Influence of OH- and SO42- Anions on Morphologies of the Nanosized Nickel Hydroxide

The nickel hydroxides (beta-Ni(OH)(2)) with different shapes such as hexagonal nanosheets, irregular nanosheets, and nanoparticles were synthesized in the absence of SO42- ions and in the presence of 0.00-3.00 mmol of the added NaOH using a hydrothermal method. The beta-Ni(OH)(2) phase with brucite-type structure was confirmed by an energy-dispersive spectrum (EDS), Fourier transform infrared spectra (FM), and powder X-ray diffraction (XRD). The effect of the free OH- ions and the SO42- ions in the hydrothermal system on morphologies of the Ni(OH)(2) products was investigated in detail. In the absence of SO42- ions system, when the added NaOH amount is less than 0.02 mmol, the irregular thin nickel hydroxide nanosheets with thickness of about 20-50 nm were obtained; when the added NaOH amount is between 0.35 and 0.55 mmol, the products have the regular hexagonal morphology with a width of 150-500 nm and thickness of 40-80 nm; while when the added NaOH amount is 1.50-3.00 mmol, the nickel hydroxide products became polyhedral nanoparticles with an average diameter of ca. 50-90 nm. The Ni(SO4)(0.3)(OH)(1.4) nanowires or alpha-Ni(OH)(2) nanowires containing the intercalated SO42- anions can only be obtained in the presence of SO42- ions. They have lengths of several micrometers and widths of 20-30 nm. A possible growth mechanism of the nanosheets, nanoparticles, and nanowires is suggested.