Manganese Vanadate/Graphene Oxide Nanocomposites as High Energy Density Supercapacitor Materials

The electrochemical supercapacitors have been studied extensively in recent years as an alternative type of energy storage device, owing to their fast charge and discharge rates, long cycle lifetime, and reliability. They have much larger energy density than conventional capacitors, and much larger power density and charging/discharging rate capability than batteries [1]. Transition metal oxides are good electrodic materials candidates for pseudocapacitors, which use faradaic reactions for storing energy [2]. Recently, manganese oxides have been attracted a lot of attention for this issue because of their earth-abundant and non-toxic nature [3]. In this study, nanostructured manganese vanadate as a ternary manganese oxide has been synthesized using hydrothermal method. Its crystal structure and morphology were determined by XRD and TEM, respectively. Then the surface of a piece of stainless steel has been covered by nanostructured manganese vanadate using electrophoretic method, which was used as working electrode in electrochemical tests. The specific capacity of manganese vanadate was determined using cyclic voltammetry, charge-discharge curves and electrochemical impedance spectroscopy. To modify its electrical conductivity, some nanocomposites containing manganese vanadate and different amounts of graphene oxide were prepared and their capacitive behavior were investigated