KR102234684B1 - Method for preparing N-doped titanium carbide and the N-doped titanium carbide obtained thereof - Google Patents

Abstract

The present invention relates to a method for producing nitrogen-doped titanium carbide by using a state change according to the temperature of a nitrogen-containing single molecule, and a nitrogen-doped titanium carbide prepared by the above production method, and an electrode material comprising the same. It is about.

Description

Nitrogen-doped titanium carbide and its manufacturing method {Method for preparing N-doped titanium carbide and the N-doped titanium carbide obtained thereof}

The present invention relates to a method for producing nitrogen-doped titanium carbide by using a state change according to the temperature of a nitrogen-containing single molecule, and a nitrogen-doped titanium carbide prepared by the above production method, and an electrode material comprising the same. Is about

As a two-dimensional material similar to graphene, MXen is formed from a layered structure called MAX. At this time, M is a transition metal, A is a group 13 or 14 element, X is carbon and/or nitrogen.

Mexin has excellent properties such as electrical conductivity, chemical resistance, and processability, so it is actively applied to electrodes, but its use is still limited. In particular, development to further improve electrical properties along with thinning for use as a two-dimensional material is still insufficient.

On the other hand, a method of doping nitrogen is used in order to realize more excellent electrical properties of mexin. As such a nitrogen doping method, a hydrothermal synthesis method using urea has been mainly used. However, transition metals are easily oxidized in the air or in a solution, and thus transition metal oxides are easily formed during the process, and the nitrogen doping rate is not high, so there has been a limitation in implementing electrical characteristics.

Accordingly, there is a need for a study on a method for producing a nitrogen-doped transition metal carbide having a two-dimensional structure that can efficiently prevent oxidation of the transition metal and further improve the doping rate of nitrogen.

"Two dimensional nanocrystals produced by exfoliation of Ti3AlC2", Adv. Mater., (2011), 23, 4248

The present invention has been conceived to solve the above problems, and in the case of a nitrogen doping method using a hydrothermal synthesis method, it is recognized that oxidation of a transition metal is easily performed, and a simple process prevents the formation of titanium oxide while at the same time doping with nitrogen. An object of the present invention is to provide a method for producing nitrogen-doped titanium carbide having a two-dimensional structure that can greatly improve the amount of the titanium dioxide.

In addition, the present invention is to provide a titanium carbide manufactured by the above manufacturing method and having a high nitrogen doping rate, and an electrode material including the same.

In order to achieve the above object, one aspect of the present invention,

(a) reacting a mixed solution containing at least one mexin (MXene) and cyanamide (NH _{2 CN) selected from Ti 3} C ₂ and Ti _{2 C,}

(b) heat-treating the mexine-cyanamide product obtained by the above reaction at 400°C to 1,200°C under a nitrogen atmosphere, and

(c) acid treatment of the heat-treated product

It is to provide a method for producing a nitrogen-doped titanium carbide comprising a.

In the method for producing nitrogen-doped titanium carbide according to an embodiment of the present invention, the heat treatment is performed at 400° C. to 600° C. for 10 to 300 minutes, and the heat treatment is performed at 600 to 800° C. for 10 to 300 minutes. It may include maintaining the temperature for a while.

In the method for producing nitrogen-doped titanium carbide according to an embodiment of the present invention, the heat treatment may be controlled at a temperature increase rate of 1° C. to 30° C. per minute.

In the method for producing nitrogen-doped titanium carbide according to an embodiment of the present invention, step (a) may include ultrasonic dispersion of the mixed solution and stirring at 70 to 90°C.

In the method for producing nitrogen-doped titanium carbide according to an embodiment of the present invention, the acid treatment in step (c) is any one or more components selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and chloride sulfonic acid. It may be carried out by using.

In addition, another aspect of the present invention is to provide a nitrogen-doped titanium carbide manufactured by the above-described manufacturing method.

In addition, another aspect of the present invention is to provide an electrode material including the above-described nitrogen-doped titanium carbide.

The method for producing nitrogen-doped titanium carbide according to the present invention can efficiently prevent the formation of titanium oxide by being easily oxidized in the atmosphere or in a solution through a dry synthesis method, and a two-dimensional nitrogen-doped structure capable of realizing excellent electrode characteristics. Carbide is manufactured by a simple process and has the advantage of improving its productivity.

Further, the nitrogen-doped titanium carbide produced by the manufacturing method according to the present invention has the advantage of having a high efficiency nitrogen doping effect, thereby dramatically improving the storage capacity.

1 schematically shows a method for producing nitrogen-doped titanium carbide according to the present invention.
2 is a TEM image result of a two-dimensional titanium carbide shape according to temperature ((A) pristine Ti ₃ C ₂ , (B) 500-N-Ti ₃ C ₂ , (C) 700-N-Ti ₃ C ₂ , (D ) 900-N-Ti ₃ C ₂ ).
3 shows the results of an X-ray diffraction pattern (XRD) according to temperature.
4 shows the results of TGA analyzing polymer growth and pyrolysis properties.
5 shows elemental analysis mapping of nitrogen-doped titanium carbide using EDS.
6 shows XRD(a) and XPS(b) of chemical composition and crystallinity analysis according to Comparative Example 1.
7 is a graph showing the electrode experiment results through the cyclic current method.
8 is a graph showing a current value according to a scanned voltage.
9 is a graph showing the results of the charging and discharging experiment.
10 is a graph showing a charging capacity value according to an applied current.

Hereinafter, a method for producing nitrogen-doped titanium carbide of the present invention, a nitrogen-doped titanium carbide obtained therefrom, and an electrode material including the same will be described in detail with reference to the accompanying drawings. The invention can be better understood by the following examples. The following examples are for illustrative purposes of the present invention and are not intended to limit the scope of protection defined by the appended claims. In this case, the technical terms and scientific terms used have meanings that are commonly understood by those of ordinary skill in the technical field to which this invention belongs, unless otherwise defined.

The inventors of the present invention note that the transition metal is easily oxidized in the air or in a solution to form a transition metal oxide in manufacturing a transition metal carbide that implements excellent electrode characteristics, thereby preventing the oxidation of the transition metal while preventing the doping content of nitrogen. While intensifying research on the production method of nitrogen-doped transition metal carbide, which can increase the amount of nitrogen, it maintains a structurally stable two-dimensional structure by using the state change according to the temperature of a single molecule containing nitrogen, while at the same time maintaining a high content of nitrogen. The present invention was completed by discovering that it is possible to prepare titanium carbide doped with T, which can improve electrode efficiency with high capacitance characteristics, and has low resistance and high electrolyte ion diffusion effect.

Specifically, the method for producing nitrogen-doped titanium carbide according to an aspect of the present invention

(a) reacting a mixed solution containing at least one mexin (MXene) and cyanamide (NH _{2 CN) selected from Ti 3} C ₂ and Ti _{2 C,}

(b) heat-treating the mexine-cyanamide product obtained by the above reaction at 800 to 1,200°C under a nitrogen atmosphere, and

(c) acid treatment of the heat-treated product

Includes.

According to an aspect of the present invention, _{any one or more mexins selected from Ti 3} C ₂ and Ti ₂ C are not limited in the preparation method, but are prepared from an inorganic compound having a _{Ti n+1} AC _{n composition.} Can be. At this time, A is any one selected from Group 12, Group 13, Group 14, Group 15, and Group 16 elements of the Periodic Table of the Elements, and n is 1, 2 or 3.

For example, the mexine is a layered hexagonal carbide on MAX, and a Ti carbide layer and an A atomic layer in which unit cells in which one carbon atom is located inside Ti atoms, which are six transition metals arranged in an octahedral shape, are arranged in two dimensions. It has a structure that is arranged alternately. In other words, it has a structure in which the mexin layer and the atomic layer of A are stacked by an ionic metal bond. By selectively removing the A atomic layer from the MAX phase, any one or more mexins selected from _{Ti 3} C ₂ and Ti _{2 C may be obtained.} The method of selectively removing the A atomic layer may be carried out under acidic conditions. The acid may be an organic acid or an inorganic acid, and specifically, may be a strong acid containing a fluorine atom, for example, hydrofluoric acid (HF). The process of removing the atomic layer A may be performed at 20 to 200°C, specifically 30 to 100°C, but is not limited thereto. After the atomic layer A is removed, the two-dimensional structure of M _n+1 X _n T _s can be obtained through filtration and drying processes. At this time, T _s is a functional group bonded to the surface of the mexin layer, and may be O, OH or F. Thereafter, the M _n+1 X _n T _s may be reduced to obtain mexine. The mexin has a two-dimensional planar structure, and may have little or no functional groups on the surface.

The mexine may be a plurality of layers in which a plurality of single crystal layers from which crystal layers having a composition of _{Ti 3} C ₂ or Ti _{2 C are separated from each other are stacked, and the plurality of layers may be bonded by van der Waals force.}

The mexine is not limited in particle size, but may be 0.1 µm to 100 µm, specifically 0.2 µm to 50 µm, and more specifically 0.5 µm to 20 µm. It has an advantageous effect in achieving the object within the above range.

In the method for producing nitrogen-doped titanium carbide according to an aspect of the present invention, first, a step of mixing and reacting at least one mexin selected from _{Ti 3} C ₂ and Ti _{2 C and cyanamide is performed.}

The cyanamide is a single molecule that has nucleophilic and electrophilic properties at the same time, and is inserted into the mexine layer to enable polymerization according to the reaction energy, and nitrogen-substituted graphitic-C ₃ It has an advantage of having a _{N 4} (gC ₃ N ₄ ) or polymeric-C ₃ N ₄ (pC ₃ N _{4) structure.}

The mixing reaction step of mexine and cyanamide includes adding mexine and cyanamide to a solvent and reacting the mixed solution while stirring. At this time, the solvent may be any one or more selected from the group consisting of ethanol, acetone, and water, and specifically, ethanol may be used, but is not limited thereto.

The mixture of mexin and cyanamide may be dispersed using an ultrasonic disperser. At this time, the ultrasonic treatment may be performed at 500 to 5,000 Hz for 5 minutes to 1 hour, and the ultrasonic frequency and treatment time are not particularly limited and may be adjusted within a range to achieve the object of the present invention.

The reaction temperature range in the mixing reaction step of mexine and cyanamide is not particularly limited, but may be 70 to 90°C, specifically 75 to 85°C. It is effective in that the reactivity of mexine and cyanamide within the above range is good, so that the yield of the mexine-cyanamide product can be increased.

The content range of mexin and cyanamide in the mixture of mexin and cyanamide may be adjusted. Specifically, cyanamide may be 0.1 to 5 moles, more specifically 0.2 to 1 mole, per 1 mole of mexin. In the above range, it is more effective in that cyanamide is smoothly inserted into the mexin layer in combination with the heat treatment process, and the doping efficiency of nitrogen can be increased through the polymerization of _{carbon nitride (C 3} N _{4) in the heat treatment process.}

In addition, the content of the solvent in the mixture of mexine and cyanamide is not significantly limited within the range in which the reaction can proceed smoothly, specifically, the total weight of mexine and cyanamide is 10 to 80% by weight, specifically 20 It can be adjusted to be within the range of 70% by weight.

The mixed solution after the reaction may be filtered using a solvent. The solvent used for filtration may be the same as the solvent in the mixed solution. After the filtration is finished, drying is performed to obtain a powdery mexine-cyanamide (MXene-NH ₂ CN) product. In this case, the drying may be performed under vacuum, and may be performed at 20 to 90°C, specifically 30 to 80°C, but is not limited thereto.

Next, a step of heat-treating the obtained powdery mexin-cyanamide product in a nitrogen atmosphere is carried out.

The heat treatment process is performed in a temperature range of 400° C. to 1200° C., and specifically, is performed while raising the temperature to a final temperature range within 800° C. to 1200° C. The final temperature range may be specifically, 850°C to 1150°C, and more specifically 900°C to 1100°C. This is effective in that the nitrogen content of nitrogen-doped titanium carbide can be maximized, and excellent electrode characteristics can be realized when applied as an electrode material through a stable two-dimensional structure.

The heat treatment process may be carried out by placing the powdery mexin-cyanamide product obtained above into a furnace chamber and allowing nitrogen to flow in the chamber to create a nitrogen atmosphere, and then applying heat.

In the heat treatment process, heating may be performed within the range of a temperature increase rate of 1°C to 30°C per minute, specifically 2°C to 25°C per minute, and more specifically 5 to 20°C. Within the above range, it is effective not only to ensure structural stability of titanium carbide, but also to increase the nitrogen doping rate.

According to a preferred embodiment of the present invention, the heat treatment process is in a temperature range of 400 to 600°C, specifically 450°C to 550°C, and in a temperature range of 600 to 800°C, specifically 650°C to 750°C, each It may include holding for 10 minutes to 300 minutes, specifically, 20 minutes to 240 minutes, more specifically 30 minutes to 180 minutes. Such a temperature maintenance process is effective in synthesizing cyanamide to form a chemical bond stably on the MXene surface, thereby synthesizing polymerized carbon nitride between the mexin layers. In addition, it is more effective in allowing the carbon nitride to have a regularly arranged structure and to be polymerized.

According to a more specific aspect of the present invention, the heat treatment process may be to perform heat treatment step by step. In one aspect, the step of raising the temperature to a first temperature range of 400° C. to 600° C. and then maintaining the temperature for 10 to 300 minutes is performed, and then raising the temperature to a second temperature range of 600 to 800° C. and then 10 minutes to It may include maintaining the temperature for 300 minutes. The first temperature range and the second temperature range are performed with a temperature difference within a range to achieve a desired effect. This multi-stage heat treatment process is effective in terms of stably securing the two-dimensional structure of Mexin. Furthermore, it is more effective in that the nitrogen doping rate can be further improved on the titanium carbide of the two-dimensional structure.

According to an aspect of the present invention, in the heat treatment step, in the process of raising the temperature up to a temperature range of 800 to 1200°C, the carbon nitride is inserted between layers in the mexin by inducing a state change according to the temperature of the cyanamide single molecule. The polymeric-C ₃ N ₄ (pC ₃ N ₄ ) structure can be synthesized through the polymerization of. This makes it possible to prepare titanium carbide having a two-dimensional structure doped with nitrogen by synthesizing _{pC 3} N ₄ between the two-dimensional titanium carbide layers and then thermally decomposing it at a high temperature.

The product after the heat treatment step may remove unreacted substances or foreign substances through acid treatment.

The acid treatment material used for the acid treatment is not largely limited as long as it removes unreacted substances or foreign substances including cyanamide, but specifically, selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and chloride sulfonic acid. Any one or more components may be mentioned. As an example, 1 to 10% by weight of hydrochloric acid may be used, but is not limited thereto.

Thereafter, filtration, washing, and drying are performed using a solvent to obtain final nitrogen-doped titanium carbide.

According to another aspect of the present invention, a nitrogen-doped titanium carbide prepared by the above-described method is provided.

The nitrogen-doped titanium carbide has a very high nitrogen doping content, specifically 15 element% or more, and more specifically 18 to 30 element%.

In addition, in another aspect, the present invention provides an electrode material comprising the prepared nitrogen-doped titanium carbide.

The electrode material including the nitrogen-doped titanium carbide shows a remarkable improvement in the storage capacity when the electric double layer capacitor electrode is applied as a specific example, and in addition, excellent electrode characteristics such as improved charge/discharge performance, high electrode efficiency, and ion diffusion performance. It has an effect that can be implemented. In addition, it has the effect of improving the durability of the electrode.

The electrode material containing titanium carbide doped with nitrogen according to an aspect of the present invention has high utility for various materials such as electrochemical energy devices, and can be specifically used for fuel cells or secondary cells, and is limited thereto. no.

Hereinafter, a method for producing nitrogen-doped titanium carbide according to the present invention, a nitrogen-doped titanium carbide produced therefrom, and an electrode material including the same will be described in more detail through the following examples. However, the following examples are only one reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

(Example 1)

MAX phase Ti ₃ AlC ₂ (MAXTHAL 312, KANTHAL) was added to 40 wt% HF and stirred at room temperature for 5 hours _{to synthesize Mexine (Ti 3} C ₂ , particle size: 20 μm). A solution obtained by mixing 100 mg of mexine (Ti ₃ C ₂ ) and 100 mg of cyanamide (NH ₂ CN) in 100 ml of ethanol was placed in an ultrasonic disperser (500 Hz) and dispersed for 30 minutes. The dispersed solution was heated to 80° C. and then stirred for 12 hours.

Thereafter, the solution was filtered using ethanol, and then the obtained MXene-NH ₂ CN powder was vacuum-dried at 80°C. The dried MXene-NH ₂ CN powder was placed in a furnace chamber and heated to 900° C. at a rate of 10° C. per minute under a nitrogen atmosphere, but heat treatment was performed while maintaining at 500° C., 700° C. and 900° C. for 60 minutes, respectively. After washing with 5% by weight HCl to remove residual cyanamide, washing with ethanol and vacuum drying at 80° C. was performed to prepare titanium carbide doped with nitrogen. The prepared nitrogen-doped titanium carbide could be confirmed through FIGS. 2 and 3.

(Example 2)

In Example 1, Example 1 except that the process of maintaining the temperature at 500°C and 700°C was not performed in the process of putting the _{dried MXene-NH 2 CN powder into the furnace chamber and performing heat treatment under a nitrogen atmosphere.} It was carried out in the same way as.

(Example 3)

In Example 1, in _{the process of putting the dried MXene-NH 2} CN powder into a furnace chamber and performing heat treatment under a nitrogen atmosphere, except that the time to maintain the temperature at 500°C and 700°C, respectively, was changed to 5 minutes. It was carried out in the same manner as in Example 1.

(Comparative Example 1)

Mexine (Ti ₃ C ₂ ) 100 mg was vacuum-dried at 80° C. and then placed in a furnace chamber, and heat-treated in the same manner as in Example 1 under a nitrogen atmosphere, and the obtained product was confirmed through XRD and XPS analysis.

(Comparative Example 2)

500 mg of mexine (Ti ₃ C ₂ ) was added to 10 ml of 10 ml of 50 wt% aqueou solution of urea, mixed, and then reacted at 60° C. for 24 hours. Thereafter, distilled water was added and dispersed for 6 hours using an ultrasonic disperser (500Hz), followed by centrifugation. Next, it was washed with ethanol and distilled water, and then dried in a vacuum oven (80°C) for 24 hours. _{Ti 3} C ₂ powder obtained after drying was mixed with the same amount of urea, and carbonization was performed at 500° C. under a nitrogen atmosphere to obtain nitrogen-doped titanium carbide.

(evaluation)

(1) electrode characteristics

In order to examine the electrode characteristics, a stack cell (two-electrodes) was prepared. Sludge was prepared by ultrasonically dispersing in N-methyl pyrrolidone (NMP) at a weight ratio of nitrogen-doped mexin and polyvinylidene fluoride (PVDF) (95:5), and then re-dispersing through a mixer. The prepared slurry was coated on an aluminum foil to a thickness of 100 μm using a bar coater, and then dried in a vacuum oven at 80° C. for 5 hours to prepare an electrode.

To evaluate the characteristics of the prepared electrode, a circulating current measurement (Scan rate 10 mV/s-100 mV/s, 0.0-0.75 V) was performed using a charge/discharge tester (CHI 660D, CH Instruments, Inc). In the case of the electrolyte used at this time, 1M KOH was used. In addition, a charge/discharge measurement (Current 1 A/g 0.0-0.75 V) was performed to calculate the capacitance. In the case of impedance measurement, it was measured in the range of 100 kHz to 0.01 Hz.

[Table 1] Nitrogen doping content

As shown in Table 1, the examples according to an aspect of the present invention showed a high nitrogen content. In particular, Example 1 showed a very high amount of nitrogen doping, which can be confirmed to have excellent electrode characteristics with improved capacitance. On the other hand, the comparative examples showed no nitrogen doping or a very low content.

1 schematically shows a method for producing nitrogen-doped titanium carbide according to Example 1, which is an aspect of the present invention. A mexine-cyanamide product (2) in which cyanamide is chemically bonded to the mexin surface is prepared by reaction of pristine MXene (1) from which Al has been removed from MAX and cyanamide. Next, after the C ₃ N ₄ polymerized at 500°C was synthesized between the mexin layers (3), pyrolysis proceeded at 700°C (4), and the pyrolysis was completed at 900°C. Titanium carbide doped with nitrogen is prepared by doping with (5).

2 is a TEM image confirming the shape change of the two-dimensional titanium carbide according to the temperature at each stage as shown in FIG. 1 ((A) pristine Ti ₃ C ₂ , (B) 500-N-Ti ₃ C ₂ , (C) 700-N-Ti ₃ C ₂ , (D) 900-N-Ti ₃ C ₂ ), it can be seen that nitrogen-doped titanium carbide is produced through a heat treatment process.

FIG. 3 shows the XRD according to the step temperature in FIG. 2, and it was confirmed that a stable titanium carbide having a two-layer structure doped with nitrogen was prepared in _{900-N-Ti 3} C _2. This could also be confirmed through elemental analysis mapping of titanium carbide doped with nitrogen using EDS in FIG. 4. 5 shows the results of TGA analyzing polymer growth and pyrolysis properties, and it was possible to confirm the reaction products of _{mexine (MXene) and cyanamide (NH 2 CN).}

6 shows the results of XPS(a) and XRD(b) for chemical composition and crystallinity analysis according to Comparative Example 1. In Comparative Example 1, when heat treatment was performed without the addition of cyanamide _{, the peak of titanium oxide (TiO 2} ) increased as the temperature increased, and it was confirmed that nitrogen was not confirmed and the oxygen peak increased as the temperature increased. .

7 to 10 show electrode characteristics comparing nitrogen-doped titanium carbide at 900° C. and a material formed at different temperatures including raw materials. Specifically, as a result of an electrode experiment through a cyclic current method, nitrogen doped titanium at 900° C. Carbide (900-N-Ti ₃ C ₂ ) showed a high capacitor (FIG. 7), and a current value (R ² ) according to the scanned voltage was 0.9999, showing high electrode efficiency (FIG. 8). In addition, as a result of the charging and discharging experiments, excellent charging and discharging performance was shown (FIG. 9), and the charging capacity value according to the applied current reached 326 F/g (FIG. 10).

Although a preferred embodiment of the present invention has been described above, it is clear that various changes, modifications, and equivalents can be used in the present invention, and the same can be applied by appropriately modifying the above embodiment. Therefore, the above description does not limit the scope of the present invention determined by the limits of the following claims.

Claims (7)

A mixture of mexene and cyanamide prepared from an inorganic compound of Ti _n+1 AC _{n is} subjected to multistage heat treatment at a temperature range of 400 to 1200°C, and carbon nitride between the mexine layers at a first temperature range of 400 to 600°C. Forming a polymer in a regularly arranged structure; A step of thermal decomposition in a second temperature range of 600 to 800°C; And raising the temperature to a final temperature range of 800 to 1200° C.; the nitrogen doping content is 10.26 to 30 element%, and having a stable two-dimensional structure in the temperature range of 800 to 1200° C., nitrogen-doped titanium carbide .
(A is any one selected from Group 12, Group 13, Group 14, Group 15, and Group 16 elements of the Periodic Table of the Elements, and n is 1, 2 or 3) delete The method of claim 1,
The heat treatment is nitrogen-doped titanium carbide comprising maintaining the temperature at 400°C to 600°C for 10 to 300 minutes, and maintaining the temperature at 600 to 800°C for 10 to 300 minutes. The method of claim 1,
The heat treatment is nitrogen-doped titanium carbide that is controlled at a temperature increase rate of 1 ℃ to 30 ℃ per minute. The method of claim 1,
After the heat treatment, nitrogen-doped titanium carbide is subjected to acid treatment using one or more components selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and chlorinated sulfonic acid. An electrode material comprising the nitrogen-doped titanium carbide of claim 1. delete

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