Ultra-selective epoxidation of styrene on pure Cu{111} and the effects of Cs promotion

Styrene undergoes efficient epoxidation to styrene epoxide on the Cu{111} surface. At the optimum condition (Theta(O) = 0.03 ML) similar to 20% of the styrene is converted to the epoxide with almost 100% selectivity. Comparison with Ag{111} shows that the epoxidation activity and selectivity of Cu greatly exceed those of Ag. Incipient oxidation of the Cu{111} surface does not suppress the adsorption of styrene, but the oxidised metal is catalytically inert. Submonolayer amounts of Cs enhance styrene uptake and increase conversion to the epoxide without adversely affecting epoxidation selectivity. This effect is due to inhibition of Cu oxidation by Cs. Our findings are discussed in the light of current understanding of Ag-catalysed alkene epoxidation.