阅读说明：本技术 碳包覆氮化碳纳米线及其制法和光催化降解双酚a的应用 (Carbon-coated carbon nitride nanowire, preparation method thereof and application of carbon-coated carbon nitride nanowire in photocatalytic degradation of bisphenol A ) 是由 王雅君 姜桂元 李宇明 刘萌萌 于 2020-06-09 设计创作，主要内容包括：本发明提供一种碳包覆氮化碳纳米线及其制法和光催化降解双酚A的应用。制备方法包括：将聚乙二醇-聚丙二醇-聚乙二醇三嵌段共聚物加入水中,在搅拌的条件下加入硝酸,待聚乙二醇-聚丙二醇-聚乙二醇三嵌段共聚物溶解后,加入双氰胺继续搅拌得到混合溶液；将其移至反应釜中进行水热反应,反应的产物冷冻干燥后得到碳包覆氮化碳纳米线的前驱体；将碳包覆氮化碳纳米线的前驱体进行高温煅烧获得碳包覆氮化碳纳米线。该碳包覆氮化碳纳米线为三维网络结构,纳米线的直径为50～100nm,其具有较强的机械强度；将其应用于光催化降解双酚A,具有高光催化降解活性,与单纯氮化碳相比,比表面积明显增加,光谱响应范围大大拓展,降解速率明显提高。(The invention provides a carbon-coated carbon nitride nanowire, a preparation method thereof and application of photocatalytic degradation of bisphenol A. The preparation method comprises the following steps: adding a polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer into water, adding nitric acid under the stirring condition, adding dicyandiamide after the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer is dissolved, and continuously stirring to obtain a mixed solution; moving the carbon-coated carbon nitride nanowire to a reaction kettle for hydrothermal reaction, and freeze-drying a reaction product to obtain a precursor of the carbon-coated carbon nitride nanowire; and calcining the precursor of the carbon-coated carbon nitride nanowire at high temperature to obtain the carbon-coated carbon nitride nanowire. The carbon-coated carbon nitride nanowire is of a three-dimensional network structure, the diameter of the nanowire is 50-100 nm, and the nanowire has strong mechanical strength; the composite material is applied to photocatalytic degradation of bisphenol A, has high photocatalytic degradation activity, and has the advantages of obviously increased specific surface area, greatly expanded spectral response range and obviously improved degradation rate compared with the pure carbon nitride.)

1. A preparation method of carbon-coated carbon nitride nanowires comprises the following steps:

mixing the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer with water, adding nitric acid under the condition of stirring, adding dicyandiamide after the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer is dissolved, and continuously stirring to obtain a mixed solution;

transferring the mixed solution into a reaction kettle for hydrothermal reaction, and freeze-drying a reaction product to obtain a precursor of the carbon-coated carbon nitride nanowire;

and calcining the precursor of the carbon-coated carbon nitride nanowire at high temperature to obtain the carbon-coated carbon nitride nanowire.

2. The method of claim 1, wherein the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer has the following structural formula (I):

wherein x is an integer of 15-25, y is an integer of 55-85, and z is an integer of 15-25.

3. The method according to claim 1 or 2, wherein the mass ratio of the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, the nitric acid and the dicyandiamide is (1-10): (0.315-15.12): (2-8).

4. The method according to claim 1, wherein the step of adding nitric acid under stirring is constant-temperature stirring at 10-70 ℃ for 10-40 h;

preferably, the step of adding dicyandiamide and continuously stirring is constant-temperature stirring at 10-70 ℃ for 10-40 h.

5. The method according to claim 1, wherein the temperature of the hydrothermal reaction is 50-120 ℃, and the time of the hydrothermal reaction is 12-48 h;

preferably, the freeze drying time is 2-8 days.

6. The method according to claim 1, wherein the high-temperature calcination is a staged-heating calcination method, and the temperature is sequentially raised to 80-150 ℃ at a rate of 1-5 ℃/min for 0.5-2 hours, to 200-250 ℃ for 1-4 hours, and to 500-550 ℃ for 3-6 hours.

7. The carbon-coated carbon nitride nanowire prepared by the preparation method of any one of claims 1 to 6;

preferably, the diameter of the carbon-coated carbon nitride nanowire is 50-100 nm.

8. Use of the carbon-coated carbon nitride nanowires as defined in claim 7 for photocatalytic degradation of bisphenol a.

9. A method for photocatalytic degradation of bisphenol a, comprising the steps of:

the carbon-coated carbon nitride nanowire of claim 7 is used as a photocatalyst, added into a target pollutant containing bisphenol A, and subjected to photocatalytic degradation reaction to degrade bisphenol A by using a xenon lamp as a light source after adsorption equilibrium in the dark.

10. The method according to claim 9, wherein the xenon lamp has a power of 300W and is loaded with a cut-off filter in the 420nm band, and the light source is located 10cm from the reaction liquid surface.

Technical Field

The invention belongs to the technical field of photocatalytic materials, and relates to a carbon-coated carbon nitride nanowire, a preparation method thereof and application of the carbon-coated carbon nitride nanowire in photocatalytic degradation of bisphenol A.

Background

With the rapid development of industry, environmental pollution has become one of the most serious threats to human society, and especially, the problem of water pollution has attracted great attention. The photocatalysis technology is a new technology which is rapidly developed in recent decades, can completely mineralize organic pollutants into carbon dioxide and water without secondary pollution, and has unique advantages of degrading organic pollutants with high toxicity and low concentration in a water environment. Graphite phase carbon nitride (g-C)₃N₄) The carbon nitride structure is the most stable carbon nitride structure at room temperature, can absorb part of visible light as a visible light catalyst without metal components, has good thermal stability and light stability, has good visible light absorption capacity and higher conduction band position, and is a hotspot in the research of the field of photocatalysis at present. However, the bulk carbon nitride has the defects of small specific surface area, high recombination rate of photo-generated electron-hole pairs, narrow visible light absorption range and the like.

In order to further improve the photocatalytic efficiency and the utilization rate of visible light of carbon nitride, a number of methods have been reported for modifying carbon nitride. Hu et al (Hu et al. enhanced visual light catalytic performance of g-C₃N₄photocatalysts co-doped with iron andphosphorus[J]Applied Surface Science 2014,331,164-171.) iron and phosphorus co-doped carbon nitride was prepared using dicyandiamide monomer, ferric nitrate and diammonium phosphate as precursors, and the research results showed that the addition of the dopant inhibited the crystal growth of graphite phase carbon nitrideThe length is long, the specific surface area of the carbon nitride is improved, the band gap width is reduced, and the recombination of photo-generated electrons and holes is inhibited; however, the light absorption is only 550nm, and it is difficult to achieve a wide spectral response, a large specific surface area, and a high photocatalytic activity.

Therefore, the problem to be solved in the art is to provide a preparation method of a carbon nitride modified material which is cheap, efficient, environment-friendly, large in specific surface area and wide in spectral response.

Disclosure of Invention

Based on the problems in the prior art, the invention aims to provide a preparation method of a carbon-coated carbon nitride nanowire; the invention also aims to provide the carbon-coated carbon nitride nanowire prepared by the method; the invention also aims to provide the application of the carbon-coated carbon nitride nanowire in photocatalytic degradation of bisphenol A; the invention also aims to provide a method for degrading bisphenol A by photocatalysis.

The purpose of the invention is realized by the following technical means:

in one aspect, the invention provides a method for preparing a carbon-coated carbon nitride nanowire, which comprises the following steps:

mixing the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer with water, adding nitric acid under the condition of stirring, adding dicyandiamide after the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer is dissolved, and continuously stirring to obtain a mixed solution;

transferring the mixed solution into a reaction kettle for hydrothermal reaction, and freeze-drying a reaction product to obtain a precursor of the carbon-coated carbon nitride nanowire;

and calcining the precursor of the carbon-coated carbon nitride nanowire at high temperature to obtain the carbon-coated carbon nitride nanowire.

The carbon-coated carbon nitride nanowire is prepared by taking a polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer as a template agent, performing interaction with dicyandiamide in the presence of nitric acid, performing hydrothermal reaction, freeze drying and calcining; the prepared carbon-coated carbon nitride nanowire is of a three-dimensional network structure, and the diameter of the nanowire is 50-100 nm.

In the invention, the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer is not only used as a soft template agent, but also plays an important role in regulating and controlling the morphology of the prepared carbon-coated carbon nitride nanowire; in the subsequent calcining process, the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer forms a carbon layer on the surface of the carbon nitride nanowire, so that the light absorption range of the catalyst is greatly expanded by the carbon layer, the charge separation of the photocatalyst is promoted, and the photocatalytic activity is improved; the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer not only plays a role in structure guiding, but also plays a role in forming a precursor of a carbon layer.

In the invention, the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer can be quickly dissolved in the presence of nitric acid. The polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer reacts with dicyandiamide under the chemical cutting action of nitric acid.

The carbon-coated carbon nitride nanowire prepared by the invention not only has a one-dimensional structure of the nanowire, so that the transmission of electrons in the carbon nitride nanowire is one-dimensional, and the one-dimensional structure shortens the path of the photo-generated electrons and holes transferred to the surface of a catalyst, promotes the separation of photo-generated carriers, and improves the utilization rate of the carriers; meanwhile, the carbon-coated carbon nitride nanowire prepared by the invention also has a three-dimensional network structure, and the three-dimensional network structure can provide a larger specific surface area in a certain space and expose more reactive sites, so that the photocatalytic degradation has a better effect.

The carbon-coated carbon nitride nanowire prepared by the invention has a wider spectral response range due to the action of the outer carbon layer, the visible light absorption range of the carbon nitride is greatly widened, the light absorption range can be expanded to 800nm, and visible light in the solar spectrum is utilized to a larger extent; the composite material is applied to photocatalytic degradation of bisphenol A, has high photocatalytic degradation activity, and has the advantages of obviously increased specific surface area, greatly expanded spectral response range and obviously improved degradation rate compared with the pure carbon nitride.

In the above method, preferably, the structural formula of the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer is shown as the following formula (I):

wherein x is an integer of 15-25, y is an integer of 55-85, and z is an integer of 15-25.

In the above method, preferably, the ratio of the amount of the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer to the amount of the water is (1 to 5) g: (50-250) mL.

In the above method, preferably, the mass ratio of the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, the nitric acid and the dicyandiamide is (1-10): (0.315-15.12): (2-8).

In the above method, preferably, the concentration of the nitric acid is 0.5 to 8 mol/L.

In the method, preferably, the step of adding the nitric acid under the stirring condition is constant-temperature stirring, the temperature is 10-70 ℃, and the stirring time is 10-40 hours.

In the method, preferably, the step of adding dicyandiamide and continuously stirring is constant-temperature stirring at the temperature of 10-70 ℃ for 10-40 h.

In the above method, the temperature of the hydrothermal reaction is preferably 50 to 120 ℃, and the time of the hydrothermal reaction is preferably 12 to 48 hours.

In the above method, the freeze-drying time is preferably 2 to 8 days.

In the method, preferably, the high-temperature calcination is a staged heating calcination manner, and the temperature is sequentially raised to 80-150 ℃ at a heating rate of 1-5 ℃/min for 0.5-2 h, raised to 200-250 ℃ for 1-4 h, and raised to 500-550 ℃ for 3-6 h.

On the other hand, the invention also provides the carbon-coated carbon nitride nanowire prepared by the preparation method.

The diameter of the carbon-coated carbon nitride nanowire is 50-100 nm.

In another aspect, the invention also provides an application of the carbon-coated carbon nitride nanowire in photocatalytic degradation of bisphenol A.

In still another aspect, the present invention provides a method for photocatalytic degradation of bisphenol a, comprising the steps of:

the carbon-coated carbon nitride nanowire is used as a photocatalyst, added into a target pollutant containing bisphenol A, and subjected to photocatalytic degradation reaction to degrade the bisphenol A by using a xenon lamp as a light source after adsorption balance in the dark.

In the above method, the xenon lamp preferably has a power of 300W, a cut-off filter having a wavelength band of 420nm is mounted thereon, and the light source is preferably located at a distance of 10cm from the reaction liquid surface.

The invention has the beneficial effects that:

(1) the preparation method of the carbon-coated carbon nitride nanowire is simple and environment-friendly; the diameter of the prepared carbon-coated carbon nitride nanowire is 50-100 nm, the carbon-coated carbon nitride nanowire has a one-dimensional structure of the nanowire, so that the transmission of electrons in the carbon nitride nanowire is one-dimensional, the one-dimensional structure shortens the path of the photo-generated electrons and holes transferred to the surface of a catalyst, the separation of photo-generated carriers is promoted, and the utilization rate of the carriers is improved; meanwhile, the photocatalyst has a three-dimensional network structure, can provide a larger specific surface area in a certain space, exposes more reaction active sites, and has a better photocatalytic degradation effect.

(2) The carbon-coated carbon nitride nanowire prepared by the method has a wider spectral response range, the visible light absorption range of carbon nitride is greatly widened, the light absorption range can be expanded to 800nm, and visible light in solar spectrum is utilized to a larger extent; the composite material is applied to photocatalytic degradation of bisphenol A, has high photocatalytic degradation activity, and has the advantages of obviously increased specific surface area, greatly expanded spectral response range and obviously improved degradation rate compared with the pure carbon nitride.

(3) In the preparation process of the carbon-coated carbon nitride nanowire, the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer not only plays a role in structure guiding, but also plays a role in forming a precursor of a carbon layer.

Drawings

Fig. 1 is an SEM image of carbon-coated carbon nitride nanowires prepared in example 1 of the present invention;

fig. 2 is a TEM image of carbon-coated carbon nitride nanowires prepared in example 1 of the present invention;

FIG. 3 is a graph showing the relationship between the rate of photocatalytic degradation of bisphenol A by carbon-coated carbon nitride nanowires and time in example 2 of the present invention;

FIG. 4 is an SEM image of a carbon nitride photocatalyst prepared in comparative example 1 of the present invention;

FIG. 5 shows N of the carbon-coated carbon nitride nanowires prepared in example 1 of the present invention and the carbon nitride photocatalyst prepared in comparative example 1₂Comparing the adsorption and desorption isotherms;

FIG. 6 is a graph comparing the UV-VIS diffuse reflectance spectra of carbon-coated carbon nitride nanowires prepared in example 1 of the present invention with the carbon nitride photocatalyst prepared in comparative example 1;

FIG. 7 is a comparison graph of XPS C1s spectra of carbon-coated carbon nitride nanowires prepared in example 1 of the present invention and carbon nitride photocatalysts prepared in comparative example 1;

FIG. 8 is a graph of the rate of photocatalytic degradation of bisphenol A by a carbon nitride photocatalyst prepared in comparative example 1 of the present invention under the conditions of example 2 versus time;

fig. 9 is a graph of the rate of photocatalytic degradation of bisphenol a versus time for the carbon-coated carbon nitride nanowires prepared in example 1 of the present invention and the carbon nitride photocatalyst prepared in comparative example 1 under the conditions of example 2.

Detailed Description

The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.

The starting materials used in the following examples are all commercially available. The polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer is purchased from Sigma Aldrich company (Sigma-Aldrich), and the product number is as follows: 435465, having the formula: