CN105381812B - A kind of method for preparing the composite semiconductor material with meso-hole structure - Google Patents

Abstract

The invention relates to a method for preparing a compound semiconductor material with a mesoporous structure, comprising the following steps: step 1) dispersing graphite-like carbon nitride precursors and hard template _SiO2 balls in water, stirring at 25-50°C for 10 ~60 minutes, wherein, the mass ratio of the graphite-like carbon nitride precursor to water is 1-20, and the mass ratio of the SiO ₂ balls to water is 0.1-1; step 2) according to the mass ratio of 0-2 Add the Ce source to the solution obtained in step 1), and stir at 25-50°C for 0.5-6 hours; step 3) evaporate the solution obtained in step 2) to dryness, and dry overnight to obtain a powder mixture; step 4) 3) The obtained powder mixture is calcined at 300-600°C for 1-4 hours to obtain a light yellow powder; step 5) remove the hard template from the light yellow powder obtained in step 4), centrifuge and dry to obtain a composite with a mesoporous structure semiconductors.

Description

A method for preparing compound semiconductor material with mesoporous structure

technical field

The invention provides a method for preparing a compound semiconductor (N-CeO ₂ /mpg-C ₃ N ₄ ) with a mesoporous structure by a hard template. The material prepared by the method not only has a higher specific surface area, but also N-doped CeO ₂ can be prepared, and the composite semiconductor material can realize photocatalytic conversion of CO ₂ to CH ₄ and CO under simulated sunlight. The invention belongs to the technical field of catalytic materials and nanometer materials, and relates to a new preparation method based on graphite-like carbon nitride mesoporous compound semiconductor materials.

Background technique

Mesoporous materials have attracted much attention due to their high specific surface area, large pore volume, adjustable mesoscopic structure and pore size. Many studies have shown that particle size and pore size are important factors in determining the application range of mesoporous materials, especially in the fields of adsorption of biomacromolecules (enzymes, proteins, etc.) and reactions involving macromolecules.

In 2009, Wang Xinchen et al. reported the synthesis of carbon nitride materials with a graphite-like structure and used them in photo-splitting water for hydrogen production. This 2D material has attracted widespread attention due to its high nitrogen content, superior chemical and thermal stability, special electronic structure, low cost (mainly composed of nitrogen and carbon), and simple preparation. In recent years, gC ₃ N ₄ has been widely studied in the fields of organic photodegradation and oxygen reduction reaction. However, the specific surface area of the gC ₃ N ₄ material prepared by direct calcination is low, and the photogenerated electron-hole recombination is easy to occur, resulting in low photocatalytic efficiency. In order to solve these problems, the hard template method can be used to prepare gC ₃ N ₄ materials with mesoporous structure to increase its specific surface area; by preparing composite semiconductor photocatalysts, the migration and effective utilization of photogenerated electrons and holes can be improved, thereby improving the efficiency of photocatalysts. catalytic activity.

Environmental problems such as energy shortage and greenhouse effect are two major problems that people are currently facing. Among the existing solutions, _CO2 can be converted into compounds with high chemical energy such as HC at room temperature through photocatalytic conversion. Realize the conversion of solar energy into chemical energy. However, the previously reported catalysts still have problems such as low catalytic activity, so the development of new catalyst systems is urgently needed.

The present invention explores a simple hard template method to prepare a compound semiconductor material with a mesoporous structure. The precursor of gC ₃ N ₄ can provide a rich nitrogen source for CeO ₂ , realize in-situ N doping during the calcination process, and prepare N by a one-step calcination method. Doped CeO ₂ material, and then remove the hard template by etching to obtain N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material with mesoporous structure.

Contents of the invention

The purpose of the present invention is to provide a method for preparing N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material with mesoporous structure, and use it for photocatalytic conversion of CO ₂ at room temperature.

Here, the present invention provides a method for preparing a compound semiconductor material with a mesoporous structure, which includes the following steps: Step 1) dispersing the graphite-like carbon nitride precursor and hard template _SiO2 balls in water, Stirring for 10-60 minutes, wherein, the mass ratio of the graphite-like carbon nitride precursor to water is 1-20, and the mass ratio of the _SiO2 balls to water is 0.1-1, preferably 0.2-1;

Step 2) adding the Ce source into the solution obtained in step 1) according to the mass ratio of 0-2, and stirring at 25-50° C. for 0.5-6 hours;

Step 3) Evaporate the solution obtained in step 2) to dryness and dry overnight to obtain a powder mixture;

Step 4) Calcining the powder mixture obtained in step 3) at 300-600° C. for 1-4 hours to obtain a light yellow powder;

Step 5) removing the hard template from the light yellow powder obtained in step 4), centrifuging and drying to obtain a compound semiconductor material with a mesoporous structure.

The invention provides a new method for preparing a high specific surface area N-CeO ₂ /mpg-C ₃ N ₄ composite semiconductor photocatalyst with a mesoporous structure. In this method, _SiO2 is used as a hard template, and at least one of cerium nitrate, cerous chloride, cerium acetylacetonate hydrate, cerium carbonate, and cerium _sulfate is used as a Ce source. During the calcination process, the precursor of _gC3N4 is CeO2 provides a nitrogen source, enabling in _- situ N doping. The prepared catalyst has a higher specific surface area. By adjusting the type of precursor, the proportion of reactants, the calcination temperature and the heating rate, the optimal design of the catalyst can be realized. The composite semiconductor catalyst synthesized by this method can realize the conversion of _CO2 to HC compounds at room temperature with high stability. The preparation process of the invention is simple and easy, the method is novel, the cost is low, and the efficiency is high, and it shows broad application prospects in the fields of _CO2 photocatalytic conversion and the like.

In the present invention, the graphite-like carbon nitride soluble precursor in step 1) is at least one of urea, cyanamide and dicyandiamide.

Preferably, the particle size of the hard template SiO ₂ spheres in step 1) is 4-12 nm.

In the present invention, in step 2), at least one of cerium nitrate, cerous chloride, cerium acetylacetonate hydrate, cerium carbonate and cerium sulfate is selected as the Ce source.

In the present invention, the temperature for evaporating water to dryness in step 3) is 50-100°C.

Also, the overnight drying temperature in step 3) is 50-80°C.

Preferably, the heating rate of the calcination in step 4) is 2-10K min ^-1 .

Preferably, NH ₄ HF is used to remove the hard template in step 5).

In the present invention, the prepared compound semiconductor material with mesoporous structure has a specific surface area of 50-300m ² g ^-1 , a pore volume of 0.5-2 cm ³ g ^-1 and a pore diameter of 4-12nm.

Also, in the prepared compound semiconductor material having a mesoporous structure, CeO ₂ has a polycrystalline structure.

Description of drawings

Fig. 1 a and Fig. 1 b are the scanning electron microscope (SEM) photos of the mesoporous N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material obtained in Example 1;

Fig. 2 a is the transmission electron microscope (TEM) photo of the mesoporous N-CeO ₂ /mpg-C ₃ N ₄ composite semiconductor material obtained in Example 1;

Figure 2b is a high resolution electron microscope (HRTEM) photo of the mesoporous N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material obtained in Example 1;

Fig. 3a is the _N2 adsorption-desorption isotherm curve of the mesoporous N _- CeO2/mpg _- C3N4 compound semiconductor material obtained in Example ₁ ;

FIG. 3 b is the corresponding pore size distribution diagram of the mesoporous N-CeO2/mpg-C ₃ N ₄ compound semiconductor material obtained in Example 1. FIG.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, not to limit the present invention.

The invention provides a method for preparing compound semiconductor material with mesoporous structure. The compound semiconductor material is synthesized by a simple one-step hard template method. The compound semiconductor material has two-dimensional (2D) material structure characteristics and uniform pore distribution, and the material has high specific surface area and pore volume, which is very conducive to the diffusion and adsorption of reactant molecules, such as CO ₂ , H ₂ O and petroleum catalytic products, etc. Moreover, the prepared compound semiconductor material has an organic-inorganic hybrid framework, and has broad application prospects in the fields of biology, adsorption, catalysis, and separation. The synthesis method of the invention is simple, novel, low in cost and high in efficiency.

The method of the present invention comprises:

(1) Dissolve gC ₃ N ₄ precursors (urea, cyanamide, dicyandiamide, melamine, etc.) in silica sol, and stir at 25-50°C for _10-60 minutes _. The mass ratio of silica sol to water is 1～20, and silica sol is made by adding SiO spheres into water at a mass ratio of 0.1～ ₁ (preferably 0.2～1);

(2) Dissolving the Ce source in the above solution according to the mass ratio of 0-2 (preferably >0 and ≤2), stirring at 25-50°C for 0.5-6 hours;

(3) evaporate moisture, dry overnight in oven afterwards;

(4) calcining in a muffle furnace to obtain a light yellow powder;

(5) After that, NH ₄ HF was used to remove the hard template, and the product was obtained after centrifugal drying.

Wherein, as a preferred solution, the precursor of gC ₃ N ₄ in step (1) may be a soluble precursor of gC ₃ N ₄ . The Ce source in step (2) is at least one of cerium nitrate, cerous chloride, cerium acetylacetonate hydrate, cerium carbonate, and cerium sulfate.

As a preferred version, the evaporation water temperature in step (3) is 50-100°C.

As a preferred solution, the temperature of the oven in step (3) is 50-80°C.

As a preferred solution, the calcination temperature of the muffle furnace in step (4) is 300-600° C., and the time is 1-4 hours.

As a preferred solution, the heating rate of the muffle furnace in step (4) is 2-10K min ^-1 .

As a preferred solution, the hard template SiO2 selected for the compound semiconductor material has a particle size of 4-12 nm.

As a preferred solution, the compound semiconductor material with 2D structure has a specific surface area of 50-300 m ² g ^-1 , a pore volume of 0.5-2 cm ³ g ^-1 , and a pore diameter of 4-12 nm.

The characteristics of the invention are: the invention provides a new method for preparing a high specific surface area N-CeO ₂ /mpg-C ₃ N ₄ composite semiconductor photocatalyst with a mesoporous structure. In this method, _SiO2 is used as a hard template, and at least one of cerium nitrate, cerous chloride, cerium acetylacetonate hydrate, cerium carbonate, and cerium _sulfate is selected as a Ce source. During the calcination process, the precursor of _gC3N4 Provide nitrogen source for CeO2 to realize in _- situ N doping. The prepared catalyst has a higher specific surface area. By adjusting the type of precursor, the proportion of reactants, the calcination temperature and the heating rate, the optimal design of the catalyst can be realized. The composite semiconductor catalyst synthesized by this method can realize the conversion of _CO2 to HC compounds at room temperature with high stability.

Examples are given below to describe the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention, and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the above contents of the present invention all belong to the present invention scope of protection. The specific process parameters and the like in the following examples are only examples of suitable ranges, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values exemplified below.

Example 1

Weigh 3g of cyanamide, dissolve it in 20mL water, add 3g of SiO ₂ spheres with a particle size of 10nm, stir at room temperature for 10 minutes, add 0.2g Ce(NO ₃ ) ₃ 6H ₂ O, stir to dissolve in in the above solution. Stir at 30°C for 30 minutes, then dry at 90°C while stirring to remove water. Place in an oven at 80°C overnight. The obtained powder sample was placed in a muffle furnace, calcined at 550° C. for 3 hours, and a brown-yellow product was obtained after cooling. The obtained product was dispersed in 4M NH ₄ HF solution, the hard template was removed, centrifuged and dried to obtain the final product.

1a and 1b are scanning electron microscope (SEM) photos of the mesoporous N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material obtained in Example 1. It can be seen from the photos that the prepared mesoporous material has a regular pore arrangement structure.

Fig. 2a and Fig. 2b are transmission electron microscope (TEM) photos and high resolution electron microscope (HRTEM) photos of the mesoporous N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material obtained in Example 1. It can be seen from the figure that the pore size of the prepared semiconductor material is about 10nm.

Fig. 3 a is the N ₂ adsorption-desorption isotherm curve of the mesoporous N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material obtained in Example 1; Fig. 3 b is the mesoporous N-CeO ₂ /mpg obtained in Example 1 - Corresponding pore size distribution diagram _{of C3N4} compound semiconductor material. Combining Figure 3a and Figure 3b, it can be shown that the prepared mesoporous material has a high specific surface area and a pore size of about 10 nm.

Industrial applicability: the preparation process of the present invention is simple and easy, the method is novel, the cost is low, and the efficiency is high, and it shows broad application prospects in the fields of _CO2 photocatalytic conversion and the like.

Claims (10)

1. a method for preparing N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor materials with mesoporous structure, is characterized in that, comprises the following steps: Step 1) Disperse the graphite-like carbon nitride soluble precursor and hard template SiO ₂ balls in water, and stir at 25-50°C for 10-60 minutes, wherein the mass of the graphite-like carbon nitride soluble precursor and water Ratio is 1～20, and the mass ratio of described _SiO2ball and water is 0.1～1; Step 2) Dissolve the Ce source in the solution obtained in step 1) according to a mass ratio of 0 to 2 but not 0, stir at 25 to 50°C for 0.5 to 6 hours, and dissolve the Ce source in cerium nitrate, cerous chloride, acetyl hydrate At least one of cerium acetonate, cerium carbonate, and cerium sulfate is selected as a Ce source; Step 3) Evaporate the solution obtained in step 2) to dryness and dry overnight to obtain a powder mixture; Step 4) Calcining the powder mixture obtained in step 3) at 300-600° C. for 1-4 hours to obtain a light yellow powder; Step 5) remove the hard template from the light yellow powder obtained in step 4), centrifuge and dry to obtain a N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material with a mesoporous structure. 2 . The method according to claim 1 , wherein the graphite-like carbon nitride soluble precursor in step 1) is at least one of urea, cyanamide, dicyandiamide, and melamine. 3. The method according to claim 1, characterized in that the particle size of the hard template SiO ₂ spheres in step 1) is 4-12 nm. 4. The method according to claim 1, characterized in that the temperature for evaporating water to dryness in step 3) is 50-100°C. 5. The method according to claim 1, characterized in that the overnight drying temperature in step 3) is 50-80°C. 6. The method according to claim 1, characterized in that the heating rate of the calcination in step 4) is 2-10 K/min. 7. The method according to claim 1, characterized in that, in step 5), NH ₄ HF is used to remove the hard template. 8. The method according to any one of claims 1-7, characterized in that the prepared N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material with a mesoporous structure has a specific surface area of 50-300 m ² g ^-1 , the pore volume is 0.5-2 cm ³ g ^-1 , and the pore diameter is 4-12 nm. 9. The method according to any one of claims 1 to 7, characterized in that, in the prepared N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material with mesoporous structure, CeO ₂ has polycrystalline structure. 10. The method according to claim 8, characterized in that, in the prepared N-CeO ₂ /mpg-C ₃ N ₄ compound semiconductor material having a mesoporous structure, CeO ₂ has a polycrystalline structure.