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 free-atom-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.

合金化提供了一种手段，可以调节金属催化剂的电子结构，从而调整其性能。但是，金属中的平均场行为具有一定的局限性。为了获得前所未有的催化性能，材料必须表现出新兴的特性，而不仅仅是组成成分特性的简单内插。在这里，我们显示了单原子合金中出现的电子结构，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出现了类似自由原子的电子结构。这种异常的电子结构改变了少数元素的吸附特性，因此与被吸附物的键合类似于分子金属络合物中的键合。我们用稀释在铜中的AgCu合金证明了这种现象，其中Cu d态几乎不受其自由原子态的干扰。原位电子光谱表明，这种不寻常的电子结构在反应条件下仍然存在，并且在甲醇重整中比本体Cu的活化势垒小0.1 eV。理论预测，其他几种稀合金也会出现这种现象，这提供了一种设计方法，可能导致合金具有空前的催化性能。