Vibrational characterization of carbon monoxide adsorption on sulfur modified Ni(100) surfaces |
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Authors: | John L. Gland Robert J. Madix Robert W. McCabe Craig DeMaggio |
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Affiliation: | Physical Chemistry Department, GM Research Laboratories, Warren, Michigan, USA;Chemical Engineering Department, Stanford University, Stanford, California, USA;Physical Chemistry Department, GM Research Laboratories, Warren, Michigan, USA |
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Abstract: | Carbon monoxide adsorption has been studied on a series of presulfided Ni(100) surfaces using vibrational spectroscopy. The sulfided Ni(100) surfaces were characterized using Auger electron spectroscopy and low energy electron diffraction, binding states were isolated by heating CO-dosed surfaces to prescribed temperatures, corresponding to the desorption temperatures of the CO. Adsorption of CO on Ni(100) with a p(2 × 2) array of sulfur lead to CO stretching frequencies of 1740 and 1930 cm?1 corresponding to desorption temperatures of 370 and 290 K, respectively. Adsorption of CO into the c(2 × 2)S structure resulted in a CO stretching frequency of 2115 cm?1 and a desorption peak near 140 K. The binding sites on the p(2 × 2)S structure were interpreted as metal four-fold hollows and bridging sites. The high frequency state was interpreted as weak bonding into the four-fold hollow with back donation into the π1 orbital on CO restricted by stearic hindrance due to adsorbed sulfur. Both the thermal desorption and vibrational results indicated that local CO-sulfur interactions are dominant on the presulfided Ni(100) surface in the coverage range studied. |
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