Octahedral PtNi nanoparticles with controlled surface structure and composition for oxygen reduction reaction

Controlling the surface structure and composition at the atomic level is an effective way to tune the catalytic properties of bimetallic catalysts. Herein, we demonstrate a generalized strategy to synthesize highly monodisperse, surfactant-free octahedral Pt_xNi_1−x nanoparticles with tunable surface structure and composition. With increasing the Ni content in the bulk composition, the degree of concaveness of the octahedral Pt_xNi_1−x nanoparticles increases. We systematically studied the correlation between their surface structure/composition and their observed oxygen reduction activity. Electrochemical studies have shown that all the octahedral Pt_xNi_1−x nanoparticles exhibit enhanced oxygen reduction activity relative to the state-of-the-art commercial Pt/C catalyst. More importantly, we find that the surface structure and composition of the octahedral Pt_xNi_1−x nanoparticles have significant effect on their oxygen reduction activity. Among the studied Pt_xNi_1−x nanoparticles, the octahedral Pt₁Ni₁ nanoparticles with slight concaveness in its (111) facet show the highest activity. At 0.90 V vs. RHE, the Pt mass and specific activity of the octahedral Pt₁Ni₁ nanoparticles are 7.0 and 7.5-fold higher than that of commercial Pt/C catalyst, respectively. The present work not only provides a generalized strategy to synthesize highly monodisperse, surfactant-free octahedral Pt_xNi_1−x nanoparticles with tunable surface structure and composition, but also provides insights to the structure-activity correlation. © 2017, Science China Press and Springer-Verlag Berlin Heidelberg.