Graphene/carbon nitride composite material and preparation method and application thereof
阅读说明：本技术 一种石墨烯/氮化碳复合材料及其制备方法、应用 (Graphene/carbon nitride composite material and preparation method and application thereof ) 是由 盖婷婷 杨亚东 于 2020-05-29 设计创作，主要内容包括：本发明提供了一种石墨烯/氮化碳复合材料,所述复合材料具有层状结构；氮化碳复合在所述石墨烯片上,形成层状结构。本发明将石墨烯和氮化碳进行复合,得到了具有特定形貌的复合材料,该材料中氮化碳复合在石墨烯片上,具有层状结构。本发明得到的层状结构的石墨烯/氮化碳复合材料,具有优异的光催化活性,进而能够同时实现降解有机物和产氢,这种在光催化产氢的过程中,同时能够实现有机物的降解的作用至关重要。而且本发明提供的类石墨烯g-C-(3)N-(4)与石墨烯复合材料的制备方法,工艺简单、易操作、成本低及适合大规模制备,具有较好的应用前景。(The invention provides a graphene/carbon nitride composite material, which has a layered structure; and carbon nitride is compounded on the graphene sheet to form a laminated structure. According to the invention, graphene and carbon nitride are compounded to obtain the composite material with a specific morphology, and the carbon nitride in the material is compounded on a graphene sheet and has a layered structure. Hair brushThe graphene/carbon nitride composite material with the layered structure has excellent photocatalytic activity, and can be used for simultaneously degrading organic matters and producing hydrogen, and the function of simultaneously degrading the organic matters is very important in the process of producing hydrogen through photocatalysis. The invention also provides the graphene-like g-C 3 N 4 The preparation method of the graphene composite material has the advantages of simple process, easiness in operation, low cost, suitability for large-scale preparation and better application prospect.)
1. A graphene/carbon nitride composite material, wherein the carbon nitride is composited on the graphene sheet;
the carbon nitride has a non-layered structure.
2. The composite material of claim 1, wherein the carbon nitride comprises graphite phase carbon nitride;
the carbon nitride has a flocculent and/or cellular shape;
the graphene sheet comprises a graphene micro-nano sheet;
the mass ratio of the graphene sheet to the carbon nitride is (0.3-0.5): 1;
the carbon nitride is uniformly compounded on the surface of the graphene sheet and/or among graphene sheet layers.
3. The composite material of claim 1, wherein the graphene sheets have a sheet diameter of 5 to 15 μm;
the thickness of the graphene sheet is 1-10 nm;
the size of the carbon nitride is 5-20 mu m;
the height of the carbon nitride is 5-10 nm.
4. The composite material according to claim 1, wherein the composite is in particular attached to the graphene sheets by recrystallization;
the composite material has a wrinkled micro-topography;
the folds comprise mountain folds and/or wave folds;
the carbon nitride is densely distributed at folds and/or edges of the graphene sheets;
the carbon nitride has a porous morphology.
5. A preparation method of a graphene/carbon nitride composite material is characterized by comprising the following steps:
1) dispersing expanded graphite, a surfactant and water to obtain a dispersion liquid, and centrifuging and grinding to obtain a graphene micro-nano sheet;
2) mixing the graphene micro-nano sheet obtained in the step, a nitrogen source and water, and then continuously grinding to obtain powder;
3) and under a semi-closed condition, calcining the powder obtained in the step for the first time, and then calcining the powder for the second time under an open condition to obtain the graphene/carbon nitride composite material.
6. The method of claim 5, wherein the surfactant comprises one or more of N-methyl pyrrolidone, ethylenediamine, octadecyl trimethyl ammonium chloride, polyetherimide, hexadecyl dimethyl allyl ammonium chloride, tetradecyl dimethyl benzyl ammonium chloride, dodecyl dimethyl hydroxyethyl ammonium chloride, and dodecyl trimethyl ammonium chloride;
the mass ratio of the expanded graphite to the surfactant is (0.5-3): 100, respectively;
the mass ratio of the expanded graphite to water is (0.5-3): 100, respectively;
the dispersing mode comprises ultrasonic stirring and dispersing;
the ultrasonic frequency of the ultrasonic stirring dispersion is 20-40 KHz;
the rotating speed of the ultrasonic stirring dispersion is 300-500 rpm;
the ultrasonic stirring and dispersing time is 120-360 min;
the centrifugation process specifically comprises the following steps: the supernatant is obtained by low-speed centrifugation, and the supernatant is obtained by high-speed centrifugation.
7. The preparation method according to claim 6, wherein the rotation speed of the low-speed centrifugation is 500 to 1000 rpm;
the low-speed centrifugation time is 3-5 min;
the rotating speed of the high-speed centrifugation is 3000-5000 rpm;
the high-speed centrifugation time is 5-10 min;
a drying step is also included after the centrifugation;
the drying is vacuum drying;
the drying temperature is 40-80 ℃;
the drying time is 6-24 h.
8. The preparation method according to claim 6, wherein the grinding time is 30-60 min;
the rotation speed of the grinding is 1000-1500 rpm;
the mass ratio of the graphene micro-nano sheet to the nitrogen source is (0.1-0.5): 1;
the nitrogen source comprises one or more of thiourea, melamine, dicyandiamide, cyanamide and urea;
a drying step is further included before the continuous grinding;
the fineness of the powder is 20-50 mu m;
the semi-closed is closed but not sealed;
the graphene/carbon nitride composite material can realize simultaneous photocatalytic degradation of organic matters and hydrogen production.
9. The preparation method according to claim 6, wherein the temperature rise rate of the first calcination is 2 to 5 ℃/min;
the temperature of the first calcination is 450-550 ℃;
the time for the first calcination is 0.5-2 h;
the step of grinding again is also included after the first calcination;
the temperature rise rate of the second calcination is 2-5 ℃/min;
the temperature of the second calcination is 450-550 DEG C
The time of the second calcination is 0.5-2 h;
the temperature rise rate of the first calcination is the same as that of the second calcination.
10. The graphene/carbon nitride composite material according to any one of claims 1 to 4 or the graphene/carbon nitride composite material prepared by the preparation method according to any one of claims 5 to 9 is applied to the aspects of organic matter degradation and/or hydrogen production.
Technical Field
The invention belongs to the technical field of graphite phase carbon nitride materials, and relates to a graphene/carbon nitride composite material and a preparation method and application thereof.
Background
With the rapid exhaustion of non-renewable fuel petroleum coal fuel, people face the challenge of energy crisis, and the method has sustainable development, and environment-friendly energy sources (wind energy, water energy, solar energy and the like) are continuously developed and utilized. The solar energy is used as green energy for photocatalytic decomposition of water to prepare hydrogen, which is a sustainable development way. In addition, due to the appearance of a large number of chemical enterprises, a large number of organic matters appear in rivers and underground water, and the life health of people is seriously threatened.
Carbon nitride is a new covalent compound with hardness comparable to diamond and has not been found in nature, and its structure was predicted theoretically in 1989 and synthesized successfully in the laboratory in 1993. C3N4There are 5 structures in total, namely alpha phase, beta phase, cubic phase, quasi-cubic phase and graphite-like phase. The hardness of all 4 other structural materials, except the graphite-like phase, is comparable to that of diamond. However, among these, the graphite-like phase (g-C)3N4) The structure of (a) is the most stable, having a graphite-like layered structure and comprising two allotropes. In nature, no natural g-C has been found to exist to date3N4And (4) crystals. Thus g-C3N4Mainly comes from experimental synthesis. Selecting proper carbon source and nitrogen source, and obtaining g-C under certain reaction conditions3N4. The preparation method commonly used at present mainly comprises the following steps: high temperature and high pressure synthesis, physical and chemical vapor deposition, electrochemical deposition, solvent thermal polymerization, and pyrolysis of organic compounds.
Among numerous photocatalysts, the graphite-phase carbon nitride g-C with a unique structure3N4Due to the good photocatalytic performance, the photocatalyst can degrade organic compounds such as methyl blue and the like, and becomes a hotspot of current research. Compared with other photocatalysts, the photocatalyst has the advantages that: the material can absorb visible light, has good thermal stability and chemical stability, excellent electrical characteristics, low price, no toxicity, rich sources, simple preparation and forming process and the like. Thus, graphite phase carbon nitride acts as a kindThe visible light catalyst is applied to hydrogen production by water photolysis, and attracts extensive attention of researchers.
However g-C3N4The photocatalytic efficiency is still limited by the high recombination rate of photogenerated carriers and the low specific surface area, so that many methods are tried to improve the g-C3N4The photocatalytic efficiency of (c). For example: non-metal doping, noble metal deposition, preparation of nano-or porous g-C3N4And the like, but still has the problems of complex process and high cost.
Therefore, how to obtain an improvement to further improve the photocatalytic efficiency and better expand the application range is simple and feasible, and is suitable for industrial popularization and application, and becomes one of the problems to be solved by a plurality of front-line researchers and scientific research type enterprises.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a graphene/carbon nitride composite material, and a preparation method and an application thereof, wherein the graphene/carbon nitride composite material provided by the present invention has excellent photocatalytic activity, can better simultaneously degrade organic matters and produce hydrogen, and has the advantages of simple preparation method, easy operation, low cost, and suitability for industrial popularization and application.
The invention provides a graphene/carbon nitride composite material, wherein carbon nitride is compounded on a graphene sheet;
the carbon nitride has a non-layered structure.
Preferably, the carbon nitride comprises graphite phase carbon nitride;
the carbon nitride has a flocculent and/or cellular shape;
the graphene sheet comprises a graphene micro-nano sheet;
the mass ratio of the graphene sheet to the carbon nitride is (0.3-0.5): 1;
the carbon nitride is uniformly compounded on the surface of the graphene sheet and/or among graphene sheet layers.
Preferably, the sheet diameter of the graphene sheet is 5-15 μm;
the thickness of the graphene sheet is 1-10 nm;
the size of the carbon nitride is 5-20 mu m;
the height of the carbon nitride is 5-10 nm.
Preferably, the graphene sheet is attached to the composite material by a recrystallization method;
the composite material has a wrinkled micro-topography;
the folds comprise mountain folds and/or wave folds;
the carbon nitride is densely distributed at folds and/or edges of the graphene sheets;
the carbon nitride has a porous morphology.
The invention provides a preparation method of a graphene/carbon nitride composite material, which comprises the following steps:
1) dispersing expanded graphite, a surfactant and water to obtain a dispersion liquid, and centrifuging and grinding to obtain a graphene micro-nano sheet;
2) mixing the graphene micro-nano sheet obtained in the step, a nitrogen source and water, and then continuously grinding to obtain powder;
3) and under a semi-closed condition, calcining the powder obtained in the step for the first time, and then calcining the powder for the second time under an open condition to obtain the graphene/carbon nitride composite material.
Preferably, the surfactant comprises one or more of N-methyl pyrrolidone, ethylenediamine, octadecyl trimethyl ammonium chloride, polyetherimide, hexadecyl dimethyl allyl ammonium chloride, tetradecyl dimethyl benzyl ammonium chloride, dodecyl dimethyl hydroxyethyl ammonium chloride and dodecyl trimethyl ammonium chloride;
the mass ratio of the expanded graphite to the surfactant is (0.5-3): 100, respectively;
the mass ratio of the expanded graphite to water is (0.5-3): 100, respectively;
the dispersing mode comprises ultrasonic stirring and dispersing;
the ultrasonic frequency of the ultrasonic stirring dispersion is 20-40 KHz;
the rotating speed of the ultrasonic stirring dispersion is 300-500 rpm;
the ultrasonic stirring and dispersing time is 120-360 min;
the centrifugation process specifically comprises the following steps: the supernatant is obtained by low-speed centrifugation, and the supernatant is obtained by high-speed centrifugation.
Preferably, the rotating speed of the low-speed centrifugation is 500-1000 rpm;
the low-speed centrifugation time is 3-5 min;
the rotating speed of the high-speed centrifugation is 3000-5000 rpm;
the high-speed centrifugation time is 5-10 min;
a drying step is also included after the centrifugation;
the drying is vacuum drying;
the drying temperature is 40-80 ℃;
the drying time is 6-24 h.
Preferably, the grinding time is 30-60 min;
the rotation speed of the grinding is 1000-1500 rpm;
the mass ratio of the graphene micro-nano sheet to the nitrogen source is (0.1-0.5): 1;
the nitrogen source comprises one or more of thiourea, melamine, dicyandiamide, cyanamide and urea;
a drying step is further included before the continuous grinding;
the fineness of the powder is 20-50 mu m;
the semi-closed is closed but not sealed;
the graphene/carbon nitride composite material can realize simultaneous photocatalytic degradation of organic matters and hydrogen production.
Preferably, the temperature rise rate of the first calcination is 2-5 ℃/min;
the temperature of the first calcination is 450-550 ℃;
the time for the first calcination is 0.5-2 h;
the step of grinding again is also included after the first calcination;
the temperature rise rate of the second calcination is 2-5 ℃/min;
the temperature of the second calcination is 450-550 DEG C
The time of the second calcination is 0.5-2 h;
the temperature rise rate of the first calcination is the same as that of the second calcination.
The invention also provides the application of the graphene/carbon nitride composite material prepared by any one of the technical schemes or the preparation method of any one of the technical schemes in the aspects of organic matter degradation and/or hydrogen production.
The invention also provides the application of the graphene/carbon nitride composite material in the technical scheme or the graphene/carbon nitride composite material prepared by the preparation method in any one of the technical schemes in the aspects of organic matter degradation and/or hydrogen production.
The invention provides a graphene/carbon nitride composite material, wherein carbon nitride is compounded on a graphene sheet; the carbon nitride has a non-layered structure. Compared with the prior art, the invention aims at the existing g-C3N4The photocatalytic efficiency of (A) is still limited by a high recombination rate of photo-generated carriers and a low specific surface area, and the synthesized carbon nitride has a high recombination rate of photo-generated carriers, a low specific surface area and a low quantum efficiency, thereby resulting in low photocatalytic efficiency, although many methods have been tried to improve g-C3N4The photocatalysis efficiency of the method is high, but the traditional preparation method has the problems of complex process, high cost and the like.
The present inventors have conducted intensive studies and considered that g-C3N4The composition with the high-conductivity material is to improve g-C3N4The technical direction of better photocatalytic performance. According to the invention, graphene and carbon nitride are creatively compounded, and a composite material with a specific morphology is obtained through the nitrogen source recrystallization effect, wherein the carbon nitride is compounded on a graphene sheet and has a non-laminated structure, the graphene sheet has a two-dimensional sheet structure, and the two are combined to form a more three-dimensional micro-nano structure, so that the graphene-carbon nitride composite material obtained by the invention has the advantages of being provided with a more three-dimensional micro-nano structureThe photocatalytic activity is excellent, and then organic matter degradation and hydrogen production can be realized simultaneously, and the function of organic matter degradation is important in the photocatalytic hydrogen production process. The invention also provides the graphene-like g-C3N4The preparation method of the graphene composite material has the advantages of simple process, easiness in operation, low cost, suitability for large-scale preparation and better application prospect.
The experimental result shows that the compounding of the carbon nitride and the graphene can improve the hydrogen production rate of the carbon nitride and the degradation rate of organic matters; compared with a single carbon nitride catalyst, the hydrogen production rate of the graphene/carbon nitride composite catalyst and the degradation rate of rhodamine B in 4 hours are respectively 5.7 times and 1.3 times of the hydrogen production rate and the rhodamine B degradation rate.
Drawings
Fig. 1 is a schematic flow chart of a preparation process of a graphene/carbon nitride composite material according to an embodiment of the present invention;
fig. 2 is a surface micro-topography of the graphene/carbon nitride composite material prepared in example 2 of the present invention;
FIG. 3 is a graph comparing the hydrogen production rates of a single carbon nitride material prepared in example 1 and a graphene/carbon nitride composite catalyst prepared in example 3;
FIG. 4 is a comparison graph of hydrogen production rates of the graphene/carbon nitride composite catalyst prepared in example 3 of the present invention in water and rhodamine B solution;
FIG. 5 is a graph comparing degradation curves of a single carbon nitride material prepared in example 1 and a graphene/carbon nitride composite material catalyst prepared in example 3 for degrading rhodamine B;
fig. 6 is a photocurrent density-time curve of a single carbon nitride material prepared in example 1 of the present invention and a graphene/carbon nitride composite catalyst prepared in example 3;
FIG. 7 shows a single carbon nitride material prepared in example 1 of the present invention and N of graphene/carbon nitride composite catalyst prepared in example 32Adsorption-desorption isotherm plot.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All the raw materials of the present invention are not particularly limited in their purity, and the present invention preferably employs analytical grade or conventional purity used in the field of lithium sulfur battery separator preparation.
The invention provides a graphene/carbon nitride composite material, wherein carbon nitride is compounded on a graphene sheet;
the carbon nitride has a non-layered structure.
The selection of the carbon nitride is not particularly limited in principle, and a person skilled in the art can select and adjust the carbon nitride according to the actual application condition, the product requirement and the quality requirement3N4。
In the present invention, carbon nitride (g-C)3N4) Like graphene, all have a lamellar structure. The carbon nitride of the present invention has a non-layered structure, which means that the carbon nitride sheets of the sheet layer are microscopically assembled into a non-layered structure, but are preferably assembled into a flocculent and/or honeycomb shape.
The structure of the carbon nitride is not particularly limited in principle, and a person skilled in the art can select and adjust the structure according to the actual application condition, the product requirement and the quality requirement.
The carbon nitride has no particular limitation on the parameters of the carbon nitride in principle, and a person skilled in the art can select and adjust the parameters according to the actual application condition, the product requirement and the quality requirement, and the carbon nitride has the advantages that the specific structure and morphology of the composite material are better ensured, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the size (namely the width or the transverse size) of the carbon nitride is preferably 5-20 micrometers, more preferably 7-18 micrometers, more preferably 9-16 micrometers, and more preferably 11-14 micrometers. The height (i.e., thickness, or radial dimension) of the carbon nitride is preferably 5 to 10nm, more preferably 6 to 9nm, and even more preferably 7 to 8 nm.
The morphology of the carbon nitride is not particularly limited in principle, and a person skilled in the art can select and adjust the morphology according to the actual application condition, the product requirement and the quality requirement.
The structure of the graphene sheet is not particularly limited in principle, and a person skilled in the art can select and adjust the structure according to the actual application condition, the product requirement and the quality requirement.
The invention has no special limitation on the parameters of the graphene sheet in principle, and a person skilled in the art can select and adjust the parameters according to the actual application condition, the product requirement and the quality requirement, and the invention provides more active sites and higher active surface area for better ensuring the specific structure and morphology of the composite material, thereby improving the photocatalytic activity and simultaneously realizing the degradation of organic matters and the hydrogen production, and the sheet diameter of the graphene sheet preferably comprises 5-15 μm, more preferably 7-13 μm, and more preferably 9-11 μm. The thickness of the graphene sheet is preferably 1-10 nm, more preferably 3-8 nm, and still more preferably 5-6 nm.
The mass ratio of the graphene sheet to the carbon nitride is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the mass ratio of the graphene sheet to the carbon nitride preferably comprises (0.3-0.5): 1, more preferably (0.33 to 0.47): 1, more preferably (0.36 to 0.43): 1, more preferably (0.39 to 0.41): 1.
the invention has no particular limitation on the type of the compound in principle, and a person skilled in the art can select and adjust the compound according to the actual application condition, the product requirement and the quality requirement.
The invention has no particular limitation on the compounding mode in principle, and a person skilled in the art can select and adjust the compounding mode according to the actual application condition, the product requirement and the quality requirement.
The morphology of the composite material is not particularly limited in principle, and a person skilled in the art can select and adjust the morphology according to the actual application condition, the product requirement and the quality requirement. The corrugations preferably comprise mountain corrugations and/or wave corrugations, more preferably mountain corrugations or wave corrugations. In the present invention, the carbon nitride is preferably uniformly compounded between the graphene sheet surfaces and/or graphene sheet layers, and more preferably uniformly compounded between the graphene sheet surfaces and graphene sheet layers. Further, the carbon nitride is preferably densely distributed at folds and/or edges of the graphene sheet.
The invention also provides a preparation method of the graphene/carbon nitride composite material, which comprises the following steps:
1) dispersing expanded graphite, a surfactant and water to obtain a dispersion liquid, and centrifuging and grinding to obtain a graphene micro-nano sheet;
2) mixing the graphene micro-nano sheet obtained in the step, a nitrogen source and water, and then continuously grinding to obtain powder;
3) and under a semi-closed condition, calcining the powder obtained in the step for the first time, and then calcining the powder for the second time under an open condition to obtain the graphene/carbon nitride composite material.
The selection, composition and structure of the materials in the preparation method of the graphene/carbon nitride composite material and the corresponding preferred principle of the invention can correspond to the selection, composition and structure of the materials corresponding to the graphene/carbon nitride composite material and the corresponding preferred principle, and are not described in detail herein.
The selection of the surfactant is not particularly limited in principle, and a person skilled in the art can select and adjust the surfactant according to actual application conditions, product requirements and quality requirements, the specific structure and morphology of the composite material are better ensured, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, and organic matter degradation and hydrogen production can be simultaneously realized Polyetherimide, hexadecyl dimethyl allyl ammonium chloride, tetradecyl dimethyl benzyl ammonium chloride, dodecyl dimethyl hydroxyethyl ammonium chloride or dodecyl trimethyl ammonium chloride.
The mass ratio of the expanded graphite to the surfactant is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the mass ratio of the expanded graphite to the surfactant preferably comprises (0.5-3): 100, more preferably (1-2.5): 100, more preferably (1.5-2): 100.
the mass ratio of the expanded graphite to water is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the mass ratio of the expanded graphite to water preferably comprises (0.5-3): 100, more preferably (1-2.5): 100, more preferably (1.5-2): 100.
the dispersion mode is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement.
The ultrasonic stirring dispersion parameters are not particularly limited in principle, and can be selected and adjusted by technicians in the field according to actual application conditions, product requirements and quality requirements, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the ultrasonic frequency of the ultrasonic stirring dispersion is preferably 20-40 KHz, more preferably 23-37 KHz, more preferably 26-34 KHz, and more preferably 29-31 KHz. The rotation speed of the ultrasonic stirring dispersion is preferably 300-500 rpm, more preferably 330-470 rpm, more preferably 360-440 rpm, and more preferably 390-410 rpm. The ultrasonic stirring and dispersing time is preferably 120-360 min, more preferably 170-310 min, and more preferably 220-260 min.
The invention has no particular limitation on the specific centrifugal process in principle, and a person skilled in the art can select and adjust the specific centrifugal process according to the actual application condition, the product requirement and the quality requirement, so that the invention provides more active sites and higher active surface area for better ensuring the specific structure and morphology of the composite material, further improves the photocatalytic activity and can simultaneously realize the degradation of organic matters and the hydrogen production, and the centrifugal process is particularly preferably as follows: the supernatant is obtained by low-speed centrifugation, and the supernatant is obtained by high-speed centrifugation.
The parameters of the low-speed centrifugation are not particularly limited in principle, and a person skilled in the art can select and adjust the parameters according to the actual application condition, the product requirement and the quality requirement, so that the specific structure and morphology of the composite material are better ensured, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, the degradation of organic matters and the production of hydrogen can be realized simultaneously, and the rotating speed of the low-speed centrifugation is preferably 500-1000 rpm, more preferably 600-900 rpm, and more preferably 700-800 rpm. The time of the low-speed centrifugation is preferably 3-5 min, more preferably 3.3-4.7 min, more preferably 3.6-4.4 min, and more preferably 3.9-4.1 min.
The high-speed centrifugation parameter is not particularly limited in principle, and a person skilled in the art can select and adjust the high-speed centrifugation parameter according to the actual application condition, the product requirement and the quality requirement, so that the specific structure and morphology of the composite material are better ensured, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the low-speed centrifugation rotating speed is preferably 3000-5000 rpm, more preferably 3300-4700 rpm, more preferably 3600-4400 rpm, and more preferably 3900-4100 rpm. The high-speed centrifugation time is preferably 5-10 min, more preferably 6-9 min, and more preferably 7-8 min.
The preparation method is an integral preparation process of a complete and refined process, better ensures the specific structure and morphology of the composite material, provides more active sites and higher active surface area, further improves the photocatalytic activity, can simultaneously realize the degradation of organic matters and the production of hydrogen, and preferably comprises a drying step after centrifugation.
The drying mode is not particularly limited in principle, and a person skilled in the art can select and adjust the drying mode according to the actual application condition, the product requirement and the quality requirement.
The specific drying parameters are not particularly limited in principle, and a person skilled in the art can select and adjust the specific drying parameters according to actual application conditions, product requirements and quality requirements, so that the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the drying temperature is preferably 40-80 ℃, more preferably 45-75 ℃, more preferably 50-70 ℃ and more preferably 55-65 ℃. The drying time is preferably 6-24 hours, more preferably 9-21 hours, and more preferably 12-18 hours.
The specific parameters of the grinding are not particularly limited in principle, and a person skilled in the art can select and adjust the specific parameters according to the actual application condition, the product requirement and the quality requirement, so that the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, the degradation of organic matters and the hydrogen production can be realized simultaneously, and the grinding time is preferably 30-60 min, more preferably 35-55 min, and more preferably 40-50 min. The rotation speed of the grinding is preferably 1000-1500 rpm, more preferably 1100-1400 rpm, and more preferably 1200-1300 rpm.
According to the invention, the graphene micro-nano sheet obtained in the step, a nitrogen source and water are mixed, and then the mixture is continuously ground to obtain powder.
The mass ratio of the graphene micro-nano sheet to the nitrogen source is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure and morphology of the composite material are better guaranteed, more active parts and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the mass ratio of the graphene micro-nano sheet to the nitrogen source is preferably (0.1-0.5): 1, more preferably (0.15 to 0.45): 1, more preferably (0.25 to 0.4): 1, more preferably (0.3 to 0.35): 1.
the selection of the nitrogen source is not particularly limited in principle, and a person skilled in the art can select and adjust the nitrogen source according to the actual application condition, the product requirement and the quality requirement.
The invention is a complete and refined integral preparation scheme, better ensures the specific structure and morphology of the composite material, provides more active sites and higher active surface area, further improves the photocatalytic activity, can simultaneously realize the degradation of organic matters and the production of hydrogen, and also comprises a drying step before the continuous grinding. The drying temperature is preferably 40-80 ℃, more preferably 45-75 ℃, more preferably 50-70 ℃, and more preferably 55-65 ℃. The drying time is preferably 6-24 hours, more preferably 9-21 hours, and more preferably 12-18 hours.
The fineness of the powder is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and quality requirements, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the fineness of the powder is preferably 20-50 micrometers, more preferably 25-45 micrometers, and more preferably 30-40 micrometers.
Finally, under a semi-closed condition, calcining the powder obtained in the step for the first time, and then calcining the powder for the second time under an open condition to obtain the graphene/carbon nitride composite material.
The semi-closed structure is preferably closed but not sealed, namely, the system is isolated from the outside, but the gas is not limited to be completely exchanged, and particularly, the semi-closed structure can be a reaction system covered by a cover.
The temperature rise rate of the first calcination is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the temperature rise rate of the first calcination is preferably 2-5 ℃/min, more preferably 2.5-4.5 ℃/min, and more preferably 3-4 ℃/min.
The temperature of the first calcination is not particularly limited in principle, and a person skilled in the art can select and adjust the temperature according to the actual application condition, the product requirement and the quality requirement, so that the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the temperature of the first calcination is preferably 450-550 ℃/min, more preferably 470-530 ℃/min, and more preferably 490-510 ℃/min.
The time for the first calcination is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the time for the first calcination is preferably 0.5-2 hours, more preferably 0.8-1.7 hours, and more preferably 1.1-1.4 hours.
The invention is a complete and refined integral preparation process, better ensures the specific structure and morphology of the composite material, provides more active sites and higher active surface area, further improves the photocatalytic activity and can simultaneously realize the degradation of organic matters and the production of hydrogen, and preferably comprises the step of grinding again after the first calcination.
The temperature rise rate of the second calcination is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the temperature rise rate of the second calcination is preferably 2-5 ℃/min, more preferably 2.5-4.5 ℃/min, and more preferably 3-4 ℃/min.
The temperature of the second calcination is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the temperature of the second calcination is preferably 450-550 ℃/min, more preferably 470-530 ℃/min, and more preferably 490-510 ℃/min.
The time of the second calcination is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the quality requirement, the specific structure and morphology of the composite material are better guaranteed, more active sites and higher active surface area are provided, the photocatalytic activity is further improved, organic matter degradation and hydrogen production can be simultaneously realized, and the time of the second calcination is preferably 0.5-2 hours, more preferably 0.8-1.7 hours, and more preferably 1.1-1.4 hours.
The invention is a complete and refined integral preparation process, better ensures the specific structure and morphology of the composite material, provides more active sites and higher active surface area, further improves the photocatalytic activity and can simultaneously realize the degradation of organic matters and the hydrogen production, and the heating rate of the first calcination is preferably the same as that of the second calcination.
The invention is a complete and refined integral preparation process, better ensures the specific structure and morphology of the composite material, provides more active sites and higher active surface area, further improves the photocatalytic activity and can simultaneously realize the degradation of organic matters and the production of hydrogen, and the preparation method of the graphene/carbon nitride composite material can specifically comprise the following steps:
firstly, adding a certain amount of expanded graphite and a surfactant into deionized water, and performing ultrasonic dispersion to form a dispersion liquid; then centrifuging at low speed, taking the upper layer liquid, centrifuging at high speed, taking the lower layer, and finally drying in vacuum, drying and grinding to form the expanded graphite microchip;
secondly, firstly weighing thiourea with a certain mass, dissolving the thiourea in deionized water, stirring and dissolving the thiourea, then adding graphene nanoplatelets with a certain mass, magnetically stirring the mixture evenly, drying the mixture in a drying box, grinding the mixture, and collecting powder A;
thirdly, weighing a certain mass of powder A, placing the powder A in a ceramic crucible, lightly compacting the powder A, and covering a cover; placing the mixture in a muffle furnace, heating the mixture to a calcining temperature at a certain heating rate, calcining, naturally cooling, taking out a sample, grinding and collecting powder B; and putting the collected powder into a crucible without covering the crucible, heating to a calcination temperature at the same heating rate, calcining, and naturally cooling to obtain the graphene/carbon nitride composite material.
Referring to fig. 1, fig. 1 is a schematic flow chart of a preparation process of a graphene/carbon nitride composite material according to an embodiment of the present invention.
The invention also provides the application of the graphene/carbon nitride composite material prepared by any one of the technical schemes or the preparation method of any one of the technical schemes in the aspects of organic matter degradation and/or hydrogen production.
In the invention, the graphene/carbon nitride composite material prepared by the method has more active sites and higher active surface area, further has higher photocatalytic activity, and can realize the simultaneous photocatalytic degradation of organic matters and hydrogen production.
The invention provides a graphene/carbon nitride composite material with a laminated structure, and a preparation method and application thereof. The invention uses graphene and g-C3N4And compounding, namely uniformly attaching a nitrogen source to the surface of the graphene micro-nano sheet by a recrystallization method to obtain a composite material with a specific morphology, wherein flocculent and/or honeycomb-shaped carbon nitride in the material is uniformly compounded on the graphene sheet and has a non-layered structure, the graphene sheet has a two-dimensional lamellar structure, and the two are combined to form a more three-dimensional micro-nano structure similar to a blade with a villus structure on the surface. The graphene-carbon nitride composite material obtained by the invention has excellent photocatalytic activity, and further can simultaneously degrade organic matters and produce hydrogen, and the function of simultaneously degrading the organic matters is very important in the process of producing hydrogen by photocatalysis; simultaneously under parallel conditionsThe composite material provided by the invention can effectively improve the specific surface area of the carbon nitride. The invention also provides the graphene-like g-C3N4With the preparation method of the graphene composite material, the preparation of the graphene and carbon nitride composite material can be realized through simple secondary high-temperature calcination, and the preparation method has the advantages of simple process, easiness in operation, low cost, suitability for large-scale preparation and good application prospect.
The experimental result shows that the compounding of the carbon nitride and the graphene can improve the hydrogen production rate of the carbon nitride and the degradation rate of organic matters; compared with a single carbon nitride catalyst, the hydrogen production rate of the graphene/carbon nitride composite catalyst and the degradation rate of rhodamine B in 4 hours are respectively 5.7 times and 1.3 times of the hydrogen production rate and the rhodamine B degradation rate.
For further illustration of the present invention, the following will describe in detail a graphene/carbon nitride composite material, and a preparation method and an application thereof, with reference to the following examples, but it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and the detailed embodiments and specific procedures are given, only for further illustration of the features and advantages of the present invention, but not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
Example 1
Weighing a certain amount of thiourea, dissolving the thiourea in deionized water, stirring and dissolving, drying in a drying oven at 40 ℃, grinding and collecting powder A; then 13.00g of powder A is weighed and placed in a ceramic crucible and lightly compacted, and a cover is covered; placing the mixture in a muffle furnace, heating the mixture to 550 ℃ at the heating rate of 2 ℃/min, calcining the mixture for 2 hours, naturally cooling the mixture, taking out a sample, grinding the sample, and collecting powder B; and putting the collected powder into a crucible without covering the crucible, heating to 500 ℃ at the heating rate of 2 ℃/min, calcining for 2h, and naturally cooling to obtain the carbon nitride material.
The carbon nitride material alone prepared in example 1 of the present invention was examined.
And (4) detecting results, namely comparing results of the graphene/carbon nitride composite material prepared in the subsequent step with those of the graphene/carbon nitride composite material prepared in the example 3.
Example 2
Firstly, adding a certain amount of expanded graphite and a surfactant into deionized water, wherein the mass ratio of the expanded graphite to the deionized water is 1: 100, forming a mixed solution, and performing ultrasonic dispersion for 120min to form a dispersion solution; centrifuging at low speed of 500rmp/min for 5min, collecting the upper layer solution, centrifuging at high speed of 5000r/min for 10min, collecting the lower layer solution, and washing; and then drying and grinding the graphene nanoplatelets in vacuum drying at 60 ℃ overnight to obtain the graphene nanoplatelets.
And secondly, firstly weighing certain thiourea, dissolving the thiourea in deionized water, stirring and dissolving, and then adding the graphene nanoplatelets with certain mass, and uniformly stirring by magnetic force, wherein the mass ratio of the graphene to the thiourea is 0.1: 1, drying in a drying oven at 40 ℃, grinding and collecting powder A; then 13.00g of powder A is weighed and placed in a ceramic crucible and lightly compacted, and a cover is covered; placing the mixture in a muffle furnace, heating the mixture to 550 ℃ at the heating rate of 2 ℃/min, calcining the mixture for 2 hours, naturally cooling the mixture, taking out a sample, grinding the sample, and collecting powder B; and putting the collected powder into a crucible without covering the crucible, heating to 500 ℃ at the heating rate of 2 ℃/min, calcining for 2h, and naturally cooling to obtain the graphene/carbon nitride composite material.
The graphene/carbon nitride composite material prepared in embodiment 2 of the present invention is characterized.
Referring to fig. 2, fig. 2 is a surface micro-topography of the graphene/carbon nitride composite material prepared in example 2 of the present invention.
As can be seen from fig. 2, in the graphene/carbon nitride composite material prepared by the present invention, porous carbon nitride having flocculent and cellular shapes is uniformly attached to the surface of the graphene sheet layer to form a blade structure similar to a fluff. The graphene sheet has a sheet diameter of about 5 μm and a mountain-vein-like wrinkle appearance, and it can be seen that carbon nitride is relatively densely distributed at the wrinkles and edges of the graphene sheet layer compared with other positions.
Example 3
Firstly, adding a certain amount of expanded graphite and a surfactant into deionized water, wherein the mass ratio of the expanded graphite to the deionized water is 1: 100, forming a mixed solution, and performing ultrasonic dispersion for 120min to form a dispersion solution; centrifuging at low speed of 500rmp/min for 5min, collecting the upper layer solution, centrifuging at high speed of 5000r/min for 10min, collecting the lower layer solution, and washing; and then drying and grinding the graphene nanoplatelets in vacuum drying at 60 ℃ overnight to obtain the graphene nanoplatelets.
Secondly, firstly weighing certain thiourea, dissolving the thiourea in deionized water, stirring and dissolving, and then adding graphene micro-sheets with certain mass, and uniformly stirring by magnetic force, wherein the mass ratio of the graphene to the thiourea is 0.3: 1, drying in a drying oven at 40 ℃, grinding and collecting powder A; then 13.00g of powder A is weighed and placed in a ceramic crucible and lightly compacted, and a cover is covered; placing the mixture in a muffle furnace, heating the mixture to 550 ℃ at the heating rate of 2 ℃/min, calcining the mixture for 2 hours, naturally cooling the mixture, taking out a sample, grinding the sample, and collecting powder B; and putting the collected powder into a crucible without covering the crucible, heating to 500 ℃ at the heating rate of 2 ℃/min, calcining for 2h, and naturally cooling to obtain the graphene/carbon nitride composite material.
The graphene/carbon nitride composite material prepared in example 3 of the present invention and the single carbon nitride material prepared in example 1 were compared and tested for their properties.
The hydrogen detection method comprises the following steps:
the catalyst and solution added to the reactor and the operation are as follows: accurately weighing a catalyst, and ultrasonically dispersing the catalyst in deionized water of rhodamine B (organic pollutants in simulated water of the rhodamine B); the reactor was connected to a photocatalytic unit, and condensed water was connected and evacuated through the unit. And after all the set parameters are stable, turning on the light source and starting the reaction. Under the condition of visible light illumination with the current of 15A, the catalyst can decompose water to generate hydrogen, the hydrogen is stored in a quartz pipeline, after the hydrogen is illuminated for 1 hour, the amount of the actually generated hydrogen within 1 hour is detected on line through a gas chromatography, and then sample detection is carried out every hour until the reaction is finished.
Referring to fig. 3, fig. 3 is a graph comparing the hydrogen production rates of the single carbon nitride material prepared in example 1 and the graphene/carbon nitride composite catalyst prepared in example 3.
As can be seen from FIG. 3, in the rhodamine B solution, the hydrogen production rates of the single carbon nitride catalyst and the photocatalytic decomposition water of the graphene/carbon nitride composite catalyst are respectively 0.201 mmol.h-1·g-1And 1.146mmol · h-1·g-1The photocatalytic activity of the catalyst can be improved by the loaded graphene.
Referring to fig. 4, fig. 4 is a comparison graph of hydrogen production rates of the graphene/carbon nitride composite catalyst prepared in example 3 of the present invention in water and rhodamine B solution.
As can be seen from FIG. 4, the hydrogen production rates of the graphene/carbon nitride composite catalyst in water and rhodamine B solution through photocatalytic decomposition are respectively 0.713 mmol.h-1·g-1And 1.146mmol · h-1·g-1The existence of organic rhodamine B can improve the photocatalytic activity of the catalyst.
The method for detecting rhodamine B degradation J comprises the following steps:
and (4) evaluating the degradation rate of rhodamine B.
The solution before and after the reaction was centrifuged to remove the supernatant, which was transferred to a quartz cuvette to measure the absorbance. The degradation rate of the rhodamine B solution is calculated by comparing the absorbance of the solution before and after the reaction, and the calculation formula is (C)0-Ct)/C0In which C is0The absorbance of the rhodamine B solution before reaction; ctThe absorbance of the TC solution is th when the light is irradiated.
Referring to fig. 5, fig. 5 is a graph comparing degradation curves of a single carbon nitride material prepared in example 1 and a graphene/carbon nitride composite material catalyst prepared in example 3 for degrading rhodamine B.
As can be seen from FIG. 5, after illumination for 4 hours, the degradation rates of the single carbon nitride catalyst and the graphene/carbon nitride composite catalyst on rhodamine B are 76.5% and 99.5%, respectively, which indicates that the photocatalytic activity of the carbon nitride catalyst can be improved by the supported graphene.
The photoelectric property electric detection method comprises the following steps:
the electrochemical workstation used, model No. CHI660D, tested the photoelectric properties of the catalyst, and the method used in the test was a three-electrode method. For preparing working electrodesThe process is as follows: uniformly dispersing a certain amount of catalyst in an ethanol solvent, and then uniformly coating the catalyst on the conductive glass of the FTO, wherein the coating area is 1cm2Finally, the solvent is naturally volatilized and dried at room temperature.
Referring to fig. 6, fig. 6 is a graph of photocurrent density versus time for a single carbon nitride material prepared in example 1 and a graphene/carbon nitride composite catalyst prepared in example 3 according to the present invention.
As can be seen from fig. 6, the photocurrent density value of the graphene/carbon nitride composite material prepared in example 3 is much higher than that of the carbon nitride material prepared in example 1, which indicates that the loaded graphene can promote the transmission of photo-generated electrons.
The products prepared in examples 1 and 3 of the invention were subjected to N2Adsorption-desorption test.
The specific surface area of the composite material is greatly influenced by the preparation mode, and the difference of the preparation modes can cause the large difference of the specific surface areas, so that the preparation method is the same for better parallel testing, and the comparison has practical significance.
Referring to fig. 7, fig. 7 shows a single carbon nitride material prepared in example 1 of the present invention and N of graphene/carbon nitride composite catalyst prepared in example 32Adsorption-desorption isotherm plot.
As can be seen from FIG. 7, the specific surface area of the carbon nitride prepared in example 1 of the present invention is 63.25m2·g-1The specific surface area of the graphene and carbon nitride composite material prepared in example 3 is 303.25m2·g-1This shows that the specific surface area of the carbon nitride is greatly increased by 5 times by the composite material with a specific structure provided by the invention in the same preparation mode.
Example 4
Firstly, adding a certain amount of expanded graphite and a surfactant into deionized water, wherein the mass ratio of the expanded graphite to the deionized water is 1: 100, forming a mixed solution, and performing ultrasonic dispersion for 120min to form a dispersion solution; centrifuging at low speed of 500rmp/min for 5min, collecting the upper layer solution, centrifuging at high speed of 5000r/min for 10min, collecting the lower layer solution, and washing; and then drying and grinding the graphene nanoplatelets in vacuum drying at 60 ℃ overnight to obtain the graphene nanoplatelets.
Secondly, firstly weighing certain thiourea, dissolving the thiourea in deionized water, stirring and dissolving, and then adding graphene micro-sheets with certain mass, and uniformly stirring by magnetic force, wherein the mass ratio of the graphene to the thiourea is 0.5: 1, drying in a drying oven at 40 ℃, grinding and collecting powder A; then 13.00g of powder A is weighed and placed in a ceramic crucible and lightly compacted, and a cover is covered; placing the mixture in a muffle furnace, heating the mixture to 550 ℃ at the heating rate of 2 ℃/min, calcining the mixture for 2 hours, naturally cooling the mixture, taking out a sample, grinding the sample, and collecting powder B; and putting the collected powder into a crucible without covering the crucible, heating to 500 ℃ at the heating rate of 2 ℃/min, calcining for 2h, and naturally cooling to obtain the graphene/carbon nitride composite material.
The graphene/carbon nitride composite material with a layered structure, the preparation method and the application thereof provided by the present invention are described in detail, and the principle and the embodiment of the present invention are illustrated herein by using specific examples, which are only used to help understand the method of the present invention and the core idea thereof, including the best mode, and also to enable any person skilled in the art to practice the present invention, including making and using any device or system, and implementing any combined method. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
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