In situ preparation of CdS decorated ZnWO4 nanorods as a photocatalyst for direct conversion of sunlight into fuel and RhB degradation

Abstract

CdS nanoparticles have been grown on the surface of ZnWO₄ nanorods via an in situ hydrothermal approach and their photocatalytic activities towards hydrogen (H₂) evolution and dye degradation under solar light have been demonstrated. The structural, optical and morphological studies of CdS@ZnWO₄ heterostructures with varying contents of CdS have been conducted. High resolution transmission electron microscopy (HRTEM) analysis showed sensitization of CdS nanoparticles (25 nm) on ZnWO₄ nanorods of diameter 30 nm and length −200 nm. A decrease in the photoluminescence intensity of ZnWO₄ was observed with increasing amounts of CdS nanoparticles which indicates inhibition of charge carrier recombination. Considering the band gap in the visible region, a photocatalytic study has been performed for hydrogen (H₂) production from H₂O and Rhodamine B (RhB) dye degradation under natural sunlight. The rate of photocatalytic H₂ evolution for CdS@ZnWO₄ is 105 times higher than that of pristine ZnWO₄. Similarly, excellent photocatalytic activity was observed for CdS@ZnWO₄ (20% CdS) composites against RhB degradation which is 4.7 times higher than that of pristine ZnWO₄. With increase in the amount of CdS nanoparticle loading on ZnWO₄ nanorods, the H₂ generation rate was observed to be decreased after 15% CdS loading whereas, the dye degradation rate is increased. Such nano-heterostructures may have potential in other photocatalytic reactions.