KR20190125231A - 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 manufacturing nitrogen-doped titanium carbide using a state change according to a temperature of a single molecule containing nitrogen; nitrogen-doped titanium carbide manufactured by the manufacturing method; and an electrode material comprising the same. The method for manufacturing nitrogen-doped titanium carbide according to the present invention can manufacture nitrogen-doped carbide having a two-dimensional structure capable of implementing excellent electrode properties in a simple process, and can improve productivity thereof.

Description

Method of preparing N-doped titanium carbide and the N-doped titanium carbide obtained}

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

As a graphene-like two-dimensional material, MXen is formed from a layered structure called MAX. In this case, M is a transition metal, A is a group 13 or 14 element, X is carbon and / or nitrogen, and is a crystalline combination of MX and Z and other metal elements A.

Mexin has excellent properties such as electrical conductivity, chemical resistance, processability, and has been actively applied to the electrode, but there are still limitations to use. In particular, the development to further improve the electrical properties with the thinning to be used as a two-dimensional material is still insufficient.

Meanwhile, a method of doping nitrogen is used to realize better electrical properties of mexin. This nitrogen doping method has been mainly used hydrothermal synthesis method using urea. However, the transition metal is easily oxidized in the air or in the solution, so that the transition metal oxide is easily formed in the process, and the nitrogen doping rate is not high, and thus there are limitations in implementing electrical characteristics.

Therefore, there is a need for a method of manufacturing a nitrogen-doped transition metal carbide having a two-dimensional structure that can effectively 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 made to solve the above problems, in the case of the nitrogen doping method using the hydrothermal synthesis method recognizes that the transition metal is easily oxidized, while at the same time preventing the formation of titanium oxide in a simple process doping of nitrogen It is intended to provide a method for producing nitrogen-doped titanium carbide having a two-dimensional structure that can greatly improve the content.

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

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

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

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

(c) acid treating the heat treated product

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

In the method for producing nitrogen-doped titanium carbide according to an embodiment of the present invention, the heat treatment is maintained for 10 minutes to 300 minutes at 400 ℃ to 600 ℃, 10 to 300 minutes at 600 to 800 ℃ Maintaining the temperature for a while.

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

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

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

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

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

Nitrogen-doped titanium carbide production method according to the present invention can effectively prevent the formation of titanium oxide is easily oxidized in the air or in the solution through a dry synthesis method, nitrogen-doped two-dimensional structure that can implement excellent electrode properties Carbide is manufactured in a simple process, and has the advantage of improving its productivity.

Furthermore, the nitrogen-doped titanium carbide prepared by the production method according to the present invention has a high efficiency of nitrogen doping effect has the advantage that can significantly improve the storage capacity.

Figure 1 schematically shows a method for producing nitrogen-doped titanium carbide according to the present invention.
2 is a TEM image of two-dimensional titanium carbide shape with 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 ) is shown.
Figure 3 shows the X-ray diffraction pattern (XRD) results with temperature.
Figure 4 shows the TGA results analyzed the polymer growth and pyrolysis characteristics.
FIG. 5 shows elemental analysis mapping of nitrogen doped titanium carbide using EDS.
Figure 6 shows the XRD (a) and XPS (b) of the 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 the scanned voltage.
9 is a graph showing the results of charge and discharge experiments.
10 is a graph showing the charge capacity value according to the applied current.

Hereinafter, a method for preparing nitrogen-doped titanium carbide, 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 invention and are not intended to limit the scope of protection defined by the appended claims. In this case, unless otherwise defined, the technical and scientific terms used have the meanings that are commonly understood by those of ordinary skill in the art.

The inventors of the present invention, in the preparation of transition metal carbides that exhibit excellent electrode properties, note that the transition metals are easily oxidized in the air or in solution to form transition metal oxides, and thus doping content of nitrogen while preventing the oxidation of the transition metals. While research into the preparation method of transition metal carbide doped with nitrogen that can increase the concentration is carried out, it is possible to maintain structurally stable two-dimensional structure by using the state change according to temperature of single molecule containing nitrogen, Tungsten-doped titanium carbide can be prepared, which can improve electrode efficiency with high capacitance characteristics, and has low resistance and high electrolyte ion diffusion effect, thereby completing the present invention.

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

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

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

(c) acid treating the heat treated product

It includes.

According to an aspect of the present invention, any one or more mexins (MXene) selected from Ti ₃ C ₂ and Ti ₂ C is not particularly limited in its preparation method, but is prepared from an inorganic compound having Ti _{n + 1} AC _n composition. It may be. In this case, A is any one selected from Group 12, Group 13, Group 14, Group 15, and Group 16 elements of the periodic table, and n is 1, 2 or 3.

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

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

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

Nitrogen-doped titanium carbide production method according to an embodiment of the present invention is first performed by mixing any one or more mexin and cyanamide selected from Ti ₃ C ₂ and Ti ₂ C.

The cyanamide is a single molecule having both nucleophilic and electrophilic properties, and is inserted into the mexican layer to allow polymerization according to reaction energy, and nitrogen-substituted graphitic-C ₃ It is advantageous to have 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 putting the mixed solution of mexine and cyanamide in a solvent while stirring the mixed solution. In this case, 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 for 5 minutes to 1 hour at 500 to 5,000 Hz, the ultrasonic frequency and the treatment time is 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 the mexine and cyanamide is not particularly limited, but may be 70 to 90 ° C, specifically 75 to 85 ° C. The reactivity of mexine and cyanamide in the above range is good, so it is effective in increasing the yield of mexine-cyanamide product.

The amount of mexin and cyanamide in the mixed solution of mexine and cyanamide can be controlled. Specifically, the cyanamide may be 0.1 to 5 moles, more specifically 0.2 to 1 mole with respect to 1 mole of mexin. Insertion of cyanamide into the mexine layer is smoothly combined with the heat treatment process in the above range, and is more effective in terms of increasing the doping efficiency of nitrogen through polymerizing carbon nitride (C ₃ N ₄ ) in the heat treatment process.

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

The reaction mixture after the reaction can be filtered using a solvent. The solvent used in the filtration may be the same as the solvent in the mixed solution. Filtration is followed by drying to give a powdered mexine-cyanide (MXene-NH ₂ CN) product. At this time, the drying may be carried out under a vacuum, it may be carried out at 20 to 90 ℃, specifically 30 to 80 ℃, but is not limited thereto.

Next, the step of heat-treating the powdery mexine-cyanamide product obtained under nitrogen atmosphere.

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

The heat treatment process may be carried out by placing the powdered mexixane-cyanide product obtained above into a furnace chamber, allowing nitrogen to flow in the chamber, and then applying nitrogen to heat.

In the heat treatment process, the heating may be carried out within a range of a temperature increase rate of 1 ℃ to 30 ℃, specifically 2 ℃ to 25 ℃, more specifically 5 to 20 ℃ per minute. Within this range, not only can the structural stability of the titanium carbide be secured, but it is also effective in increasing the nitrogen doping rate.

According to one preferred aspect of the invention, the heat treatment process is in the temperature range of 400 to 600 ℃, specifically 450 ℃ to 550 ℃, and also in the temperature range of 600 to 800 ℃, specifically 650 ℃ to 750 ℃, respectively 10 minutes to 300 minutes, specifically, 20 minutes to 240 minutes, more specifically 30 minutes to 180 minutes can be included. This temperature holding process stably forms a chemical bond on the surface of the cyanamide MXene, which is effective in synthesizing the polymerized carbon nitride between the mexin layer. It is also more effective in allowing carbon nitride to have a regularly arranged structure and polymerize.

According to a more specific aspect of the present invention, the heat treatment step may be to perform a heat treatment step by step. In one aspect, the step of increasing the temperature to the first temperature range of 400 ℃ to 600 ℃ and then maintaining the temperature for 10 minutes to 300 minutes, and then to the second temperature range of 600 to 800 ℃ and then 10 minutes to Maintaining the temperature for 300 minutes. The first temperature range and the second temperature range are carried out with a temperature difference within a range to achieve the desired effect. This multi-stage heat treatment process is effective in stably securing the two-dimensional structure of mexin. Furthermore, it is more effective in the aspect which can improve nitrogen doping rate to the titanium carbide of a two-dimensional structure.

According to one aspect of the invention, the heat treatment step in the temperature increase process up to a temperature range of 800 to 1200 ℃, by inserting the carbon nitride between the layers in the mexine by inducing a state change according to the temperature of the cyanamide single molecule, the carbon nitride Through polymerization of polymeric-C ₃ N ₄ (pC ₃ N ₄ ) structure can be synthesized. This makes it possible to produce titanium carbide having a two-dimensional structure doped with nitrogen by synthesizing pC ₃ N ₄ between two-dimensional titanium carbide layers and pyrolyzing at high temperature.

After the heat treatment step, the product may remove unreacted substances or foreign substances through acid treatment.

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

The final nitrogen doped titanium carbide can then be obtained by filtration, washing and drying with a solvent.

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

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

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

In one embodiment, the electrode material containing titanium carbide doped with nitrogen shows a dramatic improvement in storage capacity when an electric double layer capacitor electrode is applied, and in addition, excellent electrode characteristics such as improved charging and discharging performance, higher electrode efficiency, and ion diffusion performance. Has the effect of implementing 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 is highly applicable to various materials such as an electrochemical energy device, and specifically, may be used in a fuel cell or a secondary battery, and the like. no.

Hereinafter, a method for preparing nitrogen-doped titanium carbide according to the present invention, a nitrogen-doped titanium carbide prepared therefrom, and an electrode material including the same will be described in more detail with reference to 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 Co., Ltd.) was put in 40% by weight of HF, and prepared by stirring mexicin (Ti ₃ C ₂ , particle size: 20㎛) at room temperature for 5 hours. A solution of 100 mg of mexin (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 raised to 80 ° C. and stirred for 12 hours.

Thereafter, the solution was filtered using ethanol, and 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 up to 900 ° C. at a temperature increase rate of 10 ° C. per minute under a nitrogen atmosphere, and then heat-treated at 500 ° C., 700 ° C. and 900 ° C. for 60 minutes. After washing with 5% by weight HCl to remove the residual cyanamide, washed with ethanol and dried under vacuum at 80 ℃ to prepare a titanium carbide doped with nitrogen. The prepared titanium doped titanium carbide was confirmed through FIGS. 2 and 3.

(Example 2)

In Example 1, except that the dried MXene-NH ₂ CN powder in the furnace chamber and the heat treatment under a nitrogen atmosphere was not carried out to maintain the temperature at 500 ℃, 700 ℃ respectively. It was carried out in the same manner as.

(Example 3)

In Example 1, except that the dried MXene-NH ₂ CN powder in the furnace chamber and the heat treatment under a nitrogen atmosphere to maintain the temperature at 500 ℃, 700 ℃ each 5 minutes It carried out by the same method as Example 1.

(Comparative Example 1)

100 mg of mexin (Ti ₃ C ₂ ) 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. The obtained product was confirmed by XRD and XPS analysis.

(Comparative Example 2)

500 mg of mexin (Ti ₃ C ₂ ) was added to 10 ml of 10 ml of 50 wt% aqueou solution of urea, mixed, and reacted at 60 ° C. for 24 hours. Then, distilled water was added and dispersed for 6 hours using an ultrasonic disperser (500 Hz), followed by centrifugation. Next, the resultant 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 carbonized at 500 ° C. under a nitrogen atmosphere to obtain nitrogen-doped titanium carbide.

(evaluation)

(1) electrode characteristics

To examine the electrode characteristics, a stack cell (two-electrodes) was prepared. Sludge was prepared by ultrasonic dispersion in N-methyl pyrrolidone (NMP) at a weight ratio of nitrogen-doped mexin and polyvinylidene fluoride (PVDF) (95: 5). The slurry was coated on 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.

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

Table 1 Nitrogen Doping Content

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

Figure 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) having cyanamide chemically bonded to the surface of the mexine was prepared by reacting pristine MXene (1) with cyanide removed from MAX with cyanamide. Next, C ₃ N ₄ polymerized at 500 ° C. was synthesized between mexine layers (3), and pyrolysis proceeded at 700 ° C. (4). As the pyrolysis was completed at 900 ° C., nitrogen was chemically reacted with carbon of titanium carbide. Titanium carbide doped with nitrogen is prepared (5).

Figure 2 is confirmed by the TEM image of the shape change of two-dimensional titanium carbide according to the step temperature as shown in Figure 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 the titanium carbide doped with nitrogen is prepared through the heat treatment process.

Figure 3 shows the XRD according to the temperature step by step in Figure 2, it was confirmed that the stable titanium carbide of the two-layer structure doped with nitrogen in 900-N-Ti ₃ C ₂ was prepared. This was also confirmed through elemental analysis mapping of nitrogen-doped titanium carbide using EDS in FIG. 4. Figure 5 shows the results of TGA analysis of the polymer growth and pyrolysis characteristics, it was confirmed that the reaction of mexin (MXene) and cyanamide (NH ₂ CN).

Figure 6 shows the results of XPS (a) and XRD (b) for the chemical composition and crystallinity analysis according to Comparative Example 1. In Comparative Example 1, when the heat treatment was performed without the addition of cyanamide, the peak of titanium oxide (TiO ₂ ) increased as the temperature was increased, and the oxygen peak was increased as the temperature was increased without nitrogen being confirmed. .

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

Although the preferred embodiment of the present invention has been described above, it is clear that the present invention may use various changes, modifications, and equivalents, and that the above embodiments may be appropriately modified in the same manner. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

Claims (6)

Nitrogen-doped titanium carbide having a nitrogen doping content of 10.26 to 30 element%. The method of claim 1,
The nitrogen-doped titanium carbide is a nitrogen-doped titanium carbide, which is a heat treatment of the mexin-cyanide product, The method of claim 2,
The heat treatment is nitrogen-doped titanium carbide comprising maintaining the temperature for 10 to 300 minutes at 400 ℃ to 600 ℃, and for 10 to 300 minutes at 600 to 800 ℃. The method of claim 2,
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 2,
After the heat treatment, nitrogen-doped titanium carbide which is subjected to acid treatment using any one or more components selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and sulfonic acid chloride. An electrode material comprising the titanium carbide doped with nitrogen of claim 1.

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