Competition Between Ionic Current and Electronic Current: Regulation of TiO₂ Nanotube Growth

Titanium dioxide (TiO₂) nanotubes have been explored for applications in various fields, and their performance is influenced by their length. To investigate the factors affecting the length of anodic TiO₂ nanotubes, samples were fabricated under different applied voltages and in electrolytes with varying poly(ethylene glycol) (PEG) concentrations. The study found that the steady-state current density in the current density-time curve exhibits a strong linear relationship with nanotube length. High PEG concentrations lead to a significant reduction in nanotube length (Compared to the electrolyte containing 25 wt % PEG, the nanotube length obtained in the electrolyte containing 75 wt % PEG was reduced by 82.0%.). From the perspectives of ionic current and electronic current, high concentrations of PEG suppress electronic current, reducing oxygen generation. This leads to a decrease in nanotube length and an increase in wall thickness, even resulting in nanotubes with closed tops. These results indicate that nanotube length is not related to the field-assisted dissolution rate. Instead, it depends on the ionic current density and electronic current density during anodization.