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

Multi-walled carbon nanotubes (MWCNTs) coated with TiO2 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/TiO2 consisted mainly of anatase phase. The introduction of MWCNTs inhibited TiO2 grain growth. Moreover, the adsorption edge of MWCNTs/TiO2 shifted toward long-wavelength region compared with bare TiO2. The photocatalytic ability of MWCNTs/TiO2 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 SO2 on denitration was observed. In contrast, O2 and H2O played a promotional role in the photocatalytic denitration. At optimal conditions (73 mg/m3 NO, 8% O2, 5% H2O), NO removal efficiency of 46% was achieved. In addition, the reaction mechanism of denitration was proposed.

Graphical AbstractMWCNTs provide another transfer pathway for photogenerated electrons, assisting in electron and hole separation. This electron-scavenging character of MWCNTs causes MWCNTs/TiO2 to perform better in photocatalytic denitration than bare TiO2.Figure optionsDownload full-size imageDownload as PowerPoint slide