To reduce Pt loading in proton exchange membrane (PEM) fuel cells, we synthesized (111) faceted octahedral PtNi nanoparticles supported by carbon black (octahedral PtNi NPs/C) using a new chemical method, and evaluated the effect of reduction of Pt loading and durability in actual PEM fuel cells. We confirmed that the synthesized particles were octahedral and the PtNi alloy nanoparticles had a size of 10-15 nm. In high resolution transmission electron microscopy analysis, nearly all exposed surfaces of the octahedral PtNi NPs were identified as (111) facets. Energy dispersion X-ray spectroscopy analysis showed that the corners and edges of the octahedral PtNi NPs were richer in platinum than the internal region, thus it was determined that the octahedral PtNi NPs adopted a core -shell structure. Mass activity of octahedral PtNi NPs/C as a cathode in fuel cells was 3.4 times higher than that of commercial Pt catalysts. This corresponds to a 71% reduction of Pt for the cathode. In potential cycling tests, the octahedral PtNi NPs/C also exhibited better durability than the commercial Pt catalysts. (C) 2014 Elsevier B.V. All rights reserved.