Hierarchical ZIF-67 of dodecahedral structure on binder-free carbon nanofiber for flexible supercapacitors

Binder-free, highly flexible carbon nanofibers decorated with ZIF-67 dodecahedral structures are synthesized via electrospinning and impregnation for use in supercapacitor applications. Because cobalt ions from ZIF-67 are highly attracted to carbon rings and the oxygen functional groups of polyvinylpyrrolidone (PVP), the concentration of PVP is varied to tune the morphology of ZIF-67. Accordingly, morphology tuning via PVP inclusion enhances the electron transfer within the ZIF-67-derived CoOx dodecahedral structure. Parametric studies are conducted to investigate the effect of PVP concentration on the electrochemical performance of carbon nanofibers decorated with ZIF-67. The optimal sample yields a capacitance of 444 mF⋅cm−2 at a current rate of 5 mA⋅cm−2. The corresponding capacitance retention is 94 % after 30,000 cycles with a potential window of 1 V. Furthermore, the energy density increases by 262.7 % when the potential window is increased from 1 to 1.5 V. These results confirm the long-term stability and outstanding energy-storage capabilities of the fabricated supercapacitor electrodes.