Novel Ag2ZnGeO4 photocatalyst for dye degradation under visible light irradiation
We report a multiple-metal oxide Ag2ZnGeO4 with cristobalite-related structure as a visible light-sensitive photocatalyst (Eg 2.29 eV) for dye degradation. The physical characteristics of the samples were examined by techniques such as XRD, UV–vis diffuse reflectance spectroscopy and SEM. The photocatalytic activity of Ag2ZnGeO4 was confirmed by Rhodamine B (RhB) and Orange II photodegradation in aqueous phase. After 360 min of visible light (λ > 420 nm) irradiation, the conversions of RhB and Orange II reached 100% and 69.2%, respectively. The electronic structure of Ag2ZnGeO4 was investigated by band structure calculation based on the density function theory (DFT). Results revealed that the hybridized Ag 4d10 and O 2p6 orbitals form the valence band top of Ag2ZnGeO4, which leads to a much narrowed band gap as compared with that of the Na2ZnGeO4 parent sample. We propose that the specific cristobalite structure of Ag2ZnGeO4 favors the mobility of photo-generated carriers, and that this contributes positively to the observed photocatalytic activity for dye degradation.
Graphical abstractA cristobalite structure-related multiple-metal oxide, viz. Ag2ZnGeO4, had been developed as a visible light-sensitive photocatalyst with the band gap of 2.29 eV. The Ag2ZnGeO4 photocatalyst showed good activity for RhB and Orange II photodegradation. Under typical reaction conditions and after 360 min of visible light (λ > 420 nm) irradiation, RhB could be completely degraded and 69.2% of Orange II was converted. The unique energy band structure and crystal structure determined the overall photocatalytic performance of Ag2ZnGeO4.Figure optionsDownload full-size imageDownload as PowerPoint slide
Journal: Applied Catalysis A: General - Volume 334, Issues 1–2, 1 January 2008, Pages 51–58