Synthesis and comparative photocatalytic activity of Pt/WO_3 and Au/WO_3 nanocomposites under sunlight-type excitation

摘要

The article deals with the synthesis of highly active visible-light-driven nanocomposite for the decontamination of water hazards under sunlight-type excitation. The surface of visible-light-active nano-structured photocatalyst tungsten oxide (WO_3} was modified with noble metals, such as platinum (Pt) and gold (Au) nanoparticles, and the resulting photocatalytic activity of the nanocomposites was investigated by studying the removal of Methyl Orange and 2,4-Dichlorophenoxyacetic acid (2,4-D) under sunlight-type excitation. The study revealed that the deposited noble metals are not always favorable for the enhancement of photocatalytic response of catalysts; the activity of WO_3 was enhanced manyfold (~8 times) by depositing an optimum amount of Pt nanoparticles after certain photo-deposition time whereas the presence of Au nanoparticles onto the WO_3 surface, under identical experimental conditions, affected the removal process negatively. The variation in the photocatalytic activity of nanocomposites was attributed to the size of the deposited metals; Pt nanoparticles were uniformly dispersed with narrow size distribution (2-4 nm) while the size distribution of Au nanoparticles was found to be 10-15 nm for similar preparation conditions. The effects of critical parameters, such as metal deposition time and metal contents, on the photocatalytic activity of WO_3 were investigated. Furthermore, Pt/WO_3 nanocomposites showed good stability and recyclability under the conditions studied.