Enhanced visible-light-driven photoactivities of single-walled carbon nanotubes coated with N doped TiO2 nanoparticles

Abstract

A two-step hydrothermal method is used to prepare N doped single-walled carbon nanotube–TiO₂ (SWCNT–N/TiO₂) hybrids with different contents of SWCNTs from 1.25 wt% to 10 wt%. The photocatalysts were characterized by X-ray diffraction analysis, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The UV-vis diffuse reflectance spectra show an apparent enhancement of absorption throughout the visible light region. Raman spectroscopy further confirms the chemical interaction between N/TiO₂ and SWCNTs in the hybrid. SWCNT–N/TiO₂ hybrid presents a superior photocatalytic activity to DWCNT–N/TiO₂ (N doped double-walled carbon nanotube–TiO₂) and MWCNT–N/TiO₂ (N doped multi-walled carbon nanotube–TiO₂) based on the results of the photocatalytic degradation of sulfathiazole under visible light irradiation, which is attributed to the synergetic effects of SWCNT modification and N doping. N doping induces visible light absorption by either introducing localized electronic states within the band gap or contributing electrons to the valence band and metal-like SWCNT can act as an electron conductor to facilitate the fast injection of the photogenerated electrons into the conduction band of N/TiO₂, leading to significantly enhanced visible-light-driven photocatalytic activity.