3D interpenetrating networks of MnO₂/Carbon-CNTs composites derived from ZIF-67 MOF and their application to supercapacitors

3D interpenetrating networks of carbon modified MnO₂ nanocrystals being connected by carbon nanotubes (MnO₂/Carbon-CNTs) have been prepared using cobalt modified Carbon-CNTs, which is derived from CNTs joined ZIF-67 MOF crystals, as sacrificial template. Due to the coexistence of amorphous carbon and carbon nanotubes (CNTs) and their diversity upon oxidization, the CNTs can be remained preferentially after the oxidizing by KMnO₄ solution. As results, carbon content in the resulted MnO₂/Carbon-CNTs networks can be turned from 7 to 18 wt% by simply controlling the concentration of KMnO₄ and the reaction time. The MnO₂/Carbon-CNTs have been explored as electrode for supercapacitors and they show excellent performance. The capacitance measured with a three-electrode configuration using 2 M KOH aqueous solution as electrolyte at current density of 0.5 A g⁻¹ reaches 508.8 F g⁻¹. Such a superior electrochemical performance can be related to the interpenetrating network of the sample, in which CNTs can not only increase the electrical conductivity of the material but also play a role in supporting and fastening the 3D architectures, which also improves greatly the specific surface area of the composite. All these characters are favorable to their electrochemical performance when MnO₂/Carbon-CNTs are used as electrode for supercapacitor or other energy storage systems.