Characterization of boron-doped TiO 2 nanotube arrays prepared by electrochemical method and its visible light activity

Abstract

The boron-doped TiO 2 nanotube arrays were fabricated by potentiostatic anodization of titanium in an aqueous electrolyte containing fluoride ion and sodium fluoroborate (NaBF 4). The highly ordered nanotube arrays with an inner pore diameter of approximately 80 nm and a length of 1.4 μm are obtained. X-ray photoelectron spectroscopy (XPS) data indicate that the boron atoms are successfully incorporated into the TiO 2 matrix, forming Ti–B–O bond in the sample with small amount of boron (1.5 at.%), and the chemical environment surrounding boron is more similar to that in B 2O 3 in the samples with larger amounts of boron (3.1 and 3.8 at.%). The B-doped TiO 2 nanotube arrays with a mixture of anatase phase and very little rutile phase upon thermal annealing at 500 °C for 2 h were identified by X-ray diffraction (XRD). Red shifts and enhanced absorption intensities in both UV and visible light regions are observed in the spectra of UV–vis absorption of B-doped samples. The B-doped nanotube arrays show improved photochemical capability under both simulated sunlight and UV irradiation. By comparison, the sample with 3.1 at.% of boron exhibits the best photoelectrochemical properties, and its photocurrent densities under simulated sunlight and UV irradiation are approximately 1.17 and 1.27 times of those of TiO 2 nanotube arrays, respectively. The visible photoelectrocatalytic (PEC) activities of the prepared electrodes were evaluated using atrazine as a test substance under simulated sunlight irradiation. The kinetic constant of PEC degradation of atrazine using B-doped electrode with 3.1 at.% of boron is 53% higher than that using non-doped one. A synergetic effect of the photocatalytic (PC) and electrochemical (EC) processes is observed.