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