CN111732103A - Fluorine-free Mo2CTx MXenes material, preparation method and application thereof - Google Patents

Fluorine-free Mo2CTx MXenes material, preparation method and application thereof Download PDF

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CN111732103A
CN111732103A CN202010523800.7A CN202010523800A CN111732103A CN 111732103 A CN111732103 A CN 111732103A CN 202010523800 A CN202010523800 A CN 202010523800A CN 111732103 A CN111732103 A CN 111732103A
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mxenes
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CN111732103B (en
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王昌达
宋礼
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University of Science and Technology of China USTC
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Abstract

The invention provides fluorine-free Mo2CTxThe preparation method of the MXenes material comprises the following steps: s1) mixing, heating and grinding the molybdenum carbide nano powder and the metal gallium to obtain a mixture; the molar ratio of the molybdenum carbide nano powder to the metal gallium is less than1: 2; s2) sintering the mixture at high temperature under the conditions of sealing and low vacuum to obtain Mo2Ga2C MAX precursor; s3) adding Mo2Ga2Mixing the C MAX precursor with concentrated hydrochloric acid, and performing hydrothermal reaction to etch to obtain fluorine-free Mo2CTxMXenes material. Compared with the prior art, the invention realizes the fluorine-free Mo2CTxSafe and controllable preparation of MXenes, and Mo obtained2CTxMXenes surface only contains oxygen group and chlorine group, and the surface chlorine group is easily substituted by other groups, so that Mo is increased2CTxAdjustability of MXenes materials.

Description

Fluorine-free Mo2CTxMXenes material, preparation method and application thereof
Technical Field
The invention belongs to the technical field of nano materials, and particularly relates to a fluorine-free nano materialMo2CTxMXenes material, preparation method and application thereof.
Background
The two-dimensional layered MXenes is a general name of a class of transition metal carbide, nitride or carbon nitride compound with a general formula of Mn+ 1XnTx(n-1, 2,3) wherein M represents a transition metal (Nb, Sc, Ti, V, Mo, etc.), X represents carbon or nitrogen, and T representsxRepresents a surface group (-Cl, -OH, -O, -F, etc.). Based on the advantages of unique layered structure, abundant surface groups, large specific surface area, excellent conductivity and the like of MXenes materials, the MXenes materials have excellent application prospects in the fields of supercapacitors, secondary batteries, catalysts, electromagnetic shielding and the like, and are widely concerned and researched. Meanwhile, researches show that the surface group of the Mxenes material has obvious influence on the electron energy band structure of the Mxenes material and has important significance on the development and application of MXenes, so that a great deal of research work is devoted to the regulation and control of the MXenes surface group.
Theoretical calculation and experimental research prove that MXenes surface fluorine F groups have negative effects on the voltage window and specific capacity of an energy storage device, so that the energy density of the energy storage device is limited, and the further application of the MXenes electrode material is greatly hindered, and therefore, the content of the MXenes surface F is reduced as much as possible in the preparation process. As a representative of MXenes, Mo2CTxMXenes has the advantages of small molar volume, high conductivity, good thermal stability and the like, and is an ideal electrode material in a lithium/sodium ion battery. However, the current preparation involves Mo2CTxThe most widely used method for the MXenes materials is to etch the corresponding MAX phase by HF or HCl/LiF mixed solution, and the intervention of fluorine causes the surface of the finally obtained MXenes to inevitably contain a large amount of F functional groups, thereby influencing the energy storage application and controllable research of the MXenes. Therefore, how to realize the controllable preparation of the fluorine-free MXenes becomes an important technical challenge in the MXenes field.
Researchers have also conducted corresponding prior research and made some progress, such as the preparation of fluorine-free Ti by using high-temperature concentrated alkaline hydrothermal (27.5M KOH, 270 ℃)3C2TxPreparing fluorine-free Ti by electrochemical etching method3C2TxAnd V2CTxPreparation of fluorine-free Ti by fused Lewis acid etching3C2TxAnd Ti2CTxAnd the like. However, for fluorine-free Mo2CTxThe controllable preparation of MXenes is still lack of effective means. Thus, a fluorine-free Mo was developed2CTxThe controllable preparation method of MXenes has important research significance and value for the development of MXenes.
Disclosure of Invention
In view of the above, the present invention provides a fluorine-free Mo2CTxMXenes material, preparation method and application thereof, and the preparation method is adjustable.
The invention provides fluorine-free Mo2CTxThe preparation method of the MXenes material is characterized by comprising the following steps:
s1) mixing, heating and grinding the molybdenum carbide nano powder and the metal gallium to obtain a mixture; the molar ratio of the molybdenum carbide nano powder to the metal gallium is less than 1: 2;
s2) sintering the mixture at high temperature under the conditions of sealing and low vacuum to obtain Mo2Ga2C MAX precursor;
s3) adding Mo2Ga2Mixing the C MAX precursor with concentrated hydrochloric acid, and performing hydrothermal reaction to etch to obtain fluorine-free Mo2CTxMXenes material.
Preferably, the mesh number of the molybdenum carbide nano powder is more than or equal to 325 meshes; the molar ratio of the molybdenum carbide nano powder to the metal gallium is more than or equal to 1: 8.
Preferably, the temperature of the heating and grinding in the step S1) is 30-80 ℃; the time for heating and grinding is 30-60 min.
Preferably, the vacuum degree of the low vacuum in the step S2) is less than or equal to 1 torr; the temperature of the high-temperature sintering is 800-900 ℃; the high-temperature sintering time is 2-4 days.
Preferably, after high-temperature sintering, the sintered product is heated and ground for the second time, and then under the conditions of sealing and low vacuum,secondary high-temperature sintering is carried out to obtain a secondary sintered product; washing the secondary sintered product with acid to remove redundant metal gallium, then washing the secondary sintered product with water to be neutral, and freeze-drying to obtain Mo2Ga2C MAX precursor.
Preferably, the Mo2Ga2The ratio of cmax precursor to concentrated hydrochloric acid was 10 mg: (0.8-1.2) ml; the concentration of the concentrated hydrochloric acid is 6-12 mol/L.
Preferably, the temperature of the hydrothermal reaction in the step S3) is 120-160 ℃; the hydrothermal reaction time is 5-7 days.
Preferably, after the etching is performed through the hydrothermal reaction in the step S3), the obtained product is cooled to room temperature, washed to be neutral by water and absolute ethyl alcohol, and freeze-dried to obtain fluorine-free Mo2CTxMXenes material.
The invention also provides the fluorine-free Mo prepared by the preparation method2CTxMXenes material.
The invention also provides the fluorine-free Mo prepared by the preparation method2CTxThe MXenes material is applied to electrochemical catalysis, rechargeable batteries and super capacitors.
The invention provides fluorine-free Mo2CTxThe preparation method of the MXenes material comprises the following steps: s1) mixing, heating and grinding the molybdenum carbide nano powder and the metal gallium to obtain a mixture; the molar ratio of the molybdenum carbide nano powder to the metal gallium is less than 1: 2; s2) sintering the mixture at high temperature under the conditions of sealing and low vacuum to obtain Mo2Ga2C MAX precursor; s3) adding Mo2Ga2Mixing the CMAX precursor with concentrated hydrochloric acid, and carrying out hydrothermal reaction to etch to obtain fluorine-free Mo2CTxMXenes material. Compared with the prior art, the method obtains Mo by sintering the molybdenum carbide nano powder and the gallium under low vacuum2Ga2C MAX precursor, and then etching Ga by using concentrated hydrochloric acid hydrothermal method to obtain fluorine-free Mo2CTxMXenes nano material completely avoids the use of HF and F-containing reagent and realizes the fluorine-free Mo2CTxSafe and controllable preparation of MXenes, and Mo obtained2CTxMXenes surface only contains oxygen group and chlorine group, and the surface chlorine group is easily substituted by other groups, so that Mo is increased2CTxThe adjustability of the MXenes material improves the application prospect of the MXenes material in a plurality of fields such as catalysis, energy storage, composite materials and the like.
Drawings
FIG. 1 shows Mo obtained in example 1 of the present invention by first sintering2Ga2cMAX material (a) and Mo obtained by second sintering2Ga2cMAX precursor and fluorine-free Mo2CTxX-ray diffraction pattern of MXenes material (b);
FIG. 2 shows Mo obtained in example 1 of the present invention2Ga2cMAX precursor (a) and fluorine-free Mo2CTxScanning electron microscopy of MXenes material (b);
FIG. 3 shows Mo obtained in example 1 of the present invention2Ga2SEM EDS of cmax precursor;
FIG. 4 shows Mo obtained in example 1 of the present invention2Ga2SEM Mapping diagram of C MAX precursor;
FIG. 5 shows fluorine-free Mo obtained in example 1 of the present invention2CTxSEM EDS images of MXenes material;
FIG. 6 shows fluorine-free Mo obtained in example 1 of the present invention2CTxSEM Mapping graph of MXenes material;
FIG. 7 shows Mo obtained in example 1 of the present invention2Ga2cMAX precursor (a) and fluorine-free Mo2CTxTransmission electron microscopy of MXenes material (b);
FIG. 8 shows Mo obtained in example 2 of the present invention2CTxX-ray diffraction patterns of MXenes material;
FIG. 9 shows Mo obtained in example 3 of the present invention2CTxX-ray diffraction patterns of MXenes material;
FIG. 10 is an X-ray diffraction pattern of a reacted material obtained in comparative example 1 of the present invention;
FIG. 11 is an X-ray diffraction pattern of the reacted material obtained in comparative example 2 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides fluorine-free Mo2CTxThe preparation method of the MXenes material comprises the following steps: s1) mixing, heating and grinding the molybdenum carbide nano powder and the metal gallium to obtain a mixture; the molar ratio of the molybdenum carbide nano powder to the metal gallium is less than 1: 2; s2) sintering the mixture at high temperature under the conditions of sealing and low vacuum to obtain Mo2Ga2C MAX precursor; s3) adding Mo2Ga2Mixing the CMAX precursor with concentrated hydrochloric acid, and carrying out hydrothermal reaction to etch to obtain fluorine-free Mo2CTxMXenes material.
In the present invention, the sources of all raw materials are not particularly limited, and they may be commercially available.
Mixing molybdenum carbide nano powder with gallium metal, heating and grinding to obtain a mixture; the mesh number of the molybdenum carbide nano powder is preferably more than or equal to 325 meshes; the molar ratio of the molybdenum carbide nanopowder to the gallium metal is less than 1:2, namely the gallium metal is excessive, in the invention, the molar ratio of the molybdenum carbide nanopowder to the gallium metal is preferably less than 1:2 and is more than or equal to 1: 8; the temperature of the heating and grinding is preferably 30-80 ℃, more preferably 40-70 ℃, further preferably 50-70 ℃, and most preferably 60 ℃; the time for heating and grinding is preferably 30-60 min, and more preferably 40-50 min.
Sintering the mixture at high temperature under the conditions of closed low vacuum; in the present invention, the mixture is preferably sealed in a glass tube of low vacuum for high temperature sintering; the inner diameter of the glass tube is preferably 5-12 mm; the length of the glass tube is preferably 10-30 cm; the vacuum degree of the low vacuum is preferably less than or equal to 1 torr; the high-temperature sintering temperature is preferably 800-900 ℃, more preferably 820-880 ℃, further preferably 840-860 ℃ and most preferably 850 ℃; the high-temperature sintering time is preferably 2-4 days, and more preferably 3 days; the heating rate of the high-temperature sintering is preferably 5-15 ℃/min, more preferably 8-12 ℃/min, and further preferably 10 ℃/min.
After high-temperature sintering, preferably naturally cooling to room temperature, and secondarily heating and grinding a sintered product; the temperature of the secondary heating and grinding is preferably 30-80 ℃, more preferably 40-70 ℃, further preferably 50-70 ℃ and most preferably 60 ℃; the time for the secondary heating and grinding is preferably 30-60 min, and more preferably 40-50 min; then preferably, the product after the secondary heating and grinding is sintered for the second time at high temperature under the closed low vacuum condition to obtain a secondary sintered product; in the invention, the product after the secondary heating and grinding is preferably sealed in a low-vacuum glass tube for secondary high-temperature sintering to obtain a secondary sintered product; the inner diameter of the glass tube is preferably 5-12 mm; the length of the glass tube is preferably 10-30 cm; the vacuum degree of the low vacuum is preferably less than or equal to 1 torr; the temperature of the secondary high-temperature sintering is preferably 800-900 ℃, more preferably 820-880 ℃, further preferably 840-860 ℃ and most preferably 850 ℃; the time of the secondary high-temperature sintering is preferably 2-4 days, and more preferably 2-3 days; the heating rate of the secondary high-temperature sintering is preferably 5-15 ℃/min, more preferably 8-12 ℃/min, and further preferably 10 ℃/min.
In the present invention, it is preferable that the secondary sintered product is washed with an acid to remove excess metal gallium; the acid is preferably concentrated hydrochloric acid; the concentration of the concentrated hydrochloric acid is preferably 6-12 mol/L, more preferably 10-12 mol/L, and still more preferably 12 mol/L; the ratio of the total mass of the metal gallium and the molybdenum carbide nano powder to the acid is preferably (10-30) g: 100ml, more preferably (15 to 25) g: 100ml, more preferably (18 to 22) g: 100ml, most preferably 19.1 g: 100 ml; the cleaning method is preferably to slowly drop acid into the sintered product and to stand for reaction; the standing time is preferably 20-30 h, more preferably 22-28 h, and still more preferably 24-26 h.
Then preferably washed with water to a neutral state,cooling and drying to obtain Mo2Ga2C MAX precursor; the water is preferably deionized water; the temperature of the freeze drying is preferably-50 ℃ to-80 ℃, more preferably-60 ℃ to-80 ℃, and further preferably-70 ℃ to-80 ℃; the vacuum degree of the freeze drying is preferably lower than 20 Pa, more preferably 5-15 Pa, and further preferably 10 Pa; the freeze drying time is preferably 20-30 hours, more preferably 22-28 hours, and still more preferably 24-26 hours.
Mixing the Mo2Ga2Mixing the C MAX precursor with concentrated hydrochloric acid, and etching by hydrothermal reaction; the concentration of the concentrated hydrochloric acid is preferably 6-12 mol/L, more preferably 10-12 mol/L, and still more preferably 12 mol/L; the Mo2Ga2The preferred ratio of cmax precursor to concentrated hydrochloric acid is 10 mg: (0.8-1.2) ml, more preferably 10 mg: (0.9-1.1) ml, preferably 10 mg: 1 ml; the temperature of the hydrothermal reaction is preferably 120-160 ℃, more preferably 130-150 ℃, and further preferably 140 ℃; the time of the hydrothermal reaction is preferably 5-7 days, and more preferably 5-6 days; the hydrothermal reaction is preferably carried out under closed conditions, so that the volume of the added concentrated hydrochloric acid directly affects the pressure during the reaction, and the volume ratio of the concentrated hydrochloric acid to the container of the hydrothermal reaction is preferably 1: (2-3), more preferably 1: (2-2.8), preferably 1: (2.2-2.5).
After the reaction is finished, the reaction solution is preferably cooled to room temperature, more preferably naturally cooled to room temperature, washed to neutrality by using water and absolute ethyl alcohol, and freeze-dried to obtain Mo2CTxMXenes material; the water is preferably deionized water; the temperature of the freeze drying is preferably-50 ℃ to-80 ℃, more preferably-60 ℃ to-80 ℃, and further preferably-70 ℃ to-80 ℃; the vacuum degree of the freeze drying is preferably lower than 20 Pa, more preferably 5-15 Pa, and further preferably 10 Pa; the freeze drying time is preferably 20-30 hours, more preferably 22-28 hours, and still more preferably 24-26 hours.
The invention obtains Mo by sintering molybdenum carbide nano powder and gallium metal in low vacuum2Ga2C MAX precursor, and then etching Ga by using concentrated hydrochloric acid hydrothermal method to obtain fluorine-free Mo2CTxMXenes nano material, finishThe use of HF and F-containing reagent is avoided completely, and the preparation of Mo by etching with the HF and the F-containing reagent is greatly reduced2CTxThe damage of MXenes to experimenters realizes the fluorine-free Mo2CTxSafe and controllable preparation of MXenes, and Mo obtained2CTxMXenes surface only contains oxygen group and chlorine group, and the surface chlorine group is easily substituted by other groups, so that Mo is increased2CTxThe adjustability of the MXenes material improves the application prospect of the MXenes material in a plurality of fields such as catalysis, energy storage, composite materials and the like.
The invention also provides fluorine-free Mo prepared by the method2CTxMXenes material; the fluorine-free Mo2CTxThe size of the MXenes material is preferably 3-10 microns.
The invention also provides the fluorine-free Mo prepared by the method2CTxMXenes material electrochemical catalysis, rechargeable battery and super capacitor.
In order to further illustrate the present invention, the following examples are provided to illustrate a fluorine-free Mo2CTxMXenes materials, methods of making them and uses thereof are described in detail.
The reagents used in the following examples are all commercially available.
Example 1
Weighing 28 g of metal gallium, weighing 10.2 g of 325-mesh molybdenum carbide nano powder, wherein the molar ratio of the metal gallium to the molybdenum carbide nano powder is about 8:1, putting the materials in a mortar, heating to 60 ℃, and grinding for 40 minutes until the materials are uniform to obtain a mixed material.
And after the mixed material is cooled, putting the mixed material into a glass tube with the inner diameter of 8 mm, vacuumizing the glass tube to about 1torr by using a mechanical pump, and sealing the glass tube.
And (3) putting the obtained sealed glass tube filled with the mixed material into a muffle furnace, heating to 850 ℃ at a heating rate of 10 ℃/min, maintaining for 3 days, and then naturally cooling to room temperature.
The contents of the glass tube were taken out and placed in a 500 ml beaker, 200 ml of concentrated hydrochloric acid was slowly added dropwise and left to react for 24 hours in order to remove the excess gallium metal.
Washing with deionized water for several times to neutrality, and freeze drying at-80 deg.C under vacuum degree of 10 Pa for 24 hr to obtain Mo2Ga2A C MAX material.
And taking out the materials in the glass tube after the first sintering, putting the materials in a mortar, heating to 60 ℃, and grinding for 40 minutes until the materials are uniform to obtain a mixed material.
And after the mixed material is cooled, putting the mixed material into a glass tube with the inner diameter of 8 mm, vacuumizing the glass tube to about 1torr by using a mechanical pump, and sealing the glass tube.
And (3) putting the obtained sealed glass tube filled with the mixed material into a muffle furnace, heating to 850 ℃ at a heating rate of 10 ℃/min, maintaining for 2 days, and then naturally cooling to room temperature.
The contents of the glass tube were taken out and placed in a 500 ml beaker, 200 ml of concentrated hydrochloric acid was slowly added dropwise and left to react for 24 hours in order to remove the excess gallium metal.
Washing with deionized water for several times until neutral, and freeze drying at-80 deg.C under vacuum degree of 10 Pa for 24 hr to obtain Mo for further experiment2Ga2C MAX precursor.
400 mg of Mo2Ga2And putting the C MAX precursor into a polytetrafluoroethylene lining with the volume of 100ml, adding 40ml of 12 mol/L concentrated hydrochloric acid, putting the mixture into a stainless steel reaction kettle, reacting for 5 days in a drying oven at the temperature of 140 ℃, and naturally cooling to room temperature after the reaction is finished.
Repeatedly cleaning with deionized water and anhydrous ethanol to neutrality, and drying at-80 deg.C and vacuum degree of 10 Pa for 24 hr by freeze drying technology to obtain fluorine-free Mo2CTxMXenes material.
The first-sintered Mo obtained in example 1 was subjected to X-ray diffraction2Ga2cMAX materials and twice-sintered Mo for further experiments2Ga2cMAX precursor and fluorine-free Mo2CTxMXenes material was analyzed to obtain its X-ray diffraction pattern as shown in FIG. 1, where a is Mo in the first sintering2Ga2X-ray diffraction pattern of C MAX material, b is Mo for secondary sintering of further experiment2Ga2cMAX precursor and fluorine-free Mo2CTxX-ray diffraction pattern of MXenes. As can be seen from FIG. 1, Mo is sintered for the first time2Ga2The C MAX material has more Mo2C impurity, Mo after secondary sintering2Ga2The CMAX precursor has a very high purity. After being etched by the experimental method, Mo is positioned at 34.1 degrees, 37.3 degrees, 39.9 degrees, 42.5 degrees and the like2Ga2The characteristic peak of C is obviously reduced, and proves that Ga is successfully removed from Mo2Ga2Etching the C MAX precursor layer; fluorine-free Mo2CTxThe X-ray diffraction spectrum of MXenes also shows Mo2Ga2Different characteristic peak of C MAX precursor, located at 6.97 ° (0002) compared with Mo2Ga2The 8.98 deg. drop in C also demonstrates the success of the etch.
Scanning electron microscope was used for Mo obtained in example 12Ga2cMAX precursor and fluorine-free Mo2CTxMXenes material was analyzed to obtain its scanning electron micrograph shown in FIG. 2, where a is Mo2Ga2Scanning electron microscopy of C MAX precursor, b is fluorine-free Mo2CTxScanning electron microscopy of MXenes material. As can be seen from FIG. 2, Mo2Ga2The C MAX precursor is a uniform nanosheet of 3-10 microns, and after etching, fluorine-free Mo2CTxMXenes shows a layered structure but no significant overall change.
Mo obtained in example 1 was subjected to energy dispersive X-ray spectroscopy using a scanning electron microscope2Ga2The SEM EDS diagram of the C MAX precursor is shown in figure 3, and the SEM Mapping diagram is shown in figure 4. It can be seen from FIGS. 3 and 4 that the three elements Mo, Ga and C are uniformly distributed in Mo2Ga2On the nanometer sheet of the C MAX precursor, Mo is relatively intuitively proved2Ga2The preparation of the C MAX precursor is successful.
Using a scanning electron microscope andx-ray energy dispersive Spectroscopy on fluorine-free Mo obtained in example 12CTxMXenes material is analyzed to obtain the fluorine-free Mo2CTxSEM EDS diagram of MXenes is shown in FIG. 5; obtaining fluorine-free Mo2CTxThe SEMMapping diagram for MXenes is shown in FIG. 6. As can be seen from FIG. 5, the alloy is comparable to Mo2Ga2The content of the C MAX precursor and the Ga is obviously reduced, which proves that the Ga atoms are successfully prepared from Mo by using the experimental method in the invention2Ga2And etching the C MAX precursor layers. At the same time, the oxygen content and the chlorine content are increased, which shows that the prepared fluorine-free Mo2CTxThe MXenes material surface contains chlorine and oxygen-containing groups, wherein the atomic ratio of chlorine is about 2-5%, and the atomic ratio of oxygen is about 20-30%. As can be seen from FIG. 6, the content of Ga element is greatly reduced, and O and Cl elements are uniformly distributed in Mo2CTxMXenes nanosheet surface, demonstrates fluorine-free Mo2CTxThe MXenes material is successfully prepared.
Mo obtained in example 1 was subjected to a transmission electron microscope2Ga2cMAX precursor and fluorine-free Mo2CTxMXenes material was analyzed and its transmission electron micrograph is shown in FIG. 7, where a is Mo2Ga2Transmission electron microscopy of the cmax precursor; b is fluorine-free Mo2CTxTransmission electron microscopy of MXenes material. From FIG. 7, Mo is seen2Ga2The C MAX precursor is compact and flaky, and the fluorine-free Mo is obtained after the treatment of the C MAX precursor by the experimental method in the invention2CTxMXenes materials are more easily peeled into few or single layers, showing a more pronounced layered structure.
Example 2
210 mg of Mo obtained in example 1 were added2Ga2And putting the C MAX precursor into a polytetrafluoroethylene lining with the volume of 50ml, adding 22ml of 12 mol/L concentrated hydrochloric acid, putting the mixture into a stainless steel reaction kettle, reacting for 5 days in a drying oven at the temperature of 140 ℃, and naturally cooling to room temperature after the reaction is finished.
Repeatedly cleaning with deionized water and anhydrous ethanol to neutrality, and freeze dryingDrying at-80 deg.C and vacuum degree of 10 Pa for 24 hr to obtain fluorine-free Mo2CTxMXenes material.
X-ray diffraction technique on Mo obtained in example 22CTxMXenes material was analyzed to obtain its X-ray diffraction pattern as shown in FIG. 8. As can be seen from FIG. 8, Mo2CTxThe X-ray diffraction spectrum of MXenes also shows Mo2Ga2Different characteristic peak of C MAX precursor, located at 6.83 deg. (0002) compared with Mo2Ga2The 8.98 deg. drop in C also demonstrates the success of the etch.
Example 3
400 mg of Mo obtained in example 12Ga2And putting the C MAX precursor into a polytetrafluoroethylene lining with the volume of 100ml, adding 40ml of 12 mol/L concentrated hydrochloric acid, putting the mixture into a stainless steel reaction kettle, reacting for 5 days in a drying oven at the temperature of 120 ℃, and naturally cooling to room temperature after the reaction is finished.
Repeatedly cleaning with deionized water and anhydrous ethanol to neutrality, and drying at-80 deg.C and vacuum degree of 10 Pa for 24 hr by freeze drying technology to obtain Mo2CTxMXenes material.
X-ray diffraction technique on Mo obtained in example 32CTxMXenes material was analyzed to obtain its X-ray diffraction pattern as shown in FIG. 9. As can be seen from FIG. 9, Mo2CTxMo belonging to MXenes with X-ray diffraction spectrum of 8.98 °2Ga2The characteristic peak of C is obviously reduced but still exists, which proves that Mo2Ga2C is partially etched, mainly due to the lower temperature and pressure, which slows down the etch rate, but the etch is still effective.
Comparative example 1
200 mg of Mo obtained in example 12Ga2Putting the C MAX precursor into a polytetrafluoroethylene lining with the volume of 50ml, adding 25ml of deionized water and 8.025 g of ammonium chloride, putting the mixture into a stainless steel reaction kettle, reacting in an oven at the temperature of 140 ℃ for 5 days, and naturally cooling to room temperature after the reaction is finished.
Repeatedly washing with deionized water and anhydrous ethanol to neutrality, and drying at-80 deg.C and vacuum degree of 10 Pa for 24 hr by freeze drying technology to obtain reacted material.
The material obtained in comparative example 1 was analyzed by the X-ray diffraction technique to obtain an X-ray diffraction pattern thereof, as shown in fig. 10. As can be seen from FIG. 10, Mo2Ga2The characteristic peak of C still exists, Mo is not existed2CTxCharacteristic peaks of MXenes appeared indicating that etching was not successful, while distinct molybdenum oxide impurity peaks appeared at 8.6 °, 21.7 ° and 25.9 °.
Comparative example 2
200 mg of Mo obtained in example 12Ga2And putting the C MAX precursor into a polytetrafluoroethylene lining with the volume of 50ml, adding 23ml of deionized water and 2ml of dimethyl sulfoxide, putting the mixture into a stainless steel reaction kettle, reacting in an oven at the temperature of 140 ℃ for 5 days, and naturally cooling to room temperature after the reaction is finished.
Repeatedly washing with deionized water and anhydrous ethanol to neutrality, and drying at-80 deg.C and vacuum degree of 10 Pa for 24 hr by freeze drying technology to obtain reacted material.
The material obtained in comparative example 2 was analyzed by the X-ray diffraction technique to obtain an X-ray diffraction pattern thereof, as shown in fig. 11. As can be seen from FIG. 11, Mo2Ga2The characteristic peak of C still exists, and Mo is not existed2CTxThe characteristic peak of MXenes appears, and proves that Mo2Ga2C was not successfully etched.

Claims (10)

1. Fluorine-free Mo2CTxThe preparation method of the MXenes material is characterized by comprising the following steps:
s1) mixing, heating and grinding the molybdenum carbide nano powder and the metal gallium to obtain a mixture; the molar ratio of the molybdenum carbide nano powder to the metal gallium is less than 1: 2;
s2) sintering the mixture at high temperature under the conditions of sealing and low vacuum to obtain Mo2Ga2C MAX precursor;
s3) adding Mo2Ga2Mixing the C MAX precursor with concentrated hydrochloric acid, and performing hydrothermal reaction to etch to obtain fluorine-free Mo2CTxMXenes material.
2. The preparation method according to claim 1, wherein the molybdenum carbide nanopowder has a mesh number of 325 mesh or more; the molar ratio of the molybdenum carbide nano powder to the metal gallium is more than or equal to 1: 8.
3. The method according to claim 1, wherein the temperature of the heat grinding in the step S1) is 30 to 80 ℃; the time for heating and grinding is 30-60 min.
4. The method as claimed in claim 1, wherein the vacuum degree of the low vacuum in step S2) is less than or equal to 1 torr; the temperature of the high-temperature sintering is 800-900 ℃; the high-temperature sintering time is 2-4 days.
5. The preparation method according to claim 1, wherein after the high-temperature sintering in step S2), the sintered product is secondarily heated and ground, and then secondarily sintered at high temperature under a closed low vacuum condition to obtain a secondarily sintered product; washing the secondary sintered product with acid to remove redundant metal gallium, then washing the secondary sintered product with water to be neutral, and freeze-drying to obtain Mo2Ga2C MAX precursor.
6. The method according to claim 1, wherein the Mo is2Ga2The ratio of cmax precursor to concentrated hydrochloric acid was 10 mg: (0.8-1.2) ml; the concentration of the concentrated hydrochloric acid is 6-12 mol/L.
7. The preparation method according to claim 1, wherein the temperature of the hydrothermal reaction in the step S3) is 120 ℃ to 160 ℃; the hydrothermal reaction time is 5-7 days.
8. The method of claim 1The preparation method is characterized in that after the etching is carried out through the hydrothermal reaction in the step S3), the obtained product is cooled to the room temperature, washed to be neutral by water and absolute ethyl alcohol, and freeze-dried to obtain the fluorine-free Mo2CTxMXenes material.
9. The fluorine-free Mo prepared by the preparation method of any one of claims 1to 82CTxMXenes material.
10. The fluorine-free Mo prepared by the preparation method of any one of claims 1to 82CTxThe MXenes material is applied to electrochemical catalysis, rechargeable batteries and super capacitors.
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