A preparation method of sulfur-doped MXene material and its products and applications

Abstract

The present invention discloses a method for preparing a sulfur-doped MXene material. The method comprises placing sulfur powder in a plasma-enhanced section of a chemical vapor deposition apparatus, placing the MXene powder in a heating section, and introducing hydrogen and argon gases under vacuum to carry out a sulfur-doping reaction to obtain the sulfur-doped MXene material. The present invention also discloses the sulfur-doped MXene material obtained by the above-mentioned preparation method and its application in capacitive deionization. The present invention significantly shortens the sulfur-doping time through plasma doping, and the resulting sulfur-doped MXene material exhibits excellent electrochemical properties.

Description

Technical Field

[0001] The present invention relates to the field of water treatment technology, and in particular to a preparation method of a sulfur-doped MXene material, and its products and applications. Background Art

[0002] With the rapid growth of the global population and the overexploitation of natural resources, access to clean water is becoming increasingly difficult and has become a critical issue for human survival and technological progress. Capacitive deionization is an emerging water purification technology based on rapid physical and chemical reactions at the solid-liquid interface. It offers advantages such as low energy consumption, environmental friendliness, and ease of operation.

[0003] Transition metal carbonitride (MXene) is a novel cationic adsorption material with a unique two-dimensional layered nanostructure. When used for capacitive deionization, it offers advantages such as high charging efficiency, rapid adsorption, and excellent cycling performance. Limited by its specific surface area and slow ion transport, its adsorption capacity is insufficient to support practical industrial applications. Introducing heteroatoms onto the MXene surface is an important research direction to address this issue. Currently used doping methods mostly involve liquid-phase and solid-phase reactions, which are time-consuming and require large amounts of reagents. For example, Chinese patent publication number CN 113683092 A discloses nitrogen-sulfur co-doped Ti3C2-MXene nanosheets. Ti3C2-MXene nanosheets are ground and mixed with thiourea, then calcined in an Ar atmosphere furnace and cooled to room temperature. The product is then ground again, washed by centrifugation with deionized water, and finally dried to obtain the nitrogen-sulfur co-doped Ti3C2-MXene nanosheets. For example, Chinese patent publication number CN109449405A discloses a sulfur-oxygen doped MXene-carbon nanotube composite material. The composite material is prepared from MAX phase ceramic powder by vapor deposition, and oxygen-doped MXene-carbon nanotubes are obtained by hydrogen peroxide immersion treatment, and then sulfur is added by ball milling and hot melting.

[0004] Therefore, for this field, there is still a need to develop an efficient and fast method for doping MXene materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a sulfur-doped MXene material, which shortens the sulfur doping time and has good electrochemical properties.

[0006] The present invention provides the following technical solutions:

[0007] A method for preparing a sulfur-doped MXene material comprises placing sulfur powder in a plasma enhancement section of a chemical vapor deposition device, placing MXene powder in a heating section, introducing hydrogen and argon under vacuum to perform a sulfur doping reaction, and obtaining the sulfur-doped MXene material.

[0008] The preparation method provided by this invention uses sulfur plasma to purge MXene powder with the aid of hydrogen and argon gases, thereby anchoring sulfur atoms on the MXene surface and effectively improving the material's cation adsorption capacity. This plasma doping method significantly shortens conventional heteroatom doping time, features a simple process, utilizes abundant raw material resources, and offers low production costs, promising promising applications and economic benefits.

[0009] The chemical vapor deposition equipment may be a chemical vapor deposition tube furnace.

[0010] The preparation method of MXene powder is as follows: first, a MXene solution is prepared by HCl / LiF etching method, and then MXene powder is obtained by freeze drying method. Specifically, the preparation method of MXene powder includes:

[0011] (1) After dissolving LiF powder and hydrochloric acid, Ti3AlC2 powder was added to react to obtain MXene solution;

[0012] (2) Freeze-dry the MXene solution to obtain MXene powder.

[0013] Furthermore, the preparation method of the MXene powder includes:

[0014] (1) Dissolve LiF powder in 9 mol L -1 In the hydrochloric acid solution, stir under ice bath for 30 minutes, then slowly add appropriate amount of Ti3AlC2 powder within 10 minutes and stir at 35℃ for 24 hours:

[0015] The mass of the LiF powder is 2 g, the volume of the hydrochloric acid solution is 40 mL, the mass of the Ti3AlC2 powder is 2 g, and the stirring container is a 100 mL polytetrafluoroethylene bottle. The above materials and devices can be expanded in the same proportion.

[0016] (2) The mixed solution was centrifuged and washed with water 6 to 8 times until the pH of the supernatant reached 6. The precipitate was collected and dissolved in deionized water. After ice bath ultrasonication, centrifugation was performed for one hour, and the resulting supernatant was collected.

[0017] The centrifugal washing speed is 7000-8500 rpm, the ice bath ultrasonic time is 30 minutes, the speed of the last centrifugation is 3500 rpm, and the transfer process after centrifugation should avoid shaking as much as possible.

[0018] (3) The supernatant obtained in step (2) is freeze-dried to obtain MXene powder:

[0019] The concentration of the supernatant should be controlled at 5-10 mg L -1 The freeze drying temperature was -80°C and the time was 12 hours.

[0020] The mass ratio of the sulfur powder to the MXene powder should be within the range of 0.5:1 to 2:1. Considering the loss of sulfur powder during the actual reaction, the mass ratio should not be too small. After reaching a certain ratio, the doping ratio reaches its peak. Therefore, by limiting the ratio of the two, an appropriate sulfur doping ratio is achieved.

[0021] Preferably, the heating temperature of the heating section is 400-500°C, the heating rate is 10-15°C / minute, and the power of the plasma generator in the chemical vapor deposition equipment is 250-350 W. By limiting the above process conditions, the present invention ensures that the sulfur doping reaction of sulfur plasma with MXene has a suitable doping rate.

[0022] Further preferably, the heating temperature of the heating section is 450° C., the heating rate is 15° C. / min, the reaction time is 1 hour, and the power of the plasma generator in the chemical vapor deposition equipment is 300W.

[0023] Preferably, the volume ratio of hydrogen and argon should be in the range of 1:1 to 1:3. Hydrogen helps to remove F functional groups on the surface of MXene and assists S doping, while argon is a protective gas. Therefore, the ratio of the two should not be too large or too small; the pressure of the mixed gas should be 10-30 Pa. Excessive pressure is not conducive to the generation of plasma.

[0024] During the sulfur doping reaction, a porous tubular furnace plug needs to be placed at the rear end of the heating section to increase the temperature at the rear end of the tubular furnace and reduce the escape of sulfur vapor.

[0025] Preferably, the preparation method further includes placing the sulfur-doped MXene material obtained by the sulfur doping reaction in a carbon disulfide solution for repeated washing to remove residual elemental sulfur, and then washing with an ethanol solution: the number of washing times is 2 to 3 times, the stirring speed during the washing process is 300 to 500 rpm, and after the washing is completed, the carbon disulfide is washed away with an ethanol solution.

[0026] The present invention also provides a sulfur-doped MXene material obtained according to the above preparation method.

[0027] The present invention also provides an application of the above-mentioned sulfur-doped MXene material in capacitive deionization.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The preparation method provided by the present invention circumvents the traditional liquid-phase and solid-phase doping methods. It uses a plasma generator to convert sulfur powder into sulfur plasma, and uses hydrogen and argon to blow the sulfur plasma onto the MXene surface, which significantly accelerates the doping speed and thus greatly shortens the sulfur doping time.

[0030] 2. The high-energy sulfur plasma involved in the preparation method provided by the present invention can interact with the MXene surface to form a relatively strong chemical bond, thereby enhancing the cation adsorption capacity.

[0031] 3. The preparation method provided by the present invention has a simple process, abundant raw material sources, low production cost, and good application prospects and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The scanning electron microscope image and X-ray energy dispersion spectrum of the sulfur-doped MXene material prepared in Example 1 of the present invention are shown;

[0033] Figure 2 This is a transmission electron micrograph of the sulfur-doped MXene material prepared in Example 1 of the present invention;

[0034] Figure 3 This is an X-ray diffraction spectrum of the sulfur-doped MXene material prepared in Example 1 of the present invention (S-MXene is a sulfur-doped MXene material, and MXene is a MXene material not doped with sulfur);

[0035] Figure 4 This is an X-ray photoelectron spectrum of the sulfur-doped MXene material prepared in Example 1 of the present invention;

[0036] Figure 5 This is the cyclic voltammetry test curve of the sulfur-doped MXene material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] To make the present invention more clearly understood, the present invention will be further described below with reference to specific embodiments and accompanying drawings. The embodiments described below are only used to illustrate the present invention and do not limit the present invention in any form or substance.

[0038] Example 1

[0039] A method for preparing a sulfur-doped MXene material comprises the following steps:

[0040] (1) Dissolve 2 g of LiF powder in 40 mL of 9 mol L -1After stirring the hydrochloric acid solution in an ice bath for 30 minutes, 2 g of Ti3AlC2 powder was slowly added within 10 minutes and slowly stirred at 35°C for 24 hours.

[0041] (2) The mixed solution obtained in step (1) was centrifuged and washed with water for 6 to 8 times at a speed of 7000 to 8500 rpm until the pH of the supernatant reached 6. The precipitate was collected and dissolved in deionized water. After ultrasonication in an ice bath for 30 minutes, the mixture was centrifuged at a speed of 3500 rpm for one hour, and the supernatant was collected.

[0042] (3) Dilute the supernatant obtained in step (2) to 5 mg L -1 , and freeze-dried at -80 °C for 12 h to obtain MXene powder.

[0043] (4) The sulfur powder was placed in the plasma enhancement section of the chemical vapor deposition tube furnace, and the MXene powder was placed in the heating section with a mass ratio of 1:1. After vacuuming, hydrogen and argon were introduced into the tube at a flow rate of 5 cc. The plasma generator power was set to 300 W and the heater temperature was set to 450 °C for sulfur doping reaction, and then cooled to room temperature.

[0044] (5) The solid product obtained in step (4) is placed in a carbon disulfide solution and repeatedly washed to remove residual elemental sulfur, and then washed with an ethanol solution to obtain a sulfur-doped MXene material.

[0045] The sulfur-doped MXene material prepared in the present invention was subjected to the following characterization tests:

[0046] The surface morphology and element ratio of the materials were tested using a Hitachi SU-8010 field emission scanning electron microscope. Figure 1 As shown in Figure 2, the mass ratio of S element is 3.52%. The microstructure of the material was determined using a Hitachi HT-7700 field emission transmission electron microscope. Figure 2 As shown in Figure 2, the sample has a typical nanosheet morphology. The layered structure of the material was tested using an X-pert powder X-ray diffraction spectrometer. Figure 3 As shown in Figure 2, the significant (002) intensity peak indicates that the sample has a good two-dimensional layered structure. The surface element distribution of the material was tested using an X-ray photoelectron spectrometer model VG Escalab Mark II, as shown in Figure 2. Figure 4 As shown in Figure 3, the analysis results indicate that a relatively strong Ti-S chemical bond is formed during the doping process.

[0047] like Figure 5As shown in the figure, the electrochemical performance of the sulfur-doped MXene material prepared in Example 1 was tested using an electrochemical workstation model PGSTAT302N. The test method was cyclic voltammetry with a scan rate of 5 mV s -1 The mass specific capacitance was measured to be 308.4 F g -1 .

[0048] The above is a detailed description of the present invention in combination with embodiments, but the implementation methods of the present invention are not limited to the above embodiments. Any other changes, replacements, combination simplifications, etc. made under the core guiding idea of ​​the patent of the present invention are included in the scope of protection of the patent of the present invention.

Claims

1. A method for preparing a sulfur-doped MXene material, characterized in that: The preparation method comprises: placing sulfur powder in a plasma enhancement section of a chemical vapor deposition device, placing MXene powder in a heating section, introducing hydrogen and argon under vacuum to perform a sulfur doping reaction to obtain a sulfur-doped MXene material; The mass ratio of the sulfur powder to the MXene powder is 0.5 to 2:1; The heating temperature of the heating section is 400-500°C, the heating rate is 10-15°C / min, and the power of the plasma generator in the chemical vapor deposition equipment is 250-350W; The volume ratio of the hydrogen and argon is 1:1-3, and the pressure of the mixed gas is 10-30 Pa.

2. The method for preparing sulfur-doped MXene material according to claim 1, characterized in that: The preparation method of the MXene powder comprises: (1) After dissolving LiF powder and hydrochloric acid, Ti3AlC2 powder was added to react to obtain MXene solution; (2) Freeze-dry the MXene solution to obtain MXene powder.

3. The method for preparing sulfur-doped MXene material according to claim 1, characterized in that: During the sulfur doping reaction, a porous tubular furnace plug needs to be placed at the rear end of the heating section.

4. A sulfur-doped MXene material obtained according to the preparation method according to any one of claims 1 to 3.

5. Use of the sulfur-doped MXene material according to claim 4 in capacitive deionization.

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