Diborane Interactions with Pt7/Alumina: Preparation of Size-Controlled Borated Pt Model Catalysts
2018
Baxter, Eric T. | Hà, Mai Anh | Cass, Ashley C. | Zhai, Huanchen | Alexandrova, Anastassia N. | Anderson, Scott L.
Bimetallic catalysts provide the ability to tune catalytic activity, selectivity, and stability. Model catalysts with size-selected bimetallic clusters on well-defined supports offer a useful platform for studying catalytic mechanisms; however, producing size-selected bimetallic clusters can be challenging. In this study, we present a way to prepare bimetallic model (PtₙBₘ/alumina) cluster catalysts by depositing size-selected Pt₇ clusters on an alumina thin film, then selectively adding boron by exposure to diborane, and heating. The interactions between Pt₇/alumina and diborane were probed using temperature-programmed desorption/reaction (TPD/R), X-ray photoelectron spectroscopy (XPS), low-energy ion scattering (ISS), plane wave density functional theory (PW-DFT), and molecular dynamic (MD) simulations. It was found that the diborane exposure/heating process does result in preferential binding of B in association with the Pt clusters. Borated Pt clusters are of interest because they are known to exhibit reduced affinity to carbon deposition in catalytic dehydrogenation. At high temperatures, theory, in agreement with experiment, shows that boron tends to migrate to sites beneath the Pt clusters, forming Pt–B–Oₛᵤf bonds that anchor the clusters to the alumina support.
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