Figure 3From: Transparent TiO2 nanotube array photoelectrodes prepared via two-step anodization (a) The strategy to control the thickness of the two-step anodized transparent TiO 2 NT films, where the graph shows a typical anodization current profile of the single-step anodization and the circled numbers show the duration of the second step anodization, and (b) SEM images show NT films of various thicknesses; the circled numbers correspond to those in (a). Back to article page