A computational study of H2 dissociation on silver surfaces: The effect of oxygen in the added row structure of Ag(110)

Abstract

We studied computationally the activation of H₂ on clean planar (111), (110) and stepped (221) as well as oxygen pre-covered silver surfaces using a density functional slab model approach. In line with previous data we determined clean silver to be inert towards H₂ dissociation, both thermodynamically and kinetically. The reaction is endothermic by ∼40 kJ mol⁻¹ and exhibits high activation energies of ∼125 kJ mol⁻¹. However, oxygen on the surface, modeled by the reconstructed surface p(2 × 1)O/Ag(110) that exhibits –O–Ag–O– added rows, renders H₂ dissociation clearly exothermic and kinetically feasible. The reaction was calculated to proceed in two steps: first the H–H bond is broken at an Ag–O pair with an activation barrier E_a ∼70 kJ mol⁻¹, then the H atom bound at an Ag center migrates to a neighboring O center with E_a ∼12 kJ mol⁻¹.