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

Abstract

Analog sulfur-containing precursors (ASCPs) were employed to prepare activated carbon (AC) for supercapacitor by potassium hydroxide (KOH) chemical activation. The influence of sulfate, K2SO4, FeSO4, and CaSO4 on pore structure of resultant AC and its capacitance performance was investigated extensively. The results indicate that FeSO4 and K2SO4 in ASCPs can be involved deeply in activation reaction. K2SO4 can play a synergistic activation role in increasing porosity and capacitance performance, while FeSO4 can react with and consume a certain amount of KOH, thus decreasing the performance of AC. Compared with K2SO4 and FeSO4, CaSO4 in ASCPs has low reactivity; namely, only a small part of CaSO4 was involved in activation reaction, while most of it was transformed into CaCO3 residued in AC during washing process. Due to coexistence of CaCO3 with AC, the porosity and capacitance performance of AC were decreased obviously. Furthermore, it is noteworthy that in comparison with K+ and Ca2+, Fe2+ in ASCPs is more beneficial for transformation of inorganic sulfate into organic thioether in AC.