Elevated-pressure chemical reactivity of carbon monoxide over Au(111)

A systematic study of elevated-pressure gas–surface interactions is presented. Surface X-ray diffraction is used to study the interaction of carbon monoxide with the Au(111)-reconstructed surface. Thirteen orders of magnitude difference in pressure are probed from ultrahigh vacuum up to 2 bar of CO. Several variables are shown to influence the gas–surface interaction, including pressure, temperature, X-ray exposure and sample electric potential in the presence of X-rays. At elevated pressures of CO, the interactions range from modest rearrangement to substantial lifting of the reconstruction. There is clear evidence of a thermally activated chemical reaction involving significant displacements of gold atoms. The reactions and atomic displacements are unexpected, based on prior vacuum and theoretical studies of CO/Au, thus revealing the considerable differences associated with high gas pressures.