Core–shell N-doped carbon spheres for high-performance supercapacitors

Surface-nitrogen enriched carbon spheres with core–shell structure were prepared by a facile and general strategy with dopamine and melamine as the precursors. This strategy includes three steps: the polymerization of dopamine to form polydopamine (PDA) spheres, the soaking of spheres in melamine (MA) and the pyrolysis of PDA spheres/MA. The resulting carbon spheres as electrode materials for supercapacitors display better performances than common N-doped carbon spheres (NCS) with a high specific capacitance (203 F/g at 0.5 A/g), acceptable rate capability (66% retention at 5 A/g) and good long-term stability (94.6% retention after 5000 cycles at 2 A/g). This formation of polymer spheres-soaking in inflating agent-pyrolysis strategy makes it easy to produce surface-nitrogen-rich and hierarchically porous carbon spheres on a large scale with different sources. These carbon spheres hold great potential applications in energy storage and conversion devices such as supercapacitors and fuel cells due to their unique structure and hierarchical composition.