Carbon monoxide adsorption on the kinked Pt(321) surface

Carbon monoxide adsorption and desorption were studied on the kinked Pt(321) surface using high resolution electron energy loss spectroscopy, thermal desorption spectroscopy, Auger electron spectroscopy, and low energy electron diffraction. Two chemisorbed states are observed for CO adsorption on the Pt(321) surface. Carbon monoxide adsorbed along the rough steps (which have a high density of kinks) has an adsorption energy of 151 kJ/mol (36 kcal/mol). Carbon monoxide adsorbed on the terraces has an adsorption energy of 96 kJ/mol (23 kcal/mol). Both terminal and bridge bonded CO adsorb on the atomically rough steps although terminal binding is the dominant adsorption mode. Adsorption along the rough steps and terraces does not occur sequentially at 100K indicating that the CO mobility is restricted on the rough Pt(321) surface. However, sequential desorption does occur since CO desorbs from the terraces before it desorbs from steps. Molecular adsorption of CO on the Pt(321) kinked surface clearly dominates. In fact, weakening of the carbon-oxygen bond does not occur contrary to several recent suggestions that surface defects on platinum weaken the carbon-oxygen bond.