Preparation Of Porous Carbon Nanosheets For Supercapacitors And Their Electrochemical Properties

As an environmentally friendly energy storage device, supercapacitors have attracted increasing attention because of their high power density, rapid charge and discharge, long cycle life. In this paper, petroleum pitch, coal tar and anthracene oil are employed as carbon sources for the synthesis of porous carbon nanosheets(PCNs),respectively using calcium carbonate as template coupled with potassium hydroxide(KOH) activation. PCNs were characterized by field emission scanning electron microscope, transmission electron microscope, N2 adsorption/desorption, X-ray photoelectron spectroscopy, Raman techniques. The electrochemical properties of PCNs were studied in details. The main conclusions are as follows.PCNs were prepared from petroleum pitch by calcium carbonate template strategy coupled with KOH activation. Under optimal conditions, PCN made with the mass of petroleum pitch, calcium carbonate, KOH at 4 g, 12 g, 12 g at 850 oC is named as PCN4-850. The specific surface area, total pore volume, average pore size of PCN4-850 reaches 1922 m2/g, 1.21 cm3/g and 2.51 nm, respectively. The specific capacitance and energy dentisy of PCN4-850 is 293 F/g and 10.2 Wh/kg at 0.05 A/g in 6M KOH electrolyte, respectively. The capacitance retention of PCN4-850 is 78.8%when the current density is increased four hundred times. What's more, the capacitance retention of PCN4-850 remains 95.0% after 5000 cycles at 5 A/g, showing perfect cycle stability. Meanwhile, the specific capacitance of PCN4-850 and energy dentisy of PCN4-850 supercapacitor is 267 F/g and 148.3 Wh/kg at 0.05 A/g in BMIMPF6 electrolyte, exhibiting superior electrochemical performance both in 6 M KOH electrolyte and in BMIMPF6 electrolyte.PCNs were synthesized from coal tar using calcium carbonate as template coupled with KOH activation. Under optimal conditions, PCN made with the mass of coal tar, calcium carbonate, KOH at 6 g, 12 g, 12 g at 950 oC is named as PCN6-12-12-950.Results show that PCNs possess high specific surface area(2079 m2/g), large total pore volume(1.52 cm3/g), big average pore size(3.65 nm). When evaluated as the electrode material for supercapacitors, the specific capacitance of PCN6-12-12-950 and energy dentisy of PCN6-12-12-950 supercapacitor reaches 172 F/g and 95.12 Wh/kg at0.05 A/g in BMIMPF6 electrolyte, respectively. The usable energy density still reaches12.98 Wh/kg, even at a high power density up to 15055 W/kg. The capacitanceretention of PCN6-12-12-950 remains at 61.82% after 500 cycles at 1 A/g in BMIMPF6 electrolyte.Curly porous carbon nanosheets(CPCNs) were obtained from anthracene oil using calcium carbonate as template coupled with KOH activation. Under optimal conditions, the CPCNs made with the mass of anthracene oil, calcium carbonate,KOH at 6 g, 9 g, 12 g at 950 oC is named as CPCN6-950. With the increase temperature from 900 oC to 1000 oC, the specific surface area and total pore volume decreases from1822 m2/g to 1090 m2/g, and from 4.11 cm3/g to 2.55 cm3/g, respectively. CPCN6-950 shows the highest specific capacitance and energy density, reaching 256 F/g and142.75 Wh/kg at 0.05 A/g in BMIMPF6 electrolyte, respectively. What's more, the capacitance retention of CPCN6-950 remains at 94.7% after 5000 cycles at 5 A/g in 6 M KOH electrolyte, exhibiting excellent cycle stability.