CN109772419B

CN109772419B - Preparation method for constructing carbon nitride-based ultrathin nanosheet composite material in confined space

Info

Publication number: CN109772419B
Application number: CN201910178756.8A
Authority: CN
Inventors: 杨占旭; 王崇泽; 谭文; 崔博洋
Original assignee: Liaoning Shihua University
Current assignee: Liaoning Shihua University
Priority date: 2019-03-11
Filing date: 2019-03-11
Publication date: 2021-12-28
Anticipated expiration: 2039-03-11
Also published as: CN109772419A

Abstract

The invention belongs to the field of photocatalysis, and particularly relates to a preparation method for constructing a carbon nitride-based ultrathin nanosheet composite material in a confined space, which is implemented according to the following steps: (1) mixing cyanamide and vermiculite, heating to 300-400 ℃ by a program, and slowly cooling to room temperature to obtain a cyanamide intercalated vermiculite precursor: (2) stirring and reacting the cyanamide intercalated vermiculite precursor with an organic solution, filtering, washing and drying; heating to 500-650 ℃ in air, and slowly cooling to room temperature; (3) and reacting the obtained product with strong acid, filtering, washing and drying the filter cake. The invention has low cost, easy industrial production, good dispersibility of the target product and excellent photocatalytic performance.

Description

Preparation method for constructing carbon nitride-based ultrathin nanosheet composite material in confined space

Technical Field

The invention belongs to the field of photocatalysis, and particularly relates to a preparation method for constructing a carbon nitride-based ultrathin nanosheet composite material in a confined space.

Background

Energy, information and materials are three pillars for the development of contemporary society, and with the continuous development of socioeconomic in recent years, the shortage of energy has become an important factor for limiting the development of economy. In order to further promote sustainable development, various new green energy sources must be vigorously developed, the semiconductor photocatalysis technology is a new technology of high-efficiency, clean, environment-friendly and renewable energy sources, a series of chemical reactions can be driven by natural sunlight to convert solar energy into chemical energy (such as hydrogen energy), and the semiconductor photocatalysis technology has great potential in environmental purification and new energy source development, so that the semiconductor photocatalysis technology becomes the key research direction of the current science.

In the literature, Nature, 1972, 238: 37-38, Japanese scientists Fujishma and Honda found that TiO2 can be used as a photocatalyst to decompose water to prepare hydrogen and oxygen, and titanium dioxide (TiO2) is a relatively mature photocatalyst and has the advantages of low price, no toxicity, high stability, high ultraviolet light catalysis efficiency and the like. However, the wide band gap and non-responsiveness to visible light of TiO2 limit its application in the field of visible light photocatalysis to some extent. In the literature Nature Materials, 2009, 8: 76-80, Wang et al have first discovered that graphite phase carbon nitride (g-C3N4) has relatively good response and catalytic performance in the visible. However, the graphite-phase carbon nitride (g-C3N4) semiconductor photocatalyst material prepared by the traditional method is formed by stacking irregularly stacked slabs, and the photocatalytic performance of the material is greatly influenced by the shape of the layered agglomerated particles and the corrugated stacked slabs. In addition, the graphite phase carbon nitride (g-C3N4) material can only absorb ultraviolet light with the wavelength range in sunlight, and the ultraviolet light band accounts for a small proportion in the sunlight. Therefore, the applications of these semiconductor materials in visible light catalysis are greatly limited. To address this problem, doping the existing semiconductor and bonding the noble metal, i.e., an effective promoter, to the surface of the photocatalyst material are two effective ways to extend the range of light absorbed into the visible portion. However, the sample is not stable after doping, and the dopant can become a new carrier recombination center, so that the photo-generated carrier pair is reduced. And the cost of combining the noble metal with the surface of the photocatalyst material is high. Therefore, it is important to develop a novel photocatalyst material to replace the traditional graphite phase carbon nitride (g-C3N4) semiconductor photocatalyst material.

Compared with the graphite-phase carbon nitride (g-C3N4) semiconductor photocatalyst material prepared by the traditional method, the carbon nitride-based ultrathin nanosheet composite material constructed in the confined space not only presents a nanosheet with a fragment structure which is small in size, transparent, smooth and thin, and part of the flakes are laminated together, but also has good dispersibility. The electronic state of the semiconductor nano-flake is transited from the energy band of the bulk material to the energy level with a discrete structure along with the size reduction, and is reflected in the absorption spectrum from a wide absorption band without a structure to the absorption characteristic with a structure. In addition, compared with a graphite-phase carbon nitride (g-C3N4) semiconductor photocatalyst, the forbidden bandwidth of the carbon nitride-based ultrathin nanosheet composite material constructed in the confined space is obviously reduced, which indicates that the material has stronger light absorption and utilization rate. In the carbon nitride-based ultrathin nanosheet material, the carbon ring and the carbon nitride form a planar heterostructure, and the carbon has a good conduction effect on electrons, so that the separation of photo-generated electron-hole pairs on the surface of the semiconductor photocatalytic material can be promoted, the recombination of electrons and holes in a body is inhibited, and the photocatalytic performance is effectively improved. At present, the main synthesis method reported at home and abroad about the carbon nitride-based composite material is to prepare the material by mixing organic compounds such as glucose and the like with high carbon content with melamine through a hydrothermal method or a solvothermal method. But the material obtained by the method still has the non-regular thick sheet-like morphology. And the research of constructing the carbon nitride-based ultrathin nanosheet composite material in the confined space for applying to a photocatalytic hydrogen production system has not been reported.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides the preparation method for constructing the carbon nitride-based ultrathin nanosheet composite material in the confined space, which has the advantages of low cost, easiness in industrial production, good dispersibility of a target product and excellent photocatalytic performance.

In order to solve the technical problem, the invention is realized as follows:

a preparation method for constructing a carbon nitride-based ultrathin nanosheet composite material in a confined space can be implemented according to the following steps:

(1) mixing cyanamide and vermiculite, heating to 300-400 ℃ by a program, and slowly cooling to room temperature to obtain a cyanamide intercalated vermiculite precursor:

(2) stirring and reacting the cyanamide intercalated vermiculite precursor in the step (1) with an organic solution, filtering, washing and drying; heating to 500-650 ℃ in air, and slowly cooling to room temperature;

(3) and (3) reacting the product obtained in the step (2) with strong acid, filtering, washing and drying the filter cake.

As a preferable scheme, in the step (1), after being uniformly mixed, the cyanamide and the vermiculite are placed in an alumina crucible, heated to 300-400 ℃ at a speed of 1-10 ℃/min in the air, maintained for 1-4 h, and then slowly cooled to room temperature.

Further, in the step (2), the cyanamide intercalated vermiculite precursor and 1-40 mL of organic solution are stirred and reacted for 2-60 hours at 40-90 ℃, and dried at 40-80 ℃ after being filtered and washed; heating the mixture to 500-650 ℃ in air, maintaining the temperature for 1-4 hours, and then slowly cooling the mixture to room temperature.

Further, in the step (3), the obtained product and strong acid are stirred and react for 2-60 hours at the temperature of 40-90 ℃, and the filter cake is filtered, washed by deionized water and dried at the temperature of 40-80 ℃.

In step (1), the cyanamide is one or a mixture of two or more of cyanamide, dihydrodiammine, and melamine.

Further, the mass ratio of the cyanamide to the vermiculite is 1: 1-20.

Further, in the step (2) of the present invention, the organic solution is an aldehyde solvent.

Further, the aldehyde solvent is one or a mixture of more than two of formaldehyde solvent, acetaldehyde solvent or butyraldehyde solvent.

Further, the heating rate of the invention in air is 1-10 ℃/min.

Further, in step (3) of the present invention, the strong acid is one or a mixture of two or more of hydrochloric acid, sulfuric acid, and hydrofluoric acid.

The invention has the advantages that cyanamide is intercalated between vermiculite laminates, the morphological size and phase of an interlayer object substance can be controlled by the physical limiting action of the laminates, the polycondensation reaction of cyanamide molecules in corresponding interfaces is different from the traditional open system, and the formed carbon nitride-based ultrathin nanosheet composite material is an ultrathin nanosheet with regular shape, small size and good dispersibility. The invention has simple process and low cost of raw materials, and is easy for industrial large-scale production.

Drawings

The invention is further described with reference to the following figures and detailed description. The scope of the invention is not limited to the following expressions.

Fig. 1 is an XRD pattern of the composite material obtained in example 1.

FIG. 2 is a TEM image of the composite material obtained in example 2.

FIGS. 3-a and 3-b are solid UV images of the composite material obtained in example 3.

FIG. 4 is a graph of the photocatalytic performance of the composite material obtained in example 4.

Detailed Description

Example 1.

(1) Weighing 3g of dicyandiamide and vermiculite, placing the mixed sample into a crucible, heating the mixed sample to 400 ℃ at the speed of 5 ℃/min in the air, maintaining the temperature for 3h, and slowly cooling the mixed sample to room temperature according to the mass ratio of 1: 6. The precursor of dicyandiamide intercalated vermiculite is stirred and reacted with 20mL of formaldehyde solution for 8 hours at 40 ℃, and dried at 80 ℃ after being filtered, washed and washed. Heating to 560 deg.C in air at 5 deg.C/min for 2h, and slowly cooling to room temperature.

(2) And stirring and reacting the sintered sample with a mixed solution of hydrofluoric acid and hydrochloric acid at 40 ℃ for 4 hours, performing suction filtration, washing a filter cake with deionized water, and drying at 80 ℃ to obtain the carbon nitride-based ultrathin nanosheet composite material.

(3) 3g of dicyandiamide was weighed into a muffle furnace and was programmed to 560 ℃ for 2h and then slowly cooled to room temperature to obtain g-C3N4 material. As shown in fig. 1, the XRD pattern demonstrates that the material is different from the conventional g-C3N4 material, which is a carbon nitride based composite material.

Example 2.

(1) Weighing 2g of cyanamide and vermiculite, placing the mixed sample into a crucible, heating the mixed sample to 320 ℃ at the speed of 5 ℃/min in the air, maintaining the temperature for 3h, and slowly cooling the mixed sample to room temperature according to the mass ratio of 1: 6. The precursor of the cyanamide intercalated vermiculite is stirred and reacted with 20mL of acetaldehyde solution at 40 ℃ for 12 hours, and dried at 80 ℃ after being filtered and washed. Heating to 620 ℃ at the speed of 5 ℃/min in the air for 2h, and then slowly cooling to room temperature.

(2) And stirring and reacting the sintered sample with a mixed solution of hydrofluoric acid and sulfuric acid at 40 ℃ for 6 hours, performing suction filtration, washing a filter cake with deionized water, and drying at 80 ℃ to obtain the carbon nitride-based ultrathin carbon nanosheet composite material. As shown in fig. 2, TEM observes that the synthesized carbon nitride-based ultrathin nanosheet composite material has the morphology of ultrathin nanosheets.

Example 3.

(1) Weighing 4g of melamine and vermiculite, putting the mixed sample into a crucible according to the mass ratio of 1:8 of the melamine to the vermiculite, heating the mixed sample to 320 ℃ in air at a speed of 5 ℃/min, maintaining the temperature for 3h, and slowly cooling the mixed sample to room temperature. Stirring and reacting the precursor of the melamine intercalated vermiculite with 20mL of acetaldehyde solution for 8 hours at 40 ℃, filtering, washing and drying at 80 ℃. Heating to 600 deg.C at 5 deg.C/min in air for 4 hr, and slowly cooling to room temperature.

(2) And stirring and reacting the sintered sample with a mixed solution of hydrofluoric acid and sulfuric acid at 40 ℃ for 4 hours, performing suction filtration, washing a filter cake with deionized water, and drying at 80 ℃ to obtain the carbon nitride-based ultrathin nanosheet composite material.

(3) Weighing 4g of melamine, placing the melamine in a muffle furnace, raising the temperature to 600 ℃ by program, maintaining the temperature for 4h, and then slowly cooling to room temperature to obtain the g-C3N4 material. As shown in FIG. 3, the UV spectrum shows that the material has broader spectral absorption properties than the g-C3N4 material.

Example 4.

(1) Weighing 2g of dicyandiamide and vermiculite, placing the mixed sample into a crucible, heating the mixed sample to 320 ℃ at the speed of 5 ℃/min in the air, maintaining the temperature for 3h, and slowly cooling to room temperature according to the mass ratio of 1: 8. The precursor of dicyandiamide intercalated vermiculite is stirred and reacted with 20mL of butyraldehyde solution for 8 hours at 40 ℃, and dried at 80 ℃ after suction filtration and washing. Heating to 580 deg.C at 5 deg.C/min in air for 2 hr, and slowly cooling to room temperature.

(2) And stirring and reacting the sintered sample with a mixed solution of hydrofluoric acid and hydrochloric acid at 70 ℃ for 4 hours, performing suction filtration, washing a filter cake with deionized water, and drying at 80 ℃ to obtain the carbon nitride-based ultrathin nanosheet composite material. And weighing 2g of dicyandiamide, placing the dicyandiamide into a muffle furnace, carrying out temperature programming to 580 ℃ for 2h, slowly cooling to room temperature to obtain the g-C3N4 material.

(3) Weighing 50mg of sample and 80mL of sample, putting the sample and the 80mL of sample into a photocatalytic reactor, adding 10mL of triethanolamine aqueous solution as a sacrificial agent, and carrying out a photocatalytic hydrogen production experiment under the condition of using an atmosphere lamp (provided with an optical filter with lambda being more than or equal to 420 n). As shown in FIG. 4, the photocatalytic performance graph shows that the material has better photocatalytic performance compared with g-C3N 4.

It is understood that various other changes and modifications may be made by those skilled in the art based on the technical idea of the present invention, and all such changes and modifications should fall within the protective scope of the claims of the present invention.

Claims

1. A preparation method for constructing a carbon nitride-based ultrathin nanosheet composite material in a confined space is characterized by comprising the following steps:

(1) uniformly mixing cyanamide and vermiculite, placing the mixture in an alumina crucible, heating the mixture to 300-400 ℃ at a speed of 1-10 ℃/min in the air, maintaining the temperature for 1-4 hours, and then slowly cooling the mixture to room temperature to obtain a cyanamide intercalated vermiculite precursor; the cyanamide is one or a mixture of more than two of cyanamide, dihydrodiammine or melamine; the mass ratio of the cyanamide to the vermiculite is 1: 1-20;

(2) stirring and reacting cyanamide intercalated vermiculite precursor with 1-40 mL of organic solution at 40-90 ℃ for 2-60 h, filtering, washing and drying at 40-80 ℃; heating to 500-650 ℃ in air, maintaining for 1-4 h, and then slowly cooling to room temperature; the organic solution is an aldehyde solvent; the aldehyde solvent is one or a mixture of more than two of formaldehyde solvent, acetaldehyde solvent or butyraldehyde solvent;

(3) stirring and reacting the obtained product with strong acid at 40-90 ℃ for 2-60 h, performing suction filtration, washing a filter cake with deionized water, and drying at 40-80 ℃; the strong acid is one or a mixture of more than two of hydrochloric acid, sulfuric acid or hydrofluoric acid.