Synthesis and Oxygen Reduction Electrocatalytic Property of Platinum Hollow and Platinum-on-Silver Nanoparticles

Pt-on-Ag bimetallic nanoparticles were prepared based on a heterogeneous nucleation and growth method. Interestingly, platinum hollow nanoparticles could be obtained by selectively removing the silver cores from Pt-on-Ag nanoparticles. High-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) analysis with a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM), and X-ray diffraction (XRD) were used to characterize these nanostructures. The observation that Pt hollows can be produced from Pt-on-Ag nanoparticles through the dissolution of Ag metal cores indicates that particle-on-particle nanodendrites were most likely derived from the products formed through the Stranski−Krastanov (SK) growth. The carbon-supported Pt hollow catalysts, which possessed much higher catalytic activity in oxygen reduction reaction (ORR) than the Pt-on-Ag nanoparticles, were also better than a commercial Pt catalyst (E-tek, 20% Pt). The nanometer-sized textures of the wall of Pt hollow spheres could contribute to the enhancement of the electrocatalytic activity.