Synergistic experimental and computational study of Zn and Cd doped PEDOT: PSS/MgO nanocomposites for enhanced supercapacitor performance

Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate/magnesium oxide (PEDOT: PSS/MgO) nanohybrids infused with zinc (Zn) and cadmium (Cd) were synthesized using a co-precipitation method. Structural and morphological analyses using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FTIR) confirmed successful incorporation of dopants and formation of the composite structure. Zn-, and Cd- doped PEDOT: PSS/MgO showed a specific capacitance of 146 Fg⁻¹ and 204 Fg⁻¹ at 10 mVs⁻¹, while galvanostatic charge-discharge measurements showed 15.2 and 27.5 Fg-1 at 0.25 Ag-1 indicating diffusion limitations at higher current densities. The charge transfer resistance of Zn-, and Cd- doped PEDOT: PSS/MgO showed 12.8 Ω and 10.5 Ω showing that Cd- doped PEDOT: PSS/MgO exhibits a lower value suggesting lower charge transfer resistance and faster electron transport at the electrode-electrolyte interface. The Cd-doped electrode produced an open-circuit voltage of 1.33 V and effectively powered a red LED, indicating practical applicability. Density Functional Theory (DFT) simulations further validated that Cd doping reduces the HOMO-LUMO energy gap (2.64 eV) and facilitates charge transfer by reinforcing Cd-O and Cd-Mg interactions. The integration of experimental and theoretical investigations confirms that Cd-doped PEDOT: PSS/MgO is a durable electrode material, providing enhanced charge transport, elevated energy density, and prolonged electrochemical stability for next-generation supercapacitors.