Atomistic Models for Highly‐Dispersed PtSn/γ‐Al2O3 Catalysts: Ductility and Dilution Affect the Affinity for Hydrogen

Abstract

AbstractSupported platinum‐based sub‐nanometric particles play a central role in many catalytic applications. In particular, platinum‐tin active phases supported on γ‐Al2O3 are largely employed for dehydrogenation of alkanes and catalytic reforming of naphtha cuts, although geometric and electronic effects of the active phase in the presence of hydrogen still remains highly debated. Thanks to periodic density functional theory (DFT), we propose structural models of such systems containing thirteen metal atoms (PtxSn13‐x with 0≤x≤13) deposited on the (100) γ‐Al2O3 surface. We thus unravel the intricate effects of the composition (Pt/Sn ratio), of the support (γ‐Al2O3) and the hydrogen coverage on the stability of platinum‐tin sub‐nanometric clusters, in the case where tin is reduced (Sn0). A detailed investigation of the interaction of the supported Pt10Sn3 cluster with hydrogen by velocity‐scaled molecular dynamics provides a mapping of the hydrogen coverage as a function of the operating conditions (T, P(H2)). Our study highlights significant differences between Pt13 and PtxSn13‐x clusters in terms of ductility and dilution (also called ensemble) effects which may be at the origin of the different reactivities usually reported for Pt and PtSn supported catalysts.