Preparation method and application of coal-based quantum dot nano material

Abstract

The invention discloses a preparation method and application of a coal-based quantum dot nano-material. The preparation method comprises the following steps: S1, sequentially adding a coal-based raw material into a hydrochloric acid solution and a hydrofluoric acid solution for pickling and impurity removal, washing a precipitate to be neutral, and drying to obtain the pickled coal-based raw material; s2, adding the acid-washed coal-based raw material obtained in the step S1 into a reaction container, adding DMF, carrying out ultrasonic treatment, heating to a preset temperature, carrying out a reaction, dropwise adding a hydrogen peroxide solution at the same time, and after the reaction is finished, carrying out self-heating cooling to room temperature so as to obtain a cooled solution; s3, centrifugally separating the cooled solution obtained in the step S2, dialyzing supernate in a dialysis bag, and freeze-drying the dialyzed solution to obtain the coal-based quantum dot nano material. The preparation method of the coal-based quantum dot nano material is simple to operate, high in conversion rate, low in cost and capable of being popularized and applied on a large scale.

Description

Technical Field

[0001] The present invention belongs to the field of carbon quantum dot materials, and relates to a preparation method and application of a coal-based quantum dot nanomaterial, specifically to a method for preparing a novel zero-dimensional carbon nanomaterial using coal (semicoke, liquefaction residue) as a raw material. Background Art

[0002] Semicoke and liquefaction residue are a novel carbon-rich solid material obtained by pyrolysis of biomass / coal under anoxic or anaerobic conditions at a certain temperature. They can be used as a novel carbon material, with relatively low prices, high fixed carbon content, high specific resistance, high chemical activity, and low aluminum, sulfur, and phosphorus content, and are considered high-quality materials for downstream industrial clusters. However, compared with traditional fossil fuels, the combustion efficiency and calorific value of semicoke are relatively low, which means that more semicoke is required to generate the same amount of energy. The storage and transportation of semicoke are also very complex, and appropriate storage conditions are required to prevent quality degradation. The surfaces of coal-based materials (raw coal, semicoke, liquefaction residue) contain a large number of oxygen-containing functional groups, but they have not been well developed and utilized. Therefore, before being put into application, the problems of reducing the particle size of semicoke and fully exposing the oxygen-containing functional groups must be solved.

[0003] Since quantum dots are a type of semiconductor at the nanoscale, their electronic properties are greatly affected by quantum mechanics, especially the quantum confinement effect of electrons. In recent years, a large number of preparation methods for carbon quantum dots have been reported, which have attracted wide attention due to different carbon sources and processes used.

[0004] Currently, the methods for preparing carbon quantum dots are mainly divided into "top-down" and "bottom-up" methods. The top-down method uses methods such as laser ablation, electrochemical oxidation, and arc discharge to crack large carbon particles; while the bottom-up method mainly includes template method, combustion method, hydrothermal / solvothermal method, microwave-assisted method, etc. However, these methods have the disadvantages of cumbersome and complex preparation processes, high process conditions requirements, long preparation time, difficult operation; irregular product shapes, uneven morphologies, and too thick external carbon layers, resulting in difficulty in large-scale promotion and application.

[0005] CN 202211019821.0 discloses a coal-based carbon quantum dot and a preparation method thereof. The preparation uses coal as a raw material, mixes it with sodium hydroxide and sodium nitrite, and performs molten salt oxidation at high temperature to obtain coal-based carbon quantum dots. The coal-based carbon quantum dots can obtain variable-color fluorescence with different emission wavelengths under different semiconductor laser excitations. However, this patent uses molten salt oxidation, with a complex process, high equipment requirements, high costs, and it is difficult to fully develop and utilize coal-based materials, which is not conducive to large-scale promotion. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method and application of coal-based quantum dot nanomaterials with simple operation and excellent performance, so as to fully develop and utilize coal-based materials, reduce costs, improve conversion rates, and can be widely promoted and applied on a large scale.

[0007] To achieve the above purpose, the present invention provides a preparation method of coal-based quantum dot nanomaterials, including the following steps:

[0008] S1. Add the coal-based raw material to hydrochloric acid solution and hydrofluoric acid solution in sequence for pickling and impurity removal, wash the precipitate until neutral, and dry to obtain the pickled coal-based raw material;

[0009] S2. Add the pickled coal-based raw material obtained in step S1 to a reaction vessel, add N,N-dimethylformamide (DMF), perform ultrasonic treatment, heat up to a predetermined temperature for reaction, and simultaneously drop in hydrogen peroxide solution. After the reaction ends, cool down to room temperature by self-heating to obtain the cooled solution;

[0010] S3. Centrifuge the cooled solution obtained in step S2, take the supernatant and dialyze it in a dialysis bag, and freeze-dry the dialyzed solution to obtain coal-based quantum dot nanomaterials;

[0011] In step S1, the coal-based raw material is one or more of raw coal, semi-coke, and liquefaction residue.

[0012] Preferably, in step S1, the concentration of the hydrochloric acid solution is 1-6 mol / L.

[0013] Preferably, in step S1, the mass percentage concentration of HF in the hydrofluoric acid solution is 0.5-5%.

[0014] Preferably, in step S1, the precipitate is placed in a vacuum drying oven and vacuum dried at a temperature of 60-100 °C for 12-48 h.

[0015] Preferably, in step S2, heat up to 60-100 °C and react for 0.5 h-2 h.

[0016] Preferably, in step S2, the mass fraction of the hydrogen peroxide solution is 10-30%.

[0017] Preferably, in step S3, centrifuge the cooled solution at a speed of 6000-10000 r / min for 5-30 min.

[0018] Preferably, in step S3, take the supernatant and dialyze it in a dialysis bag for 24-72 h, and change the water every 12 h.

[0019] Preferably, in step S3, the dialyzed solution is placed in a petri dish, frozen solid in a refrigerator, and then fully freeze-dried in a freeze dryer to obtain the coal-based quantum dot nanomaterial.

[0020] The present invention also provides the application of the coal-based quantum dot nanomaterial in a battery separator, using it as a battery separator modification material.

[0021] The present invention also provides the application of the coal-based quantum dot nanomaterial in a zinc-ion battery electrode material, using it as an adjuvant for the copper oxide positive electrode material of a zinc-ion battery.

[0022] The beneficial technical effects of the present invention are as follows:

[0023] (1) The present invention provides a preparation method of a coal-based quantum dot nanomaterial, which is simple in operation, high in conversion rate, low in cost, and can be widely promoted and applied on a large scale.

[0024] (2) The present invention also provides the application of the coal-based quantum dot nanomaterial in a battery separator, using it as a battery separator modification material. The modified separator is applied to a zinc-ion battery and a zinc-ion capacitor, showing enhanced electrochemical performance.

[0025] (3) The present invention also provides the application of the coal-based quantum dot nanomaterial in a zinc-ion battery electrode material, using it as an adjuvant for the copper oxide positive electrode material of a zinc-ion battery. It can coat copper oxide ions and expand the layer spacing. The modified copper oxide positive electrode material is applied to a zinc-ion battery, showing excellent zinc storage performance. Description of the Drawings

[0026] Figure 1 It is a transmission electron microscope image of the coal-based quantum dot nanomaterial prepared in Example 1 of the present invention;

[0027] Figure 2 It is an infrared image of the coal-based quantum dot nanomaterial prepared in Example 1 of the present invention;

[0028] Figure 3 It is an XPS image of the coal-based quantum dot nanomaterial prepared in Example 1 of the present invention;

[0029] Figure 4 It is an XRD image of the coal-based quantum dot nanomaterial prepared in Example 1 of the present invention;

[0030] Figure 5 It is a transmission electron microscope image of the coal-based quantum dot nanomaterial prepared in Example 2 of the present invention;

[0031] Figure 6 It is an application image of the coal-based quantum dot nanomaterial prepared in Example 1 of the present invention in a zinc-ion battery separator;

[0032] Figure 7 Application diagram of the coal-based quantum dot nanomaterial prepared in Example 1 of the present invention in cupric oxide as the positive electrode of a zinc ion battery. Detailed implementation manners

[0033] The following will clearly and completely describe the detailed implementation manners of the present invention with reference to the accompanying drawings.

[0034] Example 1

[0035] A preparation method of a coal-based quantum dot nanomaterial, comprising the following steps:

[0036] S1. Add the coal-based raw material into 200 mL of 1 mol / L hydrochloric acid solution and stir for 3 h, then add it into 200 mL of hydrofluoric acid solution with a mass percentage concentration of 1% and stir for 3 h. Wash the precipitate until the pH test paper shows neutrality, put it into a vacuum drying oven, and vacuum dry at 80 °C for 24 h to obtain the pickled coal-based raw material. The coal-based raw material is raw coal;

[0037] S2. Take 10 g of the pickled coal-based raw material and add it into a reaction vessel. Add 10 mL of DMF, ultrasonically treat for 10 min, then place it in an oil bath at 80 °C and react for 1 h. At the same time, slowly drop 90 mL of hydrogen peroxide solution. After the reaction ends, cool it to room temperature by self-heating to obtain the cooled solution;

[0038] S3. Centrifuge the cooled solution at a speed of 8000 r / min for 10 min. Take the supernatant and dialyze it in a dialysis bag for 48 h, changing the water every 12 h. Put the dialyzed solution into a petri dish, freeze it solid in the refrigerator, and then fully freeze-dry it in a freeze dryer to obtain the coal-based quantum dot nanomaterial.

[0039] The coal-based quantum dot nanomaterial prepared in Example 1 was observed by transmission electron microscopy. The results are shown in Figure 1 , and it can be seen from Figure 1 that the spherical quantum dots obtained in this example have relatively uniform particle sizes and are about 2 - 3.5 nm in size.

[0040] The infrared, XPS, and XRD results of the coal-based quantum dot nanomaterial prepared in Example 1 are shown in Figures 2 to 4 , and it can be seen from Figure 2 that the coal-based nanomaterial obtained in this example shows peaks at 1630 cm -1 and 3315 cm -1 , which are related to the stretching vibrations of the C=O bond and the O-H bond, respectively.

[0041] It can be seen from Figure 3It can be seen that the coal-based nanomaterials obtained in this embodiment are mainly composed of three elements, namely C, O, and N. Among them, the content of nitrogen element is relatively small while the content of oxygen element is relatively large, indicating that this coal-based nanomaterial contains abundant oxygen-containing functional groups. The C1s spectrum has three peaks at 284.2 eV (C-C), 285.6 eV (C-O), and 288.3 eV (C=O), while the O1s spectrum has two peaks at 531.52 eV (C-O) and 533.02 eV (C=O). Combining Figure 2 the infrared spectral data, it is inferred that this coal-based nanomaterial contains abundant oxygen-containing functional groups such as hydroxyl groups and carboxyl groups.

[0042] Such as Figure 4 It can be seen that the coal-based nanomaterials obtained in this embodiment show a peak at 23°, indicating that this coal-based nanomaterial has an amorphous structure.

[0043] Example 2

[0044] A preparation method of coal-based quantum dot nanomaterials includes the following steps:

[0045] S1. Add the coal-based raw material into 200 mL of 2 mol / L hydrochloric acid solution and stir for 3 h, then add it into 200 mL of hydrofluoric acid solution with a mass percentage concentration of 2% and stir for 3 h. Wash the precipitate until the pH test paper shows neutrality, put it into a vacuum drying oven, and vacuum dry at 90 °C for 12 h to obtain the pickled coal-based raw material. The coal-based raw material is semi-coke;

[0046] S2. Take 10 g of the pickled coal-based raw material and add it into a reaction vessel. Add 10 mL of DMF, ultrasonically treat for 10 min, then put it into an oil bath at 80 °C and react for 1 h. At the same time, slowly drop 90 mL of hydrogen peroxide solution. After the reaction ends, cool it to room temperature by self-heating to obtain the cooled solution;

[0047] S3. Centrifuge the cooled solution at a speed of 9000 r / min for 8 min, take the supernatant and dialyze it in a dialysis bag for 60 h, change the water every 12 h. Put the dialyzed solution into a watch glass, freeze it solid in the refrigerator, and then fully freeze-dry it in a freeze dryer to obtain the coal-based quantum dot nanomaterials.

[0048] The coal-based quantum dot nanomaterials prepared in Example 2 were observed by transmission electron microscopy. The results are shown in Figure 5 From Figure 5 it can be seen that the spherical quantum dots obtained in this embodiment have relatively uniform particle sizes, about 2 - 3.5 nm in size.

[0049] Example 3

[0050] Using the coal-based quantum dot nanomaterials prepared in Example 1 as a battery separator modification material, the specific steps are as follows:

[0051] S1. Cut the battery separator into circular materials with a diameter of 16 mm, and soak them in the coal-based quantum dot solution prepared in Example 1. The separator can be a cellulose separator such as glass fiber or filter paper.

[0052] S2. Take out the separator after soaking for 6 - 8 h. Try not to squeeze out the quantum dot solution absorbed inside the separator when taking it out, and dry it at room temperature to obtain the quantum dot-modified separator.

[0053] S3. Assemble the battery in the order of negative electrode case, positive electrode, modified separator, electrolyte, negative electrode, gasket, and positive electrode case.

[0054] The positive electrode material in the zinc-ion battery is vanadium pentoxide, activated carbon, etc. The assembly process is a conventional technology in this field. As Figure 6 shown, the modified separator is applied to zinc-ion batteries and zinc-ion hybrid capacitors, showing excellent cycle stability and high capacity retention rate, and improving the electrochemical performance of zinc-ion batteries.

[0055] Example 4

[0056] Use the coal-based quantum dot nanomaterial prepared in Example 1 as an adjuvant for the copper oxide positive electrode material of the zinc-ion battery. The specific steps are as follows:

[0057] S1. Use the simple co-precipitation method to mix sodium hydroxide solution, CuSO4·5H2O, sodium citrate, and coal-based quantum dot solution to form a conversion-type copper-based electrode material that can provide an ideal redox potential and a high theoretical capacity.

[0058] S2. Uniformly coat the coal-based quantum dot-assisted conversion-type copper-based electrode material, Ketjen black, and PTFE on a stainless steel disc with a diameter of 12 mm in a ratio of 8:1:1 to obtain the positive electrode material, and assemble the zinc-ion battery. The assembly process is a conventional technology in this field.

[0059] The coal-based quantum dot nanomaterial prepared in Example 1 is applied to the positive electrode material of the zinc-ion battery. The modified zinc-ion battery shows excellent zinc storage performance. As Figure 7 shown, as Figure 7 known, at 0.1 Ag -1 −1, the discharge capacity of Cu2O-CDs is as high as 425 mAh g -1 −1, and there is still a discharge capacity of 260 mAh g -1 −1 after 100 cycles. The addition of the coal-based quantum dot nanomaterial helps to enhance the charge transfer ability of the electrode material.

[0060] The above are only the preferred embodiments of the present invention, which only describe the implementation manners of the present invention. It does not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A method for preparing coal-based quantum dot nanomaterials, characterized in that: The following steps are involved: S1. Add the coal-based raw material to a hydrochloric acid solution and a hydrofluoric acid solution in sequence for pickling and impurity removal, wash the precipitate to neutrality, and dry it to obtain the pickled coal-based raw material; S2, adding the acid-washed coal-based raw material obtained in step S1 into a reaction container, adding N,N-dimethylformamide (DMF), ultrasonically treating, heating to a predetermined temperature for reaction, and simultaneously dropping a hydrogen peroxide solution, and after the reaction is completed, auto-cooling to room temperature to obtain a cooled solution; S3, centrifuging the cooled solution obtained in step S2, taking the supernatant and dialyzing it in a dialysis bag, and freeze-drying the dialyzed solution to obtain a coal-based quantum dot nanomaterial; In step S1, the coal-based raw material is one or more of raw coal, semi-coke and liquefied residue.

2. The method for preparing coal-based quantum dot nanomaterials according to claim 1, characterized in that: In step S1, the concentration of the hydrochloric acid solution is 1-6 mol / L.

3. The method for preparing coal-based quantum dot nanomaterials according to claim 1, characterized in that: In step S1, the mass percentage concentration of HF in the hydrofluoric acid solution is 0.5-5%.

4. The method for preparing coal-based quantum dot nanomaterials according to claim 1, characterized in that: In step S1, the precipitate is placed in a vacuum drying oven and vacuum dried at a temperature of 60 to 100° C. for 12 to 48 hours.

5. The method for preparing coal-based quantum dot nanomaterials according to claim 1, characterized in that: In step S2, the temperature is raised to 60-100°C and the reaction is carried out for 0.5-2h.

6. The method for preparing coal-based quantum dot nanomaterials according to claim 1, characterized in that: In step S2, the mass fraction of the hydrogen peroxide solution is 10-30%.

7. The method for preparing coal-based quantum dot nanomaterials according to claim 1, characterized in that: In step S3, the cooled solution is centrifuged at a speed of 6000 to 10000 r / min for 5 to 30 min.

8. A coal-based quantum dot nanomaterial, characterized in that: The method for preparing the coal-based quantum dot nanomaterial according to any one of claims 1 to 7 is used.

9. Use of the coal-based quantum dot nanomaterial in battery separators according to claim 8 as a battery separator modification material.

10. Use of the coal-based quantum dot nanomaterial according to claim 8 in zinc ion battery electrode materials, using it as an auxiliary agent for copper oxide positive electrode materials of zinc ion batteries.

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