Synthesis and Enhanced Visible-Light Photoelectrocatalytic Activity of p-n Junction BiOI/TiO2 Nanotube Arrays

p-n junction BiOI/TiO2 nanotube arrays (NTs) were prepared by coating BiOI on the tube wall of the self-organized TiO2 NTs using a novel impregnating-hydroxylation method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis absorption spectroscopy. The photoelectrocatalytic (PEC) activity toward degradation of methyl orange (MO) aqueous solutions under visible-light irradiation (lambda > 420 nm) by p-n junction BiOI/TiO2 NTs was investigated. The results from the current study demonstrate that the as-prepared BiOI/TiO2 counterparts due to the synergetic effects of several factors including the strong visible absorption the formation of p-n junction, and the impact of external electrostatic field. The proposed mechanism responsible for the enhanced performance was further confirmed by the transient photocurrent response experiments.