INTERACTIONS OF O2, CO, CO2, AND D2 WITH THE STEPPED CU(311) CRYSTAL-FACE - COMPARISON TO CU(110)

Carbon dioxide is shown to chemisorb and dissociate to carbon monoxide and atomic oxygen on Cu(311) at 150 K in ultra-high vacuum. The reverse reaction of carbon monoxide and surface oxygen to form carbon dioxide is also shown to occur in the range of 150 to 400 K. At about 0.4 ML oxygen on Cu(311), a poorly ordered p(2 x 1) surface structure forms. Increasing the oxygen coverage further enhances surface disorder. Oxygen blocks only one of the three CO adsorption sites, and has little effect on CO2 adsorption and dissociation. Adsorption of D2 on Cu(311) is enhanced by pre-adsorbed oxygen. We contrast the high reactivity of Cu(311) for CO2 and D2 dissociative adsorption, and for CO oxidation to CO2 with the relatively inactive Cu(110). These chemisorption studies suggest that methanol synthesis over copper may be a structure sensitive reaction.