When more is less: Nonmonotonic trends in adsorption on clusters in alloy surfaces

What is it about?

Single-atom alloy catalysts have attracted significant attention in recent years, as they can exhibit unusual chemical and electronic properties. These catalysts consist of a single more reactive metal atom embedded in a more inert surface (e.g., a Cu atom embedded in a Ag surface). Here, we studied a somewhat broader class of materials, where 1–3 atoms of a guest metal are doped into the surface of a host metal. In several cases, we find counterintuitive, nonmonotonic trends in adsorption energies, in sharp contrast to findings on other alloy surfaces. For example, Mo binds H much stronger than Ag, but we find that a Ag surface embedded with 2 Mo atoms binds H more weakly than pure Ag. This is not the case for 1 or 3 Mo atoms embedded in Ag. We link this unintuitive behavior to the sharp, localized electronic states in these surfaces, which makes them similar to supported or unsupported nanoclusters. This strengthens and generalizes previous links between single atom alloys and supported single-atom catalysts.

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Photo by Ricardo Gomez Angel on Unsplash

Photo by Ricardo Gomez Angel on Unsplash