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.