Nickel doping induced morphological and structural transformation of electrochemically deposited ZnO nanostructures via ethylene glycol based electrolyte

The synthesis of undoped and Ni-doped-ZnO (NZO) has been successfully demonstrated through an in-situ electrochemical deposition process using ethylene glycol (EG) electrolyte on FTO glass substrates. The doping concentration varied as 0, 1, 3, 4, and 5 mol%. Chronoamperometry studies show a significant increase in current density with higher doping levels, confirming typical electrochemical deposition behavior. SEM and EDX studies show a sponge-like porous ZnO with a lack of Zn-ions at 0 mol%, and the morphology turned into a spherical nanostructure when the doping concentration increased. Interestingly, at 5 mol%, multiple homogeneous and independent nuclei of NZO formed, resulting in a thin-film NZO nanostructure with three-dimensional grain growth mode. Further, the XRD analysis indicates that both undoped and NZO possess a pure-phase hexagonal wurtzite structure with dominant preferential orientation along the [101] plane. The undoped and NZO show nearly 100% atomic packing fraction (APF), implying a good atomic arrangement, and the density of NZO is nearly 50% higher than that of the undoped-ZnO. The sponge-like, undoped, and highly dense spherical nanostructure NZO can be tailored for energy storage applications and mechanical properties enhancement. Experimental results indicate that highly dense with nearly 100% APF, having a tunable morphology of ZnO structure, can be synthesized by electrochemical deposition using an EG-based electrolyte.