A dimer path for CO dissociation on PtSn

Abstract

Density functional theory calculations are used to investigate CO adsorption, dissociation and SnO_X formation on Pt₃Sn. We find that direct CO dissociation is prevented by high activation energies. An energetically feasible path is instead CO dimer formation followed by C–O bond cleavage. Dimers are formed in the presence of Sn adatoms which effectively stabilize anionic OCCO⁻ species. The presence of Sn adatoms is crucial as dimers are unstable on Pt-only systems. The proposed mechanism may explain recent experimental observations of SnO_X and C–C formation as Pt_xSn is exposed to CO.