Facile synthesis and capacitive performance of the Co(OH)2 nanostructure via a ball-milling method

Co(OH)2 nanoparticles were synthesized using only CoSO4·7H2O and NaOH as reactants without other auxiliary reagents via a simple, low-cost and practical ball-milling technique and investigated as the active electrode materials for supercapacitors. The structure and morphology of the resulting Co(OH)2 samples were examined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The observations revealed the formation of brucite-like phase of β-Co(OH)2, which had an irregular sphere-like shape with an average size of 50–100 nm. When investigated as electrode materials for supercapacitors, the β-Co(OH)2 exhibited good energy-storage performances in terms of high specific capacitance of 599 F g−1 and excellent capacity retention, suggesting its potential application in the electrode material for supercapacitors.