Photo-catalytic activity of titanium dioxide carbon nanotube nano-composites modified with silver and palladium nanoparticles

Photo-catalytic noble metallic and bimetallic nano-composites (Ag or Pd/-TiO2/CNT) were synthesized using a commercial source of multi-walled carbon nanotubes via a modified dry-mix metal-organic chemical vapour deposition method (MOCVD). The titania loading was varied from 10-40 wt.%, and the optimum TiO2/CNT photo-catalyst was determined using methylene blue degradation as a model probe reaction. Furthermore, acid-treated nanotubes and non-acid treated nanotubes were compared as a substrate for the synthesis of various titania nano-composites, and it was found that the acid treatment decreased the photo-catalytic activity of the titania CNT nano-composites. The 20 wt.% titania on CNT samples were then further modified with silver, palladium, and a combination of both metals using the MOCVD technique. It was found that the silver titania CNT nano-composites were the most effective photo-catalyst for the degradation of methylene blue. The deposition of 2% Ag on 20% TiO2/MWCNT resulted in 92% degradation of 50 mg/L MB in 4 h with 1 g/L of photo-catalyst. Palladium had little effect in altering the photo-catalytic activity of the titania CNT nano-composites, and the combination of both metals suppressed the photo-catalytic activity of the titania CNT nano-composites.