Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (06): 1327-1335.doi: 10.3866/PKU.WHXB201303212

• CATALYSIS AND SURFACE SCIENCE • Previous Articles     Next Articles

Surface Modification of CNTs and Improved Photocatalytic Activity of TiO2-CNTs Heterojunction

YANG Han-Pei, ZHANG Ying-Chao, FU Xiao-Fei, SONG Shuang-Shuang, WU Jun-Ming   

  1. Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing 210098, P.R.China
  • Received:2013-01-25 Revised:2013-03-20 Published:2013-05-17
  • Supported by:

    The project was supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry of China (20071256).

Abstract:

Carbon nanotubes (CNTs) have been ultrasonically treated with the mixed acid (H2SO4/HNO3, 3:1, volume ratio), embedding the active -COOH groups onto the surface of the CNTs. As a result, the acid-treated CNTs serve as chemical reactors for subsequent grafting of L-lysine or octadecylamine (ODA). It was revealed that L-lysine and ODA covalently bond to the surface of the oxidized CNTs through amidation of carboxylic acid groups (CNTs-COOH) and lysine or ODA via intermediate acyl chlorides (CNTs-COCl). The hydrophilic and lipophilic CNTs have high aquatic and ethanol solubility, and the solubility of the surface modified CNTs in water and ethanol were measured to be as high as 6.85 and 10.15 mg·mL-1, respectively. The surface nature of modified CNTs and the properties of TiO2-CNTs composite photocatalysts, which were prepared through sol-gel or low temperature hydrothermal synthesis, were investigated by Fourier transform infrared (FTIR), laser Raman, X-ray diffraction (XRD), Brunauer-Emmett-Teller N2 adsorption, transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS). Improved photocatalytic performance was observed for TiO2 coupled by hydrophilic or lipophilic CNT, which were obtained by low temperature hydrothermal and sol-gel synthesis, respectively, and it was revealed that there is an affinity between the photocatalytic performance of TiO2-CNTs hybrids and the dispersibility of CNTs. It is proposed that the improved photocatalytic activity of CNT-TiO2 compared with pure TiO2 photocatalysts can be mainly attributed to the homogeneous and dense dispersion of TiO2 on the modified CNTs and the intimate contact between TiO2 and CNTs, which results in dense heterojunctions at the interface of TiO2 and CNTs through the Ti-O-C structure.

Key words: Carbon nanotubes, Surface modification, Solubility, TiO2, Photocatalytic degradation

MSC2000: 

  • O643