Co/CoO core-shell nanostructure on the 3D nickel foam has been synthesized by a hydrothermal method following by annealing the precursor in hydrogen atmosphere and air respectively. Different shell thicknesses of the CoO are designed and controlled by annealing the nanostructured Co in the air at 50 °C, 100 °C, 150 °C, 200 °C for 2 h, which were characterized by X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscope (SEM), transmission electron microscopy (TEM), X–ray photoelectronspectroscopy (XPS). As a result, Co/CoO core-shell nanostructure annealed...
