COMPETING PATHWAYS FOR METHOXY DECOMPOSITION ON OXYGEN-COVERED MO(110)

The reactions of methanol (CH3OH) are investigated on a range of oxyge n overlayers on Mo(110), with Bo from similar to 0.5 to >1 ML, using a combination of vibrational spectroscopies and temperature-programmed reaction. Infrared spectroscopy identifies a common? tilted methoxy in termediate at high temperature on all overlayers studied; electron ene rgy loss spectroscopy shows that this intermediate decomposes to depos it oxygen exclusively in high-coordination sites; While C-O bond sciss ion to evolve gas-phase methyl radicals is the only reaction observed for methoxy on highly oxidized Mo(110), on the surface oxygen overlaye rs competition between dehydrogenation and methyl evolution is highly sensitive to oxygen coverage. The enhanced selectivity for hydrocarbon formation from methanol reaction on oxygen-modified Mo(110) relative to the clean surface is attributed to inhibition of dehydrogenation pa thways rather than to marked changes in the C-O bond potential of meth oxy. (C) 1998 American Institute of Physics. [S0021-9606(98)00438-3].