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- Title
Thermal Ramping Rate during Annealing of TiO<sub>2</sub> Nanotubes Greatly Affects Performance of Photoanodes.
- Authors
Raza, Waseem; Hwang, Imgon; Denisov, Nikita; Schmuki, Patrik
- Abstract
Herein, highly ordered TiO2 nanotube (NT) arrays on a Ti substrate is synthesized in a fluoride-containing electrolyte, using the electrochemical anodization method, which yields amorphous oxide tubes. The effects of different thermal annealing profiles for the crystallization of the amorphous TiO2 NTs are studied. It is found that the temperature ramping rate has a significant impact on the magnitude of the resulting photocurrents (incident photon-to-current conversion efficiency [IPCE]) from the tubes. No appreciable changes are observed in the crystal structure and morphology of the TiO2 NTs for different annealing profiles (to a constant temperature of 450 °C). The electrochemical properties of the annealed TiO2 NTs are investigated using intensity-modulated photocurrent spectroscopy (IMPS), open-circuit potential decay, and Mott-Schottky analysis. The results clearly show that the annealing ramping rate of 1 °C s-1 leads to the highest IPCE performance. This beneficial effect can be ascribed to a most effective charge separation and electron transport (indicating the least amount of trapping states in the tubes). Therefore, the results suggest that controlling the annealing ramping rate is not only a key factor affecting the defect structure but also a powerful tool to tailor the physical properties, and photocurrent activity of TiO2 NTs.
- Subjects
TITANIUM dioxide; NANOTUBES; OPEN-circuit voltage; ANNEALING of metals; ELECTRON transport; CRYSTAL morphology; CRYSTAL structure
- Publication
Physica Status Solidi. A: Applications & Materials Science, 2021, Vol 218, Issue 12, p1
- ISSN
1862-6300
- Publication type
Article
- DOI
10.1002/pssa.202100040