Residual carbon from coal gasification fine slags synergistically activated by KOH-KCl eutectic molten salts for high-performance supercapacitors

Coal gasification slags (CGSs), as by-products of the coal chemical industries, are favorable carbon precursor materials and more economical to mass-produce than biomass. In this study, coal gasification slags were utilized as carbon sources for the fabrication of activated carbon supercapacitor electrode materials. Residual carbon (RC) was first obtained by the gravity separation method from CGSs. Then, RC was then synergistically activated by KOH-KCl eutectic molten salts under the optimized conditions of 420 °C and 3 h and obtained activated carbon ACRC3. The specific surface areas (SSAs) and pore volume of the ACRC3 were 745.83 m 2 /g and 0.75 cm 3 /g, respectively. The electrochemical tests showed that the high specific capacitance of the ACRC3 was 190.0 F/g at the current density of 0.5 A/g. Symmetrical supercapacitors (ACRC3//ACRC3) exhibited 99 % capacitance retention at 0.3 A/g after undergoing 10,000 cycles. These electrochemical properties of ACRC3 were more excellent than those of the commercial activated carbon electronic materials (PEC-2, YP-50F or YP-80F). The low-temperature and simple activation of RC as high-performance supercapacitors can provide new directions for recycling CGSs.