Effect of Microwave Power and Cu Doping on MnO2 Nanostructures and Its Supercapacitor Performance

The enhanced specific surface area of electrode activematerialsprovides a convenient way for the flow of electrolytic ions, resultingin improved electrochemical energy storage performance. In this study,synthesis of Cu-doped MnO2 nanomaterials was demonstratedusing the microwave-assisted hydrothermal method. Upon reducing themicrowave power from 400 to 250 W, the morphology of Cu-doped MnO2 nanostructures changed from nanorods (similar to 50-100nm diameter) to nanoflowers with similar to 10-20 nm thick petalson the surface. The flower-like morphology shows enhanced supercapacitorperformance with a specific capacitance value of 433.15 F g(-1) at 0.5 A g(-1) current density. This feature isdue to the synergistic effect of the enhanced conductivity by Cu dopingand increased Brunauer-Emmett-Teller (BET) specificsurface area (144.35 m(2) g(-1)). Further,a two-electrode asymmetric supercapacitor (ASC) device was developedand it showed a maximum energy density of 77.78 Wh kg(-1) at a power density of 1000 W kg(-1). The deviceshowed capacitance retention up to 102.86% after 20,000 charge-dischargecycles at 20 A g(-1) current density. This study suggeststhat the Cu-doped MnO2 nanostructure is a promising electrodeactive material for enhanced supercapacitor performance with excellentrate capability.