Graphene material prepared from waste tire and preparation method thereof

Abstract

A graphene material prepared using waste tires and a preparation method thereof. Waste tires are crushed to 30-200 meshes to obtain tire powders. The tire powders are mixed with KOH or an aqueous solution of KOH to obtain a homogeneous mixture. The mixture is dried at 50-90° C. for 12-48 hours, heated and calcinated in a tube furnace under a protective gas for 1-48 hour to obtain a black lump. The black lump is washed with distilled water, dilute hydrochloric acid or dilute sulfuric acid for at least 3 times, and then washed with deionized water for at least 3 times to obtain a black powder. The black powder is dried to obtain the graphene material. The graphene material has a three-dimensional structure composed of oligolayer graphene intertwined and connected with each other, has a high crystallinity, is not easily agglomerated, and thus can maintain nano-effect of the graphene material.

Claims

1. A method for preparing a graphene material using waste tires, comprising the steps of: (1) crushing waste tires to 30-200 meshes to obtain a tire powder; (2) mixing 1 part by weight of the tire powder obtained in step (1) with 1-10 parts by weight of KOH or an aqueous solution containing 1-10 parts by weight of KOH to obtain a homogeneous mixture; (3) drying the mixture obtained in step (2) at 50° C.-90° C. for 12-48 h; (4) placing the dried mixture in a tube furnace and heating and calcining under a protective gas for 1-48 h to obtain a black lump; and (5) washing the black lump obtained in the step (4) with water, dilute hydrochloric acid or dilute sulfuric acid for at least 3 times, then washing it with water for at least 3 times to obtain a black powder, and then drying the black powder to obtain the graphene material.

2. The method in claim 1, wherein the tire powder in step (1) is 50-150 meshes.

3. The method in claim 1, wherein in step (2), 1 part by weight of the tire powder obtained in the step (1) is mixed with 1-7 parts by weight of KOH or an aqueous solution containing 1-7 parts by weight of KOH.

4. The method in claim 1, wherein in step (2), 1 part by weight of the tire powder obtained in the step (1) is mixed with 2-5 parts by weight of KOH or an aqueous solution containing 2-5 parts by weight of KOH.

5. The method in claim 1, wherein the temperature for the drying in step (3) is 60° C.-80° C., and the duration for the drying is 12-24 h.

6. The method in claim 1, wherein the protective gas in step (4) is at least one of nitrogen gas, argon gas and helium gas.

7. The method in claim 1, wherein: the rate of the heating in step (4) is 0.1° C.-20° C. per minute; the temperature for the calcination is 800° C.-1200° C.; and the duration for the calcination after reaching 800° C.-1200° C. is 1-48 h.

8. The method in claim 1, wherein: the rate of the heating in step (4) is 2° C.-15° C. per minute; the temperature for the calcination is 900° C.-1100° C.; and the duration for the calcination after reaching 900° C.-1100° C. is 3-12 h.

9. The method in claim 1, wherein the concentration of the dilute hydrochloric acid in step (5) is 0.1-0.5 mol/l.

10. The method in claim 1, wherein the concentration of the dilute hydrochloric acid in step (5) is 0.2-0.4 mol/l.

11. The method in claim 1, wherein the concentration of the dilute sulfuric acid in step (5) is 0.1-0.5 mol/l.

12. The method in claim 1, wherein the concentration of the dilute sulfuric acid in step (5) is 0.2-0.4 mol/l.

13. The method in claim 1, wherein the drying in step (5) is air drying at room temperature or oven drying.

Description

BRIEF DESCRIPTION OF FIGURES

(1) The following detailed descriptions, given by way of example, and not intended to limit the present invention solely thereto, will be best be understood in conjunction with the accompanying figures:

(2) FIG. 1 is a transmission electron micrograph of the graphene material obtained in Example 1 of the present invention;

(3) FIG. 2 is a high-resolution transmission electron micrograph of the graphene material obtained in Example 1 of the present invention;

(4) FIG. 3 is an atomic force micrograph of the graphene material obtained in Example 1 of the present invention;

(5) FIG. 4 is an X-ray diffraction pattern of the graphene material obtained in Example 1 of the present invention;

(6) FIG. 5 is a Raman spectrum of the graphene material obtained in Example 1 of the present invention;

(7) FIG. 6 is a cyclic voltammetry curve of the graphene material obtained in Example 1 of the present invention;

(8) FIG. 7 is a graph showing the charge and discharge life of the graphene material obtained in Example 1 of the present invention;

(9) FIG. 8 is a graph showing an adsorption curve (DFT mode) of the graphene material obtained in Example 1 of the present invention;

(10) FIG. 9 is a graph showing the pore size distribution of the graphene material obtained in Example 1 of the present invention, wherein FIG. 9A is a micropore distribution curve graph, and FIG. 9B is a mesopore distribution curve graph;

(11) FIG. 10 is a transmission electron microscope (TEM) image of the graphene sample of Comparative Example 1;

(12) FIG. 11 is a high-resolution transmission electron microscope (HRTEM) image of the graphene sample of Comparative Example 1;

(13) FIG. 12 is a schematic diagram showing the comparison between the electron conduction of the graphene sample of Comparative Example 1 and the electron conduction of the three-dimensional porous graphene material of the present invention;

(14) FIG. 13 is a graph showing the charge and discharge life of the graphene sample of Comparative Example 1;

(15) FIG. 14 is an SEM image of the graphene material obtained in Example 2 of the present invention; and

(16) FIG. 15 is an SEM image of the graphene material obtained in Example 3 of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(17) The present invention is further described in detail with reference to the specific embodiments thereof below. The examples are given only to illustrate the present invention but not intended to limit the scope of the present invention.

Example 1

(18) (1) crushing waste tires to a 100-mesh tire powder;

(19) (2) mixing 5 g of the tire powder in step (1) with 15 ml of an aqueous solution containing 10 g of KOH and grinding them to uniformity to obtain a mixture slurry;

(20) (3) placing the slurry ground to uniformity into an oven and drying it at 80° C. for 12 h;

(21) (4) placing the dried mixture in a nickel crucible, and calcining it in a tube furnace under the protection of argon gas; setting the heating rate to 5° C./min, raising the temperature to 1000° C. and calcining it at 1000° C. for 8 h to obtain a black lump; and

(22) (5) cooling the black lump to room temperature in a tube furnace, taking it out followed by washing it with 0.3 mol/l dilute sulfuric acid for 5 times, and then washing it with deionized water for 3 times to obtain a black powder, and drying the black powder at 90° C. for 12 h to obtain a graphene material.

(23) Performance Test and Characterization

(24) The graphene material obtained in Example 1, conductive carbon black, and polytetrafluoroethylene (PTFE) were ground and mixed uniformly at a mass ratio of 8:0.5:1, and then they were rolled into a thin film of about 1.5 mg/cm.sup.2. The thin film was cut into 1 cm.sup.2 sheet, which was subjected to the supercapacitor performance with three electrodes in a KOH electrolyte with a concentration of 6 mol/l. A −1V-0V cyclic voltammetry test and a constant-current charge and discharge test were performed at room temperature. The cycle life was tested by performing 10000 charge and discharge cycles at a current density of 5 A/g.

(25) FIG. 1 is a transmission electron micrograph of the graphene material obtained in this example. As can be seen from FIG. 1, the obtained graphene material has a three-dimensional structure and exhibits many distinct wrinkle textures. FIG. 2 is a high-resolution transmission electron micrograph of the graphene material obtained in this example. The high-resolution transmission electron microscopy shows that these wrinkle textures are composed of few-layer graphene intertwined and connected with each other. The intertwined graphene sheets are independent of and interconnected with each other, thereby avoiding stacking of graphene while maintaining the nano-effect of the graphene material.

(26) FIG. 3 is an atomic force micrograph of the graphene material obtained in this example, and shows that the thickness of the graphene sheet is 4 nm or less. FIG. 4 is an X-ray diffraction pattern of the graphene material obtained in this example. The X-ray diffraction pattern shows a sharp peak at 26 degrees, which indicates the appearance of a high-quality graphite crystal structure, thereby indicating that the graphene material of the present invention has a good crystal structure.

(27) FIG. 5 is a Raman spectrum of the graphene material obtained in this example. The Raman spectrum can illustrate the structure and the number of layers of the graphite material. FIG. 5 shows a distinct 2D peak, which is a unimodal peak with good symmetry, reflecting the structure of a typical few-layer graphene. The G peak is a sharp peak, which also indicates that the material has a good graphite crystal structure. At the same time, the D peak at around 1330 cm.sup.−1 reflects possible existence of many defective structures in the graphite sheet. These defect structures may be related to the porosity of the material, which facilitate the storage of energy in the material and indicate more active sites.

(28) FIG. 6 is a cyclic voltammetry curve of the graphene material obtained in this example. The cyclic voltammetry curve test shows a rectangular-like volt-ampere curve, which indicates that the material exhibits the desired electrochemical behavior. Moreover, the volt-ampere curve maintains a good rectangular shape as the scan rate increases, which indicates that the material can maintain a good structural stability at different voltages. This benefits from the three-dimensional intertwined graphene structure.

(29) The cyclic life of the material was tested by multiple repeated constant-current charge and discharge tests. FIG. 7 is a graph showing the charge and discharge life of the graphene material obtained in this example. FIG. 7 shows that the final capacitive retention is up to 96% after 10000 cycle charge and discharge tests at a current density of 5 A g.sup.−1. This indicates that the obtained graphene material has an excellent stability.

(30) The porous properties of the material were characterized by a nitrogen gas desorption curve using Micromeritics ASAP2020 Rapid Specific Surface and Porosity Analyzer (Micromeritics Instrument Corp.). FIG. 8 is a graph showing the adsorption curve (DFT mode) of the graphene material obtained in this example. FIG. 9 is a graph showing a pore size distribution of the graphene material obtained in Example 1 of the present invention, wherein FIG. 9A is a micropore distribution curve graph, and FIG. 9B is a mesopore distribution curve graph. FIG. 8 shows that there is a vertically rising linear region in the low-pressure region, the adsorption in the low-pressure region corresponds to the existence of a large number of micropores, and the increase in the adsorption cumulative volume in the medium-high pressure region indicates the existence of the mesoporous structure. It can be seen from the pore size distribution curve graph shown in FIG. 9 that a distinct peak appears in both the micropore region and the mesopore region, indicating that the material has a distinct gradient porosity.

Comparative Example 1

(31) The graphene material used in this comparative example is a mechanically stripped single-layer graphene sample purchased from Nanjing XFNANO Materials Tech Co., Ltd. with a product number: XF001W.

(32) FIG. 10 is a transmission electron microscope (TEM) image of the graphene sample of this comparative example. FIG. 11 is a high-resolution transmission electron microscope (HRTEM) image of the graphene sample of this comparative example. FIG. 12 is a schematic diagram showing the comparison between the electron conduction of the graphene sample of this comparative example and the electron conduction of the three-dimensional porous graphene material of the present invention. FIG. 13 is a graph showing the charge and discharge life of the graphene sample of this comparative example.

(33) Conventional graphene has a two-dimensional (2D) structure, and can conduct electrons only in a two-dimensional plane when serving as electrode material. The three-dimensional (3D) graphene structure obtained in the present invention provides a shorter path for electron conduction, has easier ion diffusion, smallest electron transport resistance, and thus has a better high-current charge and discharge performance. In addition, conventional 2D graphene will stack on each other during charge and discharge due to the intermolecular forces, thereby losing original nano properties and leading to degradation of performance. The present invention obtains such an intertwined 3D structure that can well inhibit the mutual stacking of the 2D nanosheets, thereby maintaining very good electron conduction performance all the time, and thus maintaining a good performance stability during repeated charge and discharge processes.

Example 2

(34) (1) crushing waste tires to a 100-mesh tire powder;

(35) (2) mixing 5 g of the tire powder obtained in step (1) with 15 ml of an aqueous solution containing 10 g of KOH and grinding them to uniformity to obtain a mixture slurry;

(36) (3) placing the slurry ground to uniformity into an oven and drying it at 60° C. for 24 h;

(37) (4) placing the dried material in a nickel crucible, calcining it in a tube furnace under the protection of argon gas, setting the heating rate to 10° C./min, heating to 1050° C. and calcining it at 1050° C. for 5 h to obtain a black lump; and

(38) (5) cooling the black lump to room temperature in a tube furnace, taking it out followed by washing it with 0.3 mol/l dilute hydrochloric acid for 4 times, and then washing it with deionized water for 3 times to obtain a black powder, and drying the black powder at 90° C. for 12 h to obtain a three-dimensional porous graphene material, which has a similar X-ray diffraction spectrum with that of the material prepared in Example 1.

Example 3

(39) (1) crushing waste tires to a 150-mesh tire powder;

(40) (2) mixing 5 g of the tire powder obtained in step (1) with 15 ml of an aqueous solution containing 10 g of KOH and grinding them to uniformity to obtain a mixture slurry;

(41) (3) placing the slurry ground to uniformity into an oven and drying it at 80° C. for 12 h;

(42) (4) placing the dried material in a nickel crucible, and calcining it in a tube furnace under the protection of argon gas, setting the heating rate to 5° C./min, heating to 1000° C. and calcining it at 1000° C. for 8 h to obtain a black lump; and

(43) (5) cooling the black lump to room temperature in a tube furnace, taking it out followed by washing it with 0.3 mol/l dilute sulfuric acid for 5 times, and then washing it with deionized water for 3 times to obtain a black powder, and drying the black powder at 90° C. for 12 h to obtain a three-dimensional porous graphene material, which has a similar X-ray diffraction spectrum with that of the material prepared in Example 1.

Example 4

(44) (1) crushing waste tires to a 50-mesh tire powder;

(45) (2) mixing 5 g of the tire powder obtained in step (1) with 15 ml of an aqueous solution containing 10 g of KOH and magnetic stirring them for 24 h to uniformity to obtain a mixture slurry;

(46) (3) placing the slurry ground to uniformity into an oven and drying it at 80° C. for 12 h;

(47) (4) placing the dried material in a nickel crucible, calcining it in a tube furnace under the protection of argon gas, setting the heating rate to 5° C./min, heating to 1100° C. and calcining it at 1100° C. for 3 h to obtain a black lump; and

(48) (5) cooling the black lump to room temperature in a tube furnace, taking it out followed by washing it with deionized water for 6 times to obtain a black powder, and drying the black powder at 80° C. for 12 h to obtain a three-dimensional porous graphene material, which has a similar X-ray diffraction spectrum with that of the material prepared in Example 1.

Example 5

(49) (1) crushing waste tires to a 120-mesh tire powder;

(50) (2) mixing 5 g of the tire powder obtained in step (1) with 15 ml of an aqueous solution containing 20 g of KOH and grinding them to uniformity to obtain a mixture slurry;

(51) (3) placing the slurry ground to uniformity into an oven and drying it at 80° C. for 12 h;

(52) (4) placing the dried material in a nickel crucible, calcining it in a tube furnace under the protection of argon gas, setting the heating rate to 10° C./min, heating to 1000° C. and calcining it at 1000° C. for 5 h to obtain a black lump; and

(53) (5) cooling the black lump to room temperature in a tube furnace, taking it out followed by washing it with 0.3 mol/l dilute sulfuric acid for 5 times, and then washing it with deionized water for 3 times to obtain a black powder, and air drying the black powder at room temperature to obtain a three-dimensional porous graphene material, which has a similar X-ray diffraction spectrum with that of the material prepared in Example 1.

(54) FIG. 14 is an SEM image of the graphene material obtained in Example 2 of the present invention; and FIG. 15 is an SEM image of the graphene material obtained in Example 3 of the present invention. As can be seen from FIG. 14 and FIG. 15, after the preparation conditions vary, the obtained graphene material still has a three-dimensional structure composed of few-layer graphene intertwined and connected with each other. The intertwined graphene sheets are independent of and interconnected with each other, thereby avoiding stacking of graphene while maintaining the nano-effect of the graphene material.

(55) Finally, it should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention, but not intended to be limiting; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features therein may be equivalently substituted; and the modifications or substitutions do not deviate the nature of the corresponding technical solution from the scopes of the technical solutions of the embodiments of the present invention, and they all fall within the scope of the claims and the description of the present invention.