Catalytic reduction of SO 2 by CO over Au 4 Pt 2 (CO) n and Au 6 Pt(CO) n clusters: a first-principles study.

The catalytic properties of the magic gold-platinum bimetallic clusters (Au ₄ Pt ₂ and Au ₆ Pt) for the reduction of SO ₂ by CO, without or with preadsorbing CO molecules, are firstly investigated using density functional theory calculations. We find that the catalytic activities improve effectively with the preadsorption of CO onto the catalysts and that the catalytic activities of Au ₆ Pt(CO) _n are better than those of Au ₄ Pt ₂ (CO) _n as more CO molecules are adsorbed onto the catalysts. During the reaction process, the Au ₄ Pt ₂ (CO) _n clusters always keep two-dimensional morphologies except for when n = 5 and the Au ₆ Pt(CO) _n clusters have three-dimensional geometries except for when n = 0. The most stable adsorption site for SO ₂ molecules on the catalysts is the site of preadsorbing the next CO molecule on the corresponding catalysts. The largest activation energy (E) is related to the metal 5d (M-5d) band center and the charge transfer (C _t ) as well as the bond length (R _b ) between COS and the catalyst contribute to the desorption energy (E _d ) of COS corporately. We propose that Au ₆ Pt(CO) ₆ is a cost-effective gold-platinum bimetallic catalyst for the reduction of SO ₂ by CO.