Preparation and photocatalytic behavior of MoS₂ and WS₂ nanocluster sensitized TiO₂

A new approach has been developed for the fabrication of visible light photocatalysts. Nanoclusters of MoS₂ and WS₂ are coupled to TiO₂ by an in situ photoreduction deposition method taking advantage of the reducing power of the photogenerated electrons from TiO₂ particles. The photocatalytic degradation of methylene blue and 4-chlorophenol in aqueous suspension has been employed to evaluate the visible light photocatalytic activity of the powders. The blue shift in the absorption onset confirms the size quantization of MS₂ nanoclusters, which act as effective and stable sensitizers, making it possible to utilize visible light in photocatalysis. Quantum size effects alter the energy levels of the conduction and valence band edges in the coupled semiconductor systems, which favors the interparticle electron transfer. In addition, the coupled systems are believed to act in a cooperative manner by increasing the degree of charge carrier separation, which effectively reduces recombination. Copyright © 2004 American Chemical Society.