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Abstract:
Silver–copper alloys have been proposed as catalysts for ethylene epoxidation due to their superior
selectivity compared to pure silver, the predominant catalyst for this reaction. Under reaction
conditions it has been previously shown that, rather than a two-dimensional (2D) Ag–Cu alloy, a thin
copper oxide-like layer forms on top of silver, and several possible surface structures were identified
(Phys. Rev. Lett., 2010, 104, 035503). By means of density-functional theory calculations, we study the
mechanism of ethylene epoxidation catalyzed by the thin oxide-like surface structures. We identify
different reaction pathways that will compete and/or synergetically interplay in the catalysis. In general,
the reaction mechanism is structure-dependent and the reaction does not always proceed through the
formation of (meta)stable intermediates, in contrast to clean Ag and the 2D alloy. Analyzing the
competing reactions, we discuss how the addition of Cu improves the selectivity and stress the overall
importance of accounting for the effect of ambient conditions.
