CN103816888A - Preparation method of visible light response type quadrivalent niobium self-doping niobate photocatalyst - Google Patents

Abstract

The invention discloses a preparation method of a visible light-responsive tetravalent niobium self-doping niobate photocatalyst, which is characterized in that it comprises the following steps: 1) selecting niobate as a precursor; 2) uniformly mixing the precursor with a solvent , pass protective gas into the mixed solution, stir, and irradiate with ultraviolet light; 3) centrifuge the solution irradiated by ultraviolet light, centrifuge to obtain a solid powder, and dry the powder in vacuum to obtain a visible light-responsive tetravalent niobium self- Doped with niobate compounds. The method is simple, cheap and efficient.

Description

Preparation method of a visible light-responsive tetravalent niobium self-doped niobate photocatalyst

technical field

The invention relates to a preparation method of a semiconductor nanometer material, and more specifically to a preparation method of a visible light-responsive tetravalent niobium self-doped niobate photocatalyst.

Background technique

Due to the unsustainability of fossil fuels themselves, as well as serious global problems such as the greenhouse effect and environmental pollution caused by the large amount of _CO2 released by burning fossil fuels, it has become imperative to build a clean, environmentally friendly non-fossil fuel renewable new energy system. It has become the focus and major strategy of all countries in the world. Due to its inexhaustible, clean and non-polluting, renewable and other advantages, solar energy will surely occupy a pivotal position in the development of new energy in the future. Hydrogen energy has the advantages of high combustion value, and the combustion product is water without environmental pollution. Therefore, the use of solar semiconductors to photocatalytically split water to produce hydrogen as one of the new energy sources for sustainable development is increasingly attracting great attention from the international community. After more than 40 years of development, the use of solar semiconductors to photocatalyze water splitting to produce hydrogen has made great progress, but there is still a certain distance from practical applications. At present, the photocatalysts that have been studied more and have better photocatalytic effects are still concentrated on ultraviolet light-responsive semiconductor materials. However, ultraviolet light in the solar spectrum only accounts for 4% of the total energy, while visible light accounts for 43%. Therefore, the development of visible light Responsive high-efficiency semiconductor photocatalysts are of great significance. Although niobate photocatalysts (such as Nb ₂ O ₅ , K ₄ Nb ₆ O _17, etc.) have good photocatalytic activity, they can only respond to ultraviolet light, which limits their practical application value. Sex matters. Although the common modification methods such as transition metal and non-metal doping can also improve the visible light activity of niobate materials, the defects caused by doped ions tend to become the recombination centers of photogenerated electrons and holes, which limits the increase in its catalytic activity. Recent studies have shown that metal ion self-doped semiconductor oxides (such as Ti ³⁺ self-doped TiO ₂ , Ta ⁴⁺ self-doped NaTaO _{3 ,} etc.) exhibit better visible light absorption characteristics and catalytic activity. However, there are no literature reports about Nb ⁴⁺ self-doping niobate photocatalysts, and the preparation methods of metal ion self-doping semiconductor oxides that have been reported so far have many steps and are expensive. Therefore, developing a simple and cheap method to prepare metal ion self-doping semiconductor oxides can not only simplify the synthesis process and improve the preparation efficiency, but also greatly accelerate the practical application process of visible light-responsive semiconductor nanomaterials.

Contents of the invention

The technical problem to be solved by the present invention is to provide a visible-light-responsive preparation method of tetravalent niobium self-doped niobate visible-light photocatalyst, which is simple, cheap and efficient.

In order to solve the above-mentioned first technical problem, the present invention adopts the following technical solutions:

A method for preparing a visible light-responsive tetravalent niobium self-doped niobate visible light photocatalyst, the method comprising the following steps:

1) select niobate as the precursor;

2) Mix the precursor and the solvent evenly, pass protective gas into the mixed solution, stir, and irradiate with ultraviolet light;

3) centrifuging the solution irradiated by ultraviolet light to obtain a solid powder, and vacuum drying the powder to obtain a visible light-responsive tetravalent niobium self-doping niobate compound.

Preferably, the niobate in step 1) is selected from Nb ₂ O ₅ , K ₄ Nb ₆ O ₁₇ , K ₂ Nb ₈ O ₂₁ .

Preferably, the dosage of the precursor in step 2) is 0.02-0.5g, and the dosage of the solvent is 15-25ml.

Preferably, the solvent in step 2) is selected from a mixed solution of water and methanol at a volume ratio of 4:1, a mixed solution of water and lactic acid at a volume ratio of 4:1, and a mixture of water and isopropanol at a volume ratio of 4:1 solution, a mixed solution of water and triethanolamine at a volume ratio of 4:1 or an aqueous solution of sodium sulfide and sodium sulfite, wherein the aqueous solution of sodium sulfide and sodium sulfite is an aqueous solution formed by dissolving 0.002mol of sodium sulfide and 0.006mol of sodium sulfite in 20 mL of water.

Preferably, the mixing in step 2) is carried out in a quartz container.

Preferably, the protective gas in step 2) is selected from nitrogen or argon.

Preferably, the time for introducing the protective gas in step 2) is 30-60 minutes.

Preferably, the ultraviolet light source in step 2) is a high-pressure ultraviolet lamp of 300-500W, and the radiation intensity is 50-100mW/cm2; the irradiation time of ultraviolet light is 0.5-6h.

Preferably, the centrifugation speed described in step 3) is 8000-12000 rpm, and the centrifugation time is 5-10 minutes.

Preferably, the vacuum drying conditions in step 3) are vacuum-0.05MPa, 40°C drying for 1-4h.

The beneficial effects of the present invention are as follows:

1) A new type of visible light-responsive self-doping niobate nanophotocatalyst is prepared in the present invention, which enriches the types of self-doping semiconductor nanomaterials;

2) A facile, cheap and efficient method is developed in this invention, which can be used to prepare different types of Nb ⁴⁺ self-doped niobate semiconductor nanomaterials.

3) Several kinds of Nb ⁴⁺ self-doping niobate photocatalysts prepared in the present invention have good visible light and near-infrared photoresponse capabilities, and have potential applications in energy, environment and other fields, laying a solid foundation for their application research base.

4) The preparation method used in the present invention can also be used to prepare other types of metal self-doping semiconductor photocatalysts with visible light response.

Description of drawings

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Fig. 1 shows the X-ray diffraction spectrogram of semiconductor material;

_Figure 2a shows the scanning electron micrograph of _Nb2O5 ;

Figure 2b shows the scanning electron micrograph of K ₄ Nb ₆ O ₁₇ ;

Figure 2c shows a scanning electron micrograph of K ₂ Nb ₈ O ₂₁ ;

Figure 3a shows the real photo of Nb ⁴⁺ self-doped Nb ₂ O ₅ before illumination;

Fig. 3b shows the real photo of Nb ⁴⁺ self-doped Nb ₂ O ₅ after illumination.

Detailed ways

In order to illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not limit the protection scope of the present invention.

Example 1

1) Add 0.1g Nb ₂ O ₅ into 20mL of a mixed solution of water and methanol with a volume ratio of 4:1, and stir at room temperature for 0.5h; Nb ₂ O ₅ is a commercial powder, and its crystal structure is shown in Figure 1 As shown in the a curve, it shows that it is a pure phase. The SEM photograph of Fig. 2a shows that the particle size of _Nb2O5 powder is in the _range of 0.1–0.5 μm.

2) Transfer the above solution into a 50mL quartz test tube;

3) Introduce nitrogen gas into the above solution without stirring, and the aeration time is 30 minutes;

4) Seal the quartz test tube and irradiate it under a 500W high-pressure mercury lamp for 6 hours. After centrifugation, the obtained dark blue powder is dried in a vacuum at -0.05Mpa at 40°C for 3 hours to obtain Nb ⁴⁺ that responds to visible light. Self- _{doped Nb2O5} photocatalyst. It can be seen from Figure 3a that the color of the Nb ₂ O ₅ powder before irradiation is white, and after a period of ultraviolet light irradiation, the blue Nb ₂ O ₅ powder in Figure 3b can be obtained, and the blue powder is Nb ^{4 +} Self-doped Nb ₂ O ₅ photocatalyst, the generation of the blue powder further proves that the preparation of visible light-responsive Nb ⁴⁺ self-doped Nb ₂ O ₅ photocatalyst can be realized by using a simple ultraviolet light irradiation method.

Example 2

Visible light photocatalytic decomposition of water hydrogen production performance test:

The 100mg blue Nb ⁴⁺ self-doping Nb ₂ O ₅ powder obtained in Example 1 is evenly dispersed in the mixed solution containing 20mL water and methanol volume ratio of 4:1, and the above solution is transferred to 50mL quartz Put nitrogen into the test tube for 30 minutes, then seal the quartz test tube and irradiate it under a 300W xenon lamp (equipped with a 420nm ultraviolet filter to allow only visible light with a wavelength greater than 420nm to pass through) 8 Hours, the amount of hydrogen produced was detected by gas chromatography. The experimental results show that the blue Nb ⁴⁺ self-doped Nb ₂ O ₅ photocatalyst has good photocatalytic water splitting hydrogen production performance and catalytic stability under visible light, and the hydrogen production rate is 15 μmol/h/g.

Example 3

Repeat Example 1, the difference is that the amount of Nb ₂ O ₅ added is changed, the amount of Nb ₂ O ₅ added is 0.05g, and other conditions remain unchanged, blue Nb ⁴⁺ self-doping Nb ₂ O ₅ can still be produced catalyst of light.

Example 4

Repeat Example 1, the difference is that the ratio of water to methanol is changed to 1:4, and other conditions remain unchanged; the experimental results show that the existence of electron sacrificial agent methanol is the key to generate Nb4+ self-doped Nb ₂ O ₅ photocatalyst . In the absence of methanol, the Nb ⁴⁺ self-doped Nb ₂ O ₅ photocatalyst will not be formed no matter how long the ultraviolet light is irradiated.

Example 5

Repeat Example 1, the difference is that the mixed solution of water and methanol is replaced by pure methanol solution, and other conditions remain unchanged, the blue Nb ⁴⁺ self-doping type Nb ₂ O ₅ photocatalyst can still be obtained, and the corresponding preparation time will shorten.

Example 6

Repeat Example 1, the difference is that methanol is replaced by lactic acid, and other conditions remain unchanged, the blue Nb ⁴⁺ self-doping Nb ₂ O ₅ photocatalyst can still be prepared.

Example 7

Repeat Example 1, the difference is that methanol is replaced by triethanolamine, and other conditions remain unchanged, the blue Nb ⁴⁺ self-doping Nb ₂ O ₅ photocatalyst can still be prepared.

Example 8

Repeat Example 1, the difference is that methanol is replaced by a mixed solution of sodium sulfide and sodium sulfite, and other conditions remain unchanged, and the blue Nb ⁴⁺ self-doping Nb ₂ O ₅ photocatalyst can still be prepared.

Example 9

Repeat Example 1, the difference is that methanol is replaced by isopropanol, and other conditions remain unchanged, the blue Nb ⁴⁺ self-doping Nb ₂ O ₅ photocatalyst can still be prepared.

Example 10

Repeat Example 1, the difference is that the 500W high-pressure mercury lamp is replaced by a 300W high-pressure mercury lamp, and other conditions remain unchanged, the blue Nb ⁴⁺ self-doping type Nb ₂ O ₅ photocatalyst can still be produced, only due to the ultraviolet The reduction of light irradiation intensity will prolong the preparation time of corresponding materials.

Example 11

Repeat Example 1, the difference is that nitrogen is replaced by argon, and other conditions remain unchanged, and the blue Nb ⁴⁺ self-doping Nb ₂ O ₅ photocatalyst can still be prepared.

Example 12

Example 1 was repeated except that Nb ₂ O ₅ was replaced by K ₄ Nb ₆ O ₁₇ , its crystal structure is shown in the b curve in Figure 1, indicating that it is a pure phase, and the scanning electron micrograph in Figure 2b shows that K The size of the ₄ Nb ₆ O ₁₇ micron spheres is in the range of 1-3 microns, and the nanosheets constituting the microspheres are ultra-thin structures, and the thickness of the nanosheets is only 5-10 nm. Other conditions remain unchanged, the visible light responsive Nb ⁴⁺ self-doped K ₄ Nb ₆ O ₁₇ photocatalyst can be obtained.

Example 13

Example 2 was repeated, except that the blue Nb ⁴⁺ self-doped Nb ₂ O ₅ was replaced by black Nb ⁴⁺ self-doped K ₄ Nb ₆ O ₁₇ , and other conditions remained unchanged. The experimental results show that the black Nb ⁴⁺ self-doped K ₄ Nb ₆ O ₁₇ exhibits better hydrogen production performance in visible light splitting of water, and the hydrogen production rate is about 60 _μ mol/h/g.

Example 14

Example 1 was repeated except that Nb ₂ O ₅ was replaced by K ₂ Nb ₈ O ₂₁ , its crystal structure is shown in the c curve in Figure 1, indicating that it is a pure phase, and the scanning electron micrograph in Figure 2c shows that K The diameter of the ₂ Nb ₈ O ₂₁ nanorod is 100-200 nanometers, and the length of the nanorod is 1-3 microns. Other conditions remain unchanged, and visible light responsive Nb ⁴⁺ self-doped K ₂ Nb ₈ O ₂₁ photocatalyst can be obtained.

Example 15

Example 2 was repeated, except that the blue Nb ⁴⁺ self-doped Nb ₂ O ₅ was replaced by blue Nb ⁴⁺ self-doped K ₂ Nb ₈ O ₂₁ , and other conditions remained unchanged. The experimental results show that the blue Nb ⁴⁺ self-doped K ₂ Nb ₈ O ₂₁ also exhibits good hydrogen production performance in visible light splitting of water, and the hydrogen production rate is about 32 _μ mol/h/g.

Example 16

Repeating Example 1, the difference is that Nb ₂ O ₅ is replaced by TiO ₂ , and other conditions remain unchanged, a Ti ³⁺ self-doped TiO ₂ photocatalyst responding to visible light can be obtained.

Example 17

Example 2 was repeated, except that the blue Nb ⁴⁺ self-doped Nb ₂ O ₅ was replaced by blue Ti ³⁺ self-doped TiO ₂ , and other conditions remained unchanged. The experimental results show that the blue Ti ³⁺ self-doped TiO ₂ also has the performance of visible light splitting water to produce hydrogen, and the hydrogen production rate is about 13 μmol/h/g.

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those of ordinary skill in the art can also make It is impossible to exhaustively list all the implementation modes here, and any obvious changes or changes derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims (10)

1. a preparation method for visible-light response type tetravalence niobium auto-dope niobate photocatalyst, is characterized in that, comprises the steps:

1) choose niobates as presoma;

2), by even to presoma and solvent, in mixed solution, pass into protective gas, stirring, UV-irradiation;

3) solution after UV-irradiation is carried out centrifugal, the centrifugal pressed powder that obtains, carries out vacuum drying by powder, obtains visible-light response type tetravalence niobium auto-dope niobates compound.

2. preparation method according to claim 1, is characterized in that: step 1) described niobates is selected from Nb ₂o ₅, K ₄nb ₆o ₁₇, K ₂nb ₈o ₂₁.

3. preparation method according to claim 1, is characterized in that: step 2) consumption of described presoma is 0.02-0.5g, solvent load is 15-25mL.

4. preparation method according to claim 1, it is characterized in that: step 2) described solvent is selected from water and methyl alcohol mixed solution, water and isopropyl alcohol mixed solution, water and the triethanolamine mixed solution of 4:1 or the aqueous solution of vulcanized sodium and sodium sulfite by volume of 4:1 by volume of mixed solution, water and the ammonium lacate volume ratio 4:1 of 4:1 by volume, and the aqueous solution of described vulcanized sodium and sodium sulfite is that 0.002mol vulcanized sodium and 0.006mol sodium sulfite are dissolved in the aqueous solution forming in 20mL water.

5. preparation method according to claim 1, is characterized in that: step 2) in, described in to mix be to carry out in the container of quartzy material.

6. preparation method according to claim 1, is characterized in that: step 2) in, described protective gas is selected from nitrogen or argon gas.

7. preparation method according to claim 1, is characterized in that: step 2) in, described in pass into protective gas time be 30-60min.

8. preparation method according to claim 1, is characterized in that: step 2) in, the high-pressure sodium lamp that ultraviolet source is 300-500W, radiation intensity is 50-100mW/cm ²; The time of described UV-irradiation is 0.5-6h.

9. preparation method according to claim 1, is characterized in that: step 3) in, described centrifugal speed is 8000-12000 rev/min, centrifugation time 5-10 minute.

10. preparation method according to claim 1, is characterized in that: step 3) in, described vacuum drying condition is-0.05Mpa, 40 ℃ of dry 1-4h.

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