Abstract
Carbon steels (CSs) were anodized in an ethylene glycol solution containing 3 vol.% H2O and 0.1 m NH4F to coat with nanotube arrays film. The as anodized nanotube arrays film were annealed in argon atmosphere at various temperatures ranging from 250 to 550 °C for 4 h. The morphology and crystal phases of the film developed after annealing processes were examined using field emission scanning electron microscopy, X-ray diffraction. Morphology transforms from nanobube arrays to nanotube bundles at 250 °C, to nanobube bundles with nanoflakes at 350 and 450 °C, to nanotube bundles with nanobelts at 550 °C. Amorphous transformed completely into maghemite at 350 °C and hematite with minor magnetite at 450 and 550 °C. Diffuse reflectance ultraviolet and visible spectra revealed iron oxide nanotube film annealed at 350 °C, or higher than 350 °C behaved tremendous absorbance ability in visible spectra range. Mott–Schottky analysis and linear scan voltammetry were performed in 1 m NaOH to show that iron oxide nanotube film annealed at 450 °C exhibited best charge carrier transfer ability upon illumination and superior photoelectrochemical properties compared with the films annealed at other temperatures. The film annealed at 450 °C displayed the photocurrent density of 0.13 mA cm−2 at 0.2 VAg/AgCl, but the film annealed at other temperatures with the photocurrent densities of lower than 0.05 mA cm−2 at 0.2 VAg/AgCl. The morphology and phase transform of iron oxide nanotube film at different annealing temperature results in the change of their photoelectrochemical properties.
Original language | English |
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Pages (from-to) | 1278-1284 |
Number of pages | 7 |
Journal | Surface and Interface Analysis |
Volume | 48 |
Issue number | 12 |
DOIs | |
State | Published - 1 Dec 2016 |
Keywords
- annealing effect
- anodization
- carbon steel
- iron oxide nanotube
- photoelectrochemical water splitting