Hybrid via Zoom and
KIT, Campus Süd
Geb. 11.21
Lecture hall 006
Kaiserstraße 12
76131 Karlsruhe

15:00

Prof. Dr. Melissa Santala

Metal nanoparticles on metal-oxides play a critical role in catalysis since most industrial catalytic processes depend on supported catalyst particles. The activity and selectivity of metal nanoparticles (NPs) used in heterocatalysis depends on their size, shape, and interactions between the metal and the oxide support. In this work, transmission electron microscopy (TEM) characterization of a model Pt/y-alumina system are used to guide and validate density functional theory (DFT) based calculations. Pt NPs were formed in dense y-alumina through solid-state precipitation into sapphire partially amorphized by high-energy ion implantation of Pt. Thermal annealing re-crystallizs the amorphized alumina as a y-alumina and precipitates Pt NPs. The Pt NPs take a cube-on-cube orientation relationship with the y-alumina and are in the form of tetrahedra and truncated tetrahedra bound by primarily by {111} facets. Aberration corrected atomic-resolution scanning TEM (STEM) images of the these Pt/y-alumina interfaces are compared two experimentally-based bulk models of y-alumina and a density functional theory (DFT) based model of (111) interfaces with different chemical terminations (O, Al1, Al2) of the y-alumina. The oxygen-terminated interface model best fits the experimental data and provides a very good match at the interface. However, the fit of the interface model is poorer beyond the third atomic layer in the y-alumina. This is attributed to compromises required in the design of the model to limit the cell size and computational time required for DFT calculations. Understanding the accuracy and limits of the structural models of y-alumina and Pt/y-alumina interfaces is important to further the understanding the structure/property relationships in this system