A method for preparing a fluorine-induced defect type titanium dioxide-based composite material and applications thereof

Abstract

The present application belongs to the field of material preparation, by adding titanium n-butoxide into the polytetrafluoroethylene kettle, then dropping into hydrofluoric acid solution and ultrasonicating at room temperature, heating at 190 DEG C for 24 hours, collecting titanium dioxide powder. The obtained titanium dioxide powder and copper nitrate are added into deionized water and stirred and mixed, and after vacuum rotary evaporation, a titanium dioxide-based composite material is obtained. The obtained titanium dioxide-based composite material and ammonium fluoride are added into an organic solvent, and after hydrothermal reaction, a defective titanium dioxide-based composite material is finally obtained. The defective titanium dioxide-based composite material is prepared by synthesis, and is applied to photocatalytic reduction of carbon dioxide, and has potential application value in the field of photocatalysis.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation and photocatalysis. Specifically, it proposes a method for preparing a defective titanium dioxide-based composite material initiated by fluorine, which is then used for photocatalytic reduction of carbon dioxide. Background Technology

[0002] Human survival and sustainable social development depend on a continuous supply of energy. Our energy resources primarily rely on fossil fuels such as coal, oil, and natural gas. These non-recyclable energy sources account for 80% of the world's total energy supply. The limited reserves of fossil fuels and the unrestrained exploitation by humans have not only led to energy shortages but also caused severe environmental pollution and climate change. Effectively reducing atmospheric CO2 levels has become a significant challenge for contemporary science. While excessive CO2 emissions severely impact human life, CO2 is also a potential carbon resource, characterized by its low cost, wide distribution, and large reserves. Converting CO2 into valuable compounds, such as carbon monoxide (CO), methane (CH4), methanol (CH3OH), and ethanol (CH3CH2OH), can effectively mitigate global warming. Since Inoue et al. first reported the photocatalytic reduction of CO2 on semiconductor materials in 1979, TiO2 has become a favored photocatalyst due to its availability, stability, low cost, and low toxicity. However, the efficiency of TiO2 photocatalytic reactions is relatively low due to the rapid recombination of photogenerated electron-hole pairs and the limited utilization of solar energy. Furthermore, the weak adsorption and interaction of CO2 on the TiO2 surface also limits the efficiency of CO2 photocatalytic reduction.

[0003] Numerous methods for improving the photocatalytic reduction efficiency of TiO2 have been reported, including preparing TiO2 with different structures or morphologies, modifying TiO2 with noble metals, and combining TiO2 with other materials. However, for commercial viability, their quantity, cost, and toxicity have become issues. One interesting approach to address this problem is the use of single-atom photocatalysts. The idea of ​​utilizing atomic efficiency for photocatalytic CO2 reduction has recently attracted considerable attention. To better utilize visible light in the solar spectrum, researchers have undertaken extensive work, such as defect engineering using self-doping or heteroatom doping in TiO2 catalysts. Certain defects in semiconductor crystals can modulate the electronic structure, improve surface properties, reduce the adsorption energy of intermediate products, and ultimately accelerate photocatalytic reaction kinetics.

[0004] In this invention, TiO2 with a specific defect structure induced by fluoride ions has a high reduction capacity for CO2, and the constructed defective titanium dioxide-based composite material is of great research significance for promoting the activation and reduction of CO2. Summary of the Invention

[0005] The purpose of this invention is to synthesize a fluorine-initiated defective titanium dioxide-based composite material for photocatalytic reduction of carbon dioxide. This invention promotes further research on titanium dioxide-based composite materials and provides a theoretical basis for understanding the photocatalytic mechanism.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing a fluorine-initiated defect-type titanium dioxide-based composite material includes the following steps: (1) Add titanium butoxide to a polytetrafluoroethylene reactor, then add hydrofluoric acid solution dropwise and sonicate at room temperature for 1 hour. Seal the autoclave and heat at 190 °C for 24 hours to obtain titanium dioxide powder.

[0007] (3) Add titanium dioxide powder and copper nitrate into deionized water and stir for 12 hours, and then evaporate under vacuum to obtain titanium dioxide-based composite material.

[0008] (2) The prepared titanium dioxide-based composite material and ammonium fluoride were added to isopropanol, stirred, and hydrothermally reacted at 120°C for 20 hours to obtain the defective titanium dioxide-based composite material. The volume ratio of titanium butoxide and hydrofluoric acid solution in step (1) is 25:5; wherein the concentration of hydrofluoric acid solution is 40wt%.

[0009] The mass ratio of titanium dioxide to copper nitrate in step (2) is 100:1.

[0010] The mass ratio of the titanium dioxide-based composite material and ammonium fluoride in step (3) is 3:4.

[0011] Application: The defective titanium dioxide-based composite material is used in the photocatalytic reduction of carbon dioxide to produce carbon monoxide.

[0012] The significant advantages of this invention are: 1) This invention obtains a defective titanium dioxide-based composite material by using titanium butoxide, hydrofluoric acid, isopropanol, ammonium fluoride and copper nitrate through a series of methods. The resulting material has more surface defects and heteroatoms, which is beneficial to the transport of electrons and holes and exhibits good activity in the photocatalytic decomposition and reduction of carbon dioxide.

[0013] 2) The equipment and chemical reagents used in the synthesis method of the present invention are readily available, the process is simple to operate, the process conditions are simple, the applicability is strong, the industrial application value is high, and it is easy to promote and utilize. Attached Figure Description

[0014] Figure 1This is the X-ray powder diffraction pattern of CuFT obtained through experiments and fitting; the agreement between the experimental and fitting results indicates the successful synthesis of CuFT. Figure 2 This is a SEM image of CuFT; it can be observed that CuFT has a nanosheet morphology with a specific surface area of ​​approximately 40 m². 2 / g, with a particle size of approximately 100 nm; Figure 3 This is the UV-Vis absorption spectrum of CuFT; the absorption range of CuFT covers the UV spectral region; Figure 4 This is the Cu 2p X-ray photoelectron spectrum of CuFT; the experimental results show that the Cu loading was successful. Figure 5 This is the O 1s X-ray photoelectron spectrum of CuFT; the experimental results show that oxygen vacancies exist in titanium dioxide. Figure 6 This is a graph showing the yield of CuFT in the photocatalytic reduction of carbon dioxide to carbon monoxide under full light conditions as a function of cycle number: Figure 7 The product was prepared without Cu and F doping, and the other preparation conditions were the same as in Example 1. A comparative diagram of the resulting products is shown below: Figure 8 The product was not Cu-doped, and the other preparation conditions were the same as in Example 1. The resulting products are plotted in a comparison graph. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer and easier to understand, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0016] Example 1 25 ml of titanium n-butoxide was added to a polytetrafluoroethylene reactor, followed by the dropwise addition of 5 ml of hydrofluoric acid solution (volume ratio 25:5) and sonication at room temperature for 1 hour. The autoclave was then sealed and heated at 190 °C for 24 hours. After the hydrothermal reaction, the white precipitate was collected and placed in a muffle furnace and heated at 500 °C for 2 hours to collect the prepared titanium dioxide powder.

[0017] Weigh 100 mg of titanium dioxide powder and 1 mg of copper nitrate, add them to 50 mL of deionized water, sonicate for 30 min, stir for 12 h, and then vacuum evaporate at 50 °C for 2 h to obtain a 1 wt% Cu-TiO2 sample.

[0018] Cu-TiO2 (300 mg) and ammonium fluoride (400 mg) were added to 60 ml of isopropanol, stirred and hydrothermally reacted at 120 °C for 20 hours. After cooling to room temperature, the mixture was washed three times with deionized water and vacuum dried at 60 °C for 12 hours to obtain a light blue powder CuFT.

[0019] Comparative Example 1 Without Cu or F doping, and with the other preparation conditions the same as in Example 1, the resulting products were used as comparative examples for photocatalytic performance comparison. The reason for the poorer application effect compared to Example 1 is that Cu can promote CO2 adsorption and the separation of photogenerated electrons and holes. F can promote water dissociation, CO2 adsorption, and increase the reduction potential of titanium dioxide, thereby enhancing its reduction capacity for CO2.

[0020] Comparative Example 2 Without Cu doping, the preparation conditions were the same as in Example 1. The resulting product was used as a comparative example for photocatalytic performance comparison. The reason for the poorer application effect compared to Example 1 is that the visible light absorption range was reduced, and the adsorption of CO2 and the separation of photogenerated electrons and holes were also reduced.

[0021] Application Example 1 10 mg of CuFT sample was weighed and placed in a quartz dish, 2 mL of water was added, and the mixture was sonicated for 5 minutes and then dried at 70°C for 1 hour. The dish was then placed in a quartz glass reactor, separated by a perforated quartz sheet. 10 mL of water was added to the bottom of the reactor. The reactor was evacuated and CO2 gas was introduced. Full-light irradiation was simulated using a 300 W xenon lamp at 290–398 K. During the photocatalytic reaction, the gas composition after the photocatalytic reaction was detected by gas chromatography every hour. After four hours of irradiation, the average value was calculated. The quartz dish was then removed and placed in the dark for 6 hours, and then placed back into the quartz glass reactor, separated by a perforated quartz sheet. 10 mL of water was added to the bottom of the reactor, and the reactor was evacuated. Full-light irradiation was simulated using a 300 W xenon lamp at 290–398 K. This cycle was repeated three times, and the yield of carbon dioxide to carbon monoxide was calculated for each cycle.

[0022] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. The application of a defective titanium dioxide-based composite material in the photocatalytic reduction of carbon dioxide to carbon monoxide, characterized in that: The preparation method of the defective titanium dioxide-based composite material includes the following steps: (1) Add titanium butoxide to a polytetrafluoroethylene reactor, then add hydrofluoric acid solution dropwise and sonicate at room temperature for 1 hour. Seal the autoclave and heat at 190 °C for 24 hours to obtain titanium dioxide. (2) Add titanium dioxide and copper nitrate to deionized water and stir for 12 hours, then evaporate under vacuum to obtain titanium dioxide-based composite material; (3) Add the titanium dioxide-based composite material and ammonium fluoride into a polytetrafluoroethylene reactor containing isopropanol, and after hydrothermal reaction at 120 °C for 20 hours, collect the light gray precipitate to obtain the defective titanium dioxide-based composite material. The volume ratio of titanium butoxide and hydrofluoric acid solution in step (1) is 25:5; wherein the concentration of hydrofluoric acid solution is 40 wt%. The mass ratio of titanium dioxide to copper nitrate in step (2) is 100:1; The mass ratio of the titanium dioxide-based composite material to ammonium fluoride in step (3) is 3:4; The defective titanium dioxide-based composite material exhibits oxygen vacancies and Cu... 0 / Cu + .

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