Fabrication, characterization and photocatalytic properties of CdS nanoparticles modified by N-doped TiO₂ NTs

Highly ordered TiO₂ nanotube arrays (TiO₂ NTs) were prepared by anodic oxidizing method on a surface of Ti substrate. Fabrication of nitrogen-doped TiO₂ nanotube arrays (N-TiO₂ NTs) was carried out by immersion in ammonia solution. CdS nanoparticles loaded N-doped TiO₂ nanotube arrays (CdS/N-TiO₂ NTs) were obtained by successive ionic layer adsorption and reaction (SILAR) technique. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL) emission spectra and ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy (DRS). The results indicate that the TiO₂ nanotube diameter and wall thickness are 100 nm to 120 nm and 20 nm to 30 nm, respectively. Moreover, the morphology and structure of the highly ordered TiO₂ NTs are not affected by N-doping. Furthermore, CdS nanoparticles are evenly distributed on the surface of TiO₂ NTs. Finally, the photocatalytic activity of CdS/N-TiO₂ NTs was evaluated by degradation of MO under visible-light irradiation. Compared with TiO₂ NTs, N-TiO₂ NTs, CdS/N-TiO₂ NTs exhibited enhanced photocatalytic properties, and the highest degradation rate of CdS/N-TiO₂NTs could reach 97.6 % after 90 min of irradiation.