CN114062444B - Based on low coordination Co 3 O 4 Triethylamine gas sensor of mesoporous nano-sheet assembled hierarchical microsphere sensitive material and preparation method thereof - Google Patents

Based on low coordination Co 3 O 4 Triethylamine gas sensor of mesoporous nano-sheet assembled hierarchical microsphere sensitive material and preparation method thereof Download PDF

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CN114062444B
CN114062444B CN202111330144.XA CN202111330144A CN114062444B CN 114062444 B CN114062444 B CN 114062444B CN 202111330144 A CN202111330144 A CN 202111330144A CN 114062444 B CN114062444 B CN 114062444B
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卢革宇
孔德颢
高原
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Jilin University
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Abstract

Co based on low coordination 3 O 4 A triethylamine gas sensor of mesoporous nano-sheet assembled hierarchical microsphere sensitive material and a preparation method thereof belong to the technical field of semiconductor oxide gas sensors. The sensor is made of Al with a pair of parallel annular gold electrodes on both sides of the outer surface 2 O 3 Ceramic tube substrate coated on Al 2 O 3 Sensitive material on the outer surface of the ceramic tube and the gold electrode, placed on Al 2 O 3 A nickel-chromium metal heating coil in the ceramic tube; the sensitive material is low coordination Co 3 O 4 The mesoporous nano-sheet assembled hierarchical microsphere sensitive material is formed by hierarchical assembly of mesoporous nano-sheets. The invention utilizes the structural advantage of mesoporous nano-sheet assembly and low-coordination Co 3 O 4 The higher catalytic activity effectively improves the gas-sensitive characteristic of the sensor to the triethylamine gas, expands the detection range of the triethylamine gas, improves the sensitivity, has good selectivity and lower detection lower limit, and has wide application prospect in the aspect of detecting the triethylamine gas.

Description

Based on low coordination Co 3 O 4 Triethylamine gas sensor of mesoporous nano-sheet assembled hierarchical microsphere sensitive material and preparation method thereof
Technical Field
The invention belongs to the technical field of semiconductor metal oxide gas sensors, and particularly relates to a low-coordination Co-based gas sensor 3 O 4 A triethylamine gas sensor of hierarchical microsphere sensitive material assembled by mesoporous nano-sheets and a preparation method thereof.
Background
Triethylamine is a volatile organic compound, and the volatilized gas is colorless and has an ammonia-like smell, and is often used as a solvent, a catalyst, a preservative, etc. in the organic synthesis industry. Triethylamine is corrosive and can irritate human skin, respiratory system, digestive system, etc. If people are exposed to high-concentration triethylamine for a long time, cough, gastroenteritis, pulmonary edema and other diseases can be caused, and even death is caused in severe cases. Triethylamine also has the property of being highly flammable and explosive, and when mixed with air and exposed to a fire source, can cause explosions. The maximum acceptable concentration of triethylamine in air was 10ppm, as specified by the U.S. occupational safety and health administration. Furthermore, dead marine organisms also release triethylamine and the gas concentration increases over time. Therefore, judging the quality of seafood by detecting the concentration of triethylamine is also an effective method. In summary, it is necessary to find an appropriate method for detecting triethylamine gas.
Gas sensors based on metal oxide semiconductors have attracted considerable attention due to their pure solid state, small space occupation, low cost, etc. Co (Co) 3 O 4 As a typical p-type metal oxide semiconductor having a spinel structure, although sensitivity is lower than that of an n-type metal oxide semiconductor, it has Co 2+ And Co 3+ Two different active sites can realize oxygen adsorption rich at low temperature, and have obvious advantages in reducing the gas detection working temperature and improving the selectivity. Meanwhile, the two-dimensional nano sheet structure has high specific surface area and a large number of high-efficiency active sites exposed on the surface and used for surface reaction, and has great development potential in the field of gas sensing, so that two-dimensional Co can be prepared 3 O 4 The material is used for detecting triethylamine gas.
Disclosure of Invention
The invention aims to provide a low-coordination Co-based catalyst 3 O 4 A triethylamine gas sensor of hierarchical microsphere sensitive material assembled by mesoporous nano-sheets and a preparation method thereof. As shown in FIG. 2 (d-f), the hierarchical microspheres were three-dimensional spherical structures assembled from two-dimensional mesoporous nanoplatelets in a hierarchical manner, with a size of about 3. Mu.m. The sensor obtained by the invention has the advantages of low detection lower limit, high response recovery speed and good selectivity besides high sensitivity.
The triethylamine sensor of the invention uses low coordination Co 3 O 4 Hierarchical microsphere assembled by mesoporous nano sheets is a sensitive material, and on one hand, two-dimensional Co 3 O 4 The mesoporous nano-sheet has large specific surface area and more active sites, and is beneficial to the contact and reaction of gas; on the other hand, orderly assembling of nano-sheets is preventedThe surface stacking is stopped, the gas diffusion is promoted, and the contact resistance is reduced; in addition, the specific surface area of the material, co 2+ The increase of the content and oxygen vacancies enhances the catalytic activity and reaction capacity of the material surface. The combined action of the aspects promotes the reaction efficiency between the sensitive material and the triethylamine gas, and improves the sensitivity and selectivity of the material. The invention prepares the low coordination Co at different annealing temperatures by using PVP K30 as a structure guiding agent and a reducing agent through a hydrothermal method 3 O 4 The mesoporous nano-sheet assembled graded microsphere is used for improving the gas-sensitive performance of the material. Co assembled based on low-coordination mesoporous nano-sheets obtained by annealing at 300 DEG C 3 O 4 The chemoresistance type gas sensor of the graded microsphere can realize sensitive detection of triethylamine gas as low as 0.5ppm at the working temperature of 150 ℃.
The invention relates to a Co based on low coordination 3 O 4 As shown in figure 1, the triethylamine gas sensor of the hierarchical microsphere sensitive material assembled by mesoporous nano-sheets is formed by a pair of parallel annular gold electrodes on two sides of the outer surface and connecting Al of two platinum wire leads on each gold electrode 2 O 3 Ceramic tube substrate coated on Al 2 O 3 Sensitive material on the outer surface of the ceramic tube and the gold electrode, placed on Al 2 O 3 A nickel-chromium metal heating coil in the ceramic tube; the sensitive material is low coordination Co 3 O 4 The mesoporous nano-sheet assembled hierarchical microsphere sensitive material is prepared by the following steps:
(1) 0.8g of cobalt acetate (C) 4 H 6 CoO 4 ·4H 2 O) and 0.3-0.5 g PVP K30 ((C) 6 H 9 NO) n ) Adding the mixture into 30-35 mL of ethylene glycol, stirring to form a uniform solution, continuously stirring for 2-5 hours, and standing and aging the solution at room temperature for 20-30 hours;
(2) Adding the uniform solution obtained after aging in the step (1) into a stainless steel autoclave with a polytetrafluoroethylene lining, and keeping the stainless steel autoclave for 15 to 20 hours at 180 to 200 ℃ after good sealing; after the autoclave is naturally cooled to room temperature, centrifugally collecting the precipitate, alternately cleaning the precipitate for 5-8 times by using water and ethanol, and drying the obtained product for 10-20 hours at 70-90 ℃ in vacuum to obtain solid powder;
(3) Calcining the solid powder obtained in the step (2) in air at 300-400 ℃ for 1.5-3.0 hours, and heating up at a rate of 1.5-3.0 ℃/min to obtain the low-coordination Co 3 O 4 The mesoporous nano-sheets are assembled into the hierarchical microsphere sensitive material.
The invention relates to a Co based on low coordination 3 O 4 The preparation method of the triethylamine gas sensor of the hierarchical microsphere sensitive material assembled by the mesoporous nano-sheets comprises the following steps:
(1) Taking 10-20 mg of low coordination Co 3 O 4 The mesoporous nano-sheet assembled hierarchical microsphere sensitive material is put into an agate mortar, 3 to 5 drops of ethanol are dripped into the mortar, fully mixed and ground into paste, and then a proper amount of paste is dipped into the paste and evenly coated on Al 2 O 3 Forming a sensitive material layer with the thickness of 15-30 mu m on the outer surface of the ceramic tube, and enabling the sensitive material to completely cover a pair of parallel annular gold electrodes on two sides of the outer surface of the ceramic tube; al (Al) 2 O 3 The length of the ceramic tube is 4.0-4.5 mm, and the inner diameter and the outer diameter are respectively 0.8-1.0 mm and 1.2-1.5 mm; the width of the single annular gold electrode is 0.4-0.5 mm, and the interval between the two gold electrodes is 0.5-0.6 mm; a platinum wire is led out from the gold electrode, and the length of the platinum wire is 4-6 mm;
(2) Coating the outer surface obtained in the step (1) with Al of a sensitive material 2 O 3 Calcining the ceramic tube in air at 200-300 ℃ for 1.5-3.0 hours to improve the stability of sensitive materials, heating the ceramic tube at a heating rate of 3-6 ℃/min, and allowing a nichrome heating coil with a resistance value of 36-39 omega to pass through the ceramic tube as a heating wire after the temperature is reduced to room temperature; finally, the device is welded on a hexagonal tube seat, thus preparing the Co-based low coordination 3 O 4 A bypass type triethylamine gas sensor of hierarchical microsphere sensitive material is assembled by mesoporous nano-sheets.
The invention relates to a low coordination Co-based catalyst 3 O 4 The triethylamine gas sensor of the hierarchical microsphere sensitive material assembled by the mesoporous nano-sheets has the following advantages:
(1) Mesoporous preparation by simple solvothermal methodNanoplatelet assembled low coordination Co 3 O 4 The method for classifying the microsphere sensitive material is simple and the cost is low;
(2) Mesoporous Co is prepared by using PVP K30 as a structure guiding agent and a reducing agent 3 O 4 Nanoplatelets assembled as low coordination Co 3 O 4 The graded microsphere improves the detection range (0.5-100 ppm) and the sensitivity (34.1-100 ppm) of triethylamine gas, and has good selectivity and lower detection lower limit.
(3) The device has simple process, low cost and small volume and is suitable for mass production by using a commercially available tubular sensor.
Drawings
Fig. 1: the invention relates to a low coordination Co-based catalyst 3 O 4 A structural schematic diagram of a triethylamine side heating type gas sensor of a hierarchical microsphere sensitive material assembled by mesoporous nano sheets;
name of each part: al (Al) 2 O 3 A ceramic tube 1, a platinum wire lead 2, a gold electrode 3, a sensitive material 4 and a nichrome heating coil 5.
Fig. 2: comparative examples 1, 2, 3 and 1, 2 and 4 of the present invention prepared mesoporous nanoplatelets Co 3 O 4 And low coordination Co 3 O 4 SEM morphology photographs of the mesoporous nano-sheet assembled hierarchical microsphere sensitive material; the size of the mesoporous nano-sheet is 1.3-3.2 mu m, and the size of the hierarchical microsphere sensitive material assembled by the mesoporous nano-sheet is about 3 mu m.
Fig. 3: co prepared in comparative examples and examples of the present invention 3 O 4 XRD pattern of the sensitive material; all sensitive materials are typically cubic Co 3 O 4 And (3) phase (C).
Fig. 4: sensitivity curves of the gas sensors prepared in comparative example 1, comparative example 2, comparative example 3, comparative example 4, example 1 and example 2; the optimum working temperature of each device is 150 ℃, 160 ℃, 190 ℃, 170 ℃, 150 ℃ and 150 ℃, and the sensitivity to 100ppm triethylamine gas is 10.2, 5.4, 5.0, 11.2, 34.1 and 32.7 respectively; the sensors of examples 1 and 2 had the highest sensitivity to triethylamine relative to the sensors of the comparative example.
Fig. 5: comparative examples 1, 2, 3, 4, 1 and 2 are graphs showing the selectivity of the gas sensors prepared in examples 1 and 2 to 100ppm of different gases, respectively, at their optimal operating temperatures; the sensors of comparative example 1, example 1 and example 2 are shown to have a good selectivity for triethylamine gas.
Fig. 6: response recovery curves for the gas sensors in examples 1 and 2 for 100ppm triethylamine gas at 150 ℃ operating temperature; the response recovery times of example 1 were shown to be 138 seconds and 86 seconds, respectively, and the response recovery times of example 2 were shown to be 116 seconds and 70 seconds, respectively, with higher sensitivity.
Fig. 7: response recovery curves for different concentrations of triethylamine gas when the gas sensor of example 1 was operated at 150 ℃; the sensitivity is obviously improved along with the increase of the concentration of the triethylamine gas, and the concentration range of the triethylamine detected by the sensor is 0.5 ppm-200 ppm.
Fig. 8: the sensor in example 1 has a repeatability profile for 100ppm triethylamine gas at 150 ℃ operating temperature; indicating that the sensor sensitivity has good repeatability.
Note that: the sensitivity (response value) of the device is defined as the ratio of the resistance value between the two gold electrodes in the measured gas to the resistance value in air, and the response and recovery time are the time taken for the resistance value change amount of the sensor to reach 90% of the total change value after changing the gas environment (from air to triethylamine gas or from triethylamine gas to air) in which the device is located. Testing was performed using a static test system: the device is placed in a 1 liter gas cylinder, a certain concentration of gas to be measured is configured in the gas cylinder, the resistance change is observed and recorded, and the corresponding sensitivity value and response recovery time are obtained through calculation.
Detailed Description
Comparative example 1:
1. first, 0.8g of cobalt acetate was added to 32mL of ethylene glycol, and stirring was continued for 3 hours after stirring to form a uniform solution.
2. The solution obtained in step 1 was left to stand and age at room temperature for 24 hours.
3. The solution obtained in step 2 was put into a 40mL stainless steel autoclave lined with polytetrafluoroethylene, and after good sealing, it was placed in an oven at 190 ℃ for 18 hours. After the reaction was completed and the autoclave was naturally cooled to room temperature, the precipitate was collected by centrifugation and washed with water and ethanol alternately 6 times. The obtained product is put into a vacuum oven and dried for 12 hours at 80 ℃ to obtain pink Co (OH) 2 And (3) powder.
4. Co (OH) obtained in step 3 2 Transferring the powder to a porcelain boat, placing in a muffle furnace, calcining for 2 hours at 300 ℃ in air, and heating at a rate of 2 ℃/min to obtain mesoporous nanosheets Co 3 O 4 Sensitive material.
5. Adding 15mg of the sensitive material obtained in the step 4 into an agate mortar, dripping 3 drops of ethanol, fully mixing and grinding into paste, dipping a proper amount of the paste, and uniformly coating the paste on Al 2 O 3 The outer surface of the ceramic tube is provided with a sensitive material layer with the thickness of 20 mu m, so that the sensitive material can completely cover the annular gold electrodes on the two sides of the outer surface of the ceramic tube. Al (Al) 2 O 3 The ceramic tube had a length of 4mm and inner and outer diameters of 0.8mm and 1.2mm, respectively. The width of a single annular gold electrode is 0.45mm, and the interval between two gold electrodes is 0.55mm; the platinum wire is led out from the gold electrode, and the length of the platinum wire is 5mm.
6. Coating the outer surface obtained in the step 5 with Al of a sensitive material 2 O 3 The ceramic tube is transferred to a ceramic boat and placed in a muffle furnace, and is calcined for 2 hours at 250 ℃ in air, the heating rate is 5 ℃/min, and the stability of sensitive materials is improved. After the temperature was lowered to room temperature, a nichrome heating coil having a resistance value of 38Ω was passed through the inside of the ceramic tube as a heating wire, and finally the above-mentioned device was welded to a hexagonal tube holder, to prepare a triethylamine gas sensor of comparative example 1.
Comparative example 2:
1. first, 0.8g of cobalt acetate was added to 32mL of ethylene glycol, and stirring was continued for 3 hours after stirring to form a uniform solution.
2. The solution obtained in step 1 was left to stand and age at room temperature for 24 hours.
3. The step 2 is carried outThe solution was placed in a 40mL stainless steel autoclave lined with polytetrafluoroethylene, well sealed and placed in an oven at 190 c for 18 hours. After the reaction was completed and the autoclave was naturally cooled to room temperature, the precipitate was collected by centrifugation and washed with water and ethanol alternately 6 times. The obtained product is put into a vacuum oven and dried for 12 hours at 80 ℃ to obtain pink Co (OH) 2 And (3) powder.
4. Co (OH) obtained in step 3 2 Transferring the powder to a porcelain boat, placing in a muffle furnace, calcining for 2 hours at 400 ℃ in air, and heating at a rate of 2 ℃/min to obtain mesoporous nanosheets Co 3 O 4 Sensitive material.
5. Adding 15mg of the sensitive material obtained in the step 4 into an agate mortar, dripping 3 drops of ethanol, fully mixing and grinding into paste, dipping a proper amount of the paste, and uniformly coating the paste on Al 2 O 3 The outer surface of the ceramic tube is provided with a sensitive material layer with the thickness of 20 mu m, so that the sensitive material can completely cover the annular gold electrodes on the two sides of the outer surface of the ceramic tube. Al (Al) 2 O 3 The ceramic tube had a length of 4mm and inner and outer diameters of 0.8mm and 1.2mm, respectively. The width of a single annular gold electrode is 0.45mm, and the interval between two gold electrodes is 0.55mm; the platinum wire is led out from the gold electrode, and the length of the platinum wire is 5mm.
6. Coating the outer surface obtained in the step 5 with Al of a sensitive material 2 O 3 The ceramic tube is transferred to a ceramic boat and placed in a muffle furnace, and is calcined for 2 hours at 250 ℃ in air, the heating rate is 5 ℃/min, and the stability of sensitive materials is improved. After the temperature was lowered to room temperature, a nichrome heating coil having a resistance value of 38Ω was passed through the inside of the ceramic tube as a heating wire, and finally the above-mentioned device was welded to a hexagonal tube holder, to prepare a triethylamine gas sensor of comparative example 2.
Comparative example 3:
1. first, 0.8g of cobalt acetate was added to 32mL of ethylene glycol, and stirring was continued for 3 hours after stirring to form a uniform solution.
2. The solution obtained in step 1 was left to stand and age at room temperature for 24 hours.
3. Adding the solution obtained in the step 2 into 40mL of polytetrafluoroethyleneIn a stainless steel autoclave lined with ethylene, after good sealing, it was placed in an oven, the temperature was set to 190 ℃, and the time was kept for 18 hours. After the reaction was completed and the autoclave was naturally cooled to room temperature, the precipitate was collected by centrifugation and washed with water and ethanol alternately 6 times. The obtained product is put into a vacuum oven and dried for 12 hours at 80 ℃ to obtain pink Co (OH) 2 And (3) powder.
4. Co (OH) obtained in step 3 2 Transferring the powder to a porcelain boat, placing in a muffle furnace, calcining for 2 hours at 500 ℃ in air, and heating at a rate of 2 ℃/min to obtain mesoporous nanosheets Co 3 O 4 Sensitive material.
5. Adding 15mg of the sensitive material obtained in the step 4 into an agate mortar, dripping 3 drops of ethanol, fully mixing and grinding into paste, dipping a proper amount of the paste, and uniformly coating the paste on Al 2 O 3 The outer surface of the ceramic tube is provided with a sensitive material layer with the thickness of 20 mu m, so that the sensitive material can completely cover the annular gold electrodes on the two sides of the outer surface of the ceramic tube. Al (Al) 2 O 3 The ceramic tube had a length of 4mm and inner and outer diameters of 0.8mm and 1.2mm, respectively. The width of a single annular gold electrode is 0.45mm, and the interval between two gold electrodes is 0.55mm; the platinum wire is led out from the gold electrode, and the length of the platinum wire is 5mm.
6. Coating the outer surface obtained in the step 5 with Al of a sensitive material 2 O 3 The ceramic tube is transferred to a ceramic boat and placed in a muffle furnace, and is calcined for 2 hours at 250 ℃ in air, the heating rate is 5 ℃/min, and the stability of sensitive materials is improved. After the temperature was lowered to room temperature, a nichrome heating coil having a resistance value of 38Ω was passed through the inside of the ceramic tube as a heating wire, and finally the above-mentioned device was welded to a hexagonal tube holder, to prepare a triethylamine gas sensor of comparative example 3.
Comparative example 4:
1. first, 0.8g of cobalt acetate and 0.5g of PVP K30 were added to 32mL of ethylene glycol, and stirring was continued for 3 hours after stirring to form a homogeneous solution.
2. The solution obtained in step 1 was left to stand and age at room temperature for 24 hours.
3. Adding the solution obtained in the step 2 into a 40mL polytetrafluoroethylene liningIn a stainless steel autoclave, after good sealing, it was placed in an oven at 190 ℃ for 18 hours. After the reaction was completed and the autoclave was naturally cooled to room temperature, the precipitate was collected by centrifugation and washed with water and ethanol alternately 6 times. The obtained product is put into a vacuum oven and dried for 12 hours at 80 ℃ to obtain pink Co (OH) 2 And (3) powder.
4. Co (OH) obtained in step 3 2 Transferring the powder to a porcelain boat, placing in a muffle furnace, calcining for 2 hours at 500 ℃ in air, and heating at a rate of 2 ℃/min to obtain low-coordination Co 3 O 4 The mesoporous nano-sheets are assembled into the hierarchical microsphere sensitive material.
5. Adding 15mg of the sensitive material obtained in the step 4 into an agate mortar, dripping 3 drops of ethanol, fully mixing and grinding into paste, dipping a proper amount of the paste, and uniformly coating the paste on Al 2 O 3 The outer surface of the ceramic tube is provided with a sensitive material layer with the thickness of 20 mu m, so that the sensitive material can completely cover the annular gold electrodes on the two sides of the outer surface of the ceramic tube. Al (Al) 2 O 3 The ceramic tube had a length of 4mm and inner and outer diameters of 0.8mm and 1.2mm, respectively. The width of a single annular gold electrode is 0.45mm, and the interval between two gold electrodes is 0.55mm; the platinum wire is led out from the gold electrode, and the length of the platinum wire is 5mm.
6. Coating the outer surface obtained in the step 5 with Al of a sensitive material 2 O 3 The ceramic tube is transferred to a ceramic boat and placed in a muffle furnace, and is calcined for 2 hours at 250 ℃ in air, the heating rate is 5 ℃/min, and the stability of sensitive materials is improved. After the temperature was lowered to room temperature, a nichrome heating coil having a resistance value of 38Ω was passed through the inside of the ceramic tube as a heating wire, and finally the above-mentioned device was welded to a hexagonal tube holder, to prepare a triethylamine gas sensor of comparative example 4.
Example 1:
1. first, 0.8g of cobalt acetate and 0.5g of PVP K30 were added to 32mL of ethylene glycol, and stirring was continued for 3 hours after stirring to form a homogeneous solution.
2. The solution obtained in step 1 was left to stand and age at room temperature for 24 hours.
3. Adding the solution obtained in the step 2 into 40mL of polytetrafluoroethyleneThe alkene-lined stainless steel autoclave was placed in an oven after good sealing at 190 ℃ for 18 hours. After the reaction was completed and the autoclave was naturally cooled to room temperature, the precipitate was collected by centrifugation and washed with water and ethanol alternately 6 times. The obtained product is put into a vacuum oven and dried for 12 hours at 80 ℃ to obtain pink Co (OH) 2 And (3) powder.
4. Co (OH) obtained in step 3 2 Transferring the powder to a porcelain boat, placing in a muffle furnace, calcining for 2 hours at 300 ℃ in air, and heating at a rate of 2 ℃/min to obtain low-coordination Co 3 O 4 The mesoporous nano-sheets are assembled into the hierarchical microsphere sensitive material.
5. Adding 15mg of the sensitive material obtained in the step 4 into an agate mortar, dripping 3 drops of ethanol, fully mixing and grinding into paste, dipping a proper amount of the paste, and uniformly coating the paste on Al 2 O 3 The outer surface of the ceramic tube is provided with a sensitive material layer with the thickness of 20 mu m, so that the sensitive material can completely cover the annular gold electrodes on the two sides of the outer surface of the ceramic tube. Al (Al) 2 O 3 The ceramic tube had a length of 4mm and inner and outer diameters of 0.8mm and 1.2mm, respectively. The width of a single annular gold electrode is 0.45mm, and the interval between two gold electrodes is 0.55mm; the platinum wire is led out from the gold electrode, and the length of the platinum wire is 5mm.
6. Coating the outer surface obtained in the step 5 with Al of a sensitive material 2 O 3 The ceramic tube is transferred to a ceramic boat and placed in a muffle furnace, and is calcined for 2 hours at 250 ℃ in air, the heating rate is 5 ℃/min, and the stability of sensitive materials is improved. After the temperature was lowered to room temperature, a nichrome heating coil having a resistance value of 38Ω was passed through the inside of the ceramic tube as a heating wire, and finally the above-mentioned device was welded to a hexagonal tube holder, to prepare a triethylamine gas sensor of example 1.
Example 2:
1. first, 0.8g of cobalt acetate and 0.5g of PVP K30 were added to 32mL of ethylene glycol, and stirring was continued for 3 hours after stirring to form a homogeneous solution.
2. The solution obtained in step 1 was left to stand and age at room temperature for 24 hours.
3. Adding the solution obtained in the step 2 into 40mLIn a stainless steel autoclave lined with polytetrafluoroethylene, after good sealing, it was placed in an oven at 190 ℃ for 18 hours. After the reaction was completed and the autoclave was naturally cooled to room temperature, the precipitate was collected by centrifugation and washed with water and ethanol alternately 6 times. The obtained product is put into a vacuum oven and dried for 12 hours at 80 ℃ to obtain pink Co (OH) 2 And (3) powder.
4. Co (OH) obtained in step 3 2 Transferring the powder to a porcelain boat, placing in a muffle furnace, calcining for 2 hours at 400 ℃ in air, and heating at a rate of 2 ℃/min to obtain low-coordination Co 3 O 4 The mesoporous nano-sheets are assembled into the hierarchical microsphere sensitive material.
5. Adding 15mg of the sensitive material obtained in the step 4 into an agate mortar, dripping 3 drops of ethanol, fully mixing and grinding into paste, dipping a proper amount of the paste, and uniformly coating the paste on Al 2 O 3 The outer surface of the ceramic tube is provided with a sensitive material layer with the thickness of 20 mu m, so that the sensitive material can completely cover the annular gold electrodes on the two sides of the outer surface of the ceramic tube. Al (Al) 2 O 3 The ceramic tube had a length of 4mm and inner and outer diameters of 0.8mm and 1.2mm, respectively. The width of a single annular gold electrode is 0.45mm, and the interval between two gold electrodes is 0.55mm; the platinum wire is led out from the gold electrode, and the length of the platinum wire is 5mm.
6. Coating the outer surface obtained in the step 5 with Al of a sensitive material 2 O 3 The ceramic tube is transferred to a ceramic boat and placed in a muffle furnace, and is calcined for 2 hours at 250 ℃ in air, the heating rate is 5 ℃/min, and the stability of sensitive materials is improved. After the temperature was lowered to room temperature, a nichrome heating coil having a resistance value of 38Ω was passed through the inside of the ceramic tube as a heating wire, and finally the above-mentioned device was welded to a hexagonal tube holder, to prepare a triethylamine gas sensor of example 2.

Claims (3)

1. Co based on low coordination 3 O 4 A triethylamine gas sensor with hierarchical microballoons assembled by mesoporous nano-sheets is prepared from Al with a pair of parallel annular gold electrodes on both sides of external surface and two platinum wires connected to each gold electrode 2 O 3 Ceramic tube substrate coated on Al 2 O 3 Sensitive material on the outer surface of the ceramic tube and the gold electrode, placed on Al 2 O 3 A nickel-chromium metal heating coil in the ceramic tube; the method is characterized in that: the sensitive material is low coordination Co 3 O 4 The mesoporous nano-sheet assembled hierarchical microsphere sensitive material is prepared by the following steps:
(1) Adding 0.8-g cobalt acetate and 0.3~0.5 g PVP K30 into 30-35 mL of ethylene glycol, stirring to form a uniform solution, continuing stirring for 2-5 hours, and standing and aging the solution at room temperature for 20-30 hours;
(2) Adding the uniform solution obtained after aging in the step (1) into a stainless steel autoclave with a polytetrafluoroethylene lining, and keeping the stainless steel autoclave for 15-20 hours at 180-200 ℃ after good sealing; after the autoclave is naturally cooled to room temperature, centrifugally collecting the precipitate, alternately cleaning the precipitate with water and ethanol for 5-8 times, and drying the obtained product for 10-20 hours under vacuum at 70-90 ℃ to obtain solid powder;
(3) Calcining the solid powder obtained in the step (2) in air at 300-400 ℃ for 1.5-3.0 hours, and heating at a rate of 1.5-3.0 ℃ per minute to obtain low-coordination Co 3 O 4 The mesoporous nano-sheets are assembled into the hierarchical microsphere sensitive material.
2. A low coordination Co-based catalyst according to claim 1 3 O 4 The triethylamine gas sensor of hierarchical microballoon is assembled to mesoporous nano-sheet, its characterized in that: al (Al) 2 O 3 The length of the ceramic tube is 4.0-4.5 mm, and the inner diameter and the outer diameter are respectively 0.8-1.0 mm and 1.2-1.5 mm; the width of each annular gold electrode is 0.4-0.5 mm, and the distance between two gold electrodes is 0.5-0.6 mm; a platinum wire is led out from the gold electrode, and the length of the platinum wire is 4-6 mm; the resistance value of the nickel-chromium heating coil is 36-39Ω.
3. A low coordination Co-based catalyst according to claim 1 or 2 3 O 4 The preparation method of the triethylamine gas sensor with the hierarchical microspheres assembled by mesoporous nano sheets comprises the following steps:
(1) Taking 10-20 mg of low-coordination Co 3 O 4 Mesoporous nanoThe slice-assembled graded microsphere sensitive material is put into an agate mortar, 3-5 drops of ethanol are dripped into the mortar, the mixture is fully mixed and ground into paste, and then a proper amount of paste is dipped into the paste to be uniformly coated on Al 2 O 3 Forming a sensitive material layer with the thickness of 15-30 mu m on the outer surface of the ceramic tube, and enabling the sensitive material to completely cover a pair of parallel annular gold electrodes on two sides of the outer surface of the ceramic tube;
(2) Coating the outer surface obtained in the step (1) with Al of a sensitive material 2 O 3 Calcining the ceramic tube in air at 200-300 ℃ for 1.5-3.0 hours, wherein the heating rate is 3-6 ℃ per minute; after the temperature is reduced to room temperature, a nichrome heating coil passes through the ceramic tube to be used as a heating wire; finally, the device is welded on the hexagonal tube seat, thus preparing the Co based on low coordination 3 O 4 A bypass type triethylamine gas sensor of hierarchical microsphere sensitive material is assembled by mesoporous nano-sheets.
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CN108007978A (en) * 2017-11-20 2018-05-08 吉林大学 One kind is based on rGO-Co3O4The room temperature NO of compound2Sensor and preparation method thereof
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CN108007978A (en) * 2017-11-20 2018-05-08 吉林大学 One kind is based on rGO-Co3O4The room temperature NO of compound2Sensor and preparation method thereof
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