Visible-light-sensitive nanoscale Au-ZnO photocatalysts

The role of gold nanoparticles supported on ZnO in photocatalytic activity for dye degradation was investigated. To this end, gold nanoparticles supported on ZnO (Au-ZnO) were prepared using a simple co-precipitation method. The prepared nanocatalyst was characterized by high-resolution transmission electron microscopy, X-ray diffraction, temperature-programmed reduction, X-ray photoelectron spectroscopy, UV-Vis absorption, and photoluminescence. The photocatalytic activity of Au-ZnO was examined by the degradation of methylene blue in aqueous solution using a light source that has more than 95 % (i.e., energy) of emitted photons between 400 and 800 nm. Highly enhanced photocatalytic degradation of methylene blue in air at room temperature was observed from these Au-ZnO nanocatalysts with gold particle size ranging from 2 to 7 nm, with an average size of 3.8 nm. The observed rate constant for MB degradation on Au-ZnO was 0.0118/min compared with 0.0007/min for pure ZnO. Furthermore, the charge transfer pathway for the degradation of methylene blue in Au-ZnO is suggested.