阅读说明：本技术 多孔二维氮化碳@石墨烯@氮化碳三明治结构光催化材料的制备方法及应用 (Preparation method and application of porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material ) 是由 宋亭 于 2019-10-31 设计创作，主要内容包括：本发明公开多孔二维氮化碳@石墨烯@氮化碳三明治结构光催化材料的制备方法及应用。首先采用改进的Hummer法合成GO纳米片,然后以三聚氰胺为氮源,采用简单的局部原位热氧侵蚀策略,即可制得多孔二维氮化碳@石墨烯@氮化碳三明治结构光催化材料。本发明只需采用低廉环保的溶剂和可控加热过程,无需采用有毒试剂和繁琐的后处理过程,与纯的CN相比,本发明优化的GOCN复合材料显示出明显改善的光催化产氢活性,产氢率可高达12.48mmol g<Sup>-1</Sup>h<Sup>-1</Sup>,比CN在相同的条件下高32.0倍。(The invention discloses a preparation method and application of a porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material. Firstly, synthesizing GO nano sheets by adopting an improved Hummer method, then taking melamine as a nitrogen source, and adopting a simple local in-situ thermal oxidation erosion strategy to prepare the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material. The invention only needs cheap and environment-friendly solvent and controllable heating process, does not need toxic reagent and complex post-treatment process, and compared with pure CN, the optimized GOCN composite material shows obviously improved photocatalytic hydrogen production activity, and the hydrogen production rate can reach 12.48mmol g ‑1 h ‑1 32.0 times higher than CN under the same conditions.)

1. The preparation method of the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material is characterized by comprising the following steps of:

(1) synthesizing GO, namely synthesizing GO nanosheets by adopting an improved Hummer method;

(2) synthesizing a porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure by ultrasonic and stirring according to the weight ratio of 0.15-0.3: dispersing melamine into H at a solid-to-liquid ratio of 40-700 g/mL ₂And in O, under the condition of continuous stirring, mixing the materials according to the weight ratio of 0.005-0.016: uniformly dispersing GO in water at a solid-to-liquid ratio of 8-12 g/mL, dropwise adding the GO dispersion liquid into melamine dispersion liquid, stirring again, evaporating water to obtain opaque powder, and calcining the powder in a nitrogen atmosphereAnd calcining in an air atmosphere to finally obtain the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material which is marked as GOCN.

2. The preparation method of the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material according to claim 1, wherein the specific steps of the step (1) are as follows: first, NaNO was added in an ice bath ₃And graphite powder are gradually dispersed in the concentrated H according to the mass ratio of 1: 1.8-2.2 ₂SO ₄In the solution, the concentration of graphite powder is controlled to be 0.03-0.05 g/mL, then the temperature of the mixture is kept at 0-3 ℃, and then KMnO is added into the mixture ₄，KMnO ₄And the mass of the graphite powder is 2.5-4: 1, stirring the mixture at 30-40 ℃ for 4-8H to complete oxidation reaction, then adding water for dilution, and adding H ₂O ₂The reaction was terminated to reduce the residual KMnO ₄And finally, washing and drying to obtain the solid GO nanosheet.

3. The preparation method of the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material according to claim 2, wherein in the step (1), the graphite powder is natural graphite powder.

4. The preparation method of the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material according to claim 2, wherein in the step (1), the drying is freeze drying.

5. The preparation method of the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material according to claim 1, wherein in the step (2), the continuous stirring time is 1.5-3 hours.

6. The preparation method of the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material according to claim 1, wherein in the step (2), the re-stirring time is 5-8 hours.

7. The preparation method of the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material according to claim 1, wherein in the step (2), the calcination in a nitrogen atmosphere specifically comprises: the temperature is 500-600 ℃, the time is 4-7 hours, and the heating rate is 8-12 ℃ min ^-1(ii) a The calcination in the air atmosphere is specifically as follows: the temperature is 480-540 ℃, the time is 1-2 hours, and the heating rate is 1-4 ℃ min ^-1。

8. Use of the photocatalytic material obtained by the preparation method according to any one of claims 1 to 7 in photocatalytic hydrogen production.

Technical Field

The invention relates to a semiconductor photocatalytic material, in particular to a preparation method and application of a porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material.

Background

With the advancement of science and technology, the whole society has made great progress from the first industrial revolution, then the second industrial revolution, to the third industrial revolution, to the fourth industrial revolution today, for over two hundred years. Particularly, the demand of the society for energy is getting larger and larger when the information age and the intelligent age are entered. The energy drives the whole society to advance forward and plays a key role in enabling the whole society to operate continuously. However, fossil fuels account for a significant portion of the energy infrastructure. This leads to environmental problems and energy crisis that are common today. Hydrogen is one of the cleanest fuels in the 21 st century because of its advantages of water origin, high energy density, no secondary pollution and the like. Among the many methods of preparation, photocatalytic decomposition of water to produce hydrogen, among which semiconductor visible light photocatalysis is the most ideal method for producing hydrogen. The traditional photocatalyst can only absorb ultraviolet light (the ultraviolet light only accounts for 3% -5% of the whole radiant solar energy) due to the excessively wide band gap, so that the practical application of the traditional photocatalyst is influenced.

In recent years, graphite phase Carbon Nitride (CN) has been introduced to the photocatalytic hydrogen production field due to its good stability, non-metallic and visible light activity. However, CN has very low photocatalytic hydrogen production efficiency due to limited visible light absorption capacity and severe recombination of photogenerated carriers. Therefore, many efforts have been made to improve the photocatalytic activity of CN, such as heterostructures, metal deposition (Pt, Ni, Fe, Au, Ag, etc.), elemental doping (I, B, P, S, C) and morphology control. It is well known that graphene is one of the most ideal electron acceptor candidates due to its strong mechanical strength, electrical conductivity and unique optical properties. In general, loading thick CN nanoplatelets on the graphene surface to construct a 2D/2D heterojunction will hinder the separation of photogenerated charge carriers, impair the utilization of visible light and reduce the corresponding active sites. Interestingly, placing a graphene sheet rich in functional groups between two-dimensional CN sheets can greatly improve the spatial separation efficiency of photo-induced charge carriers compared to conventional 2D/2D. Furthermore, modulating the morphology, especially rich in porous networks, can greatly enhance visible light capture and promote diffusion kinetics of reactants and products. In the invention, a method for preparing a porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich photocatalytic material and application of the material in photocatalytic hydrogen production are provided for the first time.

Disclosure of Invention

The invention provides a preparation method and application of a porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich photocatalytic material, aiming at the problems of low process yield, long process, serious pollution or high cost and the like of the existing semiconductor material for actual photocatalytic hydrogen production.

The technical scheme of the invention is as follows:

the preparation method of the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material comprises the following steps:

(1) synthesizing GO, namely synthesizing GO nanosheets by adopting an improved Hummer method;

(2) synthesizing a porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure by ultrasonic and stirring according to the weight ratio of 0.15-0.3: dispersing melamine into H at a solid-to-liquid ratio of 40-700 g/mL ₂And in O, under the condition of continuous stirring, mixing the materials according to the weight ratio of 0.005-0.016: the method comprises the steps of uniformly dispersing GO in water at a solid-liquid ratio of 8-12 g/mL, dropwise adding a GO dispersion liquid into a melamine dispersion liquid, stirring again, evaporating water to obtain opaque powder, and respectively calcining the powder in a nitrogen atmosphere and an air atmosphere to obtain the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material, which is marked as GOCN.

Further, the specific steps of step (1) are as follows: first, NaNO was added in an ice bath ₃And graphite powder are gradually dispersed in the concentrated H according to the mass ratio of 1: 1.8-2.2 ₂SO ₄In the solution, the concentration of graphite powder is controlled to be 0.03-0.05 g/mL, then the temperature of the mixture is kept at 0-3 ℃, and then KMnO is added into the mixture ₄， KMnO ₄And the mass of the graphite powder is 2.5-4: 1, stirring the mixture at 30-40 ℃ for 4-8H to complete oxidation reaction, then adding water for dilution, and adding H ₂O ₂The reaction was terminated to reduce the residual KMnO ₄And finally, washing and drying to obtain the solid GO nanosheet.

Further, in the step (1), the graphite powder is natural graphite powder.

Further, in the step (1), the drying is freeze drying.

Further, in the step (2), the stirring is continued for 1.5 to 3 hours.

Further, in the step (2), the re-stirring time is 5-8 hours.

Further, in the step (2), the calcination in a nitrogen atmosphere specifically includes: the temperature is 500-600 ℃, the time is 4-7 hours, and the heating rate is 8-12 ℃ min ^-1(ii) a The calcination in the air atmosphere is specifically as follows: the temperature is 480-540 ℃, the time is 1-2 hours, and the heating rate is 1-4 ℃ min ^-1。

The photocatalytic material obtained by the preparation method is applied to photocatalytic hydrogen production.

The invention has the beneficial effects that:

(1) according to the invention, a simple local in-situ thermal oxidation erosion strategy is adopted, only a cheap and environment-friendly solvent and a controllable heating process are adopted, no toxic reagent and a complicated post-treatment process are adopted, and the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material is prepared, so that the preparation process is simple and reliable.

(2) Compared with pure CN (bulk carbon nitride, obtained by direct thermal polymerization method and hereinafter referred to as CN), the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material prepared by the method has the advantages that the optimized GOCN composite material shows obviously improved photocatalytic hydrogen production activity, and the hydrogen production rate can reach 12.48mmol g ^-1h ^-132.0 times higher than CN under the same conditions. This is because the GOCN composite has large and strong interfacial contact, and is an ultra-thin structure, excellent visible light absorption, a porous structure, spatially separated redox sites, and rapid separation of photo-induced charge carriers.

Therefore, the preparation method of the porous two-dimensional carbon nitride @ graphene @ carbon nitride sandwich structure photocatalytic material provided by the invention has the characteristics of low cost, environmental friendliness, no pollution, mild process conditions, suitability for large-scale production and the like.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of the GOCN material obtained in example 1.

FIG. 2 is a Transmission Electron Micrograph (TEM) of the GOCN material obtained in example 1.

FIG. 3 is an Atomic Force Microscope (AFM) image (a) and corresponding height profile map (b) of CN.

FIG. 4 is a graph showing the results of the hydrogen production activity cycle test of GOCN and CN obtained in example 1.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the present invention is not limited thereto.