Pd and Pd-Co oxygen reduction nanocatalysts in acidic media

Palladium (Pd) and palladium-cobalt (Pd-Co) nanocatalysts were successfully synthesized by the chemical reduction method and characterized for the molecular oxygen reduction reaction (ORR) in acid medium. Both Pd and Pd-Co nanoparticles were prepared by the chemical reduction of palladium (II) chloride, PdCl ₂, and cobalt (II) chloride, CoCl ₂, as precursors and polyvinylpyrrolidine (PVP) as a protecting agent. The synthesized Pd/C and Pd-Co/C materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results conducted to the formation of bimetallic nanoparticles with an average size of 5 to 12 nm and a good dispersion of Pd-Co on carbon, as well as the formation of some nano-sized clusters particles. The crystallographic planes identified as (111) and a (200) corresponds to the formation of face-centered cubic (FCC) Pd with nanocrystalline structure.The nanocatalyst were supported on Vulcan® carbon XC-72 by the impregnation method and their electrochemical activity for the ORR was evaluated by cyclic voltammetry and rotating disk electrode techniques. The obtained results demonstrated that the Pd-based catalysts promoted the activity toward the ORR through a multi-electron charge transfer mechanism for the oxygen reduction to water formation.