CN111039274B

CN111039274B - Liquid phase stripping method of graphdiyne

Info

Publication number: CN111039274B
Application number: CN201811192055.1A
Authority: CN
Inventors: 毛兰群; 颜海龙; 李玉良; 于萍; 蒋亚楠
Original assignee: Institute of Chemistry CAS
Current assignee: Institute of Chemistry CAS
Priority date: 2018-10-12
Filing date: 2018-10-12
Publication date: 2021-10-22
Anticipated expiration: 2038-10-12
Also published as: CN111039274A

Abstract

A liquid phase exfoliation method of graphdiyne, the method comprising: adding the graphite powder or particles to SiF-containing₆ ^2‑Stirring and separating the aqueous solution of the alkali metal or alkaline earth metal salt to obtain the exfoliated graphite alkyne. The yield of the product produced by the process of the present application is about 75 wt%. The prepared eGDY is dispersed in isopropanol to obtain the concentration of 5 mg.mL^‑1The graphdine dispersion of (1). Analysis of the thickness of the eGDY using atomic force microscopy revealed that about 85% of the flakes were 1-5 layers thick, of which about 18% were monolayers. Meanwhile, compared with graphite alkyne particles or powder which is not treated by the method, the stripping method is based on non-covalent acting force and does not introduce any defect into the graphite alkyne structure as proved by characterization results of Raman spectrum, infrared spectrum, photoelectron spectrum, high-resolution transmission electron microscope and fast Fourier transform.

Description

Liquid phase stripping method of graphdiyne

Technical Field

The application belongs to the technical field of preparation of a graphyne material, and particularly relates to a liquid-phase stripping method of graphyne.

Background

The carbon element can be in sp, sp based on the four valence electrons of the outer orbital of the atom²、sp³Three hybridization modes are combined to construct allotropes of carbon with various forms, such as fullerene, carbon nano tube, graphene and the like. The materials are used in the fields of catalysis, sensing, electronic devices, energy storage and conversion, life science and the likeShow remarkable application prospect. Researches prove that the geometrical structure, the physical and chemical properties of the carbon material and the hybridization mode among carbon atoms are closely related. Thus, scientists have been exploring new carbon materials consisting of different hybrid forms of carbon atoms and expecting more novel physicochemical properties thereof. As a novel two-dimensional carbon material, Graphyne (GDY) is a two-dimensional planar structure formed by connecting benzene rings by 1, 3-diyne bonds, and has the characteristics of a large conjugated system, uniform holes, excellent semiconductor performance and the like.

Disclosure of Invention

In 2010, the leiliana subject group of the chemical research institute of the academy of sciences in china prepared a large-area multilayer graphite alkyne film for the first time by a method of catalytic polymerization of small molecules on the surface of a copper foil, see guying Li et al, chem.

The chemical structure of the graphyne is shown as a formula (I), and the graphyne is a two-dimensional plane structure formed by connecting benzene rings through 1, 3-diyne bonds. The graphitic alkynes prepared by the method reported in the Liyuelian group were observed microscopically to be in the form of blocks due to the pi-pi stacking effect between the graphitic alkyne layers.

With the progress of research, the graphdiyne has excellent performance in the fields of lithium ion batteries, oil-water separation, electrocatalysis, sensing and the like. In addition, studies have reported that the conductivity of graphdiyne and the lithium storage capacity show a relationship that increases with decreasing film thickness, which can be referred to xueimin Qian et al, sci.rep.,2015,5, 7756-; changshui Huang et al, Nano Energy,2015,11, 481-489. In order to explore the intrinsic properties of several layers or even a single layer of graphdiyne, researchers have developed various methods for preparing ultrathin graphdiyne, such as chemical vapor deposition, liquid phase epitaxial growth, copper nanowire surface growth, and the like. However, these methods have disadvantages of complicated operation and severe synthesis conditions, and it is difficult to obtain a large amount of single-layer graphdiyne. Therefore, there is a need to develop a simple, efficient and nondestructive graphite alkyne exfoliation method, and the liquid phase exfoliation method provides a new approach to this demand.

In various methods for preparing two-dimensional materials, liquid phase stripping is taken as a typical strategy from top to bottom, and has the advantages of high yield, high quality and high preparation speed. By combining the technologies of ultrasound, microwave radiation, electrochemical intercalation and the like, the liquid phase stripping mechanism mainly comprises the following two mechanisms: firstly, charged substances are inserted between layers or ions with the same charge in the exchange layers, so that the interlayer distance can be increased, and the energy required by the mutual attraction and the stripping between the layers can be reduced; and secondly, the ultrasonic-assisted pure solvent stripping is realized, and the solvent with the surface energy similar to that of the layered material is beneficial to the dispersion and preservation of the two-dimensional sheet, so that the two-dimensional sheet is prevented from being aggregated again. At present, liquid phase stripping has been successfully applied to obtain single-layer sheets of various layered materials, such as graphene, black phosphorus, molybdenum disulfide, carbon nitride, and the like, and a liquid phase stripping method for graphdine has not been reported.

In order to solve the above problems, the present invention provides a liquid-phase exfoliation method of graphdiyne, the method comprising: adding the graphite powder or particles to SiF-containing₆ ^2-The alkali metal salt or alkaline earth metal salt of (a) is stirred and separated to obtain exfoliated graphdine (eddy).

According to the invention, the SiF-containing material₆ ^2-The aqueous solution of an alkali metal salt or alkaline earth metal of (A) is preferably SiF-containing₆ ^2-Is preferably an aqueous solution of an alkali metal salt of (2), further preferably containing SiF₆ ^2-An aqueous solution of a lithium or potassium salt of (a).

According to the invention, the mass ratio of the graphdiyne powder or particles to the alkali metal salt or alkaline earth metal is 1 (3-12), preferably 1 (5-10).

According to the invention, the SiF-containing material₆ ^2-The concentration of the aqueous solution of an alkali metal or alkaline earth metal salt of (2) is in the range of 5 to 30mg/mL, preferably 8 to 25mg/mL, and more preferably 10 mg/mL.

According to the invention, the stirring temperature in the method is 0-30 ℃, preferably 15-25 ℃.

According to the invention, the stirring time in the method is 1-72 hours, preferably 24-72 hours, and further preferably 60-72 hours.

According to the invention, the method of separation comprises: centrifuging the stirred solution, taking supernatant, filtering, and washing with water and alcohol solvent.

The alcohol solvent is selected from ethanol, propanol or isopropanol, preferably isopropanol.

As an example, the preparation method comprises: adding graphite alkyne powder into Li₂SiF₆Or K₂SiF₆Stirring the mixture for 60 hours at normal temperature and normal pressure according to the mass ratio of 1:5 to obtain uniform black colloid, slowly centrifuging the mixture (500 revolutions per minute) for 5 minutes to remove a small amount of large particles at the bottom, taking supernatant, performing suction filtration, and removing Li by using deionized water₂SiF₆Or K₂SiF₆And then vacuum drying to obtain fluffy solid eGDY, and dispersing the fluffy solid eGDY in isopropanol to obtain a stable eGDY dispersion liquid. The isopropanol has the characteristics of strong polarity and easy volatilization, so that the isopropanol can be used for dispersing ultrathin graphite alkyne; at the same time, the isopropyl alcohol dispersion of eddy facilitates further solution processing.

The graphite alkyne powders or particles described in the present application can be prepared by the method described in the guying Li et al, chem. commun.,2010,46, 3256-3258.

The invention also provides the exfoliated graphdiyne prepared by the method.

The invention also provides the application of the eGDY, which can be used in the fields of solar cells, supercapacitors, monatomic catalysis, separation and purification, sensing and the like.

Advantageous effects

The inventors have first proposed a liquid phase exfoliation method of graphdine with a yield of about 75 wt% of the product produced by the process of the present application. The prepared eGDY is dispersed in isopropanol to obtain the concentration of 5 mg.mL^-1The graphdine dispersion of (1). Analysis of the thickness of the eGDY using atomic force microscopy revealed that about 85% of the flakes were 1-5 layers thick, of which about 18% were monolayers. At the same time, in contrast to not adopting the present applicationThe characterization results of the graphite alkyne particles or powder treated by the method, such as Raman spectrum, infrared spectrum, photoelectron spectrum, high-resolution transmission electron microscope and fast Fourier transform, prove that the stripping method is based on non-covalent acting force, and no defect is introduced into the graphite alkyne structure. In addition, under the same experimental conditions, the inventors placed graphite alkyne powder or particles in deionized water, lithium chloride (LiCl), lithium hexafluorophosphate (LiPF), respectively₆) Lithium tetrafluoroborate (LiBF)₄) Ammonium hexafluorosilicate ((NH)₄)₂SiF₆) After the solution is continuously stirred, most of the powder or particles still presents a compact accumulation state, the stripping effect is poor, and the dissociated SiF is proved₆ ^2-Plays a key role in successfully stripping the graphdine with alkali metal ions or alkaline earth metals. Therefore, the high-quality eGDY dispersion prepared by the liquid-phase stripping method lays a foundation for researching the intrinsic properties of single-layer or few-layer graphyne in the future. The simple, high-yield, non-destructive liquid phase exfoliation method will facilitate the potential application of single-or few-layered graphdine in numerous fields, such as solar cells, supercapacitors, monatomic catalysis, separation and purification, sensing, etc.

Drawings

Fig. 1 is an optical microscope image of the graphdine powder obtained in preparation example 1.

FIG. 2 is a graph of the graphite acetylene powder in Li in example 1₂SiF₆Images of the graphdine dispersion after the aqueous solution was stirred for 60 hours, wherein fig. 2(a) is an image of the crude eGDY product after stirring, and fig. 2(b) is a transmission electron microscope image of the crude eGDY product.

Fig. 3 is an image of eGDY prepared in example 1, in which fig. 3(a) is an image of eGDY after suction filtration and washing with a poly-nylon filter membrane, and fig. 3(b) is an image of an isopropyl alcohol dispersion of eGDY. Fig. 3(c) is an image of the diluted eddy dispersion after laser irradiation.

Fig. 4 is a transmission electron microscope image of the eGDY, fig. 4(b) is an atomic force microscope image of the eGDY, fig. 4(c) is an atomic force microscope image of a single layer of the eGDY and the corresponding thickness, and fig. 4(d) is a layer number statistical result of the eGDY, wherein the topography and the thickness analysis of the eGDY are prepared in example 1.

Fig. 5 shows the structural and element characterization results of eGDY prepared in example 1, wherein fig. 5(a) is a high resolution transmission electron microscope image of eGDY, fig. 5(b) is a fast fourier transform image of eGDY, fig. 5(C) is photoelectron spectra of GDY powder and eGDY, and fig. 5(d) is a photoelectron spectrum of C1s of GDY powder and eGDY.

Detailed Description

The technical solution of the present invention will be further described in detail with reference to specific embodiments. The following examples are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of the invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

The bulk graphdine powder in the examples described below was composed and provided from the Liyura subject, and other materials, reagents, and the like used therein were commercially available without specific reference.

Preparation example 1

The preparation example references the methods described in guying Li et al, chem.commun.,2010,46, 3256-. An optical microscope image of the prepared graphdine powder is shown in fig. 1. As can be seen from fig. 1, the graphdine powder was stacked by the interlayer pi-pi action and was in the form of a bulk powder.

Example 1

Liquid phase exfoliation of graphdiyne powder of formula (I)

1.1 liquid phase exfoliation of graphdiyne powder

Mixing 100mg of Li₂SiF₆Dissolved in 10mL of deionized water, 20mg of the graphdine powder prepared in preparation example 1 was added to the solution, and stirred at room temperature and pressure for 60 hours, and it was found that the black particles at the bottom of the vessel almost disappeared to obtain a uniformly dispersed black colloid, as shown in FIG. 2 (a). The dispersion was characterized by transmission electron microscopy and ultra-thin exfoliated graphyne with Li was found₂SiF₆Crystals (dark small particles) as shown in fig. 2 (b).

1.2 purification of the thin-layer exfoliated graphdiyne

Slowly centrifuging the above gel (500 revolutions)One minute) for 5 minutes, removing a small amount of large particles at the bottom, taking supernatant, performing suction filtration by a nylon filter membrane, sequentially and repeatedly cleaning with deionized water and isopropanol, and removing Li₂SiF₆And then vacuum dried to obtain a fluffy black film, which is weighed and calculated as shown in fig. 3(a), and the yield is about 75 wt%. Ultrasonic dispersion of eGDY in isopropanol gave stable eGDY dispersion as shown in FIG. 3 (b). The diluted eddy dispersion showed a significant tyndall effect under laser irradiation, as shown in fig. 3 (c).

1.3 topography characterization and thickness analysis of eGDY

The eGDY dispersion liquid is dripped on the surface of the copper grid and dried, and the transmission electron microscope characterization result proves that the method obtains the ultrathin eGDY and the Li₂SiF₆Has been removed by washing as shown in fig. 4 (a).

And dropwise adding the eGDY dispersion liquid on the surface of the silicon chip and drying, wherein the atomic force microscope characterization result proves that the prepared eGDY is a few layer or even a single layer, and the thickness of the single layer eGDY is 0.6 nm. The prepared eGDY has a thickness of about 85% of 1-5 layers, 18% of which is a single layer, as shown in FIG. 4 (b-d). The results directly prove that the method successfully realizes the stripping of the graphyne and lays a foundation for researching the intrinsic properties of single-layer or few-layer graphyne in the future.

1.4 structural and elemental characterization of eGDY

The eGDY dispersion was dropped on the copper grid surface and dried, and its structure was characterized by high resolution transmission electron microscopy and fast Fourier transform, the lattice constant of eGDY was 0.455nm, which is consistent with the result of the graphite alkyne powder, as shown in FIG. 5 (a). In addition, the bright spots in the fast fourier transform image in the hexagonal distribution demonstrate that the eGDY has high crystallinity, as shown in fig. 5 (b). These results demonstrate that the eGDY prepared by this method does not introduce structural defects, yet retains the original high crystallinity of graphdine.

The dispersion of eGDY, which is mainly composed of carbon element (C), in which oxygen element (O) may be derived from oxygen adsorption or a small amount of oxygen-containing functional group, was dropped on the surface of the silicon wafer and dried, and its elemental composition was characterized by photoelectron spectroscopy, which is almost identical to the characterization result of the graphite alkyne particles (GDY powder), as shown in FIG. 5 (C-d). Indicating that no other elements or functional groups were introduced into the eddy prepared by the method of the present application, the eddy still retained its elemental composition prior to exfoliation.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for liquid phase exfoliation of graphdiyne, the method comprising: adding the graphdine powder to the SiF-containing₆ ^2-Stirring and separating the alkali metal salt aqueous solution to obtain the exfoliated graphyne;

the SiF-containing₆ ^2-The aqueous solution of alkali metal salt of (a) is Li₂SiF₆An aqueous solution;

the method produces exfoliated graphdiyne.

2. The method according to claim 1, wherein the mass ratio of the graphdiyne powder to the alkali metal salt is 1 (3-12).

3. The method of claim 1, wherein the SiF-containing compound is₆ ^2-The concentration of the aqueous solution of alkali metal salt of (1) is in the range of 5 to 30 mg/mL.

4. The method of claim 1, wherein the SiF-containing compound is₆ ^2-The concentration of the aqueous solution of alkali metal salt of (1) is in the range of 8 to 25 mg/mL.

5. The method of claim 1, wherein the SiF-containing compound is₆ ^2-The concentration of the aqueous solution of alkali metal salt of (4) is in the range of 10 mg/mL.

6. The method according to claim 3, wherein the stirring temperature in the method is 0-30 ℃.

7. The method according to claim 6, wherein the stirring time in the method is 1 to 72 hours.

8. The method of any one of claims 1-7, wherein the method of separating comprises: centrifuging the stirred solution, taking supernatant, filtering, and washing with water and alcohol solvent.

9. The method of claim 8, wherein the method comprises: adding graphite alkyne powder into Li₂SiF₆Stirring in water solution at normal temperature and pressure for 60 hr at a mass ratio of 1:5 to obtain uniform black colloid, slowly centrifuging for 5 min to remove small amount of large particles at the bottom, vacuum filtering supernatant, and removing Li with deionized water₂SiF₆And then vacuum drying treatment is carried out to obtain the exfoliated graphyne (eGDY).