Morphological, structural, and electrochemical properties of ZnO- and Ni-doped ZnO nanocrystals formed using different reducing agents in the chemical co-precipitation technique

This study investigates the effects of reducing agents on the structural, morphological, and electrochemical properties of ZnO- and Ni-doped ZnO nanocrystals, which were synthesized via the chemical precipitation method without any capping agent. The morphological and compositional analyses were conducted using field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The results suggested that the reducing agent influenced the particle size and morphology, and 6-7 at% Ni was found in the doped ZnO nanocrystals. Crystallographic characterization was performed using X-ray diffraction (XRD), where the crystallinity of the samples was slightly influenced by Ni doping, and wurtzite hexagonal polycrystalline nanocrystals with average crystal sizes between 17 and 25 nm, where the average crystal size increases with Ni doping. Moreover, Raman spectra analyses showed that all samples have the characteristic Raman modes of the ZnO, and the asymmetry ratio analyses of the E2 (high) mode decreased for the Ni-doped ZnO compared to pristine ZnO for both reducing agents. The electrochemical behavior of the ZnO- and Ni-doped ZnO samples was examined through cyclic voltammetry, and the nanocrystals synthesized via NaOH solution had a higher current density. The results showed that using different reducing agents and doping with Ni significantly impacted the morphological, structural, and electrochemical properties of the ZnO-based nanocrystals.