Preparation And Electricity Storage Performance Of Porous Carbon Nanosheets From Fluorene For Supercapacitor

Chemical by-products and biomass are the carbon precursors for preparing the electrode materials of supercapacitors.Generally,the complicated molecular structures of these carbon precursors can not be effectively measured due to the lack of efficient analysis methods,resulting in that it is difficult to study their reaction mechanism.Because fluorene is less virulent,featuring simple molecular structure,carbon nanosheets were prepared from fluorene with MgO,Mg?OH?₂,Ca?OH?₂ as template or template precursor in argon atmosphere,respectivly,coupled with KOH activation.The pore structure parameters and surface morphology were characterized by nitrogen adsorption-desorption,TEM and FESEM.The surface functional group and graphitic degree were analyzed by XPS and Raman spectroscopy.The electrochemical properties of electrodes from porous carbon nanosheets were investigated by galvanostatic charge-discharge,cycle voltammetry and AC impedance spectroscopy in 6 M KOH electrolyte.The main conclusions are as follows:Porous carbon nanosheets?PCNSs?were prepared from fluorene by MgO template strategy coupled with KOH activation.PCNS_3-1173 made with the mass of fluorene,MgO,KOH at 5 g,10 g,15 g at 1173 K,contains interconnected shell structure with a lot of pore.The BET specfic surface area,average pore size and total pore volume of PCNS_3-1173 reaches 2550 m² g^-1,2.40 nm,1.57 cm³ g^-1,respectively.The PCNS_3-1173 specfic capacitance is 313 F g^-1 and 211 F g^-1 at 0.05 A g^-1 and 100 A g^-1,respectively.The PCNS_3-1173 exhibts good rate performance?67.4%?.The specfic capacitance retention of PCNS_3-1173 is 95%at 5 A g^-1 after 15000 cycles,exhibting good cycle stability.Lamellar porous carbons?LPCs?were prepared from fluorene by Mg?OH?₂ template strategy coupled with KOH activation.The LPC_2.5 with foliated structure was made with the mass of fluorene,Mg?OH?₂,KOH at 6 g,12 g,15 g at 1173 K.The BET specfic surface area,average pore size and total pore volume of LPC_2.5 reaches1879 m² g^-1,2.40 nm,2.22 cm³ g^-1,respectively.The LPC_2.5 specfic capacitance is231 F g^-1 and 173 F g^-1 at 0.05 A g^-1 and 100 A g^-1,respectively.The LPC_2.5 exhibts good rate performance?74.9%?.The specfic capacitance retention of LPC_2.5 is 92.8%at 5 A g^-1 after 10000 cycles,exhibting excellent cycle stability.Plicated porous carbon nanosheets?PPCNs?were prepared from fluorene by Ca?OH?₂ template strategy coupled with KOH activation.The PPCN_6-12-12-1173 with fold foliated structure was made with the mass of fluorene,Ca?OH?₂,KOH at 6 g,12g,12 g at 1173 K.The BET specfic surface area,average pore size and total pore volume reaches 2563 m² g^-1,2.26 nm,1.45 cm³ g^-1,respectively.The specfic capacitance of PPCN_6-12-12-1173 is 344 F g^-1 and 278 F g^-1 at 0.05 A g^-1 and 100 A g^-1,respectively.The PPCN_6-12-12-1173 exhibts excellent rate performance?80.8%?.After10000 cycles,the specfic capacitance of PPCN_6-12-12-1173 remains at 90.2%,only droping from 290 to 261 F g^-1 at 5 A g^-1,exhibting good cycle stability.