Au nanoparticle modified three-dimensional pine needle-like TiO2 nanotube array, preparation method and application thereof

Abstract

The application discloses Au nanoparticle modified three-dimensional loose needle-shaped TiO2 nanotube arrays and a preparation method and application thereof. The preparation method comprises the following steps: uniformly mixing potassium titanium oxalate, diethylene glycol and deionized water, then performing hydrothermal reaction, performing solid-liquid separation, water washing, drying and first annealing to obtain the three-dimensional loose needle-shaped TiO2 nanotube arrays; depositing Au nanoparticles on the surface of the three-dimensional loose needle-shaped TiO2 nanotube arrays by a magnetron sputtering method, then performing second annealing to obtain the Au nanoparticle modified three-dimensional loose needle-shaped TiO2 nanotube arrays. The simple hydrothermal method is used to prepare three-dimensional loose needle-shaped anatase TiO2, and the magnetron sputtering method is combined to obtain an anatase TiO2-based heterostructure photocatalyst with more active sites and faster electron transmission speed, so that CO2 can be more effectively reduced into CO.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic reduction of CO2 to CO, and in particular to a three-dimensional pine needle-like TiO2 nanotube array modified with Au nanoparticles, its preparation method and application. Background Technology

[0002] The increasing consumption of fossil fuels worldwide has accelerated global energy consumption, leading to a surplus of carbon dioxide production and contributing to the energy crisis and global climate change. Therefore, the development of renewable, green, and alternative energy sources is urgently needed. Inoue et al. utilized semiconductor materials such as WO3, TiO2, and CdS to reduce CO2 to hydrocarbons such as CO, CH4, CH3OH, and HCOOH, and analyzed the reaction mechanism of photocatalytic CO2 reduction, opening up a new direction in the field of semiconductor photocatalytic CO2 reduction. Consequently, research on the use of solar energy for photocatalytic water reduction of CO2 to produce renewable hydrocarbon fuels based on semiconductors has received considerable attention in recent years. Research on CO2 capture, storage, and conversion is increasingly valued, and developing green and clean CO2 conversion technologies is crucial in this field.

[0003] Titanium dioxide is widely used in photocatalysis, particularly in water splitting, organic pollutant degradation, and CO2 reduction, due to its low cost, non-toxicity, and good photostability. However, its photocatalytic performance is limited by its wide bandgap (lacking visible light absorption) and high electron-hole recombination rate. Over the past few decades, researchers have focused on improving the photocatalytic efficiency of titanium dioxide, including broadening its response range to the solar spectrum and enhancing the efficient separation and transport of electron-hole pairs. One of the most widely used methods is surface modification of titanium dioxide, such as altering its morphology, surface area, surface defects, impurity doping, and metal deposition.

[0004] When modifying the surface of titanium dioxide with nano-metal deposition, metal nanoparticles are generally prepared in situ using a seeding method. This method is complex and prone to introducing impurities. Alternatively, metal nanoparticles can be introduced through magnetron sputtering, but this often results in uneven distribution of the nanoparticles. For example, Chinese patent CN 104404565 B discloses an Au / TiO2 nanotube composite photoelectrode and its preparation method. This patent first prepares TiO2 nanotubes using anodizing, and then sputters an Au thin film onto the nanotubes followed by annealing to obtain the Au / TiO2 composite structure. This method results in Au nanoparticles being distributed only at one end of the nanotube, rather than throughout the entire nanotube, failing to achieve uniform distribution of Au nanoparticles. This leads to a significant reduction in active sites, which is detrimental to improving the catalytic effect. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose an Au nanoparticle-modified three-dimensional pine needle-like TiO2 nanotube array, its preparation method and application, thereby solving the technical problems of complex preparation technology of Au nanoparticle-modified TiO2 composite materials and poor photocatalytic effect caused by the difficulty in controlling the distribution of metal nanoparticles in the existing technology.

[0006] In a first aspect, the present invention provides a method for preparing a three-dimensional pine needle-like TiO2 nanotube array modified with Au nanoparticles, comprising the following steps:

[0007] Potassium titanium oxalate, diethylene glycol, and deionized water were mixed evenly, and then the reaction solution was subjected to a hydrothermal reaction. After the hydrothermal reaction was completed, the solution was separated into solid and liquid, washed with water, dried, and subjected to a first annealing to obtain a three-dimensional pine needle-like TiO2 nanotube array.

[0008] Au nanoparticles were deposited on the surface of a three-dimensional pine needle-shaped TiO2 nanotube array by magnetron sputtering, followed by a second annealing to obtain an Au nanoparticle-modified three-dimensional pine needle-shaped TiO2 nanotube array.

[0009] In a second aspect, the present invention provides an Au nanoparticle-modified three-dimensional pine needle-like TiO2 nanotube array, which is obtained by the preparation method of the Au nanoparticle-modified three-dimensional pine needle-like TiO2 nanotube array provided in the first aspect of the present invention.

[0010] Thirdly, the present invention provides an application of Au nanoparticles modified with a three-dimensional pine needle-like TiO2 nanotube array, which is used for photocatalytic reduction of CO2 to CO.

[0011] Compared with the prior art, the beneficial effects of the present invention include:

[0012] This invention utilizes a simple hydrothermal method to prepare three-dimensional needle-like anatase TiO2 and combines it with magnetron sputtering to obtain anatase TiO2-based heterostructure photocatalysts with multiple active sites and faster electron transport speeds. The nanotube array heterostructure of this invention can more effectively reduce CO2 to CO, showing great promise for photocatalytic CO2 reduction to produce carbon-based fuels and renewable energy. Attached Figure Description

[0013] Figure 1 The images shown are (a) scanning electron microscope (SEM) image (with the inserted portion being the corresponding SEM cross-sectional image) and (b) XRD pattern of the three-dimensional pine needle-like TiO2 nanotube array obtained in Example 1 of this invention.

[0014] Figure 2The images shown are scanning electron microscope (SEM) images of heterostructure samples obtained by depositing Au on the surface of pine needle-like TiO2 at different deposition times of 5, 10, and 15 min, as obtained in Example 1 of this invention: (a) Au (5 min) / TiO2, (b) Au (10 min) / TiO2, (c) Au (15 min) / TiO2, and (d), (e), and (f) are magnified SEM images of (a), (b), and (c), respectively.

[0015] Figure 3 XPS spectra of the Au(10min) / TiO2 heterostructure sample obtained in Example 1 of this invention: (a) Ti 2p; (b) O1s; (c) Au 4f;

[0016] Figure 4 The following are performance tests of the photocatalytic reduction of CO2 to CO obtained in Example 1 of this invention: (a) CO production curves of TiO2 and Au(10min) / TiO2 heterostructure composite materials over time, and (b) the cycle performance of photocatalytic reduction of CO2 to CO of Au(10min) / TiO2 heterostructure composite materials. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] In a first aspect, the present invention provides a method for preparing a three-dimensional pine needle-like TiO2 nanotube array modified with Au nanoparticles, comprising the following steps:

[0019] S1. Potassium titanium oxalate, diethylene glycol, and deionized water were mixed evenly, and then the reaction solution was subjected to a hydrothermal reaction. After the hydrothermal reaction, solid-liquid separation, washing, drying, and a first annealing were performed to obtain a three-dimensional pine needle-like TiO2 nanotube array. The concentration of potassium titanium oxalate in the reaction solution was 10–25 mg / mL, more preferably 15–20 mg / mL; the volume ratio of deionized water to diethylene glycol was 1:(3–6), more preferably 1:(4–5); the hydrothermal reaction temperature was 165–175℃, more preferably 170℃; the hydrothermal reaction time was 10–12 h, more preferably 11 h; drying was performed by nitrogen gas blowing; the first annealing temperature was 450–550℃, more preferably 500℃; the first annealing time was 0.5–1.5 h, more preferably 1 h. Hydrothermal preparation of TiO2 semiconductor materials is a common method, but different preparation conditions result in different morphologies and phase structures. This invention successfully prepared a three-dimensional pine needle-like TiO2 nanotube array in the anatase phase by strictly controlling the types and proportions of raw materials, as well as hydrothermal and annealing conditions. This facilitates the uniform loading of Au nanoparticles in the subsequent process. Furthermore, compared to rutile TiO2, anatase TiO2 is more suitable as a photocatalytic material because it is more easily photocatalyzed to generate electron-hole pairs, has a more negative conduction band potential, and exhibits stronger reduction properties due to the photogenerated electrons.

[0020] S2. Au nanoparticles were deposited on the surface of a three-dimensional pine needle-like TiO2 nanotube array by magnetron sputtering, followed by a second annealing to obtain an Au nanoparticle-modified three-dimensional pine needle-like TiO2 nanotube array. The sputtering power was 80–120 W, more specifically 100 W; the deposition time was 5–15 min, more specifically 10 min; the second annealing temperature was 400–500 °C, more specifically 450 °C; and the second annealing time was 5–15 min, more specifically 10 min.

[0021] This invention utilizes a one-step hydrothermal reaction combined with a simple and feasible magnetron sputtering system to successfully fabricate a high specific surface area three-dimensional pine needle-like hierarchical titanium dioxide nanotube array heterostructure loaded with Au nanoparticles. Under UV-Vis irradiation, this structure exhibits enhanced efficient light trapping due to plasmon resonance, which improves electron-hole pair generation, effectively separates charge carriers, and results in a higher specific surface area and faster charge transport speed. The three-dimensional pine needle-like nanostructure possesses a higher surface area and a longer effective light absorption path, providing abundant active sites for electrochemical reactions and an effective transport pathway for rapid charge transport, thereby improving electron collection and electron-hole separation. Furthermore, the anatase phase TiO2 is more readily photocatalyzed to generate electron-hole pairs, has a more negative conduction band potential, and exhibits stronger reduction performance in photogenerated electrons. This nanotube array heterostructure can effectively reduce CO2 to CO, showing great promise for the photocatalytic reduction of CO2 to prepare carbon-based fuels and renewable energy.

[0022] In a second aspect, the present invention provides an Au nanoparticle-modified three-dimensional pine needle-like TiO2 nanotube array, which is obtained by the preparation method of the Au nanoparticle-modified three-dimensional pine needle-like TiO2 nanotube array provided in the first aspect of the present invention.

[0023] Thirdly, the present invention provides an application of Au nanoparticles modified with a three-dimensional pine needle-like TiO2 nanotube array, which is used for photocatalytic reduction of CO2 to CO.

[0024] Example 1

[0025] (1) Clean the 3cm×3cm FTO glass. First, ultrasonically clean it with deionized water for 15min, then ultrasonically clean it with isopropanol and chloroform for 15min each, and set it aside. Dissolve 0.73g of potassium titanium oxalate in deionized water, then add diethylene glycol, where the volume ratio of deionized water to diethylene glycol is 1:4.7, keeping the total volume of the mixed solution at 40ml. Stir with a magnetic rod for 30min, then put the mixed solution into a 50ml reaction vessel. Place the reaction vessel in an oven and set the temperature in the oven to 170℃. React for 11h. After the sample is taken out, clean it with deionized water and dry it with a nitrogen gun. Anneal the prepared sample in a tube furnace at 500℃ for 1h in an air atmosphere to remove residual organic matter, and obtain a three-dimensional pine needle-like TiO2 nanotube array.

[0026] (2) After the successful preparation of the three-dimensional pine needle-like TiO2 nanotube array, Au nanoparticles were deposited on the three-dimensional pine needle-like TiO2 nanotube array film using simple magnetron sputtering to obtain a uniformly distributed Au / TiO2 composite heterostructure. The Au content could be controlled by simply adjusting the Au deposition time, with deposition times of 5, 10, and 15 min and an Au sputtering power of 100 W. Subsequently, the prepared samples were annealed in air at 450 °C for 10 min. The Au-deposited three-dimensional pine needle-like TiO2 nanotube heterostructure films were obtained and named Au(5 min) / TiO2, Au(10 min) / TiO2, and Au(15 min) / TiO2, respectively.

[0027] Please see Figure 1 The microstructure and morphological details of the three-dimensional pine needle-like TiO2 nanotube array obtained in Example 1 are as follows: Figure 1 As shown in (a), the inset is a cross-sectional view obtained by scanning electron microscopy (SEM). The SEM image reveals that a three-dimensional, pine-needle-like hierarchical TiO2 nanotube array, consisting of a vertically oriented nanotube trunk approximately 5 μm long grafted with numerous short branches approximately 300 nm long, was directly grown on an FTO substrate using a simple one-step hydrothermal method. The SEM results show that the three-dimensional TiO2 nanotube array can completely cover and uniformly arrange itself on the FTO glass, and can grow uniformly on a large scale. This three-dimensional structure gives the composite structure a larger specific surface area, which can increase active sites and effectively improve the direct charge transport path, thereby potentially enhancing the photocatalytic performance of TiO2. The structure of the three-dimensional pine-needle-like hierarchical TiO2 nanotube array was analyzed using XRD, as shown below. Figure 1 As shown in (b), XRD results show diffraction peaks at 25.4° and 38°, which are the (101) and (200) diffraction peaks of anatase TiO2 (JCPDS No. 21-1272). No characteristic peaks of any impurities were observed in the XRD, indicating that the method successfully prepared a three-dimensional pine needle-like anatase TiO2 nanotube array film.

[0028] Please see Figure 2 , Figure 2 (a), (b), and (c) are scanning electron microscope (SEM) images of the Au nanoparticle composite structure after deposition times of 5 min, 10 min, and 15 min, respectively. Figure 2 (d), (e), and (f) are respectively Figure 2 The corresponding magnified scanning electron microscope images (a), (b), and (c) show that Au nanoparticles are uniformly deposited on a three-dimensional pine needle-like TiO2 nanotube array. With increasing Au deposition time, the size of the Au nanoparticles significantly increases, indicating that this invention successfully prepared an Au / TiO2 hierarchical heterostructure nanotube array via a one-step hydrothermal reaction combined with a simple and feasible magnetron sputtering system.

[0029] The elemental chemical valence states of Au(10min) / TiO2 were analyzed using X-ray photoelectron spectroscopy (XPS), such as... Figure 3 As shown. Please refer to [the original text]. Figure 3 , Figure 3 (a) shows the XPS spectrum of Ti 2p. The figure shows that the binding energies of Ti 2p are 464.3 eV and 458.5 eV, respectively, corresponding to Ti 2p... 3 / 2 and Ti2p 1 / 2 The peak, which is related to Ti 4+ The ion binding energies are consistent. The O 1S peak is at 529.9 eV, which is a typical Ti-O-Ti signal, as shown below. Figure 3 As shown in (b). Figure 3 (c) shows the XPS spectral peaks of Au 4f at 82.8 and 86.6 eV, which belong to Au 4f, respectively. 7 / 2 and Au 4f 5 / 2 This proves that Au nanoparticles exist in metallic form in this structure.

[0030] The photocatalytic reduction performance of three-dimensional pine needle-like hierarchical TiO2 nanotube arrays and Au(10min) / TiO2 nanocomposite heterostructures was evaluated under UV-Vis irradiation. Figure 4 As shown. Please refer to [the original text]. Figure 4 ,from Figure 4 (a) It can be seen that the three-dimensional pine needle-like layered TiO2 nanotube array and the Au(10min) / TiO2 nanocomposite structure have a significant impact on the photocatalytic activity of CO2 photoreduction. Within 6 hours, the total CO release from the Au(10min) / TiO2 nanocomposite was 12 μmol / 10g, approximately 2.4 times that of the pure TiO2 nanotube array. To investigate the stability of the Au(10min) / TiO2 nanocomposite, a cycle performance test for CO2 photoreduction to CO was conducted 3 months after the first experiment. Figure 4 As shown in (b), under the same conditions, the Au(10min) / TiO2 nanocomposite material maintained high CO2 photoreduction photocatalytic activity after 3 months, indicating that the Au / TiO2 photocatalyst is very stable. When Au nanoparticles are coupled with TiO2, the LSPR effect enhances the local electric field, thereby increasing the absorption of light by TiO2 and improving the utilization rate of sunlight. On the other hand, the LSPR effect allows TiO2 to absorb low-energy photons and generate high-energy hot electrons, which can lower the CO2 activity barrier. In addition, Au nanoparticles can act as electron trap centers, effectively preventing electron-hole recombination, thereby effectively improving the photocatalytic reduction performance of CO2.

[0031] In summary, this invention successfully prepared a high specific surface area three-dimensional pine-tree-like hierarchical TiO2 nanotube array composite film loaded with Au nanoparticles via a one-step hydrothermal reaction combined with a simple and feasible magnetron sputtering system. The photoreduction of carbon dioxide results showed that the Au / TiO2 hierarchical nanotube array heterostructure exhibited excellent photocatalytic performance and stability. This invention overcomes the shortcomings of existing preparation techniques, such as complex processes and difficulty in controlling the distribution of metal nanoparticles, and provides a method for preparing Au / TiO2 hierarchical nanotube array heterostructures with high electron-hole pair generation rate, effective carrier separation, higher specific surface area, faster charge transport speed, good catalytic activity, and low cost. The films prepared by this method have high quality, high density, and high binding strength. Furthermore, the method is simple, easy to operate, the process is easy to control, and the production has good repeatability, making it suitable for large-area preparation.

[0032] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing Au nanoparticle decorated three-dimensional pine needle-like TiO2 nanotube arrays, characterized in that, The method comprises the following steps: mixing potassium titanyl oxalate, diethylene glycol and deionized water uniformly, then carrying out hydrothermal reaction on the reaction solution, carrying out solid-liquid separation, water washing, drying and first annealing after the hydrothermal reaction to obtain three-dimensional pine needle-like TiO2 nanotube arrays; depositing Au nanoparticles on the surface of the three-dimensional pine needle-like TiO2 nanotube arrays by a magnetron sputtering method, then carrying out second annealing to obtain Au nanoparticle modified three-dimensional pine needle-like TiO2 nanotube arrays; wherein, the concentration of the potassium titanyl oxalate in the reaction solution is 10-25 mg / mL, and the volume ratio of the deionized water to the diethylene glycol is 1:(3-6); the temperature of the hydrothermal reaction is 165-175 ℃, and the time of the hydrothermal reaction is 10-12 h; the temperature of the first annealing is 450-550 ℃, and the time of the first annealing is 0.5-1.5 h; in the process of the magnetron sputtering, the sputtering power is 80-120 W, and the deposition time is 5-15 min; the temperature of the second annealing is 400-500 ℃, and the time of the second annealing is 5-15 min.

2. The method for preparing Au nanoparticle modified three-dimensional pine needle-like TiO2 nanotube arrays according to claim 1, characterized in that, the concentration of the potassium titanyl oxalate in the reaction solution is 15-20 mg / mL, and the volume ratio of the deionized water to the diethylene glycol is 1:(4-5).

3. The method for preparing Au nanoparticle modified three-dimensional pine needle-like TiO2 nanotube arrays according to claim 1, characterized in that, the temperature of the hydrothermal reaction is 170 ℃, and the time of the hydrothermal reaction is 11 h.

4. The use of the Au nanoparticle modified three-dimensional pine needle-like TiO2 nanotube array prepared by the method of any one of claims 1 to 3, characterized in that, the Au nanoparticle modified three-dimensional pine needle-like TiO2 nanotube arrays are applied to photocatalytic reduction of CO2 into CO.

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