Graphene is a two-dimensional carbon material composed […]
Graphene is a two-dimensional carbon material composed of a single layer of sp2 hybrid carbon atoms arranged in a hexagon. It has a large theoretical specific surface area, a high intrinsic carrier mobility, and a high thermal conductivity. Coefficient, ultra-high conductivity at room temperature and other advantages. Due to its unique structure and properties, graphene has gradually become one of the most attractive applied materials.
Graphene also has shortcomings. For example, in the field of digital electronics, due to the lack of band gap between the electrons of graphene, it is difficult to stop once the data is transferred. The best solution is to form a porous structure by drilling holes in the graphene surface to form a band gap or integrating two-dimensional graphene to construct a graphene with a specific three-dimensional structure.
Preparation method of porous graphene
1. Template method
The template method can be divided into hard template method and soft template method according to the composition and characteristics of the template.
2. Hard template method
The preparation of porous graphene materials by the hard template method mainly involves the following four aspects: (1) preparation of a hard template; (2) functionalization/modification of the template surface to obtain suitable surface properties; (3) by various methods Apply graphene or its derivatives, such as graphene oxide, on the template; (4) Selectively remove the template.
The hard template method also has many shortcomings, such as relatively low yields, which cannot achieve high output, greater restrictions when using a multi-step synthesis process, and insufficient structural robustness when the template is removed.
3. Soft template method
The soft template method is a self-assembly reaction between the carbon precursor and the soft template. After high-temperature carbonization and polymerization, porous graphene is obtained. Its pore structure mainly depends on the synthesis conditions, such as the ratio of reactants, solvent type, and reaction temperature. This method can be directly used to synthesize mesoporous or macroporous graphene materials.
Compared with the hard template, the soft template is essentially synthesized at the molecular level, using chemical bonds or hydrophilic/hydrophobic interactions to construct a porous structure at the same time, which plays an important role in the process of preparing the porous graphene material by the soft template method. It is the chemical reaction between the template and the surfactant.
4. No template method
The template-less method includes etching method, solvothermal method and chemical vapor deposition method.
5. Etching method
The etching method is a method that uses a chemical reaction between an etchant and graphene to cause carbon atoms on the surface of the graphene to be reacted and etched to leave a pore structure. This method has obvious selectivity for the etching of materials, that is, the etching is stopped immediately after the etching is completed, and the materials on the remaining layers will not be damaged.
6. Solvothermal method
Solvothermal method is a method that uses water or organic solvent as the reaction system in a specific high-pressure reaction kettle and heats it to a critical temperature to synthesize materials in the high-pressure reaction system. This method greatly reduces environmental pollution. And the prepared porous graphene material has the advantage of controllable pore size.
7. Chemical vapor deposition
The main process for preparing porous graphene materials by chemical vapor deposition is to deposit carbon-containing gas such as methane and acetylene, and then deposit the gaseous carbon source on the surface of the solid body substrate to prepare graphene, and then gradually heat up in the protective gas to finally obtain porous A method of graphene materials. The method is simple to operate, can be mass-produced, and the obtained porous graphene material has a complete structure and excellent conductive properties.
Application of porous graphene and its composite materials
1. Electrode material
Taking porous graphene or composite materials as electrode materials, its highly connected network structure greatly promotes the rapid transport of ions, so that the material exhibits higher capacity and power characteristics.
2. Environmental adsorption materials
Porous graphene has a rich pore structure. Due to the difference in preparation methods, the surface contains many defects, which can easily introduce different functional groups. Porous graphene and its composite materials have many applications in oil/water separation, metal ion adsorption, and dye molecule removal.
3. Separation field
Through model building and computer simulation, it is found that porous graphene has high permeability and selectivity to gas molecules such as hydrogen (H2), nitrogen (N2) and hydrogen sulfide (H2S), and can effectively separate H2/CH4 and CO2/N2 And H2S/CH4 and other mixed gases.