CN104692457A - A kind of litchi-like micro-nano hierarchical structure TiO2 crystal and its synthesis method - Google Patents

Abstract

The invention relates to a _TiO2 crystal with litchi-like micro-nano hierarchical structure and a synthesis method thereof. The uniformly dispersed spherical amorphous precursor TiO ₂ is first prepared, and then the precursor TiO ₂ and a solvent are crystallized in a hydrothermal environment to obtain TiO ₂ crystals with litchi-like micro-nano hierarchical structure. The prepared _TiO2 crystal is spherical, with a diameter of 500-700nm, and spherical protrusions with a diameter of 10-20nm are evenly distributed on the spherical surface. The TiO ₂ crystal has an anatase structure and has important applications in solar cells, photocatalysis, and self-cleaning. At the same time, this method provides a new idea for the surface graded modification of other particles.

Description

A kind of litchi-like micro-nano hierarchical structure TiO2 crystal and its synthesis method

technical field

The invention relates to a _TiO2 micro-nano material, in particular to a litchi-like micro-nano hierarchical structure _TiO2 crystal and its synthesis method

technical background

Titanium dioxide (TiO ₂ ) has excellent photoelectric properties and physical properties, and has a wide range of applications in chromatographic separation, lithium-ion batteries, dye-sensitized solar cells, gas sensors, catalysis and other fields, and its low cost and environmental friendliness have also been studied Therefore, it has always been a research hotspot in information energy and environmental materials.

Monodisperse spherical _TiO2 materials have shown many real and emerging applications due to spherical morphology with uniform close packing, tunable surface curvature, fluidity, etc. Using the liquid phase method, TiO ₂ powder particles with various shapes have been synthesized. For example, spherical TiO ₂ particles are synthesized by using the traditional sol-gel process combined with surfactants, using polystyrene balls, SiO ₂ balls, C balls, PMMA Spheres and other prefabricated templates to synthesize porous TiO ₂ spheres. However, most of the above-mentioned preparation processes are for the synthesis of micron-scale monodisperse TiO ₂ spheres, and for nano-scale monodisperse spheres, there are still disadvantages such as uncontrollable morphology and dispersibility, and complicated processes.

The microstructure of the material and its spatial arrangement will have an important impact on the performance of the material. The preparation of low-dimensional nanostructure materials occupies a dominant position in the field of nanostructures, and compounds with secondary nanostructures are due to their novel structures and unique The chemical and physical properties and the great influence of shape and size on properties make it possible to have more novel properties in terms of light, electricity, and magnetism. Therefore, the research on the secondary structure of _TiO2 particle morphology is becoming more and more extensive, and its application field has a broader prospect.

The present invention is based on the principle of process simplification, by first synthesizing micron-scale monodisperse precursor materials, and then modifying the secondary microstructure of materials in a mild liquid phase environment, and synthesizing _TiO2 powder particles with novel shapes, expecting can be applied more widely.

Contents of the invention

The invention provides a _TiO2 crystal with litchi-shaped micro-nano hierarchical structure and a synthesis method thereof, which is characterized in that the _TiO2 crystal with litchi-shaped micro-nano hierarchical structure is spherical, and spherical protrusions with small particle sizes are distributed on the surface of the spherical shape. The type is anatase;

The TiO ₂ spherical diameter of the lychee-shaped micro-nano hierarchical structure is 500-700nm, and the diameter of the spherical protrusion is 10-20nm.

Preferably, the preparation steps of litchi-like micro-nano hierarchical structure _TiO crystals are as follows:

(1) At room temperature, make a mixed solution A with PVP, water and n-propanol with a W/V/V of 1.5-2:25:75, and slowly pour the Ti(SO ₄ ) ₂ solution into the mixed solution A , after stirring evenly, heat in a water bath at 70°C for 3h-6h to obtain the mixed solution B, after the mixed solution B is cooled to room temperature, centrifuge and wash, age in a KOH solution with a molar concentration of 1-2mol/L at 60°C for 12h, centrifuge and wash , obtain precursor _TiO2 powder C after drying;

(2) Mix the precursor powder C and the solvent D evenly, the mass volume ratio of the precursor powder C and the solvent D is 0.4:20, put it into a hydrothermal kettle and heat it at 180°C for 2 hours, centrifuge, wash and dry Finally, TiO ₂ crystal powder with litchi-like micro-nano hierarchical structure is obtained.

Preferably, in the step (1), the molar concentration of the Ti(SO ₄ ) ₂ solution is 0.8mol/L, and the volume ratio V/V between the Ti(SO ₄ ) ₂ solution and the mixed solution A described in this step is 1: 2.

Preferably, in the step (2), the solvent D is one of ethylene glycol, 0.01g/mL cetyltrimethylammonium bromide aqueous solution or the DMF/water solution whose volume ratio V/V is 1:1 kind.

The main advantages of the present invention are as follows:

(1) The obtained lychee-like TiO ₂ crystal with micro-nano hierarchical structure has a spherical diameter of 500-700nm, belonging to the micro-nano scale, and the large particle diameter makes it easy to recycle when the TiO ₂ crystal is used as a catalyst.

(2) The lychee-like hierarchical structure is obtained by modifying the surface of the precursor. The final product retains the morphology of the precursor and forms a secondary microstructure, which is conducive to increasing the specific surface area of the material and further improving its photocatalytic properties. .

Description of drawings

Fig. 1 is the scanning electron micrograph of precursor TiO in embodiment ₁ ;

Fig. 2 is litchi-shaped micro-nano hierarchical structure TiO in embodiment ₁ The scanning electron microscope picture of crystal;

Fig. 3 is the XRD figure of precursor TiO in embodiment ₁ and lychee _shape micro-nano hierarchical structure TiO ;

Fig. 4 is litchi shape micro-nano hierarchical structure TiO in embodiment ₂ Scanning electron microscope picture of crystal;

Fig. 5 is litchi-shaped micro-nano hierarchical structure TiO in embodiment ₃ Scanning electron microscope figure of crystal;

Fig. 6 is the scanning electron micrograph of precursor _TiO in embodiment 5;

Fig. 7 is the scanning electron micrograph of precursor _TiO in embodiment 6;

Fig. 8 is the test result of degrading methylene blue in embodiment 7.

Detailed ways

Example 1

(1) Mix 2g PVP, 25mL water and 75mL n-propanol to prepare mixed solution A, slowly pour 50mL 0.8mol/L Ti(SO ₄ ) ₂ aqueous solution into mixed solution A, stir well, and heat in a water bath at 70°C for 3h -6h to obtain the mixed solution B, after the mixed solution B is cooled to room temperature, centrifuge and wash, age in 1mol/L KOH solution at 60°C for 12h, centrifuge, wash and dry to obtain TiO ₂ precursor powder C;

(2) Add 0.4g of precursor powder C to 20mL of DMF/water solution with a volume ratio of 1:1 and mix evenly, pour into a 25mL hydrothermal kettle and heat at 180°C for 2h, centrifuge, wash and dry to obtain litchi TiO ₂ crystal powder with micro-nano hierarchical structure.

Fig. 1 is the scanning electron micrograph of the precursor _TiO2 powder in this embodiment, it can be seen that the precursor _TiO2 is a uniformly distributed spherical shape with a diameter of about 700nm.

Fig. 2 is the scanning electron microscope picture of the litchi-shaped micro-nano hierarchical structure _TiO2 crystal obtained in this embodiment. It can be seen that the _TiO2 crystal is spherical as a whole, with a diameter of about 700nm, and the spherical surface is evenly distributed with spherical particles with a diameter of about 20nm. raised.

Fig. 3 is the XRD figure of the precursor TiO of the present embodiment and litchi-like micro-nano hierarchical structure _TiO crystal, as can _be seen, the XRD spectrum of the _precursor TiO basically does not have a peak, indicating that the precursor _TiO has not formed crystallization, Belongs to the amorphous state. Litchi-like micro-nano hierarchical structure TiO ₂ crystals are anatase type, without impurity phase, indicating that the crystal structure is complete, and the peak shape is slightly broadened, indicating that nanostructures are generated.

Example 2

(1) Mix 2.0g PVP, 25mL water and 75mL n-propanol to prepare mixed solution A, slowly pour 50mL 0.8mol/L Ti(SO ₄ ) ₂ aqueous solution into mixed solution A, stir well, and heat in a water bath at 70°C 3h-6h to obtain the mixed solution B, after the mixed solution B is cooled to room temperature, centrifuge and wash, age in 1.0mol/L KOH solution at 60°C for 12h, centrifuge, wash and dry to obtain the TiO ₂ precursor powder C;

(2) Add 4g of precursor powder C to 20mL of ethylene glycol solution with a volume of 20mL and mix evenly, pour into a 25mL hydrothermal kettle and heat at 180°C for 2h, centrifuge, wash, and dry to obtain litchi-shaped micro-nano Hierarchical TiO ₂ crystal powder.

The scanning electron microscope image of the obtained litchi-like micro-nano hierarchical structure TiO ₂ crystal is shown in Fig. 4 . It can be seen that the TiO ₂ crystal is generally spherical, with a diameter of about 500 nm, and spherical protrusions with a diameter of about 10 nm are evenly distributed on the spherical surface.

Example 3

(1) Mix 2g PVP, 25mL water and 75mL n-propanol to prepare mixed solution A, slowly pour 50mL 0.8mol/L Ti(SO ₄ ) ₂ aqueous solution into mixed solution A, stir well, and heat in a water bath at 70°C for 3h -6h to obtain the mixed solution B, after the mixed solution B is cooled to room temperature, centrifuge and wash, age in 1mol/L KOH solution at 60°C for 12h, centrifuge, wash and dry to obtain TiO ₂ precursor powder C;

(2) Add 0.4g of precursor powder C to 20mL 0.01g/mL cetyltrimethylammonium bromide aqueous solution and mix evenly, pour into a 25mL hydrothermal kettle and heat at 180°C for 2h, centrifuge, wash, After drying, TiO ₂ crystal powder with litchi-like micro-nano hierarchical structure is obtained.

The scanning electron microscope image of the obtained litchi-like micro-nano hierarchical structure TiO ₂ crystal is shown in FIG. 5 . It can be seen that the TiO ₂ crystal is generally spherical, with a diameter of about 600 nm, and spherical protrusions with a diameter of about 10 nm are evenly distributed on the spherical surface.

Example 4

(1) Mix 200g PVP, 2500mL water and 7500mL n-propanol to prepare mixed solution A, slowly pour 5000mL 0.8mol/L Ti(SO ₄ ) ₂ aqueous solution into mixed solution A, stir well, and heat in a water bath at 70°C for 3h -6h to obtain the mixed solution B, after the mixed solution B is cooled to room temperature, centrifuge and wash, age in 1mol/L KOH solution at 60°C for 12h, centrifuge, wash and dry to obtain TiO ₂ precursor powder C;

(2) Add 40g of precursor powder C to 2000mL of DMF/water solution with a volume ratio of 1:1 and mix evenly, pour into a 2500mL hydrothermal kettle and heat at 180°C for 2h, centrifuge, wash, and dry to obtain a litchi-like TiO ₂ crystal powder with micro-nano hierarchical structure.

The scanning electron microscope picture of the precursor _TiO2 powder obtained in this embodiment, the scanning electron microscope picture of the litchi-shaped micro-nano hierarchical structure _TiO2 crystal and the XRD figure of the precursor _TiO2 and the litchi-shaped micro-nano hierarchical structure _TiO2 crystal are the same as the implementation Figures 1-3 in Example 1.

Example 5

This embodiment is used as a comparative example to detect the effect of PVP addition on litchi-like micro-nano hierarchical structure TiO ₂ crystals. The PVP addition is 1.5g, and the rest of the conditions are the same as in Example _1. The scanning electron microscope image of the obtained precursor TiO As shown in Figure 6, it can be seen that the precursor TiO ₂ has agglomeration phenomenon, because the surfactant concentration is not high and the steric hindrance effect is not obvious.

Example 6

This embodiment is used as a comparative example to detect the effect of KOH addition concentration in step (1) during aging on the influence of lychee-like micro-nano hierarchical structure _TiO2 crystals during aging. The KOH addition concentration is 2mol/L, and all the other conditions are the same as in Example 1 . The scanning electron microscope image of the obtained precursor TiO ₂ is shown in Figure 7. It can be seen that the shape of the precursor TiO ₂ is not uniform, and there are small particles or pits on the sphere. The reason is that the concentration of KOH is too high, which has a corrosive effect on the precursor.

Example 7

Embodiment 1-3 is carried out degrading methylene blue experiment: 50mg composite photocatalyst degrades the methylene blue solution of 30mL, 20mg/L, irradiates with ultraviolet lamp as light source, takes a sample once every 15 minutes, measures absorbance after centrifugation (stirs 30min under dark condition first Sampling, taking the absorbance of the solution after dark adsorption as blank), a total of 6 samples were taken. The results are shown in Figure 8. The samples of the three examples can completely degrade the methylene blue solution within 60 minutes, and the best degradation effect is that of Example 1, which is completely degraded within 45 minutes.

Embodiment group 1-3 has the efficiency of good photocatalytic degradation methylene blue, and reason is that the adsorption property of embodiment 1-3 sample is very big, and in photocatalytic reaction surface adsorption ability has very big influence to catalytic activity, relatively The strong adsorption capacity of TiO ₂ can increase the photocatalytic reaction rate, while the litchi-like micro-nano hierarchical TiO ₂ crystal surface structure increases the surface area and improves the photocatalytic rate.

Claims (4)

1. a lychee-like micro-nano hierarchical structure _TiO2Crystal and synthetic method thereof, it is characterized in that, described lychee-like micro-nano hierarchical structure _TiO2The crystal is spherical, and the spherical surface is distributed with spherical protrusions of small particle size, crystal form Anatase type; The TiO ₂ spherical diameter of the lychee-shaped micro-nano hierarchical structure is 500-700nm, and the diameter of the spherical protrusion is 10-20nm. 2. a kind of lychee shape micro-nano hierarchical structure TiO as claimed in claim ₁ Crystal and synthetic method thereof, is characterized in that, preparation step is as follows: (1) Under room temperature conditions, PVP, water and n-propanol are made into mixed solution A, the mass volume volume ratio of PVP, water and n-propanol is 1.6-2:25:75, and Ti(SO ₄ ) Slowly pour _{the 2} solution into the mixed solution A, stir evenly, heat in a water bath at 70°C for 3h-6h to obtain the mixed solution B, after the mixed solution B is cooled to room temperature, centrifuge and wash, the molar concentration is 1-1.8mol/L Aged in KOH solution at 60°C for 12h, centrifuged, washed and dried to obtain precursor TiO ₂ powder C; (2) Mix the precursor powder C and the solvent D evenly, the mass volume ratio of the precursor powder C and the solvent D is 0.4:20, put it into a hydrothermal kettle and heat it at 180°C for 2 hours, centrifuge, wash and dry Finally, TiO ₂ crystal powder with litchi-like micro-nano hierarchical structure is obtained. 3. A kind of lychee-like micro-nano hierarchical structure TiO ₂ crystal and its synthesis method as claimed in claim 2, characterized in that: in the step (1), the molar concentration of Ti(SO ₄ ) ₂ solution is 0.8mol/ L, the volume ratio V/V of the Ti(SO ₄ ) ₂ solution to the mixed solution A is 1:2. 4. a kind of lychee-like micro-nano hierarchical structure TiO as claimed in claim ₂ crystal and synthesis method thereof, is characterized in that: in described step (2), solvent D is ethylene glycol, 0.01g/mL hexadecanol Alkyltrimethylammonium bromide aqueous solution or DMF/water solution with a volume ratio of 1:1.