Synthesis, properties and applications of flowerlike Ni-NiO composite microstructures

In this paper, we report the successful synthesis of flowerlike Ni-NiO composite microstructures with room-temperature magnetism via a simple water-DMF (N,N-dimethylformamide) mixed solvothermal process with sequential thermal treatment, using sodium hypophosphite hydrate (NaH2PO2 center dot H2O) and nickel sulfate (NiSO4 center dot 6H(2)O) as the starting reactants. The phase and morphology of the as-prepared product are characterized by means of powder X-ray diffraction, energy dispersive spectrometry, selected area electron diffraction (SAED), transmission electron microscopy, and scanning electron microscopy. Experiments show that the flowerlike Ni-NiO composite microstructures are obtained by the shape-preserved conversion of the precursor. Our investigation reveals that the as-prepared flowerlike Ni-NiO composite microstructures exhibit good electrochemical responses in 1 M NaOH solution and can be used as an electrochemical catalyst for the oxidation of methanol. Also, the as-prepared flowerlike Ni-NiO composite microstructures have a stronger catalytic activity for the chemical reduction of 4-nitrophenol to 4-aminophenol by NaBH4 than pure Ni nanospheres or flowerlike NiO microstructures.