Visible-light-activation of TiO2 nanotube array by the molecular iron oxide surface modification

Uniform and adhesive TiO2 nanotube arrays (TiO2-NTAs) have been prepared by a two-step anodization in ethylene glycol solution containing NH4F. The UV-light-activity of TiO2-NTAs prepared by changing the electrolytic voltage and calcination temperature was studied for the degradation of 2-naphthol. Further, the surface of TiO2-NTA has been modified with iron oxide species at a molecular scale by the chemisorption–calcination cycle technique. The iron oxide-surface modification endows TiO2-NTA with a high level of visible-light-activity, concomitantly increasing the UV-light-activity. Under optimum conditions, the iron oxide-surface modified TiO2-NTA exhibits a UV-light-activity comparable with that of highly active TiO2 particles (P-25, Degussa).

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► TiO2 nanotube arrays (NTA) were formed by a two-step anodization on Ti plate.
► The TiO2-NTA shows a UV-light-activity comparable with that of TiO2 particles.
► The surfaces of TiO2-NTA were modified with molecular iron oxides.
► The iron oxide-surface modification significantly increases the UV-light-activity.
► The iron oxide-surface modification causes a high level of visible-light-activity.