title: Solvothermal synthesis of platinum alloy nanoparticles for oxygen reduction electrocatalysis.
abstract: Platinum alloy nanoparticles show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. We report here on the use of N,N-dimethylformamide (DMF) as both solvent and reductant in the solvothermal synthesis of Pt alloy nanoparticles (NPs), with a particular focus on Pt-Ni alloys. Well-faceted alloy nanocrystals were generated with this method, including predominantly cubic and cuboctahedral nanocrystals of Pt(3)Ni, and octahedral and truncated octahedral nanocrystals of PtNi. X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), coupled with energy dispersive spectroscopy (EDS), were used to characterize crystallite morphology and composition. ORR activities of the alloy nanoparticles were measured with a rotating disk electrode (RDE) technique. While some Pt(3)Ni alloy nanoparticle catalysts showed specific activities greater than 1000 μA/cm(2)(Pt), alloy catalysts prepared with a nominal composition of PtNi displayed activities close to 3000 μA/cm(2)(Pt), or almost 15 times that of a state-of-the-art Pt/carbon catalyst. XRD and EDS confirmed the presence of two NP compositions in this catalyst. HAADF-STEM examination of the PtNi nanoparticle catalyst after RDE testing revealed the development of hollows in a number of the nanoparticles due to nickel dissolution. Continued voltage cycling caused further nickel dissolution and void formation, but significant activity remained even after 20,000 cycles.
authors.affiliation: Electrochemical Energy Research Lab, General Motors R&D Center, Warren, Michigan 48090, United States. michael.k.carpenter@gm.com
authors.forename: Michael K
authors.initials: MK
authors.lastname: Carpenter
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Moylan
authors.forename: Ratandeep Singh
authors.initials: RS
authors.lastname: Kukreja
authors.forename: Mohammed H
authors.initials: MH
authors.lastname: Atwan
authors.forename: Misle M
authors.initials: MM
authors.lastname: Tessema