Oxygen Reduction on Well-Defined Core−Shell Nanocatalysts: Particle Size, Facet, and Pt Shell Thickness Effects

• Published in: Journal of the American Chemical Society Vol. 131; no. 47; pp. 17298 - 17302
• Main Authors: Wang, Jia X, Inada, Hiromi, Wu, Lijun, Zhu, Yimei, Choi, YongMan, Liu, Ping, Zhou, Wei-Ping, Adzic, Radoslav R
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 02-12-2009
• Subjects: 30 DIRECT ENERGY CONVERSION; BINDING ENERGY; CONTRACTION; core-shell nanoparticle catalysts; ELECTRONS; ENERGY-LOSS SPECTROSCOPY; fuel cell; functional nanomaterials; FUNCTIONALS; OPTIMIZATION; OXYGEN; oxygen reduction; PARTICLE SIZE; STRAINS; SURFACE AREA; THICKNESS; TRANSMISSION ELECTRON MICROSCOPY
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja9067645

We examined the effects of the thickness of the Pt shell, lattice mismatch, and particle size on specific and mass activities from the changes in effective surface area and activity for oxygen reduction induced by stepwise Pt-monolayer depositions on Pd and Pd3Co nanoparticles. The core−shell structure was characterized at the atomic level using Z-contrast scanning transmission electron microscopy coupled with element-sensitive electron energy loss spectroscopy. The enhancements in specific activity are largely attributed to the compressive strain effect based on the density functional theory calculations using a nanoparticle model, revealing the effect of nanosize-induced surface contraction on facet-dependent oxygen binding energy. The results suggest that moderately compressed (111) facets are most conducive to oxygen reduction reaction on small nanoparticles and indicate the importance of concerted structure and component optimization for enhancing core−shell nanocatalysts’ activity and durability.