AB-INITIO STUDY ON THE ADSORPTION AND DISSOCIATION PROCESS OF METHANOL ON A SILVER SURFACE

The geometries of methanol adsorbed on an oxygen-free silver surface, a promoted silver surface and an oxygen preadsorbed silver surface wer e optimized at the MP2 level and the energies were calculated at the M P4 level. Our calculations showed that weak physisorption of methanol occurs on the clean silver surface, but stable molecular chemisorption occurs in the other two cases. The adsorption and dissociation proces s of methanol was postulated to occur via two pathways, i.e. the Eley- Rideal mode and the Langmuir-Hinshelwood mode. The calculations also s howed that the presence of atomic oxygen at a silver surface is essent ial for the cleavage of the O-H bond in the methanol. The dissociation of methanol in the Langmuir-Hinshelwood mode has a small energy barri er but has no energy barrier in the Eley-Rideal mode. (C) 1998 Elsevie r Science B.V.