Synthesis of carbon supported ordered tetragonal pseudo-ternary Pt2M′M″ (M = Fe, Co, Ni) nanoparticles and their activity for oxygen reduction reaction

Alloying Pt with 3d transition metals has attracted much attention due to their reduced Pt content and reports of enhanced electrocatalytic activity for proton exchange membrane fuel cell applications. However, synthesizing ordered nanocrystalline intermetallics in the sub-10 nm range can be challenging. Here, we report on the co-reduction synthesis of ordered ternary Pt-base transition metal intermetallics with particle sizes in the regime of 3-5 nm. Since differences in the activity of PtM (M = Fe, Co, Ni) for oxygen reduction reaction (ORR) have been reported, we explored their combinations: Pt2FeCo, Pt2FeNi, and Pt2CoNi. These ternary intermetallic nanoparticles crystallized in P4/mmm space group upon annealing in a protective KCl matrix. The electrocatalysts were prepared by dispersing these intermetallics onto a carbon support using ethylene glycol and various sonication techniques. A combination of analytical techniques including powder X-ray diffraction, thermogravimetric analysis, electron microscopy and electrochemical methods have been used in this study. The oxygen reduction reaction activity and stability of the catalysts were tested in 0.1 M HClO4 and 0.1 M H2SO4 using cyclic voltammetry and rotating disk electrode voltammetry. The correlations between the composition, structure, morphology and activity of the intermetallics have been established and are discussed.