Photocatalytic removal of nitric oxide by multi-walled carbon nanotubes-supported TiO2

Abstract

Multi-walled carbon nanotubes (MWCNTs) coated with TiO 2 were prepared by a sol-gel method and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and UV-Vis diffuse reflectance spectroscopy. It was found that MWCNTs/TiO 2 consisted mainly of anatase phase. The introduction of MWCNTs inhibited TiO 2 grain growth. Moreover, the adsorption edge of MWCNTs/TiO 2 shifted toward long-wavelength region compared with bare TiO 2 . The photocatalytic ability of MWCNTs/TiO 2 for NO removal was experimentally investigated in a fixed-bed reactor. The results showed that a lower initial NO concentration was conducive to NO removal. A negative effect of SO 2 on denitration was observed. In contrast, O 2 and H 2 O played a promotional role in the photocatalytic denitration. At optimal conditions (73 mg/m 3 NO, 8% O 2 , 5% H 2 O), NO removal efficiency of 46% was achieved. In addition, the reaction mechanism of denitration was proposed. MWCNTs provide another transfer pathway for photogenerated electrons, assisting in electron and hole separation. This electron-scavenging character of MWCNTs causes MWCNTs/TiO 2 to perform better in photocatalytic denitration than bare TiO 2 .