Influence of Cobalt Content on Phase Formation and Morphology in Co-Zn-O Oxides

Co–Zn–O–based materials have attracted attention for applications in energy storage and catalysis. In this study, the effects of cobalt incorporation on the crystal phase and particle morphology of Co–Zn–O oxides were investigated. ZnO-based oxides were synthesized using a reflux method, and the influence of cobalt content on phase formation and morphology was systematically evaluated. As the cobalt precursor concentration increased, scanning electron microscopy–energy dispersive X-ray spectroscopy confirmed higher cobalt incorporation. This compositional variation was accompanied by changes in particle morphology, including nanoparticles, disk-like structures, and occasional rod-like features. X-ray diffraction and Raman spectroscopy showed that samples with low cobalt content retained the wurtzite ZnO phase, whereas higher cobalt concentrations led to formation of a ZnO/ZnCo2O4 composite. X-ray photoelectron spectroscopy revealed comparable binding energies among samples, while differences in peak width suggested variations in the local coordination environment of cobalt. These results indicate that cobalt content significantly influences phase composition and particle morphology in Co–Zn–O oxides synthesized under reflux conditions.