Purification of catalytically produced carbon nanotubes for use as support for fuel cell cathode Pt catalyst

A purification method based on HCl treatment under reflux was employed for purification of carbon nanotube (CNT) samples, obtained by the electric discharge method utilizing Zr(Co0.5Ni0.5)2, Ce3 (Co0.5Ni0.5)2 and Ce(Co0.5Ni0.5)5 as catalysts. Raman Spectroscopy provided information on the SWCNT presence in the untreated samples. Scanning Electron Microscopy (SEM) showed CNT with different diameters and lengths. Different acid treatment conditions were employed and the best results were achieved for HCl 3 mol/L aqueous solution during 24 h reflux. Transmission Electron Microscopy (TEM) images, associated with EDS, revealed the catalyst removal from the original sample and the presence of other carbon structures near the CNT formation. CNT acid functionalization for Pt nanoparticles dispersion was successful, resulting in a homogeneously dispersed system, as seen in TEM images. Temperature Programmed Oxidation (TPO) analysis of the raw and purified samples indicated that after purification there are three different carbon species present on the purified material, each one showing a different behavior towards O2 oxidation