A n-butanol gas sensor composite material and methods of making and using the same

Abstract

The application belongs to the technical field of gas sensors, and particularly relates to a n-butanol gas sensor composite material and a preparation and use method thereof. The response effect of single In2O3 and CoSnO3 on n-butanol is not ideal in the prior art. A precursor CoSn(OH)6 is prepared by using a cobalt sulfate and sodium stannate aqueous solution, an In(OH)3 precursor is prepared by hydrothermal reaction of an indium nitrate aqueous solution, CoSn(OH)6 is mixed with In(OH)3 and then ground and calcined to obtain a CoSnO3-In2O3 composite material. The sensor prepared from the composite material has high sensitivity, good selectivity and repeatability to n-butanol at 250 DEG C, and the detection limit is as low as 20 ppb, and has good practical application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of gas sensors, and particularly relates to a n-butanol gas sensor composite material and a preparation and use method thereof. BACKGROUND

[0002] N-butanol is a colorless transparent volatile organic compound with a pungent odor and is widely used in industrial production. If a human body inhales high-concentration n-butanol vapor for a long time, respiratory tract irritation, cough, chest tightness and other discomfort symptoms may occur. Therefore, it is necessary to effectively and timely monitor the concentration of n-butanol. Metal oxide semiconductor sensors are the first choice for detecting toxic and harmful gases due to their simple operation, low cost and easy real-time monitoring.

[0003] Indium oxide (In2O3) is a typical n-type semiconductor with a wide direct band gap of 3.0 eV to 3.5 eV. It has high conductivity, rich defects, adjustable shape and size, and large specific surface area, and is therefore considered as a promising sensing material. However, single indium oxide has the disadvantages of low sensitivity and poor selectivity. Building a composite material is an effective way to improve gas sensing performance. For example, the patent "Preparation method of n-butanol gas sensitive material and device and preparation method thereof" (CN108609664A) uses indium chloride, cobalt nitrate, nickel nitrate and urea as raw materials to prepare a NiCo2O4-In2O3 composite material by a two-step hydrothermal method. The response value of the sensor prepared from the composite material to 10 ppm formaldehyde gas is 3.1 at room temperature. However, this material has a disadvantage, that is, compared with pure In2O3 material (whose response value to 10 ppm formaldehyde gas is 2.6), the improvement of the response value of the composite material is not particularly significant.

[0004] CoSnO3 is a typical perovskite structure and belongs to a p-type semiconductor. Due to its unique structure, adjustable band gap, high carrier mobility, and excellent chemical stability, thermal stability and catalytic performance, it has shown certain development potential in the field of gas sensing. However, single CoSnO3 also has unsatisfactory effect on gas detection. The patent "n-butanol gas sensitive material and preparation method, n-butanol gas sensitive device and preparation method" (CN108609664A) uses CoSnO3 prepared by hydrothermal method combined with high-temperature calcination to detect n-butanol gas, and the sensitivity of CoSnO3 to 100 ppm n-butanol gas is 18-24, which has a low response. SUMMARY

[0005] Therefore, the present application aims to provide a n-butanol gas sensor composite material and a preparation and use method thereof; the n-butanol gas sensor disclosed by the present application adopts a CoSnO3-In2O3 composite material, and high sensitivity, low detection limit and high selectivity detection of n-butanol gas are achieved.

[0006] The CoSnO3-In2O3 composite material is obtained by calcining CoSn(OH)6 and In(OH)3 after mixing and grinding, and the mass ratio of CoSn(OH)6 to In(OH)3 is 1:(20-500). The detection lower limit of the composite material for n-butanol is 20 ppb, and the detection range is 20 ppb-400 ppm.

[0007] The preparation method of the n-butanol gas sensor composite material disclosed by the present application is as follows:

[0008] Step 1: a cobalt sulfate aqueous solution and a sodium stannate aqueous solution are mixed, the molar ratio of cobalt sulfate to sodium stannate is 1:1, and a powder CoSn(OH)6 is obtained after the reaction is completed;

[0009] Step 2: an indium nitrate aqueous solution is subjected to a hydrothermal reaction to obtain a powder In(OH)3;

[0010] Step 3: CoSn(OH)6 obtained in step 1 and In(OH)3 obtained in step 2 are mixed and ground, and a CoSnO3-In2O3 composite material is obtained after calcination; the mass ratio of CoSn(OH)6 to In(OH)3 is 1:(20-500).

[0011] In step 1, the concentration of cobalt sulfate is 0.05 mol / L-0.2 mol / L, the concentration of sodium stannate is 0.05 mol / L-0.2 mol / L, the stirring reaction is performed for 2 h-6 h, the obtained product CoSn(OH)6 is centrifuged and washed with water and ethanol alternately for 2-5 times after the reaction is completed, and the product is dried at 50℃-80℃ for 10 h-24 h for standby.

[0012] Step 2 includes the following contents: indium nitrate is dissolved in water and stirred for 20 min-40 min to prepare an indium nitrate aqueous solution; the hydrothermal reaction temperature is 110℃-180℃, and the time is 8 h-24 h; the concentration of indium nitrate is 0.015 mol / L-0.065 mol / L; the obtained product In(OH)3 is centrifuged and washed with water and ethanol alternately for 2-5 times; and the product is dried at 50℃-80℃ for 10 h-24 h for standby.

[0013] In step 3, the calcination temperature is 300℃-500℃; the calcination time is 1 h-4 h; and the heating rate is 1℃ / min-5℃ / min.

[0014] In the step 2, when the concentration of the indium nitrate solution is within the range, the generated In(OH)3 precursor presents a good cubic morphology, which is beneficial to the compounding with CoSn(OH)6. When the concentration of the indium nitrate solution is <0.015 mol / L or >0.065 mol / L, the generated In(OH)3 precursor will no longer present a good cubic morphology, which is not conducive to the subsequent compounding, and thus affects the response effect of the CoSnO3-In2O3 composite material on n-butanol.

[0015] The use method of the n-butanol gas sensor composite material is as follows:

[0016] Step 1: The CoSnO3-In2O3 composite material is made into a slurry, the slurry is coated on the surface of a substrate to form a sensing material layer, and an n-butanol gas sensor is obtained.

[0017] The specific content includes the following: the CoSnO3-In2O3 composite material is mixed with ethanol to make a slurry, the slurry is uniformly coated on the surface of an alumina ceramic tube substrate to form a sensing material layer, and after the ethanol is volatilized, the n-butanol gas sensor is obtained after aging at 200-300 DEG C for 24-48 h.

[0018] Step 2: The n-butanol gas sensor is placed in a gas atmosphere to be measured, and under the condition of an excitation voltage of 3-24 V, the sensor is placed in a working temperature range of 175-325 DEG C, and the response value of the sensor to the gas to be measured is tested by using the calculation method of R a / R g (wherein R a and R g are the resistance values of the sensor in air and in the gas atmosphere to be measured, respectively).

[0019] The CoSnO3-In2O3 heterostructure composite material is prepared by mixing, grinding and calcining the above two precursors. The prepared CoSnO3-In2O3 heterostructure composite material has low cost and simple compounding method, has high sensitivity and good selectivity to n-butanol, has a detection limit as low as 20 ppb, has a detection range of 20 ppb-400 ppm, and has better performance than the currently reported n-butanol sensors. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The scanning electron microscope (SEM) of the sensing material prepared for the comparative examples and the examples is shown in the figure, wherein (a) represents comparative example 1, (b) represents example 2, (c) represents example 3, and (d) represents example 6.

[0021] Figure 2 Transmission electron microscopy (TEM) images of the sensing material prepared in Example 3; where (a) and (b) are TEM images of the 1% CoSnO3-In2O3 composite material, and (c) and (d) are... Figure 2 (b) is a magnified view of a portion of the image;

[0022] Figure 3 XRD patterns of the sensing materials prepared in Comparative Examples 1 and 3 and Examples 2, 3 and 6;

[0023] Figure 4 The graph shows the response value of the sensor prepared from the sensing materials obtained in Comparative Example 1 and Examples 2, 3, and 6 to 100 ppm n-butanol as a function of operating temperature.

[0024] Figure 5 The gas-sensing performance of sensors prepared from the sensing materials obtained in Comparative Example 1 and Examples 2, 3, and 6 at 250°C for different concentrations (10ppm~400ppm) of n-butanol gas.

[0025] Figure 6 The transient cyclic sensing curve of the sensor prepared from the sensing material obtained in Example 3 at 250°C for 100 ppm n-butanol is shown.

[0026] Figure 7 Radar graph of the response values ​​of sensors made from the sensing materials obtained in Comparative Example 1 and Example 3 to 100 ppm of different VOC gases at 250°C.

[0027] Figure 8 The following are gas-sensing performance test graphs of sensors prepared from the sensing materials obtained in Examples 1 to 6 at 250°C for different concentrations (5 ppm to detection limit) of n-butanol gas; where (a) is Example 1, (b) is Example 2, (c) is Example 3, (d) is Example 4, (e) is Example 5, and (f) is Example 6.

[0028] Figure 9 The gas-sensing performance of the sensors prepared from the sensing materials obtained in Comparative Examples 1 and 2 at 250°C for different concentrations (5 ppm to the detection limit) of n-butanol gas is shown in the figure. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be noted that the embodiments described in this invention are only for further explanation and illustration, and not for limiting their application scope. Based on this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention.

[0030] Example 1: 0.2%CoSnO3-In2O3 composite material

[0031] The n-butanol sensing material is a CoSnO3-In2O3 composite material, which is obtained by calcining after mixing and grinding CoSn(OH)6 and In(OH)3, and the mass ratio of CoSn(OH)6 to In(OH)3 is 1:500.

[0032] Step 1: Dissolve 0.75 mmol of cobalt sulfate in 15 mL of deionized water to form solution A, and dissolve 0.75 mmol of sodium stannate in 15 mL of deionized water to form solution B; pour solution B into solution A, mix and stir for 2 h, centrifuge and wash with water and ethanol alternately for 2 times, and dry at 50°C for 24 h to obtain a purple powder CoSn(OH)6, which is ready for use;

[0033] Step 2: Weigh 1.95 mmol of indium nitrate and dissolve it in 30 mL of deionized water, and stir for 20 min; transfer the above solution to a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene liner, and put it into a 150°C oven for 8 h; centrifuge and wash with water and ethanol alternately for 2 times, and dry in a 50°C oven for 24 h to obtain a white powder In(OH)3, which is ready for use;

[0034] Step 3: Weigh 0.2 mg of the powder in step 1 and 100 mg of the powder in step 2, mix and grind, and put it into a muffle furnace with a heating rate of 1°C / min, and calcine at 300°C for 4 h to obtain the product 0.2%CoSnO3-In2O3 composite sensing material.

[0035] The 0.2%CoSnO3-In2O3 composite material is used to prepare a n-butanol gas sensor, and the specific method is as follows:

[0036] Step 1: Weigh 3 mg of the sensing material sample prepared by the above method into 10 µL of ethanol to make a slurry, and ultrasonic treat for 1 min, and then use a pipette gun to drop an appropriate amount of slurry onto the surface of an alumina ceramic tube to form a uniform sensing material layer;

[0037] Step 2: After natural air drying, pass the Ni-Cr heating wire through the alumina ceramic tube, and weld it on the six-legged base with solder;

[0038] Step 3: Place the prepared sensor on an aging table and age at 200°C for 48 h to obtain a n-butanol gas sensor based on the 0.2%CoSnO3-In2O3 composite material.

[0039] Example 2: 0.5%CoSnO3-In2O3 composite material

[0040] The n-butanol sensing material is a CoSnO3-In2O3 composite material, which is prepared by mixing and grinding CoSn(OH)6 and In(OH)3 and then calcining, and the mass ratio of CoSn(OH)6 to In(OH)3 is 1:200.

[0041] Step 1: Dissolve 2 mmol of cobalt sulfate in 15 mL of deionized water to form solution A, and dissolve 2 mmol of sodium stannate in 15 mL of deionized water to form solution B; pour solution B into solution A, mix and stir for 4 h, centrifuge and wash with water and ethanol alternately for 3 times, and dry at 60℃ for 12 h to obtain purple powder CoSn(OH)6, which is ready for use;

[0042] Step 2: Weigh 1 mmol of indium nitrate and dissolve it in 30 mL of deionized water, and stir for 30 min; transfer the above solution to a polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle, and place it in a 130℃ oven for 12 h; centrifuge and wash with water and ethanol alternately for 3 times, and dry in a 60℃ oven for 12 h to obtain white powder In(OH)3, which is ready for use;

[0043] Step 3: Mix and grind 0.5 mg of the powder in step 1 and 100 mg of the powder in step 2, and place them in a muffle furnace with a heating rate of 2℃ / min, and calcine at 400℃ for 2 h to obtain the product 0.5% CoSnO3-In2O3 composite sensing material. The scanning electron microscope image of the composite material is shown in Figure 1 (b), and the XRD pattern is shown in Figure 3 .

[0044] Prepare a n-butanol gas sensor using the 0.5% CoSnO3-In2O3 composite material, and the specific method is as follows:

[0045] Step 1: Weigh 3 mg of the sensing material sample prepared by the above method and add 10 µL of ethanol to make a slurry, and ultrasonic treat for 2 min; use a pipette gun to take an appropriate amount of slurry and drop it onto the surface of an alumina ceramic tube to form a uniform sensing material layer;

[0046] Step 2: After natural air drying, pass the Ni-Cr heating wire through the alumina ceramic tube and weld it on the six-legged base with solder;

[0047] Step 3: Place the prepared sensor on an aging table and age at 250℃ for 24 h to obtain a n-butanol gas sensor based on the 0.5% CoSnO3-In2O3 composite material.

[0048] Example 3: 1% CoSnO3-In2O3 composite material

[0049] The n-butanol sensing material is a CoSnO3-In2O3 composite material, which is prepared by mixing and grinding CoSn(OH)6 and In(OH)3 and then calcining, and the mass ratio of CoSn(OH)6 to In(OH)3 is 1:100.

[0050] Step 1: 2 mmol of cobalt sulfate was dissolved in 15 mL of deionized water to form solution A, and 2 mmol of sodium stannate was dissolved in 15 mL of water to form solution B; solution B was poured into solution A, mixed and stirred for 4 h, and then centrifuged and washed with water and ethanol for 3 times. After drying at 60℃ for 12 h, a purple powder CoSn(OH)6 was obtained and reserved for use;

[0051] Step 2: 1 mmol of indium nitrate was weighed and dissolved in 30 mL of deionized water and stirred for 30 min; the solution was transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle, which was placed in a 130℃ oven for reaction for 12 h; and then centrifuged and washed with water and ethanol for 3 times. After drying at 60℃ for 12 h, a white powder In(OH)3 was obtained and reserved for use;

[0052] Step 3: 1 mg of the powder in step 1 and 100 mg of the powder in step 2 were mixed and ground, and then placed in a muffle furnace with a heating rate of 2℃ / min, and calcined at 400℃ for 2 h to obtain the product 1% CoSnO3-In2O3 composite sensing material. The scanning electron microscope image of the composite material is shown in Figure 1 (c), the transmission electron microscope image is shown in Figure 2 (a) and Figure 2 (b), Figure 2 (c) proves the existence of amorphous structure CoSnO3, Figure 2 (d) proves the existence of In2O3, and the XRD pattern is shown in Figure 3 .

[0053] The 1% CoSnO3-In2O3 composite material was used to prepare a n-butanol gas sensor, and the specific method was as follows:

[0054] Step 1: 4 mg of the sensing material sample prepared by the above method was weighed and added into 10 µL of ethanol to form a slurry, which was ultrasonically treated for 3 min, and then an appropriate amount of the slurry was taken by a pipette and dropped onto the surface of an alumina ceramic tube to form a uniform sensing material layer;

[0055] Step 2: After natural air drying, a Ni-Cr heating wire was passed through the alumina ceramic tube and welded on a six-legged base with solder;

[0056] Step 3: The prepared sensor was placed on an aging table and aged at 250℃ for 24 h to obtain a n-butanol gas sensor based on the 1% CoSnO3-In2O3 composite material.

[0057] Example 4: 2%CoSnO3-In2O3 composite material

[0058] The n-butanol sensing material is a CoSnO3-In2O3 composite material, which is prepared by mixing and grinding CoSn(OH)6 and In(OH)3 and then calcining. The mass ratio of CoSn(OH)6 to In(OH)3 is 1:50.

[0059] Step 1: Dissolve 2.5 mmol of cobalt sulfate in 15 mL of deionized water to form solution A, and dissolve 2.5 mmol of sodium stannate in 15 mL of deionized water to form solution B; pour solution B into solution A, stir for 6 h, centrifuge with water and ethanol alternately, wash 5 times, and dry at 80°C for 8 h to obtain a purple powder CoSn(OH)6, which is ready for use;

[0060] Step 2: Weigh 0.6 mmol of indium nitrate and dissolve it in 30 mL of deionized water, and stir for 30 min; transfer the above solution to a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene liner, and place it in a 180°C oven for 8 h; centrifuge with water and ethanol alternately, wash 5 times, and dry in an 80°C oven for 8 h to obtain a white powder In(OH)3, which is ready for use;

[0061] Step 3: Weigh 2 mg of the powder in Step 1 and 100 mg of the powder in Step 2, mix and grind, place in a muffle furnace, and heat at a rate of 5°C / min, then calcine at 500°C for 1 h to obtain the product 2%CoSnO3-In2O3 composite sensing material.

[0062] Prepare a n-butanol gas sensor using the 2%CoSnO3-In2O3 composite material, with the specific method as follows:

[0063] Step 1: Weigh 4 mg of the sensing material sample prepared by the above method into 10 µL of ethanol to make a slurry, and ultrasonically treat for 3 min; use a pipette to take an appropriate amount of slurry and drop it onto the surface of an alumina ceramic tube to form a uniform sensing material layer;

[0064] Step 2: After natural air drying, pass the Ni-Cr heating wire through the alumina ceramic tube and weld it on a six-legged base with solder;

[0065] Step 3: Place the prepared sensor on an aging table and age at 300°C for 36 h to obtain a n-butanol gas sensor based on the 2%CoSnO3-In2O3 composite material.

[0066] Example 5: 3%CoSnO3-In2O3 composite material

[0067] The n-butanol sensing material is a CoSnO3-In2O3 composite material, which is obtained by mixing and grinding CoSn(OH)6 and In(OH)3 and then calcining, and the mass ratio of CoSn(OH)6 to In(OH)3 is 1:33.3.

[0068] Step 1: Dissolve 3 mmol of cobalt sulfate in 15 mL of deionized water to form solution A, and dissolve 3 mmol of sodium stannate in 15 mL of deionized water to form solution B; pour solution B into solution A, stir for 3 h, centrifuge and wash with water and ethanol alternately for 4 times, dry at 70°C for 18 h to obtain purple powder CoSn(OH)6, which is ready for use;

[0069] Step 2: Weigh 0.45 mmol of indium nitrate and dissolve it in 30 mL of deionized water, and stir for 40 min; transfer the above solution to a polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle, and place it in a 110°C oven for 10 h; centrifuge and wash with water and ethanol alternately for 4 times, and dry in a 70°C oven for 18 h to obtain white powder In(OH)3, which is ready for use;

[0070] Step 3: Weigh 3 mg of the powder in step 1 and 100 mg of the powder in step 2, mix and grind, and place in a muffle furnace with a heating rate of 3°C / min, and calcine at 500°C for 3 h to obtain the product 3%CoSnO3-In2O3 composite sensing material.

[0071] Prepare a n-butanol gas sensor using the 3%CoSnO3-In2O3 composite material, and the specific method is as follows:

[0072] Step 1: Weigh 4 mg of the sensing material sample prepared by the above method into 10 µL of ethanol to make a slurry, and ultrasonic treat for 4 min; use a pipette to take an appropriate amount of slurry and drop it onto the surface of an alumina ceramic tube to form a uniform sensing material layer;

[0073] Step 2: After natural air drying, pass the Ni-Cr heating wire through the alumina ceramic tube and weld it on the six-legged base with solder;

[0074] Step 3: Place the prepared sensor on an aging table and age at 200°C for 48 h to obtain a n-butanol gas sensor based on the 3%CoSnO3-In2O3 composite material.

[0075] Example 6: 5%CoSnO3-In2O3 composite material

[0076] The n-butanol sensing material is a CoSnO3-In2O3 composite material, which is obtained by mixing and grinding CoSn(OH)6 and In(OH)3 and then calcining, and the mass ratio of CoSn(OH)6 to In(OH)3 is 1:33.3.

[0077] Step 1: 2 mmol of cobalt sulfate was dissolved in 15 mL of deionized water to form solution A, and 2 mmol of sodium stannate was dissolved in 15 mL of deionized water to form solution B; solution B was poured into solution A, stirred for 4 h, centrifuged and washed with water and ethanol alternately for 3 times, and dried at 60℃ for 12 h to obtain a purple powder CoSn(OH)6, which was used for later use;

[0078] Step 2: 1 mmol of indium nitrate was weighed and dissolved in 30 mL of deionized water, and stirred for 30 min; the above solution was transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reaction kettle, and placed in a 130℃ oven for reaction for 12 h; centrifuged and washed with water and ethanol alternately for 3 times, and dried in a 60℃ oven for 12 h to obtain a white powder In(OH)3, which was used for later use;

[0079] Step 3: 5 mg of the powder in step 1 and 100 mg of the powder in step 2 were mixed and ground, and placed in a muffle furnace with a heating rate of 2℃ / min, and calcined at 400℃ for 2 h to obtain a product 5% CoSnO3-In2O3 composite sensing material. The scanning electron microscope image of the composite material is shown in FIG. (d), and the XRD pattern is shown in FIG. Figure 1 Figure 3

[0080] A n-butanol gas sensor was prepared using the 5% CoSnO3-In2O3 composite material, and the specific method was as follows:

[0081] Step 1: 5 mg of the sensing material sample prepared by the above method was weighed and added into 10 µL of ethanol to form a slurry, which was ultrasonically treated for 5 min, and an appropriate amount of the slurry was taken by a pipette and dropped onto the surface of an alumina ceramic tube to form a uniform sensing material layer;

[0082] Step 2: After natural air-drying, a Ni-Cr heating wire was passed through the alumina ceramic tube and welded on a six-legged base with solder;

[0083] Step 3: The prepared sensor was placed on an aging table and aged at 280℃ for 18 h to obtain a n-butanol gas sensor based on the 5% CoSnO3-In2O3 composite material.

[0084] Comparative Example 1: In2O3 material without modification

[0085] The n-butanol sensing material was In2O3 material without compounding.

[0086] 1 mmol of indium nitrate was weighed and dissolved in 30 mL of deionized water, and stirred for 30 min; the above solution was transferred to a polytetrafluoroethylene-lined high-pressure reaction kettle, and placed in a 130℃ oven for reaction for 12 h; centrifuged and washed with water and ethanol alternately for 3 times, and dried in a 60℃ oven for 12 h to obtain a white powder In(OH)3; ​​

[0087] The obtained powder was placed in a muffle furnace, the heating rate was 2°C / min, and calcination was carried out at 400°C for 2h to obtain a yellowish product In2O3 sensing material. The scanning electron microscope image thereof is shown in FIG. 2(a), and the XRD pattern thereof is shown in FIG. 2(b). Figure 1 Figure 3

[0088] A n-butanol gas sensor was prepared using the In2O3 material, and the specific method was as follows:

[0089] Step 1: 4mg of the sensing material sample prepared by the above method was weighed into 10µL of ethanol to form a slurry, which was ultrasonically treated for 3min, and an appropriate amount of the slurry was taken with a pipette and dropped onto the surface of the alumina ceramic tube to form a uniform sensing material layer;

[0090] Step 2: After natural air drying, the Ni-Cr heating wire was threaded through the alumina ceramic tube and welded to the six-legged base with solder;

[0091] Step 3: The prepared sensor was placed on an aging table and aged at 250°C for 24h to obtain an n-butanol gas sensor based on the In2O3 material.

[0092] Comparative Example 2: 7% CoSnO3-In2O3 composite material

[0093] The n-butanol sensing material was a CoSnO3-In2O3 composite material, which was obtained by calcining after mixing and grinding CoSn(OH)6 and In(OH)3, and the mass ratio of CoSn(OH)6 to In(OH)3 was 1:14.3.

[0094] Step 1: 2mmol of cobalt sulfate was dissolved in 15mL of deionized water to form solution A, and 2mmol of sodium stannate was dissolved in 15mL of deionized water to form solution B; solution B was poured into solution A, stirred for 4h, and then centrifuged and washed with water and ethanol alternately for 3 times. After drying at 60°C for 12h, a purple powder CoSn(OH)6 was obtained for standby use;

[0095] Step 2: 1mmol of indium nitrate was dissolved in 30mL of deionized water and stirred for 30min; the solution was transferred to a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene liner, and placed in a 130°C oven for reaction for 12h; then it was centrifuged and washed with water and ethanol alternately for 3 times, and dried in a 60°C oven for 12h to obtain a white powder In(OH)3 for standby use;

[0096] Step 3: 7mg of the powder in Step 1 and 100mg of the powder in Step 2 were mixed and ground, and then placed in a muffle furnace, the heating rate was 2°C / min, and calcination was carried out at 400°C for 2h to obtain a product 7% CoSnO3-In2O3 composite sensing material.

[0097] ​​A n-butanol gas sensor was prepared using a 7% CoSnO3-In2O3 composite material, and the specific method was as follows:

[0098] Step 1: 4 mg of the sensing material sample prepared by the above method was weighed into 10 μL of ethanol to form a slurry, which was ultrasonically treated for 3 min, and an appropriate amount of the slurry was taken by a pipette and dropped onto the surface of an alumina ceramic tube to form a uniform sensing material layer;

[0099] Step 2: After natural air-drying, the Ni-Cr heating wire was threaded through the alumina ceramic tube and welded to the six-legged base with solder;

[0100] Step 3: The prepared sensor was placed on an aging table and aged at 250°C for 24 h to obtain a n-butanol gas sensor based on a 7% CoSnO3-In2O3 material.

[0101] Comparative Example 3: CoSnO3 material

[0102] The n-butanol sensing material was a CoSnO3 material without compounding.

[0103] 2 mmol of cobalt sulfate was dissolved in 15 mL of deionized water to form solution A, and 2 mmol of sodium stannate was dissolved in 15 mL of deionized water to form solution B; solution B was poured into solution A, stirred for 4 h, and then washed with water and ethanol by centrifugation for 3 times. After drying at 60°C for 12 h, a purple powder CoSn(OH)6 was obtained.

[0104] The obtained powder was placed in a muffle furnace and heated at a rate of 2°C / min, and then calcined at 400°C for 2 h to obtain a black product CoSnO3 sensing material. The XRD pattern is shown in Figure 3 . Figure 3 The CoSnO3 in

[0105] A n-butanol gas sensor was prepared using a CoSnO3 material, and the specific method was as follows:

[0106] Step 1: 4 mg of the sensing material sample prepared by the above method was weighed into 10 μL of ethanol to form a slurry, which was ultrasonically treated for 3 min, and an appropriate amount of the slurry was taken by a pipette and dropped onto the surface of an alumina ceramic tube to form a uniform sensing material layer;

[0107] Step 2: After natural air-drying, the Ni-Cr heating wire was threaded through the alumina ceramic tube and welded to the six-legged base with solder;

[0108] Step 3: The prepared sensor was placed on an aging table and aged at 250°C for 24 h to obtain a n-butanol gas sensor based on a 7% CoSnO3-In2O3 material.

[0109] Sensing performance test of the gas sensor

[0110] The response value of the sensor made of different sensing materials to 100 ppm n-butanol gas was tested at 10 V excitation voltage and at a temperature ranging from 175 to 325 °C, and the results are shown in Figure 4 Figure 4 It can be found that the response value of the 1% CoSnO3-In2O3 sensor to n-butanol is 903.8, which is higher than that of the 0.5% CoSnO3-In2O3 sensor (344.6) and the 5% CoSnO3-In2O3 sensor (679.7), and is 9 times of that of the pure In2O3 sensor.

[0111] The response of the sensors made of the CoSnO3-modified In2O3 materials (0.5% CoSnO3-In2O3, 1% CoSnO3-In2O3 and 5% CoSnO3-In2O3) and the unmodified In2O3 to 10 ppm, 20 ppm, 30 ppm, 50 ppm, 80 ppm, 100 ppm, 150 ppm, 200 ppm, 300 ppm and 400 ppm n-butanol at 250 °C is shown in Figure 5 It can be seen that the response value of the sensor to n-butanol increases with the increase of the gas concentration.

[0112] Figure 6 The cyclic response transient curve of the sensor made of the 1% CoSnO3-In2O3 composite material obtained in Example 3 to 100 ppm n-butanol at 250 °C is shown in the figure, from which it can be seen that the response of the sensor to n-butanol has good repeatability. The response values of the 1% CoSnO3-In2O3 sensor to n-butanol, n-propanol, isopropanol, ethanol, methanol, triethylamine, acetone, toluene and aniline at 250 °C are shown in Figure 7 903.8, 143.4, 61.9, 63.6, 33.1, 24.2, 36.0, 6.9 and 9.4, respectively, which indicates that the 1% CoSnO3-In2O3 sensor has good selectivity to n-butanol.

[0113] The response value of the sensors made of the CoSnO3-In2O3 composite materials obtained in Examples 1, 2, 3, 4, 5 and 6 to low-concentration n-butanol (5 ppm to the lower limit of detection) was tested, and the results are shown in Figure 8 Figure 8 ​​As can be seen from (a), (b), (c), (d), (e), (f) in Table 1, the detection limit of the sensors based on 0.5% CoSnO3-In2O3 and 1% CoSnO3-In2O3 is as low as 20 ppb, and the response values for n-butanol are 1.75 and 1.8, respectively. From (g) in Table 1, it can be seen that the detection lower limit of unmodified In2O3 is 500 ppb, and the detection lower limit of the sensor based on 7% CoSnO3-In2O3 is significantly improved to 3 ppm. Figure 9

[0114] Table 1 Response time, recovery time and detection lower limit of the sensors prepared from the CoSnO3-In2O3 composite materials obtained in Examples 1, 2, 3, 4, 5, 6 and Comparative Examples 1, 2 for n-butanol at 250°C

[0115] Example Sensing material Response time (s) @ 5 ppm Recovery time (s) @ 5 ppm Lower detection limit (ppb) Response value corresponding to lower detection limit Example 1 0.2% CoSnO3-In2O3 4 14 100 1.74 Example 2 0.5% CoSn03-In203 32 20 20 1.75 Example 3 1% CoSnO3-In2O3 86 29 20 1.8 Example 4 2% CoSn03-In203 7 21 50 1.68 Example 5 3% CoSnO3-In2O3 12 16 50 1.76 Example 6 5% CoSnO3-In2O3 2 22 200 1.45 Comparative Example 1 In2O3 225 23 500 1.63 Comparative Example 2 7% CoSnO3-In2O3 1 1 3000 1.51 ​

Claims

1. A composite material for a n-butanol gas sensor, characterized in that, The composite material is a CoSnO3-In2O3 composite material, which is obtained by mixing and grinding CoSn(OH)6 and In(OH)3 and then calcining it. The mass ratio of CoSn(OH)6 to In(OH)3 is 1:(20~500); the detection limit of the composite material for n-butanol is 20 ppb. The preparation method of the n-butanol gas sensor composite material includes the following: Step 1: Mix cobalt sulfate aqueous solution and sodium stannate aqueous solution to react. After the reaction is complete, CoSn(OH) is obtained. 6； Step 2: Indium nitrate aqueous solution undergoes a hydrothermal reaction to obtain In(OH)3; Step 3: Mix and grind the CoSn(OH)6 obtained in Step 1 and the In(OH)3 obtained in Step 2, and calcine them to obtain the CoSnO3-In2O3 composite material.

2. The n-butanol gas sensor composite material according to claim 1, characterized in that, In step 1, the concentration of cobalt sulfate is 0.05 mol / L to 0.2 mol / L, the concentration of sodium stannate is 0.05 mol / L to 0.2 mol / L, and the reaction is stirred for 2 to 6 hours to obtain CoSn(OH)6.

3. The n-butanol gas sensor composite material according to claim 1, characterized in that, Step 2 includes the following: dissolving indium nitrate in water and stirring for 20 min to 40 min to prepare an indium nitrate aqueous solution; the hydrothermal reaction temperature is 110℃ to 180℃, the time is 8 h to 24 h, and the concentration of indium nitrate is 0.015 mol / L to 0.065 mol / L.

4. The n-butanol gas sensor composite material according to claim 1, characterized in that, In step 3, the calcination temperature is 300℃~500℃, the calcination time is 1h~4h, and the heating rate is 1℃ / min~5℃ / min.

5. The n-butanol gas sensor composite material according to claim 1, characterized in that, The CoSn(OH)6 obtained in step 1 and the In(OH)3 obtained in step 2 are first centrifuged and washed 2 to 5 times with water and ethanol respectively, and then dried at 50℃ to 80℃ for 10 to 24 hours before being used in step 3 to prepare the composite material.

6. A method of using the n-butanol gas sensor composite material according to claim 1, characterized in that, Includes the following: Step 1: Prepare a slurry from the CoSnO3-In2O3 composite material, coat the slurry onto the surface of the substrate to form a sensing material layer, and obtain a n-butanol gas sensor; Step 2: Place the n-butanol gas sensor in the atmosphere of the gas to be measured, under a certain excitation voltage, and keep the sensor within the operating temperature range of 175℃~325℃, using R... a / R g The calculation method tests the sensor's response value to the gas being measured, where R... a and R g These are the resistance values ​​of the sensor in air and in the atmosphere of the gas being measured, respectively.

7. The method of using the n-butanol gas sensor composite material according to claim 6, characterized in that, Step 1 includes the following: mixing CoSnO3-In2O3 composite material with ethanol to form a slurry, ultrasonicating for 1 min to 5 min, and uniformly coating the slurry onto the surface of an alumina ceramic tube substrate to form a sensing material layer; after the ethanol evaporates, aging at 200℃ to 300℃ for 24 h to 48 h to obtain a n-butanol gas sensor; the excitation voltage in Step 2 is 3V to 24V.

8. A n-butanol gas sensor, characterized in that, The n-butanol-sensitive material in the gas sensor is the composite material described in claim 1.

Images