Synthesis and Visible Light Photocatalytic Activity of Spinel MAl<sub>2</sub>O<sub>4 </sub>(M=Mg, Zn, Cu)

Aluminium spinel MAl 2 O 4 (M = Mg, Zn, Cu) photocatalysts were prepared by a sol-gel method. The prepared samples were characterized by X-ray diffraction and transmission electron microscope. The results indicated that the samples possess a single spinel-type structure. Ultraviolet-visible diffuse reflectance spectra showed an extension of light absorption into the visible region. The spinel MAl 2 O 4 photocatalysts exhibited high photocatalytic activity for the degradation of industrial dyes under high pressure mercury lamp and visible light irradiation, especially CuAl 2 O 4 . With the decrease of band gap of MAl 2 O 4 (M = Mg, Zn, Cu), the photocatalytic activity increases. The possible reasons are discussed from the crystal field theory and energy band theory. These characteristics make the aluminium spinel MAl 2 O 4 (M = Mg, Zn, Cu) photocatalysts to be promising candidates for the photocatalytic degradation of dyes.