Theoretical Evidence of PtSn Alloy Efficiency for CO Oxidation
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- 作者：Cé ; line Dupont ; Yvette Jugnet ; and David Loffreda
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：July 19, 2006
- 年：2006
- 卷：128
- 期：28
- 页码：9129 - 9136
- 全文大小：387K
- 年卷期：v.128,no.28(July 19, 2006)
- ISSN：1520-5126
文摘
The efficiency of PtSn alloy surfaces toward CO oxidation is demonstrated from first-principlestheory. Oxidation kinetics based on atomistic density-functional theory calculations shows that the Pt3Snsurface alloy exhibits a promising catalytic activity for fuel cells. At room temperature, the correspondingrate outstrips the activity of Pt(111) by several orders of magnitude. According to the oxidation pathways,the activation barriers are actually lower on Pt3Sn(111) and Pt3Sn/Pt(111) surfaces than on Pt(111). Ageneralization of Hammer's model is proposed to elucidate the key role of tin on the lowering of the barriers.Among the energy contributions, a correlation is evidenced between the decrease of the barrier and thestrengthening of the attractive interaction energy between CO and O moieties. The presence of tin modifiesalso the symmetry of the transition states which are composed of a CO adsorbate on a Pt near-top positionand an atomic O adsorption on an asymmetric mixed PtSn bridge site. Along the reaction pathways, aCO2 chemisorbed surface intermediate is obtained on all the surfaces. These results are supported by athorough vibrational analysis including the coupling with the surface phonons which reveals the existenceof a stretching frequency between the metal substrate and the CO2 molecule.