Electrospun carbon nanofibers embedded with MOF-derived N-doped porous carbon and ZnO quantum dots for asymmetric flexible supercapacitors

Abstract

All-solid-state asymmetric supercapacitors with flexible electrode materials have been widely applied in wearable electronic devices. Herein, hierarchical and porous carbon nanofibers (CNF) embedded with MOF-derived N-doped porous carbon (NPC) nanoparticles and decorated with ZnO quantum dots (ZnO QDs) are fabricated by co-electrospinning and carbonization processes. In the as-prepared ZnO QD/NPC/CNF composite, the embedding of NPC nanoparticles greatly improves the specific surface area and the conductivity of carbon nanofibers to accelerate the electron transfer and stabilize the mechanical structure of carbon nanofibers, while the addition of ZnO QDs provides abundant pseudo-capacitive active sites. As a result, the ZnO QD/NPC/CNF electrode as a self-supporting and binder-free positive electrode exhibits a high specific capacity of 71.6 mA h g⁻¹ (644.4 F g⁻¹) at 1 A g⁻¹. Based on a “one for two” strategy, the NPC/CNF as a negative electrode material is simply prepared by etching the positive electrode with acid. The assembled flexible all-solid-state asymmetric supercapacitor achieves a high energy density of 33.8 W h kg⁻¹ at a power density of 800 W kg⁻¹, excellent mechanical flexibility and cycling stability (83.1% of the initial capacity after 5000 cycles). The rational design of this work provides an effective way to construct a new electrode material of a high-performance energy storage system for wearable electronic devices.