Novel NiO nanodisks and hollow nanodisks derived from Ni(OH)2 nanostructures and their catalytic performance in epoxidation of styrene

Abstract

A microwave-solvothermal (MS) method combining a calcination process was conducted to synthesize nickel oxide (NiO) nanodisks and hollow nanodisks. First, Nickel hydroxide (Ni(OH)2) nanodisks and hollow nanodisks had been synthesized through the MS method in the presence of oleylamine or sodium oleate. The X-ray powder diffraction (XRD) results of the products illustrate that the as-prepared nanostructures have a Ni(OH)2 and NiO phase. The transmission electron microscopy (TEM) images of the products illustrate that Ni(OH)2 nanodisks prepared in the presence of oleylamine have a thickness of ~ 10 nm and diameter of ~ 100 nm, while Ni(OH)2 hollow nanodisks synthesized in the presence of sodium oleate have a hole in the middle with a thickness of ~ 10 nm and diameter of ~ 250 nm. Second, the NiO nanodisks and hollow nanodisks could be obtained from the precursor without changing their morphologies by a simple calcination procedure. The as-synthesized NiO nanostructures displayed efficient catalytic epoxidation of styrene with conversion (60%) and selectivity (60–80%).