Magic Number Pt13 and Misshapen Pt12 Clusters: Which One is the Better Catalyst?
Magic Number Pt13 and Misshapen Pt12 Clusters: Which One is the Better Catalyst?
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DOI：
10.1021/ja405922m
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发表时间：
2013-09-04
影响因子：
15
通讯作者：
Yamamoto, Kimihisa
中科院分区：
文献类型：
--
作者：
Imaoka, Takane;Kitazawa, Hirokazu;Yamamoto, Kimihisa
金属颗粒的大小与其催化活性之间的关系已在纳米级(2-10 nm)内建立起来。然而，在亚纳米尺度(0.5-2 nm)上应用是困难的，一个可能的原因是活性不再依赖于尺寸，而是作为团簇(或超原子)化合物的几何结构。我们现在报道，当只从由13个铂原子组成的魔数簇(铂-13)中移除一个原子时，氧还原反应(ORR)的催化活性显著提高。通过以树枝状大分子配体为模板，严格定义金属原子数，实现了原子级的精确合成。令人惊讶的是，铂-12簇的催化活性是铂-13簇的2倍以上。ESI-TOF-MASS和EXAFS分析提供了有关结构的信息。这些分析表明，铂-12具有变形的配位，而铂-13具有众所周知的二十面体原子配位，作为稳定团簇系列的一部分。基于密度泛函理论(DFT)的理论分析也支持这一观点。目前的结果暗示了亚稳态团簇的潜在活性，尽管它们在传统的统计合成中一直是“缺失的”物种。
A relationship between the size of metal particles and their catalytic activity has been established over a nanometer scale (2-10 nm). However, application on a subnanometer scale (0.5-2 nm) is difficult, a possible reason being that the activity no longer relies on the size but rather the geometric structure as a cluster (or superatomic) compound. We now report that the catalytic activity for the oxygen reduction reaction (ORR) significantly increased when only one atom was removed from a magic number cluster composed of 13-platinum atoms (Pt-13). The synthesis with an atomic-level precision was successfully achieved by using a dendrimer ligand as the macromolecular template strictly defining the number of metal atoms. It was quite surprising that the Pt-12 cluster exhibited more than 2-fold catalytic activity compared with that of the Pt-13 cluster. ESI-TOF-mass and EXAFS analyses provided information about the structures. These analyses suggested that the Pt-12 has a deformed coordination, while the Pt-13 has a well-known icosahedral atomic coordination as part of the stable cluster series. Theoretical analyses based on density functional theory (DFT) also supported this idea. The present results suggest potential activity of the metastable clusters although they have been "missing" species in conventional statistical synthesis.