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Oxidative addition of CH_4 to the catalyst surface produces CH_3 and H. If the CH_3 species generated on the surface couple with each other, reductive elimination of C_2H_6 may be achieved. Similarly,... H’s could couple to form H_2. This is the outline of nonoxidative coupling ofmethane (NOCM). It is difficult to achieve this reaction on a typical Pt catalyst surface. This is because methane is overoxidized and coking occurs. In this study, the authors approach this problem from a molecular aspect, relying on organometallic or complex chemistry concepts. Diagrams obtained by extending the concepts of the Walsh diagram to surface reactions are used extensively. C–H bond activation, i.e., oxidative addition, and C–C and H–H bond formation, i.e., reductive elimination, on metal catalyst surfaces are thoroughly discussed from the point of view of orbital theory. The density functional theory method for structural optimization and accurate energy calculations and the extended Hückel method for detailed analysis of crystal orbital changes and interactions play complementary roles. Limitations of monometallic catalysts are noted. Therefore, a rational design of single atom alloy (SAA) catalysts is attempted. As a result, the effectiveness of the Pt_1/Au(111) SAA catalyst for NOCM is theoretically proposed. On such an SAA surface, one would expect to find a single Pt monatomic site in a sea of inert Au atoms. This is desirable for both inhibiting overoxidation and promoting reductive elimination.show more
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