The structures of titania nanotube arrays synthesized by one-faced anodization

Highly ordered titania (TiO2) nanotube arrays were synthesized via one-faced and single-step anodization method. Titanium foils were anodized in ethylene glycol based electrolytes containing 0.25 wt% NH4F, 2 vol% H2O, and doped with various concentrations of K3[Fe(CN)6] at applied voltage of 50 V for 2 h at room temperature. As-anodized samples were annealed at 450 ๐C for 2 h in order to transform the amorphous titania to nanocrystalline anatase, Highly ordered titania nanotube arrays were obtained after K3[Fe(CN)6] at different concentrations was introduced. The surfaces of TiO2 nanotubes were smoother after increasing concentrations of K3[Fe(CN)6], confirmed by AFM investigation. The absorption spectra of the samples were extended in range of 200 to 375 nm and slightly increased in band gap energies of titania when K3[Fe(CN)6] was doped. Doping with 0,20 wt% K3[Fe(CN)6] caused Ti 2p shifted towards lower binding energy due to the reduction of Ti4+ to Ti3+ and led to improved electrochemical performance of titania nanotubes. The 0.2o wt% K3[Fe(CN)6] doped titania nanotube sample was used as photoanode in DSSC and exhibited higher solar cell efficiency than other samples. This work suggests an alternative method for fine tuning the size of TiO2 nanotube arrays that can be used as energy conversion materials.