Double perovskite material of highly active, monoclinic, ordered Ni₂ZnMoO₆ for an effective quasi-solid state supercapacitor

In the present study, monoclinic Ni₂ZnMoO₆ double perovskites (monoclinic NZMO DP) electrodes were synthesized using hydrothermal method for supercapacitors application. The structural, elemental, vibrational, and optical characterization were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy Dispersive X-ray analysis (HR-SEM & EDX), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET), Fourier Transform Infrared spectroscopy(FTIR) and UV-Visible Diffusion reflectance Spectroscopy (UV-DRS). A monoclinic structure with a space group of P 2/m and lattice parameters of a = 11.4377, b = 9.2961, c = 6.8301, and β = 97.710 was fitted using Rietveld refinement, and the cell volume was 719.6458 ų. The surface area of monoclinic NZMO DP was found to be 50.45 m² g⁻¹ with a pore volume of 0.15 cm³ g^−1. Electrochemical characterization was done using Cyclic voltammetry (CV), Electrochemical Impedance spectroscopy (EIS), and galvanostatic charge-discharge (GCD) measurements. An equivalent-circuit model R(CR)(CR) is iterated to interpret the EIS responses. The R_ct found to be less than 100 ohms in the present study can be attributed to Mott variable range hopping (VRH) conduction. The GCD analysis of ASC monoclinic NZMO DP//AC in 6 M KOH at 0.5 Ag⁻¹ in the potential window of 0–1.6 V yields a maximum specific capacitance of 160.45 Fg⁻¹. Excellent electrochemical stability of the monoclinic NZMO DP was ascertained by the specific capacitance retention of the electrode material at 91.37 % after 6000 cycles. The ASC-NZMO monoclinic DP shows an excellent power density of 646.25 W/kg with an energy density of 20.53 Wh/kg. The excellent power storage efficiency and application possibilities of supercapacitors make them a promising technology in various fields.