Photocatalysis of Ag-Loaded TiO₂ Nanotube Arrays Formed by Atomic Layer Deposition

Anodic aluminum oxide (AAO) film was used as a template to fabricate TiO 2 nanotubes. TiO 2 was deposited into the AAO pores by atomic layer deposition (ALD) at 100 °C. After the top layer of TiO 2 and the AAO template were removed, an ordered array of TiO 2 nanotubes remained on the substrate. The tube thickness increased with the cycle number of ALD. The UV–vis absorption spectra of the samples exhibited a red shift as the thickness increased or after annealing. The photocatalytic activity increased with the increase in the wall thickness of TiO 2 nanotubes. With deposition of Ag nanoparticles on the tubes, the nanoparticles could act as an electron trapper to slow the electron–hole recombination rate, and thus enhance the efficiency of photodecomposition of methyl orange.