High electroactivity performance in Pt/MWCNT and PtNi/MWCNT electrocatalysts

This work presents the synthesis, characterization and electrochemical evaluation of electrocatalysts for PEM fuel cells base on Pt and Pt-Ni nanoparticles over multi-walled carbon nanotubes (MWCNT). The MWCNT were synthesized by spray pyrolysis of toluene, using ferrocene and nickelocene as catalytic agents. The Pt nanoparticles were deposited using the ultrasound assisted aqueous deposition method, followed by either thermal or chemical reduction. The materials were characterized by scanning and transmission electron microscopy, as well as X-ray diffraction. The MWCNT exhibit lengths of 200 μm (using ferrocene) and 30 μm (using nickelocene) and diameters around 50-70 nm. Pt nanoparticles showed sizes between 4 and 8 nm. The electrochemical active area toward the hydrogen oxidation reaction was evaluated by cyclic voltammetry (CV) in a standard three electrodes cell. In addition to corroborate the electrochemical active area, CO stripping tests were done. From both, the CV and CO stripping analyses, it was found that the synthesized electrocatalysts exhibited an electrochemical activity higher (140-230 m ²gr^-1) than 10%Pt/Vulcan (Etek).