invention relates to the field of gas sensors, and in particular to a gas-sensitive material, a gas-sensitive sensor, and a preparation method and application thereof. Background Art

[0002] With the progress of industrial production and the improvement of human quality of life, environmental issues have always been one of the most concerned topics in the country and even the world. Establishing a timely and accurate gas environment supervision mechanism and building an environmental Internet of Things have become urgent issues to be solved. The gas sensor is the core of the gas detection system. In essence, a gas sensor is a converter that converts the type and concentration of a certain gas into a corresponding electrical signal. At present, gas sensors are widely used in the detection of toxic, flammable, explosive, and organic volatile compounds, and are the most basic part of the environmental Internet of Things. High-performance gas sensor devices can improve the gas information collection and processing capabilities, improve the accuracy of real-time accident prediction, and significantly reduce the occurrence of major accidents. At the same time, it can also effectively realize the electronicization of production safety supervision, change passive disaster relief to active disaster prevention, and make production safety scientific.

[0003] Among them, metal oxide semiconductor materials have become the most widely used sensing materials due to their many advantages such as high sensitivity, fast response speed, long life and good stability. Nickel oxide, as a typical p-type semiconductor material, has the characteristics of low operating temperature and high catalytic activity. It has been widely used in catalysts, battery electrodes, photoelectric conversion materials, etc. Its application performance and surface structure are closely related to the preparation method. The main preparation methods include sol-gel method, liquid phase chemical precipitation method, solid phase reaction method, etc. At present, there are reports on the preparation of nickel oxide using NiSO4·7H2O and NaOH, or NH4HCO3 and NiCl2·6H2O and surfactants, or NiCl2·6H2O and NaOH as raw materials, but the precursor preparation process is relatively complicated and not conducive to practical application. The organic complex precursor method is an important preparation method for oxide nanomaterials. The principle is to use a complex that can be easily removed by thermal decomposition, use citric acid as a complexing agent and dispersant, and use the multiple carboxyl groups of citric acid to complex with metal ions to form a citric acid complex. A highly dispersed precursor is obtained through the coordination of the complex and the metal ions, and finally the organic complex is removed by thermal decomposition to obtain nano-oxides. This provides a new strategy for the preparation of gas-sensitive sensing materials. However, nickel precursors are prone to agglomeration during high-temperature calcination, and even form larger micron-sized nickel oxide particles, which affects the gas-sensitive performance of the sensor. In addition, artificially synthesized citric acid is produced by fermenting sugar-containing substances such as sugar, molasses, starch, and grapes, and the process is relatively cumbersome. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the nickel precursor of the organic complex precursor method in the prior art that it is easy to agglomerate during high-temperature calcination, affecting the gas-sensitive performance of the sensor, and the relatively complicated process of artificially synthesized citric acid, thereby providing a gas-sensitive material using orange peel as raw material, a gas-sensitive sensor, and a preparation method and application thereof.

[0005] In a first aspect, the present invention provides a method for preparing a gas-sensitive material, comprising the following steps:

[0006] (1) soaking orange peel in a nickel nitrate solution to obtain a composite material having a metal nickel complex nanoarray on the surface;

[0007] (2) The composite material obtained in step (1) is subjected to heat treatment to oxidize it, thereby obtaining a gas-sensitive material having a nickel oxide nanoarray on its surface.

[0008] Furthermore, the nickel nitrate solution is obtained by dissolving nickel nitrate in deionized water, and in the nickel nitrate solution, the mass volume ratio of nickel nitrate to deionized water is 0.05-0.06 g / mL, preferably 0.058 g / mL;

[0009] The mass ratio of the orange peel to the nickel nitrate is 0.22-0.28:1, preferably 0.2355:1.

[0010] Furthermore, in step (1), the soaking time is 10-12 hours.

[0011] Furthermore, in step (1), the orange peel is washed with deionized water and dried before soaking.

[0012] Furthermore, in step (2), the heat treatment conditions are: heating to 400-500° C. at a rate of 5-10° C. / min, keeping the temperature for 1-3 hours, and cooling naturally;

[0013] Preferably, the composite material is dried at 60-80° C. before the heat treatment.

[0014] In a second aspect, the present invention provides a gas-sensitive material obtained by the preparation method.

[0015] In a third aspect, the present invention provides a gas sensor, comprising the gas-sensitive material obtained by the preparation method or the gas-sensitive material.

[0016] In a fourth aspect, the present invention provides a method for preparing the gas sensor, comprising the following steps: applying a slurry obtained by mixing and grinding the gas sensitive material and anhydrous ethanol on the surface of a ceramic tube, drying, passing a nickel-chromium heating wire through the ceramic tube, welding, and packaging to obtain the gas sensor.

[0017] Furthermore, the mass volume ratio of the gas-sensitive material to anhydrous ethanol is 0.2 g / mL.

[0018] Furthermore, a liner pen with a diameter of 0.15 cm was used in the coating step.

[0019] Furthermore, the drying temperature is 60-80°C.

[0020] In a fifth aspect, the present invention provides the use of the gas-sensitive material obtained by the preparation method, the gas-sensitive material, the gas-sensitive sensor or the gas-sensitive sensor obtained by the preparation method in ethylene glycol gas detection.

[0021] The technical solution of the present invention has the following advantages:

[0022] The invention provides a method for preparing a gas-sensitive material. The orange peel is used as a raw material. Based on the fact that the orange peel itself contains natural citric acid and has a layered structure, a complex formed by a nickel salt and citric acid can be better dispersed on the surface of the orange peel, thereby solving the problem that nickel oxide particles are large and easy to agglomerate after annealing. The grown nickel oxide nanowires have a smaller size than microspheres agglomerated after general calcination, thereby realizing the combination of nanomaterials and micron materials, having rich micro-nano structures and reactive active sites, and being beneficial to improving the gas-sensitive performance of the material. The raw materials for preparation have the advantages of being non-toxic, green, abundant, easily available, and low in cost. The preparation process is simple and easy to operate. The gas-sensitive sensor prepared by using the gas-sensitive material has excellent selectivity and high sensing response to ethylene glycol gas, and can meet the needs of ethylene glycol gas detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 is a scanning electron microscope image of the gas-sensitive material prepared in Example 1 of the present invention;

[0025] Figure 2 is an X-ray diffraction pattern of the gas-sensitive material prepared in Example 1 of the present invention;

[0026] Figure 3 is a scanning electron microscope image of the orange peel without any treatment in Example 1 of the present invention;

[0027] Figure 4 is a scanning electron microscope image of the composite material having a metal nickel complex nanoarray on the surface obtained in step (2) of Example 1 of the present invention;

[0028] Figure 5 1 is a scanning electron microscope image of the gas-sensitive material obtained in the comparative example of the present invention, wherein (a) is the gas-sensitive material obtained by direct oxidation of the nickel nitrate drug in comparative example 1; (b) is the gas-sensitive material prepared by the electrostatic spinning method in comparative example 2;

[0029] Figure 6 1 is a performance test result diagram of the gas sensors prepared in the embodiments and comparative examples of the present invention, wherein (a) is a dynamic response curve diagram of the gas sensors prepared in Embodiment 1, Comparative Examples 1 and 2 to 100 ppm ethylene glycol at 150°C; (b) is a curve diagram of the response of the gas sensors prepared in Embodiment 1, Comparative Examples 1 and 2 to 100 ppm ethylene glycol as a function of temperature; (c) is a curve diagram of the baseline resistance of the gas sensors prepared in Embodiment 1, Comparative Examples 1 and 2 as a function of temperature; (d) is a selectivity test result of the gas sensors prepared in Embodiment 1, Comparative Examples 1 and 2 to ethanol, acetone, methanol, nitrogen dioxide, carbon monoxide, hydrogen and ethylene glycol at 150°C;

[0030] Figure 7 1 and 2 are performance test results of the gas sensors prepared in the embodiments and comparative examples of the present invention, wherein (a) is the repeatability test result of the gas sensors prepared in Embodiment 1 and Comparative Examples 1 and 2 for 100 ppm ethylene glycol at 150°C for 6 consecutive tests; (b) is the test result of the gas sensors prepared in Embodiment 1 and Comparative Examples 1 and 2 for the full spectrum of 1-500 ppm ethylene glycol at 150°C. DETAILED DESCRIPTION

[0031] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0032] Sources of reagents and instruments

[0033] Ceramic tube: purchased from Zhengzhou Weisheng Electronic Technology Co., Ltd., the dimensions of the ceramic tube are length × outer diameter × wall thickness, 4 × 1.35 × 0.35 mm;

[0034] Orange peel: obtained from Sichuan Danleng unknown fire mandarin orange purchased from Sichuan Guozhuangyuan Agricultural Technology Co., Ltd.

[0035] Nickel nitrate (molecular formula: Ni(NO3)2·6H2O) (purity ≥ 98.0%): purchased from Chengdu Kelong Chemical Co., Ltd.;

[0036] Anhydrous ethanol: purchased from Chengdu Kelong Chemical Reagent Factory;

[0037] WS-30A gas sensor tester: purchased from Zhengzhou Weisheng Electronic Technology Co., Ltd.;

[0038] FGL-25 / 30 / 1 open tube furnace: purchased from Hefei Fisher Thermal Technology Co., Ltd.;

[0039] Electric constant temperature drying oven: purchased from Kangheng Instrument Co., Ltd.

[0040] Micro-injector: purchased from Shanghai Guangzheng Medical Instrument Co., Ltd.

[0041] Nickel-chromium heating wire: purchased from Zhengzhou Weisheng Electronic Technology Co., Ltd.

[0042] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the art can be used. The raw materials or instruments used are all conventional products that can be obtained commercially, including but not limited to the raw materials or instruments used in the examples of this application.

[0043] Example 1

[0044] This embodiment provides a method for preparing a gas sensor, the steps are as follows:

[0045] (1) preparing a nickel nitrate solution: dissolving 0.58 g of nickel nitrate in 10 mL of deionized water and stirring with a magnetic stirrer for 30 min to obtain a nickel nitrate solution;

[0046] (2) Soaking orange peel: 0.1366 g of orange peel was washed with deionized water and dried, then soaked in the nickel nitrate solution prepared in step (1), soaked for 12 hours, then taken out and dried to obtain a composite material with a metal nickel complex nanoarray on the surface;

[0047] (3) Oxidation of orange peel: The composite material obtained in step (2) was dried in a constant temperature drying oven at 60° C., and then placed in a tube furnace for heat treatment. The temperature was raised to 450° C. at a rate of 5° C. / min, and the temperature was kept for 1 h. The composite material was then cooled in the furnace to obtain a gas-sensitive material having a nickel oxide nanoarray on the surface.

[0048] (4) Preparation of a gas sensor: 0.1 g of the gas-sensitive material obtained in step (3) is placed in a mortar, and 0.5 mL of anhydrous ethanol is added, and the mixture is ground into a uniform slurry. The slurry is then applied to the surface of a ceramic tube using a stainless steel needle of a liner pen. The coated ceramic tube is placed in a constant temperature drying oven at 60° C. for drying, and a nickel-chromium heating wire is passed through the ceramic tube. The tube is then welded and packaged according to a common indirect-heated gas sensor to obtain a gas sensor.

[0049] The scanning electron microscope image of the gas-sensitive material obtained in step (3) of this embodiment is as follows: Figure 1Its X-ray diffraction pattern is shown in Figure 2 As shown; the scanning electron microscope image of the orange peel without any treatment in the embodiment is as shown Figure 3 As shown; the scanning electron microscope image of the composite material having a metal nickel complex nanoarray on the surface obtained in step (2) is as shown Figure 4 shown.

[0050] Example 2

[0051] This embodiment provides a method for preparing a gas sensor, which is different from Embodiment 1 only in that the heat treatment conditions in step (3) are: heating to 400°C at a rate of 5°C / min, keeping the temperature for 1 hour, and then cooling in the furnace.

[0052] Example 3

[0053] This embodiment provides a method for preparing a gas sensor, which is different from Embodiment 1 only in that the heat treatment conditions in step (3) are: heating to 500°C at a rate of 5°C / min, keeping the temperature for 1 hour, and then cooling in the furnace.

[0054] Comparative Example 1

[0055] This comparative example provides a method for preparing a gas sensor, the steps are as follows:

[0056] (1) Oxidation of nickel nitrate: 0.58 g of nickel nitrate was placed in a tube furnace for oxidation at a heating rate of 5°C / min to 450°C, kept at that temperature for 1 hour, and then cooled with the furnace to obtain a nickel oxide gas-sensitive material;

[0057] (2) Preparation of gas sensor: refer to step (4) of Example 1.

[0058] The scanning electron microscope image of the gas-sensitive material obtained in step (1) of this comparative example is as follows: Figure 5 (a) shown.

[0059] Comparative Example 2

[0060] This comparative example provides a method for preparing a gas sensor, the steps are as follows:

[0061] (1) Prepare the precursor solution: Stir a mixture of 5 mL C2H5OH and 5 mL DMF vigorously at room temperature for 1 h, add 0.58 g Ni(NO3)2·6H2O and 0.68 g PVP to the mixture, and stir for 12 h to form a uniform precursor solution;

[0062] (2) Electrospinning nanofibers: The precursor solution prepared in step (1) was injected into a 5 mL syringe and electrospun at a DC voltage of 15 kV;

[0063] (3) Preparation of nickel oxide nanofibers: Collect the electrospun nanofiber film, place it in a tubular furnace for oxidation, and heat it up to 450°C at a rate of 5°C / min, keep it at that temperature for 1 hour, and then cool it in the furnace to obtain a nickel oxide gas-sensitive material;

[0064] (4) Preparation of gas sensor: refer to step (4) of Example 1.

[0065] The scanning electron microscope image of the gas-sensitive material obtained in step (3) of this comparative example is as follows: Figure 5 (b) as shown.

[0066] Test Example 1: Response of gas sensor to ethylene glycol gas

[0067] The gas-sensing performance of the device was tested at 150°C using the WS-30A gas sensor tester. The sensor was first exposed to air for 3-5 minutes, and then a micro-injector was used to inject a specific concentration of the test gas into the chamber. After the gas fully reacted with the sensor, the device was exposed to the atmosphere to obtain the gas-sensitive response curve.

[0068] like Figure 6 As shown in (a), the gas sensors prepared in Example 1 and Comparative Examples 1 and 2 were tested for 100 ppm ethylene glycol at 150°C. It can be seen that the response value of the sensor obtained in Example 1 is 24.9, which proves that the gas sensor prepared in the present invention can sensitively detect ethylene glycol gas at a relatively low temperature and has excellent response characteristics.

[0069] Test Example 2 Response of Gas Sensor at Different Temperatures

[0070] The gas-sensing performance of the device was tested at 100-200°C using the WS-30A gas sensor tester. The sensor was first exposed to the air atmosphere for 3-5 minutes, and then a micro-injector was used to inject a specific concentration of the test gas into the chamber. After the gas fully reacted with the sensor, the device was exposed to the atmosphere to obtain a gas-sensitive response.

[0071] like Figure 6 As shown in (b), the gas sensors prepared in Example 1 and Comparative Examples 1 and 2 were tested with 100ppm ethylene glycol at 100-200°C. It can be seen that the response value of the sensor obtained in Example 1 increases with the increase of temperature before 150°C and reaches the highest value at 150°C. When the temperature is higher than 150°C, the sensor response decreases with the increase of temperature, which proves that the optimal operating temperature of the sensor is 150°C.

[0072] Test Example 3 Baseline resistance of gas sensor at different temperatures

[0073] All performance tests of the gas sensor are completed on the WS-30A gas sensor tester. The operating temperature is changed by changing the voltage of the nickel-chromium heating wire, and the baseline resistance of the sensor is measured at different operating temperatures.

[0074] like Figure 6 As shown in (c), the baseline resistance of the gas sensors prepared in Example 1 and Comparative Examples 1 and 2 at different temperatures were tested. It can be seen that with the increase of temperature, the baseline resistance gradually decreases, which satisfies the resistance change law of semiconductor metal oxides with temperature, proving that the gas sensor prepared in the present invention is a semiconductor type.

[0075] Test Example 4: Selectivity of Gas Sensor to Ethylene Glycol Gas

[0076] Consistent with the conditions of Test Example 1, seven interfering gases including ethylene glycol gas were tested at the optimal working temperature of 150°C.

[0077] like Figure 6 As shown in (d), the responses of the gas sensors prepared in Example 1 and Comparative Examples 1 and 2 to ethylene glycol gas are significantly higher than those of the other six interfering gases, which proves that the sensor prepared in the present invention exhibits outstanding selectivity to ethylene glycol gas.

[0078] Test Example 5: Repeatability of the gas sensor's response to ethylene glycol gas

[0079] Consistent with the conditions of Test Example 1, the gas sensors prepared in Example 1, Comparative Examples 1 and 2 were subjected to six cycle tests in a 100 ppm ethylene glycol atmosphere at 150°C.

[0080] like Figure 7 As shown in (a), it can be seen that the sensor prepared by the present invention has good repeatability and can achieve multiple consecutive repeatability tests.

[0081] Test Example 6: Full spectrum of the gas sensor's response to ethylene glycol gas

[0082] Consistent with the conditions of Test Example 1, the gas sensors prepared in Example 1, Comparative Examples 1 and 2 were subjected to full spectrum testing in a 1-500 ppm ethylene glycol atmosphere at 150°C.

[0083] like Figure 7 As shown in (b), it can be seen that the sensor prepared by the present invention has a good response to ethylene glycol gas of different concentrations and has good practical application value.

[0084] Based on the above performance test results, the optimal operating temperature of the gas sensor prepared in Example 1 of the present invention is 150°C, and the response to 100ppm ethylene glycol gas at the optimal operating temperature is 24.9, and it has excellent selectivity and good repeatability. Compared with Comparative Example 1, although the method of directly oxidizing the gas-sensitive material by nickel nitrate is simpler, the sensing performance of ethylene glycol gas is not as good as that of the sensor prepared in Example 1 of the present invention; for Comparative Example 2, the method of preparing nickel oxide nanofibers by electrospinning is more complicated than the preparation method of the present invention, and the sensing performance of ethylene glycol gas is not as good as that of the sensor prepared in Example 1 of the present invention. Therefore, the present invention provides a method for preparing an ethylene glycol gas sensor with a simple preparation method and low cost.

[0085] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing a gas-sensitive material, characterized in that: The following steps are involved: (1) soaking orange peel in a nickel nitrate solution to obtain a composite material having a metal nickel complex nanoarray on the surface, wherein the nickel nitrate solution is obtained by dissolving nickel nitrate in deionized water, in which the mass volume ratio of nickel nitrate to deionized water is 0.05-0.06 g / mL, and the mass ratio of the orange peel to the nickel nitrate is 0.22-0.28:1; (2) heat-treating the composite material obtained in step (1) to oxidize it, thereby obtaining a gas-sensitive material having a nickel oxide nanoarray on its surface, wherein the heat treatment conditions are: heating to 400-500° C. at a rate of 5-10° C. / min, keeping the temperature for 1-3 hours, and cooling naturally.

2. The method for preparing a gas-sensitive material according to claim 1, characterized in that: In the nickel nitrate solution, the mass volume ratio of nickel nitrate to deionized water is 0.058 g / mL; the mass ratio of the orange peel to the nickel nitrate is 0.2355:

1.

3. The method for preparing a gas-sensitive material according to claim 1, characterized in that: In step (1), the soaking time is 10-12 hours.

4. The method for preparing a gas-sensitive material according to claim 1, characterized in that: In step (1), the orange peel is washed with deionized water and dried before soaking.

5. The method for preparing a gas-sensitive material according to claim 1, characterized in that: In step (2), the composite material is dried at 60-80° C. before heat treatment.

6. A gas-sensitive material obtained by the preparation method according to any one of claims 1 to 5.

7. A gas sensor, characterized in that: The invention comprises the gas-sensitive material obtained by the preparation method according to any one of claims 1 to 5 or the gas-sensitive material according to claim 6.

8. The method for preparing the gas sensor according to claim 7, characterized in that: The following steps are involved: The slurry obtained by mixing and grinding the gas-sensitive material and anhydrous ethanol is coated on the surface of the ceramic tube and dried, and a nickel-chromium heating wire is passed through the ceramic tube, welded, and packaged to obtain the gas sensor.

9. The method for preparing a gas sensor according to claim 8, characterized in that: The mass volume ratio of the gas-sensitive material to anhydrous ethanol is 0.2 g / mL; Use a 0.15 cm diameter liner pen during the coating step; The drying temperature is 60-80℃.

10. Use of the gas-sensitive material obtained by the preparation method according to any one of claims 1 to 5, the gas-sensitive material according to claim 6, the gas sensor according to claim 7, or the gas sensor obtained by the preparation method according to claim 8 or 9 in ethylene glycol gas detection.

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