Self-Organized TiO2–MnO2 Nanotube Arrays for Efficient Photocatalytic Degradation of Toluene

Abstract

Vertically oriented, self-organized TiO2–MnO2 nanotube arrays were successfully obtained by one-step anodic oxidation of Ti–Mn alloys in an ethylene glycol-based electrolyte. The as-prepared samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis absorption, photoluminescence spectroscopy, X-ray diffraction (XRD), and micro-Raman spectroscopy. The effect of the applied potential (30–50 V), manganese content in the alloy (5–15 wt. %) and water content in the electrolyte (2–10 vol. %) on the morphology and photocatalytic properties was investigated for the first time. The photoactivity was assessed in the toluene removal reaction under visible light, using low-powered LEDs as an irradiation source (λmax = 465 nm). Morphology analysis showed that samples consisted of auto-aligned nanotubes over the surface of the alloy, their dimensions were: diameter = 76–118 nm, length = 1.0–3.4 μm and wall thickness = 8–11 nm. It was found that the increase in the applied potential led to increase the dimensions while the increase in the content of manganese in the alloy brought to shorter nanotubes. Notably, all samples were photoactive under the influence of visible light and the highest degradation achieved after 60 min of irradiation was 43%. The excitation mechanism of TiO2–MnO2 NTs under visible light was presented, pointing out the importance of MnO2 species for the generation of e− and h+.

Mixed oxide nanotubes in nanomedicine: A dead-end or a bridge to the future?

“…8 a–e shows the surface and cross-sectional SEM micrographs of nanotube arrays in the absence and presence of 3–10% Mn, where the diameter and length is ~110 nm and ~3.5 μm, respectively. Vertically oriented, self-ordered MONs (TiO 2 –MnO 2 NTs) were also prepared by single-step anodization process of Ti–Mn alloys in EG electrolyte [ 187 ]. From the microstructural assessments, the anodized specimens were composed of auto-aligned nanotubes over the surface of the Ti–Mn alloys, where the diameter, length and wall thickness of the MONs are in the range of 76–118 nm, 1.0–3.4 μm and 8–11 nm, respectively.…”

Electrochemically Obtained TiO2/CuxOy Nanotube Arrays Presenting a Photocatalytic Response in Processes of Pollutants Degradation and Bacteria Inactivation in Aqueous Phase

“…The first represents the idea of using larger structures, which can be further controlled in the nanoscale, whereas the second includes the miniaturization of components with the self-assembly process. There are a variety of forms of modified nanostructures-nanoparticles, nanotubes (NTs), nanosheets, or nanocubes obtained using many methods such as electrodeposition [6], self-assembly examples, atomic layer deposition, or anodization [8][9][10].…”

Growth, Structure, and Photocatalytic Properties of Hierarchical V2O5–TiO2 Nanotube Arrays Obtained from the One-step Anodic Oxidation of Ti–V Alloys

“…Nevertheless, despite the proven visible light absorption of V 2 O 5 -TiO 2 nanotubes, there is still a lack of data regarding the photoactivity of the V 2 O 5 -TiO 2 NTs obtained from the anodization of Ti-V alloys. In our previous work [ 63 ], self-organized TiO 2 -MnO 2 NTs were successfully obtained by the one-step anodization of Ti-Mn alloys in a fluoride-containing ethylene glycol (EG)-based electrolyte. The as-prepared layers were highly organized and showed visible-light photoactivity towards the degradation of toluene in the gas phase.…”