In situ vanadophosphomolybdate impregnated into conducting polypyrrole for supercapacitor

The fast modernization and advancement in lifestyle increase the consumption of power daily due to all innovative technologies, e.g., hybrid vehicles, solar cells, smart power grid, communication devices, artificial hearts, etc. Conducting organic polymer-based energy storage devices had attracted much attention due to the conductive nature for a long time. However, its application has been restricted because of swelling and shrinking capability during the charge and discharge cycle. The combination of redox-active inorganic metal oxides, such as polyoxometalates (multi-metal oxide cluster) with conduction polymers, could enhance the material's stability due to its fast multi-electron redox property. Here, we report the two polypyrroles combined vanadophosphomolybdates, namely PPy-H₄[PVMo₁₁O₄₀] and PPy-H₅[PV₂Mo₁₀O₄₀] nanohybrid electrode materials. The PPy-H₅[PV₂Mo₁₀O₄₀] electrode material behaves as pseudocapacitance and can deliver an excellent capacitance of 561.1 F/g in 0.1 M H₂SO₄ electrolyte solution at a 0.2 A/g current density, indicating capacitive composite material. The electrochemical impedance spectroscopy (EIS) reveals that PPy-H₅[PV₂Mo₁₀O₄₀] is more capacitive than PPy-H₄[PVMo₁₁O₄₀] and PPy with equivalent series resistance (ESR) of 5.74 Ω. The cell capacitance of PPy-H₅[PV₂Mo₁₀O₄₀] and PPy-H₄[PVMo₁₁O₄₀] are found to be 5.38 and 9.15 mF, stipulating in small SC cell application. Likewise, the PPy-H₅[PV₂Mo₁₀O₄₀] nanohybrid electrode shows better responsive behavior with a relaxation time of 0.16 ms. Furthermore, the PPy-H₅[PV₂Mo₁₀O₄₀] electrode exhibits outstanding cycle stability, retaining ~95% of its capacitance after 4500 cycles as compare to PPy-H₄[PVMo₁₁O₄₀] (~91%) electrode.