A capacitor circuit model for theoretical derivation of anodizing current

The formation mechanism of porous anodic oxide has been investigated for several decades. However, the anodizing current density-time curves of anodic TiO2 nanotubes obtained under constant voltage are still not well-understood. In addition, existing theory cannot interpret the relationship between different parameters and anodizing current properly. Herein a capacitor circuit model is proposed to overcome these challenges. Based on the capacitor circuit model, theoretical expression of anodizing current is derived. And the influences of different anodizing parameters were quantified. The present results demonstrate that anodizing current density depends on the applied voltage, electrode distance, anodization temperature and electrolyte composition. The fitting curves are in accordance with the measured ones. The influence of the electrode distance on anodizing current was investigated for the first time, which provided evidences for the capacitor circuit model. (C) 2016 Elsevier Ltd. All rights reserved.