Synthesis and electrochemical characterization of Ni nanoparticles by hydrazine reduction using hydroxyethyl cellulose as capping agent

The controlled-size synthesis of well-dispersed metal nanoparticles has been the aim of many research works during the last two decades. In this context, simple and controlled methods are the most suitable to obtain metal nanoparticles. The reduction of transition metal salts in solution is the most widely used method for generating colloidal suspensions of metals. In this work, nickel nanoparticles were synthesized from NiCl₂·6H ₂O in an ethanol solution with hydrazine hydrate and an appropriate amount of NaOH in the presence of hydroxyethyl cellulose (HEC) used as a capping agent to avoid the coalescence of the nanostructures. Size effects on the nickel nanostructures were studied by varying the concentration of the reducing agent and temperature. The obtained nickel nanostructures were characterized by X-ray diffraction (XRD), showing a face-centered cubic (fcc) structure. Particle sizes from 7 to 13 nm were determined by the Scherrer equation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed spherical sponge-like nanostructures formed by thin laminar structures. Additionally, infrared spectroscopy showed the presence of HEC functional groups on the surface of the nickel nanostructures after the purification step. Finally, the obtained Ni nanostructures were also characterized by electrochemical techniques and magnetic measurements to determine their electrocatalytic properties and magnetic response, respectively.