In this study, a simple in situ growth method is used to directly synthesize nitrogen−oxygen co-doped carbon-coated porous silica@CNT (CNT@mSiO 2 @NC) composites with opentip and multilayer sandwich tubular structures. As the sacrificial template method is used to etch most of the porous SiO 2 layer, the obtained nanotube has excellent properties. The composite has a high specific capacity of about 300 F g −1 at 2 A g −1 , and the capacity retention rate reaches 91.30% after 10,000 cycles at 40 A g −1 . The reasons for the superior performance can be ascribed to the synergistic effect of a suitable specific area (483.18 m 2 g −1 ), abundant nitrogen/oxygen functional groups (4.70 at. % N and 7.52 at. % O), and a porous silica supporting template. The power density of the assembled symmetric supercapacitor is 760 W kg −1 at the energy density of 16 W h kg −1 . Moreover, the capacity retention rate is 82.70% after 2500 cycles at a current density of 2 A g −1 . The N/O co-doped porous CNT@mSiO 2 @NC electrode material has adjustable porosity and enriched active sites, which has broad application prospects in high-performance supercapacitors.

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