Preparation method and application of antioxidant and high-selectivity Ti3C2Tx material

Abstract

The invention discloses a preparation method and application of an antioxidant and high-selectivity Ti3C2Tx material, Ti3AlC2 is etched by NaF and an HCl solution to prepare intrinsic Ti3C2Tx, then the intrinsic Ti3C2Tx is mixed with an antioxidant and a sodium tungstate / thioacetamide mixed solution, and a hydrothermal reaction is performed to obtain the antioxidant and high-selectivity Ti3C2Tx material. The Ti3C2Tx material prepared by the invention has relatively high sensitivity and selectivity on SF6 decomposition gas SO2 gas, and can be applied to a gas sensor for detecting the SO2 gas, so that the gas sensor has high sensitivity, quick response and elimination of the influence of interference gas, and meanwhile, due to the addition of the antioxidant, the service life is prolonged, and the service life of the gas sensor is prolonged. The selectivity is further improved, and the practical application value is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensor material preparation, and specifically relates to a preparation method and application of an antioxidant and highly selective Ti 3 C 2 T x material. Background Art

[0002] SF 6 is a strongly electronegative gas. Its molecules are extremely easy to adsorb free electrons to form heavy negative ions, weakening the collision ionization process in the gas. Therefore, its electrical insulation strength is very high, about 2.5 times that of air insulation strength in a uniform electric field. SF 6 gas shows a peak of thermal decomposition at t≈2000K. Therefore, at the moment when the alternating current arc current passes through zero, SF 6 has a much stronger cooling effect on the arc path than air, and its arc extinguishing ability is about 100 times that of air. Due to the excellent arc extinguishing performance, insulation performance and good chemical stability of SF 6 gas, it has been used as the arc extinguishing medium of high-voltage circuit breakers since the late 1950s. In ultra-high voltage and extra-high voltage circuit breakers, SF 6 as the arc extinguishing medium has replaced oil and has largely replaced compressed air; and SF 6 is still the current mainstream insulating gas.

[0003] Subject to SF 6 gas insulation equipment design, manufacturing, transportation, installation, operation and maintenance and other links will inevitably lead to various internal insulation defects, affecting the safe operation of SF 6 gas insulation equipment. Local overheating, spark discharge and other faults are likely to occur in the area of internal defects, thus decomposing to produce SO 2 、SF 4 、S 2 F 2 、SF2、SOF 2 、SO 2 F 2 、SOF 4 and HF, etc., all of which have strong corrosiveness and toxicity; and SO 2 can be used as an indicator of serious partial discharge faults in SF 6 gas insulation equipment. Therefore, it is very necessary to detect the SO 6 component in SF 2 .

[0004] SF 6 decomposition component detection methods include detection tube method, gas chromatography, mass spectrometry, optical detection method, electrochemical detection method, etc. For example, Chinese Patent CN103105441B discloses a qualitative and quantitative analysis of SF6 A method for decomposing gas discharge products, which uses a gas chromatography-mass spectrometry (GC-MS) instrument to qualitatively and quantitatively analyze samples, realizes the synchronous detection of CF 4 、C 2 F 6 、CO 2 、SO 2 F 2 、SOF 4 、SOF 2 、SO 2 、H 2 S and other 8 components, can perform rapid identification and accurate quantitative analysis, which helps to understand the internal insulation state of electrical equipment and accurately judge the cause of faults. However, there are problems such as the high price of detection equipment and the complexity of detection methods.

[0005] Ti 3 C 2 T x is a two-dimensional (2D) nanosheet material from the MXene family, with excellent electrical conductivity, mechanical strength and good chemical stability, so it has broad application prospects in the fields of energy storage, sensors and catalysis. Research shows that Ti 3 C 2 T x sensors have high selectivity for acetone, ethanol and ammonia.

[0006] Chinese Patent CN112255278B discloses a room-temperature ammonia sensor based on Ti 3 C 2 T x / WO 3 composite nanomaterials and its preparation method and application. Using WO 3 nanoparticles have the advantages of being sensitive to ammonia, fast response time, good long-term stability, easy synthesis, and having rich oxygen active sites. When combined with Ti 3 C 2 T x materials, the response sensitivity of the sensor to ammonia is greatly improved.

[0007] However, when the Ti 3 C 2 T x sensor is applied to the detection of SF 6 decomposition components, there are problems such as the sensitivity needs to be enhanced, and the recognition selectivity for SO 2 gas is low, and it is easily affected by other interfering gases during the detection process. Summary of the Invention

[0008] In view of the above technical problems, the present invention provides an antioxidant and highly selective Ti 3 C2 T x Preparation method and application of materials, introducing antioxidants, tungsten and intrinsic Ti 3 C 2 T x Co-preparing XMene materials, improving the antioxidant property and sensitivity of XMene materials to SO 2 gas, and further increasing the selectivity of XMene materials for gases, making the selectivity of SO 2 gas enhanced to 8.2 times that of SO 2 F 2 gas and 32 times that of H 2 S gas.

[0009] To achieve the above object, the present invention provides a preparation method of antioxidant and highly selective Ti 3 C 2 T x materials, comprising the following steps: (1) Preparing intrinsic Ti 3 C 2 T x , diluting and dispersing in an ice bath to obtain a Ti 3 C 2 T x dispersion; (2) Adding an antioxidant to the Ti 3 C 2 T x dispersion and mixing evenly to obtain a Ti-P mixed solution; (3) Mixing the tungstate / thioacetamide mixed solution with the Ti-P mixed solution, adjusting the pH to 3-4 while stirring, and performing a hydrothermal reaction under inert gas protection; (4) Filtering to retain the precipitate, washing and centrifuging multiple times, and then obtaining antioxidant and highly selective Ti 3 C 2 T x materials.

[0010] Preferably, the preparation method of the intrinsic Ti 3 C 2 T x in step (1) comprises the following steps: S1: Mixing and dissolving NaF and HCl solution, adding Ti 3 AlC 2 , and stirring and reacting to obtain a product; S2: Washing and centrifuging the reaction product until the upper liquid is black, collecting the upper black liquid, performing ultrasonic treatment in an ice bath and centrifuging to obtain a dispersion; S3: Collecting the lower precipitate in the dispersion, repeating step S2, and drying the obtained dispersion to obtain intrinsic Ti3 C 2 T x 。

[0011] Further preferably, the molar ratio of NaF to HCl in step S1 is 1:100 - 110, and the molar ratio of NaF to Ti 3 AlC 2 is 7 - 8:6; the stirring reaction conditions are stirring at 40°C for 5 - 7 h.

[0012] Preferably, the mass ratio of Ti 3 C 2 T x to the antioxidant in step (2) is 1:0.5 - 2 Further preferably, the antioxidant is sodium phosphate.

[0013] Preferably, the mass ratio of sodium tungstate to thioacetamide in the tungstate / thioacetamide mixed solution in step (3) is 7:3.

[0014] Preferably, the volume ratio of the tungstate / thioacetamide mixed solution to the Ti-P mixed solution in step (3) is 1:1.

[0015] Further preferably, the tungstate is sodium tungstate or potassium tungstate.

[0016] Preferably, the hydrothermal reaction conditions in step (3) are reacting at 160 - 200°C for 10 - 20 h.

[0017] Further preferably, the hydrothermal reaction conditions are 180°C and 10 h.

[0018] The present invention also provides an application of the antioxidant and highly selective Ti 3 C 2 T x material prepared by the preparation method, and the application is in a gas sensor.

[0019] Preferably, the application is to selectively identify SO 2 gas in a gas sensor.

[0020] The beneficial effects of the present invention are as follows: 1. Using NaF and hydrochloric acid, the intrinsic Ti 3 C 2 T x is prepared in a relatively mild manner, which not only provides sufficient F ions for etching but also improves the etching safety.

[0021] 2. Using sodium phosphate as the antioxidant and sodium tungstate as the dopant, the intrinsic Ti 3 C 2T x was modified to prepare Ti 3 C 2 T x materials with antioxidant properties and high selectivity, enabling Ti 3 C 2 T x materials to increase the selectivity for SO 2 gas to 8.2 times that of SO 2 F 2 gas and 32 times that of H 2 S gas, and can more sensitively detect SO 6 gas in the decomposition gas products of SF 2 gas, reducing the influence of other interfering gases.

[0022] 3. The prepared Ti 3 C 2 T x materials have a short response time, a short recovery time, and good long-term stability, and can optimize the detection effect of SF 6 decomposition gas SO 2 in a shorter time, and can also maintain the complete morphology for a long time, thus realizing the long-term gas detection function.

[0023] 4. The present invention uses a relatively mild experimental method, avoiding the harm of HF to operators. In addition, the precipitate is repeatedly dispersed and centrifugally expanded, improving the yield. Description of the Drawings

[0024] Figure 1 is the flow chart of the preparation method of the present invention.

[0025] Figure 2 is the scanning electron micrograph of Ti 3 C 2 T x materials. In the figure, A is Ti 3 C 2 T x -2 prepared in Comparative Example 3, and B is P-Ti 3 C 2 T x -2 prepared in Example 3.

[0026] Figure 3 is the high-resolution transmission electron micrograph of Ti 3 C 2 T x materials. In the figure, A is the transmission electron micrograph of Ti 3 C 2 T x prepared in Comparative Example 3, and B is the transmission electron micrograph of Ti 3 C2 T x Lattice fringe pattern. C is WO prepared in Example 3 3 Transmission electron microscope image. D is WO prepared in Example 3 3 Lattice fringe pattern.

[0027] Figure 4 P-Ti prepared in Example 3 3 C 2 T x XPS energy spectrum of -2. In the figure, A is the full spectrum, B is the C 1s fine spectrum, C is the Ti 2p fine spectrum, D is the O 2p fine spectrum, E is the F 2p fine spectrum, and F is the W 4f fine spectrum.

[0028] Figure 5 P-Ti prepared in Example 3 3 C 2 T x I-V curve of -2.

[0029] Figure 6 Ti at room temperature 3 C 2 T x Gas sensing response curve of the material to 5 ppm SO 2

[0030] Figure 7 Ti in Example 8 3 C 2 T x Gas sensing response curve of the material to 0.1 ppm - 100 ppm SO 2 In the figure, A is the actual response curve, B is the response value of the Ti 3 C 2 T x Material and the fitting curve graph of the SO 2 Concentration.

[0031] Figure 8 Schematic diagram of the gas sensing experiment platform in Example 8.

[0032] Figure 9 Effect of the antioxidant on the Ti 3 C 2 T x Material in Example 9. In the figure, a is the selectivity bar graph of the Ti 3 C 2 T x -2, b is the selectivity bar graph of the P-Ti 3 C 2 T x -2, C is the selectivity bar graph of the Ti 3 C 2 T​x Line graph of the response time change of -2, where D is P-Ti 3 C 2 T x Line graph of the response time change of -2

[0033] Figure 10 For the antioxidant's effect on Ti in Example 9 3 C 2 T x Effect on the morphology of the Ti material. In the figure, A is P-Ti 3 C 2 T x -2, B is Ti 3 C 2 T x -2 Detailed implementation method

[0034] The technical solution of the present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only the preferred embodiments of the present invention and should not be construed as limitations on the present invention. The protection scope of the present invention should be determined by the content recorded in the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative efforts fall within the protection scope of the present invention

[0035] Example 1 Prepare intrinsic Ti by etching with hydrochloric acid and sodium fluoride. The preparation method is as follows 3 C 2 T x , as follows (1) Take 3.9 g of NaF and mix it with 30 mL of HCl aqueous solution (9 M) in a polytetrafluoroethylene beaker, stir at a speed of 40 r / min for 30 min to obtain a mixed solution (2) In a fume hood, add 3 g of the precursor Ti 3 AlC 2 to the mixed solution, continuously stir and react at 40 °C for 6 h, and filter to retain the precipitate as the reaction product (3) Wash and centrifuge-expand the reaction product with deionized water. The volume of the centrifuged precipitate gradually increases. Continue to add deionized water for washing and centrifugation until the upper layer liquid is black (4) Take the upper black liquid, ultrasonicate it in an ice-water bath for 30 min, and centrifuge to obtain a single-layer or few-layer dispersion (5) Collect the lower precipitate after separating the upper black liquid and the precipitate after separating the single-layer or few-layer dispersion. Mix them and repeat steps (3)-(4) twice to obtain the single-layer or few-layer dispersion for the second time (6) Combine the single-layer or few-layer dispersions and vacuum dry them at 60 °C to obtain intrinsic Ti3 C 2 T x 。

[0036] The mass concentration of the intrinsic Ti 3 C 2 T x is 14 mg / mL, and the yield is 46%.

[0037] Example 2 Prepare an antioxidant and highly selective Ti 3 C 2 T x material, and the preparation method is as follows: (1) Take the intrinsic Ti 3 C 2 T x prepared in Example 1, and dilute it with deionized water to 1 mg / mL as the Ti 3 C 2 T x dispersion; (2) Add 10 mg of sodium phosphate to 10 mL of the Ti 3 C 2 T x dispersion, and stir to dissolve to obtain a Ti-P mixed solution; (3) Take 105 mg of K 2 WO 4 ·2H 2 O and 60 mg of thioacetamide, add them to 7 mL of deionized water, and stir magnetically for 2 h to dissolve to obtain a potassium tungstate / thioacetamide mixed solution; (4) Mix the potassium tungstate / thioacetamide mixed solution and the Ti-P mixed solution in a volume ratio of 1:1, and stir for 30 min to obtain a mixed solution; (5) While stirring, slowly add hydrochloric acid solution (1 M) to the mixed solution until the pH value is 3, then transfer it to a reaction kettle, purge the air in the reaction kettle with helium bubbling, and carry out a hydrothermal reaction at 180 °C for 10 h. After the reaction, filter to retain the precipitate; (6) Wash the precipitate with anhydrous ethanol and deionized water multiple times, and centrifuge at 5000 rpm / min to obtain the product, which is the antioxidant and highly selective Ti 3 C 2 T x material, denoted as P-Ti 3 C 2 T x -1; (7) Redisperse the product in deionized water, and store it refrigerated with helium bubbling.

[0038] Example 3 The method and steps are the same as those in Example 2, except that the volume ratio of the potassium tungstate / thioacetamide mixture to the Ti-P mixed solution is changed to 2:1, and the obtained product is denoted as P-Ti 3 C 2 T x -2

[0039] Example 4 The method and steps are the same as those in Example 2, except that the volume ratio of the potassium tungstate / thioacetamide mixture to the Ti-P mixed solution is changed to 4:1, and the obtained product is denoted as P-Ti 3 C 2 T x -4

[0040] Comparative Example 1 The method and steps are the same as those in Example 2, except that the potassium tungstate / thioacetamide mixture is not used, and the obtained product is denoted as P-Ti 3 C 2 T x .

[0041] Comparative Example 2 The method and steps are the same as those in Example 2, step (2) is omitted, and the volume ratio of the potassium tungstate / thioacetamide mixture to the Ti-P mixed solution is changed to 2:1, and the obtained product is denoted as Ti 3 C 2 T x -2

[0042] Comparative Example 3 The method and steps are the same as those in Example 2, step (2) is omitted, and the potassium tungstate / thioacetamide mixture is not used, and the obtained product is denoted as Ti 3 C 2 T x .

[0043] Example 5 The method and steps are the same as those in Example 2, except that the amount of sodium phosphate in step (2) is changed to 5 mg, and the obtained product is prepared

[0044] Example 6 The method and steps are the same as those in Example 2, except that the amount of sodium phosphate in step (2) is changed to 15 mg, and the obtained product is prepared

[0045] Comparative Example 4 The method and steps are the same as those in Example 2, except that step (2) is omitted and sodium phosphate is not used, and the obtained product is prepared

[0046] Comparative Example 5 The method and steps are the same as those in Example 2, except that the amount of sodium phosphate in step (2) is changed to 20 mg, and the obtained product is prepared

[0047] Example 7 The MXene materials prepared in the above examples and comparative examples were characterized by using an X-ray powder diffractometer (XRD, XRD-6100, Shimadzu) with Cu-Kα radiation; the morphology of the materials was characterized by field emission electron microscopy and (SEM, Zeiss, SIGMA) transmission electron microscopy (TEM, JEOL JEM-F200), the surface element content and valence state were analyzed by X-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific, ESCALAB250Xi), and the specific surface area and adsorption / desorption profile of the sensing materials were tested by a fully automatic specific surface area and pore size analyzer (Quantachrome, Quadrasorb evoTM).

[0048] The results showed that: compared with the Ti 3 C 3 T 2 material without doping WO x -2, obvious doped WO 3 particles could be seen in P-Ti 2 C x T 3 -2, and the wrapping property was relatively high, indicating that WO 3 was successfully doped, and the particle size distribution of WO 3 particles was uniform, the preparation effect was good, and the addition of sodium phosphate did not have a negative impact on the doping. The two-dimensional sheet structure and well-dispersed Ti 3 C 2 T x material ( Figure 2 ) could still be seen.

[0049] It Figure 3 could be seen that the crystal plane spacing of Ti 3 C 2 T x was 0.257 nm (Ti 3 C 2 T x (006)), and the crystal plane spacing of WO 3 was d1 = 0.363 nm (WO 3 (200)), which confirmed the existence of WO 3 nanoparticles on Ti 3 C 2 T x .

[0050] It Figure 4In (a) is the full spectrum, and (b)-(f) are the fine spectra of C 1s, Ti 2p, O 2p, F 2p, and W 4f. It can be seen from the full spectrum that the sample contains five elements: C, Ti, O, F, and W. It can be seen that after peak fitting of the C 1s fine spectrum, five spectral peaks are obtained at 281.1 / 281.7 / 283.4 eV, 284.5 eV, and 288.5 eV, corresponding to Ti-C-T x bonds, C-C bonds, and O=C-O bonds. The remaining bonding situations are shown in the figure.

[0051] Example 8 Take the MXene materials prepared in the above examples and comparative examples, and conduct SO 2 gas-sensing experiments. The steps are as follows: (1) Spray gold electrodes on the SiO 2 substrate by magnetron sputtering to obtain fingertip electrodes of 3 mm×3 mm; (2) Take 0.1 μg of MXene material and coat it on the fingertip electrode part of the sensor, and place the sensor in a vacuum oven at 45 °C for 6 h to dry; (3) Use dry air and SO 2 as the recovery gas and response gas respectively, and dynamically configure the gas concentration and flow rate for gas-sensing testing with a GC400 gas distributor to detect the response value of the sensor.

[0052] Detect the I-V curve of P-Ti 3 C 2 T x -2. The results are as Figure 2 shown. Its I-V curve passes through the zero point, and gas-sensing experiments can be carried out.

[0053] It can be seen from Figure 6 that compared with P-Ti 3 C 2 T x (prepared in Comparative Example 2), P-Ti 3 C 2 T x -2 (prepared in Example 3) has an increase in the response time and recovery time for SO 2 sensing detection.

[0054] It can be seen from Figure 7 that compared with P-Ti 3 C 2 T x (prepared in Comparative Example 2), P-Ti 3 C 2 T x -2 has good dynamic response performance and fast recovery ability. In addition, P-Ti3 C 2 T x -2 has the highest gas-sensing response in the range of 1 to 1000 ppm for SO 2 and the theoretical lowest detection limit reaches 0.3 ppm. The detection method is as follows: (1) Install the sensor on the sensing base in the gas chamber. After ensuring good contact between the contacts and the sensor electrodes, close the upper cover of the gas chamber; (2) Connect the electrochemical workstation to the laptop computer and perform hardware tests on the electrochemical workstation to ensure normal connection between the electrochemical workstation and the laptop computer and normal operation of the electrochemical workstation; (3) Introduce the background gas SF 6 (flow rate 1000 mL / min) for 5 minutes, and close the gas inlet / outlet valves of the gas chamber and let it stand for 20 minutes; (4) Select the IMPT (time impedance) mode of the electrochemical workstation for signal measurement. Set the DC bias voltage to 0.5 V, the scanning voltage amplitude to 0.005 V, the scanning voltage frequency to 100 Hz, and the sampling interval to 1 s; (5) Turn on the IMPT measurement mode of the electrochemical workstation. Prepare the test gas with different concentrations through a dynamic gas mixer. Control the on / off and switching of the gas according to the preset time to obtain the gas-sensing response signal ( Figure 8 ).

[0055] Example 9 Take the MXene materials prepared in the above examples and comparative examples, conduct gas-sensing experiments after storing for different times, and observe the change of the gas-sensing response value to SO 2 gas at different times to reflect the antioxidant performance of the MXene materials.

[0056] The results are as Figure 9 shown. The selectivities of un-anti-oxidation-treated Ti 3 C 2 T x -2 to SO 2 are 7.3 times and 27.5 times that of SO 2 F 2 and H 2 S respectively; after anti-oxidation treatment, the selectivities of P-Ti 3 C 2 T x -2 to SO 2 are 8.2 times and 32 times that of SO 2 F 2 and H 2 S respectively, indicating a certain enhancement in selectivity. At the same time, from Figure 9(C) and (D) show that the long-term stability after antioxidant treatment has been greatly improved.

[0057] After 200 days, the non-antioxidant-treated Ti 3 C 2 T x -2 has undergone severe decomposition, while the antioxidant-treated P-Ti 3 C 2 T x -2 has a relatively complete morphology, with only a certain degree of decomposition at the edges ( Figure 10 ), which is consistent with Figure 9 the improvement in long-term stability.

Claims

1. An oxidation-resistant and highly selective Ti3C2T x The method for preparing the material is characterized by: The steps include: (1) Preparation of intrinsic Ti3C2T x , dilute and disperse in an ice bath to obtain Ti3C2T x Dispersion liquid; (2) Towards Ti3C2T x adding an antioxidant to the dispersion and mixing well to obtain a Ti-P mixed solution; (3) After the tungstate / thioacetamide mixed solution and the Ti-P mixed solution are mixed, the pH is adjusted to 3 while stirring, and a hydrothermal reaction is carried out under the protection of an inert gas; (4) Filter and retain the precipitate, wash and centrifuge multiple times to obtain the antioxidant and highly selective Ti3C2T x Material.

2. The preparation method according to claim 1, characterized in that: Step (1) Intrinsic Ti3C2T x The preparation method comprises the following steps: S1: Mix and dissolve NaF and HCl solution, add Ti3AlC2, and stir to react to obtain the product; S2: washing the reaction product, centrifuging and expanding until the upper liquid is black, collecting the upper black liquid, ultrasonicating in an ice bath, and centrifuging to obtain a dispersion; S3: Collect the lower sediment in the dispersion and repeat step S2 to obtain the dispersion and dry it to obtain intrinsic Ti3C2T x .

3. The preparation method according to claim 2, characterized in that: The molar ratio of NaF to HCl in step S1 is 1:100-110, and the molar ratio of NaF to Ti3AlC2 is 7-8:6; the stirring reaction condition is stirring the reaction at 40°C for 5-7h.

4. The preparation method according to claim 1, characterized in that: Ti3C2T in step (2) x The mass ratio of antioxidant is 1:0.5-2.

5. The preparation method according to claim 4, characterized in that: The antioxidant is sodium phosphate.

6. The preparation method according to claim 1, characterized in that: The mass ratio of tungstate to thioacetamide in the sodium tungstate / thioacetamide mixed solution in step (3) is 7:

4.

7. The preparation method according to claim 1, characterized in that: The volume ratio of the tungstate / thioacetamide mixed solution to the Ti-P mixed solution in step (3) is 1:

1.

8. The preparation method according to claim 1, characterized in that: The hydrothermal reaction conditions in step (3) are 160-200° C. for 10-20 hours.

9. An oxidation-resistant, highly selective Ti3C2T prepared by the preparation method according to any one of claims 1 to 8 x The application of the material is characterized by: The application is application in a gas sensor.

10. The use according to claim 9, characterized in that: The application is to selectively identify SO2 gas in a gas sensor.

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