Preparation And Energy Storage Performance Of Coking Byproduct-based Porous Carbon Nanosheets

Coal is one of the most important fossil resources and occupies irreplaceable position in China.Coal coking is one of the major utilization methods of coal,resulting in plenty of coking byproducts.In this article,coal tar,coal tar pitch,anthracene oil is used as carbon precursor,respectively.Mg?OH?₂ is employed as template precursor and KOH is used as activation agent.High temperature activation,carbonization and other methods were used to prepare porous carbon nanosheets?PCNS?for supercapacitors.Transmission electron microcopy,field scanning electron microscopy and nitrogen adsorption/desorption were employed to investigate the morphology and pore structure.Galvanosatic charge/discharge and cycle voltammetry were used to evaluate the electrochemical performance of the PCNS supercapacitors.The main conclusions are as follows:?1?Coal tar,Mg?OH?₂,KOH were employed as carbon precursor,template precursor,activation agent,respectively.In the process of experiment,the mass of three raw materials is 5 g,10 g,20 g,and final activation temperature is 800 oC,the specific surface area of porous carbon nanosheets(PCNS_20-800)reaches 3235 m2 g^-1,its average pore size is 2.24 nm.The specific capacitance reaches 296 F g^-1 at 0.05 A g^-1 and 220 F g^-1 at 20 A g^-1.The capacitance retention is 74.32%,exhibiting excellent high capacitance and rate performance.All the CV curves show good quais-rectangular shapes,indicating ideal capacitive behavior at low and high scan rates.The equivalent series resistance of PCNS_20-800 is 0.029 ?,indicating good conductivity.After 10000 cycles at 5 A g^-1,its capacitance retention reaches 97.2%,showing outstanding cycle stability.?2?Coal tar pitch,which is the residue of coal tar distillation,Mg?OH?₂,KOH,were used as carbon source,template precursor,activation agent,respectively.The mass of coal tar pitch,Mg?OH?₂,KOH is 3 g,18 g,18 g respectively and final activation temperature is 800 oC,the specific surface area of porous carbon nanosheets(PCNS_18-800)is 3145 m2 g^-1,average pore size is 2.3 nm.The specific capacitance reaches 272 F g^-1 at 0.05 A g^-1 and 217 F g^-1 at 20 A g^-1,the capacitance retention is 79.78%,showing high capacitance and cexcellent rate performance.After 10000 galvanostatic charge/discharge cycles at 5 A g^-1,its capacitance retention remains 96.69%,showing outstanding cycle stability.?3?Anthracene oil,which is the lighter component in the process of coal tar distillation,Mg?OH?₂,KOH,were used as carbon source,template precursor,activation agent,respectively.The mass of anthracene oil,Mg?OH?₂,KOH is 12 g,24 g,24 g,respectively.Only changing the final activation temperature and other conditions were not changed.When the final activation temperature is 900 oC,the specific surface area of porous carbon nanosheets(PCNS₉₀₀)is 2087 m2 g^-1,average pore size is 2.7 nm.The specific capacitance of PCNS₉₀₀ reaches 245 F g^-1 at 0.05 A g^-1 and 201 F g^-1 at 20 A g^-1,the specific capacitance retention is 82.04%,indicating outstanding rate performance.After 5000 galvanostatic charge/discharge times at 5 A g^-1,its capacitance retention remains 96.52%,showing excellent cycle stability.