Star-Shaped Pd@Pt Core-Shell Catalysts Supported On Reduced Graphene Oxide With Superior Electrocatalytic Performance

Reduced graphene oxide (RGO)-supported bimetallic Pd-Pt nanostructures with core-shell Pd@Pt (Pd@Pt/RGO) and alloyed PdPt (PdPt/RGO) were prepared by a one-pot reduction approach using L-ascorbic acid for the reduction of both the metal precursors and the graphene oxide supports. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), and Raman spectroscopy revealed that the three-dimensionally shaped Pd-Pt nanostructures were uniformly deposited onto the reduced graphene oxide surface. The RGO-supported core-shell Pd@Pt and alloyed PdPt catalysts were confirmed and investigated by high-angle annular dark-field scanning TEM (HADDF-STEM) with energy-dispersive X-ray spectroscopy (EDX) in addition to X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and cyclic voltammetry (CV). With the synergetic effects of the binary Pd-Pt system and the RGO support, these catalysts exhibited considerably enhanced catalytic activities and stabilities for the oxidation of methanol in an alkaline solution compared to monometallic Pt/RGO and commercially available carbon-supported Pt (Pt/C) catalysts. The star-shaped core-shell Pd@Pt/RGO catalysts exhibited the greatest improvement in electrocatalytic performance in terms of current density, onset potential, stability, and the charge transfer rate.