CN101301619A - Method for preparing high efficiency metallic, non-metallic ion co-doped nano-TiO2 visible-light responsive photocatalyst - Google Patents

Abstract

The invention discloses a method for preparing high-efficiency metal and nonmetal ion co-doped nano TiO ₂ visible light catalyst, which belongs to the scope of photocatalysis technology. It uses titanate as precursor, metal salt and non-metal element-containing compound as dopant, and adopts sol-gel method to prepare nano- _TiO2- based photocatalyst with dual-phase doping and high-efficiency visible light catalytic activity. The visible light catalytic activity of the catalyst greatly exceeds that of single-doped non-metal ion TiO ₂ . The present invention has the following innovations: 1. By co-doping metal and non-metallic ions, the _TiO2- based catalyst can generate discontinuous localized doping energy levels below the conduction band energy level and above the valence band energy level, thereby enhancing The visible light absorption of the catalyst is greatly improved. 2. Due to the existence of doping energy levels, the recombination of photogenerated carriers is inhibited, the probability of photogenerated carriers participating in photocatalytic reactions is increased, and pollutant molecules are effectively degraded.

Description

Preparation method of high-efficiency metal and non-metal ion co-doped nano-TiO2 visible light catalyst

【Technical field】

The invention belongs to the field of photocatalytic technology research, is mainly used in the environmental purification of water and air (removal of organic and inorganic pollutants in the environment), and is a method for preparing a novel, high-efficiency, dual-phase doped nano _TiO2 visible light catalyst.

【Background technique】

TiO ₂ has the special function of sterilizing and degrading environmental pollutants under ultraviolet light irradiation, and has the advantages of low price and good stability. It is a kind of environmental purification material with good performance. Using nano- _TiO2- based photocatalysts to use solar energy to purify the environment, it not only saves energy, but also can sterilize and degrade pollutants (organic and inorganic pollutants) in the atmosphere and water. It is an ideal science and technology for environmental governance. In recent years, it has attracted the attention of the scientific community.

However, there are still key problems in the research of _TiO2 -based catalysts in the treatment of the environment: the utilization rate of solar energy and the low photocatalytic efficiency. The reason is that TiO ₂ has a band gap of 3.2eV (corresponding to an excitation wavelength of 387.5nm), and can only absorb ultraviolet light, while the ultraviolet light component in sunlight only accounts for 5%, so the utilization rate of pure TiO ₂ to solar energy is very low; In addition, most of the photogenerated carriers recombine in the bulk phase of _TiO2 , and only a few of them participate in the photocatalytic reaction, resulting in low photocatalytic efficiency. Therefore, the application of this technology in the field of environmental governance is restricted.

In recent years, in order to improve the visible-light photocatalytic efficiency of TiO ₂ , the preparation of nano-TiO ₂ visible-light catalysts single-doped with metal or non-metal ions has attracted much attention. Internationally, Professor MR Hoffmann of California Institute of Technology in the United States doped TiO ₂ with various metal ions to study its catalytic activity under ultraviolet and visible light. Professor H. Kisch from the University of Erlangen-Nuremberg in Germany prepared a highly active TiO ₂ visible light catalyst with Pt and Au ion doping. Shahed UMKhan et al prepared a C ion-doped highly active TiO ₂ visible light catalyst. Professor R.Asahi of Toyota Central Research Institute University in Japan prepared a highly active TiO ₂ visible light catalyst doped with N ions. In China, the Chinese Academy of Sciences and various universities (Tsinghua University, Peking University, Fuzhou University, etc.) have also achieved good results in the preparation, performance and mechanism research of doped nano- _TiO2- based visible light catalysts. Single-doped nano-TiO ₂ related patents have been reported, for example: preparation method of nitrogen-doped titanium dioxide powder (application number: 02155201.0), preparation method of photocatalytically active nitrogen-doped titanium dioxide nanomaterial (application number: 200310109841.8), nitrogen Nano-doped titanium dioxide modified photocatalytic coating and its preparation method (application number: 200510011793.8), preparation method of photocatalytically active chlorine-doped titanium dioxide nanomaterial (application number: 200310109844.1), preparation of photocatalytically active fluorine-doped titanium dioxide nanomaterial Method (application number: 200310109845.6), preparation method of photocatalytically active bromine-doped titanium dioxide nanomaterial (application number: 200310109843.7), a glass coated with zinc-doped titanium dioxide film capable of sterilization and self-cleaning (application number: 200410020616.1) , rhenium-doped nano-titanium dioxide catalyst for degradation of organic pollutants (application number: 200610046163.9), cerium-doped titanium dioxide/silica gel composite photocatalyst and its preparation method (application number: 200710027809.3), and tin-doped nano-titanium dioxide photocatalyst with high catalytic activity induced by visible light Preparation method (application number: 200610011238.X).

So far, nano- _TiO2- based visible light catalysts mainly doped with single ions have certain visible light catalytic activity, but the visible light absorption efficiency and the utilization rate of photogenerated carriers are low, and the photocatalytic activity is not obvious.

The present invention adopts a new preparation method and control technology to develop "high-efficiency metal and non-metal ion co-doped nano-TiO ₂ (Ti _1-x A _x O _2-y By _y , A and B represent metal and non-metal respectively Element) Visible Light Catalyst” preparation method, and established and perfected new technologies for regulating the structure, performance and function of the catalyst, which laid the foundation for the realization of high efficiency, high performance and practical application in the field of environmental purification of visible light catalysts. The present invention proves that there is no relevant literature report through domestic and foreign patent science and technology novelty search.

【Content of invention】

The present invention prepares high-efficiency metal and nonmetal ion co-doped nano-titanium dioxide (Ti _{1 -x} A _x O 2-y By ₎ on the basis of single-doped non-metallic titanium dioxide (TiO _2-y By ) visible light _catalyst Visible light catalyst is the target product, with titanate as precursor, metal salt and non-metal element-containing compound as dopant, and the sol-gel preparation technology is used to prepare a new structure of "high-efficiency metal and non-metal ion Co-doped nano-titanium dioxide (Ti _1-x A _x O _2-y By _y ) visible light catalyst" (the visible light catalytic activity of this catalyst has exceeded that of single-doped non-metal ion TiO _2-y By _y (B represents non-metallic elements) catalyst ), and establish its preparation method and technical route. Ti _1-x A _x O _2-y By _y visible photocatalyst has the characteristics of two-phase co-doping and microscopic surface multi-component structure. Compared with single-doped non-metal ion TiO _2-y By _y , the catalyst has a greatly enhanced visible light absorption ability, effectively inhibits the recombination of photogenerated carriers, and leads to a significant increase in visible light catalytic activity.

Innovations of the present invention: 1. By co-doping metal and non-metallic ions, the TiO _2- based catalyst can produce discontinuous localized state doping energy levels below the conduction band energy level and above the valence band energy level, which is different from single doping The visible light absorption of non-metal ion TiO _2-y By _y is enhanced compared with that of non-metal ion TiO 2-y By y, so that the visible light catalytic activity of the catalyst is greatly _improved compared with single-doped non-metal ion TiO _2-y By y. 2. Due to the existence of dual-phase doping energy levels, the suppression of recombination of photogenerated carriers is enhanced, the probability of photogenerated carriers participating in photocatalytic reactions is increased, and pollutant molecules are effectively degraded. Therefore, the visible-light photocatalytic activity of the catalyst is significantly improved.

Compared with pure TiO ₂ and single-doped non-metal ion TiO _2-y By _y photocatalyst, the visible light catalytic activity of the catalyst is greatly improved, and the catalyst has the advantages of simple preparation process, low equipment requirements, and suitable for large-scale production. It has potential application prospects in the fields of environmental science and engineering applications.

【Description of drawings】

The X-ray diffraction (XRD) spectrum of Fig. 1 Example 1 (Ti _1-x Ni _x O _2-y N _y ) (compared with TiO ₂ and TiO _2-y N _y , both are in the anatase crystal form);

The ultraviolet-visible reflection absorption spectrum of Figure 2 Example 1 (Ti _1-x Ni _x O _2-y N _y ) (compared with TiO ₂ and TiO _2-y N _y , its visible light absorption is enhanced, resulting in the improvement of visible light catalytic activity );

The visible light degradation p-chlorophenol (4-chlorophenol) curve (compared with the comparative sample) of Fig. 3 embodiment 1 (Ti _1-x Ni _x O _2-y N _y );

The X-ray diffraction (XRD) spectrum of Figure 4 Example 2 (Ti _1-x Zn _x O _2-y By ₎ (compared with TiO ₂ and TiO _2-y By _y , both are anatase crystal form);

The visible light degradation p-chlorophenol (4-chlorophenol) curve (compared with the comparative sample) of Fig. 5 embodiment 2 (Ti _1-x Zn _x O _{2-y By} );

The X-ray diffraction (XRD) spectrogram of Fig. 6 embodiment 3 (Ti _1-x Sn _x O _2-y N _y ) (compared with TiO ₂ , TiO _2-y N _y and Ti _1-x Sn _x O ₂ , Both are anatase crystal form);

The visible light degradation p-chlorophenol (4-chlorophenol) curve (compared with the comparative sample) of Fig. 7 embodiment 3 (Ti _1-x Sn _x O _2-y N _y );

【Detailed ways】

1. Preparation of metal and non-metal ion co-doped visible light catalyst (Ti _1-x A _x O _2-y B _y ):

At room temperature, dissolve a certain amount of metal salt in a certain amount of diluent, then drop a certain amount of titanate into the solution, stir for 0-2 hours, add a certain amount of acid catalyst (control the sol- The hydrolysis process of the gel system, so that the polycondensation reaction is complete), stirring, after standing and aging for 0-24 hours, slowly drop a certain amount of compounds containing non-metallic elements (or its alcohol solution, or aqueous solution) during the stirring process ), stirring at room temperature until the system becomes a gel, drying the gel at 50-200°C, grinding it into powder, and sintering at 350-600°C for 0.5-10 hours to obtain metal and non-metal ion co- Sample doped with visible light catalyst (Ti _1-x A _x O _2-y B _y ).

2. In order to compare the activity, two comparative samples of pure titanium dioxide (TiO ₂ ) and single-doped non-metal ion TiO _2-y B _y were prepared respectively during the implementation process:

① Preparation of single-doped non-metal ion TiO _2-y By _y catalyst

The preparation steps are similar to Ti _1-x A _x O _2-y By _y , except that no metal salt is added.

② Preparation of pure TiO ₂ catalyst

The preparation steps are similar to Ti _1-x A _x O _2-y By _y , except that no metal salt is added, and high-purity water (18.2MΩcm ^-1 ) or corresponding alcohol is used to replace the solution of the compound containing non-metal elements for dropwise addition.

3. When preparing the above sol, the addition amount of various reactants is:

The molar ratio of metal salt to titanate is 1:1000-1:2

The volume ratio of diluent to titanate is 1:10-20:1

The volume ratio of acid catalyst to titanate is 1:30-1:2

The molar ratio of compounds containing non-metallic elements to titanate is 1:30-10:1

The titanate is any one or a mixture of tetrabutyl titanate, isopropyl titanate, propyl titanate or ethyl titanate.

The diluent is any one or a mixture of absolute ethanol, absolute methanol, propanol or isopropanol.

The acid catalyst is any one or a mixture of hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, perchloric acid or nitric acid.

The compounds containing non-metallic elements mainly refer to: ① nitrogen-containing compounds, namely urea, thiourea, ethylamine, ethylenediamine, triethylamine, triethanolamine, ammonia water, ammonium carbonate, ammonium bicarbonate, ammonium chloride Any one or a combination of several; ②Boron-containing compounds, that is, boric acid, boron trioxide, any one or a mixture of two kinds; ③Sulfur-containing compounds, that is, thiourea; ④Bromine-containing compounds, that is, bromic acid, bromine water , Bromoacetic acid, any one or a mixture of several; ⑤ Iodine-containing compounds, that is, any one or a mixture of iodine, iodic acid, iodine trichloride, and iodoacetic acid.

The metal salt is V, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Mo, Ru, Pd, Ag, In, Sn, Ta, W, Re, Pt, Au, Pb, Bi, La elements Any one or several mixtures of salts of any element that are soluble in the above diluents.

The evaluation method of photocatalytic activity is as follows: 400W Philips HPA 400/30S lamp is used as the external light source, the radiation wavelength is λ≥320nm, in the visible light experiment, a filter of λ≥400nm is used to filter out ultraviolet light, and the catalyst dosage is 10mg. The distance between the reactor and the light source is 15cm, and 40ml of p-chlorophenol solution with a _{concentration} of 5× ^10-5 mol·L ^-1 is used as the target degradation product. Uniform, fan air cooling to keep the reaction temperature at [(25±2)°C], extract 2mL of the reaction solution every 2 hours, centrifuge, take the supernatant, use 4-aminoantipyridine as the developer, and use ultraviolet light - Visible spectrophotometer (UV-16PC, Shimadzu Corporation) measures the concentration of p-chlorophenol solution to measure the catalytic activity of the catalyst.

For a better understanding of the present invention, the present invention will be further described in detail below in conjunction with the examples, but the scope of protection claimed by the present invention is not limited to the range indicated by the examples.

Example 1

1. Preparation of nitrogen and nickel ion co-doped visible light catalyst (Ti _1-x Ni _x O _2-y N _y )

At room temperature, dissolve 628.4mg of NiCl ₂ ·5H ₂ O in 40ml of absolute ethanol, stir until completely dissolved, slowly drop 15ml of tetrabutyl titanate into the reaction system, stir for 0.5h, then dropwise Add 4.16ml of concentrated hydrochloric acid (to control the hydrolysis process of the sol-gel system, so that the polycondensation reaction is complete), stir, and after standing for 12 hours, slowly drop 3ml of ammonia water in the stirring process, and a large amount of white precipitates appear . After stirring at room temperature for 3 hours, the system became a white gel, which was dried at 100°C, ground into powder, and sintered at 450°C for 2 hours to obtain a nitrogen-nickel ion co-doped visible light catalyst ( Ti _1-x Ni _x O _2-y N _y ) samples.

2. Preparation of TiO _2-y N _y catalyst

The preparation steps are similar to Ti _1-x Ni _x O _2-y N _y , except that NiCl ₂ ·5H ₂ O is not added.

3. Preparation of pure _TiO2 catalyst

The preparation steps are similar to Ti _1-x Ni _x O _2-y N _y , except that NiCl ₂ ·5H ₂ O is not added, and high-purity water (18.2MΩcm ^-1 ) is used instead of ammonia water for dropwise addition.

Example 2

1. Preparation of boron and zinc ion co-doped visible light catalyst (Ti _1-x Zn _x O _2-y B _y )

Dissolve 1.098g of zinc acetate (molecular formula Zn(CH3COO) ₂ 2H ₂ O) in 25ml of absolute ethanol, stir to dissolve, slowly drop 15ml of tetrabutyl titanate into the reaction system, stir for 0.5h, and then gradually Add dropwise the concentrated hydrochloric acid of 4.16ml (control the hydrolysis process of this sol-gel system, make the polycondensation reaction carry out completely), stir, after standing and aging for 2 hours, slowly drop into the ethanol solution of boric acid (0.307g boric acid dissolved in 25ml of absolute ethanol), continue stirring at room temperature until the system becomes a gel, dry the gel at 100°C, grind it into powder, and sinter at 450°C for 2 hours to obtain boron and zinc Sample of ion co-doped visible photocatalyst (Ti _1-x Zn _x O _2-y B _y ).

2. Preparation of TiO _2-y By _y catalyst

The preparation steps are similar to Ti _1-x Zn _x O _2-y By _y , except that zinc acetate is not added.

3. Preparation of pure _TiO2 catalyst

The preparation steps are similar to Ti _1-x Zn _x O _2-y By _y , except that zinc acetate is not added, and absolute ethanol is used instead of ethanol solution of boric acid for dropwise addition.

Example 3

1. Preparation of nitrogen and tin ion co-doped visible light catalyst (Ti _1-x Sn _x O _2-y N _y )

Dissolve 0.2ml of anhydrous tin tetrachloride in 40ml of absolute ethanol, stir, slowly drop 12ml of tetrabutyl titanate into the reaction system, and then add a certain amount of concentrated hydrochloric acid dropwise to make the pH of the reaction system 0.5 (control the hydrolysis process of this sol-gel system, polycondensation reaction is carried out completely), stir, leave standstill aging after 1 hour, slowly drip 3ml ammoniacal liquor in stirring process, continue to stir until system becomes gel at room temperature, will The gel was dried at 100°C, ground into powder, and sintered at 450°C for 2 hours to prepare a sample of nitrogen and tin ion co-doped visible light catalyst (Ti _1-x Sn _x O _2-y N _y ) .

2. Preparation of TiO _2-y N _y catalyst

The preparation steps are similar to Ti _1-x Sn _x O _2-y N _y except that anhydrous tin tetrachloride is not added.

3. Preparation of pure _TiO2 catalyst

The preparation steps are similar to Ti _1-x Sn _x O _2-y N _y , except that anhydrous tin tetrachloride is not added, and high-purity water (18.2MΩcm ^-1 ) is used instead of ammonia water for dropwise addition.

Claims (7)

1, a kind of metal, non-metallic ion co-doped preparation high-activity nano TiO of utilizing ₂The method of visible light catalyst is characterized in that with the titanate esters being precursor, with slaine, to contain the nonmetalloid compound be adulterant, prepares nano-TiO with sol-gel process ₂Visible light catalyst.

2, a kind of preparation metal according to claim 1, non-metallic ion co-doped TiO ₂The method of visible light catalyst is characterized in that described preparation method is as follows:

1. metal, non-metallic ion co-doped visible light catalyst (Ti _1-xA _xO _2-yB _y, A, B represent metal, nonmetalloid respectively) preparation:

At normal temperatures, a certain amount of slaine is dissolved in a certain amount of diluent, in this solution, drip a certain amount of titanate esters again, stir 0-2h, add a certain amount of acid catalyst and (control the hydrolytic process of this collosol-gelatum system, polycondensation reaction is carried out) fully, stir, after still aging 0-24 hour, in whipping process, slowly splash into a certain amount of compound (or its alcoholic solution that contains nonmetalloid, or the aqueous solution), be stirred to this system under the room temperature and become gel, this gel is dried down at 50-200 ℃, grind into powder at 350-600 ℃ of following sintering 0.5-10 hour, promptly makes metal, non-metallic ion co-doped visible light catalyst (Ti _1-xA _xO _2-yB _y) sample.

2. for carrying out the activity contrast, in implementation process, prepared pure titinium dioxide (TiO respectively ₂) and singly mix nonmetallic ion TiO _2-yB _y(B represents nonmetalloid) two comparative sample:

I singly mixes nonmetallic ion TiO _2-yB _yPreparation of catalysts

Preparation process and Ti _1-xA _xO _2-yB _ySimilar, just do not add slaine.

The pure TiO of II ₂Preparation of catalysts

Preparation process and Ti _1-xA _xO _2-yB _ySimilar, just do not add slaine, and with high purity water (18.2M Ω cm ^-1) or the corresponding alcohol solution that replaces containing the compound of nonmetalloid drip.

When 3. preparing above colloidal sol, the addition of various reactants is:

The mol ratio of slaine and titanate esters is 1: 1000-1: 2

The volume ratio of diluent and titanate esters is 1: 10-20: 1

The volume ratio of acid catalyst and titanate esters is 1: 30-1: 2

Containing the compound of nonmetalloid and the mol ratio of titanate esters is 1: 30-10: 1

3, a kind of preparation metal according to claim 1 and 2, non-metallic ion co-doped TiO ₂The method of visible light catalyst is characterized in that described titanate esters is selected from following a kind of or several mixing and adds: butyl titanate, isopropyl titanate, titanium propanolate or tetraethyl titanate.

4, a kind of preparation metal according to claim 1 and 2, non-metallic ion co-doped TiO ₂The method of visible light catalyst is characterized in that described slaine is any or several mixing in the salt that dissolves in above-mentioned diluent of arbitrary element in V, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Mo, Ru, Pd, Ag, In, Sn, Ta, W, Re, Pt, Au, Pb, Bi, the La element.

5, a kind of preparation metal according to claim 1 and 2, non-metallic ion co-doped TiO ₂The method of visible light catalyst, it is characterized in that the described compound that contains nonmetalloid mainly refers to: 1. nitrogen-containing compound, i.e. any or several mixing in urea, thiocarbamide, ethamine, ethylenediamine, triethylamine, triethanolamine, ammoniacal liquor, ammonium carbonate, carbonic hydroammonium, the ammonium chloride; 2. boron-containing compound, i.e. any or two kinds of mixing in boric acid, the diboron trioxide; 3. sulfur-containing compound, i.e. thiocarbamide; 4. bromine-containing compound, i.e. any or several mixing in bromic acid, bromine water, the bromoacetic acid; 5. contain iodine compound, i.e. any or several mixing in iodine, acid iodide, iodine trichloride, the iodoacetic acid.

6, a kind of preparation metal according to claim 1 and 2, non-metallic ion co-doped TiO ₂The method of visible light catalyst is characterized in that described diluent is selected from following a kind of or several mixing and adds: absolute ethyl alcohol, absolute methanol, propyl alcohol or isopropyl alcohol.

7, a kind of preparation metal according to claim 1 and 2, non-metallic ion co-doped TiO ₂The method of visible light catalyst is characterized in that described acid catalyst is selected from following a kind of or several mixing and adds: hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, perchloric acid or nitric acid.

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