High surface N-/O-doped microporous carbons for stable supercapacitor and carbon dioxide sorption applications

Abstract

Abstract A series of N-/O-doped microporous carbon materials are prepared through the KOH activation of N-doped microporous carbon nanospheres (MCNs) directly prepared from the carbonization of as-prepared mesoporous silica nanospheres (MSNs). Different amounts of KOH are employed to prepare KOH-activated MCNs: MCN–nKOH (where n denotes the weight ratio of KOH to MCN). Compared to nonactivated N-doped MCN, the N-/O-doped MCN–nKOH series reveal superior gas uptake abilities. The MCN–2KOH sorbs 496.8 cm3 g−1 (22.17 mmol g−1) of CO2 at 196 K, 2.12 wt% (10.50 mmol g−1) of H2 at 77 K, and 185.5 cm3 g−1 (8.27 mmol g−1) of CH4 at 196 K. The electrochemical capacitive properties are evaluated by both 3-electrode and 2-electrode measurements. Compared to MCN, the MCN–nKOHs displays enhanced rate capabilities of capacitance. MCN–2KOH shows the highest specific capacitance of 459.6 F g−1 and maximum specific energy of 37.6 Wh kg−1 at 0.1 A g−1. It also exhibits high specific power of 53323 W kg−1 at 120 A g−1. The MCN–nKOH electrodes show superior electrochemical cycling stabilities up to 30000 cycles. The symmetric 2-electrode MCN–2KOH supercapacitor also displays high capacitance of 322.6 F g−1 and energy density of 14.8 Wh kg−1 at 0.1 A g−1.