Abstract
TiO2nanotubes (TNTs) promoted by copper (5%) (Cu-TNT) and iron (5%) (Fe-TNT) were prepared for visible-light photocatalysis. By X-ray absorption near edge structure (XANES) spectroscopy, it is found that the enhanced photocatalytic degradation of methylene blue (MB) on Cu-TNT and Fe-TNT is associated with the predominant surface photoactive sites A2((Ti=O)O4). By extended X-ray absorption fine structure (EXAFS) spectroscopy, the dispersed copper and iron also cause increases in the Ti–O and Ti–(O)–Ti bond distances by 0.01-0.02 and 0.04-0.05 Å, respectively. The decreased Ti–O bonding energy may lead to an increase of photoexcited electron transport. The copper- or-iron promoted TNT can thus enhance photocatalytic degradation of MB under the visible-light radiation.
Highlights
Titanium nanotubes (TNTs) having a high surface area, chemical stability, and sunlight sensitization have been employed for potential applications in photoinduced reactions [1], sensitized electrodes [2, 3], and driven water cleavage for hydrogen generation [4]
By X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS), Jang and coworkers [11] found that the surface iron species were composed of iron hydrate on TNT (Fe-TNT)
The energy dispersive X-ray spectrometry (EDS) spectra indicate that about 5.3% of Cu and 4.2% of Fe are dispersed on the Cu-TNT and Fe-TNT, respectively
Summary
Titanium nanotubes (TNTs) having a high surface area, chemical stability (under alkali or acidic conditions), and sunlight sensitization have been employed for potential applications in photoinduced reactions [1], sensitized electrodes [2, 3], and driven water cleavage for hydrogen generation [4]. It was found that the nitrogendoped TiO2 nanotube (N-TNT) thin film was not very effective for photocatalytic remediation of oil spill on seawater under the visible-light radiation. Transition metals such as chromium, iron, nickel, copper, and zinc have been considered as promoters for improving the photoactivity of TNTs. Zhang et al [10] demonstrated that the Cr2O3/TNT nanocomposite could enhance photocatalytic yield of H2 under visible-light. The Fe-TNT had a greater photocurrent generation but poor photocatalytic performances for water splitting and dye degradation. Nickelintercalated TNT had a greater photocatalytic yield of H2 than the TNT under ultraviolet (UV) illumination [12]. A nanosize ZnO decorated TNT was preferable for rhodamine B degradation under UV light [14]
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