As the catalysis community works toward fully rational catalyst design, an important area of study is the interaction between a catalyst and its support, especially the behavior at the interface. To gain an atomic level understanding of this interaction, a combined experiment and theory approach is necessitated. The interaction between catalyst and support affects many catalytically relevant properties of the system, including catalyst dispersion, particle shape, and electronic structure. Pt/γ-Al2O3 is an important catalyst system due to its widespread use in fuel cells, catalytic converters, and petroleum reforming. Commercially available γ-Al2O3 is highly polycrystalline and thus, it is difficult to directly correlate results from experiments with results from systems used in theoretical simulations, which possess specific crystal orientations and no impurities. To bridge this gap, we have synthesized a model catalyst using Pt nanoparticles of well-defined size and morphology on a single crystal γ-Al2O3 (111) thin film that enables us to study specific structural and electronic properties of the system at the nanoscale that can then be directly compared with computational results. By using electron energy loss spectroscopy (EELS) experiments in combination with EELS simulations—using the FEFF9 program—we have correlated some of the inter-related electronic and structural properties of the system. Our previous EELS data revealed an unusual feature in the electronic structure related to the local oxygen coordination that was seen only at the interface but not in the bulk γ-Al2O3. By creating different models of the Pt/γ-Al2O3 interface and calculating the expected EELS spectra for each model, we have determined that the most probable interface structure consists of Pt anchored at an O vacancy with free O atom(s) bonded to the Pt. Using this method, we also validated the use of the monoclinic γ-Al2O3 model—an approximate but computationally less demanding structure—as sufficiently accurate for EELS simulation, reducing the time and cost required. With this approach, we can now move further to study the nanoscale structural dynamics between the Pt catalyst and the underlying γ-Al2O3 support during reaction through in situ environmental TEM.

Atomic structure of the Pt/γ-Al2O3 interface through a combined experiment and theory approach: A model catalyst study

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.