Theoretical studies of the interaction of PtSn systems with H2

The reaction of the PtSn system with the hydrogen molecule is studied theoretically. The results are compared with experimental reports of commercial-type catalysts and previous theoretical studies of Pt + H2 and Pt2 + H2 reactions. All the calculations were made by the ab initio MC-SCF + MRCI method including relativistic core potentials approximation. We consider two main geometrical approaches of the hydrogen molecule to the SnPt system: parallel and perpendicular. The theoretical and geometrical parameters were taken from our previous studies and from experiments. Many states were studied: Some of them are repulsive and others present weak capture of hydrogen; none scisse the H2 molecule. The main conclusion of this work is that the platinum activity, when Pt and Sn form alloys, is inhibited by the tin, suggesting that the interaction between the two metals occurs through an oxygen atom of the support.