GRAPHENE OXIDE MATERIAL, HALOGENATED GRAPHENE MATERIAL, PREPARATION METHODS THEREFOR, AND ELECTROLYSIS SYSTEM

Abstract

The present invention relates to a graphene oxide material, a halogenated graphene material, preparation methods therefor, and an electrolysis system. A method for producing a graphene oxide material in an electrolysis system comprises the following steps: applying a voltage between a working electrode and a counter electrode, and exfoliating graphite and/or amorphous carbon under the action of electrolysis so as to generate the graphene oxide material, wherein before applying the voltage and/or in the process of applying the voltage, light irradiation is performed on the electrolysis system.

Claims

1-44. (canceled)

45. A method for preparing a halogenated graphene material in an electrolysis system, wherein, said electrolysis system comprises: a working electrode, said working electrode comprises graphite and/or amorphous carbon; a counter electrode, said counter electrode is an electrical conductor; and an electrolyte solution, said electrolyte solution is a conductive solution comprising a halide ion and/or a halogen-containing complex ion; wherein, said method comprises the following steps: applying a voltage between the working electrode and the counter electrode, so that the graphite and/or amorphous carbon is exfoliated under the action of electrolysis to generate a halogenated graphene; wherein, before and/or during applying the voltage, applying a light illumination to the electrolysis system; wherein said light illumination reaches an intensity as follows: said light illumination is capable of reducing the absorbance value at 650 nm of a chromogenic solution with a volume equal to that of the electrolyte solution by 10% or more within 30 minutes, the chromogenic solution is an aqueous solution containing methylene blue and oxalic acid, with a methylene blue concentration of 10.sup.−6M, and an oxalic acid concentration of 0.1M; said light illumination applies light having a wavelength of a nm, a=10˜2500.

46. A method for preparing a graphene oxide material in an electrolysis system, wherein, said electrolysis system comprises: a working electrode, said working electrode comprises graphite and/or amorphous carbon; a counter electrode, said counter electrode is an electrical conductor; and an electrolyte solution, said electrolyte solution is a conductive solution comprising a carboxyl group; wherein, said method comprises the following steps: applying a voltage between the working electrode and the counter electrode, so that the graphite and/or amorphous carbon are exfoliated under the action of electrolysis to generate a graphene oxide material; wherein, before and/or during applying the voltage, applying a light illumination to the electrolysis system; wherein said light illumination reaches an intensity as follows: said light illumination is capable of reducing the absorbance value at 650 nm of a chromogenic solution with a volume equal to that of the electrolyte solution by 10% or more within 30 minutes, the chromogenic solution is an aqueous solution containing methylene blue and oxalic acid, with a methylene blue concentration of 10.sup.−6M, and an oxalic acid concentration of 0.1M; said light illumination applies light having a wavelength of a nm, a=10˜2500.

47. The method according to claim 45, characterized by one or more of the following: said light illumination applies light having a wavelength of a nm, a=10˜2000; said light illumination applies light having an optical power density greater than or equal to 100 mW/cm.sup.2; said light illumination applies light having a power of 10˜100 W to per liter of said electrolyte solution; said light illumination has a duration time of 30 minutes or more; and the working electrode and/or the electrolyte solution are subjected to the light illumination before and/or during applying the voltage.

48. The method according to claim 45, characterized by one or more of the following: wherein said light illumination reaches an intensity as follows: said light illumination is capable of reducing the absorbance value at 650 nm of a chromogenic solution with a volume equal to that of the electrolyte solution by 20% or more within 30 minutes; said light illumination applies light having a wavelength of a nm, a=200˜2500; and said light illumination applies light having a wavelength of a nm, a=200˜400.

49. The method according to claim 45, said light illumination uses a light source which is a xenon lamp or an ultraviolet lamp.

50. The method according to claim 45, characterized by one or more of the following; said voltage has a value of 2˜1000 V; said voltage is applied for a total time of 5 minutes or more; and a square wave voltage of −0.5V to 10V is firstly applied between the working electrode and the counter electrode for 10˜60 minutes, and then a constant voltage of 10˜1000V is applied for 5 minutes or more.

51. The method according to claim 45, characterized by one or more of the following: said graphite is one or more selected from the group consisting of highly orientated pyrolytic graphite (HOPG), graphite foil, graphite rod, and graphite flake; and said amorphous carbon is one or more selected from the group consisting of charcoal, coal, coke, and carbon black.

52. The method according to claim 45, characterized by one or more of the following: said electrolyte solution comprises NaX, wherein X represents F, Cl, Br or I; and said electrolyte solution has a concentration of halogen ions and/or halogen-containing complex ions of 0.001˜10 mol/L.

53. The method according to claim 46, characterized by one or more of the following: said light illumination applies light having a wavelength of a nm, a=10˜2000; said light illumination applies light having an optical power density greater than or equal to 100 mW/cm.sup.2; said light illumination applies light having a power of 10˜100 W to per liter of said electrolyte solution; said light illumination has a duration time of 30 minutes or more; and the working electrode and/or the electrolyte solution are subjected to the light illumination before and/or during applying the voltage.

54. The method according to claim 46, characterized by one or more of the following: wherein said light illumination reaches an intensity as follows: said light illumination is capable of reducing the absorbance value at 650 nm of a chromogenic solution with a volume equal to that of the electrolyte solution by 20% or more within 30 minutes; said light illumination applies light having a wavelength of a nm, a=200˜2500; and said light illumination applies light having a wavelength of a nm, a=200˜400.

55. The method according to claim 46, said light illumination uses a light source which is a xenon lamp or an ultraviolet lamp.

56. The method according to claim 46, characterized by one or more of the following; said voltage has a value of 2˜1000 V; said voltage is applied for a total time of 5 minutes or more; and a square wave voltage of −0.5V to 10V is firstly applied between the working electrode and the counter electrode for 10˜60 minutes, and then a constant voltage of 10˜1000V is applied for 5 minutes or more.

57. The method according to claim 46, characterized by one or more of the following: said graphite is one or more selected from the group consisting of highly orientated pyrolytic graphite (HOPG), graphite foil, graphite rod, and graphite flake; and said amorphous carbon is one or more selected from the group consisting of charcoal, coal, coke, and carbon black.

58. The method according to claim 46, characterized by one or more of the following: said electrolyte solution comprises one or more of the following substances: carboxylic acid and carboxylate salt; said electrolyte solution comprises one or more of the following substances: oxalic acid and oxalate salt; said electrolyte solution further comprises a hydroxyl group; said the electrolyte solution has a carboxyl group concentration of 0.001˜10 mol/L; and said electrolyte solution has a pH of 0˜12.

59. The method according to claim 58, characterized by one or more of the following: the carboxylic acid is one or more selected from the group consisting of formic acid, oxalic acid, tricarballylic acid, and butanetetracarboxylic acid; and the carboxylate salt is one or more selected from the group consisting of formate salt, oxalate salt, tricarballylate salt, and succinate salt.

60. The method according to claim 59, characterized by one or more of the following: said electrolyte solution comprises Na.sup.+; said electrolyte solution comprises SO.sub.4.sup.2−; said electrolyte solution comprises Na.sub.2SO.sub.4; and said electrolyte solution has a SO.sub.4.sup.2− concentration of 0.001˜10 mol/L.

61. The method according to claim 46, wherein the graphene oxide material has an XPS spectrum with the following characteristics: the XPS spectrum has a C1s peak, when subjected to a peak-split process, generating a peak corresponding to 287.8˜288.3 eV and a peak corresponding to 286.0˜286.5 eV having a ratio 0.3˜2:1.

62. The method according to claim 46, wherein the graphene oxide material has a XPS spectrum with the following characteristics: the XPS spectrum has a C1s peak and a O1s peak with an area ratio of 0.8˜2.2:1.

63. A halogenated graphene material, which is prepared by the method according to claim 45.

64. A graphene oxide material, which is prepared by the method according to claim 46.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0173] FIG. 1 shows the scanning electron microscope photograph of the EGO of Example 1.1.

[0174] FIG. 2 shows the atomic force microscope photograph of the EGO of Example 1.1.

[0175] FIG. 3 shows the transmission electron microscope photograph of the EGO of Example 1.1.

[0176] FIG. 4 shows the XRD patterns of the EGO of Example 1.1, of the CGO of Comparative Example 3 and of unexfoliated graphite (C).

[0177] FIG. 5 shows the SERS spectrum of the EGO of Example 1.1.

[0178] FIG. 6 shows the FTIR spectra of the EGO of Example 1.1 and of the CGO of Comparative Example D3.

[0179] FIG. 7 shows the XPS patterns of the EGO of Example 2.2, of the EGO-D2 of Comparative Example D2 and of the CGO of Comparative Example D3.

[0180] FIG. 8 shows the CGO thermogravimetric curves of the EGO of Example 1.1 and of the CGO of Comparative Example D3.

[0181] FIG. 9 shows the fitting patterns of the fine spectra of the C is peaks of the XPS patterns of the EGOs of Example 1.1 (FIG. 9a), of Example 2.4 (FIG. 9b) and of Example 2.2 (FIG. 9c).

[0182] FIG. 10 shows the XRD patterns of the EGO membrane and of the MEGO membrane of Example 3.

[0183] FIG. 11 shows the cross-sectional scanning electron microscope photograph of the MEGO membrane of Example 3.

[0184] FIG. 12 shows the XPS spectrum of the electrolysis product of Comparative Example 4.

[0185] FIG. 13 shows the XPS spectrum of the electrolysis product of Example 4.

[0186] FIG. 14 shows the schematic diagram of an electrolysis system of one example.

[0187] FIG. 15 shows the schematic diagram of an electrolysis system of yet another example.

[0188] FIG. 16 shows the schematic diagram of an electrolysis system of yet another example.

[0189] FIG. 17 shows the schematic diagram of an electrolysis system of yet another example.

[0190] FIG. 18 shows the schematic diagram of an electrolysis system of yet another example.

SPECIFIC MODELS FOR CARRYING OUT THE PRESENT INVENTION

[0191] The embodiments of the present invention are described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. If a specific condition is not indicated in the examples, it is carried out according to the conventional condition or the condition suggested by the manufacturer. The reagents or instruments used without the manufacturer's indication are conventional products that can be obtained from the market.

[0192] FIG. 14 shows a schematic diagram of an electrolysis system. The electrolysis system can be used to implement the method for preparing a graphene oxide or the method for preparing a halogenated graphene of the present disclosure. The electrolysis system comprises a light treatment device 1 and an electrolysis device 2. The light treatment device 1 comprises a light source 12. The light source 12 is used to illuminate the electrolyte solution in the electrolysis system. The electrolysis device 2 comprises an electrolysis vessel 20, a working electrode 21, a counter electrode 22 and a power source 23. The electrolysis vessel 20 is used to contain the electrolyte solution and provide a place where an electrolysis reaction occurs. The power source 23 is respectively electrically connected to the working electrode 21 and the counter electrode 22 to provide the electric energy required for electrolysis. In this embodiment, the electrolysis vessel 20 is provided with a light-transmitting structure 11, and the light source 12 can illuminate the interior of the electrolysis vessel 20 through the light-transmitting structure 11, thereby illuminating the electrolyte solution inside the electrolysis vessel 20.

Example 1.1

[0193] A graphene oxide was electrochemically prepared using the above electrolysis system, in which the working electrode 21 was a graphite rod (8 mm in diameter, purchased from Qingdao Dadi Carbon Technology Co., Ltd.), the counter electrode 22 was a Pt sheet, and 250 mL of an aqueous solution containing 0.1 M oxalic acid and 0.05 M Na.sub.2SO.sub.4 was used as the electrolyte solution.

[0194] The electrolysis vessel 20 was a transparent electrolysis cell (5×5×15 cm), in which the working electrode 21 and the counter electrode 22 were placed.

[0195] The method for preparing graphene oxide material by electrolysis comprised: a voltage was applied between the working electrode and the counter electrode, and the voltage program was as follows: firstly, a square wave voltage was applied for 20 minutes, and the square wave voltage program was as follows: square wave period T=2 s, in one cycle, 10V was maintained for 1 s, and −0.5V was maintained for 1 s. Then, a constant voltage of 15V was applied for 5 hours.

[0196] The electrolyte solution was illuminated with a xenon lamp (CME-Xe300UV Xenon lamp, luminescence spectral range: 200˜2500 nm) throughout the electrolysis. The optical power density of the xenon lamp was 450 mW/cm.sup.2, and the spot diameter was 5 cm (equivalent to an optical power of 8.8 W). Other than that, there were no other light sources.

[0197] During electrolysis, it was found that after applying a constant voltage (15V) for 5 minutes, the electrolyte solution showed a light yellow color, indicating that graphene oxide had been formed. After the electrolysis, a solid powder was filtered and collected from the electrolyte solution, the collected solid powder was dispersed in N,N-dimethylformamide under ultrasonic, then a solid was filtered and collected, which was the graphene oxide material.

Examples 1.2˜1.8

[0198] Examples 1.2 to 1.8 differed from Example 1.1 in the parameter differences, and the specific differences were shown in the following table:

TABLE-US-00001 Example No. 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Constant 15 10 15 15 15 15 15 15 voltage/V Oxalic acid 0.1 0.1 0.01 0.05 0.2 0.1 0.1 0.1 concentration/ M Time/hour 5 5 5 5 5 3 7 9 Yield/g 2.5 1.2 0.7 1.1 2.0 1.4 3.7 4.1

Examples 2.1˜2.5

[0199] Examples 2.1 to 2.5 differed from Example 1.1 in some parameter differences, which were shown in the following table for details. For other steps and parameters not described in detail, they were all referred to Example 1.1.

[0200] The light with wavelength of 200˜400 nm was obtained by the following method: a short-pass filter was used to block a xenon lamp (CME-Xe300UV Xenon lamp, the emission spectrum range was 200˜2500 nm) to filter out the light above 400 nm, and thus the light with wavelength of 200˜400 nm was obtained, the optical power density was adjusted to 450 mW/cm.sup.2, and the spot diameter was 5 cm. Other than that, there were no other light sources.

Comparative Example D1

[0201] Comparative Example D1 differed from Example 1.1 only in that the whole preparation process was carried out under natural light without direct sunlight in the summer afternoon. Other steps and parameters were the same. The obtained product was numbered as EGO-D1.

Comparative Example D2

[0202] Comparative Example D2 differed from Example 2.2 only in that the whole preparation process was carried out under natural light without direct sunlight in the summer afternoon. Other steps and parameters were the same. The obtained product was numbered as EGO-D2.

[0203] The preparation method parameters and product property parameters of Examples 1.1, 2.1˜2.5, and Comparative Examples D1˜D2 were shown in the following table: including electrolyte solution composition, working electrode, light illumination wavelength, constant voltage, electrolysis time, product weight, proportion of single-layer graphene oxide sheets in product, area ratio of C1s peak to O1s peak in XPS spectrum of product, carbon-to-oxygen atomic ratio in product, and area ratio of carboxyl peak to non-carboxyl peak in product.

TABLE-US-00002 1.1 2.1 2.2 2.3 2.4 2.5 D1 D2 Electrolyte solution 0.1M 0.1M 0.1M 0.1M 0.1M 0.1M 0.1M 0.1M Oxalic Oxalic Formic Tricarballylic Butanetetracarboxylic Formic Oxalic Formic acid acid acid acid acid acid acid acid 0.05M Na.sub.2SO.sub.4 0.05M Na.sub.2SO.sub.4 Working electrode Graphite Graphite Graphite Graphite Graphite Charcoal Graphite Graphite rod rod rod rod rod rod rod rod Light wavelength/nm 200-2500 200-400 Natural light Constant voltage/V 15 V 30 V 30 V 30 V 30 V 30 V 15 V 30 V Electrolysis time/h 5 h 5 h 5 h 5 h 5 h 5 h 5 h 5 h Product weight/g 2.5 g 4.0 g 6.0 g 2.8 g 5.5 g 0.8 g 5.7 g Proportion of single-layer 90% 90% 90% 90% 90% 10% 90% graphene oxide sheets Area ratio of C1s peak to 1.08:1 0.87:1 0.96:1  1.79:1 1.37:1 2.16:1 1.12:1 O1s peak Carbon-to-oxygen atomic  2.6:1  2.1:1 2.3:1  4.3:1  3.3:1  5.2:1 3.2:1  2.7:1 ratio Area ratio of carboxyl peak 0.46:1 0.36:1 2.0:1 0.38:1 1.27:1 0.33:1 1.81:1 to non-carboxyl peak

Comparative Example D3

[0204] Chemically synthesized graphene oxide (CGO) was prepared by Hummers method.

[0205] Specifically, graphite powder (1.0 g) and NaNO.sub.3 (0.8 g) were added to concentrated sulfuric acid in an ice bath and stirred, and then KMnO.sub.4 (4.5 g) was slowly added thereto. The temperature was then raised and stirring was continued at 38° C. for 5 days. Finally, water and hydrogen peroxide at a concentration of 30 wt % were added. The resulting suspension was dialyzed, centrifuged and concentrated for later use. The obtained product was numbered as CGO.

[0206] Comparison of Light Illumination Characteristics of Examples 1.1 and 2.1 with Comparative Examples D1 and D2

[0207] The light sources of Examples 1.1 and 2.1 were xenon lamp, and the light sources of Comparative Examples D1 and D2 were natural light. In order to compare the effect of light source on the content of hydroxyl radicals in the solution, the following analysis was carried out:

[0208] A freshly prepared 250 mL of chromogenic solution was provided, the chromogenic solution was an aqueous solution containing methylene blue (radicals (such as OH) would oxidize the chromogenic solution, causing its color to become lighter) and oxalic acid, the concentration of methylene blue was 10.sup.−6 M, the concentration of oxalic acid was 0.1M. The chromogenic solution was placed in a transparent electrolysis cell (15×15×30 cm).

[0209] The xenon lamp of Example 1.1, the short-wave xenon lamp of Example 2.1 and the natural light of Comparative Example D1/D2 were used to illuminate the above-mentioned chromogenic solution respectively, and an ultraviolet photometer was used to record the absorbance A.sub.0 of the chromogenic solution at a wavelength of 650 nm before the experiment started, and the absorbance values of the chromogenic solution when the illustration was performed for 0.5 h, 1 h, 2 h and 3 h (A.sub.n, n=0.5, 1, 2, 3). When calculating absorbance, the decrease in absorbance of the chromogenic solution itself caused by simple illumination was deducted. From the detected absorbance values, the absorbance decrease rate η.sub.n was calculated:

[00002]$\mathrm{Absorbance}\mathrm{decrease}\mathrm{rate}{\eta }_n=\frac{A_0-A_n}{A0}\times 100\%$

[0210] The results were as follows:

TABLE-US-00003 Absorbance Light illumination time/h decrease rate η.sub.n 0.5 1 2 3 Example 1.1 28.6% 52.1% 51.6% 49.8% Example 2.1 24.3% 47.8% 46.2% 45.1% Natural light 0.01% 0.017% 0.038% 0.057%

[0211] The above results showed that the natural light hardly caused discoloration of the chromogenic solution. The light illumination in Examples 1.1 and 2.1 rapidly decreased the absorbance of the chromogenic solution.

[0212] Analysis and Detection

[0213] FIG. 1 showed a scanning electron microscope photograph of the EGO of Example 1.1. As shown in the figure, the average sheet size of EGO was 1.5 μm, and the EGO with sheet size ranging from 1 to 2 μm accounted for 55%. The sheet diameter size distribution of EGO was shown in the table below.

TABLE-US-00004 Sheet diameter/μm <1 1-2 2-4 4-10 4-10 Percent/% 17 55 16 11 1

[0214] FIG. 2 showed an atomic force microscope photograph of the EGO of Example 1.1. As shown in the figure, the thickness of the single-layer EGO was about 0.9 nm. The layer number distribution of the EGO was shown in the table below.

TABLE-US-00005 Layers 1 2 3 4-10 Percent/% 92.6 4.4 2.1 0.9

[0215] FIG. 3 showed a transmission electron microscope photograph of the EGO of Example 1.1. The inset of FIG. 3 was the electron diffraction pattern. As shown in the figure, the EGO was in a transparent state, and the electron diffraction pattern had a six-fold symmetrical structure, indicating that the EGO of Example 1.1 had a high degree of crystallinity.

[0216] The X-ray diffraction analysis was performed on powdered EGO (Example 1.1), CGO (Comparative Example D3) and unexfoliated graphite.

[0217] FIG. 4 showed the XRD patterns of powdered EGO (of Example 1.1), CGO (Comparative Example 3D) and unexfoliated graphite (C). The unexfoliated graphite powder had a narrow half-width peak near 2θ=26°, while an obvious peak near this 20 angle could hardly be observed for the EGO, which indicated that the interlayer spacing of EGO was significantly different from that of unexfoliated graphite, and the layers of EGO were randomly stacked. At the same time, EGO and CGO had a broad half-width peak near 2θ=10.

[0218] The EGO of Example 1.1 was characterized by surface-enhanced Raman spectroscopy (SERS).

[0219] FIG. 5 showed the SERS spectrum of the EGO of Example 1.1. As shown in the figure, there were five characteristic peaks D, G, 2D, D+D′ and 2D′ in the figure. Among them, the G peak (G-band) was located near 1590 cm.sup.−1, the D peak (D-band) was located near 1363 cm.sup.−1, and the intensity ratio of the D peak to the G peak was greater than 1. In addition, there were two characteristic peaks at 1135 cm.sup.−1 and 1742 cm.sup.−1, which existed in the form of shoulder peaks of the G peak and the D peak, respectively, and they were the vibration peaks of C—O and C═O, respectively, indicating the existence of oxygen-containing functional groups in EGO.

[0220] Fourier transform infrared absorption spectrometer (FTIR) was used to characterize the EGO of Example 1.1 and the CGO of Comparative Example D3.

[0221] FIG. 6 showed the FTIR spectra of the EGO of Example 1.1 and of the CGO of Comparative Example D3. As shown in the figure, there were peaks representing four functional groups C═O (1756 cm.sup.−1), C—O (1063 cm.sup.−1, 1281 cm.sup.−1, 1569 cm.sup.−1), C═C (1644 cm.sup.−1) and O—H (3439 cm.sup.−1) functional group peaks.. In addition, although the C═O (1756 cm.sup.−1) peak of the EGO was weaker than the corresponding peak of the CGO, it was still clearly visible, indicating that the EGO of Example 1.1 had a higher degree of oxidation. In addition, the intensity of the C═O peak was lower than that of the C—O peak, indicating that the EGO contained more C—O functional groups.

[0222] The EGO of Example 1.1, the EGO of Comparative Example D1 and the CGO of Comparative Example D3 were characterized by X-ray photoelectron spectroscopy (XPS).

[0223] FIG. 7 showed the XPS patterns of the EGO-2.2 of Example 2.2, of the EGO-D2 of Comparative Example D2 and of the CGO of Comparative Example D3. The figure showed the C1s peak and the O1s peak of graphene oxide.

[0224] According to the calculation for the patterns in FIG. 7, the carbon/oxygen atomic ratio (C/O) of the EGO-2.2 of Example 2.2 was 2.3:1, and the carbon/oxygen atomic ratio (C/O) of the EGO-D2 of Comparative Example D2 was 2.7:1. EGO-2.2 had a lower carbon-to-oxygen atomic ratio than EGO-D2, indicating that EGO-2.2 had a higher degree of oxidation. It could be seen that the light illumination could indeed improve the oxidation degree of the electrochemically prepared EGO.

[0225] In addition, Example 2.2 also had a higher yield than Comparative Example 2.2. This indicated that the light illumination could also improve the yield of the electrochemically prepared EGO.

[0226] The carbon/oxygen atomic ratio (C/O) of EGO-2.2 of Example 2.2 was 2.3:1, and the carbon/oxygen atomic ratio (C/O) of CGO of Comparative Example D3 was 2.3:1, which showed that the graphene oxide material obtained by the method of Example 2.2 had a comparable degree of oxidation as compared with the Hummer's method.

[0227] In addition, the carbon-to-oxygen atomic ratios of the graphene oxide products of Example 1.1 and Comparative Example D1 were also detected. The carbon/oxygen atomic ratio (C/O) of EGO-1.1 of Example 1.1 was 2.6:1, and the carbon/oxygen atomic ratio (C/O) of EGO-D1 of Comparative Example D1 was 3.2:1. EGO-1.1 had a lower carbon-to-oxygen atomic ratio than EGO-D1, indicating that EGO-1.1 had a higher degree of oxidation. It could be seen that the light illumination could indeed improve the oxidation degree of the electrochemically prepared EGO.

[0228] FIG. 9 showed the fitting patterns of the fine spectra of the C is peaks of the XPS patterns of the EGOs of Example 1.1 (FIG. 9a), of the EGOs of Example 2.4 (FIG. 9b) and of the EGOs of Example 2.2 (FIG. 9c). As shown in the figures, the horizontal axis was the binding energy and the vertical axis was the intensity. The peaks around 287.8˜288.3 eV correspond to carboxyl groups, the peaks around 285.8˜286.3 eV correspond to non-carboxyl groups (hydroxyl and ether groups), and the peaks around 284˜284.5 eV correspond to alkenyl groups.

[0229] As shown in FIG. 9a, for the EGO of Example 1.1, the area ratio of carboxyl peak (that was, the peak representing C═O) to non-carboxyl peak (that was, the superposition of the peaks representing C—OH and C—O—C) in the XPS pattern was 1.8:1.

[0230] As shown in FIG. 9b, for the EGO of Example 2.4, the ratio of carboxyl peak to non-carboxyl peak in the XPS pattern was 1.27:1.

[0231] As shown in FIG. 9c, for the EGO of Example 2.2, the ratio of carboxyl peak to non-carboxyl peak in the XPS pattern was 2.0:1. In contrast, the ratio of carboxyl peak to non-carboxyl peak in the XPS pattern of the EGO of Comparative Example 2D was 1.81:1.

[0232] The above experimental results showed that using an electrolyte solution containing oxalic acid, formic acid or butanetetracarboxylic acid in combination with light illumination could obtain graphene oxide with a higher proportion of carboxyl groups.

[0233] Thermogravimetric analysis was performed on the EGO of Example 1.1 and the CGO of Comparative Example D3.

[0234] FIG. 8 showed thermogravimetric curves of the EGO of Example 1.1 and of the CGO of Comparative Example D3. As shown, the overall weight change trends of EGO and CGO were similar. The weight loss in the temperature range below and at 100° C. was due to the evaporation of a small amount of water in their adsorption environment. The rapid weight loss in the range of 100˜220° C. was caused by the reduction of most of the oxygen-containing functional groups to produce gases such as CO and CO.sub.2. During the heating from 100° C. to 800° C., the mass loss of EGO was about 41%, and the mass loss of CGO was about 47%. From this, it could be inferred that EGO and CGO had similar oxidation degrees.

[0235] From the above data, it could be known that the graphene oxide with a higher degree of oxidation was obtained by the method of the examples by applying light illumination to the electrolysis system, and the oxidation degree of the graphene oxide was significantly higher than that prepared by applying natural light, and was comparable to the degree of oxidation of the graphene oxide prepared by the Hummers method.

[0236] In addition, the method of the examples also had the advantages of high production efficiency, high proportion of single-layer graphene oxide in the graphene oxide material, and large graphene oxide sheet diameter.

Example 3

[0237] The EGO prepared in Example 1.1 was dispersed in 50 mL of water to obtain a dispersion of 0.5 μg/mL. The above dispersion was filtered using a 0.2 μm pore size PTFE filter membrane at a negative pressure of 0.1 bar, so that EGO was deposited on the PTFE membrane as a membrane. The deposited membrane on the PTFE membrane was dried at 50° C. for 24 h to obtain a dry EGO membrane with a thickness of 220 nm.

[0238] The dried EGO membrane was placed in a 0.25 M aniline solution (the solvent was an aqueous ethanol solution, and the volume ratio of ethanol to water was 1:1) for 24 hours, taken out and washed, and then dried at 50° C. for 24 h to obtain a dry MEGO membrane with a thickness of 220 nm.

[0239] X-ray diffraction (XRD) analysis was performed on the EGO membrane and MEGO membrane. FIG. 10 showed the XRD patterns of the EGO membrane and of the MEGO membrane. As shown in the figure, MEGO membrane and EGO membrane had characteristic peaks around 2θ=10°, but the 2θ angles of the characteristic peaks of the two were slightly different, and the MEGO membrane had a smaller 2θ angle, which indicated that the interlayer spacing of the graphene oxide in the MEGO membrane was increased in some extent as compared to that of the EGO membrane.

[0240] FIG. 11 showed a cross-sectional electron microscope photograph of the MEGO membrane. As shown, the MEGO membrane had a compact layered structure.

[0241] The water flux test was carried out on the EGO membrane and MEGO membrane. The test method was as follows: first, the volume of water flowing through the membrane was measured under different water pressures, and then the volume of water was divided by the area of the membrane and the measurement time. The result was the water flux, and the results were as follows:

TABLE-US-00006 Water pressure/bar Flux/L m.sup.−2h.sup.−1 1 2 3 4 5 EGO membrane 3.01 6.13 8.80 12.15 15.57 MEGO membrane 4.72 9.01 11.98 16.3 19.87

[0242] As shown in the table above, the water flux of the MEGO membrane was about 1.6 times higher than that of the EGO membrane under the water pressure of 1-5 bar.

[0243] The NaCl retention rates of the EGO membrane and MEGO membrane were detected at different time intervals. The detection method was as follows: first, the conductivity of the sodium chloride aqueous solution before passing through the membrane was measured, then the sodium chloride aqueous solution was subjected to the nanofiltration membrane treatment at a pressure of 5 bar, and finally the diluted sodium chloride solution collected after the nanofiltration membrane treatment was subjected to conductivity test. The retention rate of salt could be obtained from the relation between the conductivity and the ion concentration. The results were shown in the table below.

TABLE-US-00007 Time (minutes) 5 10 20 30 60 90 EGO membrane retention rate 23.1 25.6 28.8 29.9 31.4 32.8 (%) MEGO membrane retention 27.8 38.2 46.9 51.5 58.2 59.4 rate (%)

[0244] The retention rates of NaCl, KCl, and MgCl.sub.2 for the EGO membrane and MEGO membrane were detected respectively. The detection method was as follows: first, the electrical conductivity of the aqueous solutions of the three salts before passing through the membranes was measured, and then the three aqueous solutions were subjected to the nanofiltration membrane treatment under a pressure of 5 bar, and finally the diluted solution collected after the nanofiltration membrane treatment was subjected to conductivity test. The retention rate of salt could be obtained from the relation between the conductivity and the ion concentration. The results were shown in the table below.

TABLE-US-00008 NaCl KCl MgCl.sub.2 EGO membrane retention rate (%) 31.4 39.9 47.8 MEGO membrane retention rate (%) 58.2 64.9 71.8

[0245] The above test results demonstrated that MEGO membrane had improved water flux and enhanced ion retention rate as compared to the EGO membrane. Therefore, the MEGO membrane was very suitable for desalination/dessalement of water.

Example 4: Preparation and Characterization of Chlorinated Graphene Oxide

[0246] Chlorinated graphene oxide was prepared using the same two-electrode system as used in Example 1.1, wherein the graphite rod was used as the working electrode, the Pt sheet was used as the counter electrode, and the electrolyte solution was 0.1 M NaCl.

[0247] The electrolysis cell was subjected to light illumination, and the light illumination conditions were the same as those in Example 2.1.

[0248] Then, a square wave voltage was applied to the two-electrode system, and the square wave voltage program was as follows: the square wave period T=4 s, in one cycle, 10V was maintained for 1 s, and 0V was maintained for 3 s. The electrolysis time was 6 h.

[0249] After electrolysis, the electrolyte solution was filtered with a polytetrafluoroethylene (PTFE) filter membrane with a pore size of 0.2 μm to obtain a solid powder. The solid powder was washed with water, filtered, and the above operation was repeated 3 times. The collected solid powder was dispersed in N,N-dimethylformamide, subjected to ultrasonic for 15 minutes in an ice-water bath, then the product after ultrasonic was suction filtrated with a PTFE filter membrane, and a solid product was finally collected with a mass of 0.20 g.

Comparative Example 4

[0250] Comparative Example 4 differed from Example 4 in that natural light was used instead of the xenon lamp equipped with filter. Condition of natural light was the same as D1 The mass of the product was 0.98 g.

[0251] XPS Analysis

[0252] The electrolysis products of Example 4 and Comparative Example 4 were subjected to XPS analysis.

[0253] FIG. 12 showed the XPS spectrum of the electrolysis product of Comparative Example 4, specifically the fine spectrum of C1s. The fine spectrum was fitted and subjected to a peak-split process, and no peak corresponding to C—Cl (286.8 eV) group was observed, and the corresponding fitting peak of the electron binding energy was not observed. In addition, the bonding information of Cl was characterized in the range of 190˜210 eV of the XPS spectrum, and no fine spectrum was observed. This showed that the Cl atom did not form a bond with the C atom in graphene oxide, or the Cl content was extremely low, which was lower than the detection limit of XPS.

[0254] FIG. 13 showed the XPS spectrum of the electrolysis product of Example 4. After fitting and peak-split process of the spectrum in the range of 190˜210 eV, two distinct peaks appeared near 200.04 eV and 201.82 eV, corresponding to the inner electron binding energy of 2p3/2 and 2p1/2 of Cl atom, respectively, which were close to the values of the inner electron binding energy of the Cl atom in the C—Cl bond. This indicated that chlorinated graphene oxide could be prepared under light illumination conditions.

[0255] FIG. 15 shows a schematic diagram of yet another electrolysis system. The electrolysis system can be used to implement the method for preparing a graphene oxide or the method for preparing a halogenated graphene of the present disclosure. The electrolysis system comprises a light treatment device 1 and an electrolysis device 2. The light treatment device 1 comprises a light source 12. The light source 12 is used to illuminate the electrolyte solution in the electrolysis system. The electrolysis device 2 comprises an electrolysis vessel 20, a working electrode 21, a counter electrode 22 and a power source 23, and the electrolysis vessel is used for accommodating an electrolytic solution and providing a place for electrolysis reaction to occur. The power source 23 is electrically connected to the working electrode 21 and the counter electrode 22, respectively. In this embodiment, the light source 12 is located inside the electrolysis vessel 20 and can illuminate the electrolyte solution in the electrolysis vessel 20.

[0256] FIG. 16 shows a schematic diagram of yet another electrolysis system. The electrolysis system can be used to implement the method for preparing a graphene oxide or the method for preparing a halogenated graphene of the present disclosure. The electrolysis system comprises a light treatment device 1 and an electrolysis device 2. The light treatment device 1 comprises a light treatment vessel 10 and a light source 12, the light treatment vessel 10 is used for accommodating an electrolyte solution, and the light source 12 can illuminate the interior of the light treatment vessel 10, thereby illuminating the electrolyte solution contained therein. In this embodiment, a light-transmitting structure 11 is provided on the light treatment vessel, and the light source 12 can illuminate the interior of the light treatment vessel through the light-transmitting structure. The electrolysis device 2 comprises a power source 23, a working electrode 21, a counter electrode 22 and an electrolysis vessel 20, and the electrolysis vessel 20 provides a place where an electrolysis reaction occurs. The power source 23 is electrically connected to the working electrode 21 and the counter electrode 22, respectively. The light treatment vessel 10 has a liquid outlet 16 extending into the electrolysis vessel 20. The light treatment vessel 10 can supply the electrolysis vessel 20 with an electrolyte solution subjected to light treatment.

[0257] FIG. 17 shows a schematic diagram of yet another electrolysis system. The electrolysis system can be used to implement the method for preparing a graphene oxide or the method for preparing a halogenated graphene of the present disclosure. The electrolysis system comprises a light treatment device 1 and an electrolysis device 2. The light treatment device 1 has a light source 12. The electrolysis device 2 comprises a power source 23, a working electrode 21, a counter electrode 22 and an electrolysis vessel 20. The electrolysis vessel 20 is used to contain the electrolyte solution and provide a place where the electrolysis reaction occurs. The power source 23 is electrically connected to the working electrode 21 and the counter electrode 22, respectively. In this embodiment, the electrolysis vessel 20 is provided with a light-transmitting structure 11, and the light source 12 can illuminate the interior of the electrolysis vessel 20 through the light-transmitting structure 11, thereby performing light treatment on the electrolyte solution inside the electrolysis vessel 20. The electrolysis system also comprises a circulation loop 51. The electrolysis container 20 is provided with a first liquid inlet 14 and a first liquid outlet 15. The circulation loop 51 is in liquid communication with the first liquid inlet 14 and the first liquid outlet 15 respectively. The circulation loop 51 is provided with a pump 52 and a valve 53. A solid-liquid separating device 30 is connected in series with the circulation loop 51. Based on this, the electrolyte solution in the electrolysis vessel enters the circulation loop 51 for circulation. During the circulation process, the electrolyte solution is subjected to solid-liquid separation treatment when passing through the solid-liquid separating device 30, the solid is collected by the solid-liquid separating device 30, and the liquid continues to circulate back to the electrolysis solution. The electrolysis system can efficiently collect products exfoliated from the working electrode during electrolysis, such as graphene oxide materials or a halogenated graphene materials.

[0258] In some embodiments, as shown in FIG. 17, the solid-liquid separating device has a second liquid inlet 31 and a second liquid outlet 32, and the second liquid inlet 31 and the second liquid outlet 32 are in liquid communication with the circulation loop 51. The solid-liquid separating device 30 also comprises a filter membrane 33, the filter membrane 33 is configured to filter the electrolyte solution passing through the solid-liquid separating device. The filter membrane 33 is located between the second liquid inlet 31 and the second liquid outlet 32.

[0259] In some embodiments, as shown in FIG. 17, the solid-liquid separating device 30 is provided with a liquid storage tank 34, and the liquid storage tank 34 is located below the filter membrane 33. The second liquid inlet 31 is located above the filter membrane 33, and the second liquid outlet 32 is located below the filter membrane 33. Based on this, the electrolyte solution can enter the liquid storage tank 34 through the filter membrane 33 under the action of gravity to realize the filtration of the electrolyte solution.

[0260] FIG. 18 is a schematic diagram of an electrolysis system of yet another embodiment. The electrolysis system comprises an electrolysis device 2, and the electrolysis device 2 comprises a power source 23, a working electrode 21, a counter electrode 22 and an electrolysis vessel 20. The electrolysis vessel 20 is used to contain the electrolyte solution and provide a place where the electrolysis reaction occurs. The electrolysis system further comprises a circulation loop 51, and the circulation loop 51 is connected with a solid-liquid separating device 30 in series. Based on this, the electrolyte solution in the electrolysis vessel enters the circulation loop 51 for circulation. During the circulation process, the electrolyte solution is subjected to solid-liquid separation treatment when passing through the solid-liquid separating device 30, the solid is collected by the solid-liquid separating device 30, and the liquid continues to circulate back to the electrolyte solution. Based on this, the products exfoliated from the working electrode during the electrolysis process, such as graphene oxide materials or a halogenated graphene materials, can be efficiently collected.

[0261] In some embodiments, as shown in FIG. 18, the electrolysis vessel 20 is provided with a first liquid inlet 14 and a first liquid outlet 15, and the circulation loop 51 is in liquid communication to the first liquid inlet 14 and the first liquid outlet 15 respectively. The circulation loop 51 is provided with a pump 52 and a valve 53. The solid-liquid separating device has a second liquid inlet 31 and a second liquid outlet 32, the solid-liquid separating device further comprises a filter membrane 33, and the filter membrane 33 is located between the second liquid inlet 31 and the second liquid outlet 32.

[0262] In some embodiments, as shown in FIG. 18, the solid-liquid separating device 30 is provided with a liquid storage tank 34, and the liquid storage tank 34 is located below the filter membrane 33. The second liquid inlet 31 is located above the filter membrane 33, and the second liquid outlet 32 is located below the filter membrane 33. Based on this, the electrolyte solution can enter the liquid storage tank 34 through the filter membrane 33 under the action of gravity to realize the filtration of the electrolyte solution.

[0263] Although specific embodiments of this invention have been described in detail, those skilled in the art will understand that in light of all the teachings disclosed, various changes in detail can be made and are within the scope of this invention. The full scope of the present invention is given by the appended claims and any equivalents thereof.