Hollow core-shell structure nitrogen-doped TiO2Method for preparing microspheres
阅读说明：本技术 一种中空型核壳结构的掺氮TiO2微球的制备方法 (Hollow core-shell structure nitrogen-doped TiO2Method for preparing microspheres ) 是由 杨晟尧 孔洋波 林路云 张捷 于 2019-08-30 设计创作，主要内容包括：本发明属于光催化纳米材料领域,提供了一种中空型核壳结构的掺氮TiO_2微球的制备方法,包括如下步骤：(1)制备二氧化钛溶胶,(2)制备PAM@TiO_2单壳层核壳微球,(3)制备SiO_2@PAM@TiO_2双壳层核壳微球,(4)制备SiO_2@@TiO_2-xNx中空型核壳结构微球；本发明采用提供N元素的聚丙烯酰胺和二氧化钛混合形成单壳层核壳微球,再进行二氧化硅外壳的覆膜形成双壳层核壳微球,在高温煅烧下,作为中间壳层的聚丙烯酰胺一方面发生热分解去除形成空腔,一方面热分解后提供N元素热扩散掺杂进入二氧化钛中,得到中空型核壳结构的掺氮TiO2微球,制备方法简单,二氧化钛改性和核壳结构二氧化钛改性和核壳结构一体成型,降低了成本,提高了光催化产品的光催化效率和稳定性。(The invention belongs to the field of photocatalytic nano materials, and provides nitrogen-doped TiO with a hollow core-shell structure 2 The preparation method of the microsphere comprises the following steps: (1) preparing titanium dioxide sol, (2) preparing PAM @ TiO 2 Single shell core-shell microball, (3) preparing SiO 2 @PAM@TiO 2 Double-shell core-shell microspheres, and (4) preparation of SiO 2 @@TiO 2 -xNx hollow core-shell structure microspheres; the invention adopts polyacrylamide and titanium dioxide which provide N element to mix to form single-shell nuclear shell microspheres, and then carries out film coating of silicon dioxide shellThe preparation method is simple, the titanium dioxide modification and the core-shell structure titanium dioxide modification are integrally formed, the cost is reduced, and the photocatalysis efficiency and the stability of a photocatalysis product are improved.)
1. Hollow core-shell structure nitrogen-doped TiO2The preparation method of the microsphere is characterized by comprising the following steps:
step 1: preparing titanium dioxide sol, slowly adding a mixed solution of butyl titanate and absolute ethyl alcohol into a nitric acid solution, and uniformly stirring to obtain colorless and transparent titanium dioxide sol;
step 2: preparation of PAM @ TiO2Mixing the titanium dioxide sol prepared in the step 1 with a polyacrylamide aqueous solution, adding an initiator to perform polymerization reaction, and cleaning and drying a polymerization product for multiple times to obtain the single-shell core-shell microspheres with polyacrylamide coated on the surface of titanium dioxide;
and step 3: preparation of SiO2@[email protected]2Carrying out silica film coating on the surface of the single-layer shell-core microsphere obtained in the step 2 by adopting a sol-gel method to obtain PAM @ TiO2The surface of the shell is wrapped with the double-shell core-shell microspheres of silicon dioxide;
and 4, step 4: preparation of SiO2@@TiO2Removing a polyacrylamide intermediate shell layer in the double-shell nuclear shell microsphere by adopting a high-temperature calcination method, doping N element generated by thermal decomposition of polyacrylamide into titanium dioxide in the process, cooling and grinding after calcination is finished to obtain the nitrogen-doped TiO with the hollow nuclear shell structure2And (3) microspheres.
2. Such asThe hollow core-shell structure of claim 1, wherein the doped TiO is doped with nitrogen2The preparation method of the microspheres is characterized in that in the step 1, the mass ratio of butyl titanate to absolute ethyl alcohol substances in the mixed solution is 1: 3-8, the concentration of the nitric acid solution is 0.8-1.2 mol/L, and the volume ratio of the mixed solution to the nitric acid solution is 1: 2-5.
3. The preparation method of the nitrogen-doped TiO2 microsphere with the hollow core-shell structure according to claim 1, wherein the concentration of the polyacrylamide aqueous solution in the step 2 is 0.1-0.3%.
4. The hollow core-shell structure of claim 1, wherein said TiO is doped with nitrogen2The preparation method of the microsphere is characterized in that the initiator in the step 2 is one or more of ammonium persulfate, potassium persulfate or sodium bisulfite.
5. The hollow core-shell structure of claim 1, wherein said TiO is doped with nitrogen2The preparation method of the microspheres is characterized in that the polymerization product in the step 2 is sequentially subjected to anhydrous formaldehyde cleaning, nitrogen drying, anhydrous acetone cleaning and nitrogen drying.
6. The hollow core-shell structure of claim 5, wherein the doped TiO is doped with nitrogen2The preparation method of the microspheres is characterized in that the anhydrous acetone cleaning adopts a Soxhlet extraction method.
7. The hollow core-shell structure of claim 1, wherein said TiO is doped with nitrogen2The preparation method of the microspheres is characterized in that in the step 4, the high-temperature calcination is carried out by adopting a muffle furnace, and the calcination temperature is 500-700 ℃.
8. The hollow core-shell structure of claim 1, wherein said TiO is doped with nitrogen2The preparation method of the microsphere is characterized in that before the step 4, the double-shell core-shell microsphere obtained in the step 3 is corroded by corrosive agent steamSo as to remove part of the silicon dioxide shell to form an opening.
9. The hollow core-shell structure of claim 8, wherein the doped TiO is doped with nitrogen2The preparation method of the microsphere is characterized in that the corrosive is hydrofluoric acid or inorganic strong base.
10. The hollow core-shell structure of claim 1, wherein said TiO is doped with nitrogen2The preparation method of the microsphere is characterized in that the grinding in the step 4 adopts a ball milling method.
Technical Field
The invention belongs to the field of photocatalytic nano materials, and particularly relates to a hollow core-shell structure nitrogen-doped TiO2A method for preparing microspheres.
Background
Titanium dioxide (chemical formula: TiO)2) The titanium dioxide photocatalyst has the advantages of good photocatalysis, no toxicity, low cost, easy obtaining, simple preparation, stable performance, no occurrence of photo corrosion and the like, so the titanium dioxide photocatalyst is considered to be one of the photocatalysts with the best performance and the most promising development prospect, after the titanium dioxide is excited by ultraviolet light, electrons and holes are separated, the generated strong redox capacity can even break C-H bonds, and therefore the titanium dioxide photocatalyst can be used for decomposing most organic matters and is widely applied to the fields of environmental catalysis, energy storage, sterilization, photocells, sensor devices and the like.
Because titanium dioxide has stronger redox ability, the surface of an organic carrier can be corroded while organic matters are decomposed, and a layer of silicon dioxide is coated on the surface of titanium dioxide nano particles by a common method such as a sol-gel method so as to protect the organic carrier from being corroded by titanium dioxide nano particles; however, since silica is an insulator, electrons or holes cannot reach the surface of the titania nanoparticles, thereby affecting the catalytic activity of the titania nanoparticles. In order to solve the problems, at present, researchers wrap a hollow silica protective layer on the surface of titanium dioxide nano particles, and due to the existence of the hollow layer, the problem that titanium dioxide corrodes an organic carrier is well solved, and meanwhile, certain catalytic activity is kept, but after titanium dioxide is treated, the catalytic activity of the titanium dioxide is reduced to a certain extent, and the catalytic activity of the titanium dioxide is researched to be 60% -80% of that before the titanium dioxide is treated.
In addition, because the titanium dioxide has a large bandwidth, only ultraviolet light with a wavelength less than 400nm can be absorbed and utilized, and the titanium dioxide has no catalytic efficiency under the light irradiation with a wavelength more than 400nm, the absorption and utilization capacity of the titanium dioxide to visible light is limited, so how to further improve the visible light catalytic action of the titanium dioxide becomes a research hotspot and difficulty of new environment-friendly catalytic materials.
The photocatalytic activity of titanium dioxide is affected by factors such as its own crystal structure, specific surface area, particle size, energy band structure, surface hydroxyl concentration, etc., and in order to improve the photocatalytic activity of semiconductors, in the past research, the research of doping various transition metals is widely used for expanding the visible region of the light absorption range, the metal ions can effectively improve the photocatalysis of the titanium dioxide, however, because the thermodynamics of metal ions is unstable, the problem of the compounding of photocarrier ions is easily caused, and in order to effectively improve the problem, researches find that non-metal elements can be added into titanium dioxide to neutralize the reaction of different ions, the non-metal element N is doped into the titanium dioxide, and the solid phase reaction can strengthen the reaction with visible light, so that the titanium dioxide has visible light photocatalytic activity and is considered as a breakthrough of titanium dioxide visible light photocatalysis.
In summary, the modification of titanium dioxide by doping a non-metal N element while performing the structure setting of the silica protective layer on the titanium dioxide is significant for improving the photocatalytic activity of titanium dioxide, and the existing method is to prepare titanium dioxide microspheres with hollow core-shell structures first, and then to dope nitrogen into titanium dioxide particles by using a modification technology, so as to enhance the response of the titanium dioxide microspheres to visible light, and the process is tedious, affects the stability of the product, and needs to be improved urgently.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a preparation method of a hollow core-shell structure nitrogen-doped TiO2 microsphere, which does not need to prepare a template, can prepare a protective shell at one time by construction and N doping, avoids a complicated preparation process, can reduce the cost and improve the stability of a product.
The technical scheme adopted by the invention provides a preparation method of a nitrogen-doped TiO2 microsphere with a hollow core-shell structure, which comprises the following steps:
step 1: preparing titanium dioxide sol, slowly adding a mixed solution of butyl titanate and absolute ethyl alcohol into a nitric acid solution, and uniformly stirring to obtain colorless and transparent titanium dioxide sol;
step 2: preparation of PAM @ TiO2Slowly adding polyacrylic acid into water to dissolve under the conditions that the water temperature is 40 ~ 60 ℃ and the stirring speed is 100 ~ 300r/min, preparing a 0.15% polyacrylic acid aqueous solution, mixing the obtained polyacrylamide aqueous solution with the titanium dioxide sol prepared in the step 1, adding an initiator to perform polymerization reaction, cleaning and drying the polymerization product for multiple times to obtain the single-shell core-shell microspheres with the surfaces of the titanium dioxide coated with the polyacrylamide;
and step 3: preparation of SiO2@[email protected]2Carrying out silica film coating on the surface of the single-layer shell-core microsphere obtained in the step 2 by adopting a sol-gel method to obtain PAM @ TiO2The surface of the shell is wrapped with the double-shell core-shell microspheres of silicon dioxide;
and 4, step 4: preparation of SiO2@@TiO2-xNxRemoving the shell obtained in the step 4 by adopting a high-temperature calcination method to form a polyacrylamide intermediate shell layer in the perforated double-shell-layer core-shell microsphere, wherein in the high-temperature calcination process, N element generated by thermal decomposition of polyacrylamide is subjected to thermal diffusion doping and enters TiO2The crystal lattices can be uniformly mixed at the molecular level, and the nitrogen-doped TiO with a hollow core-shell structure is obtained by cooling and grinding after the calcination2And (3) microspheres.
Furthermore, the quantity ratio of the butyl titanate to the absolute ethyl alcohol substance in the mixed solution in the step 1 is 1:3 ~ 8, the concentration of the nitric acid solution is 1 ~ 1.5.5 mol/L, and the volume ratio of the mixed solution to the nitric acid solution is 1:2 ~ 5.
Further, the concentration of the polyacrylamide aqueous solution in step 2 was 0.1 ~ 0.3.3%.
Further, in the step 2, the initiator is one or more of ammonium persulfate, potassium persulfate and sodium bisulfite.
Further, the polymerization product in the step 2 is sequentially subjected to anhydrous formaldehyde cleaning, nitrogen drying, anhydrous acetone cleaning and nitrogen drying.
Further, the anhydrous acetone washing adopts a soxhlet extraction method, a soxhlet extractor is adopted to extract the single-shell core-shell microspheres, and anhydrous acetone is used for condensation and reflux for 24 ~ 48h to remove polymers physically adsorbed on the surfaces of the single-shell core-shell microspheres.
Further, the high-temperature calcination in the step 4 adopts a muffle furnace for calcination, and the calcination temperature is 500 ~ 700 ℃.
Further, before the step 4, the double-shell core-shell microspheres obtained in the step 3 are subjected to corrosion treatment by using corrosive agent steam to remove part of the silica shell to form open pores, and the open pores can enable TiO to be arranged2The inner core is partially exposed, so that the photocatalytic performance is better improved.
Further, the corrosive agent is hydrofluoric acid or inorganic strong base.
Furthermore, the grinding in the step 4 adopts a ball milling method, the hollow titanium dioxide microspheres prepared by the ball milling method have uniform particle size and small size, and the particle size range of the hollow titanium dioxide microspheres is 200 ~ 600 nm.
The invention has the beneficial effects that:
1. the invention adopts polyacrylamide and titanium dioxide which provide N element to mix to form single-shell nuclear shell microsphere, then carries out film covering of silicon dioxide shell to form double-shell nuclear shell microsphere, under high temperature calcination, on one hand, the polyacrylamide which is used as an intermediate shell layer is thermally decomposed to remove and form a cavity, on the other hand, the N element is provided after thermal decomposition to be thermally diffused and doped into the titanium dioxide, and the nitrogen-doped TiO with hollow nuclear shell structure is obtained2The microsphere greatly simplifies the conventional preparation process of firstly modifying the crystal structure and then modifying titanium dioxide by a modification method, the preparation method is simple, the titanium dioxide modification and the core-shell structure are integrally formed, the cost is reduced, and the photocatalytic efficiency and the stability of a photocatalytic product are improved;
2. after the hollow core-shell structure provided by the silicon dioxide is used for protection, the problem that the titanium dioxide corrodes the organic carrier is avoided, the organic carrier can be protected from being damaged, other molecules can be absorbed by the inner cavity part of the hollow core-shell structure, the contact between reactants and the photocatalyst is enhanced, the photocatalytic activity is improved, meanwhile, the band gap of TiO2 can be narrowed by substituting a small amount of lattice oxygen with N element provided by thermal decomposition of polyacrylamide, the visible light catalytic capability of the titanium dioxide is effectively improved under the condition of not sacrificing the ultraviolet light activity, and the application range of the photocatalyst is enlarged.
Detailed Description
The technical solution of the present invention will be further described with reference to the specific embodiments of the present invention.