Fabrication Of TiO2 Nanotube Arrays Research Articles

High-throughput fabrication of TiO2 nanotube arrays by 4-electrode bipolar electrochemistry

Size tunable TiO2 nanotube arrays (TNAs) are promising materials in biomedical applications and photocatalysis. Rapidly screening an optimal dimension of TNAs under various application conditions is challengeable, for which a high-throughput TNA platform is significantly important. Herein, 4-electrode bipolar electrochemistry (4EBPE) was proposed to implement a controllable fabrication of gradient TNAs. Theoretical calculations showed that the shift of cathode/anode boundary is the principal cause of uncontrollable overpotential distribution over the bipolar electrode (BPE) and undesirable gradient of the TNAs for normal bipolar anodization. The 4EBPE could improve the anodization process of gradient TNAs through an extra imposed overpotential on the BPE. The dimension of TNAs fabricated by 4EBPE is linearly dependent on the position over the electrode, and the gradient ranges of TNAs can be freely controlled through the electrochemical parameters. The gradient TNAs fabricated by the 4EBPE are promising platforms for high-throughput research.

All-solid-state formation of titania nanotube arrays and their application in photoelectrochemical water splitting

The present work demonstrates for the first time the facile fabrication of TiO2 nanotube arrays (TNTAs) by a fluoride-free solid-state anodization process using LiClO4 containing solid polymeric electrolyte. The resulting nanotubes were tested for photoelectrochemical water splitting. The elimination of liquid electrolytes in electrochemical anodization constitutes a paradigm shift for the formation of nanoporous and nanotubular metal oxides. Our results open a new area of research that uses the distinctive properties of solid polymer electrolytes to achieve targeted doping and nano-morphologies. Characterization of the grown TNTAs indicated solid state anodized TNTAs to consist purely of the anatase phase of titania. The solid-state anodization process provides several advantages over conventional liquid electrolytes such as easy handling and processing, better charge transport, environmentally benign chemicals and methodology. Photoelectrochemical water splitting experiments were performed which confirmed the viability of TNTAs grown by the new solid-state process for photocatalytic applications.

Electrochemical Investigation on the Inhibitive Nature of Barrier Layer on the Growth Rate of TiO2 Nanotube Arrays

Electrochemical anodization is a cost effective and easy to scale-up method for the fabrication of TiO2 nanotube arrays. In this article we have elucidated the role of barrier layer on nanotube growth by analyzing nanotube arrays fabricated at different anodization times (1 minute – 24 hours). During the growth process, at the initial stage, a very fast growth (∼1.5 μmmin−1) is observed, which slows down as time progresses. The growth efficiency has been calculated by using the charge consumed for each specimen anodized for different time duration. The impact of barrier layer on the growth of the nanotube arrays has been studied using Electrochemical Impedance Spectroscopy (EIS) and Mott-Schottky (M-S) analysis. The thickness of the barrier layers was calculated from the barrier layer capacitance values. The minimum barrier layer resistance of 375 Ω paves the way for the very high growth rate obtained. The decrease in the carrier densities or defects (from 42 × 1019 to 1.86 × 1019 cm−3) with increase in the anodization duration limits the ion transfer rate. Thinner barrier layers (∼30 nm) with higher carrier density and lower resistance ensures rapid growth rate of nanotube arrays during anodization.

Fabrication of TiO2 nanotube arrays of different dimension for photocatalytic decomposition of IPA in air streams

TiO2 nanotube arrays (TNTs) were fabricated by anodization under various operational conditions. Dimensions of fabricated TNTs were significantly influenced by the temperature and water content of ethylene glycol-based electrolyte prepared for anodization. TNTs of longer length, larger inner diameter, and thinner wall thickness were fabricated in electrolytes of higher temperatures. For TNTs fabricated in electrolyte containing higher water contents, the relatively fast dissolution of TiO2 led to the formation of TNTs of shorter tube length and larger inner diameter. TNTs were fabricated under different anodization conditions (mainly the water content in ethylene glycol electrolyte and anodization time) to exhibit similar tube length and different inner diameters. Experiments conducted using TNTs of longer tube lengths and smaller inner diameters demonstrated higher photocatalytic decompositions of gaseous isopropyl alcohol (IPA); however, the photocatalytic application of TNTs is limited by the penetration of illumination.

In situ fabrication of TiO2 nanotube arrays sensitized by Ag nanoparticles for enhanced photoelectrochemical performance

We presented the employment of ascorbic acid as the reducing agent for the in situ deposition of Ag nanoparticles on the surface of TiO2 nanotube arrays (TiO2 NTs/Ag). The structural investigation by scanning electron microscopy and transmission electron microscopy indicated that Ag nanoparticles with average diameters of 15nm uniformly grew on TiO2 NTs walls. The possible formation mechanism of TiO2 NTs/Ag was proposed. UV–vis absorption and photoelectrochemical measurements indicated that the Ag sensitization extended the visible light absorption region, improved the photocurrent response, and enhanced solar-induced photoelectrocatalytic activities.

Fabrication of TiO2 Nanotube Arrays by Rectified Alternating Current Anodization

Anodization is a popular method of preparing TiO2 nanotube array films (TiNTs) by using direct current (DC) power as the driving voltage. In this study, three driving voltage modes, namely, the sine alternating current (sine) mode, the full-wave rectification of sine waves via four diodes (sine-4D, where D means diode) mode, and the DC mode, were used to prepare TiNTs by anodization. At 20 V, TiNTs were formed under sine-4D mode but only irregular porous TiO2 films were formed under DC mode. At 50 V, TiNTs formed under both the sine-4D and DC modes. No TiNTs formed in the sine mode anodization at either 20 or 50 V. Compared with the DC mode, the sine-4D mode required a lower oxidation voltage for TiNT formation, which suggests that sine-4D is an economical, convenient, and efficient driving voltage for TiNT preparation by anodization. The morphologies and structures of TiNT samples anodized at 50 V in the sine-4D and DC modes at different oxidation time (1, 5, 10, 30, 60, and 120 min) were analyzed. TiNT growth processes were similar between the studied modes. However, the growth rate of the films was faster under the sine-4D mode than the DC mode during the first 30 min of anodization.

Effect of Anode-Cathode Spacing on Anodic Formation of Self-Organized TiO<sub>2</sub> Nanotube Arrays

We report on the effect of anode-cathode spacing on the fabrication of TiO2 nanotube arrays by using a facile two-electrode anodization system. The experimental results show that the formation of nanotubes is affected by the anode-cathode spacing and the possible mechanism is also discussed. The as-formed TiO2 nanotube arrays were mainly examined by using a field emission scanning electron microscope. The present results are believed to be generalized to fabricate self-organized oxide nanotube arrays in other anodizing systems.

Fabrication of open-ended TiO2 nanotube arrays by anodizing a thermally evaporated Ti/Au bilayer film

Fabrication of TiO2 nanotube arrays (TNAs) with through-hole morphology is practical significance to enhance the photocatalytic activity of TNAs, as well as expanding their applications. In present work, open-ended TNAs are synthesized on a conductive Au layer by anodizing a thermally evaporated Ti/Au bilayer film. In the anodizing process, the upper Ti layer is transformed into well-aligned TNAs. The barrier layer under the growing TNAs ultimately touches the Au layer and is completely dissolved by the electrochemical etching. In order to avoid the bubble disruption of TNAs caused by the water electrolysis after the Au layer is exposed to the electrolyte, a specific non-aqueous electrolyte is used. The XRD results reveal that the as-formed open-ended TNAs are amorphous and can be transformed into anatase by annealing at 350°C.

Tunable Fabrication of TiO2 Nanotube Arrays with High Aspect Ratio and its Application in Dye Sensitized Solar Cell

TiO2 nanotube arrays were fabricated by anodization of titanium foils in the viscous nonaqueous electrolytes.Effects of anodization parameters on TiO2 nanotube were intensively studied.The photo-electrochemical property of dye sensitized solar cell(DSSC) based on TiO2 nanotube arrays was tested and the influence of TiO2 nanotube morphology on the performance of DSSC was investigated.The result indicates that the growth of TiO2 nanotube arrays with high aspect ratio depends highly on the nonaqueous solution which is enhanced by the applied potential and anodizing time.TiO2 nanotube arrays with aspect ratio up to 313.6 are fabricated in 0.5wt%NH4F in glycerol glycol at 50V for 17h.DSSC based on TiO2 nanotube arrays(fabricated in 0.5wt%NH4F in glycerol at 40V for 13h)exhibits an open circuit potential of 0.723V,2.15mA/cm2 short circuit current density.