Catalyst nanoparticles hold the key to more efficient conversion of biomass-derived molecules to fuels. Most of the current biomass catalysts are noble metallic nanoparticles, such as Pt and Pd, on a support. Incorporation of less expensive elements can both increase the conversion efficiency and reduce the cost of catalysts. For example, Ro et al. have shown that deposition of Mo onto Pt/SiO<sub>2</sub> catalyst can increase the turnover frequency of the reverse water gas shift and acetone hydrogenation reactions by a factor of 55 and 200, respectively. Despite their ubiquity and importance, catalysts nanoparticles are often developed by trial and error, in part due to the difficulty in identifying and quantifying the atomic-scale structure, a key step in a rational design catalyst design scheme.<br/>In this work, we investigated the atomic arrangement of PtMo catalyst nanoparticles &lt; 5 nm in diameter, small enough to have reasonable catalytic efficiency, using quantitative high angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM). An example of the HAADF STEM analysis is shown in the figure. By comparing the experimental HAADF intensity map, shown on the left, with simulations, the number of atoms and species in each atomic columns can be determined. A unit cell by unit cell strain map is shown on the right of the figure, with the color scale indicating the magnitude of the strain in the direction of the arrow. The map shows overall lattice expansion at the particle edge, compared to its center. The effects of beam damage at higher dose than used in the figure and results of computational structure refinement against quantitative STEM will also be presented.

Lattice expansion and elemental distribution in PtMo catalyst nanoparticles: Quantitative high angle annular dark-field STEM analysis

254th National Meeting (2017)

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