While single-site catalysts exhibit unique catalytic properties, their corresponding segregation tendencies can have a significant effect on their reactivity. Cu-based single atom alloys (SAA) are known for their potential to replace bulk precious metal catalysts, as the Cu host prevents the coking of noble metal active sites. However, Cu readily oxidizes, which must be taken into account in the underlying computational models if they are to reflect the complexities that are observed experimentally. Here, we take into account the effect of an oxide layer on the segregation tendencies of atomically dispersed noble metal atoms through a first principles-based model of a thin-film copper oxide layer that is deposited over Cu(111). We find that metal adatoms are stabilized when deposited over such a thin-film oxide layer (Figure 1, left panel) as compared to when they are deposited over a metallic Cu(111) substrate. However, when a thin-film oxide is deposited over a SAA surface (Figure 1, right panel) a local spatial distortion of the oxide overlayer is induced, causing the SAA to be destabilized as compared to when the thin-film oxide is absent. In this work, we identify the dominant driving factors of segregation, which switches from surface energy to SAA mixing energy in the presence of the oxide. Further insights into the influence of the oxygen on the segregation tendencies are elucidated by investigating the interaction between oxygen and SAAs on Cu(111) at low oxygen coverages. Our work demonstrates that the presence of thin-film oxides on Cu play a significant role in the segregation tendencies of SAAs, and must be taken into account during the screening of SAA systems on a theoretical and an experimental level.

Effect of thin-film copper oxide on Cu(111) based single-atom alloys

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