Origin of the Enhanced Photocatalytic Activities of Semiconductors: A Case Study of ZnO Doped with Mg2+

Abstract

A series of Zn1−xMgxO samples with dopant content ranging from x = 0 to 0.10 were prepared by a novel rheological phase reaction route. All Zn1−xMgxO samples were investigated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, inductive coupled plasma optical emission spectroscopy, infrared and UV−vis absorption spectroscopy, and the Barrett−Emmett−-Teller technique. The effects of Mg2+ doping in ZnO on the electronic structures and photogradation of methylene blue dye solution were investigated experimentally and theoretically. All Zn1−xMgxO samples exhibit high photoactivities comparable to Degussa P-25, which first increased with the Mg doing content up to x = 0.05, and then slightly decreased with further doping of Mg to x = 0.10. Density function theory calculations revealed that the substitutions of Mg for Zn ions in the wurtzite ZnO structure largely affected the conduction band, but left the valence band nearly unchanged. The bottom of the conduction band shifted...