Solvothermal Synthesis of Platinum Alloy Nanoparticles for Oxygen Reduction Electrocatalysis

• Published in: Journal of the American Chemical Society Vol. 134; no. 20; pp. 8535 - 8542
• Main Authors: Carpenter, Michael K, Moylan, Thomas E, Kukreja, Ratandeep Singh, Atwan, Mohammed H, Tessema, Misle M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 23.05.2012
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja300756y

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 Pt3Ni, 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 Pt3Ni alloy nanoparticle catalysts showed specific activities greater than 1000 μA/cm2 Pt, alloy catalysts prepared with a nominal composition of PtNi displayed activities close to 3000 μA/cm2 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.