CN104888858B - A kind of ternary high efficiency composition visible-light photocatalysis material and preparation method thereof - Google Patents

Abstract

The invention discloses a ternary high-efficiency composite visible light photocatalyst and its preparation method and application, which are characterized in that N-K 2 Ti 4 O 9 and g-C 3 N 4 are prepared by a calcination method, and N-K ₂ Ti ₄ O ₉ and g-C ₃ N ₄ are prepared by electrostatic attraction. K ₂ Ti ₄ O ₉ /g‑C ₃ N ₄ binary composite material, and then self-assembled into N‑K ₂ Ti ₄ O ₉ /g‑C ₃ N ₄ /UiO‑66 ternary high-efficiency composite visible light by solvothermal method catalyst of light. In the present invention, N-K ₂ Ti ₄ O ₉ has a good visible light response, g-C ₃ N ₄ has a strong ability to conduct electrons and holes, and UiO-66 has the characteristics of large adsorption capacity of MOF materials, and combines the advantages of the three components to synthesize a ternary compound Under the action of recombination-promoted separation of photogenerated charges, photocatalysts have significantly enhanced photocatalytic degradation activity of organic dyes under visible light, and have broad application prospects in the field of photocatalysis.

Description

A ternary high-efficiency composite visible light photocatalytic material and its preparation method

technical field

The invention belongs to the fields of material preparation, visible light photocatalysis technology and environmental protection, and specifically relates to the preparation of ternary high-efficiency composite photocatalyst NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 and its catalytic degradation of organic pollution in water under visible light application of things.

Background technique

Today's energy shortages and environmental pollution have attracted more and more attention, and the sustainable development of human society is facing enormous challenges. Photocatalytic technology is a new treatment technology for degrading environmental pollutants. It has the advantages of low-carbon, clean, and environmentally friendly. Therefore, it is an ideal way to solve energy and environmental problems. However, traditional photocatalysts such as titanium dioxide have high band gaps, The shortcomings of photogenerated electron-hole recombination rate and other shortcomings limit the practical application of photocatalytic technology. How to prepare high-efficiency photocatalyst is a key problem that needs to be solved in the application of photocatalytic technology.

Potassium titanate (K ₂ Ti ₄ O ₉ ) is generally regarded as a reliable material due to its non-toxic, stable properties, easy availability of materials, and unique photoelectric properties. However, due to its high band gap energy (3.2-3.4eV), it can only be excited by ultraviolet light, so it is of great significance to improve its photocatalytic activity to broaden the application range of related materials. Doping nitrogen into K ₂ Ti ₄ O ₉ (marked as "NK ₂ Ti ₄ O ₉ ") is a common method to reduce the band gap, and the photocatalytic activity is improved after doping, but NK ₂ Ti ₄ O ₉ and other low-bandgap semiconductors generally have defects such as small specific surface area, poor adsorption of hydrophobic organic substances, and fast photogenerated electron-hole recombination rate in a single material, which limits the further improvement of its photocatalytic performance. gC ₃ N ₄ is a polymer composed of triazine units. It is a non-metallic semiconductor with strong thermal and chemical stability. It has delocalized conjugated π bonds (which can effectively conduct photogenerated carriers). Visible light catalysis is mainly used for photolysis of water and degradation of organic pollutants, etc. However, gC ₃ N ₄ photocatalyst also has disadvantages such as small specific surface area and serious recombination of photogenerated carriers. The study found that acid treatment of gC ₃ N ₄ can increase its specific surface area and promote charge separation. Moreover, gC ₃ N ₄ is acid-treated and its nitrogen atom is protonated to make it positively charged, and it is easy to effectively recombine with other negatively charged materials through electrostatic attraction. Metal-organic framework (MOF) material is a new type of porous material that has attracted widespread attention in the past ten years. It has a particularly large specific surface area (the specific surface area of most MOFs is above 1000m ² /g, which is larger than conventional porous materials). Its open and through pores are conducive to the adsorption of pollutant molecules in the concentrated environment to the surface and interior of the material. Among them, UiO-66 is a MOF material formed by the coordination reaction of Zr ^IV and terephthalic acid, which has the advantages of large specific surface area and adsorption capacity, and stable physical and chemical properties. In view of the excellent adsorption performance of UiO-66, loading it on the surface of other materials to form a composite structure can improve the adsorption photocatalytic performance of the material.

The present invention combines the advantages of good visible light response of NK ₂ Ti ₄ O ₉ , strong ability of gC ₃ N ₄ to conduct electrons and holes, and large adsorption capacity of MOF materials to prepare NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 The ternary composite material has high adsorption performance, can effectively separate photogenerated electron-hole pairs, and has significantly enhanced visible light photocatalytic activity.

Contents of the invention

The purpose of the present invention is to provide a NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light photocatalyst and its preparation method to overcome the defects of a single catalytic material and promote the separation of photogenerated charges by composite The preparation method is simple, and the photocatalytic effect of degrading rhodamine B is remarkable.

To achieve the above object, the present invention adopts the following technical solutions:

The ternary high-efficiency composite visible light photocatalyst of the present invention is characterized in that: the ternary high-efficiency composite visible light photocatalyst is composed of NK ₂ Ti ₄ O ₉ , gC ₃ N ₄ and UiO-66, denoted as NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66.

The preparation method of the ternary high-efficiency composite visible light photocatalyst of the present invention is characterized in that:

(1) Mix K ₂ CO ₃ and TiO ₂ in a molar ratio of 1:9-4:9 and grind them evenly, then calcinate at 400-1000°C for 4-10 hours, and finally cool naturally to room temperature to obtain K ₂ Ti ₄ O ₉ ;

After mixing K ₂ Ti ₄ O ₉ and urea at a mass ratio of 1:5 to 3:5, calcining at 300 to 500°C for 3 to 6 hours, and then naturally cooling to room temperature to obtain NK ₂ Ti ₄ O ₉ ;

Add NK ₂ Ti ₄ O ₉ to an aqueous solution of sodium oxalate with a concentration of 0.10-0.30 mol/L, stir, sonicate, then filter, wash, dry, and grind to obtain pretreated NK ₂ Ti ₄ O ₉ ;

(2) Calcining melamine at 400-600°C for 3-8 hours, then cooling to room temperature and grinding to obtain gC ₃ N ₄ ;

The gC ₃ N ₄ was added to a nitric acid solution with a concentration of 0.5-2.0 mol/L, and kept at 135°C for 6 hours, and the obtained sample was washed until neutral and dried to obtain pretreated gC ₃ N ₄ ;

(3) Mix the pretreated NK ₂ Ti ₄ O ₉ obtained in step (1) and the pretreated gC ₃ N ₄ obtained in step (2) in ethanol at a mass ratio of 1:2 to 7:2, and then Stir for 20-40 hours, filter, wash, and dry to obtain NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composite material;

(4) Add the NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composite material and ZrCl ₄ obtained in step (3) to N,N-dimethylformamide at a mass ratio of 1:2 to 7:2 In, then add terephthalic acid and benzoic acid (the mass ratio of terephthalic acid, ZrCl ₄ and benzoic acid is 0.64:1:10), it is transferred to polytetrafluoroethylene reactor after ultrasonic 30min in 100～ After reacting at 150°C for 18-32 hours, the obtained product was filtered, washed and dried to obtain NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light photocatalyst.

The invention also discloses the application of the above ternary high-efficiency composite visible light photocatalyst as a catalyst for visible light photocatalytic degradation of organic pollutants in aqueous solution.

The beneficial effects of the present invention are reflected in:

(1) The present invention applies the composite photocatalyst NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 to the field of photocatalysis for the first time. It is a new type of photocatalyst for degrading organic pollutants. The preparation method is simple and feasible. Visible light catalytic efficiency is high, and it has broad application prospects in the field of photocatalysis;

(2) The present invention prepares NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composites through modification-induced electrostatic attraction, and then utilizes coordination reaction assembly to prepare NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 Ternary composite materials for synergistic photocatalytic purification of organic pollutants in water;

(3) The present invention combines the advantages of good visible light response of NK ₂ Ti ₄ O ₉ , thin-layered gC ₃ N ₄ is easy to combine with other materials and has a strong ability to conduct electrons and holes, and the advantages of large adsorption amount of UiO-66. The combination not only increases The specific surface area of the catalyst also improves the separation efficiency and photocatalytic efficiency of photogenerated carriers.

Description of drawings

Figure 1 is the present invention NK ₂ Ti ₄ O ₉ , gC ₃ N ₄ and UiO-66, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composites and NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO XRD pattern of -66(3:2) ternary high-efficiency composite visible light photocatalyst;

Fig. 2 is UiO-66 (a), NK ₂ Ti ₄ O ₉ (b), gC ₃ N ₄ (c) and NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 (3:2) of the present invention TEM image of ternary high-efficiency composite visible light photocatalyst (d);

Fig. 3 shows NK ₂ Ti ₄ O ₉ , gC ₃ N ₄ , UiO-66, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composites and NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO of the present invention -66 (3:2) ternary high-efficiency composite visible light photocatalyst for visible light photocatalysis of Rhodamine B;

Fig. 4 is a visible light photocatalytic effect diagram of different ratios of NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light photocatalyst on rhodamine B in the present invention.

detailed description

The following examples are given to further illustrate the present invention.

Example 1

In this example, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light photocatalyst was prepared according to the following steps:

1. Preparation of NK ₂ Ti ₄ O ₉

Mix 6.6g K ₂ CO ₃ and 12.0g TiO ₂ (molar ratio 1:3) into a mortar, grind the powder thoroughly, put the powder into a crucible, calcinate at 150°C for 2h, then raise the temperature to 960°C, Calcined for 10h, after cooling, K ₂ Ti ₄ O ₉ was obtained;

Mix 1.0g K ₂ Ti ₄ O ₉ and 2.0g urea in 15g ethanol, heat to evaporate the solvent, move to a muffle furnace for calcination at 400°C for 4 hours, cool, wash with water, and dry to obtain NK ₂ Ti ₄ O ₉ . The XRD pattern of the obtained NK ₂ Ti ₄ O ₉ is shown in Fig. 1, and the TEM pattern is shown in Fig. 2(b).

2. NK ₂ Ti ₄ O ₉ pretreatment

Add the NK ₂ Ti ₄ O ₉ obtained in Step 1 into 100 mL of sodium oxalate aqueous solution (0.22 mol L ^-1 ), stir for 2 h, ultrasonicate for 1 h, filter, wash with water, dry at 70°C for 5 h, and grind to obtain pretreated NK ₂ Ti ₄ O ₉ .

3. Preparation of gC ₃ N ₄

Put 5.0g of melamine into a crucible, move it to a muffle furnace, heat it up to 520°C at a rate of 3°C per minute, keep it warm for 4 hours, then cool to room temperature and grind to obtain gC ₃ N ₄ . The XRD pattern of the obtained gC ₃ N ₄ is shown in Figure 1, and the TEM image is shown in Figure 2(c).

4. Nitrogen protonation of gC ₃ N ₄

The gC ₃ N ₄ obtained in Step 3 was put into a nitric acid (0.5 mol·L ^-1 ) solution, and transferred to a polytetrafluoroethylene reactor at 135° C. for 6 h. The sample was taken out, washed until neutral, and dried at 70°C for 5 hours to obtain pretreated gC ₃ N ₄ .

5. Preparation of NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composite photocatalyst

1.0g of the pretreated NK ₂ Ti ₄ O ₉ obtained in step 2 and 0.5g of the pretreated gC ₃ N ₄ obtained in step 4 were mixed and stirred in 50mL ethanol solution for 24h, filtered, washed, and dried to obtain NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composites. The XRD pattern of the obtained NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composite is shown in FIG. 1 .

6. Preparation of NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light photocatalyst

Weigh 0.080g of the NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composite material prepared in step 5, 0.053g of ZrCl ₄ , 0.034g of terephthalic acid and 0.530g of benzoic acid and add it to 42ml of N,N- Dimethylformamide, then sonicated for 30min, transferred to a 50mL polytetrafluoroethylene reactor at 120°C for 24h, then cooled to room temperature, filtered and washed several times with DMF and _CHCl3 , dried under reduced pressure to obtain ternary Efficient composite visible light photocatalyst NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 (3:2) (that is, the mass ratio of NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ binary composite to ZrCl ₄ is 3 :2).

The XRD pattern of the obtained product is shown in Figure 1, and the TEM image is shown in Figure 2(d).

In order to compare the photocatalytic performance, this example also prepared UiO-66 according to the following steps:

Weigh 0.053g ZrCl ₄ (0.227mmol), 0.034g terephthalic acid (0.227mmol) and 0.530g benzoic acid (4.344mmol) and join in 25ml of N,N-dimethylformamide, then sonicate after 30min It was transferred to a 30ml polytetrafluoroethylene reactor and reacted at 120°C for 24h. After the reaction, it was cooled to room temperature, filtered and washed several times with DMF and CHCl ₃ , and dried under reduced pressure to obtain UiO-66. The XRD pattern of the obtained UiO-66 is shown in Figure 1, and the TEM image is shown in Figure 2(a).

In order to explore the application of NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 to degrade organic pollutants, and compare NK ₂ Ti ₄ O ₉ , gC ₃ N ₄ , UiO-66, NK ₂ Ti ₄ O ₉ /gC The photocatalytic performance of ₃ N ₄ binary composites and NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 as catalysts was tested as follows: 20 mg of each catalyst was added to 100 mL of 10 mg/L Rhodamine B In the aqueous solution, the dark place was adsorbed for 12 hours to reach equilibrium, and then the light source was turned on for the photocatalytic experiment. The catalyst and the solution were mixed evenly by blowing air throughout the experiment, and the temperature of the reactor was kept constant by using circulating cooling water. After sampling, it was filtered through a 0.22 μm filter, and the absorbance was measured on a Shimadzu UV 2550 UV-Vis spectrophotometer. The results are shown in Figure 3. The binary NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ composite has better photocatalytic performance than the pure material, and the ternary NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 composite the best photocatalytic effect.

Example 2

In this example, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light photocatalyst was prepared in the same manner as in Example 1, the only difference being that in step 6, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ The mass of the binary composite is changed to 0.027g. The photocatalytic performance of the obtained product NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 (1:2) is shown in Fig. 4 .

Example 3

In this example, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light photocatalyst was prepared in the same manner as in Example 1, the only difference being that in step 6, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ The mass of the binary composite is changed to 0.035g. The photocatalytic performance of the obtained product NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 (2:3) is shown in Figure 4 .

Example 4

In this example, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light photocatalyst was prepared in the same manner as in Example 1, the only difference being that in step 6, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ The mass of the binary composite is changed to 0.053g. The photocatalytic performance of the obtained product NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 (1:1) is shown in Figure 4.

Example 5

In this example, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light photocatalyst was prepared in the same manner as in Example 1, the only difference being that in step 6, NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ The mass of the binary composite is changed to 0.106g. The photocatalytic performance of the obtained product NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 (2:1) is shown in Figure 4 .

Comparing Examples 1 to 5, it can be seen that NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ /UiO-66 ternary high-efficiency composite visible light is prepared by NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ and ZrCl ₄ according to different mass ratios. The catalysts all have good photocatalytic performance, and the photocatalytic performance of the composite material is the best when the mass ratio of NK ₂ Ti ₄ O ₉ /gC ₃ N ₄ and ZrCl ₄ is 3:2.

Claims (4)

1. a kind of ternary high efficiency composition visible-light photocatalyst it is characterised in that：Described ternary high efficiency composition visible light photocatalysis Agent is by N-K₂Ti₄O₉、g-C₃N₄It is combined with UiO-66 and constitutes, be designated as N-K₂Ti₄O₉/g-C₃N₄/UiO-66；

The preparation method of described ternary high efficiency composition visible-light photocatalyst, comprises the following steps：

(1) by K₂CO₃With TiO₂In molar ratio 1:9～4:9 mix and grind uniformly, then calcine 4 at 400～1000 DEG C～ 10h, finally naturally cools to room temperature, obtains K₂Ti₄O₉；

By K₂Ti₄O₉With carbamide in mass ratio 1:5～3:After 5 mixing, calcine 3～6h at 300～500 DEG C, then naturally cool to Room temperature, obtains N-K₂Ti₄O₉；

By N-K₂Ti₄O₉It is added in sodium oxalate water solution, stirring, ultrasonic, then filter, washing, be dried, grind, obtain pre- locating Reason N-K₂Ti₄O₉；

(2) tripolycyanamide is calcined 3～8h at 400～600 DEG C, be subsequently cooled to room temperature, grinding, obtain g-C₃N₄；

By described g-C₃N₄It is added in salpeter solution, and is incubated 6h at 135 DEG C, gained sample is washed to neutrality, is dried, Obtain pretreatment g-C₃N₄；

(3) the pretreatment N-K that step (1) is obtained₂Ti₄O₉The pretreatment g-C being obtained with step (2)₃N₄It is in mass ratio 1:2～7:2 are mixed in ethanol, then stir 20～40h, filter, and washing is dried, and obtains N-K₂Ti₄O₉/g-C₃N₄Binary is multiple Condensation material；

(4) N-K that step (3) is obtained₂Ti₄O₉/g-C₃N₄Binary composite and ZrCl₄In mass ratio 1:2～7:2 additions To in DMF, it is subsequently adding p-phthalic acid and benzoic acid, after ultrasonic 30min, transfers them to polytetrafluoroethyl-ne 18～32h is reacted at 100～150 DEG C, products therefrom through filtering, washing, be dried, that is, obtains N-K in alkene reaction kettle₂Ti₄O₉/g- C₃N₄/ UiO-66 ternary high efficiency composition visible-light photocatalyst；

Wherein p-phthalic acid, ZrCl₄It is 0.64 with benzoic mass ratio:1:10.

2. ternary high efficiency composition visible-light photocatalyst according to claim 1 it is characterised in that：Described in step (1) The concentration of sodium oxalate water solution is 0.10～0.30mol/L.

3. ternary high efficiency composition visible-light photocatalyst according to claim 1 it is characterised in that：Nitric acid in step (2) Concentration be 0.5～2.0mol/L.

4. the ternary high efficiency composition visible-light photocatalyst described in a kind of claim 1 application it is characterised in that：For conduct The catalyst of organic pollution in Photocatalytic Activity for Degradation aqueous solution.