Insight into Single-Atom-Induced Unconventional Size Dependence over CeO2-Supported Pt Catalysts

Identification of the structure-performance relationship at the atomic level is vital for getting a deep understanding of the size-dependence behavior of metal catalysts. Here, an unconventional size dependence of Pt toward selective hydrogenation of p-chloronitrobenzene has been extensively investigated over CeO2 support. An upturned volcanic curve toward the selectivity of p-chloroaniline was found by decreasing the size of Pt from nanoparticles to single atoms. Differences on predominant orbitals among diverse coordination-environment Pt sites were identified to be the key factors influencing the modes of interaction with the C-CI bond of p-chloroaniline. Specifically, electrostatic repulsion between nonbonding orbitals of CI and predominant orbitals of Pt sites with high steric hindrance were speculated to be responsible for the suppression of dehalogenation and the high selectivity. This strategy to build correlation between the valence orbitals of active sites and their catalytic behavior could well be expanded to other structure-sensitive reactions and atomically dispersed catalysts.