Surface Composition of Silver Nanocubes and Their Influence on Morphological Stabilization and Catalytic Performance in Ethylene Epoxidation.

Silver nanocubes with exposed (100) facets are reported to have improved selectivity with respect to their spherical counterparts for ethylene epoxidation. In the present study, we observe that the surface composition of the silver nanocubes also has a critical impact on activity. Detailed investigation of the surface composition of silver nanocubes has been carried out using HRTEM, SEM, EDS, EELS, and EFTEM. Surfaces of silver nanocubes are "passivated" by chloride, and its removal is essential to achieve any catalytic activity. However, the surface chloride is apparently essential for stabilizing the cubic morphology of the particles. Attempts were made to understand the competing effects of the surface species for retaining the morphology of the nanocubes and on their catalytic activity in ethylene epoxidation.