Barium ion single-doped / double-doped brookite titanium dioxide nanorod catalyst and preparation and application thereof

Abstract

The invention discloses a barium ion single-doped / double-doped brookite titanium dioxide nanorod catalyst as well as preparation and application, the catalyst synthesized by a thermal decomposition method comprises brookite phase titanium dioxide and doped barium ions, and the nanorod-shaped catalyst containing oxygen vacancy defects has the width of 4-6 nanometers and the length of 20-50 nanometers. The piezoelectric property of brookite titanium dioxide is induced through doping of barium ions, charge separation is promoted through a built-in electric field, meanwhile, oxygen vacancies are induced through a charge compensation mechanism, the piezoelectric catalysis and photocatalytic efficiency is promoted, and the problems mentioned in the background technology are solved.

Description

Technical Field

[0001] The present invention relates to a technology in the fields of photocatalysis and piezocatalysis, specifically a barium ion single-doped / double-doped perovskite titanium dioxide nanorod catalyst and its preparation and application. Background Art

[0002] Titanium dioxide is a benchmark photocatalyst for basic theoretical research and practical applications, and is also the only commercially produced semiconductor photocatalyst at present. It has characteristics such as chemical stability, economy, and high reactivity, and has great application potential in fields such as water splitting, pollutant degradation, and solar cells. However, its wide bandgap leads to low solar energy utilization; at the same time, the rapid recombination of carriers limits its photocatalytic effect. Piezocatalysis is also an efficient and environmentally friendly advanced oxidation process, and because the piezoelectric potential can act as an internal electric field, the electron-hole pairs can be effectively separated. Through piezopolarization, the charge separation in both the bulk and the surface can be promoted simultaneously, which is conducive to achieving higher catalytic efficiency. However, there is currently a lack of a method for inducing the piezoelectricity of single-phase titanium dioxide in the current research. Summary of the Invention

[0003] Aiming at the deficiency that the prior art cannot prepare ultra-small and uniform one-dimensional doped titanium dioxide nanorods, the present invention provides a barium ion single-doped / double-doped perovskite titanium dioxide nanorod catalyst and its preparation and application. By doping barium ions to induce the piezoelectricity of perovskite titanium dioxide, the internal electric field promotes charge separation. At the same time, oxygen vacancies are induced through the charge compensation mechanism to promote the piezocatalytic and photocatalytic efficiency, solving the problems mentioned in the above background art.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a barium ion-doped perovskite titanium dioxide nanorod catalyst, which includes titanium dioxide in the perovskite phase and doped barium ions. The width of the catalyst in the form of nanorods containing oxygen vacancy defects is 4-6 nanometers, and the length is 20-50 nanometers.

[0006] The barium ions exist in the form of Ba 2+ , and its doping concentration is 0.05-10 mol% of the titanium ion content, so as to induce the piezoelectricity of perovskite titanium dioxide. The piezopolarization promotes charge separation, and can further improve the catalytic efficiency of the nanorods.

[0007] The oxygen vacancy defects are used for electron capture traps to promote charge separation.

[0008] The doping is single doping of barium ions or double doping of barium ions and transition metals or rare earth elements, preferably double doping of barium ions and elements such as iron, cobalt, nickel, vanadium, chromium, lanthanum, cerium, praseodymium, neodymium, erbium or thulium. Among them, when double doping, the content of each ion is 0.05-10 mol%.

[0009] The present invention relates to a preparation method of the above-mentioned double-doped brookite titanium dioxide nanorod catalyst, which comprises the following steps:

[0010] S1. Using sodium oleate, chloride salt, ethanol, and n-hexane as raw materials, heating and reacting after mixing with deionized water to prepare oleate salts;

[0011] The chloride salt mentioned refers to chloride salts of barium ions, transition metal ions, or rare earth ions.

[0012] The heating reaction mentioned refers to: after adding deionized water, heating to 60 - 80 °C and stirring for 2 - 5 h, and after sufficient reaction, taking the oil phase to dry to obtain the corresponding oleate salts.

[0013] The addition ratio of sodium oleate, chloride salt, ethanol, n-hexane, and deionized water is 12 - 48 mmol: 6 - 24 mmol: 16 - 64 mL: 28 - 112 mL: 12 - 48 mL.

[0014] S2. Mixing barium oleate, oleate salts, oleic acid, oleylamine, and 1-octadecene, injecting titanium tetrachloride under a nitrogen atmosphere, heating and reacting sufficiently, and then extracting the precipitate to obtain double-doped brookite titanium dioxide nanorods.

[0015] The sufficient heating reaction mentioned refers to: heating to 240 °C - 320 °C and maintaining the reaction for 0.5 - 1.5 h until the reaction is sufficient.

[0016] The addition ratio of oleic acid, oleylamine, 1-octadecene, and titanium tetrachloride is 3 - 12 mL: 9 - 36 mL: 8 - 32 mL: 0.2 - 4 mmol; preferably 6 mL: 18 mL: 16 mL: 0.40 mmol.

[0017] The molar ratio of the addition amounts of barium oleate and titanium tetrachloride is 0.05 - 80%.

[0018] The present invention relates to a preparation method of the above-mentioned single-doped brookite titanium dioxide nanorod catalyst. Mix barium oleate, oleic acid, oleylamine, and 1-octadecene, inject titanium tetrachloride under a nitrogen atmosphere, heat and react sufficiently, and then extract the precipitate to obtain single-doped brookite titanium dioxide nanorods.

[0019] The present invention relates to the application of the above-mentioned nanorod catalyst, specifically: as a photocatalyst or as a piezoelectric catalyst to remove organic pollutants or biological pathogens. Technical effects

[0020] The present invention synthesizes barium ion single-doped / double-doped brookite titanium dioxide nanorod catalysts with piezoelectricity by a thermal decomposition method. The operation method is simple, and the morphology presents a one-dimensional nanorod shape. The prepared nanorods can also be transferred into the aqueous phase by connecting hydrophilic ligands through a ligand exchange method to increase their availability. The barium ion single-doped / double-doped prepared generates oxygen vacancy defects in brookite titanium dioxide, which act as electron capture traps to promote charge separation. The barium ion single-doped / double-doped induces lattice distortion to endow brookite titanium dioxide with piezoelectricity. Polarization promotes the separation of bulk charges, endows titanium dioxide with piezoelectric catalytic properties, and improves its efficiency in photocatalysis at the same time. Description of the Drawings

[0021] Figure 1 Schematic diagram of the mechanism of barium ion single-doped / double-doped brookite titanium dioxide nanorod catalysts;

[0022] Figure 2 Transmission electron microscope schematic diagram of barium ion-doped brookite titanium dioxide nanorod catalysts prepared in Example 2;

[0023] Figure 3 HAADF-STEM image of barium ion-doped brookite titanium dioxide nanorod catalysts prepared in Example 2 and elemental distributions of corresponding EDS-mapping Ba, Ti, and O;

[0024] Figure 4 XRD pattern of barium ion-doped brookite titanium dioxide nanorod catalysts prepared in Example 3;

[0025] Figure 5 EPR spectrum of barium ion-doped brookite titanium dioxide nanorod catalysts prepared in Example 3;

[0026] Figure 6 Phase retardation curve and amplitude butterfly curve of barium ion-doped brookite titanium dioxide nanorod catalysts prepared in Example 3;

[0027] Figure 7 Kinetic curves of the catalytic activities of catalysts prepared in Examples 1-4 and Comparative Example, commercial barium titanate, and P25 titanium dioxide for piezoelectric catalytic degradation of Rhodamine B;

[0028] Figure 8 Kinetic curves of the catalytic activities of catalysts prepared in Example 2 and Comparative Example, commercial barium titanate, and P25 titanium dioxide for photocatalytic degradation of Rhodamine B. Detailed Description of the Invention Example 1

[0029] Prepare barium ion-doped brookite titanium dioxide nanorods, specifically including:

[0030] 1) Synthesis of barium oleate: Sodium oleate, barium chloride, ethanol, n - hexane, and deionized water were mixed in a ratio of 24 mmol:12 mmol:32 mL:56 mL:24 mL, stirred at 60 - 80 °C for 2 - 5 h, placed in a separatory funnel. After stratification, the oil phase was taken out and dried to obtain barium oleate;

[0031] 2) Barium oleate, oleic acid, oleylamine, and 1 - octadecene were mixed in a ratio of 0.02 mmol:6 mL:18 mL:16 mL. Vacuum was applied at 100 °C for 1 h, nitrogen was introduced, 0.40 mmol of titanium tetrachloride was injected, heated to 240 °C - 320 °C, and the reaction was maintained for 0.5 - 1.5 h. Ethanol was used for precipitation and centrifugation to obtain anatase titanium dioxide nanorods doped with 1.9 mol% of barium ions. Example 2

[0032] Preparation of barium - ion - doped anatase titanium dioxide nanorods specifically includes:

[0033] 1) Synthesis of barium oleate: Sodium oleate, barium chloride, ethanol, n - hexane, and deionized water were mixed in a ratio of 24 mmol:12 mmol:32 mL:56 mL:24 mL, stirred at 60 - 80 °C for 2 - 5 h, placed in a separatory funnel. After stratification, the oil phase was taken out and dried to obtain barium oleate;

[0034] 2) Barium oleate, oleic acid, oleylamine, and 1 - octadecene were mixed in a ratio of 0.04 mmol:6 mL:18 mL:16 mL. Vacuum was applied at 100 °C for 1 h, nitrogen was introduced, 0.40 mmol of titanium tetrachloride was injected, heated to 240 °C - 320 °C, and the reaction was maintained for 0.5 - 1.5 h. Ethanol was used for precipitation and centrifugation to obtain anatase titanium dioxide nanorods doped with 4.5 mol% of barium ions.

[0035] As Figure 1 and Figure 2 shown, the transmission electron microscope image (TEM) shows that the prepared barium - ion - doped anatase titanium dioxide nanorods exhibit a rod - like structure, with an average width of 4 - 6 nanometers and a length of 20 - 50 nanometers. HRTEM shows that the interplanar spacing of the lattice fringes is about 0.346 nm, corresponding to the (111) plane. The uniform distribution of barium ions in the nanorods was confirmed by high - angle annular dark - field (HAADF) - STEM imaging and energy - dispersive spectrometer (EDS) elemental mapping. Example 3

[0036] Preparation of barium - ion - doped anatase titanium dioxide nanorods specifically includes:

[0037] 1) Synthesis of barium oleate: Sodium oleate, barium chloride, ethanol, n - hexane, and deionized water were mixed in a ratio of 24 mmol:12 mmol:32 mL:56 mL:24 mL, stirred at 60 - 80 °C for 2 - 5 h, placed in a separatory funnel. After phase separation, the oil phase was taken out and dried to obtain barium oleate;

[0038] 2) Barium oleate, oleic acid, oleylamine, and 1 - octadecene were mixed in a ratio of 0.08 mmol:6 mL:18 mL:16 mL. Vacuum was applied at 100 °C for 1 h, nitrogen was introduced, 0.40 mmol of titanium tetrachloride was injected, heated to 240 °C - 320 °C, and the reaction was maintained for 0.5 - 1.5 h. Precipitation was carried out with ethanol and centrifuged to obtain anatase titanium dioxide nanorods doped with 5.3 mol% of barium ions.

[0039] As Figure 3 shown, it is the synthesized anatase - phase titanium dioxide nanorods. As Figure 4 shown, it can be known from electron paramagnetic resonance spectroscopy (EPR) that the synthesized nanorods contain oxygen vacancies. As Figure 5 shown, it is a typical butterfly curve and phase - lag curve. Therefore, barium - ion doping endows anatase titanium dioxide with piezoelectricity, and its piezoelectric coefficient is calculated to be 1.316 pm / V. Example 4

[0040] Preparation of barium - ion - doped anatase titanium dioxide nanorods specifically includes:

[0041] 1) Synthesis of barium oleate: Sodium oleate, barium chloride, ethanol, n - hexane, and deionized water were mixed in a ratio of 24 mmol:12 mmol:32 mL:56 mL:24 mL, stirred at 60 - 80 °C for 2 - 5 h, placed in a separatory funnel. After phase separation, the oil phase was taken out and dried to obtain barium oleate;

[0042] 2) Barium oleate, oleic acid, oleylamine, and 1 - octadecene were mixed in a ratio of 0.32 mmol:6 mL:18 mL:16 mL. Vacuum was applied at 100 °C for 1 h, nitrogen was introduced, 0.40 mmol of titanium tetrachloride was injected, heated to 240 °C - 320 °C, and the reaction was maintained for 0.5 - 1.5 h. Precipitation was carried out with ethanol and centrifuged to obtain anatase titanium dioxide nanorods doped with 5.8 mol% of barium ions. Example 5

[0043] Preparation of barium - and - praseodymium - ion - co - doped anatase titanium dioxide nanorods specifically includes:

[0044] 1) Synthesis of barium oleate: Sodium oleate, barium chloride, ethanol, n - hexane, and deionized water were mixed in a ratio of 24 mmol:12 mmol:32 mL:56 mL:24 mL, stirred at 60 - 80 °C for 2 - 5 h, placed in a separatory funnel. After layering, the oil phase was taken out and dried to obtain barium oleate;

[0045] 2) Synthesis of praseodymium oleate: Sodium oleate, praseodymium chloride, ethanol, n - hexane, and deionized water were mixed in a ratio of 24 mmol:8 mmol:32 mL:56 mL:24 mL, stirred at 60 - 80 °C for 2 - 5 h, placed in a separatory funnel. After layering, the oil phase was taken out and dried to obtain praseodymium oleate; (3) Barium oleate, praseodymium oleate, oleic acid, oleylamine, and 1 - octadecene were mixed in a ratio of 0.04 mmol:0.04 mmol:6 mL:18 mL:16 mL, evacuated at 100 °C for 1 h, purged with nitrogen, 0.40 mmol of titanium tetrachloride was injected, heated to 240 °C - 320 °C, and the reaction was maintained for 0.5 - 1.5 h. The product was precipitated with ethanol and centrifuged to obtain barium - praseodymium ion double - doped brookite titanium dioxide nanorods. Example 6

[0046] Preparation of barium - iron ion double - doped brookite titanium dioxide nanorods specifically includes:

[0047] 1) Synthesis of barium oleate: Sodium oleate, barium chloride, ethanol, n - hexane, and deionized water were mixed in a ratio of 24 mmol:12 mmol:32 mL:56 mL:24 mL, stirred at 60 - 80 °C for 2 - 5 h, placed in a separatory funnel. After layering, the oil phase was taken out and dried to obtain barium oleate;

[0048] 2) Synthesis of iron oleate: Sodium oleate, iron chloride, ethanol, n - hexane, and deionized water were mixed in a ratio of 24 mmol:8 mmol:32 mL:56 mL:24 mL, stirred at 60 - 80 °C for 2 - 5 h, placed in a separatory funnel. After layering, the oil phase was taken out and dried to obtain iron oleate; (3) Barium oleate, iron oleate, oleic acid, oleylamine, and 1 - octadecene were mixed in a ratio of 0.04 mmol:0.04 mmol:6 mL:18 mL:16 mL, evacuated at 100 °C for 1 h, purged with nitrogen, 0.40 mmol of titanium tetrachloride was injected, heated to 240 °C - 320 °C, and the reaction was maintained for 0.5 - 1.5 h. The product was precipitated with ethanol and centrifuged to obtain barium - iron ion double - doped brookite titanium dioxide nanorods. Comparative Example

[0049] Preparation of brookite titanium dioxide nanorods, including: mixing oleic acid, oleylamine and 1-octadecene in a ratio of 6 mL: 18 mL: 16 mL, evacuating at 100 °C for 1 h, introducing nitrogen, injecting 0.40 mmol of titanium tetrachloride, heating to 240 °C - 320 °C, and maintaining the reaction for 0.5 - 1.5 h, precipitating with ethanol and centrifuging to obtain pure brookite titanium dioxide nanorods.

[0050] This example relates to the piezocatalytic application of the above-mentioned nanorod catalyst, specifically: degrading Rhodamine B.

[0051] Taking the nanorod catalysts prepared in all examples and comparative examples, as well as the commercially purchased barium titanate (99.9%, spherical, D50 = 0.6 - 1 μm, tetragonal crystal - ferroelectric) and P25 titanium dioxide (Degussa) as the test objects, detecting their effects on degrading Rhodamine B (RhB). Generally, 0.02 g of the sample is added to 20 mL of RhB solution (10 ppm). To establish a complete adsorption - desorption equilibrium, the suspension is stirred in the dark for 30 minutes, and then irradiated using an ultrasonic cleaner (35 kHz, 180 W). Every 10 minutes, 1 mL of the reaction solution sample is extracted, then centrifuged, and the supernatant is used to record the absorption spectrum at 544 nm with a UV - visible spectrophotometer to determine the concentration of RhB. The results are as Figure 6 shown, the reaction rate constant k of the barium ion - doped brookite titanium dioxide nanorods is up to 0.172 min -1 , which is about 1430% higher than the degradation efficiency of pure brookite titanium dioxide nanorods, and shows higher catalytic performance than commercially available P25 titanium dioxide and ferroelectric barium titanate.

[0052] Taking the nanorod catalysts prepared in Example 2 and the comparative example as the test objects, detecting their photocatalytic degradation effect on Rhodamine B (RhB). Generally, 0.02 g of the sample is added to 20 mL of RhB solution (10 ppm). To establish a complete adsorption - desorption equilibrium, the suspension is stirred in the dark for 30 minutes, and then irradiated with light / ultrasound. Subsequently, irradiation is carried out using a solar simulator (450 W) or an ultrasonic cleaner (35 kHz, 180 W). Every 10 minutes, 1 mL of the reaction solution sample is extracted, then centrifuged, and the supernatant is used to record the absorption spectrum at 544 nm with a UV - visible spectrophotometer to determine the concentration of RhB. The results are as Figure 7 shown, compared with the pure brookite titanium dioxide nanorods prepared in the comparative example, the reaction rate constant k of the barium ion - doped brookite titanium dioxide nanorod catalyst for RhB degradation has increased by 230%.

[0053] Compared with the prior art, the performance index improvement of the present device / method (i.e., the effect obtained by adopting new technology in which link above) lies in that: by doping barium ions into brookite TiO2 nanorods, piezoelectricity is imparted to titanium dioxide. Through piezoresponse force microscopy testing, typical piezoelectric response butterfly curves and hysteresis loops are shown. The built-in electric field of the piezoelectric response improves the catalytic performance of titanium dioxide under ultrasound, and the reaction rate constant k is increased by about 1430%. At the same time, the built-in electric field promotes charge separation and improves the photocatalytic performance of titanium dioxide.

[0054] The above specific implementation can be locally adjusted by those skilled in the art in different ways without departing from the principles and purposes of the present invention. The protection scope of the present invention is subject to the claims and is not limited by the above specific implementation. All implementation schemes within its scope are subject to the present invention.

Claims

1. A barium ion-doped brookite titanium dioxide nanorod catalyst, characterized in that, It is a nanorod structure containing oxygen vacancy defects, including anatase-phase titanium dioxide and doped barium ions, where: the barium ions used to induce the piezoelectricity of anatase titanium dioxide exist in the form of Ba 2+ , and its doping concentration is 0.05 to 10 mol% of the titanium ion content; The doping is single doping with barium ions or double doping with barium ions and transition metals or rare earth elements.

2. The barium ion-doped brookite titanium dioxide nanorod catalyst according to claim 1, characterized in that, The doping is specifically double doping with barium ions and elements such as iron, cobalt, nickel, vanadium, chromium, lanthanum, cerium, praseodymium, neodymium, erbium or thulium, where: the content of each ion is 0.05 - 10 mol%.

3. A method for preparing the double-doped brookite titanium dioxide nanorod catalyst according to claim 1 or 2, characterized in that, It includes the following steps: S1. Using sodium oleate, chloride salts, ethanol, and n - hexane as raw materials, prepare oleates by heating and reacting after mixing with deionized water. S2. After mixing barium oleate, oleates, oleic acid, oleylamine, and 1 - octadecene, inject titanium tetrachloride under a nitrogen environment and heat and react sufficiently, then extract the precipitate to obtain double - doped brookite titanium dioxide nanorods.

4. The method for preparing the double-doped brookite titanium dioxide nanorod catalyst according to claim 3, characterized in that, The chloride salts mentioned refer to chloride salts of barium ions, transition metal ions, or rare earth ions.

5. The method for preparing the double-doped brookite titanium dioxide nanorod catalyst according to claim 3, characterized in that, The heating reaction mentioned means: after adding deionized water, heat to 60 - 80 °C and stir for 2 - 5 h, and after sufficient reaction, take the oil phase and dry it to obtain the corresponding oleates.

6. The method for preparing the double-doped brookite titanium dioxide nanorod catalyst according to claim 3, characterized in that, The addition ratio of sodium oleate, chloride salts, ethanol, n - hexane, and deionized water is 12 - 48 mmol: 6 - 24 mmol: 16 - 64 mL: 28 - 112 mL: 12 - 48 mL.

7. The method for preparing the double-doped brookite titanium dioxide nanorod catalyst according to claim 3, characterized in that, The sufficient heating reaction means: heat to 240 °C - 320 °C and maintain the reaction for 0.5 - 1.5 h until the reaction is sufficient.

8. The method for preparing the double-doped brookite titanium dioxide nanorod catalyst according to claim 3 or 6, characterized in that, The addition ratio of oleic acid, oleylamine, 1 - octadecene, and titanium tetrachloride is 3 - 12 mL: 9 - 36 mL: 8 - 32 mL: 0.2 - 4 mmol.

9. A method for preparing the single-doped brookite titanium dioxide nanorod catalyst according to claim 1, characterized in that, After mixing barium oleate, oleic acid, oleylamine, and 1 - octadecene, inject titanium tetrachloride under a nitrogen environment and heat and react sufficiently, then extract the precipitate to obtain single - doped brookite titanium dioxide nanorods.

10. An application based on the brookite titanium dioxide nanorod catalyst according to claim 1 or 2, characterized in that, As a photocatalyst or as a piezoelectric catalyst to remove organic pollutants or biological pathogens.

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