Titania nanotubes self-assembled by electrochemical anodization: Semiconducting and electrochemical properties
| Autor: | L. Giorgi, Nicola Lisi, Maria Luisa Grilli, Th. Dikonimos Makris, Enrico Leoni, Rossella Giorgi, E. Salernitano |
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| Přispěvatelé: | Lisi, N., Grilli, M. L., Leoni, E., Giorgi, R., Dikonimos Makris, T., Salernitano, E. |
| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Materials science
Scanning electron microscope Impedance spectroscopy Nanotechnology 02 engineering and technology 010402 general chemistry Self-organized nanotubes Semiconducting properties Titanium oxide Electrochemical anodization 01 natural sciences Materials Chemistry Surface states Metals and Alloys Surfaces and Interfaces 021001 nanoscience & nanotechnology 0104 chemical sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Dielectric spectroscopy Amorphous solid Semiconducting propertie Field electron emission Self-organized nanotube Chemical engineering Saturated calomel electrode Linear sweep voltammetry Charge carrier 0210 nano-technology |
| Popis: | Titania nanotubes (TNT), thanks to their semiconducting properties, have received wide attention for application in many fields such as photoelectrolysis, dye sensitized solar cells, photocatalysis, and sensors. In this work, highly ordered TNT were grown by controlled electrochemical anodization of titanium sheets. Scanning electron microscope equipped with a field emission gun and electrochemical DC/AC techniques was used to characterize the TNT. Semiconducting properties were investigated through linear sweep voltammetry and electrochemical impedance spectroscopy. Donor concentration (Ned) was obtained by recording Mott-Schottky plots. The high Ned of TNT (around 1026 m-3) allows an optimal electron transfer when used as photoelectrode. Frequency dispersion of flat band potential from Mott-Schottky plots (-0.38 ÷ + 0.40 V vs. saturated calomel electrode, SCE) was used as an indicator of the amorphous semiconductor behaviour. The dispersion of flat band in heat treated samples was extremely reduced (0.48-0.51 V vs. SCE) because of the conversion to crystalline semiconductor. The depth of space charge was comparable to the TNT wall thickness, meaning that the entire TiO2 nanotube walls formed the space charge layer. Considering the high charge carrier concentration, we can hypothesise a high density of electronic defects (e.g., surface states) that enhances the electron transport by percolation inside a porous photoelectrode. The transition from amorphous to crystalline structure of TNT was detected from the change of semiconducting properties and confirmed by Raman spectroscopy. © 2015 Elsevier B.V. All rights reserved. |
| Databáze: | OpenAIRE |
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