Polycrystalline and Mesoporous 3-D BiO Nanostructured Negatrodes for High-Energy and Power-Asymmetric Supercapacitors: Superfast Room-Temperature Direct Wet Chemical Growth.

Superfast (≤10 min) room-temperature (300 K) chemical synthesis of three-dimensional (3-D) polycrystalline and mesoporous bismuth(III) oxide (BiO) nanostructured negatrode (as an abbreviation of negative electrode) materials, viz., coconut shell, marigold, honey nest cross section and rose with different surface areas, charge transfer resistances, and electrochemical performances essential for energy storage, harvesting, and even catalysis devices, are directly grown onto Ni foam without and with poly(ethylene glycol), ethylene glycol, and ammonium fluoride surfactants, respectively. Smaller diffusion lengths, caused by the involvement of irregular crevices, allow electrolyte ions to infiltrate deeply, increasing the utility of inner active sites for the following electrochemical performance. A marigold 3-D BiO electrode of 58 m·g surface area has demonstrated a specific capacitance of 447 F·g at 2 A·g and chemical stability of 85% even after 5000 redox cycles at 10 A·g in a 6 M KOH electrolyte solution, which were higher than those of other morphology negatrode materials. An asymmetric supercapacitor (AS) device assembled with marigold BiO negatrode and manganese(II) carbonate quantum dots/nickel hydrogen-manganese(II)-carbonate (MnCOQDs/NiH-Mn-CO) positrode corroborates as high as 51 Wh·kg energy at 1500 W·kg power and nearly 81% cycling stability even after 5000 cycles. The obtained results were comparable or superior to the values reported previously for other BiO morphologies. This AS assembly glowed a red-light-emitting diode for 20 min, demonstrating the scientific and industrial credentials of the developed superfast BiO nanostructured negatrodes in assembling various energy storage devices.