Controlled fabrication of nitrogen-doped carbon hollow nanospheres for high-performance supercapacitors

Nitrogen-doped carbon hollow nanospheres (NCHNs) have been recognized as promising electrode materials for supercapacitors, due to their large specific surface area coupled with large interior void space fraction for fast mass and charge transport. Herein we report the controllable fabrication of NCHNs by facile copolymerization of N-contained pyrrole and aniline in the presence of Triton X-100 as a surfactant followed by thermal annealing of the resulting copolymer nanoparticles. The diameter of NCHNs and N-doping level are readily regulated by controlling the Triton X-100 concentration and carbonization temperature respectively. The relationship between the nanostructure, N-doping composition of NCHNs and their electrochemical performance is investigated systematically. As expected, the supercapacitor based on a NCHN with the smallest size (an outer and inner diameter of 80, and 30 nm, respectively) and the highest N-doping level (6.1%) exhibits the highest specific capacitance (283 F g−1), the highest energy density (19.3 Wh kg−1), high rate capability, and long cycling stability, showing a huge potential for advanced energy storage.