Preparation And Electrochemical Performance Of Porous Carbon Materials From Coal Liquefaction Residue

Carbon based supercapacitor is characterized by its stability, high specific power and long life. Liquefaction residue of coal (CLR) which is rich in carbon, is a good raw material for synthesizing porous carbon materials which could be used as electrode of supercapacitor. The application of the CLR-based carbons for supercapacitors can expand the carbon origins, increase the economic value of the CLR and reduce the net cost of the supercapacitors.In this thesis, porous carbons were prepared from coal liquefaction residue by KOH activation with addition of AI2O3, MgO, SiO2and Na2SiO3as inorganic additives while Urea, Sucrose and CTAB as organic additives. N2adsorption and desorption, SEM, TEM, FT-IR, TG-DTG and ultimate analysis were used for characterizing the porous structures of the obtained materials; then cyclic voltammetry, constant current charge-discharge and AC impendence were used for studying the electrochemical properties in6mol-L-1KOH solution. The main work and results are shown as follows:1) Carbon materials synthesized with Al2O3and MgO as additions have high specific area, pore volume and mesoporosity, while with SiO2and Na2SiO3as addition have high microporosity. Samples with different additives dosages were prepared and characterized. The carbon materials synthesized respectively with mass ratio of CLR:Al2O3being5:3, CLR:MgO being5:2and CLR: SiO2being5:1, have optimal electrochemical property among the series. Specific capacitance of the materials are166F·g-1,184F·g-1and162F·g-1at the scanning rate of5mV·s-1. All the obtained materials had good charging/discharging properties, as well as small internal resistance and long life time. Resultant carbons which had good electrochemical performance were ascribed to their hierarchical structure or high specific area. Samples prepared with Na2SiO3and SiO2as addition have similar properties which indicate that SiO2can affect the carbon porous structure in shape of silicate probably.2) Urea, sucrose and CTAB were chosen as organic additions. The results show that all of the three organic matters can improve the microporosity of the materials. A series of samples were prepared to find out the optimal additives dosage. The materials with mass ratios of CLR:Urea=5:3, CLR:Sucrose=5:1and CLR:CTAB=10:1have the highest capacitances, up to174F·g-1,169F·g-1and186F·g-1at the scanning rate of5mV·s-1, respectively. And all the three materials have good electronic charging/discharging, small resistance, and good property at big current density charge and discharge test.