Flexible freestanding carbon nanofiber mats decorated with Zn/Co oxide nanostructures derived from zeolitic imidazolate frameworks as supercapacitor electrodes

Carbon nanofibers (CNFs) are excellent materials for hosting metal-carbon-nitrogen frameworks derived from zeolitic imidazole frameworks (ZIFs) that exhibit high electrical conductivity for energy storage devices. In this study, polyacrylonitrile (PAN) nanofibers are decorated with a Zn-Co bimetallic ZIF under open-air conditions using an eco-friendly water solvent and a wet chemical impregnation method to produce freestanding ZnO/ CoOx@CNF supercapacitor electrodes. Highly textured Zn-based ZIFs or ZIF-L(Zn) PAN fibers are produced by optimizing the salt-ligand concentration ratio. Moreover, highly textured Co-based ZIFs / ZIF-L(Co) PAN fibers are fabricated. Finally, the optimal concentrations are used to synthesize PAN nanofibers decorated with Zn and Co bimetallic ZIFs. The Zn-Co-decorated PAN nanofibers are then carbonized at 800 degrees C in an Ar environment to construct a ZnO/CoOx@CNF supercapacitor. Using an aqueous electrolyte (6 M KOH), the optimal ZnO/ CoOx@CNF sample produces an areal capacitance of 274 mF center dot cm-2 and a capacitance retention of 92 % after galvanostatic charge-discharge 40,000 cycles. Furthermore, the flexible supercapacitor cell exhibits a capacitance retention of 70 % after 1000 bending cycles, indicating the electrochemical stability and mechanical resilience of the ZnO/CoOx@CNF supercapacitor.