Atomic-Scale Insights into Nanoparticle Exsolution at Dislocations in Dislocation-Engineered Catalysts.

Achieving control over properties such as density and lateral distribution of catalytic nanoparticles under operation conditions is a major challenge for the development of active and durable catalysts, where nanoparticle coarsening is often the cause of performance degradation. While metal exsolution catalysts are regarded to be robust against this degradation mode, coarsening and increased concentrations of exsolved metal nanoparticles have been detected near extended defects. The present study examines the role of dislocations in metal exsolution reactions and explores the potential of dislocation-engineering for the synthesis of dislocation-associated nanoparticles. An atomic-level correlation between bulk dislocations and surface nanoparticle locations is demonstrated through a novel approach for engineering epitaxial thin films with confined regions of increased dislocation densities in combination with in situ scanning transmission electron microscopy. While nanoparticle exsolution proceeds across the entire sample, two primary reasons for the frequent nucleation of dislocation-associated nanoparticles are identified: the accumulation of exsolution-active acceptors along dislocations and lattice distortions that are likely to lower the energy barrier for nanoparticle nucleation. This work establishes a proof of concept for using engineered dislocations in exsolution catalysts to synthesize nanoparticles with modified nanoparticle-support properties relevant for the thermal stability and the lateral distribution of exsolved nanoparticles.