A preparation method and application of a plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide

Abstract

The present application relates to a kind of preparation method and application of plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide, belong to gas sensitive material technical field.The present application is added oxalic acid in aqueous solution containing nickel nitrate and ferric nitrate, is stirred uniformly by magnetic force, iron-doped nickel oxalate precursor is prepared using hydrothermal reaction in the stainless steel high-pressure reaction kettle lined with Teflon, and after centrifugal washing, vacuum drying, the plate-shaped iron-doped nickel oxide material is obtained by calcining the dried precursor material.The plate-shaped iron-doped nickel oxide material is coated on the surface of typical ceramic tube, and ceramic tube gas sensor is made, and the test of hydrogen sulfide sensitive performance is realized.The preparation method of the present application is simple and controllable, and the obtained material has good hydrogen sulfide sensitive performance, can realize the rapid sensitive continuous detection of hydrogen sulfide, one of the decomposition products of sulfur hexafluoride in industrial production process, improve the anti-poisoning ability to hydrogen sulfide, and has wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of gas-sensitive materials technology, specifically relating to a method for preparing and applying a plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide. Background Technology

[0002] SF6 gas insulation equipment is widely used in power systems. However, during equipment operation, phenomena such as arcing can occur, causing SF6 gas decomposition and severely affecting the normal operation of the system. As one of the characteristic components of SF6 gas, the detection of hydrogen sulfide (H2S) is of great significance for judging the decomposition status of SF6 and the severity of internal equipment faults.

[0003] Traditional H2S detection methods, such as gas chromatography, iodometric titration, and optical detection, rely on large instruments, are cumbersome to operate, and are time-consuming, failing to meet the current demands for integrated, intelligent, portable, and miniaturized sensors. With the development of technologies such as artificial intelligence and the Internet of Things, and the increasing maturity of microelectromechanical systems (MEMS) technology, gas sensors are gradually developing towards high sensitivity, low power consumption, miniaturization, and intelligence, creating a broad market demand. Gas sensors can respond to the chemical properties of external gases and convert them into detectable electrical signals, enabling accurate detection of specific gases and their concentrations. Semiconductor sensors, in particular, feature high gas sensitivity, long-term stability, and strong anti-interference capabilities. Resistive semiconductor gas sensors, using metal oxides as the key sensing material, are widely used due to their low cost, high response, long lifespan, and simple circuit structure. Metal oxide semiconductor gas sensors operate based on the principle that during contact between the sensing material and the target gas in the surrounding environment, the reaction of oxygen anions on the material surface with the target gas causes the migration of charge carriers, resulting in a change in the sensor's resistance. The main ways to enhance the sensitivity of H2S gas-sensitive materials include adjusting the material morphology and size, modifying with noble metals, constructing heterojunctions, doping modification, and combining with other materials. Nickel oxide is a p-type semiconductor with a band gap of 3.6-4.0 eV, and its common crystal structure is cubic. Due to its high thermal stability and special magnetic, chemical, and optical properties, nickel oxide has wide applications in photocatalysis, gas sensors, supercapacitors, and other fields, and is also considered one of the best candidate materials for H2S detection.

[0004] Although significant progress has been made in using nickel oxide as a gas-sensitive material for H2S, a survey of the current research status at home and abroad revealed that there are still many problems. For example, the prepared nickel oxide-based materials have high operating temperatures, slow response recovery, poor selectivity, poor long-term stability, and poor resistance to poisoning, which limit their development and application in industrial production or as one of the decomposition products of sulfur hexafluoride.

[0005] The invention disclosed in CN109264796A is a rod-shaped NiO / α-Fe2O3 composite gas-sensitive material, its preparation method and application. However, this material is a rod-shaped NiO / α-Fe2O3 composite material, which is used for the detection of acetone gas. Summary of the Invention

[0006] To address the aforementioned issues, this application utilizes the thermal reaction of oxalic acid, nickel salt, and iron salt to generate an iron-doped nickel oxalate precursor, which is then calcined to prepare a plate-like iron-doped nickel oxide material with abundant surface cracks, high specific surface area, and resistance to hydrogen sulfide.

[0007] The technical solution adopted in this invention is:

[0008] A method for preparing plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide includes the following steps:

[0009] 1) Add Ni(NO3)2·6H2O and Fe(NO3)3·9H2O to deionized water and dissolve by magnetic stirring;

[0010] 2) Add C2H2O4·2H2O to the mixed solution obtained in step 1), stir magnetically for 30 minutes to form a light green solution;

[0011] 3) Transfer the light green solution obtained in step 2) into a stainless steel high-pressure reactor lined with Teflon, and place the reactor in a forced-air drying oven for heating and reaction.

[0012] 4) After the reaction is complete, wait for the reactor to cool to room temperature, then centrifuge and wash the iron-doped nickel oxalate precursor in the reactor.

[0013] 5) Place the centrifuged and washed iron-doped nickel oxalate precursor into a constant temperature vacuum drying oven to dry the sample completely.

[0014] 6) The dried iron-doped nickel oxalate precursor was placed in a muffle furnace and calcined in air to obtain plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide.

[0015] Furthermore, in the above preparation method, in step 1), the molar ratio of Fe(NO3)3·9H2O and Ni(NO3)2·6H2O is 0 to 1:10.

[0016] Furthermore, in the above preparation method, in step 2), the molar ratio of C2H2O4·2H2O and Ni(NO3)2·6H2O is 1 to 3:1.

[0017] Furthermore, in the above preparation method, in step 3), the heating reaction temperature is 100–180°C, and the reaction time is 8–24 h.

[0018] Furthermore, in the above preparation method, in step 4), the centrifugation speed is 3000-5000 r / min, the number of centrifugation washings is 5-7 times, the first 3-4 times are washed with deionized water, and the last 2-3 times are washed with anhydrous ethanol.

[0019] Furthermore, in the above preparation method, in step 5), the temperature of the constant temperature vacuum drying oven is set to 60°C, the vacuum degree is maintained at 600-800 Pa, and the drying time is controlled at 10-14 h.

[0020] Furthermore, in the above preparation method, step 6), the calcination conditions are to raise the temperature to 400-500℃ at a rate of 2℃ / min and hold it for 1-3 hours.

[0021] Application of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide prepared by any of the above preparation methods in the testing of hydrogen sulfide sensitivity.

[0022] Furthermore, the above application method includes the following steps:

[0023] 1) Add 0.01-0.03g of plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide into a mortar, add 0.05-0.15mL of deionized water dropwise, mix and grind until a uniform paste is formed;

[0024] 2) Use a fine brush to apply the prepared slurry from step 1) evenly to the surface of the ceramic tube. After coating, the gold electrodes on the surface of the ceramic tube are not exposed. The coated ceramic tube element is then subjected to aging treatment to obtain a ceramic tube gas sensor.

[0025] 3) Insert the ceramic tube gas sensor into the test base connected to the digital multimeter to perform a gas-sensing performance test.

[0026] Furthermore, in the above application, the aging treatment conditions are aging at 300°C for 2-3 days.

[0027] This invention provides a high specific area plate-structured iron-doped nickel oxide material. Gas sensors made from this material are used for detecting hydrogen sulfide, one of the decomposition products of sulfur hexafluoride, during production processes. These sensors exhibit a sensitive response to hydrogen sulfide, rapid response recovery, and resistance to hydrogen sulfide poisoning. The preparation method and the resulting material of this invention have the following advantages and beneficial effects:

[0028] 1. The high specific area plate-shaped iron-doped nickel oxide gas-sensitive material provided by the present invention exhibits a rapid, sensitive, and continuous response to hydrogen sulfide, achieving a high-efficiency response to hydrogen sulfide and possessing good stability.

[0029] 2. The plate-like iron-doped nickel oxide material provided by this invention is a plate structure composed of particles with an average diameter of 50 nm, resulting in a specific surface area as high as 395.46 m². 2 / g, iron-doped nickel oxide materials can provide more adsorption sites, thereby improving the adsorption-desorption and response to hydrogen sulfide.

[0030] 3. The preparation method of the present invention is simple to operate, easy to control, and uses common chemical reagents, which are inexpensive and can promote the practical application of hydrogen sulfide detection and realize large-scale production. Attached Figure Description

[0031] Figure 1 The image shows the X-ray diffraction pattern of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2.

[0032] Figure 2 The images shown are scanning electron microscope (SEM) images of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2. In Figure a, a is a low-magnification (40000×, 2μm) SEM image, and b is a high-magnification (160000×, 500nm) SEM image of the corresponding region in Figure a.

[0033] Figure 3 The images shown are transmission electron microscope (TEM) images of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2. In the images, a is a low-magnification (1 μm) TEM image, b is a magnified (200 nm) image of the corresponding region in a, c is a high-magnification TEM image of b (5 nm), d is the corresponding Fourier transform image in c, and e is the diffraction ring after selected area electron diffraction of the material.

[0034] Figure 4 This is an energy dispersive X-ray image of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2.

[0035] Figure 5 The image shows the X-ray photoelectron spectrum of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2.

[0036] Figure 6 The N2 adsorption / desorption curves of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 are shown.

[0037] Figure 7 The graph shows the sensitivity characteristics of the plate-shaped iron-doped nickel oxide material obtained in Example 2 to different concentrations of hydrogen sulfide.

[0038] Figure 8 The image shows the response recovery time of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 to 100 ppm hydrogen sulfide.

[0039] Figure 9 This is a series of response diagrams of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 to 100 ppm hydrogen sulfide.

[0040] Figure 10 The bar chart shows the response of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 to 100 ppm of different gases. Detailed Implementation

[0041] Example 1

[0042] 1) Accurately weigh 2 mmol Ni(NO3)2·6H2O and 0.048 g Fe(NO3)3·9H2O, pour them into a beaker containing 35 mL of deionized water, and stir magnetically to dissolve them;

[0043] 2) Weigh 0.50g of C2H2O4·2H2O and pour it into a beaker containing a mixed solution of Ni(NO3)2·6H2O and Fe(NO3)3·9H2O. Stir magnetically for 30 minutes to form a light green solution.

[0044] 3) Transfer the light green solution in the beaker to a 50mL stainless steel high-pressure reactor lined with Teflon. Place the reactor in a forced-air drying oven and heat it to react at a temperature of 120℃ for 12 hours.

[0045] 4) After the reaction is completed, wait for the reactor to cool to room temperature, then centrifuge and wash the iron-doped nickel oxalate precursor in the reactor. The centrifugation speed is 4000 r / min, and the number of centrifugation and washing is 6 times. The first 3 times are washed with deionized water, and the last 3 times are washed with anhydrous ethanol.

[0046] 5) Place the iron-doped nickel oxalate precursor after centrifugation and washing into a constant temperature vacuum drying oven to dry the sample completely. The temperature of the constant temperature vacuum drying oven is set to 60℃, the vacuum degree is maintained at 800Pa, and the drying time is controlled at 12h.

[0047] 6) The dried iron-doped nickel oxalate precursor was placed in a muffle furnace and heated to 450°C at 2°C / min in an air atmosphere. The temperature was held for 2 hours to obtain plate-shaped iron-doped nickel oxide material that is sensitive to hydrogen sulfide.

[0048] 7) Add 0.02g of plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide to a mortar, add 0.10mL of deionized water dropwise, mix and grind until a uniform paste is formed;

[0049] 8) Use a fine brush to dip into the prepared slurry and evenly coat it on the surface of the ceramic tube. After coating, the gold electrode on the surface of the ceramic tube is not exposed. The ceramic tube is aged at 300℃ for 3 days to obtain the ceramic tube gas sensor.

[0050] 9) Insert the ceramic tube gas sensor into the test base connected to the digital multimeter to perform a gas-sensing performance test.

[0051] Example 2

[0052] 1) Accurately weigh 2 mmol Ni(NO3)2·6H2O and 0.065 g Fe(NO3)3·9H2O, pour them into a beaker containing 35 mL of deionized water, and stir magnetically to dissolve them;

[0053] 2) Weigh 0.50g of C2H2O4·2H2O and pour it into a beaker containing a mixed solution of Ni(NO3)2·6H2O and Fe(NO3)3·9H2O. Stir magnetically for 30 minutes to form a light green solution.

[0054] 3) Transfer the light green solution in the beaker to a 50mL stainless steel high-pressure reactor lined with Teflon. Place the reactor in a forced-air drying oven and heat it to react at a temperature of 120℃ for 12 hours.

[0055] 4) After the reaction is completed, wait for the reactor to cool to room temperature, then centrifuge and wash the iron-doped nickel oxalate precursor in the reactor. The centrifugation speed is 4000 r / min, and the number of centrifugation and washing is 6 times. The first 3 times are washed with deionized water, and the last 3 times are washed with anhydrous ethanol.

[0056] 5) Place the iron-doped nickel oxalate precursor after centrifugation and washing into a constant temperature vacuum drying oven to dry the sample completely. The temperature of the constant temperature vacuum drying oven is set to 60℃, the vacuum degree is maintained at 800Pa, and the drying time is controlled at 12h.

[0057] 6) The dried iron-doped nickel oxalate precursor was placed in a muffle furnace and heated to 450°C at 2°C / min in an air atmosphere. The temperature was held for 2 hours to obtain plate-shaped iron-doped nickel oxide material that is sensitive to hydrogen sulfide.

[0058] 7) Add 0.02g of plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide to a mortar, add 0.10mL of deionized water dropwise, mix and grind until a uniform paste is formed;

[0059] 8) Use a fine brush to dip into the prepared slurry and evenly coat it on the surface of the ceramic tube. After coating, the gold electrode on the surface of the ceramic tube is not exposed. The ceramic tube is aged at 300℃ for 3 days to obtain the ceramic tube gas sensor.

[0060] 9) Insert the ceramic tube gas sensor into the test base connected to the digital multimeter to perform a gas-sensing performance test.

[0061] Example 3

[0062] 1) Accurately weigh 2 mmol Ni(NO3)2·6H2O and 0.08 g Fe(NO3)3·9H2O, pour them into a beaker containing 35 mL of deionized water, and stir magnetically to dissolve them;

[0063] 2) Weigh 0.50g of C2H2O4·2H2O and pour it into a beaker containing a mixed solution of Ni(NO3)2·6H2O and Fe(NO3)3·9H2O. Stir magnetically for 30 minutes to form a light green solution.

[0064] 3) Transfer the light green solution in the beaker to a 50mL stainless steel high-pressure reactor lined with Teflon. Place the reactor in a forced-air drying oven and heat it to react at a temperature of 140℃ for 16 hours.

[0065] 4) After the reaction is completed, wait for the reactor to cool to room temperature, then centrifuge and wash the iron-doped nickel oxalate precursor in the reactor. The centrifugation speed is 4000 r / min, and the number of centrifugation and washing is 6 times. The first 3 times are washed with deionized water, and the last 3 times are washed with anhydrous ethanol.

[0066] 5) Place the iron-doped nickel oxalate precursor after centrifugation and washing into a constant temperature vacuum drying oven to dry the sample completely. The temperature of the constant temperature vacuum drying oven is set to 60℃, the vacuum degree is maintained at 600Pa, and the drying time is controlled at 12h.

[0067] 6) The dried iron-doped nickel oxalate precursor was placed in a muffle furnace and heated to 500°C at 2°C / min in an air atmosphere. The temperature was held for 2 hours to obtain plate-shaped iron-doped nickel oxide material that is sensitive to hydrogen sulfide.

[0068] 7) Add 0.03g of plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide to a mortar, add 0.15mL of deionized water dropwise, mix and grind until a uniform paste is formed;

[0069] 8) Use a fine brush to dip into the prepared slurry and evenly coat it on the surface of the ceramic tube. After coating, the gold electrode on the surface of the ceramic tube is not exposed. The ceramic tube is aged at 300℃ for 3 days to obtain the ceramic tube gas sensor.

[0070] 9) Insert the ceramic tube gas sensor into the test base connected to the digital multimeter to perform a gas-sensing performance test.

[0071] Figure 1The X-ray diffraction pattern of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 shows that the diffraction peaks of the precursor correspond one-to-one with the diffraction peaks in NiC2O4·2H2O (JCPDS NO.14-0742). Strong diffraction peaks (111), (200), (220), (311), and (222) are observed in both the nickel oxide and iron-doped nickel oxide spectra in the figure, and correspond well with NiO (JCPDS NO.47-1049). All peaks in the figure are sharp and clear, without any other disordered peaks, indicating that the samples have high purity and crystallinity. 2+ ionic radius with Fe 3+ ionic radius The structures are almost identical, so Fe can be easily incorporated into the NiO lattice without forming a phase of Fe-related material.

[0072] Figure 2 The image shown is a scanning electron microscope image of the plate-like iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2. It indicates that the material has a plate-like structure composed of numerous stacked nanoparticles. The material surface is slightly rough and contains cracks. The rough surface increases the opportunity for H2S gas to contact the material surface, while the cracks facilitate the diffusion of gas into the deeper layers of the material, promoting the reaction of adsorbed oxygen ions and H2S gas, and improving the gas-sensing performance of the material.

[0073] Figure 3 The transmission electron microscope (TEM) image of the plate-like iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 shows that the material is mainly composed of non-uniform nanoparticles with an average diameter of about 50 nm. In the corresponding high-resolution TEM image c, clear lattice fringes are observed with lattice spacings of 0.24 nm and 0.21 nm, which match the (200) and (111) planes of NiO, respectively. No Fe-related phase crystal planes were observed. The Fast Fourier Transform (FFT) mode of the corresponding region in the image is shown in d, further confirming the existence of the (111) and (200) lattice planes. Selected area electron diffraction (SAED) characterization of the sample was performed. Figure e shows the SAED pattern of iron-doped NiO, which is a ring-shaped pattern, indicating the polycrystalline nature of the material. The fringe spacing of the crystal planes was measured to correspond to the (111), (200), (220), (311), and (222) crystal planes of the cubic phase NiO.

[0074] Figure 4The energy dispersive X-ray image of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 shows a weak Fe signal, mainly due to the low doping content. The combined results of X-ray diffraction, transmission electron microscopy, and selected area electron diffraction indicate that iron has been doped into NiO.

[0075] Figure 5 The image shows the X-ray photoelectron spectrum of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2. The full-range XPS spectrum shows that Ni, O and Fe are the main elements in the iron-doped nickel oxide material. The C element peak in the curve represents the correction peak, and no other impurity peaks appear.

[0076] Figure 6 The image shows the N2 adsorption / desorption curves of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2, with a BET specific surface area of ​​395.46 m². 2 / g, the sample exhibits a type IV isotherm. The plate-like structure with a large specific surface area provides more reaction sites for the adsorption process, which can improve the gas sensing performance of the material.

[0077] Figure 7 To illustrate the sensitivity of the plate-shaped iron-doped nickel oxide material to different concentrations of hydrogen sulfide obtained in Example 2, the continuous cyclic response curves of the gas sensor made from the iron-doped nickel oxide material to 1-200 ppm H2S show that the material exhibits excellent gas-sensing performance. Once exposed to different concentrations of H2S, the sensor provides rapid and significant responses, and the response increases accordingly with increasing gas concentration from 1 to 200 ppm, while the response / recovery time decreases. Under low-high-low concentration cyclic testing, the material's response to the same concentration is almost identical; the slight difference in resistance change is mainly due to differences in baseline resistance, demonstrating the material's good reproducibility.

[0078] Figure 8 The response and recovery time of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 to 100 ppm hydrogen sulfide is shown. A fast response is crucial for rapid detection in gas sensors. The sensor's response time to 100 ppm H2S is 16 s, and its recovery time is 26 s, both superior to most semiconductor sensors. The sensor's excellent response and recovery performance is due to its large specific surface area, which provides more active sites for rapid gas adsorption.

[0079] Figure 9The figure shows the repeated responses of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 to 100 ppm hydrogen sulfide. The sensor was used to detect 100 ppm H2S gas, and 10 gas injection / exhaust cycles were performed to evaluate its repeatability. The small change in baseline resistance is negligible, demonstrating the good repeatability of the sensor in detecting H2S gas.

[0080] Figure 10 This is a bar chart showing the response of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 to different gases at 100 ppm. To examine the material's selectivity for H2S during detection, common gases from industrial production processes and other products of sulfur hexafluoride decomposition, such as SO2, were selected for selectivity testing. Figure 10 As shown, for different gases at 100 ppm, the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide obtained in Example 2 only showed a higher response to H2S, exhibiting good selectivity.

Claims

1. The application of a plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide in the testing of its sensitivity to hydrogen sulfide, characterized in that, The preparation method of the plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide includes the following steps: 1) Add Ni(NO3)2·6H2O and Fe(NO3)3·9H2O to deionized water and stir magnetically to dissolve them; 2) Add C2H2O4·2H2O to the mixed solution obtained in step 1), stir magnetically for 30 min, and a light green solution is formed; 3) Transfer the light green solution obtained in step 2) into a stainless steel high-pressure reactor lined with Teflon, and place the reactor in a forced-air drying oven for heating and reaction; 4) After the reaction is complete, wait for the reactor to cool to room temperature, then centrifuge and wash the iron-doped nickel oxalate precursor in the reactor. 5) Place the centrifuged and washed iron-doped nickel oxalate precursor into a constant temperature vacuum drying oven to dry the sample completely. 6) The dried iron-doped nickel oxalate precursor was placed in a muffle furnace and calcined in air to obtain plate-shaped iron-doped nickel oxide material that is sensitive to hydrogen sulfide.

2. The application according to claim 1, characterized in that, In step 1), the molar ratio of Fe(NO3)3·9H2O and Ni(NO3)2·6H2O is 0~1:

10.

3. The application according to claim 1, characterized in that, In step 2), the molar ratio of C2H2O4·2H2O and Ni(NO3)2·6H2O is 1~3:

1.

4. The application according to claim 1, characterized in that, In step 3), the heating reaction temperature is 100~180℃ and the reaction time is 8~24 h.

5. The application according to claim 1, characterized in that, In step 4), the centrifugation speed is 3000~5000 r / min, and the number of centrifugation washing times is 5~7 times. The first 3~4 times are washed with deionized water, and the last 2~3 times are washed with anhydrous ethanol.

6. The application according to claim 1, characterized in that, In step 5), the temperature of the constant temperature vacuum drying oven is set to 60°C, the vacuum degree is maintained at 600~800 Pa, and the drying time is controlled at 10~14 h.

7. The application according to claim 1, characterized in that, In step 6), the calcination conditions are to raise the temperature to 400~500℃ at a rate of 2℃ / min and hold it for 1~3 h.

8. The application according to claim 1, characterized in that, The method includes the following steps: 1) Add 0.01~0.03 g of plate-shaped iron-doped nickel oxide material sensitive to hydrogen sulfide into a mortar, add 0.05~0.15 mL of deionized water dropwise, mix and grind until a uniform paste is formed; 2) Use a fine brush to apply the prepared slurry from step 1) evenly to the surface of the ceramic tube. After coating, the gold electrodes on the surface of the ceramic tube are not exposed. The coated ceramic tube element is then subjected to aging treatment to obtain a ceramic tube gas sensor. 3) Insert the ceramic tube gas sensor into the test base connected to the digital multimeter to perform a gas-sensing performance test.

9. The application according to claim 8, characterized in that, The aging process is performed at 300°C for 2-3 days.

Images