A Template Method Coupled With Chemical Activation For The Preparation Of Carbon Nanosheets And Their Electrochemical Performance

In this paper, carbon nanosheets were prepared from coal tar or anthrecene oil, KOH as active agent by using MgO or melamine as template. The morphology and chemical composition of as-prepared carbon materials were characterized by nitrogen adsorption-desorption, field emission scanning electron microscopy, transmission electron microscopy analysis, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectrum analysis, etc. The electrochemical performance of the electrodes in different electrolytes was evaluated by using cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The main conclusions are as follows:(1) Porous carbon nanosheets(PCNs) were prepared from coal tar using melamine as template coupled with KOH activation. The PCN made with the mass of coal tar, melamine, KOH at 6g, 3g, 12 g at 800 ?in nitrogen atmosphere is named as PCN800-N2. With the increases of activation temperature, the specific surface area increases from 1336 to 1865 m2 g-1, the total pore volume increases from 0.62 to 0.91 cm3 g-1 and average pore size increases from 1.86 to 1.94 nm. The specific capacitance and energy density of PCN800-N2 are 274 F g-1and 9.5 Wh kg-1 at 0.05 A g-1; while they are 191 F g-1 and 4.2 Wh kg-1 at 20 A g-1, the capacitance retention is 69.7%, and showing good cycle stability with capacitance retention of 92.1% after 10000 cycles at 5 A g-1.(2) Based on the above experiments, interconnected layered carbon nanosheets(ILCNs) were prepared from coal tar using MgO as template. The ILCN made with the mass of coal tar, Mg O, KOH at 6g, 9g, 12 g at 900 ? is named as ILCN2-900. With the increases of activation temperature or the mass ratio of KOH/coal tar, the specific surface area, micropore specific surface area and yield are drops, but the average pore size rises. The specific surface area ranges from 2350 to 2887 m2 g-1 and the average pore size ranges from 2.27 to 2.78 nm. The specific capacitance and energy density of ILCN2-900 are 313 F g-1and 10.9 Wh kg-1 at a current density of 0.05 A g-1; while they are 261 F g-1 and 7.6 Wh kg-1 at 20 A g-1, the capacitance retention is 83.4%. The capacitance retention remains 92.7% after 10000 cycles at a current density of 5 Ag-1.(3) Based on the above experiments, interconnected porous carbon nanosheets(IPCNs) were prepared from anthrecene oil. The IPCN made with the mass of anthrecene oil, MgO, KOH at 6g, 9g, 12 g at 950 ? is named as IPCN9-950. The specific surface area ranges from 2942 to 3342 m2 g-1, the total volume and average pore size ranges from 2.31 to 3.75 cm3 g-1 and from 2.77 to 5.10 nm. In BMIMPF6 ionic liquid electrolyte, the specific capacitance and energy density of IPCN9-950 are 271 F g-1and 150.4 Wh kg-1 at 0.05 A g-1, when the values are 159 F g-1 and 37.0 Wh kg-1 at 20 A g-1, the capacitance retention is 58.7%. In 6 M KOH aqueous electrolyte, the specific capacitance and energy density of IPCN9-900 are 300 F g-1and 10.4 Wh kg-1 at 0.05 A g-1. The specific capacitance retention remains 89.7% after 10000 cycles at 5 Ag-1.