Hydrothermal synthesis of ZnO Crystals: Diverse morphologies and characterization of the photocatalytic properties

Zinc oxide (ZnO) microstructures including the ZnO nanorods (R-ZnO), ZnO nanopillars (C-ZnO), and multistage microspheres composed of ZnO nanosheets (M-ZnO) have been synthesized using a two-step hydrothermal approach by adjusting the concentrations of the growth solution. Scanning Electron Microscopy (SEM) was employed to observe the surface morphology of the fabricated samples. X-ray diffraction (XRD) was utilized for the structure characterization, which the results reveal a hexagonal wurtzite ZnO structure in all three samples with different microstructures. X-ray Photoelectron Spectroscopy (XPS) was used to investigate their defects, indicating that the oxygen vacancy ratios were 34.3 %, 21.8 %, and 51.5 % respectively for R-ZnO, C-ZnO, and M-ZnO. The band gaps of R-ZnO, C-ZnO, and M-ZnO, determined through Ultraviolet-Visible Absorption Spectroscopy (UV-Vis), were found to be 3.35 eV, 3.6 eV, and 3.19 eV, respectively. Finally, the photocatalytic performances of the prepared ZnO samples were investigated under simulated sunlight irradiation by observing the degradation of methyl orange, which the M-ZnO samples obtained a superior photocatalytic efficiency of 79 %.

Automated summary

Zinc oxide microstructures, including nanorods, nanopillars, and multistage microspheres, were synthesized using a two-step hydrothermal approach. The concentration of the growth solution was adjusted to achieve different microstructures. Characterization using SEM, XRD, and XPS revealed hexagonal wurtzite ZnO structures in all samples. The band gaps of the different microstructures were measured using UV-Vis spectroscopy, and the photocatalytic performance of the samples was evaluated. The M-ZnO samples exhibited the highest photocatalytic efficiency.