Templateless Nanofiber Photoelectrode Prepared Using Mild Hydrothermal Conditions

Abstract

The templateless synthesis of titania nanofibers on a Ti foil using a simple and mild approach has been demonstrated. The growth of TiO 2 nanofibers with a diameter of 15 nm on a Ti foil was obtained when Ti foil was hydrothermally treated at 30-95°C in the presence of TiO 2 powder in 0.1-10 M NaOH solutions. Scanning electron microscopy ͑SEM͒ observations revealed that TiO 2 seeds clearly appeared on the TiO 2 foil within 20 s and that fiber-shaped films were formed in less than 90 s. A potential formation mechanism for the titania nanofibers on Ti foil is proposed in terms of SEM observations. After the seeds were formed on the Ti foil, the end-on attachments of the nanoparticles resulted in the linear growth of fiberlike structures, upon which nanoparticles were then self-organized to form solid nanofibers. By calcining at a temperature of 550°C, the TiO 2 nanofiber films exhibited optimal photocatalytic activity due to a fine nanofiber structure and good crystallinity of the anatase-rutile mixed phase. The photocatalytic and photoelectrocatalytic activities of the TiO 2 nanofiber electrodes were also assessed with respect to their ability to degrade methyl orange.Titania is used in diverse applications such as in paint pigments, as an absorbent, in lithium batteries, in sensing applications, in photovoltaic solar cells, and in photocatalysis. 1-6 Nanostructured titania films especially merit attention due to their high surface-to-volume ratio and their interesting properties. Several methods have been explored to produce nanostructured titania nanotubes such as templating, 7-9 anodic oxidation, 10 and hydrothermal reactions. 11-17 Among them, the hydrothermal approach without the need for a template is relatively simple and straightforward.Titania nanotubes prepared by hydrothermal processing were introduced by Kasuga et al., who synthesized nanotubes by chemically treating sol-gel-derived fine TiO 2 -based powders initially with 5-10 M NaOH aqueous solutions at 110°C for 20 h. 11 The investigation suggested titania nanotubes were formed in the subsequent acid treatment following the alkali treatment stage. 12 Seo et al. showed that anatase phase powder digested at 150°C for 12 h with 5 M NaOH has the highest specific surface area. 13 Titania nanotubes and nanorods were synthesized by treating rutile with 10 M NaOH for 48 h at 150 and 180°C, respectively. 14 In order to obtain large oriented arrays and continuous films of TiO 2 nanotubes, the Ti foil containing the predeposited TiO 2 nanoparticles was reacted with 10 M NaOH at 95-160°C for 6 h. 15 However, the preparation conditions for titania nanotubes as cited in the literature are severe ͑i.e., high concentrations, high temperatures, and long hydrothermal durations by autoclaving͒. Moreover, much effort has been directed toward the use of TiO 2 powders as a means to form nanotubes, while similar materials grown on films are rarely mentioned. Although Tian et al. prepared large arrays of TiO 2 -based nanotubes on continuous films, the Ti substrate needed t...

Turning Bulk Titanium into Rutile Nanorods in One Step: Synthesis, Mechanism, and Application

“…The concentration of MO during reaction (denoted as C) was monitored by an UV−vis spectrophotometer (PerkinElmer's LAMBDA 35) at 465 nm wavelength. 11 At each time point, a 2 mL solution was extracted, and the UV−vis measurement was subsequently measured. Afterward, the extracted solution was introduced back into the cell to…”

“…Nanostructured TiO 2 materials are of great interest for their possible applications in the field of fiber-optic cable sensors, fuel cells, photocatalysts, electrochemical water splitting, and dye sensitized solar cells. − The properties and applications of nanostructured TiO 2 materials are strongly related to their phase, dimension, and surface structure. As such, tremendous effort has been directed toward the design and synthesis of TiO 2 nanomaterials with various kinds of surface structure. ,− To date, TiO 2 nanostructures in the forms of tubes, rods, fibers, wires, flowers, spheres, and belts have been successfully fabricated by various methods. − Among them, several techniques have been developed for the fabrication of TiO 2 nanofibers/nanorods, viz., the sol–gel template process, electrospinning, and hydrothermal treatment. ,,− TiO 2 nanofibers with diameters of 22–300 nm have been synthesized using a sol–gel method with self-assembled supramolecular structures and alumina membranes as the templates . Electrospinning has also been extensively explored to synthesize polymetric and oxide nanofibers with diameters ranging from tens of nanometers to several micrometers .…”

“…Titanium tetrachloride has also been used as the starting reagent for the growth of rutile nanorods under hydrothermal process conditions in different solutions . However, all of the methods mentioned above involve using Ti-containing precursor materials, such as TiO 2 nanoparticles, titanium isopropoxide, titanium tetrachloride, or tetrabutyltitanate to initiate the crystal growth, and all require multiple steps in the fabrication process. ,,− Therefore, it is clear that a one-step method is a significant improvement in the manufacture of TiO 2 nanomaterials. In addition, synthetic TiO 2 nanocrystals with well-controlled morphology is of great importance in applications associated with their field emission properties .…”

Solvent-controlled formation and photoelectrochemical sensing properties of 3-dimensional TiO2 nanostructures

“…Other work also confirmed the formation of the sodium titanate layer composed of nanoparticles after Ti foil was thermally treated in a NaOH solution for a very short time. 37 This layer contained some statistically distributed ''breakdown sites'' when the layer was above a critical oxide thickness, which were closely related to the volume change accompanying the oxidation of titanium. In this period, these pits grew and pronounced dissolution of the sodium titanate at the bottom of the pits took place that made them significantly deeper, to become cracks.…”

Sensor response of sol–gel multiwalled carbon nanotubes-TiO2 composites deposited by screen-printing and dip-coating techniques

“…Titanium dioxide has been used as a building block to develop new nanoarchitectures with advanced properties for achieving high-performance sensing [1][2][3][4], improved photocatalytic power [5,6], and superior photovoltaic results [7,8]. Similarly, carbon nanotubes (CNTs) are graphene sheets rolled up to build seamless tubes with nanometric diameters with outstanding electronic, chemical and physical properties, in such a way that the design of carbon hybrid materials with potential applications as efficient molecular sensors has become an active area of research [9][10][11][12][13][14][15][16][17].…”