Fabrication, Modification, and Emerging Applications of TiO₂ Nanotube Arrays by Electrochemical Synthesis: A Review

Figure 3

The electrochemical anodization process and typical morphologies: (a) (I) metal electropolishing, (II) formation of compact anodic oxides, (III) self-ordered oxides (nanotubes or nanopores), (IV) ordered nanoporous layers, and (V) rapid (disorganized) oxide nanotube formation. Examples of morphologies of obtained structures: (b) classical ordered TiO₂ nanopores (b1), nanotubes (b2), sponge-like nanoporous structures (b3) anodized in F⁻ ions containing electrolyte, and (c) disordered TiO₂ nanotubes growing in bundles anodized in F⁻ ions free electrolyte.

(a) Set-up and mophology

(b) F⁻ ions electrolyte

(c) F⁻ ions free electrolyte