High-performance supercapacitor based on nanocages with nanoporous thin-walled graphitic shells

• N-doping structure of graphitic shells is a defect and oxidized easily.
• Oxidization of N-doping structure forms carboxyl groups and nitro-groups.
• Partially removing the groups creates nanopores in the shells of nanocages.
• Such nanoporous shells increases surface area and capacitance of materials.

Thin-walled graphitic nanocages (GNCs) made up from highly nanoporous shells have been prepared by removing nitrogen-doping (N-doping) template. N-doping template is carboxyl groups and nitro-groups, which have formed from oxidation of N-doped structure of GNCs by acid-treatment. After partially removing N-doping template by annealing in vacuum, nanopores are created in the shells of the thin-walled GNCs. Thus, their specific surface area (1100 vs. 700 m2 g−1) and specific capacitance (370 vs. 300 F g−1 at current density of 0.1 A g−1) are sharply raised. With current density increasing to 1 A g−1, the capacitance of the GNCs is still high (230 F g−1), indicating such GNCs is a superb electrode material of supercapacitor.

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