N- and O-doped hollow carbonaceous spheres with hierarchical porous structure for potential application in high-performance capacitance

Hollow carbonaceous spheres (HCSs) have been extensively investigated due to their valuable potentials in the applications of energy storage devices such as solar cells, fuel cells, and supercapacitors. It is highly desirable to develop abundant pore structures and introduce heteroatoms in the resultant HCSs to improve capacitance of the devices. Herein, N-, and O-doped HCSs with macro/micro/mesoporous structures are successfully prepared by one-step carbonization of polypyrrole coated polystyrene nanoparticles followed by chemical activation with KOH. The huge specific surface area (up to 935 m² g⁻¹) and hierarchical porous structures can effectively facilitate the transportation and exchange of ions and electrons. Besides, high heteroatom content (∼30%) are believed to provide pseudocapacitance contributed from the redox faradic reactions of these electrochemically active functional groups. The as-prepared activated HCSs possess a high capacitance of 535 F g⁻¹ at a current density of 0.2 A g⁻¹, and maintains 55% of the highest capacitance even at a current density of 10 A g⁻¹. The newly prepared HCSs thus show great potential as the electrode materials of supercapacitors.