Site-Selective Oxide Rearrangement in a Tandem Metal–Metal Oxide Catalyst Improves Selectivity in Oxidative Dehydrogenation of Propane

Abstract

Tandem metal–metal oxide catalysts, where metallic and metal oxide active sites work synergistically to drive complex chemistries, have been shown to improve the catalyst stability, activity, and selectivity. Although experimental techniques have probed the active site structure of such catalysts, the key atomic features that drive structure evolution under synthesis and reaction conditions remain poorly understood. Here, we develop a computational framework to elucidate the chemical, geometric, and stoichiometric features of the tandem overcoated catalyst, Pt-InOxHy, in driving the Oxidative Propane Dehydrogenation (ODHP) reaction, integrating propane dehydrogenation (PDH) and Selective Hydrogen Combustion (SHC). Exploration of the chemical space of stable InOxHyphases on Pt relevant to the experimental conditions reveals that the pore formation of the ALD-deposited InOxHycatalyst results from the oxide destabilization on well-coordinated Pt-terrace sites and preferential decoration around under-coordinated Pt-step sites. Reaction mechanistic analysis of the Pt-InOxHycatalyst reveals a dual-site mechanism for SHC, where O* activates on Pt and subsequently forms OH* at the InOxHysites, facilitating water formation and controlling overoxidation. Further, due to passivation of the under-coordinated Pt-step sites, the Pt-InOxHysurface exhibits similar PDH activity as that on a well-coordinated Pt-terrace surface, in addition to enhanced stability by destabilizing deep-dehydrogenated intermediates. These insights establish a structure–performance relationship of the Pt-InOxHycatalyst for ODHP chemistry, with key features being the extent of reducibility of the metal oxide and the sensitivity of the oxide structure to the oxygen chemical potential. This framework can be extended to other metal–metal oxide systems and complex reactions to develop next-generation tandem catalysts.