; Mechanisms of H2O and CO2 Formation from Surface Oxygen Reduction on Co(0001)

摘要

Surface O removal by H and CO on Co(0001) has been studied using periodic density functional method (revised Perdew-Burke-Ernzerhof; RPBE) and ab-initio atomistic thermodynamics, On the basis of the quantitative agreement in the H2O formation barrier between experiment (1.34 +/- 0.07 eV) and theory (1.32 eV), H2O formation undergoes a consecutive hydrogenation process [O + 2H -> OH + H -> H2O], while the barrier of H2O formation from OH disproportionation [2OH -> H2O + O] is much lower (0.72 eV). The computed desorption temperatures of H-2 arid H2O under ultrahigh-vacuum conditions agree perfectly with the experiment. Surface O removal by CO has a high barrier (1.41 eV) and is strobsly endothermic (0.94 eV). Precoveted O and OH species do not significantly affect the barriers of H2O and CO2 formation. All of these results indicate that the present RPBE Method and the larger surface Model are more suitable for studying cobalt systems.