A Photoelectrochemical Study of Highly Ordered TiO[sub 2] Nanotube Arrays as the Photoanodes for Cathodic Protection of 304 Stainless Steel

Abstract

Highly ordered TiO 2 nanotube ͑TN͒ arrays with a regular top porous morphology were fabricated by a facile two-step electrochemical anodization in an ethylene glycol solution containing NH 4 F and H 2 O. The morphology, crystalline phase, and composition of the TN films were characterized systematically by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and ultraviolet-visible spectroscopy. The photoelectrochemical properties of the TNs in 0.5 M NaCl solution were evaluated through electrochemical measurements under illumination and dark conditions. The nanoporous TNs exhibited a drastically enhanced photocurrent in the UV light region. The electrode potentials of 304 stainless steel coupled with the TiO 2 nanotube arrays negative shift values are no less than 354 mV under a white light irradiation. The experimental results indicated that the photoelectrochemical performance of the nanoporous-structured TNs was markedly influenced by the crystallization and the novel porous nanotubular architecture. And the nanoporous-structured TNs with a comparable high aspect ratio were able to effectively function photogenerated cathodic protection for metals under UV and visible light illumination. It is possible for such photogenerated cathodic protection to last for a period of 24 h, even in darkness.TiO 2 as a wide bandgap semiconductor has been broadly investigated in water splitting, 1 dye-sensitized solar cells, 2,3 photocatalysis, 4 and sensors 5 because of its chemical stability and unique functional properties. Compared with nanoparticles, TiO 2 nanowires or nanotubes have been reported to be superior in photoelectrochemical performance. 6-9 The advantages of TiO 2 nanotubes on titanium substrates lie in its large surface area, high aspect ratio, open hollow structure, strong adhesion to the substrate, and excellent controllability. Considering the above advantages of TiO 2 , it is highly desirable to further develop other functional applications based on this interesting one dimensional ͑1D͒ nanostructure. [9][10][11][12][13][14] Recently, intensive efforts have been undertaken to develop the photogenerated cathodic protection of metals under ultraviolet ͑UV͒ illumination by pure nano structured TiO 2 or its composites with other dopants, which are coated on metal substrate. 15-27 Yuan and Tsujikawa 15 first reported the photocathodic protection of copper by using a sol-gel derived TiO 2 coating. In addition, the photocathodic protection of other materials, such as stainless steel 17,18 and carbon steel, 19 by using pure TiO 2 , TiO 2 -WO 3 , 22 TiO 2 -SnO 2 , 23-26 TiO 2 -CeO 2 composite films, 27 and TiO 2 nanotubes 28,29 have been extensively reported. The principle of photocathodic protection is that e − -h + pairs are created because of the particles transition between the bands; when TiO 2 coated or coupled to a metallic substrate is exposed to UV irradiation, the photogenerated electrons can fill into the metallic substrate and adjust its Fermi level, and thereby shift the ...

Liquid phase deposition (LPD) of TiO2 thin films as photoanodes for cathodic protection of stainless steel

“…1. The measurements were performed using Model 263A potentiostat/galvanostat (EG&G Instruments, Inc., USA, Princeton Applied Research) connected to a SBP300 grating spectrometer with a LPX 150 W Xe lamp as the illumination source [11][12][13][14][15]. During the photoelectrochemical measurements, a polytetrafluoroethene (PTFE) container with a quartz window to transmit the light was used as the photoelectrochemical cell.…”

“…Subasri et al [10] have demonstrated that the effective cathodic protection of copper could be achieved by the sol-gel-derived TiO 2 -based photoanodes. Using the titanium foils as substrates, both the anodization and hydrothermal technique were developed to prepare the TiO 2 nanotubes [11][12][13] as well as the net-like [14] and flower-like [15] TiO 2 films served as photoanodes for the cathodic protection of stainless steel. However, a relatively higher temperature (above 450 • C) heat treatment process is usually necessary for the above methods to prepare the anatase TiO 2 films, which would lead to some unfavorable changes on the microstructure and composition of the underlying substrates.…”

Preparation of SnIn4S8/TiO2 Nanotube Photoanode and Its Photocathodic Protection for Q235 Carbon Steel Under Visible Light

“…To overcome the above disadvantages, numerous approaches have been proposed to heighten the photocathodic protection ability of TiO 2 -based photoelectrodes. These approaches include surface modification [13], designing highly ordered TiO 2 nanotubes (NTs) [14], doping with metals or non-metals [15][16][17][18], and constructing heterojunctions [19][20][21]. More specifically, constructing heterojunctions by combining with other materials has proven to be a valid method for improving the photoelectrochemical properties of TiO 2 .…”

Photocathodic protection properties of TiO2–V2O5 composite coatings

“…Recently, the application of the TiO 2 coatings to photocathodic protection of metals has inviting prospects and has drawn the considerable attention of corrosion researchers 9–18. In the area of photocathodic protection, some marked progresses have already been made in preparing TiO 2 coatings and researching their photo‐electronchemical properties.…”