Carbon Quantum Dots–Anchored Polyaniline on Electrospun Carbon Nanofibers as Freestanding Electrodes for Symmetric Solid-state Supercapacitor

Abstract

A binder-free and freestanding electrode was designed by uniformly immobilizing carbon quantum dots (CQDs)-anchored polyaniline (PANI) heterostructures onto electrospun carbon nanofibers (CNFs) via a facile hierarchical assembly process. The fabricated freestanding CNFs/PANI/CQDs electrode exhibits a unique three-dimensional (3D) network nanostructure, which accelerates ion migration between the interior and surface of electrode, thereby enhancing its charging and discharging performance. Moreover, the functional groups on the surface of CQDs could anchor PANI through possible chemical bonding, which not only improves the stability of the PANI/CQDs heterojunction but also creates an additional conductive channel for the PANI polymer. As expected, the CQDs-anchored electrode possesses a specific capacitance of 756.5 F g⁻¹ at 0.5 A g-1, which is 1.78 times better than the capacitance of CNFs/PANI and 17.4 times higher than that of CNFs. Benefiting from the excellent electrical conductivity and freestanding structure of the electrode, the assembled symmetric solid-state supercapacitor exhibits an excellent capacitance stability rate of 94.69 % following 8,000 cycles and remains at 81.25 % after 10,000 cycles of operation at 1 A g-1. The remarkable cyclic durability may be due to the superior 3D network nanostructure and the stable PANI/CQDs heterostructure created through chemical bonding. This work offers new design concepts for fabricating binder-free and freestanding electrodes with unique 3D structures for application in other energy storage devices.