Palladium Nanoshell Catalysts Synthesis on Highly Ordered Pyrolytic Graphite for Oxygen Reduction Reaction

A novel approach for the synthesis of palladium (Pd) nanoshells on highly ordered pyrolytic graphite (HOPG) surfaces for the oxygen reduction reaction (ORR) is described. Magnetron sputtering deposition was used to synthesize Pd thin films and nanoshells of different thicknesses on HOPG surfaces. Electrospun polymer fibers mats of poly(ethylene) oxide (PEO) were used as templates for the Pd nanoshells formation. The palladium thicknesses between 25 and 95 nm were deposited by magnetron sputtering. Scanning electron microscopy and energy-dispersive X-ray fluorescence spectroscopy were used to study the morphology and composition of the Pd nanoshells. Electrocatalytic activity toward the ORR and methanol tolerance in oxygen saturated 0.5 M H2SO4 solution was determined. Palladium nanoshells presented higher electrocatalytic activity toward ORR than Pd thin films of similar electrodes thicknesses and geometric area. Since palladium has higher methanol tolerance than platinum, the Pd nanoshells are promising electrode materials for direct methanol fuel cells (DMFC).