NSF-DFG MISSION: Elucidating the dynamics of nanocrystal formation and transformation using multimodal in-situ electron microscopy

Advanced electron microscopy and comprehensive computer simulations allow for the in-depth analysis and prediction of intricate nanostructures in situ and operando. A focal point is material interfaces, where chemical reactions and phase changes occur. Dominated by these interfaces, nanocrystals (NCs) have applications spanning medicine, electronics, and energy, offering heightened efficiency and performance. Although numerous reproducible NC synthesis methods exist, many were developed through trial and error. The exact nucleation mechanism and NC shape evolution remain unclear. NC dissolution also provides insights into corrosion and material degradation. Investigating NC formation and dissolution is complex due to the rapid yet sporadic nucleation process and the data limitations from two-dimensional interfaces compared to three-dimensional structures. Advanced electron microscopy bridges some information gaps but combining it with computer simulations is essential for a holistic understanding. We propose to utilize multimodal and multi-dimensional in-situ electron microscopy combined with multiscale computer simulations to delve into the atomic processes and kinetic pathways of NC formation and transformation under system-realistic and application-relevant conditions. Our proposal comprises two Specific Aims. In Aim 1, we will i) probe symmetry breaking during kinetically controlled synthesis of anisotropic non-precious-metal NCs, analyzing reaction intermediates; ii) initiate in-situ electrochemically-controlled seed-mediated reduction, observing structural evolution; iii) detail kinetic pathways for both seedless and seeded NC growth via multiscale simulations. In Aim 2, our approach is to i) examine dynamic alterations in the composition, shape, and crystalline phase of precision-crafted NC electrocatalysts using in-situ electron microscopy and ii) employ simulations to grasp the structural dynamics and deactivation processes of NC catalysts. Our goal is to offer atomic-level perspectives on the kinetic restructuring of individual NCs. These insights will be crucial for designing NCs with enhanced properties and stability.