Controllable synthesis of nano-spherical and spinel structure hausmannite for asymmetric supercapacitor electrode application with long-term cyclic stability and its photocatalytic activity

Spinel structured materials have been developed as a potential candidate for energy storage applications due to their tunable electronic and structural properties. The nano spherical Mn3O4 spinel structure was synthesized using a polyvinylpyrrolidone (PVP) assisted hydrothermal approach. Owing to the smaller nano spherical architecture, and the impressive surface properties, the Mn3O4 shows outstanding surface characteristics to provide more reaction centers and shorten the ion transport path. Here, the addition of PVP reduces the battery-like diffusive behavior of the Mn3O4 electrode, induces capacitive behavior, and improves both high energy density and power density in a single material and cycling stability. In three-electrode configurations, Mn3O4 exhibits specific capacitance (628.7 Fg−1 at 1 Ag−1) and long-term cyclic stability (94% at 100 mV s−1 for 5000 cycles) in 1 M Na2SO4 electrolyte. The asymmetric device offers a high energy density of 35.41 Wh kg−1 with a power density of 850 W kg−1 and cyclic stability of 96.5% after 10000 charge/discharge cycles at 12 Ag−1. Density functional theory (DFT) is explained by electronic structural features and further investigated the photocatalytic activity of Mn3O4 samples on the model dye of Methylene Blue degradation.