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 ...

In this paper we report a spectroelectrochemical investigationrelevant to the elucidation of rebar corrosion processes-based on in situ optical second-harmonic generation spectroscopy. We studied the corrosion behaviour of a carbon steel electrode in contact with an alkaline aqueous solution-simulating the electrolyte of freshly prepared cement paste-containing glutamic acid, a candidate corrosion inhibitor [1]. The non-linear time-dependent optical response to exciting radiation at 1064 nm has been recorded as a function of applied potential. This approach allows to obtain detailed information regarding the dynamic electronic structure of the corrosion interface, which is not available from other electrochemical or spectroelectrochemical approaches.