Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The adsorption of water on Ni(110) has been studied by electron stimulated desorption ion angular distributions (ESDIAD), Fourier transform infrared-reflection absorption spectroscopy (FTIR-RAS), low energy electron diffraction (LEED), nuclear reaction analysis (NRA), and work function measurements ({dollar}\Delta\Phi{dollar}). The major findings in this study are: The saturation coverage of the first chemisorbed layer of water is 0.5 water molecules per surface Ni atom or 0.5 ML (1 ML = monolayer = 1.14 {dollar}\times{dollar} 10{dollar}\sp{lcub}15{rcub}{dollar} molecules cm{dollar}\sp{lcub}-2{rcub}{dollar}). The first chemisorbed layer exhibits c(2 x 2) symmetry, and is bonded to the surface monomerically (no evidence of intermolecular hydrogen bonding) with the plane of the water molecule oriented nearly parallel to the surface. The slightly less strongly bound second layer of water can be distinguished from subsequent layers by a discrete work function change. Population of the second layer, which is nearly saturated after an additional 0.5 ML, reorients the original first layer molecules via hydrogen bonding so that the plane of the molecule lies much closer to the surface normal. Free (non hydrogen-bonded) O-D (O-H) groups at the surface of ice layers have been identified by infra-red measurements through their high frequency, narrow band width and behavior upon condensation of H{dollar}\sb2{dollar}O (D{dollar}\sb2{dollar}O) ice. The enhancement of the absorption coefficient of the OD stretch upon formation of hydrogen bonds in D{dollar}\sb2{dollar}O ice layers on Ni(110) is found to lie between 30 and 36 compared to "free" OD groups.;Water has been observed to partially dissociate forming hydroxyls at a temperature of 208 K. Water is stabilized on the surface by hydrogen bonding to hydroxyls in a proposed linear OH-H{dollar}\sb2{dollar}O complex at 220 K. Clean Ni(110) is observed to be unreactive towards water under experimental conditions between 250 and 425 K. At T {dollar}>{dollar} 425 K, water is observed to completely dissociate to form adsorbed oxygen and H{dollar}\sb2{dollar} gas in a process which is itself catalyzed, and ultimately poisoned, by the adsorbed oxygen product. This catalytic process is believed to be initiated on defect sites. The adsorbed oxygen-induced catalytic rate of water dissociation proceeds at a maximum rate of 600 K.



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