Ultrasmall Cluster Model for Investigating Single Atom Catalysis: Dehydrogenation of 1-Propanamine by Size-Selected Pt 1 Zr 2 O 7 Clusters Supported on HOPG.

The selective dehydrogenation of hydrocarbons and their functionalized derivatives is a promising pathway in the realization of endothermic fuel systems for powering important technologies such as hypersonic aircraft. The recent surge in interest in single atom catalysts (SACs) over the past decade offers the opportunity to achieve the ultimate levels of selectivity through the subnanoscale design tailoring of novel catalysts. Experimental techniques capable of investigating the fundamental nature of the active sites of novel SACs in well-controlled model studies offer the chance to reveal promising insights. We report here an approach to accomplish this through the soft landing of mass-selected, ultrasmall metal oxide cluster ions, in which a single noble metal atom bound to a metal oxide moiety serves as a model SAC active site. This method allows the preparation of model catalysts in which monodispersed neutral SAC model active sites are decorated across an inert electrically conductive support at submonolayer surface coverage, in this case, PtZrO clusters supported on highly oriented pyrolytic graphite (HOPG). The results contained herein show the characterization of the PtZrO/HOPG model catalyst by X-ray photoelectron spectroscopy (XPS), along with an investigation of its reactivity toward the functionalized hydrocarbon molecule, 1-propanamine. Through temperature-programmed desorption/reaction (TPD/R) experiments it was shown that PtZrO/HOPG decomposes 1-propanamine exclusively into propionitrile and H, which desorb at 425 and 550 K, respectively. Conversely, clusters without the single platinum atom, that is, ZrO/HOPG, exhibited no reactivity toward 1-propanamine. Hence, the single platinum atom in PtZrO/HOPG was found to play a critical role in the observed reactivity.