Periodic Trends in Adsorption Energies around Single-Atom Alloy Active Sites

Single-atom alloys (SAAs) make up
a special class of alloy surface
catalysts that offer well-defined, isolated active sites in a more
inert metal host. The dopant sites are generally assumed to have little
or no influence on the properties of the host metal, and transport
of chemical reactants and products to and from the dopant sites is
generally assumed to be facile. Here, by performing density functional
theory calculations and surface science experiments, we identify a
new physical effect on SAA surfaces, whereby adsorption is destabilized
by ≤300 meV on host sites within the perimeter of the reactive
dopant site. We identify periodic trends for this behavior and demonstrate
a zone of exclusion around the reactive sites for a range of adsorbates
and combinations of host and dopant metals. Experiments confirm an
increased barrier for diffusion of CO toward the dopant on a RhCu
SAA. This effect offers new possibilities for understanding and designing
active sites with tunable energetic landscapes surrounding them.