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

TL;DR

This study reveals a periodic trend in adsorption energies around single-atom alloy active sites, showing a zone of exclusion that influences reactant diffusion and offers new avenues for catalyst design.

Contribution

It uncovers a previously unrecognized physical effect causing destabilization of adsorption near dopant sites, supported by DFT calculations and experiments.

Findings

Adsorption destabilization up to 300 meV near dopant sites.

Identification of a zone of exclusion around reactive sites.

Experimental confirmation of increased diffusion barriers for CO.

Abstract

Single-Atom Alloys (SAAs) are 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 destabilised by up to 300 meV on host sites within the perimeter of the reactive dopant site. We identify periodic trends for this behaviour, 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 CO diffusion towards the dopant on a RhCu SAA. This effect offers new possibilities for understanding and designing active sites with tunable energetic landscapes surrounding them.