Preparation and application of ammonia gas sensor based on iron-doped nickel oxide modified molybdenum oxide
By preparing Fe-Ni2O3@MoO3, a composite material with iron-doped nickel oxide modified molybdenum oxide, the problem of high temperature and high cost of existing ammonia sensors is solved, and fast and accurate ammonia detection is achieved at room temperature, which is suitable for safety and health monitoring in multiple fields.
Patent Information
- Application Number
- CN202510385981.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-30
- Publication Date
- 2025-07-08
AI Technical Summary
The existing ammonia sensors have high operating temperatures, resulting in high power consumption and safety risks, and are costly, making it difficult to achieve fast and accurate ammonia detection at room temperature.
Fe-Ni2O3@MoO3, a composite material of iron-doped nickel oxide modified molybdenum oxide was prepared by hydrothermal method and high-temperature calcination, and coated on the surface of Al2O3 ceramic tube to form an ammonia sensor.
It realizes rapid response and recovery to ammonia at room temperature, with a sensitivity of up to 2.2, a response time of 32s to 20ppm NH3, a recovery time of 31s, and a detection limit of 500ppb. It has good selectivity and long-term stability, and is suitable for industrial safety, agricultural environmental monitoring, food processing and water treatment.
Smart Images
Figure CN120271370A_ABST
Abstract
Description
Technical Field:
[0001] The present invention belongs to the technical field of layered heterostructure composite gas sensors and environmental monitoring, and specifically relates to the preparation and application of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide, which can be applied to the detection of ammonia concentration in industrial safety, agricultural environmental monitoring, food processing quality control, and water treatment processes to ensure the safety and health of the production and living environment. Background Art:
[0002] With the rapid development of modern industry and agriculture, the emissions of ammonia have increased significantly. Ammonia occupies a very important position in industry and has a wide range of uses, playing a key role in many fields such as fertilizer manufacturing, chemical production, refrigeration, and energy. As a common toxic gas pollutant, when the ammonia concentration in the environment is too high, it will affect people's physical health. However, the existing commercial sensors for ammonia detection have relatively high operating temperatures and generally have the problem of high cost. The high operating temperature not only causes high power consumption but also may lead to safety risks. Therefore, there is an urgent need for ammonia detection technology at room temperature.
[0003] Currently, various materials for detecting ammonia have been studied, such as metal oxides, conductive polymers, and carbon-based materials. Metal oxides such as zinc oxide, copper oxide, and tin oxide are often used for ammonia detection due to their good responses. For example, I. Lee et al. conducted gas-sensing tests on LaCoO3, A. Bhardwaj et al. on SnO2, and W. W. Meng et al. on TiO2, and these materials all showed good gas-sensing properties, but the required operating temperatures are much higher than room temperature. Most similar metal oxide gas-sensing materials cannot detect gases at room temperature, but being at high temperatures for a long time will shorten the device life and increase additional power consumption, which is not conducive to the long-term use of the device and will also pose a huge safety risk. Therefore, it is necessary to develop a sensor that can detect ammonia at low temperatures.
[0004] Therefore, accurately and real-time monitoring the ammonia concentration is of great significance, and ammonia sensors, as a key gas detection device, have broad application prospects.
[0005] The resistive ammonia sensor has the advantages of low price, simple operation and high sensitivity, and is the most common gas-sensitive sensor for detecting the change of ammonia concentration. The core part of the resistive ammonia sensor is the gas-sensitive semiconductor material, which can adsorb ammonia and undergo a chemical reaction, and convert this reaction into a resistance signal. The performance of the gas-sensitive material directly determines the performance of the ammonia sensor, such as sensitivity, selectivity and stability. At present, the commonly used sensor materials for ammonia sensors mainly include metal oxides, semiconductor materials, organic functional materials and layered structure composite materials, etc. The layered structure composite material has good chemical and thermal stability. For example, molybdenum disulfide (MoS2) and layered double hydroxide (LDH) are used. LDH forms a core-shell structure or an intercalated structure between layers on the surface of MoS2 through chemical bonds or physical coating. The resistivity of this material will change significantly in the presence of ammonia. In addition, different structures and morphologies of the material may also lead to different performances of the sensor. Surface functionalization design is also an important way to improve the performance of the ammonia sensor. For example, combining nanotechnology and functionalized surface design can improve the performance of the ammonia sensor, realize the accurate monitoring of ammonia concentration, and provide effective protection for environmental protection and human health. The composite material based on iron-doped nickel oxide modified molybdenum oxide of the present invention has high gas-sensing performance, good sensitivity to ammonia, and can quickly and accurately detect the change of the concentration of the target gas. The gas-sensitive material has low production cost, good stability and high sensitivity, and has broad application prospects in the fields of ammonia sensors and the like. Summary of the Invention:
[0006] The present invention belongs to the technical field of nanocomposite gas sensors and environmental monitoring, and specifically relates to the preparation and application of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide. The present invention develops a high-performance NH3 gas sensor with fast response to NH3 in the atmospheric environment at room temperature. The sensitivity of the sensor to 20 ppm NH3 is as high as 2.2, the response time is 32 s, and the recovery time is 31 s. In addition, the sensor also exhibits good selectivity and long-term stability. The lowest detection limit of the sensor is about 500 ppb. It can be widely used in the detection of a wide range of NH3 concentrations from 1 ppm to 500 ppm in industrial safety, agricultural environmental monitoring, food processing quality control and water treatment processes, ensuring the safety and health of the production and living environment.
[0007] A Fe-doped nickel oxide modified molybdenum trioxide composite material of the present invention has a chemical formula of Fe-Ni2O3@MoO3. Dissolve ferric chloride hexahydrate: nickel chloride hexahydrate (zinc nitrate hexahydrate) = 3 in pure water according to this molar mass ratio, add sodium hydroxide solution until the pH is 10, stir to form a small amount of precipitate, add molybdenum disulfide according to a certain molar ratio, heat in a water bath at 70 °C for 6 hours, take out and stir, pour off the supernatant, add pure water, centrifuge, wash with water until neutral - use a pH test reagent, dry at 80 °C, and grind to obtain the Fe-doped nickel oxide modified molybdenum trioxide composite material, Fe-Ni2O3@MoO3.
[0008] The present invention synthesizes MoS2 by a hydrothermal method, grinds the synthesized Fe-doped nickel oxide modified molybdenum trioxide composite material, then coats the material on the surface of an Al2O3 ceramic tube, ages it on the ceramic tube, and welds the base to obtain an ammonia sensor. Since this material has excellent adsorption performance as a gas-sensitive material, its selectivity and stability are also relatively ideal, and it has broad application prospects.
[0009] The preparation and application of an ammonia sensor based on Fe-doped nickel oxide modified molybdenum trioxide of the present invention are as follows:
[0010] A. Dissolve 1.7 g of sodium molybdate dihydrate and 2.3 g of thiourea in 30 ml of pure water, ultrasonically dissolve, put it into a reaction kettle, heat at 180 - 240 °C for 24 hours, dry, and grind to obtain MoS2.
[0011] B. Dissolve ferric chloride hexahydrate: nickel chloride hexahydrate = 3 in pure water according to this molar mass ratio, add sodium hydroxide solution until the pH is 10, stir to form a small amount of precipitate, add molybdenum disulfide according to a certain molar ratio, heat in a water bath for 6 hours, take out and stir, pour off the supernatant, add pure water, centrifuge, wash with water until neutral - use a pH test reagent, dry at 80 °C, sinter at 300 - 500 °C, and grind to obtain the Fe-doped nickel oxide modified molybdenum trioxide composite material.
[0012] C. Finally, grind the Fe-doped nickel oxide modified molybdenum trioxide composite material, then coat the material on the surface of an Al2O3 ceramic tube, heat at a high temperature for 5 h, age and sinter at 8 h, take out, add a heating wire, and weld the base to obtain the ammonia sensor.
[0013] The design idea of the present invention is as follows: At present, the mainstream ammonia-sensitive materials in ammonia sensors all face problems such as long response time and poor selectivity. Although doping modification with noble metals (Au, Pt), rare earths (La, Ce, Pr), etc. can improve the sensing performance of gas-sensitive materials to a certain extent, it still cannot meet the development requirements of low-cost commercialization. Molybdenum disulfide, combined with the advantages of the layered structure of hydrotalcite, not only greatly improves the hole-electron combination, but also increases the adsorption area and the number of active sites. The performance of the ammonia sensor is improved, and it has broad development prospects.
[0014] The obtained materials were characterized, and the performance test results of the ammonia sensor are shown in Figure 1-11 .
[0015] As can be seen from Figure 1 Figure, it is the scanning electron microscope (SEM) characterization diagram of Fe-Ni2O3@MoO3 obtained in step (2) of Example 1, which is a uniformly grown layered structure based on iron-doped nickel oxide modified molybdenum oxide.
[0016] As can be seen from Figure 2 Figure, it is the X-ray diffraction (XRD) characterization diagram of Fe-Ni2O3@MoO3 obtained in step (2) of Example 1.
[0017] As can be seen from Figure 3 Figure, it is the X-ray photoelectron spectroscopy (XPS) characterization diagram of Fe-Ni2O3@MoO3 obtained in step (2) of Example 1.
[0018] Figure 4 As can be seen from Figure, it is the change curve of the response value of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide obtained in step (5) of Example 1 with respect to ammonia at a certain concentration as the temperature changes. It can be seen from the figure that the optimal operating temperature is 250 °C.
[0019] Figure 5 As can be seen from Figure, it is the change curve of the response value of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide obtained in step (5) of Example 1 with respect to different concentrations of ammonia.
[0020] Figure 6 Figure is the fitting of the change curve of the response value of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide obtained in step (5) of Example 1 with respect to different concentrations of ammonia. It is calculated that the lowest detection limit of this sensor is about 500 ppb. It can be widely used for the detection of NH3 concentration in the wide range from 1 ppm to 500 ppm in industrial safety, agricultural environment monitoring, food processing quality control, and water treatment processes.
[0021] Figure 7It is the repeatability test curve of the response and recovery of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide obtained in step (5) of Example 1. During the continuous injection of 20 ppm NH3, it can be seen from the same dynamic response curve that the response is stable for four consecutive times and the recovery is good, proving the repeatability of the sensor.
[0022] Figure 8 It is the response and recovery time curve of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide obtained in step (5) of Example 1. It can be seen from the figure that the sensor has a fast response and recovery time, and the recovery performance is good. The response time is 32 s and the recovery time is 31 s.
[0023] Figure 9 It is the response degree of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide obtained in step (5) of Example 1 to different gases. It can be seen from the figure that it has high selectivity.
[0024] Figure 10 It is the stability curve of the response degree of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide obtained in step (5) of Example 1 to 20 ppm within one month. It can be seen from the figure that a high response value is still maintained after one month, indicating that the material has long-term stability. This ammonia sensor has broad development prospects and can be used in actual production and life.
[0025] Figure 11 It is the application diagram of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide obtained in step (5) of Example 1. It can be seen from the figure the application scenario and process of the device.
[0026] In summary, compared with other two-dimensional materials, the prepared iron-doped nickel oxide modified molybdenum oxide material has more active sites and a larger surface area. After calcination, nickel-iron oxide is determined to be generated through SEM characterization. By adjusting the nickel-iron ratio in the reaction, a gas-sensitive material with good ammonia sensing performance (fast response, high selectivity, and strong stability) is generated.
[0027] Advantages of the present invention: A layered heterostructure composite material Fe-Ni2O3@MoO3 is prepared by using simple and easy-to-operate hydrothermal method and high-temperature calcination methods. Since (Fe-Ni2O3@MoO3) has more active sites, ammonia can be adsorbed strongly. This method is simple, fast, and low-cost, and the obtained material has good structure and strong adsorption. The sensor has a sensitivity as high as 2.2 to 20 ppm NH3, a response time of 32 s, and a recovery time of 31 s. In addition, the sensor also exhibits good selectivity and long-term stability, and the lowest detection limit of the sensor is about 500 ppb. It can be widely used in the detection of NH3 concentration in a wide range from 1 ppm to 500 ppm in industrial safety, agricultural environment monitoring, food processing quality control, and water treatment processes to ensure the safety and health of production and living environments. Description of the drawings:
[0028] Figure 1 It is the scanning electron microscope (SEM) characterization of the iron-doped nickel oxide modified molybdenum oxide composite material in Example 1.
[0029] Figure 2 It is the X-ray diffraction (XRD) characterization of the iron-doped nickel oxide modified molybdenum oxide composite material in Example 1.
[0030] Figure 3 It is the X-ray photoelectron spectroscopy (XPS) characterization of the iron-doped nickel oxide modified molybdenum oxide composite material in Example 1.
[0031] Figure 4 It is the response curve graph of the gas-sensitive element in Example 1 to a certain concentration of ammonia at different working temperatures.
[0032] Figure 5 It is the dynamic response curve graph of the gas-sensitive element in Example 1 to different concentrations of ammonia at the optimal working temperature.
[0033] Figure 6 It is the linear fitting graph of the relationship between ammonia concentration and response value of the gas-sensitive element in Example 1 at the optimal working temperature.
[0034] Figure 7 It is the repeatability curve graph of the gas-sensitive element in Example 1 to 20 ppm ammonia at the optimal working temperature.
[0035] Figure 8 It is the response and recovery time curve graph of the gas-sensitive element in Example 1 to 20 ppm ammonia at the optimal working temperature.
[0036] Figure 9 It is the selectivity graph of the gas-sensitive element in Example 1 to different kinds of gases at the optimal working temperature.
[0037] Figure 10 It is a graph of the long-term stability test of the gas sensor element in Example 1 within one month at the optimal operating temperature.
[0038] Figure 11 It is a schematic diagram of the application of the gas sensor element in Example 1 at the optimal operating temperature. Specific implementation method:
[0039] To make the technical solutions, advantages, and objectives of the present invention clearer and more complete, the following further explains with specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments in this application, the technical features involved in various embodiments of the present invention described should all fall within the scope of protection of this application.
[0040] In the following embodiments, the test methods are all conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial channels unless otherwise specified.
[0041] Example 1:
[0042] The preparation and application of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide include the following steps:
[0043] (1) 1.7 g of sodium molybdate dihydrate and 2.3 g of thiourea are mixed and dissolved in 30 ml of pure water, ultrasonically dissolved, placed in a reaction kettle, heated at 180 - 240 °C for 24 hours, dried, and ground to obtain MoS2.
[0044] (2) Dissolve ferric chloride hexahydrate: nickel chloride hexahydrate = 3 according to this molar mass ratio in pure water, add sodium hydroxide solution until the pH is 10, stir until a small amount of precipitate is formed, add molybdenum disulfide according to a certain molar ratio, heat in a water bath for 6 hours, take out and stir, pour off the supernatant, add pure water, centrifuge, wash with water until neutral - using a pH test reagent, dry at 80 °C, calcine and anneal at 300 - 500 °C, and grind to obtain an iron-doped nickel oxide modified molybdenum oxide composite material.
[0045] (3) Take Fe-Ni2O3@MoO3 and grind it, then coat the material on the surface of an Al2O3 ceramic tube, heat at a high temperature for 5 h, age and sinter for 8 h, take out, add a heating wire, and weld the base to obtain an ammonia sensor.
[0046] (4) Use a sampling needle to inject a certain concentration of ammonia water into a gas-sensitive analyzer, use the corresponding resistance as the ordinate and time as the abscissa, record the change of resistance, and establish an ammonia response curve, where the response value (S) = R g / R a .
[0047] Example 2:
[0048] Preparation and application of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide, comprising the following steps:
[0049] (1) 1.7 g of sodium molybdate dihydrate and 2.3 g of thiourea are mixed and dissolved in 30 ml of pure water, ultrasonically dissolved, placed in a reaction kettle, heated at 180 - 240 °C for 24 hours, dried, and ground to obtain MoS2.
[0050] (2) Ferric chloride hexahydrate: nickel chloride hexahydrate = 3 is dissolved in pure water according to this molar mass ratio, sodium hydroxide solution is added until the pH is 10, and a small amount of precipitate is formed by stirring. Molybdenum disulfide is added according to a certain molar ratio, heated in a water bath for 6 hours, taken out and stirred, the supernatant is poured off, pure water is added, centrifuged, washed with water until neutral - tested with a pH test paper, dried at 80 °C, calcined and annealed at 300 - 500 °C, and ground to obtain an iron-doped nickel oxide modified molybdenum oxide composite material.
[0051] (3) Take Fe-Ni2O3@MoO3 and grind it, then coat the material on the surface of an Al2O3 ceramic tube, heat at a high temperature for 5 h, age and sinter for 6 h, take it out, add a heating wire, and weld the base to obtain an ammonia sensor.
[0052] (4) Use a sampling needle to inject a certain concentration of ammonia water into a gas-sensing analyzer, with its corresponding resistance as the ordinate and time as the abscissa, record the change of resistance, establish an ammonia response curve, where the response value (S) = R g / R a .
[0053] Example 3:
[0054] Preparation and application of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide, comprising the following steps:
[0055] (1) 1.7 g of sodium molybdate dihydrate and 2.3 g of thiourea are mixed and dissolved in 30 ml of pure water, ultrasonically dissolved, placed in a reaction kettle, heated at 180 - 240 °C for 24 hours, dried, and ground to obtain MoS2.
[0056] (2) Ferric chloride hexahydrate: nickel chloride hexahydrate = 3 is dissolved in pure water according to this molar mass ratio, sodium hydroxide solution is added until the pH is 10, and a small amount of precipitate is formed by stirring. Molybdenum disulfide is added according to a certain molar ratio, heated in a water bath for 6 hours, taken out and stirred, the supernatant is poured off, pure water is added, centrifuged, washed with water until neutral - tested with a pH test paper, dried at 80 °C, calcined and annealed at 300 - 500 °C, and ground to obtain an iron-doped nickel oxide modified molybdenum oxide composite material.
[0057] (3) Grind Fe-Ni2O3@MoO3, then coat the material on the surface of the Al2O3 ceramic tube, heat at a high temperature for 5 h, age and sinter for 4 h, take it out, add a heating wire, and weld the base to obtain the ammonia sensor.
[0058] (4) Use a sampling needle to inject a certain concentration of ammonia water into the gas sensor analyzer, with the corresponding resistance as the ordinate and time as the abscissa, record the change of resistance, and establish an ammonia response curve, where the response value (S) = R g / R a .
Claims
1. Preparation and application of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide, including establishing an ammonia sensor based on an iron-doped nickel oxide modified molybdenum oxide composite material, the specific steps are as follows: (1) Prepare MoS2 by hydrothermal synthesis method; (2) Dissolve ferric chloride hexahydrate: nickel chloride hexahydrate = 3 according to this molar mass ratio in pure water, add sodium hydroxide solution until the pH is 10, stir until a small amount of precipitate is formed, add molybdenum disulfide according to a certain molar ratio, heat in a water bath for 6 hours, take out and stir, pour out the supernatant, add pure water, centrifuge, wash with water until neutral - use a pH test reagent, dry at 80 °C, calcine and anneal at 300 - 500 °C, and grind to obtain an iron-doped nickel oxide modified molybdenum oxide composite material. (3) Take the iron-doped nickel oxide modified molybdenum oxide composite material for grinding, then coat the material on the surface of an Al2O3 ceramic tube, age and sinter at 300 - 500 °C for 8 h, take out, and weld the base and the heating wire to obtain the ammonia sensor.
2. The preparation method according to claim 1, characterized in that, The process of preparing MoS2 by hydrothermal synthesis method in step (1) is as follows: 1.7 g of sodium molybdate dihydrate and 2.3 g of thiourea are mixed and dissolved in 30 ml of pure water, ultrasonically dissolved, placed in a reaction kettle, heated at 180 - 240 °C for 24 hours, dried, and ground to obtain MoS2.
3. The preparation method according to claim 1, characterized in that, In step (2), the heating temperature in the water bath is 70 °C.
4. The preparation method according to claim 1, wherein In step (3), the aging temperature is 300 - 500 °C; the aging environment is air aging; the heating rate is 3 °C·min -1 .
5. The preparation method according to claim 1, characterized in that, In step (3), the length of the Al2O3 ceramic tube is 4 mm; the outer diameter is 1.2 mm; 0.8 mm ≤ electrode spacing ≤ 1 mm; 0.5 mm ≤ electrode width ≤ 1 mm. The inside of the ceramic tube of the sensor is a nickel-chromium alloy heating wire; the heating wire and the Pt wire leads at both ends of the ceramic tube are welded to the base with tin wire; the welding temperature is 250 °C.
6. The preparation and application of an ammonia sensor based on iron-doped nickel oxide modified molybdenum oxide according to claim 1, characterized in that: The composite material used in step (3) is a flaky material, with the characteristics of flexibility and transparency, having more active sites, and having a good adsorption effect on ammonia.
7. The ammonia sensor prepared by the preparation method according to any one of claims 1 - 6, wherein the ammonia sensor is a resistive ammonia sensor.
8. Application of the ammonia sensor according to claim 7 in detecting ammonia under high-temperature conditions.