Thermal annealing of ordered TiO2 nanotube arrays with water vapor-assisted crystallization under a continuous gas flow for superior photocatalytic performance

Michael Sebek, Tim Peppel, Henrik Lund, Igor Medic, Armin Springer, Pawel Mazierski, Adriana Zaleska-Medynska, Jennifer Strunk, Norbert Steinfeldt

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Ordered titanium dioxide nanotube arrays fabricated via electrochemical route are considered as a promising material for photocatalytic applications. Due to their amorphous character, a subsequent crystallization step is usually required. In this work, well-aligned nanotube arrays were annealed under flowing gas streams of different compositions (air/steam, air, N2/steam, N2, and O2/steam) in a temperature range from 140 to 543 °C. Under continuous gas flow, the morphology of the crystallized titanium dioxide is strongly affected by the gas atmosphere. When using a dry gas for annealing, the tube structure was almost destroyed after 1 h treatment at 473 °C. In contrast, when annealing the titania nanotube array in a water vapor/gas stream, the tube morphology can be maintained up to 543 °C and 10 h annealing time. Moreover, nanotube arrays crystallized in a flowing gas atmosphere containing water vapor showed a significantly higher photocatalytic activity for phenol degradation under UV irradiation than nanotube arrays crystallized in a dry gas stream. Reasons for this behavior might be the preservation of the tubular structure as well as a lower concentration or density of structural defects in presence of water vapor which leads to an enhanced generation of reactive oxygen species when the arrays are exposed to UV-light.

Original languageEnglish
Article number130619
JournalChemical Engineering Journal
Volume425
DOIs
StatePublished - 1 Dec 2021
Externally publishedYes

Keywords

  • Crystallization
  • Degradation
  • Nanotube array
  • Phenol
  • Titania
  • Water vapor

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