Hydrothermal synthesis of CdS nanorods anchored on α-FeO nanotube arrays with enhanced visible-light-driven photocatalytic properties.

As an n-type semiconductor with an excellent physicochemical properties, iron oxide (FeO) has been extensively used in the fields of environmental pollution control and solar energy conversion. However, the high recombination rate of the photoinduced electron-hole pairs and poor charge mobility for FeO nanomaterial generally result in low photocatalytic efficiency. Herein, an uniform CdS nanorods grown directly on one-dimensional α-FeO nanotube arrays (NTAs) are successfully synthesized by a facile hydrothermal method and the constructed heterojunction can be a kind of efficient and recyclable photocatalysts. Successful deposition of CdS nanorods onto the α-FeO NTAs is verified by field emission scanning electron microscopy(FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS). UV-Vis diffuse reflectance spectroscopy indicates that α-FeO/CdS NTAs possess the intense visible light absorption and also display a red-shift of the band-edge compared with the pure α-FeO NTAs. The as-obtained α-FeO/CdS NTAs display excellent photocatalytic activity for decomposition of methylene blue (MB), methyl orange (MO), and phenol under visible light illumination. Among all the tested photocatalysts, the film synthesized for 3h with good stability exhibits the best photocatalytic properties and produces the highest photocurrent of 1.43 mA/cm at 0.8 V vs. Ag/AgCl electrode, owing to its well formed heterojunction structure, effective electron-hole pair separation and direct electron transfer pathway along the CdS nanorods and α-FeO NTAs. Besides, the photogenerated holes (h) and superoxide radicals (O) play dominant roles in the photocatalytic process. On the basis of the photocatalytic results and energy band diagram, the photocatalytic process mechanism is proposed. Considering the easy preparation and excellent performance, α-FeO/CdS NTAs could be a promising and competitive visible-light-driven photocatalyst in the field of environment remediation.