TiO2 Nanowires on Anodic TiO2 Nanotube Arrays (TNWs/TNAs): Formation Mechanism and Photocatalytic Performance

Abstract

TiO2 nanowires connected directly with TiO2 nanotubes arrays (TNWs/TNAs) were successfully fabricated with a mixture of ethylene glycol and water that contained NH4F electrolyte via a one-step method without mechanical stirring. The morphology of the TNWs/TNAs structure was investigated by changing the anodizing voltage and processing time to elucidate its formation mechanism. Well-developed anodic oxide nanowires are only observed under specific anodizing voltage and processing time conditions. The evolution of TNWs follows four stages: (1) thinning of the tube wall thickness with high roughness near the TNA mouths, (2) forming strings of through holes in the upper section of the TNAs, (3) splitting into nanowires, and (4) collapsing and further thinning of nanowires. For photocatalytic application, TNWs/TNAs film demonstrated a better photocatalytic performance than regular TNAs due to higher surface area predominantly and improved charge transport. Moreover, TNWs/TNAs film (20 nm wire/40 nm pore diameter) achieved a performance comparable to that of the film made from TiO2 nanoparticles. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.063208jes] All rights reserved.