Predominated capacitive behavior of Ag-doped magnesium vanadate as a novel electrode material for supercapacitors

Transition metal vanadate nanostructures are getting significant importance as an efficient electrode material for modern energy storage applications. In this work, a simple hydrothermal method is employed for the synthesis of magnesium vanadate (MgV2O5) and Ag-doped magnesium vanadate (Ag doped MgV3O8) nanomaterials. The X-ray diffraction (XRD) analysis reveals the formation of an orthorhombic structure for magnesium vanadate, whereas the Ag-doped magnesium vanadate results in a monoclinic structure. Interestingly, the optical bandgap is observed to increase from 2.85 eV to 3.92 eV with the increase in Ag-doping as revealed from Tauc's plot of the UV-visible absorption spectrum. The electrochemical performance of magnesium vanadate electrodes is thoroughly investigated by cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy. The Ag-doped magnesium vanadate shows higher specific capacitance (Cs = 706 Fg−1) in comparison to undoped (325 Fg−1) at a current density J = 5 Ag−1. The theoretical investigations through Dunn's model demonstrate a major contribution arises from surface-controlled processes, which increase as high as 91% at scan rate of 60 mVsec−1. Our findings indicate that Ag-doping significantly improves the overall electrochemical response of magnesium vanadate as an efficient electrode material for supercapacitor applications.