Metal-Organic frameworks encapsulated with vanadium-substituted heteropoly acid for highly stable asymmetric supercapacitors

Herein, we report on a facile one pot synthesis of polyoxometalates encapsulated zeolite imidazolate framework cages (PMo10V2@ZIF-67). The morphological and structural properties of the as synthesized materials were investigated via FESEM, EDS, XRD and FTIR techniques. Moreover, N-2 adsorption/desorption isotherms and XPS measurements were carried out to elucidate the textural properties and composition of the fabricated materials. Upon their use as supercapacitor electrodes, the PMo10V2@ZIF-67 electrode exhibited a maximum specific capacitance of 765 F/g at a scan rate of 5 mV/s. Furthermore, a supercapacitor device was assembled using activated carbon as the negative electrode and PMo10V2@ZIF-67 as the positive electrode, delivering a specific power of 702 W/kg and a corresponding specific energy of 20.9 Wh/kg at a charging current density of 1 A/g. In addition, the device shows an excellent long term stability and high Columbic efficiency over 5000 charging and discharging cycles at a charging and discharging current density of 5 A/g.