Influence of local chemical environment on the catalytic properties of Ir1/CeO2 single-atom catalysts in CO oxidation

Supported single-atom catalysts (SACs) are of great interest in catalysis due to their highly efficient use of costly noble metals and unique reactivities, which are deeply influenced by the local coordination environment of the active site. Herein, the catalytic properties of single Ir adatoms on CeO$_2$ have been simulated at finite temperature with \emph{ab-initio} thermodynamics and microkinetic modelling, deriving analytical expressions for the turnover frequency of the catalyst at different operative regimes, compatible with experimental conditions. According to our findings, the adsorption geometry of single Ir adatoms on CeO$_2$ is governed by the surface termination, resulting in remarkably different catalytic activities: on the (110) surface, the high stability of square-planar IrO$_x$(CO)$_y$ units results in a high propensity towards CO poisoning. On the (111) surface, the local environment of the Ir adatom allows for a greater number of ligands, resulting in greater catalytic activity.