Fine-tuning metal clusters
Fine-tuning metal clusters
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DOI：
10.1038/372320a0
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发表时间：
1994-11
期刊：
影响因子：
64.8
通讯作者：
M. Boudart
中科院分区：
文献类型：
--
作者：
M. Boudart
今天使用的许多工业催化剂是散布在多孔材料内表面上的金属，作为载体或支撑物。这样的催化剂具有每克催化剂暴露许多平方米金属的巨大表面积。金属通常是以包含10-100个原子的簇的形式存在。每个簇中的许多金属原子，有时接近100%，暴露于反应混合物，这在昂贵的铂族金属的情况下是特别理想的。但由于簇是如此之小（1-10 nm），出现了簇大小对催化活性的影响的问题。当团簇包含的原子少于50个时，这个问题就变得很难解决，部分原因是很难合成具有均匀大小的团簇，每个团簇的原子数是已知的。在过去的十年里，人们已经收集了大量的自由团簇，但是现在，在本期第346页报道的工作中，盖茨和他的同事们已经成功地生产出了用于催化测试的支持团簇。首先是一些定义。催化剂是通过提供循环路径而引起化学反应的物质，反应物沿着该循环路径沿着变成产物，而催化剂在循环结束时被回收。催化剂的活性用每秒循环的转数表示，表示为周转频率（TOF）。后者是一
MANY industrial catalysts used today are metals that are spread over the internal surface of porous materials acting as carriers or supports. Such catalysts have enormous surface areas of many square metres of metal exposed per gram of catalyst. The metal is usually in the form of clusters containing 10-100 atoms. Many, sometimes close to 100 per cent, of the metal atoms in each cluster are exposed to the reacting mixtures, and this is especially desirable in the case of expensive platinum-group metals. But as the clusters are so tiny (1-10 nm), the question arose as to the effect of cluster size on catalytic activity. Answering that question becomes hard when the clusters contain fewer than about 50 atoms, in part because of the difficulty of synthesizing clusters of uniform size with a known number of atoms per cluster. Collections of free clusters have been made in the past decade, but now, in work reported on page 346 of this issue1, Gates and colleagues have succeeded in producing supported clusters for catalytic testing. First, some definitions. A catalyst is a substance that brings about a chemical reaction by providing a cyclic path along which reactants become products, while the catalyst is recovered at the end of the cycle. The activity of the catalyst is expressed by the number of revolutions of the cycle per second, expressed as a turnover frequency (TOF). The latter is a