Synthesis and characterization of hierarchical Sr-doped ZnO hexagonal nanodisks as an efficient photocatalyst for the degradation of methylene blue dye under sunlight irradiation

Abstract

This study presents the synthesis and comprehensive characterization of hierarchical hexagonal nanodisks of zinc oxide (ZnO) and strontium (Sr) doped ZnO, prepared via a hydrothermal method. The experimental synthesis procedure involved dissolving zinc nitrate in a water–ethanol mixture, followed by the addition of polyethylene glycol (PEG 200), sonication, and subsequent hydrothermal treatment. Different concentrations of Sr were introduced into the ZnO lattice to generate Sr-doped ZnO samples. Analysis of the obtained results revealed successful incorporation of Sr, evidenced by shifts in the X-ray diffraction (XRD) pattern and alterations in lattice parameters. Moreover, the Williamson-Hall plot indicated minimal strain and high structural stability in both pristine ZnO and Sr-doped ZnO. The morphology of the synthesized Sr-doped ZnO was confirmed through field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), revealing a hexagonal nano disk-shaped morphology akin to pristine ZnO. Elemental composition analysis conducted via X-ray photoelectron spectroscopy (XPS) further confirmed the presence of Sr in the doped ZnO samples. Evaluation of photocatalytic activity against methylene blue dye demonstrated superior performance of the 5 % Sr-doped ZnO catalyst, attributed to its increased surface area compared to pristine ZnO. Notably, the highest degradation rate constant (k) of 0.0389 min−1 was observed for the 5 % Sr-doped ZnO catalyst, emphasizing its efficacy in environmental remediation applications. This research underscores the potential of Sr-doped ZnO as a promising photocatalyst, offering stability, reusability, and effective utilization of UV and visible light for catalytic processes.