Molecular N2 chemisorption—specific adsorption on step defect sites on Pt surfaces

Infrared reflection-absorption spectroscopy and density functional theory, within the generalized gradient approximation, were used to investigate both experimentally and theoretically N2 chemisorption on stepped and smooth Pt surfaces. N2 chemisorption was observed to occur only on the edge atoms of step defect sites in atop configuration by both methods. The calculated vibrational frequency of N2 chemisorbed on Pt(112) step sites (2244 cm−1) is in good agreement with the frequency observed experimentally (2231–2234 cm−1) at saturation coverage on Pt(335) and Pt(779). The predicted small N2 binding energy confirmed its weak chemisorption on Pt surfaces claimed in previous studies. The calculations indicate that N2 decreases and CO increases the work function of the Pt(112) surface. N2 could be coadsorbed with CO below saturation coverage of the steps with CO and there is a charge transfer between the two adspecies through the substrate.