Dynamic Behavior of Platinum Atoms and Clusters in the Native Oxide Layer of Aluminum Nanocrystals.

Abstract

Strong metal-support interactions (SMSIs) are well-known in the field of heterogeneous catalysis to induce the encapsulation of platinum (Pt) group metals by oxide supports through high temperature H₂ reduction. However, demonstrations of SMSI overlayers have largely been limited to reducible oxides, such as TiO₂ and Nb₂O₅. Here, we show that the amorphous native surface oxide of plasmonic aluminum nanocrystals (AlNCs) exhibits SMSI-induced encapsulation of Pt following reduction in H₂ in a Pt structure dependent manner. Reductive treatment in H₂ at 300 °C induces the formation of an AlO_<i>x</i> SMSI overlayer on Pt clusters, leaving Pt single-atom sites (Pt_iso) exposed available for catalysis. The remaining exposed Pt_iso species possess a more uniform local coordination environment than has been observed on other forms of Al₂O₃, suggesting that the AlO_<i>x</i> native oxide of AlNCs presents well-defined anchoring sites for individual Pt atoms. This observation extends our understanding of SMSIs by providing evidence that H₂-induced encapsulation can occur for a wider variety of materials and should stimulate expanded studies of this effect to include nonreducible oxides with oxygen defects and the presence of disorder. It also suggests that the single-atom sites created in this manner, when combined with the plasmonic properties of the Al nanocrystal core, may allow for site-specific single-atom plasmonic photocatalysis, providing dynamic control over the light-driven reactivity in these systems.