The crystal phase and structure information of samples are
further unraveled by XRD analysis. Fig. 4 shows XRD patterns of
Co3O4 and Co3O4@Co core/shell nanowire arrays. In the XRD
pattern of the Co3O4 nanowires, apart from Ni substrate peaks, all
diffraction peaks are assigned to the spinel Co3O4 crystal structure
(JCPDS 42-1467). In the XRD pattern of the Co3O4@Co, new
characteristic diffraction peaks of cobalt appear, confirming the
successful deposition of metal cobalt on the Co3O4 nanowires