A comparative study on the photocatalytic efficiency of ZnO nanowires doped by different transition metals∗

Abstract

We synthesized transition metal doped ZnO nanowires by an easy and efficient hydrothermal method using three different metals: iron, silver, and cobalt at different molar percentage (1%, 2%, and 3%). Scanning electron microscopy showed quite homogeneous ZnO nanowire arrays for all doped samples. The photocatalytic efficiency was tested by degrading a methyl orange solution. All doped samples showed better efficiency than undoped samples, the most efficient for each dopant being the ZnO:Fe 3%, the ZnO:Ag 2%, and the ZnO:Co 2%. The photocatalytic efficiency enhancement can be attributed to two effects: the reduction of the band-gap energy allowing more photons to be absorbed; and the increase in oxygen vacancies and the dopant ions on the nanowire surface reducing the electron–hole recombination rate.