WO2019165806A1

WO2019165806A1 - Method for preparing mxene nanosheet with mo vacancy

Info

Publication number: WO2019165806A1
Application number: PCT/CN2018/117079
Authority: WO
Inventors: 吴文剑; 赵玉飞; 张美丽; 蔡丽蓉; 范洪波; 汪国秀
Original assignee: 东莞理工学院
Priority date: 2018-03-02
Filing date: 2018-11-23
Publication date: 2019-09-06
Also published as: CN108383121A; CN108383121B

Abstract

A method for preparing a MXene nanosheet with Mo vacancy, comprising the steps of: dispersing a Mo-containing MXene nano material in a dispersing liquid to obtain a nano dispersion liquid; coating the nano dispersion liquid onto a working electrode; constituting the working electrode coated with the nano dispersion liquid, a reference electrode and a counter electrode into a three-electrode system, the pH value of the electrolytic solution of the three-electrode system being 0 to 6; and applying a voltage to the three-electrode system to perform electrochemical stripping and activation so as to obtain a MXene nanosheet having Mo vacancy.

Description

Method for preparing MXene nanosheet with Mo vacancy

Technical field

The invention relates to the field of new materials technology, in particular to a method for preparing MXene nanosheets with Mo vacancies.

Background technique

MXene is a new type of two-dimensional layered material, including transition metal carbides, nitrides and the like. Due to its excellent electrical conductivity, chemical stability and hydrophilicity, MXene exhibits excellent electrochemical performance in lithium/sodium ion batteries, lithium-sulfur batteries, supercapacitors, and water decomposition. Theoretical calculations indicate that the O-termination site of the MXene surface is the catalytically active site for the electrocatalytic hydrogen evolution reaction. However, the electrocatalytic activity of MXene prepared at present is not ideal. Therefore, screening MXene with better electrocatalytic activity and modifying it is the research hotspot of MXene in the field of electrocatalysis. Moreover, the current preparation of MXene nanosheets is mainly carried out by the intercalation of an organic solvent, however, this method generally requires relatively complicated steps and a low yield.

Summary of the invention

Based on this, it is necessary to aim at the electrocatalytic activity of the currently prepared MXene, and the method of using the organic solvent to embed the MXene material for stripping is complicated, and the yield is low, and the MXene nanometer with Mo vacancies is provided. The preparation method of the tablet.

A method for preparing MXene nanosheets with Mo vacancies, comprising the steps of:

Dispersing the Mo-containing MXene nano material in the dispersion to obtain a nano-dispersion liquid;

Applying the nanodispersion to a working electrode;

The working electrode coated with the nano-dispersion liquid and the reference electrode and the counter electrode constitute a three-electrode system, and the pH of the electrolyte of the three-electrode system is 0-6;

Electrochemical stripping and activation of the applied voltage of the three-electrode system yielded MXene nanosheets with Mo vacancies.

Details of one or more embodiments of the invention are set forth in the accompanying drawings and description below. Other features, objects, and advantages of the invention will be apparent from the description and appended claims.

DRAWINGS

1 is a process flow diagram of a method for preparing an MXene nanosheet having Mo vacancies according to an embodiment;

2 is a schematic flow chart of a method for preparing a MXene nanosheet having Mo vacancies shown in FIG. 1;

3 is a scanning electron micrograph of the Mo-containing MXene nanomaterial of Example 1 before (a), during peeling (b, c), and after peeling (d);

4 is a schematic view showing a peeling process of a Mo-containing MXene nanomaterial corresponding to FIG. 3;

5 is a scanning transmission electron micrograph of the Mo ₂ TiC ₂ nanomaterial prepared in Example 1;

6 is a scanning transmission electron micrograph of a Mo ₂ TiC ₂ nanosheet prepared in Example 1;

7 is an electrochemical activity diagram of a Mo ₂ TiC ₂ nanomaterial in Example 1 subjected to a constant potential scan;

8 is a polarization curve of a cathode linear scan of a Mo ₂ TiC ₂ nanomaterial in Example 5, wherein (a) the number of scanning turns is 1, (b) the number of scanning turns is 100, and (c) the number of scanning cycles is 200, (d) the number of scanning circles is 1000, (e) the number of scanning circles is 1500, and (f) the number of scanning circles is 2000;

9 is a polarization curve of a cathode linear scan of a Mo ₂ TiC ₂ nanosheet obtained by peeling off an organic solution in Example 10, and the number of scanning turns is 1.

Detailed ways

The preparation method of the MXene nanosheet having Mo vacancies will be further described in detail below with reference to the specific embodiments and the accompanying drawings.

Referring to FIG. 1, a method for preparing an MXene nanosheet having Mo vacancies according to an embodiment includes the following steps:

S110. Preparing a MXene nano material containing Mo.

The precursors MAX and hydrofluoric acid (HF) are generally used as raw materials for the preparation of MXene nanomaterials. The structure of the precursor MAX is generally M _n+1 AX _n , where M, A and X represent transition metals, respectively, IIIA or IVA Elemental, carbon or nitrogen. The exposed faces of the upper and lower layers in the MAX structure are typically transition metals. The process of preparing MXene from MAX generally requires more stringent synthesis conditions. The commonly used method is to treat the precursor M _n+1 AX _n MAX with HF, and etch away the Al element in the MAX structure to obtain the corresponding MXene. During the etching process, the transition metal surface of MXene is replaced by -O, -OH or -F elements. MXene, which is currently widely prepared and studied, mainly includes Ti ₂ C, V ₂ C, Nb ₂ C, Ti ₃ C ₂ , Nb ₄ C ₃ , Mo ₂ C, and Mo ₂ TiC ₂ . Theoretical calculations show that the MXene at the -O stop position is the catalytically active site for the electrocatalytic hydrogen evolution reaction. However, the electrocatalytic activity of the currently prepared MXene is not ideal. The alternative MXene for electrocatalytic hydrogen evolution reaction is mainly based on transition metal Mo as the main exposed surface, including Mo ₂ C, Mo ₂ TiC _{2 ,} etc., which can improve the catalytic hydrogen evolution activity of MXene nanosheets.

In one embodiment, the step of preparing the Mo-containing MXene nanomaterial comprises:

S111, adding the precursor MAX to the HF acid and reacting at a temperature of 35 ° C to 55 ° C for 24 to 48 hours to obtain a reaction liquid.

In one embodiment, the precursor MAX is Mo ₂ Ga ₂ C or Mo ₂ TiAlC ₂ . Further, when the current body MAX is Mo ₂ Ga ₂ C, a Mo ₂ C nano material is prepared; when the current body MAX is Mo ₂ TiAlC ₂ , a Mo ₂ TiC ₂ nano material is prepared.

In one embodiment, the precursor MAX is in the form of a powder, and the precursor MAX is directly placed in an HF acid solution for heating and stirring. The mass concentration of the HF acid solution is 30% to 50%. In one embodiment, the ratio of the precursor MAX to the HF acid is from 0.0167 g/mL to 0.2 g/mL.

In one embodiment, the heating temperature is 35 to 55 ° C, and the stirring rate during stirring is 100 to 400 rpm.

S112. After centrifuging the reaction solution, the lower layer solid is washed until the pH of the supernatant liquid is 6-7.

After the reaction solution was centrifuged, the lower solid was separated, and the lower solid was washed with water. In one embodiment, the lower solid is dispersed in water to wash the lower solid, and the solid is deposited by centrifugation, and the above operation is repeated until the supernatant obtained after centrifugation has a pH of 6-7.

S113, lyophilizing the underlying solid to obtain MXene nanomaterial.

In one embodiment, the lower solid is dried in a freeze dryer at a temperature of from -30 ° C to -80 ° C and a pressure of from 10 Pa to 80 Pa.

S120, dispersing Mo-containing MXene nano material in a dispersion to obtain a nano-dispersion liquid.

In one embodiment, the Mo-containing MXene nanomaterial is a Mo ₂ TiC ₂ nano material or a Mo ₂ C nano material. In this embodiment, the Mo ₂ TiC ₂ nano material or the Mo ₂ C nano material is prepared by the step S110. In other embodiments, the Mo ₂ TiC ₂ nano material or the Mo ₂ C nano material may also be directly purchased. obtain.

In one embodiment, the dispersion is selected from at least one of water, isopropanol, and ethanol. Further, the dispersion is a mixture of water and isopropyl alcohol or a mixture of water and ethanol. When the dispersion is a mixture of water and isopropanol, the volume ratio of water to isopropanol is 1:4 to 4:1; when the dispersion is a mixture of water and ethanol, the volume ratio of water to ethanol is 1:4~4:1.

In one embodiment, when the Mo-containing MXene nanomaterial is dispersed in the dispersion, the ratio of the Mo-containing MXene nanomaterial to the dispersion is from 1 mg/mL to 10 mg/mL.

In one embodiment, the Mo-containing MXene nanomaterial is dispersed in the dispersion by ultrasonic dispersion, the ultrasonic dispersion power is 60 W to 100 W, and the ultrasonic dispersion time is 30 min to 90 min.

S130. Applying the nano dispersion to the working electrode.

In one embodiment, the working electrode is a glassy carbon electrode or a carbon paper electrode. In one embodiment, the glassy carbon electrode is purchased from a glassy carbon electrode of CHI Corporation, and the glassy carbon electrode has a diameter of 3 mm. The carbon paper electrode is carbon paper.

In one embodiment, the nanodispersion is applied directly to the surface of the working electrode, and the nanodispersion is applied to the working electrode in an amount of from 0.04 mg/cm ² to 0.5 mg/cm ² . Further, preferably, the coating amount of the nano-dispersion liquid on the glassy carbon electrode is 0.04 mg/cm ² ; and the coating amount of the nano-dispersion liquid on the carbon paper electrode is 0.5 mg/cm ² . Further, after coating the nano-dispersion on the working electrode, drying treatment is performed until the nano-dispersion is dried.

In other embodiments, the nanodispersion is mixed with a binder solution and then dispensed onto the working electrode to enable the Mo-containing MXene nanomaterial to adhere to the working electrode.

S140. The working electrode coated with the nano-dispersion liquid and the reference electrode and the counter electrode constitute a three-electrode system.

In one embodiment, the reference electrode is a mercury sulphate electrode and the counter electrode is a carbon rod electrode. Further, the reference electrode is a mercury sulphate electrode purchased from China Gao Shi Ruilian, and the counter electrode is a carbon rod electrode purchased from China Gao Shi Ruilian.

In one of the embodiments, the electrolyte is included in the three-electrode system. The pH of the electrolyte is 0-6.

In one embodiment, the electrolyte is selected from at least one of H ₂ SO ₄ , HCl, H ₃ PO _{4 ,} and HClO ₄ . The molar concentration of the electrolyte is from 0.01 M to 0.5 M.

It should be noted that in the three-electrode system, the electrolyte has a great influence on the stripping of MXene nanomaterials. Through a large number of experiments, it is found that the stripping effect of MXene nanomaterials decreases with the increase of the pH value of the electrolyte. However, there is substantially no peeling effect in the neutral solution, and in the alkaline solution, the MXene nanomaterial reacts with the alkaline solution to cause destruction of the structure of the MXene nanomaterial.

S150, performing electrochemical reaction on the applied voltage of the three-electrode system.

In one embodiment, the voltage is applied to the electrochemical reaction by means of a constant potential sweep. Further, in the potentiostatic scanning mode, the potential is 100 mV vs RHE ～500 mV vs RHE, and the time for applying the voltage by the constant potential scanning is 2 h to 100 h.

In another embodiment, a voltage is applied to the electrochemical reaction by means of a linear scan of the cathode. Further, in the mode of linear scanning of the cathode, the scanning range of the potential is 0 to -A mV vs RHE, wherein 400≤A≤550; the rate of potential scanning is 5 mV/s to 100 mV/s, and the number of turns of the potential scanning is 1000. Circle ~ 5000 laps.

S160. The electrolyte is subjected to suction filtration treatment, and the solid is washed and freeze-dried.

In one embodiment, after the electrolytic solution is subjected to suction filtration treatment, a solid substance is obtained, and the solid precipitate is freeze-dried to obtain a MXene nanosheet having Mo vacancies.

The preparation method of the MXene nanosheet with Mo vacancies is carried out by electrochemical stripping to remove the MXene nano material containing Mo, which can completely strip the nanosheet material, avoid using a large amount of organic solvent, and the process is simpler and The yield is obviously improved. In addition, MXene nanosheets with Mo vacancies can be prepared by using MXene nanomaterials containing Mo, and the surface properties can be controlled by electrochemical stripping to prepare MXene with a large number of Mo vacancies. The nanosheets make the MXene nanosheets with Mo vacancies have better electrocatalytic hydrogen evolution reaction activity. In addition, by electrochemical stripping, the surface oxidation of MXene nanomaterials can be avoided, and the -O termination position is maximized to further improve the catalytic activity of the electrocatalytic hydrogen evolution reaction.

The application of the MXene nanosheets with Mo vacancies prepared by the above-mentioned preparation method of Mo vacancies in the electrocatalytic hydrogen evolution reaction expands the application range of MXene and also provides more catalysts for electrocatalytic hydrogen evolution reaction. s Choice. MXene has very good conductivity and hydrophilicity. The -O stop position on the surface is the catalytic active site of electrocatalytic hydrogen evolution reaction. Exposing more -O termination sites as much as possible can maximize the electrocatalytic hydrogen evolution. Reactivity, which not only extends the electrochemical application of MXene from energy storage to energy conversion, but also enriches the range of electrocatalytic hydrogen evolution catalysts.

The MXene nanosheets with Mo vacancies prepared by the above preparation method of MXene nanosheets with Mo vacancies can be used in the electrocatalytic hydrogen evolution reaction to enhance the catalytic hydrogen evolution reaction activity.

It should be noted that in other embodiments, step S110 and step S160 may be omitted.

The following is a description of specific examples, and the following examples, unless otherwise specified, do not contain other components not specifically indicated except for unavoidable impurities.

Example 1

(1) Add 0.5 g of Mo ₂ TiAlC ₂ to 10 mL of a 50% by mass HF acid solution, heat to 35 ° C for 48 h to obtain a reaction solution, centrifuge the reaction solution, and wash the lower layer of solid to the supernatant. When the pH of the liquid was 6, the lower layer solid was freeze-dried to obtain a Mo ₂ TiC ₂ nanomaterial.

(2) 4 mg of Mo ₂ TiC ₂ nanomaterial was dispersed in 1 mL of a dispersion to obtain a nanodispersion, wherein the dispersion was a mixture of water and isopropyl alcohol in a volume ratio of 1:1.

(3) The nano-dispersion was applied to a glassy carbon electrode, and the coating amount of the nano-dispersion on the glassy carbon electrode was 0.04 mg/cm ² .

(4) The glassy carbon electrode, the mercury sulphate electrode and the carbon rod electrode are combined to form a three-electrode system. The electrolyte of the three-electrode system is a H ₂ SO ₄ solution having a molar concentration of 0.5 M, and the pH of the electrolyte is zero.

(5) Electrochemical reaction was carried out on the applied voltage of the three-electrode system by means of potentiostatic scanning. The potential was -250 mV vs RHE, and the potentiometric scanning time was 25 h.

(6) The electrolytic solution was subjected to suction filtration treatment, and the solid precipitate was washed and freeze-dried to obtain a Mo ₂ TiC ₂ nanosheet.

Example 2

(1) 0.5 g of Mo ₂ TiAlC _{2 was} added to 30 mL of a 35% by mass HF acid solution, and heated to 55 ° C for 24 hours to obtain a reaction solution. After centrifuging the reaction solution, the lower layer of solid was washed to the supernatant. When the pH of the liquid is 7, the underlying solid is dried and ground to obtain a Mo ₂ TiC ₂ nanomaterial.

(2) 10 mg of Mo ₂ TiC ₂ nanomaterial was dispersed in 10 mL of a dispersion to obtain a nanodispersion, wherein the dispersion was a mixture of water and ethanol in a volume ratio of 1:4.

(3) The nano-dispersion was applied to a glassy carbon electrode, and the coating amount of the nano-dispersion on the glassy carbon electrode was 0.08 mg/cm ² .

(4) The above-mentioned glassy carbon electrode, mercury sulphate electrode and carbon rod electrode constitute a three-electrode system, and the electrolyte of the three-electrode system is a H ₂ SO ₄ solution having a molar concentration of 0.1 M, and the pH of the electrolyte is 3.

(5) Electrochemical reaction was carried out on the applied voltage of the three-electrode system by means of potentiostatic scanning. The potential was -100 mV vs RHE, and the potentiometric scanning time was 100 h.

(6) Centrifuging the electrolytic solution and washing and drying the solid precipitate to obtain a Mo ₂ TiC ₂ nanosheet.

Example 3

(1) 2 g of Mo ₂ TiAlC _{2 was} added to 10 mL of a 50% by mass HF acid solution, and heated to 50 ° C for 30 hours to obtain a reaction solution. After the reaction solution was centrifuged, the lower layer of solid was washed to the supernatant. When the pH value is 7, the underlying solid is dried and ground to obtain a Mo ₂ TiC ₂ nanomaterial.

(2) 100 mg of Mo ₂ TiC ₂ nanomaterial was dispersed in 10 mL of a dispersion to obtain a nanodispersion, wherein the dispersion was isopropyl alcohol.

(3) The nano-dispersion was applied to a carbon paper electrode, and the coating amount of the nano-dispersion on the carbon paper electrode was 0.5 mg/cm ² .

(4) The carbon paper electrode, the mercury sulphate electrode and the carbon rod electrode are combined to form a three-electrode system. The electrolyte of the three-electrode system is a H ₂ SO ₄ solution having a molar concentration of 0.05 M, and the pH of the electrolyte is 4.

(5) Electrochemical reaction was carried out on the applied voltage of the three-electrode system by means of potentiostatic scanning. The potential was -500 mV vs RHE, and the potentiometric scanning time was 2 h.

Example 4

(1) 2 g of Mo ₂ AlC was added to 30 mL of a 30% by mass HF acid solution, heated to 45 ° C for 48 h to obtain a reaction solution, and the reaction liquid was centrifuged to wash the lower layer of the solid to the supernatant. At a pH of 6, the underlying solid is dried and ground to obtain a Mo ₂ C nanomaterial.

(2) 60 mg of Mo ₂ C nanomaterial was dispersed in 10 mL of a dispersion to obtain a nanodispersion, wherein the dispersion was a mixture of water and isopropyl alcohol in a volume ratio of 4:1.

(5) Electrochemical reaction was carried out on the applied voltage of the three-electrode system by means of potentiostatic scanning. The potential was -450 mV vs RHE, and the potentiometric scanning time was 48 h.

(6) Centrifuging the electrolyte and washing and drying the solid precipitate to obtain a Mo ₂ C nanosheet.

Example 5

(1) 2 g of Mo ₂ TiAlC _{2 was} added to 30 mL of a 35% by mass HF acid solution, and heated to 45 ° C for 48 h to obtain a reaction solution. The reaction solution was centrifuged and the lower layer of solid was washed until the supernatant was washed. When the pH value is 6, the lower layer solid is dried to obtain a Mo ₂ TiC ₂ nano material.

(2) 6 mg of Mo ₂ TiC ₂ nanomaterial was dispersed in 1 mL of a dispersion to obtain a nanodispersion, wherein the dispersion was a mixture of water and ethanol in a volume ratio of 3:1.

(4) The above-mentioned glassy carbon electrode, mercury sulphate electrode and carbon rod electrode constitute a three-electrode system, and the electrolyte of the three-electrode system is a H ₂ SO ₄ solution having a molar concentration of 0.05 M, and the pH of the electrolyte is 4.

(5) Electrochemical reaction was carried out on the applied voltage of the three-electrode system by means of cathode linear scanning. The potential scanning range was 0--400 mV vs RHE, the potential scanning rate was 5 mV/s, and the potential scanning circle was 2000. ring.

Example 6

(1) Add 1 g of Mo ₂ AlC to 20 mL of a 40% by mass HF acid solution, heat to 45 ° C for 40 h to obtain a reaction solution, centrifuge the reaction solution, and wash the lower layer of the solid to the supernatant. At a pH of 6, the underlying solid is dried and ground to obtain a Mo ₂ C nanomaterial.

(2) 50 mg of Mo ₂ C nanomaterial was dispersed in 10 mL of a dispersion to obtain a nanodispersion, wherein the dispersion was a mixture of water and isopropyl alcohol in a volume ratio of 2:1.

(5) Electrochemical reaction of the applied voltage of the three-electrode system by means of cathode linear scanning, wherein the potential scanning range is 0--550 mV vs RHE, the potential scanning rate is 100 mV/s, and the potential scanning circle is 2000. ring.

Example 7

(2) 10 mg of Mo ₂ TiC ₂ nanomaterial was dispersed in 10 mL of a dispersion to obtain a nanodispersion, wherein the dispersion was a mixture of water and ethanol in a volume ratio of 1:1.

(4) The above-mentioned glassy carbon electrode, mercury sulphate electrode and carbon rod electrode constitute a three-electrode system, and the electrolyte of the three-electrode system is a H ₂ SO ₄ solution having a molar concentration of 0.01 M, and the pH of the electrolyte is 6.

(5) Electrochemical reaction of the applied voltage of the three-electrode system by means of cathode linear scanning, wherein the potential scanning range is 0--500 mV vs RHE, the potential scanning rate is 50 mV/s, and the potential scanning circle is 3000. ring.

Example 8

(1) 0.5 g of Mo ₂ TiAlC _{2 was} added to 30 mL of a 30% by mass HF acid solution, and heated to 55 ° C for 24 hours to obtain a reaction solution. After the reaction solution was centrifuged, the lower layer of solid was washed to the supernatant. When the pH of the liquid is 7, the underlying solid is dried and ground to obtain a Mo ₂ TiC ₂ nanomaterial.

(4) The above-mentioned glassy carbon electrode, mercury sulphate electrode and carbon rod electrode constitute a three-electrode system, and the electrolyte of the three-electrode system is a phosphate buffer solution, and the pH of the electrolyte is 7.

(6) Centrifuging the electrolyte and washing and drying the solid precipitate.

The results show that when the pH of the electrolyte is adjusted to 7, the Mo ₂ TiC ₂ nanomaterial is substantially not peeled off under a neutral electrolytic system.

Example 9

(2) 50 mg of Mo ₂ C nanomaterial was dispersed in 10 mL of a dispersion to obtain a nanodispersion, wherein the dispersion was a mixture of water and isopropyl alcohol in a volume ratio of 1:1.

(3) The nano-dispersion was applied to a glassy carbon electrode, and the coating amount of the nano-dispersion on the glassy carbon electrode was 0.06 mg/cm ² .

(4) The above-mentioned glassy carbon electrode, mercury sulphate electrode and carbon rod electrode constitute a three-electrode system, and the electrolyte of the three-electrode system is a KOH solution having a molar concentration of 1 M, and the pH of the electrolyte is 12.

The results show that when the pH of the electrolyte is adjusted to 12, the Mo ₂ TiC ₂ nanomaterial reacts with the alkaline solution under an alkaline electrolysis system, thereby destroying the sheet structure of the Mo ₂ TiC ₂ nanomaterial.

Example 10

(1) Add 0.5 g of Mo ₂ TiAlC ₂ to 10 mL of a 50% by mass HF acid solution, heat to 35 ° C for 48 h to obtain a reaction solution, centrifuge the reaction solution, and wash the lower layer of solid to the supernatant. When the pH of the liquid is 6, the lower solid is dried to obtain a Mo ₂ TiC ₂ nanomaterial.

(2) The Mo ₂ TiC ₂ MXene obtained above was redispersed into 10 ml of an aqueous solution, and 1 ml of tetrabutylammonium hydroxide having a mass fraction of 40% was further added. Stir under argon protection for 1 h. After centrifugation at 3500 rpm for 1 h, the supernatant was collected and the Mo ₂ TiC ₂ nanosheets obtained by peeling off the organic solution.

The MXene nanomaterials containing Mo before, during, and after stripping of Example 1 were subjected to scanning electron microscopy. The results are shown in FIG. Among them, the scanning electron microscope test was carried out by using a scanning electron microscope tester of the type Zeiss Supra 55VP.

The Mo ₂ TiC ₂ nanomaterials prepared in Example 1 and the Mo ₂ TiC ₂ nanosheets were respectively subjected to scanning transmission electron microscopy, and the results are shown in FIGS. 5 and 6. Among them, the scanning electron microscope test was carried out by using a scanning electron microscope (STEM) model of STEM, JEOL JEM-ARM200F.

As can be seen from Figure 3, we collected samples of Mo ₂ TiC ₂ during the reaction to study the change in morphology during the reaction. As shown in Fig. 3, before the reaction, it can be seen that Mo ₂ TiC ₂ is a relatively loose layered structure, and the surface is relatively flat. After a period of reaction, the surface and edges of the reaction change greatly, and a lot of Cracks and curls on the surface. After the end of the scanning, it can be seen that the Mo ₂ TiC ₂ layered nanosheets are formed. 4 is a schematic view showing the peeling process of the Mo-containing MXene nanomaterial corresponding to FIG. 3, reflecting the peeling process of the Mo-containing MXene nanomaterial.

5 is a scanning transmission electron micrograph of the Mo ₂ TiC ₂ nanomaterial prepared in Example 1. It can be seen from the figure that the Al atom layer is removed during the HF treatment, and the Ti atom layer is sandwiched by two layers of Mo atoms. in the middle.

6 is a scanning transmission electron micrograph of the Mo ₂ TiC ₂ nanosheet prepared in Example 1. After electrocatalytic activation, atomic defects, that is, Mo vacancies, were observed on the Mo ₂ TiC ₂ nanosheet.

7 is an electrochemical activity diagram of the Mo ₂ TiC ₂ nanomaterial in Example 1 subjected to constant potential scanning. During the potentiostatic scanning process, the current density can be observed to increase sharply in the first 10 hours, and gradually tend to be in the first 15 hours. stable.

8 is a polarization curve of a Mo ₂ TiC ₂ nanomaterial in a cathode linear scan in Example 5. In the cyclic cathode linear scanning process, as the number of scanning turns increases, the current density also increases, after 1000 cycles. becoming steady.

8, Mo _₂ TiC ₂ MXene during the scanning process, as the number of turns scanning electrochemical properties of hydrogen is gradually increased, reached a maximum at the time of 1000 cycles, after which the catalytic activity stable. The improvement in performance during hydrogen evolution is mainly due to the electrochemical stripping of Mo ₂ TiC ₂ MXene. Mo ₂ TiC ₂ nanosheets exposed more catalytically active surfaces and caused a large amount of Mo vacancies during electrochemical stripping.

Fig. 9 is a graph showing the electrocatalytic hydrogen evolution performance of a Mo ₂ TiC ₂ nanosheet obtained by peeling off with an organic solvent in Example 10. This catalytic activity is relatively low, compared to Mo ₂ TiC ₂ MXene and electrochemically stripped Mo ₂ TiC ₂ nanosheets. The main reason is that some of the organic solvent used in the stripping process remains on the surface of the Mo ₂ TiC ₂ nanosheet, and a certain bond is formed between the surface group, such as the O-termination site and the OH-termination site. The binding to H ₃ O ⁺ in the solution is blocked, thereby reducing the catalytic hydrogen evolution reaction activity.

The technical features of the above-described embodiments may be arbitrarily combined. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be considered as the scope of this manual.

The above-described embodiments are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Claims

A method for preparing MXene nanosheets with Mo vacancies, comprising the steps of:

Dispersing the Mo-containing MXene nano material in the dispersion to obtain a nano-dispersion liquid;

Applying the nanodispersion to a working electrode;

The working electrode coated with the nano-dispersion liquid and the reference electrode and the counter electrode constitute a three-electrode system, and the pH of the electrolyte of the three-electrode system is 0-6;

Electrochemical stripping and activation of the applied voltage of the three-electrode system yielded MXene nanosheets with Mo vacancies.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 1, wherein the Mo-containing MXene nanomaterial is one selected from the group consisting of Mo 2 TiC 2 nano materials and Mo 2 C nano materials.
The method for producing a MXene nanosheet having Mo vacancies according to claim 1, wherein the dispersion is at least one selected from the group consisting of water, isopropyl alcohol, and ethanol.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 3, wherein the dispersion is a mixture of water and isopropyl alcohol, wherein a volume ratio of the water to the isopropyl alcohol It is 1:4 to 4:1.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 3, wherein the dispersion is a mixture of water and ethanol, wherein a volume ratio of the water to the ethanol is 1:4 ~4:1.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 1, wherein the ratio of the Mo-containing MXene nanomaterial to the dispersion is from 1 mg/mL to 10 mg/mL.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 1, wherein the step of dispersing the Mo-containing MXene nanomaterial in the dispersion is performed by ultrasonic dispersion, the ultrasonic dispersion The power is 60 W to 100 W, and the ultrasonic dispersion time is 30 min to 90 min.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 1, wherein the working electrode is selected from one of a glassy carbon electrode and a carbon paper electrode, and the nanodispersion liquid is at the working electrode The coating amount on the coating is from 0.04 mg/cm 2 to 0.5 mg/cm 2 .
The method for preparing a MXene nanosheet having Mo vacancies according to claim 8, wherein a coating amount of the nanodispersion liquid on the glassy carbon electrode is 0.04 mg/cm 2 , the nanodispersion liquid The coating amount on the carbon paper electrode was 0.5 mg/cm 2 .
The method for preparing a MXene nanosheet having Mo vacancies according to claim 1 or 8, wherein the reference electrode is a mercury sulphate electrode, and the counter electrode is a carbon rod electrode.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 1, wherein the step of electrochemically reacting the applied voltage of the three-electrode system to obtain a MXene nanosheet having Mo vacancies adopts a constant potential The scanning method is applied with an applied voltage to perform an electrochemical reaction. The potential of the constant potential scanning method is -100 mV vs RHE ～-500 mV vs RHE, and the time for applying the voltage for electrochemical reaction by the method of constant potential scanning is 2 h to 100 h. .
The method for preparing a MXene nanosheet having Mo vacancies according to claim 1, wherein the step of electrochemically reacting the applied voltage of the three-electrode system to obtain a MXene nanosheet having Mo vacancies adopts cathode linearity. The scanning method is applied with an applied voltage to perform an electrochemical reaction. The scanning range of the potential in the linear scanning mode of the cathode is 0 to -A mV vs RHE, wherein 400 ≤ A ≤ 550; the rate of potential scanning is 5 mV/s to 100 mV/ s, the number of turns of the potential scan is 1000 to 5000 circles.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 1, wherein the electrolyte of the three-electrode system is at least one selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, and perchloric acid.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 13, wherein the electrolyte solution has a molar concentration of 0.01 M to 0.5 M.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 1, wherein the step of dispersing the Mo-containing MXene nanomaterial in the dispersion to obtain a nano-dispersion further comprises preparing MXene containing Mo The step of the nano material: the precursor MAX is added to the HF acid to react at a temperature of 35 ° C to 55 ° C for 24 h to 48 h to obtain a reaction liquid, and the reaction liquid is centrifuged to wash the lower layer solid to the pH of the supernatant. It is 6 to 7.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 15, wherein the precursor MAX is selected from the group consisting of Mo 2 Ga 2 C and Mo 2 TiAlC 2 .
The method for preparing a MXene nanosheet having Mo vacancies according to claim 15, wherein the HF acid has a mass concentration of 30% to 50%.
The method for preparing a MXene nanosheet having Mo vacancies according to claim 15, wherein the ratio of the precursor MAX to the HF acid is 0.0167 g/mL to 0.2 g/mL.
The method for preparing an MXene nanosheet having Mo vacancies according to claim 1, wherein the step of electrochemically stripping and activating the applied voltage of the three-electrode system further comprises: treating the three-electrode system The electrolytic solution is subjected to suction filtration to obtain a solid matter, and the solid matter is washed and freeze-dried.