Carbon nanotube/titanium nanotube composites loaded platinum nanoparticles as high performance photocatalysts

Abstract

The multi-walled carbon nanotubes, titania nanotubes, and Pt metal (Pt/TNT-MWCT) hybrids; synthesized via hydrothermal-deposition methods, were tested toward photocatalytic degradation of methylene blue (MB) dye under visible light (λ > 420 nm) in comparison with the binary hybrid Pt/TNT and Pt/graphene photocatalysts. These catalysts were characterized using X-ray diffraction (XRD), UV-vis diffuse reflectance (DRUV-vis), Fourier transform infrared spectroscopy (FTIR), N2 sorptiometry, photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM) attached with energy dispersive X-ray spectroscopy (EDX). DRUV-vis analysis confirmed the enhancement in the absorption of Pt/TNT following MWCNT incorporation. TEM images showed the coverage of MWCNTs by brookite TNT that has been substantiated by EDX. The higher photo-activity of Pt/TNT-MWCNT (100% degradation in 140 min under visible irradiation) was attributable to the better contact between MWCNT and TNT; exhibited via formation of the TiOC bond, which promoted the charge separation and electron transportation. Reduced charge recombination was evidenced for Pt containing samples and a further reduction was existed following MWCNTs incorporation; as investigated by PL measurements. The adsorption of MB by MWCNTs played major role in the removal efficiency. On the other hand, Pt/graphene presented appreciable activity, however, lower than Pt/TNT-MWCNT both in UV and vis light spectral regions due to decreasing the photocatalytic effect of the former than that of the latter. A mechanism for the MB oxidation was proposed based on the obtained results. © 2014 Elsevier B.V. All rights reserved.