Abstract
We reported Ce and its oxide-modified TiO2 nanotube arrays (TNTs) and their semiconductor properties. The TNTs were prepared by anodic oxidation on pure Ti and investigated by electrochemical photocurrent response analysis. Then, the TNT electrodes were deposited of Ce by cathodic reduction of Ce(NO3)3 6H2O. After deposition, the TNT electrodes were fabricated by anodic oxidation at E = 1.0 V(SCE) for various electricity as Ce-Ce2O3-CeO2 modification. The Ce-deposited TNTs (band gap energy Eg = 2.92 eV) exhibited enhanced photocurrent responses under visible light region and indicated more negative flat band potential (Efb) compared with the TNTs without deposition. After anodic oxidation, the mixed Ce and its oxide (Ce2O3-CeO2)-modified TNT photoelectrodes exhibited higher photocurrent responses under both visible and UV light regions than the TNTs without deposition. The photocurrent responses and Efb were found to be strongly dependent on the contents of Ce2O3 and CeO2 deposited on TNTs. A new characteristic of Eg = 2.1 ± 0.1 eV was investigated in the Ce2O3- and CeO2-modified photoelectrodes. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were also employed to characterize various modified TNTs photoelectrodes.
Highlights
One-dimensional TiO2 nanotubes arrays (TNTs) can provide higher surface area [1] and higher interfacial electricity transfer rate rather than spherical particles [2]
The rare earth metal Ce with f electron distribution has received extensive attention [5] for its energy levels located in the forbidden band of TiO2 which can form additional levels to accelerate the separation of electrons and holes [6]
A potential E = −6 V was applied in the threeelectrode system until a total electricity Q = 0.01 C to reduce Ce3+ into elemental Ce deposition on TNTs
Summary
One-dimensional TiO2 nanotubes arrays (TNTs) can provide higher surface area [1] and higher interfacial electricity transfer rate rather than spherical particles [2]. The rare earth metal Ce with f electron distribution has received extensive attention [5] for its energy levels located in the forbidden band of TiO2 which can form additional levels to accelerate the separation of electrons and holes [6]. The oxides of Ce indicate different semiconductor characteristics such as Ce2O3, with narrow bandgap energy (Eg = 2.4 eV), which is able to absorb visible light and CeO2, with wide bandgap energy (Eg = 3.16 eV), which can. Different proportions of Ce mixtures (Ce, CeO2, and Ce2O3) deposited TNTs were prepared to investigate their photocurrent responses and semiconductor characteristics
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