Preparation method and application of single-atom Ni coupled SnO2 nanorods with abundant oxygen vacancies

Abstract

The present invention discloses a preparation method and application of single-atom Ni-coupled SnO2 (Ni SA / ROV-SnO2) nanorods with abundant oxygen vacancies. The preparation method comprises the following steps: first, synthesizing SnO2 nanorods by a solvothermal method, then introducing a Ni source by an impregnation method, and calcining in an H2 / N2 atmosphere to obtain NiSA / ROV-SnO2 nanorods. The preparation method of the present invention is simple, the reaction conditions are mild, and the prepared NiSA / ROV-SnO2 nanorods are size-controllable. The prepared single-atom Ni-coupled SnO2 (Ni SA / ROV-SnO2) nanorods with abundant oxygen vacancies are used to prepare gas sensors, showing good selectivity, high sensitivity, and low detection limit for SO2 gas.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic materials, and in particular to a preparation method and application of single-atom Ni-coupled SnO2 nanorods with abundant oxygen vacancies. Background Art

[0002] With the rapid development of industrial technology, people's awareness of safety and health is increasing. Therefore, there is an urgent need to monitor air quality, toxic and harmful gases, and flammable and explosive gases in various living and production places to prevent accidents that endanger health and safety, thereby ensuring the safety of people and property. Currently, the detection of toxic and harmful gases mainly uses gas sensors, among which semiconductor metal oxides are the most widely studied and applied gas-sensitive materials.

[0003] SnO2 is one of the most widely used materials in the research and application of semiconductor metal oxide gas sensors. Typically, single SnO2 exhibits poor selectivity and sensitivity for toxic and hazardous gases, necessitating modification to enhance its performance. Compared to nanoparticle loading, single atoms, proposed by Academician Zhang Tao of the Dalian Institute of Chemical Physics, possess more reactive sites and higher catalytic activity. The application of single atoms in gas sensors is of great significance for both improving sensor performance and exploring gas-sensing mechanisms. Summary of the Invention

[0004] In response to the above-mentioned technical problems, the present invention provides a preparation method and application of single-atom Ni coupled SnO2 nanorods with abundant oxygen vacancies.

[0005] The technical solution of the present invention is:

[0006] A method for preparing single-atom Ni-coupled SnO2 (Ni SA / ROV-SnO2) nanorods with abundant oxygen vacancies comprises the following steps:

[0007] S1. Preparation of SnO2 nanorods

[0008] S1-1: Add anhydrous tin tetrachloride to the NaOH aqueous solution and stir in an ice-water bath for 30-90 min to obtain a transparent solution S;

[0009] S1-2: Prepare a mixture of sodium lauryl sulfate dissolved in heptane solution and n-hexanol solution, stir magnetically for 10 to 60 minutes, then add a certain amount of the above-mentioned transparent solution S, and continue stirring for 0.5 to 3 hours;

[0010] S1-3: Transfer the obtained solution into a reactor and perform hydrothermal reaction at 150-220°C for 12-24 hours;

[0011] S1-4: After the reactor is naturally cooled to room temperature, it is repeatedly centrifuged and washed with deionized water and anhydrous ethanol, and dried at 60-80°C for 6-12 hours to obtain white powder SnO2 nanorods;

[0012] The SnO2 nanorods prepared by the method of the present invention are highly uniform and evenly dispersed. Currently, there are few reports on the preparation of SnO2 nanorods, which are basically nanorod arrays or nanoflowers composed of nanorods grown on substrates. There are few reports on the preparation of evenly dispersed nanorods.

[0013] Prior art publication CN110117027A reports SnO2 nanorods produced through a hydrothermal reaction of urea and tin tetrachloride. Scanning electron micrographs of the SnO2 nanorods provided by the researchers reveal that the resulting nanorods are highly uneven, varying in length and thickness, with some appearing like rods and others like spheres, and exhibiting poor crystallinity. This significantly differs from the SnO2 nanorods produced using the present invention's solvothermal method, which produces uniform, regular nanorods with excellent crystallinity.

[0014] S2. Preparation of Ni SA / ROV-SnO2 nanorods

[0015] S2-1: Ultrasonic dispersion of the SnO2 nanorods prepared in S1 in anhydrous ethanol to obtain a SnO2 nanorod suspension with a concentration of 0.01 to 1 mol / L;

[0016] S2-2: Add 0.01 mol / L nickel chloride solution to the SnO2 nanorod suspension and stir magnetically for 3 to 8 hours;

[0017] S2-3: centrifugation, drying, and finally calcining the material under H2 / N2 atmosphere to obtain the Ni SA / ROV-SnO2 nanorods.

[0018] Description: Single-atom catalysis is currently a hot frontier field of catalysis. Single-atom catalysis means that active metals are loaded on the surface of a carrier in the form of single atoms.

[0019] When the size of nanocrystals is reduced to atomic clusters or single atoms, their energy level structure and electronic structure will undergo fundamental changes. It is precisely because of this unique structural feature that single-atom catalysts often exhibit activity, selectivity and stability different from traditional nanocatalysts.

[0020] The present invention introduces the concept of single-atom catalysis into gas sensors, loads Ni single atoms on SnO2 nanorods, and performs gas-sensitive detection. The material shows high sensitivity and high selectivity to SO2 gas. Even at a SO2 concentration as low as 100ppb, it still shows an obvious response. This excellent gas-sensing performance is an active performance that is difficult to achieve with composite nanocrystals. The introduction of Ni single atoms enables 100% utilization of Ni atoms, and each single atom is an active site. The intrinsic bonding adsorption of Ni atoms on SO2 and the activation of adsorbed oxygen promoted by oxygen vacancies make the material show excellent gas-sensing performance for SO2 gas.

[0021] Furthermore, in the above scheme, in step S1-1, the concentration of the NaOH aqueous solution is 6 to 8 mol / L.

[0022] Furthermore, in the above scheme, in step S1-1, the molar ratio of NaOH to anhydrous SnCl4 is 10-30:1.

[0023] Furthermore, in the above scheme, in step S1-2, the volume ratio of the transparent solution S, the heptane solution, and the n-hexanol solution is 1:4-5:1-2.5.

[0024] Furthermore, in the above scheme, the molar ratio of nickel element to SnO2 in step S2-2 is 0.01 to 0.03:1.

[0025] Furthermore, in the above scheme, the calcination temperature in step S2-3 is 250-500° C., and the calcination time is 1-6 hours.

[0026] Furthermore, the calcination temperature in step S2-3 is 300° C., and the calcination time is 4 hours. The calcination temperature in step S2-3 is 300° C., and the calcination time is 4 hours.

[0027] The present invention also provides the application of the single-atom Ni coupled SnO2 nanorods with abundant oxygen vacancies prepared by the above method as a gas sensitive material.

[0028] Furthermore, the single-atom Ni coupled with SnO2 nanorods having abundant oxygen vacancies is applied to gas sensors.

[0029] The single-atom Ni coupled SnO2 (Ni SA / ROV-SnO2) nanorods with rich oxygen vacancies prepared by the present invention have a diameter of about 130nm and a length of about 5-8μm. The single-atom Ni is uniformly dispersed on the SnO2 nanorods, and the molar ratio of the single-atom Ni loading content to the SnO2 is 0.01-0.03.

[0030] Compared with the prior art, the beneficial effects of the present invention are embodied in the following aspects:

[0031] 1) The present invention synthesizes SnO2 nanorods by a simple solvothermal method, and disperses isolated single Ni atoms as active sites on the SnO2 nanorods to obtain single-atom Ni-coupled SnO2 nanorod materials with abundant oxygen vacancies.

[0032] 2) Ni SA / ROV-SnO2 nanorods have abundant oxygen vacancies, which are conducive to the adsorption and activation of oxygen, thereby improving the response sensitivity to SO2 gas.

[0033] 3) Single atoms have high activity and selectivity, and Ni has a specific adsorption for SO2 through Ni-O and Ni-S bonds. Therefore, the prepared Ni SA / ROV-SnO2 nanorods have high selectivity for SO2 gas.

[0034] 4) The obtained Ni SA / ROV-SnO2 nanorods were applied to gas sensing tests. It was found that the sensitivity to gases such as NO, H2, NH3, ethanol, acetone, and formaldehyde was not high, but the sensitivity to SO2 gas was outstanding. The material has high selectivity for SO2 gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 X-ray diffraction (XRD) patterns of the single-atom Ni-coupled SnO2 nanorods with abundant oxygen vacancies prepared in Example 1 and the SnO2 nanorods with abundant oxygen vacancies prepared in the comparative example.

[0036] Figure 2 Scanning transmission electron microscopy (STEM) and X-ray energy spectrum elemental imaging analysis technology (EDS-Mapping) maps of single-atom Ni coupled SnO2 nanorods with abundant oxygen vacancies prepared in Example 1.

[0037] Figure 3 This is the scanning electron microscope (SEM) image of the single-atom Ni coupled SnO2 nanorods with abundant oxygen vacancies prepared in Example 1.

[0038] Figure 4 Electron spin resonance (ESR) spectra of the single-atom Ni-coupled SnO2 nanorods with abundant oxygen vacancies prepared in Example 1 and the SnO2 nanorods with abundant oxygen vacancies prepared in the comparative example.

[0039] Figure 5 X-ray absorption fine spectroscopy (XAFS) of single-atom Ni coupled SnO2 nanorods with abundant oxygen vacancies prepared in Example 1.

[0040] Figure 6Gas-sensitive response diagrams to 20 ppm SO2 at different temperatures after the Ni-coupled SnO2 nanorods with abundant oxygen vacancies prepared in Examples 1, 2, and 3 and the SnO2 nanorods with abundant oxygen vacancies described in the comparative example were respectively prepared into gas-sensitive test elements.

[0041] Figure 7 After the single-atom Ni-coupled SnO2 nanorods with abundant oxygen vacancies described in Example 1 and the SnO2 nanorods with abundant oxygen vacancies described in the comparative example were respectively prepared into gas-sensitive test elements, the response sensitivity spectra to SO2, NO, H2, NH3, ethanol, acetone, and formaldehyde gases with a concentration of 20 ppm were obtained at the optimal working temperature.

[0042] Figure 8 The single-atom Ni coupled SnO2 nanorods with abundant oxygen vacancies described in Example 1 and the SnO2 nanorods with abundant oxygen vacancies described in the comparative example are respectively prepared into gas-sensitive test elements, and the response sensitivity spectrum to 0.1-40ppm SO2 gas at the optimal working temperature.

[0043] Figure 9 The long-term stability spectra of the single-atom Ni-coupled SnO2 nanorods with abundant oxygen vacancies described in Example 1 and the SnO2 nanorods with abundant oxygen vacancies described in the comparative example are respectively prepared into gas-sensitive test elements, and then tested at the optimal working temperature for 60 days to 20 ppm SO2 gas. DETAILED DESCRIPTION

[0044] In order to better understand the present invention, the content of the present invention is further illustrated in conjunction with specific examples below. However, it should be understood that the following examples are only preferred embodiments of the present invention. For ordinary technicians in this field, it is possible to make several improvements and changes without departing from the creative concept of the present invention. These all fall within the scope of protection of the present invention.

[0045] Example 1

[0046] Preparation of single-atom Ni-coupled SnO2 (Ni SA / ROV-SnO2) nanorod materials with abundant oxygen vacancies and a Ni to SnO2 molar ratio of 0.02:

[0047] 1. Preparation of SnO2 nanorods

[0048] Accurately weigh 200 mmol of NaOH and dissolve it in 30 mL of deionized water. After magnetic stirring for 30 minutes, add 10 mmol of anhydrous tin tetrachloride (SnCl4) to the NaOH aqueous solution in an ice-water bath and continue magnetic stirring for 1 hour to form a transparent solution S. Subsequently, weigh 20 mmol of sodium dodecyl sulfate and dissolve it in a mixture of 20 mL of heptane solution and 6 mL of n-hexanol solution. Continue magnetic stirring for 30 minutes, then add 4 mL of the transparent solution S dropwise and continue stirring for 1 hour. The resulting solution is transferred to a reactor and hydrothermally reacted at 200°C for 20 hours. After the reactor cools naturally to room temperature, it is repeatedly centrifuged and washed with deionized water and anhydrous ethanol, and dried at 60°C for 12 hours to obtain white powder SnO2 nanorods.

[0049] 2. Preparation of Ni SA / ROV-SnO2 Nanorods

[0050] 100 mg of SnO2 nanorod powder was dissolved in 20 mL of ethanol and ultrasonically dispersed for 30 minutes to obtain a SnO2 nanorod suspension. 1328 μL of nickel chloride solution (0.01 mol / L, 10 mL) was then added to the suspension. After magnetic stirring for 6 hours, the suspension was dried at 60°C for 24 hours. Finally, the material was calcined under a H2 / N2 atmosphere to obtain the Ni SA / ROV-SnO2 nanorods.

[0051] The XRD pattern of Ni SA / ROV-SnO2 nanorods obtained in this example is as follows Figure 1 As shown in the figure, the diffraction peak of Ni SA / ROV-SnO2 is consistent with JCPDS No.77-0448, which is the characteristic diffraction peak of tetragonal rutile SnO2. There is no obvious Ni characteristic diffraction peak in the figure because the Ni loading amount is small and Ni is highly dispersed on the SnO2 surface.

[0052] The STEM EDS-mapping pattern of the Ni SA / ROV-SnO2 nanorods obtained in this example is shown in FIG. Figure 2 As shown in the figure, Ni can be seen to be evenly distributed on the surface of SnO2 nanorods.

[0053] The SEM electron microscope image of the Ni SA / ROV-SnO2 nanorods obtained in this example is as follows: Figure 3 As shown in the figure, it can be seen that the morphology of the material is nanorods with a diameter of about 130nm and a length of about 5-8μm.

[0054] The ESR electron microscope image of the Ni SA / ROV-SnO2 nanorods obtained in this example is shown in FIG. Figure 4As shown in the figure, it can be seen that the peak of NiSA / ROV-SnO2 nanorods at a g value of 2.003 corresponds to the single-electron signal of surface oxygen vacancies, indicating that the NiSA / ROV-SnO2 nanorod sample contains abundant oxygen vacancies.

[0055] The XAFS spectrum of Ni SA / ROV-SnO2 nanorods obtained in this example is shown in FIG. Figure 5 As shown in the figure, it can be seen that Ni SA / ROV-SnO2 is only There is a main peak at , which corresponds to Ni-O coordination, and there is no Ni-Ni coordination, indicating that there is only single-atom Ni on the surface of SnO2 nanorods.

[0056] 3. Performance test of Ni SA / ROV-SnO2 nanorods prepared in this example for gas sensitive materials

[0057] The NiSA / ROV-SnO2 nanorods prepared in this embodiment were placed in an agate mortar and ground evenly. A certain amount of water, ethylene glycol and glycerol were added and continued to grind until a fine and uniform slurry was obtained. The slurry was evenly coated on a gold interdigitated electrode on an alumina substrate to form a gas-sensitive test element. After the slurry on the gas-sensitive element was dried on an 80°C hot plate, it was placed in a tube furnace and calcined and aged for 2 hours at 400°C in a H2 / N2 atmosphere. Then, the gas-sensitive element was placed in a gas-sensitive tester and aged for 24 hours by current flow. A gas-sensitive element of NiSA / ROV-SnO2 nanorods was obtained, and its gas-sensing performance was tested.

[0058] The Ni SA / ROV-SnO2 nanorods obtained in this example were prepared into gas-sensitive test elements. The gas-sensitive responses to 20 ppm SO2 at different temperatures were shown in the figure below. Figure 6 As shown in the figure, it can be seen that when the working temperature is 250℃, the Ni SA / ROV-SnO2 nanorod sensor has the highest gas sensitive response to SO2.

[0059] After the Ni SA / ROV-SnO2 nanorods obtained in this example were prepared into gas-sensitive test elements, gas-sensitive tests were performed on SO2, NO, H2, NH3, ethanol, acetone, and formaldehyde gases with a concentration of 20 ppm at a working temperature of 250°C. Figure 7 As shown in the figure, it can be seen that Ni SA / ROV-SnO2 nanorods show good selectivity for SO2 gas.

[0060] After the Ni SA / ROV-SnO2 nanorods obtained in this embodiment were prepared into gas-sensitive test elements, the response sensitivity to 0.1-40ppm SO2 gas at a working temperature of 250°C was as follows: Figure 8As shown in the figure, it can be seen that as the SO2 gas concentration increases, the response of the Ni SA / ROV-SnO2 nanorod sensor to SO2 gradually increases. The Ni SA / ROV-SnO2 nanorod sensor has a fast response recovery time, with a response time of 52s and a recovery time of 45s for 20ppm SO2.

[0061] The Ni SA / ROV-SnO2 nanorods obtained in this example were prepared into gas sensing test elements at a working temperature of 250°C. The long-term stability spectrum of 20 ppm SO2 gas for 60 days is shown in FIG. Figure 9 As shown in the figure, it can be seen that after 60 days of testing, the response of the NiSA / ROV-SnO2 sensor to SO2 gas only decreased by 4.5%, indicating that the sensor has excellent long-term stability.

[0062] Example 2

[0063] Preparation of single-atom Ni-coupled SnO2 (Ni SA / ROV-SnO2) nanorod materials with abundant oxygen vacancies and a Ni to SnO2 molar ratio of 0.01:

[0064] 1. Preparation of SnO2 nanorods

[0065] Accurately weigh 200 mmol of sodium hydroxide (NaOH) and dissolve it in 30 mL of deionized water. After magnetic stirring for 30 minutes, 10 mmol of anhydrous tin tetrachloride (SnCl4) was added to the NaOH aqueous solution in an ice-water bath and magnetic stirring was continued for 1 hour to form a transparent solution S. Subsequently, 20 mmol of sodium dodecyl sulfate was weighed and dissolved in a mixture of 10 mL of heptane solution and 3 mL of n-hexanol solution. Magnetic stirring was continued for 30 minutes, followed by the dropwise addition of 2 mL of the transparent solution S and stirring for another hour. The resulting solution was transferred to a reactor and hydrothermally reacted at 200°C for 20 hours. After the reactor cooled naturally to room temperature, the solution was repeatedly washed by centrifugation with deionized water and anhydrous ethanol and dried at 60°C for 12 hours to obtain white powdered SnO2 nanorods.

[0066] 2. Preparation of Ni SA / ROV-SnO2 Nanorods

[0067] 100 mg of SnO2 nanorod powder was dissolved in 20 mL of ethanol and ultrasonically dispersed for 30 minutes to obtain a SnO2 nanorod suspension. 664 μL of nickel chloride solution (0.01 mol / L, 10 mL) was then added to the suspension. After magnetic stirring for 6 hours, the suspension was dried at 60°C for 24 hours. Finally, the material was calcined under a H2 / N2 atmosphere to obtain the 0.01-Ni SA / ROV-SnO2 nanorods.

[0068] 3. Performance test of Ni SA / ROV-SnO2 nanorods prepared in this example for gas sensitive materials

[0069] Take an appropriate amount of the single-atom Ni coupled SnO2 nanorods with rich oxygen vacancies obtained in this example, place them in an agate mortar and grind them evenly, add a certain amount of water, ethylene glycol and propylene glycol and continue grinding until a fine and uniform slurry is obtained, and the slurry is evenly coated on the gold interdigitated electrode on the alumina substrate to form a gas-sensitive test element. After the slurry on the gas-sensitive element is dried on an 80°C hot plate, it is placed in a tubular furnace and calcined and aged for 2 hours at 400°C in an H2 / N2 atmosphere. Then, the gas-sensitive element is placed in a gas-sensitive tester and aged for 24 hours by current flow. A gas-sensitive element of single-atom Ni coupled SnO2 nanorods with rich oxygen vacancies is obtained, and the gas-sensitive performance test is performed.

[0070] The 0.01-Ni SA / ROV-SnO2 nanorods obtained in this example were prepared into gas-sensitive test elements. The gas-sensitive responses to 20 ppm SO2 at different temperatures were shown in the figure below. Figure 6 As shown in the figure, it can be seen that when the operating temperature is 250°C, the Ni SA / ROV-SnO2 nanorod sensor has the highest gas sensitive response to SO2, but the response effect is worse than that of Example 1.

[0071] Example 3

[0072] Preparation of Ni-coupled SnO2 (Ni SA / ROV-SnO2) nanorod material with abundant oxygen vacancies and a Ni to SnO2 molar ratio of 0.03:

[0073] 1. Preparation of SnO2 nanorods

[0074] 300 mmol of sodium hydroxide (NaOH) was dissolved in 40 mL of deionized water and magnetically stirred for 30 minutes. Then, 10 mmol of anhydrous tin tetrachloride (SnCl4) was added to the NaOH solution in an ice-water bath and magnetic stirring continued for 1 hour to form a transparent solution S. Subsequently, 30 mmol of sodium dodecyl sulfate was dissolved in a mixture of 20 mL of heptane and 10 mL of n-hexanol. Magnetic stirring was continued for 30 minutes, followed by the dropwise addition of 4 mL of the transparent solution S and stirring continued for 1 hour. The resulting solution was transferred to a reactor and hydrothermally reacted at 200°C for 20 hours. After the reactor cooled to room temperature, the solution was repeatedly washed by centrifugation with deionized water and anhydrous ethanol and dried at 60°C for 12 hours to obtain white powdered SnO2 nanorods.

[0075] 2. Preparation of Ni SA / ROV-SnO2 Nanorods

[0076] 100 mg of SnO2 nanorod powder was dissolved in 20 mL of ethanol and ultrasonically dispersed for 30 minutes to obtain a SnO2 nanorod suspension. 1992 μL of nickel chloride solution (0.01 mol / L, 10 mL) was then added to the suspension. After magnetic stirring for 6 hours, the suspension was dried at 60°C for 24 hours. Finally, the material was calcined under a H2 / N2 atmosphere to obtain the 0.03-Ni SA / ROV-SnO2 nanorods.

[0077] 3. Performance test of Ni SA / ROV-SnO2 nanorods prepared in this example for gas sensitive materials

[0078] Take an appropriate amount of the single-atom Ni coupled SnO2 nanorods with rich oxygen vacancies obtained in this example, place them in an agate mortar and grind them evenly, add a certain amount of water, ethylene glycol and propylene glycol and continue grinding until a fine and uniform slurry is obtained, and the slurry is evenly coated on the gold interdigitated electrode on the alumina substrate to form a gas-sensitive test element. After the slurry on the gas-sensitive element is dried on an 80°C hot plate, it is placed in a tubular furnace and calcined and aged for 2 hours at 400°C in an H2 / N2 atmosphere. Then, the gas-sensitive element is placed in a gas-sensitive tester and aged for 24 hours by current flow. A gas-sensitive element of single-atom Ni coupled SnO2 nanorods with rich oxygen vacancies is obtained, and the gas-sensitive performance test is performed.

[0079] After the Ni SA / ROV-SnO2 nanorod samples prepared in Example 1, Example 2, and Example 3 were prepared into gas-sensitive test elements, 20 ppm SO2 gas was tested at different temperatures. Figure 6 As shown, it can be seen that they all exhibit the highest gas-sensitive response to SO2 at 250°C. Among them, the sample prepared in Example 1 has the highest sensitivity to SO2. This is because in the sample of Example 1, Ni exists in the form of a single atom; while in the sample of Example 2, the molar ratio of Ni to SnO2 is 0.01, and the content of Ni single atoms is low, less SO2 can be activated, and the gas-sensitive performance is not high; and in the sample of Example 3, due to the high loading of Ni, it is easy to migrate and agglomerate into nanoparticles during the pyrolysis process. Therefore, the Ni in this sample exists in the form of Ni clusters or Ni particles, resulting in a decrease in gas-sensitive performance. By comparison, it can be seen that when the molar ratio of Ni to SnO2 is 0.02, the material exhibits the best gas-sensitive performance to SO2.

[0080] Comparative Example

[0081] A SnO2 nanorod with abundant oxygen vacancies (ROV-SnO2) is prepared by a method comprising the following steps:

[0082] (1) Accurately weigh 200 mmol of sodium hydroxide (NaOH) and dissolve it in 30 mL of deionized water. After magnetic stirring for 30 minutes, add 10 mmol of anhydrous tin tetrachloride (SnCl4) to the NaOH aqueous solution in an ice-water bath and continue magnetic stirring for 1 hour to form a transparent solution S. Subsequently, weigh 20 mmol of sodium dodecyl sulfate and dissolve it in a mixed solution of 20 mL of heptane solution and 6 mL of n-hexanol solution. Continue magnetic stirring for 30 minutes, then add 4 mL of transparent solution S dropwise and continue stirring for 1 hour. The resulting solution is transferred to a reactor and hydrothermally reacted at 200°C for 20 hours. After the reactor is cooled to room temperature naturally, it is repeatedly centrifuged and washed with deionized water and anhydrous ethanol, and dried at 60°C for 12 hours to obtain white powder SnO2 nanorods.

[0083] (2) 100 mg of SnO2 nanorod powder was dissolved in 20 mL of ethanol and ultrasonically dispersed for 30 min to obtain a SnO2 nanorod suspension. The suspension was then magnetically stirred for 6 h and dried at 60°C for 24 h. Finally, the material was calcined under a H2 / N2 atmosphere to obtain the ROV-SnO2 nanorods.

[0084] (3) Take an appropriate amount of the ROV-SnO2 nanorods obtained in this example and place them in an agate mortar for uniform grinding. Add a certain amount of water, ethylene glycol and propylene glycol and continue grinding until a fine and uniform slurry is obtained. The slurry is evenly coated on a gold interdigitated electrode on an alumina substrate to form a gas-sensitive test element. After the slurry on the gas-sensitive element is dried on an 80°C hot plate, it is placed in a tubular furnace and calcined and aged for 2 hours at 400°C in a H2 / N2 atmosphere. Then, the gas-sensitive element is placed in a gas-sensitive tester and aged for 24 hours by current flow. The ROV-SnO2 nanorod gas-sensitive element is obtained, and the gas-sensitive performance test is performed.

[0085] The XRD pattern of ROV-SnO2 nanorods obtained in this comparative example is shown in Figure 1 The diffraction peak of ROV-SnO2 in the figure is consistent with JCPDS No.77-0448, which is the characteristic diffraction peak of tetragonal rutile SnO2.

[0086] The SEM spectrum of ROV-SnO2 nanorods obtained in this comparative example is shown in Figure 3 B, consistent with the example, the morphology of the ROV-SnO2 material is nanorods with a diameter of about 130 nm and a length of about 5-8 μm.

[0087] The ESR spectrum of ROV-SnO2 nanorods obtained in this comparative example is shown in Figure 4 , consistent with Example 1, the peak with a g value of 2.003 corresponds to the single electron signal of surface oxygen vacancies, indicating that the ROV-SnO2 nanorod sample contains abundant oxygen vacancies.

[0088] After the ROV-SnO2 nanorods obtained in this comparative example were prepared into gas-sensitive test elements, the gas-sensitive response diagrams to 20ppm SO2 at different temperatures were shown in FIG. Figure 6 As can be seen from the figure, the gas-sensitive response to SO2 is the highest at an operating temperature of 250°C. Compared with Example 1, the response value of Ni SA / ROV-SnO2 is higher, which is because the loaded single-atom Ni promotes the adsorption of SO2.

[0089] After the ROV-SnO2 nanorods obtained in this comparative example were prepared into gas-sensitive test elements, the response sensitivity to SO2, NO, H2, NH3, ethanol, acetone, and formaldehyde gases with a concentration of 20 ppm was shown at a working temperature of 250°C. Figure 7 The results compared with those in Example 1 show that the present invention couples single-atom Ni with SnO2 nanorods rich in oxygen vacancies and applies them to gas sensors, which exhibits excellent selectivity for SO2 gas.

[0090] After the ROV-SnO2 nanorods obtained in this comparative example were prepared into a gas-sensitive test element, the response sensitivity to 0.1-40ppm SO2 gas at a working temperature of 250°C was as follows: Figure 8 The results compared with those of Example 1 show that the Ni SA / ROV-SnO2 sensor prepared in the present invention has a lower detection limit for SO2 gas, with the lowest detection limit being 100 ppb.

[0091] After the ROV-SnO2 nanorods obtained in this comparative example were prepared into a gas-sensitive test element, the long-term stability spectrum of 20ppm SO2 gas for 60 days at a working temperature of 250°C was shown in FIG. Figure 9 .

[0092] The results of comparison with Example 1 show that the Ni SA / ROV-SnO2 and ROV-SnO2 sensors prepared in the present invention both have good long-term stability.

Claims

1. A method for preparing single-atom Ni-coupled SnO2 nanorods with abundant oxygen vacancies, characterized in that: The following steps are involved: S1. Preparation of SnO2 nanorods S1-1: Add anhydrous tin tetrachloride to a NaOH aqueous solution, and stir in an ice-water bath for 30 to 90 minutes to obtain a transparent solution S, wherein the molar concentration of the NaOH aqueous solution is 6 to 8 mol / L; S1-2: Prepare a mixture of sodium lauryl sulfate dissolved in heptane solution and n-hexanol solution, stir magnetically for 10 to 60 minutes, then add a certain amount of the above-mentioned transparent solution S, and continue stirring for 0.5 to 3 hours; S1-3: Transfer the obtained solution into a reactor and perform hydrothermal reaction at 150-220°C for 12-24 hours; S1-4: After the reactor is naturally cooled to room temperature, it is repeatedly centrifuged and washed with deionized water and anhydrous ethanol, and dried at 60-80°C for 6-12 hours to obtain white powder SnO2 nanorods; S2. Preparation of Ni SA / ROV-SnO2 nanorods S2-1: Ultrasonic dispersion of the SnO2 nanorods prepared in S1 in anhydrous ethanol to obtain a SnO2 nanorod suspension with a concentration of 0.01 to 1 mol / L; S2-2: Add 0.01 mol / L nickel chloride solution to the SnO2 nanorod suspension and stir magnetically for 3 to 8 hours; S2-3: centrifugation, drying, and finally calcining the material in a H2 / N2 atmosphere at a temperature of 250-500°C for 1-6 hours to obtain the Ni SA / ROV-SnO2 nanorods; The Ni SA / ROV-SnO2 nanorods are used as gas sensitive materials and applied to gas sensors.

2. The method for preparing a single-atom Ni-coupled SnO2 nanorod with abundant oxygen vacancies according to claim 1, characterized in that: In the step S1-1, the molar ratio of NaOH to anhydrous SnCl4 is 10 to 30:

1.

3. The method for preparing a single-atom Ni-coupled SnO2 nanorod with abundant oxygen vacancies according to claim 1, characterized in that: In the step S1-2, the ratio of the transparent solution S, the heptane solution, and the n-hexanol solution is 1:4-5:1-2.

5.

4. The method for preparing a single-atom Ni-coupled SnO2 nanorod with abundant oxygen vacancies according to claim 1, characterized in that: In the step S2-2, the ratio of nickel element to SnO2 is 0.01-0.03:

1.

5. The method for preparing single-atom Ni-coupled SnO2 nanorods with abundant oxygen vacancies according to claim 4, characterized in that: In step S2-2, the molar ratio of nickel element to SnO2 is 0.02:

1.

6. The method for preparing single-atom Ni-coupled SnO2 nanorods with abundant oxygen vacancies according to claim 1, characterized in that: The calcination temperature in step S2-3 is 300° C. and the calcination time is 4 hours.

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