Adsorption and dissociation of O2 on Cu(111):: thermochemistry, reaction barrier and the effect of strain

The adsorption and dissociation of dioxygen on the Cu(1 1 1) surface have been studied using periodic self-consistent density functional calculations. Two types of di-sigma -type chemisorbed molecular precursors are identified: a non-magnetic type located over threefold hollows and a paramagnetic type over bridge sites, both with a binding energy of ca. -0.50 eV with respect to a gas-phase O-2 molecule. Atomic oxygen is found to prefer threefold hollows. with a binding energy of ca. -4.3 eV with respect to a gas-phase O atom. Possible pathways for the dissociation Of O-2 are explored, and the lowest activation energy is calculated to be ca. 0.20 eV. Expansive strain parallel to the surface plane is shown to enhance the binding of atomic and molecular oxygen on the surface as well as to decrease the transition state energy of O-2 dissociation. (C) 2001 Published by Elsevier Science B.V.