Synthesis and Study of Structurally Ordered FePt Nanoparticles As Highly Active and Durable Catalysts for Oxygen Reduction Reaction

Abstract

Finding a highly active and durable nanocatalyst under routinely used proton exchange membrane fuel cell operating conditions (60 - 80 oC) is urgent for the commercialization of fuel cells. Many nanocatalysts have been reported to have much improved oxygen reduction reaction (ORR) activity compared to the commercially used Pt/C catalyst. However, few of them can meet the durability requirement. In this report, monodisperse face-centered-tetragonal (fct) (L10) FePt nanoparticles with size of ~ 9 nm were synthesized from dumbbell-like face-centered-cubic (fcc)-FePt-Fe3O4 nanoparticles. The durability of C-fct-FePt nanoparticles as ORR catalysts at 60 oC was studied and it was found that these nanoparticles served as a highly active and durable ORR catalyst. Its mass activity was found to be about 5.4 times that of commercial Pt/C. Also, no obvious loss in ORR activity was observed after 10,000 cycles. A perchloric acid-treatment and subsequent annealing treatment were found to improve the durability of fct-FePt nanoparticles at 60 oC. The highly ordered L10 structure, with alternating layers of Fe and Pt atoms, as well as the Pt skin formed after the acid-treatment, were hypthesized to be the main reason for the durability enhancement. Our work demonstrates a reliable approach to structurally ordered FePt nanoparticles as a promising candidate for practical use in fuel cells.