Effects of organic solvents in anodization electrolytes on the morphology and tube-to-tube spacing of TiO2 nanotubes

Abstract In order to study effects of different solvents on Ti anodization process, we compared the morphology changes of TiO2 nanotubes in three fluoride-containing electrolytes composed of ethylene glycol (EG), glycerol, diethylene glycol (DEG), respectively. Results show that close-packed nanotubes are obtained in EG electrolyte, spaced nanotubes are obtained in DEG electrolyte. In this paper, the formation mechanism of spaced nanotubes is discussed. The difference in three solvent effects is that the weak ability of DEG to bind protons leads to strong solution etching effect, which is the key to form spaced nanotubes.