Highly undercoordinated transition metal surface features have long been known to possess reactivity properties significantly different from those of idealized, close-packed metal surfaces. These unusual reactivities, in turn, suggest that undercoordinated features such as metal adclusters might serve as important active sites for various catalytic and electrocatalytic reactions. However, to date, neither the catalytic activity nor the stability of such clusters has been comprehensively studied.

In this contribution, we use first principles Density Functional Theory calculations to probe the reactivity of metal adatoms and adclusters for significant reactions in electrochemistry, including CO electrooxidation. We compare our theoretical results to corresponding activity measurements on adcluster-covered Pt(111) surfaces, and we present a simple thermodynamic formalism that can be used to understand the stability of these clusters on a variety of metal substrates.