Highly Stable Subnanometric Pt Clusters in All Silica K-Doped Zeolites: Implications for the CO Oxidation Reaction

Abstract

Small metal clusters can provide improved catalytic activity compared with single metal atoms and larger metal nanoparticles of the same element. The stabilization of metal ensembles of a few atoms is extremely challenging, however, because reductive sintering and oxidative fragmentation are phenomena that often occur at low temperatures in reactive atmospheres. In this regard, the CO oxidation reaction is particularly challenging because CO tends to aggregate noble metals on nonreducible supports, such as SiO₂, whereas O₂ triggers the formation of (less active) single atoms on reducible supports, such as CeO₂. Accordingly, state-of-the-art Pt/CeO₂ catalysts undergo severe deactivation under practical CO oxidation conditions in excess of O₂. In this contribution, we report a highly active CO oxidation catalyst that is able to overcome both sintering and fragmentation instabilities under conditions that make other alternatives fail. The catalyst is based on small Pt clusters inside K-MFI that benefit from both strong metal/support interactions at defective sites of the zeolite and strong electronic promotion by the support, to attain highly stable, highly active, electron-rich Pt clusters.