A preparation method of a Ni-doped SnO 2 gas sensor modified with CuO

Abstract

The present invention relates to the field of gas sensing technology, and discloses a gas sensor modified with Ni-doped SnO 2 and CuO. Using sucrose, nickel chloride, and tin tetrachloride as raw materials, through hydrothermal treatment and calcination, nickel-doped tin oxide is obtained. Using it as the substrate and copper nitrate as the copper source, nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers are obtained, which have a super high specific surface area, facilitating more sufficient contact with gases such as CO, thereby improving the sensitivity of the sensor. Ni 2+ -doped tin oxide generates oxygen defects, forming more gas adsorption active sites, while reducing the resistance value and improving the gas sensing performance of the sensor. Copper oxide and tin oxide form a p-n heterojunction structure, increasing the grain boundary barrier and promoting the transfer of electrons between adsorbed oxygen and oxide grains, thereby improving the conductivity and accelerating the occurrence of the gas sensing reaction, thus reducing the response and recovery time of the sensor and enabling the sensor to have excellent CO gas sensing performance.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and specifically provides a method for preparing a Ni-doped SnO 2 modified CuO gas sensor. Background Art

[0002] The power system is the economic foundation of the whole country. As a central equipment, the safety and reliability of power transformers are crucial during the power transmission and transformation process. Currently, power transformers above 110 kV are still mainly oil-immersed transformers, and the H 2 and CO gases dissolved in the oil are likely to cause failures in oil-immersed transformers. Therefore, it is necessary to detect the H 2 and CO gases in oil-immersed transformers to prevent the transformers from being damaged by gases without being noticed, thus affecting people's lives. The gas sensor technology is the key to implementing real-time analysis of dissolved gases in oil, which can enable people to detect the gas content in transformers in real time, so as to master the real-time usage situation of transformers and avoid damage. However, the semiconductor sensors on the current market have problems such as poor selectivity, unstable performance, and short service life. Therefore, it is necessary to develop new and efficient semiconductor sensors.

[0003] Tin oxide is a new type of functional material with many unique electrical, optical, and catalytic properties such as a high melting point, good thermal stability, and excellent chemical stability. It is widely used in the fields of semiconductors, gas sensors, liquid crystal displays, and optical technologies. As an n-type semiconductor metal oxide, tin oxide has advantages such as a long service life and low cost, and is widely used in the field of semiconductor resistive gas sensors. However, problems such as poor doping sensitivity and long response and recovery times have greatly limited its application range. The p-type semiconductor copper oxide has excellent electrical conductivity and good sensitivity and is widely used in the field of gas sensors. When compounded with tin oxide, it significantly improves the comprehensive performance of tin oxide, and at the same time, element doping further improves the gas-sensing performance of tin oxide.

[0004] (I) Technical Problems to be Solved

[0005] Aiming at the deficiencies of the prior art, the present invention provides a method for preparing a Ni-doped SnO 2 modified CuO gas sensor, which solves the problems of poor sensitivity and long response and recovery times of tin oxide.

[0006] (II) Technical Solutions

[0007] To achieve the above object, the present invention provides the following technical solution: A Ni-doped SnO 2 modified CuO gas sensor, wherein the Ni-doped SnO 2The preparation method of the gas sensor modified with CuO is as follows:

[0008] (1) adding deionized water solvent, sucrose, nickel chloride, and tin tetrachloride to a reaction flask, dispersing them evenly, transferring them into a reaction kettle, performing a hydrothermal reaction, cooling them to room temperature, filtering them, washing them with deionized water and anhydrous ethanol, and drying them to obtain a nickel-doped tin oxide precursor;

[0009] (2) placing the nickel-doped tin oxide precursor in a resistance furnace, calcining it, and cooling it to room temperature to obtain nickel-doped tin oxide hollow spheres;

[0010] (3) adding ethanol solvent, sodium hydroxide, urotropine, copper nitrate, and nickel-doped tin oxide hollow spheres to a reaction flask, dispersing them evenly, transferring them into a reaction kettle, performing a solvent thermal reaction, cooling them to room temperature, centrifuging them, washing them with deionized water and anhydrous ethanol, and drying them to obtain nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers;

[0011] (4) Add ethanol solvent, dispersant polyethylene glycol, nickel-doped tin oxide hollow spheres modified copper oxide nanoflowers to the reaction bottle, disperse them evenly, and evenly apply them on the surface of the alumina ceramic tube with a gold electrode. After drying, sinter and solidify at 350-450° C. for 1-3 hours, cool to room temperature, insert a Ni-Cr resistance heating wire into the interior of the alumina ceramic tube, and weld it to the tube seat to make a side-heated gas sensor to obtain a Ni-doped SnO 2 Modified CuO gas sensor.

[0012] Preferably, in step (1), the mass ratio of sucrose, nickel chloride and tin tetrachloride is 80-180:1.5-3.5:100.

[0013] Preferably, the hydrothermal reaction in step (1) is carried out at 170-210° C. for 18-30 hours.

[0014] Preferably, the calcination condition in step (2) is calcination at 550-650° C. for 2-4 hours.

[0015] Preferably, in step (3), the mass ratio of sodium hydroxide, urotropine, copper nitrate and nickel-doped tin oxide hollow spheres is 3-5:20-35:25-45:100.

[0016] Preferably, the solvothermal conditions in step (3) are solvothermal reaction at 100-140° C. for 12-18 hours.

[0017] (III) Beneficial technical effects

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] The Ni-doped SnO 2 modified CuO gas sensor, where sucrose molecules undergo polymerization and carbonization to form loose and porous carbon spheres. Abundant hydroxyl and other functional groups on its surface adsorb Sn 4+ onto the surface of the carbon spheres. In an alkaline environment, Sn 4+ reacts with OH - to form a precipitate of tin hydroxide, which gradually decomposes into an oxide layer. After calcination, the template carbon spheres are burned off, and the generated gases and the gases produced by the decomposition of tin hydroxide make the product loose and porous, thus obtaining SnO 2 porous hollow spheres. SnO 2 has a unique porous hollow spherical morphology with a rich pore structure and a super-high specific surface area, which is conducive to more sufficient contact with gases such as CO. At the same time, using nickel chloride doping source, nickel-doped tin oxide is obtained. Using it as the substrate, under the action of the surfactant hexamethylenetetramine, copper oxide nanosheets are in-situ grown and assembled into copper oxide nanoflowers, and further a Ni-doped SnO 2 modified CuO gas sensor is obtained. The unique nanoflower-like morphology of copper oxide has a super-high specific surface area, which is conducive to further more sufficient contact with gases such as CO, thereby improving the sensitivity of the sensor.

[0020] The Ni-doped SnO 2 modified CuO gas sensor, Ni 2+ replaces Sn 4+ to enter the unit cell of tin oxide, generating oxygen vacancies and forming more gas adsorption active sites, thus quickly adsorbing more gases. And in the process of forming oxygen vacancies, free electrons are generated and enter the conduction band of tin oxide, increasing the carrier concentration in the conduction band, thereby reducing the resistance value and improving the gas-sensing performance of the sensor. Copper oxide has a high work function, while tin oxide has a high electron affinity, enabling electrons to transfer from the bottom of the conduction band of tin oxide to the bottom of the conduction band of copper oxide, forming a p-n heterojunction, increasing the grain boundary potential barrier, and promoting the transfer of electrons between adsorbed oxygen and oxide grains, thereby improving the conductivity and accelerating the occurrence of the gas-sensing reaction, thus reducing the response and recovery time of the sensor and making the sensor have excellent CO gas-sensing performance. Specific embodiments

[0021] To achieve the above object, the present invention provides the following specific embodiments and examples: A Ni-doped SnO 2 modified CuO gas sensor. The preparation method of the Ni-doped SnO 2 modified CuO gas sensor is as follows:

[0022] (1) Add deionized water solvent, sucrose, nickel chloride, and tin tetrachloride into a reaction flask. The mass ratio of the three is 80 - 180:1.5 - 3.5:100. Disperse them evenly, transfer them into a reaction kettle, and carry out hydrothermal reaction at 170 - 210 °C for 18 - 30 h. Cool to room temperature, carry out suction filtration, wash with deionized water and absolute ethanol until clean, and dry to obtain a nickel-doped tin oxide precursor;

[0023] (2) Place the nickel-doped tin oxide precursor in a resistance furnace and calcine it at 550 - 650 °C for 2 - 4 h. Cool to room temperature to obtain nickel-doped tin oxide hollow spheres;

[0024] (3) Add ethanol solvent, sodium hydroxide, hexamine, copper nitrate, and nickel-doped tin oxide hollow spheres into a reaction flask. The mass ratio of the four is 3 - 5:20 - 35:25 - 45:100. Disperse them evenly, transfer them into a reaction kettle, and carry out solvothermal reaction at 100 - 140 °C for 12 - 18 h. Cool to room temperature, carry out centrifugal separation, wash with deionized water and absolute ethanol until clean, and dry to obtain nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers;

[0025] (4) Add ethanol solvent, dispersant polyethylene glycol, and nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers into a reaction flask. Disperse them evenly, evenly coat them on the surface of an alumina ceramic tube with a gold electrode, dry, and then sinter and solidify at 350 - 450 °C for 1 - 3 h. Cool to room temperature, insert a Ni-Cr resistance heating wire inside the alumina ceramic tube, and weld it on the tube seat to make a side-heated gas sensor element, obtaining a gas sensor with Ni-doped SnO 2 modified with CuO.

[0026] Example 1

[0027] (1) Add deionized water solvent, sucrose, nickel chloride, and tin tetrachloride into a reaction flask. The mass ratio of the three is 80:1.5:100. Disperse them evenly, transfer them into a reaction kettle, and carry out hydrothermal reaction at 170 °C for 18 h. Cool to room temperature, carry out suction filtration, wash with deionized water and absolute ethanol until clean, and dry to obtain a nickel-doped tin oxide precursor;

[0028] (2) Place the nickel-doped tin oxide precursor in a resistance furnace and calcine it at 550 °C for 2 h. Cool to room temperature to obtain nickel-doped tin oxide hollow spheres;

[0029] (3) Add ethanol solvent, sodium hydroxide, hexamine, copper nitrate, and nickel-doped tin oxide hollow spheres into a reaction flask. The mass ratio of the four is 3:20:25:100. Disperse them evenly, transfer them into a reaction kettle, and carry out solvothermal reaction at 100 °C for 12 h. Cool to room temperature, carry out centrifugal separation, wash with deionized water and absolute ethanol until clean, and dry to obtain nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers;

[0030] (4) Add ethanol solvent, dispersant polyethylene glycol, and nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers into the reaction flask, disperse them evenly, and evenly coat them on the surface of the alumina ceramic tube with a gold electrode. After drying, sinter and solidify at 350 °C for 1 h, cool to room temperature, insert a Ni-Cr resistance heating wire inside the alumina ceramic tube, and weld it on the tube seat to make a side-heated gas sensor element, obtaining Ni-doped SnO 2 Gas sensor modified with CuO.

[0031] Example 2

[0032] (1) Add deionized water solvent, sucrose, nickel chloride, and tin tetrachloride into the reaction flask, with a mass ratio of 105:2:100 for the three. Disperse them evenly, transfer them into the autoclave, carry out hydrothermal reaction at 180 °C for 21 h, cool to room temperature, filter by suction, wash with deionized water and absolute ethanol, and dry to obtain the nickel-doped tin oxide precursor;

[0033] (2) Place the nickel-doped tin oxide precursor in an electric resistance furnace, calcine at 575 °C for 2.5 h, and cool to room temperature to obtain nickel-doped tin oxide hollow spheres;

[0034] (3) Add ethanol solvent, sodium hydroxide, hexamethylenetetramine, copper nitrate, and nickel-doped tin oxide hollow spheres into the reaction flask, with a mass ratio of 3.5:24:30:100 for the four. Disperse them evenly, transfer them into the autoclave, carry out solvothermal reaction at 110 °C for 13.5 h, cool to room temperature, centrifuge, wash with deionized water and absolute ethanol, and dry to obtain nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers;

[0035] (4) Add ethanol solvent, dispersant polyethylene glycol, and nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers into the reaction flask, disperse them evenly, and evenly coat them on the surface of the alumina ceramic tube with a gold electrode. After drying, sinter and solidify at 375 °C for 1.5 h, cool to room temperature, insert a Ni-Cr resistance heating wire inside the alumina ceramic tube, and weld it on the tube seat to make a side-heated gas sensor element, obtaining Ni-doped SnO 2 Gas sensor modified with CuO.

[0036] Example 3

[0037] (1) Add deionized water solvent, sucrose, nickel chloride, and tin tetrachloride into the reaction flask, with a mass ratio of 130:2.5:100 for the three. Disperse them evenly, transfer them into the autoclave, carry out hydrothermal reaction at 190 °C for 24 h, cool to room temperature, filter by suction, wash with deionized water and absolute ethanol, and dry to obtain the nickel-doped tin oxide precursor;

[0038] (2) Place the nickel-doped tin oxide precursor in a resistance furnace and calcine it at 600 °C for 3 h. Cool it to room temperature to obtain nickel-doped tin oxide hollow spheres;

[0039] (3) Add ethanol solvent, sodium hydroxide, hexamethylenetetramine, copper nitrate, and nickel-doped tin oxide hollow spheres to a reaction flask. The mass ratio of the four is 4:28:35:100. Disperse them evenly, transfer them into a reaction kettle, carry out a solvothermal reaction at 120 °C for 15 h, cool to room temperature, centrifuge and separate, wash with deionized water and absolute ethanol until clean, and dry to obtain nickel-doped tin oxide hollow sphere modified copper oxide nanoflowers;

[0040] (4) Add ethanol solvent, dispersant polyethylene glycol, and nickel-doped tin oxide hollow sphere modified copper oxide nanoflowers to a reaction flask. Disperse them evenly, evenly coat the surface of an alumina ceramic tube with a gold electrode, dry, and then sinter and cure at 400 °C for 2 h. Cool to room temperature, insert a Ni-Cr resistance heating wire inside the alumina ceramic tube, and weld it to the tube seat to make a side-heated gas sensor element, obtaining a Ni-doped SnO 2 gas sensor modified with CuO.

[0041] Example 4

[0042] (1) Add deionized water solvent, sucrose, nickel chloride, and tin tetrachloride to a reaction flask. The mass ratio of the three is 155:3:100. Disperse them evenly, transfer them into a reaction kettle, carry out a hydrothermal reaction at 200 °C for 27 h, cool to room temperature, filter by suction, wash with deionized water and absolute ethanol until clean, and dry to obtain a nickel-doped tin oxide precursor;

[0043] (2) Place the nickel-doped tin oxide precursor in a resistance furnace and calcine it at 625 °C for 3.5 h. Cool it to room temperature to obtain nickel-doped tin oxide hollow spheres;

[0044] (3) Add ethanol solvent, sodium hydroxide, hexamethylenetetramine, copper nitrate, and nickel-doped tin oxide hollow spheres to a reaction flask. The mass ratio of the four is 4.5:32:40:100. Disperse them evenly, transfer them into a reaction kettle, carry out a solvothermal reaction at 130 °C for 16.5 h, cool to room temperature, centrifuge and separate, wash with deionized water and absolute ethanol until clean, and dry to obtain nickel-doped tin oxide hollow sphere modified copper oxide nanoflowers;

[0045] (4) Add ethanol solvent, dispersant polyethylene glycol, and nickel-doped tin oxide hollow sphere modified copper oxide nanoflowers to a reaction flask. Disperse them evenly, evenly coat the surface of an alumina ceramic tube with a gold electrode, dry, and then sinter and cure at 425 °C for 2.5 h. Cool to room temperature, insert a Ni-Cr resistance heating wire inside the alumina ceramic tube, and weld it to the tube seat to make a side-heated gas sensor element, obtaining a Ni-doped SnO 2 gas sensor modified with CuO.

[0046] Example 5

[0047] (1) Add deionized water solvent, sucrose, nickel chloride, and tin tetrachloride into a reaction flask. The mass ratio of the three is 180:3.5:100. Disperse them evenly, transfer them into a reaction kettle, carry out hydrothermal reaction at 210 °C for 30 h, cool to room temperature, filter by suction, wash with deionized water and absolute ethanol until clean, and dry to obtain a nickel-doped tin oxide precursor;

[0048] (2) Place the nickel-doped tin oxide precursor in a resistance furnace, calcine at 650 °C for 4 h, and cool to room temperature to obtain nickel-doped tin oxide hollow spheres;

[0049] (3) Add ethanol solvent, sodium hydroxide, hexamethylenetetramine, copper nitrate, and nickel-doped tin oxide hollow spheres into a reaction flask. The mass ratio of the four is 5:35:45:100. Disperse them evenly, transfer them into a reaction kettle, carry out solvothermal reaction at 140 °C for 18 h, cool to room temperature, separate by centrifugation, wash with deionized water and absolute ethanol until clean, and dry to obtain nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers;

[0050] (4) Add ethanol solvent, dispersant polyethylene glycol, and nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers into a reaction flask. Disperse them evenly, evenly coat them on the surface of an alumina ceramic tube with a gold electrode, dry, sinter and solidify at 450 °C for 3 h, cool to room temperature, insert a Ni-Cr resistance heating wire inside the alumina ceramic tube, and weld it on the tube seat to make a side-heated gas sensor, obtaining a gas sensor with Ni-doped SnO 2 modified with CuO.

[0051] Comparative Example 1

[0052] (1) Add deionized water solvent, sucrose, nickel chloride, and tin tetrachloride into a reaction flask. The mass ratio of the three is 64:1.2:100. Disperse them evenly, transfer them into a reaction kettle, carry out hydrothermal reaction at 180 °C for 24 h, cool to room temperature, filter by suction, wash with deionized water and absolute ethanol until clean, and dry to obtain a nickel-doped tin oxide precursor;

[0053] (2) Place the nickel-doped tin oxide precursor in a resistance furnace, calcine at 600 °C for 3 h, and cool to room temperature to obtain nickel-doped tin oxide hollow spheres;

[0054] (3) Add ethanol solvent, sodium hydroxide, hexamethylenetetramine, copper nitrate, and nickel-doped tin oxide hollow spheres into a reaction flask. The mass ratio of the four is 2.4:16:20:100. Disperse them evenly, transfer them into a reaction kettle, carry out solvothermal reaction at 120 °C for 14 h, cool to room temperature, separate by centrifugation, wash with deionized water and absolute ethanol until clean, and dry to obtain nickel-doped tin oxide hollow spheres modified with copper oxide nanoflowers;

[0055] (4) Ethanol solvent, dispersant polyethylene glycol, and nickel-doped tin oxide hollow sphere modified copper oxide nanoflowers were added to the reaction flask, dispersed evenly, and evenly coated on the surface of the alumina ceramic tube with a gold electrode. After drying, it was sintered and cured at 400 °C for 2 h, cooled to room temperature, and a Ni-Cr resistance heating wire was inserted into the inside of the alumina ceramic tube and welded to the tube seat to make a side-heated gas sensor element, obtaining Ni-doped SnO 2 Gas sensor modified with CuO.

[0056] The CGS-8 type intelligent gas sensor analysis system was used to test the CO gas sensing performance of the Ni-doped SnO 2 Gas sensor modified with CuO. The sensitivity is the ratio of the resistance of the gas sensor element in air to the resistance in the test gas, and the test standard is GB / T 15653-1995.

[0057]

[0058]

Claims

1. A Ni-doped SnO 2 gas sensor modified with CuO It is characterized in that: The Ni-doped SnO 2 The preparation method of the CuO-modified gas sensor is as follows: (1) Sucrose, nickel chloride, and tin tetrachloride are added to a deionized water solvent, dispersed evenly, transferred into a reaction kettle, subjected to hydrothermal reaction, cooled, filtered by suction, washed, and dried to obtain a nickel-doped tin oxide precursor; (2) The nickel-doped tin oxide precursor is placed in an electric resistance furnace, calcined, and cooled to obtain nickel-doped tin oxide hollow spheres; (3) Sodium hydroxide, hexamine, copper nitrate, and nickel-doped tin oxide hollow spheres are added to an ethanol solvent, dispersed evenly, transferred into a reaction kettle, subjected to solvothermal reaction, cooled, centrifuged, washed, and dried to obtain nickel-doped tin oxide hollow sphere-modified copper oxide nanoflowers; (4) Add the dispersant polyethylene glycol and nickel-doped tin oxide hollow sphere modified copper oxide nanoflowers to the ethanol solvent, disperse them evenly, and evenly coat them on the surface of the alumina ceramic tube with a gold electrode. After drying, sinter and solidify at 350-450 °C for 1-3 h, cool down, insert a Ni-Cr resistance heating wire inside the alumina ceramic tube, and weld it on the tube base to make a side-heated gas sensor element, obtaining a Ni-doped SnO 2 gas sensor modified with CuO; In the step (1), the mass ratio of sucrose, nickel chloride, and tin tetrachloride is 80-180:1.5-3.5:100; The conditions of the hydrothermal reaction in the step (1) are hydrothermal reaction at 170-210 °C for 18-30 h; The conditions of the calcination in the step (2) are calcination at 550-650 °C for 2-4 h; In the step (3), the mass ratio of sodium hydroxide, hexamine, copper nitrate, and nickel-doped tin oxide hollow spheres is 3-5:20-35:25-45:100; The conditions of the solvothermal reaction in the step (3) are solvothermal reaction at 100-140 °C for 12-18 h.

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