Enhanced photocatalytic activity of ZnO thin films deriving from a porous structure

Abstract

ZnO thin films are prepared by sol–gel method. Their surface and sectional morphologies have been observed by scanning electron microscopy (SEM). It is found that the Sr-doping leads to a porous structure in ZnO thin films and this kind of porous structure distributes throughout the whole film rather than only distribute on the film surface. Furthermore, the variation of Sr-doping concentration can tailor the pore density in the films. The formation of the porous structure probably results from the lattice distortion due to the large difference between the ion radiuses of Sr2+ and Zn2+. The mapping of the samples shows that the Sr element is uniformly distributed in the whole thin films. The photocatalytic experiments show that the photocatalytic activity of Sr-doped ZnO thin films has been enhanced compared with that of undoped ZnO thin films. This enhancement should be attributed to the increase of specific surface area deriving from the porous structure.