Catalytic reduction of SO₂ by CO over Au₄Pt₂(CO)_n and Au₆Pt(CO)_n clusters: a first-principles study

The catalytic properties of the magic gold-platinum bimetallic clusters (Au₄Pt₂ and Au₆Pt) for the reduction of SO₂ 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 Au₆Pt(CO)_n are better than those of Au₄Pt₂(CO)_n as more CO molecules are adsorbed onto the catalysts. During the reaction process, the Au₄Pt₂(CO)_n clusters always keep two-dimensional morphologies except for when n = 5 and the Au₆Pt(CO)_n clusters have three-dimensional geometries except for when n = 0. The most stable adsorption site for SO₂ 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 Au₆Pt(CO)₆ is a cost-effective gold-platinum bimetallic catalyst for the reduction of SO₂ by CO.