Nitrogen–Oxygen Co-Doped Carbon-Coated Porous Silica/Carbon Nanotube Composites: Implications for High-Performance Capacitors

In this study, a simple in situ growth method is used to directly synthesize nitrogen–oxygen co-doped carbon-coated porous silica@CNT (CNT@mSiO2@NC) composites with open-tip and multilayer sandwich tubular structures. As the sacrificial template method is used to etch most of the porous SiO2 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 m2 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@mSiO2@NC electrode material has adjustable porosity and enriched active sites, which has broad application prospects in high-performance supercapacitors.