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

María C Nevárez-Martínez,Patricio J Espinoza-Montero,Adriana Zaleska-Medynska,Anna Malankowska,Grzegorz Trykowski,Grażyna Szczepańska,Paweł Mazierski,Marek P Kobylański,Magda Kozak

doi:10.3390/molecules22040580

María C Nevárez-Martínez, Patricio J Espinoza-Montero + Show 7 more

Open Access

https://doi.org/10.3390/molecules22040580

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Abstract

V2O5-TiO2 mixed oxide nanotube (NT) layers were successfully prepared via the one-step anodization of Ti-V alloys. The obtained samples were characterized by scanning electron microscopy (SEM), UV-Vis absorption, photoluminescence spectroscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (DRX), and micro-Raman spectroscopy. The effect of the applied voltage (30–50 V), vanadium content (5–15 wt %) in the alloy, and water content (2–10 vol %) in an ethylene glycol-based electrolyte was studied systematically to determine their influence on the morphology, and for the first-time, on the photocatalytic properties of these nanomaterials. The morphology of the samples varied from sponge-like to highly-organized nanotubular structures. The vanadium content in the alloy was found to have the highest influence on the morphology and the sample with the lowest vanadium content (5 wt %) exhibited the best auto-alignment and self-organization (length = 1 μm, diameter = 86 nm and wall thickness = 11 nm). Additionally, a probable growth mechanism of V2O5-TiO2 nanotubes (NTs) over the Ti-V alloys was presented. Toluene, in the gas phase, was effectively removed through photodegradation under visible light (LEDs, λmax = 465 nm) in the presence of the modified TiO2 nanostructures. The highest degradation value was 35% after 60 min of irradiation. V2O5 species were ascribed as the main structures responsible for the generation of photoactive e− and h+ under Vis light and a possible excitation mechanism was proposed.

Highlights

Over the past few decades, photocatalytic processes on the surface of TiO2 have been intensively studied due to a wide range of industrially oriented applications based on the conversion of sunlight into usable chemical energy [1,2,3,4,5,6]
The series of samples synthesized from alloys with a 10 wt % vanadium content generally exhibited a sponge-like structure integrated by overlapped layers with a tubular appearance
V2 O5 -TiO2 mixed oxide layers were successfully synthesized through the one-step anodization of Ti-V alloys in a fluoride-containing ethylene glycol (EG)-based electrolyte

Summary

Introduction

Over the past few decades, photocatalytic processes on the surface of TiO2 have been intensively studied due to a wide range of industrially oriented applications based on the conversion of sunlight into usable chemical energy [1,2,3,4,5,6]. 4% of the incident solar energy [17], and by the fast recombination rate of charge carriers [18,19]. V2 O5 is a small-bandgap semiconductor (~2.3 eV) which can extend the light absorption to the visible range [33]. Photogenerated electrons and holes can be efficiently separated, and the surface charge carrier transfer rate is enhanced [34,35]

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