A greener methodology to grow TiO2 nanotubes in a non-corrosive, low-hazard, fluoride-free ethylene glycol/water electrolytic bath is presented. Results demonstrate that the formation of nanostructures by anodization of Ti foils in NaCl solutions requires glycol/water solutions with water contents (> 50%) and moderate voltages (< 30 V). Nanotube growth was dependent on the surface characteristics; anodization performed on mechanically polished surfaces showed that randomly oriented nanotubes grow on pits while vertically oriented TiO2 nanotubes were obtained on electropolished surfaces. An electropolishing methodology was developed to obtain surfaces with submicrometer roughness that favours the growth control of vertically oriented TiO2 nanotubes.
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