Hierarchical decoration of anodic TiO2 nanorods for enhanced photocatalytic degradation properties

• We synthesize arrays of aligned TiO2 nanorods by anodization of Ti covered with an Al layer.
• The incorporation of Al into the TiO2 nanorods inhibits crystallization at temperatures as high as 550 °C.
• The photocatalytic degradation of Acid Orange 7 dye can be strongly enhanced after applying a TiO2 nanoparticle coating.
• The anatase structure of the coating and the enhanced light absorption volume results in up to a 12x enhancement in performance.

In the present work vertically aligned TiO2 nanorods were fabricated by anodization of Al/Ti dual layer structures. Anodization of Al leads to the formation of a porous alumina layer which is used as a template for the growth of TiO2 nanorods. We have studied the characteristics of these nanorods after annealing by high resolution TEM, showing a core–shell structure along the length of the nanorods formed from the expansion of the TiO2 nanorod into the alumina template during growth. Modification of the nanorods by spin coating of a solution of titanium isopropoxide (TIPO) in isopropanol yields enhanced photocatalytic activity up to 12 times due to the increase in surface area, light absorption volume, and the creation of a crystalline coating with an anatase-phase.