Mo2c / moo3 flake-like heterostructure gas-sensitive material and preparation method and application thereof

Abstract

The application provides a Mo2C / MoO3 flaky heterostructure gas-sensitive material and a preparation method and application thereof. The application has simple preparation process and low cost. MoO3 nanosheets are obtained by intercalating block MoO3 with organic amine. Mo2C nanosheets are obtained by high-temperature carbonization in an inert atmosphere. The Mo2C nanosheets are annealed in air to obtain the flaky Mo2C / MoO3 heterostructure. Molybdenum carbide has a wide d-orbital structure similar to noble metal Pt, and shows similar catalytic performance to Pt. The catalytic performance is conducive to the sensing reaction, and molybdenum carbide has good conductivity, which is conducive to the electron transfer in the sensing process, thereby improving the gas-sensitive performance of the MoO3 gas-sensitive material to triethylamine. The Mo2C / MoO3 flaky heterostructure gas-sensitive material has ultrahigh response (R a / R g =551,50 ppm,110℃) and excellent repeatability and selectivity to triethylamine, and can be used for high-sensitivity detection of triethylamine.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor metal oxide functional materials and gas sensing technology, specifically relating to a Mo2C / MoO3 sheet-like heterostructure gas sensing material, its preparation method, and its application. Background Technology

[0002] Triethylamine (TEA) is a volatile organic compound (VOC) widely used in agriculture, fisheries, aviation, and many other fields, as well as in medicine and health. For example, it can be used as a preservative, surfactant, organic solvent, and catalyst. Furthermore, studies have shown that decaying fish and shellfish release TEA. Therefore, TEA can be used as a standard for fish freshness. However, the harm of TEA to humans is mainly due to its strong irritation of the skin, mucous membranes, and central nervous system. Long-term exposure to TEA has led to emphysema in some individuals, and even death. Therefore, there is an urgent need to develop novel sensors with high responsiveness and good selectivity to achieve continuous monitoring of trace amounts of TEA in biomedical, chemical, everyday work environments, and product manufacturing processes.

[0003] In recent years, metal-oxide-semiconductor (MOS) based gas sensors have become a research hotspot for TEA detection due to their controllable physicochemical properties, low manufacturing cost, fast response speed, and low detection cost. Among them, MoO3, with its unique electrical properties, excellent high stability, high reactivity, and surface effect, possesses unique advantages as a traditional gas monitoring sensing material. However, current MoO3-based TEA gas sensors still suffer from problems such as high operating temperature, low response, and poor selectivity. Constructing heterojunctions is one strategy to improve the gas-sensing performance of MoO3 for TEA. For example, Zhang et al. constructed a ZnO / MoO3 heterostructure, and the ZnO / MoO3 sensor achieved a response of 519 to 100 ppm TEA gas at 180℃, with a detection limit as low as 10 ppb. Dogra et al. prepared MoSe2 / MoO3, which greatly improved the gas-sensing response to TEA. In recent years, it has been found that the use of noble metals plays a more crucial role in improving the gas-sensing performance of MoO3-based TEA gases. For example, Liu et al. prepared Ag / MoO3 nanoribbons that exhibited high sensitivity to TEA, with a response value of 26.58 at 5 ppm. Zheng et al. synthesized Au-supported In2O3 nanospheres and showed good response recovery characteristics to triethylamine. However, the high cost of precious metals makes them unsuitable for practical applications. Therefore, developing efficient and inexpensive non-precious metal gas-sensitive catalysts is of great significance.

[0004] Molybdenum carbide (Mo2C) possesses electronic structures, hydrogen adsorption, and catalytic properties similar to noble metals (Pt, Pd, etc.), and is abundant and relatively inexpensive, making it a promising material to replace noble metal catalysts. However, the unavoidable high-temperature operation during Mo2C synthesis makes it prone to aggregation, leading to a reduction in active surface area and catalytic sites. In a patent (application number CN202210390801.8), researchers described a method for synthesizing Mo@Mo2C nanocomposites. This method uses a gradient high-temperature pyrolysis reduction method to prepare Mo@Mo2C with a bulk structure, which is unfavorable for gas adsorption and sensing reactions. This application uses an organic amine intercalation and high-temperature carbonization method to prepare sheet-like Mo2C nanosheets, and then uses annealing to prepare Mo2C / MoO3 with a sheet-like heterostructure, greatly improving the gas-sensing performance of MoO3. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing a Mo2C / MoO3 sheet-like heterostructure gas-sensitive material. The preparation process of this invention is simple and low-cost.

[0006] This invention obtains MoO3 nanosheets by intercalating bulk MoO3 with an organic amine. Subsequently, Mo2C nanosheets are obtained by high-temperature carbonization in an inert atmosphere. The resulting Mo2C nanosheets are then annealed in air to obtain a sheet-like Mo2C / MoO3 heterostructure. The formation of the heterostructure endows the material with more oxygen vacancies and other defect sites, thereby increasing the concentration of adsorbed oxygen participating in the sensing reaction. Molybdenum carbide has a relatively wide d-orbital structure similar to the noble metal Pt, which also gives it catalytic performance similar to Pt. Its catalytic performance is beneficial to the sensing reaction. Furthermore, molybdenum carbide has excellent electrical conductivity, which is beneficial to electron transport during the sensing process, thus improving the gas-sensing performance of the MoO3 gas-sensitive material for triethylamine, resulting in an ultra-high response (R0). a / R g It exhibits excellent repeatability and selectivity (551.50 ppm, 110℃). It can be used for highly sensitive detection of triethylamine, which is of great significance for monitoring and real-time surveillance of triethylamine in industrial production activities.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A Mo2C / MoO3 sheet-like heterostructure gas-sensitive material is provided, wherein the Mo2C / MoO3 sheet-like heterostructure gas-sensitive material is composed of a thin layer of MoO3 wrapping an inner layer of Mo2C nanosheets. The heterostructure formed between Mo2C and MoO3 can achieve the regulation of the electronic structure of the material, thereby enhancing the gas-sensing performance of the material.

[0009] This invention obtains MoO3 nanosheets with a large amount of residual amine through dodecylamine intercalation, followed by high-temperature carbonization to obtain Mo2C nanosheets. Finally, annealing at different temperatures yields Mo2C / MoO3 sheet-like heterostructures with different proportions of Mo2C and MoO3. The sensor prepared by this method exhibits good sensitivity (R0) to triethylamine (TEA) at an operating temperature of 110℃. a / R g =551@50ppm), selectivity, and stability. It exhibits higher response and faster response recovery time compared to pure MoO3 nanosheets. Specifically, it includes the following steps:

[0010] (1) MoO3 nanoblocks were obtained by high-temperature calcination of molybdenum salt in a muffle furnace;

[0011] (2) Add the MoO3 nanoblocks prepared in step (1) to a mixed solution of organic amine and alcohol, reflux at a certain temperature, centrifuge the resulting mixed solution and collect the precipitate, and dry at 60°C overnight to obtain MoO3 nanosheets.

[0012] (3) The MoO3 nanosheets obtained in step (2) were placed in a tube furnace and calcined at high temperature under an inert atmosphere to obtain Mo2C nanosheets.

[0013] (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and calcined at high temperature in air atmosphere to obtain Mo2C / MoO3 nanosheets, namely Mo2C / MoO3 sheet-like heterostructure gas-sensitive materials.

[0014] Furthermore, the molybdenum salt in step (1) is any one or more of ammonium molybdate, ammonium phosphomolybdate, molybdenum acetate, and molybdenum chloride.

[0015] Furthermore, the calcination temperature in step (1) is 400-550℃, the heating rate is 1-10℃ / min, and the calcination time is 2-4h.

[0016] Furthermore, the organic amine in step (2) is any one of dodecylamine, hexadecylamine, and octadecylamine; the alcohol is any one or more of methanol, ethanol, and propanol; and the mass-volume ratio of organic amine to alcohol in the mixed solution is (4-5) g: 60 ml.

[0017] Furthermore, the reflux temperature in step (2) is 60-90℃, and the reflux time is 8-24h.

[0018] Furthermore, the inert atmosphere in step (3) is nitrogen, argon, or helium.

[0019] Furthermore, the calcination temperature in step (3) is 700-750℃, the heating rate is 1-5℃ / min, and the time is 5-10h.

[0020] Furthermore, the calcination temperature in step (4) is 300-370℃, the heating rate is 1-5℃ / min, and the time is 2-5h.

[0021] The present invention also provides the application of the aforementioned Mo2C / MoO3 sheet-like heterostructure gas-sensitive material in a triethylamine gas sensor, which has a response value of 551 to 50ppm triethylamine at an operating temperature of 110℃.

[0022] The key innovation of this invention lies in a method for preparing a Mo2C / MoO3 sheet-like heterostructure gas-sensitive material. While many methods exist for preparing Mo2C / MoO3, the resulting heterostructures have small specific surface areas, bulky microstructures, few active sites, and poor gas-sensing performance.

[0023] The beneficial effects of this invention are as follows: The method is unique, employing organic amine intercalation and high-temperature carbonization to prepare sheet-like Mo2C nanosheets, followed by annealing to prepare Mo2C / MoO3 with a sheet-like heterostructure. The Mo2C / MoO3 sheet-like heterostructure possesses a very high specific surface area. The preparation method is simple, the raw materials are inexpensive, and it exhibits excellent gas-sensing properties to triethylamine. At an operating temperature of 110℃, the response value to 50 ppm triethylamine is 551, which is 10 times the response of pure MoO3 nanosheets (R0). a / R g =55), with shorter response and recovery times. Furthermore, it demonstrates excellent application value in fields such as nanosensing, adsorption, catalysis, and electrochemistry. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope (SEM) image of the MoO3 nanosheets prepared in Example 2.

[0025] Figure 2 This is a scanning electron microscope (SEM) image of the Mo2C nanosheets prepared in Example 2.

[0026] Figure 3 This is a scanning electron microscope (SEM) image of Mo2C / MoO3 prepared in Example 2.

[0027] Figure 4 This is the XRD pattern of the Mo2C nanosheets prepared in Example 2.

[0028] Figure 5 This is the XRD pattern of Mo2C / MoO3 prepared in Example 2.

[0029] Figure 6 The gas-sensitive response of MoO3 nanosheets and Mo2C / MoO3 nanosheets prepared in Example 2 to 50 ppm triethylamine at different operating temperatures is shown.

[0030] Figure 7 The gas-sensing performance of the Mo2C / MoO3 nanosheets prepared in Example 2 at 110℃ for 50 ppm triethylamine is shown.

[0031] Figure 8 This is a gas-sensitive selectivity diagram of the Mo2C / MoO3 nanosheets prepared in Example 2 for 50 ppm triethylamine at 110 °C. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention.

[0033] Example 1

[0034] The preparation method of the square Mo2C / MoO3 nanosheets in this embodiment is as follows:

[0035] (1) Weigh 8g of ammonium phosphomolybdate and place it in a muffle furnace. Calcine at 450℃ for 4h at a rate of 2℃ / min to obtain MoO3 nanoblocks.

[0036] (2) The prepared MoO3 nanoblocks were added to a mixed solution prepared by dissolving 4g dodecylamine in 60ml ethanol, and refluxed at 80℃ for 8h. The mixed solution obtained by reflux was washed three times with ethanol, collected by centrifugation, and dried at 60℃ overnight to obtain MoO3 nanosheets with a large amount of residual organic amine.

[0037] (3) The MoO3 nanosheets obtained in step (2) were placed in a tube furnace and heat-treated at 730°C for 5 h at a heating rate of 5°C / min under an argon atmosphere to obtain square Mo2C nanosheets.

[0038] (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and annealed at 340°C for 3 hours in air atmosphere at a heating rate of 5°C / min to obtain square Mo2C / MoO3 nanosheets.

[0039] Example 2

[0040] The method for preparing the irregular Mo2C / MoO3 nanosheets in this embodiment is as follows:

[0041] (1) Weigh 8g of ammonium molybdate and place it in a muffle furnace. Calcine at 500℃ for 4h at a rate of 2℃ / min to obtain MoO3 nanoblocks.

[0042] (2) The prepared MoO3 nanoblocks were added to a mixed solution prepared by dissolving 4.5g dodecylamine in 70ml ethanol, and refluxed at 80℃ for 12h. The mixed solution obtained by reflux was washed three times with ethanol, collected by centrifugation, and dried at 60℃ overnight to obtain MoO3 nanosheets with a large amount of residual organic amine.

[0043] (3) The MoO3 nanosheets obtained in step (2) were placed in a tube furnace and heat-treated at 750°C for 5 hours under an argon atmosphere at a heating rate of 5°C / min to obtain irregular Mo2C nanosheets.

[0044] (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and annealed at 350°C for 2 hours in air atmosphere at a heating rate of 5°C / min to obtain irregular Mo2C / MoO3 nanosheets.

[0045] Example 3

[0046] The method for preparing rectangular Mo2C / MoO3 nanosheets in this embodiment is as follows:

[0047] (1) Weigh 8g of molybdenum acetate and place it in a muffle furnace. Calcine at 550℃ for 4h at a rate of 5℃ / min to obtain MoO3 nanoblocks.

[0048] (2) The prepared MoO3 nanoblocks were added to a mixed solution prepared by dissolving 4.6g dodecylamine in 60ml ethanol solution, and refluxed at 80℃ for 14h. The mixed solution obtained by reflux was washed three times with ethanol, collected by centrifugation, and dried at 60℃ overnight to obtain MoO3 nanosheets with a large amount of residual organic amine.

[0049] (3) The MoO3 nanosheets obtained in step (2) were placed in a tube furnace and heat-treated at 750°C for 5 hours under an argon atmosphere at a heating rate of 5°C / min to obtain rectangular Mo2C nanosheets.

[0050] (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and annealed at 350°C for 2 hours in air atmosphere at a heating rate of 5°C / min to obtain rectangular Mo2C / MoO3 nanosheets.

[0051] Example 4

[0052] The preparation method of the strip-shaped Mo2C / MoO3 nanosheets in this embodiment is as follows:

[0053] (1) Weigh 8g of molybdenum chloride and place it in a muffle furnace. Calcine it at 400℃ for 4h at a rate of 3℃ / min to obtain MoO3 nanoblocks.

[0054] (2) The prepared MoO3 nanoblocks were added to a mixed solution prepared by dissolving 4.2g dodecylamine in 60ml methanol, and refluxed at 80℃ for 18h. The mixed solution obtained by reflux was washed three times with methanol, collected by centrifugation, and dried at 60℃ overnight to obtain MoO3 nanosheets with a large amount of residual organic amine.

[0055] (3) The MoO3 nanosheets obtained in step (2) were placed in a tube furnace and heat-treated at 730°C for 5 h at a heating rate of 5°C / min under an argon atmosphere to obtain strip-shaped Mo2C nanosheets.

[0056] (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and annealed at 360°C for 2 hours in air atmosphere at a heating rate of 5°C / min to obtain strip-shaped Mo2C / MoO3 nanosheets.

[0057] Example 5

[0058] The preparation method of Mo2C / MoO3 nanosheets with high Mo2C content in this embodiment is as follows:

[0059] (1) Weigh 8g of ammonium molybdate and place it in a muffle furnace. Calcine at 5000℃ for 4h at a rate of 2℃ / min to obtain MoO3 nanoblocks.

[0060] (2) The prepared MoO3 nanoblocks were added to a mixed solution prepared by dissolving 4.5g of hexadecylamine in 60ml of methanol, and refluxed at 80℃ for 12h. The mixed solution obtained by reflux was washed three times with methanol, collected by centrifugation, and dried at 60℃ overnight to obtain MoO3 nanosheets with a large amount of residual organic amine.

[0061] (3) The MoO3 nanosheets obtained in step (2) were placed in a tube furnace and heat-treated at 750°C for 5 hours under an argon atmosphere at a heating rate of 5°C / min to obtain Mo2C nanosheets.

[0062] (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and annealed at 350°C for 1 hour in air atmosphere at a heating rate of 5°C / min to obtain Mo2C / MoO3 nanosheets with high Mo2C content.

[0063] Example 6

[0064] The preparation method of Mo2C / MoO3 nanosheets with high MoO3 content in this embodiment is as follows:

[0065] (1) Weigh 8g of ammonium molybdate and place it in a muffle furnace. Calcine at 5000℃ for 4h at a rate of 2℃ / min to obtain MoO3 nanoblocks.

[0066] (2) The prepared MoO3 nanoblocks were added to a mixed solution prepared by dissolving 4.5g of hexadecylamine in 60ml of methanol, and refluxed at 80℃ for 12h. The mixed solution obtained by reflux was washed three times with methanol, collected by centrifugation, and dried at 60℃ overnight to obtain MoO3 nanosheets with a large amount of residual organic amine.

[0067] (3) The MoO3 nanosheets obtained in step (2) were placed in a tube furnace and heat-treated at 750°C for 5 hours under an argon atmosphere at a heating rate of 5°C / min to obtain Mo2C nanosheets.

[0068] (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and annealed at 350°C for 4 hours in air atmosphere at a heating rate of 5°C / min to obtain Mo2C / MoO3 nanosheets with high MoO3 content.

[0069] Example 7

[0070] The preparation method of Mo2C / MoO3 nanosheets with equivalent Mo2C and MoO3 content in this embodiment is as follows: (1) Weigh 4g of molybdenum acetate and put it into a muffle furnace and calcine at 450°C for 4h at a rate of 2°C / min to obtain MoO3 nanoblocks;

[0071] (2) The prepared MoO3 nanoblocks were added to a mixed solution prepared by dissolving 4g of hexadecylamine in 60ml of methanol, and refluxed at 70℃ for 14h. The mixed solution obtained by reflux was washed three times with methanol, collected by centrifugation, and dried at 60℃ overnight to obtain MoO3 nanosheets with a large amount of residual organic amine.

[0072] (3) The MoO3 nanosheets obtained in step (2) were placed in a tube furnace and heat-treated at 700℃ for 10h at a heating rate of 5℃ / min under a helium atmosphere to obtain Mo2C nanosheets.

[0073] (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and annealed at 350°C for 3 hours in air atmosphere at a heating rate of 5°C / min to obtain Mo2C / MoO3 nanosheets with equivalent Mo2C and MoO3 content.

[0074] Example 8

[0075] The preparation method of the layered Mo2C / MoO3 in this embodiment is as follows:

[0076] (1) Weigh 8g of molybdenum chloride and place it in a muffle furnace. Calcine at 450℃ for 4h at a rate of 5℃ / min to obtain MoO3 nanoblocks.

[0077] (2) The prepared MoO3 nanoblocks were added to a mixed solution prepared by dissolving 4g of hexadecylamine in 60ml of methanol, and refluxed at 80℃ for 8h. The mixed solution obtained by reflux was washed three times with ethanol, collected by centrifugation, and dried at 60℃ overnight to obtain MoO3 nanosheets with a large amount of residual organic amine.

[0078] (3) The MoO3 nanosheets obtained in step (2) were placed in a tube furnace and heat-treated at 750°C for 5 hours under an argon atmosphere at a heating rate of 5°C / min to obtain layered Mo2C nanosheets.

[0079] (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and annealed at 350°C for 2 hours in air atmosphere at a heating rate of 5°C / min to obtain layered Mo2C / MoO3 nanosheets.

[0080] Table 1 Comparison of gas-sensing properties of Mo2C / MoO3 nanosheets with different molybdenum carbide contents to TEA

[0081]

[0082] By controlling the heat treatment time of molybdenum carbide, Mo2C / MoO3 nanosheets with different molybdenum carbide contents were obtained. The response value of Mo2C / MoO3 with high Mo2C content to 50 ppm TEA at 110℃ reached 231, while the response value of Mo2C / MoO3 sample with high MoO3 content to 50 ppm TEA at 160℃ reached 364. However, the response value of Mo2C / MoO3 nanosheets with suitable Mo2C content to 50 ppm TEA at 110℃ reached 551, which is much higher than the response of pure MoO3 nanosheets.

[0083] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a Mo2C / MoO3 sheet-like heterostructure gas-sensitive material, characterized in that... Includes the following steps: (1) MoO3 nanoblocks were obtained by calcining molybdenum salt in a muffle furnace at high temperature; (2) Add the MoO3 nanoblocks prepared in step (1) to a mixed solution of organic amine and alcohol, reflux at a certain temperature, centrifuge the resulting mixed solution and collect the precipitate, and dry overnight to obtain MoO3 nanosheets; (3) The MoO3 nanosheets obtained in step (2) are placed in a tube furnace and calcined at high temperature under an inert atmosphere to obtain Mo2C nanosheets; (4) The Mo2C nanosheets obtained in step (3) are placed in a tube furnace and calcined at high temperature in air atmosphere to obtain Mo2C / MoO3 nanosheets, namely Mo2C / MoO3 sheet-like heterostructure gas-sensitive materials. The Mo2C / MoO3 sheet-like heterostructure gas-sensitive material consists of a thin layer of MoO3 encapsulating an inner layer of Mo2C nanosheets. The heterostructure formed between Mo2C and MoO3 can adjust the electronic structure of the material, thereby enhancing its gas-sensitive performance.

2. The method for preparing the Mo2C / MoO3 sheet-like heterostructure gas-sensitive material according to claim 1, characterized in that: The molybdenum salt in step (1) is any one or more of ammonium molybdate, ammonium phosphomolybdate, molybdenum acetate, and molybdenum chloride.

3. The method for preparing the Mo2C / MoO3 sheet-like heterostructure gas-sensitive material according to claim 1, characterized in that: The calcination temperature in step (1) is 400-550℃, the heating rate is 1-10℃ / min, and the calcination time is 2-4 h.

4. The method for preparing the Mo2C / MoO3 sheet-like heterostructure gas-sensitive material according to claim 1, characterized in that: The organic amine in step (2) is any one of dodecylamine, hexadecylamine, or octadecylamine; the alcohol is any one or more of methanol, ethanol, or propanol; the mass-volume ratio of organic amine to alcohol in the mixed solution is (4-5) g: 60 ml.

5. The method for preparing the Mo2C / MoO3 sheet-like heterostructure gas-sensitive material according to claim 1, characterized in that: The reflux temperature in step (2) is 60-90 ℃ and the reflux time is 8-24 h.

6. The method for preparing the Mo2C / MoO3 sheet-like heterostructure gas-sensitive material according to claim 1, characterized in that: The inert atmosphere in step (3) is nitrogen, argon, or helium.

7. The method for preparing the Mo2C / MoO3 sheet-like heterostructure gas-sensitive material according to claim 1, characterized in that: The calcination temperature in step (3) is 700-750℃, the heating rate is 1-5℃ / min, and the time is 5-10h.

8. The method for preparing the Mo2C / MoO3 sheet-like heterostructure gas-sensitive material according to claim 1, characterized in that: The calcination temperature in step (4) is 300-370℃, the heating rate is 1-5℃ / min, and the time is 2-5 h.

9. The application of the Mo2C / MoO3 sheet-like heterostructure gas-sensitive material prepared by the method according to claim 1 in a triethylamine gas sensor, characterized in that: The response value to 50 ppm triethylamine is 551 at an operating temperature of 110 °C.

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