Effect of potassium sulfate in mineral precursor on capacitance behavior of as-prepared activated carbon

Activated carbon (AC) used as supercapacitor electrode materials was successfully synthesized from analog sulfur-containing precursors (ASCPs). The materials were characterized by means of X-ray adsorption near-edge structure spectroscopy (XANES), elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), ion chromatography and N2 physical adsorption/desorption. The capacitance behavior was performed by electrochemical measurements. The results indicate that as the mass ratio of KOH to petroleum coke (PC) is 3:1 and 4:1, the synergistic activation effect from K2SO4 and KOH can increase pore volume and capacitance performance of AC. However, as for KOH/PC mass ratio is 5:1, the pore structure generated during activation process is destroyed due to K2SO4 over-activation, namely, the specific surface area, porosity and capacitance performance of AC decreased. Comparatively, the role of K2SO4 is quite different from those of other sulfur species, such as organic dibenzothiophene (DBT) and inorganic FeS2 during AC activation process.