Preparation of high-capacitance N,S co-doped carbon nanospheres with hierarchical pores as supercapacitors

Abstract The N,S co-doped carbon nanospheres with/without hierarchical pores (N,S-HPCNs/N,S-CNs) are prepared by the pyrolysis of polypyrrole and (NH 4 ) 2 S 2 O 8 with/without F127 as the pore-foaming agent in flowing N 2 . The results show that the combination of the hierarchical pores and N,S co-doping improves the electrochemical properties of carbon materials. As a result, the specific capacitance of N,S-HPCNs is as high as 416 F g −1 at a current density of 0.2 A g −1 , which is much higher than that of N,S-CNs (138 F g −1 ). At a current density of 10 A g −1 , the specific capacitance of 313 F g −1 for N,S-HPCNs is obtained, which keeps a capacitance retention of 75.2%, while the N,S-CNs has only the capacitance retention of 44.2%. After 5000 cycles, the retention ratio of N,S-HPCNs as high as 95.8% is obtained and the columbic efficiency of N,S-HPCNs is close to 100%. The symmetric supercapacitor device assembled using N,S-HPCNs exhibited a high energy density of 18.1 Wh kg −1 at a power density of 100 W kg −1 . The exhibited excellent electrochemical performances of N,S-HPCNs are attributed to a high content of doped heteroatoms N and S and the hierarchical pore structure.