Humic Acid-derived Porous Carbons And Their EDLC Performances

Supercapacitors,taking advantages of high power density,short charge-discharge time,long life span and being environmentally friendly,have attracted more and more attention among researchers.Among them,the carbon-based electric double layer capacitors?EDLCs?possess the characteristics of ultrahigh power density,light weight and good physicochemical stability,and have become the popular study.However,the low energy density of EDLCs limits its wide applications.In this paper,we engineered carbon materials with reasonable pore structure in order to improve capacitance and enhance energy density eventually.Humic acid?HA?was employed as raw materials to fabricate hierarchical porous carbon via vacuum freeze drying,KOH activation and subsequent annealing.First of all,moderate macropores came from vacuum freeze drying process,while abundant micropores were obtained by KOH activation.In addition,high-temperature annealing further removed a large number of rebundant oxygen-containing groups.When used as EDLC electrode material,the porous carbons perform high energy density of 30.75Wh/kg?10 A/g?in 1 mol/L TEABF₄/PC and 6.58 Wh/kg?100 A/g?in 6 mol/L KOH.Leonardite humic acid?LHA?was used as precursor to prepare porous carbons by hydrothermal carbonization and KOH activation.The above two processes together enhanced the carbon yield,at the same time,adjusted the morphology and pore structure of porous carbons.The resulted porous carbons?at hydrothermal carbonization temperature of 150°C?behave good EDLC performance in 6 mol/L KOH aqueous electrolyte,including a high capacitance of 287.8 F/g at 0.05 A/g with excellent C_100/0.05 of 72.4%,superior rate capacity of 99.2%after 20,000 cycles at 10A/g.More importantly,a high energy density of 7.23 Wh/kg was obtained at 100 A/g.