Free-atom-like d states in single-atom alloy catalysts
Free-atom-like d states in single-atom alloy catalysts
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DOI：
10.1038/s41557-018-0125-5
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发表时间：
2018-10-01
期刊：
影响因子：
21.8
通讯作者：
Schloegl, R.
中科院分区：
文献类型：
--
作者：
Greiner, M. T.;Jones, T. E.;Schloegl, R.
合金化提供了一种调整金属催化剂的电子结构从而调整其性能的方法；然而，金属中的平均场行为施加了限制。为了获得前所未有的催化行为，材料必须表现出突现性质，而不是简单地插入组成成分的性质。在这里，我们展示了单原子合金中的一种新兴电子结构，即少数元素和多数元素之间的弱波函数混合导致少数元素上的自由原子状电子结构。这种不寻常的电子结构改变了少数元素的吸附特性，使得与吸附剂的键合类似于分子金属配合物中的键合。我们在Cu中稀释的AgCu合金中证明了这一现象，其中Cu d态几乎不受自由原子态的干扰。原位电子能谱表明，这种不寻常的电子结构在反应条件下持续存在，并且在甲醇重整中表现出比本体Cu小0.1 eV的激活势垒。理论预测，其他几种稀释合金也表现出这种现象，这提供了一种设计方法，可能导致合金具有前所未有的催化性能。
Alloying provides a means by which to tune a metal catalyst's electronic structure and thus tailor its performance; however, mean-field behaviour in metals imposes limits. To access unprecedented catalytic behaviour, materials must exhibit emergent properties that are not simply interpolations of the constituent components' properties. Here we show an emergent electronic structure in single-atom alloys, whereby weak wavefunction mixing between minority and majority elements results in a freeatom-like electronic structure on the minority element. This unusual electronic structure alters the minority element's adsorption properties such that the bonding with adsorbates resembles the bonding in molecular metal complexes. We demonstrate this phenomenon with AgCu alloys, dilute in Cu, where the Cu d states are nearly unperturbed from their free-atom state. In situ electron spectroscopy demonstrates that this unusual electronic structure persists in reaction conditions and exhibits a 0.1 eV smaller activation barrier than bulk Cu in methanol reforming. Theory predicts that several other dilute alloys exhibit this phenomenon, which offers a design approach that may lead to alloys with unprecedented catalytic properties.