Carbon-based
materials, as electrodes for supercapacitors, have attracted tremendous
attention. Therefore, nitrogen-doped porous carbons (NPCs) were prepared
through a facile carbonization/activation strategy by treating different
mass ratios of melamine–urea–formaldehyde resin and
KOH. It is clearly demonstrated that because of the introduction of
KOH, the resulting NPCs were shown to have increased specific surface
area and a rich pore structure, and the best sample possessed a large
specific surface area of 2248 m2 g–1 and
high N content, which contributed to the good electrochemical performance
for supercapacitors. Accordingly, a three-electrode system assembles
NPCs as an electrode using aqueous KOH solution; the specific capacitance
was 341 F g–1 under the current density of 1 A g–1 and retained a specific capacitance of almost 92%
after 5000 cycles. The maximum energy output for a symmetrical solid-state
supercapacitor with NPCs as the electrode material was 9.60 W h kg–1 at 1 A g–1. NPCs have promising
applications on high-performance supercapacitors and other energy-storage
devices.