Coverage and potential dependent CO adsorption on Pt(1111), (711) and (100) electrode surfaces studied by infrared reflection absorption spectroscopy

Abstract

The structure of CO adsorbed on stepped electrode surfaces was studied by infrared reflection absorption method. Three kinds of (100) terrace surfaces which exhibited different step densities, Pt(1111)[6(100) × (111)], Pt(711)[4(100) × (111)] and Pt(100), were examined. At least four kinds of absorption bands of CO were found on each electrode surface: on-top CO on steps at 2045 cm −1, on-top CO on terraces at 2060 cm −1, symmetric bridge CO at 1880 cm −1, and asymmetric bridge CO at 1920 cm −1. The population at each CO adsorption site could be controlled by changing the electrode potential and CO coverage. At negative electrode potentials, CO preferred a bridge site on terrace atoms and an on-top site on step atoms, while at positive potentials, on-top CO on terraces predominated. The coverages at which on-top CO on the terrace surface started to appear were 0.40 on Pt(100), 0.35 on Pt(1111) and 0.25 on Pt(711).