Shape-selective synthesis of NiO nanostructures for hydrazine oxidation as a nonenzymatic amperometric sensor

Abstract

In this work, we demonstrate the shape-dependent electrocatalytic activity of NiO NPs towards hydrazine oxidation. For this purpose, NiO NPs, having pellet, rod, dot and cuboid-shapes, were synthesized using a variety of reducing agents such as sodium hydroxide (NaOH) with polyethylene glycol (PEG), NaOH without PEG, ammonia (NH₃), and sodium carbonate (Na₂CO₃) via a simple and low cost sol–gel approach. Moreover, NiO–silica core–shell (NiO@SiO₂) NPs were prepared using TEOS as a source of the porous silica. The morphological structures of these NPs were characterized by field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). From the X-ray diffraction (XRD) results, a face-centered cubic (fcc) NiO crystalline structure was confirmed and the estimated size of the crystalline NPs was in the range of 2.7–12.5 nm depending on the reducing agents utilized for the synthesis. Moreover, their characteristics were further investigated by Raman spectroscopy. From the cyclic voltammetry results, it was shown that the nano-pellet shape NiO exhibited the best electrocatalytic performance for hydrazine oxidation and stability, promising for fuel cell application.