Freestanding doubly open-ended TiO₂nanotubes for efficient photocatalytic degradation of volatile organic compounds

We synthesized freestanding doubly open-ended TiO₂nanotubes (DNT) film and compared their photocatalytic activity and durability during the repeated degradation cycles of volatile organic compounds (VOCs) with those of TiO₂nanotubes (TNT) film. DNT exhibited higher activity and durability for the photocatalytic degradation of gaseous acetaldehyde and toluene than TNT. The doubly open-ended structure of DNT allows O₂molecules to be easily supplied to the active sites, which increases not only the intrinsic photocatalytic activity but also the resistance to catalyst deactivation. The freestanding DNT film was additionally loaded with TiO₂nanoparticles (NP@DNT) in the inner wall to further increase the activity for VOC degradation. The photocatalytic activity of NP@DNT was higher than bare DNT and bare TNT by 1.3 and 1.8 times, respectively. Unlike the case of DNT, the TiO₂nanoparticles loaded TNT (NP@TNT) exhibited a lower activity than bare TNT, probably because the TiO₂nanoparticles blocked the TNT channels with hindering the mass transfer of O₂and VOC molecules. DNT with doubly open-ended structure serves as a versatile platform of fabricating nanostructured photocatalysts with maintaining the open channel structure that facilitates the mass transfer of O₂and VOC molecules.