阅读说明：本技术 一种以多孔二氧化硅纤维为载体的近红外响应性光催化剂的制备方法及光催化剂 (Preparation method of near-infrared responsive photocatalyst with porous silica fiber as carrier and photocatalyst ) 是由 温世鹏 苏玉仙 刘力 于 2018-08-07 设计创作，主要内容包括：本发明提供了一种以多孔二氧化硅纤维为载体的近红外响应性的光催化剂制备方法,属于纳米科学技术领域。本发明首先以稀土氧化物为原料采用水热法获得粒径分布均匀的具有近红外响应性的核壳型纳米催化剂颗粒,然后通过静电纺丝技术结合模板法制备多孔结构的二氧化硅纤维,最后将均匀的核壳型纳米催化剂颗粒负载多孔二氧化硅纤维上。本发明制备的多孔二氧化硅纤维的表面和内壁上均匀分布着核壳型纳米催化剂颗粒,表现出良好的分散性和稳定性。另外,该制备方法成本低廉,能够实现将光催化剂的光响应范围扩展至近红外区。(The invention provides a preparation method of a near-infrared responsive photocatalyst taking porous silica fiber as a carrier, belonging to the technical field of nano science. According to the method, rare earth oxide is used as a raw material, a hydrothermal method is adopted to obtain core-shell type nano-catalyst particles with uniform particle size distribution and near-infrared responsiveness, then a silica fiber with a porous structure is prepared by combining an electrostatic spinning technology and a template method, and finally the uniform core-shell type nano-catalyst particles are loaded on the porous silica fiber. The surface and the inner wall of the porous silicon dioxide fiber prepared by the invention are uniformly distributed with core-shell type nanometer catalyst particles, and the core-shell type nanometer catalyst particles show good dispersibility and stability. In addition, the preparation method is low in cost, and the photoresponse range of the photocatalyst can be expanded to a near infrared region.)

1. A method for preparing a near-infrared responsive photocatalyst by taking porous silica fiber as a carrier is characterized by comprising the following steps:

(1) preparing upconversion crystal powder by taking rare earth oxide as a raw material and adopting a hydrothermal method;

(2) dispersing the upconversion crystal powder obtained in the step (1) in a solvent to obtain an upconversion crystal dispersion liquid, uniformly mixing a titanium dioxide precursor, a surfactant, water and absolute ethyl alcohol to obtain a titanium dioxide precursor liquid, mixing and stirring the upconversion crystal dispersion liquid and the titanium dioxide precursor liquid for 1-10 hours, reacting for 2-14 hours at 150-200 ℃, centrifuging, washing and drying a reaction product to obtain an upconversion luminescent material with a core-shell structure;

(3) dissolving polyacrylonitrile and a water-soluble polymer in a solvent, performing electrostatic spinning to obtain composite fibers, dissolving the composite fibers in water to obtain porous polyacrylonitrile fibers, placing the porous polyacrylonitrile fibers in a mixed solution of a silicon dioxide precursor, a core-shell structure up-conversion luminescent material, a surfactant and an acidic aqueous solution, fully stirring, and calcining at 700-1200 ℃ for 30 min-3 h in an inert atmosphere to obtain the photocatalyst.

2. The photocatalyst preparation method according to claim 1, characterized in that:

the rare earth oxide is selected fromY₂O₃、Yb₂O₃、Tm₂O₃、Er₂O₃、Ho₂O₃At least one of (1).

3. The photocatalyst preparation method according to claim 2, characterized in that:

the rare earth oxide comprises Y₂O₃、Yb₂O₃And Tm₂O₃Wherein the molar ratio of Y, Yb and Tm is (74.9-80): (15-25): (0.1-10.1).

4. The photocatalyst preparation method according to claim 1, characterized in that:

the titanium dioxide precursor is selected from at least one of titanium isopropoxide, butyl titanate, titanium tetrachloride, titanium sulfate and diisopropyl di (acetylacetonate) titanate.

5. The photocatalyst preparation method according to claim 1, characterized in that:

the silicon dioxide precursor is selected from at least one of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate.

6. The photocatalyst preparation method according to claim 1, characterized in that:

the water-soluble polymer is at least one selected from polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, polymaleic anhydride, polyquaternary ammonium salt and polyethylene glycol.

7. The photocatalyst preparation method according to claim 1, characterized in that:

the surfactant is at least one selected from ethylenediamine tetraacetic acid, trisodium citrate, polyvinylpyrrolidone, tartaric acid, oxalic acid, sulfosalicylic acid, cetyl trimethyl ammonium bromide and cetyl trimethyl ammonium chloride.

8. The photocatalyst preparation method according to claim 1, characterized in that:

in the step (2), the mass ratio of the up-conversion crystal, the titanium dioxide precursor and the surfactant is 5: (2-20): (5-20).

9. The photocatalyst preparation method according to claim 1, characterized in that:

in the step (3), the proportion of the up-conversion luminescent material with the core-shell structure in the silicon dioxide precursor is 0.05-10 g/L.

10. A photocatalyst obtained by the method for preparing a near-infrared responsive photocatalyst using a porous silica fiber as a carrier according to any one of claims 1 to 9.

Technical Field

The invention relates to the field of inorganic photocatalytic materials, in particular to a preparation method of a near-infrared responsive photocatalyst taking porous silica fibers as a carrier and the photocatalyst.

Background

In recent years, various organic pollutants are increased, and the application of photocatalysis technology as an advanced oxidation engineering to the degradation of photocatalysis in the aspect of dyes is also increased. However, most of the materials can only be used under the condition of ultraviolet light, and have great limitation on practical application. Therefore, it has become necessary to prepare a catalyst having a good catalytic effect under sunlight.

Titanium dioxide (TiO)₂) As an important semiconductor photocatalyst, the photocatalyst has the advantages of high catalytic activity, good stability, low price, no secondary pollution, wider band gap and the like, and is a semiconductor photocatalyst commonly used in the research of the technical field of photocatalysis at present. However, TiO₂The wide forbidden band characteristic of the semiconductor limits the optical response range of the semiconductor, and only can absorb specific ultraviolet light (lambda)<387 nm). How to extend TiO₂The range of light response is currently a focus of this area of research. At present, the TiO is doped with nonmetal, deposited with noble metal or compounded with semiconductor₂The photoresponse range extends into the visible region.

To enhance the activity of the catalyst, nanoparticles with high surface area, up to 50m in specific surface area, are often used²In the order of/g. However, such small-sized particles are too fine to be easily agglomerated and deactivated in practical use and not easily sedimented, resulting in difficulty in separation, recovery and reuse thereof.

Disclosure of Invention

To overcome the above problems in the prior art, the present invention first employs an up-conversion material to convert TiO into TiO₂The photoresponse range is expanded to a near infrared region, the up-conversion luminescent nano material can absorb long-wave radiation with low photon energy and then radiate short-wave radiation with high photon energy, so that near infrared light with low energy can be converted into ultraviolet light with high energy.

In addition, the present invention selectively uses porous adsorbent supports, wherein catalyzed molecules can be adsorbed near the photocatalytic sites, prolonging the reaction process and thereby enhancing the degradation process. In addition, the adsorbent support can retain reaction intermediates formed during photocatalytic oxidation, leading to better electron-hole separation, thereby also improving overall photocatalytic activity. The silica material has the characteristics of neutral framework, light hydrophobicity, transparency, light diffraction capability, wide aperture range and the like, and becomes an ideal choice of the photocatalytic carrier material.

Accordingly, the invention provides a hydrothermal method for synthesizing a near-infrared light-responsive up-conversion luminescent material with a core-shell structure, and aims to prepare nano particles with uniform appearance, small particle size and uniform dispersion, and then load the nano particles onto porous silica nano fibers prepared by combining an electrostatic spinning technology and a template method to obtain a near-infrared light-responsive photocatalyst taking the porous silica fibers as a carrier, which has important guiding significance for the application of the nano materials in sewage treatment.

One of the purposes of the invention is to provide a preparation method of a near-infrared responsive photocatalyst taking porous silica fiber as a carrier, which comprises the following steps:

(1) with rare earth oxides (RE)₂O₃) The upconversion crystal powder is prepared by a hydrothermal method.

The preparation method of the up-conversion crystal adopts a hydrothermal process commonly used in the field.

Preferably, the method comprises the steps of: mixing rare earth oxide (RE)₂O₃) Dissolving the mixture in strong acid, heating until water in the solution is evaporated, dissolving the mixture in water to obtain a rare earth salt dispersion liquid with the concentration of 0.01 mmol/L-10 mol/L, dissolving a surfactant in water to obtain a surfactant dispersion liquid with the concentration of 0.01 mmol/L-10 mol/L, dropwise adding the surfactant dispersion liquid into the rare earth salt dispersion liquid, violently stirring for 10 min-1 h until a white complex is formed, dropwise adding a NaF aqueous solution with 3-12 mmol of the NaF aqueous solution, continuously stirring for 1-10 h, heating the obtained mixed solution to 180-220 ℃, reacting for 2-14 h, centrifuging, washing and drying the obtained product to obtain the product with the upconversion conversion functionCrystalline powder of optical character.

The rare earth oxide is preferably Y₂O₃、Yb₂O₃、Tm₂O₃、Er₂O₃、Ho₂O₃More preferably, comprises Y₂O₃、Yb₂O₃And Tm₂O₃Wherein the molar ratio of Y, Yb and Tm is (74.9-80): (15-25): (0.1-10.1).

The strong acid is one of concentrated hydrochloric acid, concentrated nitric acid and concentrated sulfuric acid.

(2) Dispersing the upconversion crystal powder obtained in the step (1) in a solvent to obtain an upconversion crystal dispersion liquid, uniformly mixing a titanium dioxide precursor, a surfactant, water and absolute ethyl alcohol to obtain a titanium dioxide precursor liquid, mixing and stirring the upconversion crystal dispersion liquid and the titanium dioxide precursor liquid for 1-10 hours, reacting for 2-14 hours at 150-200 ℃, centrifuging, washing and drying a reaction product to obtain the upconversion luminescent material with the core-shell structure.

Wherein, the titanium dioxide precursor is preferably at least one of titanium isopropoxide, butyl titanate, titanium tetrachloride, titanium sulfate and diisopropyl di (acetylacetonato) titanate.

The mass ratio of the up-conversion crystal to the titanium dioxide precursor to the surfactant is 5: (2-20): (5-20), preferably 5: (2-10): (5-10).

The surfactant is preferably at least one selected from ethylenediaminetetraacetic acid (EDTA), trisodium citrate, polyvinylpyrrolidone (PVP), tartaric acid, oxalic acid, sulfosalicylic acid, cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC).

(3) Dissolving polyacrylonitrile and a water-soluble polymer in a solvent, performing electrostatic spinning to obtain composite fibers, dissolving the composite fibers in water to obtain porous polyacrylonitrile fibers, placing the porous polyacrylonitrile fibers in a mixed solution of a silicon dioxide precursor, a core-shell structure up-conversion luminescent material, a surfactant and an acidic aqueous solution, fully stirring, and calcining at 700-1200 ℃ for 30 min-3 h in an inert atmosphere to obtain the photocatalyst.

Preferably, the electrospinning process in the step (3) comprises: dissolving polyacrylonitrile and a water-soluble polymer into a solvent, stirring for 1-3 hours to obtain a uniform and transparent spinning solution, placing the spinning solution on an electrostatic spinning device, wherein the advancing speed is 1-10 mL/h, the distance between a needle point and a receiving device is 5-25 cm, and the rotating speed of a roller on the receiving device is 300-1000 rpm to obtain the composite fiber. The mass ratio of polyacrylonitrile to water-soluble polymer is (0.5-3): 1.

wherein the silica precursor is preferably at least one selected from the group consisting of methyl orthosilicate (TMOS), ethyl orthosilicate (TEOS), propyl orthosilicate (TPOS), and butyl orthosilicate (TBOS).

The proportion of the up-conversion luminescent material with the core-shell structure in the silicon dioxide precursor is 0.05-10 g/L, and preferably 0.2-4 g/L.

The water-soluble polymer is preferably at least one selected from polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, polymaleic anhydride, polyquaternary ammonium salt and polyethylene glycol.

The concentration of the surfactant in the step (3) is preferably 0.01-0.2 mol/L.

The acidic aqueous solution is one or more of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, carbonic acid or acetic acid. The concentration of the acidic aqueous solution is preferably 0.1-0.5 mol/L.

The solvent is at least one of absolute ethyl alcohol, xylene, dimethyl sulfoxide (DMSO), cyclohexane, N-propanol, acetone, Tetrahydrofuran (THF), N-methylpyrrolidone (NMP), diethyl ether, propylene oxide, dichloromethane (CH2Cl2), trichloromethane (CHCl3), triethanolamine and N, N-Dimethylformamide (DMF).

The inert atmosphere is one or more of nitrogen, helium, neon, argon, krypton, xenon and radon.

The invention also aims to provide a photocatalyst obtained by the preparation method of the near-infrared response photocatalyst taking porous silica fiber as a carrier.

According to the invention, porous silica fiber is used as a nano carrier, and the core-shell type up-conversion crystal prepared by a hydrothermal method is loaded in the cavity and on the surface of the core-shell type up-conversion crystal, so that the core-shell type up-conversion luminescent material loaded porous silica fiber composite material is finally obtained. The process can obtain the core-shell up-conversion luminescent material with good crystal form stability, uniform particle size distribution and uniform shell thickness, and the core-shell up-conversion luminescent material is loaded on the porous silica fiber substrate with uniform diameter and uniform pore diameter, so that the obtained composite material has uniform diameter, the core-shell up-conversion luminescent material can be uniformly distributed on the surface and inside of the fiber, the specific surface area and the stability of the fiber are improved, the photodegradation of pollutants under sunlight can be realized, and a strong photocatalysis effect can be achieved. In addition, the invention has the advantages of simple equipment, easy operation, good controllability, recycling and the like.

Drawings

FIG. 1 is a Scanning Electron Micrograph (SEM) of upconverting nanocrystals prepared according to example 13 of the present invention.

FIG. 2 is a Transmission Electron Micrograph (TEM) of the upconversion luminescent material prepared in example 13 of the present invention.

FIG. 3 is a plot of upconversion fluorescence spectra of upconverting nanocrystals and core-shell upconversion phosphors prepared in example 13 of the present invention, excited with a 980nm diode.

NaYF₄After coating titanium dioxide with Yb, Tm, the emission peak is reduced as a whole. The ultraviolet light almost disappears at 290 nm, 345 nm and 362nm, and 451 nm, 475 nm and 651 nm are obviously weakened, which shows that the core-shell upconversion luminescent material is successfully prepared, and the titanium dioxide can effectively absorb the purple light emitted by the upconversion crystal.

Fig. 4 is a scanning electron microscope (TEM) of the core-shell upconversion luminescent material-supported porous silica fiber composite prepared in example 13.

Detailed Description

The present invention will be further described with reference to the following specific embodiments, but the present invention is not limited to the following examples.