Photoelectrocatalytic performance of TiO2 nanoparticles incorporated TiO2 nanotube arrays

Highly ordered TiO2 nanotube arrays decorated by TiO2 nanoparticles were prepared via electrochemical anodization method, followed by evaporation induced self-assembly (EISA) strategy. Their photocatalytic (PC) and photoelectrocatalytic (PEC) degradation performance on different dyes were investigated. The dyes used were methylene blue (MB), methyl orange (MeO), rhodamine B (RhB) and reactive brilliant red (K-2G). The structure and compositions of photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The optical properties of the samples were evaluated by UV–vis spectra. Effects of the incorporation of TiO2 nanoparticles on the charge transfer rate and charge carrier concentration of the TiO2 nanotube arrays during the photocatalytic and photoelectrocatalytic reactions were investigated with electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. In spite of the negative effects such as the decreased absorption in UV region and increased charge transfer resistance, incorporation of TiO2 nanoparticles into TiO2 nanotube arrays was found to not only increase the surface area of TiO2 nanotube arrays, but also enhance the width of space charge layer which promotes the separation of the photo-generated hole/electron pairs efficiently under external bias. Moreover, anodic bias can improve the degradation rates of anionic dyes more than cationic dyes.

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► TiO2 nanotube arrays decorated by TiO2 nanoparticles were prepared.
► Decoration decreases absorption in UV region.
► Decoration increases the width of space charge layer.
► Decoration improves the photoelectrocatalytic performance of nanotube arrays.