Comparative transition molybdates (XMoO4 (X = Co, Mn, Ni, and Zn)) for high-performance supercapacitors

Abstract

Owing to its exceptional rate capability, long-term stability, and quick charge–discharge capability, supercapacitors (SCs) have garnered significant interest of researchers. Practical SCs demand inexpensive and stable electrode materials. Owing to their appealing physical and chemical properties, transition metal molybdates are considered as a prospective electrode material. Herein, metal molybdate (XMoO₄, X = Co, Mn, Ni, Zn) have been synthesized employing a facile sol–gel auto combustion process. X-ray powder diffractometer was employed to validate the synthesis of the nanostructures. The prepared samples surface morphological characteristics and elemental composition were examined employing an energy dispersive X-ray spectroscope combined with a scanning electron microscope. The morphologies were further investigated by transmission electron microscope. X-ray photoelectron spectroscope was employed to examine the synthesized samples for element oxidation states. The electrochemical behaviour of different samples was examined in two-electrode SC system employing electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge/discharge (GCD) techniques. EIS along with CV and GCD confirm the SC electrode behaviour of the synthesized materials. The impact of the inherent characteristics of electrodes on specific capacitance was examined by the comparative experimental study. Co based molybdate showed excellent specific capacitance (318.22F g⁻¹), specific power (0.89 kW kg⁻¹) and specific energy (11.04 Wh kg⁻¹) at a current density of 0.5 A g⁻¹, while the best cyclic stability (capacitance retention of about 95 % after 10,000 cycles) was displayed by Mn based molybdate. The high electrical conductivity and superior quality of the sample, that facilitates rapid ion movement and aqueous electrolyte medium interaction, may be accounted for the remarkable electrochemical performances. Overall, the observed results emphasize the significance of molybdate nanostructures as a potential electrode material for next-generation energy storage applications.