In Situ Growth of MnO2 Nanosheets on N‐Doped Carbon Nanotubes Derived from Polypyrrole Tubes for Supercapacitors

: Nitrogen-doped porous carbon nanotubes@MnO2 (N-CNTs@MnO2 ) nanocomposites are prepared through the in situ growth of MnO2 nanosheets on N-CNTs derived from polypyrrole nanotubes (PNTs). Benefiting from the synergistic effects between N-CNTs (high conductivity and N doping level) and MnO2 nanosheets (high theoretical capacity), the as-prepared N-CNTs@MnO2 -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 MnO2 nanosheets (128 F g-1 ) and PNTs (42 F g-1 ) in 0.5 m Na2 SO4 solution. Meanwhile, the capacitance retention of 86.8 % (after 1000 cycles at 10 A g-1 ) indicates an excellent electrochemical performance of N-CNTs@MnO2 prepared in this work.