Template-free synthesis of mesoporous nickel oxide electrode material with three-dimensional flowerlike morphology

•Mesoporous NiO was fabricated by a template-free synthesis method.•Dependence of the hydrolysis reaction of CO(NH2)2 upon temperature was utilized.•The formation mechanism of the mesoporous NiO was clarified.

In this work, mesoporous NiO with three-dimensional flowerlike morphology were synthesized from precursor α-Ni(OH)2 by a facile template-free modified homogeneous precipitation method, where CO(NH2)2 could be acted as a chelating agent at lower temperatures, and source material of OH− utilizing the hydrolysis reaction at high temperatures. The structures of the NiO materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. The specific surface area of NiO was 140 m2 g−1, which was about 86% of the specific surface of precursor α-Ni(OH)2 (163 m2 g−1). The pore diameter of NiO and α-Ni(OH)2 were approximately 3.6 nm and 1.7 nm, corresponding to mesoporous and microporous, respectively. The NiO material used as an electrode in 6 mol L−1 KOH electrolyte exhibited a specific capacitance of 289 F g−1 at a current density of 5 A g−1, and could still retain 262 F g−1 at 10 A g−1 and 257 F g−1 at 20 A g−1, respectively. In addition, almost no decrease of the capacitance was observed after 4000th charge-discharge cycles at a current density of 10 A g−1.

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