CN103818954B - The anatase octahedrite TiO of face exposure that one has (001) 2the preparation method of tiny balloon - Google Patents

Abstract

This invention relates to a method for preparing anatase _TiO2 hollow microspheres with exposed (001) surfaces, comprising: reacting a titanium salt or titanium alkoxide with an alkaline solution to obtain a precipitate, dissolving it in a hydrofluoric acid solution, and then carrying out a hydrothermal reaction at 100–200°C; after the reaction, washing the product until neutral and drying it to obtain the final product. This invention is low-cost, simple in process, and produces anatase titanium dioxide with complete crystal structure and novel composition, which has wide applications in photocatalysis, dye-sensitized solar cells, lithium batteries, and other fields.

Description

A preparation method of anatase TiO2 hollow microspheres with (001) surface exposure

technical field

The invention belongs to the field of preparation of anatase _TiO2 microsphere materials, in particular to a preparation method of anatase _TiO2 hollow microspheres with (001) surface exposure.

Background technique

Titanium dioxide is a very important transition metal oxide. It has the advantages of non-toxicity, stable chemical properties and low cost. Therefore, it is widely used in the fields of photocatalysis, self-cleaning, sensors, lithium batteries, coatings and cosmetics.

The application of titanium dioxide is not only related to the crystal phase and particle size, but also related to the exposed surface of the crystal. In recent years, _TiO2 with high energy surface has been extensively studied. From theoretical and experimental studies, it is found that the (001) plane of anatase TiO ₂ has higher catalytic activity than the (101) plane. How to prepare TiO ₂ with (001) face has received more and more attention. However, the (001) face of anatase TiO ₂ has a relatively high average surface energy of 0.90J/m ² , which follows in the crystal growth process. Based on the principle of surface energy minimization, the (001) plane will quickly become smaller until it disappears, while the (101) plane has a lower surface energy (0.44J/m ² ), and will maintain a thermodynamically stable state during crystal growth, so the current Most of the exposed anatase TiO ₂ is the low-energy (101) plane, so that it is difficult to make a large part of the (001) plane of TiO ₂ . On the other hand, titanium dioxide nanoparticles are easy to agglomerate, which leads to a decrease in specific surface area and accelerated grain boundary recombination, while hollow spheres on the exposed surface of the high-energy (001) surface can overcome this shortcoming; titanium dioxide hollow spheres can be used as scattering particles and lightweight materials for solar cells. It has broad application prospects in practical application and basic research. Therefore, the preparation of (001) surface exposed _TiO2 hollow microspheres with low density, high specific surface area and high catalytic performance has important application value.

Many literatures and patents at home and abroad disclose the preparation method and performance research of TiO ₂ with (001) surface. Yang et al reported in [Nature.Vol.453(2008)pp.638～642] that titanium tetrafluoride and hydrofluoric acid were used as reactants to synthesize anatase TiO ₂ with 47% (001) plane for the first time Single crystal with a particle size greater than 1.0 μm. It is further reported in the literature [Journal of the American Chemical Society. Vol. 131 (2009) pp. 4078-4083] that after adding isopropanol, the ratio of (001) planes is greatly improved. Subsequently, literature [Journal of the American Chemical Society.Vol.131(2009)pp.3152～3153], [Chemistry-AEuropeanJournal.Vol.18(2012)pp.7525～7532], [MaterialsLetters.Vol.66(2012)pp.308～ 310], [Journal of Alloys and Compounds.Vol.548(2013)pp.194～200], [Applied Surface Science.Vol.265(2013)pp.438～442], [RSCAdvances.Vol.3(2013)pp.1222～1226] etc. used titanium tetrachloride, titanium powder, titanium sulfate, titanium isopropoxide, titanium tetrafluoride, etc. as titanium sources, and prepared anatase TiO ₂ with (001) plane by different methods. Patent [CN201010231407.7] discloses a preparation method of anatase _TiO2 single crystal with large (001) surface area, which uses titanium powder as raw material and dissolves titanium powder in hydrogen through hydrothermal reaction. Hydrofluoric acid solution, then the dissolved hydrofluoric acid is mixed with dilute hydrogen peroxide, and hydrothermally reacted again to obtain (001) surface TiO ₂ single crystal. Subsequently, the patent [CN201110312094.2] disclosed a titanium dioxide with a high-energy surface hollow structure and its preparation method, mainly using titanium powder, hydrogen fluoride and hydrogen peroxide as reactants, and reacting under hydrothermal conditions. Titanium dioxide with a hollow structure composed of flake particles agglomerated.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing anatase _TiO2 hollow microspheres with exposed (001) faces. The inventive method is easy to operate, simple in equipment and process, and does not require surfactants or inhibitors. Low cost and no post-treatment; wet _TiO2 precipitation is used in this invention, which has high chemical activity and less hydrofluoric acid in the reaction; the crystal form of titanium dioxide prepared by this invention is anatase, with complete crystallization and novel structure. It has been widely used in photocatalysis, dye-sensitized solar cells, lithium batteries and other fields.

A method for preparing anatase _TiO2 hollow microspheres with exposed (001) faces of the present invention, comprising:

(1) Preparation of fluorotitanic acid solution

Disperse the titanium source in the solvent, then add ammonia water dropwise, stir, then add deionized water, after stirring, heat to 60°C, and magnetically stir for 2-4h, after the reaction is completed, cool to room temperature to obtain hydrated titanium oxide or hydroxide Titanium, washed to obtain a wet precipitate; wherein the volume ratio of titanium source, solvent, ammonia water, and deionized water is 4:80:1:1-4:160:2:3; add the wet precipitate to 30-70ml of deionized In water, stir magnetically, then add hydrofluoric acid dropwise, stir to obtain a transparent or light blue fluorotitanic acid solution; wherein the molar concentration ratio of F- and Ti ⁴⁺ in the fluorotitanic acid solution is 6:1-10: 1;

The reaction process is shown in formula 1-1:

TiO ₂ +6HF→H ₂ TiF ₆ +2H ₂ O(1-1)

(2) Hydrothermal treatment of fluorotitanic acid solution

The above fluorotitanic acid solution is subjected to hydrothermal treatment at a temperature of 100-200°C for 5-20 hours, then washed and dried to obtain anatase _TiO2 hollow microspheres with exposed (001) faces.

The reaction process is shown in formula 1-2:

H ₂ TiF ₆ +2H ₂ O→TiO ₂ +6HF(1-2)

The hydrothermal treatment specifically includes putting the fluorotitanic acid solution into a polytetrafluoroethylene-lined reactor, putting the reactor into an oven at 100-200° C., and reacting for 5-20 hours.

The titanium source in the step (1) is titanium salt or titanium alkoxide.

The titanium source in the step (1) is an inorganic salt of titanium, tetrabutyl titanate, ethyl titanate or isopropyl titanate and the like.

The solvent in the step (1) is ethanol.

Stirring in the step (1) is first stirring for 30-60 minutes, then adding deionized water, stirring for 10-20 minutes, adding hydrofluoric acid dropwise, and stirring for 60-120 minutes.

The washing in the step (1) is to wash the precipitate with ethanol and deionized water until the pH value is 7.

The mass percent concentration of hydrofluoric acid in the step (1) is 20.0%-40.0%.

The washing in the step (2) is to wash with deionized water until the pH value of the product is 7; the drying temperature is 50-110°C, and the drying time is 5-30h.

The anatase TiO ₂ hollow microspheres with (001) surface exposed in the step (2) have a wall thickness of 70-300 nm, a particle size of 0.7-2.0 μm, and a grain size of 30-100 nm.

In the present invention, because the price of titanium powder is higher and the reaction is violent, inhibitors are needed in the hydrothermal process; crystallized TiO ₂ internal particles are arranged regularly, the reactivity is low, and a large amount of strong corrosive solvent is needed in the reaction process; and wet precipitation of amorphous TiO There are a large number of defects and dislocations on the surface and in the crystal of ₂ , which can easily become the recombination center of holes and electrons, which can accelerate the reaction with hydrofluoric acid. Therefore, the present invention is mainly a hollow titanium dioxide microsphere with a (001) surface prepared by direct hydrothermal reaction of wet _TiO2 precipitation and hydrofluoric acid aqueous solution.

In the present invention, hydrofluoric acid has a great influence on the morphology of _TiO with high energy (001) face, and the (001) face of _TiO has higher surface energy, and F ions can be preferentially adsorbed to the high energy (001) face, then The growth rate along the (001) plane is slowed down, which is beneficial to the growth of the (101) plane with lower surface energy, so F ions can be used as a crystal plane directing agent in the hydrothermal reaction to stabilize the (001) crystal plane and form a high proportion (001) facet exposed anatase TiO ₂ ; on the other hand, F ions also act as a stabilizer to inhibit the rapid growth of TiO ₂ .

Beneficial effect

(1) The method of the present invention is easy to operate, simple in equipment and process, does not require surfactants or inhibitors, has low cost, and does not require post-treatment;

(2) In the present invention, wet _TiO is adopted Precipitation, high chemical activity, less hydrofluoric acid consumption in the reaction;

(3) The crystal form of titanium dioxide prepared by the present invention is anatase, with complete crystallization and novel structure, and is widely used in photocatalysis, dye-sensitized solar cells, lithium batteries and other fields;

(4) The grain size of titanium dioxide prepared in the present invention is 30-100 nm, and the particle size is 0.7-2.0 μm, which can be controlled by hydrothermal time and temperature.

Description of drawings

Fig. 1 is TiO that the embodiment of the present invention 1 makes has (001) plane exposed _TiO Hollow microsphere X-ray diffraction figure;

Fig. 2 is the TiO2 hollow microsphere emission scanning electron microscope picture FE-SEM with (001) surface exposure that the embodiment 1 of the present invention makes _; Wherein the illustration is the _TiO2 Hollow microsphere section field emission scanning electron microscope (FE-SEM) photo ;

Fig. 3 is the TiO ₂ hollow microspheres transmission electron micrograph TEM with (001) plane exposed that the embodiment of the present invention 1 makes; Wherein a has the TiO ₂ hollow microspheres that make (001) plane exposes the low-magnification transmission Electron micrograph; b is a high-magnification transmission electron micrograph with (001) exposed _TiO2 hollow microspheres;

Fig. ₄ is the N adsorption/desorption isotherm of the exposed _TiO hollow microspheres with (001) surface prepared in Example 1 of the present invention, and the inset is a pore size distribution curve;

Fig. 5 is an emission scanning electron microscope (FE-SEM) photo (a) and a transmission electron microscope photo TEM (b) of _TiO2 hollow microspheres with (001) surface exposure prepared in Example 2 of the present invention;

Figure 6 is an emission scanning electron microscope (FE-SEM) photo of _TiO2 hollow microspheres with (001) surface exposure prepared in Example 3 of the present invention; (a) is a low magnification field emission SEM photo; (b) is a high magnification Field emission scanning electron microscope photo;

Fig. 7 is the N ₂ adsorption/desorption isotherm of TiO ₂ hollow microspheres with exposed (001) plane prepared in Example 3 of the present invention.

detailed description

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

At room temperature, weigh 2.0ml of tetrabutyl titanate and disperse it in 100ml of absolute ethanol. After stirring evenly, add 1ml of ammonia water and stir for 60 minutes; then slowly add 1.5ml of deionized water, stir for 20 minutes, and heat the oil bath to 60°C Stir magnetically for 4 h. After the reaction is complete, cool to room temperature and wash the precipitate with ethanol and deionized water until the pH value reaches 7.

Add 50ml of deionized water to the wet precipitate obtained in the previous step, stir magnetically for 30min, add 0.7ml of 40.0wt% hydrofluoric acid, put it into the reaction kettle, stir for 10min, put the reaction kettle into an oven at 180°C, and react 15h. After the reaction, the reaction product was washed with deionized water until the pH value of the product was 7; then the obtained product was dried in an oven at 100° C. for 24 hours, thereby obtaining the hollow TiO ₂ microspheres.

Analyze and test the powder prepared in the above steps. Fig. 1 is the _TiO hollow microsphere X-ray diffractogram with (001) plane exposed that is made in the present embodiment, by contrasting with standard card (JCPDSNo.21-1272), it can be seen that the product obtained is pure anatase TiO ₂ , and the strength of the (004) crystal plane is significantly increased, indicating that the surface of the obtained TiO ₂ hollow sphere is surrounded by the (001) plane _; Field emission scanning electron microscope image, it can be clearly seen from the figure that the particle size of the hollow TiO ₂ microsphere is 1.2 μm, and the surface of the TiO ₂ microsphere is composed of shortened tetrahedral pyramids, and the length and width of the tetrahedron are 50-100nm respectively , and the diameter of the hollow sphere in the middle is 150nm; Fig. 3 is a TiO ₂ hollow microsphere photomicrograph with (001) face exposed that the embodiment of the present invention makes; Wherein Fig. 3 a has (001) that the embodiment of the present invention makes Surface exposed TiO2Hollow microspheres low-magnification transmission electron microscope photographs, as can be seen from the figure, the _TiO2 prepared is a hollow sphere, and the surface is composed of regular tetrahedral pyramids _; High magnification transmission electron microscope photos of TiO ₂ hollow microspheres exposed on the (001) plane. It can be seen from the figure that there is a crystal plane spacing of 0.237nm, which corresponds to the (004) crystal plane, indicating that there is a high-energy (001) plane on the TiO ₂ surface. Fig. 4 is that there is (001) surface that the embodiment of the present invention makes and exposes _{TiO 2} The N adsorption/desorption isotherms of hollow microspheres, the illustration is a pore size distribution curve, as can be seen from the figure, the prepared TiO ₂ hollow microspheres The specific surface area of the ball is 36.1m ² g ^-1 , and the pore size distribution is between 2.0nm and 100nm.

Example 2

At room temperature, weigh 1.5ml of tetrabutyl titanate and disperse in 80ml of absolute ethanol. After stirring evenly, add 0.65ml of ammonia water and stir for 60min; then slowly add 1.1ml of deionized water, stir for 20min, and heat the oil bath to 60 ℃ magnetic stirring for 4 h, after the reaction was completed, cooled to room temperature, washed with ethanol and deionized water until the pH reached 7.

Add 50ml of deionized water to the wet precipitate obtained in the previous step, stir magnetically for 30min, add 0.6ml of 40.0wt% hydrofluoric acid, put it into the reaction kettle, stir for 10min, put the reaction kettle into an oven at 200°C, and react 10h. After the reaction, the reaction product was washed with deionized water until the pH value of the product was 7; then the obtained product was dried in an oven at 100° C. for 24 hours, thereby obtaining the hollow TiO ₂ microspheres.

Fig. 5 is the emission scanning electron micrograph and the transmission electron micrograph of the _TiO2 hollow microsphere with (001) surface exposure prepared by the embodiment of the present invention; Fig. 5a is the _TiO2 with (001) surface exposure prepared by the embodiment of the present invention Scanning electron microscope image of hollow microspheres, the obtained hollow titanium dioxide particles have an average size of 1 μm, and flake particles with high-energy (001) planes are evenly distributed on the surface of titanium dioxide; Transmission electron microscope photo of TiO ₂ hollow microspheres. It can be seen from the figure that the prepared titanium dioxide has a hollow structure.

Example 3

At room temperature, weigh 1.0ml of tetrabutyl titanate and disperse it in 60ml of absolute ethanol. After stirring evenly, add 0.4ml of ammonia water and stir for 60min; then slowly add 0.7ml of deionized water, stir for 20min, and heat the oil bath to 60 ℃ magnetic stirring for 4 h, after the reaction was completed, cooled to room temperature, washed with ethanol and deionized water until the pH reached 7.

Add 50ml of deionized water to the wet precipitate obtained in the previous step, stir magnetically for 30min, add 0.8ml of 40.0wt% hydrofluoric acid, put it into the reactor, stir for 10min, put the reactor into an oven at 150°C, and react 20h. After the reaction, the reaction product was washed with deionized water until the pH value of the product was 7; then the obtained product was dried in an oven at 100° C. for 24 hours, thereby obtaining the hollow TiO ₂ microspheres.

Fig. 6 is the _TiO2 hollow microsphere scanning electron micrograph that has (001) surface exposure that the embodiment of the present invention makes ; Figure 6b is a high-magnification scanning electron microscope image, it can be seen that the surface of titanium dioxide is composed of circular flakes, the size of the flake particles is uniform, and it is densely distributed on the surface of titanium dioxide; it can be seen from Figure 7 that the (001) surface exposed by the embodiment of the present invention is made The specific surface area of TiO ₂ hollow microspheres is 80.8m ² g ^-1 .

Example 4

At room temperature, weigh 0.5ml of tetrabutyl titanate and disperse it in 40ml of absolute ethanol. After stirring evenly, add 0.2ml of ammonia water and stir for 60min; then slowly add 0.35ml of deionized water, stir for 20min, and heat the oil bath to 60 ℃ magnetic stirring for 4 hours, after the reaction was completed, cooled to room temperature, washed with ethanol and deionized water until the pH value reached 7.

Add 50ml of deionized water to the wet precipitate obtained in the previous step, stir magnetically for 30min, add 0.5ml of 40.0wt% hydrofluoric acid, put it into the reaction kettle, stir for 10min, then put the reaction kettle into an oven at 100°C, Reaction 5h. After the reaction, the reaction product was washed with deionized water until the pH value of the product was 7; then the obtained product was dried in an oven at 100° C. for 24 hours, thereby obtaining the hollow TiO ₂ microspheres.

Claims (7)

1. a kind of anatase _TiO with (001) face exposure The preparation method of hollow microspheres, comprising: (1) Disperse the titanium source in the solvent, then add ammonia water to stir, then add deionized water, after stirring, heat to 60°C and magnetically stir for 2-4h, after the reaction is completed, cool to room temperature, wash to obtain a wet precipitate; The volume ratio of titanium source, solvent, ammonia water, and deionized water is 4:80:1:1-4:160:2:3; add the wet precipitate to deionized water, stir magnetically, then add hydrofluoric acid, stir, Obtain fluorotitanic acid solution; wherein the molar concentration ratio of F in the fluorotitanic acid solution ^- and Ti ⁴⁺ is 6:1-10:1; wherein the solvent is ethanol; (2) The above-mentioned fluorotitanic acid solution is subjected to hydrothermal treatment at a temperature of 100-200° C. for 5-20 hours, then washed and dried to obtain anatase TiO ₂ hollow microspheres with exposed (001) faces. 2. a kind of anatase _TiO2 hollow microspheres with (001) surface exposure according to claim 1, is characterized in that: in described step (1), titanium source is titanium salt or titanium alkoxide . 3. a kind of anatase _TiO with (001) face exposure according to claim 1 The preparation method of hollow microspheres, it is characterized in that: in described step (1), titanium source is the inorganic salt of titanium, titanium butyl titanate or ethyl titanate. 4. a kind of anatase _TiO with (001) face exposure according to claim 1 The preparation method of hollow microspheres, it is characterized in that: washing in described step (1) is washing with ethanol and deionized water Precipitate to pH 7. 5. a kind of anatase _TiO with (001) face exposure according to claim 1 The preparation method of hollow microspheres is characterized in that: the mass percentage concentration of hydrofluoric acid in the described step (1) is 20.0%-40.0%. 6. a kind of anatase _TiO with (001) face exposure according to claim 1 The preparation method of hollow microspheres, it is characterized in that: washing in described step (2) is washing with deionized water until product The pH value of the product is 7; the drying temperature is 50-110°C, and the drying time is 5-30h. 7. a kind of anatase _TiO2 hollow microspheres with (001) face exposure according to claim 1 preparation method, it is characterized in that: have (001) face exposed anatase in described step (2) Ore TiO ₂ hollow microspheres, the wall thickness is 70-300nm, the particle size is 0.7-2.0μm, and the grain size is 30-100nm.