Oxygen Reduction Activity of Carbon-Supported Pt−M (M = V, Ni, Cr, Co, and Fe) Alloys Prepared by Nanocapsule Method

Abstract

Monodispersed Pt and Pt−M (M = V, Cr, Fe, Co, and Ni) alloy nanoparticles supported on carbon black (denoted as Pt/CB and Pt−M/CB) were prepared by the simultaneous reduction of platinum acetylacetonate and the second metal acetylacetonate within nanocapsules formed in diphenyl ether in the presence of carbon black. For the Pt/CBs, the average Pt diameters measured by scanning transmission electron microscopy (STEM) or X-ray diffraction (XRD) ranged from 2.0 to 2.5 nm, regardless of the catalyst-loading level from 10 to 55 wt % on CB. The alloy composition was found to be well-controlled to the projected value among the supported particles. The activities for the oxygen reduction reaction (ORR) at Nafion-coated catalysts in O₂-saturated 0.1 M HClO₄ solution were evaluated by using a channel flow electrode (CFE) cell at 30 °C. The area-specific ORR activities at Pt−M/CB were found to be 1.3 to 1.8 times higher than that at Pt/CB. The ORR activity increased in the order Pt/CB < Pt−Ni/CB < Pt−Fe/CB < Pt−Co/CB < Pt−V/CB < Pt−Cr/CB.