In contrast to bulk metal alloys, single atom alloys exhibit unique catalytic properties, which allow them to break the ubiquitous linear scaling relations. This desirable behavior is usually achieved by alloying a more reactive single atom into the surface of a less reactive metal.1 In this configuration, a reactant can be easily activated over the single reactive atom and its constituent fragments can spill over to the less reactive host surface. Thus, it is feasible to combine low activation barriers with weak adsorbate binding.2 While the possibilities of single atom alloy catalysis seem endless, one challenge is to find stable alloy combinations. To fulfill its catalytic role, the reactive metal must reside as isolated atom on the surface; however, reactive metals are generally more likely to adopt a high coordination number and segregate into the bulk. Alternatively, they may form clusters on the surface to maximize the number of strongly binding partners. Given the large number of synthesized and reported single atom alloy systems that break this rule of thumb, it is obvious that exceptions exist, but it is less obvious how they can be quickly identified. Thus, we used density functional theory to calculate the stability of 900 binary dilute metal alloys and differentiated between single atom alloy, ad-atom, dimer and subsurface geometries. We then analyzed this data set in several ways and derived a back-of-the-envelope estimate to predict the most stable geometry for any dilute metal alloy. While the predictions are not foolproof, they are rather valuable in guiding synthesis efforts and the discovery of new single atom alloy catalysts.

Back-of-the-envelope prediction of single atom alloy stability

2019 Fall National Meeting

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