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

Abstract

TiO2/CuxOy nanotube (NT) arrays were synthesized using the anodization method in the presence of ethylene glycol and different parameters applied. The presence, morphology, and chemical character of the obtained structures was characterized using a variety of methods—SEM (scanning electron microscopy), XPS (X-ray photoelectron spectroscopy), XRD (X-ray crystallography), PL (photoluminescence), and EDX (energy-dispersive X-ray spectroscopy). A p-n mixed oxide heterojunction of Ti-Cu was created with a proved response to the visible light range and the stable form that were in contact with Ti. TiO2/CuxOy NTs presented the appearance of both Cu2O (mainly) and CuO components influencing the dimensions of the NTs (1.1–1.3 µm). Additionally, changes in voltage have been proven to affect the NTs’ length, which reached a value of 3.5 µm for Ti90Cu10_50V. Degradation of phenol in the aqueous phase was observed in 16% of Ti85Cu15_30V after 1 h of visible light irradiation (λ > 420 nm). Scavenger tests for phenol degradation process in presence of NT samples exposed the responsibility of superoxide radicals for degradation of organic compounds in Vis light region. Inactivation of bacteria strains Escherichia coli (E. coli), Bacillus subtilis (B. subtilis), and Clostridium sp. in presence of obtained TiO2/CuxOy NT photocatalysts, and Vis light has been studied showing a great improvement in inactivation efficiency with a response rate of 97% inactivation for E. coli and 98% for Clostridium sp. in 60 min. Evidently, TEM (transmission electron microscopy) images confirmed the bacteria cells’ damage.

Morphology- and Crystalline Composition-Governed Activity of Titania-Based Photocatalysts: Overview and Perspective

“…Titania nanotubes, nanowires, 1D-oriented nanopores, and other 1D nanostructures (such as nanorods) have been extensively investigated for various applications, including solar cells, photocatalysis, batteries, filtration membranes, biomedical use, and as templates for the synthesis of other nanostructures [5,[130][131][132][133]. Kasuga et al were probably the first who prepared titania nanotubes (TNTs) by the chemical method [134,135], whereas Imai et al obtained TNTs in porous alumina membrane by a deposition technique [136].…”

“…It should be pointed that different morphologies could be obtained by changing the anodization conditions, e.g., TNTs, as well as the mesoporous and nanoporous structures, as shown in Figure 11. Recently, a very interesting approach has been proposed by the Zaleska-Medynska group, i.e., the anodization of titanium alloys to prepare modified titania by a one-step reaction, e.g., TiO 2 /Ag 2 O/Ag [132] and TiO 2 /Cu x O y [131] from Ti/Ag and Ti/Cu alloys, respectively. alumina membrane by a deposition technique [136].…”

Nanomaterials for Environmental Purification and Energy Conversion

“…Accordingly, the Special Issue "Nanomaterials for Environmental Purification and Energy Conversion" is a collection of 17 papers, including 16 research papers and one review. Eleven papers present heterogeneous photocatalysis for efficient degradation of organic pollutants (phenol [17,18], 2-propanol [19], dyes [20][21][22], humic acid [23]), inactivation of microorganisms (Escherichia coli, Staphylococcus epidermidis [24], Bacillus subtilis, and Clostridium sp. [18]), H 2 evolution [25], and CO 2 reduction [26,27].…”

“…Eleven papers present heterogeneous photocatalysis for efficient degradation of organic pollutants (phenol [17,18], 2-propanol [19], dyes [20][21][22], humic acid [23]), inactivation of microorganisms (Escherichia coli, Staphylococcus epidermidis [24], Bacillus subtilis, and Clostridium sp. [18]), H 2 evolution [25], and CO 2 reduction [26,27]. Six other papers focus on conventional catalysis ("dark" reactions), reporting efficient H 2 production [28,29], synthesis of ethanol and butanol [30], direct conversion of CO 2 and methanol to dimethyl carbonate [31], water purification [32], and advanced characterization of catalysts by X-ray absorption fine structure (EXAFS) spectroscopy [33].…”

“…Six other papers focus on conventional catalysis ("dark" reactions), reporting efficient H 2 production [28,29], synthesis of ethanol and butanol [30], direct conversion of CO 2 and methanol to dimethyl carbonate [31], water purification [32], and advanced characterization of catalysts by X-ray absorption fine structure (EXAFS) spectroscopy [33]. The majority of studies have been performed with particulate catalysts (nanoparticles (NPs)), but organized nanostructures, such as nanotubes (TiO 2 /Cu x O y [18], carbon nanotubes (CNTs) [30,32]) and nanowires (CeO 2 [31]) have also been used.…”