Aerobic epoxidation of propene over silver (1 1 1) and (1 0 0) facet catalysts

Catalytic performance of single-crystal Ag(1 0 0) and Ag(1 1 1) catalysts for propene oxidation has been investigated by means of Raman spectroscopy and mass spectrometry, and the energy profile has been obtained at the DFT-D level. It has been theoretically found and confirmed by Raman spectroscopy that Ag(1 0 0) surface is more reactive toward O2 dissociation than Ag(1 1 1) and that adsorbed oxo-species are more strongly bonded to the Ag(1 0 0) facet. The higher selectivity toward propylene oxide (PO) observed for the Ag(1 0 0) catalyst can be rationalized from theoretical calculations indicating that the activation barriers for formation of the allylic intermediate – precursor of combustion products – are rather similar on both silver surfaces, whereas energy barriers on the reaction pathways for formation of PO and carbonylic products (acetone and propanal) are systematically smaller on the Ag(1 0 0) surface.