TWI537209B - Method for manufacturing a nitrogen-doped carbon nanotubes - Google Patents

Description

Method for preparing nitrogen-containing carbon nanotubes

The invention relates to a preparation method of a carbon nanotube, in particular to a preparation method of a nitrogen-containing carbon nanotube.

The carbon nanotube system is a homologue of carbon, has a cylindrical nanostructure, and its length is proportional to the diameter. The carbon atoms in the carbon nanotubes are bonded in the form of sp ² to provide a higher structural strength relative to the sp ³ bond while still maintaining good electrical conductivity. In addition, the carbon nanotubes have the advantages of high hardness and good thermal conductivity.

The nitrogen-containing nanocarbon tube system is doped with nitrogen atoms in the structure of the carbon nanotubes, and can cause defects on the surface, change the electrochemical characteristics of the carbon nanotubes and enhance its applicability, and can be used for photoreaction, touch In the field of media. In addition, the nitrogen-containing carbon nanotubes can improve the storage of lithium and are used in lithium ion batteries because of the better reactivity of nitrogen and metal oxide nanoparticles.

The preparation method of the conventional nitrogen-containing carbon nanotubes mostly uses a small molecular carbon compound mixed nitrogen compound as a precursor, and in the synthesis process, it is necessary to mix a catalytic metal such as iron, cobalt or nickel in a flowing gas phase to synthesize at a high temperature. . Therefore, in addition to the selection of a suitable carbon source, nitrogen source and catalyst, special flow gas phase mixing equipment must be used to complete the preparation of nitrogen-containing carbon nanotubes. As a result, the conventional method for manufacturing a nitrogen-containing carbon nanotube has problems such as inconvenient preparation of the precursor material, cumbersome operation process, and high equipment cost.

Therefore, it is necessary to provide a method for preparing a nitrogen-containing carbon nanotube to solve the problem of a conventional method for producing a nitrogen-containing carbon nanotube.

The main object of the present invention is to provide a method for preparing a nitrogen-containing carbon nanotube, which is simple and easy to obtain.

A further object of the present invention is to provide a method for preparing a nitrogen-containing carbon nanotube, which is simple in process and does not require special equipment.

The invention provides a preparation method of a nitrogen-containing carbon nanotube, which comprises: providing a Prussian blue compound, the Prussian blue compound is nickel ferricyanide (KNiFe(CN) ₆ ), copper ferricyanide (KCuFe ( CN) ₆ ) or iron ferrocyanide (KFeFe(CN) ₆ ); and heating the Prussian blue compound at a temperature of 550 ° C for 5 hours under a protective atmosphere.

The method for producing a nitrogen-containing carbon nanotube of the present invention, wherein the protective atmosphere is argon or nitrogen.

In the method for preparing a nitrogen-containing carbon nanotube of the present invention, since the Prussian blue compound provides a carbon source and a nitrogen source by cyanide ions, and contains iron, cobalt or nickel having a high carbon solubility as a catalyst, The Prussian blue compound is used as a single preparation material to prepare the nitrogen-containing carbon nanotube to replace the conventional carbon compound, nitrogen compound and metal catalyst. Thereby, the preparation material of the invention is simpler and easier to obtain than the conventional preparation process, so that the preparation method of the nitrogen-containing carbon nanotube of the invention can achieve the effects of simplifying the process and shortening the preparation time of the raw materials.

In addition, due to the coordination structure of the Prussian blue compound, it can be used as a catalyst for the iron, cobalt or nickel ions contained in the cyanide ion, and the carbon and nitrogen in the cyanide ion together form the nitrogen-containing nanocarbon. tube. Therefore, the present invention eliminates the need to add a catalyst in a flowing gas phase, and can directly pass the heating of the Prussian blue compound to obtain the nitrogen-containing carbon nanotube, so that the preparation method of the nitrogen-containing carbon nanotube of the present invention can be achieved. The manufacturing equipment is simple and saves manufacturing costs.

Figure 1: Microscopic image of the carbon material of Group A1

Figure 2: Microscopic image of the nitrogen-containing carbon nanotubes of Group A2.

Figure 3: X-ray diffraction pattern of the nitrogen-containing carbon nanotubes of Group A2.

Figure 4: Microscopic image of the nitrogen-containing carbon nanotubes of Group B1.

Figure 5: Microscopic image of the nitrogen-containing carbon nanotubes of Group B2.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The nitrogen-containing carbon nanotube of the present invention is prepared by heating a Prussian blue compound to form a nitrogen-containing carbon nanotube.

In detail, the Prussian blue compound is a coordination compound having the general formula of L _x AB(CN) ₆ ‧nH ₂ O, wherein the L is an alkali gold ion such as potassium ion, sodium ion, or the like, and The x system is a positive integer used to balance the electrical properties of the Prussian blue compound. A is a transition metal ion, which may be any iron ion, nickel ion or copper ion in an oxidized state; and B is an iron ion, cobalt ion or nickel ion in any oxidation state. Further, the order of A and B may be exchanged in writing habit, and the present invention is not limited. The cyanide ion (CN ^- ) is used to provide a coordinate bond, and the n system is a positive integer or zero, which varies depending on the degree of drying of the Prussian blue compound, and is generally known to those skilled in the art to which the present invention pertains. understanding.

For example, the Prussian blue compound may be nickel ferricyanide (KNiFe(CN) ₆ ), copper ferricyanide (KCuFe(CN) ₆ ) or iron ferrocyanide (KFeFe(CN) ₆ ), etc. The invention is not limited. In addition, the Prussian blue compound can be directly purchased, preferably a high-purity powder, to increase the formation efficiency of the nitrogen-containing carbon nanotubes, and to prevent the impurities from affecting the formation of the nitrogen-containing carbon nanotubes. . In this embodiment, the Prussian blue compound can be prepared by titration, for example, by mixing an aqueous solution of potassium ferricyanide (K ₃ Fe(CN) ₆ ) with an aqueous solution of nickel nitrate (Ni(NO ₃ ) ₂ ). Nickel ferricyanide.

The Prussian blue compound contains cyanide ions, so that a carbon source and a nitrogen source can be provided. Further, since the Prussian blue compound contains iron ions, cobalt ions or nickel ions having a high carbon solubility, it is used as a catalyst for the formation of the nitrogen-containing carbon nanotubes. In addition, since the Prussian blue compound has a coordination structure, the cyanide ion is adjacent to the iron ion, the cobalt ion or the nickel ion, so that the iron ion, the cobalt ion or the nickel ion easily catalyze the carbon and nitrogen in the cyanide ion to form the nitrogen. Carbon nanotubes. Therefore, it is only necessary to heat the Prussian blue compound, that is, the Prussian blue compound can be pyrolyzed at a high temperature to form the nitrogen-containing carbon nanotube.

The protective atmosphere refers to a gas which does not react with the Prussian blue compound to prevent the Prussian blue compound from being oxidized during heating, and for example, argon gas or nitrogen gas may be used as the protective atmosphere. Further, the present invention is heated at a temperature of 550 to 1200 ° C for 30 minutes to 12 hours, and the Prussian blue compound is pyrolyzed at a high temperature to form the nitrogen-containing carbon nanotube. If the heating temperature is lower than 550 ° C, sufficient energy cannot be provided, and the Prussian blue compound will form a hollow nano-particle carbon material after pyrolysis; conversely, if the temperature is higher than 1200 ° C, the nitrogen-containing nano-nitride may be destroyed. The structure of the carbon tube. In addition, the Prussian blue compound needs to be heated for 30 minutes to 12 hours, so that the Prussian blue compound has sufficient time to pyrolyze the nitrogen-containing carbon nanotubes, and the heating time is too long to destroy the nitrogen-containing carbon nanotubes. The structure. In this embodiment, the Prussian blue compound is heated at a temperature of 550 ° C for 5 hours, so that most of the Prussian blue compound can be pyrolyzed to form the nitrogen-containing carbon nanotube to enhance the nitrogen-containing nanometer. The efficiency of preparation of carbon tubes. In this embodiment, the Prussian blue compound powder is placed in a crucible and placed in a high temperature tubular furnace, and argon gas is continuously supplied for about 30 minutes to discharge the air in the high temperature tubular furnace and continue to be heated.

In the preparation method of the nitrogen-containing carbon nanotube of the present invention, the Prussian blue compound is heated at a temperature of 550 to 1200 ° C for 30 minutes by providing the Prussian blue compound having a coordination structure. Up to 12 hours, the Prussian blue compound can be pyrolyzed at a high temperature to form the nitrogen-containing carbon nanotube.

In order to confirm that the preparation method of the nitrogen-containing carbon nanotube of the present invention can surely complete the preparation of the nitrogen-containing carbon nanotube by heating the Prussian blue compound, the following experiment is carried out.

(A) Effect of heating temperature on the preparation of nitrogen-containing carbon nanotubes

A 40 mM aqueous solution of nickel nitrate and a 20 mM aqueous solution of potassium ferricyanide were prepared for titration, and nickel ferricyanide was formed at a temperature of 70 ° C to obtain the Prussian blue compound in Groups A1 and A2. After the completion of the titration, the reaction was completed overnight, and the supernatant was removed by centrifugation, and deionized water was continuously added and centrifuged again to wash the Prussian blue compound. After washing several times, the Prussian blue compound was taken out and dried. The Prussian blue compound of Groups A1 and A2 was placed in a crucible and placed in a high temperature tubular furnace, and argon gas was introduced as the protective atmosphere, and heated for 5 hours. The heating temperature of the group A1 is 500 ° C, and the heating temperature of the group A2 is 550 ° C.

Please refer to Figures 1 and 2 for the microscopic images of Groups A1 and A2 above. Among them, the Prussian blue compound of the group A1 has a heating temperature of only 500 ° C, so that a carbon nanomaterial is formed after pyrolysis. The heating temperature of the group A2 was 550 ° C, and the nitrogen-containing carbon nanotubes were formed after pyrolysis. The nitrogen-containing carbon nanotubes of Group A2 were analyzed and contained 17% by weight of carbon, 1% nitrogen, 2% oxygen, 32% iron, and 48% nickel. Further, the A2 carbon nanotubes were pickled with 1 M hydrochloric acid for 1 hour, and X-ray diffraction was continued. The results are shown in Fig. 3. The figure marked with * is the diffraction peak of the graphitized structure, and the rest is the diffraction peak of Ni ₃ Fe.

From the above results, it was confirmed that the Prussian blue compound can be used as a raw material for preparation and pyrolyzed at a high temperature to form the nitrogen-containing carbon nanotube. Further, if the heating temperature is less than 550 ° C, the formation of a nanoparticle carbon material is caused.

(B) preparing the nitrogen-containing carbon nanotubes with copper ferricyanide and iron ferrocyanide

Prepare a 40 mM aqueous solution of copper nitrate (Cu(NO ₃ ) ₂ ) and a 20 mM aqueous solution of potassium ferricyanide (K ₃ Fe(CN) ₆ ) for titration, and form copper ferricyanide at room temperature as Group B1. The Prussian blue compound. Another 40 mM aqueous solution of ferric chloride (FeCl ₃ ) and 20 mM potassium ferrocyanide (K ₄ Fe(CN) ₆ ) aqueous solution were prepared for titration reaction, and iron ferrocyanide was formed at room temperature as the second B2. The group of Prussian blue compounds. Subsequently, the groups B1 and B2 were washed and dried under the same conditions as in the above experiment (A), and heated at a temperature of 550 ° C for 5 hours to form the nitrogen-containing carbon nanotube.

Please refer to Figures 4 and 5, which are the nitrogen-containing carbon nanotubes prepared in the above groups B1 and B2. From the above experiment, it was confirmed that after heating the Prussian blue compound of the formula L _x AB(CN) ₆ ‧ nH ₂ O, the Prussian blue compound can be pyrolyzed to form the nitrogen-containing carbon nanotube.

In the method for preparing a nitrogen-containing carbon nanotube of the present invention, since the Prussian blue compound provides a carbon source and a nitrogen source by cyanide ions, and contains iron, cobalt or nickel having a high carbon solubility as a catalyst, The Prussian blue compound is used as a single preparation material to prepare the nitrogen-containing carbon nanotube to replace the conventional carbon compound, nitrogen compound and metal catalyst. Thereby, the preparation material of the invention is simpler and easier to obtain than the conventional preparation process, so that the preparation method of the nitrogen-containing carbon nanotube of the invention can achieve the effects of simplifying the process and shortening the preparation time of the raw materials.

In addition, due to the coordination structure of the Prussian blue compound, it can be used as a catalyst for the iron, cobalt or nickel ions contained in the cyanide ion, and the carbon and nitrogen in the cyanide ion together form the nitrogen-containing nanocarbon. tube. Therefore, the present invention eliminates the need to add a catalyst in a flowing gas phase, and can directly pass the heating of the Prussian blue compound to obtain the nitrogen-containing carbon nanotube, so that the preparation method of the nitrogen-containing carbon nanotube of the present invention can be achieved. The manufacturing equipment is simple and saves manufacturing costs.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

Claims (2)

The invention relates to a method for preparing a nitrogen-containing carbon nanotube, comprising: providing a Prussian blue compound, the Prussian blue compound is nickel ferricyanide (KNiFe(CN) ₆ ), copper ferricyanide (KCuFe(CN) ₆ ) Or iron ferrocyanide (KFeFe(CN) ₆ ); and heating the Prussian blue compound at a temperature of 550 ° C for 5 hours under a protective atmosphere. The method for preparing a nitrogen-containing carbon nanotube according to claim 1, wherein the protective atmosphere is argon or nitrogen.