CN107132252A - A kind of preparation method of tin dope nickel oxide gas sensitive - Google Patents

Abstract

The invention discloses a preparation method of a tin-doped nickel oxide gas-sensitive material: nickel nitrate hexahydrate and tin chloride hexahydrate with a certain atomic ratio are used as precursors, and ordered mesoporous silica is used as a template agent. Impregnation, removal of templates and centrifugation techniques to obtain highly dispersed, uniform particle size tin-doped nickel oxide bundle nanowire composite material. The tin-doped nickel oxide bundle nanowires prepared by the invention belong to p-type semiconductor materials and are suitable for early warning of low-concentration dangerous gases. The high-valent tin doping further regulates the carrier concentration of the hole accumulation layer, and shows good sensitivity and response recovery characteristics to ethanol gas.

Description

A kind of preparation method of tin-doped nickel oxide gas sensitive material

technical field

The invention relates to a preparation method of a tin-doped nickel oxide gas-sensitive material, which can be used to prepare a semiconductor gas sensor and effectively detect and monitor low-concentration dangerous gases.

Background technique

A gas sensor is a device or device that can convert information such as the type and concentration of the external atmosphere into corresponding electrical signals by using chemical reactions or physical effects. Therefore, it can realize the safe and effective detection, monitoring and alarm of flammable and explosive gases as well as toxic and harmful gases. Compared with other instruments used for gas analysis, such as gas chromatography, infrared analysis and thermal conductivity analyzer, etc., gas sensors have the advantages of small and portable, low price, high sensitivity, fast detection rate and stable performance. In recent years, as the country has paid more and more attention to the monitoring of toxic, harmful, flammable and explosive gases in industrial production and living environments, and people's awareness of safety and environmental protection has increased, higher requirements have been put forward for gas sensors.

At present, the research of gas sensors mainly focuses on the research and development of semiconductor metal oxides, such as SnO ₂ , ZnO, Sn ₂ O ₃ , In ₂ O ₃ , NiO, CuO and so on. Among them, NiO is a transition metal oxide material with direct bandgap and wide bandgap P-type conduction, which has broad application prospects in the fields of catalysis, transparent conduction, gas sensitivity, and electrochromism.

Semiconductor metal oxide gas sensors are mainly based on the conductance changes caused by the adsorption and desorption of gas molecules on the surface of materials to detect gases. When the P-type semiconductor gas sensor is exposed to the air, the oxygen molecules in the air will be adsorbed on the surface of the material, and the electrons in the valence band of the material surface will be captured and converted into oxygen anions (O ₂ ^- , O ^- , O ^2- ). Since the surface valence band electrons are captured by oxygen anions, the electron concentration decreases (that is, the hole concentration increases), and a hole accumulation layer is formed near the surface of the material, resulting in a decrease in the shell resistance of the material. When a reducing gas is introduced, the reducing gas is adsorbed on the surface of the material, and undergoes a redox reaction with oxygen anions, and the previously captured surface electrons will be released and returned to the valence band of the material, thereby restoring the conductance of the semiconductor material. normal.

Generally, there are two main ways to improve the gas-sensing performance of semiconductor materials, namely, regulating the morphology and size structure of the material, and through surface modification and doping. Regulating the morphology and size structure of the material (one-dimensional nanostructure, hierarchical structure, mesoporous structure, etc.) can increase the specific surface area of the material and increase the reactive sites on the surface of the material. Surface modification and doping of materials, on the one hand, use asymmetric metal elements to adjust the carrier concentration inside the material, thereby affecting the resistance value of the material. On the other hand, doping elements are used as surface catalysts and adsorbents to improve the adsorption capacity of the material surface for oxygen molecules and accelerate the reaction between the gas to be measured and oxygen negative ions, thereby improving the gas-sensing performance of the material. Therefore, on the basis of ensuring good morphology and size structure, doping the P-type semiconductor metal oxide gas-sensing material can further improve the response value and selectivity of the material.

Contents of the invention

Aiming at the deficiencies in the sensitivity and selectivity of the current pure P-type gas-sensitive materials, the present invention designs a tin-doped nickel oxide bundle nanowire, which can be used as a sensitive material for low-concentration gas sensors, and has relatively high sensitivity to ethanol gas. High sensitivity, fast response recovery rate.

NiO nanomaterial is a typical P-type metal oxide semiconductor material with a band gap between 3.6eV and 4.0eV at room temperature. It has stable physical and chemical properties and good thermal stability, so it can be used as a semiconductor gas sensor. Excellent gas sensitive material.

Doping the tetravalent metal element tin (Sn) can reduce the hole concentration inside the nickel oxide material and increase the resistance of the nickel oxide material in the air, so doping tin can significantly improve the gas-sensing performance of the NiO material.

The invention adopts the template replication method to synthesize the Sn-doped NiO bundle nanowire. The ordered template (SBA-15) is used to synthesize the anti-SBA-15 pore structure, which has a large specific surface area, increases surface defects, and improves the ability to absorb oxygen, thereby increasing the sensitivity of the sensor.

A preparation method of a tin-doped nickel oxide gas-sensitive material is as follows, and the specific steps are as follows: 1. Synthesis of template SBA-15: 8.8g of block polymer P123 is dissolved in 141g of 1.6-2M HCl and 141g of Fully stir in the mixed solution of ionic water for 2~4h. After P123 is completely dissolved, pour the mixture into a constant temperature water bath cup at 37-45°C and stir for 2h-6h. Add 20~22ml of tetraethyl orthosilicate dropwise to the solution, stir for 5 minutes after the addition, and continue to stand in a water bath at 45°C for 24 hours. The solution was transferred to a hydrothermal kettle, placed in an oven, and crystallized at 70-130°C for 24 hours. After natural cooling, the product was washed with deionized water and absolute ethanol until neutral, and dried at 80°C for 24 hours to obtain a white powder sample. Put the white sample into a muffle furnace and calcinate at 450~750℃ for 4~8h to obtain SBA-15. 2. Put a certain amount of SnCl ₄ •6H ₂ O and Ni(NO ₃ ) ₂ •6H ₂ O into a polytetrafluoroethylene cup according to the atomic ratio of Sn : (Sn+Ni) = 0~0.09, and then : (Sn+Ni)= 1:2 atomic ratio Add a certain amount of SBA-15, use alcohol and n-hexane as solvents to fully disperse and stir until dry powder, wash off the precursor adsorbed on the surface after heating at 260°C , to obtain tin-doped nickel oxide/SBA-15 composites. 3. Calcinate in a muffle furnace at 450-750°C for 5-8 hours, remove SBA-15 with 2 mol/L NaOH solution at 60-80°C, and wash with deionized water and ethanol until neutral to obtain tin-doped Heterogeneous NiO bundle nanowire material.

Advantages of the present invention: 1. The synthesis of Sn-doped NiO bundle nanowires in the present invention replicates the microstructure of ordered mesoporous materials in structure, ensuring the uniformity and orderliness of the structure and composition of Sn-doped NiO bundle nanowires . 2. The gas sensor made of Sn-doped NiO bundle-shaped nanowire material has high sensitivity. At a working temperature of 340°C, the response value of NiO bundle-shaped nanowire with a Sn content of 0.05 to 100ppm ethanol reaches 15.60. The time is 19s and the recovery time is 24s.

Description of drawings

Fig. 1 is the XRD graph of the Sn-doped NiO bundle nanowire prepared by the specific embodiment one; Fig. 2 is the SBA-15 scanning electron microscope image prepared by the specific embodiment one; Fig. 3 is the Sn-doped NiO prepared by the specific embodiment one Miscellaneous NiO bundle nanowire transmission electron microscope picture; Fig. 4 is the Sn-doped NiO bundle nanowire prepared by the specific embodiment one to the gas-sensing characteristic temperature and the sensitivity test graph of 100 ppm ethanol; Fig. 5 is the specific embodiment one Response recovery curve of the prepared Sn-doped NiO bundle nanowires to 100ppm ethanol at 340°C.

detailed description

Specific embodiment one: a kind of preparation method of iron-doped nickel oxide gas-sensing material, specifically finish according to the following steps: 1, the synthesis of template SBA-15: the block type polymer P123 of 8.8g is dissolved in 141g Fully stir in the mixed solution of 2M HCl and 141g deionized water for 2h. After P123 was completely dissolved, the mixture was poured into a constant temperature water bath cup at 45°C and stirred for 2 hours. Add 20.1ml of tetraethyl orthosilicate dropwise to the solution, stir for 5 minutes after the addition, and continue to stand in a water bath at 45°C for 24 hours. The solution was transferred to a hydrothermal kettle, placed in an oven, and crystallized at 130° C. for 24 hours. After natural cooling, the product was washed with deionized water and absolute ethanol until neutral, and dried at 80°C for 24 hours to obtain a white powder sample. The white sample was calcined in a muffle furnace at 550°C for 6h to obtain SBA-15. 2. Put a certain amount of SnCl ₄ •6H ₂ O and Ni(NO ₃ ) ₂ •6H ₂ O into a polytetrafluoroethylene cup according to the atomic ratio of Sn : (Sn+Ni) = 0.05, and then according to Si : ( Add a certain amount of SBA-15 at an atomic ratio of Sn+Ni) = 1:2, fully disperse with alcohol and n-hexane as solvents and stir until dry powder, wash off the precursor adsorbed on the surface after heating at 260 °C, and obtain Tin-doped nickel oxide/SBA-15 composite. 3. Calcinate in a muffle furnace at 550 °C for 6 h, remove SBA-15 with 2 mol/L NaOH solution at 80 °C, and wash with deionized water and ethanol until neutral to obtain tin-doped NiO bundle nanowires Material.

Specific embodiment two: a kind of preparation method of tin-doped nickel oxide gas-sensing material, specifically finish according to the following steps: 1, the synthesis of template SBA-15: the block type polymer P123 of 8.8g is dissolved in 141g Fully stir in the mixed solution of 1.6M HCl and 141g deionized water for 2h. After P123 was completely dissolved, the mixture was poured into a constant temperature water bath cup at 37°C and stirred for 2 hours. Add 20ml of tetraethyl orthosilicate dropwise to the solution, stir for 5 minutes after the addition, and continue to stand in a water bath at 45°C for 24 hours. The solution was transferred to a hydrothermal kettle, placed in an oven, and crystallized at 70°C for 24h. After natural cooling, the product was washed with deionized water and absolute ethanol until neutral, and dried at 80°C for 24 hours to obtain a white powder sample. The white sample was calcined at 450°C for 4 hours in a muffle furnace to obtain SBA-15. 2. Put a certain amount of SnCl ₄ •6H ₂ O and Ni(NO ₃ ) ₂ •6H ₂ O into a polytetrafluoroethylene cup according to the atomic ratio of Sn : (Sn+Ni) = 0.03, and then according to Si : ( Add a certain amount of SBA-15 at an atomic ratio of Sn+Ni) = 1:2, fully disperse with alcohol and n-hexane as solvents and stir until dry powder, wash off the precursor adsorbed on the surface after heating at 260 °C, and obtain Tin-doped nickel oxide/SBA-15 composite. 3. Calcinate in a muffle furnace at 450 °C for 5 h, remove SBA-15 with 2 mol/L NaOH solution at 60 °C, and wash with deionized water and ethanol until neutral to obtain tin-doped NiO bundle nanowires Material.

Specific embodiment three: a preparation method of a tin-doped nickel oxide gas-sensitive material, which is specifically completed in the following steps: 1. Synthesis of template SBA-15: 8.8g of block polymer P123 is dissolved in 141g of Fully stir in the mixed solution of 1.8M HCl and 141g deionized water for 3h. After P123 was completely dissolved, the mixture was poured into a constant temperature water bath cup at 40°C and stirred for 4 hours. Add 21ml of ethyl orthosilicate dropwise to the solution, stir for 5 minutes after the addition, and continue to stand in a water bath at 45°C for 24 hours. The solution was transferred to a hydrothermal kettle, placed in an oven, and crystallized at 100°C for 24h. After natural cooling, the product was washed with deionized water and absolute ethanol until neutral, and dried at 80°C for 24 hours to obtain a white powder sample. The white sample was calcined in a muffle furnace at 550°C for 6h to obtain SBA-15. 2. Put a certain amount of SnCl ₄ •6H ₂ O and Ni(NO ₃ ) ₂ •6H ₂ O into a polytetrafluoroethylene cup according to the atomic ratio of Sn : (Sn+Ni) = 0.07, and then according to Si : ( Add a certain amount of SBA-15 at an atomic ratio of Sn+Ni) = 1:2, fully disperse with alcohol and n-hexane as solvents and stir until dry powder, wash off the precursor adsorbed on the surface after heating at 260 °C, and obtain Tin-doped nickel oxide/SBA-15 composite. 3. Calcinate in a muffle furnace at 550 °C for 6 h, remove SBA-15 with 2 mol/L NaOH solution at 70 °C, and wash with deionized water and ethanol until neutral to obtain tin-doped NiO bundle nanowires Material.

Embodiment 4: A preparation method of a tin-doped nickel oxide gas-sensitive material, which is specifically completed in the following steps: 1. Synthesis of template SBA-15: 8.8g of block polymer P123 is dissolved in 141g of Fully stir in the mixed solution of 2M HCl and 141g deionized water for 4h. After P123 was completely dissolved, the mixture was poured into a constant temperature water bath cup at 45°C and stirred for 6 hours. Add 22 ml of tetraethyl orthosilicate dropwise to the solution, stir for 5 minutes after the addition, and continue to stand in a water bath at 45°C for 24 hours. The solution was transferred to a hydrothermal kettle, placed in an oven, and crystallized at 130° C. for 24 hours. After natural cooling, the product was washed with deionized water and absolute ethanol until neutral, and dried at 80°C for 24 hours to obtain a white powder sample. The white sample was calcined at 650°C for 8 hours in a muffle furnace to obtain SBA-15. 2. Put a certain amount of SnCl ₄ •6H ₂ O and Ni(NO ₃ ) ₂ •6H ₂ O into a polytetrafluoroethylene cup according to the atomic ratio of Sn : (Sn+Ni) = 0.09, and then according to Si : ( Add a certain amount of SBA-15 at an atomic ratio of Sn+Ni) = 1:2, fully disperse with alcohol and n-hexane as solvents and stir until dry powder, wash off the precursor adsorbed on the surface after heating at 260 °C, and obtain Tin-doped nickel oxide/SBA-15 composite. 3. Calcinate in a muffle furnace at 650 °C for 8 h, remove SBA-15 with 2 mol/L NaOH solution at 80 °C, and wash with deionized water and ethanol until neutral to obtain tin-doped NiO bundle nanowires Material.

Embodiment 5: A preparation method of a tin-doped nickel oxide gas-sensitive material, which is specifically completed in the following steps: 1. Synthesis of template SBA-15: 8.8g of block polymer P123 is dissolved in 141g of Fully stir in the mixed solution of 2M HCl and 141g deionized water for 2h. After P123 was completely dissolved, the mixture was poured into a constant temperature water bath cup at 45°C and stirred for 2 hours. Add 20ml of tetraethyl orthosilicate dropwise to the solution, stir for 5 minutes after the addition, and continue to stand in a water bath at 45°C for 24 hours. The solution was transferred to a hydrothermal kettle, placed in an oven, and crystallized at 130° C. for 24 hours. After natural cooling, the product was washed with deionized water and absolute ethanol until neutral, and dried at 80°C for 24 hours to obtain a white powder sample. The white sample was calcined at 750°C for 4 hours in a muffle furnace to obtain SBA-15. 2. Put a certain amount of SnCl ₄ •6H ₂ O and Ni(NO ₃ ) ₂ •6H ₂ O into the polytetrafluoroethylene cup according to the atomic ratio of Sn : (Sn+Ni) = 0, and then according to Si : ( Add a certain amount of SBA-15 at an atomic ratio of Sn+Ni) = 1:2, fully disperse with alcohol and n-hexane as solvents and stir until dry powder, wash off the precursor adsorbed on the surface after heating at 260 °C, and obtain Tin-doped nickel oxide/SBA-15 composite. 3. Calcinate in a muffle furnace at 750 °C for 5 h, remove SBA-15 with 2 mol/L NaOH solution at 80 °C, and wash with deionized water and ethanol until neutral to obtain tin-doped NiO bundle nanowires Material.

Embodiment 6: A preparation method of a tin-doped nickel oxide gas-sensitive material, which is specifically completed in the following steps: 1. Synthesis of template SBA-15: 8.8 g of block polymer P123 is dissolved in 141 g of Fully stir in the mixed solution of 2M HCl and 141g deionized water for 2h. After P123 was completely dissolved, the mixture was poured into a constant temperature water bath cup at 45°C and stirred for 2 hours. Add 20.1ml of tetraethyl orthosilicate dropwise to the solution, stir for 5 minutes after the addition, and continue to stand in a water bath at 45°C for 24 hours. The solution was transferred to a hydrothermal kettle, placed in an oven, and crystallized at 100°C for 24h. After natural cooling, the product was washed with deionized water and absolute ethanol until neutral, and dried at 80°C for 24 hours to obtain a white powder sample. The white sample was calcined at 650°C for 6h in a muffle furnace to obtain SBA-15. 2. Put a certain amount of SnCl ₄ •6H ₂ O and Ni(NO ₃ ) ₂ •6H ₂ O into a polytetrafluoroethylene cup according to the atomic ratio of Sn : (Sn+Ni) = 0.01, and then according to Si : ( Add a certain amount of SBA-15 at an atomic ratio of Sn+Ni) = 1:2, fully disperse with alcohol and n-hexane as solvents and stir until dry powder, wash off the precursor adsorbed on the surface after heating at 260 °C, and obtain Tin-doped nickel oxide/SBA-15 composite. 3. Calcinate in a muffle furnace at 650 °C for 6 h, remove SBA-15 with 2 mol/L NaOH solution at 80 °C, and wash with deionized water and ethanol until neutral to obtain tin-doped NiO bundle nanowires Material.

Fig. 1 is the XRD pattern of the Sn-doped NiO bundle nanowire prepared by the specific embodiment one, as can be seen from the figure, what obtains are all crystal phases, and the peak position of each diffraction peak in the measured spectrogram is consistent with the The peak positions of the standard JCPDS card (65-5745) are exactly the same.

Fig. 2 is a scanning electron microscope image of SBA-15 prepared in Embodiment 1. It can be seen from the figure that the prepared rod-shaped SBA-15 has a diameter of 1-2 microns and a length of about 4-6 microns.

Fig. 3 is a transmission electron microscope image of the Sn-doped NiO bundle nanowires prepared in Embodiment 1. It can be seen from the figure that the prepared Sn-doped NiO nanomaterials are bundle nanowires, and there are holes between the wires.

Fig. 4 is the Sn-doped NiO beam-shaped nanowire prepared by specific embodiment 1 to the gas-sensing characteristic temperature and the sensitivity test figure of 100 ppm ethanol, it can be seen from the figure that the optimum working temperature of the Sn-doped NiO beam-shaped nanowire is 340°C and the sensitivity is as high as 15.60.

Fig. 5 is the response recovery time diagram of the gas-sensing characteristics of the Sn-doped NiO bundle nanowires prepared in Embodiment 1 to 100ppm ethanol at 340°C. From the figure, it can be seen that the response recovery times of the Sn-doped NiO bundle nanowires are respectively for 19 and 24 s.

Claims (4)

1. A preparation method of a tin-doped nickel oxide gas-sensitive material, characterized in that its preparation method first adopts a hydrothermal method to prepare a hard template SBA-15, and then uses SBA-15 as a template, adopts a nano-replication method, and is separated by centrifugation Obtain highly dispersed mesoporous tin-doped nickel oxide nanowires; the specific steps are as follows: 1. Synthesis of SBA-15: 8.8g of block polymer P123 was dissolved in 141g of 1.6M ~ 2M HCl and 141g of deionized water Fully stir in the mixed solution for 2~4 h; after the P123 is completely dissolved, pour the mixed solution into a constant temperature water bath cup at 37~45°C and stir for 2h~6h; add tetraethyl orthosilicate 20 ~22ml, stir for 5min after the dropwise addition, continue to stand in a 45°C water bath for 24h; transfer the solution to a hydrothermal kettle, put it in an oven, and crystallize at 70~130°C for 24h; after natural cooling , the product was washed with deionized and absolute ethanol until neutral, and dried at 80°C for 24h to obtain a white powder sample; the white sample was put into a muffle furnace and calcined at 450~750°C for 4~8h to obtain an ordered mesoporous Silicon oxide rod-shaped SBA-15; 2. Put a certain amount of SnCl ₄ •6H ₂ O and Ni(NO ₃ ) ₂ •6 H ₂ O into the polymer according to the atomic ratio of Sn : (Sn+Ni) = 0.01~0.09 In the tetrafluoroethylene cup, add a certain amount of SBA-15 according to the atomic ratio of Si : (Sn+Ni) = 1:2, fully disperse with alcohol and n-hexane as solvents and stir until dry powder, heat at 260°C Finally, the precursor adsorbed on the surface was washed off to obtain the tin-doped nickel oxide/SBA-15 composite material; 3. After calcination at 450-750 ℃ for 5-8 h in a muffle furnace, the SBA-15 was removed at 60-80°C, and washed with deionized water and ethanol until neutral to obtain tin-doped nickel oxide bundle nanowires. 2. according to the preparation method of a kind of tin-doped nickel oxide gas-sensing material described in claim 1, it is characterized in that ordered mesoporous SBA-15 exists in rod shape, and the diameter of rod-shaped SBA-15 is 1～2 micron, length Between 4-6 microns, it is beneficial for the precursor to fill the pores; the specific synthesis conditions are hydrothermal temperature 70-130°C, calcination temperature 450-750°C, and calcination time 4-8h. 3. according to the preparation method of a kind of tin-doped nickel oxide gas-sensing material described in claim 1, it is characterized in that adopt orderly template synthesis to have anti-SBA-15 porous structure tin-doped nickel oxide gas-sensing nanowire, There are pores between the lines, which increase the specific surface area of the material, thereby increasing surface defects, improving the ability to absorb oxygen, and improving sensor sensitivity. 4. according to the preparation method of a kind of tin-doped nickel oxide gas-sensitive material described in claim 1, it is characterized in that high-valence Sn doping atomic ratio is 0.01～0.09, in order to increase material surface hole accumulation layer thickness, further Improve sensor sensitivity.