Core-shell palladium@platinum/graphene composite (denoted as Pd@Pt/GNs (PDDA)) was synthesized by successive reduction with formic acid as a reducing agent and poly(diallyldimethylammonium chloride) solution (PDDA) as a structure-directing agent at ambient temperature. The as-synthesized Pd@Pt/GNs (PDDA) was characterized by transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicate that hydrangea-like PtPd bimetallic nanoclusters on graphene (GNs) are formed with the aid of morphology control of PDDA. Especially, they are in a typical core-shell structure with Pd as core and Pt as shell, which are uniformly dispersed on the surface of GNs. Electrocatalytic tests show that Pd@Pt/GNs (PDDA) exhibits superior electrocatalytic activity for methanol oxidation (with the mass activities of 870.8mAmg(-1) Pt) in comparison with the commercial Pt/C and alloyed Pd-Pt/GNs (PDDA) catalysts owing to its unique Pd core Pt shell hydrangea-like structure and the synergistic effects between Pd@Pt and GNs. (C) 2017 Elsevier B.V. All rights reserved.