Growth and Photocatalytic Properties of NiO Nanostructures Prepared in Acidic and Alkaline Solutions with Same Reagents

Different Ni compound nanomaterials have been prepared successfully by simple hydrothermal synthesis, in which only the dosages of the reactants and the pH values of the solutions are controlled. Under acidic conditions, NiC 2 O 4 ·2H 2 O nanotubes are prepared, whereas under alkaline conditions, single crystalline Ni(OH) 2 nanosheets can be made. For the first time, the crystalline structure of NiC 2 O 4 ·2H 2 O is obtained based on X-ray diffraction. After annealing, the as-prepared nanostructures become NiO nanotubes and nanosheets. However, their crystalline structures are different from the original counterparts for the loss of H 2 O molecules. The photocatalytic properties of the final NiO products are measured. The nanotubes show a much stronger performance in the degradation of methylene blue than the nanosheets. The mechanisms for growth and photocatalysis are also discussed.