A Photoelectrochemical Study of Highly Ordered TiO2 Nanotube Arrays as the Photoanodes for Cathodic Protection of 304 Stainless Steel

Highly ordered TiO2 nanotube (TN) arrays with a regular top porous morphology were fabricated by a facile two-step electrochemical anodization in an ethylene glycol solution containing NH4F and H2O. 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 TiO2 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. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3528278] All rights reserved.