Study of oxygen reduction reaction kinetics on multi-walled carbon nano-tubes supported Pt–Pd catalysts under various conditions

Multi-walled carbon nano-tube supported Pt–Pd nanoparticles catalysts were prepared using NaBH4 as a reducing agent in either KOH or water for use as a cathode catalyst in polymer electrolyte membrane fuel cells (PEMFCs). X-ray diffraction (XRD) showed that compared to catalyst prepared in the absence of KOH, other catalyst has smaller particle sizes. Using the resulting multi-walled carbon nano-tube supported Pt–Pd catalysts, the catalyst particle size affects on the kinetics of the oxygen reduction reaction (ORR) were analyzed using cyclic voltammetry (CV) and rotating disk electrode (RDE) voltammetry. From RDE voltammetric studies, it was found that for both catalysts; the number of electrons, n, involved in the ORR was nearly four at potential 0.3 V versus Ag/AgCl (3 M KCl). Results also showed that the 2-step four electron reduction of O2 to H2O precede more favorably on the catalyst with smaller particle size.