A titanium carbide with a narrow layer spacing, a preparation method thereof, a sensing chip and an application thereof

Abstract

The present invention belongs to the technical field of sensing materials, and particularly relates to a titanium carbide with a narrow layer spacing (Ti3C2T X ), a preparation method thereof, a sensing chip and an application thereof. By controlling the annealing temperature of Ti3C2T X , the layer spacing of Ti3C2T X is regulated, and the provided Ti3C2T X with a narrow layer spacing has an accordion-like multi-layer structure; the layer spacing of the Ti3C2T X is #imgabs0# When the layer spacing of Ti3C2T X is within #imgabs1#, interfering gases with a large kinetic molecular diameter can be blocked, and only NH3 can enter the interlayer of Ti3C2T X , thereby improving its selectivity to ammonia. At the same time, the two-dimensional confinement space constructed by the narrow layer spacing has a phenomenon similar to pumping at the nanoscale, which can suck ammonia molecules outside the interlayer into the interlayer, thereby effectively improving the response speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensing materials, and particularly relates to a titanium carbide with a narrow layer spacing (Ti3C2T X ), a preparation method thereof, a sensing chip and an application thereof. Background Art

[0002] The recognition and monitoring of gaseous substances such as NO2, CO, H2S, and NH3 are crucial for human health, industrial production safety, and ecological environment protection. Emerging two-dimensional transition metal carbides / nitrides (collectively referred to as MXenes) have the advantages of adjustable surface properties, adjustable band gaps, excellent mechanical stability, and controllable layer spacing. These characteristics make MXenes an ideal platform for gas sensing, where the gas adsorption sites mainly include surface adsorption and interlayer adsorption. In recent years, related research has predicted the applicability of titanium carbide (Ti3C2T X , one of the MXenes, T x representing surface functional groups) as an ammonia sensing material. However, experiments have found that titanium carbide has varying degrees of response to polar gases, which leads to its low selectivity. In an environment with multiple different polar gases, the sensing signal for ammonia will be interfered with, thus affecting the sensing performance of ammonia. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a titanium carbide with a narrow layer spacing (Ti3C2T X ), a preparation method thereof, a sensing chip and an application thereof. The titanium carbide with a narrow layer spacing prepared by the present invention X has high selectivity for ammonia.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a titanium carbide with a narrow layer spacing, which is Ti3C2T X having an accordion-like multi-layer structure; the layer spacing of the Ti3C2T X is

[0006] Preferably, the particle size of the titanium carbide with a narrow layer spacing is 5-30 μm.

[0007] The present invention also provides a preparation method of the titanium carbide with a narrow layer spacing as described in the above technical solution, including the following steps:

[0008] Mix aluminum titanium carbide and an etching solution containing HF, and perform etching and drying in sequence to obtain Ti3C2T X powder;

[0009] The Ti3C2T XThe powder is annealed to obtain titanium carbide with a narrow layer spacing; the annealing temperature is 300 - 375 °C.

[0010] Preferably, the mass ratio of titanium aluminum carbide to the molar amount of HF in the etching solution containing HF is (1 - 1.25) g : (0.06 - 0.075) mol; the molar concentration of HF in the etching solution containing HF is 1.5 - 1.8 mol / L.

[0011] Preferably, the etching temperature is 25 - 35 °C; the etching time is 48 - 52 h.

[0012] Preferably, the heat preservation time for annealing is 1 - 1.5 h; the annealing pressure is -0.1 - -0.09 MPa.

[0013] Preferably, the heating rate for rising to the annealing temperature is 5 - 10 °C / min.

[0014] Preferably, the drying temperature is 40 - 60 °C; the drying time is 10 - 12 h; the drying is vacuum drying; the pressure for vacuum drying is -0.1 - -0.09 MPa.

[0015] The present invention also provides a sensing chip, including a sensing substrate composed of a platinum interdigital electrode and an alumina substrate, and titanium carbide with a narrow layer spacing attached to the surface of the alumina substrate; the titanium carbide with a narrow layer spacing is the titanium carbide with a narrow layer spacing described in the above technical solution or the titanium carbide with a narrow layer spacing prepared by the preparation method described in the above technical solution.

[0016] The present invention also provides the application of the sensing chip described in the above technical solution in ammonia detection.

[0017] The present invention provides a titanium carbide with a narrow layer spacing (Ti3C2T X ) having a multi-layer accordion-like structure of Ti3C2T X ; the layer spacing of the Ti3C2T X is The present invention controls the annealing temperature of Ti3C2T X to regulate the layer spacing of Ti3C2T X , and the provided titanium carbide with a narrow layer spacing Ti3C2T X has a multi-layer accordion-like structure. When the layer spacing of Ti3C2T X is within , it can block interfering gases with a large kinetic molecular diameter, and only NH3 can enter Ti3C2T XIn the interlayer, thereby improving its selectivity to ammonia. At the same time, the two-dimensional confined space constructed with a narrow layer spacing has a phenomenon similar to pumping at the nanoscale, which can suck ammonia molecules outside the layer into the layer, thereby effectively improving the response speed. The Ti3C2T prepared by the present invention X When used as a gas-sensitive material in an ammonia sensor, the obtained ammonia sensor exhibits ultra-high ammonia selectivity, fast response speed and good stability. Experimental results show that the narrow-layer-spacing Ti3C2T prepared by the present invention X When used as a gas-sensitive material in an ammonia sensor, it shows good ammonia selectivity, and the highest response is 13.5 times that of other interfering gases (the response value of Ti3C2T annealed at 300 °C to ammonia is 0.238 / the average response value to other interfering gases is 0.0176). X

[0018] The present invention also provides a preparation method of the above-mentioned titanium carbide with a narrow layer spacing, including the following steps: mixing titanium aluminum carbide and an etching solution containing HF, and performing etching and drying in sequence to obtain Ti3C2T X powder; annealing the Ti3C2T X powder to obtain titanium carbide with a narrow layer spacing; the annealing temperature is 300-375 °C. In the present invention, after the precursor MAX phase Ti3AlC2 is etched to remove Al, accordion-like multi-layer Ti3C2T X is obtained. Annealing can remove the interlayer intercalated water and -OH functional groups, thereby reducing the spacing. The present invention regulates the layer spacing of Ti3C2T X powder by regulating the annealing environment, and only allows NH3 to enter the interlayer of Ti3C2T X , thereby improving its selectivity to ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the X-ray diffraction pattern of Ti3C2T obtained in Example 1 and Comparative Example 1 of the present invention; X

[0020] Figure 2 is the field emission scanning electron microscope image of Ti3C2T obtained in Example 1 and Comparative Example 1 of the present invention; X

[0021] Figure 3 is the scanning transmission electron microscope image of Ti3C2T obtained in Example 1 and Comparative Example 1 of the present invention; X

[0022] Figure 4 is the response comparison diagram of Ti3C2T obtained in Example 1 and Comparative Examples 1-4 of the present invention as a sensing material under different gases; X

[0023] Figure 5 Ti3C2T obtained in Example 1 of the present invention X Response linearity diagram as a sensing material under different concentrations of ammonia gas;

[0024] Figure 6 Schematic diagram of ammonia gas and interfering gas sensing tests. Specific implementation manners

[0025] The present invention provides a titanium carbide with a narrow layer spacing, Ti3C2T having an accordion-like multi-layer structure X ; the Ti3C2T X has a layer spacing of

[0026] In the present invention, the layer spacing of the Ti3C2T X is preferably The particle size of the titanium carbide with a narrow layer spacing is preferably 5 - 30 μm, more preferably 10 - 30 μm.

[0027] The layer spacing of the Ti3C2T powder provided by the present invention X is can block interfering gases with large kinetic molecular diameters, and only NH3 can enter the interlayer of the Ti3C2T X , thereby improving its selectivity to ammonia gas.

[0028] The present invention also provides a preparation method of the titanium carbide with a narrow layer spacing, comprising the following steps:

[0029] Mix aluminum titanium carbide and an etching solution containing HF, and perform etching and drying in sequence to obtain Ti3C2T X powder;

[0030] Anneal the Ti3C2T X powder to obtain titanium carbide with a narrow layer spacing; the annealing temperature is 300 - 375 °C.

[0031] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used for preparation, and commercially available products well-known to those skilled in the art can be used.

[0032] The present invention mixes aluminum titanium carbide and an etching solution containing HF, performs etching, and obtains a mixed solution containing Ti3C2T X .

[0033] In the present invention, the aluminum titanium carbide is preferably aluminum titanium carbide powder; the particle size of the aluminum titanium carbide powder is preferably 400 mesh.

[0034] In the present invention, the mass ratio of titanium aluminum carbide to the molar amount of HF in the etching solution containing HF is preferably (1 - 1.25) g : (0.06 - 0.075) mol, more preferably 1 g : 0.068 mol; the molar concentration of HF in the etching solution containing HF is preferably 1.5 - 1.8 mol / L, more preferably 1.75 mol / L, and the molar concentration of lithium chloride is preferably 1.5 - 2 mol / L, more preferably 1.5 mol / L.

[0035] In the present invention, the preparation method of the etching solution containing HF is preferably to mix lithium fluoride and hydrochloric acid to obtain the etching solution containing HF. In the present invention, the mass ratio of lithium fluoride to the volume of hydrochloric acid is preferably (1.6 - 1.8) g : (40 - 45) mL, more preferably 1.6 g : 40 mL; the concentration of hydrochloric acid is preferably 5 - 6 mol / L, more preferably 6 mol / L; the mixing is preferably carried out under stirring; the stirring rate is preferably 400 - 600 rpm, more preferably 500 rpm; the stirring time is preferably 15 - 20 min, more preferably 15 min.

[0036] During the mixing process, lithium fluoride reacts with hydrochloric acid to form lithium chloride and hydrofluoric acid. The specific reaction is: LiF + HCl → LiCl + HF.

[0037] In the present invention, the mixing of titanium aluminum carbide and the etching solution containing HF is preferably to add titanium aluminum carbide to the etching solution containing HF. In the present invention, titanium aluminum carbide is slowly added to the etching solution containing HF to avoid violent reaction.

[0038] In the present invention, the etching temperature is preferably 25 - 35 °C, more preferably 25 °C; the etching time is preferably 48 - 52 h, more preferably 48 h; the etching is preferably carried out under stirring; the stirring rate is preferably 400 - 600 rpm, more preferably 500 rpm.

[0039] In the present invention, the etching reaction is: Ti3AlC2 + 3HF → AlF3 + 3 / 2H2 + Ti3C2; in the present invention, the Al element is removed by etching to obtain a Ti3C2T X solution, T x represents surface functional groups, x represents the number of functional groups, and the functional groups include -OH, -F, -O. When a 002 peak appears between 5 - 10° in the XRD pattern and the EDS energy spectrum analysis shows that the Al content < 1 At%, the etching is complete.

[0040] After obtaining the mixture containing Ti3C2T X In the present invention, it is preferred to use the mixture containing Ti3C2T XThe mixed solution is successively subjected to hydrochloric acid washing, water washing and filtration to obtain multi-layer titanium carbide precipitate. In the present invention, the concentration of the hydrochloric acid is preferably 0.5 to 1 mol / L, more preferably 1 mol / L; the hydrochloric acid washing is preferably mixing the mixed solution containing Ti3C2T X with hydrochloric acid, centrifuging to obtain a precipitate; the volume ratio of the mixed solution containing Ti3C2T X to hydrochloric acid is preferably 1:1 to 5, more preferably 1:4; the centrifugation rate is preferably 3500 to 4000 rpm, more preferably 3500 rpm; the centrifugation time is preferably 5 to 10 min, more preferably 5 min; the number of times of hydrochloric acid washing is preferably 2 to 3 times, more preferably 2 times. In the present invention, LiCl in the mixed solution containing Ti3C2T X is removed by hydrochloric acid washing. In the present invention, the water washing is preferably mixing the precipitate obtained by hydrochloric acid washing with water, centrifuging to obtain multi-layer titanium carbide precipitate. In the present invention, the centrifugation rate is preferably 3500 to 4000 rpm, more preferably 3500 rpm; the centrifugation time is preferably 5 to 10 min, more preferably 5 min; the number of times of water washing is preferably 6 to 8 times, more preferably 6 times; the water washing is carried out until the pH value of the obtained washing solution is 6 to 7, more preferably 7. In the present invention, HCl and HF on the surface of titanium carbide are removed by water washing. In the present invention, the filtration is preferably suction filtration.

[0041] After obtaining the multi-layer titanium carbide precipitate, the present invention dries the multi-layer titanium carbide precipitate to obtain Ti3C2T X powder.

[0042] In the present invention, the drying temperature is preferably 40 to 60 °C, more preferably 50 °C; the drying time is preferably 10 to 12 h, more preferably 10 h; the drying is preferably vacuum drying; the pressure of the vacuum drying is preferably -0.1 to -0.09 MPa, more preferably -0.09 MPa.

[0043] The present invention anneals the dried Ti3C2T X powder to avoid affecting the regulation of the layer spacing of the Ti3C2T X powder. The Ti3C2T X powder with incomplete drying will make the layer spacing of the Ti3C2T X powder obtained by annealing uneven, with some large and some small.

[0044] After obtaining the Ti3C2T X powder, the present invention anneals the Ti3C2T X powder to obtain titanium carbide with a narrow layer spacing.

[0045] In the present invention, the annealing temperature is 300 to 375 °C, more preferably 300 to 350 °C; the holding time of the annealing is preferably 1 to 1.5 h, more preferably 1 to 1.2 h; the pressure of the annealing is preferably -0.1 to -0.09 MPa, more preferably -0.09 MPa; the heating rate for heating to the annealing temperature is preferably 5 to 10 °C / min, more preferably 5 °C / min.

[0046] After the annealing, the present invention preferably cools the product obtained by the annealing to room temperature; the present invention has no special limitation on the cooling, and natural cooling to room temperature is sufficient.

[0047] The present invention regulates the interlayer spacing of Ti3C2T X powder by regulating the annealing environment. When the interlayer spacing is 10 to 10.55 , it can block the interfering gas with a large kinetic molecular diameter, and only NH3 can enter the interlayer of Ti3C2T X , thereby improving its selectivity to ammonia.

[0048] The present invention also provides a sensing chip, which includes a sensing substrate composed of a platinum interdigital electrode and an alumina substrate, and a titanium carbide with a narrow interlayer spacing attached to the surface of the alumina substrate; the titanium carbide with a narrow interlayer spacing is the titanium carbide with a narrow interlayer spacing described in the above technical solution or the titanium carbide with a narrow interlayer spacing prepared by the preparation method described in the above technical solution.

[0049] The present invention has no special limitation on the sensing substrate, and a sensing substrate well-known in the art can be used. In the embodiment of the present invention, the sensing substrate is composed of a platinum interdigital electrode and an alumina substrate, and is purchased from Wuhan Huachuang Ruike Technology Co., Ltd., and is the substrate used in the four-channel material gas sensing performance tester.

[0050] In the present invention, the amount of the above-mentioned titanium carbide with a narrow interlayer spacing attached to the surface of the sensing substrate is preferably 0.6 to 2.4 mg, more preferably 1.5 mg.

[0051] In the present invention, the preparation method of the sensing chip is preferably to mix titanium carbide with a narrow interlayer spacing and water to obtain a mixed solution of titanium carbide with a narrow interlayer spacing; uniformly coat the mixed solution of titanium carbide with a narrow interlayer spacing on the alumina substrate of the sensing substrate, and dry it to obtain a sensing chip. In the present invention, the concentration of titanium carbide with a narrow interlayer spacing in the mixed solution of titanium carbide with a narrow interlayer spacing is preferably 3 to 8 mg / mL, more preferably 5 mg / mL; the drying temperature is preferably 40 to 60 °C, more preferably 50 °C; the drying time is preferably 20 to 30 min, more preferably 20 min.

[0052] In an embodiment of the present invention, the preparation method of the sensing chip is specifically as follows: Mix the narrow-layer-spacing titanium carbide and water to obtain a narrow-layer-spacing Ti3C2T mixed solution with a concentration of 5 mg / mL. X Apply 200 μL of the narrow-layer-spacing titanium carbide mixed solution evenly on the alumina substrate of the sensing substrate, and then place it in an oven at 50 °C and dry it for 20 min to obtain the sensing chip.

[0053] The present invention also provides the application of the sensing chip described in the above technical solution in ammonia detection.

[0054] The present invention has no special limitation on the application method of the sensing chip in ammonia detection, and the well-known application methods in the art can be adopted.

[0055] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention, but they should not be understood as limiting the protection scope of the present invention.

[0056] Example 1

[0057] Add 1.6 g of LiF to 40 mL of 6 mol / L HCl and stir at 500 rpm for 15 min to obtain an etching solution containing HF; slowly add 1 g of Ti3AlC2 (titanium aluminum carbide) to the etching solution containing HF and continuously etch at 500 rpm at 35 °C for 48 h to obtain a mixed solution containing Ti3C2T. X In 20 mL of the mixed solution containing Ti3C2T X add 30 mL of 1 mol / L HCl, centrifuge and wash at 3500 rpm for 5 min, then repeat the hydrochloric acid washing process to obtain a precipitate, and then repeat the centrifugal washing process with deionized water 6 times until the pH value of the washing solution is 7, and filter by suction to obtain a multi-layer titanium carbide precipitate, and vacuum dry at -0.09 MPa and 50 °C for 10 h to obtain Ti3C2T X powder. Put the Ti3C2T X powder into an alumina crucible with dimensions of 100×50×30 mm, place it in a tube annealing furnace, and increase the temperature to 300 °C at a heating rate of 5 °C / min. Keep the temperature at 300 °C under a vacuum degree of -0.09 MPa for 1 h for annealing, and then slowly cool to room temperature with the furnace to obtain narrow-layer-spacing titanium carbide (Ti3C2T X ).

[0058] Comparative Example 1

[0059] The difference from Example 1 is that no annealing treatment is carried out to obtain Ti3C2T X , and the rest is the same as Example 1.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that the annealing temperature is 200 °C, and Ti3C2T is obtained X , and the rest is the same as in Example 1.

[0062] Comparative Example 3

[0063] The difference from Example 1 is that the annealing temperature is 400 °C, and Ti3C2T is obtained X , and the rest is the same as in Example 1.

[0064] Comparative Example 4

[0065] The difference from Example 1 is that the annealing temperature is 500 °C, and Ti3C2T is obtained X , and the rest is the same as in Example 1.

[0066] Application Example 1

[0067] The narrow-layer-spacing Ti3C2T obtained in Example 1 X and water were mixed to obtain a narrow-layer-spacing Ti3C2T mixture with a concentration of 5 mg / mL X 200 μL of the narrow-layer-spacing Ti3C2T X mixture was evenly coated on the alumina substrate of the sensing substrate (composed of a platinum interdigital electrode and an alumina substrate, purchased from Wuhan Huachuang Ruike Technology Co., Ltd., and the substrate used for the four-channel material gas sensing performance tester), and then placed in an oven at 50 °C for 20 min to dry, obtaining a sensing chip.

[0068] Comparative Application Example 1

[0069] The difference from Application Example 1 is that the Ti3C2T of Comparative Example 1 was used X to fabricate the sensing chip, and the rest is the same as in Application Example 1.

[0070] Comparative Application Example 2

[0071] The difference from Application Example 1 is that the Ti3C2T of Comparative Example 2 was used X to fabricate the sensing chip, and the rest is the same as in Application Example 1.

[0072] Comparative Application Example 3

[0073] The difference from Application Example 1 is that the Ti3C2T of Comparative Example 3 was used X to fabricate the sensing chip, and the rest is the same as in Application Example 1.

[0074] Comparative Application Example 4

[0075] The difference from Application Example 1 is that the Ti3C2T of Comparative Example 4 was used X to fabricate the sensing chip, and the rest is the same as in Application Example 1.

[0076] Performance test

[0077] (1) Perform XRD tests on the Ti3C2T prepared in Example 1 and Comparative Example 1, and the results are as X shown. Figure 1 shown.

[0078] It can be seen from Figure 1 that diffraction peaks appear at 5-10° for both the annealed Ti3C2T X and the unannealed Ti3C2T X , proving the successful synthesis of the Ti3C2T X material. And the diffraction peak of the annealed Ti3C2T X at 5-10° is shifted backward compared to that of the unannealed one, indicating that the interlayer spacing has become smaller.

[0079] (2) Perform electron microscopy scans on the Ti3C2T X powder prepared in Example 1 and Comparative Example 1, and the results are as Figure 2 shown, where a is the Ti3C2T X of Example 1, and b is the Ti3C2T X of Comparative Example 1.

[0080] It can be seen from Figure 2 that the interlayer of the annealed Ti3C2T X is smaller than that of the unannealed Ti3C2T X . Only ammonia can enter the interlayer of the annealed Ti3C2T X powder, and interfering gases with large kinetic diameters are difficult to enter the interlayer, resulting in a decrease in the relevant response, thereby improving the selectivity of the annealed Ti3C2T X to ammonia.

[0081] (3) Perform electron microscopy scans on the Ti3C2T X prepared in Example 1 and Comparative Example 1, and the results are as Figure 3 shown, where a is the Ti3C2T X of Comparative Example 4, and b is the Ti3C2T X of Comparative Example 1.

[0082] It can be seen from Figure 3 that in order to highlight the difference in interlayer spacing, STEM images of the Ti3C2T X powder annealed at 500 °C and unannealed are compared, and it is found that the higher the annealing temperature, the smaller the interlayer spacing. The interlayer spacing range that only allows ammonia to enter is about The optimal interlayer spacing that allows ammonia to enter without affecting the ammonia response value is

[0083] (4) Ti3C2T prepared at different annealing temperatures X Selectivity to different types of gases

[0084] The selectivity of the sensing chips obtained in Application Example 1 and Comparative Application Examples 1-4 to ammonia and interfering gases (methanol, ethanol, and isopropanol) was tested. The results are as Figure 4 and Figure 5 shown. The specific test method is as Figure 6 shown. When detecting ammonia, ammonia is introduced from the gas cylinder into the gas flow control module, and argon is also introduced from the gas cylinder as a dilution gas into the gas flow control module. After dilution, the ammonia flows into the sensing test chamber of the sensor. The computer is connected to the sensor to provide the voltage required by the sensor, and the results are output to the computer through a signal amplifier.

[0085] It can be seen from Figure 4 that as the annealing temperature increases, the response to interfering gases (methanol, ethanol, and isopropanol) decreases. When Ti3C2T obtained by annealing at 300 °C X has the best selectivity to ammonia while maintaining a high ammonia response. The response value to 100 ppm ammonia is 0.24. The Ti3C2T annealed at 300 °C X has a response value to ammonia of 0.238, and the average response to other interfering gases is 0.0176. The ammonia response is 13.5 times higher than that of other interfering gases.

[0086] It can be seen from Figure 5 that the ammonia sensor prepared with Ti3C2T annealed at 300 °C X shows good linearity and stability in the ammonia concentration range of 50-1000 volume fractions, and the goodness of fit is greater than 0.98.

[0087] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A titanium carbide with a narrow interlayer spacing, Ti3C2T with an accordion-like multi-layer structure X ; The Ti3C2T X has an interlayer spacing of The particle size of the titanium carbide with narrow layer spacing is 5 - 30 μm; The preparation method of the titanium carbide with narrow layer spacing includes the following steps: Mix aluminum titanium carbide with an etching solution containing HF, and perform etching and drying in sequence to obtain Ti3C2T X powder; Anneal the Ti3C2T X powder to obtain titanium carbide with a narrow layer spacing; the annealing temperature is 300 to 375 °C.

2. The preparation method of titanium carbide with a narrow layer spacing according to claim 1, characterized in that, including the following steps: Mix aluminum titanium carbide with an etching solution containing HF, and perform etching and drying in sequence to obtain Ti3C2T X powder; Anneal the Ti3C2T X powder to obtain titanium carbide with a narrow interlayer spacing; the annealing temperature is 300 to 375 °C.

3. The preparation method according to claim 2, characterized in that, The mass ratio of titanium aluminum carbide to HF in the etching solution containing HF is (1 - 1.25) g : (0.06 - 0.075) mol; the molar concentration of HF in the etching solution containing HF is 1.5 - 1.8 mol / L.

4. The preparation method according to claim 2 or 3, characterized in that, The temperature of the etching is 25 - 35 °C; the time of the etching is 48 - 52 h.

5. The preparation method according to claim 2, characterized in that, The heat preservation time of the annealing is 1 - 1.5 h; the pressure of the annealing is -0.1 - -0.09 MPa.

6. The preparation method according to claim 2 or 5, characterized in that, The heating rate for rising to the annealing temperature is 5 - 10 °C / min.

7. The preparation method according to claim 2, characterized in that, The temperature of the drying is 40 - 60 °C; the time of the drying is 10 - 12 h; the drying is vacuum drying; the pressure of the vacuum drying is -0.1 - -0.09 MPa.

8. A sensing chip, comprising a sensing substrate composed of a platinum interdigital electrode and an alumina substrate, and titanium carbide with narrow layer spacing attached to the surface of the alumina substrate; the titanium carbide with narrow layer spacing is the titanium carbide with narrow layer spacing as described in claim 1 or the titanium carbide with narrow layer spacing prepared by the preparation method described in any one of claims 2 - 7.

9. Application of the sensing chip described in claim 8 in ammonia detection.

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