Three-dimensional flowerlike, two-dimensional sheet-like, and one-dimensional rod-like mesoporous Bi2O3 nanostructures for high performance asymmetric supercapacitors

Multidimensional metal oxide nanostructures have attracted much attention for applications in electrical energy storage due to their unique features and high surface area. In this study, we determined the growth mechanisms for two three-dimensional (3D) flower-like, two-dimensional sheet-like, and one-dimensional rod-like nanostructures of Bi2O3 synthesized via a simple and fast precipitation technique using sodium dodecyl sulfate, polyethylene glycol, and polyvinylpyrrolidone as templates. Analyses showed that the Bi2O3 nanostructures were obtained without any impurities. The effect of the morphology on the electrochemical performance was evaluated based on cyclic voltammetry, galvanometric charge/discharge, electrochemical impedance spectroscopy, and cycling stability tests. The results showed that the 3D structure comprising tetrahedrons with a specific surface area of 38 m2 g−1 reached a specific capacity of 558 F g−1 at a current density of 2 A g−1 with chemical stability of 93.2% after 6000 cycles, and it exhibited the best electrochemical performance compared with other structures in this study. The short propagation length due to the distance between tetrahedrons led to the deep diffusion of electrolyte ions to enhance the number of active sites. An asymmetric supercapacitor was prepared using the flowerlike 3D structure of Bi2O3 comprising tetrahedrons as the negative electrode and carbon nanofiber as the positive electrode, with 6 M KOH as the electrolyte. The energy density and power were 31 Wh kg−1 and 16213 W kg−1, respectively, at optimal conditions with cycling stability of 94.9% after 6000 cycles for this supercapacitor, which is comparable or even better compared with previous studies of SCs prepared using Bi2O3. Finally, the device was used to illuminate yellow and red light-emitting diodes for 25 min, and it may provide a promising alternative for the development of electrical energy storage facilities.