Simulation of anodizing current-time curves and morphology evolution of TiO2 nanotubes anodized in electrolytes with different NH4F concentrations. (10th September 2015)

• Record Type: Journal Article
• Authors: Zhang, Yulian; Fan, Haowen; Ding, Xu; Yan, Qinghai; Wang, Liping; Ma, Weihua
• Is Part Of: Electrochimica acta. Volume 176(2015)
• Page Start: 1083
• Page End: 1091
• Publication Date: 2015-09-10
• Subjects: TiO2 nanotubes -- Anodization -- Ionic current -- Electronic current.; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2015.07.110
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Total current curve could be separated into two parts: ionic current and electronic current. Correlation between NH4 F concentration and morphology of TiO2 films is elucidated. Nanotube length is determined by the ionic current rather than the total current. Surface morphology is related to the electronic current and the evolution rate of O2 . We also propose a feasible method to predict nanotube length. Abstract: Anodic TiO2 nanotubes (ATNTs) have been investigated for many years. However, the kinetics of oxide growth still remains unclear as well as the relationship between structural features and anodizing parameters. Here, the simulation and separation of anodizing current-time curves are proposed to overcome this challenge. A series of constant voltage anodizing processes in different concentrations of NH4 F solutions have been compared in detail. The effect of NH4 F concentration on the morphological structure and length were systematically investigated. The morphology images show that ATNTs with lotus-root-shaped nanostructure can also be fabricated when the same voltage are adopted in the second-step anodization as the first-step anodization. We separate the total anodizing current into ionic current and electronic current according to a theoretical formula and find a linear relationship between nanotube length and steady-state ionic current. The interesting results indicated that, the growth of nanotubes is more dependent on the ionic current while the surface morphology of TiO2 nanotubes is related to electronic current and high NH4 F concentration is beneficial to the growth of ribs around the nanotubes.