Journal
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY
Volume 11, Issue 4, Pages 2944-2951Publisher
AMER SCIENTIFIC PUBLISHERS
DOI: 10.1166/jnn.2011.3899
Keywords
Metal Alloys; Oxygen Reduction Reaction; Density Functional Theory; Nanoparticle Catalyst; Electronic Structures
Categories
Funding
- New Energy and Industrial Technology Development Organization (NEDO)
- Special Coordination Funds for the Global Center of Excellence (CUE) program [H08]
- Grants-in-Aid for Scientific Research [22510107] Funding Source: KAKEN
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Bimetallic systems such as Pt-based alloys or non-alloys have exhibited interesting catalytic properties but pose a major challenge of not knowing a priori how the electronic and chemical properties will be modified relative to the parent metals. In this work, we present the origin of the changes in the reactivity of Pt/Cr and Pt/Ni catalysts, which have been of wide interest in fuel cell research. Using spin-polarized density functional theory calculations, we have shown that the modification of Pt surface reactivity in Pt/Ni is purely of geometric origin (strain). We have also found that the Pt-Ni bonding is very weak, which explains the observed instability of Pt-Ni catalysts under electrochemical measurements. On the other hand, Pt/Cr systems are governed by strong ligand effect (metal-metal interaction), which explains the experimentally observed reactivity dependence on the relative composition of the alloying components. The general characteristics of the potential energy curves for O-2 dissociative adsorption on the bimetallic systems and the pure Pt clarify why the d-band center still works for Pt/Cr despite the strong Pt-Cr bonding and high spin polarization of Pt d-states. On the basis of the above clarifications, viable Pt-Cr and Pt-Ni structures, which involve nano-sized alloys and non-alloy bulk catalyst, which may strike higher than the currently observed oxidation reduction reaction activity are proposed.
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