Preparation method and application of fluoride-free MXenes gas sensitive material
By using a method for preparing fluorine-free MXenes gas-sensitive materials, fluorine-free MXenes are synthesized under an inert atmosphere using leucate etchants, solving the problem of methane detection under extreme conditions, achieving low-cost, low-hazard, and efficient monitoring, and expanding the application scenarios of the sensor.
Patent Information
- Application Number
- CN202511748611.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-26
- Publication Date
- 2026-02-10
AI Technical Summary
Existing technologies cannot effectively detect ppm-level methane under extreme conditions of oxygen deficiency, resulting in sensor failure. Furthermore, traditional MXenes synthesis methods are highly hazardous and cause severe environmental pollution.
A method for preparing fluorine-free MXenes gas-sensitive materials was developed. Fluorine-free MXenes were synthesized in an inert atmosphere using leucate etchant. Sensing was achieved through hydrogen bonding between halogens and methane, avoiding the use of hazardous fluorine compounds. The preparation process is simple, low-cost, and low-hazard.
Rapid response and recovery of ppm-level methane were achieved under an inert atmosphere, broadening the monitoring scenarios, meeting the detection needs in extreme environments, and reducing the danger and environmental pollution of the preparation process.
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Figure CN121493983A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of gas sensing, and more particularly to a fluorine-free MXenes gas sensitive material preparation method and application thereof in CH4 monitoring under inert atmosphere. BACKGROUND
[0002] Methane (CH4) is the simplest hydrocarbon, and methane is the main component of natural gas. Methane is mainly derived from the anaerobic fermentation of plant and animal remains or household garbage under natural conditions. Methane is a colorless and odorless gas at normal temperature and pressure. Methane is a gas that can easily ignite and explode. As long as the methane content in the air is in the range of 4.4-17%, it is easy to catch fire or explode. Methane is also a suffocating gas that can replace oxygen in a closed space. If the oxygen is replaced by methane and the content is less than 19.5%, it may cause suffocation. When there are buildings near the landfill site, methane may penetrate into the buildings, exposing residents in the buildings to high levels of methane. Therefore, real-time and rapid detection of methane concentration is of great importance to ensure the safety of industrial production and human life.
[0003] The detection of methane (CH4) is carried out by adsorption and activation of the sensitive material on the adsorption sites and active sites on the surface of the sensitive material. After activation, the charge of the sensitive material changes, causing a change in the resistivity of the sensitive material. In general, the reaction between the gas and the sensitive material depends on the participation of surface active oxygen species, and the surface active oxygen is derived from oxygen. However, under some extreme conditions, the lack of oxygen can cause the sensing process to fail.
[0004] Research has found that two-dimensional transition metal carbides (MXenes) have a layered structure, and their surfaces have a large number of groups that can increase the contact area between the material and the gas, provide more pathways for gas diffusion, and provide more active sites for gas adsorption and reaction. MXenes are obtained by selective etching of MAX phase. The conventional synthesis process involves the use of fluoride salt or hydrofluoric acid, which is dangerous and harmful to the environment. The molten salt etching process uses Lewis acid as an etchant, so the etching process is less dangerous and less harmful to the environment than traditional methods. At the same time, molten salt etching can adjust the surface functional groups of MXenes, and the difference in the surface functional groups of MXenes will affect their gas sensing performance and selectivity. Fluorine-free MXenes etched with different Lewis acid salts can directly rely on the interaction between halogen and hydrogen in methane to complete the sensing process, which is different from the traditional sensing process of sensitive materials that relies on active oxygen.
[0005] Therefore, providing a gas sensing material capable of detecting ppm-level CH4 fast response and recovery under inert atmosphere and a preparation method thereof is a technical problem to be solved by those skilled in the art. SUMMARY
[0006] Therefore, the application provides a preparation method of a fluorine-free MXenes gas sensitive material and application thereof. The preparation method is simple, does not involve the use of high-end instruments and equipment, and is conducive to the industrial production of the material. The fluorine-free MXenes gas sensitive material synthesized by the method has a response to ppm-level CH4 under inert conditions.
[0007] To achieve the above object, the application adopts the following technical scheme: A preparation method of a fluorine-free MXenes gas sensitive material, comprising the following steps: (1) uniformly mixing and grinding Ti3AlC2 (400 mesh) and a Lewis acid salt to obtain a mixed powder; (2) uniformly spreading the mixed powder in an alumina crucible, then placing the alumina crucible with the powder in a tube furnace, leak testing the tube furnace, and continuously introducing inert gas for purging; (3) after purging, adjusting the gas purging flow rate, heating and holding the tube furnace, and after holding, taking out the alumina crucible when the tube furnace cools to room temperature; (4) taking out the powder in the alumina crucible, washing it with an ammonium persulfate solution, centrifuging after washing, and obtaining a precipitate; (5) adding deionized water to the precipitate obtained by centrifuging for washing, and centrifuging again to obtain a secondary precipitate.
[0008] (6) placing the precipitate obtained in step (5) in a vacuum drying box to obtain a fluorine-free MXenes gas sensitive material.
[0009] Further, the molar ratio of Ti3AlC2 to the Lewis acid salt in step (1) is 1:6. The Lewis acid salt is any one of CuCl2, CuBr2, and Cu2I.
[0010] Further, the grinding time in step (1) is not less than 20 min.
[0011] Further, the inert gas purging flow rate in step (2) is 0.5 L / min, and the purging interval is not less than 20 min.
[0012] Further, after purging in step (3), the gas purging flow rate is adjusted to 0.1 L / min. The temperature increasing and holding method is: increasing the temperature from room temperature to 700℃ at a rate of 5℃ / min and then holding for 7h; Further, the cooling method is: after the holding is completed, continuously introducing the inert gas until the alumina crucible is cooled to room temperature; the inert gas flow rate is kept at 0.1L / min during the cooling process.
[0013] Further, the concentration of the ammonium persulfate solution in step (4) is 0.5mol / L. The stirring speed in the cleaning process is 400rpm, and the stirring time is 30min. The centrifugal speed is 6000rpm, and the centrifugal time is 5min.
[0014] The beneficial effect of the above further scheme is that the copper particles generated in the reaction are removed by the oxidizing property of ammonium persulfate, thereby improving the effect of the prepared material.
[0015] Further, the stirring speed in the cleaning process in step (5) is 400rpm, and the stirring time is 30min. The centrifugal speed is 6000rpm, and the centrifugal time is 5min.
[0016] The beneficial effect of the above further scheme is that the continuous stirring can accelerate the reaction of ammonium persulfate and copper particles, and long-time stirring helps to completely remove the copper particles.
[0017] Further, the drying temperature of the quick drying oven in step (6) is 60℃, and the drying time is 24h.
[0018] In the technical scheme and all embodiments of the present application, the purity of Ti3AlC2(400 mesh) is ≥98%, the purity of CuI2 is ≥98%, the purity of CuCl2 is ≥98%, the purity of CuBr2 is ≥98%, the purity of ammonium persulfate is ≥98%, and the purity of nitrogen is ≥99%.
[0019] The present application also provides the application of the fluorine-free MXenes gas-sensitive material prepared by the above method in detecting ppm-level CH4 in an inert atmosphere, which comprises the following steps: 1) dispersing the obtained fluorine-free MXenes gas-sensitive material in ethanol water to prepare a uniform dispersion liquid, uniformly coating the dispersion liquid on a finger electrode, and naturally drying to obtain a gas-sensitive device; 2) using the obtained gas-sensitive device to monitor CH4 gas in an inert atmosphere.
[0020] Further, the volume ratio of ethanol to water in the ethanol water in step 1) is 1:1. The concentration of the fluorine-free MXenes gas-sensitive material in the dispersion is 0.03 g / ml.
[0021] Furthermore, the inert atmosphere mentioned in step 2) is an Ar or N2 atmosphere; The operating temperature range of the gas-sensitive device is 300-400℃.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention has the advantages of simple preparation method, low cost, low risk of preparation process and little environmental harm compared with traditional method.
[0023] (2) The fluorine-free MXenes gas sensing material prepared by this method completes the sensing process by hydrogen bonding between different halogens and methane. This is different from the traditional sensing material which requires active oxygen to carry out the sensing process, thus further expanding the monitoring scenarios and meeting the monitoring needs in extreme environments. Attached Figure Description
[0024] Figure 1 The response of the molten salt etched Ti3C2I2 gas-sensitive material prepared in Example 2 to 500 ppm CH4 is shown in the figure. Figure 2 Ti3C2T etched using HF in Example 2 x Response diagram of gas-sensitive material to 500 ppm CH4; Figure 3 This is a SEM image of the molten salt etched Ti3C2I2 gas-sensitive material prepared in Example 2. Detailed Implementation
[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0026] Example 1 A method for preparing fluorine-free MXenes gas-sensitive materials and their applications: (1) Place Ti3AlC2 (400 mesh) and CuI2 in a mortar and mix thoroughly (the molar ratio of Ti3AlC2 to CuI2 is 1:6), and grind for 25 minutes. Then spread the uniformly mixed powder evenly in an alumina crucible.
[0027] (2) Place the alumina crucible covered with powder into a tube furnace. After checking the tube furnace for leaks, purge it with inert gas continuously at a flow rate of 0.5 L / min for 35 min.
[0028] (3) After purging, adjust the gas purging flow rate to 0.1 L / min and heat the tube furnace at a heating rate of 5 °C / min. After heating to 700 °C, hold for 7 h. After holding, continuously pass inert gas at a gas flow rate of 0.1 L / min until the tube furnace cools to room temperature. After the tube furnace cools to room temperature, remove the alumina crucible.
[0029] (4) Take out the powder from the alumina crucible and place it in a beaker. Use 0.5 mol / L ammonium persulfate solution to stir and clean it. The stirring speed is 400 rpm and the stirring time is 30 min. After cleaning, centrifuge at 6000 rpm for 5 min.
[0030] (5) Add deionized water to the precipitate obtained by centrifugation and wash it. Then centrifuge at 6000 rpm for 5 min.
[0031] (6) The obtained precipitate was placed in a vacuum drying oven and dried at 60°C for 24 hours to obtain Ti3C2I2 gas sensitive material.
[0032] (7) Disperse the obtained Ti3C2Cl2 gas-sensitive material in water:ethanol (V H2O :V 乙醇 A uniform dispersion of gas-sensitive material was prepared by mixing a 1:1 ratio of gas-sensitive material with an added element concentration of 0.03 g / ml. The dispersion was then uniformly coated onto the finger electrodes and allowed to dry naturally to obtain the gas-sensitive device.
[0033] (8) The obtained gas-sensitive device is used to monitor methane gas at 300°C in an inert atmosphere.
[0034] To further demonstrate the difference in methane gas-sensing performance between fluorinated and non-fluorinated MXenes under high-temperature and oxygen-free conditions, Ti3C2T etched with HF was used. x The prepared Ti3C2Cl2 and Ti3C2Br2MXenes were used as sensitive materials, and gas-sensing tests were performed under the same conditions as in this example.
[0035] The results show that the Ti3C2I2 gas-sensitive material synthesized in Example 1 has a 15% response to CH4 concentrations in the 500ppm range at 300℃, while the Ti3C2T gas-sensitive material etched with HF under the same conditions... x Ti3C2Cl2 and Ti3C2Br2MXenes showed no response.
[0036] Example 2 A method for preparing fluorine-free MXenes gas-sensitive materials and their applications: (1) Place Ti3AlC2 (400 mesh) and CuI2 in a mortar and mix thoroughly (the molar ratio of Ti3AlC2 to CuI2 is 1:6), and grind for 25 minutes. Then spread the uniformly mixed powder evenly in an alumina crucible.
[0037] (2) Place the alumina crucible covered with powder into a tube furnace. After checking the tube furnace for leaks, purge it with inert gas continuously at a flow rate of 0.5 L / min for 35 min.
[0038] (3) After purging, adjust the gas purging flow rate to 0.1 L / min and heat the tube furnace at a heating rate of 5 °C / min. After heating to 700 °C, hold for 7 h. After holding, continuously pass inert gas at a gas flow rate of 0.1 L / min until the tube furnace cools to room temperature. After the tube furnace cools to room temperature, remove the alumina crucible.
[0039] (4) Take out the powder from the alumina crucible and place it in a beaker. Use 0.5 mol / L ammonium persulfate solution to stir and clean it. The stirring speed is 400 rpm and the stirring time is 30 min. After cleaning, centrifuge at 6000 rpm for 5 min.
[0040] (5) Add deionized water to the precipitate obtained by centrifugation and wash it. Then centrifuge at 6000 rpm for 5 min.
[0041] (6) The obtained precipitate was placed in a vacuum drying oven and dried at 60°C for 24 hours to obtain Ti3C2I2 gas sensitive material.
[0042] (7) Disperse the obtained Ti3C2I2 gas-sensitive material in water:ethanol (V H2O :V 乙醇 A uniform dispersion of gas-sensitive material was prepared by mixing a 1:1 ratio of gas-sensitive material with an added element concentration of 0.03 g / ml. The dispersion was then uniformly coated onto the finger electrodes and allowed to dry naturally to obtain the gas-sensitive device.
[0043] (8) The obtained gas-sensitive device is used to monitor methane gas at 350°C in an inert atmosphere.
[0044] To further demonstrate the difference in methane gas-sensing performance between fluorinated and non-fluorinated MXenes under high-temperature and oxygen-free conditions, Ti3C2T etched with HF was used. x The prepared Ti3C2Cl2 and Ti3C2Br2MXenes were used as sensitive materials, and gas-sensing tests were performed under the same conditions as in this example.
[0045] The results show that the Ti3C2I2 gas-sensitive material synthesized in Example 2 has a 65% response to CH4 concentrations in the 500ppm range at 350℃, while the Ti3C2T gas-sensitive material etched with HF under the same conditions... x Ti3C2Cl2 and Ti3C2Br2MXenes showed no response.
[0046] Example 3 A method for preparing fluorine-free MXenes gas-sensitive materials and their applications: (1) Place Ti3AlC2 (400 mesh) and CuI2 in a mortar and mix thoroughly (the molar ratio of Ti3AlC2 to CuI2 is 1:6), and grind for 25 minutes. Then spread the uniformly mixed powder evenly in an alumina crucible.
[0047] (2) Place the alumina crucible covered with powder into a tube furnace, check the tube furnace for leaks, and then purge it with inert gas continuously at a flow rate of 0.5 L / min for 35 min.
[0048] (3) After purging, adjust the gas purging flow rate to 0.1 L / min and heat the tube furnace at a heating rate of 5 °C / min. After heating to 700 °C, hold for 7 h. After holding, continuously pass inert gas at a gas flow rate of 0.1 L / min until the tube furnace cools to room temperature. After the tube furnace cools to room temperature, remove the alumina crucible.
[0049] (4) Take out the powder from the alumina crucible and place it in a beaker. Use 0.5 mol / L ammonium persulfate solution to stir and clean it. The stirring speed is 400 rpm and the stirring time is 30 min. After cleaning, centrifuge at 6000 rpm for 5 min.
[0050] (5) Add deionized water to the precipitate obtained by centrifugation and wash it. Then centrifuge at 6000 rpm for 5 min.
[0051] (6) The obtained precipitate was placed in a vacuum drying oven and dried at 60°C for 24 hours to obtain Ti3C2I2 gas sensitive material.
[0052] (7) Disperse the obtained Ti3C2I2 gas-sensitive material in water:ethanol (V H2O :V 乙醇 A uniform dispersion of gas-sensitive material was prepared by mixing a 1:1 ratio of gas-sensitive material with an added element concentration of 0.03 g / ml. The dispersion was then uniformly coated onto the finger electrodes and allowed to dry naturally to obtain the gas-sensitive device.
[0053] (8) The obtained gas-sensitive device is used to monitor methane gas at 300°C in an inert atmosphere.
[0054] To further demonstrate the difference in methane gas-sensing performance between fluorinated and non-fluorinated MXenes under high-temperature and oxygen-free conditions, Ti3C2T etched with HF was used. x The prepared Ti3C2Cl2 and Ti3C2Br2MXenes were used as sensitive materials, and gas-sensing tests were performed under the same conditions as in this example.
[0055] The results show that the Ti3C2I2 gas-sensitive material synthesized in Example 3 has a 45% response to CH4 concentrations in the 500ppm range at 400℃, while the Ti3C2T gas-sensitive material etched with HF under the same conditions... x Ti3C2Cl2 and Ti3C2Br2MXenes showed no response.
[0056] Example 4 A method for preparing fluorine-free MXenes gas-sensitive materials and their applications: (1) Place Ti3AlC2 (400 mesh) and CuI2 in a mortar and mix thoroughly (the molar ratio of Ti3AlC2 to CuI2 is 1:6), and grind for 25 minutes. Then spread the uniformly mixed powder evenly in an alumina crucible.
[0057] (2) Place the alumina crucible covered with powder into a tube furnace. After checking the tube furnace for leaks, purge it with inert gas continuously at a flow rate of 0.5 L / min for 35 min.
[0058] (3) After purging, adjust the gas purging flow rate to 0.1 L / min and heat the tube furnace at a heating rate of 5 °C / min. After heating to 700 °C, hold for 7 h. After holding, continuously pass inert gas at a gas flow rate of 0.1 L / min until the tube furnace cools to room temperature. After the tube furnace cools to room temperature, remove the alumina crucible.
[0059] (4) Take out the powder from the alumina crucible and place it in a beaker. Use 0.5 mol / L ammonium persulfate solution to stir and clean it. The stirring speed is 400 rpm and the stirring time is 30 min. After cleaning, centrifuge at 6000 rpm for 5 min.
[0060] (5) Add deionized water to the precipitate obtained by centrifugation and wash it. Then centrifuge at 6000 rpm for 5 min.
[0061] (6) The obtained precipitate was placed in a vacuum drying oven and dried at 60°C for 24 hours to obtain Ti3C2I2 gas sensitive material.
[0062] In summary, existing etching methods using organic Lewis acid etchants, such as trifluoromethanesulfonic acid (TfOH), allow for simultaneous etching and intercalation. However, these etchants are highly corrosive, causing severe burns to the skin, mucous membranes, and respiratory tract. Their vapors are also harmful, posing a significant threat to operator and equipment safety. Direct halogen etching also poses environmental and operator hazards. Furthermore, it increases defects and reduces the properties of the etched products. This method also requires sophisticated reaction vessels and piping, is prone to external leaks, and is unsuitable for large-scale synthesis. In contrast, Lewis acid molten salt etching uses etchants (CuCl2, CuBr2, Cu2I) that are low-cost, environmentally friendly, and safe, enabling large-scale production while reducing environmental and operator hazards.
[0063] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.
Claims
1. A method for preparing a fluorine-free MXenes gas-sensitive material, characterized in that, Includes the following steps: (1) Mix Ti3AlC2 with Lewis acid salt and grind evenly to obtain a mixed powder; (2) Spread the uniformly mixed powder evenly in the alumina crucible, and then place the alumina crucible with powder in the tube furnace; check the tube furnace for leaks and continuously purge it with inert gas. (3) After purging, adjust the gas purging flow rate, heat the tube furnace and keep it at the temperature. After the heat preservation is completed, take out the alumina crucible after the tube furnace cools down to room temperature. (4) Remove the powder from the alumina crucible, wash it with ammonium persulfate solution, and centrifuge it after washing to obtain the precipitate; (5) Add deionized water to the precipitate obtained by centrifugation and wash it. Centrifuge again to obtain a secondary precipitate. (6) Place the precipitate obtained in step (5) in a vacuum drying oven to obtain fluorine-free MXenes gas-sensitive material.
2. The method for preparing a fluorine-free MXenes gas-sensitive material according to claim 1, characterized in that, The molar ratio of Ti3AlC2 to Lewisite in step (1) is 1:6; The leucate is any one of CuCl2, CuBr2, and Cu2I.
3. The method for preparing a fluorine-free MXenes gas-sensitive material according to claim 1, characterized in that, The inert gas purging flow rate in step (2) is 0.5 L / min, and the purging time is not less than 20 min.
4. The method for preparing a fluorine-free MXenes gas-sensitive material according to claim 1, characterized in that, After the purging is completed in step (3), adjust the gas purging flow rate to 0.1 L / min; The heating and holding method is as follows: the temperature is increased from room temperature to 700℃ at a heating rate of 5℃ / min and then held for 7 hours. The cooling method is as follows: after the heat preservation is completed, inert gas is continuously introduced until the alumina crucible cools to room temperature.
5. The method for preparing a fluorine-free MXenes gas-sensitive material according to claim 1, characterized in that, The concentration of the ammonium persulfate solution in step (4) is 0.5 mol / L; the stirring speed during the cleaning process is 400 rpm and the stirring time is 30 min; The centrifugation speed was 6000 rpm and the centrifugation time was 5 min.
6. The method for preparing a fluorine-free MXenes gas-sensitive material according to claim 1, characterized in that, The stirring speed during the cleaning process described in step (5) is 400 rpm and the stirring time is 30 min; The centrifugation speed was 6000 rpm and the centrifugation time was 5 min; The drying temperature of the fast drying oven mentioned in step (6) is 60℃ and the drying time is 24h.
7. The application of a fluorine-free MXenes gas-sensitive material prepared by the method of any one of claims 1-6 in the detection of ppm-level CH4 under an inert atmosphere.
8. The application of the fluorine-free MXenes gas-sensitive material according to claim 7 in the detection of ppm-level CH4 under an inert atmosphere, characterized in that, Includes the following steps: 1) The obtained fluorine-free MXenes gas-sensitive material was dispersed in ethanol and water to prepare a uniform dispersion. The dispersion was then uniformly coated onto the interdigitated electrode and allowed to dry naturally to obtain the gas-sensitive device. 2) The obtained gas-sensitive device was used for CH4 gas monitoring under an inert atmosphere.
9. The application of the fluorine-free MXenes gas-sensitive material according to claim 8 in the detection of ppm-level CH4 under an inert atmosphere, characterized in that, In step 1), the volume ratio of ethanol to water in the ethanol-water mixture is 1:
1. The concentration of the fluorine-free MXenes gas-sensitive material in the dispersion is 0.03 g / ml.
10. The application of the fluorine-free MXenes gas-sensitive material according to claim 8 in the detection of ppm-level CH4 under an inert atmosphere, characterized in that, The inert atmosphere mentioned in step 2) is an Ar or N2 atmosphere; The operating temperature of the gas-sensitive device is 300-400℃.