COMPRESSION STRUCTURES OF CARBON-MONOXIDE ON A PT(111) ELECTRODE SURFACE STUDIED BY INSITU SCANNING TUNNELING MICROSCOPY

The structure of carbon monoxide adsorbed on a platinum (111) single crystal electrode surface was examined by in situ electrochemical scanning tunneling microscopy in a 0.5 M H2SO4 solution containing CO. Four different structures were observed depending on the electrode potential and the CO coverage. At CO saturation, distorted (1/4 1/5) and (3 x 1) structures were found on a Pt(111) electrode surface at the electrode potential of 0.55 V against the normal hydrogen electrode, At lower coverages, the (square-root 3 X square-root 3)R30-degrees structure known under ultrahigh vacuum was observed at 0.55 V, and a periodic domain structure based on (square-root 3 X square-root 3)R30-degrees was also found at 0.30 V.