Preparation and enhanced visible-light driven photocatalytic properties of Au-loaded TiO2 nanotube arrays

Abstract

In this work, Au nanoparticles loaded on TiO2 nanotube arrays (Au/TNTAs) were prepared by photodeposition of Au nanoparticles on the surface of TNTAs using HAuCl4⋅3H2O as gold source. The loading amount of Au nanoparticles was adjusted by different loading cycles of photoreduction of the chloroauric acid solution. The as-prepared samples were characterized by field-emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Ultraviolet–visible spectroscopy (UV–vis) and fluorescence emission spectrum. The photocatalytic activities of the as-prepared Au/TNTAs composite photocatalysts were evaluated by photodegradation of Rhodamine B (RhB) under visible-light irradiation. The experimental results showed that the photocatalytic activities of Au/TNTAs were significantly affected by the loading amount of Au nanoparticles. Compared with the unmodified TNTAs, the sample of Au/TNTAs(I) (0.68wt% Au) exhibited obviously enhanced photocatalytic activity in the degradation of RhB under visible light illumination, which could be attributed to the increased photoresponse both in the UV and in the visible region, and high electron–hole separation efficiency resulting from the potential gradient established by the Schottky barrier between TNTAs and Au nanoparticles. With the increase of the loading amount of Au nanoparticles, the photocatalytic activities of Au/TNTAs were on the contrary reduced, which could be ascribed to the weaker ultraviolet light absorption and the less photoactive surface area of TNTAs as well as the possible additional e−−h+ recombination centers derived from the excessive loading of the large Au nanoparticles.