Temperature-programmed reaction/desorption (TPR/D), reflection-absorption infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the reactions of FCH2CH2OH and ClCH2CH2OH on Ni(111) and oxygen-precovered Ni(111) (O/Ni(111)). In the chemical process of FCH2CH2OH on Ni(111), only FCH2CH2O- is found to be the stable reaction intermediate, which starts to appear at ∼190 K. At low coverages, this intermediate decomposes into H2 and CO. Additional C 2H4 (219 K) is generated at higher exposures. On Ni(111) at 200 K, ClCH2CH2OH mainly dissociates to form ClCH 2CH2O- and -CH2CH2O- at lower exposures, with H2 and CO as the final products, while ClCH 2CH2O- becomes predominant at higher exposures and is responsible for the extra C2H4 channel of 218 K. C 2H4 is also generated at 161 and 174 K as the exposure is increased to render multilayer adsorption. Due to the competition in the scission of the carbon-halogen and carbon-hydrogen bonds, ClCH 2CH2OH has better reactivity toward C2H 4 formation than FCH2CH2OH. No -CH 2CH2OH is found in the decomposition of FCH 2CH2OH and ClCH2CH2OH on Ni(111), which is the intermediate in the reaction of ICH2CH2OH on Ni(100) and Pd(111). The presence of preadsorbed oxygen can enhance the ethylene formation at low coverages of FCH2CH2OH and ClCH 2CH2OH. At higher coverages, additional acetaldehyde is formed in the reaction of FCH2CH2OH, in contrast to the ethylene oxide from ClCH2CH2OH.
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