Engineering selectivity in heterogeneous catalysis: Ag nanowires as selective ethylene epoxidation catalysts.

Controlling selectivity in heterogeneous catalysis is critical for the design of environmentally friendly catalytic processes that minimize the production of undesired byproducts and operate with high energy efficiency. We show that the Ag nanowire catalysts exhibit higher selectivity in the ethylene epoxidation reaction than conventional spherical particle catalysts. The higher selectivity of the nanowire catalysts was attributed to a higher concentration of the Ag(100) surface facets in the nanowire catalysts compared to the particle catalysts. Density functional theory calculations show that the transformation of the surface oxametallacycle intermediate to form the selective product, EO, is more favorable on the Ag(100) than on Ag(111). The studies show that recent advances in the controlled synthesis of uniform nanostructures with well-defined surface facets might provide an important platform for the design of highly selective heterogeneous catalysts.