Structure, optical property, and photo-catalytic activity of solid-solution β-AgAl1−xGaxO2 under visible light

Visible-light responsive β-AgAl1−xGaxO2 photocatalysts were prepared through a sol-gel method combined with a cation exchange reaction. The samples were characterized by X-ray diffraction, scanning electron microscopy, UV–vis absorption spectrum, and photoluminescence spectrum. The results demonstrated that the solid-solution β-AgAl1-xGaxO2 with delafossite structure showed high crystallinity. The microparticles with smooth surface were polycrystal and had polyhedron crystal morphologies. The optical band gap of the β-AgAl1−xGaxO2 was modulated in the range of 2.31–2.70 eV; meanwhile the photoluminescence spectra showed a red shift by varying the molar ratio of Ga/Al from 0.25 to 4 attributed to the decrease of band gap. The photo-catalytic degradation of methyl orange was studied under visible light irradiation (wavelength>420 nm). The degradation process followed the first-order kinetics. The β-AgAl0.2Ga0.8O2 with the reaction rate of 0.0402 min−1 showed the highest photo-catalytic activity. This might be resulted from the narrow band gap of 2.31 eV for the β-AgAl0.2Ga0.8O2 which could utilize visible light efficiently to photo-generate electrons and holes. The β-AgAl1−xGaxO2 had potential applications in degrading organic dyes by using visible light efficiently.