Response surface optimization design of coal-derived activated carbon with high capacitance performance using decreased amount of KOH activated agent

Coal-derived activated carbon (CAC) is considered as an important direction for high-economic utilization and sustainable development of coal resources. However, this process is limited due to the overall promotion of environmental protection. In this paper, CAC was prepared by H2O activation combined with KOH solution impregnation re-activation of Taixi anthracite. The addition of a small amount of KOH (less than 60 wt% of CACI) significantly promoted the pore formation of CAC, and in addition, a high CAC yield (about 56%) was also obtained. The effects of impregnation conditions of KOH on the specific capacitance of CACII were analyzed by response surface optimization, and the optimal preparation parameters (12.5 mol/L, 82°C and 8.3 h) were obtained. The specific capacitance of CACII prepared under this optimal condition is 334.2 F/g because it has a large specific surface area of 1909.92 m2/g and a defect degree greater than 1. KOH activation improves the wettability of CACII by introducing hydroxy groups. The assembled CACII//CACII symmetrical device also has a higher specific capacitance (224.3 F/g at 0.5 A/g) than the commercial YP-50F. At the same time, it also has a high energy density of 31.15 Wh/kg at 500 W/kg. The physical-chemical multi-stage activation method can significantly reduce the consumption of corrosive chemical reagents in the preparation of CAC, which greatly relieves the pressure of equipment and environment, and lays the foundation for the industrial production of CAC.