Porous (001)-faceted Zn-doped anatase TiO2 nanowalls and their heterogeneous photocatalytic characterization

Abstract

The synthesis of a poriferous and high energy (001) faceted anatase Zn-doped TiO₂ nanowall (ZnTNW), vertically grown on an indium tin oxide substrate, is presented. The ZnTNW was prepared using a modified liquid phase deposition method using zinc nitrate (Zn(NO₃)₂·xH₂O) as a fluoride scavenger in the presence of hexamethylenetetramine. In a typical procedure, the ZnTNW nanowall with length and thickness of approximately 2 μm and 60 nm, respectively, can be obtained from the reaction during a 5 h growth process. X-ray diffraction analysis shows that the nanowall has an anatase structure with a dominant high energy (001) basal plane. Meanwhile, the X-ray energy dispersive analysis confirms the presence of Zn in the TiO₂ nanowall. High resolution transmission electron microscopy analysis results reveal, surprisingly, that the ZnTNW is single crystalline in nature although it has a highly porous (surface and bulk) structure. Photocatalytic properties of the ZnTNW were examined in the degradation of methylene blue. It was found that the ZnTNW exhibits excellent photocatalytic efficiency with kinetic reaction rate, turnover number and turnover frequency as high as 0.004 min⁻¹, 760 and 11 min⁻¹, respectively. The photocatalytic performance of the ZnTW was found to be higher for about 10% and 50% than the pristine TiO₂ nanowalls and (001) faceted poriferous TiO₂ microtablet, which reflected the effective effect of the Zn doping. The ZnTNW may find potentially use in photocatalytic heterogeneous applications.