Step Site-Specific Semihydrogenation of Acetylene on the Au Surface

Supported Au catalysts are highly selective and size-sensitive in catalytic hydrogenation of alkynes under mild conditions. Using thermal-programmed desorption and density functional theory calculations, we study the hydrogenation reactions of C-2 hydrocarbons with atomic H and clarify the site-specific selective hydrogenation of C2H2 on Au(997) at low temperatures. On atomic H(a) covered Au(997), hydrogenation of C2H2 goes with 100% selectivity to C2H4 at steps, yet no hydrogenation occurs at terraces; adsorbed C2H4 on neither steps nor terraces reacts with H(a). DFT calculations suggest that the increased adsorption free energies and appropriate reaction barriers of C-2 species at steps lead to the step-site specific semihydrogenation of C2H2. These results elucidate the elementary surface reactions between C-2 hydrocarbons and atomic H on Au surfaces at the molecular level and significantly deepen the fundamental understanding of the unique selectivity of Au catalysts.

Automated summary

This study demonstrates the high selectivity of Au catalysts in the hydrogenation of C2H2, especially at the step sites on the surface, where C2H2 is selectively semi-hydrogenated to C2H4 with 100% selectivity.