MXene / MoS2 / polyazole composite material and preparation method and application thereof

Abstract

The application discloses a kind of MXene / MoS2 / Polypyrrole composite material, by MXene, MoS2 And polypyrrole are compounded to obtain, wherein, MoS2 It is nanosheet structure, growth in MXene surface, form MXene-MoS2, again in MXene-MoS2 Outside coating polypyrrole is obtained, particle size is 5-6 μm.Its preparation method includes the following steps:1, the preparation of MXene;2, the loading of MoS2;3, the coating of polypyrrole.A kind of based on MXene / MoS2 / Polypyrrole sensor and its preparation method, with based on MXene / MoS2 / Polypyrrole as foundation gas sensor, with selectivity to NH3;In detection minimum limit is 10ppm;Response time is 43.6s, recovery time is 40.8s.A kind of based on MXene / MoS2 / Polypyrrole sensor as the application of unknown ammonia concentration sensor, including the following steps: a, the obtaining of concentration data is marked;B, the determination of unknown concentration.Has the following advantages: room temperature condition has the sensitivity, stability and selectivity of ammonia detection;Quantitative test can be realized, and simple process, low cost, stable performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a MXene / MoS2 / polyazole composite material and a preparation method and application thereof. BACKGROUND

[0002] Ammonia is an air pollutant and is harmful to human health. Even at a low concentration of less than 50 ppm, ammonia can cause serious irritation or burn accidents to the eyes and skin. In order to meet the environmental detection requirements and ensure human health, the detection lower limit of the ammonia sensor needs to reach 25 ppm; and it is necessary to avoid the interference of other gases on the ammonia response in the presence of numerous interfering VOC gases.

[0003] The common ammonia sensor at present is based on metal oxide semiconductor. For example, existing document 1 (Progress in Natural Science: Materials International, 2017, Vol. 27, DOI: 10.1016 / j.pnsc.2017.07.002) influences the gas sensitive behavior of nanocrystalline ZnO film by laser doping Al, and realizes a response rate of 50% to 150 ppm ammonia at a working temperature of 165℃. Although this technical solution has the advantages of high response and low cost, its working temperature is much higher than room temperature, which seriously limits the application; in addition, this technical solution also has the problems of high power consumption and safety hazards.

[0004] In order to solve the problem of working temperature higher than room temperature, transition metal chalcogen compounds can be used as sensors. For example, existing document 2 (Analytica Chimica Acta, 2021, Vol. 4, DOI: 10.1016 / j.aca.2021.338576) realizes the working temperature from 150℃ to room temperature by doping MoS2 in SnO2, and the response to 200 ppm ammonia is increased from 1.2% to 6.7%. Although this technical solution realizes the reduction of the working temperature of the sensor to room temperature, and improves the response rate and selectivity of the sensor to ammonia, since the micro-morphology size of MoS2 is only 100 nm, MoS2 is prone to aggregation, thereby reducing the response to ammonia at room temperature.

[0005] MoS2 is induced to grow by providing a suitable carrier, so as to realize uniform distribution of MoS2, and further solve the agglomeration problem of MoS2. Researches according to the present application show that MXene has the characteristics of a large number of oxygen-containing functional groups, and can obtain anchoring effect as a carrier of MoS2, form MXene / MoS2 composite material, and thus improve the loading effect and dispersion effect of MoS2. However, only by adding MXene to form MXene / MoS2 composite material, the stability is improved, but still cannot meet the stability requirement; in addition, the addition of MXene cannot improve the response rate.

[0006] In order to further improve the stability of the MXene / MoS2 composite material, the MXene / MoS2 composite material can be coated. However, only by using conventional coating materials, the stability problem can be solved, but the response rate cannot be improved.

[0007] Researches according to the present application show that by using a conductive polymer as a coating material, the response rate of the composite material can be improved by using the high conductivity of the conductive polymer. SUMMARY

[0008] The purpose of the present application is to provide a MXene / MoS2 / polypyrrole composite material and a preparation method thereof, and on this basis, a sensor is prepared for detecting ammonia.

[0009] The present application solves the above problems by using the following principles and methods in view of the technical problems existing in the prior art.

[0010] 1. MXene is used as a substrate, which not only plays a supporting role, but also improves the loading effect of MoS2 by utilizing a large number of oxygen-containing functional groups;

[0011] 2. MoS2 is used as a load, which not only reduces the working temperature, but also improves the ammonia response rate and selectivity;

[0012] 3. Polypyrrole is used as a coating layer, which improves the conductivity and stability of the MXene / MoS2 composite material, and further enhances the gas sensing performance through the synergistic effect of polypyrrole and MoS2.

[0013] In order to achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows:

[0014] A MXene / MoS2 / polypyrrole composite material is obtained by compounding MXene, MoS2 and polypyrrole, wherein MoS2 is in a nanosheet structure, grows on the surface of MXene to form MXene-MoS2, and then polypyrrole is coated outside the MXene-MoS2 to obtain the MXene / MoS2 / polypyrrole composite material, and the particle size is 5-6 μm.

[0015] A preparation method of MXene / MoS2 / polypyrrole composite material, comprising the following steps:

[0016] Step 1, preparation of MXene, mixing titanium aluminum carbide with 30% concentration hydrofluoric acid, and carrying out water bath etching under certain conditions to obtain MXene;

[0017] In the step 1, the water bath etching conditions are that the water bath temperature is 30 DEG C, and the water bath time is 36h;

[0018] Step 2, loading of MoS2, placing the MXene obtained in step 1 in water, and carrying out ultrasonic under certain conditions to obtain a suspension; then, placing the thiourea, ammonium molybdate and citric acid monohydrate in the suspension to meet a certain amount of substance ratio, and carrying out hydrothermal reaction under certain conditions, after the reaction is completed, carrying out centrifugation under certain conditions, and then drying under certain conditions to obtain MXene-MoS2;

[0019] In the step 2, the ultrasonic conditions are that the ultrasonic power is 500w, and the ultrasonic time is 5min;

[0020] The MXene, thiourea, ammonium molybdate and citric acid monohydrate meet the amount of substance ratio of 30:1:7;

[0021] The hydrothermal reaction conditions are that the hydrothermal temperature is 180 DEG C, and the hydrothermal time is 20h;

[0022] The centrifugation conditions are that the centrifugal speed is 7000r / min, and the centrifugal time is 5min;

[0023] The drying conditions are that the drying temperature is 60 DEG C, and the drying time is 24h;

[0024] Step 3, coating of polypyrrole, placing the MXene / MoS2 obtained in step 2 and sodium dodecyl benzene sulfonate to meet a certain mass ratio, mixing and stirring the MXene / MoS2 and sodium dodecyl benzene sulfonate in deionized water to obtain a mixed solution, then adding pyrrole and ammonium persulfate to meet a certain mass ratio under the stirring condition, to obtain a reaction solution, finally, carrying out polymerization reaction of the reaction solution under certain conditions to obtain MXene / MoS2 / polypyrrole composite material, which is abbreviated as MXene / MoS2 / polypyrrole;

[0025] In the step 3, the mass ratio of MXene / MoS2 and sodium dodecyl benzene sulfonate is 1:4;

[0026] Before adding pyrrole and ammonium persulfate, the ammonium sulfate is pre-cooled in an ice water mixture;

[0027] The mass ratio of the pyrrole and ammonium persulfate is 1:3.8;

[0028] The conditions of the polymerization reaction are that the polymerization temperature is 3 DEG C and the polymerization time is 5 h under stirring.

[0029] A MXene / MoS2 / poly-pyrrole sensor based on MXene / MoS2 / poly-pyrrole, which is selective to NH3 among NH3, H2, NO2, CO2, CH3CH2OH and DMF gas; the minimum detection limit of NH3 is 10 ppm at room temperature; the response time is 43.6 s and the recovery time is 40.8 s under the condition of room temperature and humidity of 45%.

[0030] A preparation method of a MXene / MoS2 / poly-pyrrole sensor, first, MXene / MoS2 / poly-pyrrole and anhydrous ethanol are mixed and ground to obtain a mixed solution; then, the mixed solution is added dropwise to the surface of a gold interdigital electrode and baked; then, 0.25% naphthol is added dropwise for capping; finally, the gold interdigital electrode is connected with a gas chamber to obtain a MXene / MoS2 / poly-pyrrole sensor, i.e. a gas sensitive test system.

[0031] An application of a MXene / MoS2 / poly-pyrrole sensor as an unknown ammonia concentration sensor, comprising the following steps:

[0032] Step a, obtaining of concentration data, by performing ammonia concentration detection experiments under known and determined temperature, humidity and ammonia concentration conditions, standard ammonia concentration data is obtained;

[0033] Step b, determination of unknown concentration, under the conditions of given temperature and humidity, ammonia concentration detection experiment is performed on the unknown concentration of the to-be-tested ammonia, and the test result is compared with the standard ammonia concentration data, so that the concentration of the to-be-tested ammonia is confirmed.

[0034] The MXene / MoS2 / poly-pyrrole composite material is tested by SEM, and it is shown that the MoS2 nanosheet is successfully grown on the surface of MXene, and the poly-pyrrole also successfully coats the MXene / MoS2 composite material.

[0035] The MXene / MoS2 / poly-pyrrole composite material is tested by XRD, and it is shown that the XRD spectrum contains characteristic peaks of MXene and MoS2, indicating that the synthesis is successful.

[0036] The MXene / MoS2 / poly-pyrrole composite material is tested by the best gas sensitive performance, and it is shown that

[0037] 1. Selectivity to NH3 in NH3, H2, NO2, CO2, CH3CH2OH and DMF gas; the minimum limit of detection of NH3 is 10 ppm at room temperature;

[0038] 2. Response time is 43.6 s and recovery time is 40.8 s at room temperature and humidity of 45%;

[0039] 3. Resistance and response rate increase with the increase of ammonia concentration in the range of 10-200 ppm;

[0040] 4. Response rate decreases with the increase of humidity in the range of 30%-90% in air.

[0041] According to the test results, the present application has the following advantages compared with the prior art:

[0042] 1. The working temperature is room temperature, which expands the application range of the sensor;

[0043] 2. High sensitivity and stability of ammonia detection;

[0044] 3. High selectivity to ammonia among common gases;

[0045] 4. Quantitative testing of ammonia concentration can be performed;

[0046] 5. The preparation process is simple, which is a combination of in-situ chemical polymerization and hydrothermal method, i.e. low cost; and the product performance is stable, meeting the requirements of large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 SEM image of MXene prepared in Example 1;

[0048] Figure 2 SEM image of MXene / MoS2 prepared in Example 1;

[0049] Figure 3 SEM image of MXene / MoS2 / poly-pyrrole prepared in Example 1;

[0050] Figure 4 XRD spectrum of MXene / MoS2 / poly-pyrrole prepared in Example 1;

[0051] Figure 5 Resistance change curve of MXene / MoS2 / poly-pyrrole prepared in Example 1 to ammonia concentration;

[0052] Figure 6 Response rate change curve of MXene / MoS2 / poly-pyrrole prepared in Example 1 to ammonia concentration;

[0053] Figure 7 MXene / MoS2 / polyazole ammonia gas response recovery time curve prepared in Example 1;

[0054] Figure 8 MXene / MoS2 / polyazole humidity ammonia gas response rate influence change prepared in Example 1;

[0055] Figure 9 MXene / MoS2 / polyazole ammonia gas and other gas selectivity diagram prepared in Example 1.

[0056] Figure 10 Example 1, Comparative Example 1 and Comparative Example 2 response rate comparison diagram for different concentrations of ammonia gas. DETAILED DESCRIPTION

[0057] The present application will be further described in detail by combining the content of the application with the accompanying drawings of the specification, but is not limited to the application.

[0058] Example 1

[0059] A preparation method of a MXene / MoS2 / polyazole composite material, comprising the following steps:

[0060] Step 1, preparation of MXene, titanium aluminum carbide is mixed with 30% concentration hydrofluoric acid, and water bath etching is carried out under the condition that the water bath temperature is 30℃ and the water bath time is 36h, so that MXene can be obtained;

[0061] In order to prove the micro morphology of MXene, i.e. the successful preparation of MXene, SEM test is carried out. The test results are shown in Figure 1 As shown, the etched MXene is in the form of an accordion.

[0062] Step 2, loading of MoS2, the MXene obtained in step 1 is placed in water, ultrasonic treatment is carried out with an ultrasonic power of 500w and an ultrasonic time of 5min to obtain a suspension; then, 6mM thiourea, 0.2mM ammonium molybdate and 1.4mM monohydrate citric acid are placed in the suspension to satisfy the molar ratio of MXene, thiourea, ammonium molybdate and monohydrate citric acid, i.e. 30:1:7, hydrothermal reaction is carried out with a hydrothermal temperature of 180℃ and a hydrothermal time of 20h, after the reaction is completed, centrifugation is carried out with a centrifugal speed of 7000r / min and a centrifugal time of 5min, and then drying is carried out at a drying temperature of 60℃ and a drying time of 24h, so that MXene-MoS2 can be obtained.

[0063] In order to prove the micro morphology of MXene / MoS2, i.e. the influence of loading MoS2 on the micro morphology, SEM test is carried out. The test results are shown inFigure 2 As shown in the figure, the MoS2 nanosheet is loaded on the MXene.

[0064] Step 3, coating of polypyrrole, 20 mg of MXene / MoS2 obtained in step 2 and 80 mg of sodium dodecylbenzenesulfonate are mixed in 14 ml of deionized water and stirred for 30 min to obtain a mixed solution, then 76 μl of pyrrole and 252 mg of ammonium persulfate are added to the mixed solution under stirring to obtain a reaction solution, and finally, the reaction solution is subjected to polymerization reaction under stirring at a polymerization temperature of 3 ℃ and a polymerization time of 5 h to obtain MXene / MoS2 / poly pyrrole composite material, which is abbreviated as MXene / MoS2 / poly pyrrole.

[0065] In order to prove the micro-morphology of MXene / MoS2 / poly pyrrole, i.e. the effect of polypyrrole coating on the micro-morphology, SEM test is performed. The test results are as shown in the figure. Figure 3 As shown in the figure, polypyrrole is coated on the surface of MXene / MoS2 composite material.

[0066] In order to further prove the successful preparation of MXene / MoS2 / poly pyrrole, XRD test is performed. The test results are as shown in the figure. Figure 4 As shown in the figure, MXene / MoS2 / poly pyrrole contains characteristic peaks of MXene and MoS2. The test results show that MXene / MoS2 / poly pyrrole is successfully prepared.

[0067] In order to prove that MXene / MoS2 / poly pyrrole has the performance of detecting ammonia gas, i.e. can be used as ammonia gas sensor, MXene / MoS2 / poly pyrrole based sensor is prepared, and gas concentration detection experiment is performed.

[0068] A preparation method of MXene / MoS2 / poly pyrrole based sensor, first, 6 mg of MXene / MoS2 / poly pyrrole and 1 mL of anhydrous ethanol are mixed and ground to obtain a mixed solution; then, 20 μL of the mixed solution is added dropwise to the surface of gold interdigital electrode and baked; then, 1 μL of 0.25% naphthol is added dropwise for sealing; finally, the gold interdigital electrode is connected with the gas chamber to obtain the MXene / MoS2 / poly pyrrole based sensor, i.e. the gas sensitive test system.

[0069] A performance test method of MXene / MoS2 / poly pyrrole based sensor, which is simply called gas concentration detection experiment, i.e. the application of MXene / MoS2 / poly pyrrole based sensor as ammonia gas sensor, the specific method is as follows: under certain temperature and humidity conditions, a certain concentration of gas is introduced into the gas chamber, the resistance of the MXene / MoS2 / poly pyrrole based sensor is measured, and the response rate is calculated.

[0070] The ammonia concentration detection experiment based on the MXene / MoS2 / polyazole sensor was carried out under the conditions of a temperature of 25°C and a humidity of 45%, and the test results are shown in Table 1, Figure 5 and Figure 6 The detection lower limit of the MXene / MoS2 / polyazole sensor is 10 ppm, and it can be concluded that the resistance and response rate of the MXene / MoS2 / polyazole sensor increase with the increase of the ammonia concentration.

[0071] Table 1 Resistance and response rate change of MXene / MoS2 / polyazole sensor to different concentrations of ammonia at room temperature

[0072]

[0073]

[0074] In addition, in order to prove the response-recovery performance of the MXene / MoS2 / polyazole sensor, a response-recovery test was carried out. The test results are shown in Figure 7 The response time is 43.6 s, and the recovery time is 40.8 s, that is, the MXene / MoS2 / polyazole sensor has the characteristics of fast response and fast recovery.

[0075] In order to prove the influence of humidity on the MXene / MoS2 / polyazole sensor, a humidity influence test was carried out. The test results under the conditions of a humidity of 30%-90% are shown in Figure 8 and Table 2, and there is a rule that the response rate decreases with the increase of the humidity in the air.

[0076] Table 2 Influence of humidity on the response rate of the MXene / MoS2 / polyazole sensor

[0077] Ammonia concentration (ppm) Humidity (%) Response rate (%) 100 30 23 100 40 21.768 100 50 13.255 100 60 9.891 100 70 8.556 100 80 4.846 100 90 4.743

[0078] In order to prove that the MXene / MoS2 / polyazole sensor has selectivity to ammonia, NO2, CO2, H2, CH3CH2OH, and DMF were used to carry out gas concentration detection experiments. Under the condition of room temperature, the response rate of the MXene / MoS2 / polyazole sensor to 100 ppm gas is shown in Figure 9 and Table 3, the response rate of NO2 is-5.4%; the response rate of CO2 is 3.6%; the response rate of H2 is 4.2%; the response rate of CH3CH2OH is 2.5%; and the response rate of DMF is 0.4%.

[0079] From the above test results, it can be proved that the MXene / MoS2 / polyazole sensor has selectivity to ammonia.

[0080] Table 3 MXene / MoS2 / poly pyrrole sensor selectivity test table

[0081] Gas species Gas concentration (ppm) Response rate (%) [CAT] 100 21.12 NO2 100 -5.4 CO2 100 3.6 [H2] 100 4.2 CH3CH2OH 100 2.5 DMF 100 0.4

[0082] An application of a MXene / MoS2 / poly pyrrole sensor as an unknown ammonia concentration sensor, comprising the following steps:

[0083] Step a, obtaining of concentration data, by performing ammonia concentration detection experiments under known and determined temperature, humidity and ammonia concentration conditions, obtaining standard ammonia concentration data;

[0084] Step b, determination of unknown concentration, under the conditions of given temperature and humidity, ammonia concentration detection experiment of unknown concentration of the measured ammonia, comparison of the test results with the standard ammonia concentration data, that is, the concentration of the measured ammonia can be confirmed.

[0085] In order to prove the influence of the poly pyrrole coating conditions on the performance, comparative example 1 and comparative example 2 are provided, and the polymerization time of poly pyrrole is 3h and 7h respectively to prepare MXene / MoS2 / poly pyrrole.

[0086] Comparative example 1

[0087] A MXene / MoS2 / poly pyrrole composite material with a poly pyrrole polymerization time of 3h, the steps not specifically specified are the same as example 1, the difference is that the polymerization time of poly pyrrole in step 3 is 3h, and the obtained material is named as MXene / MoS2 / poly pyrrole-3.

[0088] The ammonia concentration detection results of MXene / MoS2 / poly pyrrole-3 are as shown in Figure 10 and table 4, the response rate of MXene / MoS2 / poly pyrrole-3 to 100ppm ammonia at room temperature is 9.83%, which is much lower than the response rate of MXene / MoS2 / poly pyrrole-5 to ammonia under the same conditions.

[0089] Comparative example 2

[0090] A MXene / MoS2 / poly pyrrole composite material with a poly pyrrole polymerization time of 7h, the steps not specifically specified are the same as example 1, the difference is that the polymerization time of poly pyrrole in step 3 is 3h, and the obtained material is named as MXene / MoS2 / poly pyrrole-7.

[0091] The ammonia concentration detection results of MXene / MoS2 / poly pyrrole-7 are as shown in Figure 10As shown in Table 4, the response rate of MXene / MoS2 / polyazole-7 to 100 ppm ammonia gas at room temperature is 4.92%, which is much lower than the response rate of MXene / MoS2 / polyazole-5 to ammonia gas under the same conditions.

[0092] Table 4: Comparison of response rates of examples 1 and comparative examples

[0093]

[0094] As can be seen by comparing Comparative Example 1, Comparative Example 2 and Example 1, the gas sensing performance of the MXene / MoS2 / polyazole composite material is best and the response rate is highest when the polyazole coating time is 5 h.

Claims

1. A method for preparing an MXene / MoS2 / polypyrrole composite material, characterized in that... Includes the following steps: Step 1, Preparation of MXene: Titanium aluminum carbide is mixed with 30% hydrofluoric acid and etched in a water bath under certain conditions to obtain MXene. Step 2, MoS2 loading: The MXene obtained in Step 1 is placed in water and sonicated under certain conditions to obtain a suspension; then, MXene, thiourea, ammonium molybdate and citric acid monohydrate are placed in the suspension in a certain molar ratio and subjected to a hydrothermal reaction under certain conditions. After the reaction is completed, the mixture is centrifuged under certain conditions and then dried under certain conditions to obtain MXene-MoS2. In step 2, the molar ratio of MXene, thiourea, ammonium molybdate, and citric acid monohydrate is 30:1:

7. Step 3, polypyrrole coating: MXene / MoS2 and sodium dodecylbenzenesulfonate obtained in Step 2 are mixed in deionized water at a certain mass ratio to obtain a mixed solution. Then, pyrrole and ammonium persulfate are added to the mixed solution at a certain mass ratio under stirring to obtain a reaction solution. Finally, the reaction solution is subjected to a polymerization reaction under certain conditions to obtain the MXene / MoS2 / polypyrrole composite material, abbreviated as MXene / MoS2 / polypyrrole. In step 3, the mass ratio of MXene / MoS2 to sodium dodecylbenzenesulfonate is 1:4; In step 3, the mass ratio of pyrrole to ammonium persulfate is 1:3.8; In step 3, before adding pyrrole and ammonium persulfate, the ammonium sulfate is pre-cooled in an ice-water mixture; In step 3, the polymerization conditions are as follows: under stirring conditions, the polymerization temperature is 3℃ and the polymerization time is 5 h. The resulting MXene / MoS2 / polypyrrole is obtained by combining MXene, MoS2 and polypyrrole. Among them, MoS2 is a nanosheet structure that grows on the surface of MXene to form MXene-MoS2. Then, polypyrrole is coated on the outside of MXene-MoS2 to obtain the MXene / MoS2 / polypyrrole composite material with a particle size of 5-6µm.

2. The preparation method according to claim 1, characterized in that: In step 1, the conditions for water bath etching are: water bath temperature of 30°C and water bath time of 36 h.

3. The preparation method according to claim 1, characterized in that: In step 2, the ultrasound conditions are: ultrasound power of 500 W and ultrasound time of 5 min. In step 2, the hydrothermal reaction conditions are: hydrothermal temperature of 180 ℃ and hydrothermal time of 20 h. In step 2, the centrifugation conditions are: centrifugation speed of 7000 r / min and centrifugation time of 5 min. In step 2, the drying conditions are: drying temperature of 60 ℃ and drying time of 24 h.

4. The preparation method according to claim 1, characterized in that: The method for preparing MXene / MoS2 / polypyrrole-based sensors is as follows: First, MXene / MoS2 / polypyrrole and anhydrous ethanol are mixed and ground to obtain a mixture. Then, the mixture was dropped onto the surface of the gold interdigitated electrode and dried; then, 0.25% naphthol was added for sealing; finally, the gold interdigitated electrode was connected to the gas chamber to obtain a gas-sensitive testing system based on the MXene / MoS2 / polypyrrole sensor. The gas sensor based on MXene / MoS2 / polypyrrole exhibits selectivity for NH3 among NH3, H2, NO2, CO2, CH3CH2OH and DMF gases; the detection limit for NH3 is 10 ppm at room temperature; and the response time is 43.6 s and the recovery time is 40.8 s at room temperature and 45% humidity.

5. The preparation method according to claim 1, characterized in that: The preparation of the obtained MXene / MoS2 / polypyrrole-based sensor for use as a sensor for unknown ammonia concentration includes the following steps: Step a, obtaining the standard concentration data, involves conducting an ammonia concentration detection experiment under known and determined temperature, humidity and ammonia concentration conditions to obtain standard ammonia concentration data; Step b, determination of unknown concentration: Under the given temperature and humidity conditions, the ammonia gas of unknown concentration is tested in an ammonia concentration detection experiment. The test results are compared with the standard ammonia concentration data to confirm the concentration of the ammonia gas to be tested.

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