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

A series of N-/O-doped micmporous 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 cm(3)g(-1) (22.17 g(-1)) of CO2 at 196 K, 2.12 wt% (10.50 mmol g(-1) ) of H-2 at 77 K, and 185.5 cm(3) g(-1) (8.27 mmol g(-1)) of CH) 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).