Correlating Catalytic Activity of Ag–Au Nanoparticles with 3D Compositional Variations

Significant elemental segregation is shown to exist within individual hollow silver–gold (Ag–Au) bimetallic nanoparticles obtained from the galvanic reaction between Ag particles and AuCl₄^–. Three-dimensional compositional mapping using energy dispersive X-ray (EDX) tomography within the scanning transmission electron microscope (STEM) reveals that nanoparticle surface segregation inverts from Au-rich to Ag-rich as Au content increases. Maximum Au surface coverage was observed for nanoparticles with approximately 25 atom % Au, which correlates to the optimal catalytic performance in a three-component coupling reaction among cyclohexane carboxyaldehyde, piperidine, and phenylacetylene