Ordered TiO₂ Nanotubes with Improved Photoactivity through Self-organizing Anodization with the Addition of an Ionic Liquid: Effects of the Preparation Conditions

Abstract

Modifying the geometric and surface parameters of oriented TiO 2 nanotubes (NTs) is beneficial to the utilization of solar energy for chemical reactions, and this performance may be further improved. Thus, the effects of adding an ionic liquid (IL), 1-butylpiridinium chloride [BPy][Cl], and the effects of the water content and preparation conditions on the surface morphological, physicochemical, photocatalytic, and photoelectrochemical properties of TiO 2 NTs were thoroughly examined and presented. The anodic oxidation of Ti foil in an organic electrolyte containing a small amount of [BPy][Cl] allowed for obtaining IL_NTs with a well-ordered structure, even at low voltages (10 V). Additionally, the application of [BPy][Cl] enabled one of the geometric parameters of the IL_NTs, namely, the diameter, to be tuned, whereas the length remained the same (i.e., control over the diameter was first noted). Improvements in the photocatalytic and photoelectrochemical activities of the IL_NTs in comparison with those of the pristine sample were observed (approximately 2.5 times higher due to the better utilization of incident photons). It is evident that the most significant parameter to influence the photoactivity was the electrolyte composition, especially the water and IL contents (15 vol. % and 0.01 wt. %, respectively). Consequently, the interaction between [BPy][Cl] and the TiO 2 NT surface was demonstrated by X-ray photoelectron spectroscopy (XPS) results.

One Step before Synthesis: Structure–Property–Condition Relationship Models to Sustainable Design of Efficient TiO2-Based Multicomponent Nanomaterials

“…The data from 113 TiO 2 -based NTs modified by metal and non-metal nanoparticles derived from the literature were collected into one matrix ( Table S1 ) [ 11 , 12 , 13 , 14 , 15 , 16 ]. The designed TiO 2 -based NTs were characterized by experimental conditions, structural modification of TiO 2 -based NTs, and photocatalytic properties ( Table S2 ).…”

“…The HCA indicates that TiO 2 -based NTs were grouped into nine clusters of self-organized TiO 2 nanotube arrays interlaced with metal and non-metals particles. Each cluster differs from the others in terms of the presence of metal and non-metal nanoparticles that belong to a given group, such as (A) well-ordered nanotubes in the presence of different types of ionic liquids (TiO 2 /ILs) [ 13 ], (B) hierarchical V 2 O 5 –TiO 2 NPs obtained from Ti-V alloys (TiO 2 /V 2 O 5 ) [ 20 ], (C) TiO 2 –MnO 2 NPs obtained from alloys (TiO 2 /MnO 2 ), (D) rare-earth metals-modified TiO 2 NTs (TiO 2 /REE) [ 16 ], (E) calcinated titanium dioxide nanotubes [ 21 ], (F) monometallic-modified TiO 2 (Er, Yb, Ho, Tb, Gd, Pr, Cu, Ag, Bi, Pt), bimetallic modified (AgCu) and BiS quantum dots modified TiO 2 NTs [ 17 , 22 , 23 ], (G) self-organized TiO 2 interlaced with silver nanoparticles (TiO 2 /Ag 2 O) [ 15 ], (H) nitrogen doped TiO 2 NTs (TiO 2 /N) [ 14 ], and (I) nanotubes modified with the presence of ionic liquids in different conditions (TiO 2 /ILs) [ 11 , 12 ]. HCA analysis indicates that the presence of metal and non-metal elements that incorporate into the TiO 2 structure during nanotube formation is crucial for controlling the morphological features of the designed TiO 2 -based NTs.…”

“…The PCA analysis was performed for the groups with a defined endpoint expressed as phenol photodegradation rate (λ, μmol·dm −3 ·min −1 ) under VIS and UV-VIS light ( Table S2 ). Thus, the final PCA analysis was performed for clusters selected from HCA ( Figure 1 ), such as: (A) well-ordered nanotubes in the presence of different types of ionic liquids (TiO 2 /ILs) [ 13 ], (D) rare-earth metals-modified TiO 2 NTs (TiO 2 /REE) [ 16 ], (E) calcinated titanium dioxide nanotubes [ 21 ], (F) monometallic-modified TiO 2 (Er, Yb, Ho, Tb, Gd, Pr, Cu, Ag, Bi, Pt), bimetallic modified (AgCu), and BiS quantum dots modified TiO 2 NTs [ 17 , 22 , 23 ], (G) self-organized TiO 2 interlaced with silver nanoparticles (TiO 2 /Ag 2 O) [ 15 ], (H) nitrogen-doped TiO 2 NTs (TiO 2 /N) [ 14 ], and nanotubes modified with the presence of ionic liquids in different conditions (TiO 2 /ILs) [ 11 , 12 ] ( Figure 1 ). Thus, the final PCA analysis was prepared for 32 TiO 2 -based NTs.…”

“…During the anodization process, layers of organized titanium dioxide nanotubes are obtained [ 5 ]. Many heterogeneous NP-base photocatalysts have been described in the literature, for example, different types or concentrations of an electrolyte, such as ionic liquids [ 11 , 12 , 13 ], or urea as nitrogen precursor [ 14 ], titanium foil used as working electrode interlaced with modifiers [ 15 , 16 ] or decorated by Pt nanoparticles and Bi 2 S 3 quantum dots [ 17 ].…”

Rational Regulation of Surface Free Radicals on TiO2 Nanotube Arrays via Ag2O–AgBiO3 towards Enhanced Selective Photoelectrochemical Detection

“…They can provide large inner and outer surface areas and offer a direct path for electron transmission, resulting in improved carrier transportation and light scattering ability [ 4 , 5 , 6 , 7 , 8 , 9 ]. A kind of advanced 1D morphology for high-efficient photoelectrochemical (PEC) reaction is the self-organized titanium dioxide nanotube arrays (TiO 2 NTAs) produced by electrochemical anodization on a Ti substrate [ 10 , 11 , 12 , 13 ]. Previous works have demonstrated the use of TiO 2 NTA-based photoanodes for organic pollutant degradation and renewable energy production [ 14 , 15 , 16 , 17 , 18 ], in which TiO 2 NTAs exhibit considerable performance due to their large surface area, high chemical and mechanical stability, oriented electron transport, and tunable morphologies [ 19 , 20 , 21 ].…”