Optimization of Hydrothermal Synthesis of Nickel Oxide with Flower-Like Structure

Herein, nano-flower NiO is successfully fabricated via a simple hydrothermal process using urea and nickel(II) nitrate as reactants, followed by a calcination reaction. Final products with different morphologies are obtained by varying the molar ratio of the reactants, varying the solvent, and using a surfactant. The results reveal that the NiO particles obtained using a molar ratio of 1:2 (Ni: urea) in a mixture of water and ethanol as the solvent and in the presence of cetyl trimethyl ammonium bromide (CTAB) exhibit the best uniformity and an excellent BET specific surface area of 62.97 m2 g–1. The increase in uniformity and decrease in particle size can be attributed to the ethanol in the solvent, which slows ion diffusion in the solution and CTAB, thereby controlling the growth of particles.