Irradiation Preparation Method of Nitrogen and Sulfur Co-Doped Titanium Dioxide Quantum Dot Graphene Aerogel

Abstract

The present invention relates to a method for irradiating and preparing a nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel. First, graphene oxide is prepared by a known technical method; it is dispersed in an acetic acid solution; then a titanium tetrabutoxide ethanol solution is added thereto and rapidly stirred and mixed; afterwards, it is transferred to a reaction kettle for hydrothermal reaction. After hydrothermal treatment, the reaction product is transferred to an ethanol solution, cysteine and polyethylene glycol are added thereto, and the pH of the mixed solution is adjusted to 8-10. Subsequently, the mixed solution is irradiated in a 2.5 MeV, 40 mA electron accelerator. Then, the irradiated reaction product is alternately washed with ethanol and deionized water, and then centrifuged and separated by a high-speed centrifuge. Finally, the solid obtained by centrifugation and separation is dried in a vacuum freeze dryer, and the nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material is obtained after drying. This preparation method is environmentally friendly, has a simple process, is convenient to operate, and is convenient for large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of chemical preparation, and particularly relates to a method for irradiating and preparing a nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel. Background Art

[0002] Titanium dioxide (TiO2) has the characteristics of low cost, excellent chemical stability, non-toxicity, etc., and is easy to synthesize different morphologies such as nanotube arrays or nanoparticles. Among them, the theoretical specific capacitance of anatase TiO2 is ~860 F g -1 , has a large voltage window, and the specific capacitance is almost constant, which can effectively compensate for its lower experimental specific capacitance. The above physical properties determine that TiO2 has strong application prospects in energy conversion and energy storage systems. Existing research has shown that when anatase is used as a supercapacitor material, it has shown pseudocapacitance behavior, and the contribution of its pseudocapacitance to the total charge storage increases with the decrease in particle size. Therefore, designing and preparing small-sized TiO2 electrode materials has a certain promoting effect on improving its pseudocapacitance capacity.

[0003] As a transition metal oxide, the inherent insulation of TiO2 leads to low surface reaction efficiency, which hinders its application in the field of energy storage materials. Therefore, improving the conductivity is extremely important for titanium dioxide. Composite with carbon-based conductive materials is also an effective way to improve the conductivity and electrochemical performance of materials. Among them, graphene aerogel has a three-dimensional conductive network and high chemical stability, and can be used as an ideal platform for composite with metals, metal oxides, and conductive polymers for supercapacitor energy storage applications. In addition, the conductivity of the material can also be improved by introducing oxygen vacancies or heteroatom doping. Both of these introduce donor states below the conduction band, and these donor states are easily ionized and increase the charge carrier density of anatase. There has been research on doping fluorine atoms into anatase titanium dioxide, where monovalent fluorine replaces oxygen atoms, and the extra electrons related to oxygen reduce titanium from Ti 4+ to Ti 3+ state. Electrochemical characterization shows that its electron carrier density, local conductivity, and specific capacitance all increase. In recent years, doping heteroatoms into graphene has become an effective strategy to improve the electrochemical capacity of graphene. These heteroatoms can generate defects, improve the conductivity of graphene, and make the doped graphene material have better capacitance performance.

[0004] The reported methods for preparing quantum dot-level TiO2 particles mainly include chemical solution growth method, epitaxial growth method, and electric field confinement method. Most of them have high costs, harsh reaction conditions, and long reaction times, which are not conducive to large-scale production. For the preparation methods of heteroatom doping, defect modification of TiO2, and composite with carbon-based conductive substrates, they mainly include chemical deposition method, separation growth method, arc discharge method, plasma treatment and other methods. Most of these methods require the use of a large amount of chemical reagents that are toxic and harmful to the environment, and have low reaction efficiency and limited yield, making it difficult to meet the needs of practical applications.

[0005] Therefore, it is necessary to invent an irradiation preparation method for nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel. Summary of the Invention

[0006] The purpose of the present invention is to provide an irradiation preparation method for nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel in view of the deficiencies in the prior art. This method first uses the hydrothermal method to prepare an amorphous titanium dioxide colloid and graphene aerogel composite material. Then, under the condition of high-energy pulsed electron beam irradiation, the amorphous titanium dioxide colloid grows on the surface of the graphene aerogel to form titanium dioxide quantum dots about 10 nm in size, and at the same time, two heteroatoms, nitrogen and sulfur, are doped into the composite material. The method of the present invention has the advantages of simple process, mild reaction conditions, green and environmentally friendly synthesis method, cheap and easily available raw materials, being suitable for large-scale production needs, and the nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material prepared by this method has good supercapacitor performance.

[0007] To achieve the above purpose, the present invention provides the following technical solution: An irradiation preparation method for nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel, comprising the following steps:

[0008] S1, Disperse 80 mg of graphene oxide in 20 mL of deionized water, place it in an ultrasonic oscillator and ultrasonically disperse it evenly to obtain a graphene oxide suspension, and dropwise add 50 - 150 mL of acetic acid to it while stirring.

[0009] S2, Add 2 - 3 mL of ethanol solution of tetrabutyl titanate to the mixed solution obtained in the above step S1, and stir vigorously to mix.

[0010] S3, Transfer the mixed solution obtained in the above step S2 to a stainless steel autoclave with a Teflon lining, and perform hydrothermal treatment at 150 - 200 °C for 10 - 16 hours.

[0011] S4, After hydrothermal treatment, centrifuge and separate the product obtained in step S3, take 0.5 g after freeze-drying, and disperse it in 500 mL of 70% - 95% ethanol aqueous solution.

[0012] S5. To the mixed solution obtained in step S4, add 0.3 - 0.6 g of cysteine and 50 - 100 mg of polyethylene glycol 1500 (PEG - 1500), and adjust the pH of the solution to 8 - 10 with ammonia water.

[0013] S6. Put the mixed solution obtained in step S5 above into an irradiation bag, seal it, and place it in a 2.5 MeV, 40 mA electron accelerator for irradiation. The irradiation dose is 70 - 280 kGy to obtain an irradiated reaction product.

[0014] S7. Wash the irradiated product obtained in step f alternately with ethanol and deionized water, and then centrifuge and separate it with a high - speed centrifuge.

[0015] S8. Place the product obtained in step S7 in a vacuum freeze - dryer, and freeze - dry it for 24 - 48 hours at a temperature of - 50°C and a vacuum degree of 20 Pa to obtain a black solid nitrogen - sulfur co - doped titanium dioxide quantum dot graphene aerogel composite material.

[0016] Preferably, in step S2, the volume ratio of the ethanol solution is 1:6 - 1:10.

[0017] The beneficial effects of the present invention are as follows:

[0018] The process of the present invention is simple, the reaction conditions are mild. By using the irradiation method, nitrogen - sulfur co - doping is completed while generating titanium dioxide quantum dots. Moreover, the synthesis method is green and environmentally friendly, the raw materials are cheap and easily available, and it meets the needs of large - scale production. The prepared nitrogen - sulfur co - doped titanium dioxide quantum dot graphene aerogel composite material has good supercapacitor performance. The electron accelerator used in the method of the present invention has an accelerating electron energy of 0.1 to 5 MeV and an electron beam current intensity adjustable from 0.1 to 100 mA. Description of the Drawings

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained according to the provided drawings.

[0020] The structures, ratios, sizes, etc. depicted in this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have a technical essence. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention.

[0021] Figure 1 Transmission electron microscopy (TEM) image of the nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite prepared in the embodiment of the present invention;

[0022] Figure 2 Scanning transmission image of the nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite prepared in the embodiment of the present invention and elemental distribution maps of carbon, nitrogen, oxygen, sulfur, and titanium;

[0023] Figure 3 High-resolution X-ray photoelectron spectroscopy (XPS) spectrum of titanium element in the nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite prepared in the embodiment of the present invention;

[0024] Figure 4 Cyclic stability test chart of the nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite prepared in the embodiment of the present invention at a current density of 5 A g -1 for 5000 charge-discharge cycles. Detailed implementation manners

[0025] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0026] Referring to the attached Figures 1-4 drawings, an irradiation preparation method of a nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel provided by the present invention includes the following steps:

[0027] S1, Disperse 80 mg of graphene oxide in 20 mL of deionized water, place it in an ultrasonic oscillator for ultrasonic dispersion to obtain a graphene oxide suspension, and gradually add 50 - 150 mL of acetic acid dropwise while stirring;

[0028] S2, Add 2 - 3 mL of an ethanol solution of tetrabutyl titanate to the mixed solution obtained in step S1 above, and stir vigorously to mix;

[0029] S3, Transfer the mixed solution obtained in step S2 above to a stainless steel autoclave with a Teflon lining, and perform hydrothermal treatment at 150 - 200 °C for 10 - 16 hours;

[0030] S4, After hydrothermal treatment, centrifuge the product obtained in step S3, take 0.5 g after freeze-drying, and disperse it in 500 mL of a 70% - 95% ethanol aqueous solution;

[0031] S5, Add 0.3 - 0.6 g of cysteine and 50 - 100 mg of polyethylene glycol 1500 (PEG-1500) to the mixed solution obtained in step S4, and adjust the pH of the solution to 8 - 10 with ammonia water.

[0032] S6. Place the mixed solution obtained in the above step S5 into an irradiation bag, seal it, and place it in a 2.5 MeV, 40 mA electron accelerator for irradiation. The irradiation dose is 70 - 280 kGy to obtain an irradiated reaction product.

[0033] S7. Wash the irradiated product obtained in step f alternately with ethanol and deionized water, and then centrifuge and separate it with a high-speed centrifuge.

[0034] S8. Place the product obtained in step S7 into a vacuum freeze dryer, and freeze-dry it for 24 - 48 hours at a temperature of -50 °C and a vacuum degree of 20 Pa to obtain a black solid nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material.

[0035] In the above step S2, the volume ratio of the ethanol solution is 1:6 - 1:10.

[0036] To verify the successful synthesis of the nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material by the electron beam irradiation method of the present invention, its morphology and composition were characterized. Figure 1 This is a transmission electron microscope (TEM) photo of the nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material prepared in this example. In the figure, it can be observed that titanium dioxide quantum dots with a particle size of about 10 nm are evenly distributed on the graphene aerogel. Figure 2 This is a scanning transmission image and element distribution maps of carbon, nitrogen, oxygen, sulfur, and titanium of the nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material prepared in this example. Figure 2 a It can be seen that small particles of titanium dioxide quantum dots are evenly dispersed on the graphene aerogel. Figure 2 b - f It can be seen that the five elements of carbon, nitrogen, oxygen, sulfur, and titanium are evenly distributed in the composite material, proving that the material contains these five elements. Figure 3 This is a high-resolution X-ray photoelectron spectroscopy (XPS) spectrum of titanium element of the nitrogen-sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material prepared in this example. In the figure, the horizontal axis represents the electron binding energy (eV), and the vertical axis represents the diffraction intensity. The titanium element in the figure shows the characteristic peak of Ti 3+ indicating that oxygen vacancies are formed on its surface by electron beam irradiation.

[0037] Testing of supercapacitor performance:

[0038] To verify the performance of the nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material synthesized by the electron beam irradiation method of the present invention, the prepared nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material was mixed according to the ratio of active material: acetylene black: polytetrafluoroethylene (PTFE) = 80:10:10, and adjusted into a uniform slurry with isopropanol. The slurry was coated on the cleaned nickel foam (1 cm × 1.5 cm), and the coating area was 1 cm × 1 cm. Then it was pressed into shape by a tablet press to make an electrode. Subsequently, the electrode was placed in a vacuum oven and dried at 60 °C, and then immersed in 6 M KOH solution for 24 hours to fully immerse the electrode material in the electrolyte. The chronopotentiometry and cyclic voltammetry characteristics of the material were tested using an electrochemical workstation. Among them, the scanning rate of CV was 5 mV s -1 ~100 mV s -1 , and the EIS frequency range was from 0.01 to 105 Hz. Figure 4 is the cyclic stability test diagram of the nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material prepared in this example at a current density of 5 A g -1 . In the figure, the abscissa represents the number of cycles, and the ordinate represents the specific capacity (F / g) and retention efficiency. The results show that after 5000 charge and discharge cycles, its specific capacity still remains 78.3%, showing excellent cyclic stability.

[0039] The above are only the preferred embodiments of the present invention. Any person skilled in the art may modify the present invention by using the technical solutions described above or modify them into equivalent technical solutions. Therefore, any simple modification or equivalent replacement made according to the technical solutions of the present invention falls within the scope of protection required by the present invention.

Claims

1. An irradiation preparation method of nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel, characterized in that: It includes the following steps: S1. Disperse 80 mg of graphene oxide in 20 mL of deionized water, place it in an ultrasonic oscillator for ultrasonic dispersion until uniform to obtain a graphene oxide suspension, and gradually add 50 - 150 mL of acetic acid dropwise while stirring; S2. Add 2 - 3 mL of an ethanol solution of tetrabutyl titanate to the mixed solution obtained in the above step S1, and stir vigorously to mix; S3. Transfer the mixed solution obtained in the above step S2 to a Teflon-lined stainless steel autoclave, and perform hydrothermal treatment at 150 - 200 °C for 10 - 16 hours; S4. After hydrothermal treatment, centrifuge the product obtained in step S3, take 0.5 g after freeze-drying, and disperse it in 500 mL of a 70% - 95% ethanol aqueous solution; S5. Add 0.3 - 0.6 g of cysteine and 50 - 100 mg of polyethylene glycol 1500 (PEG - 1500) to the mixed solution obtained in step S4, and adjust the pH of the solution to 8 - 10 with ammonia water; S6. Put the mixed solution obtained in the above step S5 into an irradiation bag, seal it and place it in a 2.5 MeV, 40 mA electron accelerator for irradiation, with an irradiation dose of 70 - 280 kGy to obtain an irradiated reaction product; S7. Wash the irradiated product obtained in step f alternately with ethanol and deionized water, and then centrifuge it with a high-speed centrifuge; S8. Place the product obtained in step S7 in a vacuum freeze dryer, and freeze-dry it at a temperature of -50 °C and a vacuum degree of 20 Pa for 24 - 48 hours to obtain a black solid nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel composite material.

2. The irradiation preparation method of nitrogen and sulfur co-doped titanium dioxide quantum dot graphene aerogel according to claim 1, characterized in that: In the above step S2, the volume ratio of the ethanol solution is 1:6 - 1:10.

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