High photocatalytic efficiency of a ZnO nanoplate/Fe 2 O 3 nanospindle hybrid using visible light for methylene blue degradation.

In this work, ZnO nanoplates and Fe 2 O 3 nanospindles were successfully fabricated via a simple hydrothermal method using inorganic salts as precursors. The ZnO/Fe 2 O 3 hybrid was fabricated using a mechanical mixture of two different ZnO : Fe 2 O 3 weight ratios to investigate the effect of weight ratio on catalytic properties. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that ZnO nanoplates (NPls) are about 20 nm thick with lateral dimensions of 100 × 200 nm, and Fe 2 O 3 nanospindles (NSs) are about 500 nm long and 50 nm wide. X-ray diffraction (XRD) patterns revealed the successful formation of the ZnO, Fe 2 O 3 , and ZnO/Fe 2 O 3 samples and indicated that their crystallite sizes varied from 20 to 29 nm depending on the ZnO : Fe 2 O 3 weight ratio. Ultraviolet-visible (UV-vis) spectra showed that the bandgap energies of ZnO and Fe 2 O 3 were 3.15 eV and 2.1 eV, respectively. Energy dispersive X-ray spectroscopy (EDS) results revealed the successful combination of ZnO and Fe 2 O 3 . Photocatalytic activity of the materials was evaluated through the degradation of methylene blue (MB) in aqueous solution under green light-emitting diode (GLED) irradiation. The results indicated that the ZnO/Fe 2 O 3 composite showed a remarkable enhanced degradation capacity compared to bare ZnO NPls and Fe 2 O 3 NSs. The ZnO : Fe 2 O 3 = 3 : 2 sample demonstrated the best performance among all samples under identical conditions with a degradation efficiency of 99.3% for MB after 85 min. The optimum photocatalytic activity of the sample with ZnO : Fe 2 O 3 = 3 : 2 was nearly 3.6% higher than that of the pure ZnO sample and 1.12 times more than that of the pristine Fe 2 O 3 sample. Moreover, the highest photo-degradation was obtained at a photocatalyst dosage of 0.25 g l -1 in dye solution.