From Three‐Dimensional Flower‐Like α‐Ni(OH)2 Nanostructures to Hierarchical Porous NiO Nanoflowers: Microwave‐Assisted Fabrication and Supercapacitor Properties

A facile method is presented to prepare flower‐like α‐Ni(OH) 2 involving only microwave heating of nickel nitrate hydrate in ethanol solvent without any hard/soft templates or precipitate‐controlling agents. After calcination procedure, hierarchical and porous NiO nanoflowers with large BET‐specific surface areas and controlled pore‐size distributions are readily fabricated. A possible formation mechanism is proposed based on self‐assembly under microwave heating. The structure, morphology, and crystalline phase of the products are characterized by transmission electron microscopy (TEM), X‐ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, and N 2 adsorption/desorption isotherm analysis. TEM reveals that the obtained NiO nanoflowers have uniform size and are composed of sheet‐like petals that are built up from nanocrystals. The resultant NiO nanostructures present a specific capacitance as high as 277 F/g and good cycling stability.