Recently, covalently functionalization carbon nanotubes have been received special attention because of the expansive application prospect in the areas of nanoscience and nanotechnology. Moreover, covalent functionalization of carbon nanotubes can readily deal with fundamental issues of purification, solubilization, and processing. In particular, polyaniline, due to its high electronic conductivity, good environmental stability, easy preparation and reversible acid-base doping-dedoping chemistry, has been one of the most studied conducting polymers. Recently, CNTs-PANI composites were investigated widely, such as supercapacitor, optoelectronic devices, sensing and catalysis as well. In this work, uniform structures PANI covalently grafted onto CNTs functionalization with -NH₂ groups composites have been obtained by using liquid/liquid(L/L) interfacial polymerization method. The interfacial system was established by using CNTs, FeCl₃, HCl as top aqueous phase and aniline, CH₂Cl₂ as bottom organic phase, which effective suppress second growth of PANI and obtain uniform CNTs-NH-PANI composites. Concerning CNTs-NH-PANI composites, PANI can covalently be grafted on CNTs with -NH₂ groups. The resulted CNTs-NH-PANI composites have abundant -NH₂ groups on their surface, serving as anchor centers for achieving high Pt dispersion. More important, PANI uniformly grafted on CNTs is prone to disperse the bundle of CNTs into separated lines and improve water dispersibility of obtained CNTs-NH-PANI composites. Subsequently, PtNPs were successfully deposited on the CNTs-PANI to form ternary hybrids. Potential application of the ternary hybrids as high performance catalysts for direct methanol fuel cells has been explored. The catalyst samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and electrochemical methods. TEM results showed that the hierarchical CNTs-PANI composites with uniform morphology have been successfully prepared due to hydrophilic -OH and -NH₂ groups covalently functionalized onto the surface of CNTs. Moreover, the electrochemical measurement show that the Pt/CNTs-NH-PANI hybrid have better stabilities compared with commercial JM (Pt/C) catalyst. The long-term durability test of the Pt/CNTs-CO-PANI, Pt/CNTs-NH-PANI and Pt/C catalysts shows that PANI grafted on CNTs as catalyst supports have better stabilities and more tolerant toward poisoning. Moreover, PANI covalently grafted on CNTs as catalyst supports has more excellent performance. The I_f/I_b of Pt/CNTs-NH-PANI catalyst for electrocatalytic methanol oxidation is 1.65 which is nearly 1.6 and 1.2 times than that of the commercial JM(Pt/C) and Pt/CNTs-CO-PANI catalysts, respectively. The results show that carbon nanotubes covalently grafting polyaniline as support can effectively improve the catalyst stability, increasing the service life of the catalyst.

Key words: carbon nanotube, polyaniline, covalently, catalyst, methanol oxidation, CO-tolerance