N-doped TiO2 nanotube array photoelectrode for visible-light-induced photoelectrochemical and photoelectrocatalytic activities

N-doped TiO2 nanotube arrays (TiO2NTs) were prepared by hydrothermal treatment of the crystalline TiO2NTs, and characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (DRS). The highly ordered TiO2NTs with an inner diameter of approximately 80 nm and a tube length of about 400 nm were obtained. XRD patterns showed that the TiO2 nanotube arrays before and after N doping were anatase. XPS analysis indicated that N was doped into the TiO2 lattice. A shift of the absorption edge to a low energy was observed from DRS. N-doped TiO2NTs electrode exhibited higher photoelectrochemical and photoelectrocatalytic activities than the undoped TiO2NTs electrode. The electrochemical impedance spectroscopy and photoluminescence spectra confirmed that doping N promoted the separation of the photogenerated electrons and holes.