Influence of LocalChemical Environment on the CatalyticProperties of Ir₁/CeO₂ Single-Atom Catalystsin 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 CeO₂ have been simulated at finite temperature with ab initio thermodynamics and microkinetic modeling, 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 CeO₂ is governed by the surface termination, resulting in remarkably different catalytic activities: on the (110) surface, the high stability of square-planar IrO_<i>x</i>(CO)_<i>y</i> units results in a high propensity toward 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.