Ni@Pt Core−Shell Nanoparticles:  Synthesis, Structural and Electrochemical Properties

Core−shell nanoparticles composed of a nonnoble metal core and a noble metal shell are of great significance in many areas including chemical catalysis, optical detection, and magnetic separation. Through a modification of the commonly used polyol process, Ni@Pt core−shell nanoparticles that are less than 10 nm in total size and have a very thin Pt shell can be fabricated by a sequential reduction approach. The prepared core−shell nanoparticles were characterized with TEM, XRD, molecular dynamics (MD) simulations, and electrochemical method. It was found that these core−shell particles exhibit the structural characteristics of fcc Ni nanocrystals with a slightly expanded lattice constant but the electrochemical properties of a Pt surface with a significantly shortened Pt−Pt interatomic distance than for pure Pt nanoparticles. The structural characteristics of the prepared core−shell particles revealed by the TEM, XRD, and electrochemical analyses were well verified by MD simulations of a Ni@Pt core−shell particle with a monolayer Pt shell. It is believed that the prepared Ni@Pt core−shell nanoparticles could be promising cathode catalysts in PEM fuel cells with much reduced Pt content but significantly increased catalytic activity.