Germanium as key dopant to boost the catalytic performance of small platinum clusters for alkane dehydrogenation

Pt is the most active pure metal for the dehydrogenation of light alkanes, to produce light alkenes, like ethylene and propylene. These compounds are exceedingly important products in the chemical industry. Pt, however, suffers from a low selectivity, tending to fully dehydrogenate hydrocarbons to pure carbon and giving rise to coking that blocks the active sites, deactivating the catalyst. Different dopants or coalloying agents have been proposed to tune its selectivity and produce catalysts with longer lifetimes, such as Sn, B and Si. However, often, the improved selectivity is achieved at the expense of catalytic activity. In this work we study MgO-supported Pt clusters and show that nanoalloying Pt with Ge can lead to an improved selectivity by halting deeper dehydrogenation that leads to coke, without harming the activity towards alkane dehydrogenation as compared to pure Pt clusters. Moreover, Ge reduces the propensity of Pt nanoclusters to deactivate via Ostwald ripening, and reduces the binding energy to carbon. Therefore, Ge-doped Pt nanocatalyst are more selective and resistant to deactivation. The effect of alloying Pt with Ge has an electronic origin: Ge quenches the unpaired electrons in the metal clusters, which are needed to activate alkenes for dehydrogenation. (C) 2019 Elsevier Inc. All rights reserved.