Synthesis and Photocatalytic Activity of Highly Ordered TiO₂ and SrTiO₃/TiO₂ Nanotube Arrays on Ti Substrates

Abstract

Highly ordered TiO2 nanotube arrays (TiO2‐NTAs) are produced by electrochemical anodization of a Ti foil in ammonium fluoride (NH4F)–ethylene glycol solution. Photocatalytic (PC) investigations indicate that the length of the NTAs plays an important role in their photoactivity. The PC activity increases initially with the NT length and then decreases and the optimum length that yields the highest PC is 6.2 μm for TiO2‐NTAs. The TiO2‐NTAs are further converted to heterojunction strontium titanate (SrTiO3)/TiO2‐NTAs by a hydrothermal reaction in Sr(OH)2 solution. As the hydrothermal reaction proceeds, more TiO2 is converted into SrTiO3 and the thickness of the SrTiO3 layer increases. The SrTiO3/TiO2‐NTAs exhibit variable PC activities that depend on the hydrothermal reaction time, and the SrTiO3/TiO2‐NTAs hydrothermally treated for 1 h or less have enhanced PC properties. The advantage of combining TiO2 and SrTiO3 stems from the difference in the flatband potential, thereby improving the separation of the photogenerated electron–hole pairs and consequently the PC activity.

One-Dimensional Titanium Dioxide Nanomaterials: Nanotubes

“…This is in line with several other investigations by various researchers 505,[681][682][683][684] . However, there are a number of investigations that either report a maximum in the photocatalytic activity for tube layer thicknesses around 3-7 μm, 151,681,684 or the absence of an influence of the tube length 685 .…”

Photoelectrochemical properties of TiO2/SrTiO3 combined nanotube arrays

“…This core-shell nano-structure could lower the charge recombination by building up an energy barrier at the semiconductor/ electrolyte interface and, thus, retard the reaction between the photo-generated electrons and the redox species in electrolyte [8][9][10]. The shell layer should be more negative than that of the core in order to establish an energy barrier.…”

Preparation and characterization of nanocrystalline and mesoporous strontium titanate thin films at room temperature

“…9 Recently, interest in titanium-based oxides with the perovskite crystalline phase of the form of ABO 3 for photocatalytic applications has increased. [10][11][12] These oxides have been regarded as functional materials because of their excellent dielectrical, ferroelectrical, pyroelectrical, piezoelectrical, photorestrictive, magnetorestrictive, and electro-optical characteristics. 13,14 Strontium titanate (SrTiO 3 ), being one member of this well-known family, has a broad range of the above-mentioned properties and can be used as a photocatalyst material.…”