The catalytic performance of nanoparticles (NPs) in terms of activity, selectivity, and durability, is primarily determined by the nature of the surface and near-surface atomic configurations. The surface structure and chemistry are highly dynamic during synthesis and processing treatments. Understanding the NP surface atomic structural and chemical evolution as a function of synthesis variables, including time and temperature, as well as processing environment, are imperative towards the controlled synthesis of novel NP morphologies and the discovery of new, metastable atomic configurations of NPs with optimized performance. The ability to conduct chemically sensitive imaging at atomic resolution under simulated synthesis conditions, e.g., liquid, gas, and/or temperature, in situ scanning transmission electron microscopy (STEM) provides unique insight into the localized surface evolution mechanisms. In this presentation, we will demonstrate recent liquid-cell studies that reveal the mechanisms controlling the formation of core-shell NPs by directly observing the dynamic deposition of single atoms onto seed NPs. Our controlled in situ experiments have served to elucidate how synthesis variables, such as the concentration of PVP, the absorption of ligands, and the geometry of seed NPs, influence the deposition kinetics. Furthermore, by tracking the same individual NPs during in situ annealing, the influence of post-synthesis treatments on core-shell metal NPs will be discussed.

Probing synthesis mechanisms of core-shell metal nanoparticle catalysts at the atomic scale using In Situ STEM

256th National Meeting (2018)

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