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

Abstract

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·H₂O) and nickel sulfate (NiSO₄·6H₂O) 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.