Blooming microflowers: Shaping TiO2 nanostructures via anodization in metal chloride-based electrolytes

Abstract

TiO2 microflowers, consisting of nanotubes, were generated via potentiostatic anodization in fluoride-free electrolytes infused with metal chlorides. Anodizing titanium foil at 15 V for 10 min in electrolytes containing 0.1 M of FeCl3 center dot 6H2O, CrCl3 center dot 6H2O, FeCl2 center dot 4H2O, and CuCl2 center dot 2H2O yielded nanotubes with outer diameters of approximately 30 nm, 45 nm, 50 nm, and 60 nm, respectively. The introduction of metal chloride to the electrolyte significantly altered the anodization kinetics, facilitating the growth of TiO2 microflowers. These structures consist of nanotube bundles that are of few microns in length with tunable diameters, achieved rapidly within the anodization timeframe. Microflowers formed in FeCl3 center dot 6H2O electrolyte feature high aspect ratio TiO2 nanotube bundles with smaller diameters and higher nucleation density, whereas those developed in CrCl3 center dot 6H2O, FeCl2 center dot 4H2O, and CuCl2 center dot 2H2O electrolytes exhibit less preferable morphology.