In Situ Growth of MnO 2 Nanosheets on N‐Doped Carbon Nanotubes Derived from Polypyrrole Tubes for Supercapacitors

Nitrogen‐doped porous carbon nanotubes@MnO 2 ( N ‐CNTs@MnO 2 ) nanocomposites are prepared through the in situ growth of MnO 2 nanosheets on N‐CNTs derived from polypyrrole nanotubes (PNTs). Benefiting from the synergistic effects between N‐CNTs (high conductivity and N doping level) and MnO 2 nanosheets (high theoretical capacity), the as‐prepared N‐CNTs@MnO 2 ‐800 nanocomposites show a specific capacitance of 219 F g −1 at a current density of 1.0 A g −1 , which is higher than that of pure MnO 2 nanosheets (128 F g −1 ) and PNTs (42 F g −1 ) in 0.5  m Na 2 SO 4 solution. Meanwhile, the capacitance retention of 86.8 % (after 1000 cycles at 10 A g −1 ) indicates an excellent electrochemical performance of N‐CNTs@MnO 2 prepared in this work.