Controlling Hydrocarbon (De)Hydrogenation Pathways with Bifunctional PtCu Single-Atom Alloys

The
conversions of surface-bound alkyl groups to alkanes and alkenes
are important steps in many heterogeneously catalyzed reactions. On
the one hand, while Pt is ubiquitous in industry because of its high
activity toward C–H activation, many Pt-based catalysts tend
to overbind reactive intermediates, which leads to deactivation by
carbon deposition and coke formation. On the other hand, Cu binds
intermediates more weakly than Pt, but activation barriers tend to
be higher on Cu. We examine the reactivity of ethyl, the simplest
alkyl group that can undergo hydrogenation and dehydrogenation via
β-elimination, and show that isolated Pt atoms in Cu enable
low-temperature hydrogenation of ethyl, unseen on Cu, while avoiding
the decomposition pathways on pure Pt that lead to coking. Furthermore,
we confirm the predictions of our theoretical model and experimentally
demonstrate that the selectivity of ethyl (de)­hydrogenation can be
controlled by changing the surface coverage of hydrogen.