9,10-phenanthrenequinone anchored on nitrogen-doped carbon nanotubes for symmetrical supercapacitors with enhanced performance

Electroactive organic molecules exhibit great advantages in electrochemical reversibility and cycling stability compared with conventional inorganic intercalation electrode materials. While the direct usage of electroactive organic molecules is prohibited by the electrical insulation. In this work, 9,10-phenanthrenequinone (PQ) has been non-covalently decorated on the surface of lab-made nitrogen-doped carbon nanotubes (NCNTs) via a facile refluxing method. The prepared composite PQ/NCNTs combined the excellent electrical conductivity of NCNTs and pseudocapacitance of PQ shows great electrochemical performance. The optimized PQ/NCNTs 5:5 composite exhibits high specific capacitance (749 F g⁻¹ at 1 A g⁻¹) and excellent rate capability (capacitance retention rate of 68.8% at 50 A g⁻¹). DFT calculations are performed to study the binding interaction and the mechanism of the enhanced charge storage capability of PQ/NCNTs. The symmetric supercapacitor assembled with the prepared PQ/NCNTs as electrode material delivers an energy density of 36.99 W h kg⁻¹ at a power density of 900 W kg⁻¹ in the voltage window of 0–1.8 V. Moreover, the device exhibits long cycling durability (capacitance retention rate of 89.4% after 10,000 cycles at 3 A g⁻¹). The excellent electrochemical performance of the composites including high specific capacitance, good rate capability, excellent cycle performance and improved power density and energy density imply great potential application for energy storage and can provide ideas for developing green, all carbon and high-performance supercapacitors.