Sonochemical synthesis of β-Co(OH)2 hexagonal nanoplates and their electrochemical capacitive behaviors

β-Co(OH)2 hexagonal nanoplates with an average diameter of 500 nm and a thickness of about 60 nm have been successfully synthesized via a fast efficient ultrasonic irradiation route in a very simple system composed only of water, cobalt nitrate and ammonium hydroxide. The structure and morphological characterizations of the obtained samples were investigated by X-ray diffraction analysis (XRD), Fourier transform infrared spectra (FT-IR) and scanning electron microscopy (SEM). The effects of the ultrasonic power and time on the formation of the unique hexagonal nanoplates were also tentatively discussed. Electrochemical properties were further evaluated using cyclic voltammetry (CV) and galvanostatic charge–discharge tests. A maximum specific capacitance value of 531 F g−1 at 0.5 A g−1 could be achieved in 6 mol l−1 KOH for the resulted β-Co(OH)2 hexagonal nanoplates, compared to 165 F g−1 for the block-like β-Co(OH)2 obtained without the ultrasonic irradiation treatment, showing the morphological effects on the capacitive performance. In addition, the β-Co(OH)2 nanoplates can offer a good specific capacitance retention of about 90% after 1000 cycles, suggesting its potential application in supercapacitors.

► Hexagonal β-Co(OH)2 nanoplate was prepared for ECs by a simple sonochemical method.
► A capacitance of 531 F g−1 can be obtained for the hexagonal plate-like β-Co(OH)2.
► The obtained hexagonal β-Co(OH)2 nanoplates also showed excellent cycle stability.