Nitrogen and phosphorus co-doped carbon hollow spheres derived from polypyrrole for high-performance supercapacitor electrodes

Abstract Nitrogen and phosphorus co-doped carbon hollow spheres (NPCHSs) have been prepared by a carbonization and subsequent chemical activation route using dehydrated polypyrrole hollow spheres as the precursor and KOH as the activating agent. NPCHSs are interconnected into a unique 3D porous network, which endows the as-prepared carbon to exhibit a large specific surface area of 1155 m 2  g −1 and a high specific capacitance of 232 F g −1 at a current density of 1 A g −1 . The as-obtained NPCHSs present a high-level heteroatom doping with N, O and P contents of 11.4, 6.7 and 3.5 wt%, respectively. The capacitance of NPCHSs has been retained at 89.1% after 5000 charge–discharge cycles at a relatively high current density of 5 A g −1 . Such excellent performance suggests that NPCHSs are attractive electrode candidates for electrical double layer capacitors.