CN104588065B - A rare earth composite g-C3N4-like graphene photocatalyst and preparation method thereof - Google Patents

Abstract

The invention relates to a photocatalytic material for treating organic pollutants in water and a preparation method thereof. The photocatalytic material is composed of a layered semiconductor g-C ₃ N ₄ -type graphene material with visible light response and β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ rare earth nanoparticles with up-conversion performance. β-NaYF ₄ : Yb ³⁺ , Tm ³⁺ rare earth nanoparticles are evenly distributed on the surface of g-C ₃ N ₄ -type graphene materials, forming a composite photocatalytic material with heterostructure near-infrared light response. The successful compounding of rare earth nanoparticles enables g-C ₃ N ₄ -type graphene to absorb the visible light emitted by rare earths through upconversion, thereby realizing the response to infrared light. The catalyst has strong catalytic activity under near-infrared light, can quickly reduce the concentration of organic pollutants in water in a short period of time, and finally can degrade the pollutants almost completely. The preparation method is simple and easy, the catalyst can be recycled and reused conveniently, and has broad application prospects.

Description

A kind of rare earth composite g-C3N4 graphene photocatalyst and preparation method thereof

technical field

The invention belongs to a photocatalytic material and a preparation method thereof, in particular to a rare earth composite gC ₃ N ₄ graphene photocatalyst and a preparation method thereof. The catalyst can be activated by near-infrared light to catalyze and degrade organic pollution in water thing.

Background technique

Since Fujishima discovered that titanium dioxide can split water under the action of ultraviolet light in 1972, semiconductor photocatalysis technology has gradually developed. As an environmentally friendly new catalytic technology, semiconductor photocatalysts can not only oxidize and degrade organic pollutants, but also completely mineralize many substances that are difficult to degrade biochemically. The advantages of low consumption, mild reaction conditions, simple operation, and recyclable reuse have become the research hotspots of scholars all over the world.

Most semiconductor photocatalysts can only respond to ultraviolet light or visible light. For example, titanium dioxide, which is widely used in the field of photocatalysis, can only respond to ultraviolet light, and the metal-free gC ₃ N ₄ type graphene semiconductor can only respond to visible light. Although scholars at home and abroad have conducted a lot of research on the modification of semiconductor photocatalysts, there are very limited examples of extending the photoresponse to the infrared region, and its utilization efficiency needs to be improved. Near-infrared light accounts for about 44% of the solar energy. This part of infrared light has not been effectively utilized, which greatly reduces the utilization rate of solar energy by photocatalysts, thus affecting its photocatalytic efficiency.

Rare earth up-conversion luminescent material is a material that can convert low-energy photons into high-energy photons. We compound it with gC ₃ N ₄ -type graphene in a certain way, and use the characteristics of up-conversion luminescent materials to absorb near-infrared light. , and emit short-wavelength visible light through up-conversion, so that the semiconductor can indirectly use near-infrared light and improve the comprehensive utilization rate of solar energy.

Contents of the invention

The object of the present invention is to provide a kind of rare earth composite gC ₃ N ₄ type graphene photocatalyst material and preparation method thereof, the composite photocatalyst that makes can respond to near-infrared light, improves the near-infrared light region in the field of semiconductor photocatalysis technology Utilization efficiency, thereby improving its utilization rate of solar light energy, and applying it to the field of environmental governance.

The technical scheme that the present invention takes is:

A rare earth composite gC ₃ N ₄ type graphene photocatalyst, characterized in that the photocatalyst is composed of β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ nanoparticles and gC ₃ N ₄ type graphene materials, β-NaYF ₄ : Yb ³⁺ , Tm ³⁺ nanoparticles are evenly distributed on the heterogeneous structure formed on the layered graphene nanosheets, and the preparation method steps are:

(1) Weigh 0.1 g Y ₂ O ₃ into a three-necked bottle, add 10 ml of trifluoroacetic acid and 10 ml of deionized water into it, then place the three-necked bottle in an oil bath at 75°C, and stir under magnetic force Heating under reflux for 6 h until the turbid white solution becomes transparent and clear, and finally taking it out and drying it in an oven at 80°C overnight to obtain (CF ₃ COO) ₃ Y powder product. In addition, (CF ₃ COO) ₃ Yb and (CF ₃ COO) ₃ Tm powders were prepared by the same method;

(2) Weigh 1 mmol of trifluoroacetic acid salt prepared in step (1) (the molar ratio of Y ³⁺ : Yb ³⁺ : Tm ³⁺ is 0.78:0.2:0.02) in a 100 ml three-necked bottle, and then Add 2 mmol sodium trifluoroacetate to it, and then sequentially add oleic acid, 1-octadecene and oleylamine in a molar ratio of 8:10:5. Under a nitrogen protective atmosphere, heat the three-neck flask to which various reaction reagents have been added in an oil bath at 110°C for 30 min with magnetic stirring until the mixed solution becomes clear to obtain solution A;

(3) Under a nitrogen protection atmosphere, the solution A was continuously heated at 330°C for 1 h, cooled to room temperature after the reaction was completed, washed several times with deionized water and absolute ethanol, and then dried to obtain upconversion luminescence Nanoparticles β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ .

(4) Weigh melamine powder into a covered semi-closed porcelain crucible, and then heat to 500°C at a heating rate of 10°C/min for 2 h. Then carry out further deammonization treatment, that is, heating to 520 °C for 2 h. Finally, cool down at room temperature and grind the calcined material to obtain yellow gC ₃ N ₄ powder.

(5) Weigh the gC ₃ N ₄ semiconductor powder prepared in step (4) and add it to the beaker containing methanol solution, then put the beaker into the ultrasonic machine for 30 minutes and then add the Prepared βNaYF ₄ :Yb ³⁺ , Tm ³⁺ , then placed the beaker in a fume hood and stirred magnetically for 24 hours until the methanol solution in the beaker was completely evaporated to dryness, and finally calcined the obtained product at 250°C for 1 hour to obtain Near infrared composite photocatalyst. The mass ratio of up-conversion luminescent nanoparticles β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ in the near-infrared composite photocatalyst is adjustable from 5% to 50%.

The present invention can indirectly extend the photoresponse range of the semiconductor photocatalyst to near-infrared light, and the up-conversion luminescent nanoparticle βNaYF ₄ :Yb ³⁺ , Tm ³⁺ can convert the absorbed near-infrared light into visible light, and then excite the semiconductor gC ₃ N ₄ and photocatalysis occurs. This provides a new technical path for the use of near-infrared light in the field of semiconductor photocatalysts, and is of great significance for solving the increasingly serious problem of environmental pollution.

Description of drawings

Figure 1 is a picture of rare earth β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ nanoparticles obtained according to Example 1 (transmission electron microscope photo);

Fig. 2 is the near-infrared composite photocatalyst β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ /gC ₃ N ₄ obtained according to Example 3 (transmission electron microscope photo);

Fig. 3 is the near-infrared composite photocatalyst prepared according to Example 3 with β-NaYF ₄ : Yb ³⁺ , Tm ³⁺ mass of 15% on the photocatalytic degradation curve of the organic dye methylene blue under 980nm near-infrared laser irradiation .

detailed description

The content of the present invention will be further clarified below in conjunction with specific examples, but these examples do not limit the protection scope of the present invention.

Example (1)

The preparation process of upconversion luminescent nanoparticles β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ is as follows:

(1) Weigh 0.1 g Y ₂ O ₃ into a three-necked flask, add 10 ml deionized water and 10 ml CF ₃ COOH solution into it, then place the three-necked flask in an oil bath at 75°C, Heat and reflux under stirring for 6 h until the turbid white solution becomes transparent and clear, and finally take it out and dry it in an oven at 80°C overnight to obtain (CF ₃ COO) ₃ Y powder product. In addition, (CF ₃ COO) ₃ Yb and (CF ₃ COO) ₃ Tm powders were prepared in the same manner.

(2) Weigh 0.78 mmol (CF ₃ COO) ₃ Y, 0.2 mmol (CF ₃ COO) ₃ Yb and 0.02 mmol (CF ₃ COO) ₃ Tm of the trifluoroacetic acid salt prepared in step (1) into 100 ml trifluoroacetate In the flask, 2 mmol sodium trifluoroacetate was added, followed by 10 mmol 1-octadecene, 8 mmol oleic acid and 5 mmol oleylamine.

Under nitrogen protection atmosphere, the above-mentioned three-necked flask to which various reaction reagents had been added was heated with magnetic stirring in an oil bath at 110°C for 30 min until the mixed solution became clear, and Solution A was obtained. The purpose is to remove water and oxygen in the solution and pave the way for subsequent reactions.

(3) Solution A was then heated to 330 °C, and continued to heat for 1 h under nitrogen protection atmosphere until the reaction was completed, and then cooled to room temperature. Finally, wash with a 1:1 mixture of ultrapure water and absolute ethanol for 3 to 5 times in a benchtop centrifuge at 104 rpm/10 min. After the precipitate is washed, put it in a vacuum oven and dry overnight at 80°C to obtain β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ nanoparticles with upconversion luminescent properties (Figure 1).

Example (2)

The preparation process of the semiconductor material gC ₃ N ₄ is as follows:

Weigh 5g of melamine powder into a covered semi-closed porcelain crucible, then heat to 500°C at a heating rate of 10°C/min for 2h. Then carry out further deammonization treatment, that is, heating to 520°C for 2h. Finally, cool down at room temperature and grind the calcined material to obtain yellow gC ₃ N ₄ powder.

Example (3)

_The preparation process of β- ^{NaYF 4 :Yb 3+ , Tm 3+} _{/ gC 3} ^{N 4 near} _- infrared composite photocatalyst with 15% by weight is as follows:

Weigh 0.283 g of the gC ₃ N ₄ semiconductor powder prepared in Example 2 and add it to a beaker containing 150 mL of methanol solution, then put the beaker into an ultrasonic machine for 30 min and then add 0.05 g of Example 2 Once the β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ has been prepared, place the beaker in a fume hood and stir magnetically for 24 hours until the methanol solution in the beaker is completely evaporated to dryness, then transfer it to a muffle furnace for calcination at 250°C After 1h, the near-infrared composite photocatalyst β-NaYF ₄ :Yb ³⁺ ,Tm ³⁺ /gC ₃ N ₄ with heterostructure can be obtained (Figure 2).

Embodiment (four)

β-NaYF ₄ : Yb ³⁺ , Tm ³⁺ 15% near-infrared composite photocatalyst β-NaYF ₄ : Yb ³⁺ , Tm ³⁺ /gC ₃ N ₄ degrades organic dye methylene blue under 980nm near-infrared laser irradiation The specific experimental steps are as follows:

Disperse 1 mg of the near-infrared composite photocatalyst prepared in Example 3 in a quartz centrifuge tube filled with 0.5 ml of methylene blue solution (concentration: 15 ppm), and place the evenly mixed dispersion in a light-proof dark box for 2 h to reach Adsorption equilibrium; then irradiate the reaction system in a dark box with a near-infrared semiconductor diode laser emitting at a wavelength of 980 nm (output power is 1W), and take 0.3 mL of the reaction from a quartz centrifuge tube with a 1 mL syringe at an interval of 2 hours. Put the liquid in a 2mL centrifuge tube, centrifuge at a high speed of 12000 rpm for 10 min, take 0.25mL of the supernatant in a micro-quartz cuvette, and measure its absorbance in a spectrophotometer (after the measurement, pour it back into the quartz centrifuge The photocatalytic degradation effect of methylene blue by the near-infrared composite photocatalyst under various time periods was obtained.

Figure 3 is the photocatalytic degradation curve of the prepared β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ near-infrared composite photocatalyst with 15% mass on the organic dye methylene blue under 980nm near-infrared laser irradiation. It can be seen from the figure that after 6 hours of 980nm near-infrared laser irradiation, the removal rate of the organic dye methylene blue by the near-infrared composite photocatalyst with β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ mass of 15% can reach 82.7%, However, the β-NaYF ₄ :Yb ³⁺ , Tm ³⁺ prepared in Example 1 and the gC ₃ N ₄ prepared in Example 2 as references under the same conditions had almost no effect on the removal of the organic dye methylene blue.

Claims (4)

1. a kind of rare earth is combined g-C₃N₄Class graphene photo-catalyst it is characterised in that：This photochemical catalyst is β-NaYF₄:Yb³⁺, Tm³⁺Nano particle and g-C₃N₄Class grapheme material is combined composition, β-NaYF₄:Yb³⁺,Tm³⁺Nano particle is evenly distributed in g- C₃N₄The heterojunction structure being formed on stratiform class graphene nanometer sheet.

2. a kind of rare earth is combined g-C as claimed in claim 1₃N₄Class graphene photo-catalyst, is further characterized in that, β- NaYF₄:Yb³⁺,Tm³⁺Nano particle has hexagonal phase structure；Diameter is spherical in 10-100nm；g-C₃N₄Class Graphene is stratiform The composite that nanometer sheet is formed.

3. a kind of rare earth is combined g-C as claimed in claim 1₃N₄Class graphene photo-catalyst, its preparation method is divided into three steps Suddenly：

(1) three kinds of group of the lanthanides trifluoroacetates and sodium trifluoroacetate are added in three-necked bottle, add a certain proportion of oleic acid, 1- ten Eight alkene and oleyl amine, enclose lower 330 DEG C of pyroreactions 1h in nitrogen protective atmosphere, use after room temperature to be cooled absolute ethyl alcohol and deionized water from The heart washs several times, puts into 80 DEG C of oven for drying and just can get up-conversion luminescence nano particle β-NaYF₄:Yb³⁺,Tm³⁺；

(2) weigh a certain amount of melamine to be placed with the dry pot of lid, more dry pot is put into horse expense stove high temperature calcining, control Heating rate and heat time, just can obtain flaxen semi-conducting material g-C₃N₄；

(3) by prepared g-C in step (2)₃N₄Ultrasonic 30min, obtains g-C in methyl alcohol₃N₄Dispersion liquid；Weigh step again (1) prepared β-NaYF in₄:Yb³⁺,Tm³⁺Be added thereto, under magnetic stirring continuously stirred 24h until methanol solution whole Obtained product is finally calcined 1h at 250 DEG C by evaporation, just can get rare earth and is combined g-C₃N₄Class graphene photo-catalyst.

4. a kind of rare earth is combined g-C as claimed in claim 3₃N₄Class graphene photo-catalyst preparation method, its feature also exists In quality on class graphene nanometer sheet for the rare earth nanometer particle is adjusted in the range of 5%～50%；Its specific surface area is in 10- 32.2m²Between/g.