Tuning the surface strain and atom arrangement to control the surface chemistry process is one of efficient strategies to enhance the electrocatalytic performance of nanomaterials. This research introduces an ordered Pt3Ni2/C intermetallic nanoparticle as a new type of the Pt-Ni system for the ORR, which is rarely reported at present. Besides, it focuses on the phase conversion of Pt3Ni2/C nanocatalysts from a disordered phase to an ordered phase. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements confirm the formation of ordered face-centered cubic (fcc) type Pt3Ni2/C nanocatalysts with homogeneous particle distribution and average crystallite size of 6.4 nm. The ordered fcc-Pt3Ni2/C exhibits improved electrocatalytic activities toward the oxygen reduction reaction (ORR) in 0.1 M HClO4 and 0.1 M KOH electrolyte when compared with Pt3Ni2/C disordered alloy. Besides, the robust ordered fcc-Pt3Ni2/C showed a smaller activity loss after durability tests in alkaline medium than acid electrolyte. The improved ORR activity and stability could be ascribed to the surface atom arrangement and reasonable surface strain originated from the ordered structure of Pt3Ni2/C nanoparticles relative to the disordered Pt3Ni2/C alloy, forcefully demonstrating that the Pt3Ni2/C intermetallic compound may act as highly efficient ORR electrocatalysts in energy conversion process. (C) 2018 Elsevier Ltd. All rights reserved.