Preparation And Capacitive Properties Of Coal Based Porous Carbon Materials

Porous carbon materials have been widely used in energy storage, adsorption, catalysis and other fields, because of its large specific surface area, adjustable pore structure, excellent heat resistance, acid and alkali resistance, and unique electron conductivity. How to use high quality, green and cheap carbon sources to prepare porous carbon materials has become a hot spot of current research. In all carbon sources, coal has the advantages of abundant reserves, high carbon content and low price, which is considered to be an important raw material for the production of carbon materials. In this paper, Xinjiang coal as raw material to prepare soluble coal. Coal based porous carbon materials were prepared by electrospinning, ultrasonic atomization, vacuum freeze drying, respectively. The structure and morphology of the materials were studied, and application in supercapacitor were investigated. The main contents and results are summarized as follows:1. The soluble coal was prepared by modifying the raw coal with mixed acid. The effects of different types of surfactants and pH values on the solubility were investigated, and the dissolution mechanism was studied. The results show that the raw coal is oxidized, and a large number of oxygen containing functional groups are introduced into the edge of the thick ring of the coal, the side chains or the heterocyclic rings, and cause it to dissolve in water.2. Flexible coal-based porous carbon fibers were prepared by electrospinning method using polyvinyl alcohol（PVA） and soluble coal. The morphology, structure and electrochemical properties of coal-based porous carbon fiber were studied, and the formation mechanisms were also discussed. The results show that the soluble coal adding amount, the specific surface area is large. When PVA and soluble coal mass ratio is 1:1, the porous carbon fibers exhibit the best electrochemical performance, the specific capacitance is 170 F g^-1 at 1 A g^-1.3. Coal-based porous carbon spheres were prepared by one-step ultrasonic spray pyrolysis method using soluble coal as carbon source. The effects of temperature and alkali sources on the structure, morphology and electrochemical properties of coal-based porous carbon spheres were investigated, and the formation mechanisms were discussed.The results show that the specific surface area was large when the pyrolysis temperature was high, the same pyrolysis temperature, KOH as the alkali source, the specific surface area is the largest. SDBS as the alkali source, carbon spheres as electrode materials have good electrochemical performance.4. Coal-based water sol was prepared by using soluble coal as raw material and PVA as crosslinking agent. The coal-based carbon aerogel was prepared by vacuum freeze drying method. The effects of pH value and alkali source on the morphology, structure and electrochemical properties of the samples were studied, and the formation mechanism of the coal-based carbon aerogel was also discussed. The results show that when p H > 13, the specific surface area of coal-based carbon aerogel is 1852.09 m2 g^-1. When using different alkali source, the order of the specific surface area of the samples is KOH > KHCO3 > SDBS > NH3.H2 O. When KOH as alkali source, the specific capacitance of sample reached 245 F g^-1 at a current density of 1 A g^-1, which has good electrochemical performance.