CN113213530A

CN113213530A - High-concentration anion-doped TiO2And preparation method and application thereof

Info

Publication number: CN113213530A
Application number: CN202110398687.9A
Authority: CN
Inventors: 纪效波; 邓杏兰; 邹国强; 侯红帅
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2021-04-12
Filing date: 2021-04-12
Publication date: 2021-08-06

Abstract

The invention provides high-concentration anion-doped TiO₂And a preparation method and application thereof, wherein the preparation method comprises the following steps: firstly, pre-carbonizing a titanium source, introducing oxygen vacancy defects into the pre-carbonized titanium source by a high-temperature hydrogen reduction method, then doping by diffusion of a doping source in a protective atmosphere, washing a doping product, and drying in vacuum to obtain high-concentration anion-doped TiO₂(ii) a Wherein the titanium source is Ti-MOF, anatase and rutile TiO₂The doping source is one of sublimed sulfur, selenium simple substance and red phosphorus. The preparation method of the invention introduces oxygen vacancy defects through hydrogen reduction treatment, utilizes the oxygen vacancies to assist heteroatoms to enter the crystal lattices of titanium dioxide or Ti-MOF, realizes the doping level of high-concentration anions, has the characteristics of short flow, simple operation, rapidness and high efficiency, and is beneficial to industrial production.

Description

High-concentration anion-doped TiO2And preparation method and application thereof

Technical Field

The invention relates to doped TiO₂The field of preparation technology, more specifically, relates to high-concentration anion-doped TiO₂And a preparation method and application thereof.

Background

Titanium dioxide is favorable for migration and intercalation of sodium ions due to the fact that octahedral gap positions are shared at the edges, and characteristics of small volume change, low sodium intercalation potential, semiconductors and the like in the charge-discharge process are paid attention in recent years, so that titanium dioxide is very popular in the fields of catalysis, energy storage and gas storage. However, the current preparation method of graphene is complex and high in cost, and the application of graphene is greatly limited. The graphitized carbon has the structural characteristics similar to those of graphene, has excellent electrical conductivity and thermal conductivity, and is a material most likely to replace graphene. However, anatase type TiO₂Has low electronic conductivity and slow ion diffusion, and is not beneficial to sodium ions in TiO₂Diffusion and de-intercalation in the solid phase, slow charge transfer kinetics, and great limitation on large-scale application of the solid phase in the field of energy storage. Heteroatom doping can increase TiO₂The mixed state in the electronic structure reduces the band gap, adjusts the electron cloud distribution and orbital change, promotes charge transfer/transport, modifies the electrode/electrolyte interface thermodynamics and gives pseudo-capacitance behavior. Thereby increasing the electronic conductivity and the ion migration rate of the titanium dioxide and improving the electrochemical performance, particularly the rate performance under large current.

However, since hetero atoms such as (S, Se, P, etc.) have a large atomic radius, it is difficult to incorporate them into TiO using conventional techniques such as sol-gel method, electron beam irradiation method, and physical or chemical deposition method₂In the lattice, the formation energy required for substituting lattice atoms due to the cleavage of Ti-O bonds and hetero atoms is large. Moreover, most of the methods have complex reaction, the reaction is carried out in a solvent and needs to be finished in several steps, and the doping concentration is low and cannot be effectively regulated and controlled. TiO has so far been produced by the strong interaction of Ti-O₂The doping level of the prepared heteroatom-doped titanium dioxide is still in an unsatisfactory stage, and the low doping amount and the uncontrollable doping level of the prepared heteroatom-doped titanium dioxide greatly limit the application of the titanium dioxide in other various aspects.

Disclosure of Invention

Aiming at the defects of low doping amount, uncontrollable doping amount, high energy consumption, high cost and the like in the preparation process of heteroatom-doped titanium dioxide in the prior art, the invention aims to provide the preparation method of the high-concentration anion-doped titanium dioxide, which has high doping concentration, controllable doping amount, simple and convenient operation and short period.

In order to achieve the technical purpose, the technical scheme of the invention is as follows:

high-concentration anion-doped TiO₂The preparation method comprises the steps of pre-carbonizing a titanium source, introducing oxygen vacancy defects into the pre-carbonized titanium source through a high-temperature hydrogen reduction method, doping through diffusion of a doping source in a protective atmosphere, washing a doping product, and drying in vacuum to obtain the high-concentration anion-doped TiO₂(ii) a Wherein the titanium source is Ti-MOF, anatase and rutile TiO₂The doping source is one of sublimed sulfur, selenium simple substance and red phosphorus.

The high-concentration anion-doped TiO of the invention₂The preparation process mainly uses at least one of Ti-MOF, anatase titanium source and rutile titanium dioxide as a titanium source, uses sublimed sulfur, selenium simple substance and red phosphorus as a heteroatom source, the titanium source after pre-carbonization loses oxygen atoms in hydrogen reducing atmosphere, introduces oxygen vacancy defects, and simultaneously, due to the introduction of the defects, the crystallinity of the titanium dioxide or Ti-MOF crystal is slightly deteriorated, under protective atmosphere, the heteroatoms diffuse and migrate into crystal lattices of the titanium dioxide and the Ti-MOF, occupy the positions of the oxygen vacancies, and form bonds with Ti atoms in the crystal lattices again, and finally the titanium dioxide material doped with high-concentration anions can be obtained.

In some embodiments, the mass ratio of the titanium source to the dopant source is 1: (20 to 50). More preferably, the mass ratio of the Ti-MOF precursor to the doping source is 1 (35-50).

In some embodiments, the Ti-MOF is MIL-125.

In some embodiments, the titanium source is pre-carbonized at 400 ℃ for 2 h; and/or the atmosphere of the high-temperature hydrogen reduction treatment is hydrogen-argon mixed gas, and the volume fraction of the hydrogen is 5%; the reduction temperature is 600 ℃, and the treatment time is 1-2 h.

In some embodiments, the treatment temperature in the doping process is 500 ℃ and the treatment time is 1-2 h.

In some embodiments, the temperature rise in the high-temperature hydrogen reduction is 5-10 ℃/min.

In some embodiments, the doped product is ultrasonically cleaned for 20-30 min after the organic solvent is used. Specifically, when the sulfur and selenium elements are doped, sulfur dioxide is selected as the organic solvent; when the phosphorus element is doped, the organic solvent is phosphorus tribromide.

It is another object of the present invention to provide a high concentration anion-doped TiO₂The TiO2 is produced by the production method according to any one of the above embodiments.

In some embodiments, when sulfur doping is performed, the doped TiO₂The sulfur content is 9.82 at%; when phosphorus doping is carried out, TiO after doping₂The content of the medium phosphorus is 11.5 at%; when selenium doping is performed, the doped TiO₂The content of selenium in the product is 3.76 at%.

Compared with the prior art, the invention has the following beneficial technical effects:

1) the preparation method is carried out under the condition of no solvent, and overcomes the defects of high solvent consumption and environmental pollution of hydrothermal and solvothermal methods in the prior art.

2) The preparation method of the invention introduces oxygen vacancy defects through hydrogen reduction treatment, utilizes the oxygen vacancies to assist heteroatoms to enter the crystal lattices of titanium dioxide or Ti-MOF, realizes the doping level of high-concentration anions, has the characteristics of short flow, simple operation, rapidness and high efficiency, and is beneficial to industrial production.

3) The invention prepares high-concentration anion-doped TiO for the first time₂The material can reduce the crystallinity of titanium dioxide by oxygen vacancy defect introduced by hydrogen, and break Ti-O bonds with strong interaction, thereby being beneficial to the diffusion and migration of heteroatoms with larger radius into titanium dioxide crystal lattices to form bonds with the crystal lattice Ti atoms and realizing the doping of high-concentration heteroatoms; and the content of the heteroatom can be controlled by the concentration of oxygen vacancy and the amount of the doping source, and the prepared high-concentration anion-doped TiO₂The material has high concentration of anion doping level, and can effectively increaseThe electron conductivity and the ion diffusion rate of the titanium oxide improve the bulk charge transfer dynamics of the titanium dioxide, so that the titanium dioxide can be widely applied to the fields of catalysis, energy storage and the like.

4) Anion-doped TiO produced by the production method of the present invention₂When sulfur doping is carried out, the sulfur doping amount of the doped titanium dioxide reaches 9.82 at%; when selenium doping is carried out, the selenium doping amount in the doped titanium dioxide reaches 3.76 at%; when the phosphorus doping is carried out, the phosphorus doping amount in the doped titanium dioxide reaches 11.5at percent.

Drawings

FIG. 1 shows the high concentration of sulfur-doped TiO obtained in example 1₂Material XRD pattern;

FIG. 2 shows the high concentration of sulfur-doped TiO obtained in example 1₂Scanning electron micrographs of the material;

FIG. 3 a shows the high concentration of sulfur-doped TiO obtained in example 1₂Scanning electron micrograph of the material, b is the high-concentration sulfur-doped TiO obtained in example 1₂Transmission electron micrographs of the material;

FIG. 4 shows the high concentration of sulfur-doped TiO obtained in example 1₂A Raman map of the material;

FIG. 5 shows the high concentration of sulfur-doped TiO obtained in example 1₂A nitrogen adsorption and desorption curve chart of the material;

FIG. 6 shows the high concentration of sulfur-doped TiO obtained in example 1 and comparative example 1₂An EPR map of the material;

FIG. 7 shows the high concentration of sulfur-doped TiO obtained in example 1₂XPS survey of materials

FIG. 8 shows the low concentration of sulfur-doped TiO obtained in comparative example 1₂XPS survey of materials

FIG. 9 is an EPR chart of titanium dioxide treated with hydrogen gas for 1 and 2 hours in comparative example 2

FIG. 10 shows the higher concentration of sulfur-doped TiO obtained in comparative example 2₂XPS survey of materials

FIG. 11 shows the high concentration of phosphorus-doped TiO obtained in example 2₂XRD pattern of material

FIG. 12 shows the high concentration of phosphorus-doped TiO obtained in example 2₂XPS spectra of the material, where a is the full spectrum, b is the O1s fine spectrum, c is the P2P fine spectrum, and d is the Ti 2P fine spectrum.

FIG. 13 shows the high concentration of selenium-doped TiO obtained in example 3₂XRD pattern of the material.

FIG. 14 shows the high concentration of selenium-doped TiO obtained in example 3₂XPS spectra of the material, wherein a is the full spectrum, b is the O1s fine spectrum, c is the Se 3d fine spectrum, and d is the Ti 2p fine spectrum.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather should be construed as broadly as the present invention is capable of modification in various respects, all without departing from the spirit and scope of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Example 1

2-NH is reacted₂Placing the MIL-125 precursor in a porcelain boat, heating to 400 ℃ in a muffle furnace at the heating rate of 5 ℃/min, and pre-carbonizing for 2 h; then at H₂Heating to 600 ℃ in a mixed atmosphere of/Ar (the volume fraction of hydrogen is 5%) at a heating rate of 10 ℃/min, and reacting for 2 hours at constant temperature; naturally cooling to room temperature, and collecting black titanium dioxide powder rich in oxygen vacancies; 1.0 g of sulphur sublimate powder is filled in a porcelain boat, the sulphur sublimate is placed at an upper atmosphere opening of a tube furnace, a black titanium dioxide sample is placed at a lower atmosphere opening, the temperature is raised to 500 ℃ at the heating rate of 10 ℃/min in the argon protective gas, and the temperature is kept for 2 hours; after completion of the reaction, it was cooled to room temperature and quenched with carbon disulfide (CS)₂) And Deionized (DI) water washing to remove excessive S, and vacuum drying at 65 deg.C to obtain high-concentration sulfur-doped titanium dioxide. The obtained sulfur-doped TiO₂Performing related performance tests, the test results are shown in FIGS. 1-7: fig. 1 is an XRD picture thereof, and it can be observed that the high-concentration sulfur-doped titanium dioxide prepared by the present method has all diffraction peaks of anatase. FIG. 2 is a scanning electron micrograph showing that the obtained high-concentration sulfur-doped titanium dioxide has a regular octahedral morphology. FIG. 3 shows a high resolution transmission electron micrograph of the resulting high concentration sulfur-doped titanium dioxide having a lattice spacing of 0.35nm corresponding to the (101) crystal plane of anatase. Since the radius of the sulfur atom is larger than that of the oxygen atom, the lattice spacing of titanium dioxide becomes larger after the sulfur atom is doped. FIG. 4 is a Raman spectrum of the resulting high-concentration sulfur-doped titanium dioxide, from which the characteristic Raman peak Eg at 151.9cm of anatase titanium dioxide can be clearly observed^-1,B1g at 406.3cm^-1,A1g at 510.4cm^-1,and Eg at 630.2cm^-1And the S elementary substance has no characteristic peak, which proves that the elementary substance sulfur is completely cleaned by the organic solvent. FIG. 5 is a nitrogen adsorption/desorption curve of the resulting product, which shows a type VI adsorption/desorption curve indicating that the resulting material has mesoporous characteristics and a specific surface area of 33.1m2 g^-1The specific surface area improved due to defects and doping is embodied; simultaneously from N₂The absorption and desorption can know that the pore volume of the material is 0.0078m³ g^-1. FIG. 6 shows the resulting hydrogen-treated and argon-treated TiO₂EPR diagram of the material from which a signal at g 2.035 was observed, indicating that the hydrogen-treated titanium dioxide contains oxygen vacancies and the peak at g 1.951 is predictive of Ti³⁺The presence of ions. FIG. 7 is an XPS survey spectrum of the resulting material, from which it is apparent that the material contains 9.82 at% elemental sulfur.

Comparative example 1

Pre-carbonized 2-NH₂MIL-125 was heated to the same temperature of 600 ℃ in a pure Ar atmosphere, and was maintained at the same temperature for 2 hours, and the sulfur doping process was performed by the same procedure as in example 1, and the obtained sample was expressed as low-sulfur-doped titanium dioxide. As shown in FIG. 6, the argon-treated titanium dioxide is free of oxygen vacancies and Ti³⁺Indicating that an argon atmosphere is not suitable for creating oxygen vacancies. In the XPS survey spectrum of the low sulfur doped titanium dioxide material of FIG. 8, no peak of sulfur is seenIt follows that high concentration sulfur doping in titanium dioxide cannot be achieved without the aid of oxygen vacancies.

Comparative example 2

Pre-carbonized 2-NH₂MIL-125 at H₂Heating to 600 ℃ at a heating rate of 10 ℃/min in a mixed atmosphere of/Ar (hydrogen volume fraction of 5%), reacting at a constant temperature for 1 hour, and carrying out a sulfur doping process by the same procedure as in example 1 to obtain a sample expressed as sulfur-doped titanium dioxide with a higher concentration. As shown in fig. 9, the higher concentration of sulfur-doped titanium dioxide has signals at both g 2.035 and g 1.951, but the peaks are less intense than the two hour hydrogen treated samples, indicating a lower concentration of oxygen vacancies. From the XPS spectrum of the sample of fig. 10, it can be seen that the S content in the higher concentration sulfur-doped titanium dioxide is 7.38 at%. It can be seen that the concentration of oxygen vacancies directly affects the doping amount of sulfur, and higher vacancy concentration is beneficial to realize high-concentration sulfur doping.

Example 2

2-NH is reacted₂Placing the MIL-125 precursor in a porcelain boat, heating to 400 ℃ in a muffle furnace at a heating rate of 5 ℃/min, and pre-carbonizing for 2 h; then at H₂Heating to 600 ℃ in a mixed atmosphere of/Ar (the volume fraction of hydrogen is 5%) at a heating rate of 10 ℃/min, and reacting for 2 hours at constant temperature; naturally cooling to room temperature, and collecting black titanium dioxide powder rich in oxygen vacancies; 1.0 g of red phosphorus powder is filled in a porcelain boat, the red phosphorus powder is placed in an upper atmosphere port of a tube furnace, a black titanium dioxide sample is placed in a lower atmosphere port, the temperature is raised to 500 ℃ at the heating rate of 10 ℃/min in argon protective gas, and the temperature is kept for 2 hours; after the reaction was complete, it was cooled to room temperature and treated with phosphorus tribromide (PBr)₃) And Deionized (DI) water washing to remove excessive phosphorus powder, and vacuum drying at 65 deg.C to obtain high-concentration phosphorus-doped titanium dioxide. The obtained phosphorus-doped titanium dioxide is subjected to relevant characterization tests, XRD test results are shown in figure 11, and XRD shows that the crystal form of the phosphorus-doped titanium dioxide is anatase. The XPS results of fig. 12 show that the phosphorus was successfully doped into the crystal structure of titanium dioxide, and that a doping level of up to 11.5 at% was obtained from the full spectrum of fig. 12 a. And FIGS. 12b-d are O1s, P, respectively, for phosphorus doped titanium dioxide2p and Ti 2p fine spectra. Successful incorporation of phosphorus into titanium dioxide can also be seen from these fine spectra.

Example 3

Placing the anatase precursor in a porcelain boat, heating to 400 ℃ in a muffle furnace at a heating rate of 5 ℃/min, and pre-carbonizing for 2 h; then at H₂Heating to 600 ℃ in a mixed atmosphere of/Ar (the volume fraction of hydrogen is 5%) at a heating rate of 10 ℃/min, and reacting for 2 hours at constant temperature; naturally cooling to room temperature, and collecting black titanium dioxide powder rich in oxygen vacancies; 1.0 g of selenium powder is filled in the porcelain boat, the selenium powder is placed at an upper atmosphere port of the tube furnace, the black titanium dioxide sample is placed at a lower atmosphere port, the temperature is raised to 500 ℃ at the heating rate of 10 ℃/min in the argon protective gas, and the temperature is kept for 2 hours; after completion of the reaction, it was cooled to room temperature and quenched with carbon disulfide (CS)₂) And Deionized (DI) water washing to remove excessive elemental selenium, and vacuum drying at 65 deg.C to obtain high-concentration selenium-doped titanium dioxide. The obtained selenium-doped titanium dioxide is subjected to relevant characterization tests, XRD test results are shown in figure 13, and XRD shows that the crystal form of the titanium dioxide doped with selenium is still anatase. The XPS results of fig. 14 show that Se was successfully doped into the crystal structure of titanium dioxide, and a doping level of up to 3.76 at% was obtained from the full spectrum of fig. 14 a. While FIGS. 14b-d are the O1s, Se 3d, and Ti 2p fine spectra, respectively, for phosphorus doped titania. Successful incorporation of Se into titanium dioxide can also be seen from these fine spectra.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. High-concentration anion-doped TiO₂The preparation method is characterized by comprising the following steps:

firstly, pre-carbonizing a titanium source, introducing oxygen vacancy defects into the pre-carbonized titanium source by a high-temperature hydrogen reduction method, then doping by diffusion of a doping source in a protective atmosphere, washing a doping product, and drying in vacuum to obtain high-concentration anion-doped TiO₂(ii) a Wherein the titanium source is Ti-MOF, anatase and rutile TiO₂The doping source is one of sublimed sulfur, selenium simple substance and red phosphorus.

2. The high concentration anion doped TiO of claim 1₂The preparation method is characterized in that the mass ratio of the titanium source to the doping source is 1: (20 to 50).

3. The high concentration anion doped TiO of claim 1₂The method for preparing (1), wherein the Ti-MOF is MIL-125.

4. The high concentration anion doped TiO of claim 1₂The preparation method is characterized in that the titanium source is pre-carbonized for 2 hours at 400 ℃; and/or the atmosphere of the high-temperature hydrogen reduction treatment is hydrogen-argon mixed gas, and the volume fraction of the hydrogen is 5%; the reduction temperature is 600 ℃, and the treatment time is 1-2 h.

5. The high concentration anion doped TiO of claim 1₂The preparation method is characterized in that the treatment temperature in the doping process is 500 ℃, and the treatment time is 1-2 h.

6. The high concentration anion doped TiO of claim 1₂Is characterized by a high temperatureIn the hydrogen reduction, the temperature rise is 5-10 ℃/min.

7. The high concentration anion doped TiO of claim 1₂The preparation method is characterized in that the doped product is added with an organic solvent and then is subjected to ultrasonic cleaning for 20-30 min.

8. High-concentration anion-doped TiO₂Characterized by being prepared by the preparation method of any one of claims 1 to 6.

9. The high concentration anion doped TiO of claim 8₂Characterised in that, when sulphur doping is carried out, the doped TiO is₂The sulfur content is 9.82 at%; when phosphorus doping is carried out, TiO after doping₂The content of the medium phosphorus is 11.5 at%; when selenium doping is performed, the doped TiO₂The content of selenium in the product is 3.76 at%.

10. The high concentration anion doped TiO of claim 8 or 9₂The catalyst can be used as catalyst and electrode material.