Synthesis of NiO granular nanospheres as a novel material for high-performance supercapacitors

[Display omitted] •Hydrothermally-derived synthesis was proposed to prepare NiO spheres.•Granular morphology plays a major role in improving electrochemical properties.•Electrode based on NiO spheres demonstrate high capacity and good cycling stability. We report a facile method for synthesizing NiO nanospheres with cubic structure and peculiar, so-called, granular morphology by two steps: first, porous carbon spheres were hydrothermally treated in Ni(NO3)2 and (NH2)2CO for 6 h at 110 °C and then annealed in the air for 4 h at 550 °C. The sample-based electrode for supercapacitor demonstrates advanced electrochemical characteristics: its specific capacity is 1315 F/g at 1 A/g and only 1% of total capacity is lost after 1000 charge–discharge cycles. We believe that these nanospheres are promising candidates for energy storage devices or electrocatalysts (i.e. in hydrogen evolution reaction).