Mechanisms of H<sub>2</sub>O and CO<sub>2</sub> Formation
from Surface Oxygen Reduction on Co(0001)
- Publication date
- Publisher
Abstract
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 H<sub>2</sub>O formation barrier between
experiment (1.34 ± 0.07 eV) and theory (1.32 eV), H<sub>2</sub>O formation undergoes a consecutive hydrogenation process [O + 2H
→ OH + H → H<sub>2</sub>O], while the barrier of H<sub>2</sub>O formation from OH disproportionation [2OH → H<sub>2</sub>O + O] is much lower (0.72 eV). The computed desorption temperatures
of H<sub>2</sub> and H<sub>2</sub>O under ultrahigh vacuum conditions
agree perfectly with the experiment. Surface O removal by CO has a
high barrier (1.41 eV) and is strongly endothermic (0.94 eV). Precovered
O and OH species do not significantly affect the barriers of H<sub>2</sub>O and CO<sub>2</sub> formation. All of these results indicate
that the present RPBE method and the larger surface model are more
suitable for studying cobalt systems
