Nanoarchitectonics on residual carbon from gasification fine slag upon two step low temperature activation for application in supercapacitors

In this paper, the carbon electrode materials were prepared by the KOH-HNO3 low-temperature activation technique using cheap residual carbon from gasification fine slag (CK) as raw materials. The results showed that the prepared material (CKN-2) which obtained by dry-wet sequential activation at 500°C for 1.5 h at carbon to KOH ratio of 1:2 and further at 80°C for 1 h in 2 mol/L HNO3 solution. The specific capacitance of CKN-2 reached 142 F/g at a current density of 0.5 A/g. CKN-2 was used to assemble a symmetrical (CKN-2//CKN-2) supercapacitor, which exhibited an energy density of 6.80 Wh/kg at a power density of 244.8 W/kg. The CKN-2//CKN-2 capacitor was tested for stability after 10,000 cycles, with a capacitance retention rate of 97%. These results demonstrate that residual carbon from gasification fine slag can be effectively used to produce high-performance carbon electrode materials for supercapacitors using the KOH-HNO3 low-temperature sequential co-activation technique.