Synthesis of CdS/CNT-TiO2 with a high photocatalytic activity in 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.