Preparation of ordered mesoporous carbon nanopipes with controlled nitrogen species for application in electrical double-layer capacitors

Nitrogen-doped mesoporous carbon nanopipes with various nitrogen states are prepared by controlling the carbonization temperature. Nitrogen adsorption–desorption and transmission electron microscopy (TEM) analyses reveal that the optimum carbonization temperature is 1123 K. A carbonization temperature below 1073 K is insufficient to form a mesoporous carbon framework, while collapse of the carbon structure is observed above 1173 K. X-ray photoelectron spectroscopy measurements clearly show that nitrogen species are chemically transformed into pyrrolic and quaternary state species with higher binding energies. In cyclic voltammetry measurements, polar species of quaternary nitrogen on a carbon surface show a positive effect to enhance the capacitance via an increase in hydrophilicity and wettability of carbon by the electrolyte.