One-Pot Synthesis of Polyoxometalate Decorated Polyindole for Energy Storage Supercapacitors

The demand for energy storage supercapacitor devices has increased interest in completing all innovative technologies and renewable energy requirements. Here, we report a simple method of two polyoxomolybdate (H₄[PVMo₁₁O₄₀] and H₅[PV₂Mo₁₀O₄₀]) doped polyindole (PIn) composites for electrochemical supercapacitors. The interactions between polyoxomolybdates and PIn were measured by Fourier transform infrared spectroscopy (FTIR), and powder XRD, and stability was measured by thermogravimetry. The field emission scanning microscopy (FESEM) was employed to investigate the morphology of the materials. The electrochemical measurements show that the PIn/PV₂Mo₁₀ electrode exhibits a higher capacitance of 198.09 F/g with an energy density of 10.19 Wh/kg and a power density of 198.54 W/kg at 0.2 A/g current density than the PIn/PVMo₁₁ electrode. Both electrodes show a pseudocapacitance behavior due to the doping of redox-active polyoxomolybdates on the PIn surface and enhance the electrochemical properties. The electrodes' capacitive nature was measured by electrochemical impedance spectroscopy (EIS), which shows that the PIn/PVMo₁₁ electrode has a resistive nature within the electrode-electrode interface. Moreover, the PIn/PV₂Mo₁₀ electrode offers remarkable cycle stability, retaining ∼84% of its capacitance after 10,000 cycles (∼83% for the PIn/PVMo₁₁ electrode). The higher specific capacitance, faster charge/discharge rates, and higher cycle stability make them promising electrodes in supercapacitors.