The adsorption and subsequent reaction of nitric oxide (NO) on Mo(110) has been studied by temperature programmed reaction, electron energy loss, and infrared reflectance absorbance spectroscopies. The predominant reaction pathway for a saturated NO overlayer is dissociation to atomic nitrogen and oxygen; in fact, for low NO coverages, dissociation is the only reaction and largely takes place below 300 K. At NO coverages above 65% of θsat, evolution of N2O, N2, and NO is also observed at low temperature. Temperature programmed reaction of isotopically mixed overlayers demonstrates that N2O formation occurs via reaction of two intact NO molecules, suggestive of a dimeric surface intermediate. Electron energy loss and infrared spectroscopies identify three ν(NO) features which are assigned to three distinct species; the frequencies of the ν(NO) peaks in the infrared spectrum of a saturated 14NO overlayer at 100 K are 1860, 1821, and 1720 cm−1. The 1860 and 1720 cm−1 features are assigned to monomeric NO. Based on the infrared spectrum of a mixed overlayer of 14NO and 15NO, and on comparison to reference spectra of NO adsorbed on MoO3, the 1821 cm−1 peak is identified as νs(NO) of a surface dinitrosyl complex, i.e., two NO molecules bound to one Mo site. The weakly bound NO with the stretch frequency of 1860 cm−1 is associated with NO desorption, while the dinitrosyl leads to low-temperature N2 and N2O formation and some dissociation.

The reactions of ethylene glycol on Mo(110) were studied using temperature-programmed reaction, infrared reflection absorption, high-resolution electron energy loss, and X-ray photoelectron spectroscopies. The major reaction pathway is double C−O bond scission to evolve gas-phase ethylene at 350 and 390 K. Both X-ray photoelectron and infrared spectra demonstrate the existence of two surface intermediates, a bidentate (−OCH2CH2O−) and a monodentate (−OCH2CH2OH) species, at saturation coverage of ethylene glycol. We demonstrate that all ethylene glycol in the mixed overlayer of mono- and bidentate species reacts via a bidentate surface intermediate. Furthermore, in contrast to previous studies on other surfaces, the dialkoxide ethylene glycol intermediate is shown to be more reactive than similar monoalkoxides on Mo(110). Finally, analysis of the infrared spectra demonstrates that the bidentate species adsorbs with C 2 (or lower) symmetry at 300 K.

The reactions of methanol (CH 3 OH) are investigated on a range of oxygen overlayers on Mo͑110͒, with O from ϳ0.5 to Ͼ1 ML, using a combination of vibrational spectroscopies and temperature-programmed reaction. Infrared spectroscopy identifies a common, tilted methoxy intermediate at high temperature on all overlayers studied; electron energy loss spectroscopy shows that this intermediate decomposes to deposit oxygen exclusively in high-coordination sites. While C-O bond scission to evolve gas-phase methyl radicals is the only reaction observed for methoxy on highly oxidized Mo͑110͒, on the surface oxygen overlayers competition between dehydrogenation and methyl evolution is highly sensitive to oxygen coverage. The enhanced selectivity for hydrocarbon formation from methanol reaction on oxygen-modified Mo͑110͒ relative to the clean surface is attributed to inhibition of dehydrogenation pathways rather than to marked changes in the C-O bond potential of methoxy.

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