A review on surface functionalization of carbon nanotubes: methods and applications

In this review, the radiolytic and physical methods that can be used for the functionalization of carbon nanotubes (CNTs) and their applications as a support for fuel cell electrodes are described. Alloy nanoparticles have also been examined. For example, Pt-Ru nanoparticles were deposited onto a functionalized multiwalled carbon nanotube (MWNT) composite by reducing metal ions (e.g., Pt4+ and Ru3+) here using γ-irradiation and, hence, creating Pt-Ru/MWNT catalysts. The morphology, size, and composition of these Pt-Ru/MWNT catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and elemental analysis, respectively. The efficiency of the Pt-Ru/MWNT catalyst was examined for use in the oxidation of carbon monoxide (CO) and methanol. The results of stripping voltammetry for the adsorbed CO on the Pt-Ru/MWNT catalyst electrodes indicated that CO oxidation was energetically favorable at these electrodes. Thus, Pt-Ru/MWNT catalysts were found to be suitable for electrode assembly in direct methanol fuel cells.