Synthesis of CdS/CNT-TiO₂ with a high photocatalytic activity in the photodegradation of methylene blue 

Novel CdS/CNT-TiO₂ photocatalysts were synthesized by a simple chemical routine through the drop-wise addition of Na₂S · 5H₂O solutions to cadmium acetate solutions containing purified multiwall carbon nanotubes (MWCNTs). The CdS/CNT materials obtained were treated with titanium (IV) n-butoxide to form CdS/CNT-TiO₂ composites which were characterized by N₂ adsorption, XRD, TEM, SEM, and energy-dispersive X-ray analysis. The composites were found to be porous, and the MWCNTs were homogenously dispersed in the composites without any apparent agglomeration of TiO₂ nanoparticles and CdS nanoparticles. The CdS/CNT-TiO₂ composites exhibited excellent activity for the degradation of methylene blue under UV and visible-light irradiation. This was attributed not only to the photocatalysis of the supported TiO₂ for the radical reaction and the adsorptivity of MWCNTs, but also to the introduction of the narrow-band gap semiconductor CdS that increases the transfer rate of photogenerated electrons through the surface of the MWCNTs.