Probing the Local Bonding at the Pt/γ-Al<inf>2</inf>O<inf>3</inf> Interface

Metal-support interactions significantly affect the performance of heterogeneous catalysts, of which Pt supported on γ-Al2O3 is one of the most widely used. Characterizing the bonding of Pt on the γ-Al2O3 surface is key to fully understanding the catalyst-support interaction. Herein aberration-corrected and monochromated scanning transmission electron microscopy-based electron energy-loss spectroscopy (STEM-EELS) were employed on a model Pt/γ-Al2O3(111) catalyst to locally investigate the bonding between Pt and the γ-Al2O3 support. Differences in the aluminum L2,3-edge and oxygen K-edge EELS near-edge fine structure between spectra acquired at the Pt/γ-Al2O3(111) interface and the bulk γ-Al2O3 served as signatures of the interfacial bonding environment. Fine structure in the interface-localized Al-L2,3 edge suggested a larger fraction of tetrahedrally coordinated Al atoms at the Pt/γ-Al2O3(111) interface, which was confirmed by DFT simulations. The interface-localized O-K edge EELS revealed a prepeak associated with several types of oxygen bonding. To determine the specific interfacial O bonding, O-K edge EELS spectra were simulated from an array of Pt/γ-Al2O3(111) bonding configuration models. The simulated EELS from the interfacial bonding models revealed an O bonding motif consistent with the experimental O-K edge EELS fine structure.