High density, well ordered, vertically aligned and uniform titanium oxide nano-tube arrays were fabricated on the surface of a pure titanium sheet by direct electrochemical anodic oxidation. The effect of different electrolytes on dimension and morphology has been studied. XRD and FE-SEM techniques have been used to characterize the titanium oxide nano-tube arrays. SEM shows that in an electrolyte of 0.5 wt% HF length of the nano-tubes did not increase after 20 mins. While in electrolyte of 0.5 wt% HF＋1 mol/L (NH₄)H₂PO₄, at 20 V anodizing voltage after 15 h, the average diameter of an nano-tubes was about 70～90 nm, and length of the nano-tubes was about 2.2 mm. XRD shows that after annealed for 1 h under 500 ℃ in air, the primary phase became anatase phase of TiO₂. Photo-electrochemical character curves have been measured in an electrolyte of 1 mol/L KOH under irradiation of a high-voltage mercury lamp, at photocurrent of about 3.2 mA/cm² for the nano-tubes of about 2.2 mm. Using the TiO₂ nano-tubes of about 2.2 μm in length as anode, under illumination of the high-voltage mercury lamp at 0.45 V (vs. SCE) bias potential, after 5 h, the degradation degree of an acid red G electrolyte was about 92.4%.

Key words: anodic oxidation, TiO₂ nano-tubes, acid red G, photocatalytic degradation